Obeticholic acid, a farnesoid-X receptor agonist, improves portal hypertension by two distinct pathways in cirrhotic rats
Len D. Verbeke1,Ricard Farre2, Jonel Trebicka3, Mina Komuta4, Tania Roskams4, Sabine Klein3, Ingrid Vander Elst1, Petra Windmolders1, Tim Vanuytse2l, Frederik Nevens1, Wim Laleman1
1Department of Liver and Biliopancreatic disorders, University of Leuven, Leuven, Belgium; 2Translational Research Center for Gastrointestinal Disorders,University of Leuven, Leuven, Belgium; 3Department of Internal Medicine I, University of Bonn, Bonn, Germany; 4Departments of Morphology and Molecular Pathology, Translational Cell and Tissue Research, University hospitals Leuven, Leuven, Belgium
Study purpose: The farnesoid-X-receptor (FXR) is a nuclear bile acid receptor involved in bile acid homeostasis, hepatic and intestinal inflammation, liver fibrosis and cardiovascular disease. We studied the effect of short-term treatment with obeticholic acid (INT-747), a potent selective FXR agonist, on intrahepatic hemodynamic dysfunction and signaling pathways in different rat models of cirrhotic portal hypertension. Methods: Thioacetamide (TAA)-intoxicated and bile duct ligated (BDL) rats were used as models. After gavage of 2 doses of 30mg/kg INT-747 or vehicle within 24 hours, in vivo hemodynamics were assessed. Additionally, we evaluated the direct effect of INT-747 on total intrahepatic vascular resistance (IHVR) and intrahepatic vascular tone (endothelial dysfunction and hyperresponsiveness to methoxamine) by means of an in-situ liver perfusion system and on hepatic stellate cell contraction in vitro. FXR-expression and involved intrahepatic vasoactive pathways (e. g. endothelial nitric oxide synthase: eNOS, Rho-kinase, dimethylarginine dimethylaminohydrolase: DDAH) were analyzed by immunohistochemistry, RT-PCR or Western Blot. Results: In both cirrhotic models, FXR expression was heavily decreased. Immunohistochemically, this coincided with a disappearance of the typical FXR hepatocytic nuclear staining pattern seen in healthy livers. Treatment with INT-747 in TAA and BDL reactivated the FXR downstream signaling pathway and decreased portal pressure without deleterious systemic hypotension (portal pressure decreased from 13.8 ± 0, 6 mm Hg to 11.6 ± 0, 8 mm Hg in TAA, P=0.045, n=14 and from 12.3 ± 0, 8 mm Hg to 10.1 ± 0, 6 mm Hg in BDL, P=0.037, n=15). This was related to a decrease in total intrahepatic vascular resistance during liver perfusion (relative decrease in IHVR after INT747 treatment in TAA: −8.06 ± 0.69%, P<0.001, n=10 and in BDL: −21.8 ± 2.50%, P<0.001, n=10). In the perfused TAA and BDL cirrhotic liver, INT-747 improved endothelial vasorelaxation capacity but not hyperresponsiveness. In both groups, this was associated with an increased eNOS-activity which in TAA related to down-regulation of the Rho-kinase pathway and in BDL to up-regulation of DDAH-2.Furthermore, INT-747 induced a dose-dependent relaxation of cultured rat primary hepatic stellate cells in vitro. Conclusion: FXR-agonist INT-747 improves portal hypertension in 2 different rat models of cirrhosis by decreasing the IHVR. This hemodynamic effect relates to restoration of endothelial dysfunction by increased intrahep-atic eNOS-activity. The mechanisms of eNOS activity increase differ depending on the etiology of cirrhosis.
Frederik Nevens - Grant/Research Support: Ipsen, Roche, MSD, Astellas, CAF
The following people have nothing to disclose: Len D. Verbeke, Ricard Farre, Jonel Trebicka, Mina Komuta, Tania Roskams, Sabine Klein, Ingrid Vander Elst, Petra Windmolders, Tim Vanuytsel, Wim Laleman