LRP及RAGE介导的高胆固醇在AD发生发展中的作用及机制研究

With aging of population across the world, Alzheimer’s disease (AD) has become a leading cause of death in the elderly. But so far, there are still no effective treatments available. Hypercholesterolemia play an important role in AD development, but its mechanism is not clear. In recent years, transporter Aβ receptor in blood brain barrier has been widely concerned, including the low density lipoprotein receptor related protein receptor (LRP1) and the receptor for advanced glycation end products (RAGE). The main function of LRP is to cross the blood brain barrier transport of Aβ in the brain, the Aβ transport into the blood, so as to eliminate the role of Aβin the brain. RAGE is the main transport across the blood brain barrier in the blood to brain transport of Aβ. In animal experiments, determined by the changes of Aβcontent in brain and in blood, result showed the effect of hypercholesterolemia on LRP1 and RAGE expression in blood-brain barrier endothelial cells. Studies have shown that, hypercholesterolemia can make the Aβdeposition in the brain of AD mice, decreased cognitive ability. Hypercholesterolemia, whether through the effect on the Aβtransport receptor leads to the occurrence and development of AD is not clear. We will study the regulation effect and molecular mechanisms of Hypercholesterolemia on LRP1 and RAGE in BBB of AD animal models. After LRP1 over-expressing and RAGE gene silencing, we will observe the effect of changes of Aβ transporter receptors on the capacity of transporting Aβ in AD animal models.

随着世界人口老龄化，阿尔茨海默病（AD）已成为老年人死亡最常见的疾病，目前AD尚无有效治疗方法，其防治是亟待解决的难题。高胆固醇血症在AD的进展中起重要作用，但其机制尚不清楚。最近，血脑屏障转运Aβ受体倍受关注，包括低密度脂蛋白受体相关蛋白受体（LRP1）和糖基化终产物受体（RAGE）。LRP能跨血脑屏障将脑内的Aβ转运到血液中，以清除脑内Aβ。RAGE是跨血脑屏障把血中的Aβ转运至脑内的主要受体。在动物实验中，通过脑内和血液中Aβ含量的变化的测定，发现高胆固醇血症可以对血脑屏障内皮细胞LRP1和RAGE的表达产生影响。研究已经证明，高胆固醇血症可以使脑内Aβ沉积，AD小鼠认知能力下降。高胆固醇血症是否通过影响Aβ转运受体导致AD的发生发展尚不清楚。本项目通过观察高胆固醇AD小鼠，比较血脑屏障Aβ转运受体LRP和RAGE表达的差异及Aβ转运功能的变化，探讨高胆固醇对Aβ转运受体的调控作用。

高胆固醇可加重AD的发病风险，AD的发生与Aβ在BBB中的转运密切相关。目前尚不清楚高胆固醇是否通过影响Aβ的转运而影响AD的发生。本研究旨在探讨高胆固醇是否通过LRP1和RAGE调节Aβ在BBB中的转运，从而加重AD的发生。建立高胆固醇AD小鼠模型。用MWM方法评价小鼠的空间学习记忆能力。观察LRP1和BBB的RAGE在体内的表达水平及其对Aβ转运的影响。体外分离培养脑微血管内皮细胞，观察LRP1和RAGE的表达水平。用Wnt阻滞剂DKK-1和β-连环蛋白阻滞剂XAV-939检测培养微血管内皮细胞LRP1和RAGE的表达。高胆固醇血症加重AD小鼠空间学习记忆障碍。高胆固醇血症使AD小鼠血清Aβ1-40水平升高。高胆固醇血症降低AD小鼠脑微血管内皮细胞LRP1 mRNA和蛋白的表达，增加RAGE mRNA和蛋白的表达。免疫荧光结果显示，高胆固醇血症可减少脑微血管内皮细胞和海马神经元中LRP1+/CD31+细胞的数量，增加RAGE+/CD31+细胞的数量；高胆固醇血症可增加AD小鼠神经元凋亡。体外实验表明，高胆固醇可降低脑微血管内皮细胞LRP1的表达，增加RAGE的表达，增加Aβ1-40的表达。高胆固醇通过Wnt/β-catenin信号途径调节LRP1和RAGE的表达。高胆固醇通过Wnt/β-catenin信号途径调节LRP1和RAGE启动子的转录活性。高胆固醇通过Wnt/β-catenin信号途径降低脑微血管内皮细胞LRP1的表达，增加RAGE的表达，导致BBB中Aβ转运障碍。脑内Aβ沉积增加，加重脑内神经元凋亡，导致AD小鼠认知功能损害。

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