Direct effects of anti‐inflammatory medication on barrier function in intestinal epithelial cells

Abstract

An impaired intestinal epithelial barrier (IEB) is a hallmark in the pathogenesis of inflammatory bowel diseases (IBD), including ulcerative colitis and Crohn’s disease. Most of the IBD patients are treated with anti‐inflammatory reagents including glucocorticoids, anti TNFα (tumor necrosis factor alpha) antibodies and mesasalazine. While the Immune‐modulating effects of those therapies are well documented, we hypothesized whether there are direct effects of those reagents on enterocytes and the IEB.To address this hypothesis we used Caco2 cells as well as 2D and 3D murine organoids and performed analysis of intestinal epithelial barrier function. Inflammation‐induced alterations were mimicked using cytomix for 24h (TNFα, Interleukin 1 beta and Interferon gamma). The enterocytes were treated with 100ng/ml anti‐TNFα antibody Infliximab, 1mM prednisolone or 5mM mesasalazine, respectively following the challenge with cytomix. Epithelial permeability as revealed by measurements of 4kDa FITC Dextran flux and of transepithelial electric resistance showed that Infliximab and a pre‐incubation with prednisolone for 24h attenuated inflammation‐induced breakdown of the IEB. This was not the case after application of mesasalazine or a simultaneous incubation of prednisolone. The functional changes in intestinal epithelial barrier function following incubation with Cytomix were paralleled by alterations in the expression of “leaky” tight junction protein Claudin2, as revealed by Western blots. Furthermore, immunostainings demonstrated an altered distribution of barrier sealing proteins such as Claudin1, Desmoglein2 and E‐Cadherin. All of these effects were blocked by infliximab and prednisolone.In summary, our data indicate that infliximab and prednisolone have direct effects on the IEB that may contribute to the efficacy in the treatment of IBD.