Selective inhibition of the thrombin receptor protease-activated receptor-1 attenuates hepatic ischemia-reperfusion injury in mice

Introduction: Development of liver diseases is associated with blood coagulation cascade, whose activation results in a generation of thrombin. Thrombin not only cleaves fibrinogen, but also triggers intracellular signaling in numerous hepatic nonparenchymal cells through an activation of the protease-activated receptor-1 (PAR-1). This activation has been shown to drive multiple liver pathologies including hepatic inflammation and hepatocellular injury. However, there have been few studies on the thrombin activation of PAR-1 during hepatic ischemia-reperfusion injury (IRI). This study focused on the thrombin activation of PAR-1 and researched whether vorapaxar, selective PAR-1 inhibitor, could attenuate hepatic IRI. Materials and methods: Using 60-min partial hepatic IRI model of mice, PAR-1 expression and plasma thrombin-antithrombin complex (TAT) levels were evaluated. Additionally, IRI mice were divided into the two groups: the one received intraperitoneal administration with vorapaxar (0.005mg/kg) twice before and after reperfusion and the other without it. Results: PAR-1 was expressed on sinusoidal endothelial cells in liver. PAR-1 expression and plasma TAT levels, which were equivalent to thrombin levels, were significantly increased after IRI compared to naïve liver (PAR-1/βactin: 2.45vs1.49, p=0.05; TAT: 4.946vs.0.336 ng/ml, p=0.002) (Figure). At 4 hours after reperfusion, vorapaxar significantly improved serum transaminase levels and histological liver damage (AST: 2194vs.3113, p=0.046; Suzuki's score: 3.3vs.6.7, p=0.006). Furthermore, vorapaxar markedly attenuated recruitment of neutrophil (Ly6G: 9vs.32/HPF, p=0.003) and decreased TNFα expression (1.27vs.3.46, p=0.032). Conclusion: Hepatic IRI increased a generation of thrombin, whose activation of PAR-1 drove hepatic inflammation and hepatocellular injury. Selective inhibition of PAR-1 by vorapaxar significantly attenuated hepatic IRI.