Essential role for nuclear factor κB in ischemic preconditioning for ischemia-reperfusion injury of the mouse liver

Background. Ischemic preconditioning protects various organs from subsequent ischemic insult, but the precise mechanisms underlying this phenomenon re main undefined. To investigate the molecular mechanism by which ischemic preconditioning exerts it protective effect, we examined the activity of the transcription. factor nuclear factor (NF)-kappaB and subsequent inflammatory gene expression. Methods. Mice were used for total hepatic ischemia reperfusion experiments after subcutaneous transposition of the spleen. Mouse liver was subjected to ischemia for 70 min followed by reperfusion for defined times. Ischemic preconditioning that consisted of V min of ischemia and 20 min of reperfusion was per formed before 70 min of ischemia. NF-kappaB activity was analyzed by electrophoretic mobility shift assay, an the protein and tyrosine phosphorylation. levels of in hibitor kappaB-alpha were assessed by Western blot analysis Semiquantitative reverse-transcriptase polymerase chain reaction was used to analyze tumor necrosis factor (TNF)-alpha and intercellular adhesion molecule 1 m-RNA levels. Results. NF-kappaB was activated within 30 min after initiation of reperfusion and remained activated for 4 hr. Ischemic preconditioning attenuated NF-kappaB activation after subsequent prolonged ischemia and reperfusion and simultaneously decreased the expression of TNF-alpha and intercellular adhesion molecule 1 mRNA, the former statistically significantly (P<0.05) Tyrosine phosphorylation of inhibitor kappaB-alpha was de creased in ischemic preconditioned liver. Conclusions. These results indicate that attenuation of NF-kappaB activation and subsequent reduction in TNF-alpha mRNA expression after sustained ischemia play important roles in the protective mechanism of ischemic preconditioning against hepatic ischemia-reperfusion injury.