Idiosyncratic drug-induced liver injury (DILI) is a leading cause of drug attrition and/or withdrawal. The formation of reactive metabolites is widely accepted as a key factor contributing to idiosyncratic DILI. Therefore, identifying reactive metabolites has become a critical focus during lead optimization, and a combination of GSH-/cyano-trapping and cytochrome P450 inactivation studies is recommended to identify compounds with the potential to generate reactive metabolites. Daily dose, clinical indication, detoxication pathways, administration route, and treatment duration are the most considerations when deprioritizing candidates that generate reactive metabolites. Removing the structural alerts is considered a pragmatic strategy for mitigating the risk associated with reactive metabolites, although this approach may sometimes exclude otherwise potent molecules. In this context, an in-depth insight into the structure-based reactive metabolite formation of organic functional groups can significantly aid in the rational design of drug candidates with improved safety profiles. The primary goal of this review is to delve into an analysis of the bioactivation mechanisms of organic functional groups and their potential detrimental effects with recent examples to assist medicinal chemists and metabolism scientists in designing safer drug candidates with a higher likelihood of success.

Nicotine, the primary constituent of tobacco, is one of the important factors that induce the occurrence of hepatocellular carcinoma (HCC). The β2-adrenergic receptor (β2-AR) is implicated in the growth and advancement of tumors. However, the role of β2-AR and its mediated cascades in nicotine-induced HCC remains unclear. This present study aims to observe the effects of nicotine on the proliferation, migration, and invasion of immortalized human liver epithelial (THLE-2) cells, as well as to explore the underlying mechanisms of action. The results of cell counting kit-8 (CCK-8) assay showed that 0.3125 μM nicotine had the ability to promote the proliferation of THLE-2 cells with a significant time-dependent manner. Therefore, THLE-2 cells were mainly selected for chronic treatment with 0.3125 μM nicotine in the later stage to cause transformation. After 30 passages of THLE-2 cells with 0.3125 μM nicotine treatment, chronic exposure to nicotine significantly enhanced the proliferation, metastasis, and invasion of cells. Besides, it also upregulated the intracellular levels of β2-AR, phosphoinositide 3-kinase (PI3K), AKT, matrix metalloproteinase-2 (MMP-2) and Cyclin D1, as well as downregulated the expression of p53. More importantly, the β2-AR/PI3K/AKT pathway was found to mediate the expression of MMP-2, Cyclin D1, and p53 in THLE-2 cells, playing a crucial role in their proliferation, migration, and invasion after continuous exposure to nicotine. Simply put, it demonstrated the role of β2-AR/PI3K/AKT pathway in the transformation of THLE-2 cells induced by nicotine. This study could provide valuable insights into the relationship between nicotine and HCC. Additionally, it lays the groundwork for investigating potential anticancer treatments for liver cancer linked to tobacco consumption.

Metabolic disorders are currently threatening public health worldwide. Discovering new targets and developing promising drugs will reduce the global metabolic-related disease burden. Metabolic disorders primarily consist of lipid and glucose metabolic disorders. Specifically, metabolic dysfunction-associated steatosis liver disease (MASLD) and alcohol-associated liver disease (ALD) are two representative lipid metabolism disorders, while diabetes mellitus is a typical glucose metabolism disorder. In this review, we aimed to summarize the new drug candidates with promising efficacy identified in clinical trials for these diseases. These drug candidates may provide alternatives for patients with metabolic disorders and advance the progress of drug discovery for the large disease burden.

Chiglitazar is an emerging pan-agonist of all peroxisome proliferator activated receptors (PPAR)-α, δ and γ, and has therapeutic potential for type 2 diabetes (T2D). However, to date, no clinical studies or meta-analyses have compared the efficacy and safety of chiglitazar and traditional PPAR-γ agonist thiazolidinediones (TZDs). A meta-analysis concerning this topic is therefore required.

To compare the efficacy and safety of chiglitazar and TZD in patients with T2D.

PubMed, Medline, Embase, the Cochrane Central Register of Controlled Trials, Reference Citation Analysis and Clinicaltrial.gov websites were searched from August 1994 to March 2022. Randomized controlled trials (RCTs) of chiglitazar or TZD vs placebo in patients with T2D were included. Indirect comparisons and sensitivity analyses were implemented to evaluate multiple efficacy and safety endpoints of interest.

