Anderson Don H, Talaga Kevin C, Rivest Alexander J, Barron Ernesto, Hageman Gregory S, Johnson Lincoln V
Center for the Study of Macular Degeneration, Neuroscience Research Institute, University of California, Santa Barbara, CA 93106, USA.
Exp Eye Res. 2004 Feb;78(2):243-56. doi: 10.1016/j.exer.2003.10.011.
Recent studies strongly suggest that drusen, the extracellular deposits associated with age-related macular degeneration (AMD), are a manifestation of local inflammatory events. New evidence indicates that substructural elements within drusen contain activated complement components as well as amyloid beta (Abeta), a major pro-inflammatory component of Alzheimer's disease plaques. We characterized the ultrastructural organization and histochemical staining properties of these Abeta-containing elements in order to further assess their significance in drusen formation and AMD pathogenesis.
We used differential interference contrast optics, laser scanning confocal immunofluorescence, and immunogold electron microscopy to characterize the structural properties and molecular composition of Abeta-containing elements in drusen. We obtained estimates of their frequency from montages of electron micrographs gathered from 152 human donor eyes ranging from 9 to 91 years of age.
Spherical Abeta-containing elements, which are typically organized as concentric ring-like structures, are common substructural components of drusen. They stain with thioflavin T, but are not stained by Congo red; nor do they bind cationic, lipophilic, or nucleic acid-binding fluorescent dyes. Ultrastructurally, they are composed of a central core, one or more concentric inner rings with intervening electron lucent layers, and an electron dense outer shell. Immunogold labeling indicates that most Abeta immunoreactivity is associated with the outer layers that consist of densely-packed spherical subunits. No longitudinally-oriented fibril arrays, characteristic of aggregated amyloid fibrils in the brain, are evident. Other prominent drusen-associated proteins including the terminal complement complex C5b-9, vitronectin, apolipoprotein E, serum amyloid P component, and ubiquitin are excluded from the spheres.Conclusions. These structures embedded in drusen appear to represent a new type of macromolecular assembly that contains Abeta as well as activated complement components. The presence of Abeta in these extracellular deposits is an additional indication that some of the pathogenic pathways that give rise to drusen and AMD may be shared with other neurodegenerative diseases characterized by misfolded protein deposition and aggregation.
近期研究有力地表明，与年龄相关性黄斑变性（AMD）相关的细胞外沉积物——玻璃膜疣，是局部炎症事件的一种表现。新证据表明，玻璃膜疣内的亚结构成分包含活化的补体成分以及β-淀粉样蛋白（Aβ），后者是阿尔茨海默病斑块的主要促炎成分。我们对这些含Aβ成分的超微结构组织和组织化学染色特性进行了表征，以进一步评估它们在玻璃膜疣形成和AMD发病机制中的意义。
我们使用微分干涉对比光学、激光扫描共聚焦免疫荧光和免疫金电子显微镜来表征玻璃膜疣中含Aβ成分的结构特性和分子组成。我们从152只年龄在9至91岁的人类供体眼睛收集的电子显微镜图像蒙片中获得了它们的频率估计值。
含Aβ的球形成分通常组织为同心环状结构，是玻璃膜疣常见的亚结构成分。它们用硫黄素T染色，但不被刚果红染色；也不与阳离子、亲脂性或核酸结合荧光染料结合。在超微结构上，它们由一个中央核心、一个或多个带有中间电子透明层的同心内环以及一个电子致密的外壳组成。免疫金标记表明，大多数Aβ免疫反应性与由紧密堆积的球形亚基组成的外层相关。没有明显的纵向排列的纤维阵列，而这种阵列是大脑中聚集的淀粉样纤维的特征。其他与玻璃膜疣相关的突出蛋白质，包括末端补体复合物C5b - 9、玻连蛋白、载脂蛋白E、血清淀粉样P成分和泛素，都被排除在这些球体之外。
这些嵌入玻璃膜疣的结构似乎代表了一种新型的大分子组装体，其包含Aβ以及活化的补体成分。这些细胞外沉积物中Aβ的存在进一步表明，导致玻璃膜疣和AMD的一些致病途径可能与其他以错误折叠的蛋白质沉积和聚集为特征的神经退行性疾病相同。
