The luminal short-chain fatty acid butyrate modulates NF-κB activity in a human colonic epithelial cell line

Abstract

Background & Aims: The transcription factor nuclear factor–κB (NF-κB) plays a central role in regulating immune and inflammatory responses. Because butyrate deficiency has been associated with inflammatory bowel disease, we examined the effect of butyrate on NF-κB activity in the human HT-29 colonic cell line. Methods: The influence of butyrate (4 mmol/L) on NF-κB activity was determined using the gel mobility shift assay. The effect of butyrate on the expression of NF-κB subunits and inhibitory proteins was determined by immunoblotting. NF-κB–regulated gene expression was assayed by primer extension of intercellular adhesion molecule 1 and Mn superoxide dismutase messenger RNA, and by analysis of a transfected luciferase reporter. Results: Exposure of HT-29 cells to butyrate eliminated their constitutive NF-κB, p50 dimer activity. This inhibition corresponded with a reduction in p50 nuclear localization, without a reduction in expression. Butyrate also selectively modulated activation of NF-κB, suppressing its activation by tumor necrosis factor α and phorbol ester more than 10-fold, without affecting the activity induced by interleukin (IL)-1β. Butyrate did, however, enhance formation of the stronger p65-p50 transcriptional activator in IL-1β–stimulated cells. The changes in NF-κB activation did not correlate with changes in IκBα levels. Gene expression reflected DNA binding. The influence of butyrate on NF-κB may result in part from its ability to inhibit deacetylases because the specific deacetylase inhibitor trichostatin A has a similar effect. Conclusions: These findings suggest that the influences of butyrate on colonic inflammatory responses may result in part from its influence on NF-κB activation. This activity of butyrate apparently involves its ability to inhibit deacetylases. GASTROENTEROLOGY 2000;118:724-734