Rescuing neurovascular coupling to protect neuronal plasticity and cognition

总结 越来越多的证据表明，大脑微循环的改变会导致认知障碍， 在阿尔茨海默病（AD）和AD相关性痴呆（ADRD）中观察到的痴呆。然而，缺乏方法 对小血管的成像和研究其功能阻碍了我们对 血管性认知障碍和痴呆（VCID）的病理顺序。最早的迹象， 患者和小鼠模型中的VCID通常涉及空间和短期记忆-认知缺陷 海马体中的突触可塑性至关重要。神经元的能量有限 储备，因此依赖于“及时”神经血管耦合（NVC）策略，其中活动区域发出信号 以局部扩张并增加局部血流。AD患者和小鼠模型或 CADASIL是VCID的单基因原型形式，在NVC中显示出早期恶化。我们以往的研究 发现了一种在毛细血管内皮细胞中起作用的分子缺陷，并开发了一种治疗方法， 在AD和CADASIL小鼠模型中急性恢复NVC。具体来说，我们发现全身注射 磷脂PIP 2足以通过使Kir2.1通道作为神经血管的传感器来挽救神经血管缺陷。 增加外部K+-神经元活动的产物-并将其转化为血管扩张电信号 其快速传播到上游小动脉，驱动血管舒张以产生局部充血。我们 多学科团队，在脑微循环的尖端成像方面具有互补的专业知识， 突触可塑性潜在的学习和记忆过程，将测试的假设，即NVC恢复将 减轻海马体中突触可塑性的恶化，以及在 AD.我们进一步建议调查和比较这些功能在CADASIL，血管驱动形式的ADRD。 为了实现这一目标，我们将推进基于PIP 2的策略，以长期恢复AD和CADASIL中的NVC 模型，并通过开发创新的体外成像方法评估治疗效率， 完整的毛细血管-小动脉（CaPA）制备，并在体内使用植入的分级指数 （GRIN）透镜结合2-光子显微镜来研究海马中的NVC。最终，我们将 测量NVC补救对AD和CADASIL引起的海马突触可塑性恶化的影响 条件，并使用上下文恐惧条件反射作为行为读数。完成这项研究将有助于阐明 NVC功能障碍与AD/ADRD中痴呆的联系机制，以及NVC恢复作为一种潜在的治疗方法。 这项拟议的工作有可能为大脑微循环如何维持提供范式转变的观点 学习和记忆过程。

Summary Growing evidence points towards the contribution of altered brain microcirculation to cognitive impairment and dementia observed in Alzheimer’s disease (AD) and AD-related dementia (ADRD). Yet, the lack of approaches to image the small cerebrovasculature and investigate its function has hampered our progress in understanding the pathological sequence of vascular cognitive impairment and dementia (VCID). The earliest signs of AD and VCID in patients and mouse models typically involve deficits in spatial and short-term memory—cognitive functions that are critically sustained by synaptic plasticity in the hippocampus. Neurons have limited energy reserves and thus rely on a “just-in-time” neurovascular coupling (NVC) strategy in which active regions signal to the microvasculature to locally dilate and increase local blood flow. Patients and mouse models of AD or CADASIL, a monogenic archetypal form of VCID, show an early deterioration in NVC. Our previous studies have identified a molecular defect at play in capillary endothelial cells and developed a therapeutic approach that acutely restores NVC in the mouse model of AD and CADASIL. Specifically, we found that systemic injection of phospholipid PIP2 is sufficient to rescue neurovascular deficits by enabling Kir2.1 channels to act as sensors of increases in external K+—a product of neuronal activity—and transduce this into a vasodilator electrical signal that rapidly propagates to upstream arterioles, driving vasodilation to produce local hyperemia. Our multidisciplinary team, with complementary expertise in cutting-edge imaging of brain microcirculation and synaptic plasticity underlying learning and memory processes, will test the hypothesis that NVC restoration will mitigate the synaptic plasticity deterioration in the hippocampus, and its behavioral consequences, observed in AD. We further propose to investigate and compare these functions in CADASIL, a vascular driven form of ADRD. To attain this goal, we will advance our PIP2-based strategy to chronically restore NVC in AD and CADASIL models, and assess the treatment efficiency by developing innovative imaging approaches ex vivo, with a novel intact capillary-arteriolar (CaPA) preparation established by our group, and in vivo using implanted graded-index (GRIN) lenses combined with 2-photon microscopy to investigate NVC in the hippocampus. Ultimately, we will measure the effect of NVC rescue on hippocampal synaptic plasticity deterioration caused by AD and CADASIL conditions, and use contextual fear conditioning as a behavioral readout. Completing this study will help elucidate the mechanisms linking NVC dysfunction to dementia in AD/ADRDs, and NVC restoration as a potential therapy. The proposed work has the potential to provide a paradigm-shifting view on how brain microcirculation sustains learning and memory processes.