Signal pathways involved in the regulation of prostaglandin E synthase-1 in human gingival fibroblasts

Abstract

Microsomal prostaglandin E synthase-1 (mPGES-1) is the terminal enzyme regulating the synthesis of prostaglandin E 2 (PGE 2) in inflammatory conditions. In this study we investigated the regulation of mPGES-1 in gingival fibroblasts stimulated with the inflammatory mediators interleukin-1 β (IL-1β) and tumour necrosis factor α (TNFα). The results showed that IL-1β and TNFα induce the expression of mPGES-1 without inducing the expression of early growth response factor-1 (Egr-1). Treatment of the cells with the PLA 2 inhibitor 4-bromophenacyl bromide (BPB) decreased the cytokine-induced mPGES-1 expression accompanied by decreased PGE 2 production whereas the addition of arachidonic acid (AA) upregulated mPGES-1 expression and PGE 2 production. The protein kinase C (PKC) activator PMA did not upregulate the expression of mPGES-1 in contrast to COX-2 expression and PGE 2 production. In addition, inhibitors of PKC, tyrosine and p38 MAP kinase markedly decreased the cytokine-induced PGE 2 production but not mPGES-1 expression. Moreover, the prostaglandin metabolites PGE 2 and PGF 2α induced mPGES-1 expression as well as upregulated the cytokine-induced mPGES-1 expression indicating positive feedback regulation of mPGES-1 by prostaglandin metabolites. The peroxisome proliferator-activated receptor-γ (PPARγ) ligand, 15-deoxy-Δ12,14-prostaglandin J 2 (15d-PGJ 2), decreased mPGES-1 expression but not COX-2 expression or PGE 2 production. The results indicate that the inflammatory-induced mPGES-1 expression is regulated by PLA 2 and 15d-PGJ 2 but not by PKC, tyrosine kinase or p38 MAP kinase providing new insights into the regulation of mPGES-1.