PDCD5和caspase 3在不同年龄段C57BL／6J小鼠耳蜗中的表达

Expression of PDCD5 and caspase 3 in the cochlea of different age of C57BL/6J mice

目的检测程序化细胞死亡分子5（programmed cell death 5，PDCD5）和半胱氨酸天冬氨酸蛋白酶3（caspase 3）在不同年龄段C57BL／6J小鼠耳蜗中的表达，初步探讨其在年龄相关性听力下降发生、发展中的作用。方法选择3、6、9及12月龄段C57BL／6J小鼠各15只，即按月龄分为四组。检测各组小鼠双侧短声（click）及短纯音（6、8kHz）听性脑干反应（ABR）阈值。采用免疫组化和蛋白质印迹杂交（Western blotting）检测各月龄段小鼠耳蜗PDCD5和Caspase3蛋白的表达，实时荧光定量PCR（real—time PCR）检测各月龄段小鼠耳蜗PDCD5和caspase3基因mRNA的表达。结果随着年龄的增长，C57BL／6J小鼠各频率ABR阈值逐渐提高，耳蜗PDCD5和Caspase3蛋白的表达亦逐渐增强。3月龄和6月龄小鼠耳蜗毛细胞和血管纹细胞仅出现少量PDCD5和Caspase3蛋白表达，9月龄时表达有明显增加，至12月龄时表达最强，各月龄组间比较，差异具有统计学意义（P值均〈0．05）。Real—time PCR检测显示PDCD5和caspase3基因mRNA随着年龄的增长表达逐渐增强，与其蛋白变化趋势相一致。结论C57BL／6J小鼠耳蜗PDCD5和caspase3随着年龄的增长表达增强，与耳蜗的老化密切相关，可能是老年性聋发病机制中的一个重要因素。

Objective To investigate the age related changes of the expression of programmed cell death 5 （ PDCD5 ） and caspase 3 in the cochlea of the different age of C57BL/6J mice. The relationship of PDCD5 and caspase 3 and the possible roles in the pathogenesis of presbycusis were also discussed. Methods C57 mice of 3,6, 9 and 12 months old were selected and divided into 4 groups, with 15 mice in each group. Auditory function of C57BL/6J mice was measured by auditory brainstem response （ABR） respectively. The changes of PDCD5 and Caspase 3 protein in the cochlea were detected by immunohistochemistry and Western blotting, the changes of PDCD5 mRNA and caspase 3 mRNA were detected using RT-PCR. Results With the increase of age, the mean value for ABR thresholds in response to click, 4 kHz and 8 kHz sound stimulus of C57 mice gradually increased, the expression of PDCD5 and caspase 3 were increased also. At 3 months and 6 months of age in the cochlea of C57, all sorts of expression of PDCD5 and caspase 3 and the expression were enhanced with age. There was an evident expression at 9 months age, but the highest expression was detected at 12 months age. The PDCD5 and Caspase 3 expression were statistically different in each group （ P 〈 0. 05 ） . The changes of PDCD5 and caspase 3 mRNA expression were in accordance with that of PDCD5 and Caspase 3 protein expression by the real- time PCR. Conclusions The expression levels of PDCD5 and caspase 3 in the cochlea of C57 mice increase with age, the results suggested that the expression of PDCD5 and caspase 3 might play an important role in the pathogenic mechanism of presbycusis.