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Fiore CM, Quigley K, Vorobyov I, Clancy CE, Harvey RD. Effect of the Membrane Environment on Pharmacologic Inhibition of hERG K + Channel Activity. JACC Clin Electrophysiol 2025; 11:708-719. [PMID: 39895450 PMCID: PMC12043409 DOI: 10.1016/j.jacep.2024.11.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2024] [Revised: 10/11/2024] [Accepted: 11/25/2024] [Indexed: 02/04/2025]
Abstract
BACKGROUND hERG encodes KV11.1 voltage-gated K+ channels, which generate the rapidly activating delayed rectifier K+ current that contributes to repolarization of the cardiac action potential. In addition to being targeted by many class III antiarrhythmic agents, these channels are also inhibited by a multitude of other pharmacological compounds, which can produce acquired long QT syndrome, leading to polymorphic ventricular tachycardia. While most drugs are thought to interact with a hydrophilic binding site in the channel pore, it has been postulated that some compounds act by perturbing the membrane environment or acting at hydrophobic sites accessed through the plasma membrane. OBJECTIVES Because hERG channels reside in cholesterol rich lipid raft domains, we hypothesized that disrupting the membrane environment by depleting cholesterol might alter inhibition of channel activity by certain drugs. METHODS We tested our hypothesis by examining the effect that depleting membrane cholesterol with methyl-β-cyclodextrin has on the ability of several compounds to inhibit hERG channels expressed in HEK293 cells. RESULTS We found that cholesterol depletion significantly increased the sensitivity of the whole cell current to inhibition by ibutilide, while decreasing the currents sensitivity to dofetilide and amiodarone at negative membrane potentials. CONCLUSIONS These results support the idea that the lipid environment of the plasma membrane plays a role in the ability of certain drugs to inhibit hERG channel activity. Differences in membrane cholesterol content may affect the ability of some hERG channel blockers to produce arrhythmogenic behavior.
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Affiliation(s)
- Chase M Fiore
- Department of Pharmacology, University of Nevada, Reno, Reno, Nevada, USA
| | - Kate Quigley
- Department of Pharmacology, University of Nevada, Reno, Reno, Nevada, USA
| | - Igor Vorobyov
- Department of Physiology and Membrane Biology, University of California-Davis, Davis, California, USA
| | - Colleen E Clancy
- Department of Physiology and Membrane Biology, University of California-Davis, Davis, California, USA
| | - Robert D Harvey
- Department of Pharmacology, University of Nevada, Reno, Reno, Nevada, USA.
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Leishman DJ, Holdsworth DL, Best DD, Abernathy MM, Roche BM. Demonstrating the statistical and pharmacological sensitivity of nonclinical QTc analysis using a dofetilide dose-response in nonhuman primates. J Pharmacol Toxicol Methods 2025; 131:107572. [PMID: 39689735 DOI: 10.1016/j.vascn.2024.107572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 12/03/2024] [Accepted: 12/12/2024] [Indexed: 12/19/2024]
Abstract
Nonclinical QTc studies can augment clinical QTc assessments in regulatory submissions provided they are of sufficient quality and sensitivity. Both the statistical performance and species translation play a role in determining the sensitivity of the model. The current analyses examine the effects of dofetilide or vehicle on the QT interval in nonhuman primate (NHP; n = 16) using a one-step estimated marginal means method where both treatment and animal ID are used in regression models to avoid a separate rate correction step, in comparison to other commonly utilized methods. The doses of dofetilide were chosen to span a threshold dose with exposure only just exceeding the concentration associated with 10 ms QTc prolongation in man, to a dose where exposures exceed the Emax for QTc prolongation. The primary objective was an evaluation of which doses and exposures can be detected as eliciting a statistically significant change in QTc. A group size of 8 for cross-over analysis was insufficient to detect, as statistically significant, the effects of the threshold dose of 0.01 mg/kg dofetilide using common correction and statistical analysis methods and hourly time intervals. Higher doses were all detected as causing a statistically significant effect using the same techniques. The 'One-Step' method was able to detect as statistically significant effects at all doses of dofetilide across a wide range of time and exposure. There were also temporal differences between the mean effects observed using the common and 'One-Step' methods. Preliminary concentration-QTc assessment suggests a higher maximum prolongation in concentration QTc with the 'One-Step' method. Furthermore, this analysis suggests that at exposures associated with a 10 ms QTc prolongation in man a 10 ms prolongation is also observed in NHP. The observed ED50 concentration (0.85 ng/ml unbound) is close to that described in man (0.98 ng/ml). These analyses demonstrate the statistical sensitivity of the 'One-Step' method of QTc assessment in NHP. The pharmacological sensitivity was also demonstrated and a detection threshold of 10 ms was consistent in terms of exposure between NHP and man. Overall, QTc assessment using the 'One-Step' method in NHP is a robust and sensitive model to supplement clinical QTc assessment.
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Affiliation(s)
| | | | - Derek D Best
- Eli Lilly and Company, Indianapolis, United States
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3
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Ágoston M, Kohajda Z, Virág L, Baláti B, Nagy N, Lengyel C, Bitay M, Bogáts G, Vereckei A, Papp JG, Varró A, Jost N. A Comparative Study of the Rapid (I Kr) and Slow (I Ks) Delayed Rectifier Potassium Currents in Undiseased Human, Dog, Rabbit, and Guinea Pig Cardiac Ventricular Preparations. Pharmaceuticals (Basel) 2024; 17:1091. [PMID: 39204196 PMCID: PMC11357539 DOI: 10.3390/ph17081091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Revised: 07/24/2024] [Accepted: 08/09/2024] [Indexed: 09/03/2024] Open
Abstract
To understand the large inter-species variations in drug effects on repolarization, the properties of the rapid (IKr) and the slow (IKs) components of the delayed rectifier potassium currents were compared in myocytes isolated from undiseased human donor (HM), dog (DM), rabbit (RM) and guinea pig (GM) ventricles by applying the patch clamp and conventional microelectrode techniques at 37 °C. The amplitude of the E-4031-sensitive IKr tail current measured at -40 mV after a 1 s long test pulse of 20 mV, which was very similar in HM and DM but significant larger in RM and GM. The L-735,821-sensitive IKs tail current was considerably larger in GM than in RM. In HM, the IKs tail was even smaller than in DM. At 30 mV, the IKr component was activated extremely rapidly and monoexponentially in each studied species. The deactivation of the IKr component in HM, DM, and RM measured at -40 mV. After a 30 mV pulse, it was slow and biexponential, while in GM, the IKr tail current was best fitted triexponentially. At 30 mV, the IKs component activated slowly and had an apparent monoxponential time course in HM, DM, and RM. In contrast, in GM, the activation was clearly biexponential. In HM, DM, and RM, IKs component deactivation measured at -40 mV was fast and monoexponential, while in GM, in addition to the fast component, another slower component was also revealed. These results suggest that the IK in HM resembles that measured in DM and RM and considerably differs from that observed in GM. These findings suggest that the dog and rabbit are more appropriate species than the guinea pig for preclinical evaluation of new potential drugs expected to affect cardiac repolarization.
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Affiliation(s)
- Márta Ágoston
- Department of Pharmacology and Pharmacotherapy, Albert Szent-Györgyi Medical School, University of Szeged, P.O. Box 427, 6701 Szeged, Hungary
| | - Zsófia Kohajda
- HUN-REN-SZTE Research Group for Cardiovascular Pharmacology, 6701 Szeged, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Albert Szent-Györgyi Medical School, University of Szeged, P.O. Box 427, 6701 Szeged, Hungary
- Interdisciplinary Research and Development and Innovation Centre of Excellence, University of Szeged, 6720 Szeged, Hungary
| | - Beáta Baláti
- Department of Pharmacology and Pharmacotherapy, Albert Szent-Györgyi Medical School, University of Szeged, P.O. Box 427, 6701 Szeged, Hungary
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, Albert Szent-Györgyi Medical School, University of Szeged, P.O. Box 427, 6701 Szeged, Hungary
- HUN-REN-SZTE Research Group for Cardiovascular Pharmacology, 6701 Szeged, Hungary
| | - Csaba Lengyel
- Department of Medicine, Albert Szent-Györgyi Medical School, University of Szeged, 6720 Szeged, Hungary
| | - Miklós Bitay
- Department of Cardiac Surgery, Albert Szent-Györgyi Medical School, University of Szeged, 6742 Szeged, Hungary
| | - Gábor Bogáts
- Department of Cardiac Surgery, Albert Szent-Györgyi Medical School, University of Szeged, 6742 Szeged, Hungary
| | - András Vereckei
- Department of Internal Medicine and Haematology, Semmelweis University, 1088 Budapest, Hungary
| | - Julius Gy. Papp
- Department of Pharmacology and Pharmacotherapy, Albert Szent-Györgyi Medical School, University of Szeged, P.O. Box 427, 6701 Szeged, Hungary
- HUN-REN-SZTE Research Group for Cardiovascular Pharmacology, 6701 Szeged, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, Albert Szent-Györgyi Medical School, University of Szeged, P.O. Box 427, 6701 Szeged, Hungary
- HUN-REN-SZTE Research Group for Cardiovascular Pharmacology, 6701 Szeged, Hungary
- Interdisciplinary Research and Development and Innovation Centre of Excellence, University of Szeged, 6720 Szeged, Hungary
| | - Norbert Jost
- Department of Pharmacology and Pharmacotherapy, Albert Szent-Györgyi Medical School, University of Szeged, P.O. Box 427, 6701 Szeged, Hungary
- HUN-REN-SZTE Research Group for Cardiovascular Pharmacology, 6701 Szeged, Hungary
- Interdisciplinary Research and Development and Innovation Centre of Excellence, University of Szeged, 6720 Szeged, Hungary
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Abramochkin DV, Pustovit OB, Mironov NY, Filatova TS, Nesterova T. Characterization of hERG K + channel inhibition by the new class III antiarrhythmic drug cavutilide. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2024; 397:5093-5104. [PMID: 38224347 DOI: 10.1007/s00210-023-02940-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 12/30/2023] [Indexed: 01/16/2024]
Abstract
Cavutilide (niferidil, refralon) is a new class III antiarrhythmic drug which effectively terminates persistent atrial fibrillation (AF; 84.6% of patients, mean AF duration 3 months) and demonstrates low risk of torsade de pointes (1.7%). ERG channels of rapid delayed rectifier current(IKr) are the primary target of cavutilide, but the particular reasons of higher effectiveness and lower proarrhythmic risk in comparison with other class III IKr blockers are unclear. The inhibition of hERG channels expressed in CHO-K1 cells by cavutilide was studied using whole-cell patch-clamp. The present study demonstrates high sensitivity of IhERG expressed in CHO-K1 cells to cavutilide (IC50 = 12.8 nM). Similarly to methanesulfonanilide class III agents, but unlike amiodarone and related drugs, cavutilide does not bind to hERG channels in their resting state. However, in contrast to dofetilide, cavutilide binds not only to opened, but also to inactivated channels. Moreover, at positive constantly set membrane potential (+ 60 mV) inhibition of IhERG by 100 nM cavutilide develops faster than at 0 mV and, especially, - 30 mV (τ of inhibition was 78.8, 103, and 153 ms, respectively). Thereby, cavutilide produces IhERG inhibition only when the cell is depolarized. During the same period of time, cavutilide produces greater block of IhERG when the cell is depolarized with 2 Hz frequency, if compared to 0.2 Hz. We suggest that, during the limited time after injection, cavutilide produces stronger inhibition of IKr in fibrillating atrium than in non-fibrillating ventricle. This leads to beneficial combination of antiarrhythmic effectiveness and low proarrhythmicity of cavutilide.
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Affiliation(s)
- Denis V Abramochkin
- Department of Human and Animal Physiology, Biological Faculty, Lomonosov Moscow State University, Leninskiye Gory, 1, 12, Moscow, Russia.
| | - Oksana B Pustovit
- Department of Human and Animal Physiology, Biological Faculty, Lomonosov Moscow State University, Leninskiye Gory, 1, 12, Moscow, Russia
| | | | - Tatiana S Filatova
- Department of Human and Animal Physiology, Biological Faculty, Lomonosov Moscow State University, Leninskiye Gory, 1, 12, Moscow, Russia
- Chazov National Medical Research Center for Cardiology, Moscow, Russia
- Department of Physiology, Pirogov Russian National Research Medical University, Ostrovityanova str., 1, Moscow, Russia
| | - Tatiana Nesterova
- Institute of Immunology and Physiology, Ural Branch of Russian Academy of Sciences, 620049, Ekaterinburg, Russia
- Institute of Natural Sciences and Mathematics, Ural Federal University, 620075, Ekaterinburg, Russia
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5
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Kambayashi R, Goto A, Izumi-Nakaseko H, Takei Y, Sugiyama A. Characterization of cardiovascular profile of anti-influenza drug peramivir: A reverse-translational study using the isoflurane-anesthetized dog. J Pharmacol Sci 2024; 154:218-224. [PMID: 38395523 DOI: 10.1016/j.jphs.2024.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2023] [Revised: 01/23/2024] [Accepted: 02/02/2024] [Indexed: 02/25/2024] Open
Abstract
An injectable anti-influenza drug peramivir has been reported to induce QT-interval prolongation in some phase III studies, although its thorough QT/QTc study was negative. We investigated the discrepancy among those clinical studies using isoflurane-anesthetized beagle dogs (n = 4). Peramivir in doses of 1 mg/kg/10 min (sub-therapeutic dose) followed by 10 mg/kg/10 min (clinically-relevant dose) was intravenously administered. Peramivir prolonged QT interval/QTcV and Tpeak-Tend, and tended to delay ventricular repolarization in a reverse-frequency dependent manner, indicating IKr inhibition in vivo. Meanwhile, peramivir did not alter P-wave duration, PR interval or QRS width, indicating a lack of impact on cardiac conduction via Na+ or Ca2+ channel inhibition in vivo. Peramivir prolonged Tpeak-Tend and tended to prolong terminal repolarization period, which would develop substrates for initiating and maintaining spiral reentry, respectively. Meanwhile, peramivir did not prolong J-Tpeakc, which could not induce early afterdepolarization, a trigger inducing torsade de pointes. Thus, our results support that clinical dose exposure of peramivir can delay the ventricular repolarization in influenza patients. Peramivir has only a small potential to induce torsade de pointes in patients with the intact hearts, but caution should be paid on its use for patients formerly having the trigger for torsade de pointes.
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Affiliation(s)
- Ryuichi Kambayashi
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo 143-8540, Japan
| | - Ai Goto
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo 143-8540, Japan
| | - Hiroko Izumi-Nakaseko
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo 143-8540, Japan
| | - Yoshinori Takei
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo 143-8540, Japan
| | - Atsushi Sugiyama
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo 143-8540, Japan.
