Protective Role of Trimetazidine Against Neomycin-induced Hair Cell Damage in Zebrafish

OBJECTIVES: Trimetazidine (TMZ) is known to reduce the generation of oxygen-derived free radicals. The objective of the present study was to evaluate the effects of TMZ on neomycin-induced ototoxicity in transgenic zebrafish (Brn3C: EGFP). METHODS: Five-day, postfertilization zebrafish larvae were exposed to 125 microM neomycin and one of the following TMZ concentrations for 1 hour: 10 microM, 100 microM, 500 microM, 1,000 microM, 1,500 microM, or 2,000 microM. Hair cells within the neuromasts of the supraorbital (SO1 and SO2), otic (O1), and occipital (OC1) lateral lines were analyzed using fluorescence microscopy and confocal microscopy (n=10). Hair cell survival was calculated as a percentage of hair cells in the control group that were not exposed to neomycin. Ultrastructural changes were evaluated using scanning electron microscopy. RESULTS: TMZ protected against neomycin-induced hair cell loss in the neuromasts (TMZ 1,000 microM, 11.2+/-0.4 cells; 125 microM neomycin only, 4.2+/-0.5 cells; n=10; P<0.05) and decreased the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) reaction. In the ultrastructural analysis, structures of mitochondria and hair cells within the neuromasts were preserved in zebrafish exposed to 125 microM neomycin and 1,000 microM TMZ. CONCLUSION: TMZ attenuated neomycin-induced hair cell loss in zebrafish. The results of this study suggest that neomycin induces apoptosis, and that apoptotic cell death can be prevented by treatment with tremetazidine.

Microarray Screening for Genes Involved in Oligodendrocyte Differentiation in the Zebrafish CNS

Within the vertebrate nervous system, myelination is required for the normal function of neurons by facilitating the rapid conduction of action potentials along axons. Oligodendrocytes are glial cells which myelinate axons in the central nervous system. Disruption of myelination and remyelination failure can cause human diseases such as multiple sclerosis. Despite the importance of myelination, the molecular basis of oligodendrocyte differentiation and myelination are still poorly understood. To understand the molecular mechanisms which regulate oligodendrocyte differentiation and myelination, novel genes were identified using a microarray analysis. The analysis used oligodendrocyte lineage cells isolated from transgenic zebrafish expressing fluorescent proteins in the oligodendrocyte lineage cells. Seven genes not previously known to be involved in oligodendrocyte differentiation were identified, and their expression during oligodendrocyte development was validated.