Ion channel dysfunction in small vessel disease of the brain

项目总结 脑血流量(CBF)被精确控制，以满足不同和不断变化的活动需求 神经元。流入大脑的血液是通过穿透/实质小动脉和数百英里的 毛细血管，这极大地扩展了灌流的范围。向激活的神经元输送血液(功能 充血)通过一种称为神经血管偶联(NVC)的过程被快速而精确地控制。我们 最近提供了令人信服的证据表明，大脑毛细血管作为神经活动感知网络发挥作用，以及 因此，它们远远不止是血液的简单管道。这一概念解释了快速和协调的交付 证明脑毛细血管内皮细胞(CECs)能够启动一种 响应于神经活动的电(超极化)信号，神经活动迅速上游传播以引起扩张 补充小动脉，增加局部血流量。我们已经建立了这种电子设备的机械基础 信号，表明神经元和/或星形胶质细胞来源的钾(K+)是关键的介质，并识别 强大的内向整流钾通道，Kir2.1，作为关键分子发挥作用。我们最近发现了第二个 Gq蛋白偶联启动的钙信号转导NVC的基本机制 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)水平似乎控制着电和钙之间的平衡 发信号。我们实验室的一个主要焦点是小血管疾病(SVD)的发病机制。 大脑，这是中风和痴呆症的主要原因。使用SVD的单基因模型(CADASIL)和OUR 对NVC的机械性洞察，我们发现SVD导致功能性充血的早期缺陷，这 我们认为涉及细胞外基质的改变和CEC Kir2.1通道PIP2激活的丧失和 抑制TRPV4通道。重要的是，我们能够通过以下途径挽救CADASIL的功能性充血 PIP2的外源性应用，为改善疾病中的CBF控制提供了一种广谱的方法。 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 恶化这一主要的功能性充血机制。我们建议阐明缺陷的机制 CADASIL(AIM 1)和高血压(AIM 2)的功能性充血，包括常见的分子交叉点。 这项提议的一个目标是在分子水平上创建SVD对CBF调节的影响的综合观点， 生物物理和计算建模水平，通过检查它们在日益复杂的细分市场中的操作 在体外、体内和硅胶中的脑血管系统。

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.