Circadian regulation of glucocorticoid-dependent inflammation in noise-induced synaptopathy

项目摘要 通过NIDCD基金（R21 DC 013172），我们发现噪音引起的听觉暂时性损伤 与白天相比，当暴露发生在夜间时，树突更严重。初步数据显示， 表明循环中的糖皮质激素在小鼠体内的夜间达到峰值， 对夜间噪音损伤的敏感性在不存在循环糖皮质激素的情况下（通过肾上腺切除术），暴露于 夜间噪声可使其听性脑干阈值完全恢复， 保护. RNAseq数据显示，耳蜗中的炎症通路在夜间上升，这是 在肾上腺切除的小鼠中消除，这表明炎症反应可能是更大的 听觉突触的脆弱性RNAseq在耳蜗中鉴定了7211个基因， 这些基因中有65%在夜间表现出最大表达。因为这不是标准做法， 听觉场在全天不同时间点采集样本，充分了解基因 耳蜗中缺乏白天和夜晚的调节。我们的实验室目前正在解决这个问题 挑战，目标如下： 具体目标1：识别显示昼夜节律的糖皮质激素依赖性炎症信号 这些模式是由白天或夜晚的耳蜗噪声创伤触发的。假设：GC调节 昼夜节律方式的炎症信号导致对夜间噪音创伤的更大炎症反应 与日相比。 具体目标2：确定耳蜗中的Bmal 1是否调节GC依赖性炎症反应。 信号响应白天或夜晚的噪音创伤。假设：在耳蜗中，核心时钟蛋白Bmal 1 调节响应于噪声的昼夜节律细胞因子释放并引起突触病。 具体目标3：开发针对昼夜节律机制的新药物治疗， 防止炎症引发的噪音诱发的突触病。假设：时钟的抑制 夜间可以通过抑制炎症反应来预防夜间噪声诱导的突触病。 该项目将阐明昼夜节律和糖皮质激素依赖性炎症信号如何导致耳蜗 暂时性噪音损伤后的突触病一系列功能性方法（听觉电生理学、噪声 创伤），定量形态学方法（耳蜗图，螺旋神经节神经元计数，突触前/后 计数）和分子方法（遗传小鼠模型，RNA测序）。最终， 将调节昼夜节律可能出现，以预防和治疗噪音引起的突触病。我们 结果将引入一个新的概念，听觉领域，即，时间药理学，其中最佳疗效 药物治疗的效果取决于给药的时间。这一提议的新颖理论概念是 听觉系统的最佳功能需要一段时间的活动，然后是休息， 受到生物钟基因的严格控制尽管这听起来简单明了，但这一概念既没有 以前在噪声创伤或治疗策略的背景下进行了探索。

Project Summary Through NIDCD funding (R21DC013172) we showed that noise-induced temporary damage to the auditory dendrites is more severe when the exposure occurs at night compared to the day. Preliminary data strongly suggest that circulating glucocorticoids, which peak at nighttime in mice, are responsible for the greater sensitivity to night noise trauma. In absence of circulating glucocorticoids (by adrenalectomy), mice exposed to night noise show complete recovery of their auditory brainstem thresholds, and have their synaptic ribbons protected. RNAseq data show that inflammatory pathways rise at nighttime in the cochlea, and this is abolished in adrenalectomised mice, suggesting that inflammatory response could underlie the greater vulnerability of the auditory synapse. The RNAseq identified 7211 genes in the cochlea that have circadian expression and 65% of these genes show maximal expression at night-time. Since it is not standard practice in the auditory field to collect samples at different time points throughout the day a full understanding of gene regulation during the day and the night in the cochlea is lacking. Our laboratory is currently addressing this challenge with the following aims: Specific Aim 1: To identify glucocorticoid-dependent inflammatory signals that display circadian patterns and are triggered by day or night noise trauma in the cochlea. Hypothesis: GCs modulate inflammatory signals in a circadian manner causing a greater inflammatory response to night noise trauma compared to the day. Specific Aim 2: To determine whether Bmal1 in the cochlea regulates the GC-dependent inflammatory signals in response to day or night noise trauma. Hypothesis: In the cochlea, the core clock protein Bmal1 regulates the circadian cytokine release in response to noise and causing synaptopathy. Specific Aim 3: To develop new pharmacological treatments targeting the circadian machinery to protect from inflammatory-triggered noise-induced synaptopathy. Hypothesis: Inhibition of the clock at nighttime can prevent night noise-induced synaptopathy via the inhibition of inflammatory responses. This project will clarify how circadian and glucocorticoid-dependent inflammatory signals cause cochlear synaptopathy after temporary noise trauma. A battery of functional methods (auditory electrophysiology, noise trauma), quantitative morphological methods (cochleograms, spiral ganglion neuron counts, pre/post synaptic counts) and molecular methods (genetic mouse models, RNA seq) will be used. Ultimately, novel drugs that will modulate circadian rhythms could emerge to prevent and treat from noise-induced synaptopathy. Our results will introduce a new concept to the auditory field, namely, chronopharmacology, where optimal efficacy of drug treatment depends on the time of administration. The novel theoretical concept of this proposal is that the optimal function of the auditory system requires periods of activity followed by rest that is tightly regulated by clock genes. As simple and obvious as this may sound, this concept has neither been previously explored in the context of noise trauma nor treatment strategies.