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Furutani K. Facilitation of hERG Activation by Its Blocker: A Mechanism to Reduce Drug-Induced Proarrhythmic Risk. Int J Mol Sci 2023; 24:16261. [PMID: 38003453 PMCID: PMC10671758 DOI: 10.3390/ijms242216261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 11/08/2023] [Accepted: 11/12/2023] [Indexed: 11/26/2023] Open
Abstract
Modulation of the human Ether-à-go-go-Related Gene (hERG) channel, a crucial voltage-gated potassium channel in the repolarization of action potentials in ventricular myocytes of the heart, has significant implications on cardiac electrophysiology and can be either antiarrhythmic or proarrhythmic. For example, hERG channel blockade is a leading cause of long QT syndrome and potentially life-threatening arrhythmias, such as torsades de pointes. Conversely, hERG channel blockade is the mechanism of action of Class III antiarrhythmic agents in terminating ventricular tachycardia and fibrillation. In recent years, it has been recognized that less proarrhythmic hERG blockers with clinical potential or Class III antiarrhythmic agents exhibit, in addition to their hERG-blocking activity, a second action that facilitates the voltage-dependent activation of the hERG channel. This facilitation is believed to reduce the proarrhythmic potential by supporting the final repolarizing of action potentials. This review covers the pharmacological characteristics of hERG blockers/facilitators, the molecular mechanisms underlying facilitation, and their clinical significance, as well as unresolved issues and requirements for research in the fields of ion channel pharmacology and drug-induced arrhythmias.
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Affiliation(s)
- Kazuharu Furutani
- Department of Pharmacology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, 180 Nishihama-Boji, Yamashiro-cho, Tokushima 770-8514, Japan
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7
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Rossman EI, Wisialowski TA, Vargas HM, Valentin JP, Rolf MG, Roche BM, Riley S, Pugsley MK, Nichols J, Li D, Leishman DJ, Kleiman RB, Greiter-Wilke A, Gintant GA, Engwall MJ, Delaunois A, Authier S. Best practice considerations for nonclinical in vivo cardiovascular telemetry studies in non-rodent species: Delivering high quality QTc data to support ICH E14/S7B Q&As. J Pharmacol Toxicol Methods 2023; 123:107270. [PMID: 37164235 DOI: 10.1016/j.vascn.2023.107270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 05/02/2023] [Accepted: 05/06/2023] [Indexed: 05/12/2023]
Abstract
The ICH E14/S7B Questions and Answers (Q&As) guideline introduces the concept of a "double negative" nonclinical scenario (negative hERG assay and negative in vivo QTc study) to demonstrate that a drug does not produce a clinically relevant QT prolongation (i.e., no QT liability). This nonclinical "double negative" data package, along with negative Phase 1 clinical QTc data, may be sufficient to substitute for a clinical Thorough QT (TQT) study in some specific cases. While standalone GLP in vivo cardiovascular studies in non-rodent species are standard practice during nonclinical drug development for small molecule programs, a variety of approaches to the design, conduct, analysis and interpretation are utilized across pharmaceutical companies and contract research organizations (CROs) that may, in some cases, negatively impact the stringent sensitivity needed to fulfill the new Q&As. Subject matter experts from both Pharma and CROs have collaborated to recommend best practices for more robust nonclinical cardiovascular telemetry studies in non-rodent species, with input from clinical and regulatory experts. The aim was to increase consistency and harmonization across the industry and to ensure delivery of high quality nonclinical QTc data to meet the proposed sensitivities defined within the revised ICH E14/S7B Q&As guideline (Q&As 5.1 and 6.1). The detailed best practice recommendations presented here cover the design and execution of the safety pharmacology cardiovascular study, including optimal methods for acquiring, analyzing, reporting, and interpreting the resulting QTc and pharmacokinetic data to allow for direct comparison to clinical exposures and assessment of safety margin for QTc prolongation.
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Affiliation(s)
- Eric I Rossman
- GSK, Nonclinical Safety, Safety Pharmacology, Collegeville, PA, USA.
| | - Todd A Wisialowski
- Pfizer Worldwide Research Development and Medical, Safety Pharmacology, Groton, CT, USA
| | - Hugo M Vargas
- Amgen Research, Translational Safety & Bioanalytical Sciences, Thousand Oaks, CA, USA
| | | | - Michael G Rolf
- AstraZeneca, Clinical Pharmacology & Safety Sciences, R&D, Gothenburg, Sweden
| | - Brian M Roche
- Charles River Laboratories, Global Safety Pharmacology, Ashland, OH, USA
| | - Steve Riley
- Pfizer Worldwide Research Development and Medical, Clinical Pharmacology, Groton, CT, USA
| | | | - Jill Nichols
- Labcorp Early Development Laboratories Inc., Madison, WI, USA
| | - Dingzhou Li
- Pfizer Global Product Development, Global Biometrics & Data Management, Groton, CT, USA
| | | | | | | | | | - Michael J Engwall
- Amgen Research, Translational Safety & Bioanalytical Sciences, Thousand Oaks, CA, USA
| | - Annie Delaunois
- UCB Biopharma SRL, Chemin du Foriest, B-1420 Braine-l'Alleud, Belgium
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Das N, Bhattacharya D, Bandopadhyay P, Dastidar UG, Paul B, Rahaman O, Hoque I, Patra B, Ganguly D, Talukdar A. Mitigating hERG Liability of Toll-Like Receptor 9 and 7 Antagonists through Structure-Based Design. ChemMedChem 2023; 18:e202300069. [PMID: 36999630 DOI: 10.1002/cmdc.202300069] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 03/15/2023] [Accepted: 03/29/2023] [Indexed: 04/01/2023]
Abstract
hERG is considered to be a primary anti-target in the drug development process, as the K+ channel encoded by hERG plays an important role in cardiac re-polarization. It is desirable to address the hERG safety liability during early-stage development to avoid the expenses of validating leads that will eventually fail at a later stage. We have previously reported the development of highly potent quinazoline-based TLR7 and TLR9 antagonists for possible application against autoimmune disease. Initial experimental hERG assessment showed that most of the lead TLR7 and TLR9 antagonists suffer from hERG liability rendering them ineffective for further development. The present study herein describes a coordinated strategy to integrate the understanding from structure-based protein-ligand interaction to develop non- hERG binders with IC50 >30 μM with retention of TLR7/9 antagonism through a single point change in the scaffold. This structure-guided strategy can serve as a prototype for abolishing hERG liability during lead optimization.
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Affiliation(s)
- Nirmal Das
- Department of Organic and Medicinal Chemistry, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Kolkata, 700032, WB, India
- Academy of Scientific and Innovative Research, Ghaziabad, 201002, India
| | - Debomita Bhattacharya
- Department of Organic and Medicinal Chemistry, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Kolkata, 700032, WB, India
| | - Purbita Bandopadhyay
- IICB-Translational Research Unit of Excellence Department of Cancer Biology and Inflammatory Disorders, CSIR-Indian Institute of Chemical Biology Salt Lake, Kolkata, 700091, WB, India
- Academy of Scientific and Innovative Research, Ghaziabad, 201002, India
| | - Uddipta Ghosh Dastidar
- Department of Organic and Medicinal Chemistry, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Kolkata, 700032, WB, India
- Academy of Scientific and Innovative Research, Ghaziabad, 201002, India
| | - Barnali Paul
- Department of Organic and Medicinal Chemistry, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Kolkata, 700032, WB, India
- Academy of Scientific and Innovative Research, Ghaziabad, 201002, India
| | - Oindrila Rahaman
- IICB-Translational Research Unit of Excellence Department of Cancer Biology and Inflammatory Disorders, CSIR-Indian Institute of Chemical Biology Salt Lake, Kolkata, 700091, WB, India
| | - Israful Hoque
- Department of Organic and Medicinal Chemistry, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Kolkata, 700032, WB, India
| | - Binita Patra
- Department of Organic and Medicinal Chemistry, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Kolkata, 700032, WB, India
| | - Dipyaman Ganguly
- IICB-Translational Research Unit of Excellence Department of Cancer Biology and Inflammatory Disorders, CSIR-Indian Institute of Chemical Biology Salt Lake, Kolkata, 700091, WB, India
- Academy of Scientific and Innovative Research, Ghaziabad, 201002, India
| | - Arindam Talukdar
- Department of Organic and Medicinal Chemistry, CSIR-Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Kolkata, 700032, WB, India
- Academy of Scientific and Innovative Research, Ghaziabad, 201002, India
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9
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Verkerk AO, Wilders R. Human Sinoatrial Node Pacemaker Activity: Role of the Slow Component of the Delayed Rectifier K + Current, I Ks. Int J Mol Sci 2023; 24:7264. [PMID: 37108427 PMCID: PMC10138838 DOI: 10.3390/ijms24087264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 04/07/2023] [Accepted: 04/11/2023] [Indexed: 04/29/2023] Open
Abstract
The pacemaker activity of the sinoatrial node (SAN) has been studied extensively in animal species but is virtually unexplored in humans. Here we assess the role of the slowly activating component of the delayed rectifier K+ current (IKs) in human SAN pacemaker activity and its dependence on heart rate and β-adrenergic stimulation. HEK-293 cells were transiently transfected with wild-type KCNQ1 and KCNE1 cDNA, encoding the α- and β-subunits of the IKs channel, respectively. KCNQ1/KCNE1 currents were recorded both during a traditional voltage clamp and during an action potential (AP) clamp with human SAN-like APs. Forskolin (10 µmol/L) was used to increase the intracellular cAMP level, thus mimicking β-adrenergic stimulation. The experimentally observed effects were evaluated in the Fabbri-Severi computer model of an isolated human SAN cell. Transfected HEK-293 cells displayed large IKs-like outward currents in response to depolarizing voltage clamp steps. Forskolin significantly increased the current density and significantly shifted the half-maximal activation voltage towards more negative potentials. Furthermore, forskolin significantly accelerated activation without affecting the rate of deactivation. During an AP clamp, the KCNQ1/KCNE1 current was substantial during the AP phase, but relatively small during diastolic depolarization. In the presence of forskolin, the KCNQ1/KCNE1 current during both the AP phase and diastolic depolarization increased, resulting in a clearly active KCNQ1/KCNE1 current during diastolic depolarization, particularly at shorter cycle lengths. Computer simulations demonstrated that IKs reduces the intrinsic beating rate through its slowing effect on diastolic depolarization at all levels of autonomic tone and that gain-of-function mutations in KCNQ1 may exert a marked bradycardic effect during vagal tone. In conclusion, IKs is active during human SAN pacemaker activity and has a strong dependence on heart rate and cAMP level, with a prominent role at all levels of autonomic tone.
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Affiliation(s)
- Arie O. Verkerk
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands;
- Department of Experimental Cardiology, Heart Center, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands
| | - Ronald Wilders
- Department of Medical Biology, Amsterdam Cardiovascular Sciences, Amsterdam UMC, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands;
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Song J, Kim YJ, Leem CH. Improving the hERG model fitting using a deep learning-based method. Front Physiol 2023; 14:1111967. [PMID: 36814480 PMCID: PMC9939657 DOI: 10.3389/fphys.2023.1111967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 01/23/2023] [Indexed: 02/09/2023] Open
Abstract
The hERG channel is one of the essential ion channels composing the cardiac action potential and the toxicity assay for new drug. Recently, the comprehensive in vitro proarrhythmia assay (CiPA) was adopted for cardiac toxicity evaluation. One of the hurdles for this protocol is identifying the kinetic effect of the new drug on the hERG channel. This procedure included the model-based parameter identification from the experiments. There are many mathematical methods to infer the parameters; however, there are two main difficulties in fitting parameters. The first is that, depending on the data and model, parametric inference can be highly time-consuming. The second is that the fitting can fail due to local minima problems. The simplest and most effective way to solve these issues is to provide an appropriate initial value. In this study, we propose a deep learning-based method for improving model fitting by providing appropriate initial values, even the right answer. We generated the dataset by changing the model parameters and trained our deep learning-based model. To improve the accuracy, we used the spectrogram with time, frequency, and amplitude. We obtained the experimental dataset from https://github.com/CardiacModelling/hERGRapidCharacterisation. Then, we trained the deep-learning model using the data generated with the hERG model and tested the validity of the deep-learning model with the experimental data. We successfully identified the initial value, significantly improved the fitting speed, and avoided fitting failure. This method is useful when the model is fixed and reflects the real data, and it can be applied to any in silico model for various purposes, such as new drug development, toxicity identification, environmental effect, etc. This method will significantly reduce the time and effort to analyze the data.
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Affiliation(s)
- Jaekyung Song
- Department of Physiology, Asan Medical Center, Seoul, South Korea,Department of Physiology, University of Ulsan College of Medicine, Seoul, South Korea
| | - Yu Jin Kim
- Department of Physiology, Asan Medical Center, Seoul, South Korea
| | - Chae Hun Leem
- Department of Physiology, Asan Medical Center, Seoul, South Korea,Department of Physiology, University of Ulsan College of Medicine, Seoul, South Korea,*Correspondence: Chae Hun Leem,
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11
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Cabo C. Positive rate-dependent action potential prolongation by modulating potassium ion channels. Physiol Rep 2022; 10:e15356. [PMID: 35748083 PMCID: PMC9226816 DOI: 10.14814/phy2.15356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 05/28/2022] [Accepted: 05/30/2022] [Indexed: 11/24/2022] Open
Abstract
Pharmacological agents that prolong action potential duration (APD) to a larger extent at slow rates than at the fast excitation rates typical of ventricular tachycardia exhibit reverse rate dependence. Reverse rate dependence has been linked to the lack of efficacy of class III agents at preventing arrhythmias because the doses required to have an antiarrhythmic effect at fast rates may have pro-arrhythmic effects at slow rates due to an excessive APD prolongation. In this report, we show that, in computer models of the ventricular action potential, APD prolongation by accelerating phase 2 repolarization (by increasing IKs ) and decelerating phase 3 repolarization (by blocking IKr and IK1 ) results in a robust positive rate dependence (i.e., larger APD prolongation at fast rates than at slow rates). In contrast, APD prolongation by blocking a specific potassium channel type results in reverse rate dependence or a moderate positive rate dependence. Interventions that result in a strong positive rate dependence tend to decrease the repolarization reserve because they require substantial IK1 block. However, limiting IK1 block to ~50% results in a strong positive rate dependence with moderate decrease in repolarization reserve. In conclusion, the use of a combination of IKs activators and IKr and IK1 blockers could result in APD prolongation that potentially maximizes antiarrhythmic effects (by maximizing APD prolongation at fast excitation rates) and minimizes pro-arrhythmic effects (by minimizing APD prolongation at slow excitation rates).
