Basic and Clinical Studies of Noise-Induced and Age-Related Hearing Loss

噪声引起的和与年龄相关的听力损失的基础和临床研究

• 批准号: 7769547
• 负责人: Sharon G Kujawa
• 金额: $ 37.37万
• 依托单位: MASSACHUSETTS EYE AND EAR INFIRMARY
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-03-05 至 2013-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7769547
• 关键词: 3-Dimensional; Acoustic Nerve; Acoustic Trauma; Acoustics; Acute; Address; Age; Aging; Animals; Area; Auditory; Axon; Benign; Biological Assay; Biology; Brain-Derived Neurotrophic Factor; Cell Death; Chronic; Clinical Research; Cochlea; Cochlear Nerve; Complement; Coupled; DNQX; Data; Deterioration; Development; Down-Regulation; Drug Delivery Systems; Ear; Electrophysiology (science); Elements; Environment; Epithelium; Etiology; Evaluation; Event; Excitatory Amino Acid Antagonists; Exposure to; Fiber; Functional disorder; GLAST Protein; Gene Expression; Genetic; Glutamate Agonist; Glutamate Transporter; Glutamates; Hair Cells; Hearing; Hour; Human; Immunohistochemistry; Infusion procedures; Injury; Inner Hair Cells; Interruption; Labyrinth; Link; Literature; Measurement; Mediating; Molecular Biology; Motion; Mus; NTF3 gene; Natural regeneration; Nature; Nerve Degeneration; Neuregulins; Neurons; Neuropathy; Neurotrophic Tyrosine Kinase Receptor Type 2; Noise; Noise-Induced Hearing Loss; Performance; Perfusion; Peripheral; Pharmacology; Population; Presbycusis; Presynaptic Terminals; Prevention; Process; Public Health; Recovery; Reporter; Research; Reverse Transcriptase Polymerase Chain Reaction; Role; Secondary to; Sensorineural Hearing Loss; Signal Pathway; Signal Transduction; Site; Speech; Stereocilium; Supporting Cell; Swelling; Synapses; System; Techniques; Testing; Therapeutic Intervention; Time; Tissues; Transgenic Mice; Work; age related; excitotoxicity; ganglion cell; insight; mouse model; mutant; nerve supply; neuron loss; neuronal cell body; neurotensin mimic 2; neurotransmission; neurotrophic factor; novel strategies; otoacoustic emission; overexpression; prevent; public health relevance; receptor; reconstruction; reinnervation; relating to nervous system; research study; response; spiral ganglion; uptake

DESCRIPTION (provided by applicant): Acoustic overexposure is a growing problem, and understanding the long-term consequences is critical to public health. Our recent work in a mouse model of noise and aging shows that moderate exposures, which initially appear reversible and cause no acute or chronic hair cell loss, elicit a slow-onset loss of spiral ganglion cells (SGCs) when followed for months post-exposure. Confocal immunohistochemistry suggests that many SGC peripheral terminals, and their synapses on inner hair cells, disappear within the first days or hours, consistent with acute excitotoxic effects of acoustic overexposure. We hypothesize that this acute dendritic retraction disrupts normal neurotrophin signaling among hair cells, supporting cells and neurons in the cochlear epithelium, and that this interruption initiates the slow cell-death cascade in SGCs. The proposed Aims test this hypothesis by characterizing the nature and time course of neuronal degeneration and associated pathophysiology (Aim 1), and by manipulating acute excitotoxicity (Aim 2) or neurotrophin expression (Aim 3) and assessing the effects on cochlear neurodegeneration. Quantification of neuropathy (Aim 1a), will track degeneration over post-exposure time as it progresses from synapse, to peripheral axon, to cell body. Correlations with pathophysiology at population-response and single-fiber levels (Aim 1b) will verify if we have identified the functionally important structural changes, and will test the hypothesis that noise causes a preferential loss of neurons with low spontaneous rates. To test if acute excitotoxicity is the key upstream elicitor of the neuropathy, we exploit our techniques for cochlear perfusion in mouse to either 1) block noise-induced excitotoxicity with the glutamate antagonist DNQX (Aim 2a), 2) mimic it with the glutamate agonist AMPA (Aim 2b) or 3) enhance it using mice with targeted deletion of the glutamate transporter GLAST (Aim 2c). To test the role of neurotrophins in the slow cascade of cell death, we will assay (via qRT-PCR, immunohistochemistry and a NT3-reporter mouse) gene expression levels of key molecules in the neurotrophin signaling pathway as a function of post-exposure time (Aim 3a), and attempt a rescue experiment (reduce/prevent loss of neurons; promote re-innervation of intact IHCs) using mouse lines with inducible neurotrophin overexpression in either hair cells or supporting cells (Aim 3b). Understanding the nature, etiology and possible prevention of slow-onset neurodegeneration in our noise- exposed mice has important ramifications for human hearing. It suggests that primary neuronal loss is a more common and important aspect of acquired sensorineural hearing loss than previously thought. It also raises important concerns re possible long-term consequences of apparently benign acoustic overexposures: the phenomenon of slow-onset noise-induced neurodegeneration may contribute in a major way to the main hearing-related complaint in aging humans, i.e. problems understanding speech in a noisy environment. PUBLIC HEALTH RELEVANCE Our recent work in mouse shows that noise-exposures, even those that appear to result in fully reversible threshold shifts, actually set in motion a slow cell death cascade leading to the ultimate loss of roughly half of the neural elements throughout large regions of the cochlea. If generally applicable to the mammalian ear, as there is every reason to believe it will be, the phenomenon of slow-onset, noise-induced, primary, cochlear-nerve loss is potentially a very common problem with significant public health implications. Our proposed experiments provide a powerful platform to study the phenomenon and to probe its mechanisms, using a cochlear insult (i.e. noise) that is highly relevant to the human condition.

