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- 通过密集的毛细血管网输送的营养物质。尽管进行了广泛的研究， 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）仍然知之甚少。解剖学上，脑内（实质） 小动脉形成精确控制脑血流动力学的瓶颈，毛细血管内皮细胞 位置非常适合检测神经元活动。我们建议，前列腺素E2（PGE 2），一个建议的NVC 介体，在毛细血管水平起作用以启动Ca 2+波，该Ca 2+波沿沿着内皮细胞行进以到达血管内皮细胞。 上游小动脉，通过内皮依赖性超极化触发血管舒张。我们 大量的初步数据也描述了表皮生长因子和内皮细胞之间的毛细血管信号复合物， 受体（EGFR）和瞬时受体电位香草酸3（TRPV 3）通道，其参与产生 这种PGE 2-诱导逆行Ca 2+信号。使用一种成熟的CADASIL遗传小鼠模型， 遗传性小血管疾病，我们进一步提出了导致EGFR 平滑肌中的通路抑制也抑制毛细血管中的EGFR/TRPV 3信号传导复合物，导致 NVC受损为了测试这些想法，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，天然组织和新鲜分离的细胞，辅以复杂的计算 建模目的1将探讨毛细血管PGE 2和TRPV 3信号传导如何产生逆行Ca信号， 2个以上 引起上游小动脉扩张，利用我们新开发的加压小动脉-毛细血管扩张， 体内制备使用CADASIL细胞外基质破坏特征作为框架，Aim 2将 提供了对TRPV 3通道和诱发的上游扩张的机制的第一个见解， 受EGFR及其上游调节因子TIMP 3（一种基质金属蛋白酶抑制剂）和ADAM 17（一种 介导EGFR配体HB-EGF脱落的金属蛋白酶。在我们上次报告的基础上， CADASIL导致小动脉肌细胞中电压门控性K（KV）通道上调，Aim 3将探讨 + 假设KV电流密度增加限制了小动脉传导扩张，从而限制了NVC， CADASIL中的毛细血管PGE 2/TRPV 3信号传导。拟议的工作有可能彻底改变我们的 了解大脑微循环内的通信，因此应该提供基础 来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.