Differential Transcription Factor Activation by H. pylor

幽门螺杆菌激活差异转录因子

• 批准号: 6732630
• 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/6732630
• 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疾病的认识，包括消化性溃疡和胃癌。世界卫生组织已将幽门螺杆菌列为第一类致癌物质。活性氧簇(ROS)是已知的致癌物质，已被证明在胃癌中发挥作用。我们的研究表明，幽门螺杆菌能刺激胃细胞内ROS的产生。通过将胃细胞置于促氧化状态，幽门螺杆菌增加了ROS对DNA的破坏和癌症的发生。上皮细胞通过细胞凋亡来保护自己免受DNA损伤。幽门螺杆菌诱导的细胞凋亡与核因子-kappaB和P53的激活有关。此外，幽门螺杆菌诱导的细胞凋亡与CD95/Fas通路的刺激有关。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p14ARF的表达增加和MDM2的下调有关。这项计划中计划的研究将确定P53介导的细胞凋亡和CD95/Fas介导的细胞凋亡之间是否存在相互作用，以响应幽门螺杆菌。我们假设，真核细胞内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媒介，导致氧化相关的DNA损伤和细胞凋亡。我们进一步假设，转录因子P53和NF-kappaB是幽门螺杆菌引起的ROS诱导细胞损伤的重要下游介质。我们最近的研究表明，Hp暴露后P53的升高是ARF刺激的次要作用，ARF通过阻止MDM2抑制P53活性和MDM2介导的P53降解来稳定P53。因此，ROS可能是刺激ARF导致P53升高的原因之一。本研究的具体目的是：(1)确定ROS是否导致核因子-kappaB的激活，从而使胃细胞对凋亡敏感，依赖于或不依赖于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体；(3)确定CD95(Fas/Apo-1)受体/配体系统在P53增敏Hp诱导的胃细胞凋亡中的作用。鉴定这种细菌激活的转录因子并阐明相关的凋亡途径将有助于我们制定更好的治疗策略，以防止这种感染引起的严重疾病。通过保护胃细胞免受ROS的影响，人们可能能够否定这种细菌的致癌特性。