描述（由申请人提供）：声学过度暴露是一个日益严重的问题，了解其长期后果对公众健康至关重要。我们最近在噪音和衰老小鼠模型中的研究表明，中等强度的暴露最初看起来是可逆的，不会导致急性或慢性毛细胞损失，但在暴露后数月内会引起螺旋神经节细胞（SGC）的缓慢损失。 。共聚焦免疫组织化学表明，许多 SGC 外周末梢及其在内毛细胞上的突触在最初几天或几小时内消失，这与声音过度暴露的急性兴奋毒性作用一致。我们假设这种急性树突回缩破坏了耳蜗上皮中毛细胞、支持细胞和神经元之间的正常神经营养蛋白信号传导，并且这种中断启动了 SGC 中缓慢的细胞死亡级联。拟议的目标通过表征神经元变性和相关病理生理学的性质和时间进程（目标 1），并通过操纵急性兴奋性毒性（目标 2）或神经营养蛋白表达（目标 3）并评估对耳蜗神经变性的影响来检验这一假设。神经病变的量化（目标 1a）将跟踪暴露后时间的变性，因为它从突触进展到外周轴突，再到细胞体。群体反应和单纤维水平（目标 1b）与病理生理学的相关性将验证我们是否已经识别出功能上重要的结构变化，并将检验噪声导致自发率低的神经元优先损失的假设。为了测试急性兴奋性毒性是否是神经病的关键上游诱发因素，我们利用小鼠耳蜗灌注技术来 1) 用谷氨酸拮抗剂 DNQX 阻断噪声诱导的兴奋性毒性（目标 2a），2) 用谷氨酸激动剂模拟它AMPA（目标 2b）或 3）利用小鼠靶向删除谷氨酸转运蛋白 GLAST（目标2c）。为了测试神经营养因子在细胞死亡缓慢级联中的作用，我们将测定（通过 qRT-PCR、免疫组织化学和 NT3 报告小鼠）神经营养因子信号通路中关键分子的基因表达水平作为暴露后时间的函数（目标 3a），并尝试使用在毛细胞或毛细胞中诱导神经营养素过度表达的小鼠品系进行救援实验（减少/防止神经元损失；促进完整 IHC 的重新神经支配）支持细胞（目标 3b）。了解暴露于噪声的小鼠中缓慢发生的神经变性的性质、病因和可能的预防措施对于人类听力具有重要影响。这表明原发性神经元损失是获得性感音神经性听力损失的一个比以前认为的更常见和更重要的方面。它还引起了人们对明显良性的声音过度暴露可能产生的长期后果的重要担忧：缓慢发生的噪声引起的神经变性现象可能在很大程度上导致老年人与听力相关的主要症状，即理解语音的问题。嘈杂的环境。公共健康相关性我们最近对小鼠的研究表明，噪声暴露，即使是那些似乎导致完全可逆阈值变化的噪声暴露，实际上也会启动缓慢的细胞死亡级联，导致整个大区域中大约一半的神经元件最终损失耳蜗的。如果普遍适用于哺乳动物的耳朵（有充分的理由相信它会如此），那么缓慢发生的、噪声引起的、原发性耳蜗神经丧失的现象可能是一个非常常见的问题，具有重大的公共卫生影响。我们提出的实验提供了一个强大的平台来研究这种现象并探索其机制，使用与人类状况高度相关的耳蜗损伤（即噪音）。