Alzheimer's Disease Genetic Risk and Microglial Innate Immune Memory

项目总结 阿尔茨海默病(AD)是一种与年龄相关的神经退行性疾病，其特征是认知能力下降和 淀粉样变性堆积。一种强大的遗传驱动的先天免疫成分被认为发挥了作用 阿尔茨海默病的致病作用，暗示了小胶质细胞功能障碍的中心作用。小胶质细胞是长期存在的 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)，一种功能性的重新编程过程，在这个过程中，对初始刺激的反应 形成持久的表观遗传修饰，告知对后续刺激的反应。IIM可能导致 根据初始炎症的身份增强激活(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，作为持续改变的结果 在小胶质细胞的功能上。几种常见的AD风险变异，包括CD33，聚集在一起抑制小胶质细胞 通过减少炎症信号或增加其抑制作用来激活。因此，我的总体假设 抑制性遗传AD风险变异导致的小胶质细胞IIM改变是导致AD的关键机制 观察到阿尔茨海默病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 变异体将减少细胞激活时发生的表观遗传和代谢重新连接，从而损害小胶质细胞 IIM。这种在表观遗传水平上持续的反应性改变可能会导致小胶质细胞衰竭 阿尔茨海默病的发病机制。为了解决这些假说，我建议研究人类的机制 小胶质细胞IIM对AD相关炎症刺激的反应，包括淀粉样蛋白和tau，以及 CD33风险变量对这种印记过程的影响。在目标1中，我将研究人类小胶质细胞IIM表型 用CRISPR编辑携带CD33 AD风险等位基因的HMC3s(一种人类小胶质细胞株)的结果。我要测试一下 一系列与AD相关的炎症刺激是否产生训练性或耐受性的IIM反应，以及如何 CD33基因分型影响这些结果。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HMC3s潜在的IIM。这些研究将提供机械论 洞察小胶质细胞和局部脑病理之间的纵向相互作用，以及CD33如何风险 变异体介导小胶质细胞功能障碍，最终导致阿尔茨海默病易感性。重要的是，他们还将推进我们的 对人类小胶质细胞中IIM的了解，以及他们对IIM的反应表型 阿尔茨海默病。因此，他们的成功可能会为开发潜力开辟新的途径 治疗针对阿尔茨海默病患者的小胶质细胞失调，并最终改善患者的预后。

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.