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Affiliation(s)
- Candido Cabo
- Department of Computer Systems, New York City College of Technology, Doctoral Program in Computer Science, Graduate Center, City University of New York, New York, New York, USA
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12
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Osadchii OE. Electrocardiographic marker of the cardiac action potential triangulation induced by antiarrhythmic drugs in perfused guinea-pig heart. Exp Physiol 2022; 107:864-878. [PMID: 35561081 DOI: 10.1113/ep090349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 05/09/2022] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Can triangular appearance of ventricular action potential, indicating proarrhythmic profile of antiarrhythmic agent, be approximated by specific changes on ECG? What is the main finding and its importance? The triangulation of the ventricular action potential seen when antiarrhythmic drugs induce a greater lengthening of the late repolarization compared to the initial repolarization in epicardium, is closely approximated by a greater prolongation of the T wave upslope relative to the interval between the J point and the start of the T wave (the JTstart interval) on ECG. These findings may improve the power of ECG assessments in predicting the drug-induced arrhythmia resulting from slowed phase 3 repolarization. ABSTRACT Antiarrhythmic drugs prescribed to treat atrial fibrillation can occasionally precipitate ventricular tachyarrhythmia through a prominent slowing of the phase 3 repolarization. The latter results in the triangular shape of ventricular action potential, indicating high arrhythmic risks. However, clinically, the utilility of triangulation assessments for predicting arrhythmia is limited owing to the invasive nature of the ventricular action potential recordings. This study examined whether the triangulation effect can be detected indirectly from ECG analysis. Epicardial monophasic action potentials and ECG were simultaneously recorded in perfused guinea-pig hearts. With antiarrhythmics (dofetilide, quinidine, procainamide and flecainide), a prolongation of the initial repolarization seen in the action potential recordings was closely approximated by lengthening of the interval bewteen the J point and the start of the T wave (the JTstart interval) on ECG, whereas a prolongation of the late repolarization was paralleled by widening of the T wave upslope. Dofetilide, quinidine and procainamide induced a prominent slowing of the phase 3 repolarization in epicardium, leading to triangulation of the action potential. These effects were accompanied by a greater prolongation of the T wave upslope compared to the JTstart interval. Flecainide elicited a proportional prolongation of the initial and the late ventricular repolarization, and therefore failed to induce triangulation, based on analysis of both epicardial action potential and ECG profiles. Collectively, these findings suggest that the ratio between the durations of the T wave upslope and the JTstart interval may represent ECG metric of the ventricular action potential triangulation induced by antiarrhythmic drugs. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Oleg E Osadchii
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen N, Denmark.,Department of Pharmacology, Kuban State Medical University, Sedin Street 4, Krasnodar, 350063, Russia
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13
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Wada Y, Yang T, Shaffer CM, Daniel LL, Glazer AM, Davogustto GE, Lowery BD, Farber-Eger E, Wells QS, Roden DM. Common Ancestry-Specific Ion Channel Variants Predispose to Drug-Induced Arrhythmias. Circulation 2022; 145:299-308. [PMID: 34994586 PMCID: PMC8852297 DOI: 10.1161/circulationaha.121.054883] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND Multiple reports associate the cardiac sodium channel gene (SCN5A) variants S1103Y and R1193Q with type 3 congenital long QT syndrome and drug-induced long QT syndrome. These variants are too common in ancestral populations to be highly arrhythmogenic at baseline, however: S1103Y allele frequency is 8.1% in African Americans and R1193Q 6.1% in East Asians. R1193Q is known to increase late sodium current (INa-L) in cardiomyocytes derived from induced pluripotent stem cells but the role of these variants in modulating repolarization remains poorly understood. METHODS We determined the effect of S1103Y on QT intervals among African-American participants in a large electronic health record. Using cardiomyocytes derived from induced pluripotent stem cells carrying naturally occurring or genome-edited variants, we studied action potential durations (APDs) at baseline and after challenge with the repolarizing potassium current (IKr) blocker dofetilide and INa-L and IKr at baseline. RESULTS In 1479 African-American participants with no confounding medications or diagnoses of heart disease, QT intervals in S1103Y carriers was no different from that in noncarriers. Baseline APD was no different in cells expressing the Y allele (SY, YY cells) compared with isogenic cells with the reference allele (SS cells). However, INa-L was increased in SY and YY cells and the INa-L blocker GS967 shortened APD in SY/YY but not SS cells (P<0.001). IKr was increased almost 2-fold in SY/YY cells compared with SS cells (tail current: 0.66±0.1 versus 1.2±0.1 pA/pF; P<0.001). Dofetilide challenge prolonged APD at much lower concentrations in SY (4.1 nmol/L [interquartile range, 1.5-9.3]; n=11) and YY (4.2 nmol/L [1.7-5.0]; n=5) than in SS cells (249 nmol/L [22.3-2905]; n=14; P<0.001 and P<0.01, respectively) and elicited afterdepolarizations in 8/16 SY/YY cells but only in 1/14 SS cells. R1193Q cells similarly displayed no difference in baseline APD but increased IKr and increased dofetilide sensitivity. CONCLUSIONS These common ancestry-specific variants do not affect baseline repolarization, despite generating increased INa-L. We propose that increased IKr serves to maintain normal repolarization but increases the risk of manifest QT prolongation with IKr block in variant carriers. Our findings emphasize the need for inclusion of diverse populations in the study of adverse drug reactions.
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Affiliation(s)
- Yuko Wada
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN
| | - Tao Yang
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN
| | | | - Laura L. Daniel
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN
| | - Andrew M. Glazer
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN
| | | | - Brandon D. Lowery
- Vanderbilt Institute for Clinical and Translational Research, Vanderbilt University Medical Center, Nashville, TN
| | - Eric Farber-Eger
- Vanderbilt Institute for Clinical and Translational Research, Vanderbilt University Medical Center, Nashville, TN
| | - Quinn S. Wells
- Departments of Medicine, Pharmacology, and Biomedical Informatics, Vanderbilt University Medical Center, Nashville, TN
| | - Dan M. Roden
- Departments of Medicine, Pharmacology, and Biomedical Informatics, Vanderbilt University Medical Center, Nashville, TN.,For correspondence: Dan M. Roden, M.D., Vanderbilt University Medical Center, 2215B Garland Ave, 1285 MRBIV, Nashville, TN 37232. Fax 615.343.4522, Tel 615.322.0067,
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14
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Kambayashi R, Goto A, Onozato M, Izumi-Nakaseko H, Takei Y, Matsumoto A, Kawai S, Fukushima T, Sugiyama A. Simultaneous analyses of hemodynamic and electrophysiological effects of oseltamivir along with its pharmacokinetic profile using the canine paroxysmal atrial fibrillation model. J Pharmacol Sci 2021; 148:179-186. [PMID: 34924124 DOI: 10.1016/j.jphs.2021.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 10/28/2021] [Accepted: 11/05/2021] [Indexed: 11/16/2022] Open
Abstract
Since information of antiviral drug oseltamivir on the anti-atrial fibrillation (AF) property is still limited, we assessed it using the canine paroxysmal AF model. Oseltamivir in doses of 3 and 30 mg/kg/10 min was intravenously infused to the isoflurane-anesthetized, chronic atrioventricular block dogs (n = 6) with monitoring hemodynamic and electrophysiological variables, in which AF was induced by 10 s of burst pacing on atrial septum. Oseltamivir decreased AF incidence and AF duration, and prolonged AF cycle length in a dose-dependent manner. The low and high doses attained the peak plasma drug concentrations of 9.7 and 96.5 μg/mL, which were approximately 100 and 1000 times greater than those observed in human clinical cases, respectively. The low dose of oseltamivir decreased mean blood pressure without altering sinoatrial or idioventricular rate, whereas its high dose reduced each of them. Oseltamivir delayed inter-atrial conduction in dose- and frequency-dependent manners, whereas it prolonged atrial effective refractory period in dose-dependent but frequency-independent manners. The high dose prolonged ventricular effective refractory period, which was not detected with the low dose. These findings can be used for repurposing oseltamivir as an anti-AF drug candidate.
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Affiliation(s)
- Ryuichi Kambayashi
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Ai Goto
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Mayu Onozato
- Department of Analytical Chemistry, Faculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi-shi, Chiba, 274-8510, Japan
| | - Hiroko Izumi-Nakaseko
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Yoshinori Takei
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Akio Matsumoto
- Department of Aging Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Shinichi Kawai
- Department of Inflammation & Pain Control Research, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Takeshi Fukushima
- Department of Analytical Chemistry, Faculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi-shi, Chiba, 274-8510, Japan
| | - Atsushi Sugiyama
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan; Department of Aging Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan; Department of Inflammation & Pain Control Research, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan.
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15
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Jost N, Christ T, Magyar J. New Strategies for the Treatment of Atrial Fibrillation. Pharmaceuticals (Basel) 2021; 14:ph14090926. [PMID: 34577626 PMCID: PMC8466466 DOI: 10.3390/ph14090926] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 09/07/2021] [Accepted: 09/08/2021] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia in the clinical practice. It significantly contributes to the morbidity and mortality of the elderly population. Over the past 25-30 years intense effort in basic research has advanced the understanding of the relationship between the pathophysiology of AF and atrial remodelling. Nowadays it is clear that the various forms of atrial remodelling (electrical, contractile and structural) play crucial role in initiating and maintaining the persistent and permanent types of AF. Unlike in ventricular fibrillation, in AF rapid ectopic firing originating from pulmonary veins and re-entry mechanism may induce and maintain (due to atrial remodelling) this complex cardiac arrhythmia. The present review presents and discusses in detail the latest knowledge on the role of remodelling in AF. Special attention is paid to novel concepts and pharmacological targets presumably relevant to the drug treatment of atrial fibrillation.
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Affiliation(s)
- Norbert Jost
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, 6725 Szeged, Hungary
- Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, 6725 Szeged, Hungary
- ELKH-SZTE Research Group for Cardiovascular Pharmacology, Eötvös Loránd Research Network, 6725 Szeged, Hungary
- Correspondence:
| | - Torsten Christ
- Institute of Experimental Pharmacology and Toxicology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany;
- DZHK (German Center for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, 20246 Hamburg, Germany
| | - János Magyar
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary;
- Department of Sport Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
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16
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Different voltage dependence of I CaL blockade in nonselective I Kr blockers causes their opposite effects on early afterdepolarization in drug-induced arrhythmia. J Pharmacol Sci 2021; 147:95-103. [PMID: 34294379 DOI: 10.1016/j.jphs.2021.05.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 05/05/2021] [Accepted: 05/24/2021] [Indexed: 11/20/2022] Open
Abstract
Several false-positive results in the human ether-à-gogo-related gene test suggest that blockers of the rapid component of delayed rectifier K+ current (IKr) do not necessarily produce drug-induced arrhythmias. Specifically, the occurrence of early afterdepolarization (EAD) differs among IKr blockers, even if the prolonged action potential duration is in the same range. To predict EAD in drug-induced arrhythmias, we proposed a prediction method based on the mechanisms underlying the difference in frequency of EAD among nonselective IKr blockers. The mechanisms were elucidated by examining how different blockade kinetics of L-type Ca2+ current (ICaL) affect the frequency of EAD, using mathematical models of human ventricular myocytes. Addition of voltage-independent ICaL blockade resulted in the suppression of EAD. However, when voltage-dependent ICaL blockade kinetics of amiodarone, bepridil, and terfenadine were incorporated into ICaL in the model, bepridil and terfenadine induced EAD more than the voltage-independent ICaL blockade, while amiodarone suppressed EAD more effectively. Opposite effects were accounted for by the difference in ICaL blockade at negatively polarized potential. EAD occurrence was found to be associated with ICaL blockade measured at -20 mV. These results suggest that voltage dependence of ICaL blockade may be useful in predicting the different risks of nonselective IKr blockers.
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17
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Ríos-Pérez EB, Liu F, Stevens-Sostre WA, Eichel CA, Silignavong J, Robertson GA. A stable cell line inducibly expressing hERG1a/1b heteromeric channels. J Pharmacol Toxicol Methods 2021; 110:107081. [PMID: 34058320 DOI: 10.1016/j.vascn.2021.107081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 04/07/2021] [Accepted: 05/20/2021] [Indexed: 11/24/2022]
Abstract
Heterologously expressed hERG channels represent a mainstay of in vitro drug safety screens intended to mitigate risk of cardiac IKr block and sudden cardiac death. This is true even as more channel types are adopted as part of the Comprehensive in vitro Proarrhythmia Assay (CiPA) intended to elevate specificity and thus enhance throughput of promising lead drugs. Until now, hERG1a homomeric channels have been used as a proxy for IKr despite a wealth of evidence showing that hERG1a/1b heteromers better represent native channels in terms of protein abundance and channel biophysical and pharmacological properties. Past efforts to create a stable hERG1a/1b cell line were met with unpredictable silencing of hERG1b expression despite stable integration of the gene into the HEK293 cell genome. Here we report a new cell line stably expressing hERG1a, with hERG1b reliably controlled by an inducible promoter sensitive to doxycycline. Co-immunoprecipitation, Western blot analysis and patch-clamp electrophysiology confirm the heteromeric composition of the expressed channels. Association with hERG1b was found to promote hERG1a protein levels and enhance membrane current levels. Optimal conditions for drug screening and experimental investigation were achieved at 24 h exposure to 100 ng/ml doxycycline. Differences in pharmacological sensitivity between homomeric and heteromeric channels were observed for dofetilide and ebastine, but not fluoxetine, as evaluated by their IC50 values. Using these values in the O'Hara-Rudy-CiPA in silico model revealed discrepancies in pro-arrhythmia risk, implying the hERG1a homomeric platform overestimates risk for these two drugs. Dofetilide block was use-dependent and faster for hERG1a/1b than hERG1a channels, whereas ebastine showed considerable block at rest and had a slower progression for hERG1a/1b channels. The hERG1a/1b cell line thus represents an advanced model for contemporary drug safety screening assays such as CiPA that employ IC50 values to estimate risk of proarrhythmia in computational models of ventricular cardiomyocytes. This novel technology fulfills an unmet need to enhance specificity and foster a safe yet expanded drug development pipeline.
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Affiliation(s)
- Erick B Ríos-Pérez
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America
| | - Fang Liu
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America
| | - Whitney A Stevens-Sostre
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America
| | - Catherine A Eichel
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America
| | - Jonathan Silignavong
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America
| | - Gail A Robertson
- Dept. of Neuroscience and Cardiovascular Research Center, University of Wisconsin School of Medicine and Public Health, 1111 Highland Ave. #5505, Madison, WI 53705, United States of America.
