Glutathione conjugation of environmental toxins

空隙中的卤代烯是许多超级基金网站上常见的有毒物质。在超级基金网站检测到的30种最常见的毒物中，有5种是肾毒性的液体卤代烯。与其他卤代烃不同，血管中的卤代烯通过破坏近端小管细胞而独特地损害肾脏，并导致肾癌。据认为，邻位卤代烯烃的肾毒性和肾癌作用源于它们由肝微粒体谷胱甘肽转移酶转化为谷胱甘肽结合物，在肠道内转化为半胱氨酸-S结合物，然后被肾脏半胱氨酸β-裂解酶裂解，形成有毒的卤代烷基硫醇。这些卤代烷基硫醇的产生最终导致了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以及缺乏体外模型，这一假说很难得到证实。使问题复杂化的是最近的一项发现，即存在不止一种微粒体谷胱甘肽转移酶。我们的目标是：[1]明确地确定单个MGST在调节Superfund血管内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”或过度表达的转基因动物来实现。然后将确定这些动物对超级基金地点检测到的空隙卤代烯烃的敏感性。[2]为了全面鉴定在接触低水平的这些血管卤代烯烃时其表达发生显著变化的基因，这将通过使用cDNA微阵列技术来完成。[3]利用这些信息开发新的生物标志物和动物模型，能够检测现有的组织病理学或生化技术无法检测到的微小的卤代和芳香烃损伤。目前的模型只检测由直接的组织损伤和修复或随后的肿瘤发展引起的损伤，这通常需要暴露在高剂量下。相反，在这个项目中开发的模型应该能够检测到由于暴露于低水平的血管卤代烯烃和任何其他能够产生肝或肾损害的毒素而引起的细胞内稳态的变化。

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.