Role of Brain Ferroxidases in AD and sCJD Pathogenesis

描述（由申请方提供）：几种神经退行性疾病，如散发性克雅氏病（sCJD）、阿尔茨海默病（AD）、帕金森病（PD）和亨廷顿病（HD）与患病大脑中铁稳态失衡相关，这增加了氧化还原铁诱导的氧化损伤在与这些疾病相关的神经毒性中发挥重要作用的可能性。最近来自Singh实验室的证据表明，在sCJD感染的人类和羊瘙痒病感染的小鼠大脑中，铁氧化酶活性显著降低。结合sCJD大脑表现出“明显”缺铁的表型，尽管存在正常或增加的脑铁水平，这些观察结果表明，在患病的大脑正常铁稳态机制失调。最近的一份报告表明，铁氧化酶活性降低，导致铁积累在AD脑，这表明这种现象是共享的神经退行性疾病的不同病因。在一组独立的研究中，Mukhopadhayay实验室报告说，血浆铜蓝蛋白（Cp），大脑中的一种主要铁氧化酶，被活性氧（ROS）下调。由于铁是高度氧化还原活性的，并且如果管理不当，则是ROS的主要贡献者，因此一旦由特定疾病过程引发，铁不平衡可能通过主要脑铁氧化酶的下调而被ROS永久化。基于这些观察结果，我们假设ROS介导的脑特异性铁氧化酶的失调有助于AD和sCJD的铁失衡。拟议的研究将在两个具体目标中检验这一假设。在目标1中，将在AD和朊病毒疾病的细胞模型中研究ROS在调节特定铁氧化酶中的作用。一旦鉴定出铁氧化酶，将其调节与已知通过响应ROS的mRNA衰变机制调节的Cp进行比较。随后，将鉴定负责调节ROS介导的Cp活性的3' UTR和结合蛋白的最小区域。在目的2中，将评估在ai 1中鉴定的铁氧化酶在疾病进展期间在AD和羊瘙痒病感染的小鼠模型中的表达和活性。结果将与AD和sCJD病例的人脑组织进行比较，使用铁氧化酶测定和免疫组织化学作为读数。这些研究的成功完成将阐明主要脑铁氧化酶在与AD和sCJD脑相关的铁稳态障碍中的作用，并为未来研究PD，HD和其他与脑铁失衡相关的神经退行性疾病中脑铁稳态障碍的机制提供基础工作。

DESCRIPTION (provided by applicant): Several neurodegenerative conditions such as sporadic Creutzfeldt-Jakob disease (sCJD), Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD) are associated with imbalance of iron homeostasis in diseased brains, raising the possibility that redox-iron induced oxidative damage plays a significant role in the neurotoxicity associated with these disorders. Recent evidence from the Singh laboratory indicates a significant reduction of ferroxidase activity in sCJD affected human and scrapie infected mouse brains. Combined with the fact that sCJD brains show a phenotype of 'apparent' iron deficiency despite the presence of normal or increased brain iron levels, these observations suggest dysregulation of the normal iron homeostatic machinery in diseased brains. A recent report demonstrates decreased ferroxidase activity leading to iron accumulation in AD brains, suggesting that this phenomenon is shared by neurodegenerative disorders of disparate etiology. In an independent set of studies, the Mukhopadhayay laboratory reported that ceruloplasmin (Cp), a major ferroxidase in the brain, is down regulated by reactive oxygen species (ROS). Since iron is highly redox-active and a major contributor of ROS if mismanaged, it is likely that once initiated by a specific disease process, iron imbalance is perpetuated by ROS through down regulation of major brain ferroxidases. Based on these observations, we hypothesize that ROS mediated misregulation of brain specific ferroxidases contributes to iron imbalance in AD and sCJD. The proposed studies will test this hypothesis in two specific aims. In aim 1, the role of ROS in regulating specific ferroxidases will be investigated in cell models o AD and prion disease. Once the ferroxidases have been identified, their regulation will be compared with Cp which is known to be regulated by an mRNA decay mechanism in response to ROS. Subsequently, the minimal region of 3' UTR and binding proteins responsible for regulating ROS-mediated Cp activity will be identified. In aim 2, the ferroxidases identified in ai 1 will be evaluated for their expression and activity in mouse models of AD and scrapie infection during disease progression. The results will be compared with human brain tissue from AD and sCJD cases using ferroxidase assay and immunohistochemistry as the read-out. Successful completion of these studies will clarify the role of major brain ferroxidases in iron dyshomeostasis associated with AD and sCJD brains, and provide the ground-work for future studies on the mechanism of brain iron dyshomeostasis in PD, HD, and other neurodegenerative conditions associated with brain iron imbalance.