年龄相关性听力损失大鼠听皮层、蜗核、耳蜗SOD、MDA变化及神经细胞凋亡初步观察

The Changes of SOD,MDA and Apoptosis in the Auditory Cortex,the Cochlear Nuclei and the Cochlea of the Rats with Age-Related Hearing Loss

目的通过测定年龄相关性听力减退大鼠听皮层、蜗核、耳蜗组织中超氧化物岐化酶(superoxide dismutase,SOD)活性、丙二醛(malondialdehyde,MDA)含量的变化及神经细胞凋亡率,初步探讨老年性聋与氧化损伤及神经细胞凋亡的关系。方法选用3月龄(听阈20±5dBSPL)及18月龄(听阈55±10dBSPL)Wistar大鼠各30只,硫代巴比妥酸(thibabituric acid,TBA)法测定MDA含量,黄嘌呤氧化酶法(xanthine oxidase,XO)测定总SOD活性,Annexin V-FITC/PI双染法流式细胞仪检测神经细胞凋亡率。结果①与3月龄组大鼠相比,18月龄组大鼠听皮层、蜗核、耳蜗中SOD活性下降,MDA含量升高,组间比较,差异均有显著统计学意义(P<0.05)。②18月龄组大鼠听皮层、蜗核神经细胞凋亡率比3月龄组大鼠相应部位的神经细胞凋亡率增加,组间比较,差异有显著统计学意义(P<0.05)。③神经细胞凋亡率与SOD活性呈负相关(r=-0.65,P<0.05),与MDA含量正相关(r=0.59,P<0.05)。结论听皮层、蜗核、耳蜗中氧化损伤及神经细胞凋亡与老年性聋的发生发展有关,氧化损伤可能是诱发细胞凋亡的机制之一。

Objective To explore the changes of superoxide dismutase （SOD）, malondialdehyde （MDA） and apoptosis in the auditory cortex, the cochlear nuclei and the cochlea of the rats with age- related hearing loss, and to understand the relationship between oxidative damage and apoptosis with presbyacusis. Methods Three-month -old rats （ABR 20±5 dB SPL ） and eighteen- month -old rats （ABR 55±10 dB SPL ） were used in the study. T -SOD activity was measured by xanthine oxidase （XO） method. The MDA level was examined by the thihabituric acid （TBA） method. Apoptosis was examined by Annexin V-FITC/PI staining with flow cytometry （FCM）. Results The SOD activities decreased and the MDA levels increased significantly in the auditory cortex, the cochlear nuclei and the cochlea of the eighteen-month -old rats （P〈0.05）. The apoptosis rates increased significantly in the auditory cortex and the cochlear nuclei of the eighteen-month-old rats （P〈0.05）. The apoptosis rate showed negative correlation with SOD activity （ r = - 0. 65, P〈 0. 05 ） and positive correlafion with MDA （ r = 0. 59, P〈 0.05）. Conclusion It indicated that oxidative damage and the neuron apoptosis in the auditory cortex, the cochlear nuclei and the cochlea of the rats with age -related hearing loss were important in the development of presbyacusis, and oxidative damage might be one of the mechanisms of apoptosis.