Maximizing Hearing Recovery from Peri-Synaptic Damage

主要调查者：李鸿哲项目总结 项目标题：最大限度地从突触周围损伤中恢复听力 计划摘要 耳毒性药物，如氨基糖苷类抗生素和抗肿瘤顺铂，可引起细胞质 感觉毛细胞和螺旋神经节神经元内的应激，影响突触功能和 信号传输到中枢听觉系统。我们假设耳毒性耳蜗性突触 某种程度上类似于噪音诱导的突触的损伤，解释了观察到的 在各种耳毒性侮辱后，在特定剂量范围内，在没有有效干预的情况下，听觉 尽管毛细胞损失很小或没有，但功能会永久恶化。因此，在本项目中， 我们将研究噪声或氨基糖苷类药物引起的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形成的原因。 拟议的项目旨在调查氨基糖苷类药物的治疗条件， 导致经典的突触，并寻找最佳的治疗时间窗和候选者 药物干预退变过程。以这种方式，研究结果将允许最大限度的听力 在噪音过度刺激或暴露于耳毒性侮辱后恢复。这样做的具体目的是 项目的目标是： 首先，确定产生最大耳毒性突触的氨基糖苷类药物的最佳剂量 对CBA/CAJ小鼠无功能性毛细胞损伤。已建立的14天庆大霉素方案将是 使用，与不同的剂量策略。电生理和声学措施，包括听觉 脑干反应(ABR)和失真产物耳声发射(DPOAEs)将用于 分别评估突触后(ABR)和突触前(DPOAE)外毛细胞功能。 其次，使用最优的庆大霉素剂量，我们将表征动态突触修饰 在耳毒性突触疗法中。在这里，我们将进行形态学研究，以可视化突触 脑损伤后螺旋神经节神经元在多个时间点的变化及存活 庆大霉素治疗。 第三，我们将使用遗传学方法来确定耳蜗炎对突触损伤的影响 改良的小鼠模型包括DARC和TRPV1基因敲除小鼠。两个品系的小鼠都表现出一定的 对噪声性听力损失的抵抗程度。 最后，我们将测试突触病潜在的听力康复策略，重点是 抑制炎症的皮质类固醇。这是该项目的主要康复部分，我们 将在耳毒性和噪声性耳聋模型中进行鼓室内注射几种治疗药物 突触疗法。在治疗后的几个时间段用ABR和DPOAE评估听觉功能 通过免疫标记和显微镜观察突触元件。 耳蜗性突触在听觉损伤中起着至关重要的作用，可能会影响到大脑的上丘脑。 阈值听觉功能。这些函数对于频率选择性和时间是至关重要的 处理对于语音理解和在噪声环境中的收听都很重要。这 当有效的人际沟通时，在军事环境中造成极端不利的情况 关乎生死，极大地影响着退伍军人的生活质量。这项研究建议最终是 目的：提高内耳突触损伤的康复效果。

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.