Short interfering RNA against bax attenuates TNFα-induced ototoxicity in rat organ of corti explants

Objective. Evaluate the effectiveness of short interfering RNA against Bax (Bax siRNA) as a treatment for tumor necrosis factor a (TNFa)-induced auditory hair cell (HC) loss in rat organ of Corti (OC) explants. Study Design. Basic science. Setting. Basic science laboratory, University of Miami Ear Institute. Methods. Organ of Corti explants dissected from 3-day-old rats were cultured in control media, TNFa, and TNFa 1 Bax siRNA at 0, 48, and 72 hours in vitro. Real-time polymerase chain reaction, enzyme-linked immunosorbent assay, HC viability studies, immunofluorescence, and confocal microscopy were performed. Analysis of variance with post hoc testing was used with P <.05 considered significant. Results. The TNFa-damaged explants demonstrated significant decreases in viable HCs in the basal turn with corresponding increased levels of Bax gene and protein expression, compared with control explant levels. The levels of viable HCs and Bax gene and protein expression in TNFa 1 Bax siRNA-treated explants approached levels measured in control explants. Immunolocalization studies showed increased Bax protein expression in basal turn HCs in TNFa-treated explants, whereas control explants and TNFa 1 Bax siRNA-treated explants had low levels of Bax expression. Conclusion. TNFa initiates the programmed cell death of auditory HCs in OC explants through upregulation of proapoptotic Bax gene and protein expression. Bax siRNA blocks TNFainduced apoptosis of HCs by decreasing the TNFa-induced levels of Bax mRNA and protein expression in treated explants. Bax siRNA is an effective treatment for TNFa-induced ototoxicity in OC explants in vitro and has great potential to be a therapeutic agent against trauma/inflammation-induced hearing loss.