Wiedenhoft Heather, Hayashi Lauren, Coffin Allison B
College of Arts and Sciences, Washington State University, Vancouver, WA, United States.
Knight Cancer Institute, Oregon Health & Science University, Portland, OR, United States.
Front Cell Neurosci. 2017 Oct 18;11:326. doi: 10.3389/fncel.2017.00326. eCollection 2017.
Inner ear hair cell death leads to sensorineural hearing loss and can be a direct consequence of aminoglycoside antibiotic treatment. Aminoglycosides such as gentamicin are effective therapy for serious Gram-negative bacterial infections such as some forms of meningitis, pneumonia, and sepsis. Aminoglycosides enter hair cells through mechanotransduction channels at the apical end of hair bundles and initiate intrinsic cell death cascades, but the precise cell signaling that leads to hair cell death is incompletely understood. Here, we examine the cell death pathways involved in aminoglycoside damage using the zebrafish (). The zebrafish lateral line contains hair cell-bearing organs called neuromasts that are homologous to hair cells of the mammalian inner ear and represents an excellent model to study ototoxicity. Based on previous research demonstrating a role for p53, Bcl2 signaling, autophagy, and proteasomal degradation in aminoglycoside-damaged hair cells, we used the Cytoscape GeneMANIA Database to identify additional proteins that might play a role in neomycin or gentamicin ototoxicity. Our bioinformatics analysis identified the pro-survival proteins phosphoinositide-dependent kinase-1 (PDK1) and X-linked inhibitor of apoptosis protein (Xiap) as potential mediators of gentamicin-induced hair cell damage. Pharmacological inhibition of PDK1 or its downstream mediator protein kinase C facilitated gentamicin toxicity, as did mutation, suggesting that both PI3K and endogenous Xiap confer protection. Surprisingly, aminoglycoside-induced hair cell death was highly attenuated in wild type Tupfel long-fin (TL fish; the background strain for the mutant line) compared to wild type AB zebrafish. Pharmacologic manipulation of p53 suggested that the strain difference might result from decreased p53 in TL hair cells, allowing for increased hair cell survival. Overall, our studies identified additional steps in the cell death cascade triggered by aminoglycoside damage, suggesting possible drug targets to combat hearing loss resulting from aminoglycoside exposure.
内耳毛细胞死亡会导致感音神经性听力损失，这可能是氨基糖苷类抗生素治疗的直接后果。庆大霉素等氨基糖苷类药物是治疗某些形式的脑膜炎、肺炎和败血症等严重革兰氏阴性细菌感染的有效疗法。氨基糖苷类药物通过毛束顶端的机械转导通道进入毛细胞，并引发内在的细胞死亡级联反应，但导致毛细胞死亡的确切细胞信号传导尚不完全清楚。在这里，我们使用斑马鱼研究氨基糖苷类损伤所涉及的细胞死亡途径。斑马鱼侧线包含称为神经丘的带有毛细胞的器官，这些器官与哺乳动物内耳的毛细胞同源，是研究耳毒性的优秀模型。基于先前的研究表明p53、Bcl2信号传导、自噬和蛋白酶体降解在氨基糖苷类损伤的毛细胞中起作用，我们使用Cytoscape GeneMANIA数据库来识别可能在新霉素或庆大霉素耳毒性中起作用的其他蛋白质。我们的生物信息学分析确定了促生存蛋白磷酸肌醇依赖性激酶-1（PDK1）和X连锁凋亡抑制蛋白（Xiap）是庆大霉素诱导的毛细胞损伤的潜在介质。对PDK1或其下游介质蛋白激酶C的药理抑制促进了庆大霉素毒性， 突变也是如此，这表明PI3K和内源性Xiap都具有保护作用。令人惊讶的是，与野生型AB斑马鱼相比，野生型图普费尔长鳍（TL鱼；突变系的背景品系）中氨基糖苷类诱导的毛细胞死亡高度减弱。对p53的药理操作表明，品系差异可能是由于TL毛细胞中p53减少，从而使毛细胞存活率增加。总体而言，我们的研究确定了氨基糖苷类损伤引发的细胞死亡级联反应中的其他步骤，提示了对抗氨基糖苷类暴露导致的听力损失的可能药物靶点。
