Black Joel A, Liu Shujun, Waxman Stephen G
Department of Neurology and Center for Neuroscience and Regeneration Research, Yale School of Medicine, New Haven, Connecticut 06518, USA.
Glia. 2009 Aug 1;57(10):1072-81. doi: 10.1002/glia.20830.
Microglia provide surveillance in the central nervous system and become activated following tissue insult. Detailed mechanisms by which microglia detect and respond to their environment are not fully understood, but it is known that microglia express a number of surface receptors and ion channels, including voltage-gated sodium channels, that participate in transduction of external stimuli to intra-cellular responses. To determine whether activated microglia are affected by the activity of sodium channels, we examined the expression of sodium channel isoforms in cultured microglia and the action of sodium channel blockade on multiple functions of activated microglia. Rat microglia in vitro express tetrodotoxin (TTX)-sensitive sodium channels Nav1.1 and Nav1.6 and the TTX-resistant channel Nav1.5, but not detectable levels of Nav1.2, Nav1.3, Nav1.7, Nav1.8, and Nav1.9. Sodium channel blockade with phenytoin (40 microM) and TTX (0.3 microM) significantly reduced by 50-60% the phagocytic activity of microglia activated with lipopolysaccharide (LPS); blockade with 10 microM TTX did not further reduce phagocytic activity. Phenytoin attenuated by approximately 50% the release of IL-1 alpha, IL-1 beta, and TNF-alpha from LPS-stimulated microglia, but had minimal effects on the release of IL-2, IL-4, IL-6, IL-10, MCP-1, and TGF-alpha. TTX (0.3 microM) reduced, but to a smaller extent, the release of IL-1 alpha, IL-1 beta, and TNF-alpha from activated microglia. Phenytoin and TTX also significantly decreased by approximately 50% adenosine triphosphate-induced migration by microglia; studies with microglia cultured from med mice (which lack Nav1.6) indicate that Nav1.6 plays a role in microglial migration. The results demonstrate that the activity of sodium channels contributes to effector roles of activated microglia.
小胶质细胞在中枢神经系统中发挥监测作用，并在组织受损后被激活。小胶质细胞检测并响应其周围环境的详细机制尚未完全明确，但已知小胶质细胞表达多种表面受体和离子通道，包括电压门控钠通道，这些通道参与将外部刺激转化为细胞内反应。为了确定活化的小胶质细胞是否受钠通道活性的影响，我们检测了培养的小胶质细胞中钠通道亚型的表达以及钠通道阻滞剂对活化小胶质细胞多种功能的作用。体外培养的大鼠小胶质细胞表达对河豚毒素（TTX）敏感的钠通道Nav1.1和Nav1.6以及对TTX耐药的通道Nav1.5，但未检测到Nav1.2、Nav1.3、Nav1.7、Nav1.8和Nav1.9的表达水平。苯妥英（40微摩尔）和TTX（0.3微摩尔）对钠通道的阻滞使脂多糖（LPS）激活的小胶质细胞的吞噬活性显著降低了50 - 60%；10微摩尔TTX的阻滞并未进一步降低吞噬活性。苯妥英使LPS刺激的小胶质细胞释放白细胞介素 - 1α、白细胞介素 - 1β和肿瘤坏死因子 - α减少了约50%，但对白细胞介素 - 2、白细胞介素 - 4、白细胞介素 - 6、白细胞介素 - 10、单核细胞趋化蛋白 - 1和转化生长因子 - α的释放影响极小。TTX（0.3微摩尔）减少了活化小胶质细胞释放白细胞介素 - 1α、白细胞介素 - 1β和肿瘤坏死因子 - α，但程度较小。苯妥英和TTX还使小胶质细胞由三磷酸腺苷诱导的迁移显著减少了约50%；对来自med小鼠（缺乏Nav1.6）培养的小胶质细胞的研究表明，Nav1.6在小胶质细胞迁移中起作用。结果表明，钠通道的活性有助于活化小胶质细胞的效应功能。
