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Glucocorticoids Induce Cytosolic Phospholipase A₂ and Prostaglandin H Synthase Type 2 But Not Microsomal Prostaglandin E Synthase (PGES) and Cytosolic PGES Expression in Cultured Primary Human Amnion Cells

Departments of Obstetrics and Gynecology (R.M., X.C., B.C., R.W., D.B., L.M.) and Molecular and Cellular Physiology (B.C., L.M.), University of Cincinnati, College of Medicine, Cincinnati, Ohio 45267; and Department of Physiology (K.S.), Second Military Medical University, Shanghai 200433, China

Address all correspondence and requests for reprints to: Dr. Kang Sun, Department of Physiology, Second Military Medical University, Shanghai 200433, China. E-mail: sunkang2000{at}yahoo.com.

This study examines the regulation of major enzymes in prostaglandin E₂ (PGE₂) synthesis by glucocorticoids in separate cultures of human amnion epithelial and fibroblast cells at term. Cytosolic phospholipase A₂ (cPLA₂), cytosolic PGES (cPGES), and microsomal PGES (mPGES) mRNA were expressed at similar levels in both cell types, whereas a greater prostaglandin H synthase type 2 (PGHS-2) mRNA expression was observed in amnion fibroblasts than in epithelial cells. Amnion fibroblasts produced 50-fold more PGE₂ per cell than epithelial cells. Dexamethasone (0.01–1 µM) increased PGE₂ production in amnion fibroblasts in a concentration-dependent manner but did not affect PGE₂ production in amnion epithelial cells. Both mRNA and protein expression of cPLA₂ and PGHS-2 but not cPGES and mPGES were increased in a dose-dependent manner by dexamethasone (0.01–1 µM) in amnion fibroblasts. Induction of cPLA₂ and PGHS-2 mRNA by dexamethasone was blocked by RU486. Dexamethasone did not affect PGHS-2, cPGES, and mPGES mRNA expression in amnion epithelial cells. In conclusion, amnion fibroblasts express a higher level of PGHS-2 mRNA and produced more PGE₂ per cell than amnion epithelial cells at term of human pregnancy. Glucocorticoids increase PGE₂ production only in the amnion fibroblasts mainly through induction of cPLA₂ and PGHS-2 expression.

This work was supported by National Institutes of Health RO1 Grant HD31514 and the National Basic Research Program of China (Grant G1999054000).

Abbreviations: cPGES, Cytosolic PGES; cPLA₂, cytosolic phospholipase A₂; FCS, fetal calf serum; GR, glucocorticoid receptor; GRE, glucocorticoid response element; 3ß-HSD, 3ß-hydroxysteroid dehydrogenase; mPGES, microsomal PGES; PG, prostaglandin; PGHS, PGH synthase; PR, progesterone receptor; QT-RT-PCR, quantitative real-time PCR.

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