Ion Channel Dysfunction in Small Vessel Disease of the Brain

项目概要 脑血流 (CBF) 受到精细控制，以满足活跃的多样化和不断变化的需求 神经元。流入大脑的血液是由穿透性/实质小动脉和数百英里的小动脉介导的 毛细血管，极大地扩展了灌注范围。血液输送到活跃的神经元（功能性神经元） 充血）通过称为神经血管耦合（NVC）的过程快速而精确地控制。我们 最近提供了令人信服的证据表明脑毛细血管充当神经活动感知网络，并且 因此，它们不仅仅是简单的血液管道。这个概念解释了快速、协调的交付 血液流向活跃的神经元，证明脑毛细血管内皮细胞（cEC）能够启动 电（超极化）信号响应快速向上游传播以引起扩张的神经活动 喂养小动脉并局部增加血流量。我们已经为这种电气奠定了机械基础 信号，表明神经元和/或星形胶质细胞衍生的钾 (K) 是关键介质并识别 强内向整流K通道，Kir2.1，作为关键分子。我们最近发现了第二个 基于钙 (Ca2) 信号传导的基本 NVC 机制，由 Gq 蛋白偶联启动 受体信号转导，部分由 TRPV4 通道介导。膜的动态变化 磷脂酰肌醇 4,5-二磷酸 (PIP2) 水平似乎可以控制电和 Ca2 之间的平衡 发信号。我们实验室的主要关注点是小血管疾病（SVD）的发病机制。 大脑，这是中风和痴呆症的主要原因。使用 SVD (CADASIL) 的单基因模型和我们的 通过对 NVC 的机制深入了解，我们发现 SVD 会导致功能性充血的早期缺陷，从而导致功能性充血的早期缺陷。 我们建议涉及细胞外基质变化和 cEC Kir2.1 通道 PIP2 激活的丧失， TRPV4 通道的抑制。重要的是，我们能够通过以下方式挽救 CADASIL 的功能性充血： PIP2 的外源应用，提出了一种改善疾病 CBF 控制的广谱方法。 我们进一步发现，高血压是散发性 SVD 的主要驱动因素，也会导致年龄依赖性的 这一主要功能性充血机制的恶化。我们建议阐明缺陷的机制 CADASIL（目标 1）和高血压（目标 2）的功能性充血，包括常见的分子交叉。 该提案的一个目标是从分子层面建立 SVD 对 CBF 调节影响的综合观点， 通过检查它们在日益复杂的部分中的操作来提高生物物理和计算建模水平 脑脉管系统的离体、体内和计算机模拟。

PROJECT SUMMARY Cerebral blood flow (CBF) is exquisitely controlled to meet the diverse and ever-changing demands of active neurons. Blood flow into the brain is mediated by penetrating/parenchymal arterioles and hundreds of miles of capillaries, which enormously extend the territory of perfusion. Blood delivery to active neurons (functional hyperemia) is rapidly and precisely controlled through a process termed neurovascular coupling (NVC). We recently provided compelling evidence that brain capillaries act as a neural activity-sensing network, and therefore are much more than simple conduits for blood. This concept explains the rapid and coordinated delivery of blood to active neurons, demonstrating that brain capillary endothelial cells (cECs) are capable of initiating an electrical (hyperpolarizing) signal in response to neural activity that rapidly propagates upstream to cause dilation of feeding arterioles and locally increase blood flow. We have established the mechanistic basis for this electrical signal, showing that neuron- and/or astrocyte-derived potassium (K+) is the critical mediator and identifying the strong inward rectifier K+ channel, Kir2.1, as the key molecular player. We have recently discovered a second fundamental NVC mechanism based on calcium (Ca2+) signaling, which is initiated by Gq-protein coupled receptor signaling and is partly mediated by TRPV4 channels. Dynamic changes in membrane phosphatidylinositol 4,5-bisphosphate (PIP2) levels appear to control the balance between electrical and Ca2+ signaling. A major focus of our laboratory has been on the pathogenesis of Small Vessel Disease (SVD) of the brain, which is a major cause of stroke and dementia. Using a monogenic model of SVD (CADASIL) and our mechanistic insights into NVC, we discovered that SVD precipitates early defects in functional hyperemia, which we propose involve extracellular matrix changes and a loss of PIP2 activation of cEC Kir2.1 channels and suppression of TRPV4 channels. Importantly, we are able to rescue functional hyperemia in CADASIL through exogenous application of PIP2, suggesting a broad-spectrum approach for improving CBF control in disease. We have further found that hypertension, the major driver of sporadic SVDs, also leads to age-dependent deterioration of this major functional hyperemia mechanism. We propose to elucidate mechanisms for defective functional hyperemia in CADASIL (Aim 1) and hypertension (Aim 2), including common molecular intersections. A goal of this proposal is to create an integrated view of the impact of SVD on CBF regulation at molecular, biophysical, and computational-modeling levels by examining their operation in increasingly complex segments of the brain vasculature ex vivo, in vivo, and in silico.