Neomycin-induced free radical formation and hair cell damage in the lateral line of zebrafish

Ming-Huan Chan1, Chi-Fang Liu0,2, Hwei-Hsien Chen1,2. 1Tzu Chi University, Pharmacology, Taiwan, 2National Health Research Institutes, Population Health Sciences, Taiwan

Aminoglycoside antibiotics are the most commonly used antibiotics despite their high ototoxicity. Thus, the mechanisms underlying hearing toxicity of aminoglycosides are an area of active investigation. In this report, neomycin was used as the representative aminoglycoside to study its ototoxicity to the larvae hair cells in the lateral line of zebrafish, and also to the toxic factor associated with hearing loss. Zebrafish larvae at 5-6 days post fertilization exposed to neomycin (20 microM) for 30 min resulted in a remarkable reduction in the number of cells in the lateral line neuromasts using the vital fluorescent dyes FM1-43FX and YO-PRO-1 as reliable indicators of hair cell viability. Consistently, neomycin exposure significantly generated reactive oxygen species (ROS) in hair cells, detected by a fluorescent dye dichlorofluorescein (DCF). Importantly, the antioxidants including apocynin, ascorbic acid, and N-acetylcysteine concentration-dependently protected against neomycin-induced hair cell loss and ROS production. However, these antioxidants did not affect uptake of neomycin into hair cells, based on Texas-Red conjugated neomycin uptake. Therefore, our results indicate that the antioxidants such as apocynin, ascorbic acid, and N-acetylcysteine may be useful in prevention of aminoglycoside-induced ototoxicity, associated with free radical formation in hair cells.