MAPK regulation of prostaglandin E2 production by lipopolysaccharide-stimulated macrophages is not dependent on nuclear factor κB

Background. Prostaglandin E-2 (PGE(2)) is a major contributor to the production and maintenance of immunosuppression in injured and septic patients. Although the synthesis of PGE(2) by various enzymes has been elucidated, the regulatory mechanism of these enzymes is not clear. The purpose of this study was to determine the role of MAPK cascades in COX-2 gene activation by lipopolysaccharide (LPS) -stimulated macrophages (M empty set). Materials and methods. RAW 264.7 cells, a mouse M empty set cell line, were exposed to Escherichia coli LPS (10 mug/ml) in the presence of PD98059, a selective inhibitor of (MAPK)P44/P42, and SB202190, a selective inhibitor of (MAPK)P38. COX-2 mRNA expression and PGE(2) production were measured by Northern Blot assay and ELISA, respectively. M empty set nuclear factor (NF)kappaB and cAMP-response element (CRE) activities were determined by electrophoretic mobility shift assays. Results. LPS stimulation increased M empty set COX-2 mRNA expression and PGE(2) production. PD98059 or SB202190 attenuated LPS-induced COX-2 mRNA as well as PGE(2) production in a dose-dependent fashion. Inhibition of (MAPK)P44/P42 or (MAPK)P38 had no effect on NFkappaB activation but reduced CRE activity induced by LPS stimulation. Conclusion. Our data show that MAPK cascades regulate COX-2 gene expression and PGE(2) production in LPS-stimulated M empty set through NFkappaB independent pathways. The regulatory mechanism is likely to be mediated through CRE. (C) 2003 Elsevier Inc. All rights reserved.