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18
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JIN LIAN, HUANG YANQI, ZHU HONGLEI, GENG ZIHUI, WU XIAOMEI. KEY FACTORS TO THE RATE DEPENDENCE OF EARLY AFTERDEPOLARIZATIONS: A SIMULATION STUDY. J MECH MED BIOL 2021. [DOI: 10.1142/s0219519421500020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Early afterdepolarizations (EADs) in cardiac myocytes have been reported to be associated with a series of cardiac arrhythmias. The generation of EADs has a high correlation with the excitation period, leading to repolarization dispersion over the cardiac tissue. However, the mechanism of EAD rate dependence has not been thoroughly revealed. In this study, the simulation approach was used to investigate the mechanism underlying EAD rate dependence. The results indicated that the gating variable of the delayed rectifier potassium current ([Formula: see text]-gate) and the intracellular sodium ion concentration ([Na[Formula: see text]][Formula: see text] were key factors contributing to EAD rate dependence. Also, different mathematical models showed different types of EAD rate dependence, which needs to be considered in the future simulation research related to EADs.
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Affiliation(s)
- LIAN JIN
- Electronic Engineering Department, Fudan University, 220 Handan Road Shanghai 200433, P. R. China
| | - YANQI HUANG
- Electronic Engineering Department, Fudan University, 220 Handan Road Shanghai 200433, P. R. China
| | - HONGLEI ZHU
- Electronic Engineering Department, Fudan University, 220 Handan Road Shanghai 200433, P. R. China
| | - ZIHUI GENG
- Electronic Engineering Department, Fudan University, 220 Handan Road Shanghai 200433, P. R. China
| | - XIAOMEI WU
- Electronic Engineering Department, Fudan University, 220 Handan Road Shanghai 200433, P. R. China
- Shanghai Engineering Research Center of Assistive Devices, 220 Handan Road, Shanghai 200433, P. R. China
- Key Laboratory of Medical Imaging Computing and Computer Assisted Intervention (MICCAI) of Shanghai, 220 Handan Road, Shanghai 200433, P. R. China
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Ozturk N, Uslu S, Ozdemir S. Diabetes-induced changes in cardiac voltage-gated ion channels. World J Diabetes 2021; 12:1-18. [PMID: 33520105 PMCID: PMC7807254 DOI: 10.4239/wjd.v12.i1.1] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 11/05/2020] [Accepted: 11/13/2020] [Indexed: 02/06/2023] Open
Abstract
Diabetes mellitus affects the heart through various mechanisms such as microvascular defects, metabolic abnormalities, autonomic dysfunction and incompatible immune response. Furthermore, it can also cause functional and structural changes in the myocardium by a disease known as diabetic cardiomyopathy (DCM) in the absence of coronary artery disease. As DCM progresses it causes electrical remodeling of the heart, left ventricular dysfunction and heart failure. Electrophysiological changes in the diabetic heart contribute significantly to the incidence of arrhythmias and sudden cardiac death in diabetes mellitus patients. In recent studies, significant changes in repolarizing K+ currents, Na+ currents and L-type Ca2+ currents along with impaired Ca2+ homeostasis and defective contractile function have been identified in the diabetic heart. In addition, insulin levels and other trophic factors change significantly to maintain the ionic channel expression in diabetic patients. There are many diagnostic tools and management options for DCM, but it is difficult to detect its development and to effectively prevent its progress. In this review, diabetes-associated alterations in voltage-sensitive cardiac ion channels are comprehensively assessed to understand their potential role in the pathophysiology and pathogenesis of DCM.
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Affiliation(s)
- Nihal Ozturk
- Department of Biophysics, Akdeniz University Faculty of Medicine, Antalya 07058, Turkey
| | - Serkan Uslu
- Department of Biophysics, Akdeniz University Faculty of Medicine, Antalya 07058, Turkey
| | - Semir Ozdemir
- Department of Biophysics, Akdeniz University Faculty of Medicine, Antalya 07058, Turkey
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20
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Kambayashi R, Goto A, Nunoi Y, Hagiwara-Nagasawa M, Izumi-Nakaseko H, Venkatesan G, Takei Y, Matsumoto A, Chan ECY, Sugiyama A. An exploratory analysis of effects of poyendarone, a deuterated analogue of dronedarone, on the canine model of paroxysmal atrial fibrillation. Naunyn Schmiedebergs Arch Pharmacol 2021; 394:1103-1112. [PMID: 33427928 DOI: 10.1007/s00210-020-02047-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 12/28/2020] [Indexed: 11/26/2022]
Abstract
Poyendarone, a deuterated analogue of dronedarone, is expected to reduce the onset of cardiovascular adverse events of dronedarone, including congestive heart failure and excessive QT-interval prolongation. Since information is still lacking on the anti-atrial fibrillatory property of poyendarone, we assessed it along with effects on the inter-atrial conduction time (IACT) and atrial effective refractory period (AERP) using the canine paroxysmal atrial fibrillation model. Poyendarone hydrochloride (n = 4) and dronedarone hydrochloride (n = 4) in intravenous doses of 0.3 and 3 mg/kg/30 s were cumulatively administered. Poyendarone hardly altered sinoatrial rate, but dronedarone decreased it in a dose-related manner, whereas both drugs slightly but significantly reduced idioventricular rate. Poyendarone shortened duration of burst pacing-induced atrial fibrillation, whereas such abbreviation was not observed by dronedarone. Poyendarone and dronedarone similarly prolonged IACT in a frequency-dependent manner, indicating that their INa inhibitory actions may be similar. The high dose of poyendarone prolonged AERP in a reverse frequency-dependent manner, extent of which at basic pacing cycle lengths of 300 and 400 ms was comparable to that of dronedarone. However, the extent at a basic pacing cycle length of 200 ms was tended to be greater in poyendarone than in dronedarone, suggesting greater IKs inhibitory action of poyendarone. The deuteration of dronedarone attenuated the inhibition of sinus automaticity and prolonged the AERP with keeping the blood pressure and ventricular rate stable. Thus, poyendarone may have both more potent anti-atrial fibrillatory action and wider cardiovascular safety margin than dronedarone.
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Affiliation(s)
- Ryuichi Kambayashi
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Ai Goto
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Yoshio Nunoi
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Mihoko Hagiwara-Nagasawa
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Hiroko Izumi-Nakaseko
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Gopalakrishnan Venkatesan
- Department of Pharmacy, Faculty of Science, National University of Singapore, 18 Science Drive 4, Singapore, 117543, Singapore
| | - Yoshinori Takei
- Department of Translational Research & Cellular Therapeutics, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Akio Matsumoto
- Department of Aging Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Eric Chun Yong Chan
- Department of Pharmacy, Faculty of Science, National University of Singapore, 18 Science Drive 4, Singapore, 117543, Singapore.
| | - Atsushi Sugiyama
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan.
- Department of Translational Research & Cellular Therapeutics, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan.
- Department of Aging Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan.
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21
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Varró A, Tomek J, Nagy N, Virág L, Passini E, Rodriguez B, Baczkó I. Cardiac transmembrane ion channels and action potentials: cellular physiology and arrhythmogenic behavior. Physiol Rev 2020; 101:1083-1176. [PMID: 33118864 DOI: 10.1152/physrev.00024.2019] [Citation(s) in RCA: 113] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Cardiac arrhythmias are among the leading causes of mortality. They often arise from alterations in the electrophysiological properties of cardiac cells and their underlying ionic mechanisms. It is therefore critical to further unravel the pathophysiology of the ionic basis of human cardiac electrophysiology in health and disease. In the first part of this review, current knowledge on the differences in ion channel expression and properties of the ionic processes that determine the morphology and properties of cardiac action potentials and calcium dynamics from cardiomyocytes in different regions of the heart are described. Then the cellular mechanisms promoting arrhythmias in congenital or acquired conditions of ion channel function (electrical remodeling) are discussed. The focus is on human-relevant findings obtained with clinical, experimental, and computational studies, given that interspecies differences make the extrapolation from animal experiments to human clinical settings difficult. Deepening the understanding of the diverse pathophysiology of human cellular electrophysiology will help in developing novel and effective antiarrhythmic strategies for specific subpopulations and disease conditions.
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Affiliation(s)
- András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - Jakub Tomek
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Norbert Nagy
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary.,MTA-SZTE Cardiovascular Pharmacology Research Group, Hungarian Academy of Sciences, Szeged, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
| | - Elisa Passini
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Blanca Rodriguez
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - István Baczkó
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary
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Pallandi RT, Lovell NH, Campbell TJ. Class III Antiarrhythmic Effects of Dofetilide in Rabbit Atrial Myocardium. J Cardiovasc Pharmacol Ther 2020; 1:229-234. [PMID: 10684421 DOI: 10.1177/107424849600100306] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background Dofetilide is a new class III antiarrhythmic agent with demonstrated efficacy in ventricular and atrial tachyarrhythmias. We investigated its class HI actions and their modulation by stimulation rate in rabbit atrial myocardium. Methods and Results Standard microelectrode techniques were used to record action potentials from rabbit atrial tissue at varying stimulation rates. Dofetilide produced a dose-dependent prolongation of action potential duration at concentrations from 1 nM to 1 μM at an interstimulus interval of 1000 ms. Action potential duration at 90% repolarization (action potential duration) was prolonged from 116 ± 11.7 ms in control solutions to 148 ± 13.9 ms at 1nM dofetilide and 186 ± 49.3 ms at 1 μM dofetilide ( P < .05 for 1 nM vs control; P < .01 for 1 μM vs control). Reduction of interstimulus interval to 500 ms had no significant effect on action potential duration prolongation by dofetilide. At faster rates than this, and particularly at an interstimulus interval less than 330 ms, a marked “reverse rate dependence” of the class III effect was observed. Specifically, the high therapeutic concentration of 10 nM showed no effect on action potential duration at interstimulus interval of 250 ms or 200 ms, and even at a concentration of 30 nM, the small class III effect was no longer statistically significant at these rates. Conclusion Dofetilide prolongs action potential duration in rabbit atrial myocardium, but this effect is significantly attenuated at stimulation rates above 2 Hz.
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Affiliation(s)
- RT Pallandi
- Cooperative Research Centre for Cardiac Technology, University of Technology, Sydney, Australia
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23
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Brewer KR, Kuenze G, Vanoye CG, George AL, Meiler J, Sanders CR. Structures Illuminate Cardiac Ion Channel Functions in Health and in Long QT Syndrome. Front Pharmacol 2020; 11:550. [PMID: 32431610 PMCID: PMC7212895 DOI: 10.3389/fphar.2020.00550] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 04/09/2020] [Indexed: 12/13/2022] Open
Abstract
The cardiac action potential is critical to the production of a synchronized heartbeat. This electrical impulse is governed by the intricate activity of cardiac ion channels, among them the cardiac voltage-gated potassium (Kv) channels KCNQ1 and hERG as well as the voltage-gated sodium (Nav) channel encoded by SCN5A. Each channel performs a highly distinct function, despite sharing a common topology and structural components. These three channels are also the primary proteins mutated in congenital long QT syndrome (LQTS), a genetic condition that predisposes to cardiac arrhythmia and sudden cardiac death due to impaired repolarization of the action potential and has a particular proclivity for reentrant ventricular arrhythmias. Recent cryo-electron microscopy structures of human KCNQ1 and hERG, along with the rat homolog of SCN5A and other mammalian sodium channels, provide atomic-level insight into the structure and function of these proteins that advance our understanding of their distinct functions in the cardiac action potential, as well as the molecular basis of LQTS. In this review, the gating, regulation, LQTS mechanisms, and pharmacological properties of KCNQ1, hERG, and SCN5A are discussed in light of these recent structural findings.
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Affiliation(s)
- Kathryn R. Brewer
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
| | - Georg Kuenze
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Chemistry, Vanderbilt University, Nashville, TN, United States
| | - Carlos G. Vanoye
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Alfred L. George
- Department of Pharmacology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Jens Meiler
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Chemistry, Vanderbilt University, Nashville, TN, United States
- Department of Pharmacology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Institute for Drug Discovery, Leipzig University Medical School, Leipzig, Germany
| | - Charles R. Sanders
- Center for Structural Biology, Vanderbilt University School of Medicine Basic Sciences, Nashville, TN, United States
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
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24
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Wang X, Fitts RH. Cardiomyocyte slowly activating delayed rectifier potassium channel: regulation by exercise and β-adrenergic signaling. J Appl Physiol (1985) 2020; 128:1177-1185. [DOI: 10.1152/japplphysiol.00802.2019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Results demonstrate that exercise training (TRN) downregulates ventricular IKs channel current and the channel’s responsiveness to β-agonist factors mediated by TRN-induced decline in channel subunits KCNQ1 and KCNE1 and the A-kinase anchoring protein yotiao. The reduced IKs current helps explain the TRN-induced prolongation of the action potential in basal conditions and, coupled with previously reported upregulation of the KATP channel, results in a more efficient heart that is better able to respond to beat-by-beat changes in metabolism.
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Affiliation(s)
- Xinrui Wang
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin
| | - Robert H. Fitts
- Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin
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25
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Ridder BJ, Leishman DJ, Bridgland-Taylor M, Samieegohar M, Han X, Wu WW, Randolph A, Tran P, Sheng J, Danker T, Lindqvist A, Konrad D, Hebeisen S, Polonchuk L, Gissinger E, Renganathan M, Koci B, Wei H, Fan J, Levesque P, Kwagh J, Imredy J, Zhai J, Rogers M, Humphries E, Kirby R, Stoelzle-Feix S, Brinkwirth N, Rotordam MG, Becker N, Friis S, Rapedius M, Goetze TA, Strassmaier T, Okeyo G, Kramer J, Kuryshev Y, Wu C, Himmel H, Mirams GR, Strauss DG, Bardenet R, Li Z. A systematic strategy for estimating hERG block potency and its implications in a new cardiac safety paradigm. Toxicol Appl Pharmacol 2020; 394:114961. [PMID: 32209365 PMCID: PMC7166077 DOI: 10.1016/j.taap.2020.114961] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 02/14/2020] [Accepted: 03/19/2020] [Indexed: 12/13/2022]
Abstract
Introduction hERG block potency is widely used to calculate a drug's safety margin against its torsadogenic potential. Previous studies are confounded by use of different patch clamp electrophysiology protocols and a lack of statistical quantification of experimental variability. Since the new cardiac safety paradigm being discussed by the International Council for Harmonisation promotes a tighter integration of nonclinical and clinical data for torsadogenic risk assessment, a more systematic approach to estimate the hERG block potency and safety margin is needed. Methods A cross-industry study was performed to collect hERG data on 28 drugs with known torsadogenic risk using a standardized experimental protocol. A Bayesian hierarchical modeling (BHM) approach was used to assess the hERG block potency of these drugs by quantifying both the inter-site and intra-site variability. A modeling and simulation study was also done to evaluate protocol-dependent changes in hERG potency estimates. Results A systematic approach to estimate hERG block potency is established. The impact of choosing a safety margin threshold on torsadogenic risk evaluation is explored based on the posterior distributions of hERG potency estimated by this method. The modeling and simulation results suggest any potency estimate is specific to the protocol used. Discussion This methodology can estimate hERG block potency specific to a given voltage protocol. The relationship between safety margin thresholds and torsadogenic risk predictivity suggests the threshold should be tailored to each specific context of use, and safety margin evaluation may need to be integrated with other information to form a more comprehensive risk assessment.
hERG potency/safety margin is a widely used nonclinical cardiac safety strategy. A new regulatory paradigm promotes the integration of nonclinical and clinical data. Lack of uncertainty quantification hindered using hERG potency in the new paradigm. A systematic method was established to address this limitation. Analysis supports using different safety margin thresholds in different context.
