Epithelial specific roles for GPx1 in the intestinal microenvironment

Project Summary Antioxidant proteins which regulate reactive oxygen species (ROS) are often considered to be protective in the setting of intestinal inflammation and disease, such as inflammatory bowel disease (IBD). Glutathione peroxidase 1 (GPx1) is a ubiquitously expressed selenoenzyme and potent antioxidant which decreases cellular hydrogen peroxide (H2O2). However, our previous studies using Gpx1-/- mice have indicated that unlike many antioxidants whose loss exacerbates murine colitis, loss of GPx1 confers striking protection from dextran-sodium sulfate (DSS)-induced colitis. Further investigation has suggested GPx1’s protective effect may be due, at least in part, to increased intestinal proliferation and stem cell activity which may help to prevent or repair colitis- induced injury. However, specifically testing epithelial-dependent roles for GPx1 has been hindered by the lack of necessary mouse models, as a mouse model capable of cell type-specific deletion had not yet been developed for Gpx1. Although we have improved our understanding of GPx1’s epithelial roles by use of ex vivo intestinal organoids, which indicate that the observed changes in intestinal cell growth are epithelial-cell intrinsic, our reductionist models cannot truly investigate the contribution of these findings to a complex, multifaceted disease setting such as that observed during IBD. To address this need and better leverage our previous research results, we have now generated a novel Gpx1 floxed mouse model. These mice have subsequently been crossed with the Vil-CreERT2 line, allowing us to restrict Gpx1 loss to intestinal epithelial cells. For the first time, these mice will allow us to specifically investigate GPx1’s epithelial-dependent contributions to intestinal homeostasis, stem cell biology, and experimental colitis as implicated in our K01-funded studies. These contributions will be examined in two specific aims. The first aim will clearly delineate epithelial-dependent versus -independent effects for GPx1 in intestinal homeostasis, mucosal immunology, and colitis. The second aim will complement broader epithelial-based studies by more specifically determining how GPx1 loss alters intestinal stem cell biology. This aim will also begin to explore potential mechanisms by which GPx1 may affect intestinal homeostasis and disease, with initial studies focused on roles in the WNT signaling pathway. Together, these studies will address a major technical limitation, characterize novel research reagents, and provide clarity and preliminary feasibility for future studies as we work to build upon our previous findings on GPx1 in the intestine. Thus, this award will provide greater means to expand my independent research program focused on understanding mechanisms by which GPx1 and antioxidant proteins contribute to intestinal health and disease. As previous research has indicated that optimal ROS levels are key to maintaining intestinal health, ultimately these studies will advance our knowledge of IBD pathobiology and therapeutic options to reduce development, diminish severity, and promote intestinal healing in the setting of intestinal inflammation and IBD.