基于酸敏感离子通道调控视网膜神经节细胞损伤过程的青光眼发病机制及治疗研究

Glaucoma is a group of diseases characterized by progressive optic nerve degeneration that results in visual field loss and irreversible blindness. A crucial element in the pathophysiology of all forms of glaucoma is the death of retinal ganglion cells (RGCs), a population of CNS neurons with their soma in the inner retina and axons in the optic nerve. The conduction of acid-evoked currents in central and sensory neurons is now primarily attributed to a family of proteins called acid-sensing ion channels (ASICs). ASICs are mainly expressed in the central and peripheral nervous systems, where they form homomultimeric and heteromultimeric cation channels. Moreover, the homomeric channel composed of ASIC1a subunit exhibit a high Ca2+ permeability and play important roles in synaptic plasticity and acid-induced cell death. In the retina, recent data have suggested that pH fluctuations play an important role in pathological conditions such as ischemia. There has been speculation about the physiologic and pathophysiological function of acid-gated currents in central neurons. So we hypothesize that interstitial acidosis associated with seizures and ischemia in glaucoma could trigger their activity, thereby exacerbating the pathological consequences of these conditions. Our previous studies have demonstrated that, first, ASIC 1a expressed in RGCs using immunohistochemistry. Morever, The native ASIC current is not carried by a homomeric ASIC1a or ASIC3 channel. Second, Acid-induced enhancement of ASIC currents was accompanied by an increased acidosis induced (Ca2+)i elevation. But the relation between these two phenomenons is unclear. Third, the peak amplitude of current induced by pH 6.0 was potentiated after treatment with NaCN, which suggested an important role of ASICs in RGCs during hypoxia; however, the mechanism is unclear. Based on these results, we are trying to elucidate the role of ASICs in the pathological process of glaucoma by this program. The model of chronic high intraocular pressure is established in ASIC 1a knockout mice. DBA/2J mice, a strain that spontaneously develops glaucoma, are also used in this research. This program can develop a new area in glaucoma both in pathogenesis and therapy.

青光眼导致的视网膜神经节细胞（RGCs）损伤过程中伴有组织酸化，其可通过酸敏感离子通道（ASICs）对RGCs等神经元细胞进行直接损伤。研究表明ASICs参与中枢神经系统缺血等由谷氨酸释放和酸中毒所导致的神经元死亡。同时，本课题组在前期研究中已证明：ASICs在RGCs中表达，且以异聚体（ASIC1a、ASIC3）的形式存在；酸化引起的由ASICs介导的酸电流，可导致RGCs细胞内Ca2+浓度升高，其酸电流在氰化钠处理后增加明显。因此，ASICs在RGCs病理改变中发挥重要的作用。本课题设计采用ASIC1a基因敲除小鼠建立慢性高眼压性青光眼模型、自发性青光眼模型DBA/2J小鼠以及体外培养的RGCs细胞等，研究ASICs在青光眼RGCs损伤过程中的作用及机制，从离子通道的角度丰富青光眼视功能损伤的理论，并为针对青光眼RGCs损伤的保护及药物开发提供新的靶点。

酸敏感离子通道（acid-sensing ion channels, ASICs）参与中枢神经系统等由谷氨酸释放和酸中毒导致的神经元死亡，在青光眼疾病发展过程中，其参与了视网膜神经节细胞（retinal ganglion cells, RGCs）的损伤。本课题研究结果如下：1、ASIC 1a在DBA/2J小鼠视网膜神经节细胞中高表达，在体实验通过药物干预，RGCs存活率未发生具有统计学意义的改善；而在离体实验中，通过抑制ASIC 1a，能明显提高RGCs的存活率。ASIC 1a基因敲除小鼠体外培养RGCs，在OGD情况下，其存活率明显高于野生型小鼠。RGC酸化过程中，钙离子内流受到ASIC 1a的调节。2、依达拉奉通过激活AKT信号通路，对RGCs发挥保护作用，但此过程中，ASIC 1a表达并未发生明显改变。3、ASIC 1a参与视网膜色素上皮细胞（retinal pigment epithelial cells，RPE）的氧化损伤过程，但其作用和神经系统不同。