Department of Neurology, Washington University School of Medicine, St Louis, MO, USA.
Ann Neurol. 2013 Jan;73(1):104-19. doi: 10.1002/ana.23748. Epub 2012 Dec 7.
Although amyloid-beta (Aβ) peptide deposition into insoluble plaques is a pathological hallmark of Alzheimer disease; soluble oligomeric Aβ has been hypothesized to more directly underlie impaired learning and memory in dementia of the Alzheimer type. However, the lack of a sensitive, specific, and quantitative assay for Aβ oligomers has hampered rigorous tests of this hypothesis.
We developed a plate-based single molecule counting fluorescence immunoassay for oligomeric Aβ sensitive to low pg/ml concentrations of synthetic Aβ dimers using the same Aβ-specific monoclonal antibody to both capture and detect Aβ. The Aβ oligomer assay does not recognize monomeric Aβ, amyloid precursor protein, or other non-Aβ peptide oligomers.
Aβ oligomers were detected in aqueous cortical lysates from patients with dementia of the Alzheimer type and nondemented patients with Aβ plaque pathology. However, Aβ oligomer concentrations in demented patients' lysates were tightly correlated with Aβ plaque coverage (r = 0.88), but this relationship was weaker in those from nondemented patients (r = 0.30) despite equivalent Aβ plaque pathology. The ratio of Aβ oligomer levels to plaque density fully distinguished demented from nondemented patients, with no overlap between groups in this derived variable. Other Aβ and plaque measures did not distinguish demented from nondemented patients. Aβ oligomers were not detected in cerebrospinal fluid with this assay.
The results raise the intriguing hypothesis that the linkage between plaques and oligomers may be a key pathophysiological event underlying dementia of the Alzheimer type. This Aβ oligomer assay may be useful for many tests of the oligomer hypothesis.
尽管淀粉样β（Aβ）肽沉积为不溶性斑块是阿尔茨海默病的病理学标志；但可溶性寡聚体 Aβ 被认为更直接导致阿尔茨海默型痴呆的学习和记忆受损。然而，由于缺乏敏感、特异和定量检测 Aβ 寡聚体的方法，该假说一直未能得到严格检验。
我们开发了一种基于平板的单分子计数荧光免疫测定法，用于检测寡聚体 Aβ，该方法对合成 Aβ 二聚体的低 pg/ml 浓度敏感，使用相同的 Aβ 特异性单克隆抗体进行 Aβ 的捕获和检测。该 Aβ 寡聚体测定法不识别单体 Aβ、淀粉样前体蛋白或其他非 Aβ 肽寡聚体。
在来自阿尔茨海默病患者和无痴呆的具有 Aβ 斑块病理学患者的皮质水相裂解物中检测到 Aβ 寡聚体。然而，痴呆患者裂解物中的 Aβ 寡聚体浓度与 Aβ 斑块覆盖率密切相关（r = 0.88），但在无痴呆患者中相关性较弱（r = 0.30），尽管 Aβ 斑块病理学相当。Aβ 寡聚体水平与斑块密度的比值完全区分了痴呆和非痴呆患者，在该衍生变量中两组之间没有重叠。其他 Aβ 和斑块测量值不能区分痴呆和非痴呆患者。该测定法未在脑脊液中检测到 Aβ 寡聚体。
结果提出了一个有趣的假设，即斑块和寡聚体之间的联系可能是阿尔茨海默病痴呆的关键病理生理事件。该 Aβ 寡聚体测定法可能对该假说的许多检验有用。
