钙稳态失衡导致实验性青光眼视网膜神经节细胞损伤的机制

Glaucoma is one of severe retinal diseases, which is characterized by visual loss due to the apoptotic death of retinal ganglion cells (RGCs), output neurons in the retina. Ca2+ homeostasis disorder is one of important factors for RGC apoptosis in glaucoma. Among various pathways, voltage-gated Ca2+ channels and NMDA subtype channels of glutamate receptors are major sources for elevation of intracellular Ca2+ concentration. However, voltage-gated Ca2+ channels and NMDA receptor channels have a variety of subunits. These channel subunits are differentially expressed and distributed on different parts of RGCs. If and how these subunits are involved in Ca2+ homeostasis disorder of RGCs and contribute to RGC apoptosis in glaucoma are largely unknown. In a rat chronic ocular hypertension (COH) experimental glaucoma model, our preliminary results showed that L-type Ca2+ channel currents were down-regulated, while T-type ones were kept unchanged. In the proposed research, based on our previous studies, we aim to explore the cellular and molecular mechanisms underlying Ca2+ homeostasis disorder and RGC apoptosis contributed by different subunits of Ca2+ cahnnels in RGCs and NMDA subunits distributed in different parts of RGC dendrites in COH experimental glaucoma model, using multi-disciplinary approaches. Results to be derived from this study are expected to elucidate mechanisms underlying RGC apoptosis in glaucoma, thus providing potential ways for effective prevention and cure of glaucoma.

神经性致盲眼病青光眼累及视网膜网络的输出神经元——神经节(RGC)细胞的功能，造成视觉的损伤，胞内Ca2+稳态失衡是导致青光眼RGC凋亡的重要原因之一。在众多的因素中，电压门控钙通道和谷氨酸NMDA受体通道是胞内Ca2+增高的主要途径。然而，这些通道有诸多的亚型，且在RGC上的空间分布各异，这些亚型在RGC胞内Ca2+稳态失衡中的作用和机制，进而导致RGC凋亡的机制是亟待解决的科学问题。我们的预实验结果显示，慢性高眼压大鼠RGC上T-和L-型钙通道亚型发生了不同的变化。为此，在本课题拟以慢性高眼压实验性青光眼为模型，采用多学科技术，在我们已有研究的基础上，深入研究不同的电压门控Ca2+通道亚型、RGC树突上NMDA受体亚型及其空间分布对钙稳态失衡的贡献和机制，进而分析它们在RGC损伤中的作用和机制。本课题的研究成果将为阐明实验性青光眼RGC损伤的机制，以及有效地防治青光眼提供理论参考依据。

神经性致盲眼病青光眼累及视网膜网络的输出神经元——神经节细胞(RGCs)的功能，造成视觉的损伤，胞内Ca2+稳态失衡是导致青光眼RGCs凋亡的重要原因之一。在众多的因素中，电压门控钙通道和谷氨酸NMDA受体通道是胞内Ca2+增高的主要途径。然而，这些通道有诸多的亚型，且在RGCs上的空间分布各异，它们分别在RGCs胞内Ca2+稳态失衡中的作用和机制，进而导致RGCs凋亡的机制是亟待解决的科学问题。采用多学科技术，我们的研究发现，在慢性高眼压实验性青光眼大鼠视网膜，RGCs的L-型钙通道电流和CaV1.2亚单位下调，而T-型钙通道电流和CaV3.3亚单位上调，其作用由肿瘤坏死因子-α和白介素-6介导，提示T-型钙通道阻断剂可能在治疗青光眼方面具有一定的临床应用前景和价值。玻璃体内注射NMDA通过减少突触前谷氨酸的释放、突触后AMPA受体的相对数量以及树突小棘的数量压抑了RGCs的谷氨酸能突触传递，最终导致了RGCs的凋亡，并且NR2A和NR2B亚基均参与其中。此外，我们还发现，在慢性高眼压实验性青光眼视网膜，EphA4/ephrinA3反向信号的激活下调了Müller细胞GLAST的表达和GLAST介导的电流，导致胞外谷氨酸浓度增高，参与了Müller细胞的激活和RGCs的凋亡。本课题的研究成果为阐明实验性青光眼RGCs损伤的机制，以及有效地防治青光眼提供理论参考依据。全面完成了预期目标，发表SCI论文11篇。