Defining the role of brain iron dysregulation in Huntington's disease

描述(申请人提供)：这个项目的主要目标是测试我们的核心假设，即亨廷顿病(HD)中脑内铁积累促进疾病的发生和发展。HD是一种最终致命的神经退行性疾病，仅在美国就有大约30000人受到影响，没有有效的治疗方法。Huntingtin基因中CAG重复序列的扩展导致多谷氨酰胺扩展的突变Huntingtin蛋白的表达，导致一系列下游效应，包括能量调节失调、谷氨酸信号异常、铁升高、氧化和亚硝化应激，最终导致神经元退化和丢失。越来越多的证据表明，铁稳态失调在HD以及ALS、帕金森氏症和阿尔茨海默病的发病机制中起着重要作用。然而，令人惊讶的是，对于HD是如何发生的，以及铁失调在多大程度上对整个疾病过程做出贡献，人们知之甚少。我们首次表明，铁在小鼠HD纹状体和皮质神经元中积累，这些区域有显著的变性。淀粉样前体蛋白(APP)在神经元铁输出中起关键作用。我们发现APP水平及其铁出口铁氧化物酶活性显著降低。我们还有 在可诱导突变的亨廷顿蛋白表达细胞系中显示铁含量升高，并表明抑制nNOS可以逆转这一现象。这些有趣而重要的发现指出了一氧化氮、APP和HD中的铁之间的联系，并构成了拟议的研究的基础。目的1将验证假设，即亚硝化应激中介APP蛋白水平下降，导致铁含量升高，从而加剧神经退化。在目标1A中，我们将确定APP的遗传调节对HD模型结果的影响。在目标1B中，我们研究了抑制nNOS对HD结局的影响，包括APP和铁。我们将使用转基因和全长突变的亨廷顿鼠模型，以及HD细胞系和原代神经元培养。目标2将验证与营养相关的铁摄入量增加加强大脑铁积累的假设 以及HD小鼠的神经变性。这些研究将对HD的铁调节失调的机制提供重要的见解。这些发现将确定HD大脑中铁的失调加剧疾病的程度；它们可能验证APP作为一种新的治疗靶点，并为HD患者饮食铁的调节作用提供洞察力。

DESCRIPTION (provided by applicant): The primary goal of this project is to test our core hypothesis that brain iron accumulation in Huntington's disease (HD) promotes disease onset and progression. HD is an ultimately fatal neurodegenerative disease that afflicts about 30000 people in the USA alone and has no effective treatments. CAG-repeat expansion within the huntingtin gene results in expression of a polyglutamine-expanded mutant huntingtin protein leading to a number of downstream effects including energetic dysregulation, aberrant glutamate signaling, iron elevation, oxidative and nitrosative stress, and eventually neuronal degeneration and loss. There is growing evidence that dysregulation of iron homeostasis contributes to the pathogenesis of HD as well as ALS, Parkinson's and Alzheimer's diseases. Surprisingly however, little is known about how this occurs in HD and to what degree iron dysregulation contributes to the overall disease process. We have shown for the first time that iron accumulates in mouse HD striatal and cortical neurons, regions where there is significant degeneration. Amyloid precursor protein (APP) has a key role in neuronal iron export. We show significantly decreased levels of APP as well as its iron export ferroxidase activity. We have also demonstrated elevated iron in an inducible mutant huntingtin expressing cell line and shown that nNOS inhibition reverses this. These interesting and important findings point to a link between nitric oxide, APP and iron in HD and form the basis for the proposed studies. Aim 1 will test the hypothesis that nitrosative stress mediates decreased APP protein levels resulting in elevated iron which potentiates neurodegeneration. In Aim 1A we will determine the effect of genetic modulation of APP on outcomes in HD models. In Aim 1B we study the effects of nNOS inhibition on HD outcomes including APP and iron. We will use transgenic and full-length mutant huntingtin mouse models as well as HD cell lines and primary neuron cultures. Aim 2 will test the hypothesis that nutritionally relevant elevated iron intake potentiates brain iron accumulation and neurodegeneration in HD mice. The studies will provide important insights into mechanisms of iron dysregulation in HD. Findings will determine the extent to which dysregulated iron in HD brain potentiates disease; they may validate APP as a novel therapeutic target as well as provide insight into modulatory effects of dietary iron in HD.