Platelet-activating factor stimulates eicosanoid production in cultured feline tracheal epithelial cells.

Abstract

The effect of platelet-activating factor (PAF) on eicosanoid generation and release in cultured feline tracheal epithelial cells was investigated by measuring a wide range of lipoxygenase and cyclooxygenase pathway products. Subconfluent epithelial cell cultures were stimulated by PAF and eicosanoid production was determined by high performance liquid chromatography (HPLC) of [3H]-labeled arachidonic acid (AA) metabolites and by radioimmunoassay (RIA) following HPLC separation. The HPLC chromatograms revealed that PAF augmented the release of prostaglandin (PG)E2, PGF2 alpha, 12-hydroxyeicosatetraenoic acid (HETE), and AA. Among these eicosanoids, PGE2 predominated under baseline conditions and following PAF exposure. RIAs of the nonradiolabeled HPLC elution corresponding to various eicosanoid standards demonstrated that PAF increased the production of 6-keto-PGF1 alpha, thromboxane B2 (TXB2), PGD2, 5-HETE, and 15-HETE, as well as PGE2, PGF2 alpha, and 12-HETE. The PAF-induced eicosanoid augmentation was dose-dependent and occurred within 1 hour with a prompt decline following termination of PAF exposure. This stimulating effect of PAF on eicosanoid release was blocked by two PAF receptor antagonists, Ro 19-3704 and WEB 2086. The PAF-induced increase in eicosanoid release was similar in magnitude to the increase caused by calcium ionophore (Ca-ionophore) A23187, a potent known stimulus for eicosanoid release. Cells of different culture durations (3 and 6 days) showed similar capacity for eicosanoid production. We conclude that PAF stimulates the production of cyclooxygenase and lipoxygenase pathway products from airway epithelial cells via PAF receptors, and that these epithelium-derived eicosanoids may be responsible for some of the PAF-induced respiratory physiological and pathophysiological effects.