Production of lipoxygenase metabolites of eicosapentaenoic acid by bovine alveolar macrophages in vitro.

Abstract

Lipoxygenase metabolites of arachidonic acid (AA), the leukotrienes (LTs), and hydroxyeicosatetraenoic acids (HETEs) are potent proinflammatory mediators. Release of LTs and HETEs by bovine alveolar macrophages (BAMs) was measured by reverse-phase high performance liquid chromatography. LTB4 (1.1 +/- 0.2 ng/10(6) cells) and 5-HETE (2.2 +/- 0.2 ng/10(6) cells) were the major metabolites calcium ionophore A23187-stimulated BAMs produced from endogenous AA. The tritiated forms of these compounds and their precursor fatty acids were produced following incorporation of [3H]AA into the cells and stimulation by calcium ionophore A23187. Incorporation of an alternative substrate, [3H]eicosapentaenoic acid [( 3H]EPA) into BAMs incubated in parallel resulted in production of [3H]LTB5 and [3H]5-hydroxyeicosapentaenoic acid (5-HEPE). Equivalent amounts of [3H]AA and [3H]EPA and of [3H]LTB4 and homologous [3H]LTB5 were released. BAM produced significantly greater amounts of [3H]5-HEPE than [3H]5-HETE, however. These findings indicate that the BAM 5-lipoxygenase is capable of metabolizing EPA to LTB5 and 5-HEPE, with the production of 5-HEPE preferred over 5-HETE.