摘要
目的:探讨内质网应激(ERS)对1%链脲佐菌素(STZ)诱导的糖尿病小鼠耳蜗毛细胞退行性变的影响,阐明其作用机制。方法:选取清洁级1月龄雄性昆明小鼠20只,随机分为对照组和模型组,模型组小鼠采用腹腔注射40mg·kg~(-1) STZ建立2型糖尿病模型。尾静脉采血测定小鼠空腹血糖,通过听觉脑干反应(ABR)检测小鼠的ABR阈值,耳声发射测试(OAE)实验检测OAE阈值,应用小鼠耳蜗铺片技术计算小鼠耳蜗外毛细胞的缺损率,采用Western blotting法检测小鼠耳蜗毛细胞中GRP78、caspase-12、p-ERK和Nrf2蛋白表达水平。结果:与对照组比较,第2次注射STZ后7和14d模型组小鼠空腹血糖差异无统计学意义(P>0.05),21、28和35d空腹血糖明显升高(P<0.05),35d达到最高值。与对照组比较,模型组小鼠在8、12和24kHz各个频率的ABR阈值明显升高(P<0.05)。与对照组比较,低频刺激下模型组小鼠OAE阈值无明显变化(P>0.05),在中频和高频刺激下模型组小鼠OAE阈值明显升高(P<0.05)。小鼠耳蜗外毛细胞缺损主要集中在底回端,耳蜗中回和顶回外毛细胞缺损较少;与对照组比较,模型组小鼠耳蜗中的底回外毛细胞缺损率明显升高(P<0.05),中回和顶回外毛细胞缺损率略有升高,但差异无统计学意义(P>0.05)。与对照组比较,模型组小鼠耳蜗毛细胞中GRP78和caspase-12蛋白表达水平升高(P<0.05),p-ERK和Nrf2蛋白表达水平降低(P<0.05)。结论:ERS能够引起糖尿病小鼠耳蜗外毛细胞缺损率和ABR脑干听力阈值升高,并降低p-ERK和Nrf2的蛋白表达水平,提示ERS可促进2型糖尿病小鼠耳蜗毛细胞的退行性病变。
Objective:To investigate the influence of endoplasmic reticulum stress(ERS)in the degeneration of cochlear hair cells in the type 2 diabetic mice,and to clarify its mechanism.Methods:Twenty clean Kun Ming male mice aged one month were selected and randomly divided into control group and model group(n=10).The mice in model group were injected with STZ(40 mg·kg~(-1))to establish the type 2 diabetic models.The fasting blood glucose levels of the mice were measured through collecting the vena caudalis blood of the mice.Auditory brain stem response(ABR)was used to detect the ABR threshold of the mice.Otoacoustic emission(OAE)test was used to detect the OAE threshold of mice.The defect rate of mouse cochlear outer hair cells was calculated by the mouse cochlear spreading technique.The expression levels of GRP78,caspase-12,p-ERK and Nrf2 proteins were detected by Western blotting method.Results:Compared with control group,the fasting blood glucose levels of the mice in model group at the 7 th and the 14 th days had no significant differences(P>0.05),but the levels were increased significantly at the 21 th,28 th and 35 th days and the level reached the highest value at the 35 th day.The ABR thresholds of the mice in model group at 8,12,and 24 kHZ were increased significantly compared with control group(P<0.05).Under the stimulation of low frequency,there was no significant change in the OAE threshold of the mice in model grouop compared with control group.The OAE thresholds of the mice in model group were increased significantly under the medium frequency and high frequency stimulation compared with control group(P<0.05).The defects of the cochlear hair cells were mainly concentrated on the bottom of gyrus of the mice,and the defects in middle temporal gyrus and parietal gyrus were less.Compared with control group,the defect rate in the bottom of gyrus of the mice in model group was increased significantly(P<0.05);the defect rates in the middle temporal gyrus and parietal gyrus were increased,but there was no significant difference(P>0.05).The expression levels of p-ERK and Nrf2 in the cochlear hair cells of the mice in model group were lower than those in control group(P<0.05),and the expression levels of GRP78 and caspase-12 were higher than those in control group(P<0.05).Conclusion:ERS can result in the increase of defect rate of cochlear outer hair cells and ABR brainstem hearing threshold of the diabetic mice and decrease the expression levels of p-ERK and Nrf2 proteins,suggesting that ERS can promote the degenerative lesions of cochlear hair cells in the type 2 diabetic mice.
引文
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