Innate immunity in Alzheimer's disease: Role of toll-like receptor signaling

描述（由申请人提供）：阿尔茨海默病（AD）患者在大脑中沉积聚集的淀粉样蛋白(A)。在阿尔茨海默病的病因学中，A¿积累被认为是一个因果事件。AD脑中的纤维A2沉积伴随着固有免疫反应，如激活的小胶质细胞和细胞因子水平升高。越来越多的证据支持激活的小胶质细胞（中枢神经系统中的先天免疫细胞）在AD进展中发挥关键作用的假设：通过吞噬活性清除a -沉积物或释放细胞毒性物质。toll样受体（TLRs）是先天免疫系统中的一类模式识别受体。tlr的重要作用之一是激活吞噬细胞/小胶质细胞对包括病原体和受损宿主细胞在内的损伤作出反应，从而清除病原体、受损组织和积累废物。我们假设这些保护功能是由myd88依赖性通路介导的，并且大脑中的A¿负荷可以通过TLR4信号传导调节。我们将通过完成特异性靶标1和2来确定myd88依赖通路和TLR4信号通路在A¿清除中的作用。我们进一步假设大脑中的A¿负荷和认知功能是由TLR4效应细胞因子/趋化因子调节的，这将通过执行Aim 3进行测试。在Aim 4中，我们将在AD患者和AD小鼠模型中验证A¿在大脑中的积累诱导小胶质细胞TLR4信号功能障碍导致A¿沉积加剧的假设。具体目的是（Aim 1）确定myd88缺陷遗传背景下AD小鼠模型的脑A¿负荷、炎症和行为缺陷，（Aim 2）确定过表达TLR4的AD小鼠模型的脑A¿负荷、炎症和行为缺陷，（Aim 3a）比较TLR4野生型和突变型AD小鼠模型的脑细胞因子和趋化因子表达谱。（Aim 3b）通过腺相关病毒基因传递在大脑中过表达TLR4效应细胞因子和/或趋化因子，并在AD小鼠模型中确定大脑A¿负荷、炎症和行为缺陷；（Aim 4）使用培养的小胶质细胞、AD小鼠模型和AD患者的组织样本来确定A¿是否诱导TLR信号功能障碍。本研究的长期目标是确定TLR信号及其效应细胞因子/趋化因子在AD进展中的作用。

DESCRIPTION (provided by applicant): Patients with Alzheimer's disease (AD) develop deposits of aggregated amyloid ¿-protein (A¿) in the brain. A¿ accumulation is thought to be a causal event in the etiology of AD. Fibrillar A2 deposits in AD brain are accompanied by innate immune responses such as activated microglia and increased levels of cytokines. Accumulating evidence supports the hypothesis that activated microglia, innate immune cells in the central nervous system, play a pivotal role in the AD progression: either clearing A¿ deposits by phagocytic activity or releasing cytotoxic substances. Toll-like receptors (TLRs) are a class of pattern-recognition receptors in the innate immune system. One of the important roles of TLRs is to activate phagocytes/microglia to respond to insults including pathogens and damaged host cells, leading to clearance of pathogens, damaged tissues and accumulated wastes. We hypothesize that these protective functions are mediated by MyD88-dependent pathways and that A¿ load in the brain can be modulated by TLR4 signaling. We will determine the roles of MyD88-dependent pathways and TLR4 signaling in A¿ clearance by completing the Specific Aim 1 and 2. We further hypothesize that A¿ load in the brain and cognitive functions are modulated by TLR4 effector cytokines/chemokines, which will be tested by performing Aim 3. In Aim 4, we will test the hypothesis that accumulation of A¿ in the brain induces dysfunction of TLR4 signaling in microglia resulting in exacerbation of A¿ deposition in AD patients and AD mouse models. Specific Aims are (Aim 1) to determine cerebral A¿ load, inflammation and behavioral deficits in AD mouse models on a MyD88-deficient genetic background, (Aim 2) to determine cerebral A¿ load, inflammation and behavioral deficits in AD mouse models that overexpress TLR4, (Aim 3a) to compare cerebral cytokine and chemokine expression profiles between TLR4 wild-type and mutant AD mouse models, (Aim 3b) to overexpress TLR4 effector cytokines and/or chemokines in the brain via adeno-associated virus gene delivery and determine cerebral A¿ load, inflammation and behavioral deficits in the AD mouse models, and (Aim 4) to determine whether A¿ induces dysfunction of TLR signaling, using cultured microglia, AD mouse models and tissue samples from AD patients. The long term goal of this research is to determine the roles of TLR signaling and its effector cytokines/chemokines in the AD progression.