Molecular Pharmacology, Department of Biofunctional Evaluation, Gifu Pharmaceutical University, Gifu, Japan.
J Neurosci Res. 2012 Oct;90(10):1960-9. doi: 10.1002/jnr.23078. Epub 2012 Jun 5.
We evaluated time-dependent optic nerve degeneration and the role of endoplasmic reticulum (ER) stress in this process following retinal ganglion cell death in mice. Retinal damage was induced by intravitreal injection of N-methyl-D-aspartate (NMDA). Neurofilament heavy (NFH)- and phosphorylated NFH (pNFH)-positive axons were time-dependently decreased in optic nerves at 1, 3, 7, 14, and 28 days after NMDA injection. Expression of glial fibrillary acidic protein (GFAP)-positive astroglial cells and ionized calcium-binding adaptor molecule 1 (Iba1)-positive microglial cells showed a significant increase in the optic nerve at 7, 14, and 28 days after NMDA injection. In contrast, expression of myelin basic protein (MBP)-positive oligodendrocytes showed a significant decrease in the optic nerve at 7, 14, and 28 days after NMDA injection. In quantitative RT-PCR analysis, expressions of glucose-regulated protein 78 (Grp78)/BiP, Grp94, Calreticulin, C/EBP homologous protein (Chop), and the ER degradation enhancer mannosidase alpha-like 1 (Edem1) genes were increased in the optic nerve at 14 days after NMDA injection. In addition, the Grp94 gene was increased at 7 days after NMDA injection, and the Edem1 gene was increased at 3, 7, and 28 days after NMDA injection. GRP78 and CHOP proteins were colocalized with MBP in the optic nerve after NMDA injection. These findings suggest that the axonal degeneration is dramatic until 7 days after NMDA injection and that glial cells may play some role in the degeneration of the optic nerve. Furthermore, ER stress may play a pivotal role in the decrease of MBP-positive oligodendrocytes after NMDA-induced retinal damage.
我们评估了在小鼠视网膜神经节细胞死亡后，视神经的时间依赖性变性以及内质网（ER）应激在此过程中的作用。通过玻璃体内注射 N-甲基-D-天冬氨酸（NMDA）诱导视网膜损伤。在 NMDA 注射后 1、3、7、14 和 28 天，视神经中神经丝重链（NFH）和磷酸化 NFH（pNFH）阳性轴突呈时间依赖性减少。在 NMDA 注射后 7、14 和 28 天，胶质纤维酸性蛋白（GFAP）阳性星形胶质细胞和离子钙结合衔接分子 1（Iba1）阳性小胶质细胞的表达在视神经中明显增加。相比之下，在 NMDA 注射后 7、14 和 28 天，视神经中髓鞘碱性蛋白（MBP）阳性少突胶质细胞的表达明显减少。在定量 RT-PCR 分析中，在 NMDA 注射后 14 天，视神经中葡萄糖调节蛋白 78（Grp78）/BIP、Grp94、钙网蛋白、C/EBP 同源蛋白（Chop）和内质网降解增强甘露糖苷酶 alpha 样 1（Edem1）基因的表达增加。此外，在 NMDA 注射后 7 天 Grp94 基因增加，在 NMDA 注射后 3、7 和 28 天 Edem1 基因增加。GRP78 和 CHOP 蛋白与 NMDA 注射后视神经中的 MBP 共定位。这些发现表明，在 NMDA 注射后 7 天之前，轴突变性非常明显，胶质细胞可能在视神经变性中发挥一定作用。此外，内质网应激可能在 NMDA 诱导的视网膜损伤后 MBP 阳性少突胶质细胞减少中起关键作用。
