The long-term goal of this project is to provide a mechanistic basis for the prevention of Ulcerative colitis (UC)-associated carcinogenesis (UC-Ca). Our unique UC-Ca mouse model will be used to test the hypothesis that leukocyte-NADPH oxidase and endothelial nitric oxide synthase (eNOS) play central roles in UC-Ca by driving nitro-oxidative stress-caused genetic damage and angiogenesis, and by causing cell hyperproliferation via the overproduction of prostaglandin E2 (PGE2) and Leukotriene B4 (LTB4), with the following specific aims: 1. To study the role of leukocyte-generated oxidative stress and associated DNA damage in UC-Ca by using gp91phox (leukocyte NADPH oxidase) and Ogg1 (8-hydroxydeoxyguanine DNA glycosylase) deficient mice. We will test the hypothesis that gp91phox is vital for causing oxidative DNA damage and UC-Ca, and that Ogg1 protects from UC-Ca, using gene knockout mice in the UC-Ca model. 2. To test the hypothesis that eNOS plays a key role in UC-Ca by driving nitro-oxidative stress-caused DNA damage and by promoting angiogenesis, iNOS deficient mice exhibited no difference in susceptibility to UC-Ca or nitrotyrosine formation in our model, but eNOS was expressed in active inflammatory cells. The roles of eNOS or both eNOS/iNOS in UC-Ca will be studied using an eNOS (-/-)mice and the non-selective NOS inhibitor aminoguanidine. 3. To test the hypothesis that inflammation-induced LTB4 and PGE2 overproduction contributes to UCCa by studying the effect of the combination of cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5- LOX) inhibitors. COX-2 inhibition exacerbates UC, possibly via the shunting of arachidonic acid substrate to the LTB4 pathway and increasing inflammatory injury. The combination of 5-LOX- and COX-2-specific inhibitors may overcome this problem in the treatment of UC patients. This concept will be tested in our UC-Ca model. 4. To determine the effectiveness of water-soluble and lipid-soluble antioxidants and their combination as a chemopreventive approach against UC-Ca in wild type and Ogg1(-/-) mice. The combination of vitamin E and N-acetylcysteine (NAC) may exert synergistic or additive effects against nitro-oxidative stress, inflammation, and UC-Ca. This concept will be investigated using our UC-Ca model as well as using Ogg1 knockout mice.