Regulation by dietary essential fatty acid balance of tumor necrosis factor production in mouse macrophages

Abstract

Increasing the dietary alpha-linolenate (18:3n - 3)/linoleate (18:2n - 6) ratio results in an increase in lipopolysaccharide (LPS)-stimulated tumor necrosis factor (TNF) production in mouse resident and casein-induced peritoneal macrophages [3]. We found that prostaglandin E2 (PGE2) production is inversely related to TNF production and that indomethacin abolishes the effect of changing the essential fatty acid balance in resident macrophages. The resident macrophages enriched in n - 3 did not produce a significant amount of PGE3. Accordingly, the decreased production of PGE2 appears to be a major negative regulatory factor for enhancement of TNF production in the n - 3 enriched resident macrophages. In casein-induced macrophages the situation is more complex. Indomethacin decreased PGE2 production and increased TNF production; however, the differences in TNF production between the n - 6 enriched and n - 3 enriched macrophages were not completely abolished by indomethacin treatment. Lysosomal acid phosphatase activity, a marker of activation/maturation stages, was elevated in the n - 3 enriched compared to the n - 6 enriched casein-induced macrophages but was similar in the resident macrophages of the two dietary groups. Expression of CD14, which is a receptor for LPS, was not different in casein-induced macrophages of the two dietary groups. Thus, the differences in production of TNF between the n - 3 and n - 6 enriched resident macrophages can be accounted for mostly by a difference in the production of a negative feedback effector, PGE2. However, a significant portion of the TNF production in casein-induced macrophages is regulated by a factor(s) other than PGE2 and LPS receptor; advanced activation/maturation stages induced by the diet high in alpha-linolenate may underlie the enhanced TNF production in casein-induced macrophages.