Intestinal Barrier Function: Protective Effects of Curcumin

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DESCRIPTION (provided by applicant): The intestinal epithelial monolayer pays a crucial role not only in regulating transcellular and paracellular nutrient absorption, but also by providing an innate barrier against pathogenic and commensal bacteria and microbial and dietary antigens. Breakdown of this protective barrier has been implicated in the pathogenesis of acute illnesses such as bacterial translocation leading to sepsis and multiple organ system failure. It also has been implicated in several chronic diseases having their origins during infancy that manifest in later life. These include atopic disease such eczema, food allergies, celiac enteropathy, type 1 diabetes, asthma, and inflammatory bowel disease. Important inducers of intestinal barrier dysfunctions include proinflammatory cytokines (with IFN-? as a prototypical barrier-damaging cytokine) and infiltrating and translocating neutrophils and their enzymatic products. Chronic and severe neutrophil infiltration, transepithelial migration and enzymatic and oxidative damages of the epithelium and the extracellular matrix, significantly contribute to the impairment of the epithelial barrier. In a number of inflammatory human diseases, including ischemic bowel injury, necrotizing enterocolitis, and idiopathic inflammatory bowel disease, intense neutrophil transepithelial migration is a prevalent feature and correlates with disease pathophysiology. In this proposal, we hypothesize that curcumin improves intestinal barrier through inhibition of IFN-? signaling in the CEC, inhibition of neutrophil recruitment and apical retention, and thorough inhibition of the detrimental effects of neutrophils on the barrier function during transmigration. These effects likely underlie the demonstrated protective effects of curcumin in intestinal inflammation, as demonstrated in animal models of colitis and in the clinical trial with ulcerative colitis patients. We propose to address these newly attributed functions of curcumin in three specific aims tailored to (1) identify the molecular mechanism of the inhibitory effects of curcumin on IFN-? signaling in the colonocytes; (2) identify the molecular mechanisms of inhibitory effects of curcumin on neutrophil chemokinesis and chemotaxis; and (3) to characterize the molecular mechanisms of the protective effects of curcumin on neutrophil-induced epithelial dysfunction. In summary, the proposed project will provide novel information about the mechanisms and molecular targets of curcumin in improving the intestinal barrier function. PUBLIC HEALTH RELEVANCE: This proposal is focused on a clinically relevant aspect of numerous intestinal and extraintestinal disorders initiated or exacerbated by a dysfunction or failure of the intestinal epithelial barrier. Nutritional interventions, such as with the described natural compound, curcumin, hold promise as effective supplemental therapy which may lead to improvement of symptoms, decreased relapse rate in chronic inflammatory conditions, and overall provide easily tolerated and inexpensive means of improving life quality in patients with recurring inflammatory conditions of the bowel.