OXIDATIVE INJURY TO GASTRIC EPITHELIAL CELLS BY H. PYLORI

描述（由申请人提供）：我们工作的长期目标是深入了解幽门螺杆菌感染和胃上皮其他损伤的氧化应激反应导致包括消化性溃疡疾病和胃癌在内的人类疾病的机制。作为对感染的反应，被招募到胃粘膜的吞噬细胞被激活并产生活性氧（ROS），幽门螺杆菌感染直接通过产生ROS诱导胃上皮细胞氧化应激。本项目主要研究ros诱导的无尿嘧啶/无嘧啶核酸内切酶（APE1）的激活，APE1是一种多功能蛋白，是氧化损伤DNA碱基切除修复中的限速酶。它也被称为氧化还原因子(Ref)-1，因为它能够通过还原激活转录因子（包括激活蛋白(AP)-1， NF-¿B和p53）来控制基因表达。我们最近的初步研究建立在理解ROS是由幽门螺杆菌感染期间NADPH氧化酶的激活引起的基础上。在前期研究过程中，我们观察到APE1不仅被ROS激活，而且其诱导对ROS的积累提供了负反馈。数据表明，这种反馈是基于APE1和Rac1之间新的分子相互作用。Rac1是细胞功能的重要调节因子，参与控制细菌感染和包括IBD在内的慢性炎症性疾病的发病机制。其功能之一是激活NADPH氧化酶，导致ROS的积累。APE1通过调节ROS的积累来调节胃上皮细胞反应的假设将在以下具体目标中得到验证：目的1：确定幽门螺杆菌感染期间APE1在上皮细胞ROS积累中的作用。目的2：确定APE1调节Rac1活性的机制。目的3：确定APE1调节NAPH氧化酶的机制。尽管我们对幽门螺杆菌发病机制的了解有所进展，但这种感染导致上皮细胞损伤和恶性肿瘤等疾病的机制仍然知之甚少。所提出的研究的主要目标是定义一种新的分子机制，即APE1通过NADPH氧化酶调节Rac激活和ROS的产生。利用幽门螺杆菌作为模型系统，这些研究将为氧化应激的控制提供新的知识。到5年结束时，预期的结果和里程碑包括定义APE1调节ROS积累的分子基础，包括其与Rac1和NADPH氧化酶的相互作用。这一信息将通过促进我们对与人类胃肠道疾病相关的调节Rac激活的分子机制的理解产生重要的积极影响。

DESCRIPTION (provided by applicant): The long-term goal of our work is to gain insight into mechanisms by which oxidative stress responses to H. pylori infection and other injury to the gastric epithelium lead to human disease including peptic ulcer disease and gastric carcinoma. In response to infection, phagocytes recruited to the gastric mucosa, become activated and generate reactive oxygen species (ROS) and H. pylori infection induces oxidative stress in gastric epithelial cells directly through the generation of ROS. This project has focused on ROS-induced activation of apurinic/apyrimidinic endonuclease (APE1), a multifunctional protein that is the rate-limiting enzyme in DNA base excision repair of oxidative lesions. It is also known as redox factor (Ref)-1 due to its ability to control gene expression by reductively activating transcription factors including activator protein (AP)-1, NF-¿B, and p53. Our recent preliminary studies build on the understanding that ROS arises from activation of NADPH oxidase during H. pylori infection. During the course of preliminary studies, we observed that APE1 is not only activated by ROS, but its induction provides a negative feedback on the accumulation of ROS. Data suggest that this feedback is based on novel molecular interactions between APE1 and Rac1. Rac1 is an important regulator of cell function, implicated in the control of bacterial infections and the pathogenesis of chronic inflammatory diseases including IBD. One of its functions is to activate NADPH oxidase which leads to the accumulation of ROS. The hypothesis that APE1 modulates gastric epithelial cell responses by regulating the accumulation of ROS will be tested in the following Specific Aims: Aim 1: Define the role of APE1 in ROS accumulation in epithelial cells during H. pylori infection. Aim 2: Determine the mechanisms whereby APE1 regulates Rac1 activity. Aim 3: Determine the mechanisms whereby APE1 regulates NAPH oxidase. Despite the advances in our understanding of the pathogenesis of H. pylori, the mechanisms by which this infection leads to epithelial cell injury and disease such as malignancy remain poorly understood. The broad objective for the proposed studies is to define a novel molecular mechanism whereby APE1 regulates Rac activation and the generation of ROS through NADPH oxidase. Using H. pylori as a model system, these studies will provide new knowledge of the control of oxidative stress. By the end of 5 years, the expected outcomes and milestones include a definition of the molecular basis for the regulation of ROS accumulation by APE1 including its interaction with Rac1 and NADPH oxidase. This information will have an important positive impact by advancing our understanding of the molecular mechanisms regulating Rac activation that is relevant to diseases in the human GI tract.