Liver fibrosis is driven by protease‐activated receptor‐1 expressed by hepatic stellate cells in experimental chronic liver injury

Abstract

Background Blood coagulation protease activity is proposed to drive hepatic fibrosis through activation of protease‐activated receptors (PARs). Whole‐body PAR‐1 deficiency reduces experimental hepatic fibrosis, and in vitro studies suggest a potential contribution by PAR‐1 expressed by hepatic stellate cells. However, owing to a lack of specific tools, the cell‐specific role of PAR‐1 in experimental hepatic fibrosis has never been formally investigated. Using a novel mouse expressing a conditional PAR‐1 allele, we tested the hypothesis that PAR‐1 expressed by hepatic stellate cells contributes to hepatic fibrosis. Methods PAR‐1 flox/flox mice were crossed with mice expressing Cre recombinase controlled by the lecithin retinol acyltransferase (LRAT) promoter, which induces recombination in hepatic stellate cells. Male PAR‐1 flox/flox /LRATCre and PAR‐1 flox/flox mice were challenged twice weekly with carbon tetrachloride (CCl 4 , 1 mL/kg i.p.) for 6 weeks to induce liver fibrosis. Results PAR‐1 mRNA levels were reduced (>95%) in hepatic stellate cells isolated from PAR‐1 flox/flox /LRATCre mice. Hepatic stellate cell activation was evident in CCl 4 ‐challenged PAR‐1 flox/flox mice, indicated by increased α‐smooth muscle actin labeling and induction of several profibrogenic genes. CCl 4 ‐challenged PAR‐1 flox/flox mice displayed robust hepatic collagen deposition, indicated by picrosirius red staining and type I collagen immunolabeling. Notably, stellate cell activation and collagen deposition were significantly reduced (>30%) in PAR‐1 flox/flox /LRATCre mice. Importantly, the reduction in liver fibrosis was not a consequence of reduced acute CCl 4 hepatotoxicity in PAR‐1 flox/flox /LRATCre mice. Conclusions The results constitute the first direct experimental evidence that PAR‐1 expressed by stellate cells directly promotes their profibrogenic phenotype and hepatic fibrosis in vivo .

Coagulome and the tumor microenvironment: an actionable interplay

“…This particularity defines CAFs as sensors of extravascular coagulation, especially in the context of chronic inflammation, prone to fibrosis and malignant transformation [94]. Liver fibrosis, an established precancerous state, highlights the role of PAR1 in collagen I deposition [95,96]. Thrombin can also stimulate the release of active TGF-β [97].…”

Antisense Tissue Factor Oligodeoxynucleotides Protected Diethyl Nitrosamine/Carbon Tetrachloride-Induced Liver Fibrosis Through Toll Like Receptor4-Tissue Factor-Protease Activated Receptor1 Pathway

“…In chronic liver disease, HSCs express upregulated PAR1 ( Fiorucci et al, 2004 ). Furthermore, it was found that removal of stellate cell-specific PAR1 produced a 35% reduction in the accumulation of liver collagen ( Poole et al, 2020 ) and PAR1 deficient mice appeared to be protected from CCl4-induced liver fibrosis ( Rullier et al, 2008 ; Kallis et al, 2014 ). In the line with these findings, the current study showed that PAR1 expression was significantly increased in the DEN+CCl4 intoxicated rats.…”

Bile acid-induced tissue factor activity in hepatocytes correlates with activation of farnesoid X receptor

“…Coagulation also plays a role in chronic liver injury; the fenestrated sinusoidal endothelial cells allow plasma flow from sinusoidal blood into the space of Disse [8], thereby granting contact of clotting factors with hepatocytes and cholangiocytes and facilitating local hemostatic action. Several studies demonstrate the role of hepatic coagulation activation in the pathology of liver fibrosis [13][14][15]. The key enzyme of coagulation is thrombin, which is generated by hepatocytes in a cholestatic setting in vivo and converts fibrinogen leading to fibrin deposits within the liver parenchyma [16].…”

“…The key enzyme of coagulation is thrombin, which is generated by hepatocytes in a cholestatic setting in vivo and converts fibrinogen leading to fibrin deposits within the liver parenchyma [16]. However, the predominant mechanism of thrombin-induced liver injury is caused by protease-activated receptors (PARs) on neutrophils and hepatic stellate cells which mediate neutrophil activation and induction of profibrotic mediators [15,17].…”