Impaired Vasoreactivity, Sleep Degradation, and Impaired Clearance in the APOE4 Brain

项目摘要/摘要 载脂蛋白E的ε4变异体是散发性疾病最强烈和最常见的遗传危险因素 阿尔茨海默病(AD)，占AD病例的95%以上。载脂蛋白E4已经被证明 有助于促进AD病理的一系列分子过程，包括加速 淀粉样蛋白-β和tau蛋白聚集，免疫反应性增强，脂代谢改变，受损 脑血流，但传递的AD风险的总体机制仍不清楚。作为一项主要风险 与AD一样，APOE4也是动脉粥样硬化的因子，对血管系统有深远的影响。之前的研究已经 发现神经血管偶联失调，血管扩张剂一氧化氮水平高，血流受阻。 脑内动脉周围的脑脊液，提示淋巴清除减少，这一过程 最戏剧性的发生在睡眠中。因此，生理睡眠模式也是已知的 在AD中被干扰，这表明在许多已识别的APOE4过程中有一个共同的主题-调控失调。我们 提出神经血管偶联和血管扩张的改变将改变睡眠阶段的模式并扰乱 睡眠，这会损害大脑对细胞废物的清除。许多这样的浪费 产品，如蛋白质聚集体、炎性细胞因子和代谢物，可能具有神经毒性，并可能 创造一个正反馈循环，因为它们反过来影响神经活动和血管的完整性和功能，进一步 扰乱睡眠。为了测试这一想法，我们将结合三项研究的神经生物学和技术专业知识 研究不同大脑功能水平的小组，以进行综合的、多尺度的脑生理学研究 并在携带人源化APOE4和APOE3的敲入小鼠中发挥作用。首先，我们将使用定制开发的 用于APOE4和APOE3小鼠的长期慢性脑电监测和专门机器学习的硬件 用于睡眠阶段的实时表征，以识别在以下过程中睡眠模式和质量的变化 老化(3个月至15个月)。第二，我们将量化皮质血管扩张和血管反应性的损害。 通过进行双光子成像来测量表现为APOE4和APOE3的皮质动脉直径 在衰老过程中，清醒和自然睡眠的小鼠处于不同的时间点。第三，我们将演出 APOE4和APOE3小鼠白天(光)和夜间(暗)脑组织的多重和组学分析 以量化炎症细胞因子和代谢物的水平。最后，我们将进一步 测试我们的假设，并尝试通过引入运动作为一种有效的手段来改善促进AD的病理 血管扩张剂和脑血管健康的刺激物。当建议的工作完成后，我们将会有 确定了睡眠阶段和质量改变、血管扩张受损和调节失调的轨迹 APOE4中免疫和代谢产物的产生和清除，并测试了它们之间的关系 这些病理通过从小引入运动来改善血管功能障碍。

PROJECT SUMMARY/ABSTRACT The ε4 variant of apolipoprotein E (APOE4) is the strongest and most common genetic risk factor for sporadic Alzheimer’s disease (AD), which makes up more than 95% of AD cases. APOE4 has been demonstrated to contribute to a number of molecular processes implicated as promoting AD pathology, including accelerated aggregation of amyloid-β and tau proteins, increased immunoreactivity, altered lipid metabolism, and impaired cerebral blood flow, but an over-arching mechanism of the conveyed AD risk remains unclear. As a leading risk factor for atherosclerosis as well as AD, APOE4 has profound effects on vasculature. Previous studies have found dysregulated neurovascular coupling, high levels of the vasodilator nitric oxide, and impaired flow of cerebrospinal fluid around arteries in the brain, suggesting decreased glymphatic clearance, a process that occurs most dramatically during sleep. Consequently, physiological sleep patterns are also known to be disrupted in AD, suggesting a common theme in many of the identified APOE4-dysregulated processes. We propose that altered neurovascular coupling and vasodilation will alter sleep stage patterns and disrupt sleep, which will impair the clearance of cellular waste products from the brain. Many of these waste products, such as protein aggregates, inflammatory cytokines, and metabolites can be neurotoxic, and can create a positive feedback cycle as they in turn affect neural activity and vascular integrity and function, further disrupting sleep. To test this idea, we will combine the neurobiological and technical expertise of three research groups studying distinct levels of brain function to perform an integrative, multi-scale study of brain physiology and function in knock-in mice carrying humanized APOE4 and APOE3. First, we will use custom-developed hardware for chronic, long-term EEG monitoring of APOE4 and APOE3 mice and specialized machine learning for real-time characterization of sleep stages to identify shifts in sleep patterns and quality over the course of aging (3 months to 15 months). Second, we will quantify impairment of cortical vasodilation and vasoreactivity by conducting 2-photon imaging to measure the diameter of cortical arteries in behaving APOE4 and APOE3 mice, both awake and in natural sleep, at different time points over the course of aging. Third, we will perform multiplexing and -omics assays of brain tissue from APOE4 and APOE3 mice during day (light) and night (dark) over the course of aging to quantify the levels of inflammatory cytokines and metabolites. Finally, we will further test our hypothesis and attempt to ameliorate AD-promoting pathology by introducing exercise as a potent vasodilator and stimulus of cerebrovascular health. Upon completion of the proposed work, we will have determined the trajectories of altered sleep stages and quality, impaired vasodilation, and dysregulated production and clearance of immune and metabolic products in APOE4, and tested the relationship between these pathologies by introducing exercise from young age to ameliorate vascular dysfunction.