title: Dose-dependant radiation-induced apoptosis in a cochlear cell-line.
abstract: Cisplatin and gentamycin are both ototoxic and they have been shown to induce cochlear cell apoptosis. Although radiation is also ototoxic, radiation-induced apoptosis in cochlear cells has not been studied. This study aimed to investigate the biophysical changes of dose-related radiation-induced cochlear cell apoptosis in an experimental model. Post gamma-irradiation apoptosis was demonstrated in the cochlear cell-line OC-k3 by flow cytometry and TUNEL assay. This was dose-dependant with enhanced apoptosis resulting after 20 than 5 Gy, and occurred predominantly at 72 h post-irradiation. Microarray analysis showed associated dose-dependant apoptotic gene regulation changes. Western blotting revealed p53 up-regulation of at 72 h and phosphorylation at 3, 24, 48 and 72 h after irradiation. Early activation of c-jun occurred at 3 h, but was not sustained with time. Associated dose-dependant intracellular generation of reactive oxygen species (ROS) was also demonstrated using 2', 7'-dichlorofluorescein diacetate. In conclusion, this study demonstrated a dose-dependant cochlear cell apoptosis and associated ROS generation after irradiation, with p53 possibly playing a key role. Based on this ROS-linked apoptotic model, anti-oxidants and anti-apoptotic factors could potentially be used to prevent radiation-induced sensori-neural hearing loss. As these medications can be delivered topically through the middle ear, their systematic side effects could therefore be minimized.
authors.affiliation: Department of Otolaryngology, Singapore General Hospital, Singapore, 169608, Singapore. low.wong.kein@sgh.com.sg
authors.forename: Wong-Kein
authors.initials: WK
authors.lastname: Low
authors.forename: Michelle G K
authors.initials: MG
authors.lastname: Tan
authors.forename: Li
authors.initials: L
authors.lastname: Sun
authors.forename: Alvin W C
authors.initials: AW
authors.lastname: Chua
authors.forename: Lip-Kai
authors.initials: LK
authors.lastname: Goh
authors.forename: De-Yun
authors.initials: DY
authors.lastname: Wang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000528:radiation effects*; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D003051:Cochlea / Q000166:cytology* / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005434:Flow Cytometry; D005720:Gamma Rays; D020287:In Situ Nick-End Labeling; D051379:Mice; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D016755:Proto-Oncogene Proteins c-jun; D017382:Reactive Oxygen Species; D016159:Tumor Suppressor Protein p53