Inhibition of extracellular signal-regulated kinase 1/2 augments nitric oxide production in lipopolysaccharide-stimulated RAW264.7 macrophage cells

The present study was conducted to determine effects of 00126, a specific inhibitor of mitogen-activated kinase kinase 1/2, on production of nitric oxide (NO) in RAW264.7 macrophage cells. 00126 significantly enhanced NO production in lipopolysaccharide (LPS) but not CpG DNA or interferon-gamma-stimulated RAW264.7 cells. In contrast, 00124, a negative control for 00126, did not affect LPS-induced NO production. Further, a series of inhibitors of p38, phosphatidyl-inositol 3-kinase and Janus tyrosine kinase rather caused suppression in LPS-stimulated RAW264.7 cells. 00126 was found to definitely inhibit phosphorylation of extracellular signal-regulated kinase (Erk) 1/2 and augment the levels of inducible type of NO synthase. Antisense oligonucleotides of Erk1/2 also augmented LPS-induced NO production. Inactivation of Erk1/2 by 00126 furthermore inhibited LPS-induced activating protein-1 activation, but not nuclear factor-kappa B activation. The results suggest that Erk1/2 might negatively regulate NO production in LPS-stimulated RAW264.7 cells. (c) 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.