Basic and Clinical Studies on the Role of Bile Acids in Barrett's Esophagus

描述(由申请人提供)：胃食道反流病(GERD)和巴雷特食道(BE)是美国成年人中异常常见的疾病，是食管腺癌的强烈危险因素。在过去的几十年里，与BE相关的腺癌的发生率增加了六倍以上，由于对BE发病机制和肿瘤进展的分子事件了解有限，这种致命肿瘤的化学预防治疗的发展一直受到阻碍。我们有初步数据表明，Barrett上皮细胞对脱氧胆酸(DCA)诱导的凋亡具有更强的抵抗力，DCA是一种在反流的胃液中发现的疏水性胆汁酸，而不是正常排列在食道内的鳞状细胞。这种凋亡抵抗可能是Barrett化生发生和持续存在的基础，因为屈从于胆汁酸诱导的凋亡的食道鳞状细胞被抗凋亡的Barrett细胞所取代。疏水性胆汁酸，如DCA，也被证明会导致DNA损伤，而广泛的DNA损伤通常会引发细胞凋亡。然而，我们有来自体外和体内研究的初步数据表明，Barrett细胞通过激活抗凋亡生存通路来响应胆汁酸诱导的DNA损伤。这可以通过允许持续致癌突变的细胞存活来促进巴雷特化生的肿瘤性进展。此外，我们的初步研究表明，BE患者的食道鳞状细胞可能比没有BE的GERD患者的食道鳞状细胞更容易受到DNA损伤诱导的细胞凋亡。这种食道鳞状细胞容易发生凋亡的倾向也可能参与了BE的发展。我们的初步数据表明，核因子-kB通路在Barrett化生的细胞凋亡抵抗中起着关键作用。我们也有初步的数据表明，熊去氧胆酸(UDCA)是一种亲水性胆汁酸，在体外和体内都不会引起Barrett细胞的遗传毒性损伤，甚至对DCA暴露引起的DNA损伤具有保护作用。这些发现提示UDCA具有潜在的化学预防作用。最近，我们使用端粒酶技术从患有和不患有BE的GERD患者身上获得了永生的、但良性(未转化)的Barrett细胞系和食道鳞状细胞系。我们建议使用这些细胞系和组织标本来探索胆酸反流激活的调节细胞凋亡的分子通路，以及这些通路在BE的发展和肿瘤进展中的作用。我们假设胆汁酸通过影响核因子-B途径影响食道细胞的凋亡。本研究的目的是在体外和体内研究胆汁酸对正常食管鳞状细胞和化生的Barrett细胞DNA损伤、核因子-B途径和细胞凋亡的影响，阻断关键的核因子-：B蛋白并确定这些干扰在体外对胆汁酸介导的细胞凋亡的影响，以及UDCA是否能在体外对抗毒性更大的胆汁酸对DNA损伤和细胞凋亡的影响。公共卫生相关性：与公共健康相关的是确定特定的分子标志物，这些标志物可用于从我们众多胃食道反流病患者中选择可能受益于积极的抗反流治疗以防止Barrett‘s食道发展的患者，以及选择将从预防食管腺癌的干预措施中受益最大的Barrett’s食管病患者。

DESCRIPTION (provided by applicant): Gastroesophageal reflux disease (GERD) and Barrett's esophagus (BE), which are exceptionally common disorders in adult Americans, are strong risk factors for esophageal adenocarcinoma. The frequency of BE- associated adenocarcinoma has increased more than six-fold in the past few decades, and the development of chemopreventive therapies for this lethal tumor has been hampered by limited understanding of the molecular events underlying the pathogenesis and neoplastic progression of BE. We have preliminary data showing that Barrett's epithelial cells are more resistant to apoptosis induced by deoxycholic acid (DCA), a hydrophobic bile acid found in refluxed gastric juice, than the squamous cells that normally line the esophagus. Such apoptotic resistance might underlie the pathogenesis and persistence of Barrett's metaplasia, as esophageal squamous cells that succumb to bile acid-induced apoptosis are replaced by apoptosis-resistant Barrett's cells. Hydrophobic bile acids like DCA also have been shown to cause DNA damage, and extensive DNA damage normally triggers apoptosis. However, we have preliminary data from in vitro and in vivo studies showing that Barrett's cells respond to bile acid-induced DNA damage by activating anti-apoptotic survival pathways. This could facilitate the neoplastic progression of Barrett's metaplasia by allowing the survival of cells that have sustained cancer-promoting mutations. Moreover, our preliminary studies suggest that esophageal squamous cells from patients with BE may be more susceptible to apoptosis induced by DNA damage than esophageal squamous cells from GERD patients without BE. This predisposition of esophageal squamous cells to succumb to apoptosis also may contribute to the development of BE. Our preliminary data suggest that the NF-kB pathway plays a key role in the apoptotic resistance of Barrett's metaplasia. We also have preliminary data showing that ursodeoxycholic acid (UDCA), a hydrophilic bile acid, does not induce genotoxic damage in Barrett's cells in vitro or in vivo, and even protects against the DNA damage caused by DCA exposure. These findings suggest a potential chemopreventive role for UDCA. Recently, we have used telomerase technology to generate immortal, but benign (non-transformed), Barrett's cell lines and esophageal squamous cell lines from GERD patients with and without BE. We propose to use these cell lines as well as tissue specimens to explore the molecular pathways activated by bile-acid reflux that regulate apoptosis, and the role of those pathways in the development and neoplastic progression of BE. We hypothesize that bile acids influence apoptosis in esophageal cells through effects on the NF-:B pathway. The aims of this study are to delineate the effects of bile acids on DNA damage, on the NF-:B pathway, and on apoptosis in normal esophageal squamous and metaplastic Barrett's cells in vitro and in patients in vivo, to disrupt the key NF-:B proteins and determine the effects of those disruptions on bile-acid mediated apoptosis in vitro, and to determine whether UDCA can protect against the effects of the more toxic bile acids on DNA injury and apoptosis in vitro. PUBLIC HEALTH RELEVANCE: The relevance to public health is the identification of specific molecular markers that can be used to select a subset of our many patients with gastroesophageal reflux disease who might benefit from aggressive anti- reflux therapies to prevent the development of Barrett's esophagus as well as to select a subgroup of patients with Barrett's esophagus who would benefit most from interventions to prevent esophageal adenocarcinoma.