O37 – Ursodeoxycholic acid as a mediator of intestinal epithelial cell restitution
Author(s):
Background: Dysbiosis of the intestinal microbiota is implicated in a number of gastrointestinal inflammatory diseases, including necrotizing enterocolitis. While the mechanism is unknown, bile acids may play a role. Some intestinal bacteria can metabolize bile acids into ursodeoxycholic acid (UDCA), while others generate more injurious secondary bile acids, deoxycholic (DCA) and lithocholic (LCA). The epidermal growth factor receptor (EGFR) is a known signaling target of bile acids and may play a role in the differing effects of specific bile acid metabolites.
Hypothesis: We hypothesize that UDCA modulates epithelial cell migration via regulation of EGFR.
Methods: After 24 hours of serum-starvation, rat intestinal epithelial cell (IEC-6) monolayers were subjected to a modified wound restitution assay in the presence of bile acids, EGF, the EGFR inhibitor AG1478, the ADAM17 inhibitor TAPI-1 or a combination of these. Pictures were taken at zero and six hours and compared. Western blots were used to assess EGFR phosphorylation.
Results: Most conjugated and unconjugated primary bile acids tested did not alter epithelial cell migration. DCA and LCA, meanwhile, decreased baseline migration (12% and 30%, respectively). This change was rescued by EGF administration. In contrast, UDCA and its glycine conjugate (GUDCA) stimulated cell migration at 6 hours (15% above control). UDCA reversed the inhibitory effects of DCA, while only partially reversing the LCA-induced decrease in cell migration. UDCA-stimulated cell migration was blocked by the EGFR inhibitor. Immunoblotting analysis revealed that IEC-6 treatment with UDCA led to EGFR phosphorylation at two hours. Inhibition of the metalloproteinase ADAM17 by TAPI-1 blocked both UDCA-stimulated migration and EGFR phosphorylation.
Conclusions: These data demonstrate UDCA promotes epithelial cell migration via a mechanism involving metalloproteinase-induced release of EGFR ligand. This mechanism is capable of overcoming DCA-induced inhibition of migration. These results provide a possible mechanism through which intestinal dysbiosis can lead to disease via shifting the bile acid pool toward injurious metabolites. We also identify a potential therapeutic target via manipulation of the EGFR pathway.