Role of Microglia in Neurodegeneration -Effect of ApoE

项目摘要 与阿尔茨海默氏病一样，Pron病(Prionoses)是一种构象障碍，在这种疾病中， 错误折叠的蛋白质伴有混合表现的小胶质细胞神经退行性表型(MGnD) 吞噬和炎症特性。蛋白错误折叠致小鼠神经变性模型的建立 而激活的胶质细胞反应可以用来揭示阿尔茨海默病的相关病理机制。APOEε4 等位基因是散发性阿尔茨海默病的最主要的危险因素，在异种人中其患病几率分别增加3倍和15倍 和纯合子。载脂蛋白E编码载脂蛋白(Apo)E，控制脑组织脂质稳态 并通过对可溶性物质的清除和沉积的同型特异性作用来调节阿尔茨海默病的风险 一辆β。ApoE由星形胶质细胞以apoE/HDLS的形式表达，MGnD也以贫脂颗粒的形式表达。差动 这两个apoE池对MGnD性质的贡献尚不清楚。而脂化的载脂蛋白E可能有助于 MGnD清除错误折叠的蛋白质，表达脂质贫乏的载脂蛋白E与其促炎作用有关 这些特性也受APOE基因的不同控制。在普赖恩病中，有毒的PrPSc积累 蛋白质是致病的元凶。小胶质细胞在病程早期经历激活并发挥作用 PrPSc介导的神经变性中的相反作用。虽然PrPSc的清除具有限制疾病的作用， 小胶质细胞引起的神经炎症对神经元是有害的。载脂蛋白E参与普恩病毒的发病机制 尚未得到证实，尽管有证据表明散发性克雅氏病的风险高出~2倍 (CJD)在ε4载体上。我们的初步工作表明，感染Pron的小鼠脑载脂蛋白E水平增加， ApoE在星形胶质细胞中的表达减少，在激活的小胶质细胞中表达增加。的总体效果 蛋白酪氨酸病的APOE是有益的，因为全球APOE KO通过加剧恶性循环来加剧蛋白病理 神经细胞死亡和神经炎症。MGnD对APOE-/-小鼠PrPSc和死亡神经元的清除作用 当神经元碎片夸大MGnD表型、炎性细胞因子的释放时，效率变得低下 诱导A1神经毒性星形胶质细胞。我们的研究还表明，蛋白原增多症中的载脂蛋白E效应是异构体依赖的。ε4/ε4 靶向替代(Tr)小鼠具有较短的疾病潜伏期、较高的病理负荷和小胶质细胞 ε-3/ε-3和ε-2/ε-2小鼠的高活性比较。这项初步工作引导我们提出了载脂蛋白E的假设 通过控制小胶质细胞对PrPSc介导的神经变性的反应，参与了Prion的发病；2) 基于载脂蛋白E的方法具有治疗价值；3)载脂蛋白E对人类普鲁恩病的作用是同型的。 依附的。这些假设应在格兰特的具体目标中加以探讨。目的评估星形胶质细胞的作用。 细胞特异性条件性载脂蛋白E与小胶质细胞表达载脂蛋白E在PrPSc介导的小鼠神经变性中的比较 出局了。AIM II将评估是否调节星形细胞和小胶质细胞载脂蛋白E和总载脂蛋白的水平 大脑载脂蛋白E水平调节神经退行性变。目的探讨载脂蛋白E基因对小胶质细胞的影响 普恩病毒感染的apoe tr小鼠以及散发性CJD和阿尔茨海默病患者的激活表型。

Project Summary Like Alzheimer's disease, prion diseases (prionoses) are conformational disorders, in which deposition of misfolded proteins is accompanied by microglia neurodegenerative phenotype (MGnD) displaying mixed phagocytic and inflammatory properties. Prion mouse models with misfolded protein driven neurodegeneration and activated glia response can be used to uncover Alzheimer's disease relevant pathomechanisms. APOE ε4 allele is the foremost risk factor in sporadic Alzheimer's disease, increasing its odds by 3 and 15-fold in hetero and homozygotes, respectively. APOE encodes apolipoprotein (apo) E, which controls brain lipid homeostasis and modulates Alzheimer's disease risk through isoform-specific effect on clearance and deposition of soluble Aβ. ApoE is expressed by astrocytes in form of apoE/HDLs and also by MGnD as lipid-poor particles. Differential contributions of these two apoE pools to MGnD properties remain unclear. While lipidated apoE may facilitate clearance of misfolded proteins, expression of lipid-poor apoE by MGnD is linked to their pro-inflammatory properties, which also are differentially controlled by APOE genotype. In prionoses, accumulation of toxic PrPSc protein is the culprit of pathogenesis. Microglia undergo activation early in the course of disease and exert opposing roles in PrPSc mediated neurodegeneration. While clearance of PrPSc has a disease-limiting effect, microglia-driven neuroinflammation is deleterious to neurons. Involvement of apoE in prion pathogenesis has not been established, though there is evidence for ~2-fold higher risk of sporadic Creutzfeldt-Jakob disease (CJD) in ε4 carriers. Our preliminary work shows increased brain apoE level in prion infected mice along with reduced apoE expression in astrocytes and increased expression in activated microglia. The overall effect of apoE in prionoses is beneficial as global Apoe KO exacerbates prion pathology by aggravating the vicious cycle of neuronal death and neuroinflammation. In Apoe-/- mice, clearance of PrPSc and dying neurons by MGnD becomes inefficient while neuronal debris exaggerate MGnD phenotype, release of inflammatory cytokines, and induce A1 neurotoxic astrocytes. Our studies also suggest, apoE effect in prionoses is isoform dependent. ε4/ε4 targeted replacement (TR) mice have shorter disease incubation time, increased pathology load and microglia hyperactivation compared to ε3/ε3 and ε2/ε2 mice. This preliminary work led us to hypothesize 1) apoE involvement in prion pathogenesis is by control of microglia response to PrPSc mediated neurodegeneration; 2) apoE-based approaches have therapeutic merit in prionoses; and 3) effect of apoE in human prionoses is isoform dependent. These hypotheses shall be explored in grant's specific aims. Aim I will assess the role of astrocyte vs. microglia-expressed apoE on PrPSc mediated neurodegeneration in mice with cell-specific conditional Apoe knock out. Aim II will assess whether regulating lipidation level of astrocytic and microglial apoE and the total brain apoE level modulates neurodegeneration. Aim III will explore effects of APOE genotype on microglia activation phenotype in prion infected APOE TR mice and in sporadic CJD and Alzheimer's disease patients.