Dynamics of leukotriene C production by macrophages.

Abstract

A method for the radiochemical assay of LTC production by mouse peritoneal macrophages in vitro is presented. The method involves labeling macrophages in culture with [5,6,8,9,11,12,14,15-3H]20:4 followed by stimulation of arachidonic acid (20:4) release under the experimental conditions desired. Radiolabeled leukotriene C (LTC) is recovered from the culture medium by extraction and silicic acid chromatography in 40% yield with full retention of biological activity. Because this LTC is radiochemically pure, the quantity of LTC release may be estimated from the amount of radioactivity in the sample. Use of the radioassay to study parameters affecting LTC synthesis by macrophages indicated that the time course of LTC synthesis and its relationship to the dose of a phagocytic stimulus (zymosan) were very similar to those of prostaglandin (PG) release. LTC release was also similar to that of PG in that lower levels of both metabolites were produced by Corynebacterium parvum-elicited macrophages than by resident cells. Finally, LTC release was stimulated in response to a challenge with antigen-antibody complexes, but lower maximal levels were attained than those with zymosan. The data presented here are consistent with the hypothesis that challenge of macrophages with a phagocytic stimulus leads to the release of 20:4 by an inducible phospholipase. Cyclooxygenase and lipoxygenase then compete for the released 20:4, leading to the production of PG, hydroxyeicosatetraenoic acids, and LTC.

IgE immune complexes stimulate arachidonic acid release by mouse peritoneal macrophages.

“…Release was linear for 1-2 hr and then ceased. These kinetics are similar to those reported previously for macrophages challenged with unopsonized zymosan (1,6 (Fig. 3) The use ofimmune complexes formed on the surface ofSephadex beads provides a convenient means to present insoluble stimuli to macrophages.…”

“…A major arachidonic acid metabolite of macrophages is the slow-reacting substance, leukotriene C (5S, 6R)-5-hydroxy-6-S-glutathionyl-7, 9-trans-11, 14-cis-icosatetraenoic acid) (4)(5)(6). Traditionally, the production of slow-reacting substance of anaphylaxis has been associated with IgE-mediated, immediate hypersensitivity reactions (7) in which macrophages have no known role.…”

Leukotriene C promotes prostacyclin synthesis by human endothelial cells.

“…USA 80 (1983) q I I (31). It seems possible, therefore, that in response to inflammatory stimuli their generation by macrophages (10,32) and monocytes (unpublished data), which are either in or in close approximation to the vasculature, would lead to the synthesis of prostacyclin. In addition, granulocytes (33,34) and mast cells (35) are sources of similar compounds.…”

The Role of β-Glucan Receptors on Blood and Tissue Leukocytes in Phagocytosis and Metabolic Activation

“…Zymosan-induced release of hexosaminidase is detectable after synthe sis and release of arachidonic acid metabo lites [53], suggesting that macrophage lipid metabolism is one of the earliest cellular responses activatable by zymosan interac tions with mouse peritoneal macrophages. The major macrophage membrane lipid af fected by zymosan-induced phagocytosis is arachidonic acid [53], which is oxidatively catabolized to cyclooxygenase [53,54] and 5-lipooxygenase [55,56] products. Approxi mately 67% of the released arachidonic acid metabolites are prostaglandins and thromoxancs, products of the cyclooxygenase path way, and 15-30% are sulfidopeptide leukotrienes of the 5-lipooxygenase pathway [55,56], As recently reviewed [57], these sulfidopeptide leukotrienes have subsequently been identified as leukotrienes C4, D4, and E4 and the major constituents of slow-reacting sub stance A (SRS-A), a potent broncho-and vasoconstrictor.…”