Proceedings of The Physiological Society

Physiology 2016 (Dublin, Ireland) (2016) Proc Physiol Soc 37, PCA141

Poster Communications

Bile acids regulate intestinal wound healing by FXR mediated inhibition of CFTR expression in human colonic epithelial cells

N. K. Lajczak1, M. S. Mroz1, V. Saint-Criq1, S. Keely1

1. Molecular Medicine, Royal College of Surgeons in Ireland, Dublin, Dublin, Ireland.

Introduction: Epithelial restitution is an essential process for maintenance of intestinal barrier function. Increased levels of colonic bile acids have been proposed to be involved in the pathogenesis of inflammatory bowel disease (IBD) but their roles in regulating restitution are not yet known. Here, we investigated the effects of bile acids on epithelial restitution and molecular pathways involved in colonic epithelial healing. Methods: T84 colonic epithelial cells, grown as monolayers on transparent permeable supports, were wounded by scratching with a pipette tip at T=0. Cells were treated with either the most abundant colonic bile acid, deoxycholic acid (DCA; 150 μM), the "therapeutic" bile acid, ursodeoxycholic acid (UDCA; 100 µM), a Farnesoid X Receptor agonist, GW4064 (5 μM), or a cystic fibrosis transmembrane conductance regulator (CFTR) channel blocker, CFTR(inh)-172 (10 μM). Restitution was measured as wound area after 48 h expressed as % T=0 wound area. HEK-293 cells were transfected with vector expressing luciferase gene under control of the CFTR promoter and vectors expressing FXR. Protein expression was assessed by western blotting and cell migration by Boyden chamber assay. Results: After 48 h post-wounding, wound closure in untreated cells was 63.3 ± 13.5% of that at T=0, while in cells treated with DCA (150 µM) it was reduced to 24.5 ± 13.1% (n = 5; p <0.001), whereas UDCA enhanced healing to 88 ± 4 (n = 5; p < 0.001). Furthermore, UDCA prevented inhibition of wound closure by DCA. The effects of DCA are mediated via a decrease in cell migration to 0.7 ± 0.1 fold (n = 5, p < 0.05) of that in untreated controls, rather than inhibition of cell growth. Furthermore, DCA decreased cell surface CFTR expression to 23 ± 5% of controls (n = 3, p < 0.001), while a CFTR inhibitor, CFTR(inh)-172 (10 μM), attenuated wound closure to 37 ± 2% (n = 5; p < 0.01), compared to control. Moreover, DCA decreased CFTR promoter activity, in a concentration-dependent manner that was also dependent on co-expression of FXR. Finally, GW4064 (5 µM), an agonist of FXR, mimicked DCA effects on wound healing and CFTR expression. Conclusion: Our data suggest that colonic bile acids differentially regulate intestinal epithelial restitution and that UDCA promotes healing and protects against the detrimental effects of DCA. Thus, manipulation of the colonic bile acid pool may prove to be a useful approach for promoting intestinal barrier function in IBD.

Where applicable, experiments conform with Society ethical requirements