Effect of omega‐3 and omega‐6 fatty acids on nitric oxide and IL‐6 production by RAW 264.7 macrophages

Abstract

Chronic low‐grade inflammation, or meta‐inflammation, which may occur in obese subjects, is related to the infiltration of macrophages into adipose tissue (AT) as adipocyte number and size increase. The increased count in fat cells is correlated with an increase in adipose tissue macrophages (ATMs). These ATMs can secrete pro‐inflammatory cytokines which can have effects on the surrounding adipocytes. Omega‐3 fatty acids (FAs) reduce inflammation through direct competition with omega‐6 FAs, the precursors of the inflammatory eicosanoids, as well as through changes in gene expression of inflammatory molecules. Less is known about the effects of omega FAs on pro‐inflammatory cytokine production by immune cells, such as macrophages. The objective of this research was to determine the effects of omega‐3 and omega‐6 FAs on the production of nitric oxide (NO), a signaling molecule secreted by activated macrophages which is involved in mediating inflammation and production of the pro‐inflammatory cytokine interleukin‐6 (IL‐6), in lipopolysaccharide (LPS)‐activated macrophages. RAW 264.7 (murine macrophages) were incubated with 100 μM of sodium salts of linoleic acid (LA; C18:2, omega‐6), arachidonic acid (ARA; C20:4, omega‐6), or eicosapentaenoic acid (EPA; C20:5, omega‐3) for 24 h. After pre‐incubation with FAs macrophages were stimulated with 0.01 μg/ml of LPS for 6 h. Conditioned media was collected for NO and IL‐6 quantification via Griess assay and ELISA, respectively. FA treatments were cytoprotective, resulting in higher percentages of live cells than both control and LPS‐treated cells (Trypan blue exclusion method; p<0.0001, two‐way ANOVA). LPS‐stimulated macrophages pre‐incubated with LA, ARA, or EPA produced less NO than LPS‐stimulated macrophages without FA pre‐incubation (p=0.0001, two‐way ANOVA). Pre‐incubation of macrophages with LA, ARA, or EPA decreased IL‐6 production in comparison to LPS‐stimulated macrophages, with omega‐6 FAs having a more pronounced effect than omega‐3 FAs (p<0.0001, two‐way ANOVA). In conclusion, both omega‐6 and ‐3 FAs decreased activation of murine macrophages and decreased production of the inflammatory molecules NO and IL‐6, with omega‐6 FAs having a more marked effect than omega‐3 FAs. The stronger anti‐inflammatory effect of omega‐6 FAs on murine macrophages, compared to omega‐3 FAs, warrants further investigation.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.