Role and mechanisms of excretion in manganese neurotoxicity

摘要 锰是一种必需的金属，但水平升高会导致严重的神经毒性，无法治疗。 虽然锰的直接神经毒性作用已被很好地研究，但锰主要由肝脏和 肠道，以及与血液和脑锰水平升高相关的神经毒性的高流行率被报道。 在患有肝病的患者中。此外，最近的流行病学研究表明，锰排泄的变化 由于常见的遗传多态，能力在普通人群中广泛流行。然而，这一角色 锰排泄在调节锰致神经系统疾病结局中的作用尚不清楚，关键问题是 关于锰神经毒性的风险是否取决于锰的排泄能力，目前还没有答案。 直到最近，研究锰排泄和神经毒性之间的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，由NIEHS“One”R01支持，揭示了 两种锰转运蛋白SLC30A10和SLC39A14的结合活性对锰的排泄是必需的 -SLC39A14将血液中的锰转运到肝脏和肠道，SLC30A10将细胞内的锰排出 锰变成胆汁和粪便。此外，我们对Slc30a10和/或Slc39a14基因敲除小鼠的分析表明 大脑中的锰水平主要由肝脏和肠道中这些转运蛋白的排泄活动来调节。 根据排泄在控制大脑中的锰水平中的主要作用，我们假设肝脏 和肠道中的锰排泄是锰神经毒性风险和结局的关键调节因子。我们将测试 这一假说是通过利用我们产生的肝脏或肠道特异的Slc30a10基因敲除或敲除小鼠来实现的 在One阶段，作为新的人类相关模型，分别减少或增加锰的排泄。 AIMS 1和AIMS 2将直接确定肝脏和肠道的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道特异的Slc30a10基因敲除小鼠是否表现出高度的增强 对锰神经毒性的敏感性。在目标2中，我们将测试肝脏或肠道特异的Slc30a10敲击小鼠 对锰神经毒性有保护作用。目标2中的研究具有很高的翻译相关性，因为它们可能会识别 增加锰的排泄是治疗锰神经毒性的有效策略。 目标3将建立在我们的发现基础上，增加锰暴露通过HIF1α增强SLC30A10在 肝脏，提供了一种在中毒期间增加锰排泄的方法。在目标3中，我们将阐明机制和 确定这种反应是否能预防神经毒性。这些研究将为我们提供 关于有机体水平上对锰的保护性反应的信息，尚未被描述，并设置 在其他疾病的临床试验中，测试HIF1α激活剂是否可以用于锰神经毒性的测试阶段。 总而言之，我们的研究将提供对MN的一个核心但被忽视的方面的基本见解 神经毒性，并有助于开发治疗锰引起的神经性疾病的新方法。

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.