LCA and 3-oxo-LCA mitigate dietary oxysterols-induced loss of barrier function in intestinal epithelial cells

Loss of intestinal barrier integrity is a hallmark of many intestinal inflammations and associated diseases, including inflammatory bowel disease (IBD) and colorectal cancer (CRC). One of the primary factors contributing to intestinal epithelial barrier damage is a diet high in cholesterol. The non-enzymatically oxidized forms of dietary cholesterol, collectively known as oxysterols, have recently gained attention as mediators of various inflammatory conditions. In addition, oxysterols have been found to cause intestinal barrier damage via the loss of tight junction protein expression and promote inflammation. Secondary bile acids of host-gut microbial origin, and several other gut-microbiota-derived metabolites, are known to modulate intestinal inflammation. Here, we have studied the roles of two secondary bile acids in restoring barrier integrity and reducing the extent of dietary oxysterol-induced damage in intestinal epithelial cells. We found that oxysterols exert their damaging effects by inducing matrix metalloproteinases (MMP-2 and MMP-9) and activating NF-κB, which is coupled with the production of pro-inflammatory cytokines and chemokines (CCL2, CCL5, & IL-8). Additionally, we also show that the secondary bile acids lithocholic acid (LCA) and dehydrolithocholic acid (3-oxo-LCA) counteract dietary oxysterol-induced loss of barrier function (TEER & FITC-dextran flux). Overall, these findings provide supportive evidence for the potential role for secondary bile acids in maintaining barrier integrity and modulating inflammation in intestinal epithelial cells exposed to dietary oxysterols in vitro.