Differential Transcription Factor Activation by H. pylor

幽门螺杆菌激活差异转录因子

• 批准号: 6881069
• 负责人: DUANE T. SMOOT
• 金额: $ 25.21万
• 依托单位: HOWARD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-09-30 至 2007-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6881069
• 关键词: ADP ribosylation; CD95 molecule; DNA damage; Helicobacter; apoptosis; carcinogenesis; cytotoxicity; free radical oxygen; gastrointestinal epithelium; nuclear factor kappa beta; oxidative stress; p53 gene /protein; tissue /cell culture

DESCRIPTION (provided by applicant): The discovery of Helicobacter pylori (H. pylori) infection has greatly changed our understanding of upper G.I. tract diseases, including peptic ulcer disease and stomach cancer. The world health organization has classified H. pylori as a group one carcinogen. Reactive oxygen species (ROS) are known carcinogens and have been shown to play a role in gastric cancer. Our studies have shown that H. pylori stimulates the generation of ROS within gastric cells. By placing gastric cells into a pro-oxidant state, H. pylori increases the risk of DNA damage from ROS and the development of cancer. Epithelial cells protect themselves from DNA damage by undergoing apoptosis. H. pylori induce apoptosis is associated with activation of both NF-kappaB and p53. Also H. pylori induced apoptosis is associated with stimulation of the CD95/Fas pathway. Our preliminary studies show that the increase in p53 protein after exposure of gastric cells to H. pylori is associated with increased expression of p14 ARF and down regulation of mdm2. The studies planned in this proposal will identify any interactions between p53 mediated apoptosis and CD95/Fas-mediated apoptosis in response to H. pylori We hypothesize that stimulation of intracellular reactive oxygen species within eukaryotic cells is a major mediator of H. pylori induced cellular injury resulting in oxidant associated DNA damage and apoptosis. We further hypothesize that transcription factors p53 and NF-KappaB are important downstream mediators of ROS induced cellular injury from exposure to H. pylori. Our more recent studies show that the rise in p53 after exposure to H. pylori is secondary to stimulation of ARF which stabilizes p53 by preventing Mdm2 inhibition of p53 activity and Mdm2 mediated degradation of p53. Therefore, ROS may be responsible for stimulation of ARF resulting in increased p53. The specific aims of this proposal are: (1) to determine whether or not ROS leads to activation of NF-KappaB which may sensitize gastric cells to apoptosis, dependent or independent of p53; (2) To elucidate mediators of ARF activation by H. pylori leading to increased p53 protein and apoptosis; (3) To determine the involvement of the CD95 (Fas/Apo-1) receptor/ligand system in p53 sensitization of gastric cells to apoptosis induced by H. pylori. Identification of transcription factors activated by this bacterium and elucidation of apoptotic pathways involved will assist us to develop better treatment strategies to prevent serious disease from this infection. By protecting gastric cells from ROS, one may be able to negate the carcinogenic properties of this bacterium.

描述（申请人提供）：幽门螺杆菌（H. pylori）感染的发现极大地改变了我们对上消化道的认识。消化道疾病，包括消化性溃疡病和胃癌。世界卫生组织已将幽门螺杆菌列为第一类致癌物。活性氧（ROS）是已知的致癌物质，并已被证明在胃癌中发挥作用。我们的研究表明，幽门螺杆菌刺激胃细胞内ROS的产生。通过将胃细胞置于促氧化状态，幽门螺杆菌会增加 ROS 造成的 DNA 损伤和癌症发展的风险。上皮细胞通过凋亡来保护自身免受 DNA 损伤。幽门螺杆菌诱导细胞凋亡与 NF-kappaB 和 p53 的激活相关。幽门螺杆菌诱导的细胞凋亡也与 CD95/Fas 途径的刺激有关。我们的初步研究表明，胃细胞暴露于幽门螺杆菌后p53蛋白的增加与p14 ARF表达的增加和mdm2的下调有关。本提案中计划的研究将确定 p53 介导的细胞凋亡和 CD95/Fas 介导的幽门螺杆菌响应细胞凋亡之间的任何相互作用。我们假设真核细胞内活性氧的刺激是幽门螺杆菌诱导的细胞损伤的主要介质，导致氧化剂相关的 DNA 损伤和细胞凋亡。我们进一步假设转录因子 p53 和 NF-KappaB 是 ROS 暴露于幽门螺杆菌引起的细胞损伤的重要下游介质。我们最近的研究表明，接触幽门螺杆菌后 p53 的升高继发于 ARF 的刺激，ARF 通过阻止 Mdm2 对 p53 活性的抑制和 Mdm2 介导的 p53 降解来稳定 p53。因此，ROS 可能是刺激 ARF 导致 p53 增加的原因。该提案的具体目的是：（1）确定ROS是否会导致NF-KappaB激活，从而使胃细胞对细胞凋亡敏感，依赖于或独立于p53； (2) 阐明幽门螺杆菌激活ARF导致p53蛋白增加和细胞凋亡的介质； (3)确定CD95(Fas/Apo-1)受体/配体系统在p53对幽门螺杆菌诱导的胃细胞凋亡的敏感性中的参与。鉴定这种细菌激活的转录因子并阐明所涉及的细胞凋亡途径将有助于我们制定更好的治疗策略，以预防这种感染引起的严重疾病。通过保护胃细胞免受活性氧的影响，人们或许能够消除这种细菌的致癌特性。