1
|
Guo S, Xu N, Chen P, Liu Y, Qi X, Liu S, Li C, Tang J. Rapamycin Protects Spiral Ganglion Neurons from Gentamicin-Induced Degeneration In Vitro. J Assoc Res Otolaryngol 2019; 20:475-487. [PMID: 31236744 DOI: 10.1007/s10162-019-00717-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2018] [Accepted: 03/12/2019] [Indexed: 02/06/2023] Open
Abstract
Gentamicin, one of the most widely used aminoglycoside antibiotics, is known to have toxic effects on the inner ear. Taken up by cochlear hair cells and spiral ganglion neurons (SGNs), gentamicin induces the accumulation of reactive oxygen species (ROS) and initiates apoptosis or programmed cell death, resulting in a permanent and irreversible hearing loss. Since the survival of SGNs is specially required for cochlear implant, new procedures that prevent SGN cell loss are crucial to the success of cochlear implantation. ROS modulates the activity of the mammalian target of rapamycin (mTOR) signaling pathway, which mediates apoptosis or autophagy in cells of different organs. However, whether mTOR signaling plays an essential role in the inner ear and whether it is involved in the ototoxic side effects of gentamicin remain unclear. In the present study, we found that gentamicin induced apoptosis and cell loss of SGNs in vivo and significantly decreased the density of SGN and outgrowth of neurites in cultured SGN explants. The phosphorylation levels of ribosomal S6 kinase and elongation factor 4E binding protein 1, two critical kinases in the mTOR complex 1 (mTORC1) signaling pathway, were modulated by gentamicin application in the cochlea. Meanwhile, rapamycin, a specific inhibitor of mTORC1, was co-applied with gentamicin to verify the role of mTOR signaling. We observed that the density of SGN and outgrowth of neurites were significantly increased by rapamycin treatment. Our finding suggests that mTORC1 is hyperactivated in the gentamicin-induced degeneration of SGNs, and rapamycin promoted SGN survival and outgrowth of neurites.
Collapse
Affiliation(s)
- Shasha Guo
- Department of Physiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China
| | - Nana Xu
- Department of Physiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China
| | - Peng Chen
- Department of Physiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China
| | - Ying Liu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Xiaofei Qi
- Department of Physiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China
| | - Sheng Liu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Cuixian Li
- Department of Physiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China. .,Key Laboratory of Mental Health of the Ministry of Education, Southern Medical University, Guangzhou, China. .,Institute of Mental Health, Southern Medical University, Guangzhou, China.
| | - Jie Tang
- Department of Physiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China. .,Key Laboratory of Mental Health of the Ministry of Education, Southern Medical University, Guangzhou, China. .,Institute of Mental Health, Southern Medical University, Guangzhou, China.
| |
Collapse
|