Mechanisms of Gut Epithelial Duox-mediated Intestinal Homeostasis

PROJECT SUMMARY/ABSTRACTA monolayer of gut epithelial cells covers the intestinal lumen preventing an overt immune response againstthe normal gut microbiota, while at the same time controlling infection with potentially life-threateningpathogens. Breakdown of this homeostatic relationship can lead to foodborne infections and chronic intestinalinflammation. Reactive oxidative species (ROS) play a critical role in mucosal host defense but also contributeto the inflammatory milieu. The protective host defense role of the classical NOX2/gp91phox NADPH oxidase,responsible for the oxidative burst reaction of macrophages, has been extensively researched, but the role ofanother NADPH oxidase, dual oxidase (DUOX) is less clear. Our long-term objective is to define the role ofDUOX2, the only form of DUOX expressed in the gut epithelium, in epithelial defense to maintain mucosalhomeostasis. The objective here is to determine how DUOX2 can protect epithelial cells from invasive bacteriathat produce antioxidative enzymes to shield themselves from H2O2. Our hypothesis is that activation ofDUOX2 by bacterial attachment is critical for proper handling of engulfed bacteria to maintain microbe-host homeostasis. The rationale for the proposed research is that, once it is known how DUOX2 orchestratesmucosal host defense in the intestinal epithelium, specific pharmacotherapeutics can be selected to enhanceDUOX-mediated bacterial handling, resulting in new approaches to the prevention and treatment of a varietyof GI disorders associated with increased bacterial translocation. We will test our central hypothesis and,thereby, accomplish the objective of this application by pursuing the following specific aims: 1. Investigatethe mechanisms of DUOX2 induction by mucosa-associated bacteria, 2. Define the role of DUOX2 inthe cell-autonomous containment of intestinal pathogens. 3. Study the implications of DUOX2deficiency for susceptibility to IBD. The expected outcomes, the proposed work is expected to elucidate amechanistic framework how DUOX2 is activated in response to bacteria-epithelial contact, supports cell-autonomous inactivation of intracellular bacteria, and, thereby, maintains immune homeostasis. Such resultsare expected to have an important positive impact because this immune mechanism is highly likely to providenew targets for preventative and therapeutic interventions for diseases associated with dysregulated microbe-intestinal interaction (e.g., IBD, IBS, colon cancer) in addition to fundamentally advancing the fields of gutmucosal immunity. It will also provide much-needed insight into the pathogenesis of IBD linked to DUOX2 LOFand thus the foundation to better strategize a treatment plan for these patients.