Capillary control of cerebral blood flow, and its disruption in small vessel disease

大脑中神经元的存活依赖于不间断的、动态调节的血液供应- 携带的营养物质，通过密集的毛细网络输送。尽管进行了广泛的研究，但 神经元需求和血管供应之间的功能联系的潜在机制，称为 神经血管偶联(NVC)，目前仍知之甚少。解剖学，脑内(实质) 小动脉形成了精确控制脑血流动力学的瓶颈，而毛细血管内皮细胞 这是检测神经元活动的理想位置。我们建议前列腺素E2(PGE2)，一种建议的NVC 中介物，作用于毛细血管水平，启动钙波，沿着内皮细胞到达 上游小动脉，在那里它通过内皮依赖的超极化触发血管扩张。我们的 大量的初步数据也描述了表皮生长因子之间的毛细血管信号复合体 受体(EGFR)和瞬时受体电位香草素3(TRPV3)通道参与生成 这种前列腺素E_2-诱导逆行钙信号。使用已建立的CADASIL遗传小鼠模型， 遗传性小血管疾病，我们进一步提出导致EGFR的致病机制 平滑肌中的通路抑制也抑制了毛细血管中的EGFR/TRPV3信号复合体，导致 受损的NVC。为了测试这些想法，我们采用了各种新颖的、最先进的实验方法。 使用完整的动物、自然组织和新分离的细胞，并辅之以复杂的计算 模特儿。目标1将探索毛细血管PGE2和TRPV3信号如何产生逆行钙信号 2. 引起上游小动脉扩张，利用我们新开发的加压小动脉-毛细血管EX 活体准备。以CADASIL的细胞外基质破坏特性为框架，AIM 2将 对TRPV3通道和诱发的上游扩张的机制提供了第一个见解 在EGFR及其上游调控因子TIMP3和ADAM17的调控下，a 介导EGFR配体HB-EGF脱落的金属蛋白酶。基于我们之前的报告， CADASIL引起小动脉肌细胞电压门控性K(KV)通道上调，Aim 3将探索 假设增加KV电流密度限制了小动脉传导扩张，从而限制了NVC，由 CADASIL中的毛细血管PGE2/TRPV3信号转导拟议中的工作有可能使我们的 了解大脑微循环内的交流，因此应该提供基础 以了解大脑的小血管疾病。

The survival of neurons in the brain depends on an uninterrupted, dynamically regulated supply of blood- borne nutrients, which are delivered through a dense capillary network. Despite extensive study, the mechanisms underlying the functional linkage between neuronal demand and vascular supply, termed neurovascular coupling (NVC), remains poorly understood. Anatomically, intracerebral (parenchymal) arterioles form bottlenecks that precisely control cerebral hemodynamics, and capillary endothelial cells are ideally positioned to detect neuronal activity. We propose that prostaglandin E2 (PGE2), a suggested NVC mediator, acts at the level of capillaries to initiate a Ca2+ wave that travels along endothelial cells to reach the upstream arteriole, where it triggers vasodilation through endothelium-dependent hyperpolarization. Our extensive preliminary data also describe a capillary signaling complex between the epidermal growth factor receptor (EGFR) and transient receptor potential vanilloid 3 (TRPV3) channels that is involved in generating this PGE2-induce retrograde Ca2+ signal. Using a well-established genetic mouse model of CADASIL, a hereditary form of small vessel disease, we further propose that pathogenic mechanisms that result in EGFR pathway inhibition in smooth muscle also depress EGFR/TRPV3 signaling complex in capillaries, resulting in impaired NVC. To test these ideas, we engage a wide variety of novel, state-of-the-art experimental approaches using intact animals, native tissue and freshly isolated cells, complemented by sophisticated computational modeling. Aim 1 will explore how capillary PGE2 and TRPV3 signaling generates retrograde Ca signals to 2+ cause upstream arteriolar dilation, taking advantage of our newly developed pressurized arteriole-capillary ex vivo preparation. Using extracellular matrix disruptions characteristic of CADASIL as a framework, Aim 2 will provide the first insights into the mechanisms by which TRPV3 channels and evoked upstream dilation are regulated by EGFR and its upstream regulators TIMP3, a matrix metalloproteinase inhibitor, and ADAM17, a metalloproteinase that mediates shedding of the EGFR ligand, HB-EGF. Building on our previous report that CADASIL causes voltage-gated K (KV) channel upregulation in arteriolar myocytes, Aim 3 will explore the + hypothesis that increased KV current density limits arteriolar conducted dilation, and thus NVC, initiated by capillary PGE2/TRPV3 signaling in CADASIL. The proposed work has the potential to revolutionize our understanding of communication within the brain microcirculation, and as such should provide the foundation for understanding small vessel diseases of the brain.