Cytokine-activated degradation of inhibitory kappa B 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 amel iorate inflammation in ulcerative colitis. Nuclear factor (NF) kappaB, an i nducible transcription factor that is activated in inflamed colonic tissue, is sequestered to the cytoplasm by its inhibitory I kappaB proteins. The a nti-inflammatory effects of butyrate are associated with an inhibition of N F-kappaB nuclear translocation. To investigate the mechanism of NF-kappaB i nhibition we examined the effects of butyrate on I kappaB alpha. Human aden ocarcinoma cells (SW480, SW620, and HeLa229) were treated with butyrate for up to 48 h followed by tumor necrosis factor (TNF) alpha stimulation. NF-k appaB 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 ra pid phosphorylation and degradation of I kappaB alpha followed by NF-kappaB nuclear translocation. Butyrate pretreatment successfully inhibited NF-kap paB activation. Pretreatment of adenocarcinoma cells with butyrate is assoc iated with inhibition of TNF alpha -mediated phosphorylation and degradatio n of I kappaB alpha and effective blocking of NF-kappaB nuclear translocati on. The anti-inflammatory effects of butyrate may at least in part be media ted by an inhibition of I kappaB alpha mediated activation of NF-kappaB.