Nitric oxide as an upstream signal of p38 mediates hypoxia/reoxygenation-induced neuronal death.

Nitric oxide (NO) and p38 have been shown to be involved in the ischemia/hypoxia-induced neuronal injury. In this study, we examined the activation patterns of mitogen-activated protein kinases and explored the relationship between NO and p38 in a model of hippocampal neuronal death induced by hypoxia/reoxygenation (H/R). p38 activity increased robustly during hypoxia and after reoxygenation, while the increase of c-Jun amino-terminal kinase and extracellular signal-related kinase activities showed mild tendency. Inhibition of p38 with SB203580 or SB202190 rescued neuronal death, whereas inhibition of extracellular signal-related kinases with PD98059 or c-Jun amino-terminal kinases with SP600125 offered no protection. p38 inhibitors also reduced neuronal death induced by the NO donor S-nitrosoglutathione. L-NAME, a nonspecific NO synthase inhibitor, blocked the p38 activation and rescued H/R-induced neuronal death. These results suggest that NO is an upstream signal of p38 that mediates the H/R-induced neuronal death.