Deoxyribonucleic acid alkylation repair deficient mice are susceptible to chemically induced IBD

Thesis (S.M.)--Massachusetts Institute of Technology, Biological Engineering Division, 2006.Includes bibliographical references (leaves 92-93).The two most common forms of inflammatory bowel disease (IBD) are ulcerative colitis (UC) and Crohn's Disease (CD), which affect more than 1 million Americans. Recently the incidence of IBD has been rising in Japan, Europe and North America.' Colorectal cancer is a very serious complication of IBD, and a patient's risk increases with increasing extent and duration of disease.2 There is no cure for CD, and the only cure for UC is removal of the entire colon and rectum. It is thought that cancer risk is based on chronic inflammation of the gastrointestinal mucosa. There have been many studies, which have supported this idea and have made progress toward understanding the link between chronic inflammation and cancer. In both UC and CD, it is known that there are increased levels of EA, cG, and eC, which are potentially miscoding lesions, in the DNA of affected tissues.3 Also, 3-methyladenine DNA glycosylase (Aag in mice), an initiator of the Base Excision Repair pathway, shows adaptively increasing activity in response to increased inflammation in UC colon epithelium.4 This thesis demonstrates the importance of Aag in protecting against the effects of chronic inflammation.(cont.) It was found that Aag deficient mice, treated with 5 cycles of dextran sulfate sodium (DSS) to induce chronic inflammation, showed significant signs of increased disease including decreased colon length, increased spleen weight, and increase in epithelial defects. Also, when treated with a tumor initiator, azoxymethane, prior to DSS exposure, Aag deficient mice show a 2.95 fold (p