The Role And Underlying Mechanism Of Combined Ischemic And Rapamycin Preconditioning In Regulating Liver Ischemia And Reperfusion Injury In Aged Mice

OBJECTIVE: Old livers are more damaged by hepatic ischemia and reperfusion injury(IRI)than young livers.The aim of this study was to investigate the role and underlying mechanism of ischemic and rapamycin preconditioning in regulating IR injury in old livers.METHODS: Young(8-week-old)and aged(60-week-old)mice were subjected to IR or a sham control procedure.The aged mice were randomly divided into six groups: IR(CON-IR),IR with ischemic preconditioning(IPC-IR),IR with rapamycin preconditioning(RAPA-IR),IR with combined ischemic and rapamycin preconditioning(IPC+RAPA-IR),IR with 3-methyladenine(3-MA-IR),IR with combined ischemic and rapamycin preconditioning with 3-MA pretreatment(IPC+RAPA+3-MA-IR).Mouse serum and liver tissues were collected and liver injury was evaluated 6 h after reperfusion.Hepatocellular autophagy induction was also analyzed by western blot.RESULTS: The results revealed that aged mice had aggravated liver IR injury as compared to young mice(P<0.05).In aged mice following IR,IPC+RAPA but not IPC or RAPA alleviated liver injury,as evidenced by lower levels of serum ALT(P<0.05),improved preservation of liver architecture with lower Suzuki scores(P<0.05),and decreased caspase-3 activity compared with CON(P<0.05).In addition,western blot analysis revealed that IPC or RAPA had no significant effects on the protein levels of LC3 B II and p62 as compared to control group.In contrast,increased LC3 B II but decreased p62 protein expression levels was found in the IPC+RAPA group(P<0.05),indicating that autophagic flux was restored by combined ischemic and rapamycin preconditioning.Furthermore,autophagy inhibition by the inhibitor 3-MA abrogated the protective role in the IPC+RAPA group,while no significant effects were observed in the CON group(P<0.05).CONCLUSIONS: Our results demonstrated that aging aggravated liver IR injury by suppressing hepatocyte autophagy.Combined ischemic and rapamycin preconditioning protected old livers against IR injury by restoring hepatocyte autophagy activation.