强噪声对大鼠耳蜗螺旋神经节细胞凋亡及凋亡蛋白酶的作用

Effects of strong noise on the apoptosis of spiral ganglion cells in rats and its inductive effect on apoptotic protease

目的探讨强噪声是否能诱导大鼠的耳蜗螺旋神经节细胞(SGC)的凋亡,噪声对于凋亡蛋白酶的诱发作用以及SGC的凋亡与凋亡蛋白酶半胱氨酸蛋白酶-3(Caspase-3)信号转导之间的关系。方法选用健康雄性白色大鼠40只,随机分成4组,每组10只,将实验组动物暴露于120 d B SPL 4 k Hz窄带噪声中4 h后,分别测试在噪声刺激停止后1 d、4 d、14 d及对照组大鼠的听性脑干反应(ABR)。通过透射电镜下观察以及脱氧核糖核苷酸末端转移酶介导的缺口末端标记法(TUNEL),检测SGC的凋亡,免疫组化法检测Caspase-3的表达水平。结果本实验的噪声条件,可以引起大鼠暂时或永久性的听阈位移,通过透射电镜的观察,发现实验组中SGC出现了凋亡细胞的特征性相关改变。实验组SGC中的TUNEL染色有明显增强,Caspase-3的表达明显增高,与对照组比较差异均有统计学意义(P<0.01)。结论强噪声能够诱导发生SGC的凋亡,并且对Caspase-3有诱发作用,SGC凋亡与Caspase-3的激活有着密切的相关性。

Objective To explore whether intense noise can induce spiral ganglion cell（ SGC） death in rat＇s cochlea via the apoptotic pathway and investigate the relationship between the signal transduction of apoptotic protease（ Caspase- 3） and apoptosis of SGC. Methods Twenty healthy male rats were randomly divided into 4 groups. The rats in the experiment group were exposed to 4 KHz narrow band noise at 120 d B SPL for 4 h. Auditory brainstem response（ ABR） were tested 1,4 and 14 days after the noise exposure and in the control group. Apoptosis was detected by terminal deoxynucleotidyl Transferase（ Td T）- mediated deoxyuridine triphosphate（ d- UTP） nick and labeling method（ TUNEL）and transmission electron microscopy,and expression of Caspase- 3 was tested by immunohistochemical method. Results The observation by electron microscopy showed that pathognomonic changes of apoptotic cells were found in the SGC of the experimental groups,but no in the control. TUNEL staining in SGCs were more evident in the experimental groups.There were higher expressions of Tunel- positve cells and caspase- 3 in the SGCs of experimental groups compared with the control group（ P〈0. 01）. Conclusion Apoptosis of SGC could be induced by intense noise and Caspase- 3 cascade may be involved in the course of SGC apoptosis.