REGULATION OF ARACHIDONIC-ACID RELEASE AND PROSTAGLANDIN E-2 PRODUCTION IN THYMIC EPITHELIAL-CELLS BY ATP-GAMMA-S AND TRANSFORMING GROWTH-FACTOR-ALPHA

The arachidonic acid metabolites produced by thymic epithelial cells p lay a pivotal role in thymocyte development. We have discovered that A TP and TGF-alpha regulate the arachidonic acid metabolism in TEA3A1 ra t thymic epithelial cells by activating phospholipase A(2) enzymatic a ctivity. Our present study demonstrates that ATP and its nonhydrolyzab le analog ATP gamma S stimulate both prostaglandin E-2 production and Ca2+ flux in TEA3A1 cells. The stimulation of prostaglandin E-2 produc tion and Ca2+ flux by ATP is inhibited by pertussis toxin treatment, i ndicating that ATP mediates its effect by binding to a G-protein-coupl ed purinergic receptor. Treatment of cells with ATP gamma S and transf orming growth factor-alpha results in a synergistic activation of phos pholipase A(2) and stimulation of prostaglandin E-2 production. Result s from experiments using an inhibitor of receptor-mediated Ca2+ influx indicate that the synergistic stimulation of prostaglandin E-2 produc tion by ATP gamma S and transforming growth factor-alpha requires ATP gamma S-mediated Ca2+ influx. The inhibitor of tyrosine kinase geniste in also blocked both ATP gamma S- and ATP gamma S plus transforming gr owth factor-alpha-mediated stimulation of prostaglandin E-2 production , indicating that the activation of phospholipase A(2) may involve a p rotein tyrosine phosphorylation step. (C) 1998 Academic Press.