We included 93 RCTs that compared TZD with placebo and one that compared chiglitazar with placebo. For efficacy endpoints, the augmented dose of chig-litazar resulted in greater reductions in hemoglobin (Hb)A1c [weighted mean difference (WMD) = -0.15%, 95% confidence interval (CI): -0.27 to -0.04%], triglycerides (WMD = -0.17 mmol/L, 95%CI: -0.24 to -0.11 mmol/L) and alanine aminotransferase (WMD = -5.25 U/L, 95%CI: -8.50 to -1.99 U/L), and a greater increase in homeostasis model assessment-β (HOMA-β) (WMD = 17.75, 95%CI: 10.73-24.77) when compared with TZD treatment. For safety endpoints, the risks of hypoglycemia, edema, bone fractures, upper respiratory tract infection, urinary tract infection, and weight gain were all comparable between the augmented dose of chiglitazar and TZD. In patients with baseline HbA1c ≥ 8.5%, body mass index ≥ 30 kg/m2 or diabetes duration < 10 years, the HbA1c reduction and HOMA-β increase were more conspicuous for the augmented dose of chiglitazar compared with TZD.

Augmented dose of chiglitazar, a pan-activator of PPARs, may serve as an antidiabetic agent with preferable glycemic and lipid control, better β-cell function preserving capacity, and does not increase the risk of safety concerns when compared with TZD.

Hepatic oval cells have strong proliferation and differentiation capabilities and are activated when chronic liver injury occurs or when liver function is severely impaired. Peroxisome proliferation-activated receptors (PPARs) are ligand-dependent, sequence-specific nuclear transcription factors. PPARγ is closely related to liver diseases (such as liver cancer, liver fibrosis and non-alcoholic fatty liver disease). As the main effector downstream of the Hippo signaling pathway, YAP can activate the hepatic progenitor cell program, and different expression or activity levels of YAP can determine different liver cell fates. We found that troglitazone (TRO), a classic PPARγ activator, can inhibit the growth of hepatic oval cells, and flow cytometry results showed that TRO inhibited the growth of WB-F344 cells by arresting the cells in the G_0/1 phase. Western blot results also confirmed changes in G_0/1 phase-related protein expression. Further experiments showed that PPARγ agonists induced hepatic oval cell proliferation inhibition and cell cycle G_0/1 phase arrest through the Hippo/YAP pathway. Our experiment demonstrated, for the first time, the relationship between PPARγ and the Hippo/YAP pathway in liver oval cells and revealed that PPARγ acts as a negative regulator of liver regeneration by inhibiting the proliferation of oval cells.

Deuteration is a chemical modification strategy that has recently gained traction in drug development. The replacement of one or more hydrogen atom(s) in a drug molecule with its heavier stable isotope deuterium can enhance its metabolic stability and pharmacokinetic properties. However, it remains uninterrogated if rational deuteration at bioactivation "hot-spots" could attenuate its associated toxicological consequences. Here, our preliminary screening with benzofuran antiarrhythmic agents first revealed that dronedarone and its major metabolite N-desbutyldronedarone elicited a greater loss of viability and cytotoxicity in human hepatoma G2 (HepG2) cells as compared with amiodarone and its corresponding metabolite N-desethylamiodarone. A comparison of dronedarone and its in-house synthesized deuterated analogue (termed poyendarone) demonstrated that deuteration could attenuate its in vitro toxicity in HepG2 cells by modulating the extent of mitochondrial dysfunction, reducing the dissipation of mitochondrial membrane potential, and evoking a distinct apoptotic kinetic signature. Furthermore, although pretreatment with the CYP3A inducer rifampicin or the substitution of glucose with galactose in the growth media significantly augmented the loss of cell viability elicited by dronedarone and poyendarone, a lower loss of cell viability was consistently observed in poyendarone across all concentrations. Taken together, our preliminary investigations suggested that the rational deuteration of dronedarone at its benzofuran ring reduces aberrant cytochrome P450 3A4/5-mediated bioactivation, which attenuated its mitochondrial toxicity in human hepatic HepG2 cells.

