Acid Adaptation Targets for Eradication of Helicobacter pylori

描述(由申请人提供)： 幽门螺杆菌感染了世界上一半人口的胃。这种感染是消化性溃疡疾病的主要原因，也是胃癌的高危因素。因此，根除幽门螺杆菌感染可以促进溃疡愈合，降低患胃癌的风险。在幽门螺杆菌的发现之前，人们认为胃酸为细菌感染提供了一个不适宜居住的环境。然而，幽门螺杆菌独一无二地发展了在人类胃的酸性表面生存和生长的方法，这一过程被称为酸驯化。破坏这一过程会导致在酸中丧失存活率；因此，这一过程的组成部分将为根除治疗提供新的靶点。目前的根除疗法需要在使用抑酸药物的同时使用抗生素。由于抗生素耐药性的增加，通过这些疗法成功根除的病例正在减少，导致美国的应答率约为70%。依赖生长的抗生素克拉霉素或阿莫西林除非细菌处于生长阶段，否则无效。改善酸抑制应能改善治疗结果。在第一个目标中，我们假设抑制酸分泌增加了生长阶段的细菌数量，使它们对生长依赖的抗生素敏感，这就需要在成功根除抗生素的同时还使用抑酸化合物。仅用奥美拉唑和阿莫西林，缓慢的奥美拉唑代谢物对酸的控制和有效的根除的反应得到了极大的改善，这一发现表明，酸抑制的改善增加了有机体对生长依赖抗生素的敏感性。由此可见，随着胃内pH值的更一致和更大的升高，更多的微生物处于抗生素敏感的生长阶段，而不是耐药的静止阶段。白天和晚上保持较高的pH值应该会使几乎所有的幽门螺杆菌都处于生长阶段。因此，深部酸抑制对阿莫西林杀菌作用的影响将在沙土鼠体内进行试验。UreI是一种质子门控尿素通道，至少与尿素酶和Ni2+插入亚基形成内膜复合体。这种复合体的形成和组成该复合体的其他蛋白质的相互作用将使用最先进的MS/MS技术进行鉴定。UreI的新晶体结构将被用来确定与通道相互作用的蛋白质的细胞质环结合部位。在未来，被确定为必需的环可以被用于开发新的和特定的UreI复合体形成抑制剂。成功完成这一目标可能导致根除幽门螺杆菌的单一疗法。

DESCRIPTION (provided by applicant): Helicobacter pylori infects the stomach of half of the world's population. This infection is a primary cause of peptic ulcer disease and a high risk factor for gastric cancer. Therefore, eradication of H. pylori infection leads to ulcer healing and lowers the risk of gastric cancer. Unil the discovery of H. pylori, it was thought that stomach acid presented an inhospitable environment for bacterial infection. However, H. pylori has uniquely developed the means of surviving and growing on the acidic surface of the human stomach, a process termed acid acclimation. Disruption of this process leads to loss of survival in acid; therefore, the components of this process would provide novel targets for eradication therapy. Current eradication therapies require the use of antibiotics along with acid-inhibitory drugs. The successful eradication by these therapies is decreasing because of increasing antibiotic resistance, resulting in a response rate of ~70% in the USA. The growth-dependent antibiotics clarithromycin or amoxicillin are not effective unless bacteria are in growth phase. Improving acid inhibition should improve therapeutic outcome. In the first aim, we hypothesize that inhibition of acid secretion increases the number of bacteria in growth phase, making them sensitive to growth-dependent antibiotics, necessitating the requirement for administration of acid-inhibitory compounds, in addition to antibiotics for successful eradication. The finding that slow omeprazole metabolizers respond with much improved acid control and effective eradication with omeprazole and amoxicillin alone, suggests that improved acid inhibition increases the sensitivity of the organism to growth-dependent antibiotics. From this it follows that, with more consistent and greater elevation of intragastric pH, more organisms are in the antibiotic-sensitive growth phase rather than the resistant stationary phase. Maintenance of an elevated pH for both day and night should put almost all H. pylori in growth phase. Therefore, the effect of profound acid inhibition on the bactericidal effect of amoxicillin will be tested in ivo in the gerbil. UreI, a proton-gated urea channel, forms an inner membrane complex at least with urease and the Ni2+ insertion subunits. Formation of this complex and interaction of other proteins that comprise the complex will be identified using state-of-the-art MS/MS techniques. The novel crystal structure of UreI will be used to identify the cytoplasmic loop binding sites of the proteins interacting with the channel. In the future, the loops identified as essential can be exploited for the development of novel and specific inhibitors of UreI complex formation. Successful completion of this aim could lead to an H. pylori-specific mono-therapy for eradication.