P124 MICRORNA-24 IS OVEREXPRESSED IN ULCERATIVE COLITIS AND SIGNIFICANTLY AFFECTS INTESTINAL BARRIER FUNCTION

Abstract

The integrity of tight junctions is an important part of gastrointestinal health, as they are key to maintaining the intestinal barrier. In Ulcerative Colitis (UC), the intestinal barrier is compromised, leading to increased permeability for bacteria and other damaging components to cross the epithelial layer into the gastrointestinal tract, where it can cause an exacerbated inflammatory response and tissue damage. microRNAs are small non-coding RNAs that repress gene expression through the binding of mRNA. microRNA (miR)-24 has been studied in various cancers and is implicated in tumorigenesis through the suppression of various genes and proteins, including many relevant to tight junction integrity. We hypothesize that miR-24 is elevated in UC, where it acts to alter tight junction protein expression and causes barrier deficiency. We used qPCR to measure expression of miR-24 in human colon tissue and blood. We used the barrier-forming intestinal epithelial cell lines Caco-2 and T84 plated on transwells to study barrier integrity. We transfected these cells with miR-24 precursor in order to increase the expression of miR-24. Using transepithelial electrical resistance (TEER) and dextran flux experiments, we measured barrier integrity. Changes in gene expression and protein levels were measured via qPCR and western blot, respectively. miR-24 was elevated in human UC colon tissue compared to normal, cancer, Crohn’s disease, and Irritable Bowel Syndrome patient colon tissues. Furthermore, human UC patient blood had increased miR-24 compared to normal and Crohn’s Disease. miR-24 overexpression in Caco-2 and T84 cells caused a significant decrease in TEER and a significant increase in the amount of dextran flux through the cell monolayer, suggesting significant dysfunction of the barrier integrity. miR-24 overexpression also decreased apoptosis and had no effect on proliferation, suggesting that the increased paracellular permeability is a result of changes within the tight junction. This is supported by the differential regulation of various genes and proteins related to tight junctions, including cingulin, JAM-A, claudin-4, and occludin in miR-24 overexpressing cells. miR-24 is a significant regulator of tight junction integrity and its increased expression could play a role in intestinal barrier dysfunction in UC. As such, miR-24 is a novel therapeutic target to restore tight junction integrity in the gastrointestinal tract.