Department of Otolaryngology-Head and Neck Surgery, Stanford University, Stanford, California, United States of America.
PLoS One. 2011;6(7):e22347. doi: 10.1371/journal.pone.0022347. Epub 2011 Jul 26.
Aminoglycosides (AG) are commonly prescribed antibiotics with potent bactericidal activities. One main side effect is permanent sensorineural hearing loss, induced by selective inner ear sensory hair cell death. Much work has focused on AG's initiating cell death processes, however, fewer studies exist defining mechanisms of AG uptake by hair cells. The current study investigated two proposed mechanisms of AG transport in mammalian hair cells: mechanotransducer (MET) channels and endocytosis. To study these two mechanisms, rat cochlear explants were cultured as whole organs in gentamicin-containing media. Two-photon imaging of Texas Red conjugated gentamicin (GTTR) uptake into live hair cells was rapid and selective. Hypocalcemia, which increases the open probability of MET channels, increased AG entry into hair cells. Three blockers of MET channels (curare, quinine, and amiloride) significantly reduced GTTR uptake, whereas the endocytosis inhibitor concanavalin A did not. Dynosore quenched the fluorescence of GTTR and could not be tested. Pharmacologic blockade of MET channels with curare or quinine, but not concanavalin A or dynosore, prevented hair cell loss when challenged with gentamicin for up to 96 hours. Taken together, data indicate that the patency of MET channels mediated AG entry into hair cells and its toxicity. Results suggest that limiting permeation of AGs through MET channel or preventing their entry into endolymph are potential therapeutic targets for preventing hair cell death and hearing loss.
氨基糖苷类（AG）是常用的具有强大杀菌活性的抗生素。一个主要的副作用是永久性感觉神经性听力损失，由选择性内耳感觉毛细胞死亡引起。许多工作都集中在 AG 引发细胞死亡过程上，但是，关于 AG 被毛细胞摄取的机制的研究较少。本研究调查了两种哺乳动物毛细胞中 AG 转运的拟议机制：机械感受器（MET）通道和内吞作用。为了研究这两种机制，将大鼠耳蜗外植体作为完整器官在含庆大霉素的培养基中培养。两光子成像显示 Texas Red 缀合庆大霉素（GTTR）快速且选择性地进入活毛细胞。低钙血症增加 MET 通道的开放概率，从而增加 AG 进入毛细胞。三种 MET 通道阻断剂（箭毒，奎宁和阿米洛利）可显著减少 GTTR 摄取，而内吞作用抑制剂伴刀豆球蛋白 A 则没有。Dynosore 猝灭了 GTTR 的荧光，无法进行测试。用箭毒或奎宁而不是伴刀豆球蛋白 A 或 dynosore 进行的 MET 通道药理学阻断，在与庆大霉素接触长达 96 小时时，可防止毛细胞丢失。综合数据表明，MET 通道的通透性介导了 AG 进入毛细胞及其毒性。结果表明，限制 AG 通过 MET 通道的渗透或防止其进入内淋巴可能是预防毛细胞死亡和听力损失的潜在治疗靶标。
