Role and mechanisms of excretion in manganese neurotoxicity

摘要 锰（Mn）是一种必需的金属，但水平升高会引起严重的神经毒性，无法治疗。 虽然锰的直接神经毒性作用已得到充分研究，但锰主要由肝脏排泄， 肠，并报告了与血液和脑锰水平升高相关的神经毒性的高患病率 肝脏疾病患者中。此外，最近的流行病学研究表明，锰排泄的改变， 由于常见的遗传多态性，能力在一般人群中广泛流行。然而， 锰排泄在调节锰诱导的神经系统疾病的结果中的作用尚不清楚， 锰神经毒性的风险是否取决于锰的排泄能力尚未得到回答。 直到最近，研究锰排泄和神经毒性之间关系的一个主要限制是， 锰的排泄机制尚不清楚。我们最近的工作得到了NIEHS“ONES”R 01的支持， 两种锰转运蛋白SLC 30 A10和SLC 39 A14的联合作用对锰的排出是必需的 - SLC 39 A14将血液中的锰转运到肝脏和肠道，SLC 30 A10将细胞内的锰排出 Mn进入胆汁和粪便。此外，我们对Slc 30 a10和/或Slc 39 a14敲除小鼠的分析表明， 脑Mn水平主要受肝脏和肠道中这些转运蛋白的排泄活性调节。 基于排泄在控制脑中Mn水平中的主要作用，我们假设肝 和肠道锰排泄是锰神经毒性的风险和结果的关键调节剂。我们将测试 利用肝脏或肠道特异性Slc 30 a10敲除或敲入小鼠， 在ONES阶段，作为新的人类相关模型，以减少或增加锰排泄，分别。 目的1和2将直接建立肝和肠锰排泄在锰神经毒性中的调节作用。 在目标1中，我们将确定肝脏或肠特异性Slc 30 a10敲除小鼠是否表现出增强的 锰神经毒性敏感性。在目的2中，我们将测试肝或肠特异性Slc 30 a10敲入小鼠是否 防止Mn神经毒性。目标2中的研究具有很高的翻译相关性，因为它们可以识别 增加锰排泄是锰神经毒性管理的有效策略。 目的3将建立在我们的发现基础上，即高浓度的Mn暴露通过Hif 1 α增强了SLC 30 A10的表达。 肝脏，提供了一种手段，以增加锰排泄毒性期间。在目标3中，我们将阐明机制， 以确定这种反应是否能防止神经毒性。这些研究将提供基础 关于在生物体水平上对Mn的保护性反应的信息，尚未描述， 该阶段旨在测试Hif 1 α激活剂在其他疾病的临床试验中是否可以重新用于Mn神经毒性。 总之，我们的研究将为Mn的一个核心但被忽视的方面提供基本的见解 神经毒性，并有助于开发Mn诱导的神经系统疾病的新治疗方法。

ABSTRACT Manganese (Mn) is an essential metal, but elevated levels induce severe neurotoxicity that has no treatment. While the direct neurotoxic effects of Mn are well studied, Mn is predominantly excreted by the liver and intestines, and a high prevalence of neurotoxicity associated with elevated blood and brain Mn levels is reported in patients with liver disease. Moreover, recent epidemiological studies suggest that alterations in Mn excretory capacity are widely prevalent in the general population due to common genetic polymorphisms. Yet, the role of Mn excretion in modulating the outcomes of Mn induced neurological disease is unclear, and the critical question of whether the risk of Mn neurotoxicity depends on Mn excretion capacity has not been answered. Until recently, a major limitation in studying the relationship between Mn excretion and neurotoxicity was that the mechanisms of Mn excretion were unknown. Our recent work, supported by a NIEHS “ONES” R01, revealed that the combined activities of two Mn transporters, SLC30A10 and SLC39A14, were necessary for Mn excretion — SLC39A14 transported Mn from blood into the liver and intestines, and SLC30A10 excreted the intracellular Mn into bile and feces. Further, our analyses of Slc30a10 and/or Slc39a14 knockout mice demonstrated that brain Mn levels were primarily regulated by the excretory activities of these transporters in the liver and intestines. Based on the predominant role of excretion in controlling Mn levels in the brain, we hypothesize that hepatic and intestinal Mn excretion are critical modulators of the risks and outcomes of Mn neurotoxicity. We will test this hypothesis by leveraging liver or intestine specific Slc30a10 knockout or knockin mice, which we generated in the ONES phase, as novel human relevant models to decrease or increase Mn excretion, respectively. Aims 1 & 2 will directly establish the regulatory role of hepatic and intestinal Mn excretion in Mn neurotoxicity. In Aim 1, we will determine whether liver or intestine specific Slc30a10 knockout mice exhibit heightened sensitivity to Mn neurotoxicity. In Aim 2, we will test whether liver or intestine specific Slc30a10 knockin mice are protected against Mn neurotoxicity. Studies in Aim 2 have high translational relevance as they may identify increasing Mn excretion to be an effective strategy for the management of Mn neurotoxicity. Aim 3 will build on our finding that elevated Mn exposure enhanced SLC30A10 expression via Hif1α in the liver, providing a means to increase Mn excretion during toxicity. In Aim 3, we will elucidate the mechanisms and determine whether this response protects against neurotoxicity. These studies will provide foundational information about protective responses to Mn at the organism level, which have not yet been described, and set the stage to test if Hif1α activators, in clinical trials for other diseases, can be repurposed for Mn neurotoxicity. In sum, our studies will provide fundamental insights into a central, but overlooked, aspect of Mn neurotoxicity, and aid in the development of novel therapeutic approaches for Mn induced neurological disease.