Role of Brain Ferroxidases in AD and sCJD Pathogenesis

描述(由申请人提供)：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)与疾病大脑中铁稳态的失衡有关，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。来自Singh实验室的最新证据表明，受sCJD感染的人和羊瘙痒病感染的小鼠大脑中的铁氧合酶活性显著降低。尽管大脑铁水平正常或升高，但sCJD大脑表现出明显的缺铁表型，结合这一事实，这些观察表明，疾病大脑中正常的铁平衡机制失调。最近的一份报告显示，铁氧合酶活性降低导致AD大脑中铁的积累，这表明这种现象与不同病因的神经退行性疾病相同。在另一项独立的研究中，MukHopadhayay实验室报告说，大脑中的一种主要铁氧合酶铜蓝蛋白(CP)受到活性氧物种(ROS)的下调。由于铁具有高度的氧化还原活性，如果管理不善，它是ROS的主要贡献者，很可能一旦由特定的疾病过程启动，ROS通过下调主要大脑铁氧合酶来维持铁的失衡。基于这些观察，我们假设ROS介导的脑特异性铁氧合酶的错误调节导致了AD和sCJD的铁失衡。拟议的研究将在两个具体目标上检验这一假设。在目标1中，ROS在调节特定铁氧合酶中的作用将在AD和Pron病的细胞模型中进行研究。一旦确定了铁氧合酶，就将它们的调节与CP进行比较，CP是通过ROS反应的mRNA衰变机制来调节的。随后，3‘非编码区的最小区域和负责调节ROS介导的CP活性的结合蛋白将被确定。在目标2中，将评估在ai 1中鉴定的铁氧合酶在疾病进展过程中在AD和瘙痒病感染的小鼠模型中的表达和活性。结果将与AD和sCJD患者的人脑组织进行比较，使用铁氧合酶检测和免疫组织化学方法作为读数。这些研究的成功完成将阐明脑内主要铁氧合酶在AD和sCJD脑内铁代谢紊乱中的作用，并为进一步研究PD、HD和其他与脑铁失衡相关的神经退行性疾病中脑铁代谢紊乱的机制奠定基础。

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.