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

描述（由申请人提供）：阿尔茨海默病的神经病理学特征是脑和脑血管中存在不溶性淀粉样蛋白沉积，神经元内异常磷酸化和聚集形式的tau（一种微管结合蛋白）积累和神经元丢失。虽然产生这些病理变化的确切机制尚不清楚，但淀粉样蛋白级联假说认为，构成淀粉样蛋白沉积的肽（A?）是疾病过程的原因。尽管有大量的支持性研究，AD动物模型和AD患者之间的差异仍然是A？作为阿尔茨海默病的主要诱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，为小鼠与人类的差异提供了独特的见解。我们的双基因AD小鼠模型增加了人A？小鼠一氧化氮合酶2 （NOS2）敲除背景。由此产生的表型与在AD患者中观察到的病理非常相似，包括高水平的A？多肽，tau蛋白过度磷酸化，tau蛋白再分布和聚集，神经元丧失和行为缺陷。APPSw/NOS2-/-小鼠的主要优势是由正常而非突变的tau形成病理，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来充分测试慢性疾病条件下体内淀粉样蛋白级联假说。第一个目的是通过测量a ？在特定年龄的APPSw/NOS2-/-小鼠大脑中，tau病理，神经元丧失和记忆和学习。建立a的直接因果关系？在级联中，我们提出a)减少a ？通过被动免疫提高APPSw/NOS2-/-小鼠脑内A？海马内注射A？肽混合物。第二个目标是研究NOS2的作用。我们提出a)利用慢病毒递送小干扰RNA （shNOS2慢病毒）减少脑iNOS蛋白b)测试NOS2和NO替代改变a ?介导的病理级联反应的能力。第三个目的是研究一氧化氮作用的可能机制，半胱天冬酶活性的调节。公共卫生相关性：本项目将研究源自淀粉样蛋白前体蛋白的A -肽在与慢性神经退行性疾病（如阿尔茨海默病）相关的神经病理学产生中的作用。所使用的方法将涉及产生一种具有潜在治疗价值的新型小鼠模型，并将为在临床前阶段全面研究治疗方法提供有用的工具。

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.