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Affiliation(s)
- Bradley J Ridder
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational Sciences, Center for Drug Evaluation and Research, Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA
| | - Derek J Leishman
- Department of Toxicology and Pathology, Eli Lilly and Company, Indianapolis, IN, USA
| | | | - Mohammadreza Samieegohar
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational Sciences, Center for Drug Evaluation and Research, Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA
| | - Xiaomei Han
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational Sciences, Center for Drug Evaluation and Research, Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA
| | - Wendy W Wu
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational Sciences, Center for Drug Evaluation and Research, Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA
| | - Aaron Randolph
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational Sciences, Center for Drug Evaluation and Research, Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA
| | - Phu Tran
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational Sciences, Center for Drug Evaluation and Research, Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA
| | - Jiansong Sheng
- CiPA LAB, 900 Clopper Rd, Suite 130, Gaithersburg, MD 20878, USA
| | - Timm Danker
- NMI-TT GmbH, Markwiesenstr. 55, 72770 Reutlingen, Germany
| | | | - Daniel Konrad
- B'SYS GmbH, The Ion Channel Company, Benkenstrasse 254, CH-4108, Witterswil, Switzerland
| | - Simon Hebeisen
- B'SYS GmbH, The Ion Channel Company, Benkenstrasse 254, CH-4108, Witterswil, Switzerland
| | - Liudmila Polonchuk
- F. Hoffmann-La Roche AG, F. Hoffmann-La Roche Ltd Bldg. 73/R. 103b Grenzacherstrasse, 124, CH-4070 Basel, Switzerland
| | - Evgenia Gissinger
- F. Hoffmann-La Roche AG, F. Hoffmann-La Roche Ltd Bldg. 73/R. 103b Grenzacherstrasse, 124, CH-4070 Basel, Switzerland
| | | | - Bryan Koci
- Eurofins Scientific, Eurofins Discovery, 6 Research Park Drive, St. Charles, MO 63304, USA
| | - Haiyang Wei
- Eurofins Scientific, Eurofins Discovery, 6 Research Park Drive, St. Charles, MO 63304, USA
| | - Jingsong Fan
- Bristol-Myers Squibb Company, Discovery Toxicology, Bristol-Myers Squibb, 3551 Lawrenceville, Princeton Rd, Lawrence Township, NJ 08648, USA
| | - Paul Levesque
- Bristol-Myers Squibb Company, Discovery Toxicology, Bristol-Myers Squibb, 3551 Lawrenceville, Princeton Rd, Lawrence Township, NJ 08648, USA
| | - Jae Kwagh
- Bristol-Myers Squibb Company, Discovery Toxicology, Bristol-Myers Squibb, 3551 Lawrenceville, Princeton Rd, Lawrence Township, NJ 08648, USA
| | | | - Jin Zhai
- Merck & Co., Inc, Kenilworth, NJ, USA
| | - Marc Rogers
- Metrion Biosciences Limited, Riverside 3, Suite 1, Granta Park, Great Abington, Cambridge CB21, 6AD, United Kingdom
| | - Edward Humphries
- Metrion Biosciences Limited, Riverside 3, Suite 1, Granta Park, Great Abington, Cambridge CB21, 6AD, United Kingdom
| | - Robert Kirby
- Metrion Biosciences Limited, Riverside 3, Suite 1, Granta Park, Great Abington, Cambridge CB21, 6AD, United Kingdom
| | | | - Nina Brinkwirth
- Nanion Technologies Munich, Ganghoferstrasse 70A, 80339 Munich, Germany
| | | | - Nadine Becker
- Nanion Technologies Munich, Ganghoferstrasse 70A, 80339 Munich, Germany
| | - Søren Friis
- Nanion Technologies Munich, Ganghoferstrasse 70A, 80339 Munich, Germany
| | - Markus Rapedius
- Nanion Technologies Munich, Ganghoferstrasse 70A, 80339 Munich, Germany
| | - Tom A Goetze
- Nanion Technologies Munich, Ganghoferstrasse 70A, 80339 Munich, Germany
| | - Tim Strassmaier
- Nanion Technologies, USA, 1 Naylon Place, Suite C, Livingston, NJ 07039, USA
| | - George Okeyo
- Nanion Technologies, USA, 1 Naylon Place, Suite C, Livingston, NJ 07039, USA
| | - James Kramer
- Charles River Laboratories, 14656 Neo Parkway, Cleveland, OH 44128, USA
| | - Yuri Kuryshev
- Charles River Laboratories, 14656 Neo Parkway, Cleveland, OH 44128, USA
| | - Caiyun Wu
- Charles River Laboratories, 14656 Neo Parkway, Cleveland, OH 44128, USA
| | - Herbert Himmel
- Bayer AG, RD-TS-TOX-SP-SPL1, Aprather Weg 18a, 42096 Wuppertal, Germany
| | - Gary R Mirams
- Centre for Mathematical Medicine & Biology, School of Mathematical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - David G Strauss
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational Sciences, Center for Drug Evaluation and Research, Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA
| | - Rémi Bardenet
- Université de Lille, CNRS, Centrale Lille, UMR 9189 - CRIStAL, Villeneuve d'Ascq, France
| | - Zhihua Li
- Division of Applied Regulatory Science, Office of Clinical Pharmacology, Office of Translational Sciences, Center for Drug Evaluation and Research, Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD 20993, USA.
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26
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Osadchii OE. Antiarrhythmic drug effects on premature beats are partly determined by prior cardiac activation frequency in perfused guinea-pig heart. Exp Physiol 2020; 105:819-830. [PMID: 32175633 DOI: 10.1113/ep088165] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 03/13/2020] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? Can antiarrhythmic drug effects on repolarization, conduction time and excitation wavelength in premature beats be determined by prior cardiac activation frequency? What is the main finding and its importance? In premature beats induced after a series of cardiac activations at a slow rate, antiarrhythmics prolong repolarization but evoke little or no conduction delay, thus increasing the excitation wavelength, which indicates an antiarrhythmic effect. Fast prior activation rate attenuates prolongation of repolarization, while amplifying the conduction delay induced by drugs, which translates into the reduced excitation wavelength, indicating proarrhythmia. These findings suggest that a sudden increase in heart rate can shape adverse pharmacological profiles in patients with ventricular ectopy. ABSTRACT Antiarrhythmic drugs used to treat atrial fibrillation can occasionally induce ventricular tachyarrhythmia, which is typically precipitated by a premature ectopic beat through a mechanism related, in part, to the shortening of the excitation wavelength (EW). The arrhythmia is likely to occur when a drug induces a reduction, rather than an increase, in the EW of ectopic beats. In this study, I examined whether the arrhythmic drug profile is shaped by the increased cardiac activation rate before ectopic excitation. Ventricular monophasic action potential durations, conduction times and EW values were assessed during programmed stimulations applied at long (S1 -S1 [basic drive cycle length] = 550 ms) and short (S1 -S1 = 200 ms) cycle lengths in perfused guinea-pig hearts. The premature activations were induced with extrastimulus application immediately upon termination of the refractory period. With dofetilide, a class III antiarrhythmic agent, a prolongation in action potential duration and the resulting increase in the EW obtained at S1 -S1 = 550 ms were significantly attenuated at S1 -S1 = 200 ms, in both the regular (S1 ) and the premature (S2 ) beats. With class I antiarrhythmic agents (quinidine, procainamide and flecainide), fast S1 -S1 pacing was found to attenuate the drug-induced increase in action potential duration, while amplifying drug-induced conduction slowing, in both S1 and S2 beats. As a result, although the EW was increased (quinidine and procainamide) or not changed (flecainide) at the long S1 -S1 intervals, it was invariably reduced by these agents at the short S1 -S1 intervals. These findings indicate that the increased heart rate before ectopic activation shapes the arrhythmic profiles by facilitating drug-induced EW reduction.
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Affiliation(s)
- Oleg E Osadchii
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen N, Denmark.,Department of Health Science and Technology, University of Aalborg, Aalborg, Denmark
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Zhou X, Qu Y, Passini E, Bueno-Orovio A, Liu Y, Vargas HM, Rodriguez B. Blinded In Silico Drug Trial Reveals the Minimum Set of Ion Channels for Torsades de Pointes Risk Assessment. Front Pharmacol 2020; 10:1643. [PMID: 32082155 PMCID: PMC7003137 DOI: 10.3389/fphar.2019.01643] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 12/16/2019] [Indexed: 12/11/2022] Open
Abstract
Torsades de Pointes (TdP) is a type of ventricular arrhythmia which could be observed as an unwanted drug-induced cardiac side effect, and it is associated with repolarization abnormalities in single cells. The pharmacological evaluations of TdP risk in previous years mainly focused on the hERG channel due to its vital role in the repolarization of cardiomyocytes. However, only considering drug effects on hERG led to false positive predictions since the drug action on other ion channels can also have crucial regulatory effects on repolarization. To address the limitation of only evaluating hERG, the Comprehensive in Vitro Proarrhythmia Assay initiative has proposed to systematically integrate drug effects on multiple ion channels into in silico drug trial to improve TdP risk assessment. It is not clear how many ion channels are sufficient for reliable TdP risk predictions, and whether differences in IC50 and Hill coefficient values from independent sources can lead to divergent in silico prediction outcomes. The rationale of this work is to investigate the above two questions using a computationally efficient population of human ventricular cells optimized to favor repolarization abnormality. Our blinded results based on two independent data sources confirm that simulations with the optimized population of human ventricular cell models enable efficient in silico drug screening, and also provide direct observation and mechanistic analysis of repolarization abnormality. Our results show that 1) the minimum set of ion channels required for reliable TdP risk predictions are Nav1.5 (peak), Cav1.2, and hERG; 2) for drugs with multiple ion channel blockage effects, moderate IC50 variations combined with variable Hill coefficients can affect the accuracy of in silico predictions.
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Affiliation(s)
- Xin Zhou
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Yusheng Qu
- SPARC, Amgen Research, Amgen Inc., Thousand Oaks, CA, United States
| | - Elisa Passini
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Alfonso Bueno-Orovio
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Yang Liu
- GAU, Amgen Research, Amgen Inc., South San Francisco, CA, United States
| | - Hugo M Vargas
- SPARC, Amgen Research, Amgen Inc., Thousand Oaks, CA, United States
| | - Blanca Rodriguez
- Department of Computer Science, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
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Nánási PP, Szabó Z, Kistamás K, Horváth B, Virág L, Jost N, Bányász T, Almássy J, Varró A. Implication of frequency-dependent protocols in antiarrhythmic and proarrhythmic drug testing. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2019; 157:76-83. [PMID: 31726065 DOI: 10.1016/j.pbiomolbio.2019.11.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 10/30/2019] [Accepted: 11/01/2019] [Indexed: 01/20/2023]
Abstract
It has long been known that the electrophysiological effects of many cardioactive drugs strongly depend on the rate dependent frequency. This was recognized first for class I antiarrhythmic agents: their Vmax suppressive effect was attenuated at long cycle lengths. Later many Ca2+ channel blockers were also found to follow such kinetics. The explanation was provided by the modulated and the guarded receptor theories. Regarding the duration of cardiac action potentials (APD) an opposite frequency-dependence was observed, i.e. the drug-induced changes in APD were proportional with the cycle length of stimulation, therefore it was referred as "reverse rate-dependency". The beat-to-beat, or short term variability of APD (SV) has been recognized as an important proarrhythmic mechanism, its magnitude can be used as an arrhythmia predictor. SV is modulated by several cardioactive agents, however, these drugs modify also APD itself. In order to clear the drug-specific effects on SV from the concomitant unspecific APD-change related ones, the term of "relative variability" was introduced. Relative variability is increased by ion channel blockers that decrease the negative feedback control of APD (i.e. blockers of ICa, IKr and IKs) and also by elevation of cytosolic Ca2+. Cardiac arrhythmias are also often categorized according to the characteristic heart rate (tachy- and bradyarrhythmias). Tachycardia is proarrhythmic primarily due to the concomitant Ca2+ overload causing delayed afterdepolarizations. Early afterdepolarizations (EADs) are complications of the bradycardic heart. What is common in the reverse rate-dependent nature of drug action on APD, increased SV and EAD incidence associated with bradycardia.
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Affiliation(s)
- Péter P Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; Department of Dental Physiology, Faculty of Dentistry, University of Debrecen, Debrecen, Hungary
| | - Zoltán Szabó
- Department of Emergency Medicine, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Kornél Kistamás
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - László Virág
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary; Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary
| | - Norbert Jost
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary; Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary; MTA-SZTE Research Group for Cardiovascular Pharmacology, Szeged, Hungary
| | - Tamás Bányász
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - János Almássy
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - András Varró
- Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Szeged, Szeged, Hungary; Department of Pharmacology and Pharmacotherapy, Interdisciplinary Excellence Centre, University of Szeged, Szeged, Hungary; MTA-SZTE Research Group for Cardiovascular Pharmacology, Szeged, Hungary.
