Reflux-Induced Oxidative DNA Damage Repair Early in Barrett's Carcinogenesis

Barrett 癌变早期回流诱导的氧化 DNA 损伤修复

• 批准号: 10292418
• 负责人: Kerry Brandt Dunbar
• 金额: --
• 依托单位: VA NORTH TEXAS HEALTH CARE SYSTEM
• 依托单位国家: 美国
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-07-01 至 2023-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10292418
• 关键词: Acids; Acute; Address; Barrett Epithelium; Barrett Esophagus; Barrett' s carcinogenesis; Base Excision Repairs; Bile Acids; Bile Acids and Salts; Biopsy Specimen; Cell Line; Cells; Chronic; Complication; DNA Damage; DNA Repair; DNA-(apurinic or apyrimidinic site) lyase; Data; Development; Disease; Disease susceptibility; Epithelial Cells; Esophageal Adenocarcinoma; Esophagus; Event; Frequencies; Gastric Acid; Gastroesophageal reflux disease; Genes; Genome Stability; Genomic Instability; Genomics; Impairment; In Vitro; Incidence; Inflammation; Intestines; Knowledge; Lead; Left; Maintenance; Malignant - descriptor; Malignant Neoplasms; Malignant neoplasm of esophagus; Medical; Metaplasia; Modernization; Molecular; Mucositis; Mucous Membrane; Nuclear; Oxidative Stress; Pathway interactions; Patients; Peptic Esophagitis; Perfusion; Pharmaceutical Preparations; Preventive; Production; Proteins; Proton Pump Inhibitors; Reactive Oxygen Species; Reflux; Risk Factors; Role; Site; Stomach; TP53 gene; Tissues; Veterans; Work; base; bile salts; carcinogenesis; cell type; design; endonuclease; genome integrity; improved; in vivo; nucleophosmin; oxidative DNA damage; oxidative damage; p38 Mitogen Activated Protein Kinase; prevent; repaired; response; tumor progression

Project Summary Gastroesophageal reflux disease (GERD) can be complicated by Barrett’s esophagus, the condition in which a metaplastic, intestinal-type mucosa replaces esophageal squamous mucosa that has been damaged by GERD. Both GERD and Barrett’s esophagus are risk factors for esophageal adenocarcinoma, a deadly cancer whose incidence has been increasing rapidly for decades. Chronic GERD contributes to the malignant transformation of Barrett’s esophagus by causing inflammation, oxidative stress and oxidative DNA damage in the metaplastic mucosa. The modern medical treatment of GERD is directed almost exclusively at decreasing gastric acid production with medications such as proton pump inhibitors (PPIs), which are very effective in controlling reflux esophagitis. However, the PPIs do not eliminate gastric acid secretion, they merely decrease it, and they do nothing to correct the underlying reflux diathesis. Thus, PPIs do not prevent the reflux of weakly acidic material and bile salts, both of which can inflict oxidative injury on the esophagus. This might explain why the frequency of esophageal adenocarcinoma continues to rise despite the widespread use of PPIs. To prevent Barrett’s cancers, new treatments are needed to minimize reflux-induced, oxidative genomic damage. Recent data suggest that esophageal adenocarcinomas develop as a direct consequence of GERD- induced oxidative DNA damage in Barrett’s metaplasia. Left unrepaired, this DNA damage leads to genomic instability and carcinogenesis. Maintenance of genomic integrity requires an appropriate cellular response to oxidative injury, which normally is provided by the p53 gene. This gene is inactivated frequently during carcinogenesis in Barrett’s esophagus, however. In some p53-deficient cell types, p38 can assume the role of “guardian” of genomic stability. In earlier studies, we showed that esophageal acid perfusion specifically activated p38 in the non-dysplastic Barrett’s mucosa of patients in vivo, and that Barrett’s cells in vitro were uniquely susceptible to bile acid-induced DNA damage. We also have established Barrett’s epithelial cell lines that faithfully recapitulate molecular events induced by acid and bile salts in primary tissues. We have inactivated p53 in some of these unique cell lines, which we propose to use in studies that recapitulate the early stages of Barrett’s carcinogenesis. We have preliminary data demonstrating that weakly acidic bile salts induce Barrett’s epithelial cells to generate reactive oxygen species (ROS) that cause oxidative DNA damage. This oxidative injury results in a modest, brief increase in phospho-p38 in p53-intact Barrett’s cells, while oxidative DNA damage triggers a strong, sustained phospho-p38 increase in p53-deficient Barrett’s cells. We show that inhibition of p38 impairs the ability of Barrett’s cells to remove apurinic/apyrimidinic (AP) sites, the early manifestations of oxidative DNA damage that ordinarily are eliminated by AP endonuclease-1 (APE-1), a base-excision-repair protein. We have found that acidic bile salts cause Barrett’s cells to increase their expression and nuclear localization of nucleophosmin 1 (NPM1), a protein that enhances the functional efficiency of APE-1; these events also are impaired by p38 inhibition. Based on these findings, we hypothesize that activation of the p38 pathway in Barrett’s cells by reflux-induced oxidative stress is an important cancer-preventive mechanism that works by upregulating NPM1 to enhance the efficiency of APE-1 in repairing oxidative DNA damage. Our proposed studies are designed to elucidate mechanisms whereby p38 activation regulates NPM1 to enhance APE-1 efficiency in repairing reflux-induced oxidative DNA damage in Barrett’s cells, and to demonstrate that acute reflux esophagitis in Barrett’s patients is associated with p38 activation and with markers of enhanced efficiency of APE-1 in their Barrett’s metaplasia. These studies will elucidate early cellular and molecular events that drive neoplastic progression in Barrett’s esophagus, thereby providing the basis for development of new medical treatments to prevent deadly Barrett’s cancers in our Veteran patients.

