To probe the protective effect and immunologic mechanisms of ischemia preconditioning on rats hepatic ischemia reperfusion (HIR) injury.

Eighty rats were divided randomly into five groups: sham operation (A), 20 min hepatic ischemia (B), 30 min hepatic ischemia (C), 40 min hepatic ischemia (D), and ischemia preconditioning 30 min before hepatic ischemia (E). And there were two subgroups in each group: 2-hour (n=8) and 24-hour (n=8) reperfusion after ischemia, respectively. The 24 h survival rates after reperfusion were observed. The peripheral blood was collected for measuring the levels of ALT, AST, IL-10 and IL-12. T lymphocytes, in particular regulatory T cells, were measured by flow cytometry. Liver tissues were obtained for pathological examination.

With hepatic ischemic time prolonged, the serum levels of ALT and AST increased significantly, and more inflammatory cells infiltered in the liver. The 24-hour-reperfusion survival rates in 20 min, 30 min and 40 min hepatic ischemia groups were 100%, 62.5% and 37.5%, respectively. Two hours after reperfusion in group D, IL-12 level and the proportion of CD8+ T lymphocyte were increased, while IL-10 level and the proportion of CD4+/CD8+ and Treg cells were decreased significantly. Twenty four hours after reperfusion, parameters of group B were close to the levels of sham operation group. On the contrary, in group D, IL-10 level, CD4+T lymphocytes, Treg cells and CD4+/CD8+ were still increased significantly with IL-12 levels descended remarkably. Ischemia preconditioning effectively decreased ALT, AST serum level and severity of liver pathological injury after HIR, and resulted in the high level of survival rates. Furthermore, ischemia preconditioning induced Treg cells and IL-10 level increasing, and IL-12 decreasing 2 hours after reperfusion. However, all parameters in group E were close to level of sham operation group 24 hours after reperfusion.

HIR can induce the dysfunction of T lymphocytes, in particular Treg cells and cytokines with liver injury, even death. Ischemia preconditioning can prevent HIR injury, increase Treg proportion in the early reperfusion and prevent immune dysfunction.