APOE effects on glial lipid metabolism and 25-hydroxycholesterol: Effects on aging and AD-related pathology

项目总结(APOE U19：项目2) 项目2试图提高对载脂蛋白E(ApoE)亚型如何影响神经胶质脂质的理解。 阿尔茨海默病患者免疫介导性脑损伤的代谢和炎症反应 疾病(AD)和与衰老相关的病理。有证据表明，载脂蛋白E不仅影响β 沉积和结构，它强烈地影响小胶质细胞的激活，β诱导的神经性营养不良，以及tau- 介导性神经变性。星形胶质细胞和小胶质细胞产生的载脂蛋白E在 这些效应和小胶质细胞是神经退行性变的关键效应细胞。与ApoE级联保持一致 假设，我们预计，结构差异和相关的生化性质之间的 载脂蛋白E亚型可能介导载脂蛋白E对大脑先天免疫反应的不同影响。 脂代谢和甾醇处理等因素可以通过以下方式影响小胶质细胞的反应性 与AD发病机制有关。最近的证据表明，载脂蛋白E和衰老严重影响着 大脑中的胆固醇和脂质清除，特别是在小胶质细胞中。脂质碎片在小胶质细胞中的积聚 在不同条件下与小胶质细胞活化和炎性小体介导的损伤有关。的确有 另有文献和我们有初步数据表明，25-羟基胆固醇(25HC)，一种已知的氧化类固醇 免疫调节剂，由小胶质细胞在大脑中产生，可以调节胆固醇代谢以及 小胶质细胞因子在体外以载脂蛋白E异构体依赖的方式反应。这些数据让我们了解到 假设载脂蛋白E依赖于胆固醇酯和其他脂类的调节和清除 特别是在衰老和AD中，小胶质细胞调节小胶质细胞的炎症反应。我们进一步 假设这种包括25HC产生的小胶质细胞反应影响β诱导的局部损伤，Aβ- 以载脂蛋白E、年龄和性别依赖的方式诱导tau扩散和tau介导的神经变性。我们 提出这些目标：目标1：确定载脂蛋白E及其亚型对胆固醇、胆固醇的影响 在Aβ和tau病理的背景下，在衰老过程中，星形胶质细胞和小胶质细胞中的酯和其他脂质，以及 用LXR激动剂刺激。目的2：评价具有免疫调节作用的氧合甾醇25- 羟基胆固醇(25HC)对β介导的tau扩散、tau介导的神经变性和年龄相关的影响 脑表型以及载脂蛋白E如何改变这些表型。目的3：评价载脂蛋白E亚型对细胞周期的影响。 星形胶质细胞、小胶质细胞和分泌载脂蛋白的脂质体及其作用机制 脂滴形成、载脂蛋白E信号与体外炎症的关系。我们亦会评估 CH25H对载脂蛋白E介导的体外神经退行性变影响的机制影响/整合：项目 2将与项目1、3、5、核心B、核心D、核心E、核心F和核心G在生产上密切合作， 小鼠脑胶质细胞载脂蛋白E颗粒和脂类的提纯、鉴定及IPSC 体外培养来源的神经胶质细胞。项目2中的组织学分析将以神经病理核心(核心C)进行。

PROJECT SUMMARY (APOE U19: PROJECT 2) Project 2 seeks to improve understanding of how apolipoprotein E (apoE) isoforms influence glial lipid metabolism and inflammatory responses underlying immune-mediated damage in the brain in Alzheimer’s disease (AD) and aging-related pathologies. Evidence indicates that the apoE protein not only affects Aβ deposition and structure, it strongly influences microglial-activation, Aβ-induced neuritic dystrophy, and tau- mediated neurodegeneration. ApoE produced by both astrocytes and microglia plays an important role in these effects, and microglia are critical effectors of neurodegeneration. In alignment with the ApoE Cascade Hypothesis of this U19, we anticipate that structural differences and related biochemical properties among the apoE isoforms are likely to mediate the differential effects of apoE on the brain’s innate immune response. Factors such as lipid metabolism and sterol processing, can influence microglial reactivity in ways that are relevant to AD pathogenesis. Recent evidence indicates that apoE and aging critically influence the process of cholesterol and lipid clearance in the brain, specifically in microglia. Accumulation of lipid debris in microglia under different conditions is linked with microglial activation and inflammasome-mediated damage. There is also literature and we have preliminary data that 25-hydroxycholesterol (25HC), a known oxysterol immunomodulator, is produced in the brain by microglia and can modulate cholesterol metabolism as well as the microglial cytokine response in an apoE isoform-dependent manner in vitro. These data lead us to hypothesize that apoE-dependent regulation and clearance of cholesterol esters and other lipids specifically in microglia regulates the microglial inflammatory response in aging and AD. We further hypothesize that this microglial response including 25HC production impacts Aβ-induced local damage, Aβ- induced tau spreading, and tau-mediated neurodegeneration in an apoE, age, and sex-dependent fashion. We propose these aims: Aim 1: Determine the effects of apoE and apoE isoforms on cholesterol, cholesterol esters, and other lipids in astrocytes and microglia during aging, in the setting of Aβ and tau pathology, and with LXR agonist stimulation. Aim 2: Assess the effects of the immunomodulatory oxysterol, 25- hydroxycholesterol (25HC) on Aβ-mediated tau-spreading, tau-mediated neurodegeneration, and age-related brain phenotypes and how these are modified by apoE. Aim 3: Assess the effect of apoE isoform on the lipidomic profile of astrocytes, microglia, and secreted apoE-containing lipoproteins as well as the mechanistic relationship between lipid droplet formation, apoE signaling, and inflammation in vitro. We will also assess the mechanism of the effects of ch25h on apoE-mediated neurodegeneration in vitro. Impact/Integration: Project 2 will work closely with Projects 1, 3, 5, Core B, Core D, Core E, Core F, and Core G on production, purification, and characterization of apoE particles and lipids from mouse glia in vitro and in vivo and iPSC derived glia in vitro. Histological analysis in Project 2 will be done with the Neuropathology Core (Core C).