German Center for Neurodegenerative Diseases (DZNE), Sigmund-Freud-Street 27, Bonn, 53127, Germany.
Department of Medical Biometry, Informatics and Epidemiology, University Hospital Bonn, Sigmund-Freud-Street 25, Bonn, 53127, Germany.
Glia. 2017 Sep;65(9):1550-1561. doi: 10.1002/glia.23183. Epub 2017 Jun 22.
Stroke is one of the leading causes of death and long-term disability. In the penumbra, that is, the area surrounding the infarct core, peri-infarct depolarizations (PIDs) are accompanied by strong intracellular calcium elevations in astrocytes and neurons, thereby negatively affecting infarct size and clinical outcome. The dynamics of PIDs and the cellular pathways that are involved during PID formation and progression remain incompletely understood. We have previously shown that inositol triphosphate-gated calcium release from internal stores is a major component of PID-related astroglial calcium signals, but whether external calcium influx through membrane-localized channels also contributes to PIDs has remained unclear. In this study, we investigated the role of two astroglial membrane channels, transient receptor vanilloid 4 (TRPV4) channel and aquaporin-4 (AQP4). We combined in vivo multiphoton microscopy, electrophysiology as well as laser speckle contrast imaging with the middle cerebral artery occlusion stroke model. Using knockout mice and pharmacological inhibitors, we found that TRPV4 channels contribute to calcium influx into astrocytes and neurons and subsequent extracellular glutamate accumulation during PIDs. AQP4 neither influenced PID-related calcium signals nor PID-related edema of astrocyte somata. Both channels did not alter the dynamics, frequency and cerebrovascular response of PIDs in the penumbra. These data indicate that TRPV4 channels may represent a potential target to ameliorate the PID-induced calcium overload of astrocytes and neurons during acute stroke.
中风是导致死亡和长期残疾的主要原因之一。在半影区（即梗塞核心周围的区域），周边去极化（PIDs）伴随着星形胶质细胞和神经元内钙离子的强烈升高，从而对梗塞面积和临床结果产生负面影响。PID 的动力学以及 PID 形成和进展过程中涉及的细胞途径仍不完全清楚。我们之前已经表明，来自内部储存的三磷酸肌醇门控钙释放是 PID 相关星形胶质细胞钙信号的主要组成部分，但通过膜定位通道的外部钙内流是否也有助于 PID 仍然不清楚。在这项研究中，我们研究了两种星形胶质细胞膜通道，瞬时受体香草素 4（TRPV4）通道和水通道蛋白 4（AQP4）的作用。我们结合了体内多光子显微镜、电生理学以及激光散斑对比成像与大脑中动脉闭塞性中风模型。使用基因敲除小鼠和药理学抑制剂，我们发现 TRPV4 通道有助于钙内流入星形胶质细胞和神经元，并在 PIDs 期间导致细胞外谷氨酸的积累。AQP4 既不影响 PID 相关钙信号，也不影响星形胶质细胞体的 PID 相关水肿。这两种通道都不会改变半影区 PIDs 的动力学、频率和脑血管反应。这些数据表明，TRPV4 通道可能代表一种潜在的靶点，以改善急性中风期间 PID 诱导的星形胶质细胞和神经元钙超载。