We report here a novel in vitro experimental system, the metabolism-dependent cytotoxicity assay (MDCA), for the definition of the roles of hepatic drug metabolism in toxicity. MDCA employs permeabilized cofactor-supplemented cryopreserved human hepatocytes (MetMax Human Hepatocytes, MMHH), as an exogenous metabolic activating system, and human embryonic kidney 293 (HEK293) cells, a cell line devoid of drug-metabolizing enzyme activity, as target cells for the quantification of drug toxicity. The assay was performed in the presence and absence of cofactors for key drug metabolism pathways known to play key roles in drug toxicity: NADPH/NAD+ for phase 1 oxidation, uridine 5'-diphosphoglucuronic acid (UDPGA) for uridine 5'-diphospho-glucuronosyltransferase (UGT) mediated glucuronidation, 3'-phosphoadenosine-5'-phosphosulfate (PAPS) for cytosolic sulfotransferase (SULT) mediated sulfation, and glutathione (GSH) for glutathione S-transferase (GST) mediated GSH conjugation. Six drugs with clinically significant hepatoxicity, resulting in liver failure or a need for liver transplantation: acetaminophen, amiodarone, cyclophosphamide, ketoconazole, nefazodone, and troglitazone were evaluated. All six drugs exhibited cytotoxicity enhancement by NADPH/NAD+, suggesting metabolic activation via phase 1 oxidation. Attenuation of cytotoxicity by UDPGA was observed for acetaminophen, ketoconazole, and troglitazone, by PAPS for acetaminophen, ketoconazole, and troglitazone, and by GSH for all six drugs. Our results suggest that MDCA can be applied toward the elucidation of metabolic activation and detoxification pathways, providing information that can be applied in drug development to guide structure optimization to reduce toxicity and to aid the assessment of metabolism-based risk factors for drug toxicity. GSH detoxification represents an endpoint for the identification of drugs forming cytotoxic reactive metabolites, a key property of drugs with idiosyncratic hepatotoxicity. SIGNIFICANCE STATEMENT: Application of the metabolism-dependent cytotoxicity assay (MDCA) for the elucidation of the roles of metabolic activation and detoxification pathways in drug toxicity may provide information to guide structure optimization in drug development to reduce hepatotoxic potential and to aid the assessment of metabolism-based risk factors. Glutathione (GSH) detoxification represents an endpoint for the identification of drugs forming cytotoxic reactive metabolites that may be applied toward the evaluation of idiosyncratic hepatotoxicity.

Breast cancer is a major medical threat which cannot be sufficiently addressed by current therapies because of spontaneous or acquired treatment resistance. Besides, triple-negative breast cancer (TNBC) tumors do not respond to targeted therapies, thus new therapeutic strategies are needed. In this context, we designed and prepared new desulfured troglitazone (TGZ)-derived molecules and evaluated them in vitro for their anti-proliferative activity, with a special focus on triple-negative breast cancer cell lines. Optimization of the synthetic strategies and deracemization of the lead compound were performed to give highly active compound 10 with low-micromolar potency. Further studies revealed that this compound triggers apoptosis rather than cell cycle arrest as observed with TGZ.

Rhodanines, as one of the 4-thiazolidinones subtypes, are recognized as privileged heterocycles in medicinal chemistry. The main achievements include the development of drug-like molecules with numerous biological activities as well as approved drugs. Among rhodanines, 5-ene-rhodanines are of special interest, and are often claimed as pan assay interference compounds due to Michael acceptor functionality. Areas covered: Herein, the synthetic protocols for rhodanines and their transformation are reviewed. Biological activity is briefly discussed as well as biotargets, mode of actions and optimization directions. Furthermore, the utilization of 5-ene-rhodanines in Michael additions are discussed while both pro and contra arguments have been outlined within medicinal chemistry application. Expert opinion: Rhodanines remain privileged heterocycles in drug discovery. They are accessible building blocks for optimization and transformation into related heterocycles, simplified analogues and fused heterocycles with a thiazolidine framework. Michael acceptor functionality, as well as the thesis about low selectivity towards biotargets of rhodanines, must be confirmed experimentally and it cannot be based on just the presence of conjugated α,β-unsaturated carbonyl. Moreover, the positive aspects of Michael acceptors must be considered as well as their multitarget properties. New criteria for target affinity must be found. In conclusion, rhodanines are generally not problematic per se.

