阿尔茨海默病新型体液生物标志物的发现和研究

This project was designed to identify novel body fluid biomarker for Alzheimer’s disease (AD) based on our most recent discovery in the pathological mechanism of AD. The β-Amyloid peptides (Aβ) is believed to be the key mediator of AD pathology. We recently found that Asparagine Endopeptidase (AEP) is progressively unregulated and activated during ageing in the mouse brain. Moreover, AEP is also elevated and activated in human AD brains compared to normal controls. The active AEP cleaves both amyloid precursor protein (APP) and tau, two major pathogenic players in AD. Processing of APP by AEP facilitates BACE1 to cleave APP, leading to β-amyloid upregulation. On the other hand, active AEP cleaves tau, abolishes its microtubule assembly function, induces tau aggregation, and triggers neurodegeneration. We will test the hypothesis that concentration and activity of AEP, the APP and tau fragments in the cerebrospinal fluid (CSF) and blood can serve as biomarkers for the early diagnosis of Alzheimer's disease. The mass spectrometry-based proteomics will be used to measure biomarker level in the CSF and blood that were obtained from mild cognitive impairment (MCI) and AD patients, as well as AD animal models. Implement of this project in Shanghai Jiao Tong University School of Medicine will open a new avenue for the prediction and prevention of future onset of AD.

本课题依据我们在阿尔茨海默病(AD)发病机制研究中获得的最新成果，研究和发现早期诊断AD的新型体液生物标志物。β淀粉样肽(Aβ)是AD发病的核心病理机制，我们最近发现脑组织内的天冬酰胺内肽酶(AEP)是Aβ生成级联的上游信号，AEP同时介导了Aβ生成增多和tau蛋白病变，AEP对淀粉样前体蛋白（APP）和tau的剪切加工是AD发病的早期事件；并且，AEP在年龄依赖性的AD发病中起关键作用。所以我们提出：1）AEP相关病变分子是反映AD早期病变的生物标志物； 2）AEP是早期干预AD的新靶点。为验证此科学假说，本课题应用质谱蛋白质组学技术检测血浆和脑脊液中AEP生成物的变化，研究和确定它们对早期AD的诊断效力，以及AEP的药物靶点作用。研究对象包括轻度认知损害（MCI）者、痴呆期AD患者和AD动物模型，目标是建立全新的体液（脑脊液或血浆）生化检测指标，用于AD的早期诊断和疾病干预。

课题背景是天冬酰胺内肽酶(asparagine endopeptidase, AEP)对淀粉样前体蛋白（APP）和tau的剪切加工是阿尔茨海默病（Alzheimer s disease, AD）的早期病理学事件；并且AEP在年龄依赖性的AD发病中起关键作用。所以我们提出AEP相关病变分子是反映AD早期病变的生物标志物。研究内容包括AD动物模型的脑组织和血液中AEP相关标志物的检测，AD相关的神经退行性变和认知功能损害情况，判断AEP相关标志物所处的AD病理阶段。检测阿尔茨海默病患者的体液中AEP相关的tau蛋白和淀粉样蛋白剪切片段，判断其对AD的早期预警作用。通过动物实验研究AEP抑制药物对AD动物模型的治疗作用，对脑内病变和认知损害的改善作用。重要结果之一是证明了脑组织内的AEP在阿尔茨海默病的早期阶段出现上调和活性增加，有希望成为一种新的阿尔茨海默病生物标志物。其二是证明了AEP是干预阿尔茨海默病的新靶点，选择性抑制AEP的药物能够阻止阿尔茨海默病动物模型的早期病变过程，改善AD样病变和认知功能的衰退。蛋白酶AEP将来的应用价值是：与现有的或研发中的其他生物标志物联合使用，为AD的早期诊断和早发现提供预警指标。以AEP为指标的AD诊断和治疗策略对于在全国范围内防控AD有很好的应用前景，值得在此基础上继续深入研究。

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