内质网应激参与钙粘素突变小鼠的听力损伤机制研究

Age related hearing loss (AHL) affect 40% of the population over the age of 65 , many factors can affect AHL, such as exposure to noise and ototoxic drugs and so on. Since the increase in the proportion of China's aging population, AHL seriously affect the quality of life a lot of the aging people. Currently the mechanism of AHL is not clear, and no effective drugs for therapy yet. The study of human temporal bone can provide limited information, and can only be done in postmortem. We have development a new deafness mouse model, called erlong, erl. Preliminary results show that it is characterized by the postnatal one month of a hearing loss, and gradually serious with increasing age. Until three months, the mice nearly complete loss of hearing. Compared with the control mice, caspases were significantly increased apoptosis signal in the erl mice inner ear. Administration of caspase inhibitor could protect mice hearing threshold to nearly 30 dB. Recently, it has been reported that endoplasmic reticulum stress (ER stress) induced apoptosis can result in causing many neurodegenerative diseases. Based on this, we hypothesized that inhibition of ER stress hair cells could prevent hair cell apoptosis and effectively improve the erl mice hearing. This project are planning to treat erl mice an ER stress inhibitor by intraperitoneal. We expect this ER stress inhibitor could protect hair cells and mice hearing, to provide a new way for the AHL therapy.

老年性聋(AHL)影响65岁以上人口的40%，许多因素可导致AHL，如噪声及耳毒性药暴露等。由于我国老龄人口比例增加，AHL严重影响大量老年人的生活质量。目前 AHL的发生机理尚不明确，且无有效药物。研究人类颞骨能提供有限信息，且只能在死后尸检才能做到。为此，我们培育了耳聋 erl小鼠模型，前期研究表明：出生后1个月开始听力减退，随年龄增加逐渐加重，至3个月听力近完全丧失。与对照鼠比较，erl内耳的凋亡信号Caspases显著升高；给小鼠腹腔注射caspase抑制剂后，小鼠听阈值得到近30dB的保护。有报道指出，内质网应激(ER stress)引起的细胞凋亡能够导致神经退行性疾病，因此我们提出假说：抑制毛细胞ER stress，可以抑制毛细胞凋亡，有效改善erl小鼠听力。本课题拟观察经腹腔给erl小鼠ER stress 抑制剂，预期保护听力和毛细胞，并探讨其机制，为AHL的防治提供新途径。

钙粘蛋白23（CDH23）作为内耳毛细胞顶端连接的组成部分与年龄相关性听力损失有关。本项目利用Cdh23erl/erl（erl）小鼠这种新型渐进性耳聋小鼠模型，研究了年龄相关性听力损失的分子机制。本课题对erl小鼠采用多种听功能检测方法对小鼠听力损失程度进行评估，利用形态学方法对内耳毛细胞进行观察，利用免疫荧光等技术对erl小鼠听力损失发生机制进行研究，证明内质网应激（ER stress）参与erl小鼠模型内耳毛细胞凋亡从而导致听力损失的假说，阐明ER stress在毛细胞凋亡通路中的发生机制。另外利用erl小鼠完成了多种听力保护药物的筛选工作，筛选药物包括ER stress抑制剂：四苯基丁酸（4-Phenylbutyric acid，4-PBA）、牛磺熊去氧胆酸（Tauroursodeoxycholic acid，TUDCA）、选择性eIF2去磷酸化抑制剂（Salubrinal）等。评价不同药物的听力保护作用效果，阐明ER stress抑制剂可能具有保护听力和防止毛细胞损伤的作用，并证明erl小鼠模型是试验听力保护药物的理想模型，为临床治疗老年性耳聋提供了新的研究方向。共发表SCI文章3篇。