Chiu Kin, Lam Tim Tak, Ying Li Winnie Wai, Caprioli Joseph, Kwong Kwong Jacky Man
Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong.
Brain Res. 2005 Jun 7;1046(1-2):207-15. doi: 10.1016/j.brainres.2005.04.016.
Calpain-mediated proteolysis has been implicated as a major process in neuronal cell death in both acute insults and the chronic neurodegenerative disorders in the central nerves system. However, activation of calpain also plays a protective function in the early phase of excitotoxic neuronal death. The exact role of calpains in neuronal death and recovery after exposure to N-methyl-D-aspartate (NMDA) is not clearly known. The purpose of present study was to examine the involvement of mu- and m-calpain in NMDA-induced excitotoxicity in the adult rat retina. Increased immunoreactivity of mu-calpain was noted in RGC layer cells and in the inner nuclear layer with maximal expression at 12 h after NMDA injection. This was further confirmed with Western blotting. TdT-mediated biotin-dUTP nick end labeling (TUNEL) positive cells in the inner retina co-localized with moderate or intense mu-calpain immunoreactivity. In contrast, there was no remarkable change in m-calpain immunoreactivity at any time point after NMDA injection. Simultaneous injection of 2 nmol of a calpain inhibitor (calpain inhibitor II) significantly reduced the number of TUNEL-positive cells in the inner retina at 18 h after NMDA injection and preserved RGC-like cells counted at 7 days after injection. The results of this study showed that mu-calpain may be involved in mediating NMDA-induced excitotoxicity in the rat retina and calpain inhibitors may play a therapeutic role in NMDA related disease.
钙蛋白酶介导的蛋白水解作用被认为是中枢神经系统急性损伤和慢性神经退行性疾病中神经元细胞死亡的主要过程。然而，钙蛋白酶的激活在兴奋性毒性神经元死亡的早期阶段也发挥着保护作用。钙蛋白酶在暴露于N-甲基-D-天冬氨酸（NMDA）后神经元死亡和恢复过程中的确切作用尚不清楚。本研究的目的是检测μ-钙蛋白酶和m-钙蛋白酶在成年大鼠视网膜NMDA诱导的兴奋性毒性中的作用。在NMDA注射后12小时，视网膜神经节细胞层（RGC）和内核层中μ-钙蛋白酶的免疫反应性增加，且表达量最大。蛋白质免疫印迹法进一步证实了这一点。视网膜内层TdT介导的生物素-dUTP缺口末端标记（TUNEL）阳性细胞与中等或强烈的μ-钙蛋白酶免疫反应性共定位。相比之下，NMDA注射后任何时间点m-钙蛋白酶的免疫反应性均无显著变化。同时注射2 nmol钙蛋白酶抑制剂（钙蛋白酶抑制剂II）可显著减少NMDA注射后18小时视网膜内层TUNEL阳性细胞的数量，并保留注射后7天计数的视网膜神经节样细胞。本研究结果表明，μ-钙蛋白酶可能参与介导大鼠视网膜NMDA诱导的兴奋性毒性，钙蛋白酶抑制剂可能在NMDA相关疾病中发挥治疗作用。
