Role of MyD88 signaling in systemic inflammation and Alzheimer disease

项目总结/摘要 阿尔茨海默病（Alzheimer 'sdisease，AD）患者的主要病理改变是细胞外β淀粉样蛋白（amyloid β，Aβ） 脑实质中的沉积物（淀粉样斑块）和过度磷酸化tau的异常聚集 脑神经元中的蛋白质（神经元缠结，NFT）。淀粉样斑块和NFT伴有慢性 炎症，其特征在于活化的小胶质细胞和增加的细胞因子水平。除了一小部分 早发性家族性AD病例中，绝大多数AD病例的病因未知且令人满意 目前还没有针对AD的治疗和预防措施。因此，迫切需要确定 分子机制，增加了绝大多数AD病例的风险，并制定了预防和 治疗措施。全身炎症促进AD进展，甚至启动小胶质细胞活化 和神经退化事实上，最近对晚发性AD的遗传研究已经确定了大约12种遗传性疾病， 在小胶质细胞中高度表达并参与先天免疫反应的风险变体，突出了 免疫反应的重要性，特别是活化的小胶质细胞，在晚发性AD的发病机制。老化 是AD的最大已知风险因素，其特征在于慢性全身性炎症（炎症-老化）。 由某些细菌和病毒感染引起的全身性炎症也是痴呆症的一个重要危险因素。 此外，我们的初步数据表明，通过MyD 88信号转导激活NLRP 3炎性小体， 中枢神经系统（CNS）小胶质细胞内的信号转导通路在AD发病机制中起重要作用。在Aim中 1，我们将在衰老过程中的AD小鼠模型中产生小胶质细胞特异性MyD 88缺陷，并确定它们的表达。 对Aβ和tau病理学和认知功能的影响。我们进一步假设小胶质细胞MyD 88信号转导 在加速脑Aβ和tau病理学和神经炎症中起主要作用， 慢性全身性炎症，在AD小鼠模型在老化过程中。在目标2中，我们将确定 全身LPS治疗对AD小鼠模型中Aβ和tau病理学和认知的影响 免疫细胞特异性MyD 88缺陷。在目标3中，我们将确定LPS的年龄和性别依赖性效应 治疗作为脑/小胶质细胞特异性疾病机制的NLRP 3炎性小体活化， 外周免疫细胞特异性MyD 88缺陷型AD小鼠模型。我们的假设是LPS诱导的 全身性炎症通过MyD 88信号传导引起小胶质细胞中的NLRP 3炎性小体活化，导致 AD小鼠模型中AD样病理生理学的恶化。长期目标是确定 小胶质细胞MyD 88/NLRP 3炎性体信号转导在AD发病机制中的作用，以阐明AD发病机制的分子机制。 与全身炎症相关的AD风险增加的潜在机制，并开发新的 AD的预防和治疗策略。

Project Summary / Abstract The main pathological changes found in patients with Alzheimer’s disease (AD) are extracellular amyloid β (Aβ) deposits in the brain parenchyma (amyloid plaques) and abnormal aggregates of hyperphosphorylated tau protein in brain neurons (neurofibrillary tangles, NFTs). Amyloid plaques and NFTs are accompanied with chronic inflammation characterized by activated microglia and increased levels of cytokines. Except a small subset of early-onset familial AD cases, the causes for the vast majority of AD cases are unknown and satisfactory therapeutic and preventive measures for AD are unavailable. Therefore, an urgent need exists to identify the molecular mechanisms that increase the risk for the vast majority of AD cases and to develop the preventive and therapeutic measures. Systemic inflammation promotes AD progression and even initiates microglial activation and neurodegeneration. Indeed, recent genetic studies on late-onset AD have identified about a dozen genetic risk variants that are highly expressed in microglia and involved in innate immune responses, highlighting the importance of immune responses, particularly activated microglia, in the pathogenesis of late-onset AD. Aging is the largest known risk factor for AD and is characterized by chronic, systemic inflammation (inflamm-aging). Systemic inflammation caused by certain bacterial and viral infections is a strong risk factor of dementia, also. Additionally, our preliminary data indicate that activation of NLRP3 inflammasome through the MyD88 signaling pathway in microglia in the central nervous system (CNS) plays essential roles in the AD pathogenesis. In Aim 1, we will produce a microglia specific MyD88 deficiency in AD mouse models during aging and determine their effect on Aβ and tau pathology and cognitive function. We further hypothesize that microglial MyD88 signaling plays a predominant role in accelerating brain Aβ and tau pathology and neuroinflammation, which are induced by chronic, systemic inflammation, in AD mouse models during aging. In Aim 2, we will determine the effects of systemic LPS treatment on Aβ and tau pathology and cognition in AD mouse models with brain and peripheral immune cell-specific MyD88 deficiency. In Aim 3, we will determine the age and sex dependent effects of LPS treatment on NLRP3 inflammasome activation as disease mechanisms in the brain/microglia-specific and peripheral immune cell-specific MyD88 deficient AD mouse models. Our hypothesis is that LPS-induced systemic inflammation causes NLRP3 inflammasome activation in microglia via MyD88 signaling, leading to exacerbation of AD-like pathophysiology in AD mouse models. The long term goals are to determine the role of microglial MyD88/NLRP3 inflammasome signaling in the AD pathogenesis, to elucidate the molecular mechanism underlying the increased AD risk associated with systemic inflammation and to develop new preventive and therapeutic strategies for AD.