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©The Author(s) 2018. Published by Baishideng Publishing Group Inc. All rights reserved.
Analysis of the nitric oxide-cyclic guanosine monophosphate pathway in experimental liver cirrhosis suggests phosphodiesterase-5 as potential target to treat portal hypertension
Denise Schaffner, Adhara Lazaro, Peter Deibert, Peter Hasselblatt, Patrick Stoll, Lisa Fauth, Manfred W Baumstark, Irmgard Merfort, Annette Schmitt-Graeff, Wolfgang Kreisel
Denise Schaffner, Adhara Lazaro, Peter Deibert, Manfred W Baumstark, Institute for Exercise-und Occupational Medicine, Faculty of Medicine, University of Freiburg, Freiburg 79106, Germany
Denise Schaffner, Irmgard Merfort, Department of Pharmaceutical Biology and Biotechnology, University of Freiburg, Freiburg 79104, Germany
Peter Hasselblatt, Wolfgang Kreisel, Department of Medicine II, Gastroenterology, Hepatology, Endocrinology, and Infectious Diseases, Faculty of Medicine, University of Freiburg, Freiburg 79106, Germany
Patrick Stoll, Anaesthesiological Practice, Freiburg 79104, Germany
Lisa Fauth, Annette Schmitt-Graeff, Institute of Clinical Pathology, Faculty of Medicine, University of Freiburg, Freiburg 79106, Germany
Author contributions: Kreisel W and Deibert P designed the concept of the study; Schaffner D performed the experiments and statistical calculations and provided additional ideas; Lazaro A assisted in the laboratory experiments and in writing the manuscript; Hasselblatt P supervised the PCR study and helped in the interpretation of results; Stoll P supervised Schaffner D and Kreisel W in the initial performance the operative procedure for hemodynamic measurements; Fauth L performed the histological assessment of the degree of liver damage; Baumstark MW supervised the statistical calculations; Merfort I supervised the advanced training of Schaffner D; Schmitt-Graeff A performed and interpreted the immunohistochemical data; all authors contributed in writing the manuscript.
Institutional animal care and use committee statement: The animal research protocol was approved by the local institutional animal care and use committee (Regierungspräsidium Freiburg, Germany, ref. No. G-13/89). Animal care was performed in accordance to the rules of the German animal protection law and the animal care guidelines of the European community (2010/63/EU).
Conflict-of-interest statement: There was no conflict of interest.
Data sharing statement: No additional data are available.
ARRIVE guidelines statement: The ARRIVE Guidelines have been adopted.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Wolfgang Kreisel, MD, Emeritus Professor, Department of Medicine II, Gastroenterology, Hepatology, Endocrinology, and Infectious Diseases, Faculty of Medicine, University of Freiburg, Hugstetter Str. 55, Freiburg 79106, Germany. wolfgang.kreisel@uniklinik-freiburg.de
Telephone: +49-761-27034010 Fax: +49-761-27074880
Received: July 16, 2018
Peer-review started: July 16, 2018
First decision: August 1, 2018
Revised: August 3, 2018
Accepted: August 24, 2018
Article in press: August 24, 2018
Published online: October 14, 2018
AIM
To investigate the potential effect of inhibitors of phosphodiesterase-5 (PDE-5) for therapy of portal hypertension in liver cirrhosis.
METHODS
In the rat model of thioacetamide-induced liver fibrosis/cirrhosis the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway was investigated. Expression and localization of PDE-5, the enzyme that converts vasodilating cGMP into inactive 5’-GMP, was in the focus of the study. Hepatic gene expression of key components of the NO-cGMP pathway was determined by qRT-PCR: Endothelial NO synthase (eNOS), inducible NO synthase (iNOS), soluble guanylate cyclase subunits α1 and β1 (sGCa1, sGCb1), and PDE-5. Hepatic PDE-5 protein expression and localization were detected by immunohistochemistry. Serum cGMP concentrations were measured using ELISA. Acute effects of the PDE-5 inhibitor Sildenafil (0.1 mg/kg or 1.0 mg/kg) on portal and systemic hemodynamics were investigated using pressure transducers.
RESULTS
Hepatic gene expression of eNOS (2.2-fold; P = 0.003), sGCa1 (1.7-fold; P = 0.003), sGCb1 (3.0-fold; P = 0.003), and PDE-5 (11-fold; P = 0.003) was increased in cirrhotic livers compared to healthy livers. Overexpression of PDE-5 (7.7-fold; P = 0.006) was less pronounced in fibrotic livers. iNOS expression was only detected in fibrotic and cirrhotic livers. In healthy liver, PDE-5 protein was localized primarily in zone 3 hepatocytes and to a lesser extent in perisinusoidal cells. This zonation was disturbed in cirrhosis: PDE-5 protein expression in perisinusoidal cells was induced approximately 8-fold. In addition, PDE-5-expressing cells were also found in fibrous septa. Serum cGMP concentrations were reduced in rats with cirrhotic livers by approximately 40%. Inhibition of PDE-5 by Sildenafil caused a significant increase in serum cGMP concentrations [+ 64% in healthy rats (P = 0.024), + 85% in cirrhotic rats (P = 0.018)]. Concomitantly, the portal venous pressure was reduced by 19% in rats with liver cirrhosis.
CONCLUSION
Overexpression and abrogated zonation of PDE-5 likely contribute to the pathogenesis of cirrhotic portal hypertension. PDE-5 inhibition may therefore be a reasonable therapeutic approach for portal hypertension.
Core tip: A constriction of sinusoids plays an important role in the pathogenesis of cirrhotic portal hypertension, wherein the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway plays a pivotal role. In a rat model of liver cirrhosis phosphodiesterase-5 (PDE-5) was markedly overexpressed both on the mRNA and the protein level. PDE-5 converts the vasodilating cGMP to inactive 5’-GMP. In healthy liver a zonation of PDE-5 was found which is abrogated in cirrhosis. Serum cGMP was reduced in cirrhosis. Inhibition of PDE-5 by Sildenafil normalized serum cGMP levels and lowered portal venous pressure. Hence, the inhibition of PDE-5 may be a promising adjunct in portal hypertension therapy.
