Cerebrovascular dysfunction is a hallmark feature of Alzheimer's disease (AD). One of the greatest risk factors for AD is the apolipoprotein E4 (E4) allele. The APOE4 genotype has been shown to negatively impact vascular amyloid clearance, however, its direct influence on the molecular integrity of the cerebrovasculature compared to other APOE variants (APOE2 and APOE3) has been largely unexplored. To address this, we employed a 10-plex tandem isobaric mass tag approach in combination with an ultra-high pressure liquid chromatography MS/MS (Q-Exactive) method, to interrogate unbiased proteomic changes in cerebrovessels from AD and healthy control brains with different APOE genotypes. We first interrogated changes between healthy control cases to identify underlying genotype specific effects in cerebrovessels. EIF2 signaling, regulation of eIF4 and 70S6K signaling and mTOR signaling were the top significantly altered pathways in E4/E4 compared to E3/E3 cases. Oxidative phosphorylation, EIF2 signaling and mitochondrial dysfunction were the top significant pathways in E2E2 vs E3/E3cases. We also identified AD-dependent changes and their interactions with APOE genotype and found the highest number of significant proteins from this interaction was observed in the E3/E4 (192) and E4/E4 (189) cases. As above, EIF2, mTOR signaling and eIF4 and 70S6K signaling were the top three significantly altered pathways in E4 allele carriers (i.e. E3/E4 and E4/E4 genotypes). Of all the cerebrovascular cell-type specific markers identified in our proteomic analyses, endothelial cell, astrocyte, and smooth muscle cell specific protein markers were significantly altered in E3/E4 cases, while endothelial cells and astrocyte specific protein markers were altered in E4/E4 cases. These proteomic changes provide novel insights into the longstanding link between APOE4 and cerebrovascular dysfunction, implicating a role for impaired autophagy, ER stress, and mitochondrial bioenergetics. These APOE4 dependent changes we identified could provide novel cerebrovascular targets for developing disease modifying strategies to mitigate the effects of APOE4 genotype on AD pathogenesis.

中文翻译：

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阿尔茨海默病和年龄匹配的非痴呆脑血管系统中的 APOE 基因型依赖性分子异常

脑血管功能障碍是阿尔茨海默病 (AD) 的标志性特征。AD 的最大风险因素之一是载脂蛋白 E4 (E4) 等位基因。APOE4 基因型已显示对血管淀粉样蛋白清除产生负面影响，然而，与其他 APOE 变体（APOE2 和 APOE3）相比，它对脑血管系统分子完整性的直接影响在很大程度上尚未得到探索。为了解决这个问题，我们采用了 10 重串联等压质量标签方法与超高压液相色谱 MS/MS（Q-Exactive）方法相结合，以询问来自 AD 和不同健康对照大脑的脑血管中的无偏蛋白质组变化。 APOE基因型。我们首先询问健康对照病例之间的变化，以确定脑血管中潜在的基因型特异性影响。EIF2 信号，与 E3/E3 病例相比，eIF4 和 70S6K 信号传导和 mTOR 信号传导的调节是 E4/E4 中最显着改变的途径。氧化磷酸化、EIF2 信号传导和线粒体功能障碍是 E2E2 与 E3/E3 病例中最重要的途径。我们还确定了 AD 依赖性变化及其与 APOE 基因型的相互作用，并发现在 E3/E4 (192) 和 E4/E4 (189) 病例中观察到来自这种相互作用的最大数量的重要蛋白质。如上所述，EIF2、mTOR 信号和 eIF4 和 70S6K 信号是 E4 等位基因携带者（即 E3/E4 和 E4/E4 基因型）中前三个显着改变的途径。在我们的蛋白质组学分析中鉴定的所有脑血管细胞类型特异性标志物中，内皮细胞、星形胶质细胞和平滑肌细胞特异性蛋白质标志物在 E3/E4 病例中发生了显着改变，而内皮细胞和星形胶质细胞特异性蛋白标志物在 E4/E4 病例中发生了改变。这些蛋白质组学变化为 APOE4 与脑血管功能障碍之间的长期联系提供了新的见解，暗示了自噬受损、ER 应激和线粒体生物能量学的作用。我们发现的这些依赖于 APOE4 的变化可以提供新的脑血管靶点，用于开发疾病缓解策略以减轻 APOE4 基因型对 AD 发病机制的影响。