Hearing and Speech Rehabilitation Institute, College of Special Education, Binzhou Medical University, Yantai, China.
Center for Hearing and Deafness, University at Buffalo, Buffalo, NY, USA.
Cell Death Dis. 2021 Jan 4;12(1):3. doi: 10.1038/s41419-020-03328-6.
Macroautophagy/autophagy is a highly conserved self-digestion pathway that plays an important role in cytoprotection under stress conditions. Autophagy is involved in hepatotoxicity induced by acetaminophen (APAP) in experimental animals and in humans. APAP also causes ototoxicity. However, the role of autophagy in APAP-induced auditory hair cell damage is unclear. In the present study, we investigated autophagy mechanisms during APAP-induced cell death in a mouse auditory cell line (HEI-OC1) and mouse cochlear explant culture. We found that the expression of LC3-II protein and autophagic structures was increased in APAP-treated HEI-OC1 cells; however, the degradation of SQSTM1/p62 protein, the yellow puncta of mRFP-GFP-LC3 fluorescence, and the activity of lysosomal enzymes decreased in APAP-treated HEI-OC1 cells. The degradation of p62 protein and the expression of lysosomal enzymes also decreased in APAP-treated mouse cochlear explants. These data indicate that APAP treatment compromises autophagic degradation and causes lysosomal dysfunction. We suggest that lysosomal dysfunction may be directly responsible for APAP-induced autophagy impairment. Treatment with antioxidant N-acetylcysteine (NAC) partially alleviated APAP-induced autophagy impairment and apoptotic cell death, suggesting the involvement of oxidative stress in APAP-induced autophagy impairment. Inhibition of autophagy by knocking down of Atg5 and Atg7 aggravated APAP-induced ER and oxidative stress and increased apoptotic cell death. This study provides a better understanding of the mechanism responsible for APAP ototoxicity, which is important for future exploration of treatment strategies for the prevention of hearing loss caused by ototoxic medications.
自噬是一种高度保守的自我消化途径，在应激条件下的细胞保护中起着重要作用。自噬参与了实验动物和人类中对乙酰氨基酚（APAP）诱导的肝毒性。APAP 也会引起耳毒性。然而，自噬在 APAP 诱导的听觉毛细胞损伤中的作用尚不清楚。在本研究中，我们研究了自噬机制在 APAP 诱导的小鼠听觉细胞系（HEI-OC1）和小鼠耳蜗外植体培养中的细胞死亡。我们发现 LC3-II 蛋白和自噬结构的表达在 APAP 处理的 HEI-OC1 细胞中增加；然而，SQSTM1/p62 蛋白的降解、mRFP-GFP-LC3 荧光的黄色斑点和溶酶体酶的活性在 APAP 处理的 HEI-OC1 细胞中降低。p62 蛋白的降解和溶酶体酶的表达也在 APAP 处理的小鼠耳蜗外植体中降低。这些数据表明，APAP 处理会损害自噬降解并导致溶酶体功能障碍。我们认为溶酶体功能障碍可能直接导致 APAP 诱导的自噬障碍。抗氧化剂 N-乙酰半胱氨酸（NAC）的治疗部分缓解了 APAP 诱导的自噬障碍和凋亡细胞死亡，表明氧化应激参与了 APAP 诱导的自噬障碍。通过敲低 Atg5 和 Atg7 抑制自噬加重了 APAP 诱导的 ER 和氧化应激，并增加了凋亡细胞死亡。本研究提供了对 APAP 耳毒性的机制的更好理解，这对于未来探索预防耳毒性药物引起的听力损失的治疗策略非常重要。
