Mild hypothermia exerts a protective effect against hepatic ischemia-reperfusion injury in rats by activating the PI3K/Akt signaling pathway

Objective To investigate the protective mechanism of mild hypothermia pretreatment against hepatic ischemia-reperfusion injury in rats. Methods A total of 40 male Sprague-Dawley rats were randomly divided into sham-operation group ( Sham group) , hepatic ischemia-reperfusion injury group ( HIRI group) , mild hypothermia group ( MH group) , and mild hypothermia + LY294002 group ( MH +LY group) , with 10 rats in each group. Serum and liver tissue samples were collected at 3, 6, 12, and 24 hours of hepatic ischemia-reperfusion. Western blotting was used to measure the protein expression of phosphoinositide 3-kinase ( PI3 K) , phosphorylated PI3 K ( p-PI3 K) , protein kinase-B ( Akt) , and phosphorylated Akt ( p-Akt, Ser308) in liver tissue. TUNEL and Western blotting were used to measure cell apoptosis and expression of apoptosis-related proteins in liver tissue. ELISA was used to measure the levels of superoxide dismutase ( SOD) , glutathione peroxidase ( GSH-Px) , and malondialdehyde ( MDA) in liver tissue. An automatic biochemical analyzer was used to measure the activities of alanine aminotransferase ( ALT) and aspartate aminotransferase ( AST) in serum. A one-way analysis of variance was used for comparison between multiple groups, and the SNK-q test was used for further comparison between two groups.Results The HIRI group had significantly lower relative expression levels of p-PI3 K and p-Akt than the Sham group ( q = 5. 217 and5. 456, both P < 0. 01) , and the MH group had significantly higher relative expression levels of p-PI3 K and p-Akt in liver tissue than the HIRI group ( q = 10. 434 and 14. 116, both P < 0. 01) . At 3, 6, 12, and 24 hours of hepatic ischemia-reperfusion, the HIRI group, the MH group, and the MH + LY group had significantly higher activities of AST and ALT in serum than the Sham group ( all P < 0. 001) .TUNEL staining showed that the HIRI group had a significantly higher proportion of apoptotic cells in liver tissue than the Sham group ( 42. 25% ± 3. 50% vs 3. 21% ± 0. 5%, q = 10. 187, P < 0. 01) . Compared with the HIRI group, the MH group had a significant reduction in the proportion of apoptotic cells ( q = 7. 784, P < 0. 01) , while there was no significant difference in the proportion of apoptotic cells between the HIRI group and the MH + LY group ( 42. 25% ± 3. 50% vs 38. 19% ± 2. 8%, q = 1. 059, P > 0. 05) . Western blotting showed that compared with the Sham group, the HIRI group had a significant reduction in the expression of the anti-apoptotic protein Bcl-2 ( q =2. 101, P < 0. 05) and significant increases in the expression of the pro-apoptotic proteins Bax, Fas, and Fasl ( q = 11. 016、4. 735, and10. 201, all P < 0. 01) , and the regulatory effect of HIRI on apoptotic-related proteins was downregulated by mild hypothermia treatment.According to the results of oxidative indices, the HIRI group, the MH group, and the MH + LY group had significantly lower expression of SOD and GSH-Px and significantly higher expression of MDA in liver tissue than the Sham group ( all P < 0. 05) ; compared with the HIRI group, the MH group had significantly higher expression of SOD and GSH-Px ( q = 2. 894 and 2. 731, both P < 0. 05) and significantly lower expression of MDA ( q = 5. 888, P < 0. 05) in liver tissue. In addition, mild hypothermia + LY294002 treatment significantly reduced the regulatory effect on the expression of SOD, MDA, and GSH-Px in liver tissue in the MH group ( q = 2. 999, 2. 944, and 2. 620, all P < 0. 05) . Conclusion MH exerts a protective effect against HIRI in rats, possibly by activating the PI3 K/Akt pathway to downregulate hepatocyte apoptosis and enhance antioxidant capacity in vivo.