Eicosapentaenoic Acid Prevents LPS-Induced TNF-α Expression by Preventing NF-κB Activation

Abstract

Background: Many studies have shown that fish oil supplementation inhibits tumor necrosis factor-α (TNF-α) production in mice and human subjects; however, the mechanisms remain unclear. Nuclear factor-κB (NF-κB) is a transcription factor that plays an important role in controlling the expression of pro-inflammatory genes including TNF-α. Activation of NF-κB has been shown to mediate the maximal expression of TNF-α in human monocytes. NF-κB is kept in an inactive form in the cytoplasm by IκB, the inhibitory subunit of NF-κB complex. Phosphorylation and subsequent degradation of IκB lead to NF-κB activation.Objectives: The effect of eicosapentaenoic acid (EPA), a major n-3 fatty acid in fish oil, on the lipopolysaccharide (LPS)-induced expression of TNF-α and activation of NF-κB were investigated. The mechanism underlying EPA modulation of NF-κB activation was also studied.Methods: Human monocytic THP-1 cells were pre-incubated with EPA and stimulated with LPS. The levels of secreted TNF-α were determined by ELISA. The DNA binding activity of NF-κB was analyzed by EMSA. The degradation and phosphorylation of IκB-α were examined by Western blot analysis.Results: TNF-α production and expression induced by LPS were significantly decreased in cells pre-incubated with EPA. LPS-induced NF-κB activation, translocation of p65 subunit to the nucleus, phosphorylation and degradation of IκB-α were partially prevented by EPA.Conclusions: The results suggest that suppression of the TNF-α expression by EPA is partly attributed to its inhibitory effect on NF-κB activation. EPA appears to prevent NF-κB activation by preventing the phosphorylation of IκB-α.