Introduction: Liver ischemia reperfusion injury (IRI) is a common cause of liver graft nonfunction or function failure post transplantation. It is also a main reason which restricts the use of marginal liver donors. The mechanisms of liver IRI is very complicated and have no effective method for prevention and treatment yet. In this study, we aim to explore the protective effects of trypsin inhibitor Ulinastatin (UTI) on liver graft IRI and the underlying mechanisms.

Materials and Methods: In bred C57BL/6 mouse and liver cold IRI and orthotopic transplantation models were established. The liver injury score and functions were evaluated by liver ALT, AST, LDH enzyme release and histological examination. The apoptosis of hepatocyte was detected by TUNEL staining and the cytokines were detected by western blot and QT-PCR methods.

Results: UTI supplementation to the perfusion and preservative LR solutions significantly protects the liver from cold ischemia injury. The apoptosis and Caspase-3 and Bax gene expression of liver grafts were reduced and Bcl-2 was increased significantly in UTI treated groups. The cytokines IL-6, TNF-α, and IFN-γ expression were reduced, but IL-10 expression was increased significantly in the liver grafts of UTI groups. Moreover, the liver grafts with extended cold preservation time of 1 hour in the UTI supplemented LR solution demonstrated improved graft survival time post transplantation.

Conclusions: UTI treatment prevents liver from cold IRI significantly and improves liver graft survival with the donors from extended cold preservation time. The underlying mechanisms of UTI on liver IRI may be mediated by inhibition of proinflammatory cytokines, increasing anti-apoptotic gene Bcl-2 and decreasing pro-apoptosis genes of Caspase-3 and Bax expression, and further protects hepatocytes from apoptotic death and improves the liver function.