项目概要 胃食管反流病 (GERD) 可能因巴雷特食管而并发，巴雷特食管是一种常见的食管疾病。 化生的肠型粘膜取代了受损的食管鳞状粘膜 胃食管反流病和巴雷特食管都是食管腺癌的危险因素，食管腺癌是一种致命的疾病。 几十年来，慢性胃食管反流病（GERD）的发病率一直在迅速增加，这导致了癌症的恶性发展。 通过引起炎症、氧化应激和氧化 DNA 损伤来改变巴雷特食管 GERD 的现代医学治疗几乎完全针对减少化生粘膜。 使用质子泵抑制剂 (PPI) 等药物抑制胃酸产生，这些药物非常有效 然而，质子泵抑制剂并不能消除胃酸分泌，而只是减少胃酸分泌。 它们对纠正潜在的反流素质没有任何作用，因此，质子泵抑制剂不能预防弱反流。 酸性物质和胆汁盐，两者都会对食道造成氧化损伤，这可能可以解释。 尽管质子泵抑制剂广泛使用，但食管腺癌的发病率仍然持续上升。 为了预防巴雷特氏癌症，需要新的治疗方法来最大限度地减少反流引起的氧化基因组损伤。 最近的数据表明，食管腺癌的发生是 GERD 的直接后果。 在 Barrett 化生中诱导氧化 DNA 损伤如果不加以修复，这种 DNA 损伤会导致基因组。 维持基因组完整性需要适当的细胞反应。 氧化损伤，通常由 p53 基因造成，该基因在氧化过程中经常失活。 然而，在某些缺乏 p53 的细胞类型中，p38 可以发挥作用。 在早期的研究中，我们发现食管酸灌注是基因组稳定性的“守护者”。 在体内激活患者非发育不良 Barrett 粘膜中的 p38，并且体外 Barrett 细胞 对胆汁酸诱导的 DNA 损伤特别敏感 我们还建立了 Barrett 上皮细胞系。 忠实地再现了原代组织中酸和胆汁盐诱导的分子事件。 在一些独特的细胞系中灭活了 p53，我们建议将其用于概括 巴雷特癌变的早期阶段。 我们有初步数据表明弱酸性胆汁盐诱导巴雷特上皮细胞 产生活性氧 (ROS)，导致 DNA 氧化损伤，这种氧化损伤会导致 DNA 氧化损伤。 p53 完整的 Barrett 细胞中磷酸化 p38 适度短暂增加，而氧化 DNA 损伤则引发 p53 缺陷的 Barrett 细胞中磷酸化 p38 强烈、持续增加，我们发现抑制 p38 会损害细胞。 Barrett 细胞去除无嘌呤/无嘧啶 (AP) 位点的能力，氧化的早期表现 通常由 AP 核酸内切酶-1 (APE-1)（一种碱基切除修复蛋白）消除的 DNA 损伤。 发现酸性胆汁盐会导致巴雷特细胞增加其表达和核定位 核磷蛋白 1 (NPM1) 是一种增强 APE-1 功能效率的蛋白质； 基于这些发现，我们追踪了 p38 通路的激活。 巴雷特细胞通过反流诱导的氧化应激是一种重要的癌症预防机制，其作用原理是 我们提出上调 NPM1 以增强 APE-1 修复氧化 DNA 损伤的效率。 研究旨在阐明 p38 激活调节 NPM1 以增强 APE-1 的机制 修复 Barrett 细胞中反流诱导的氧化 DNA 损伤的效率，并证明急性 Barrett 患者的反流性食管炎与 p38 激活和增强标记物相关 这些研究将阐明 APE-1 在巴雷特化生中的早期细胞和分子作用。 驱动巴雷特食管肿瘤进展的事件，从而为以下疾病的发展提供基础 新的治疗方法可以预防我们的退伍军人患者患上致命的巴雷特氏癌症。