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

描述（由申请人提供）：该项目的主要目标是测试我们的核心假设，即亨廷顿病（HD）的脑铁积累促进疾病的发生和进展。HD是一种最终致命的神经退行性疾病，仅在美国就有约30000人受到折磨，并且没有有效的治疗方法。亨廷顿蛋白基因内的CAG重复扩增导致多聚谷氨酰胺扩增的突变亨廷顿蛋白的表达，导致许多下游效应，包括能量失调、异常谷氨酸信号传导、铁升高、氧化和亚硝化应激，以及最终的神经元变性和损失。越来越多的证据表明，铁稳态的失调有助于HD以及ALS、帕金森病和阿尔茨海默病的发病机制。然而，令人惊讶的是，很少有人知道这是如何发生在HD和铁失调在多大程度上有助于整个疾病的过程。我们首次发现，铁在小鼠HD纹状体和皮质神经元中积累，这些区域存在显着的变性。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水平及其铁输出铁氧化酶活性显著降低。我们还 在可诱导的突变亨廷顿蛋白表达细胞系中证明了铁的升高，并显示nNOS抑制逆转了这一点。这些有趣而重要的发现指出了HD中一氧化氮，APP和铁之间的联系，并形成了拟议研究的基础。目的1将检验亚硝化应激介导APP蛋白水平降低导致铁升高从而增强神经变性的假设。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。在目的1B中，我们研究了nNOS抑制对HD结局（包括APP和铁）的影响。我们将使用转基因和全长突变亨廷顿蛋白小鼠模型以及HD细胞系和原代神经元培养物。目的2将检验这一假设，即营养相关的铁摄入量增加，加强脑铁积累 和神经退行性变。这些研究将为HD铁失调的机制提供重要的见解。研究结果将确定HD脑中失调的铁增强疾病的程度;它们可以验证APP作为一种新的治疗靶点，并提供对HD中膳食铁调节作用的见解。

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.