5-hydroxy-6-8-11-14-eicosatetraenoic-acid and Lymphoma

14C arachidonic acid incorporation and 14C radioactivity release as well as prostaglandin (PG) and 5-hydroxyeicosatetraenoic acid (5-HETE) synthesis were measured in the pair of murine lymphoma L5178Y (LY) cell sublines differing in radiation sensitivity. Both LY sublines, LY-R (resistant) and LY-S (sensitive), incorporated exogenous arachidonic acid and released it from membrane phospholipids. Ca2+ ionophores (ionomycin and A23187) but not PMA stimulated the liberation of 14C arachidonic acid in LY cells. PMA did not potentiate the 14C arachidonic acid release both in the presence or in the absence of A23187; this observation suggests that protein kinase C activation is not essential for the regulation of arachidonic acid release by LY-R and LY-S cells. X-irradiation (5 Gy) did not change the uptake of 14C arachidonic acid into LY-R and LY-S cells and did not potentiate the release of its total radioactivity from the cells. PG synthesis was stimulated in irradiated LY-R cells but not in LY-S cells. The susceptibility of eicosanoid metabolism to A23187 and H2O2 was altered in irradiated LY-R cells. A23187 stimulated only PG and 5-HETE synthesis in irradiated LY-R cells. H2O2 did not stimulate the synthesis of PG from exogenous arachidonic acid in irradiated LY-R and LY-S cells and 5-HETE synthesis in LY-R cells. An implication of the increased PG synthesis in LY-R cells in the protection against radiation is discussed.

Topics: Animals; Arachidonic Acid; Calcimycin; Cell Line; Hydrogen Peroxide; Hydroxyeicosatetraenoic Acids; Ionomycin; Lymphoma; Mice; Phospholipids; Prostaglandins; Radiation Tolerance; Staurosporine; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured; X-Rays

Several investigations have suggested that products of arachidonic acid metabolism have modulatory effects on the development of cellular immunity. In this report we have studied the role of arachidonic acid metabolism in the specific effects of interleukin 1 (IL 1) induction of interleukin 2 (IL 2), and also IL 2 stimulation of proliferation and interferon-gamma (IFN-gamma) production. Utilizing cell lines that are specifically responsive to IL 1 or IL 2, it was found that both interleukins stimulate lipoxygenation of arachidonic acid in their respective target cell. The ability of each interleukin to induce monohydroxyeicosatetraenoic acid (HETE) correlated with the induction of secondary lymphokine secretion. Utilizing selective and partially selective pharmacologic inhibitors of arachidonic acid metabolism, the data suggest that the participation of lipoxygenase activity is required for both IL 1 induction of IL 2 production and IL 2 regulation of proliferation and IFN-gamma secretion. The same requirement for lipoxygenase activity was seen when phorbol myristate acetate (PMA) was used as a secretory stimulant, suggesting a similar mode of action for stimulation-secretory activity between PMA and interleukins. Studies performed with an endogenous inhibitor of 5-lipoxygenase (15-HETE) demonstrated the requirement of this enzyme system for IL 2-dependent proliferation and IFN-gamma production. Although leukotrienes could replace IL 2 for IFN-gamma secretion, they had no effect on IL 2 growth promotion. The results suggest that both IL 1 and IL 2, and PMA, may share the lipoxygenase pathway of arachidonic acid metabolism which is a component of the intracellular signal transduction process that regulates secretory activity and/or cellular proliferation.

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Cell Line; Humans; Hydroxyeicosatetraenoic Acids; Indomethacin; Interleukin-1; Interleukin-2; Lipoxygenase; Lymphocyte Activation; Lymphoma; Mice; T-Lymphocytes