Arachidonic acid metabolism in cultured alveolar macrophages from normal, atopic, and asthmatic subjects

Abstract

In order to test the hypothesis that alveolar macrophages (AM) from asthmatics might manifest abnormalities in the amounts, spectrum, or glucocorticoid regulation of eicosanoid synthesis, we compared arachidonic acid (AA) metabolism under resting and ionophore A23187-stimulated conditions in cultured AM obtained by bronchoalveolar lavage from 10 asthmatic, nine atopic, and 10 nonatopic normal subjects. [14C]AA-prelabeled AM constitutively released free [14C]AA and release increased significantly with A23187 incubation. Under resting conditions, unlabeled cells produced small amounts of immunoreactive thromboxane B2 (TxB2), prostaglandin D2 (PGD2), prostaglandin E2 (PGE2), and leukotriene B4 (LTB4). With A23187 stimulation there were significant increases in the synthesis of all immunoreactive metabolites, which were produced in the following relative amounts: LTB4 much greater than TxB2 greater than PGD2 greater than leukotriene C4 greater than PGE2. High performance liquid chromatographic separation of radiolabeled eicosanoids produced by prelabeled cells confirmed the radioimmunoassay results and further indicated the production of relatively large amounts of 5-hydroxyeicosatetraenoic acid and 12-hydroxyheptadecatrienoic acid. Pretreatment (16 h) with 1 microM methylprednisolone inhibited A23187-induced synthesis of immunoreactive cyclooxygenase products to a greater extent than immunoreactive leukotrienes. We identified no significant differences among the three study groups in the quantities or profiles of eicosanoids synthesized either constitutively or with A23187 stimulation, nor in their regulation by methylprednisolone.