Capillaries as a Sensory Web that Controls Cerebral Blood Flow in Health and Disease

项目摘要 大脑中的神经元具有有限的能量储备，因此依赖于“及时”递送策略， 活动神经元向脑微血管系统发出信号以增加局部脑血流量（CBF）， 营养素和氧气以及去除有毒代谢物。尽管进行了广泛的研究， 神经元代谢需求和血管供应之间的潜在功能联系，称为 神经血管偶联（NVC）仍然知之甚少。脑血流量由脑实质介导， 小动脉和数百英里长的毛细血管，极大地扩展了灌注的范围。我们最近 提出证据支持脑毛细血管作为神经元活动感知网络的概念， 这表明脑毛细血管内皮细胞（cEC）能够启动电刺激， （超极化）信号响应神经元活动，向上传播，导致摄食扩张 小动脉，并增加信号起始部位的局部血流。我们已经建立了 这一电信号的基础，表明神经元和/或星形胶质细胞来源的钾（K+）是关键的 介质，并确定强内向整流K+通道，Kir2.1作为关键分子的球员。我们有 最近发现，第二个基本的NVC机制基于钙（Ca 2+）信号传导， 不同的动力学和调节特征，也在脑毛细血管中起作用，并且可以由假定的 NVC介导前列腺素E2（PGE 2）。我们进一步发现，Gq蛋白启动的一种机制， 偶联受体信号传导和介导的膜磷脂酰肌醇4，5- 二磷酸盐（PIP 2）水平控制电信号和Ca信号之间的平衡。补充初步 2个以上 数据支持通过Ca 2+依赖的内皮一氧化氮信号传导和周细胞- 在调节NVC中介导毛细血管血流的调节。该提案的近期目标是 创建一个电，钙离子和相关的调节信号机制在分子， 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。最终，我们建议将这些研究线索 一起创建脑中生理毛细血管到小动脉/软脑膜动脉信号传导的系统级视图， 并测试这一概念，即逐渐退化的感觉网和随之而来的渐进衰减， 脑血管的功能有助于脑的小血管疾病。

PROJECT SUMMARY Neurons in the brain have limited energy reserves and thus rely on a “just-in-time” delivery strategy in which active neurons signal to the brain microvasculature to increase regional cerebral blood flow (CBF), resupplying nutrients and oxygen as well as removing toxic metabolites. Despite extensive study, the mechanisms underlying the functional linkage between neuronal metabolic demand and vascular supply, termed neurovascular coupling (NVC), remain poorly understood. Blood flow to the brain is mediated by parenchymal arterioles and hundreds of miles of capillaries, which enormously extend the territory of perfusion. We recently presented evidence supporting the concept that brain capillaries act as a neuronal activity-sensing network, demonstrating that brain capillary endothelial cells (cECs) are capable of initiating an electrical (hyperpolarizing) signal in response to neuronal activity that propagates upstream to cause dilation of feeding arterioles and increase blood flow locally at the site of signal initiation. 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 that a second fundamental NVC mechanism based on calcium (Ca2+) signaling, with distinct kinetics and regulatory features, also operates in brain capillaries, and can be initiated by the putative NVC mediator prostaglandin E2 (PGE2). We have further found that a mechanism initiated by Gq-protein coupled receptor signaling and mediated by dynamic changes in membrane phosphatidylinositol 4,5- bisphosphate (PIP2) levels controls the balance between electrical and Ca signaling. Additional preliminary 2+ data support a role for gasotransmission via Ca2+-dependent endothelial nitric oxide signaling and pericyte- mediated regulation of capillary blood flow in modulating NVC. The immediate goals of this proposal are to create an integrated view of electrical, Ca2+ and related regulatory signaling mechanisms 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. Ultimately, we propose to weave these research threads together to create a systems-level view of physiological capillary-to-arteriole/pial artery signaling in the brain, and test the concept that gradual degradation of this sensory web and the attendant progressive decay of cerebrovascular function contributes to small vessel diseases of the brain.