Alzheimer's Disease Genetic Risk and Microglial Innate Immune Memory

项目概要 阿尔茨海默病（AD）是一种与年龄相关的神经退行性疾病，其特征是认知能力下降和 淀粉样蛋白病理的积累。人们认为强大的基因驱动的先天免疫成分发挥着作用 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。其免疫和代谢途径的激活导致 先天免疫记忆（IIM），一种功能重编程过程，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 可能会导致 根据初始炎症的特性增强激活（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 在小胶质细胞功能中。包括 CD33 在内的几种常见 AD 风险变异体汇聚在一起抑制小胶质细胞 通过减少炎症信号或增加其抑制来激活。因此，我的总体假设 抑制性 AD 风险基因变异导致小胶质细胞 IIM 的改变是潜在的关键机制 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 变体将减少细胞激活时发生的表观遗传和代谢重连，损害小胶质细胞 IIIM。这种表观遗传水平反应性的持续改变可能导致小胶质细胞失败 AD 的致病机制。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 此印记过程中存在 CD33 风险变体。在目标 1 中，我将研究人类小胶质细胞 IIM 表型 使用 CRISPR 编辑 HMC3s（一种人类小胶质细胞系）以携带 CD33 AD 风险等位基因的结果。我会测试 一系列 AD 相关炎症刺激是否产生经过训练或耐受的 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介导 AD 易感性。重要的是，他们还将推进我们的 了解人类小胶质细胞中的 IIM（人们对此知之甚少）以及它们响应时采取的 IIM 表型 AD 病理。因此，他们的成功结论可能为开发潜力开辟新途径 针对 AD 中小胶质细胞失调的治疗方法，并最终改善患者的治疗结果。

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.