Cytokine-activated degradation of inhibitory kappaB protein alpha 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) kappaB, an inducible transcription factor that is activated in inflamed colonic tissue, is sequestered to the cytoplasm by its inhibitory IkappaB proteins. The anti-inflammatory effects of butyrate are associated with an inhibition of NF-kappaB nuclear translocation. To investigate the mechanism of NF-kappaB inhibition we examined the effects of butyrate on IkappaBalpha. Human adenocarcinoma cells (SW480, SW620, and HeLa229) were treated with butyrate for up to 48 h followed by tumor necrosis factor (TNF) alpha stimulation. NF-kappaB was detected by immunofluorescence staining with an antibody against its p65 subunit. Levels of IkappBalpha and phosphorylated IkappaBalpha were determined by western blot. Stimulation with TNFalpha resulted in rapid phosphorylation and degradation of IkappaBalpha followed by NF-kappaB nuclear translocation. Butyrate pretreatment successfully inhibited NF-kappaB activation. Pretreatment of adenocarcinoma cells with butyrate is associated with inhibition of TNFalpha-mediated phosphorylation and degradation of IkappaBalpha and effective blocking of NF-kappaB nuclear translocation. The anti-inflammatory effects of butyrate may at least in part be mediated by an inhibition of IkappaBalpha mediated activation of NF-kappaB.