Thiazolidinedione (TZD) drugs used in the treatment of type 2 diabetes mellitus (T2DM) have proven effective in improving insulin sensitivity, hyperglycemia, and lipid metabolism. Though well tolerated by some patients, their mechanism of action as ligands of peroxisome proliferator-activated receptors (PPARs) results in the activation of several pathways in addition to those responsible for glycemic control and lipid homeostasis. These pathways, which include those related to inflammation, bone formation, and cell proliferation, may lead to adverse health outcomes. As treatment with TZDs has been associated with adverse hepatic, cardiovascular, osteological, and carcinogenic events in some studies, the role of TZDs in the treatment of T2DM continues to be debated. At the same time, new therapeutic roles for TZDs are being investigated, with new forms and isoforms currently in the pre-clinical phase for use in the prevention and treatment of some cancers, inflammatory diseases, and other conditions. The aims of this review are to provide an overview of the mechanism(s) of action of TZDs, a review of their safety for use in the treatment of T2DM, and a perspective on their current and future therapeutic roles.

Liver damage occurred in some patients who took troglitazone (TGZ) for type II diabetes. The 2,4-thiazolidinedione (TZD) ring in TGZ's structure has been implicated in its hepatotoxicity. To further examine the potential role of a TZD ring in toxicity we used HepG2 cells to evaluate two series of compounds containing different cyclic imides. N-phenyl analogues comprised 3-(3,5-dichlorophenyl)-2,4-thiazolidinedione (DCPT); 3-(3,5-dichlorophenyl)-2,4-oxazolidinedione (DCPO) and N-(3,5-dichlorophenyl)succinimide (NDPS). Benzylic compounds, which closely resemble TGZ, included 5-(3,5-dichlorophenylmethyl)-2,4-thiazolidinedione (DCPMT); 5-(4-methoxyphenylmethyl)-2,4-thiazolidinedione (MPMT); 5-(4-methoxyphenylmethylene)-2,4-thiazolidinedione (MPMT-I); 5-(4-methoxyphenylmethyl)-2,4-oxazolidinedione (MPMO); 3-(4-methoxyphenylmethyl)succinimide (MPMS) and 3-(4-methoxyphenylmethylene)succinimide (MPMS-I). Cytotoxicity was assessed using the MTS assay after incubating the compounds (0-250μM) with HepG2 cells for 24h. Only certain TZD derivatives (TGZ, DCPT, DCPMT and MPMT-I) markedly decreased cell viability, whereas MPMT had low toxicity. In contrast, analogues without a TZD ring (DCPO, NDPS, MPMO, MPMS and MPMS-I) were not cytotoxic. These findings suggest that a TZD ring may be an important determinant of toxicity, although different structural features, chemical stability, cellular uptake or metabolism, etc., may also be involved. A simple clustering approach, using chemical fingerprints, assigned each compound to one of three classes (each containing one active compound and close homologues), and provided a framework for rationalizing the activity in terms of structure.

α and β asarones are natural constituents of some aromatic plants, especially species of the genus Acorus (Araceae). In addition to reports of beneficial properties of asarones, genotoxicity and carcinogenicity are also reported. Due to potential toxic effects of β-asarone, a limit of exposure from herbal products of ~2 μg/kg body weight/day has been set temporarily until a full benefit/risk assessment has been carried out by the European Medicines Agency. Therefore, it is important to monitor levels of β-asarone in herbal products. In this study, we developed a simple, rapid and validated GC-MS method for quantitative determination of asarones and applied it in 20 pediatric herbal products after detecting high concentrations of β-asarone in a product suspected to be implicated in hepatotoxicity in a 3 month old infant. Furthermore, targeted toxicological effects were further investigated in human hepatocytes (THLE-2 cells) by employing various in vitro assays, with the goal of elucidating possible mechanisms for the observed toxicity. Results showed that some of the products contained as much as 4-25 times greater amounts of β-asarone than the recommended levels. In 4 of 10 samples found to contain asarones, the presence of asarones could not be linked to the labeled ingredients, possibly due to poor quality control. Cell-based investigations in THLE-2 cells confirmed the cytotoxicity of β-asarone (IC50 = 40.0 ± 2.0 μg/mL) which was associated with significant lipid peroxidation and glutathione depletion. This observed cytotoxic effect is likely due to induction of oxidative stress by asarones. Overall, the results of this study ascertained the usability of this GC-MS method for the quantitative determination of asarones from herbal products, and shed light on the importance of controlling the concentration of potentially toxic asarones in herbal products to safeguard consumer safety, especially when the target consumers are young children. Further investigations of the toxicity of asarones are warranted.

