Activation of p38 MAPK induced peroxynitrite generation in LPS plus IFN-γ-stimulated rat primary astrocytes via activation of NOS and NADPH oxidase

We have shown that immuno stimulated astrocytes produce excess nitric oxide (NO) and eventually peroxynitrite (ONOO-) that was closely associated with the glucose deprivation-potentiated death of astrocytes. The present study shows that activated p38 MAPK regulates ONOO- generation from lipopolysaccharide (LPS) plus interferon-gamma (IFN-gamma)-stimulated astrocytes. LPS + IFN-gamma-induced p38 MAPK activation and ONOO- generation were attenuated by SB203580 or SKF-86002, specific inhibitors of p38 MAPK. ONOO- generation was blocked by NADPH oxidase inhibitor, diphenyleneiodonium chloride, and nitric oxide synthase (NOS) inhibitor, N omega-nitro-L-arginine methyl ester, suggesting both enzymes are involved in ONOO- generation. Inhibition of p38 MAPK suppressed LPS + IFN-gamma-induced NO production through down-regulating inducible form of NOS expression. It also suppressed LPS + IFN-gamma-induced NADPH oxidase activation and eventually, the inducible form of superoxide production. Transfection with dominant neptive vector of p38a reduced LPS + IFN-gamma-induced ONOO- generation through blocking both iNOS-derived NO production and NADPH oxidase-derived O-2(-) production. Our results suggest that activated p38 MAPK may serve as a potential signaling molecule in ONOO- generation through dual regulatory mechanisms, involving iNOS induction and NADPH oxiclase activation. (C) 2007 Elsevier Ltd. All rights reserved.