OZONE EXPOSURE OF HUMAN TRACHEAL EPITHELIAL-CELLS INACTIVATES CYCLOOXYGENASE AND INCREASES 15-HETE PRODUCTION

We assessed the immediate and prolonged effects of ozone on arachidoni c acid (AA) metabolism by primary cultured human tracheal epithelial ( TE) cells. TE monolayers were exposed at a gas-fluid interface to air or 0.1, 0.25, or 0.5 ppm ozone (15 min air, then 45 min air/ozone), an d serially collected effluents were analyzed by thin-layer chromatogra phy (TLC) and/or high-performance liquid chromatography. Release of pr ostaglandin E(2) (PGE(2)) and AA, but not 15-hydroxyeicosatetraenoic a cid (15-HETE) or its metabolites, was detected from cultures prelabele d with [C-14]AA. PGE(2) production, measured by immunoassay, was nearl y constant during air exposure. In contrast, PGE(2) increased two- to threefold during the first 15-min exposure to all concentrations of oz one, but then progressively declined to 78 +/- 17, 57 +/- 12 (P less t han or equal to 0.05), and 45 +/- 15% (P less than or equal to 0.05) o f air controls after exposure to 0.1, 0.25, and 0.5 ppm ozone. Ozone d id not induce a new spectrum of AA metabolites; only PGE(2), lesser am ounts of PGF(2 alpha), and 15-HETE were present in media and cell extr acts of air- or ozone-exposed cultures provided with 30 mu M exogenous AA. However, cyclooxygenase (GO) activity (PGE(2) produced from 30 mu M AA) decreased to 82 +/- 9, 53 +/- 8 (P less than or equal to 0.05), and 28 +/- 6% (P less than or equal to 0.05) vs. controls after 0.1, 0.25, and 0.5 ppm ozone, whereas 15-HETE production was unimpaired. Wh en cells exposed to 0.5 ppm ozone were maintained for up to 6 h in 5% CO2-air, spontaneous PGE(2) production remained decreased and recovery of CO activity was extremely slow. TLC analysis of lipid extracts fro m [C-14]AA-labeled cells revealed a nearly twofold increase in free in tracellular 15-HETE, and hydrolysis of phospholipids demonstrated incr eased esterified 15-HETE. Exposure of human TE cells to ozone leads to a transient increase followed by prolonged decrease in PGE(2) product ion and increased intracellular retention of 15-HETE. Loss of the bron chodilator and anti-inflammatory properties of epithelial PGE(2), with or without increased 15-HETE, might contribute to ozone-induced airwa y dysfunction.