The ubiquitous shortage of primary human hepatocytes has urged the scientific community to search for alternative cell sources, such as immortalized hepatic cell lines. Over the years, several human hepatic cell lines have been produced, whether or not using a combination of viral oncogenes and human telomerase reverse transcriptase protein. Conditional approaches for hepatocyte immortalization have also been established and allow generation of growth-controlled cell lines. A variety of immortalized human hepatocytes have already proven useful as tools for liver-based in vitro testing and fundamental research purposes. The present chapter describes currently applied immortalization strategies and provides an overview of the actually available immortalized human hepatic cell lines and their in vitro applications.

Cytochrome P450 (CYP) 3A induction-mediated drug-drug interaction (DDI) is one of the major concerns in drug development and clinical practice. The aim of the present study was to develop a novel mechanistic physiologically based pharmacokinetic (PBPK)-enzyme turnover model involving both intestinal and hepatic CYP3A induction to quantitatively predict magnitude of CYP3A induction-mediated DDIs from in vitro data. The contribution of intestinal P-glycoprotein (P-gp) was also incorporated into the PBPK model. First, the pharmacokinetic profiles of three inducers and 14 CYP3A substrates were predicted successfully using the developed model, with the predicted area under the plasma concentration-time curve (AUC) [area under the plasma concentration-time curve] and the peak concentration (Cmax ) [the peak concentration] in accordance with reported values. The model was further applied to predict DDIs between the three inducers and 14 CYP3A substrates. Results showed that predicted AUC and Cmax ratios in the presence and absence of inducer were within twofold of observed values for 17 (74%) of the 23 DDI studies, and for 14 (82%) of the 17 DDI studies, respectively. All the results gave us a conclusion that the developed mechanistic PBPK-enzyme turnover model showed great advantages on quantitative prediction of CYP3A induction-mediated DDIs.

The promising activity shown by compounds containing thiazolidine-2,4-dione nucleus in numerous categories such as anti-hyperglycaemics, aldose reductase inhibitors, anti-cancer, anti-inflammatory, anti-arthritics, anti-microbials, etc. has made it an indispensable anchor for development of new therapeutic agents. Varied substituents on the thiazolidine-2,4-dione nucleus have provided a wide spectrum of biological activities. Importance of this nucleus in some activities like, peroxisome proliferator activated receptor γ (PPARγ) agonism and PPARγ-dependent and -independent anti-cancer activities are reviewed separately in literature. Short reviews on biological importance of this nucleus are also known in literature. However, owing to fast development of new drugs possessing thiazolidine-2,4-dione nucleus many research reports are generated in short span of time. So, there is a need to couple the latest information with the earlier information to understand the current status of thiazolidine-2,4-dione nucleus in medicinal chemistry research. In the present review, various derivatives of thiazolidine-2,4-diones with different pharmacological activities are described on the basis of substitution pattern around the nucleus combined with the docking studies performed in the active site of the corresponding receptors with an aim to help medicinal chemists for developing an SAR on thiazolidine-2,4-dione derived compounds for each activity. This discussion will further help in the development of novel thiazolidine-2,4-dione compounds.

Atherosclerotic cardiovascular disease is a chronic inflammatory condition. Thiazolidinediones (TZDs) are used to enhance sensitivity to insulin and have demonstrated a protective effect over a variety of cardiovascular markers and risk factors. Controversially, the TZDs are associated with the development of heart failure. Thus, lines of research have invested in the search for new molecules in order to obtain more selective and less harmful treatment alternatives for the pathogenesis of atherosclerosis and its risk factors.

