Reduced vesicular catecholamine storage mediates oxidant-induced neurotoxicity

描述(申请人提供)：帕金森病(PD)是一种衰弱的神经退行性疾病，其特征是壳核和黑质产生多巴胺的神经元失去多巴胺，导致运动障碍，如震颤、僵硬、姿势不稳定和运动迟缓。帕金森病目前被认为是环境和遗传因素共同作用的结果。目前的治疗方法包括L-多巴给药、MAOB抑制剂和DA激动剂，这些都可以增加大脑中DA信号的数量。正常情况下，DA在神经元内受到高度调节；多巴胺转运体(DAT)介导从突触选择性地摄取多巴胺，调节神经元信号的大小和持续时间。囊泡单胺转运体(VMAT2)然后将胞内DA泵入囊泡以进行胞外释放。VMAT2在调节神经元对细胞损伤的敏感性方面很重要，特别是通过防止氧化应激。VMAT2通常隔离儿茶酚胺，保护神经元免受损伤；然而，当VMAT2表达减少时，DA和NE可以在胞浆中被氧化，导致内源性氧化损伤。在DA处理功能障碍的时期，细胞的抗氧化防御被激活；但当这些防御失效时，可能会发生神经退化。为了研究VMAT2在帕金森病中的作用，许多组织试图建立VMAT2 KO小鼠，但完全消融VMAT2是致命的。此前，我们的实验室已经证明，VMAT2(VMAT2 LO)基因缺失95%的小鼠表现为纹状体DA进行性丧失、L-多巴酚A反应行为缺陷、突触核蛋白聚集和黑质多巴胺细胞丢失。我们假设，VMAT2缺陷小鼠的进行性损伤是由于随着小鼠年龄的增长，氧化应激增加所致。本研究的目的是阐明VMAT2在帕金森病发生发展中的作用，更具体地说，VMAT2在儿茶酚胺介导的毒性作用下调节神经元氧化还原状态的能力。我将通过1)确定VMAT2 LO小鼠是否存在年龄相关的氧化还原状态改变，2)研究L多巴给药是否加剧了这种改变的氧化还原状态，以及3)确定NE在氧化剂诱导的VMAT2 LO小鼠神经退化中的作用，来验证这一假设。鉴于氧化应激相关研究的重要性日益增加，尤其是与神经退行性变相关的研究，这项研究有可能阐明人类帕金森病发生的可能内源性机制。此外，通过这项研究发现的任何氧化机制都可以作为PD疾病进展中遗传和环境因素之间的联系。

DESCRIPTION (provided by applicant): Parkinson's disease (PD) is a debilitating neurodegenerative disorder, which is characterized by the loss of dopamine (DA) in the putamen and DA producing neurons of the substantia nigra, resulting in motor disturbances such as tremor, rigidity, postural instability and bradykinesia. PD is currently thought to be caused by a combination of environmental and genetic factors. Current therapies include L-DOPA administration, MAOB inhibitors, and DA agonists, which all increase the amount of DA signaling in the brain. Normally, DA is highly regulated within the neuron; the dopamine transporter (DAT) mediates selective uptake of dopamine from the synapse, adjusting the magnitude and duration of neuronal signaling. The vesicular monoamine transporter (VMAT2) then pumps cytosolic DA into vesicles for exocytotic release. VMAT2 is important in mediating neuronal susceptibility to cellular damage, particularly via the prevention of oxidative stress. VMAT2 normally sequesters catecholamines, protecting against neuronal damage; however, when VMAT2 expression is reduced, DA and NE can become oxidized in the cytosol, inducing endogenous oxidative damage. During periods of DA handling dysfunction, cellular antioxidant defenses are activated; but when these defenses fail, neurodegeneration can occur. In order to study the role of VMAT2 in PD, many groups have tried to generate VMAT2 KO mice, but completely ablating VMAT2 is lethal. Previously, our laboratory has shown that mice with a 95% genetic reduction in VMAT2 (VMAT2 LO) display progressive loss of striatal DA, L-DOPA responsive behavioral deficits, synuclein aggregation, and nigral dopamine cell loss. We hypothesize that the progressive damage in the VMAT2 deficient mice is due to increased oxidative stress as the mice age. The goal of this research is to elucidate the role of VMAT2 in the development of PD, more specifically, the ability of VMAT2 to modulate neuronal redox state in the presence of catecholamine mediated toxicity. I will test this hypothesis by 1) determining if there is an agedependent altered redox state in VMAT2 LO mice, 2) investigating if L-DOPA administration exacerbates this altered redox status, and 3) determining the role of NE in oxidant-induced neurodegeneration in the VMAT2 LO mice. Given the increasing importance of oxidative stress related research, especially as it pertains to neurodegeneration, this research has the potential to illuminate possible endogenous mechanism for the development of PD in humans. Furthermore, any oxidative mechanisms that are uncovered through this research can serve as the link between genetic and environmental factors in PD disease progression.