Protective effect of H2O2 against subsequent H2O2-induced cytotoxicity involves activation of the PI3K-Akt signaling pathway

Abstract

Preconditioning of sublethal ischemia implies a cytoprotective mechanism against subsequent ischemia-induced cell death; however, the precise mechanism by which preconditioning protects against ischemic injury is not known. In the present study, we clarified whether pretreatment with a sublethal concentration of H2O2 could counter subsequent H2O2-induced cytotoxicity and also investigated the mechanisms of the cytoprotective effect of a sublethal concentration of H2O2. Using the MTT reduction assay and Calcein-AM staining assay, we showed that pretreatment with H2O2 (10 μM, 24 hr) of COS7 cells partially protected cells against subsequent H2O2 (6 mM, 1 hr) -induced cytotoxicity. The phosphorylation of Akt/PKB, a downstream target of phosphatydylinositol-3 kinase (PI3K), at Ser473 was augmented by H2O2 (10 μM) administration. This augmentation peaked at 10 minutes after H2O2 (10 μM) treatment and fell to the basal level at 24 hr. A blocker of PI3K, LY294002, significantly attenuated H2O2 (10 μM, 24 hr) -induced cytoprotection. In addition, pretreatment with LY294002 reduced H2O2 (10 μM, 10 min) -induced phosphorylation of Akt at Ser473. These findings suggest that a sublethal concentration of H2O2 exerts a cytoprotective effect against subsequent H2O2-induced cell death and that this cytoprotective effect of H2O2 is mediated by activation of the PI3K-Akt signaling pathway.