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

描述（由申请人提供）：痴呆的主要原因是阿尔茨海默病（AD），其特征在于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AD，每年与AD和相关痴呆症相关的直接医疗保健费用超过1450亿美元。随着未来几十年人口老龄化，AD带来的医疗负担将是惊人的。了解这种年龄相关疾病的发病机制对于开发有效的治疗方法至关重要，也是本研究提案的主要动机。淀粉样蛋白沉积（3（A| 3）脑细胞外间隙中的肽构成AD的关键病理标志之一。载脂蛋白E4（apoE 4）的遗传是目前发现的晚发性AD的主要遗传危险因素，而apoE 2的遗传似乎是保护性的。A β肽的毒性蓄积可能受其产生速率及其从脑间质液（ISF）中清除的速率调节;由于apoE不影响A β的合成，因此它可能调节A β肽的毒性蓄积。|三是从ISF。我们的研究小组和其他研究小组已经表明apoE和Ap之间的结合影响Ap的沉积和从脑中的清除。大量证据表明，低密度脂蛋白受体（LDLR）是脑内主要的apoE受体，可能为可溶性Ap从ISF中清除提供重要途径。在人apoE亚型的背景下，LDLR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apoE介导的Ap从ISF中清除中的作用。我假设apoE介导的Ap从ISF中的消除是由LDLR促进的，并且遵循亚型依赖性的模式，使得apoE 2> apoE 3> apoE 4的Ap清除率。在具体目标1中，1将使用我们的体内微透析技术直接评估表达每种人apoE亚型的小鼠中的Ap清除率，并将其与缺乏LDLR的相同小鼠进行比较。为了补充这项研究，我将确定过表达LDLR和每种人apoE亚型的小鼠ISF中的AP半衰期。在特定目标2，1中，将在Ap沉积之前和之后分析过表达LDLR和每种人apoE亚型的小鼠中的Ap细胞外池，以评估LDLR对沉积物形成的脑区域中Ap水平的调节。为了评估LDLR在人apoE背景下对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apoE介导Ap清除的机制对于设计有效的AD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.