Involvement of mitogen-activated protein kinase homologues in the regulation of lipopolysaccharide-mediated induction of cyclo-oxygenase-2 but not nitric oxide synthase in RAW 264.7 macrophages

In RAW 264.7 macrophages lipopolysaccharide (LPS) stimulated the activation of p42 and p44 MAP kinases and their upstream activator mitogen-activated protein (MAP) kinase kinase (MAPKK), and induced the 69-kDa isoform of cycl o-oxygenase-2 (COX-2) and the 130-kDa isoform of nitric oxide synthase (iNO S). PD 098059, a specific inhibitor of the activation of MAPKK, prevented L PS-mediated activation of MAPKK (IC50 = 3.0 +/- 0.1 mu M, n = 3) and p42/44 MAP kinases and substantially reduced the induction of COX-2 by approximat ely 40%-70%, but was without effect upon the induction of iNOS. In parallel , LPS also stimulated the activation of p38 MAP kinase and the MAPKAP kinas e-2, a downstream target of p38 MAP kinase. SE 203580, a specific inhibitor of p38 MAP kinase prevented the activation of p38 MAP kinase (IC50 = 3.3 /- 1.4 mu M, n = 3) and MAPKAP kinase-2 by LPS and reduced the induction of COX-2 by approximately 50-90%, with no significant effect upon iNOS expres sion. These studies indicate the involvement of both the classical p42/44 M AP kinases and p38 MAP kinase in the regulation of COX-2 but not iNOS induc tion following exposure to LPS. (C) 1999 Elsevier Science Inc.