Manganese and basal ganglia dysfunction: role of NO

描述(由申请人提供)：慢性锰中毒是一种退行性运动障碍的原因，称为锰中毒，其临床特征类似帕金森氏症。最近的发现表明，大脑这一区域的损伤涉及到神经胶质细胞的正常支持功能被扰乱到激活状态，导致炎症基因如诱导型一氧化氮合酶(NOS2)的表达增加，从而产生神经毒性水平的一氧化氮(NO)。类似的有害神经-神经胶质相互作用也发生在基底节的其他退行性疾病中，如帕金森氏病和亨廷顿病，这突显了阐明这些破坏性相互作用背后的机制的必要性。这项研究计划的长期目标是更好地了解神经胶质细胞在基底节疾病发病机制中的作用。这项应用的目的是在锰中毒的实验模型中确定神经胶质细胞介导的神经元损伤的潜在机制。中心假说是，锰暴露导致胶质细胞激活和NOS2的表达，从而通过过量产生NO而导致年龄依赖性神经元损伤和基底节功能衰弱。这一假说将通过追求两个具体目标来检验：1)确定导致星形胶质细胞中NOS2诱导的锰依赖信号。这一目的的工作假设是，锰通过激活特定的MAP激酶，增加了依赖于NF-kappaB的NOS2的表达。2)确定基底节对锰的年龄易感性的机制。根据这一目标，推测在发育过程中，锰介导的NO产生导致神经胶质细胞激活和神经元损伤，从而降低随后暴露时基底神经节功能障碍的阈值。所提出的实验方法利用基因阻断核因子-kappaB途径中的特定信号分子来确定星形胶质细胞中NOS2表达的关键上游激活物。在新生和成年野生型和转基因小鼠中，确定的因子的活性将与核因子-kappaB的活性和NOS2表达的关系进行量化。预计这种创新的方法将识别重要的早期靶点，通过增加NO的合成来促进神经元损伤。这项拟议的研究具有重要意义，因为它有望促进对胶质源性NO在基底节疾病中的致病作用的理解，从而促进针对胶质细胞炎症信号通路的神经保护性治疗策略的发展。

DESCRIPTION (provided by applicant): Chronic intoxication with manganese (Mn) is the cause of a degenerative movement disorder, termed manganism, with clinical features that resemble Parkinson's disease. Recent findings suggest that injury to this region of the brain involves perturbation of the normally supportive function of glial cells to an activated state that results in increased expression of inflammatory genes such as inducible nitric oxide synthase (NOS2), that can subsequently produce neurotoxic levels of nitric oxide (NO). Similar deleterious neuro-glial interactions occur in other degenerative disorders of the basal ganglia, such as Parkinson's and Huntington's diseases, highlighting the need to elucidate the mechanisms underlying these damaging interactions. The long-term goal of this research program is to better understand role of glial cells in the pathogenesis of diseases of the basal ganglia. The objective of this application is to identify mechanisms underlying glial-mediated neuronal injury in an experimental model of manganism. The central hypothesis is that Mn exposure results in glial activation and expression of NOS2 that contributes to age-dependent neuronal injury and debilitation of basal ganglia function through overproduction of NO. This hypothesis will be tested by pursuing two specific aims: 1) Determine the Mn-dependent signals that cause induction of NOS2 in astroglial cells. The working hypothesis for this aim is that Mn increases NF-KappaB-dependent expression of NOS2 by activating specific MAP kinases. 2) Identify the mechanisms underlying age-dependent susceptibility of the basal ganglia to manganese. It is postulated under this aim that Mn-mediated production of NO during development results in glial activation and neuronal injury that decreases the threshold for basal ganglia dysfunction upon subsequent exposures. The experimental approach proposed utilizes genetic interdiction of specific signaling molecules in the NF-KappaB pathway to identify critical upstream activators of NOS2 expression in astroglial cells. The activity of the factors identified will be quantified in relation to activity of NF-KappaB and expression of NOS2 in neonatal and adult wildtype and transgenic mice exposed to Mn. It is expected that this innovative approach will identify important early targets of Mn that promote neuronal injury by increased synthesis of NO. The proposed research is significant, because it is expected to advance understanding of the pathogenic role of glial-derived NO in disorders of the basal ganglia and, thereby, to foster the development of neuroprotective therapeutic strategies that target inflammatory signaling pathways in glial cells.