TRPV1 channels in arterial smooth muscle: a novel vasoconstrictor mechanism to promote maintained cerebral blood flow during acutedecreases in blood pressure

精确控制全身动脉直径对于维持灌流压力和 血液流向重要器官，如大脑。钙离子通过L型电压依赖性钙通道的内流 (VDCCs)传统上被认为是动脉平滑肌(ASM)钙离子进入的主要途径。 控制收缩和调节动脉直径。在这里，我们提供了一秒钟的直接证据 某些类型的ASM的主要钙进入途径--瞬时受体电位香草素1(TRPV1)通道， 一种“非选择性的”钙离子通道，典型地参与感觉神经的伤害性感受。vbl.使用 “光学膜片钳”技术，我们首次测量了单个TRPV1的钙离子内流 频道(“火花”)。重要的是，我们的初步数据也证明了ASM TRPV1的参与 通过激活1-肾上腺素能受体(1-AR)-血管收缩的主要途径 交感神经系统(SNS)。SNS在维持脑血流量(CBF)方面的作用尤为明显 在急性低血压发作(如失血性休克)时很重要，部分是通过-1- AR介导的外周组织血管收缩。我们最重要的假设是，为了应对严重的 血压降低，具有ASM TRPV1通道的非脑动脉收缩调节血管 阻力将血液重新分配到脑动脉，我们发现大脑动脉缺乏TRPV1通道。 在目标1中，我们探索了-ARS激活TRPV1的基础。这一目标的目标是解开 1-ARs、ASM TRPV1通道、钙信号与动脉内径之间的联系。我们相信 TRPV1的差异表达和1-AR配体对该通道的激活在 SNS对ASM钙和动脉内径的调节作用。具体地说，我们测试了SNS引发的假设 TRPV1通道激活通过多条途径促进整体胞浆钙升高和血管收缩 包括：1)通过TRPV1通道直接钙内流；2)TRPV1介导的阳离子内流，膜 电位(Vm)去极化和增强的VDCC活性。在目标2中，我们结合了体内测量 动脉内径、ASM Ca~(2+)和CBF阐明TRPV1通道在促进动脉粥样硬化维持中的作用 脑血流在急性期血压下降，类似于失血性休克。 总而言之，该提案旨在提供前所未有的TRPV1渠道影响解决方案 动脉内径和脑血流量。确定ASM TRPV1在急性下降期间促进CBF的关键作用 在血压方面有可能提供丰富的新信息，对个体休克大有裨益 病人和我们整个社会。

Precise control of arterial diameter throughout the body is essential to maintain perfusion pressure and blood flow to vital organs, such as the brain. Ca2+ influx through L-type voltage-dependent Ca2+ channels (VDCCs) has traditionally been viewed as the major Ca2+ entry pathway in arterial smooth muscle (ASM) that controls contraction and the regulation of arterial diameter. Here, we provide direct evidence for a second major Ca2+ entry pathway in some types of ASM—the transient receptor potential vanilloid 1 (TRPV1) channel, a “non-selective” Ca2+-permeable ion channel typically involved in nociception in sensory nerves. Using “optical patch-clamping” techniques, we provide the first measurements of Ca2+ influx through single TRPV1 channels (“sparklets”). Importantly, our preliminary data also demonstrate engagement of ASM TRPV1 channels by activation of 1-adrenergic receptors (1-ARs)—the major vasoconstrictor pathway of the sympathetic nervous system (SNS). The role of the SNS in maintaining cerebral blood flow (CBF) is particularly important during episodes of acute hypotension (e.g., hemorrhagic shock) and is achieved in part through 1- AR–mediated vasoconstriction in peripheral tissue. Our overarching hypothesis is that, in response to acute decreases in blood pressure, constriction of non-brain arteries possessing ASM TRPV1 channels tunes vascular resistance to redistribute blood to cerebral arteries, which we have found to lack TRPV1 channels. Within Aim 1, we explore the basis of TRPV1 activation by -ARs. The goal of this aim is to unravel the linkages between 1-ARs, ASM TRPV1 channels, Ca2+ signaling and arterial diameter. We believe the differential expression of TRPV1 and the activation of this channel by 1-AR ligands play important roles in the regulation ASM Ca2+ and arterial diameter by the SNS. Specifically, we test the hypothesis that SNS-evoked TRPV1 channel activation promotes increased global cytosolic Ca2+ and vasoconstriction via multiple pathways including: 1) direct Ca2+ entry through TRPV1 channels and, 2) TRPV1-mediated cation influx, membrane potential (VM) depolarization and enhanced VDCC activity. In Aim 2, we combine in vivo measurements of arterial diameter, ASM Ca2+ and CBF to elucidate the role of TRPV1 channels in promoting the maintenance of CBF during acute decreases in blood pressure that mimic hemorrhagic shock. In summary, this proposal is designed to provide unprecedented resolution of TRPV1 channel impact on arterial diameter and CBF. Identifying a key role for ASM TRPV1 in promoting CBF during acute decreases in blood pressure has the potential to provide a wealth of new information of great benefit to individual shock patients and our society at large.