Regulation of Calcium Signaling in Retinal Ganglion Cells after Nerve Injury

描述（由申请人提供）： 头部钝器伤或爆炸伤导致的眼部和创伤性脑损伤（TBI）在战场上频繁发生，通常伴有多种视觉功能障碍、一只或两只眼睛的视力丧失和失明。视神经病的特征是视神经原发性损伤以及神经节细胞及其轴突的丧失。神经节细胞死亡部分是由损伤后细胞内过量的 Ca2 ([Ca2]i) 负荷介导的。与这一发现一致的是，使用 Ca2 通道拮抗剂可增强视神经挤压后视网膜神经节细胞的存活，该拮抗剂可抑制 L 型和 T 型 Ca2 电流，并减少继发性神经节细胞死亡。拟议研究的基本原理是，通过调节 Ca2+ 通道活性来降低神经节细胞细胞内 Ca2+ 水平可能是治疗视网膜损伤的保护策略的重要组成部分。抑制神经节细胞中过度升高的[Ca2]i将为神经节细胞存活和损伤后轴突恢复提供时间窗口。拟议的研究将检验神经损伤后抑制 [Ca2]i 升高可增强神经节细胞存活的假设。具体目标 1 将定义 L 型和 T 型 Ca2 通道及其辅助蛋白（23 和 124）在小鼠视网膜神经节细胞中的信号传导作用。实验将确定 a) 神经节细胞 L 型和 T 型 Ca2 通道及其辅助蛋白的表达，以及 b) 表征神经节细胞 L 型和 T 型 Ca2 电流的生理和生物物理特性。具体目标 2 将检验以下假设：视神经挤压或横断后立即和几天后神经节细胞 Ca2 信号传导失调。研究将确定 a) 神经节细胞 L 型和 T 型以及 23 和 124 Ca2 通道亚基的表达，以及 b) 视神经损伤后介导神经节细胞中 Ca2 电流和信号传导的膜机制是否存在短期（12 和 24 小时）和长期（10 和 20 天）改变。具体目标 3 将检验 Ca2 通道拮抗剂和小干扰 RNA (siRNA) 反义 Ca2 通道亚基载体调节 Ca2 信号传导并增强视神经损伤后神经节细胞存活的假设。研究将确定 a) L 型和 T 型 Ca2 通道拮抗剂洛美利嗪，b) 反义 T 型（CaV3.1 和 CaV3.2）以及 23 和 124 Ca2 通道亚基 siRNA 载体是否调节 Ca2 信号传导并增强视神经损伤后神经节细胞的存活。拟议的研究将阐明正常和受损神经节细胞中的 Ca2 信号传导，并开发控制神经损伤后细胞内 Ca2 升高的新方法，这将提高神经节细胞的存活率，这是挽救视力的关键一步。这些研究与退伍军人管理局的健康相关目标一致，即开发针对眼部损伤和疾病的高效且新颖的治疗方法。

DESCRIPTION (provided by applicant): Ocular and traumatic brain injuries (TBI) from blunt trauma or blast injury to the head occur with high frequency on the battlefield, and they are often accompanied by multiple visual dysfunctions, acuity loss and blindness in one or both eyes. Optic neuropathies are characterized by primary injury to the optic nerve, and loss of ganglion cells and their axons. Ganglion cell death is mediated in part by excessive intracellular Ca2+ ([Ca2+]i) loads following injury. Consistent with this finding is the enhancement of retinal ganglion cell survival after optic nerve crush with the administration of Ca2+ channel antagonists, which inhibit both L- and T-type Ca2+ currents, and reduce secondary ganglion cell death. The rationale underlying the proposed studies is that reduction of ganglion cell intracellular Ca2+ levels by regulation of Ca2+ channel activity may be an important component of protective strategies for the treatment of retinal injury. Suppression of excessively elevated [Ca2+]i in ganglion cells would provide a temporal window for ganglion cell survival and axonal recovery following injury. Proposed studies will test the hypothesis that suppression of elevated [Ca2+]i following nerve injury enhances ganglion cell survival. Specific aim 1 will define the signaling role of L- and T-type Ca2+ channels, and their accessory proteins (23 and 124) in mouse retinal ganglion cells. Experiments will determine a) the expression of L- and T-type Ca2+ channels and their accessory proteins by ganglion cells, and b) characterize the physiological and biophysical properties of L- and T-type Ca2+ currents of ganglion cells. Specific aim 2 will test the hypothesis that ganglion cell Ca2+ signaling is dysregulated immediately following and several days after optic nerve crush or transection. Investigations will determine if there are short (12 and 24 hours)- and long (10 and 20 days)-term alterations of a) the expression of L- and T-type, and 23 and 124 Ca2+ channel subunits by ganglion cells, and b) membrane mechanisms that mediate Ca2+ currents and signaling in ganglion cells following optic nerve injury. Specific aim 3 will test the hypothesis that Ca2+ channel antagonists and small interfering RNA (siRNA) antisense Ca2+ channel subunit vectors regulate Ca2+ signaling, and enhance ganglion cell survival after optic nerve injury. Investigations will determine if a) the L- and T-type Ca2+ channel antagonist, lomerizine, and b) antisense T-type (CaV3.1 and CaV3.2), and 23 and 124 Ca2+ channel subunit siRNA vectors, modulate Ca2+ signaling and enhance ganglion cell survival following optic nerve injury. Proposed studies will elucidate Ca2+ signaling in normal and injured ganglion cells, and develop novel approaches for controlling elevated intracellular Ca2+ following nerve injury, which will enhance ganglion cell survival, a key step in saving vision. These studies are consistent with the health-related goals of the Veterans Adminstration to develop highly effective and novel treatments for eye injury and disease.