Department of Otorhinolaryngology, Affiliated Sixth People's Hospital of Shanghai Jiaotong University, 600 Yishan Road, Shanghai 200233, PR China.
Department of Otolaryngology Head and Neck Surgery, The Third People's Hospital of Chengdu, PR China.
Neurotoxicology. 2019 Mar;71:75-86. doi: 10.1016/j.neuro.2018.12.004. Epub 2018 Dec 19.
Exposure to high levels of bilirubin in hyperbilirubinemia patients and animal models can result in sensorineural deafness. However, the mechanisms underlying bilirubin-induced damage to the inner ear, including the cochlear and vestibular organs, remain unknown. The present analyses of cochlear and vestibular organotypic cultures obtained from postnatal day 3 rats exposed to bilirubin at varying concentrations (0, 10, 50, 100, or 250 μM) for 24 h revealed that auditory nerve fibers (ANFs) and vestibular nerve endings were destroyed even at low doses (10 and 50 μM). Additionally, as the bilirubin dose increased, spiral ganglion neurons (SGNs) and vestibular ganglion neurons (VGNs) exhibited gradual shrinkage in conjunction with nuclei condensation or fragmentation in a dose-dependent manner. The loss of cochlear and vestibular hair cells (HCs) was only evident in explants treated with the highest concentration of bilirubin (250 μM), and bilirubin-induced major apoptosis most likely occurred via the extrinsic apoptotic pathway. Thus, the present results indicate that inner ear neurons and fibers were more sensitive to, and exhibited more severe damage following, bilirubin-induced neurotoxicity than sensory HCs, which illustrates the underlying causes of auditory neuropathy and vestibulopathy in hyperbilirubinemia patients.
高胆红素血症患者和动物模型中胆红素水平升高可导致感觉神经性耳聋。然而,胆红素对内耳(包括耳蜗和前庭器官)损伤的机制尚不清楚。本研究通过对出生后 3 天的大鼠的耳蜗和前庭器官培养物进行分析,这些大鼠在胆红素浓度为 0、10、50、100 或 250μM 下暴露 24 小时,结果显示,即使在低剂量(10 和 50μM)下,听觉神经纤维(ANFs)和前庭神经末梢也会被破坏。此外,随着胆红素剂量的增加,螺旋神经节神经元(SGNs)和前庭神经节神经元(VGNs)逐渐出现细胞核浓缩或碎裂,呈剂量依赖性缩小。只有在胆红素浓度最高(250μM)的实验组中,才观察到耳蜗和前庭毛细胞(HCs)的丢失,并且胆红素诱导的主要细胞凋亡很可能通过外在凋亡途径发生。因此,本研究结果表明,与感觉性 HCs 相比,内耳神经元和纤维对胆红素诱导的神经毒性更敏感,且损伤更严重,这说明了高胆红素血症患者中听觉神经病和前庭病的潜在原因。