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Sutanto H, Laudy L, Clerx M, Dobrev D, Crijns HJ, Heijman J. Maastricht antiarrhythmic drug evaluator (MANTA): A computational tool for better understanding of antiarrhythmic drugs. Pharmacol Res 2019; 148:104444. [DOI: 10.1016/j.phrs.2019.104444] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 07/10/2019] [Accepted: 09/03/2019] [Indexed: 12/14/2022]
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Lei CL, Clerx M, Beattie KA, Melgari D, Hancox JC, Gavaghan DJ, Polonchuk L, Wang K, Mirams GR. Rapid Characterization of hERG Channel Kinetics II: Temperature Dependence. Biophys J 2019; 117:2455-2470. [PMID: 31451180 PMCID: PMC6990152 DOI: 10.1016/j.bpj.2019.07.030] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 06/20/2019] [Accepted: 07/17/2019] [Indexed: 11/29/2022] Open
Abstract
Ion channel behavior can depend strongly on temperature, with faster kinetics at physiological temperatures leading to considerable changes in currents relative to room temperature. These temperature-dependent changes in voltage-dependent ion channel kinetics (rates of opening, closing, inactivating, and recovery) are commonly represented with Q10 coefficients or an Eyring relationship. In this article, we assess the validity of these representations by characterizing channel kinetics at multiple temperatures. We focus on the human Ether-à-go-go-Related Gene (hERG) channel, which is important in drug safety assessment and commonly screened at room temperature so that results require extrapolation to physiological temperature. In Part I of this study, we established a reliable method for high-throughput characterization of hERG1a (Kv11.1) kinetics, using a 15-second information-rich optimized protocol. In this Part II, we use this protocol to study the temperature dependence of hERG kinetics using Chinese hamster ovary cells overexpressing hERG1a on the Nanion SyncroPatch 384PE, a 384-well automated patch-clamp platform, with temperature control. We characterize the temperature dependence of hERG gating by fitting the parameters of a mathematical model of hERG kinetics to data obtained at five distinct temperatures between 25 and 37°C and validate the models using different protocols. Our models reveal that activation is far more temperature sensitive than inactivation, and we observe that the temperature dependency of the kinetic parameters is not represented well by Q10 coefficients; it broadly follows a generalized, but not the standardly-used, Eyring relationship. We also demonstrate that experimental estimations of Q10 coefficients are protocol dependent. Our results show that a direct fit using our 15-s protocol best represents hERG kinetics at any given temperature and suggests that using the Generalized Eyring theory is preferable if no experimental data are available to derive model parameters at a given temperature.
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Affiliation(s)
- Chon Lok Lei
- Computational Biology, Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Michael Clerx
- Computational Biology, Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Kylie A Beattie
- Computational Biology, Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Dario Melgari
- School of Physiology, Pharmacology and Neuroscience, and Cardiovascular Research Laboratories, School of Medical Sciences, University of Bristol, Bristol, United Kingdom
| | - Jules C Hancox
- School of Physiology, Pharmacology and Neuroscience, and Cardiovascular Research Laboratories, School of Medical Sciences, University of Bristol, Bristol, United Kingdom
| | - David J Gavaghan
- Computational Biology, Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Liudmila Polonchuk
- Pharma Research and Early Development, Innovation Center Basel, F. Hoffmann-La Roche, Basel, Switzerland
| | - Ken Wang
- Pharma Research and Early Development, Innovation Center Basel, F. Hoffmann-La Roche, Basel, Switzerland
| | - Gary R Mirams
- Centre for Mathematical Medicine and Biology, School of Mathematical Sciences, University of Nottingham, Nottingham, United Kingdom.
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Lei CL, Clerx M, Gavaghan DJ, Polonchuk L, Mirams GR, Wang K. Rapid Characterization of hERG Channel Kinetics I: Using an Automated High-Throughput System. Biophys J 2019; 117:2438-2454. [PMID: 31447109 PMCID: PMC6990155 DOI: 10.1016/j.bpj.2019.07.029] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 06/20/2019] [Accepted: 07/17/2019] [Indexed: 11/27/2022] Open
Abstract
Predicting how pharmaceuticals may affect heart rhythm is a crucial step in drug development and requires a deep understanding of a compound’s action on ion channels. In vitro hERG channel current recordings are an important step in evaluating the proarrhythmic potential of small molecules and are now routinely performed using automated high-throughput patch-clamp platforms. These machines can execute traditional voltage-clamp protocols aimed at specific gating processes, but the array of protocols needed to fully characterize a current is typically too long to be applied in a single cell. Shorter high-information protocols have recently been introduced that have this capability, but they are not typically compatible with high-throughput platforms. We present a new 15 second protocol to characterize hERG (Kv11.1) kinetics, suitable for both manual and high-throughput systems. We demonstrate its use on the Nanion SyncroPatch 384PE, a 384-well automated patch-clamp platform, by applying it to Chinese hamster ovary cells stably expressing hERG1a. From these recordings, we construct 124 cell-specific variants/parameterizations of a hERG model at 25°C. A further eight independent protocols are run in each cell and are used to validate the model predictions. We then combine the experimental recordings using a hierarchical Bayesian model, which we use to quantify the uncertainty in the model parameters, and their variability from cell-to-cell; we use this model to suggest reasons for the variability. This study demonstrates a robust method to measure and quantify uncertainty and shows that it is possible and practical to use high-throughput systems to capture full hERG channel kinetics quantitatively and rapidly.
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Affiliation(s)
- Chon Lok Lei
- Computational Biology, Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Michael Clerx
- Computational Biology, Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - David J Gavaghan
- Computational Biology, Department of Computer Science, University of Oxford, Oxford, United Kingdom
| | - Liudmila Polonchuk
- Pharma Research and Early Development, Innovation Center Basel, F. Hoffmann-La Roche Ltd., Basel, Switzerland
| | - Gary R Mirams
- Centre for Mathematical Medicine and Biology, School of Mathematical Sciences, University of Nottingham, Nottingham, United Kingdom.
| | - Ken Wang
- Pharma Research and Early Development, Innovation Center Basel, F. Hoffmann-La Roche Ltd., Basel, Switzerland
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Molecular Docking Guided Grid-Independent Descriptor Analysis to Probe the Impact of Water Molecules on Conformational Changes of hERG Inhibitors in Drug Trapping Phenomenon. Int J Mol Sci 2019; 20:ijms20143385. [PMID: 31295848 PMCID: PMC6678931 DOI: 10.3390/ijms20143385] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 07/04/2019] [Accepted: 07/07/2019] [Indexed: 12/17/2022] Open
Abstract
Human ether a-go-go related gene (hERG) or KV11.1 potassium channels mediate the rapid delayed rectifier current (IKr) in cardiac myocytes. Drug-induced inhibition of hERG channels has been implicated in the development of acquired long QT syndrome type (aLQTS) and fatal arrhythmias. Several marketed drugs have been withdrawn for this reason. Therefore, there is considerable interest in developing better tests for predicting drugs which can block the hERG channel. The drug-binding pocket in hERG channels, which lies below the selectivity filter, normally contains K+ ions and water molecules. In this study, we test the hypothesis that these water molecules impact drug binding to hERG. We developed 3D QSAR models based on alignment independent descriptors (GRIND) using docked ligands in open and closed conformations of hERG in the presence (solvated) and absence (non-solvated) of water molecules. The ligand–protein interaction fingerprints (PLIF) scheme was used to summarize and compare the interactions. All models delineated similar 3D hERG binding features, however, small deviations of about ~0.4 Å were observed between important hotspots of molecular interaction fields (MIFs) between solvated and non-solvated hERG models. These small changes in conformations do not affect the performance and predictive power of the model to any significant extent. The model that exhibits the best statistical values was attained with a cryo_EM structure of the hERG channel in open state without water. This model also showed the best R2 of 0.58 and 0.51 for the internal and external validation test sets respectively. Our results suggest that the inclusion of water molecules during the docking process has little effect on conformations and this conformational change does not impact the predictive ability of the 3D QSAR models.
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Osadchii OE. Effects of antiarrhythmics on the electrical restitution in perfused guinea-pig heart are critically determined by the applied cardiac pacing protocol. Exp Physiol 2019; 104:490-504. [PMID: 30758086 DOI: 10.1113/ep087531] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 02/12/2019] [Indexed: 01/11/2023]
Abstract
NEW FINDINGS What is the central question of this study? Are modifications in the restitution of ventricular action potential duration induced by antiarrhythmic drugs the same when assessed with premature extrastimulus application at variable coupling intervals (the standard stimulation protocol) and with steady state pacing at variable rates (the dynamic stimulation protocol)? What is the main finding and its importance? With class I and class III antiarrhythmics, the effects on electrical restitution determined with the standard stimulation protocol dissociate from those obtained during dynamic pacing. These findings indicate a limited value of the electrical restitution assessments based on extrasystolic stimulations alone, as performed in the clinical studies, in estimating the outcomes of antiarrhythmic drug therapies. ABSTRACT A steep slope of the ventricular action potential duration (APD) to diastolic interval (DI) relationships (the electrical restitution) can precipitate tachyarrhythmia, whereas a flattened slope is antiarrhythmic. The derangements in APD restitution responsible for transition of tachycardia to ventricular fibrillation can be assessed with cardiac pacing at progressively increasing rates (the dynamic stimulation protocol). Nevertheless, this method is not used clinically owing to the risk of inducing myocardial ischaemia. Instead, the restitution kinetics is determined with a premature extrastimulus application at variable coupling intervals (the standard stimulation protocol). Whether the two protocols are equivalent in estimating antiarrhythmic drug effects is uncertain. In this study, dofetilide and quinidine, the agents blocking repolarizing K+ currents, increased epicardial APD in perfused guinea-pig hearts, with effects being greater at long vs. short DIs. These changes were more pronounced during dynamic pacing compared to premature extrastimulations. Accordingly, although both agents markedly steepened the dynamic restitution, there was only a marginal increase in the standard restitution slope with dofetilide, and no effect with quinidine. Lidocaine and mexiletine, selective Na+ channel blockers, prolonged the effective refractory period without changing APD, and increased the minimum DI that enabled ventricular capture during extrastimulations. No change in the minimum DI was noted during dynamic pacing. Consequently, although lidocaine and mexiletine reduced the standard restitution slope, they failed to flatten the dynamic restitution. Overall, these findings imply a limited value of the electrical restitution assessments with premature extrastimulations alone in discriminating arrhythmic vs. antiarrhythmic changes during drug therapies.
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Affiliation(s)
- Oleg E Osadchii
- Department of Biomedical Sciences, University of Copenhagen, Blegdamsvej 3, 2200, Copenhagen N, Denmark.,Department of Health Science and Technology, University of Aalborg, Fredrik Bajers Vej 7E, 9220, Aalborg, Denmark
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Furutani K, Tsumoto K, Chen IS, Handa K, Yamakawa Y, Sack JT, Kurachi Y. Facilitation of I Kr current by some hERG channel blockers suppresses early afterdepolarizations. J Gen Physiol 2019; 151:214-230. [PMID: 30674563 PMCID: PMC6363420 DOI: 10.1085/jgp.201812192] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 12/06/2018] [Indexed: 01/01/2023] Open
Abstract
Some hERG channel blockers are clinically safe, but others cause fatal cardiac arrhythmias. Furutani et al. show that safe blockers facilitate channel opening in ventricular myocytes and provide a repolarization reserve at precisely the voltages and times needed to suppress arrhythmias. Drug-induced block of the cardiac rapid delayed rectifying potassium current (IKr), carried by the human ether-a-go-go-related gene (hERG) channel, is the most common cause of acquired long QT syndrome. Indeed, some, but not all, drugs that block hERG channels cause fatal cardiac arrhythmias. However, there is no clear method to distinguish between drugs that cause deadly arrhythmias and those that are clinically safe. Here we propose a mechanism that could explain why certain clinically used hERG blockers are less proarrhythmic than others. We demonstrate that several drugs that block hERG channels, but have favorable cardiac safety profiles, also evoke another effect; they facilitate the hERG current amplitude in response to low-voltage depolarization. To investigate how hERG facilitation impacts cardiac safety, we develop computational models of IKr block with and without this facilitation. We constrain the models using data from voltage clamp recordings of hERG block and facilitation by nifekalant, a safe class III antiarrhythmic agent. Human ventricular action potential simulations demonstrate the ability of nifekalant to suppress ectopic excitations, with or without facilitation. Without facilitation, excessive IKr block evokes early afterdepolarizations, which cause lethal arrhythmias. When facilitation is introduced, early afterdepolarizations are prevented at the same degree of block. Facilitation appears to prevent early afterdepolarizations by increasing IKr during the repolarization phase of action potentials. We empirically test this prediction in isolated rabbit ventricular myocytes and find that action potential prolongation with nifekalant is less likely to induce early afterdepolarization than action potential prolongation with dofetilide, a hERG channel blocker that does not induce facilitation. Our data suggest that hERG channel blockers that induce facilitation increase the repolarization reserve of cardiac myocytes, rendering them less likely to trigger lethal ventricular arrhythmias.
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Affiliation(s)
- Kazuharu Furutani
- Department of Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan .,Center for Advanced Medical Engineering and Informatics, Osaka University, Osaka, Japan.,Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Kunichika Tsumoto
- Department of Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan.,Department of Physiology, Kanazawa Medical University, Ishikawa, Japan
| | - I-Shan Chen
- Department of Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Kenichiro Handa
- Department of Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Yuko Yamakawa
- Department of Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Jon T Sack
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Yoshihisa Kurachi
- Department of Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan .,Center for Advanced Medical Engineering and Informatics, Osaka University, Osaka, Japan
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35
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Munawar S, Windley MJ, Tse EG, Todd MH, Hill AP, Vandenberg JI, Jabeen I. Experimentally Validated Pharmacoinformatics Approach to Predict hERG Inhibition Potential of New Chemical Entities. Front Pharmacol 2018; 9:1035. [PMID: 30333745 PMCID: PMC6176658 DOI: 10.3389/fphar.2018.01035] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 08/27/2018] [Indexed: 12/17/2022] Open
Abstract
The hERG (human ether-a-go-go-related gene) encoded potassium ion (K+) channel plays a major role in cardiac repolarization. Drug-induced blockade of hERG has been a major cause of potentially lethal ventricular tachycardia termed Torsades de Pointes (TdPs). Therefore, we presented a pharmacoinformatics strategy using combined ligand and structure based models for the prediction of hERG inhibition potential (IC50) of new chemical entities (NCEs) during early stages of drug design and development. Integrated GRid-INdependent Descriptor (GRIND) models, and lipophilic efficiency (LipE), ligand efficiency (LE) guided template selection for the structure based pharmacophore models have been used for virtual screening and subsequent hERG activity (pIC50) prediction of identified hits. Finally selected two hits were experimentally evaluated for hERG inhibition potential (pIC50) using whole cell patch clamp assay. Overall, our results demonstrate a difference of less than ±1.6 log unit between experimentally determined and predicted hERG inhibition potential (IC50) of the selected hits. This revealed predictive ability and robustness of our models and could help in correctly rank the potency order (lower μM to higher nM range) against hERG.
