TUMOR-NECROSIS-FACTOR-ALPHA INDUCES CYCLO-OXYGENASE-2 GENE-EXPRESSIONIN FIRST-TRIMESTER TROPHOBLASTS - SUPPRESSION BY GLUCOCORTICOIDS AND NSAIDS

Tumour necrosis factor-alpha (TNF-alpha) is a pleiotropic cytokine whi ch stimulates the synthesis and release of prostaglandins (PGs) in sev eral in vitro and in vivo models of preterm labour. While TNF-alpha-st imulated PG production has been described in decidual, amnion and myom etrial cells, to date no studies have focused on the role of TNF-alpha in the stimulation of arachidonic acid metabolism in placental tropho blast cells. Cyclo-oxygenase-2 (COX-2) is the rate-limiting enzyme in PG biosynthesis and is expressed de novo during cellular activation by cytokines. To test whether TNF-alpha alters expression of COS-2, trop hoblasts from first trimester chorionic villi were cultured as a conti nuous cell line and treated with TNF-alpha alone or with TNF-alpha and dexamethasone (Dex). Total RNA and protein were extracted from the tr ophoblasts and subjected to Northern and immunoblot analysis, respecti vely. Northern blots were hybridized with a P-32-labelled probe encodi ng the COX-2 cDNA and immunoblots were incubated with anti-COX-2 antib odies. There was a time-and dose-dependent increase in COX-2 mRNA and protein expression in cells stimulated with TNF-alpha. The effect of T NF-alpha on COX-2 mRNA and protein expression was inhibited by dexamet hasone (Dex). To examine the production of PGE(2) and PGF(2 alpha), sp ecific RIAs were performed on culture media from similarly stimulated cells. PG accumulation after TNF-alpha-stimulation occurred in a time- and dose-dependent fashion with a similar inhibition of PG accumulatio n after Des exposure. To be certain that TNF-alpha-stimulated PGE(2) p roduction was, indeed, a result of COX-2 induction, RIAs were carried out with the COX-2-selective inhibitor NS-398. Cells stimulated with t he NS-398 after TNF-alpha exposure demonstrated suppression of TNF-alp ha-stimulated PGE(2) formation. The results suggest that TNF-alpha eli cits part of its pathophysiologic effects in preterm labour via altera tions in COX-2 gene expression within the placental microenvironment. (C) 1997 W. B. Saunders Company Ltd.