Elemental And Structural Organization Of Neurons And Glia

神经元和神经胶质细胞的元素和结构组织

• 批准号: 8557000
• 负责人: S BRIAN Andrews
• 金额: $ 99.95万
• 依托单位: NATIONAL INSTITUTE OF NEUROLOGICAL DISORDERS AND STROKE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8557000
• 关键词: AMPA Receptors; Alzheimer' s Disease; Calcium; Calcium Channel; Calcium Signaling; Cell Death; Data; Dementia; Disease; Event; Free Radicals; Functional disorder; Generations; Glutamate Receptor; Glutamates; Goals; Hippocampus (Brain); Huntington Disease; Injury; Ischemia; Mediating; Mitochondria; Mitochondrial Swelling; N-Methylaspartate; Nerve Degeneration; Neurodegenerative Disorders; Neuroglia; Neuronal Injury; Neurons; Outcome; Parkinson Disease; Pathway interactions; Patients; Physiology; Play; Receptor Activation; Role; Route; Stimulus; Stroke; Toxic effect; Work; Zinc; age related; aging brain; excitotoxicity; extracellular; interest; mitochondrial dysfunction; novel therapeutics; prevent; research study; uptake; voltage

The NMDA subtype of the glutamate receptor (NMDARs) plays essential and diverse roles in normal CNS function. However over-activation of these receptors leads to excessive Ca2+ entry, mitochondrial calcium (Ca2+) overload and dysfunction, and is a crucial early event in excitotoxic injury. This recommends NMDARs as targets for anti-excitotoxic therapies, but the generally disappointing patient outcomes for such approaches strongly suggest that factors beyond the over-activation of NMDARs are at play. This information prompts searches for other important Ca2+-dependent injury pathways. Recent progress and the Specific Aims of ongoing work are summarized next. Aim #1: To define the role of voltage-gated calcium channels in calcium-dependent neurodegeneration. Although NMDARs clearly play the dominant role in toxic Ca2+ loading, evidence from our lab and others indicates that alternative routes of Ca2+ entry, for example, through voltage-gated calcium channels (VGCCs), can contribute significantly to toxicity in developmentally mature neurons. Thus, we find that while in general in hippocampal and cortical cultured neurons VGCC activation does not promote significant cell death, VGCC activation does evoke much stronger calcium elevations in a small but important subset of neurons. These neurons are characterized by elevated expression of VGCCs, which leads to cell death by mechanisms that are reminiscent of the classical excitotoxicity pathway, namely, excessive Ca2+ loading and mitochondrial dysfunction that precedes neuronal degeneration. The results demonstrate one ancillary pathway of glutamate toxicity, one whose significance is likely to increase during brain aging or in age-related dementia. Aim #2: To determine the role of zinc in glutamate excitotoxicity and ischemic injury. Elevation of intracellular zinc (Zn2+) following transient ischemia contributes to neuronal injury, but the mechanism(s) of Zn2+ toxicity remain unclear. In analogy to Ca2+, Zn2+ has been proposed to induce toxicity via mitochondrial dysfunction and/or ROS generation. Recent experiments in cultured hippocampal neurons reveal that Zn2+ can enter neurons through VGCCs and Ca2+-permeable AMPA receptors, but accumulated Zn2+ is only toxic when the extracellular medium contains unusually high (200 uM) exogenous Zn2+ concentrations, as might occur after ischemia. Under conditions that favor Zn2+ uptake, both Ca2+ and Zn2+ accumulate and co-precipitate within mitochondria, but only Ca2+ is capable of inducing mitochondrial swelling, depolarization, and free radical generation, which are the main hallmarks of mitochondrial damage. These data support the working hypothesis that classical mechanisms of excitotoxic mitochondrial dysfunction are necessarily Ca2+ dependent, so that mechanism(s) of Zn2+ toxicity, although still unknown, must be different from that of Ca2+.

谷氨酸受体 (NMDAR) 的 NMDA 亚型在正常中枢神经系统功能中发挥着重要且多样的作用。然而，这些受体的过度激活会导致过多的 Ca2+ 进入、线粒体钙 (Ca2+) 过载和功能障碍，并且是兴奋性毒性损伤的关键早期事件。这建议将 NMDAR 作为抗兴奋性毒性疗法的靶标，但此类方法的患者结果普遍令人失望，强烈表明除了 NMDAR 过度激活之外的其他因素也在发挥作用。该信息促使人们寻找其他重要的 Ca2+ 依赖性损伤途径。接下来总结了最近的进展和正在进行的工作的具体目标。 目标#1：确定电压门控钙通道在钙依赖性神经变性中的作用。 尽管 NMDAR 显然在有毒 Ca2+ 负载中发挥着主导作用，但我们实验室和其他实验室的证据表明，Ca2+ 进入的替代途径，例如通过电压门控钙通道 (VGCC)，可以显着导致发育成熟神经元的毒性。因此，我们发现，虽然一般来说，在海马和皮质培养的神经元中，VGCC 激活不会促进显着的细胞死亡，但 VGCC 激活确实会在一小部分但重要的神经元中引起更强烈的钙升高。这些神经元的特征是 VGCC 表达升高，这通过让人想起经典兴奋性毒性途径的机制导致细胞死亡，即神经元变性之前的过量 Ca2+ 负载和线粒体功能障碍。结果证明了谷氨酸毒性的一种辅助途径，其重要性可能会在大脑衰老或与年龄相关的痴呆症中增加。 目标#2：确定锌在谷氨酸兴奋性毒性和缺血性损伤中的作用。 短暂性缺血后细胞内锌 (Zn2+) 升高会导致神经元损伤，但 Zn2+ 毒性的机制仍不清楚。与 Ca2+ 类似，Zn2+ 被认为可以通过线粒体功能障碍和/或 ROS 产生来诱导毒性。最近在培养的海马神经元中进行的实验表明，Zn2+ 可以通过 VGCC 和 Ca2+ 可渗透的 AMPA 受体进入神经元，但积累的 Zn2+ 仅在细胞外介质含有异常高（200 uM）的外源 Zn2+ 浓度时才具有毒性，这可能在缺血后发生。在有利于 Zn2+ 吸收的条件下，Ca2+ 和 Zn2+ 在线粒体内积累和共沉淀，但只有 Ca2+ 能够诱导线粒体肿胀、去极化和自由基生成，这是线粒体损伤的主要标志。这些数据支持这样的工作假设：兴奋性毒性线粒体功能障碍的经典机制必然是 Ca2+ 依赖性的，因此 Zn2+ 毒性的机制虽然仍不清楚，但必定与 Ca2+ 的不同。