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Affiliation(s)
- Saba Munawar
- Research Center for Modeling and Simulation, National University of Science and Technology, Islamabad, Pakistan.,Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
| | | | - Edwin G Tse
- School of Chemistry, The University of Sydney, Sydney, NSW, Australia
| | - Matthew H Todd
- School of Chemistry, The University of Sydney, Sydney, NSW, Australia
| | - Adam P Hill
- Victor Chang Cardiac Research Institute, Sydney, NSW, Australia
| | | | - Ishrat Jabeen
- Research Center for Modeling and Simulation, National University of Science and Technology, Islamabad, Pakistan
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36
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Abramochkin DV, Hassinen M, Vornanen M. Transcripts of Kv7.1 and MinK channels and slow delayed rectifier K + current (I Ks) are expressed in zebrafish (Danio rerio) heart. Pflugers Arch 2018; 470:1753-1764. [PMID: 30116893 DOI: 10.1007/s00424-018-2193-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 07/24/2018] [Accepted: 08/06/2018] [Indexed: 12/18/2022]
Abstract
Zebrafish are increasingly used as a model for human cardiac electrophysiology, arrhythmias, and drug screening. However, K+ ion channels of the zebrafish heart, which determine the rate of repolarization and duration of cardiac action potential (AP) are still incompletely known and characterized. Here, we provide the first evidence for the presence of the slow component of the delayed rectifier K+channels in the zebrafish heart and characterize electrophysiological properties of the slow component of the delayed rectifier K+current, IKs. Zebrafish atrium and ventricle showed strong transcript expression of the kcnq1 gene, which encodes the Kv7.1 α-subunit of the slow delayed rectifier K+ channel. In contrast, the kcne1 gene, encoding the MinK β-subunit of the delayed rectifier, was expressed at 21 and 17 times lower level in ventricle and atrium, respectively, in comparison to the kcnq1. IKs was observed in 62% of ventricular myocytes with mean (± SEM) density of 1.23 ± 0.37 pA/pF at + 30 mV. Activation rate of IKs was 38% faster (τ50 = 1248 ± 215 ms) than kcnq1:kcne1 channels (1725 ± 792 ms) expressed in 3:1 ratio in Chinese hamster ovary cells. Microelectrode experiments demonstrated the functional relevance of IKs in the zebrafish heart, since 100 μM chromanol 293B produced a significant prolongation of AP in zebrafish ventricle. We conclude that AP repolarization in zebrafish ventricle is contributed by IKs, which is mainly generated by homotetrameric Kv7.1 channels not coupled to MinK ancillary β-subunits. This is a clear difference to the human heart, where MinK is an essential component of the slow delayed rectifier K+channel.
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Affiliation(s)
- Denis V Abramochkin
- Department of Human and Animal Physiology, Biological faculty, Lomonosov Moscow State University, Leninskiye Gory, 1, 12, Moscow, Russia.
- Department of Physiology, Pirogov Russian National Research Medical University, Moscow, Russia.
- Laboratory of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, Russia.
| | - Minna Hassinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
| | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
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Hegyi B, Bossuyt J, Ginsburg KS, Mendoza LM, Talken L, Ferrier WT, Pogwizd SM, Izu LT, Chen-Izu Y, Bers DM. Altered Repolarization Reserve in Failing Rabbit Ventricular Myocytes: Calcium and β-Adrenergic Effects on Delayed- and Inward-Rectifier Potassium Currents. Circ Arrhythm Electrophysiol 2018; 11:e005852. [PMID: 29437761 PMCID: PMC5813707 DOI: 10.1161/circep.117.005852] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Accepted: 12/11/2017] [Indexed: 12/25/2022]
Abstract
BACKGROUND Electrophysiological remodeling and increased susceptibility for cardiac arrhythmias are hallmarks of heart failure (HF). Ventricular action potential duration (APD) is typically prolonged in HF, with reduced repolarization reserve. However, underlying K+ current changes are often measured in nonphysiological conditions (voltage clamp, low pacing rates, cytosolic Ca2+ buffers). METHODS AND RESULTS We measured the major K+ currents (IKr, IKs, and IK1) and their Ca2+- and β-adrenergic dependence in rabbit ventricular myocytes in chronic pressure/volume overload-induced HF (versus age-matched controls). APD was significantly prolonged only at lower pacing rates (0.2-1 Hz) in HF under physiological ionic conditions and temperature. However, when cytosolic Ca2+ was buffered, APD prolongation in HF was also significant at higher pacing rates. Beat-to-beat variability of APD was also significantly increased in HF. Both IKr and IKs were significantly upregulated in HF under action potential clamp, but only when cytosolic Ca2+ was not buffered. CaMKII (Ca2+/calmodulin-dependent protein kinase II) inhibition abolished IKs upregulation in HF, but it did not affect IKr. IKs response to β-adrenergic stimulation was also significantly diminished in HF. IK1 was also decreased in HF regardless of Ca2+ buffering, CaMKII inhibition, or β-adrenergic stimulation. CONCLUSIONS At baseline Ca2+-dependent upregulation of IKr and IKs in HF counterbalances the reduced IK1, maintaining repolarization reserve (especially at higher heart rates) in physiological conditions, unlike conditions of strong cytosolic Ca2+ buffering. However, under β-adrenergic stimulation, reduced IKs responsiveness severely limits integrated repolarizing K+ current and repolarization reserve in HF. This would increase arrhythmia propensity in HF, especially during adrenergic stress.
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Affiliation(s)
- Bence Hegyi
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Julie Bossuyt
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Kenneth S Ginsburg
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Lynette M Mendoza
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Linda Talken
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - William T Ferrier
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Steven M Pogwizd
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Leighton T Izu
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Ye Chen-Izu
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.)
| | - Donald M Bers
- From the Department of Pharmacology (B.H., J.B., K.S.G., L.T.I., Y.C.-I., D.M.B.), School of Medicine, Dean's Office (L.T.), Surgical Research Facility, School of Medicine (W.T.F.), Department of Biomedical Engineering (Y.C.-I.), Department of Internal Medicine/Cardiology (Y.C.-I.), University of California, Davis; Echocardiography Laboratory, University of California, Davis Medical Center, Sacramento (L.M.M.); and Department of Medicine, University of Alabama at Birmingham (S.M.P.).
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38
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Lin Z, Xing W, Gao C, Wang X, Qi D, Dai G, Zhao W, Yan G. Inhibitory Effect of Vascular Endothelial Growth Factor on the Slowly Activating Delayed Rectifier Potassium Current in Guinea Pig Ventricular Myocytes. J Am Heart Assoc 2018; 7:JAHA.117.007730. [PMID: 29374044 PMCID: PMC5850256 DOI: 10.1161/jaha.117.007730] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Background Vascular endothelial growth factor (VEGF) exerts a number of beneficial effects on ischemic myocardium via its angiogenic properties. However, little is known about whether VEGF has a direct effect on the electrical properties of cardiomyocytes. In the present study, we investigated the effects of different concentrations of VEGF on delayed rectifier potassium currents (IK) in guinea pig ventricular myocytes and their effects on action potential (AP) parameters. Methods and Results IK and AP were recorded by the whole‐cell patch clamp method in ventricular myocytes. Cells were superfused with control solution or solution containing VEGF at different concentrations for 10 minutes before recording. Some ventricular myocytes were pretreated with a phosphatidylinositol 3‐kinase inhibitor for 1 hour before the addition of VEGF. We found that VEGF inhibited the slowly activating delayed rectifier potassium current (IKs) in a concentration‐dependent manner (18.13±1.04 versus 12.73±0.34, n=5, P=0.001; 12.73±0.34 versus 9.05±1.20, n=5, P=0.036) and prolonged AP duration (894.5±36.92 versus 746.3±33.71, n=5, P=0.021). Wortmannin, a phosphatidylinositol 3‐kinase inhibitor, eliminated these VEGF‐induced effects. VEGF had no significant effect on the rapidly activating delayed rectifier potassium current (IKr), resting membrane potential, AP amplitude, or maximal velocity of depolarization. Conclusions VEGF inhibited IKs in a concentration‐dependent manner through a phosphatidylinositol 3‐kinase–mediated signaling pathway, leading to AP prolongation. The results indicate a promising therapeutic potential of VEGF in prevention of ventricular tachyarrhythmias under conditions of high sympathetic activity and ischemia.
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Affiliation(s)
- Zhenhao Lin
- Department of Cardiology, Zhengzhou University People's Hospital, Zhengzhou, Henan, China
| | - Wenlu Xing
- Department of Cardiology, Zhengzhou University People's Hospital, Zhengzhou, Henan, China
| | - Chuanyu Gao
- Department of Cardiology, Zhengzhou University People's Hospital, Zhengzhou, Henan, China
| | - Xianpei Wang
- Department of Cardiology, Zhengzhou University People's Hospital, Zhengzhou, Henan, China
| | - Datun Qi
- Department of Cardiology, Zhengzhou University People's Hospital, Zhengzhou, Henan, China
| | - Guoyou Dai
- Department of Cardiology, Zhengzhou University People's Hospital, Zhengzhou, Henan, China
| | - Wen Zhao
- School of Pharmaceutical Sciences, Zhengzhou University, Zhengzhou, Henan, China
| | - Ganxin Yan
- Main Line Health Heart Center, Lankenau Institute for Medical Research, Wynnewood, PA
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39
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Arrhythmogenic drugs can amplify spatial heterogeneities in the electrical restitution in perfused guinea-pig heart: An evidence from assessments of monophasic action potential durations and JT intervals. PLoS One 2018; 13:e0191514. [PMID: 29352276 PMCID: PMC5774816 DOI: 10.1371/journal.pone.0191514] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 01/06/2018] [Indexed: 01/01/2023] Open
Abstract
Non-uniform shortening of the action potential duration (APD90) in different myocardial regions upon heart rate acceleration can set abnormal repolarization gradients and promote arrhythmia. This study examined whether spatial heterogeneities in APD90 restitution can be amplified by drugs with clinically proved proarrhythmic potential (dofetilide, quinidine, procainamide, and flecainide) and, if so, whether these effects can translate to the appropriate changes of the ECG metrics of ventricular repolarization, such as JT intervals. In isolated, perfused guinea-pig heart preparations, monophasic action potentials and volume-conducted ECG were recorded at progressively increased pacing rates. The APD90 measured at distinct ventricular sites, as well as the JTpeak and JTend values were plotted as a function of preceding diastolic interval, and the maximum slopes of the restitution curves were determined at baseline and upon drug administration. Dofetilide, quinidine, and procainamide reverse rate-dependently prolonged APD90 and steepened the restitution curve, with effects being greater at the endocardium than epicardium, and in the right ventricular (RV) vs. the left ventricular (LV) chamber. The restitution slope was increased to a greater extent for the JTend vs. the JTpeak interval. In contrast, flecainide reduced the APD90 restitution slope at LV epicardium without producing effect at LV endocardium and RV epicardium, and reduced the JTpeak restitution slope without changing the JTend restitution. Nevertheless, with all agents, these effects translated to the amplified epicardial-to-endocardial and the LV-to-RV non-uniformities in APD90 restitution, paralleled by the increased JTend vs. JTpeak difference in the restitution slope. In summary, these findings suggest that arrhythmic drug profiles are partly attributable to the accentuated regional heterogeneities in APD90 restitution, which can be indirectly determined through ECG assessments of the JTend vs. JTpeak dynamics at variable pacing rates.
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40
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ICaL and Ito mediate rate-dependent repolarization in rabbit atrial myocytes. J Physiol Biochem 2017; 74:57-67. [DOI: 10.1007/s13105-017-0603-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 12/04/2017] [Indexed: 01/01/2023]
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41
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Abramochkin DV, Kuzmin VS, Rosenshtraukh LV. A New Class III Antiarrhythmic Drug Niferidil Prolongs Action Potentials in Guinea Pig Atrial Myocardium via Inhibition of Rapid Delayed Rectifier. Cardiovasc Drugs Ther 2017; 31:525-533. [PMID: 29181609 DOI: 10.1007/s10557-017-6762-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
PURPOSE A new class III antiarrhythmic drug niferidil (RG-2) has been introduced as a highly effective therapy for cases of persistent atrial fibrillation, but ionic mechanisms of its action are poorly understood. In the present study, the effects of niferidil on action potential (AP) waveform and potassium currents responsible for AP repolarization were investigated in guinea pig atrial myocardium. METHODS APs were recorded with sharp glass microelectrodes in multicellular atrial preparations. Whole-cell patch-clamp technique was used to measure K+ currents in isolated myocytes. RESULTS In multicellular atrial preparations, 10-8 M niferidil effectively prolonged APs by 15.2 ± 2.8% at 90% repolarization level. However, even the highest tested concentrations, 10-6 M and 10-5 M failed to prolong APs more than 32.5% of control duration. The estimated concentration of niferedil for half-maximal AP prolongation was 1.13 × 10-8 M. Among the potassium currents responsible for AP repolarization phase, I K1 was found to be almost insensitive to niferidil. However, another inward rectifier, I KACh, was effectively suppressed by micromolar concentrations of niferidil with IC50 = 9.2 × 10-6 M. I KATP was much less sensitive to the drug with IC50 = 2.26 × 10-4 M. The slow component of delayed rectifier, I Ks, also demonstrated low sensitivity to niferidil-the highest used concentration, 10-4 M, decreased peak I Ks density to 46.2 ± 5.5% of control. Unlike I Ks, the rapid component of delayed rectifier, I Kr, appeared to be extremely sensitive to niferidil. The IC50 was 1.26 × 10-9 M. I Kr measured in ventricular myocytes was found to be less sensitive to niferidil with IC50 = 3.82 × 10-8 M. CONCLUSIONS Niferidil prolongs APs in guinea pig atrial myocardium via inhibition of I Kr.
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Affiliation(s)
- Denis V Abramochkin
- Lomonosov Moscow State University, Moscow, Russia. .,Pirogov Russian National Research Medical University, Moscow, Russia. .,Department of Human and Animal Physiology, Moscow State University, Leninskije Gory, 1, 12, Moscow, Russia.
| | - Vladislav S Kuzmin
- Lomonosov Moscow State University, Moscow, Russia.,Pirogov Russian National Research Medical University, Moscow, Russia.,Institute of Experimental Cardiology, Moscow, Russia
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42
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Characterization of loperamide-mediated block of hERG channels at physiological temperature and its proarrhythmia propensity. J Pharmacol Toxicol Methods 2017; 88:109-122. [DOI: 10.1016/j.vascn.2017.08.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 08/14/2017] [Accepted: 08/18/2017] [Indexed: 02/05/2023]
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43
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Jeevaratnam K, Chadda KR, Huang CLH, Camm AJ. Cardiac Potassium Channels: Physiological Insights for Targeted Therapy. J Cardiovasc Pharmacol Ther 2017; 23:119-129. [PMID: 28946759 PMCID: PMC5808825 DOI: 10.1177/1074248417729880] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The development of novel drugs specifically directed at the ion channels underlying particular features of cardiac action potential (AP) initiation, recovery, and refractoriness would contribute to an optimized approach to antiarrhythmic therapy that minimizes potential cardiac and extracardiac toxicity. Of these, K+ channels contribute numerous and diverse currents with specific actions on different phases in the time course of AP repolarization. These features and their site-specific distribution make particular K+ channel types attractive therapeutic targets for the development of pharmacological agents attempting antiarrhythmic therapy in conditions such as atrial fibrillation. However, progress in the development of such temporally and spatially selective antiarrhythmic drugs against particular ion channels has been relatively limited, particularly in view of our incomplete understanding of the complex physiological roles and interactions of the various ionic currents. This review summarizes the physiological properties of the main cardiac potassium channels and the way in which they modulate cardiac electrical activity and then critiques a number of available potential antiarrhythmic drugs directed at them.
