title: Anti-apoptotic effect of dexamethasone in an ototoxicity model.
abstract: BACKGROUND
  Dexamethasone (DEX) is used for the treatment of various inner ear diseases. However, the molecular mechanism of DEX on gentamicin induced hair cell damage is not known. Therefore, this study investigated the protective effect of DEX on gentamicin (GM)-induced ototoxicity and the effect of GM on the expression of apoptosis related genes.
  
  
  METHODS
  The protective effects of DEX were measured by phalloidin staining of explant cultures of organ of Corti from postnatal day 2-3 mice with GM-induced hair cell loss. Terminal deoxynucleotidyl transferase dUTP nick end labeling staining was used to detect apoptosis and immunofluorescence was done to analyze the effect of DEX on the expression of apoptosis related genes.
  
  
  RESULTS
  Cochlear explant cultures of postnatal day-4-old mice were exposed to 0, 1, 5, 10, 30, 50, and 100 μg/ml DEX and GM during culture. DEX protected from GM-induced hair cell loss in the inner ear of postnatal day 4 mice. To understand the molecular mechanisms by which DEX pre-treatment decreased hair cell loss, the testes of cochlear explant cultures of postnatal day 4 mice were examined for changes in expression of cochlear apoptosis mediators. The pro-apoptotic protein Bax was significantly down-regulated and numbers of apoptotic hair cells were decreased.
  
  
  CONCLUSIONS
  DEX has a protective effect on GM-induced hair cell loss in neonatal cochlea cultures and the protective mechanism may involve inhibition of the mitochondrial apoptosis pathway. The combination with scaffold technique can improve delivery of DEX into the inner ear to protect GM-induced ototoxicity.
authors.affiliation: Department of Advanced Materials, Hannam University, Daejeon, Korea.
authors.forename: Jin Ho
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Nanobiomedical Science & WCU Research Center, Dankook University, Cheonan, Korea.
authors.forename: Se Heang
authors.initials: SH
authors.lastname: Oh
authors.affiliation: Department of Advanced Materials, Hannam University, Daejeon, Korea.
authors.forename: Tae Ho
authors.initials: TH
authors.lastname: Kim
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, Korea University College of Medicine, Seoul, Korea.
authors.forename: Yoon Young
authors.initials: YY
authors.lastname: Go
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, Korea University College of Medicine, Seoul, Korea.
authors.forename: Jae-Jun
authors.identifier: 0000-0002-8488-9091
authors.initials: JJ
authors.lastname: Song
keywords: Dexamethasone; Explant culture; Gentamicin; Ototoxicity