Sun Fanfan, Zhang Junge, Chen Li, Yuan Yuhao, Guo Xiaotao, Dong Liuyi, Sun Jiaqiang
Department of Otolaryngology-Head and Neck Surgery, The First Affiliated Hospital of USTC, Hefei 230001, China; Department of Pharmacology, Key Laboratory of Anti-Inflammatory and Immunopharmacology of Ministry of Education, Key Laboratory of Chinese Medicine Research and Development of State Administration of Traditional Chinese Medicine, Anhui Medical University, Hefei 230032, China.
Department of Otolaryngology-Head and Neck Surgery, The First Affiliated Hospital of USTC, Hefei 230001, China.
Neuroscience. 2021 Jun 15;465:116-127. doi: 10.1016/j.neuroscience.2021.03.032. Epub 2021 Apr 7.
To investigate the role of the exchange protein directly activated by cAMP (Epac) signaling pathway in inner ear hair cell damage and apoptosis after noise exposure, we analyzed the expression level of Epac1 in a rat model of noise-induced hearing loss (NIHL), based on rat exposure to a 4-kHz and 106-dB sound pressure level (SPL) for 8 h. Loss of outer hair cells (OHCs), mitochondrial lesions, and hearing loss were examined after treatment with the Epac agonist, 8-CPT, or the Epac inhibitor, ESI-09. The effects of 8-CPT and ESI-09 on cell proliferation and apoptosis were examined by CCK-8 assays, holographic microscopy imaging, and Annexin-V FITC/PI staining in HEI-OC1 cells. The effects of 8-CPT and ESI-09 on Ca entry were evaluated by confocal Ca fluorescence measurement. We found that the expression level of Epac1 was significantly increased in the cochlear tissue after noise exposure. In NIHL rats, 8-CPT increased the loss of OHCs, mitochondrial lesions, and hearing loss compared to control rats, while ESI-09 produced the opposite effects. Oligomycin was used to induce HEI-OC1 cell damage in vitro. In HEI-OC1 cells treated with oligomycin, 8-CPT and ESI-09 increased and reduced cell apoptosis, respectively. Moreover, 8-CPT promoted Ca uptake in HEI-OC1 cells, while ESI-09 inhibited this process. In conclusion, our data provide strong evidence that the Epac1 signaling pathway mediates early pathological damage in NIHL, and that Epac1 inhibition protects from NIHL, identifying Epac1 as a new potential therapeutic target for NIHL.
为了研究环磷腺苷直接激活的交换蛋白（Epac）信号通路在噪声暴露后内耳毛细胞损伤和凋亡中的作用，我们基于大鼠暴露于4kHz、106dB声压级（SPL）8小时的噪声性听力损失（NIHL）大鼠模型，分析了Epac1的表达水平。在用Epac激动剂8-CPT或Epac抑制剂ESI-09处理后，检测外毛细胞（OHC）丢失、线粒体损伤和听力损失情况。通过CCK-8检测、全息显微镜成像以及HEI-OC1细胞中的膜联蛋白V FITC/PI染色，研究8-CPT和ESI-09对细胞增殖和凋亡的影响。通过共聚焦钙荧光测量评估8-CPT和ESI-09对钙内流的影响。我们发现噪声暴露后耳蜗组织中Epac1的表达水平显著升高。在NIHL大鼠中，与对照大鼠相比，8-CPT增加了OHC丢失、线粒体损伤和听力损失，而ESI-09则产生相反的效果。使用寡霉素在体外诱导HEI-OC1细胞损伤。在用寡霉素处理的HEI-OC1细胞中，8-CPT和ESI-09分别增加和减少了细胞凋亡。此外，8-CPT促进了HEI-OC1细胞中的钙摄取，而ESI-09抑制了这一过程。总之，我们的数据提供了强有力的证据，表明Epac1信号通路介导了NIHL的早期病理损伤，并且抑制Epac1可预防NIHL发生，确定Epac1为NIHL的一个新的潜在治疗靶点。
