The studies outlined in this application will explore the possible relationship of colonic glycoprotein composition and structure to inflammatory bowel disease. Recent studies in this laboratory have allowed the isolation of purified human colonic mucin. Homogeneous colonic mucin was found to consist of a mixture of at least six distinct mucin species (I-IV). In contrast, mucin from patients with ulcerative colitis (UC) has revealed a selective reduction of one mucin subclass (species IV). The selective reduction of species IV in UC was observed even in mucin isolated from areas of relatively noninflamed colonic mucosa. Thus there may be an underlying selective decrease in one colonic mucin subclass in UC. This research proposal outlines studies to extend these observations on mucin glycoproteins and to evaluate further the structure and function of non-mucin colonic glycoproteins. Methods developed to radiolabel mucin will be used to analyze mucin composition in colon mucosal biopsies in order to evaluate mucin composition in a wide range of disease controls (e.g., infectious, radiation and ischemic colitides). Serial studies will also be undertaken to assess the relationship of the deficiency to UC disease activity. Composition and structure of purified mucin species will be determined; oligosaccharide side chains will be isolated and structure determined using high pressure liquid chromatography (HPLC) gas chromatography-mass spectroscopy technology. In addition mucin subspecies specific antibodies will be developed using hybridoma technology. Development of these reagents will facilitate studies on mucin species localization and goblet cell function. Fluorescent labelling techniques should help delineate changes in mucin composition in health and disease. Non-mucin colonic glycoproteins will be isolated by conventional column chromatography and HPLC. Non-mucin glycoproteins will be characterized in studies paralleling those with mucin glycoproteins. Thus a comprehensive study of colonic glycoproteins is proposed to enhance our unmderstanding of their composition, function and contribution to inflammatory bowel disease.
