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

项目摘要/摘要 胃食道反流病(GERD)和巴雷特食道(BE)，这是非常常见的 在美国成年人中，疾病是食管腺癌的强烈危险因素。Be-的频率- 在过去的几十年里，相关的腺癌增加了六倍多，而且 对这种致命肿瘤的化学预防治疗由于对分子的有限了解而受到阻碍。 BE发病机制和肿瘤进展的潜在事件。我们有初步数据显示 Barrett氏上皮细胞对疏水性胆汁脱氧胆酸(DCA)诱导的细胞凋亡更具抵抗力 在反流的胃液中发现的酸，而不是通常排列在食道里的鳞状细胞。这样的凋亡性 耐药性可能是Barrett化生的发生和持续的基础，如食道鳞状上皮 屈从于胆汁酸诱导的细胞凋亡的细胞被抗凋亡的巴雷特细胞所取代。 疏水性胆汁酸，如DCA，也被证明会引起dna损伤，以及广泛的dna损伤。 正常情况下会引发细胞凋亡。然而，我们有来自体外和体内研究的初步数据表明 巴雷特细胞对胆汁酸诱导的DNA损伤的反应是通过激活抗凋亡的生存通路。这 可促进Barrett化生的肿瘤性进展 持续的致癌突变。此外，我们的初步研究表明，食道鳞状细胞 BE患者的细胞可能比食道更容易受到DNA损伤诱导的细胞凋亡 无BE的GERD患者的鳞状细胞。食道鳞状细胞的这种易感性 屈从于细胞凋亡也可能参与BE的发展。我们的初步数据表明，核因子- B通路在Barrett‘s化生的细胞凋亡抵抗中起关键作用。我们也有初步数据 表明熊去氧胆酸(UDCA)，一种亲水性胆汁酸，不会引起遗传毒性损害 无论是在体外还是在体内，Barrett‘s细胞都具有保护作用，甚至可以保护DNA免受DCA的损伤。这些 研究结果表明，UDCA具有潜在的化学预防作用。最近，我们使用了端粒酶技术 为了产生永生但良性(未转化)的Barrett细胞系和食道鳞状细胞系 来自患有和不患有BE的GERD患者。我们建议使用这些细胞系和组织标本来 探讨胆酸反流激活的调节细胞凋亡的分子途径及其作用 BE的发展和肿瘤进展中的途径。我们假设胆汁酸会影响 通过影响核因子-βB途径诱导食道细胞的凋亡。这项研究的目的是勾勒出 胆汁酸对正常食管壁DNA损伤、核因子-B途径及细胞凋亡的影响 鳞状细胞和化生的Barrett细胞在体外和体内的患者中，破坏关键的NF-B蛋白和 确定这些干扰在体外对胆汁酸介导的细胞凋亡的影响，并确定 UDCA在体外可对抗毒性较大的胆汁酸对DNA损伤和细胞凋亡的影响。

Project Summary/Abstract 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- ¿B 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.