Oral administration of geranylgeranylacetone to protect vestibular hair cells

We recently reported that the heat shock response played a major role in the protection of hair cells against stress. Oral administration of the heat shock inducer, geranylgeranylacetone (GGA) protected hair cells against intense noise. In our present study, we investigated the effect of GGA on vestibular hair cell death induced by an aminoglycoside. We used CBA/N mice aged 4–6 weeks. The mice were divided into two groups, GGA and control. Mice in the GGA group were fed a diet containing GGA (0.5%) for 4 weeks, and those in the control group were fed a standard diet. Immunohistochemical analyses for Hsp70 were performed in four animals. The utricles of the remaining animals were cultured in medium for 24h with neomycin to induce hair cell death. After fixation, the vestibular hair cells were immunohistochemically stained against calmodulin, and hair cell survival was evaluated. The vestibular hair cells of mice in the GGA group expressed Hsp70. In addition, after exposure to neomycin, vestibular hair cell survival was higher in the GGA group than in the control group. Our results demonstrated the oral administration of GGA induced the heat shock response in the vestibule and could protect sensory cells.