Docosahexaenoic acid differentially affects TNFα and IL-6 expression in LPS-stimulated RAW 264.7 murine macrophages

Docosahexaenoic acid (DHA) is generally reported to have anti-inflammatory properties, however, prior work has documented differential effects on individual pro-inflammatory cytokines: reduced IL-6, but not TNFα, mRNA expression in macrophages. To elucidate the mechanism, the roles of prostaglandin E2 (PGE2), cyclic AMP response element-binding protein (CREB), and NFκB were examined in RAW 264.7 macrophages. DHA did not influence CREB activity, but significantly reduced PGE2 production by 41% and NFκB activity by 32%. Exogenous PGE2 inhibited TNFα mRNA expression dose dependently. Unexpectedly, inhibiting PGE2 production with NS-398 also decreased TNFα mRNA expression, suggesting a concentration-dependent dual role of PGE2 in regulating TNFα expression. IL-6 expression was unaffected by endogenous or exogenous PGE2. Partial block of NFκB activation (SN50; 46%, or, BAY-11-7082; 41%) lowered IL-6 to a greater extent than TNFα mRNA expression. The differential effect of DHA on TNFα and IL-6 mRNA expression may be mediated via reduction in NFκB activity.