Formation and metabolism of leukotriene C4 in macrophages exposed to bacterial lipopolysaccharide

Abstract

Lipopolysaccharide (10 μg/ml) was found to stimulate resident mouse peritoneal macrophages to produce leukotriene C₄ (36 ± 1.3 ng/10⁶ cells, SEM, n= 20) within 16 h. Spontaneous synthesis in control cultures without lipopolysaccharide was < 1.6 ng/10⁶ cells. Leukotriene C₄ was characterized by reversed-phase high-performance liquid chromatography, ultraviolet spectrometry and radioimmunoassay. When the macrophages, prelabeled with [³H]arachidonic acid, were treated with lipopolysaccharide radioactivity was incorporated into leukotriene C₄. The amount produced varied with the method of macrophage preparation and incubation conditions and was dependent on the amount of lipopolysaccharide added (0.5–60 μg/ml), on cell counts and on the incubation time (4–16 h). The released leukotriene C₄ was converted to a compound identified as a C₆-cysteinylleukotriene, indicating metabolism of the leukotriene by the macrophages. Parallel determinations of prostaglandins E₂ and F_2α by radioimmunoassay demonstrated that leukotriene C₄ and prostaglandin E₂ are formed by mouse peritoneal macrophages to a similar degree.