Wang Shuchao, Hu Tu, Wang Zhen, Li Na, Zhou Lihong, Liao Lvshuang, Wang Mi, Liao Libin, Wang Hui, Zeng Leping, Fan Chunling, Zhou Hongkang, Xiong Kun, Huang Jufang, Chen Dan
Department of Anatomy and Neurobiology, Central South University School of Basic Medical Sciences, Changsha, Hunan, China.
PLoS One. 2017 Sep 27;12(9):e0185388. doi: 10.1371/journal.pone.0185388. eCollection 2017.
Many studies on retinal injury and repair following elevated intraocular pressure suggest that the survival ratio of retinal neurons has been improved by various measures. However, the visual function recovery is far lower than expected. The homeostasis of retinal synapses in the visual signal pathway is the key structural basis for the delivery of visual signals. Our previous studies found that complicated changes in the synaptic structure between retinal neurons occurred much earlier than obvious degeneration of retinal ganglion cells in rat retinae. The lack of consideration of these earlier retinal synaptic changes in the rescue strategy may be partly responsible for the limited visual function recovery with the types of protective methods for retinal neurons used following elevated intraocular pressure. Thus, research on the modulatory mechanisms of the synaptic changes after elevated intraocular pressure injury may give new light to visual function rescue. In this study, we found that thrombospondin 2, an important regulator of synaptogenesis in central nervous system development, was distributed in retinal macroglia cells, and its receptor α2δ-1 was in retinal neurons. Cell cultures including mixed retinal macroglia cells/neuron cultures and retinal neuron cultures were exposed to elevated hydrostatic pressure for 2 h. The expression levels of glial fibrillary acidic protein (the marker of activated macroglia cells), thrombospondin 2, α2δ-1 and presynaptic proteins were increased following elevated hydrostatic pressure in mixed cultures, but the expression levels of postsynaptic proteins were not changed. SiRNA targeting thrombospondin 2 could decrease the upregulation of presynaptic proteins induced by the elevated hydrostatic pressure. However, in retinal neuron cultures, elevated hydrostatic pressure did not affect the expression of presynaptic or postsynaptic proteins. Rather, the retinal neuron cultures with added recombinant thrombospondin 2 protein upregulated the level of presynaptic proteins. Finally, gabapentin decreased the expression of presynaptic proteins in mixed cultures by blocking the interaction of thrombospondin 2 and α2δ-1. Taken together, these results indicate that activated macroglia cells may participate in alterations of presynaptic proteins of retinal neurons following elevated hydrostatic pressure, and macroglia-derived thrombospondin 2 may modulate these changes via binding to its neuronal receptor α2δ-1.
许多关于眼内压升高后视网膜损伤与修复的研究表明，通过各种措施，视网膜神经元的存活率有所提高。然而，视觉功能的恢复远低于预期。视觉信号通路中视网膜突触的稳态是视觉信号传递的关键结构基础。我们之前的研究发现，视网膜神经元之间突触结构的复杂变化比大鼠视网膜中视网膜神经节细胞的明显退化要早得多。在救援策略中未考虑这些早期视网膜突触变化，可能是眼内压升高后采用的视网膜神经元保护方法导致视觉功能恢复有限的部分原因。因此，研究眼内压损伤后突触变化的调节机制可能为视觉功能的挽救带来新的启示。在本研究中，我们发现血小板反应蛋白2（中枢神经系统发育中突触形成的重要调节因子）分布于视网膜大胶质细胞中，其受体α2δ-1存在于视网膜神经元中。将包括混合视网膜大胶质细胞/神经元培养物和视网膜神经元培养物在内的细胞培养物暴露于升高的静水压力下2小时。在混合培养物中，升高的静水压力后，胶质纤维酸性蛋白（活化大胶质细胞的标志物）、血小板反应蛋白2、α2δ-1和突触前蛋白的表达水平升高，但突触后蛋白的表达水平未改变。靶向血小板反应蛋白2的小干扰RNA可降低升高的静水压力诱导的突触前蛋白上调。然而，在视网膜神经元培养物中，升高的静水压力并未影响突触前或突触后蛋白的表达。相反，添加重组血小板反应蛋白2蛋白的视网膜神经元培养物上调了突触前蛋白的水平。最后，加巴喷丁通过阻断血小板反应蛋白2与α2δ-1的相互作用，降低了混合培养物中突触前蛋白的表达。综上所述，这些结果表明，活化的大胶质细胞可能参与了升高静水压力后视网膜神经元突触前蛋白的改变，并且大胶质细胞衍生的血小板反应蛋白2可能通过与其神经元受体α2δ-1结合来调节这些变化。
