Co-localization of sodium channel Nav1.6 and the sodium-calcium exchanger at sites of axonal injury in the spinal cord in EAE
Co-localization of sodium channel Nav1.6 and the sodium-calcium exchanger at sites of axonal injury in the spinal cord in EAE
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DOI：
10.1093/brain/awh032
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发表时间：
2004-02-01
期刊：
影响因子：
14.5
通讯作者：
Waxman, SG
中科院分区：
文献类型：
--
作者：
Craner, MJ;Hains, BC;Waxman, SG
轴突变性导致多发性硬化症中非缓解性神经缺陷和残疾的发展，但多发性硬化症中轴突变性丧失的分子机制尚不清楚。白质轴突损伤的研究表明，电压门控钠通道可以为钠流入轴突提供一条途径，从而触发 Na+/Ca2+ 交换器 (NCX) 的反向操作，并随后流入轴突内钙的破坏水平。然而，所涉及的钠通道的分子特性尚未确定。我们之前已经证明，在实验性过敏性脑脊髓炎（EAE）中，Na(v)1.6 和 Na(v)1.2 钠通道沿脱髓鞘轴突广泛扩散表达。基于 Na(v)1.6 和 NCX 沿着脱髓鞘轴突广泛区域共定位可能使这些轴突易于损伤的假设，我们检测了 EAE 小鼠脊髓背柱中髓磷脂碱性蛋白、Na(v)1.2、Na(v)1.6、NCX 和 β-淀粉样前体蛋白 (β-APP)（轴突损伤的标志物）的表达。我们证明，EAE 中脱髓鞘轴突的数量显着增加，表现出弥漫性 Na(v)1.6 和 Na(v)1.2 钠通道免疫反应性（92.2 +/- 2.1% 的 β-APP 阳性轴突为 Na(v)1.6 阳性）。只有 38.0 +/- 2.9% 的 beta-APP 阳性轴突是 Na(v)1.2 阳性，其中 95% 与 Na(v)1.6 和 Na(v)1.2 共表达。使用三标记荧光免疫组织化学，我们证明 73.5 +/- 4.3% 的 β-APP 阳性轴突共表达 Na(v)1.6 和 NCX，而 4.4 +/- 1.0% 的 β-APP 阴性轴突共表达 Na(v)1.6 和 NCX。我们的结果表明 Na(v)1.6 和 NCX 的共表达与 EAE 中脊髓的轴突损伤有关。
Axonal degeneration contributes to the development of non-remitting neurological deficits and disability in multiple sclerosis, but the molecular mechanisms that underlie axonal loss in multiple sclerosis are not clearly understood. Studies of white matter axonal injury have demonstrated that voltage-gated sodium channels can provide a route for sodium influx into axons that triggers reverse operation of the Na+/Ca2+ exchanger (NCX) and subsequent influx of damaging levels of intra-axonal calcium. The molecular identities of the involved sodium channels have, however, not been determined. We have previously demonstrated extensive regions of diffuse expression of Na(v)1.6 and Na(v)1.2 sodium channels along demyelinated axons in experimental allergic encephalomyelitis (EAE). Based on the hypothesis that the co-localization of Na(v)1.6 and NCX along extensive regions of demyelinated axons may predispose these axons to injury, we examined the expression of myelin basic protein, Na(v)1.2, Na(v)1.6, NCX and beta-amyloid precursor protein (beta-APP), a marker of axonal injury, in the spinal cord dorsal columns of mice with EAE. We demonstrate a significant increase in the number of demyelinated axons demonstrating diffuse Na(v)1.6 and Na(v)1.2 sodium channel immunoreactivity in EAE (92.2 +/- 2.1% of beta-APP positive axons were Na(v)1.6-positive). Only 38.0 +/- 2.9% of beta-APP positive axons were Na(v)1.2 positive, and 95% of these co-expressed Na(v)1.6 together with Na(v)1.2. Using triple-labelled fluorescent immunohistochemistry, we demonstrate that 73.5 +/- 4.3% of beta-APP positive axons co-express Na(v)1.6 and NCX, compared with 4.4 +/- 1.0% in beta-APP negative axons. Our results indicate that co-expression of Na(v)1.6 and NCX is associated with axonal injury in the spinal cord in EAE.