Skeletal Muscle Mechanisms of Disease in ALS

描述（由申请人提供）：肌萎缩性侧索硬化症（ALS）是成人发病的第三大最常见的人类神经退行性疾病。它是一种致命的运动神经元麻痹性疾病，目前尚无有效的治疗方法。需要确定新的基于机制的靶点，以发现与病变MNs相关的药物。某些形式的ALS是遗传性的，是由超氧化物歧化酶-1 （SOD1）基因突变引起的，从而为MN易感性提供了线索。许多不同的SOD1突变发生，但人类SOD1 （hSOD1）对MNs的毒性机制尚不清楚。重要的是，肌萎缩侧索硬化症中MN变性的自主性是一个重要的尚未解决的问题。我们假设骨骼肌是肌萎缩侧索硬化症中触发MN变性的主要发病部位。我们已经创建了新的转基因（tg）小鼠，骨骼肌特异性表达hSOD1基因变体。这些hsod1mutg小鼠的神经和病理表型与ALS一致。利用这些新型小鼠，我们建议研究骨骼肌作为ALS的致病实体。在目的1中，我们将分析hsod1小鼠的年龄相关神经和病理表型。我们假设hsod1小鼠MN变性的机制与远端轴索病变和靶剥夺诱导的细胞凋亡一致。在Aim 2中，我们将分析氧化应激和骨骼肌线粒体通透性孔的激活作为hsod1mutg小鼠肌肉病理的介质。在Aim 3中，我们将使用培养细胞来检测骨骼肌细胞中的hSOD1表达是否会改变其细胞内氧化还原状态、Ca2+处理和离子通道功能，并破坏神经肌肉连接，从而引发MN变性。这项工作可能会导致关于肌萎缩侧索硬化症发病机制中MNs非自主死亡的新概念。在骨骼肌中发现诱发毒性或疾病进展决定因素将对开发治疗和治愈ALS的新有效疗法非常有价值。公共卫生相关性：肌萎缩侧索硬化症（ALS）是一种致命的神经肌肉疾病。这项工作将确定骨骼肌异常是否在疾病机制中具有因果作用。骨骼肌可以为ALS的药物开发提供新的组织和分子靶点。

DESCRIPTION (provided by applicant): Amyotrophic lateral sclerosis (ALS) is the 3rd most common human neurodegenerative disease with an adult onset. It is a fatal paralytic disease of motor neurons (MNs) without any effective treatments. Novel mechanism-based targets need to be identified for drug discovery relevant to diseased MNs. Some forms of ALS are inherited and are caused by mutations in the superoxide dismutase-1 (SOD1) gene, thus providing a clue about MN vulnerability. Many different SOD1 mutations occur, but the mechanisms of human SOD1 (hSOD1) toxicity to MNs are unresolved. Importantly, the autonomy of the MN degeneration in ALS is an important unresolved problem. We hypothesize that skeletal muscle is a primary site of pathogenesis in ALS that triggers MN degeneration. We have created new transgenic (tg) mice with skeletal muscle-specific expression of hSOD1 gene variants. These hSOD1mus tg mice develop neurologic and pathologic phenotypes consistent with ALS. Using these novel mice we propose to study skeletal muscle as a disease-causing entity in ALS. In Aim 1 we will analyze the age-related neurologic and pathologic phenotypes of hSOD1mus tg mice. We hypothesize that the mechanisms of MN degeneration in our hSOD1mus tg mice are consistent with distal axonopathy and target deprivation-induced apoptosis. In Aim 2, we will analyze the involvement of oxidative stress and activation of the mitochondrial permeability pore in skeletal muscle as mediators of muscle pathology in hSOD1mus tg mice. In Aim 3 we will use cultured cells to examine if hSOD1 expression in skeletal muscle cells alters their intracellular redox state, Ca2+ handling, and ion channel function and disrupts the neuromuscular junction, thus provoking MN degeneration. The work can lead to new concepts about the non-autonomous death of MNs in ALS pathogenesis. The discovery of instigating toxicities or disease progression determinants within skeletal muscle would be very valuable for development of new effective therapies in the treatment and cure of ALS. PUBLIC HEALTH RELEVANCE: Amyotrophic lateral sclerosis (ALS) is a fatal neuromuscular disorder. This work will determine if abnormalities in skeletal muscle have causal roles in the disease mechanisms. Skeletal muscle could provide new tissue- and molecular targets for drug discovery in ALS.