The Role Of Xanthine Oxidoreductase In The Regression Of Colitis And The Applied Research Of Flavonoid Inhibitors

In addition to its pivotal role in purine metabolism,xanthine oxidoreductase(XOR)is one of the key enzymes involved in superoxide radical generation.Researchs showed that xanthine oxidoreductase-medieated oxidative stress is involved in the development of cardiovascular diseases and ischemia-reperfusion injury.Meanwhile,oxidative stress is also a key pathogenic factor of other diseases.Oxidative stress-mediated tissue damage has long been associated with colitis-associated cancer(CAC)initiation,but its molecular mechanism is still unclear.Xanthine oxidoreductase maintains high activity in the liver and gastrointestinal tract.As the primary source of active oxygen free radicals in the intestine,the contribution of xanthine oxidoreductase in the progression of colon disease remains unclear.To explore whether xanthine oxidoreductase-mediated oxidative stress is involved in the development of colon diseases.Firstly,we analyzed the expression and distribution of xanthine oxidoreductase in the development of colon-related diseases in the population by using immunohistochemical methods,and then focused on the mechanisms of xanthine oxidoreductase-mediated oxidative stress in DSS-induced colitis and AOM/DSS-induced colitis-associated colorectal in mice through pharmacological and molecular biological methods.In order to obtain safe and efficient xanthine oxidoreductase inhibitors,the effect of functional factors in food on xanthine oxidoreductase activity was screened by establishing HPLC method in vitro,and evaluated the targeted inhibition of xanthine oxidoreductase by these functional factors on the prevention of colitis-associated colorectal in mice.The main results of this study are as follows:First of all,in order to confirm whether xanthine oxidoreductase is linked to the development of colon-related diseases,the expression and distribution of xanthine oxidoreductase in patients with colon disease were analyzed by immunohistochemical methods,and the results showed that xanthine oxidoreductase has a higher positive rate in patients with ulcerative colitis(17%),polyps(80%),and adenomas(50%)in the early inflammatory stages of colon cancer,while the positive rate is reduced in advanced colon cancer(11%);xanthine oxidoreductase is primary located in the intestinal epithelial cells and interstitial.Allopurinol(10 mg/kg)can effectively alleviates 3%DSS-induced ulcerative colitis in mice,similar to the results in patients with ulcerative colitis,colonic xanthine oxidoreductase expression and activity increased in the model group.Meanwhile,giving the same dose of allopurinol can effectively delay the development of AOM/DSS-induced CAC in mice.Similar to the results of patients in the early stage of colon tumor,xanthine oxidoreductase is located in intestinal epithelial cells and interstitial,and the activity is increased.Then,by using cell models,further studies focus on the the role of xanthine oxidoreductase in promoting the carcinogenesis and development of colon tumors,the results showed that pro-inflammatory factor TNF?mediate AP-1 transcription factor up-regulating the xanthine oxidoreductase expression through p38/JNK MAPK signaling pathway in colon tumor epithelial cells;TNF?and CoCl₂-induced hypoxia can mediate xanthine oxidoreductase up-regulation and cause oxidative DNA damage in colonic epithelial cells,and hydrogen peroxide and superoxide anion produced by xanthine oxidoreductase accumulated in the nucleus may directly cause DNA double-strand damage;under hypoxic conditions,xanthine oxidoreductase regulates the metabolic reprgramming of colon tumor epithelial cells by mediating HIF1?to target GLUT1 and HKII expression.Meanwhile,xanthine oxidoreductase-mediated oxidative stress simultaneously activates NRF2/p62-mediated autophagy of tumor cells to cope with the survival pressure of hypoxia;XOR also involved in LPS-induced transcription of TNF?in macrophages.Finally,in order to obtain safe and effective xanthine oxidoreductase inhibitors and establish a dietary strategy for the prevention of colon cancer development in high-risk groups of ulcerative colitis.In vitro,we evaluated the effects of 12 flavonoids and 2 phenolic acids on the xanthine oxidoreductase activity by established an HPLC method to analyze the uric acid level.The results showed that genistein can effectively inhibit xanthine oxidoreductase activity by a dose-dependent manner;in vivo,genistein alleviates DSS-induced acute colitis in mice by inhibiting xanthine oxidoreductase,and delayed the development of AOM/DSS-induced colitis-associated colorectal in mice.The above results indicate that the expression and distribution of xanthine oxidoreductase in patients with ulcerative colitis and early carcinogenesis are similar to DSS-induced ulcerative colitis and AOM/DSS-induced mouse CAC tumors,respectively,indicating that the animal model we used can be effectively mimic the role of xanthine oxidoreductase in the initiation and development of CAC;at the same time,it partially clarifies that xanthine oxidoreductase-mediated oxidative stress in the inflammation stage mediates the regression mechanism of CAC carcinogenesis by causing oxidative DNA damage to colonic epithelial cell and how colon tumor cells resist hypoxic stress,and also evaluated the feasibility of genistein prevent the development of colitis-associated colorectal by targeted xanthine oxidoreductase in high-risk populations of ulcerative colitis.