The Coagulation System Contributes to αVβ6 Integrin Expression and Liver Fibrosis Induced by Cholestasis

Abstract

Chronic injury to intrahepatic bile duct epithelial cells (BDECs) elicits expression of various mediators,including the ␣V␤6 integrin, promoting liver fibrosis. We tested the hypothesis that tissue factor (TF)-dependent thrombin generation and protease activated receptor-1 (PAR-1) activation contribute to liver fibrosis induced by cholestasis via induction of ␣V␤6 expression. To test this hypothesis, mice deficient in either TF or PAR-1 were fed a diet containing 0.025% ␣-naphthylisothiocyanate (ANIT), a BDEC-selective toxicant. In genetically modified mice with a 50% reduction in liver TF activity fed an ANIT diet, coagulation cascade activation and liver fibrosis were reduced. Similarly, liver fibrosis was significantly reduced in PAR-1 ؊/؊ mice fed an ANIT diet. Hepatic integrin ␤6 mRNA induction, expression of ␣V␤6 protein by intrahepatic BDECs, and SMAD2 phosphorylation were reduced by TF deficiency and PAR-1 deficiency in mice fed the ANIT diet. Treatment with either an anti-␣V␤6 blocking antibody or soluble transforming growth factor-␤ receptor type II reduced liver fibrosis in mice fed the ANIT diet. PAR-1 activation enhanced transforming growth factor-␤1-induced integrin ␤6 mRNA expression in both transformed human BDECs and primary rat BDECs. Interestingly, TF and PAR-1 mRNA levels were increased in livers from patients with cholestatic liver disease. These results indicate that a TF-PAR-1 pathway contributes to liver fibrosis induced by chronic cholestasis by increasing expression of the ␣V␤6 integrin, an important regulator of transforming growth factor-␤1 activation.

The Antifibrinolytic Drug Tranexamic Acid Reduces Liver Injury and Fibrosis in a Mouse Model of Chronic Bile Duct Injury

“…Vehicle-treated mice fed ANIT diet for 2 weeks developed liver injury characterized by multifocal acute hepatocellular coagulative necrosis and inflammation (six of seven mice), mild peribiliary fibrosis, and moderate lymphocytic inflammation/bile duct epithelial hyperplasia (seven of seven mice) (Fig. 2, A and B), in agreement with previous studies (Tjandra et al, 2000;Lesage et al, 2001;Sullivan et al, 2010). Treatment with TA reduced liver necrosis and inflammation in mice fed ANIT diet (Fig.…”

“…Peribiliary fibrosis and induction of several profibrogenic genes are evident in livers of mice fed ANIT for 2 weeks (Sullivan et al, 2010). We chose to evaluate the expression of mRNAs encoding gene products ANIT diet-fed mice treated with vehicle (n = 5 mice) or TA (1200 mg/kg i.p.)…”

“…Fibrin, type 1 collagen, and cytokeratin-19 (CK19) immunostaining and quantification were performed as described previously (Sullivan et al, 2010). In brief, approximately 10 low-power images (100Â) for each tissue section were captured in a random and masked fashion and were analyzed using ImageJ (rsbweb.nih.gov/ij/).…”

“…Transport of ANIT into the bile by hepatocytes injures intrahepatic BDECs (Dietrich et al, 2001), and exposure of mice to ANIT in the diet causes compensatory biliary hyperplasia, elevation in serum bile acids, portal lymphocytic inflammation, and mild to moderate hepatocellular injury (Tjandra et al, 2000;Xu et al, 2004;Sullivan et al, 2010;Golbar et al, 2013). Prolonged ANIT exposure in mice models progressive liver fibrosis characterized by exaggerated peribiliary collagen deposition (Tjandra et al, 2000;Xu et al, 2004;Sullivan et al, 2010;Golbar et al, 2013). BDEC injury in this model is associated with tissue factor-dependent activation of the blood coagulation cascade and increased plasma levels of the coagulation protease thrombin (Sullivan et al, 2010).…”

“…Prolonged ANIT exposure in mice models progressive liver fibrosis characterized by exaggerated peribiliary collagen deposition (Tjandra et al, 2000;Xu et al, 2004;Sullivan et al, 2010;Golbar et al, 2013). BDEC injury in this model is associated with tissue factor-dependent activation of the blood coagulation cascade and increased plasma levels of the coagulation protease thrombin (Sullivan et al, 2010). This increase in thrombin activity is associated with the deposition of insoluble fibrin clots in livers of mice fed ANIT diet (Luyendyk et al, 2011).…”