Hyperphosphorylation of cytoskeletal proteins seen in Alzheimer's disease is most probably the result of an imbalanced regulation in protein kinases and protein phosphatases (PP) in the affected neurons. Previous studies have revealed that PP-2A and PP-1 play important roles in the pathogenesis. Employing human neuroblastoma cells, we found that 10 nM calyculin A (CA), a selective inhibitor of PP-2A and PP-1, significantly increased phosphorylation and accumulation of neurofilament (NF) in the cells. Levels of NF-M (middle chain) and NF-L (light chain) mRNA decreased after CA treatment. Additionally, CA led to a decreased cell viability determined by MTT and crystal violet assay. Melatonin efficiently protects the cell from CA-induced alterations in NF hyperphosphorylation and accumulation, suppressed NF gene expression as well as decreased cell viability. It is concluded that inhibition of PP-2A/PP-1 by CA induces abnormalities in NF metabolism and cell survival, and melatonin efficiently arrests the lesions.

中文翻译：

---

褪黑素保护SH-SY5Y神经母细胞瘤细胞免受calyculin A诱导的神经丝损伤和神经毒性。

在阿尔茨海默氏病中发现的细胞骨架蛋白过度磷酸化很可能是受影响的神经元中蛋白激酶和蛋白磷酸酶（PP）调节失衡的结果。先前的研究表明，PP-2A和PP-1在发病机理中起重要作用。利用人类神经母细胞瘤细胞，我们发现10 nM calyculin A（CA）（PP-2A和PP-1的选择性抑制剂）显着增加了细胞中神经丝（NF）的磷酸化和积累。CA处理后，NF-M（中链）和NF-L（轻链）mRNA水平下降。另外，CA导致通过MTT和结晶紫测定法测定的细胞活力降低。褪黑素有效保护细胞免受CA诱导的NF过度磷酸化和积累的改变，抑制NF基因表达以及降低细胞活力。结论是，CA对PP-2A / PP-1的抑制作用会诱导NF代谢和细胞存活异常，而褪黑激素可以有效地抑制病变。