Alzheimer's Disease Genetic Risk and Microglial Innate Immune Memory

项目摘要 阿尔茨海默病（AD）是一种与年龄相关的神经退行性疾病，其特征在于认知能力下降， 淀粉样病变的积累。一种强大的遗传驱动的先天免疫成分被认为是 在AD中的致病作用，暗示小胶质细胞功能障碍的核心作用。小胶质细胞是长寿的居民 中枢神经系统中的先天免疫细胞。它们的免疫和代谢途径的激活导致 先天免疫记忆（IIM），一种功能性重编程过程，其中对初始刺激的反应 形成持久的表观遗传修饰，从而告知对后续刺激的反应。IIM可能导致 基于初始炎性细胞的身份，增强激活（训练）或抑制（耐受） 刺激。IIM已被证明可以改变AD小鼠模型的病理学，这是持续改变的结果。 小胶质细胞的功能几种常见的AD风险变体，包括CD33，收敛到抑制小胶质细胞 激活，通过减少炎症信号传导或增加其抑制。因此，我的总体假设 由于抑制性遗传性AD风险变异导致的小胶质细胞IIM改变是导致AD风险的关键机制。 AD中观察到的小胶质细胞功能障碍。更具体地说，我假设抑制性CD33 AD风险 变异将减少细胞活化后发生的表观遗传和代谢重新布线，损害小胶质细胞， IIM。这种在表观遗传水平上反应性的持续改变可能导致小胶质细胞作为一种神经细胞的功能衰竭。 AD的发病机制为了解决这些假设，我建议研究人类的机制， 小胶质细胞IIM对AD相关炎症刺激（包括淀粉样蛋白和tau蛋白）的反应，以及 CD33风险变体在此印记过程中。在目标1中，我将研究人类小胶质细胞IIM表型， HMC3（一种人类小胶质细胞系）的结果，该细胞系用CRISPR编辑以携带CD33 AD风险等位基因。我将测试 一系列AD相关炎症刺激是否产生训练或耐受的IIM反应，以及如何产生 CD33基因型影响这些结果。在目标2中，我将研究表观遗传和代谢机制 携带CD33风险或保护性等位基因的HMC3中的潜在IIM。这些研究将提供机制 深入了解小胶质细胞和局部脑病理学之间的纵向相互作用，以及CD33风险如何 变异介导小胶质细胞功能障碍并最终导致AD易感性。重要的是，它们还将推动我们的 了解人类小胶质细胞中的IIM，其中知之甚少，以及它们在响应中采用的IIM表型 AD病理学因此，它们的成功结束可能为开发潜力开辟新的途径。 本发明的目的是提供靶向AD中的小胶质细胞失调的治疗剂，并最终改善患者的结局。

PROJECT SUMMARY Alzheimer’s disease (AD) is an age-related neurodegenerative disease characterized by cognitive decline and an accumulation of amyloid pathology. A strong genetically-driven innate immune component is thought to play a pathogenic role in AD, implicating a central role for microglial dysfunction. Microglia are long-lived resident innate immune cells in the central nervous system. Activation of their immune and metabolic pathways lead to innate immune memory (IIM), a functional reprogramming process in which the response to an initial stimulus shapes long-lasting epigenetic modifications which inform the response to subsequent stimuli. IIM may result in enhanced activation (training) or suppression (tolerance) based on the identity of the initial inflammatory stimulus. IIM has been shown to alter pathology in AD mouse models, as a consequence of a sustained alteration in microglial functioning. Several common AD risk variants, including CD33, converge to suppress microglial activation, by decreasing inflammatory signaling or increasing its inhibition. Accordingly, my overall hypothesis is that altered microglial IIM as a result of suppressive genetic AD risk variants is a critical mechanism underlying the observed microglial dysfunction in AD. More specifically, I hypothesize that the suppressive CD33 AD-risk variant will reduce epigenetic and metabolic rewiring that occurs upon cellular activation, impairing microglial IIM. This sustained alteration of responsiveness at the epigenetic level may contribute to microglial failure as a pathogenic mechanism in AD. To address these hypotheses, I propose to examine the mechanisms of human microglial IIM in response to AD associated inflammatory stimuli, including amyloid and tau, and the effect of the CD33 risk variant on this imprinting process. In Aim 1, I will investigate human microglial IIM phenotypic outcomes in HMC3s (a human microglial cell line) edited with CRISPR to carry the CD33 AD risk allele. I will test whether a range of AD-associated inflammatory stimuli produce trained or tolerized IIM responses, and how CD33 genotype affects these outcomes. In Aim 2, I will investigate the epigenetic and metabolic mechanisms underlying IIM in HMC3s carrying the CD33 risk or protective alleles. These studies will provide mechanistic insight into longitudinal interactions between microglia and local brain pathology, as well as how the CD33 risk variant mediates microglial dysfunction and ultimately AD susceptibility. Importantly, they will also advance our understanding of IIM in human microglia, of which little is known, and the IIM phenotypes they adopt in response to AD pathologies. Their successful conclusion may thus open novel avenues for the development of potential therapeutics to target microglial dysregulation in AD, and to ultimately improve patient outcomes.