Endothelial KCa channels, Ca2+ signaling & arteriolar function in the brain

描述（申请人提供）：脑内（实质）小动脉中的血管内皮是正常脑功能的重要介质，既是物理屏障，也是脑内血流的调节剂。内皮细胞（ECs）中的Ca2+信号和Ca2+敏感的K+通道、IK和SK以及TRPV4通道激活了将血管调节信号传递到邻近平滑肌（SM）和血管内皮层的途径。这些信号也可以传递给附近的星形胶质细胞和神经元来调节神经血管耦合（NVC）。尽管脑实质小动脉（PA）内皮的重要性，但其对脑内血管张力的控制或对NVC的潜在影响知之甚少。为了支持该项目，我们提供了新的数据，表明EC SK， IK和TRPV4通道对PA张力和皮质脑血流有深远的影响。目的1将阐明内皮Ca2+信号传导方式的特性和作用，以及IK、SK和TRPV4通道在PA ECs中使用一种新的小鼠模型，表达内皮Ca2+生物传感器（GCaMP2）。利用这些GCaMP2小鼠，我们最近发现了一个局部的、固定的IP3介导的Ca2+信号在内皮细胞向SM的投射中。这个信号被称为“脉冲星”，激活共定位IK通道来调节血管张力。目的2将确定内皮功能对PAs的SM的影响，探索Ca2+信号，膜电位和血管直径。目的3建立在目的1和2的基础上，探索内皮在大脑中的作用，利用一种基于星形细胞端足Ca2+和血管反应同时测量的新方法评估其对NVC和血流的影响。拟议的项目将为PA内皮功能和与SM的沟通提供重要的新见解。该项目将揭示参与调节脑血流的新靶点，并建议不需要通过血脑屏障的治疗药物。

DESCRIPTION (provided by applicant): The vascular endothelium in intracerebral (parenchymal) arterioles is a critical mediator of normal cerebral function, serving as both a physical barrier and a modulator of blood flow within the brain. Ca2+ signaling and the Ca2+-sensitive K+ channels, IK and SK, and TRPV4 channels in endothelial cells (ECs) activate pathways that transmit vasoregulatory signals to adjacent smooth muscle (SM) and along the endothelial lining of blood vessels. These signals may also communicate to nearby astrocytes and neurons to modulate neurovascular coupling (NVC). Despite the importance of parenchymal arteriolar (PA) endothelium, little is known about its control of vascular tone or potential influence on NVC in the brain. To support the Project, we provide novel data that EC SK, IK and TRPV4 channels have a profound effect on PA tone and cortical cerebral blood flow. Aim 1 will elucidate the properties and roles of endothelial Ca2+ signaling modalities, and IK, SK and TRPV4 channels in PA ECs using a novel mouse model that expresses a Ca2+ biosensor (GCaMP2) in the endothelium. Exploiting these GCaMP2 mice, we have recently discovered a localized, stationary IP3- mediated Ca2+ signal in endothelial projections to the SM. This signal, termed a "pulsar", activates co-localized IK channels to modulate vascular tone. Aim 2 will determine the impact of endothelial function on the SM of PAs, exploring Ca2+ signaling, membrane potential and vascular diameter. Aim 3 builds on Aims 1 and 2 to explore the role of the endothelium in the context of the brain, evaluating its effects on NVC and blood flow using a novel approach based on simultaneous measurement of astrocytic endfoot Ca2+ and vascular responses. The proposed project will provide significant new insight into PA endothelial function and communication to SM. This project should reveal novel targets involved in modulating blood flow in the brain and suggest therapeutic agents that do not require passage through the blood brain barrier. PUBLIC HEALTH RELEVANCE: The cells (endothelial) that line the small blood vessels (arterioles) in the brain are critical mediators of normal cerebral function, serving as both a physical barrier and a modulator of blood flow. Endothelial cell dysfunction is a common feature of blood vessel diseases (hypertension, atherosclerosis) and a likely contributor to neurological disorders (Alzheimer's). This project will elucidate key control mechanisms by which endothelial cells in cerebral arterioles regulate blood flow in the brain.