Department of Neurology and Neurobiology and Aging, Kanazawa University Graduate School of Medical Science, Kanazawa, Japan.
Neurobiol Aging. 2012 Sep;33(9):2172-85. doi: 10.1016/j.neurobiolaging.2011.10.015. Epub 2011 Nov 25.
α-Synuclein (αS) assembly has been implicated as a critical step in the development of Lewy body diseases such as Parkinson's disease and dementia with Lewy bodies. Melatonin (Mel), a secretory product of the pineal gland, is known to have beneficial effects such as an antioxidant function and neuroprotection. To elucidate whether Mel has an antiassembly effect, here we used circular dichroism spectroscopy, photoinduced crosslinking of unmodified proteins, thioflavin S fluorescence, size exclusion chromatography, electron microscopy and atomic force microscopy to examine the effects of Mel on the αS assembly. We also examined the effects of Mel on αS-induced cytotoxicity by assaying 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide metabolism in αS-treated, primary neuronal cells. Initial studies revealed that Mel blocked αS fibril formation as well as destabilizing preformed αS fibrils. Subsequent evaluation of the assembly-stage specificity of the effect showed that Mel was able to inhibit protofibril formation, oligomerization, and secondary structure transitions. Importantly, Mel decreased αS-induced cytotoxicity. These data suggest a mechanism of action for Mel, inhibition of assembly of toxic polymers and protection of neurons from their effect.
α-突触核蛋白（αS）的聚集被认为是帕金森病和路易体痴呆等路易体疾病发展的关键步骤。褪黑素（Mel）是松果腺的分泌产物，已知具有抗氧化和神经保护等有益作用。为了阐明 Mel 是否具有抗聚集作用，我们使用圆二色性光谱、未修饰蛋白的光交联、硫黄素 S 荧光、排阻色谱、电子显微镜和原子力显微镜来研究 Mel 对 αS 聚集的影响。我们还通过测定 αS 处理的原代神经元细胞中的 3-[4,5-二甲基噻唑-2-基]-2,5-二苯基四氮唑溴化物代谢来研究 Mel 对 αS 诱导的细胞毒性的影响。初步研究表明，Mel 阻止了 αS 纤维的形成以及破坏预先形成的 αS 纤维。随后对该作用的组装阶段特异性进行评估，结果表明 Mel 能够抑制原纤维形成、寡聚化和二级结构转变。重要的是，Mel 降低了 αS 诱导的细胞毒性。这些数据表明 Mel 的作用机制是抑制毒性聚合物的组装并保护神经元免受其影响。
