Maximizing Hearing Recovery from Peri-Synaptic Damage

主要研究者：李红哲项目总结 项目名称：最大限度地从突触周围损伤中恢复听力 节目概要 耳毒性药物如氨基糖苷类抗生素和抗肿瘤顺铂， 感觉毛细胞和螺旋神经节神经元内的应力，影响突触功能， 向中央听觉系统的信号传输。我们假设耳毒性耳蜗突触 在某种程度上类似于噪声诱发的突触病的损伤，解释了观察结果， 在各种耳毒性损伤后，在特定剂量范围内，在没有有效干预的情况下， 功能永久恶化，尽管很少或没有毛细胞损失。因此，在本项目中， 我们将探讨噪声或氨基糖苷类药物引起突触损伤的相似性和差异性 并在细胞和分子水平上破译突触病的原因。 本项目拟对氨基糖苷类抗生素的处理条件进行考察， 导致典型的突触病，并寻找最佳的治疗时间窗口和候选 药物干预退化过程。通过这种方式，研究结果将允许最大的听力 在噪声过度刺激或暴露于耳毒性损伤后恢复。具体目标是 项目是： 首先，确定产生最大耳毒性突触病的最佳氨基糖苷类药物剂量 CBA/CaJ小鼠中没有功能性毛细胞损伤。将制定14天庆大霉素方案， 使用不同的剂量策略。电生理和声学测量，包括听觉测量 脑干反应（ABR）和畸变产物耳声发射（DPOAE），将用于 分别评估突触后（ABR）和突触前（DPOAE）外毛细胞功能。 其次，使用最佳庆大霉素剂量，我们将表征动态突触修饰 耳毒性突触病在这里，我们将进行形态学研究，以可视化突触 的变化和螺旋神经节神经元的存活在多个时间点后开始， 庆大霉素治疗。 第三，我们将确定耳蜗炎症对突触损伤的影响， 改良的小鼠模型，包括Darc和TrpV 1敲除小鼠。两种小鼠都表现出一定的 对噪声性听力损失的抵抗程度。 最后，我们将测试潜在的突触病听力康复策略，重点是 抑制炎症的皮质类固醇。这是该项目的主要修复部分，我们 将在耳毒性和噪声诱导的模型中进行几种治疗剂的鼓室内注射， 突触病在治疗后的几个时间，将通过ABR和DPOAE评估听觉功能 点和突触元件通过免疫标记和显微镜检查。 耳蜗突触病在听觉损伤中起着重要作用，可能影响到上皮层， 阈值听觉功能这些功能对于频率选择性和时间选择性是至关重要的。 处理，这对于在噪声环境中的语音理解和听力都很重要。这 在军事环境中，当有效的人际沟通 这意味着生死存亡，极大地影响着退伍军人的生活质量。这项研究计划最终 以提高内耳突触损伤康复的有效性。

Principal Investigator: Hongzhe Li Program Summary Project Title: Maximizing hearing recovery from peri-synaptic damage Program Summary Ototoxicants such as aminoglycoside antibiotics, and anti-neoplastic cisplatin, cause cytoplasmic stress within the sensory hair cells and the spiral ganglion neurons, affecting synaptic functionalities and signal transmission towards the central auditory system. We hypothesize that ototoxic cochlear synaptic damage that to some extent resembles noise-induced synaptopathy, accounts for the observation that after various ototoxic insults, within particular dosing range, without effective intervention, the auditory functions deteriorate permanently, despite of minimal or no hair cell loss. Thus, in the present project, we will investigate the similarity and discrepancy of synaptic damage due to noise or aminoglycosides and decipher the cause of synaptopathy at cellular and molecular levels. The proposed project is designed to investigate the aminoglycoside treatment conditions, which result in classic synaptopathy, and to search for optimal therapeutic temporal windows and candidate agents to intervene with degeneration process. In this manner, study findings will permit maximal hearing recovery after either noise over-stimulation or exposure to ototoxic insults. The specific aims of this project are to: First, determine the optimal aminoglycoside dosage that produces maximal ototoxic synaptopathy without functional hair cell damage in CBA/CaJ mice. An established 14-day gentamicin protocol will be used, with various dosing strategy. Electrophysiological and acoustical measures, including auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs), will be used to assess post-synaptic (ABR) and pre-synaptic (DPOAE) outer hair cell function, respectively. Second, using the optimal gentamicin dosing, we will characterize the dynamic synaptic modification in ototoxic synaptopathy. Here, we will conduct morphological investigation to visualize the synaptic variation and the survival of spiral ganglion neurons at multiple time points after the initiation of gentamicin treatment. Third, we will determine the effects of cochlear inflammation on synaptic damage, using genetically modified mouse models including Darc and TrpV1 knockout mice. Both strains of mice present certain degree of resistance to noise-induced hearing loss. Last, we will test potential audiologic rehabilitation strategies for synaptopathy, focusing on inflammation suppressive corticosteroids. This is the major rehabilitation component of the project, we will perform intratympanic injection of several therapeutics in the models of ototoxic and noise-induced synaptopathy. Auditory function will be assessed by ABR and DPOAE at several post-treatment time points, and synaptic element examined by immunolabeling and microscopy. Cochlear synaptopathy plays an essential role in auditory damage, likely affecting the supra- threshold auditory functions. These functions are critical for frequency selectivity and temporal processing, both important for speech understanding and listening in the noise environment. This creates an extreme adverse situation in military settings when effective interpersonal communication means life-or-death, and greatly affects the life quality of Veterans. This research proposal is ultimately to improve the effectiveness of rehabilitation from synaptic damage in the inner ear.