The amyloid cascade in a novel mouse model of Alzheimer's disease

描述(申请人提供)：阿尔茨海默病的神经病理特征是大脑和脑血管中存在不可溶的淀粉样沉积，异常磷酸化和聚集形式的tau，一种微管结合蛋白和神经元内聚集在神经元内，以及神经元丢失。尽管导致这些病变的确切机制尚不清楚，但淀粉样级联假说认为，这些多肽(A？)构成淀粉样蛋白沉积的物质是疾病过程的原因。尽管有许多支持性研究，但AD动物模型和人类AD模型之间的差异仍然是完全接受A？作为阿尔茨海默病的主要病因。通过改变小鼠大脑中的一氧化氮，我们已经产生了一种新的小鼠模型，它为研究鼠与人的差异提供了独特的见解。我们的双基因阿尔茨海默病小鼠模型增加了人A？以小鼠一氧化氮合酶2(NOS2)基因敲除为背景。由此产生的表型与在人类AD中观察到的病理高度相似，包括高水平的A？多肽、tau过度磷酸化、tau重新分布和tau聚集、神经元丢失和行为缺陷。APPSw/NOS2-/-小鼠的一个主要优势是从正常的、非突变的tau形成tau病理，并且存在显著的神经元丢失。因此，我们的模型提供了一个独特的机会，在慢性病条件下在体内全面测试淀粉样蛋白级联假说。第一个目标将通过测量特定年龄的APPSw/NOS2-/-小鼠大脑中的A？、tau病理、神经元丢失以及记忆和学习来证实APPSw/NOS2-/-小鼠大脑中的病理性级联反应。为A建立一个直接的、因果的角色？在多肽的级联中，我们提出了a)降低A？被动免疫APPSw/NOS2-/-小鼠脑组织中A？NOS2-/-小鼠海马区注射A？多肽混合物。第二个目标将研究NOS2的作用。我们建议a)通过慢病毒传递小干扰RNA(shNOS2慢病毒)来减少脑内iNOS蛋白的表达；b)检测NOS2和NO替代蛋白改变A？介导的病理级联反应的能力。第三个目标将研究NO作用的一个可能机制，即对caspase活性的调节。公共卫生相关性：该项目将研究源自淀粉样前体蛋白的Aβ多肽在产生与阿尔茨海默病等慢性神经退行性疾病相关的神经病理中的作用。所使用的方法将涉及到产生具有潜在治疗价值的新的小鼠模型，并将提供一个有用的工具来全面研究临床前阶段的治疗方法。

DESCRIPTION (provided by applicant): The neuropathological features of Alzheimer's disease are characterized by the presence of insoluble amyloid deposits in the brain and cerebrovasculature, the intra-neuronal accumulation of abnormally phosphorylated and aggregated forms of tau, a microtubule binding protein and neuronal loss. Although the exact mechanisms producing these pathological changes remain unknown, the amyloid cascade hypothesis states that the peptides (A?) that make up amyloid deposits are the cause of the disease process. Despite numerous supportive studies, discrepancies between animal models of AD and humans with AD remain an obstacle for full acceptance of A? as the primary causal agent for AD. By altering the nitric oxide in mouse brain, we have generated a novel mouse model that provides unique insights into mouse-human differences. Our bigenic mouse models of AD increase the expression of human A? on a murine nitric oxide synthase 2 (NOS2) knockout background. The resulting phenotype is highly reminiscent of the pathology observed in humans with AD including high levels of A? peptides, tau hyperphosphorylation, tau redistribution and tau aggregation, neuronal loss and behavioral deficits. A primary advantage of the APPSw/NOS2-/- mouse is the formation of tau pathology from normal, not mutated tau AND the presence of significant neuronal loss. Thus, our model provides a unique opportunity to fully test the amyloid cascade hypothesis in vivo under conditions of chronic disease. The first aim will confirm a pathological cascade in the APPSw/NOS2-/- mouse brain by measuring A?, tau pathology, neuronal loss and memory and learning in the APPSw/NOS2-/- mice brains at specific ages. To establish a direct, causal role for A? peptides in the cascade, we propose a) to reduce A? levels in the brains of APPSw/NOS2-/- mice by passive immunization and b) to increase A? levels in the brains of NOS2-/- mice using intrahippocampal injection of A? peptide mixtures. The second aim will examine the role of NOS2. We propose a) to reduce brain iNOS protein using lentivirus delivery of small interfering RNA (shNOS2 lentivirus) b) to test the ability of NOS2 and NO replacement to alter the pathological cascade mediated by A?. The third aim will examine a likely mechanism of NO's action, the regulation of caspase activity. PUBLIC HEALTH RELEVANCE: This project will examine the role of A beta peptides derived from the amyloid precursor protein in generating the neuropathology associated with chronic neurodegenerative diseases such as Alzheimer's disease. The method used will involve the generation of a novel mouse model for potential therapeutic value and will provide a useful to tool to fully investigate therapeutics in the pre-clinical stage.