Bile acids and epithelial-derived human beta-defensins (H beta Ds) are known to be important factors in the regulation of colonic mucosal barrier function and inflammation. We hypothesized that bile acids regulate colonic H beta D expression and aimed to test this by investigating the effects of deoxycholic acid (DCA) and ursodeoxycholic acid on the expression and release of H beta D1 and H beta D2 from colonic epithelial cells and mucosal tissues. DCA (10-150 mu M) stimulated the release of both H beta D1 and H beta D2 from epithelial cell monolayers and human colonic mucosal tissue in vitro. In contrast, ursodeoxycholic acid (50-200 mu M) inhibited both basal and DCA-induced defensin release. Effects of DCA were mimicked by the Takeda GPCR 5 agonist, INT-777 (50 mu M), but not by the farnesoid X receptor agonist, GW4064 (10 mu M). INT-777 also stimulated colonic H beta D1 and H beta D2 release from wild-type, but not Takeda GPCR 5(-/-), mice. DCA stimulated phosphorylation of the p65 subunit of NF-kappa B, an effect that was attenuated by ursodeoxycholic acid, whereas an NF-kappa B inhibitor, BMS-345541 (25 mu M), inhibited DCA-induced H beta D2, but not H beta D1, release. We conclude that bile acids can differentially regulate colonic epithelial H beta D expression and secretion and discuss the implications of our findings for intestinal health and disease.