Maisonneuve-Rosemont Hospital Research Centre and Department of Ophthalmology, University of Montreal, 5415 boul. de l'Assomption, Montréal, Quebec, Canada.
Brain. 2010 Sep;133(9):2612-25. doi: 10.1093/brain/awq105. Epub 2010 May 21.
Optic neuropathy is the leading cause of irreversible blindness, and a paradigm for central nervous system axonal disease. The primary event is damage to retinal ganglion cell axons, with subsequent death of the cell body by apoptosis. Trials of neuroprotection for these and other neuronal diseases have mostly failed, primarily because mechanisms of neuroprotection in animals do not necessarily translate to humans. We developed a methodology for imaging an intracellular transduction pathway that signals neuronal death in the living animal. Using longitudinal confocal scanning multilaser ophthalmoscopy, we identified the production of superoxide within retrograde-labelled rat retinal ganglion cells after optic nerve transection. Superoxide was visualized by real-time imaging of its reaction product with intravitreally administered hydroethidine and confirmed by differential spectroscopy of the specific product 2-hydroxyethidium. Retinal ganglion cell superoxide increased within 24 h after axotomy, peaking at 4 days, and was not observed in contralateral untransected eyes. The superoxide signal preceded phosphatidylserine externalization, indicating that superoxide generation was an early event and preceded apoptosis. Intravitreal pegylated superoxide dismutase blocked superoxide generation after axotomy and delayed retinal ganglion cell death. Together, these results are consistent with superoxide being an upstream signal for retinal ganglion cell apoptosis after optic nerve injury. Early detection of axonal injury with superoxide could serve as a predictive biomarker for patients with optic neuropathy.
视神经病变是导致不可逆性失明的主要原因，也是中枢神经系统轴突疾病的典型范例。首要事件是视网膜神经节细胞轴突受损，随后通过细胞凋亡导致细胞体死亡。针对这些和其他神经元疾病的神经保护试验大多失败了，主要是因为动物中的神经保护机制不一定适用于人类。我们开发了一种用于成像活体内神经元死亡的细胞内转导途径的方法。通过纵向共焦扫描多激光眼科显微镜，我们在视神经横断后识别出逆行标记的大鼠视网膜神经节细胞内产生的超氧阴离子。通过用玻璃体内给予的羟乙基噻吩实时成像其反应产物，并通过特定产物 2-羟乙基噻吩的差光谱学证实，来可视化超氧阴离子。视神经切断后 24 小时内，视网膜神经节细胞中超氧阴离子增加，在第 4 天达到峰值，在未切断的对侧眼中未观察到。超氧阴离子信号先于磷脂酰丝氨酸外翻，表明超氧阴离子的产生是一个早期事件，先于细胞凋亡。玻璃体内给予聚乙二醇化超氧化物歧化酶可阻断视神经横断后超氧阴离子的产生，并延迟视网膜神经节细胞死亡。这些结果共同表明，超氧阴离子是视神经损伤后视网膜神经节细胞凋亡的上游信号。超氧阴离子的早期检测可以作为视神经病变患者的预测生物标志物。
