Human in vivo stable isotope labeling kinetics (iSILK) to quantify brain amyloid plaque kinetics

项目摘要/摘要 鉴于FDA最近批准了一种基于抗体的药物，可以根据测量去除淀粉样斑块 通过正电子发射断层扫描靶向淀粉样蛋白(PET-淀粉样蛋白)(Aducanamab1)，FDA批准 Preciality-AD血液检测2，并提交了加速批准lecanemab和donanemab的申请- PET-淀粉样蛋白成像3-5显示基于抗体的药物也能减少斑块--迫切需要 更好地了解斑块中的天然淀粉样β蛋白(Aβ)周转。 这项建议的总体目标是定量表征斑块内Aβ周转率 用稳定同位素标记动力学研究阿尔茨海默病(AD)不同阶段人脑组织中的活体 (丝绸)。根据PET3-5的测量，多种基于抗体的药物几乎完全消除了斑块 再加上认知衰退速度的降低，支持淀粉样蛋白病理作为关键驱动因素的作用 阿尔茨海默病的发病机制。然而，治疗的持续时间和可能的停止部分取决于是否 淀粉样斑块继续生长并翻转。其他药物(如BACE抑制剂)可以阻止淀粉样斑块 生长和斑块负荷的最小逆转(~4%/年的PET)，表明有一些自然的缓慢 淀粉样斑块的周转。因此，抗淀粉样蛋白疗法的药物试验和临床应用必须基于 天然斑块生长的准确模型。 最近，对人淀粉样斑块体内代谢生长的显微分辨已经实现。 通过将丝绸与基于质谱学的成像方法(“Isilk”)相结合，以更好地表征蛋白质和 脑实质内的多肽动力学。具体地说，贝特曼实验室使用了纳米级的二次离子 与蚕丝偶联的质谱仪(NanoSIMS)直接成像蛋白质沉积的分布和速度 在3名AD6患者的死后组织中纳米级的斑块中。然而，NanoSIMS 成像无法确定哪些分子含有检测到的同位素。相比之下，基质辅助激光 解吸/电离(MALDI)基于质谱学的成像(MALDI-IMS)允许化学特异性的Aβ AD小鼠模型和死后脑病理结构的多肽成像研究 因此，该小组最近展示了MALDI与丝绸的结合 跟踪斑块形成的动力学。 使用生前口服15N-1标记的人类患者的死后组织 被标记为螺旋藻，我们将用MALDI-IMS表征具有AD病理谱的大脑中的Aβ周转。 这些测量将提供AD相关蛋白质动力学的隔室模型，从 斑块的微观结构并延伸到整个身体，这是一种特别重要的模型 临床批准的诊断生物标记物2、疾病修正疗法3-5的曙光时代，以及迫切需要 以准确了解AD的最早迹象。

Project summary / abstract Given the recent FDA approval of an antibody-based drug that can remove amyloid plaques as measured by positron-emission tomography targeting amyloid (PET-amyloid) (aducanamab1), the FDA approval of the Precivity-AD blood test2, and applications submitted for accelerated approval of lecanemab and donanemab – antibody-based drugs also shown to reduce plaque by PET-amyloid imaging3–5 – there is an urgent need to better understand the natural amyloid-beta (Aβ) turnover in plaques. The overall goal of this proposal is to quantitatively characterize the rate of Aβ turnover within plaques in vivo, in human brain tissue at various stages of Alzheimer's disease (AD) using stable isotope labeling kinetics (SILK). That multiple antibody-based drugs nearly completely remove plaques as measured by PET3–5, taken together with a reduction in the rate of cognitive decline, supports a role for amyloid pathology as critical driver of AD pathogenesis. However, the duration and possible cessation of treatment is partly dependent on whether amyloid plaques continue to grow and turn over. Other drugs (e.g. BACE inhibitors) can stop amyloid plaque growth with minimal reversal of plaque load (~4%/year by PET), suggesting that there is some natural slow turnover of amyloid plaques. Drug trials and clinical use of anti-amyloid therapies thus must be based on accurate models of natural plaque growth. Very recently, microscopic resolution of in vivo metabolic growth of human amyloid plaques was achieved by combining SILK with mass spectrometric-based imaging methods (“iSILK”) to better characterize protein and peptide kinetics within brain parenchyma. Specifically, the Bateman laboratory used nanoscale secondary ion mass spectrometry (NanoSIMS) coupled to SILK to directly image the distribution and rate of protein deposition in plaques at the nanometer level in postmortem tissue from 3 human patients with AD6. However, NanoSIMS imaging fails to specify which molecules contain the detected isotopes. In contrast, matrix-assisted laser desorption / ionization (MALDI) mass spectrometry-based imaging (MALDI-IMS) allows chemically-specific Aβ peptide imaging of pathologic structures in AD mouse models and postmortem brain, which has been pioneered by the Hanrieder lab7–10. Consequently, the group very recently demonstrated MALDI in combination with SILK to follow plaque formation dynamics10. Using postmortem tissue from human patients previously labeled during life by oral ingestion of 15N- labeled spirulina, we will characterize Aβ turnover by MALDI-IMS in brains with a spectrum of AD pathology. These measurements will inform a compartmental model of AD-related protein kinetics starting at the microscopic structure of the plaque and extending throughout the body, a particularly important model in the dawning era of clinically-approved diagnostic biomarkers2, disease-modifying therapies3–5, and the critical need for a precise understanding of the earliest signs of AD.