Developmental Factors for Reducing Dopamine Loss in Primate Models of PD & Aging

 描述(申请人提供)：在正常人脑中，中脑多巴胺能神经元的数量每十年下降约3-5%，而在帕金森病(PD)中，这种下降幅度要大得多。前脑区域多巴胺(DA)神经支配的这种不可阻挡的丧失与运动和认知功能的下降密切相关。尽管知道氧化应激是帕金森病和衰老中DA神经元功能丧失的关键因素，但目前还没有治疗方法来阻止DA神经元的磨损。这个问题的部分原因是 动物模型。成年DA神经元非常容易受到MPTP或甲基苯丙胺(METH)施加的帕金森样氧化应激的影响，但我们的团队已经证明，在生命早期的一段有限时期，灵长类大脑对这种损伤具有显著的抵抗力。这为DA神经元提供了一种新的神经保护模式，具有“内置”的抗氧化性损伤能力。这种针对MPTP或冰毒的保护窗口的存在，不能用药物水平的变化，也不能用药物毒性作用所需的关键转运体或酶的不成熟来解释。本项目的目标是了解保护幼年灵长类DA神经元免受氧化应激的因素和机制，并利用这一知识在生命的后期脆弱阶段为DA神经元提供保护。这种方法有望取得成功，因为它依赖于恢复现有的抗氧化机制，而不是试图使用可能非生理学地操纵生化信号的药物来保护DA神经元。我们已经确定了两种潜在的“幼体保护因子”，它们优先在幼年灵长类动物的大脑中表达，并具有很强的抗氧化特性：解偶联蛋白-2(UCP2)和对氧磷酶-2(PON2)。一个目的是验证UCP2在减轻线粒体活性氧水平和随后对年轻DA神经元的损伤方面起主要作用的假设，以及5‘-腺苷一磷酸活化蛋白激酶(AMPK)活性调节UCP2的假设。另一个目的是检测成年DA神经元对诱导氧化应激的保护，这是通过使用新的药物在体内激活UCP2表达来实现的。与UCP2相比，人们对PON2的了解更少，最终目的将测试有关其调控及其在保护幼年灵长类DA神经元免受氧化应激损伤中的作用的假说，并将检验成年PON2表达上调在多大程度上提供了对体内DA神经元氧化应激的保护。此外，我们还将继续研究这些青少年保护因子在灵长类动物大脑中表达的性别差异，因为这可能与女性受试者较低的帕金森病发病率有关，也为诱导DA神经元保护提供了新的途径。这项提案将利用对马尾猴的生化、组织化学和药理学研究来追求这些新方向。发育DA神经元的关键里程碑的时间显示出重要的物种差异，因此这些灵长类动物的研究具有特殊的翻译相关性。这项研究有望激发新的方法来预防DA依赖型年龄相关疾病的发生或进展。

 DESCRIPTION (provided by applicant): In normal human brain the population of midbrain dopaminergic neurons falls by about 3-5% every decade, while in Parkinson's disease (PD) this decline is much greater. This inexorable loss of dopamine (DA) innervation to forebrain regions has been firmly linked with declines in both motor and cognitive functions. Despite knowing that oxidative stress is a key conspirator in the loss of DA neuron function in PD and aging, there are no treatments to halt the attrition of DA neurons. Part of this problem is due to the inadequacy of animal models. Adult DA neurons are very susceptible to the parkinsonian-like oxidative stress exerted by either MPTP or methamphetamine (METH), but our group has demonstrated that for a restricted period early in life, the primate brain is remarkably resistant to such damage. This provides a new neuroprotection model for DA neurons, possessing "built-in" resilience to oxidative damage. The existence of this window of protection against MPTP or METH cannot be explained by altered drug levels, or by immaturity of key transporters or enzymes necessary for the toxic effect of the drugs. The goal of this project is to understand the factors and mechanisms shielding young primate DA neurons from oxidative stress and use this knowledge to provide protection to DA neurons at the later vulnerable stages of life. This approach promises to be successful as it relies on reinstating extant anti-oxidant mechanisms, rather than attempting to protect DA neurons using drugs that may manipulate biochemical signaling non-physiologically. We have identified 2 potential "juvenile protection factors" that are preferentialy expressed in the young primate brain and have strong anti-oxidant properties; uncoupling protein-2 (UCP2) and paraoxonase-2 (PON2). One aim tests the hypothesis that UCP2 plays a major role in mitigating the level of mitochondrial reactive oxygen species and subsequent damage to young DA neurons, and that 5' adenosine monophosphate-activated protein kinase (AMPK) activity regulates UCP2. Another aim examines the protection against induced oxidative stress in adult DA neurons that is achieved by using novel agents to activate UCP2 expression in vivo. Less is known about PON2 than UCP2, and the final aim will test hypotheses about its regulation and its role in protecting young primate DA neurons against oxidative stress damage, and will also examine to what extent up-regulation of PON2 expression in the adult affords protection against in vivo oxidative stress in DA neurons. In addition, we will pursue our data on male-female differences in expression of these juvenile protection factors in primate brain, as this may relate to the lower incidence of PD in female subjects and also provide new ways to induce protection in DA neurons. This proposal will pursue these novel directions using biochemical, histochemical, and pharmacological studies in vervet monkeys. The timing of critical milestones in developing DA neurons display important species differences, so these primate studies have particular translational relevance. This research is expected to stimulate new approaches to prevent the occurrence or progression of DA-dependent age-related disorders.