Department of Biochemistry and Genetics, School of Medicine, Zhejiang University, 866th Yu Hang Tang Road, Hangzhou 310058, China.
Toxicology. 2011 Dec 18;290(2-3):218-29. doi: 10.1016/j.tox.2011.09.085. Epub 2011 Oct 5.
Cyanobacteria-derived microcystin-LR (MC-LR) commonly characterized as a hepatotoxin has recently been documented to show potential neurotoxicity, but the detailed neurotoxic effects of MC-LR and its mechanisms are unclear. In the present study, the neuroendocrine PC12 cell line was used to investigate whether MC-LR causes alterations of neuronal morphology and abnormalities in the phosphorylation status of cytoskeletal-associated proteins, and to elucidate the underlying mechanisms. The results showed that treatment of PC12 cells with MC-LR-triggered microtubule (MT) and actin cytoskeleton rearrangement, leading to a loss of their filamentous distribution and the display of a similar rearrangement pattern with decreased amounts of tubules or actin fibers in the cytosol and increased amounts of these structures in the cell periphery. An increase in MT tyrosination and a decrease in MT acetylation, which demonstrated MT destabilization, were also found. Moreover, MC-LR-induced hyperphosphorylation of the neural microtubule-associated protein tau, which correlated with an increase in soluble tau and a decrease in cytoskeleton-associated tau. Besides, the phosphorylation of the actin-associated protein HSP27 was also increased in MC-LR-treated cells. Furthermore, MC-LR caused a concentration-dependent decrease in the activity of protein phosphatase 2A (PP2A), and a dramatic activation of p38 mitogen-activated protein kinase (MAPK). The dephosphorylated tau dissociated from PP2A, whereas the tau phosphorylation status paralleled the activation of p38 MAPK. Pretreatment with the p38 MAPK inhibitor SB203580 effectively abolished hyperphosphorylation of tau and HSP27, and blocked MC-LR-triggered cytoskeletal alterations. Taken together, MC-LR leads to the reorganization of cytoskeletal architectures in PC12 cells and hyperphosphorylation of tau and HSP27, which may be caused by direct PP2A inhibition and indirect p38 MAPK activation.
蓝藻衍生的微囊藻毒素-LR（MC-LR）通常被认为是一种肝毒素，最近有研究表明其具有潜在的神经毒性，但 MC-LR 的详细神经毒性作用及其机制尚不清楚。在本研究中，使用神经内分泌 PC12 细胞系来研究 MC-LR 是否引起神经元形态的改变和细胞骨架相关蛋白磷酸化状态的异常，并阐明其潜在机制。结果表明，MC-LR 处理 PC12 细胞会触发微管（MT）和肌动蛋白细胞骨架的重排，导致其丝状分布丧失，并显示出类似的重排模式，即细胞浆中的小管或肌动蛋白纤维减少，细胞边缘的这些结构增加。还发现 MT 酪氨酸化增加和 MT 乙酰化减少，这表明 MT 不稳定。此外，MC-LR 诱导神经微管相关蛋白 tau 过度磷酸化，与可溶性 tau 增加和细胞骨架相关 tau 减少相关。此外，MC-LR 处理的细胞中肌动蛋白相关蛋白 HSP27 的磷酸化也增加。此外，MC-LR 导致蛋白磷酸酶 2A（PP2A）活性呈浓度依赖性下降，p38 丝裂原激活蛋白激酶（MAPK）显著激活。去磷酸化的 tau 与 PP2A 分离，而 tau 的磷酸化状态与 p38 MAPK 的激活平行。用 p38 MAPK 抑制剂 SB203580 预处理可有效抑制 tau 和 HSP27 的过度磷酸化，并阻止 MC-LR 触发的细胞骨架改变。综上所述，MC-LR 导致 PC12 细胞骨架结构的重排以及 tau 和 HSP27 的过度磷酸化，这可能是由直接的 PP2A 抑制和间接的 p38 MAPK 激活引起的。
