Inducible nitric oxide synthase is present in motor neuron mitochondria and Schwann cells and contributes to disease mechanisms in ALS mice
Inducible nitric oxide synthase is present in motor neuron mitochondria and Schwann cells and contributes to disease mechanisms in ALS mice
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DOI：
10.1007/s00429-009-0226-4
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发表时间：
2010-03-01
影响因子：
3.1
通讯作者：
Martin, Lee J.
中科院分区：
文献类型：
--
作者：
Chen, Kevin;Northington, Frances J.;Martin, Lee J.
肌萎缩性侧索硬化症（ALS）是一种致命的运动神经元退行性疾病。ALS的分子发病机制尚不清楚，因此缺乏有效的治疗方法。某些形式的ALS是由超氧化物歧化酶-1 （SOD1）基因突变遗传的。表达人Gly93 -> Ala （G93A）突变体SOD1 （mSOD1）的转基因小鼠会发生严重的MN疾病、氧化和硝化损伤以及线粒体病理，这些病理似乎涉及一氧化氮介导的机制。我们使用G93A-mSOD1小鼠来验证MNs的退化与MNs内诱导型一氧化氮合酶（iNOS或NOS2）活性的异常上调有关的假设。Western blotting和免疫沉淀显示mSOD1小鼠脊髓线粒体富集膜部分iNOS蛋白水平在疾病症状前阶段显著升高。在疾病症状前，mSOD1小鼠脊髓线粒体富集膜组分中iNOS的催化活性也显著增加。逆转录pcr结果显示，小鼠脊髓和脑干MN区存在iNOS mRNA，且在症状前和症状早期小鼠中iNOS mRNA表达增加。免疫组织化学表明，症状前和症状早期小鼠脊髓和脑干MNs中iNOS免疫反应性首先上调，随后在疾病过程中大量小胶质细胞和少数星形胶质细胞中iNOS免疫反应性上调。mSOD1小鼠MNs线粒体中iNOS积累。周围神经雪旺细胞的iNOS免疫反应性也上调，特别是在Ranvier淋巴结的旁淋巴结区域。iNOS药物抑制剂延缓了G93A-mSOD1小鼠的发病，并显著延长了其寿命。这项工作确定了小鼠肌萎缩侧索硬化（ALS）中MN变性的两种新的潜在早期机制，涉及MN线粒体和雪旺细胞中的iNOS，并提示针对iNOS的治疗可能对治疗人类ALS有益。
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of motor neurons (MNs). The molecular pathogenesis of ALS is not understood, thus effective therapies for this disease are lacking. Some forms of ALS are inherited by mutations in the superoxide dismutase-1 (SOD1) gene. Transgenic mice expressing human Gly93 -> Ala (G93A) mutant SOD1 (mSOD1) develop severe MN disease, oxidative and nitrative damage, and mitochondrial pathology that appears to involve nitric oxide-mediated mechanisms. We used G93A-mSOD1 mice to test the hypothesis that the degeneration of MNs is associated with an aberrant up-regulation of the inducible form of nitric oxide synthase (iNOS or NOS2) activity within MNs. Western blotting and immunoprecipitation showed that iNOS protein levels in mitochondrial-enriched membrane fractions of spinal cord are increased significantly in mSOD1 mice at pre-symptomatic stages of disease. The catalytic activity of iNOS was also increased significantly in mitochondrial-enriched membrane fractions of mSOD1 mouse spinal cord at pre-symptomatic stages of disease. Reverse transcription-PCR showed that iNOS mRNA was present in the spinal cord and brainstem MN regions in mice and was increased in pre-symptomatic and early symptomatic mice. Immunohistochemistry showed that iNOS immunoreactivty was up-regulated first in spinal cord and brainstem MNs in pre-symptomatic and early symptomatic mice and then later in the course of disease in numerous microglia and few astrocytes. iNOS accumulated in the mitochondria in mSOD1 mouse MNs. iNOS immunoreactivity was also up-regulated in Schwann cells of peripheral nerves and was enriched particularly at the paranodal regions of the nodes of Ranvier. Drug inhibitors of iNOS delayed disease onset and significantly extended the lifespan of G93A-mSOD1 mice. This work identifies two new potential early mechanisms for MN degeneration in mouse ALS involving iNOS at MN mitochondria and Schwann cells and suggests that therapies targeting iNOS might be beneficial in treating human ALS.