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

项目总结/摘要 载脂蛋白E ε4变异体（APOE 4）是散发性高脂血症最强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。APOE 4已被证明 有助于促进AD病理学的许多分子过程，包括加速 淀粉样蛋白-β和tau蛋白聚集，免疫反应性增加，脂质代谢改变， 脑血流量，但传递的AD风险的过度兴奋机制仍不清楚。作为主要风险 作为动脉粥样硬化和AD的因子，APOE 4对血管系统有着深远的影响。先前的研究 发现神经血管耦合失调，血管扩张剂一氧化氮水平高， 脑动脉周围的脑脊液，表明胶质淋巴清除率降低，这一过程， 在睡眠中发生得最明显。因此，生理睡眠模式也被认为是 在AD中破坏，这表明在许多已确定的APOE 4失调过程中有一个共同的主题。我们 我认为，改变神经血管耦合和血管舒张将改变睡眠阶段模式， 睡眠，这将损害从大脑中清除细胞废物。许多这些废物 产物，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， 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完整性和功能， 扰乱睡眠为了验证这个想法，我们将联合收割机结合三个研究小组的神经生物学和技术专长， 研究不同层次的大脑功能的小组，以进行大脑生理学的综合性，多尺度研究 并在携带人源化APOE 4和APOE 3的敲入小鼠中发挥作用。首先，我们将使用定制开发的 用于APOE 4和APOE 3小鼠慢性、长期EEG监测和专门机器学习的硬件 用于睡眠阶段的实时表征，以识别睡眠模式和质量在睡眠过程中的变化， 老化（3个月至15个月）。其次，我们将量化皮质血管舒张和血管反应性的损害 通过进行双光子成像来测量表现APOE 4和APOE 3的皮质动脉的直径， 小鼠在衰老过程中的不同时间点处于清醒和自然睡眠状态。第三，我们将执行 来自APOE 4和APOE 3小鼠的脑组织在白天（光照）和夜晚（黑暗）的多重和组学测定 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，并试图通过引入运动作为一种有效的 血管扩张剂和刺激脑血管健康。在完成拟议的工作后，我们将有 确定了睡眠阶段和质量改变、血管舒张受损和调节失调的轨迹， APOE 4中免疫和代谢产物的产生和清除，并测试了 这些病理通过引入运动从年轻的年龄，以改善血管功能障碍。

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.