Role of Spinal Cord Lamina II Astrocytes in Neurophysiology and Chronic Pain

描述(由申请人提供)：越来越明显的是，星形胶质细胞积极参与神经生理学，并在许多神经疾病的发展和进展中做出贡献。星形胶质细胞是脑和脊髓中数量最多的细胞(约占中枢神经系统细胞总数的50%)，与所有细胞成分都有联系，一个星形胶质细胞可以包裹多达10万个突触。星形胶质细胞通过缓冲细胞外K+和摄取突触释放的谷氨酸，在调节神经元兴奋性方面发挥着关键作用。干扰这些特性中的任何一个都会导致神经元过度兴奋。星形胶质细胞还表现出Gs、Gi和Gq连接的G蛋白偶联受体(GPCRs)，调节一系列第二信使级联反应。星形胶质细胞内钙离子的增加导致谷氨酸、三磷酸腺苷、前列腺素E_2和D-丝氨酸等神经胶质递质的释放。这些神经递质中的每一种都在调节脊髓神经元兴奋性方面发挥重要作用，前三种被认为与慢性疼痛中伤害性神经元的敏化有关。星形胶质细胞表现出钙振荡和细胞间钙波，使它们能够通过释放胶质递质来同步神经元活动。此外，反应性星形胶质细胞释放许多被认为能敏化伤害性神经元的因子，包括NGF、NO、促炎细胞因子和前列腺素。虽然慢性疼痛领域的研究主要集中在伤害感受神经元的内在机制上，但最近的研究表明，慢性疼痛的部分原因是小胶质细胞和星形胶质细胞的激活。鉴于星形胶质细胞在神经元兴奋性调节中的突出作用，慢性疼痛的发生与反应性星形胶质细胞的出现之间存在极好的相关性也就不足为奇了。药理学和遗传学研究表明，阻断星形胶质细胞的激活可阻断某些形式的慢性疼痛的维持。这项提议中的实验将利用由电生理和共聚焦成像技术组成的实验工具包，以及转基因小鼠品系，以研究星形胶质细胞在慢性疼痛中的作用。在特定的目标1和2中，我们将确定在慢性疼痛的背景下，已知的调节神经元兴奋性的星形胶质细胞属性是否发生了变化。这些研究将包括对钾缓冲和谷氨酸摄取的分析，以及星形胶质细胞通过释放神经胶质递质来调节神经元兴奋性的能力。越来越清楚的是，炎症过程与许多神经系统疾病有关，包括慢性疼痛。在特定的目标3中，我们将检验这一假设，即星形胶质细胞中促炎症转录因子NF：B的激活在慢性疼痛的发生或维持中起重要作用。

DESCRIPTION (provided by applicant): It has become increasingly evident that astrocytes actively participate in neurophysiology, as well as contribute to the development and progression of a number of neurological disorders. Astrocytes are the most numerous cells in brain and spinal cord (~50% of all CNS cells) and associate with all cellular elements; a single astrocyte can envelop as many as 100,000 synapses. Astrocytes play a critical role in regulating neuronal excitability through their ability to buffer extracellular K+ and take up synaptically released glutamate. Interference with either of these properties leads to neuronal hyperexcitability. Astrocytes also exhibit Gs-, Gi-, and Gq-linked G-protein coupled receptors (GPCRs) regulating a host of second messenger cascades. Increases in astrocytic Ca2+ lead to the release gliotransmitters including glutamate, ATP, PGE2, and D-serine. Each of these gliotransmitters plays an important role in regulating neuronal excitability in the spinal cord and the first three are thought to be involved in the sensitization of nociceptive neurons in chronic pain. Astrocytes exhibit calcium oscillations and intercellular calcium waves that enable them to synchronize neuronal activity through the release of gliotransmitters. Further, reactive astrocytes release a number of factors thought to sensitize nociceptive neurons including NGF, NO, proinflammatory cytokines, and prostaglandins. While research in the field of chronic pain has focused primarily on mechanisms intrinsic to nociceptive neurons, more recent studies suggest that chronic pain derives, in part, from the activation of microglia and astrocytes. Given the prominent role of astrocytes in the regulation of neuronal excitability, it is not surprising that there is an excellent correlation between the development of chronic pain and the appearance of reactive astrocytes. Pharmacological as well as genetic studies indicate that blocking astrocytic activation blocks the maintenance of certain forms of chronic pain. Experiments within this proposal will take advantage of an experimental tool kit composed of electrophysiological and confocal imaging techniques, together with genetically modified lines of mice to study the role of astrocytes in chronic pain. In Specific Aims 1 and 2, we will determine if astrocytic properties known to modulate neuronal excitability are altered in the setting of chronic pain. These studies will include analyses of potassium buffering and glutamate uptake as well as the ability of astrocytes to modulate neuronal excitability through the release of gliotransmitters. It is becoming increasing clear that inflammatory processes are involved in a number of neurological diseases, including chronic pain. In Specific Aim 3 we will test the hypothesis that the activation of astrocytic NF:B, a proinflammatory transcription factor, is important in the development or maintenance of chronic pain.