Dementia with Lewy bodies is characterized by the accumulation of Lewy bodies and Lewy neurites in the CNS, both of which are composed mainly of aggregated α-synuclein phosphorylated at Ser129. Although phosphorylated α-synuclein is believed to exert toxic effects at the synapse in dementia with Lewy bodies and other α-synucleinopathies, direct evidence for the precise synaptic localization has been difficult to achieve due to the lack of adequate optical microscopic resolution to study human synapses. In the present study we applied array tomography, a microscopy technique that combines ultrathin sectioning of tissue with immunofluorescence allowing precise identification of small structures, to quantitatively investigate the synaptic phosphorylated α-synuclein pathology in dementia with Lewy bodies. We performed array tomography on human brain samples from five patients with dementia with Lewy bodies, five patients with Alzheimer’s disease and five healthy control subjects to analyse the presence of phosphorylated α-synuclein immunoreactivity at the synapse and their relationship with synapse size. Main analyses were performed in blocks from cingulate cortex and confirmed in blocks from the striatum of cases with dementia with Lewy bodies. A total of 1 318 700 single pre- or postsynaptic terminals were analysed. We found that phosphorylated α-synuclein is present exclusively in dementia with Lewy bodies cases, where it can be identified in the form of Lewy bodies, Lewy neurites and small aggregates (<0.16 µm³). Between 19% and 25% of phosphorylated α-synuclein deposits were found in presynaptic terminals mainly in the form of small aggregates. Synaptic terminals that co-localized with small aggregates of phosphorylated α-synuclein were significantly larger than those that did not. Finally, a gradient of phosphorylated α-synuclein aggregation in synapses (pre > pre + post > postsynaptic) was observed. These results indicate that phosphorylated α-synuclein is found at the presynaptic terminals of dementia with Lewy bodies cases mainly in the form of small phosphorylated α-synuclein aggregates that are associated with changes in synaptic morphology. Overall, our data support the notion that pathological phosphorylated α-synuclein may disrupt the structure and function of the synapse in dementia with Lewy bodies.

中文翻译：

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路易体痴呆中的突触磷酸化 α-突触核蛋白


路易体痴呆的特征是中枢神经系统中路易体和路易神经突的积累，两者主要由聚集的在 Ser129 处磷酸化的 α-突触核蛋白组成。尽管磷酸化α-突触核蛋白被认为对路易体痴呆和其他α-突触核蛋白病的突触产生毒性作用，但由于缺乏足够的光学显微镜分辨率来研究人类突触，因此很难获得精确突触定位的直接证据。在本研究中，我们应用阵列断层扫描（一种将组织超薄切片与免疫荧光相结合的显微镜技术，可以精确识别小结构）来定量研究路易体痴呆中的突触磷酸化 α-突触核蛋白病理学。我们对五名路易体痴呆患者、五名阿尔茨海默病患者和五名健康对照受试者的人脑样本进行了阵列断层扫描，以分析突触处磷酸化 α-突触核蛋白免疫反应性的存在及其与突触大小的关系。主要分析是在扣带皮层块中进行的，并在路易体痴呆病例的纹状体块中得到证实。总共分析了 1 318 700 个单个突触前或突触后末梢。我们发现磷酸化α-突触核蛋白仅存在于路易体痴呆病例中，可以以路易体、路易神经突和小聚集体(<0.16 µm ³ )的形式识别。 19% 到 25% 的磷酸化 α-突触核蛋白沉积物主要以小聚集体的形式存在于突触前末梢。 与磷酸化 α-突触核蛋白小聚集体共定位的突触末端明显大于未与磷酸化 α-突触核蛋白小聚集体共定位的突触末端。最后，观察到突触中磷酸化 α-突触核蛋白聚集的梯度（> 前 + > 后突触后）。这些结果表明，在路易体痴呆病例的突触前末端发现磷酸化 α-突触核蛋白，主要以小的磷酸化 α-突触核蛋白聚集体的形式存在，这些聚集体与突触形态的变化相关。总体而言，我们的数据支持这样的观点：病理性磷酸化 α-突触核蛋白可能会破坏路易体痴呆症中突触的结构和功能。