BACKGROUND Recent studies indicated that seeded fibril formation and toxicity of α-synuclein (α-syn) play a main role in the pathogenesis of certain diseases including Parkinson's disease (PD), multiple system atrophy, and dementia with Lewy bodies. Therefore, examination of compounds that abolish the process of seeding is considered a key step towards therapy of several synucleinopathies. METHODS Using biophysical, biochemical and cell-culture-based assays, assessment of eleven compounds, extracted from Chinese medicinal herbs, was performed in this study for their effect on α-syn fibril formation and toxicity caused by the seeding process. RESULTS Salvianolic acid B and dihydromyricetin were the two compounds that strongly inhibited the fibril growth and neurotoxicity of α-syn. In an in-vitro cell model, these compounds decreased the insoluble phosphorylated α-syn and aggregation. Also, in primary neuronal cells, these compounds showed a reduction in α-syn aggregates. Both compounds inhibited the seeded fibril growth with dihydromyricetin having the ability to disaggregate preformed α-syn fibrils. In order to investigate the inhibitory mechanisms of these two compounds towards fibril formation, we demonstrated that salvianolic acid B binds predominantly to monomers, while dihydromyricetin binds to oligomeric species and to a lower extent to monomers. Remarkably, these two compounds stabilized the soluble non-toxic oligomers lacking β-sheet content after subjecting them to proteinase K digestion. CONCLUSIONS Eleven compounds were tested but only two showed inhibition of α-syn aggregation, seeded fibril formation and toxicity in vitro. These findings highlight an essential beginning for development of new molecules in the field of synucleinopathies treatment.

中文翻译：

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草药提取物对α-突触核蛋白种子原纤维形成和毒性的抑制作用。

背景技术最近的研究表明，种子原纤维形成和α-突触核蛋白（α-syn）的毒性在某些疾病的发病机理中起主要作用，所述疾病包括帕金森氏病（PD），多系统萎缩和路易体痴呆。因此，检查消除播种过程的化合物被认为是治疗几种突触核蛋白病的关键步骤。方法采用生物物理，生化和细胞培养方法，对从中草药中提取的11种化合物对α-syn原纤维形成和接种过程中毒性的影响进行了评估。结果丹酚酸B和二氢杨梅素是两种强烈抑制α-syn原纤维生长和神经毒性的化合物。在体外细胞模型中，这些化合物减少了不溶性磷酸化的α-syn和聚集。同样，在原代神经元细胞中，这些化合物显示出α-syn聚集体的减少。两种化合物均具有二氢杨梅素抑制种子原纤维生长的能力，二氢杨梅素具有分解预先形成的α-syn原纤维的能力。为了研究这两种化合物对原纤维形成的抑制机制，我们证明了丹酚酸B主要与单体结合，而二氢杨梅素与寡聚体结合并且在较低程度上与单体结合。值得注意的是，这两种化合物经过蛋白酶K消化后，稳定了缺乏β-sheet含量的可溶性无毒低聚物。结论测试了11种化合物，但只有两种化合物在体外具有抑制α-syn聚集，种子原纤维形成和毒性的作用。