Histone deacetylase inhibitor sodium butyrate attenuates gentamicin-induced hearing loss in vivo

ObjectiveAlthough histone deacetylase (HDAC) inhibition has been shown to protect against gentamicin (GM)-induced hearing loss in vitro, its protective effect has not been proven in vivo. In the present study, the aim was to investigate the protective effect of sodium butyrate (NaB), a specific HDAC inhibitor, on GM-induced ototoxicity in vivo.MethodsForty 8-week-old albino guinea pigs were divided into two experimental groups. Group 1 (n = 10) underwent bilateral ear surgery to place sponges (0.3 mm3) permeated with NaB (10 μl, 100 mg/ml) and physiological saline (10 μl; control) in the right and left round window niches, respectively. The sponges were left in place for 15 days to evaluate the effects of NaB at the applied concentration. Group 2 (n = 30) underwent the same bilateral ear surgery described for Group 1, except three days after surgery, the animals received intramuscular GM injections (200 mg/kg/day) for 5 consecutive days. Seven days after the final GM injection, the protective effects of NaB were examined.ResultsAfter 15 days of NaB treatment (10 μl, 100 mg/ml), an increase in histone acetylation was detected in Corti organ samples. Auditory brainstem response (ABR) threshold shifts and hair cell loss were also reduced in NaB-treated ears after GM administration. Furthermore, GM treatment increased HDAC1 expression in outer hair cells (OHCs) in vivo, and NaB blocked this action.ConclusionGM increases HDAC1 expression in OHCs, and NaB is able to block this action. Thus, it appears that the HDAC inhibitor, NaB, attenuates GM-induced hearing loss in guinea pigs.