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Affiliation(s)
- Kamalan Jeevaratnam
- 1 Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,2 School of Medicine, Perdana University-Royal College of Surgeons Ireland, Serdang, Selangor Darul Ehsan, Malaysia
| | - Karan R Chadda
- 1 Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom.,3 Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Christopher L-H Huang
- 3 Physiological Laboratory, University of Cambridge, Cambridge, United Kingdom.,4 Division of Cardiovascular Biology, Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - A John Camm
- 5 Cardiac Clinical Academic Group, St George's Hospital Medical School, University of London, Cranmer Terrace, London, United Kingdom
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44
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Pedersen PJ, Thomsen KB, Flak JB, Tejada MA, Hauser F, Trachsel D, Buhl R, Kalbfleisch T, DePriest MS, MacLeod JN, Calloe K, Klaerke DA. Molecular cloning and functional expression of the K + channel K V7.1 and the regulatory subunit KCNE1 from equine myocardium. Res Vet Sci 2017; 113:79-86. [PMID: 28917093 DOI: 10.1016/j.rvsc.2017.09.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Revised: 08/05/2017] [Accepted: 09/07/2017] [Indexed: 10/18/2022]
Abstract
BACKGROUND The voltage-gated K+-channel KV7.1 and the subunit KCNE1, encoded by the KCNQ1 and KCNE1 genes, respectively, are responsible for termination of the cardiac action potential. In humans, mutations in these genes can predispose patients to arrhythmias and sudden cardiac death (SCD). AIM To characterize equine KV7.1/KCNE1 currents and compare them to human KV7.1/KCNE1 currents to determine whether KV7.1/KCNE1 plays a similar role in equine and human hearts. METHODS mRNA encoding KV7.1 and KCNE1 was isolated from equine hearts, sequenced, and cloned into expression vectors. The channel subunits were heterologously expressed in Xenopus laevis oocytes or CHO-K1 cells and characterized using voltage-clamp techniques. RESULTS Equine KV7.1/KCNE1 expressed in CHO-K1 cells exhibited electrophysiological properties that are overall similar to the human orthologs; however, a slower deactivation was found which could result in more open channels at fast rates. CONCLUSION The results suggest that the equine KV7.1/KCNE1 channel may be important for cardiac repolarization and this could indicate that horses are susceptible to SCD caused by mutations in KCNQ1 and KCNE1.
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Affiliation(s)
- Philip J Pedersen
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Kirsten B Thomsen
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Jon B Flak
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Maria A Tejada
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Frank Hauser
- Center for Functional and Comparative Insect Genomics, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Dagmar Trachsel
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | - Rikke Buhl
- Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Taastrup, Denmark
| | - Theodore Kalbfleisch
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Louisville, Louisville, KY, United States
| | - Michael Scott DePriest
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Louisville, Louisville, KY, United States
| | - James N MacLeod
- Maxwell H., Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, KY, United States
| | - Kirstine Calloe
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.
| | - Dan A Klaerke
- Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark
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45
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Juhász V, Hornyik T, Benák A, Nagy N, Husti Z, Pap R, Sághy L, Virág L, Varró A, Baczkó I. Comparison of the effects of I K,ACh, I Kr, and I Na block in conscious dogs with atrial fibrillation and on action potentials in remodeled atrial trabeculae. Can J Physiol Pharmacol 2017; 96:18-25. [PMID: 28892643 DOI: 10.1139/cjpp-2017-0342] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and a major cause of morbidity and mortality. Traditional antiarrhythmic agents used for restoration of sinus rhythm have limited efficacy in long-term AF and they may possess ventricular proarrhythmic adverse effects, especially in patients with structural heart disease. The acetylcholine receptor-activated potassium channel (IK,ACh) represents an atrial selective target for future AF management. We investigated the effects of the IK,ACh blocker tertiapin-Q (TQ), a derivative of the honeybee toxin tertiapin, on chronic atrial tachypacing-induced AF in conscious dogs, without the influence of anesthetics that modulate a number of cardiac ion channels. Action potentials (APs) were recorded from right atrial trabeculae isolated from dogs with AF. TQ significantly and dose-dependently reduced AF incidence and AF episode duration, prolonged atrial effective refractory period, and prolonged AP duration. The reference drugs propafenone and dofetilide, both used in the clinical management of AF, exerted similar effects against AF in vivo. Dofetilide prolonged atrial AP duration, whereas propafenone increased atrial conduction time. TQ and propafenone did not affect the QT interval, whereas dofetilide prolonged the QT interval. Our results show that inhibition of IK,ACh may represent a novel, atrial-specific target for the management of AF in chronic AF.
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Affiliation(s)
- Viktor Juhász
- a Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Tibor Hornyik
- a Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Attila Benák
- b 2nd Department of Internal Medicine and Cardiology Centre, University of Szeged, Szeged, Hungary
| | - Norbert Nagy
- c MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
| | - Zoltán Husti
- a Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - Róbert Pap
- b 2nd Department of Internal Medicine and Cardiology Centre, University of Szeged, Szeged, Hungary
| | - László Sághy
- b 2nd Department of Internal Medicine and Cardiology Centre, University of Szeged, Szeged, Hungary
| | - László Virág
- a Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
| | - András Varró
- a Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary.,c MTA-SZTE Research Group of Cardiovascular Pharmacology, Hungarian Academy of Sciences, Szeged, Hungary
| | - István Baczkó
- a Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary
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46
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Development of correction formula for field potential duration of human induced pluripotent stem cell-derived cardiomyocytes sheets. J Pharmacol Sci 2017; 135:44-50. [PMID: 28928053 DOI: 10.1016/j.jphs.2017.08.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 08/01/2017] [Accepted: 08/30/2017] [Indexed: 01/05/2023] Open
Abstract
Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have been used in many studies to assess proarrhythmic risks of chemical compounds. In those studies, field potential durations (FPD) of hiPSC-CMs have been corrected by clinically used Fridericia's and/or Bazett's formulae, however, the rationale for the use of these formulae has not been well established. In the present study, we developed a correction formula for experiments using hiPSC-CMs. First, we analyzed the effect of beating rate on FPD in the hiPSC-CMs sheets with electrical stimuli and a HCN channel inhibitor zatebradine. Next, we examined the relationship between the electrophysiological properties and the expression levels of ion channel genes in the cell sheets. Zatebradine slowed the beating rate and allowed to analyze FPD changes at various pacing cycle lengths. Rate-dependent change in the repolarization period was smaller in the cell sheets than that reported on the human hearts, which can be partly explained by lower gene expression level of hKCNJ2 and hKCNE1. Thus, non-linear equation for correcting FPD in the cell sheet; FPDc = FPD/RR0.22 with RR given in second was obtained, which may make it feasible to assess net repolarization delay by various chemical compounds with a chronotropic action.
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47
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McPheeters MT, Wang YT, Werdich AA, Jenkins MW, Laurita KR. An infrared optical pacing system for screening cardiac electrophysiology in human cardiomyocytes. PLoS One 2017; 12:e0183761. [PMID: 28837652 PMCID: PMC5570338 DOI: 10.1371/journal.pone.0183761] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Accepted: 08/10/2017] [Indexed: 01/05/2023] Open
Abstract
Human cardiac myocytes derived from pluripotent stem cells (hCM) have invigorated interest in genetic disease mechanisms and cardiac safety testing; however, the technology to fully assess electrophysiological function in an assay that is amenable to high throughput screening has lagged. We describe a fully contactless system using optical pacing with an infrared (IR) laser and multi-site high fidelity fluorescence imaging to assess multiple electrophysiological parameters from hCM monolayers in a standard 96-well plate. Simultaneous multi-site action potentials (FluoVolt) or Ca2+ transients (Fluo4-AM) were measured, from which high resolution maps of conduction velocity and action potential duration (APD) were obtained in a single well. Energy thresholds for optical pacing were determined for cell plating density, laser spot size, pulse width, and wavelength and found to be within ranges reported previously for reliable pacing. Action potentials measured using FluoVolt and a microelectrode exhibited the same morphology and rate of depolarization. Importantly, we show that this can be achieved accurately with minimal damage to hCM due to optical pacing or fluorescence excitation. Finally, using this assay we demonstrate that hCM exhibit reproducible changes in repolarization and impulse conduction velocity for Flecainide and Quinidine, two well described reference compounds. In conclusion, we demonstrate a high fidelity electrophysiological screening assay that incorporates optical pacing with IR light to control beating rate of hCM monolayers.
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Affiliation(s)
- Matthew T. McPheeters
- Pediatrics, Case Western Reserve University, Cleveland, Ohio, United States of America
- Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Yves T. Wang
- Pediatrics, Case Western Reserve University, Cleveland, Ohio, United States of America
- Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Andreas A. Werdich
- Brigham and Women's Hospital/Harvard Medical School, Cardiovascular Division, Boston, Massachusetts, United States of America
| | - Michael W. Jenkins
- Pediatrics, Case Western Reserve University, Cleveland, Ohio, United States of America
- Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Kenneth R. Laurita
- Brigham and Women's Hospital/Harvard Medical School, Cardiovascular Division, Boston, Massachusetts, United States of America
- Heart and Vascular Research Center, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio, United States of America
- Medicine, Case Western Reserve University, Cleveland, Ohio, United States of America
- * E-mail:
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VanderLugt JT, Bon C, Knuth D, Schreiber R, Ruff MD. Pharmacokinetics and Bioequivalence of Branded and Generic Formulations of Dofetilide 0.5-mg Capsules After Single-Dose Administration in Healthy Subjects. Clin Pharmacol Drug Dev 2017; 7:311-318. [PMID: 28800211 DOI: 10.1002/cpdd.371] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 05/23/2017] [Indexed: 11/10/2022]
Abstract
Class III antiarrhythmics are preferred therapy for managing atrial fibrillation/flutter. Dofetilide 0.5-mg capsules were US Food and Drug Administration (FDA) approved in 1999 to treat atrial fibrillation/flutter. Bioequivalence of generic dofetilide is important for treating arrhythmias because drug concentrations must be consistent to maintain normal sinus rhythm. Generic dofetilide 0.5-mg capsule pharmacokinetics were compared with branded product in 2 open-label, 2-way crossover, single-dose studies - 1 study each in fasted and fed healthy subjects. Blood samples were collected before and up to 48 hours after dosing. Safety was assessed by tabulating adverse events and vital signs. Seventy-three subjects were enrolled; 59 completed the studies. In fasted subjects, the 90% confidence intervals (CIs) for generic dofetilide 0.5 mg versus the reference formulation were 0.996-1.026 for the area under the plasma concentration-time curve from 0 to infinity (AUC) and 0.974-1.066 for the maximum observed concentration (Cmax ). In fed subjects, the 90%CIs for AUC and Cmax were 0.988-1.015 and 0.928-0.992, respectively. All ratios were within the FDA-established bioequivalence range. Twenty-six subjects experienced 37 adverse events (generic, 15; reference, 22); all but 1 were mild or moderate in severity. Generic dofetilide 0.5-mg capsules can be considered bioequivalent to the reference product.
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Affiliation(s)
| | - Charles Bon
- Biostudy Solutions, LLC, Wilmington, NC, USA
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49
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Osadchii OE. Role of abnormal repolarization in the mechanism of cardiac arrhythmia. Acta Physiol (Oxf) 2017; 220 Suppl 712:1-71. [PMID: 28707396 DOI: 10.1111/apha.12902] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
In cardiac patients, life-threatening tachyarrhythmia is often precipitated by abnormal changes in ventricular repolarization and refractoriness. Repolarization abnormalities typically evolve as a consequence of impaired function of outward K+ currents in cardiac myocytes, which may be caused by genetic defects or result from various acquired pathophysiological conditions, including electrical remodelling in cardiac disease, ion channel modulation by clinically used pharmacological agents, and systemic electrolyte disorders seen in heart failure, such as hypokalaemia. Cardiac electrical instability attributed to abnormal repolarization relies on the complex interplay between a provocative arrhythmic trigger and vulnerable arrhythmic substrate, with a central role played by the excessive prolongation of ventricular action potential duration, impaired intracellular Ca2+ handling, and slowed impulse conduction. This review outlines the electrical activity of ventricular myocytes in normal conditions and cardiac disease, describes classical electrophysiological mechanisms of cardiac arrhythmia, and provides an update on repolarization-related surrogates currently used to assess arrhythmic propensity, including spatial dispersion of repolarization, activation-repolarization coupling, electrical restitution, TRIaD (triangulation, reverse use dependence, instability, and dispersion), and the electromechanical window. This is followed by a discussion of the mechanisms that account for the dependence of arrhythmic vulnerability on the location of the ventricular pacing site. Finally, the review clarifies the electrophysiological basis for cardiac arrhythmia produced by hypokalaemia, and gives insight into the clinical importance and pathophysiology of drug-induced arrhythmia, with particular focus on class Ia (quinidine, procainamide) and Ic (flecainide) Na+ channel blockers, and class III antiarrhythmic agents that block the delayed rectifier K+ channel (dofetilide).
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Affiliation(s)
- O. E. Osadchii
- Department of Health Science and Technology; University of Aalborg; Aalborg Denmark
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50
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Wang W, MacKinnon R. Cryo-EM Structure of the Open Human Ether-à-go-go-Related K + Channel hERG. Cell 2017; 169:422-430.e10. [PMID: 28431243 DOI: 10.1016/j.cell.2017.03.048] [Citation(s) in RCA: 376] [Impact Index Per Article: 47.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2017] [Revised: 03/01/2017] [Accepted: 03/30/2017] [Indexed: 11/17/2022]
Abstract
The human ether-à-go-go-related potassium channel (hERG, Kv11.1) is a voltage-dependent channel known for its role in repolarizing the cardiac action potential. hERG alteration by mutation or pharmacological inhibition produces Long QT syndrome and the lethal cardiac arrhythmia torsade de pointes. We have determined the molecular structure of hERG to 3.8 Å using cryo-electron microscopy. In this structure, the voltage sensors adopt a depolarized conformation, and the pore is open. The central cavity has an atypically small central volume surrounded by four deep hydrophobic pockets, which may explain hERG's unusual sensitivity to many drugs. A subtle structural feature of the hERG selectivity filter might correlate with its fast inactivation rate, which is key to hERG's role in cardiac action potential repolarization.
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Affiliation(s)
- Weiwei Wang
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University and Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10065, USA
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University and Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10065, USA.
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