Cytokine-activated degradation of inhibitory κB protein α is inhibited by the short-chain fatty acid butyrate
Butyrate, a short-chain fatty acid, is generated by anaerobic fermentation within the colon. Clinical trials suggest that short-chain fatty acids ameliorate inflammation in ulcerative colitis. Nuclear factor (NF) κB, an inducible transcription factor that is activated in inflamed colonic tissue, is sequestered to the cytoplasm by its inhibitory IκB proteins. The anti-inflammatory effects of butyrate are associated with an inhibition of NF-κB nuclear translocation. To investigate the mechanism of NF-κB inhibition we examined the effects of butyrate on IκBα. Human adenocarcinoma cells (SW480, SW620, and HeLa229) were treated with butyrate for up to 48 h followed by tumor necrosis factor (TNF) α stimulation. NF-κB was detected by immunofluorescence staining with an antibody against its p65 subunit. Levels of IκBα and phosphorylated IκBα were determined by western blot. Stimulation with TNFα resulted in rapid phosphorylation and degradation of IκBα followed by NF-κB nuclear translocation. Butyrate pretreatment successfully inhibited NF-κB activation. Pretreatment of adenocarcinoma cells with butyrate is associated with inhibition of TNFα-mediated phosphorylation and degradation of IκBα and effective blocking of NF-κB nuclear translocation. The anti-inflammatory effects of butyrate may at least in part be mediated by an inhibition of IκBα mediated activation of NF-κB.
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