Impact of Cadmium Exposure on Transporter Function and Drug Disposition in the Kidney

项目总结/摘要 重金属镉（Cd）目前在2019年美国有毒物质管理局排名第7位， 美国毒物与疾病登记署（ATSDR），并被美国环境保护署列为优先污染物之一 （EPA）。虽然高浓度镉中毒现在很少见，但慢性低浓度镉中毒 接触镉仍然是一个主要的健康问题，因为镉是一种累积金属，具有极长的生物半衰期， 在人体内10-30年。镉暴露与多种疾病的发病率增加有关。 引人注目的是，很少有人知道慢性镉暴露是否会影响用于治疗的药物的处置。 疾病肾转运蛋白通过介导药物跨肾小管细胞转运参与药物的处置 特别是近端小管。通过摄取转运蛋白协调跨细胞转运，如有机 基底外侧膜中的阳离子转运蛋白（OCT）和有机阴离子转运蛋白（OAT）与 外排转运蛋白，如多药和毒素外排蛋白（MATE）和多药耐药相关的 肾小管上皮细胞顶膜中的MRPs被认为是肾功能的重要系统。 阳离子和阴离子药物的处置。我们最近的出版物和目前的初步结果 表明慢性镉暴露对肾脏转运蛋白（包括OCT、MATE、OAT和MRP）的广泛影响。 然而，镉对转运蛋白调控的详细机制及其对药物处置和代谢的广泛影响， 反应仍有待说明。我们假设慢性镉暴露可以改变肾脏转运蛋白， 功能，导致药物处置和肾脏毒性的改变。为了验证这一假设，我们建议 研究有三个具体目标。首先，通过使用各种细胞和分子测定，沿着 通过蛋白质组学方法，我们将揭示慢性镉暴露增强细胞凋亡的分子机制。 OCT和OAT摄取蛋白从细胞质池易位至细胞膜， 增加作为这些转运蛋白底物的小分子的细胞积累（目的1）。最 临床使用的药物是有机阳离子或有机阴离子。然后，我们建议证明的影响， 镉暴露对OCT和MATE的影响 在小鼠肾组织和人肾细胞中的表达，特别是对顺铂处置的影响 和肾毒性使用Oct 1/2-和Mate 1-deficinet小鼠（目的2）。最后，慢性镉暴露的影响 将在小鼠肾组织中表征阴离子药物转运蛋白OAT和MRP的表达 和人肾细胞，特别是镉对抗病毒替诺福韦的处置和肾毒性的影响 将使用Oat 1/3-、Mrp 4-缺陷小鼠和OAT药理学抑制进行研究（目的3）。成功 该项目的完成将提供一个基础，揭示环境镉作为一个以前未被认识到的 药物处置和反应的广泛变化的因素，有助于更好的药物治疗。

PROJECT SUMMARY/ABSTRACT The heavy metal cadmium (Cd) is currently ranked 7th on the 2019 US Agency for Toxic Substances and Disease Registry (ATSDR) and listed as one of Priority Pollutants by US Environmental Protection Agency (EPA). Although intoxication by high levels of Cd exposure is rarely seen nowadays, chronic low levels of Cd exposure is still a major health concern as Cd is a cumulative metal with an extremely long biological half-life of 10-30 years in human body. Cd exposure has been associated with increased incidence of multiple diseases. Strikingly, little is known whether chronic Cd exposure would affect the disposition of drugs that are used to treat diseases. Renal transporter proteins involve in drug disposition by mediating drug transport across tubular cells and particularly proximal tubules. Coordinated transcellular transport by uptake transporters, such as organic cation transporters (OCTs) and organic anion transporters (OATs) in the basolateral membrane in concert with efflux transporters, such as multidrug and toxin extrusion proteins (MATEs) and multidrug resistance-associated proteins (MRPs) in the apical membrane of tubular cells, is believed to be an essential system for renal disposition of cationic and anionic drugs, respectively. Our recent publications and current preliminary results indicate a broad effect by chronic Cd exposure on renal transporters including OCTs, MATEs, OATs and MRPs. However, the detail mechanism of transporter regulation by Cd and its broad impact on drug disposition and response remain to be illustrated. We hypothesize that chronic Cd exposure could alter renal transporter function, resulting in alteration in drug disposition and toxicity in the kidney. To test this hypothesis, we propose to conduct research with three specific Aims. Firstly, by using a variety of cellular and molecular assays, along with proteomic approach, we will uncover a molecular mechanism by which chronic Cd exposure enhances the translocation of OCT and OAT uptake proteins from the cytoplasmic pool to cell membrane and consequently increase the cellular accumulation of small molecules that are the substrates of these transporters (Aim 1). Most clinical used drugs are either organic cations or organic anions. We then propose to demonstrate the impact of Cd exposure on the disposition of cationic drugs by investigating the effects of Cd exposure on OCT and MATE expression in mouse kidney tissues and human renal cells, and particularly the impact on cisplatin disposition and nephrotoxicity using Oct1/2- and Mate1-deficinet mice (Aim 2). Lastly, the effects of chronic Cd exposure on expression of the anionic drug transporters OATs and MRPs will be characterized in mouse kidney tissues and human renal cells, and specifically Cd impact on the disposition and nephrotoxicity of the antiviral tenofovir will be studied with Oat1/3-, Mrp4-deficient mice and OAT pharmacological inhibition (Aim 3). Successful completion of this project will provide a foundation to uncover environmental Cd as a previously unrecognized factor for the broad variation in drug disposition and response, contributing to a better drug theray.