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

Abstract

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 (MØ). Materials and methods RAW 264.7 cells, a mouse MØ cell line, were exposed to Escherichia coli LPS (10 μg/ml) in the presence of PD98059, a selective inhibitor of MAPKP44/P42, and SB202190, a selective inhibitor of MAPKP38. COX-2 mRNA expression and PGE 2 production were measured by Northern Blot assay and ELISA, respectively. MØ nuclear factor (NF)κB and cAMP-response element (CRE) activities were determined by electrophoretic mobility shift assays. Results LPS stimulation increased MØ 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 MAPKP44/P42 or MAPKP38 had no effect on NFκB 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 MØ through NFκB independent pathways. The regulatory mechanism is likely to be mediated through CRE.