Fish oil decreases macrophage tumor necrosis factor gene transcription by altering the NF kappa B activity

Background. Fish oil-supplemented diets have anti-inflammatory and immunomo dulating effects, though the exact mechanism(s) are unknown. This study inv estigated the effects of eicosapentanenoic acid (EPA), a major component of fish oil, on transcriptional regulation of tumor necrosis factor (TNF) gen e in lipopolysaccharide (LPS)-stimulated macrophages (MO). Methods. RAW 264.7 cells, a mouse MO cell line, were grown in EPA-rich medi a for 24-48 h. MO were washed and exposed to Escherichia coli LPS (1 mu g/m l) for 2 h. TNF mRNA expression was measured by Northern blot assays. Total nuclear extracts were harvested for the measurement of NF kappa B with ele ctrophoretic mobility shift assays. Supershift assays were performed with a nti-P50 or anti-P65 antibodies to show components of NF kappa B dimers. TNF production was determined by L929 bioassays. Results. LPS stimulated RAW cell TNF mRNA expression and NF kappa B activit y. In contrast, RAW cells grown in EPA-rich media had less TNF mRNA express ion and an altered composition of the NF kappa B subunits (P65/P50 dimers) in the presence of LPS. TNF production by LPS-stimulated MO was reduced by EPA. Conclusions. The inhibitory effect of EPA on LPS-stimulated MO TNF gene tra nscription and protein elaboration is, in part, mediated through altering N F kappa B activation by reducing the P65/P50 dimers. (C) 1999 Academic Pres s.