Department of Otolaryngology Head and Neck Surgery, Chinese People's Liberation Army General Hospital, Beijing 100853, China.
Chin Med J (Engl). 2013;126(15):2923-7.
Modern research has provided new insights into the biological mechanisms of noise-induced hearing loss, and a number of studies showed the appearance of increased reactive oxygen species (ROS) and reactive nitrogen species (RNS) during and after noise exposure. This study was designed to investigate the noise exposure induced nitrotyrosine change and the mechanism of outer hair cells death in guinea pig cochlea.
Thirty guinea pigs were used in this study. The experimental animals were either exposed for 4 hours per day to broadband noise at 122 dB SPL (A-weighted) for 2 consecutive days or perfused cochleae with 5 mg/ml of the SIN1 solutions, an exogenous NO and superoxide donor, for 30 minutes. Then the cochleae of the animals were dissected. Propidium iodide (PI), a DNA intercalating fluorescent probe, was used to trace morphological changes in OHC nuclei. The distribution of nitrotyrosine (NT) in the organ of Corti and the cochlear lateral wall tissue from the guinea pigs were examined using fluorescence immunohistochemistry method. Whole mounts of organ of Corti were prepared. Morphological and fluorescent changes were examined under a confocal microscope.
Either after noise exposure or after SIN1 perfusion, outer hair cells (OHCs) death with characteristics of both apoptotic and necrotic degradation appeared. Nitrotyrosine immunolabeling could be observed in the OHCs from the control animals. After noise exposure, NT immunostaining became much greater than the control animals in OHCs. The apoptotic OHC has significant increase of nitrotyrosine in and around the nucleus following noise exposure. In the normal later wall of cochleae, relatively weak nitrotyrosine immunolabeling could be observed. After noise exposure, nitrotyrosine immunoactivity became stronger in stria vascularis.
Noise exposure induced increase of nitrotyrosine production is associated with OHCs death suggesting reactive nitrogen species participation in the cochlear pathophysiology of noise-induced hearing loss.
现代研究为噪声性听力损失的生物学机制提供了新的见解，许多研究表明，在噪声暴露期间和之后，活性氧（ROS）和活性氮（RNS）的数量增加。本研究旨在研究豚鼠耳蜗中噪声暴露诱导的硝基酪氨酸变化和外毛细胞死亡的机制。
本研究使用了 30 只豚鼠。实验动物每天暴露于 122dB SPL（A 加权）的宽带噪声中 4 小时，连续 2 天，或者用 5mg/ml 的 SIN1 溶液（外源性 NO 和超氧化物供体）灌流耳蜗 30 分钟。然后解剖动物的耳蜗。碘化丙啶（PI），一种 DNA 插入荧光探针，用于追踪 OHC 核的形态变化。使用荧光免疫组织化学方法检测豚鼠耳蜗 Corti 器官和耳蜗外侧壁组织中硝基酪氨酸（NT）的分布。制备 Corti 器官的全距。在共聚焦显微镜下检查形态和荧光变化。
无论是噪声暴露后还是 SIN1 灌注后，外毛细胞（OHC）死亡都表现出凋亡和坏死降解的特征。在对照组动物的 OHC 中可以观察到硝基酪氨酸免疫标记。噪声暴露后，NT 免疫染色比对照组动物的 OHC 更明显。凋亡的 OHC 在噪声暴露后细胞核内和周围的硝基酪氨酸明显增加。在正常耳蜗的外侧壁中，可以观察到相对较弱的硝基酪氨酸免疫标记。噪声暴露后，血管纹中的硝基酪氨酸免疫活性增强。
噪声暴露诱导的硝基酪氨酸产生增加与 OHC 死亡有关，表明活性氮参与了噪声性听力损失的耳蜗病理生理学过程。
