Mitochondrial Iron-Sulfur cluster mechanisms and therapy in Friedreich's ataxia

描述（由申请人提供）：弗里德赖希共济失调症（FRDA）是最常见的常染色体隐性运动障碍，在美国约有6000人致残，在全世界有数万人致残，目前尚无批准的治疗方法。FRDA是进行性的，发作于青少年时期，其表型包括原发性神经变性和感觉背根神经节（DRG）神经元脱髓鞘。新药的开发成本高达10亿美元，有时很难激励制药公司投资于影响数千人而不是数百万人的疾病。我们已经对1600种国际批准的药物进行了转化筛选，即已经进行了I、II和III期试验的药物，以确定哪些药物可以最迅速地重新用于治疗FRDA患者。我们对现有的最佳FRDA小鼠模型（YG8）的DRG神经元进行了微阵列，并观察到硫氧还蛋白还原酶还原的几种分子（包括GSH）存在缺陷。我们利用这一缺陷筛选了1600种目前批准的药物，以评估它们拯救FRDA患者细胞免于死亡的能力，并确定了40种。在这些药物中，一些增加了frataxin的表达，而另一些可能支持铁硫簇生物发生。我们的第一个目标包括确定40种药物的作用机制（目标1），关于frataxin表达，Fe/S簇合成和pgc -1 α诱导。在Aim 2中，药物将在组织相关的雪旺细胞和DRG神经元中进行测试，以拯救Fe/S簇，血红素缺陷和死亡。同样在Aim 2中，将确定正常frataxin和已知引起FRDA的致病性点突变挽救Fe/S簇、血红素和细胞活力的能力。在Aim 3中，我们将测试9种最具二胺保护作用的药物的活性，以检测它们在DRG外植体中挽救fraataxin表达、铁硫簇缺陷和金嘌呤蛋白敏感性的能力。此外，将在体内给药3种最有效的药物，并测量对DRG fraataxin表达、铁硫缺陷和金糠蛋白敏感性的影响。最后，对最有效的两种药物进行为期3个月的行为和铁硫生化缺陷的拯救研究。在Aim 4中，将通过重复序列、frataxin和铁硫簇蛋白的定量PCR来测试（GAA）n的年龄和组织特异性体细胞扩增关系的特定假设。在这个转化研究项目结束时，我们希望能够优先考虑已经通过FRDA患者细胞和最佳疾病动物模型的I， II和III期试验的几种抗弗里德赖希治疗药物的作用机制和效力，作为人类临床试验的初步研究，并且必须证实或拒绝DRG神经元在疾病中的选择性易感性的新假设。

DESCRIPTION (provided by applicant): Friedreich's ataxia (FRDA), is the most common autosomal recessive movement disorder, and cripples about 6000 Americans, and tens of thousands worldwide, and there is no approved therapy. FRDA is progressive, striking in the teen years, and its phenotype includes primary neurodegeneration and demyelination of sensory dorsal root ganglion (DRG) neurons. New drugs cost $1B to develop, and it is sometimes difficult to motivate pharma to invest in diseases that affect thousands rather than millions of people. We have undertaken a translational screen of 1600 internationally-approved drugs, i.e. drugs that have undergone phase I, II, and III trials already, to identify which of these can be most rapidly repurposed for treatment of FRDA patients. We microarrayed the DRG neurons of the best mouse model of FRDA available (YG8), and observed defects in several molecules reduced by thioredoxin reductase, including GSH. We used this deficiency to screen 1600 currently-approved drugs for their ability to rescue FRDA patient cells from death, and identified 40. Of those drugs, some increase frataxin expression, whereas others are likely to support iron-sulfur cluster biogenesis. Our first Aim includes the determination of mechanism of action of the 40 drugs (Aim 1), with respect to frataxin expression, Fe/S cluster synthesis, and PGC-1alpha induction. In Aim 2, the drugs will be tested in tissue-relevant Schwann cell and DRG neurons for rescue of Fe/S cluster, heme defects and death. Also in Aim 2 the ability of normal frataxin and pathogenic point mutations known to cause FRDA to rescue Fe/S cluster, heme and cell viability will be determined. In Aim 3 we will test the activity of the 9 most diamide-protective drugs for their ability to rescue frataxin expression, iron-sulfur cluster defects, and auranofin sensitivity in the context of DRG explants. Furthermore, in vivo dosing of the 3 most potent drugs will occur, and effects on DRG frataxin expression, iron-sulfur defects, and auranofin sensitivity will be measured. Lastly for the most effective two drugs, 3-month studies of rescue from behavioral and iron-sulfur biochemical defects will be carried out. In Aim 4, a specific hypothesis for the relationship of age- and tissue-specific somatic expansions of (GAA)n will be tested, by quantitative PCR of repeats and frataxin and ironsulfur cluster proteins. At the end of this translational research project, we expect to have prioritized the mechanism of action and potency of several anti-Friedreich's therapeutic drugs that have already passed through phase I, II and III trials, in FRDA patient cells and the best available animal model of the disease, as a preliminary to clinical testing in humans, and to have to have confirmed or rejected a novel hypothesis for the selective vulnerability of DRG neurons in the disease. PUBLIC HEALTH RELEVANCE: Friedreich's ataxia (FRDA) is a crippling neurodegenerative disease initiating in teen years. Based on investigation of the disease we identified a biochemical difference in FRDA patient cells, and have screened 1600 drugs already approved for use in humans, and have identified 40 which protect the cells from death. Our goals are to determine the mechanism of action of the drugs and efficacy in cell and animal models in preparation for clinical testing in humans.