Nanoscale metallomics and mineralization: advanced spectro-microscopy determination of the role of iron and calcium in Alzheimer's disease

最常见的痴呆症是阿尔茨海默病，据报道，这是一种影响全球3000万人的神经退行性疾病，但目前还没有治愈方法，准确诊断和治疗的机会也很有限。这种疾病的特点是大脑的病理特征，包括沉积在大脑灰质细胞外的致密淀粉样蛋白聚集体(斑块)，以及由于异常tau蛋白的“缠结”而在神经元内部造成的严重损害。这些斑块和缠结被认为是导致神经元死亡和大脑进行性退化的原因。这种退化究竟是如何由这些蛋白质沉积介导的，目前还没有得到正确的理解。然而，被称为自由基的高活性化学物种催化的氧化应激对神经元的损害被认为起着重要作用。此外，大量证据现在表明，铁的调节失调导致大脑中有害的活性(亚铁)过量，是导致疾病的一个促成因素，并可能与导致氧化应激的过程有关。异常蛋白质沉积与铁以及其他金属之间的相互作用是神经退行性疾病的常见特征。在阿尔茨海默病中，金属-蛋白质的相互作用被认为有助于在死后观察到的疾病脑组织中形成含有活性(有害)铁的沉积物。此外，在异常蛋白质沉积区域内观察到了不寻常的钙生物矿化，这表明钙也可能在疾病中发挥重要作用。识别这些矿物产品是描述阿尔茨海默病这一方面的重要第一步。然而，为了在诊断和治疗方面取得进展，有必要了解金属-蛋白质相互作用如何在促进治疗干预的水平上促进疾病过程，以及蛋白质沉积中产生的铁和钙矿化在多大程度上可以作为疾病的早期标志。我们的目标是使用敏感和特定的分析方法来探索阿尔茨海默病脑组织中铁和钙的化学和矿物状态，并进行实验来研究金属-蛋白质相互作用如何导致蛋白质沉积的启动和演化(化学和结构)。此外，我们将评估在人脑组织中形成的金属-蛋白质聚集体以及人工创造的聚集体对金属螯合剂治疗的反应，目前正在开发的金属螯合剂是治疗阿尔茨海默氏症和其他神经退行性疾病的潜在药物。为了确保这个项目的成功，我们组建了一个独特的跨学科研究团队，拥有强大的国际记录，以我们在这一领域的成功前期工作为基础，应用先进的同步辐射X射线显微镜和质谱学技术来探测阿尔茨海默氏症组织中生物无机化学的纳米级变化。该项目的一个重要方面是，在所有情况下，我们都将使用这些专家技术，结合传统的成像和组织学来支持我们的评估。在此基础上，我们将全面描述阿尔茨海默病的这一基本过程，解决有关金属-蛋白质相互作用以及如何修改它们的关键悬而未决的问题。蛋白质的异常沉积与铁和其他金属在相关疾病中的处理方式变化之间的相似之处，将使该项目中开发的方法易于翻译，从而能够对其他形式的神经退行性疾病产生同等影响。随着络合治疗的临床进展和临床MRI无创性追踪脑铁状态的范围的扩大，这一项目不仅及时，而且紧迫。

The most common form of dementia is Alzheimer's disease, a neurodegenerative disorder that reportedly affects 30 million people worldwide, yet for which there is no cure and only limited opportunities for accurate diagnosis and treatment. The disease is characterised by pathological hallmarks in the brain including dense amyloid protein aggregates (plaques) that are deposited outside cells in the grey matter of the brain, together with significant damage internally in neurons due to 'tangles' of abnormal tau protein. These plaques and tangles are understood to contribute to the death of neurons and the progressive degeneration of the brain. Exactly how this degeneration is mediated by these protein deposits is not yet properly understood. However, oxidative stress damage to neurons, catalysed by highly reactive chemical species known as free radicals, is understood to play a significant role. In addition, substantial evidence now suggests that the dysregulation of iron resulting in a harmful excess of reactive (ferrous) iron in the brain, is a contributing factor in the disease, and may be implicated in the processes leading to oxidative stress. Interactions between aberrant protein deposits and iron, as well as other metals, are common features of neurodegenerative disorders. In Alzheimer's disease, metal-protein interactions are hypothesized to contribute to the formation of deposits containing reactive (harmful) iron observed post-mortem in diseased brain tissue. In addition, unusual calcium bio-mineralisation has been observed within areas of aberrant protein deposition suggesting that calcium could also play a significant role in the disease. Identifying these mineral products is an important first step in describing this aspect of Alzheimer's disease. However in order to make progress in diagnosing and treating the disease, it is necessary to understand how the metal-protein interactions contribute to the disease process at a level facilitating therapeutic intervention, and the extent to which resulting iron and calcium mineralization in the protein deposits can serve as an early-stage marker of the disease. We aim to explore the chemical and mineral state of iron and calcium in Alzheimer's disease brain tissue using sensitive and specific analytical methods, as well performing experiments to investigate how metal-protein interactions can lead to the initiation and evolution (both chemical and structural) of the protein deposits. Further, we will assess how the metal-protein aggregates formed in human brain tissue, as well as those created artificially, respond to treatments with the metal chelating agents that are currently being developed as potential drug therapies for Alzheimer's and other neurodegenerative conditions. To ensure the success of this project we have assembled a unique interdisciplinary research team, with a strong international track record, to build upon our successful preliminary work in this area, applying a combination of advanced synchrotron x-ray microscopy and mass spectrometry techniques to probe nanoscale variations in the bio-inorganic chemistry occurring in Alzheimer's tissue. An important aspect of the project is that in all cases we will support our evaluation using these specialist techniques, with conventional imaging and histology. From this we will build a comprehensive description of this fundamental process in Alzheimer's disease, addressing key outstanding questions about the metal-protein interactions and how they may be modified. The parallels between aberrant protein deposition and altered handling of iron and other metals in related disorders, will allow the approach developed in this project to be readily translated, enabling equivalent impact for other forms of neurodegenerative disease. With clinical advances in chelation therapy and improved scope to track brain iron status non-invasively by clinical MRI, this project is not just timely but also urgent.