Synaptic Circuitry in Stroke

中风中的突触回路

• 批准号: 8817596
• 负责人: SERGEI A KIROV
• 金额: $ 33.09万
• 依托单位: AUGUSTA UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-15 至 2018-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8817596
• 关键词: Acute; Acute Brain Injuries; Adult; American Heart Association; Astrocytes; Axon; Binding; Blood capillaries; Blood flow; Brain; Brain Edema; Cations; Cell membrane; Cessation of life; Chloride Ion; Chlorides; Clinical; Clinical Data; Clinical Research; Cortical Contusions; Coupled; Dendrites; Dendritic Spines; Development; Edema; Electron Microscopy; Electrophysiology (science); Energy Supply; Equilibrium; Etiology; Event; Excision; Extracellular Space; Failure; Floods; Functional disorder; Future; Genetic Models; Glutamates; Heart Diseases; Image; Injury; Ion Channel; Ions; Ischemic Penumbra; Laser Scanning Microscopy; Lasers; Maintenance; Mechanics; Membrane; Metabolic; Metabolism; Modeling; Molecular; Monitor; Mus; Na(+)-K(+)-Exchanging ATPase; Neuronal Injury; Neurons; Optics; Pathway interactions; Patients; Permeability; Physiological; Process; Recovery; Recurrence; Reporting; Risk; Route; Signal Transduction; Stress; Stretching; Stroke; Structure; Swelling; Synapses; Testing; Time; Tissues; Trauma; Traumatic Brain Injury; Update; Vertebral column; Water; Work; base; brain cell; brain tissue; capillary; cell injury; cytotoxic; deprivation; design; extracellular; hippocampal pyramidal neuron; in vivo; injured; innovation; insight; meetings; mouse model; nervous system disorder; neural circuit; neuronal cell body; novel; public health relevance; statistics; synaptogenesis; therapy design; tool; two-photon; water channel

DESCRIPTION (provided by applicant): Spreading depolarizations (SDs) are waves of sustained near-complete neuronal and glial depolarization that actively propagate a collapse of ion gradients through the brain with associated dramatic neuronal and glial swelling that entails cytotoxic edema. Recovery of ion gradients depends on the sufficient sodium pump activity which is energy-dependent. In stroke and trauma patients SDs are thought to exacerbate tissue damage in the at-risk cortical territory supporting the view that SD may be an important mechanistic endpoint in clinical studies. SD-induced neuronal damage involves a plasma membrane conformational change including soma swelling and terminal dendritic beading with spine loss which signifies acute damage to synaptic circuitry. In the ischemic core, where energy deprivation is maintained, dendrites remain terminally injured by SD. In contrast, we have shown that in the penumbra SDs result in rapid dendritic beading which is reversible, but signals leading to neuronal death could be initiated during this time. Hence, dendritic beading is the hallmark of neuronal injury. Once the energy demands for recovery of penumbral dendrites are no longer met by the diminishing blood flow, SD terminally injures dendrites and spines are lost indicating acute damage to synaptic circuitry and core expansion. SD-induced cytotoxic edema contributes to stroke injury. Mammalian pyramidal neurons lack functional aquaporins, thus the molecular pathways by which they accumulate osmotically obligated water and rapidly swell during SD is unknown. Bulk water influx could occur through large-pore pannexin channels opened by SD. Neuronal cation-chloride cotransporters may also be responsible for water accumulation as well as recovery and this will be studied in aim 1. We have shown that persistent astroglial swelling is initiated and exacerbated during SD in brain tissue with moderate to severe energy deficits, likely disrupting astroglial maintenance of homeostatic function and thus their ability to support neurons. Astroglial failure should advance the damage of neighboring neurons contributing to SD-induced expansion of the injury and it will be examined in aim 2. Astrocytes are part of the synaptic circuitry tightly coupled with neurons combining with axons and dendrites to form the tripartite synapse. SD-induced injury at the level of single synapses will be investigated in aim 3 with quantitative serial section electron microscopy. The specific aims are: 1) To examine possible routes of rapid water entry during SD-induced dendritic beading. 2) To test the hypothesis that SD-inflicted dendritic injury is aggravated in tissue with selectively impaired glial metabolism. 3) To test the hypothesis that SD is the mechanism implicated in rapid synapses disruption and loss. We will combine in vivo 2-photon laser scanning microscopy of fluorescent neurons, astrocytes and blood flow in adult mouse sensorimotor cortex with other sophisticated in vivo approaches such as laser speckle and functional intrinsic optical signal imaging while simultaneously monitoring occurrence of SD with electrophysiology. The results will bring new insight to the development and recovery from acute cellular injury in stroke.

描述（由申请人提供）：扩散去极化（SD）是持续的、近乎完全的神经元和神经胶质去极化波，它主动地在大脑中传播离子梯度的崩溃，并伴有剧烈的神经元和神经胶质肿胀，从而导致细胞毒性水肿。离子梯度的恢复取决于足够的钠泵活性，而钠泵活性依赖于能量。在中风和创伤患者中，SD 被认为会加剧危险皮质区域的组织损伤，这支持了 SD 可能是临床研究中重要的机制终点的观点。 SD 诱导的神经元损伤涉及质膜构象变化，包括体细胞肿胀和末端树突珠状形成以及脊柱损失，这意味着突触回路的急性损伤。在维持能量剥夺的缺血核心中，树突仍然受到 SD 的最终损伤。相比之下，我们已经表明，在半影中，SD 会导致快速的树突珠状形成，这是可逆的，但导致神经元死亡的信号可能在此期间启动。因此，树突珠状形成是神经元损伤的标志。一旦血流减少不再满足半影树突恢复的能量需求，SD 就会最终损害树突，并且树突棘丢失，表明突触回路和核心扩张受到严重损害。 SD 诱导的细胞毒性水肿会导致中风损伤。哺乳动物锥体神经元缺乏功能性水通道蛋白，因此它们积累渗透压水并在 SD 期间快速膨胀的分子途径尚不清楚。大量水流入可通过 SD 打开的大孔 pannexin 通道发生。神经元阳离子-氯化物协同转运蛋白也可能负责水的积累和恢复，这将在目标 1 中进行研究。我们已经表明，在中度至重度能量缺乏的脑组织中，SD 期间会引发持续性星形胶质细胞肿胀并加剧，这可能会破坏星形胶质细胞维持稳态功能，从而支持神经元的能力。星形胶质细胞衰竭应该会促进邻近神经元的损伤，从而导致 SD 诱导的损伤扩大，这将在目标 2 中进行检查。星形胶质细胞是突触回路的一部分，与神经元紧密耦合，并与轴突和树突结合形成三联突触。 SD 诱导的单突触水平损伤将在目标 3 中通过定量连续切片电子显微镜进行研究。具体目标是： 1) 检查 SD 诱导的树突珠化过程中快速进水的可能途径。 2) 检验以下假设：在神经胶质代谢选择性受损的组织中，SD 造成的树突损伤会加重。 3) 检验 SD 是突触快速破坏和丢失的机制这一假设。我们将把成年小鼠感觉运动皮层中荧光神经元、星形胶质细胞和血流的体内 2 光子激光扫描显微镜与激光散斑和功能性内在光信号成像等其他复杂的体内方法结合起来，同时用电生理学监测 SD 的发生。这些结果将为中风急性细胞损伤的发展和恢复带来新的见解。