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

BACKGROUND: Prostaglandin E2 (PGE2) is a major contributor to the production and maintenance of immunosuppression in injured and septic patients. Although the synthesis of PGE2 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 (Mphi).
MATERIALS AND METHODS: RAW 264.7 cells, a mouse Mphi cell line, were exposed to Escherichia coli LPS (10 microg/ml) in the presence of PD98059, a selective inhibitor of MAPKP44/P42, and SB202190, a selective inhibitor of MAPKP38. COX-2 mRNA expression and PGE2 production were measured by Northern Blot assay and ELISA, respectively. Mphi nuclear factor (NF)kappaB and cAMP-response element (CRE) activities were determined by electrophoretic mobility shift assays.
RESULTS: LPS stimulation increased Mphi COX-2 mRNA expression and PGE2 production. PD98059 or SB202190 attenuated LPS-induced COX-2 mRNA as well as PGE2 production in a dose-dependent fashion. Inhibition of MAPKP44/P42 or MAPKP38 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 PGE2 production in LPS-stimulated Mphi through NFkappaB independent pathways. The regulatory mechanism is likely to be mediated through CRE.