Specific inhibitors of p38 and extracellular signal-regulated kinase mitogen-activated protein kinase pathways block inducible nitric oxide synthase and tumor necrosis factor accumulation in murine macrophages stimulated with lipopolysaccharide and interferon-gamma

Whether p38 and extracellular signal-regulated kinase (ERK) mitogen-activat ed protein kinase cascades are required for inducible nitric oxide synthase (iNOS) and tumor necrosis factor (TNF) accumulation in RAW 264.7 murine ma crophages exposed to lipopolysaccharide (LPS) plus recombinant interferon-g amma (rIFN-gamma) was investigated. By use of Western blotting for iNOS det ection and ELISA for quantitation of TNF secretion, three selective inhibit ors of these pathways were tested (the p38 inhibitors SB202190 and SB203580 and the MEK 1,2/ ERK inhibitor PD98059). Dose-related inhibition of iNOS p roduction was demonstrated when inhibitors were added 1 h before, simultane ously with, or 1 h after LPS plus rIFN-gamma stimulation. In contrast, inhi bition of TNF secretion was observed only when cells were preincubated with these agents. Thus, both the p38 and ERK pathways are involved in the up-r egulation of iNOS and TNF production by murine macrophages, and specific in hibitors of these pathways block macrophage iNOS production even when added 1 h after activation of these cells.