Glutathione conjugation of environmental toxins

乙烯卤代烯烃是在许多超级基金场地常见的有毒物质。在超级基金场所检测到的30种最常见的有毒物质中，有5种是肾毒性的vacinal卤代烯烃。与其他卤代烃不同，乙烯卤代烯烃通过破坏近端小管细胞而独特地损害肾脏并诱发肾癌。据信，邻位卤代烯烃的肾毒性和肾致癌作用源于其通过肝微粒体谷胱甘肽转移酶转化为GSH-缀合物，GSH-缀合物在其肠中转化为半胱氨酸-S-缀合物，半胱氨酸-S-缀合物然后被肾半胱氨酸β-裂解酶裂解以形成毒性卤代烷基硫醇。这些卤代烷基硫醇的产生最终导致肾近端小管细胞的破坏。由于三个器官系统之间复杂的相互作用和缺乏体外模型，这一假设的证实一直很困难。使问题复杂化的是最近发现存在不止一种微粒体谷胱甘肽转移酶。 我们的目标是：[1]明确确定单个MGST在调节Superfund vacinal卤代烯烃污染物的肝毒性和肾毒性中的作用。这将通过分离三种不同的MGST基因并产生“敲除”或过表达的转基因动物来实现。然后将确定这些动物对在超级基金研究中心检测到的vacinal卤代烯烃的敏感性。[2]为了全面识别在暴露于低水平的这些疫苗卤代烯后表达发生显着改变的基因，这将通过使用cDNA微阵列技术来实现。[3]利用这些信息来开发新的生物标志物和动物模型，能够检测现有组织病理学或生物化学技术无法检测到的细微卤代烃和芳香烃损伤。目前的模型只能检测到明显的组织损伤和修复引起的损伤，或随后的肿瘤发展，这通常需要暴露于高剂量。相比之下，本项目中开发的模型应该能够检测到暴露于低水平的乙烯卤代烯烃和任何其他能够产生肝或肾损伤的毒素所引起的细胞内稳态的改变。

The vacinal haloalkenes are toxicants commonly found at many Superfund sites. Of the 30 most common toxicants detected at Superfund sites, five are nephrotoxic vacinal haloalkenes. Unlike other halogenated hydrocarbons, vacinal haloalkenes uniquely damage the kidney by destroying proximal tubules cells and induce renal carcinomas. It is believed the nephrotoxic and nephrocarcinogenic effects of vicinal haloalkenes stems from their conversion by hepatic microsomal glutathione transferase to GSH-conjugates which are converted in their intestine to cysteine-S-conjugates, which are then cleaved by renal cysteine beta-lyases to form toxic haloalkylthiols. The production of these haloalkylthiols is ultimately responsible for destruction of renal proximal tubular cells. Confirmation of this hypothesis has been difficult due to the complex interaction between three organ systems and lack of in vitro models. Complicating the issue is the recent discovery there exists more than one microsomal glutathione transferase. Our objectives are: [1] to definitively determine the role of individual MGSTs in modulating hepatotoxicity & nephrotoxicity of the Superfund vacinal haloalkene contaminates. This will be accomplished by isolating the three different MGST genes and producing "knockout" or over-expressing transgenic animals. The sensitivity of these animals to the vacinal haloalkenes detected at Superfund sites will then be determined. [2] to comprehensively identify genes whose expression is dramatically altered upon exposure to low levels of these vacinal haloalkenes This will be accomplished through the use of cDNA microarray technology. [3] to use this information to develop novel biomarkers and animal models capable of detecting subtle halogenated & aromatic hydrocarbon damage not detectable by existing histopathological or biochemical techniques. Current models only detect damage arising from frank tissue damage and repair, or subsequent development of tumors, which normally require exposure to high doses. The models developed in this project, in contrast, should be able to detect alteration in cellular homeostasis arising from exposure to low-levels of the vacinal haloalkenes and any other toxin capable of producing liver or renal damage.