H. Pylori Induced Oxidative Stress

幽门螺杆菌诱导的胃癌的病因是多因素的，但其中一个重要的组成部分是 免疫反应失调，导致慢性炎症和细胞损伤。我们的实验室 发现了一种在幽门螺杆菌中产生氧化应激诱导的DNA损伤的新途径- 多胺精胺被酶氧化所致的胃上皮细胞损伤 精胺氧化酶(SMO)，产生过氧化氢(H2O2)。产生更多用于SMO的底物 以L-鸟氨酸为原料，经鸟氨酸脱羧酶催化合成多胺。我们还有 以前涉及一氧化氮(NO)，报告说这种酶诱导NO合成酶(INOS) 产生高水平的NO，这是一种已知的诱变剂，在体外和体内都被幽门螺杆菌上调。工作 在这项研究的支持下，P01显示哥伦比亚的胃癌发病率差异很大， 来自安第斯山脉高危地区的个人罹患癌症的风险是前者的25倍。 尽管幽门螺杆菌感染的流行率相同，但与低风险沿海地区的癌症患者相比，这一比例更高。 我们使用基因型匹配的幽门螺杆菌临床分离株进行的初步研究表明，与 来自低风险地区的菌株和来自高风险地区的菌株产生明显更多的SMO和氧化 体外培养的胃上皮细胞DNA损伤与胃炎组织中类似发现的相关性 这些菌株的来源患者。我们还发现，高危菌株在体外和体内诱导更多的iNOS 活着。重要的是，我们表明哥伦比亚的临床分离株可以感染小鼠和沙土鼠，而且高风险 菌株可诱导沙土鼠发育不良。用多位点序列分型方法对6株菌株进行进化分析 来自高危地区的3个毒株与来自欧洲的参考毒株聚在一起 来自低风险地区的3株毒株与来自非洲的毒株聚在一起。我们的假设 SMO的氧化应激和iNOS的亚硝化应激是H. 幽门螺杆菌感染，这些途径是由幽门螺杆菌菌株不同地调制来自高发区和。 低胃癌风险。我们的具体目标是：1.)为了证明幽门螺杆菌菌株来自高与低 胃癌高危区域表现出更强的诱导反应的能力，从而降低了 致癌；2.)证明了ODC合成多胺，SMO氧化精胺，以及 INOS产生的NO是体内胃癌风险的中介物；给微生物下定义 通过对幽门螺杆菌菌株的研究，确定氧化和亚硝化应激的决定因素，以及胃癌风险 哥伦比亚成人和儿童的纵向队列。所提出的研究具有创新性和严密性。 与本P01整合为一个整体，因为他们试图定义胃癌发生的特定机制 由来自不同癌症风险地区的幽门螺杆菌菌株在哥伦比亚自然实验室诱导。 相关性(请参阅说明)： 该项目检查氧自由基和一氧化氮对胃壁造成的损害，以便 确定这些药物在幽门螺杆菌诱发的胃癌中是否起因果作用。

The etiology of H. pylori-induced gastric cancer is multifactorial, but one important component is the dysregulated immune response that leads to chronic inflammation and resulting cellular damage. Our lab has discovered a novel pathway for the generation of oxidative stress-induced DNA damage in H. pylori- iniected gastric epithelial cells that results from oxidation of the polyamine spermine by the enzyme spermine oxidase (SMO), producing hydrogen peroxide (H2O2). Increased substrate for SMO is generated by synthesis of polyamines from L-ornithine by the enzyme ornithine decarboxylase (ODC). We have also previously implicated nitric oxide (NO), reporting that the enzyme inducible NO synthase (INOS) that produces high levels of NO, a known mutagen, is upregulated by H. pylori in vitro and in vivo. Work supported by this P01 has demonstrated dramatically different rates of gastric cancer in Colombia, such that individuals from the high risk region of the Andean mountains have a 25-fold greater risk of developing cancer than those from the low risk coastal region, despite identical prevalence rates of H. pylori infection. Our preliminary studies using genotype-matched H. pylori clinical isolates indicate that when compared to strains from the low risk region, strains from the high risk region induce significantly more SMO and oxidative DNA damage in gastric epithelial cells in vitro that correlates with similar findings in the gastritis tissues from the source patients for these strains. We also found that high risk strains induce more INOS in vitro and in vivo. Importantly, we show that Colombian clinical isolates can infect mice and gerbils, and that a high risk strain induces dyplasia in gerbils. Evolutionary analysis of 6 strains by multi-locus sequence typing revealed that the 3 strains from the high risk region clustered together and with reference strains of European origin and the 3 strains from the low risk region clustered together and with strains of African origin. Our hypothesis is that oxidative stress from SMO, and nitrosative stress from iNOS are determinants of neoplastic risk in H. pylori infection, and these pathways are differentially modulated by H. pylori strains from regions of high vs. low gastric cancer risk. Our Specific Aims are: 1.) To demonstrate that H. pylori strains from the high vs. low gastric cancer risk region exhibit increased ability to induce responses that lower the threshold for carcinogenesis; 2.) To demonstrate that polyamine synthesis by ODC, oxidation of spermine by SMO, and generation of NO by INOS are mediators of gastric cancer risk in vivo; and 3.) To define microbial determinants of oxidative and nitrosative stress, and gastric cancer risk by studying H. pylori strains from longitudinal Colombian cohorts in adults and children. The studies proposed are innovative and tightly ntegrated with this P01 as a whole, as they seek to define specific mechanisms of gastric carcinogenesis induced by H. pylori strains from regions of divergent cancer risk in the Colombian natural laboratory. RELEVANCE (See Instructions): This project examines damage to the stomach lining caused by oxygen radicals and nitric oxide in order to determine if these agents have a causal role in the gastric cancer induced by H. pylori.