Elimination of Mitochondrial Anchoring is Neuroprotective in Demyelination

消除线粒体锚定对脱髓鞘具有神经保护作用

基本信息

批准号：
8493611
负责人：
SHING Yan CHIU
金额：
$ 22.58万
依托单位：
UNIVERSITY OF WISCONSIN-MADISON
依托单位国家：
美国
项目类别：
财政年份：
2013
资助国家：
美国
起止时间：
2013-03-01 至 2015-02-28
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8493611
关键词：
Address Age Animal Model Animals Area Axon Biological Assay Cerebellum Clinical Data Demyelinating Diseases Demyelinations Disease Disease Progression Electrophysiology (science)Employee Strikes Environment Event Exhibits Experimental Autoimmune Encephalomyelitis Free Radicals Friends Future Genetic Goals Grant Health Immobilization Immunohistochemistry Inflammation Inflammatory Knockout Mice Lesion Life Expectancy Metabolic Metabolism Mitochondria Modeling Multiple Sclerosis Mus Myelin Neuraxis Neurologic Deficit Neurons Organelles Pathogenesis Pathology Phase Procedures Production Proteins Research Role Shivering Site Spinal Cord Spinal Ganglia Stream Testing Therapeutic Transgenic Organisms Up-Regulation age related axonal degeneration base density design dysmyelination foot genetic manipulation improved killings mouse model mutant myelination neuroprotection novel therapeutics prevent public health relevance research study response syntaphilin

项目摘要

DESCRIPTION (provided by applicant): Mitochondria are dynamic organelles that maintain the health of myelinated axons by metabolic matching, in which mitochondria move to and pause at regions of high energy demands. In demyelinating diseases such as multiple sclerosis (MS), there is a huge increase in energy demand as large areas of denuded axons are exposed by the loss of myelin. In response, more mitochondria move to and become immobilized at lesion sites, contributing to a large increase in axonal mitochondrial content. The prevailing hypothesis is that this increase in axonal mitochondria content is an adaptive change to maintain proper metabolism to protect axons. However, this mitochondrial increase could also be maladaptive and tip the scale to damage axons by excess free radical production. Which way the scale actually tips has never been tested. With mitochondria emerging as a key player in the pathogenesis of MS, it becomes critical to determine whether this well-known increase in axonal mitochondrial content is friend or foe. Recently we started to address this issue by genetically reducing the increase in axonal mitochondrial content in an animal model of dysmyelination (Shiverer). We interbred the Shiverer into a background lacking a mitochondrial immobilization protein (syntaphilin) that normally contributes to the increase in axonal mitochondrial content. Surprisingly, deletion of syntaphilin dramatically extends the life expectancy of the Shiverer mutant. Based on this survival data, this R21 explores whether mitochondrial anchoring contributes to axon killing in demyelination, and whether increasing mitochondrial mobility by elimination of immobilization confers neuroprotection on demyelinated axons. In Aim #1, we will use immunohistochemistry and morphologic analysis to see if axons are protected in Shiverer mice lacking syntaphilin. In Shiverer (with syntaphilin present) there is an age-dependent axonal degeneration in various regions in the CNS. We will examine if elimination of mitochondrial anchoring delays or reduces this age-dependent axonal degeneration. We will also transfect syntaphilin in the DRG to directly test if excessive mitochondrial anchoring kills axons in the spinal cord. In Aim #2, we will examine if elimination of mitochondrial anchoring similarly protects mice in EAE, an inflammatory demyelination model for MS. We will induce EAE in mice with or without syntaphilin to see if the clinical scores are improved in the syntaphilin-null background. Conclusion: This R21 proposal explores a potentially ground-breaking paradigm in mitochondrial research in MS. In contrast to existing research focusing on mitochondria as a down-stream target of upstream degenerating changes, we might have pinpointed an upstream event involving mitochondrial dynamics (excessive anchoring) that leads to downstream degeneration. It further suggests an exciting therapeutic possibility that altering the ratio of mobile to immobile mitochondria could profoundly alter disease progression. The proposed experiments will determine whether there is firm footing for a future R01 application.

描述（由申请人提供）：线粒体是动态细胞器，通过代谢匹配维持有髓轴突的健康，其中线粒体移动到高能量需求区域并在高能量需求区域暂停。在多发性硬化症（MS）等脱髓鞘疾病中，由于髓鞘质的丧失，大面积裸露的轴突暴露出来，能量需求大幅增加。作为响应，更多的线粒体移动到并固定在病变部位，导致轴突线粒体含量大幅增加。普遍的假设是，轴突线粒体含量的增加是一种适应性变化，旨在维持适当的新陈代谢以保护轴突。然而，这种线粒体的增加也可能是适应不良的，并会因过量的自由基产生而损害轴突。天平实际倾斜的方向从未被测试过。随着线粒体成为多发性硬化症发病机制中的关键参与者，确定这种众所周知的轴突线粒体含量增加是朋友还是敌人变得至关重要。最近，我们开始通过基因方法减少髓鞘形成障碍（Shiverer）动物模型中轴突线粒体含量的增加来解决这个问题。我们将颤抖犬与缺乏线粒体固定蛋白（亲合蛋白）的背景进行杂交，而线粒体固定蛋白通常有助于轴突线粒体含量的增加。令人惊讶的是，亲合蛋白的缺失显着延长了 Shiverer 突变体的预期寿命。基于这些生存数据，该 R21 探讨了线粒体锚定是否有助于脱髓鞘中轴突的杀伤，以及通过消除固定来增加线粒体活动性是否可以为脱髓鞘轴突提供神经保护。在目标 #1 中，我们将使用免疫组织化学和形态学分析来观察缺乏亲和蛋白的 Shiverer 小鼠的轴突是否受到保护。在 Shiverer（存在亲突蛋白）中，有中枢神经系统各个区域的年龄依赖性轴突变性。我们将检查线粒体锚定的消除是否会延迟或减少这种年龄依赖性轴突变性。我们还将在 DRG 中转染亲突蛋白，以直接测试过度的线粒体锚定是否会杀死脊髓中的轴突。在目标 2 中，我们将检查消除线粒体锚定是否同样可以保护 EAE（一种多发性硬化症炎症脱髓鞘模型）中的小鼠。我们将在有或没有亲和蛋白的小鼠中诱导 EAE，以观察在无亲和蛋白的背景下临床评分是否有所改善。结论：R21 提案探索了 MS 线粒体研究的潜在突破性范式。与现有研究侧重于线粒体作为上游退化变化的下游目标相反，我们可能已经确定了涉及线粒体动力学（过度锚定）的上游事件，该事件导致下游退化。它进一步表明了一种令人兴奋的治疗可能性，即改变移动线粒体与固定线粒体的比例可以深刻改变疾病进展。拟议的实验将确定未来 R01 应用是否有坚实的基础。