The Protective Effect And Mechanism Of Rapamycin On Liver Injury In Rat Sepsis Model

Objective: Marked oxidative stress has been found to play a crucial role in thesepsis-induced liver injury. Rapamycin, an inhibitor of the mammalian target ofrapamycin (mTOR), has been recently shown to regulate the oxidative stress. Thisstudy was to examine the protective effect and mechanism of rapamycin in hepaticinjury induced by sepsis in rat model.Methods: Rats were randomized to four groups: control(10mice), sepsis(10mice),sepsis plus rapamycin(20mice), sepsis plus PBS (20mice).Sepsis rat models werecaused by cecal ligation and puncture(CLP), and subjected to rapamycin(1mg/kg/d) orPBS(1mg/kg/d) treatment. The serum level of alanine transaminase(ALT), aspartateamino transferase(AST) and8-hydroxy-2’-deoxyguanosine (8-OHdG) were detectedby end-point method and enzyme linked immunosorbent assay(ELISA),respectly.Livers tissue were homogenized to10%homogenate and subjected to measure theamount of superoxide dismutase(SOD), glutathione peroxidase(GSH-Px), catalase(CAT) and malonaldehyde(MDA). The expression of mTOR、S6K、p-S6K、AKT andp-AKT were detected by Western-blot.The liver HepG2cells pretreated withrapamycin with different levels（0，10，20，40μM）for4hours were exposed to200μM hydrogen peroxide(H2O2). The intracellular reactive oxygen species (ROS) wasmeasured by dichlorodihydro-fluorescein diacetate (DCFH-DA) method. The levelsof MDA and SOD were determined by ELISA. The expression of p-S6K and p-AKTwere detected by Western-blot.Results: Compared to the sham-operation group, the serum level of ALT, AST and 8-OHdG were significantly increased, while the liver levels of SOD, GSH-Px andCAT were significantly decreased in sepsis rat induced by CLP. The activity of MDAin liver tissue was increased in sepsis rat. Although the expression of S6K and AKTwere not changed, the levels of mTOR, p-S6K and p-AKT were significantlyincreased in sepsis rat according to the results of Western-blot. The serum level ofALT, AST and8-OHdG were obviously decreased by rapamycin treatment. Inaddition, rapamycin treatment upregulated the activity of SOD, GSH-Px and CAT,while decreased the expression of MDA、p-S6K and p-AKT. Compared with theHepG2cells treated with H2O2alone, rapamycin significantly reduced H2O2-induced intracellular ROS and MOD content, while increased the expression of SODin the treated cells in a content-dependent manner. In addition, rapamycin reducedH2O2-induced activity of p-S6K and p-AKT in the treated cells.Conclusions: Rapamycin plays a protective role for liver injury in experimentalsepsis induced by CLP via decreasing oxidative stress and mTOR/S6K/AKTpathways.