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）是将耳蜗内毛细胞（IHCs）的听觉信息传递到中枢神经系统的主要传入神经元。虽然已知sgn的退化是对损伤和年龄的反应，但对体内这种病理背后的细胞或分子事件的顺序知之甚少。核因子- KB （NF KB）是一种转录因子，在包括神经元在内的许多细胞类型的损伤反应中调节细胞凋亡。NF KB还与细胞内Ca2+调节有关，其功能障碍是神经元兴奋性毒性和细胞凋亡的重要因素。该项目的目的是确定NF KB在急性损伤后sgn存活中的作用。野生型和NF KB敲除小鼠将作为动物模型。这些基因敲除小鼠随着年龄的增长表现出进行性听力损失，这与sgn的加速退化密切相关。此外，在这种基因敲除中，SGN径向树突的病理情况表明，IHC突触的传入树突存在过度的兴奋毒性。基于这些观察结果，我们假设NF KB在急性损伤后保护sgn免于退化中起抗凋亡作用，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+稳态以减少兴奋毒性作用。这些假设将通过两个具体目标进行检验。第一个目的是确定体内NF KB的激活是否可以保护sgn免受急性噪音和酒精暴露的退化。噪声和缬草碱暴露可以对SGN变性背后的兴奋毒性和细胞凋亡过程进行不同的评估。第二个目的是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、组织病理学和免疫荧光技术，以及电泳迁移量转移测定（EMSA）和实时逆转录聚合酶链反应（RT-PCR）技术。这些研究结果将有助于更好地理解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.