Development of Novel Therapies for AD Targeting Abeta Clearance

描述(由申请人提供)： 阿尔茨海默病(AD)是最常见的老年神经退行性疾病，每八名美国老年人中就有一人被诊断为AD。它也是退伍军人事务部(VA)医疗系统中最常被诊断为痴呆症的类型，也是导致退伍军人发病率和死亡率的主要原因之一。退伍军人事务部估计，2000年有60万退伍军人患有严重的阿尔茨海默病和其他形式的痴呆症，这一数字今天显著增加，因为老年退伍军人的比例越来越高，患有创伤性脑损伤(TBI)和/或创伤后应激障碍(PTSD)的退伍军人中痴呆症的患病率也增加了。因此，AD研究对退伍军人尤为重要。目前还没有治疗方法可以减缓或阻止阿尔茨海默病。迫切需要寻找更有效的治疗AD的方法，这是VA RR&D研究方向的重点之一。突触素1(Synaptojanin 1，synj1)是脑和突触中的主要磷酸肌醇(4，5)二磷酸磷酸酶[PI(4，5)P2]降解酶，最近被认为与AD有关。更重要的是，我们描述了一种新的机制，通过它，synj1调节细胞对A？的清除。Synj1的下调促进A？摄取和溶酶体运输，从而促进细胞A？清除。随后，在AD转基因小鼠模型中，synj1的减少减轻了淀粉样蛋白诱导的神经病理变化和行为缺陷。我们的发现表明，synj1的减少对AD有潜在的好处。在这些研究的基础上，我们利用“连接性图谱”对具有降低synj1蛋白水平潜力的化合物文库(总共~3,600个小分子)进行了初步筛选。我们选择了89个小分子(TOP HITS)进行进一步研究，在野生型原代神经元培养中发现了10个具有synj1/A降低作用的先导化合物。初步研究表明，一种钙通道阻滞剂尼莫地平，而不是硝苯地平，以剂量依赖的方式降低synj1和A？水平，并具有良好的剂量-效应相关性。继续给予尼莫地平一个月，能够减少大脑中synj1/A的含量，并改善AD转基因小鼠的认知功能。在这项应用中，我们建议表征具有synj1/A？降低作用的先导化合物的作用机制(目标1：机制研究)，并评估选定的先导化合物在AD转基因小鼠模型中减少A？诱导的神经病理和认知功能障碍的能力(目标2：概念验证)。从这一应用中获得的知识将为设计一个全面的项目提供基础，该项目探索用于AD治疗的先导化合物的生物利用度、药代动力学和毒理学特征。综上所述，建议的研究具有重要的临床意义和科学意义。从我们的研究中获得的信息将提高我们在开发更有效的AD疗法方面的知识，直接造福于退伍军人群体，并改善退伍军人医疗保健系统内提供的服务质量。

DESCRIPTION (provided by applicant): Alzheimer's disease (AD) is the most prevalent neurodegenerative disease of aging, with one in eight older Americans diagnosed with AD. It is also the most frequently diagnosed type of dementia within the Veterans Affairs (VA) Medical System, and one of the major causes of morbidity and mortality among veterans. The Department of VA estimates that 600,000 veterans suffered from severe AD and other forms of dementia in 2000, and this number is increased significantly today, because of the increasing proportion of older veterans and the increased prevalence of dementia in veterans that suffer from traumatic brain injury (TBI) and/or post- traumatic stress disorder (PTSD). Therefore, AD research studies are particularly important to veterans. Currently no treatment is available to slow or stop AD. There is great need for identification of more efficacious therapies for AD, which is among the priorities of VA RR&D research directions. Synaptojanin 1 (synj1), the main phosphoinositol (4,5) biphosphate phosphatase [PI(4,5)P2 degrading enzyme] in the brain and synapses, has been recently linked to AD. More importantly, we have characterized a NOVEL mechanism by which synj1 regulates cellular clearance of A¿. Down-regulation of synj1 promotes A¿ uptake and lysosomal trafficking, and thereby facilitates cellular A¿ clearance. Subsequently, reduction of synj1 attenuates amyloid induced neuropathologic changes and behavior deficits in an AD transgenic mouse model. Our findings suggest that reduction of synj1 has potential benefits for AD. Based on these studies, we performed a preliminary screening of a library of compounds (total ~3,600 small molecules) with the potential to reduce synj1 protein levels using "The Connectivity Map". We selected 89 small molecules (top hits) for further study and found 10 lead compounds with synj1/A¿-lowering effects in wild-type primary neuron cultures. Preliminary studies showed one calcium channel blocker nimodipine but not nifedipine, reduces both synj1 and A¿ levels in a dose-dependent manner with good dose-effect correlation. Further administration of nimodipine for one month, is capable of reducing brain content of synj1/A¿, as well as improving cognitive functions in an AD transgenic mouse model. In this application, we propose to characterize the mechanism of action for lead compounds exhibiting synj1/A¿ lowering effects (aim 1: Mechanistic Studies), and to evaluate the ability of selected lead compounds to reduce A¿-induced neuropathology and cognitive dysfunction in an AD transgenic mouse model (aim 2: Proof of Concept). Knowledge gained from this application will provide the foundation for designing a full-scale project exploring bioavailability, pharmacokinetics and toxicological characteristics of lead compounds for AD therapy. Taken together, the proposed studies have significant clinical relevance and scientific importance. Information obtained from our studies wil advance our knowledge in developing more potent AD therapies, directly benefits Veterans populations, and improves the quality of service provided within the VA health care system.