Manganese exposure susceptibility as a modifier of excitotoxicity in Alzheimer's Disease

总结 关于慢性锰暴露的影响如何发展的知识基础存在根本性的空白- 老年痴呆症锰中毒的神经毒性作用是已知的，以及运动 行为上的后遗症然而，长期低水平照射尚未得到研究。 阿尔茨海默病的神经病理学在严重的认知和行为障碍发作之前的几十年内发展， 痴呆症及其发展特别容易受到环境因素的影响。 因素锰是一种环境毒素，自暴露以来可能非常重要 通过多种来源（受污染的水、食物、吸入污染物和工业综合体）。此外，本发明还 暴露直接针对阿尔茨海默病病理学中涉及的许多主要机制：β-淀粉样蛋白 积累，氧化应激和神经胶质细胞的变化有关的神经炎症。我们的核心假设是， 慢性高锰（Mn）暴露通过受损的谷氨酸体内平衡驱动认知能力下降。 我们的长期目标是通过证明锰和认知能力下降之间的直接联系， 慢性锰暴露在更大程度上影响小鼠中改变的谷氨酸清除率和其他病理学， 人类干细胞模型的AD比对照组。我们将通过以下方式做到这一点：（1）证明在多大程度上 慢性Mn暴露加速AD神经病理学。锰治疗3个月后， 我们将评估AD相关神经病理学、氧化应激和神经蛋白的多种标志物， 在基因、蛋白质和细胞水平上结合直接假设检验和假设基因- 令人沮丧的方法。将在显著的β-淀粉样蛋白积累开始之前和之后评估变化（6- 10天）。 和12月龄），以及β-淀粉样蛋白阳性（APP/PSEN 1，家族性AD模型）和阴性小鼠 （APOE 4/TREM 2，散发性AD模型;和野生型小鼠）。(2)证明慢性锰中毒 暴露会影响认知能力下降。我们将评估学习和记忆在两个年龄点使用一个com- 认知和运动变化的一系列行为测试。我们将直接评估 锰影响记忆的分子基础，通过长时程增强加强突触。人类 将利用干细胞模型来验证这些发现。(3)确定脑锰水平在以下方面的作用： 突触谷氨酸稳态我们将讨论锰直接影响突触谷氨酸的假设 通过原代细胞培养和干细胞模型的稳态和评估谷氨酸摄取和释放。我们 将通过电生理记录功能性地测试脑电系统。最后，我们将利用GLT-1 基因敲除小鼠，以进一步探讨GLT-1的作用，特别是在这种关系。这些数据将证实 慢性锰暴露在AD神经病理学和认知功能下降中作用，并特别说明其影响 关于肾上腺皮质功能失调的研究了解这些机制将突出一个未充分研究的作用， 阿尔茨海默病的锰处理，并提供了一个新的目标，疾病的预防和干预。

SUMMARY There is a fundamental gap in the knowledge base about how chronic manganese exposures impacts develop- ment of Alzheimer’s disease. The neurotoxic effects of manganese poisoning are known, as well as the motor impairments that are its behavioral sequelae. However, chronic lower-level exposures have not been studied. The neuropathology of Alzheimer’s disease develops over decades prior to onset of severe cognitive and be- havioral change (dementia) and thus its development is particularly susceptible to influence from environmental factors. Manganese represents an environmental toxin with high likelihood of importance since exposure occurs through multiple sources (contaminated water, food, inhalation from pollution and industrial complexes). Further, exposure directly targets many of the primary mechanisms involved in Alzheimer’s disease pathology: β-amyloid accumulation, oxidative stress and glial changes relating to neuroinflammation. Our central hypothesis is that Chronic elevated manganese (Mn) exposure drives cognitive decline through impaired glutamate homeostasis. Our long-term objectives are to isolate the direct link(s) between Mn and cognitive decline by demonstrating how chronic Mn exposure affects altered glutamate clearance and other pathologies to a greater extent in mouse and human stem cell models of AD than in controls. We will do this by: (1) Demonstrating the extent to which chronic Mn exposure accelerates AD neuropathology. Following 3 months treatment with Mn to significantly elevate brain Mn we will assess multiple markers of AD-related neuropathology, oxidative stress and neuroin- flammation at the gene, protein and cellular level incorporating direct hypothesis testing and hypothesis gener- ating approaches. Changes will be assessed prior to- and after onset of significant β-amyloid accumulation (6- and 12 months of age), and in β-amyloid positive (APP/PSEN1, familial AD model) and negative mice (APOE4/TREM2, sporadic AD model; and wild-type mice). (2) Demonstrating the extent to which chronic Mn exposure impacts cognitive decline. We will assess learning and memory at the two age points using a com- prehensive battery of behavioral tests for cognitive and motor changes. We will directly assess the potential for Mn to impact the molecular basis of memory, synaptic strengthening through long term potentiation. Human stem cell models will be utilized to validate these findings. (3) Establishing the role of brain Mn levels in synaptic glutamate homeostasis. We will address the hypothesis that Mn directly impacts synaptic glutamate homeostasis through primary cell culture and stem cell models and assess glutamate uptake and release. We will functionally test the glutamatergic system by electrophysiological recordings. Finally we will utilize GLT-1 knockout mice to further probe the role of GLT-1 in particular in this relationship. Together these data will confirm the role of chronic Mn exposure in AD neuropathology and cognitive decline, and specifically address its impact on glutamatergic dyshomeostasis. Understanding these mechanisms will highlight an under-studied role for al- tered Mn handling in Alzheimer’s disease, and provide a new target for disease prevention and interventions.