Hydrogen peroxide preconditioning protects PC12 cells against apoptosis induced by oxidative stress

Oxidative stress can induce significant cell death by apoptosis. We explore whether prior exposure to H2O 2 (H2O 2 preconditioning) protects PC12 cells against the apoptotic consequences of subsequent oxidative damages and what role the ATP- sensitive potassium (KATP) channels play in the preconditioning protection. PC12 cells were preconditioned with 90 min exposure to H2O2 at 10 µmol/L, followed by 24-h recovery and subsequent exposures to different concentrations (20, 30, 50 and 100 µmol/L) of H2O2 for 24 h respectively. We used PI staining flow cytometry (FCM) to observe the apoptosis of PC12 cells. It was shown that 24-h exposures to H2O2 at 20, 30, 50 and 100 µmol/L respectively induced substantial cell apoptosis, which was greatly prevented in the preconditioning cells, indicating that H2O2 preconditioning protected PC12 cells against apoptosis induced by H2O2. Administration of pinacidil (10 µmol/L), an KATP channel activator, significantly attenuated the apoptosis of PC12 cells induced by H2O2 at 30 and 50 µmol/L for 24 h respectively. Glybenclamide (10 µmol/L), a KATP channel inhibitor, significantly suppressed or abolished the protective effects caused by the pinacidil but not by H2O2 preconditioning. However, when both H2O2 preconditioning and pinacidil were co- applied, their protection against the apoptosis of PC12 cells was much stronger than that of the individual one of them. These results suggest that H2O2 preconditioning protects PC12 cells against apoptosis and that the activation of KATP channels is not involved in, but synergetically enhances adaptive protection of H2O2 preconditioning.