L-N-Acetylcysteine protects against radiation-induced apoptosis in a cochlear cell line.
CONCLUSIONS
L-N-Acetylcysteine (L-NAC) significantly reduced reactive oxygen species (ROS) generation and cochlear cell apoptosis after irradiation. The safe and effective use of L-NAC in reducing radiation-induced sensorineural hearing loss (SNHL) should be verified by further in vivo studies.


OBJECTIVE
Radiation-induced SNHL is a common complication after radiotherapy of head and neck tumours. There is growing evidence to suggest that ROS play an important role in apoptotic cochlear cell death from ototoxicity, resulting in SNHL. The aim of this study was to evaluate the effectiveness of L-NAC, an antioxidant, on radiation-induced apoptosis in cochlear cells.


METHODS
The OC-k3 cochlear cell line was studied after 0 and 20 Gy of gamma-irradiation. Cell viability assay was performed using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide. Flow cytometry and TUNEL assay were done with and without the addition of 10 mmol/L of L-NAC. Intracellular generation of ROS was detected by 2',7'-dichlorofluorescein diacetate, with comparisons made using fluorescence intensity.


RESULTS
L-NAC increased the viability of cells after irradiation. Generation of ROS was demonstrated at 1 h post-irradiation and was significantly reduced by L-NAC (p<0.0001). Flow cytometry and TUNEL assay showed cell apoptosis at 72 h post-irradiation, which was diminished by the addition of L-NAC.
Low
Wong-Kein
WK
Centre for Hearing & Cochlear Implant, Department of Otolaryngology, Singapore General Hospital, Singapore. low.wong.kein@sgh.com.sg
Sun
Li
L
Tan
Michelle G K
MG
Chua
Alvin W C
AW
Wang
De-Yun
DY
D000111:Acetylcysteine / Q000627:therapeutic use*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000528:radiation effects; D002460:Cell Line; D003051:Cochlea / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D005434:Flow Cytometry; D016166:Free Radical Scavengers / Q000627:therapeutic use*; D006319:Hearing Loss, Sensorineural / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D020287:In Situ Nick-End Labeling; D051379:Mice; D008822:Mice, Transgenic; D011833:Radiation Injuries, Experimental / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D017382:Reactive Oxygen Species / Q000378:metabolism
D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D000111:Acetylcysteine