Cell survival and cell death in the auditory nerve

描述（由申请人提供）：螺旋神经节神经元（SGN）是主要传入神经元，将听觉信息从耳蜗的内毛细胞（IHC）传递到中枢神经系统。尽管已知 SGN 的退化是随着损伤和年龄的增长而发生的，但人们对体内这种病理学背后的细胞或分子事件的序列知之甚少。核因子 - KB (NF KB) 是一种转录因子，已知可调节细胞凋亡以响应包括神经元在内的许多细胞类型的损伤。 NF KB 还与细胞内 Ca2+ 调节相关，其功能障碍是神经元兴奋性毒性和细胞凋亡的重要因素。该项目的目标是确定 NF KB 在急性损伤后 SGN 存活中的作用。野生型和 NF KB 敲除小鼠将用作动物模型。这些基因敲除小鼠随着年龄的增长表现出渐进性听力损失，这与 SGN 的加速退化密切相关。此外，该敲除中 SGN 放射状树突的病理表明 IHC 突触的传入树突中存在过度的兴奋毒性。基于这些观察，我们假设 NF KB 在保护 SGN 免于急性损伤后变性中发挥抗凋亡作用，并且这种保护的潜在机制是 NF KB 活性有助于维持 SGN 中的 Ca2 稳态，从而减少兴奋性毒性作用。这些假设将通过两个具体目标进行检验。第一个目标是确定体内 NF KB 的激活是否可以保护 SGN 免于因急性噪音和哇巴因暴露而退化。噪音和哇巴因暴露可以对 SGN 变性的兴奋性毒性和细胞凋亡过程进行不同的评估。第二个目标将确定在这些急性损伤后是否需要 NF KB 活性来维持 SGN 中的 Ca2 稳态。这些实验采用电生理学、组织病理学和免疫荧光技术，以及使用电泳迁移率变动测定 (EMSA) 和实时逆转录聚合酶链反应 (RT-PCR) 的技术。这些研究的结果将有助于更好地了解 SGN 变性的细胞和分子机制，并将有助于开发预防和治疗人类感音神经性听力损失的新方法。

DESCRIPTION (provided by applicant): Spiral ganglion neurons (SGNs) are the primary afferent neurons that carry auditory information from the inner hair cells (IHCs) of the cochlea to the central nervous system. Although degeneration of SGNs is known to occur in response to injury and with age, little is known about the sequence of cellular or molecular events underlying this pathology in vivo. Nuclear factor - KB (NF KB) is a transcription factor that is known to regulate apoptosis in response to insults in many cell types, including neurons. NF KB is also associated with intracellular Ca2+ regulation, the dysfunction of which is an important factor in neuronal excitotoxicity and apoptosis. The goal of this project is to determine the role of NF KB in the survival of SGNs following acute insults. Wild type and NF KB knockout mice will be used as animal models. These knockout mice show a progressive hearing loss with age that is closely correlated with accelerated degeneration of SGNs. Moreover, the pathology of the SGN radial dendrites in this knockout suggests that excessive excitotoxicity is present in the afferent dendrites at IHC synapses. Based on these observations, we hypothesize that NF KB plays an anti-apoptotic role in the protection of SGNs from degeneration after acute injury, and that the underlying mechanism of this protection is that NF KB activity helps maintain Ca2+ homeostasis in SGNs to reduce excitotoxic effects. These hypotheses will be tested with two specific aims. The first aim will determine whether activation of NF KB in vivo protects SGNs from degeneration in response to acute noise and ouabain exposures. The noise and ouabain exposures allow differing assessments of the processes of excitotoxicity and apoptosis underlying SGN degeneration. The second aim will determine whether NF KB activity is required to maintain Ca2+ homeostasis in SGNs after these acute insults. These experiments employ electrophysiological, histopathological and immunofluorescence techniques, along with those using electrophoretic mobility shift assay (EMSA) and real-time reverse transcription polymerase chain reaction (RT-PCR). The results of these studies will lead to a better understanding of the cellular and molecular mechanisms of SGN degeneration and will contribute to the development of novel approaches to the prevention and treatment of sensorineural hearing loss in humans.