Role of Multidrug Resistance Proteins 2 and/or 4, and DMPS and DMSA in the Renal

描述（由申请人提供）：人类继续暴露于有机（CH3Hg+）和无机（Hg2+）形式的汞。这些环境毒物影响许多器官系统，但其积累和毒性的主要目标是肾脏，特别是近端小管。大量研究表明，金属螯合剂2,3-二巯基丙磺酸（DMPS）和中位2,3-二巯基丁二酸（DMSA）可以去除近端小管中的CH3Hg+和Hg2+。这种去除似乎涉及到细胞内汞离子与其中一种螯合剂形成强键的结合步骤，以及随后的输出步骤，这些汞螯合剂复合物被分泌到管状管腔中。然而，这种分泌的实际机制仍不清楚。然而，基于多药耐药蛋白（MRP）的特性，这些蛋白中的一种或多种可能参与DMPS和DMSA介导的汞离子输出。因此，本研究的目的是验证MRP2和/或MPR4在DMPS和dmsa介导的肾脏CH3Hg+和Hg2+的消除中发挥作用的假设。为了验证这一假设，我们将使用不表达Mrp2蛋白的TR-大鼠和稳定转染了OAT1和Mrp2或MRP4的Madin-Darby犬肾（MDCK）细胞。我们将首先研究DMPS和DMSA对对照和TR-大鼠CH3Hg+和Hg2+处理和处置的影响。作为一种替代模型，转染的MDCK细胞将用于研究MRP2和MRP4在各种汞输出中的作用。使用这些细胞可以分离MRP2和MRP4的活性，并能够更准确地表征每种蛋白质在汞物种运输中的作用。总的来说，这些研究将确定MRP2和/或MRP4是否在DMPS和DMSA介导的近端小管细胞CH3Hg+和Hg2+分泌中发挥作用。从这些实验中获得的数据将作为一套更广泛的研究的基础。目前和今后的研究对人类健康很重要，因为它们将作为制定其他汞中毒治疗方案的基础。汞是人类经常接触的一种普遍的环境毒物。从拟议的研究中获得的数据将提供与汞从体内排出的方式有关的重要信息。这些数据将作为开发其他汞中毒治疗方法的基础。

DESCRIPTION (provided by applicant): Humans continue to be exposed to organic (CH3Hg+) and inorganic (Hg2+) forms of mercury. These environmental toxicants affect numerous organ systems, but a major target for their accumulation and toxicity is the kidney, specifically the proximal tubule. Numerous studies have shown that CH3Hg+ and Hg2+ can be removed from proximal tubules by treatment with the metal chelators, 2,3-dimercapto-1-propanesulfonic acid (DMPS) and meso-2,3-dimercaptosuccinic acid (DMSA). This removal appears to involve a conjugation step wherein intracellular mercuric ions form strong bonds with one of these chelators, and a subsequent export step where these mercury-chelator complexes are secreted into the tubular lumen. The actual mechanisms involved in this secretion, however, remain undefined. Yet based on the characteristics of the multidrug resistance proteins (MRP), it is likely that one or more of these proteins are involved in the DMPS- and DMSA- mediated export of mercuric ions. Therefore, the purpose of the current proposal is to test the hypothesis that MRP2, and/or MPR4, play a role in the DMPS- and DMSA-mediated elimination of CH3Hg+ and Hg2+ from the kidney. To test this hypothesis, we will use TR- rats, which do not express the Mrp2 protein, and Madin-Darby canine kidney (MDCK) cells stably transfected with OAT1 and MRP2 or MRP4. We will first examine the effect of DMPS and DMSA on the handling and disposition of CH3Hg+ and Hg2+ in control and TR- rats. As an alternative model, the transfected MDCK cells will be used to study the roles of MRP2 and MRP4 in the export of various species of mercury. The use of these cells allows for the separation of MRP2 and MRP4 activities and enables a more accurate characterization of the role of each protein in the transport of mercuric species. Collectively, these studies will determine whether MRP2 and/or MRP4 play(s) a role in the DMPS- and DMSA- mediated secretion of CH3Hg+ and Hg2+ from proximal tubular cells. The data obtained from these experiments will serve as the basis for a more expanded set of studies. The current and future studies will be important to human health in that they will serve as the basis for the development of additional therapeutic regimes for mercury poisoning. Mercury is a prevalent environmental toxicant to which humans are exposed frequently. The data obtained from the proposed studies will provide important information related to the way in which mercury is eliminated from the body. These data will serve as the basis for the development of additional treatments for mercury poisoning.