Animals were fed a diet rich in fat for 10 weeks. In the last 2 weeks, animals received either pioglitazone, LPSF/GQ-02, or LPSF/GQ-16 daily through gavage. At the end of the treatment, blood was collected for biochemical analysis and the aortas were dissected for subsequent analyses.

No changes in the blood lipid profile were found following the use of the drugs in comparison to the control. However, the new thiazolidine derivatives were more efficient in improving insulin resistance in comparison to pioglitazone and the control group. Morphometric analyses revealed that neither pioglitazone nor LPSF/GQ16 led to satisfactory effects over atherosclerosis. However, LPSF/GQ-02 led to a reduction in area of the atherosclerotic lesions. Ultrastructural analyses revealed extensive degeneration of the endothelium and an increase in apoptotic cells in the subendothelial space following the use of pioglitazone and LPSF/GQ-16. However, LPSF/GQ-02 caused minimal cell alterations in the aortic endothelium. Regarding markers, endothelial nitric oxide synthase (eNOS) and matrix metalloproteinase 9 (MMP-9), LPSF/GQ-16, and pioglitazone exerted similar effects, increasing the expression of MMP-9, and had no effect on the expression of eNOS compared with the control group. On the other hand, LPSF/GQ-02 was effective in reducing the expression of MMP-9 and increased eNOS significantly.

The results suggest that the new thiazolidine derivative LPSF/GQ-02 is a promising candidate for the treatment of atherosclerosis.

The huge increase in type 2 diabetes is a burden worldwide. Many marketed compounds do not address relevant aspects of the disease; they may already compensate for defects in insulin secretion and insulin action, but loss of secreting cells (β-cell destruction), hyperglucagonemia, gastric emptying, enzyme activation/inhibition in insulin-sensitive cells, substitution or antagonizing of physiological hormones and pathways, finally leading to secondary complications of diabetes, are not sufficiently addressed. In addition, side effects for established therapies such as hypoglycemias and weight gain have to be diminished. At present, nearly 1000 compounds have been described, and approximately 180 of these are going to be developed (already in clinical studies), some of them directly influencing enzyme activity, influencing pathophysiological pathways, and some using G-protein-coupled receptors. In addition, immunological approaches and antisense strategies are going to be developed. Many compounds are derived from physiological compounds (hormones) aiming at improving their kinetics and selectivity, and others are chemical compounds that were obtained by screening for a newly identified target in the physiological or pathophysiological machinery. In some areas, great progress is observed (e.g., incretin area); in others, no great progress is obvious (e.g., glucokinase activators), and other areas are not recommended for further research. For all scientific areas, conclusions with respect to their impact on diabetes are given. Potential targets for which no chemical compound has yet been identified as a ligand (agonist or antagonist) are also described.

Breast cancer is the most prevalent cancer in women. The development of resistances to therapeutic agents and the absence of targeted therapy for triple negative breast cancer motivate the search for alternative treatments. With this aim in mind, we synthesised new derivatives of troglitazone, a compound which was formerly used as an anti-diabetic agent and which exhibits anti-proliferative activity on various cancer cell lines. Among the compounds prepared, some displayed micromolar activity against hormone-dependent and hormone-independent breast cancer cells. Furthermore, the influence of the compounds on the viability of primary cultures of human hepatocytes was evaluated. This enabled us to obtain for the first time interesting structure-toxicity relationships in this family of compounds, resulting in 6b and 8b, which show good anti-proliferative activities and poor toxicity towards hepatocytes, compared to troglitazone.

Null mutation of glutathione transferase (GST) M1 and GSTT1 was reported to correlate statistically with an abnormal increase in the plasma levels of alanine aminotransferase or aspartate aminotransferase caused by troglitazone in diabetic patients (Clin Pharmacol Ther, 73:435-455, 2003). This clinical evidence leads to the hypothesis that GSH conjugation catalyzed by GSTT1 and GSTM1 has a role in the elimination of reactive metabolites of troglitazone. However, the contribution of GST isoforms expressed in human liver to the detoxification of reactive metabolites of troglitazone has not yet been clarified. We investigated the involvement of human GST isoforms in the GSH conjugation of reactive metabolites of troglitazone using recombinant GST enzymes. Five reported GSH conjugates of reactive metabolites were produced from troglitazone after incubation with liver microsomes, NADPH, and GSH in a GSH concentration-dependent manner. Addition of human recombinant GSTA1, GSTA2, GSTM1, or GSTP1 protein to the incubation mixture further increased the GSH conjugates. However, the addition of GSTT1 did not show any catalytic effect. It is of interest that one of the reactive metabolites with a quinone structure was predominantly conjugated with GSH by GSTM1. Thus, we demonstrated that the GST isoforms contributed differently to the GSH conjugation of individual reactive metabolites of troglitazone, and GSTM1 is the most important GST isoform in the GSH conjugation of a specific reactive metabolite produced from the cytotoxic, quinone-form metabolite of troglitazone.

