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) kappaB, an inducible transcription factor that is activated in inflamed colonic tissue, is sequestered to the cytoplasm by its inhibitory I kappaB 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 I kappaB alpha. 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 I kappaB alpha and phosphorylated I kappaB alpha were determined by western blot. Stimulation with TNF alpha resulted in rapid phosphorylation and degradation of I kappaB alpha followed by NF-kappaB nuclear translocation. Butyrate pretreatment successfully inhibited NF-kappaB activation. Pretreatment of adenocarcinoma cells with butyrate is associated with inhibition of TNF alpha -mediated phosphorylation and degradation of I kappaB alpha 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 I kappaB alpha mediated activation of NF-kappaB.