褪黑素与维生素E对抗花萼海绵诱癌素毒性作用的差异

Mechanisms for Protection of Melatonin and Vitamine Eagainst Calyculin A-induced Cytotoxicities

最近的研究发现,褪黑素对花萼海绵诱癌素(calyculin A,CA)引起的骨架蛋白神经细丝异常过度磷酸化有保护作用. 为进一步探讨褪黑素对骨架蛋白τ异常过度磷酸化的保护作用及其机制,分别用CA, CA+褪黑素或CA+维生素E处理鼠野生型成神经瘤细胞(N2awt),采用MTT法测定细胞存活率,用免疫印迹法测定τ蛋白磷酸化水平,用32P-特异底物标记技术检测GSK-3和PP-2A活性,并进一步测定了细胞内脂质过氧化产物丙二醛含量,细胞内过氧化氢酶、超氧化物歧化酶和谷胱甘肽过氧化物酶活性. 结果显示:褪黑素不仅对CA引起的抗氧化酶活性降低和脂质过氧化的保护作用强于经典抗氧化剂维生素E,而且对τ蛋白磷酸化的保护作用也强于经典抗氧化剂维生素E;褪黑素可同时激活PP-2A又抑制GSK-3,而维生素E同时抑制两种酶的活性. 研究提示:褪黑素既通过抗氧化作用,也通过调节细胞内磷酸化平衡对抗CA对神经细胞的毒性作用.

It has been recently demonstrated that melatonin protects cells from calyculin A (CA)-induced neurofilament hyperphosphorylation. To further explore the mechanism of melatonin, the wild type neuroblast cells (N2awt) were treated with CA or CA and melatonin or CA and vitamin E, and detected the levels of tau phosphorylation, the activities of GSK-3 and PP-2A, as well as the antioxidant activities of melatonin and vitamin E against CA. It has been found that the antioxidant activity of melatonin and its protection on tau hyperphosphorylation at Ser199/202 and Ser396/404 and Ser422 sites are stronger than that of vitamin E, at the same time, melatonin increases the activity of PP-2A and decreases the activity of GSK-3 while vitamin E decreases the activities of PP-2A and GSK-3. These results suggest that melatonin protects neuroblast cells from CA-induced cytotoxicities not only through its antioxidant effect but also through its regulation of the phosphorylation system.