Dexamethasone suppresses cochlear Hes1 expression after noise exposure

Conclusion: Dexamethasone provides protection against noise-induced hearing loss (NIHL) possibly by suppressing cochlear Hes1 expression via a glucocorticoid receptor (GR)-dependent mechanism. Objectives: The purpose of the present study was to explore whether hairy and enhancer of split 1 (Hes1) was involved in the protective effect of dexamethasone against NIHL. Methods: Guinea pigs, which were administered intraperitoneal injections of either saline, 1.0 mg/kg dexamethasone, 20.0 mg/kg RU38,486, or a combination of both drugs (dexamethasone plus RU38,486) for 5 consecutive days, were exposed to white-band noise (115 dB sound pressure level). The expression level of Hes1 in cochleae was compared using real-time RT-PCR and Western blot analysis. Results: Noise exposure for 3 h induced auditory brainstem response (ABR) threshold elevations, outer hair cell losses, and increase of Hes1 expression. Dexamethasone pretreatment prevented the NIHL with decreased Hes1 expression, which could be blocked by GR antagonist RU38,486.