Objective: Mammalian sensory hair cells do not regenerate. Therefore, developing therapeutic agents to protect the inner ear is essential. Eight herbal medicines (Shosaikoto, Orengedokuto, Tokishakuyakusan, Shigyakusan, Hochuekkito, Juzentaihoto, Unseiin, and Shimotsuto) were screened using a zebrafish lateral line to determine their possible protective effects against neomycin insult in sensory hair cells.
Materials and Methods: Zebrafish larvae were divided into four groups: untreated control, neomycin-treated, herbal medicine–treated only, and herbal medicine + neomycin–treated groups. Each herbal medicine was administered 1 hr before exposure to 200 µM neomycin, and the larvae were fixed with 4% paraformaldehyde 1 hr later. Hair cell survival in the lateral line neuromasts was quantified to generate dose–response curves.
Results: All eight herbal preparations demonstrated protective effects against neomycin-induced hair cell injury in the zebrafish lateral line. Within 3 min of neomycin exposure, oxidative stress markers indicated a pronounced increase in reactive oxygen species within lateral line hair cells, whereas pretreatment with Shimotsuto effectively suppressed this response. Among the tested formulations, Shimotsuto exhibited the strongest otoprotective effect. Furthermore, its protective potential was confirmed in mammalian vestibular epithelia where the survival of hair cells was significantly higher in the Shimotsuto plus neomycin group compared with the neomycin-only group.
Conclusion: These findings suggest that zebrafish-based drug screening provides a rapid and reliable platform for identifying herbal formulations with inner ear protective properties, thereby contributing to determine their possible protective effects.