Inflammation in the colon can trigger clinical disorders such as Inflammatory bowel disease (IBD), in the form of ulcerative colitis (UC) and Crohn's disease (CD). These are debilitating disorders that significantly affect life-style, and can lead to development of colon cancer. The precise mechanisms that trigger inflammation which leads to the development of IBD are not clear. We have made exciting observations, leading to several publications, indicating that that American ginseng (AG, Panax quinquefolius), can suppress inflammation and is highly effective in the prevention and treatment of colitis. We have also identified the mechanisms of action of AG. Together, our studies indicated that (a) AG is an anti-oxidant that prevents and treats mouse colitis; (b) AG prevents colon cancer associated with colitis in mice; (c) AG drives apoptosis of CD4+/CD25- effector T cells through a p53-mediated pathway in vitro and in vivo; (d) a Hexane Fraction of AG (AG Fraction V) is more potent than the whole AG extract in preventing colitis and colon cancer; and (e) both AG and AG Fraction V target the Nrf2 signaling pathway as a means to suppress inflammation. Our long-term goal is to understand the epigenetic molecular and cellular pathways through which AG mediates its anti-inflammatory effects so that AG and/or one or more of its ingredients can be used as a viable treatment for IBD and prevention of colon cancer in humans. The overall objectives of this application, which is the next step toward attainment of our long-term goal, are to further delineate the ingredients in AG that have the strongest anti-inflammatory properties, as well as examine the mechanisms; focusing on the epigenetic regulation of Nrf2 and its targets. We have demonstrated that AG Fraction V attenuates UC and found that only this fraction V activates Nrf2. Thus, our central hypothesis is that Nrf2 is a critical mediator of AG-induced suppression of colonic inflammation and AG-Fraction V contains the most effective components driving Nrf2-mediated efficacy in IBD treatment. Mechanistically, we propose that the putative bio-effective components of AG mediate epigenetic regulation of Nrf2 thereby providing efficacy in IBD treatment. The rationale that underlies the proposed research is that Nrf2 signaling is a key mechanism toward suppressing inflammation, that inflammation underlies the devastating effects of colitis and eventually colon cancer, and AG/AG Fraction V target Nrf2. Therefore, it is reasonable to investigate the effects and mechanisms of AG/AG Fraction V on Nrf2 signaling. Overall, these studies will demonstrate a central role for Nrf2 in AG-induced suppression of colonic inflammation and prevention of colon cancer through an influence of AG and specific ingredients such as polyacetylenes on the Keap1:Nrf2 interface, miRNAs, and epigenetic regulation. Identifying mechanisms of action of AG will have important implications in understanding the colonic inflammation and approaches to effectively treat IBD.
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