Department of Pharmacology and Anesthesiology, University of Padova, Largo "E. Meneghetti" 2, 35131 Padova, Italy.
CNS Neurol Disord Drug Targets. 2011 Feb;10(1):44-56. doi: 10.2174/187152711794488638.
Under pathological conditions microglia (resident CNS immune cells) become activated, and produce reactive oxygen and nitrogen species and pro-inflammatory cytokines: molecules that can contribute to axon demyelination and neuron death. Because some microglia functions can exacerbate CNS disorders, including stroke, traumatic brain injury, progressive neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis, and several retinal diseases, controlling their activation might ameliorate immune-mediated CNS disorders. A growing body of evidence now points to ion channels on microglia as contributing to the above neuropathologies. For example, the ATP-gated P2X7 purinergic receptor cation channel is up-regulated around amyloid β-peptide plaques in transgenic mouse models of Alzheimer's disease and co-localizes to microglia and astrocytes. Upregulation of the P2X7 receptor subtype on microglia occurs also following spinal cord injury and after ischemia in the cerebral cortex of rats, while P2X7 receptor-like immunoreactivity is increased in activated microglial cells of multiple sclerosis and amyotrophic lateral sclerosis spinal cord. Utilizing neuron/microglia co-cultures as an in vitro model for neuroinflammation, P2X7 receptor activation on microglia appears necessary for microglial cell-mediated injury of neurons. A second example can be found in the chloride intracellular channel 1 (CLIC1), whose expression is related to macrophage activation, undergoes translocation from the cytosol to the plasma membrane (activation) of microglia exposed to amyloid β-peptide, and participates in amyloid β-peptide-induced neurotoxicity through the generation of reactive oxygen species. A final example is the small-conductance Ca2+/calmodulin-activated K+ channel KCNN4/KCa3.1/SK4/IK1, which is highly expressed in rat microglia. Lipopolysaccharide-activated microglia are capable of killing adjacent neurons in co-culture, and show markedly reduced toxicity when treated with an inhibitor of KCa3.1 channels. Moreover, blocking KCa3.1 channels mitigated the neurotoxicity of amyloid β-peptide-stimulated microglia. Excessive microglial cell activation and production of potentially neurotoxic molecules, mediated by ion channels, may thus constitute viable targets for the discovery and development of neurodegenerative disease therapeutics. This chapter will review recent data that reflect the prevailing approaches targeting neuroinflammation as a pathophysiological process contributing to the onset or progression of neurodegenerative diseases, with a focus on microglial ion channels and their neuroprotective potential.
在病理条件下,小胶质细胞(中枢神经系统固有免疫细胞)被激活,并产生活性氧和氮物种以及促炎细胞因子:这些分子可能导致轴突脱髓鞘和神经元死亡。由于小胶质细胞的一些功能可能会加剧中枢神经系统疾病,包括中风、创伤性脑损伤、进行性神经退行性疾病如阿尔茨海默病、帕金森病、肌萎缩侧索硬化症和多发性硬化症以及几种视网膜疾病,因此控制它们的激活可能会改善免疫介导的中枢神经系统疾病。越来越多的证据表明,小胶质细胞上的离子通道有助于上述神经病理学。例如,ATP 门控 P2X7 嘌呤能受体阳离子通道在阿尔茨海默病转基因小鼠模型中的淀粉样β肽斑块周围上调,并与小胶质细胞和星形胶质细胞共定位。脊髓损伤和大鼠大脑皮层缺血后,小胶质细胞上的 P2X7 受体亚型也会上调,而多发性硬化症和肌萎缩侧索硬化症脊髓中激活的小胶质细胞中的 P2X7 受体样免疫反应性增加。利用神经元/小胶质细胞共培养作为神经炎症的体外模型,小胶质细胞上的 P2X7 受体激活似乎是小胶质细胞介导的神经元损伤所必需的。第二个例子是氯离子通道 1(CLIC1),其表达与巨噬细胞激活有关,在暴露于淀粉样β肽的小胶质细胞中从细胞质易位到质膜(激活),并通过生成活性氧参与淀粉样β肽诱导的神经毒性。最后一个例子是小电导钙/钙调蛋白激活的钾+通道 KCNN4/KCa3.1/SK4/IK1,它在大鼠小胶质细胞中高度表达。脂多糖激活的小胶质细胞能够在共培养中杀死相邻的神经元,并且在用 KCa3.1 通道抑制剂处理时显示出明显降低的毒性。此外,阻断 KCa3.1 通道减轻了淀粉样β肽刺激的小胶质细胞的神经毒性。因此,离子通道介导的小胶质细胞过度激活和潜在神经毒性分子的产生,可能成为发现和开发神经退行性疾病治疗方法的可行靶点。本章将回顾反映靶向神经炎症作为导致神经退行性疾病发病或进展的病理生理过程的最新数据,重点是小胶质细胞离子通道及其神经保护潜力。
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