The role of human ApoE in soluble ABeta clearance through the LDLR in vivo

描述（由申请人提供）：痴呆症的主要原因是阿尔茨海默病（AD），其特征是认知功能和记忆的进行性丧失，最终导致死亡。据估计，目前有超过500万美国人患有阿尔茨海默病，每年与阿尔茨海默病和相关痴呆相关的直接医疗费用超过1450亿美元。随着未来几十年人口的老龄化，阿尔茨海默病带来的医疗负担将是惊人的。了解这种与年龄有关的疾病的发病机制对于开发有效的治疗方法至关重要，也是本研究计划的主要动机。淀粉样蛋白3 （A|3）肽在脑细胞外空间的沉积是AD的关键病理标志之一。载脂蛋白E4 （apoE4）遗传是目前发现的迟发性AD的主要遗传危险因素，而apoE2遗传似乎具有保护作用。A(3)肽的毒性积累可能受其产生速率及其从脑间质液（ISF）中的清除速率的调节；由于apoE不影响Ap的合成，它可能调节ISF对A|3的清除。我们的团队和其他人已经证明apoE和Ap之间的结合影响了Ap在大脑中的沉积和清除。大量证据表明，低密度脂蛋白受体（LDLR）是大脑中主要的apoE受体，可能为ISF中可溶性Ap的清除提供了重要途径。LDLR在人类apoE亚型的背景下调节Ap清除的过程仍然知之甚少。我的目的是确定LDLR在调节人类apoe介导的ISF中Ap清除中的作用。我假设apoe介导的Ap从ISF中消除是由LDLR促进的，并且遵循一种同型依赖的模式，例如apoE2 > apoE3 > apoE4的Ap清除率。在Specific Aim 1中，我将使用我们的体内微透析技术直接评估表达每种人类apoE亚型的小鼠的Ap清除率，并将它们与缺乏LDLR的小鼠进行比较。为了补充这项研究，我将测定过表达LDLR的小鼠和每个人类apoE亚型的ISF中AP的半衰期。在Specific Aim 2中，我将分析过表达LDLR的小鼠的细胞外Ap池以及在Ap沉积之前和之后年龄的每个人类apoE亚型，以评估LDLR对沉积形成的大脑区域Ap水平的调节。为了评估LDLR对人类apoE背景下Ap沉积的影响，我将量化每组小鼠脑切片中的斑块负荷。我提出的研究计划与公共卫生的相关性在于，了解LDLR和人类apoE介导Ap清除的机制对于设计有效的阿尔茨海默病新疗法至关重要。

DESCRIPTION (provided by applicant): The leading cause of dementia is Alzheimer's disease (AD), which is characterized by a progressive loss of cognitive function and memory, ultimately leading in death. It is estimated that over 5 million Americans currently suffer for AD, and the direct healthcare cost associated with AD and related dementias annually exceeds $145 billion. As the population ages over the next several decades, the health-care burden presented by AD will be staggering. Understanding the pathogenesis of this age-related disease is c critical to the development of effective therapies and is the primary motivation for this research proposal. Deposition of the Amyloidal (3 (A|3) peptide in the extracellular space of the brain constitutes one of the key pathological hallmarks of AD. Inheritance of apolipoprotein E4 (apoE4) is the major genetic risk factor for late-onset AD identified so far, while apoE2 inheritance appears to be protective. Toxic accumulation of the A(3 peptide is likely regulated by the rates of its production and its clearance from the interstitial fluid (ISF) of the brain; since apoE does not affect the synthesis of Ap, it likely regulates A|3 clearance from the ISF. Our group and others have shown that the binding between apoE and Ap influences Ap deposition and its clearance ifrom the brain. Abundant evidence indicates that the low density lipoprotein receptor (LDLR) is a major apoE receptor in the brain, likely providing an important clearance route for soluble Ap from the ISF. The process by which LDLR regulates Ap clearance in the context of human apoE isoforms remains poorly understood. My objective is to determine the role of LDLR in regulating human apoE-mediated clearance of Ap from the ISF. I hypothesize that apoE-mediated elimination of Ap from the ISF is facilitated by LDLR and follows a pattern that is isoform-dependent such that Ap clearance rate for apoE2 > apoE3 > apoE4. In Specific Aim 1,1 will use our in vivo microdialysis technique to directly assess Ap clearance in mice expressing each of the human apoE isoforms, comparing them to the same mice lacking LDLR. To complement this study, I will determine the AP half-life in the ISF of mice overexpressing LDLR and each of the human apoE isoforms. In Specific Aim 2,1 will analyze extracellular pools of Ap in mice overexpressing LDLR and each of the human apoE isoforms at ages prior to and after Ap deposition to assess LDLR's regulation of Ap levels in regions of the brain where deposits form. To assess the effect of LDLR on Ap deposition in the context of human apoE, I will quantify plaque load in brain sections from each of the groups of mice. The relevance of my proposed research plan to public health is that understanding the mechanisms by which LDLR and human apoE act to mediate Ap clearance will be critical to designing effective new therapies for AD.