Affiliated Eye Hospital of Nanchang University, Jiangxi Research Institute of Ophthalmology & Visual Science, Jiangxi Provincial Key Laboratory for Ophthalmology, Nanchang, Jiangxi, China.
Affiliated Eye Hospital of Nanchang University, Jiangxi Research Institute of Ophthalmology & Visual Science, Jiangxi Provincial Key Laboratory for Ophthalmology, Nanchang, Jiangxi, China.
Exp Eye Res. 2018 Nov;176:10-19. doi: 10.1016/j.exer.2018.06.014. Epub 2018 Jun 18.
Damage and loss of retinal ganglion cells (RGCs) can cause visual impairment. The underlying molecular mechanisms that mediate RGC death in ischemic retinal diseases are still unclear. In this study, we sought to understand the neuroprotective effect of rapamycin, the selective inhibitor of mTORC1, on RGC survival and the cellular mechanics that mediate this effect. Recent studies have reported that the epidermal growth factor (EGF) receptor shows an increase in expression in astrocytes after injury, and this receptor can promote their transformation into reactive astrocytes. Our results, along with previous works from others, show the colocalization of phosphor-EGF receptors with the astrocyte marker glial fibrillary acidic proteins in reactive astrocytes in the injured retina. In our in vitro studies, using primary astrocyte cultures of the optic nerve head of rats, showed that rapamycin significantly blocked EGF-induced mTOR signaling mainly through the PI3K/Akt pathway in primary astrocytes, but not through the MAPK/Erk pathway. Additionally, rapamycin dramatically inhibited the activation of mTOR signaling in our ratinal ischemia-reperfusion (I/R) injury model in vivo. Astrocyte activation was assessed by immunostaining retinal flat mounts or cross sections with antibody against GFAP, and we also used western blots to detect the expression of GFAP. Taken together, these results revealed that rapamycin decreases the activation of astrocytes after retinal ischemia-reperfusion injury. Furthermore, rapamycin can improve retinal RGC survival in rats during I/R, as detected by FluoroGold labeling. Our data reveals the neuroprotective effects of rapamycin in an experimental retina injury model, possibly through decreasing glial-dependent intracellular signaling mechanisms for suppressing apoptosis of RGCs. Our study also presents an approach to targeting reactive astrocytes for the treatment of optic neurodegenerations.
视网膜神经节细胞 (RGC) 的损伤和丢失可导致视力障碍。介导缺血性视网膜疾病中 RGC 死亡的潜在分子机制尚不清楚。在这项研究中，我们试图了解雷帕霉素（mTORC1 的选择性抑制剂）对 RGC 存活的神经保护作用及其介导这种作用的细胞机制。最近的研究报告称，表皮生长因子 (EGF) 受体在损伤后星形胶质细胞中的表达增加，并且该受体可以促进它们转化为反应性星形胶质细胞。我们的结果以及其他人之前的工作表明，在损伤的视网膜中，磷酸化 EGF 受体与星形胶质细胞标志物胶质纤维酸性蛋白在反应性星形胶质细胞中共定位。在我们的体外研究中，使用大鼠视神经头部的原代星形胶质细胞培养物表明，雷帕霉素通过 PI3K/Akt 通路而非 MAPK/Erk 通路显著阻断 EGF 诱导的 mTOR 信号，主要在原代星形胶质细胞中。此外，雷帕霉素在体内大鼠视网膜缺血再灌注 (I/R) 损伤模型中显著抑制 mTOR 信号的激活。通过用针对 GFAP 的抗体对视网膜平面或横截面进行免疫染色来评估星形胶质细胞激活，我们还使用 Western blot 检测 GFAP 的表达。总之，这些结果表明雷帕霉素可降低视网膜 I/R 损伤后星形胶质细胞的激活。此外，雷帕霉素可通过 FluoroGold 标记改善 I/R 期间大鼠视网膜 RGC 的存活。我们的数据揭示了雷帕霉素在实验性视网膜损伤模型中的神经保护作用，可能是通过减少依赖神经胶质的细胞内信号机制来抑制 RGC 的凋亡。我们的研究还提出了一种针对反应性星形胶质细胞的治疗视神经退行性变的方法。
