Inducible nitric oxide synthase and cyclooxgenase-2 mediate protection of hydrogen peroxide preconditioning against apoptosis induced by oxidative stress in PC12 cells

The induction of inducible nitric oxide synthase (iNOS) in response to different stress is associated with simultaneous induction of cyclooxygenase-2 (COX-2) in various cell types. Both iNOS and COX-2 have been reported to mediate the late phase of cardioprotection induced by different preconditioning. However, whether both iNOS and COX-2 are mediators in the neuroprotection induced by preconditioning with hydrogen peroxide (H2O2) at low concentration is unknown. In this study, using the neurosecretory cell line-PC12 cells to set up the model of neuroprotection of preconditioning with H2O2 against apoptosis, we first investigate what changes in expression of iNOS and COX-2 appear during H2O2 preconditioning, then determine if both iNOS inhibitor and COX-2 inhibitor interfere with the neuroprotection elicited by preconditioning with H2O2. We found that preconditioning with H2O2 at 10 μM significantly protected PC12 cells against apoptosis induced by lethal H2O2 (50 μM) and increased the expression of iNOS and COX-2 and that selective iNOS inhibitor, aminoguanidine (AG) and COX-2 inhibitor, NS-398 obviously blocked the protective effects induced by preconditioning with 10 μM H2O2. The results of this study suggest that both iNOS and COX-2 are mediators of the neuroprotection induced by preconditioning with oxidative stress (H2O2 at low concentration) in PC12 cells.