Ma Xia, Han Jingling, Wu Qiyun, Liu Hanzhang, Shi Shangshi, Wang Cheng, Wang Yueran, Xiao Jing, Zhao Jianya, Jiang Junkang, Wan Chunhua
Department of Occupational Medicine and Environmental Toxicology, School of Public Health, Nantong University, Nantong, People's Republic of China.
The Jiangsu Province Key Laboratory of Neuroregeneration, Nantong University, Nantong, People's Republic of China.
Toxicol Lett. 2015 May 19;235(1):17-27. doi: 10.1016/j.toxlet.2014.12.019. Epub 2015 Mar 16.
Overexposure to manganese (Mn) has been known to induce neuronal death and neurodegenerative symptoms. However, the precise mechanisms underlying Mn neurotoxicity remain incompletely understood. In the present study, we established a Mn-exposed rat model and found that downregulation of wild type p53-induced phosphatase 1 (Wip1) might contribute to p53 activation and resultant neuronal apoptosis following Mn exposure. Western blot and immunohistochemical analyses revealed that the expression of Wip1 was markedly decreased following Mn exposure. In addition, immunofluorescence assay demonstrated that Mn exposure led to significant reduction in the number of Wip1-positive neurons. Accordingly, the expression of Mdm2 was progressively decreased, which was accompanied with markedly increased expression of p53, as well as the ratio of Bax/Bcl-xl. Furthermore, we showed that Mn exposure decreased the viability and induced apparent apoptosis in NFG-differentiated neuron-like PC12 cells. Importantly, the expression of Wip1 decreased progressively, whereas the level of cellular p53 and the ratio of Bax/Bcl-xl were elevated, which resembled the expression of the proteins in animal model studies. Depletion of p53 significantly ameliorated Mn-mediated cytotoxic effect in PC12 cells. In addition, ectopic expression of Wip1 attenuated Mn-induced p53 signaling as well as apoptosis in PC12 cells. Finally, we observed that depletion of Wip1 augmented Mn-induced apoptosis in PC12 cells. Collectively, these findings suggest that downregulated Wip1 expression plays an important role in Mn-induced neuronal death in the brain striatum via the modulation of p53 signaling.
已知过度暴露于锰（Mn）会导致神经元死亡和神经退行性症状。然而，锰神经毒性的精确机制仍未完全了解。在本研究中，我们建立了锰暴露大鼠模型，发现野生型p53诱导磷酸酶1（Wip1）的下调可能有助于锰暴露后p53的激活及由此导致的神经元凋亡。蛋白质印迹和免疫组织化学分析显示，锰暴露后Wip1的表达明显降低。此外，免疫荧光分析表明，锰暴露导致Wip1阳性神经元数量显著减少。相应地，Mdm2的表达逐渐降低，同时p53的表达以及Bax/Bcl-xl的比值显著增加。此外，我们发现锰暴露降低了NFG分化的神经元样PC12细胞的活力并诱导明显的凋亡。重要的是，Wip1的表达逐渐降低，而细胞p53水平和Bax/Bcl-xl的比值升高，这与动物模型研究中的蛋白质表达情况相似。p53的缺失显著改善了锰对PC12细胞的细胞毒性作用。此外，Wip1的异位表达减弱了锰诱导的PC12细胞中的p53信号传导以及凋亡。最后，我们观察到Wip1的缺失增强了锰诱导的PC12细胞凋亡。总的来说，这些发现表明，Wip1表达下调通过调节p53信号传导在锰诱导的脑纹状体神经元死亡中起重要作用。
