Ameliorating systemic gentamicin uptake by sensory hair cells

说明(申请人提供)：氨基糖苷类抗生素对于治疗危及生命的细菌败血症是必不可少的，但会导致急性肾毒性和永久性耳聋/平衡障碍。在美国，这些有害的副作用每年影响多达12万人。这项提议的目的是确定氨基糖苷类药物通过血迷路屏障进入耳蜗液和感觉毛细胞以诱导细胞毒性和听力损失的分子机制。长期的目标是保护耳蜗感觉毛细胞免受药物所致的耳毒性，并维持终身听力功能。我们公布的数据表明，系统输送的庆大霉素在毛细胞摄取之前从血管纹通过血管纹进入内淋巴。我们已经确定了一种候选的氨基糖苷类转运蛋白，抑制该转运蛋白可以减少荧光标记的氨基糖苷类药物在耳蜗中的摄取。毛细胞对氨基糖苷的摄取也被先前的噪声创伤所增强，这意味着除了机械电转导通道外，还参与了额外的庆大霉素阳离子通道。该项目的具体目标是：第一，确定候选氨基糖苷类转运体是否在体内摄取庆大霉素、耳蜗转运和诱导耳毒性(目标1)所必需。第二，检测毛细胞表达的其他非选择性阳离子通道(除MET通道外)是否为庆大霉素所致并诱导细胞毒作用(目标2)。第三，由于噪音创伤和氨基糖苷类药物会引发毛细胞的氧化应激，我们将确定氧化应激是否激活体内庆大霉素的阳离子通道并增加毛细胞对庆大霉素的摄取(目标3)。识别氨基糖苷跨血脑屏障转运和进入毛细胞的分子机制，对于合理开发新的临床策略，在挽救生命的氨基糖苷治疗期间保护耳蜗功能至关重要。例如，参与这些机制的基因随后可以被筛选出在已识别的庆大霉素通道和转运体中诱导功能获得活性的单一核多态(SNP)。这将使临床医生能够更明智地使用氨基糖苷类药物，并在治疗危及生命的细菌性败血症、结核病和早产儿预防以及严重烧伤和冲击伤的伤员之前，对个别病例进行庆大霉素治疗。

DESCRIPTION (provided by applicant): Aminoglycoside antibiotics are essential for treating life-threatening bacterial sepsis, yet induce acute nephrotoxicity and permanent deafness/balance disorders. These noxious side-effects affect as many as 120,000 individuals each year in the US. The goal of this proposal is to identify the molecular mechanisms that traffic aminoglycosides across the blood-labyrinth barrier into the cochlear fluids and sensory hair cells to induce cytotoxicity and hearing loss. The long-term goal is to protect the cochlear sensory hair cells from drug-induced ototoxicity, and maintain life-long hearing function. Our published data indicate that systemically-delivered gentamicin is trafficked from the strial vasculature, across the stria vascularis, into endolymph prior to hair-cell uptake. We have identified a candidate aminoglycoside transporter, and inhibition of this transporter reduces cochlear uptake of fluorescently-tagged aminoglycosides. Aminoglycoside uptake by hair cells is also potentiated by prior noise trauma, implicating the involvement of additional gentamicin-permeant cation channels besides the mechanoelectrical transduction channel. The specific aims of this project are: First, to determine if the candidate aminoglycoside transporter is required for gentamicin uptake, cochlear trafficking and induction of ototoxicity in vivo (Aim 1). Second, to test if other non-selective cation channels (besides the MET channel) expressed by hair cells are gentamicin-permeant and induce cytotoxicity (Aim 2). And, third, since noise trauma and aminoglycosides trigger oxidative stress in hair cells, we will determine if oxidative stress activates gentamicin-permeant cation channels and enhances hair cell uptake of gentamicin in vivo (Aim 3). Identifying the molecular mechanisms of aminoglycoside trafficking across the BLB and entry into hair cells is crucial to rational development of new clinical strategies that protect cochlear function during life-saving aminoglycoside therapy. For example, the genes involved in these mechanisms can then be screened for single nuclear polymorphisms (SNP) that induce gain-of-function activity in identified gentamicin-permeant channels and transporters. This will allow clinicians to use aminoglycosides more judiciously and personalize gentamicin therapy for individual cases prior to treatment for life-threatening bacterial sepsis, tuberculosis and for prophylaxis in premature babies, and casualties with severe burns and blast injuries.