Correlation Study of Calpain and Noise-induced Cochlear Synaptopathy in Inner Hair Cells
10.3969/j.issn.1006-7299.2024.05.014
- VernacularTitle:钙蛋白酶与内毛细胞带状突触噪声损伤的相关性研究
- Author:
Ruijie CAI
1
,
2
,
3
;
Hongchao LIU
;
Weijun ZHOU
;
Huihui LIU
;
Hao WU
Author Information
1. 上海交通大学附属第九人民医院耳鼻咽喉头颈外科(上海 200011)
2. 上海交通大学医学院耳科学研究所
3. 上海市耳鼻疾病转化医学重点实验室
- Keywords:
Noise-induced hearing loss;
Ribbon synapse;
Calcium ion;
Calpain
- From:
Journal of Audiology and Speech Pathology
2024;32(5):448-453
- CountryChina
- Language:Chinese
-
Abstract:
Objective To investigate the related factor underlying the differential vulnerability of inner hair cell(IHC)ribbon synapses to noise exposure.Methods Twenty-eight C57BL/6J mice were randomly divided into the noise exposure group(NED1)and the control group(CTR)with 14 mice in each group.The noise exposure group was exposed to bandpass noise of 2～20 kHz at 103 dB SPL for two hours while the control group was bred in a quiet environment.Before and after noise exposure,auditory brainstem response was conducted to detect the audi-tory function,whole-mount immunofluorescence staining was used to observe the number of inner hair cell ribbon synapses in different turns.The calcium influx of inner hair cells in the apical and middle turn using whole-cell patch clamp recording was analyzed.Furthermore,the immunofluorescence intensity of calpain in inner hair cells from dif-ferent mouse cochlear turns using whole-mount immunofluorescence staining was compared.Western blotting was used to verify that CtBP2 was degraded by calpain.Results After noise exposure,the ABR threshold of 11.3,16.0,22.6,32.0 kHz increased significantly and the number of ribbon synapses of inner hair cells at the middle turn and basal turn of the cochlea decreased significantly.However,whole-cell patch clamp recordings showed that calcium ion channels were fewer but single-channel current was higher at the apical turn of the cochlea.The open probability of calcium ion channels in IHCs showed no significant difference between the apical turn and the middle turn of the cochlea.But the expression level of calpain of the inner hair cells at the middle and basal turn of the basi-lar membrane was significantly higher than that at the apical turn after noise exposure.The western blotting results also showed that CtBP2 was cleaved in a Ca2+-dependent manner by calpain.Conclusion Calpain may be the main related factor that accounts for the vulnerability of ribbon synapses in inner hair cells in the high frequency region of basal membrane.
