Ion Channel Dysfunction in Small Vessel Disease of the Brain

项目摘要 脑血流量（CBF）是精心控制，以满足多样化和不断变化的需求，积极 神经元血液流入大脑是由穿透/实质小动脉和数百英里的血管介导的。 毛细血管，极大地扩展了灌注的范围。血液输送到活性神经元（功能性 充血）通过称为神经血管偶联（NVC）的过程被快速和精确地控制。我们 最近提供了令人信服的证据，证明大脑毛细血管充当神经活动传感网络， 因此不仅仅是简单的血液管道。这一概念解释了快速和协调的交付 这表明，脑毛细血管内皮细胞（cEC）能够启动一个新的神经元， 响应神经活动的电（超极化）信号，快速向上游传播以引起扩张 局部增加血流量我们已经建立了这种电气的机械基础， 信号，表明神经元和/或星形胶质细胞来源钾（K+）是关键介质，并确定 强内向整流K+通道Kir2.1作为关键分子参与者。我们最近发现了第二个 基本的NVC机制基于钙（Ca 2+）信号传导，其由Gq-蛋白偶联启动 受体信号传导，部分由TRPV 4通道介导。膜的动态变化 磷脂酰肌醇4，5-二磷酸（PIP 2）水平似乎控制电和Ca 2+之间的平衡 发信号。我们实验室的一个主要重点是小血管病（SVD）的发病机制， 大脑，这是中风和痴呆症的主要原因。使用SVD的单基因模型（CADASIL）和我们的 通过对NVC机制的深入研究，我们发现SVD会导致功能性充血的早期缺陷， 我们认为涉及细胞外基质的变化和cEC Kir2.1通道PIP 2激活的丧失， 抑制TRPV 4通道。重要的是，我们能够通过以下方法挽救CADASIL中的功能性充血： PIP 2的外源性应用，表明用于改善疾病中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，也导致年龄依赖性SVD。 这种主要功能性充血机制的恶化。我们建议阐明缺陷的机制， CADASIL（Aim 1）和高血压（Aim 2）中的功能性充血，包括常见的分子交叉。 该提案的一个目标是创建SVD对CBF调节的分子影响的综合视图， 生物物理和计算建模水平，通过检查它们在日益复杂的环节中的运作， 脑血管系统的体外、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.