Dietary fish oil increases tumor necrosis factor secretion but decreases interleukin-10 secretion by murine peritoneal macrophages.

Dietary fish oil has immunomodulatory effects that are mediated in part by its effects on cytokines. Secretion of the inflammatory and the anti-inflammatory cytokines tumor necrosis factor (TNF) and interleukin (IL)-10 by murine resident peritoneal macrophages was monitored after ex vivo stimulation with lipopolysaccharide. Macrophages were obtained from mice fed a corn oil diet containing 200 g/kg corn oil or a fish oil diet containing 180 g/kg fish oil and 20 g/kg corn oil. Dietary fish oil increased secretion of the proinflammatory cytokine, TNF, but decreased secretion of the anti-inflammatory cytokine, IL-10. The cytokines appeared in the medium after 1.5 h and peaked at 6-12 h. Neutralizing antibodies against TNF and IL-10 had little effect on secretion of the other cytokine, indicating that the effects of fish oil on TNF and IL-10 secretion by these cells are independent of one another. Furthermore, although inhibiting prostaglandin production enhanced TNF secretion by macrophages from mice fed the corn oil diet, it did not affect IL-10 secretion by macrophages in this group. Blocking leukotriene B(4) production also did not affect IL-10 secretion in macrophages from mice fed a nonpurified diet. These results demonstrate that fish oil has an overall pro-inflammatory effect given its effects on secretion of both inflammatory and anti-inflammatory cytokines by resident peritoneal macrophages.