PI3K/Akt signaling pathway-induced heme oxygenase-1 upregulation mediates the adaptive cytoprotection of hydrogen peroxide preconditioning against oxidative injury in PC12 cells.

Both the phosphatidylinositol 3-kinase (PI3K)/Akt pathway and heme oxygenase-1 (HO-1) create a survival signal against oxidative stress-induced injuries. Although we have demonstrated that hydrogen peroxide (H2O2) preconditioning confers adaptive cytoprotection against oxidative stress-induced injury in PC12 cells, it remains unknown whether these defense systems are involved in the protective effect of H2O2 preconditioning. In the current study, PC12 cells were preconditioned with 100 µM H2O2 for 90 min, followed by 24 h recovery and subsequent exposure to 300 µM H2O2 for further 12 h. The findings showed that preconditioning with 100 µM H2O2 upregulated HO-1 expression. Zinc protoporphyrin IX (ZnPP), a selective inhibitor of HO-1, at a concentration of 15 µM, significantly attenuated H2O2 preconditioning-elicited cytotoxicity, apoptosis, oxidative stress and mitochondrial membrane potential (ΔΨm) loss in PC12 cells. In addition, H2O2 preconditioning enhanced phosphorylation of Akt. Treatment with 25 µM LY294002, a selective inhibitor of PI3K, for 20 min before H2O2 preconditioning blocked not only H2O2 preconditioning-induced HO-1 induction, but also the protective effect of H2O2 preconditioning against cytotoxicity. The present study provides novel evidence for the effect of preconditioning with H2O2 on the induction of HO-1, which contributes to the adaptive cytoprotection of H2O2 preconditioning against oxidative stress-induced cellular injury via a PI3K/Akt-dependent mechanism in PC12 cells.