Mechanisms of hearing loss and cell death in the cochlea of connexin mutan mice
Mechanisms of hearing loss and cell death in the cochlea of connexin mutan mice
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DOI：
10.1152/ajpcell.00483.2019
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发表时间：
2020-09-01
影响因子：
5.5
通讯作者：
Tang, Wenxue
中科院分区：
文献类型：
--
作者：
Chen, Bei;Xu, Hongen;Tang, Wenxue
已知连接蛋白 30 (Cx30) 突变会导致严重的先天性听力障碍；然而，Cx30 介导耳蜗间隙连接稳态的机制尚不清楚。我们使用基因缺失小鼠模型来探索Cx30预防听力损失的机制。我们的结果表明，尽管出生后第 18 天听觉脑干反应和耳蜗电位严重丧失，Cx30(-/-) 小鼠仅表现出外毛细胞的零星丧失。 Cx30(-/-)小鼠听力和毛细胞损失的时间进程和严重程度的不一致可能部分是由于出生后第10天开始活性氧生成的增加。Cx30(-/-)小鼠血管纹、螺旋韧带和柯蒂氏器中氧化应激基因的表达增加。此外，Cx30(-/-) 缺乏导致出生后第 18 天线粒体功能障碍，通过 ATP 水平降低和线粒体复合物 I 蛋白表达减少（尤其是在血管纹中）来评估。蛋白质组学分析进一步鉴定出 444 个在 Cx30(-/-) 小鼠中失调的蛋白质，其中包括一些参与线粒体电子传递、ATP 合成或离子传递的蛋白质。此外，促凋亡蛋白，包括 Bax。 Bad 和 caspase-3 在出生后第 18 天表达上调，为解释毛细胞损失之前发生的听力损失提供了分子基础。因此，我们的结果与 Cx30(-/-) 小鼠耳蜗氧化应激和线粒体损伤的环境一致，该环境与听力损失同时发生，但先于毛细胞损失。
Mutations in connexin 30 (Cx30) are known to cause severe congenital hearing impairment; however, the mechanism by which Cx30 mediates homeostasis of endocochlear gap junctions is unclear. We used a gene deletion mouse model to explore the mechanisms of Cx30 in preventing hearing loss. Our results suggest that despite severe loss of the auditory brain-stem response and endocochlear potential at postnatal day 18, Cx30(-/-) mice only show sporadic loss of the outer hair cells. This inconsistency in the time course and severity of hearing and hair cell losses in Cx30(-/-) mice might be explained, in part, by an increase in reactive oxygen species generation beginning at postnatal day 10. The expression of oxidative stress genes was increased in Cx30(-/-) mice in the stria vascularis, spiral ligament, and organ of Corti. Furthermore, Cx30(-/-) deficiency caused mitochondria' dysfunction at postnatal day 18, as assessed by decreased ATP levels and decreased expression of mitochondria' complex I proteins, especially in the stria vascularis. Proteomic analysis further identified 444 proteins that were dysregulated in Cx30(-/-) mice, including several that are involved in mitochondria electron transport, ATP synthesis, or ion transport. Additionally, proapoptotic proteins, including Bax. Bad, and caspase-3, were upregulated at postnatal day 18, providing a molecular basis to explain the loss of hearing that occurs before hair cell loss. Therefore, our results are consistent with an environment of oxidative stress and mitochondrial damage in the cochlea of Cx30(-/-) mice that is coincident with hearing loss but precedes hair cell loss.