title: Protective effect of corticosteroid against the cytotoxicity of aminoglycoside otic drops on isolated cochlear outer hair cells.
abstract: OBJECTIVE
  Otic drops are commonly used not only for otitis externa but also for otorrhea in the presence of tympanic membrane perforation or tympanostomy tube. Many studies demonstrated the ototoxicity of aminoglycoside. In our previous study, we observed that gentamicin (GM), when activated with liver extract, demonstrated significant cytotoxicity. The purpose of this study was to assess the protective effect of corticosteroid against the cytotoxicity of GM and tobramycin drops using isolated cochlear outer hair cells (OHCs) in vitro with liver extract.
  
  
  METHODS
  OHCs from adult chinchilla cochleae were exposed to standard bathing solution, liver extract alone, and aminoglycoside otic drops with and without corticosteroid and liver extract. All experiments were performed at an osmolality of 305 +/- 5 mOsm, at room temperature, and for up to 60 minutes. The images of OHCs were recorded using an inverted microscope and analyzed on the Image Pro-Plus 3.0 program. Time to cell death and change of cell length were measured and analyzed.
  
  
  RESULTS
  The time to cell death and percent change in cell length observed was significantly longer in the GM + liver extract + dexamethasone group than the GM + liver extract group (P <.05). The Tobradex + liver extract group showed an insignificant increase in percent change of cell length (P >.05) and significantly increased time to cell death than the tobramycin + liver extract group (P <.05).
  
  
  CONCLUSIONS
  This study demonstrated that dexamethasone significantly reduced aminoglycoside cytotoxicity.
authors.affiliation: Division of Otolaryngology-Head and Neck Surgery, Loma Linda University School of Medicine, Loma Linda, California, USA.
authors.forename: Seong Kook
authors.initials: SK
authors.lastname: Park
authors.forename: Dukjoo
authors.initials: D
authors.lastname: Choi
authors.forename: Paul
authors.initials: P
authors.lastname: Russell
authors.forename: Earnest O
authors.initials: EO
authors.lastname: John
authors.forename: Timothy T K
authors.initials: TT
authors.lastname: Jung
mesh_terms: D000617:Aminoglycosides / Q000009:adverse effects* / Q000378:metabolism; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology / Q000627:therapeutic use*; D016923:Cell Death / Q000187:drug effects; D002558:Cerebrospinal Fluid Otorrhea / Q000188:drug therapy*; D002682:Chinchilla; D003907:Dexamethasone / Q000494:pharmacology / Q000627:therapeutic use*; D004359:Drug Therapy, Combination; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects*; D014031:Tobramycin / Q000009:adverse effects* / Q000378:metabolism; D018058:Tympanic Membrane Perforation / Q000188:drug therapy*
chemical_list: D000617:Aminoglycosides; D000893:Anti-Inflammatory Agents; D003907:Dexamethasone; D014031:Tobramycin