A Novel Role of Apical Chloride Transporter (DRA) in Mucosal Tissue Repair

Jesse Brown Va Medical Center, Chicago IL

Investigators

Abstract

Inflammatory bowel diseases (IBDs) comprising of Crohn’s disease (CD) and ulcerative colitis (UC), are characterized by chronic inflammation of the GI tract with increasing incidence and prevalence worldwide. Remarkably, over 66,000 US veterans suffer from IBD and exhibit symptoms such as diarrhea, abdominal pain and increased gut permeability. Since the IBD pathogenesis is governed by multiple factors, the treatment is challenging, and repeated relapses occur. Thus, understanding the molecular mechanisms underlying IBD pathogenesis is critical for developing better therapeutic modalities. Previous studies by the PI and others have shown that DRA or SLC26A3 (a key colonic chloride transporter) plays a critical role in IBD pathogenesis. For example, DRA deficiency was shown to increase colonic permeability and alter gut microbiome. Furthermore, our novel preliminary data from RNA seq analysis and Nanostring nCounter panel analysis of DRA KO mice colons showed a significant impairment in the expression of genes related to stem cell lineage, mitochondrial function, ECM organization, cell cycle, and inflammatory response pathways. Accordingly, DRA KO mice exhibited impaired colonic tissue recovery after acute DSS colitis although mechanisms are not fully understood. Our preliminary data further demonstrated that DRA KO showed altered mitochondrial morphology by TEM microscopy, decrease in mucosal ATP levels, an increase in mitochondrial fission protein (FIS-1) and Cytochrome C protein expression as well as decreased expression of stem cell markers, LGR5, Hopx and Lrig1 along with decreased b-catenin protein expression. Gut microbiome manipulation via cohousing of DRA KO mice with WT mice partially restored the altered expression of stem cell and mitochondrial function markers. However, further studies are needed to understand the role of DRA in altered mucosal tissue repair via mitochondrial dysfunction and stem cell dysregulation in the context of intestinal inflammation. Utilizing state-of-the-art approaches including DRA KO or overexpression mice and appropriate acute and chronic models of colitis, and human and mouse enteroids, we will test the hypothesis that “loss of DRA results in impaired tissue repair in IBD via dysregulation of mitochondrial function and stem cell niche” and that strategies restoring DRA expression can counteract the dysregulation of mitochondrial and stem cell function and impaired tissue repair. Studies proposed in Aim 1 will examine the mechanisms of DRA in maintaining mitochondrial and stem cell function in intestinal tissue repair and establish the therapeutic potential of Mito Q and P110. We will also examine the role of gut microbiome and/or upregulation of DRA expression in maintenance of mitochondrial function, stem cell niche, and tissue repair upon inflammation injury (Aim 2). The successful outcome of these studies may aid in identifying novel targets for maintaining longer remission in veterans with IBD.