Up-regulation of Prostaglandin E2 Synthesis by Interleukin-1β in Human Orbital Fibroblasts Involves Coordinate Induction of Prostaglandin-Endoperoxide H Synthase-2 and Glutathione-dependent Prostaglandin E2 Synthase Expression

Rui Han,Shanli Tsui,Terry J Smith

doi:10.1074/jbc.m111246200

Abstract

Prostaglandin E(2) (PGE(2)) production involves the activity of a multistep biosynthetic pathway. The terminal components of this cascade, two PGE(2) synthases (PGES), have very recently been identified as glutathione-dependent proteins. cPGES is cytoplasmic, apparently identical to the hsp90 chaperone, p23, and associates functionally with prostaglandin-endoperoxide H synthase-1 (PGHS-1), the constitutive cyclooxygenase. A second synthase, designated mPGES, is microsomal and can be regulated. Here we demonstrate that mPGES and PGHS-2 are expressed at very low levels in untreated human orbital fibroblasts. Interleukin (IL)-1beta treatment elicits high levels of PGHS-2 and mPGES expression. The induction of both enzymes occurs at the pretranslational level, is the consequence of enhanced gene promoter activities, and can be blocked by dexamethasone (10 nm). SC58125, a PGHS-2-selective inhibitor, could attenuate the induction of mPGES, suggesting a dependence of this enzyme on PGHS-2 activity. IL-1beta treatment activates p38 and ERK mitogen-activated protein kinases. Induction of both mPGES and PGHS-2 was susceptible to either chemical inhibition or molecular interruption of these pathways with dominant negative constructs. These results indicate that the induction of PGHS-2 and mPGES by IL-1beta underlies robust PGE(2) production in orbital fibroblasts.

Highlights

The past decade has witnessed dramatic advances in our understanding of the prostanoid biosynthetic pathways in mammalian cells
IL-1␤ Up-regulates Prostaglandin E2 (PGE2) Production in Orbital Fibroblasts; This Is Associated with Induction of PGHS-2 and mPGES Proteins—Confluent orbital fibroblast monolayers were shifted to serumless medium without or with IL-1␤ (10 ng/ml) for up to 48 h
The susceptibility of cytokine-provoked mPGES induction to a highly selective inhibitor of PGHS-2 activity suggests that up-regulation of the former enzyme by IL-1␤ is dependent, at least in part, on a product of PGHS-2

Summary

Introduction

The past decade has witnessed dramatic advances in our understanding of the prostanoid biosynthetic pathways in mammalian cells. We report that the treatment of orbital fibroblasts with IL-1␤ results in dramatic increases in PGE2 production and is associated with coordinate induction of both PGHS-2 and mPGES expression. Inhibiting PGHS-2 activity results in the blockade of mPGES induction by IL-1␤, indicating some involvement of the products of the former enzyme in the expression of the latter.

Results

Conclusion