The thiazolidinedione (TZD) ring is a constituent of the glitazones that are used to treat type II diabetes. Liver injury has been reported following chronic glitazone use; however, they do not produce hepatic damage in common laboratory animal species. In contrast, 3-(3,5-dichlorophenyl)-2,4-thiazolidinedione (DCPT) causes hepatotoxicity in rats. DCPT toxicity is dependent upon the presence of an intact TZD ring and cytochrome P450 (CYP)-mediated biotransformation. To further investigate TZD ring-induced toxicity, DCPT and several structural analogues or potential metabolites were tested in vitro using wild type human hepatoma HepG2 and HepG2 cells stably transfected with the CYP3A4 isozyme. CYP3A4 activity was confirmed by measuring testosterone 6β-hydroxylation. Both cell lines were treated with 0-250 μM of the compounds in Hanks' balanced salt solution. Cell viability was measured after 24 h. DCPT and S-(3,5-dichlorophenyl)aminocarbonyl thioglycolic acid (DCTA) were the most toxic compounds of the series. Furthermore, DCPT was significantly more toxic in transfected cells (LC50=160.2±5.9 μM) than in wild type cells (LC50=233.0±19.7 μM). Treatment with a CYP3A4 inhibitor or inducer attenuated or potentiated DCPT cytotoxicity, respectively. These results suggest that DCPT-induced cytotoxicity in the transfected HepG2 cells is partially dependent on CYP3A4.

Toxicity assessment of botanical materials is difficult because they are typically complex mixtures of phytochemicals. In the present study, 16 phenolics were tested in both human (HepG2/C3A) and rat (MH1C1) hepatoma cells using a battery of eight toxicity endpoints. Cluster analysis was used to group the phenolics into four clusters for each cell type. Comparison of overall and individual liver activity of phenolics on both human and rat hepatoma cell lines showed significant differences for some endpoints. However, the cluster membership was similar across both cell types with the majority of phenolics clustering with the solvent control group (cluster 1). Each cell type produced a cluster of compounds with reported in vivo liver toxicity (cluster 2). Five herbal extracts were prepared and then tested as above. Using the cluster model developed with the phenolics, in the HepG2/C3A cells green tea was assigned to cluster 2 and the remaining four extracts to cluster 1. In the MH1C1 cells, green tea and thyme were assigned to cluster 2, cinnamon to cluster 4, and juniper berry and peppermint to cluster 1. The data suggest that this in vitro model may be useful for identifying hepatotoxic phenolics and botanical preparations rich in phenolics.

The knowledge base of drug-induced liver injury (DILI) continues to grow each year as additional drugs are identified as hepatotoxins. There is still a need to improve our ability to predict and diagnose DILI in the preclinical and post-approval settings.

This article presents the new and updated DILI registries for 2010, including the latest information on the causes and outcomes of non-acetaminophen DILI cases in the US Acute Liver Failure Study Group database. As DILI is still largely a diagnosis of exclusion, it is appropriate that causality assessment instruments are again the subject of considerable discussion.

DILI research remains extremely active including studies aimed at being better able to identify causative agents, utilize potential biomarkers, predict who is at greatest risk of injury and manage outcomes. With respect to identifying DILI risk factors at the genetic level, the field is rapidly approaching the day where 'personalized medicine' (based on pharmacogenomics) will become a reality. A large single-center series from India reminds us that geography can influence the drugs responsible for liver injury; however, Hy's law remains universal. As our DILI knowledge continues to grow, it remains essential to keep abreast of the important changes reported each year.