Ma Lan, Yu Hai-Jun, Gan Sheng-Wei, Gong Rui, Mou Ke-Jie, Xue Jun, Sun Shan-Quan
Institute of Neuroscience, Chongqing Medical University, Chongqing, China.
Bishan Hospital of the First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
Neurosci Lett. 2017 Mar 22;644:55-61. doi: 10.1016/j.neulet.2017.02.038. Epub 2017 Feb 24.
Oligodendrocyte apoptosis mediated demyelination is a pathological change characteristic of compressed spinal cord injury (CSCI). However, the mechanism of demyelination due to oligodendrocyte apoptosis is not known. In this study, after successfully establishing a rat CSCI model using a custom-made compressor, we investigated the pathological changes, MBP expression, as well as apoptosis-related protein (p53, active caspase-3) expression to determine whether or not apoptosis and demyelination occurred after injury. To understand the possible mechanism of oligodendrocyte apoptosis, caspase-12 and cytochrome C were analyzed to explore the relationship between oligodendrocyte apoptosis and endoplasmic reticulum(ER)-mitochondria interaction. The transcription factor, E2F1, was also detected by immunofluorescence and Western blot assays. The results showed that CSCI increased the expression levels of p53, E2F1 and active caspase-3 followed by the swelling and breakdown of myelin sheaths. The number of myelinated nerve fibers also decreased with down-regulated expression of MBP. Expression levels of caspase-12 and cytochrome C were enhanced along with a reduction in the number of oligodendrocytes. After treatment of CSCI in rats with Pifithrin-μ(PFT-μ), a specific inhibitor of p53, pathomorphological changes of myelin sheath improved significantly. Expression levels of E2F1, active caspase-3, caspase-12 and cytochrome C were down-regulated, consistent with reduced the number of apoptotic oligodendrocytes. These results demonstrated that over-expression of p53 could mediate oligodendrocyte apoptosis thus resulting in demyelination in two ways; by enhancing ER-mitochondria interaction and by triggering the E2F1 mediated apoptosis pathway.
少突胶质细胞凋亡介导的脱髓鞘是脊髓压迫性损伤（CSCI）的一种病理变化特征。然而，少突胶质细胞凋亡导致脱髓鞘的机制尚不清楚。在本研究中，使用定制的压迫器成功建立大鼠CSCI模型后，我们研究了病理变化、髓鞘碱性蛋白（MBP）表达以及凋亡相关蛋白（p53、活化的半胱天冬酶-3）表达，以确定损伤后是否发生凋亡和脱髓鞘。为了解少突胶质细胞凋亡的可能机制，分析了半胱天冬酶-12和细胞色素C，以探讨少突胶质细胞凋亡与内质网（ER）-线粒体相互作用之间的关系。还通过免疫荧光和蛋白质印迹分析检测了转录因子E2F1。结果显示，CSCI增加了p53、E2F1和活化的半胱天冬酶-3的表达水平，随后髓鞘肿胀和破坏。有髓神经纤维数量也随着MBP表达下调而减少。半胱天冬酶-12和细胞色素C的表达水平升高，同时少突胶质细胞数量减少。用p53的特异性抑制剂匹非尼酮-μ（PFT-μ）治疗大鼠CSCI后，髓鞘的病理形态学变化明显改善。E2F1、活化的半胱天冬酶-3、半胱天冬酶-12和细胞色素C的表达水平下调，与凋亡少突胶质细胞数量减少一致。这些结果表明，p53的过度表达可通过增强ER-线粒体相互作用和触发E2F1介导的凋亡途径这两种方式介导少突胶质细胞凋亡，从而导致脱髓鞘。
