(-)EGCG suppress amikacin-induced spiral ganglion neuron apoptosis in the rat cochlea

Objective To study the effects of(-)-epigallocatechin-3-gallate(EGCG) on amikacin-induced spiral ganglions neurons apoptosis in the rat cochlea.Methods All animals were divided into three groups:one group serving as the saline control group,one group receiving amikacin(Amk) at 450 mg/kg once a day for 14 days,one group receiving Amk plus EGCG at 50 mg/kg once a day for 14 days.Following deep anesthesia,the animals were half-body perfused intracardially with 4% paraformaldehyde(PFD),and the bullas were harvested,and fixed in PFD,and decalcified in ethylenediamine tetraacetic acid(EDTA).After decalcification,the cochlea were embedded in paraffin,and cut in a paramodiolar plane subsequently.The immunohistochemical changes were observed for detecting with terminal deoxynucleotidyl transferase(TdT) dUTP nick end labeling(TUNEL).Results The negative immunohistochemical reaction for TUNEL staining was found in the spiral ganglion neurons(SGNs) in the saline control group,and the positive reaction was found in the nucleolus of the part of the SGNs of the group receiving Amk.However,the positive staining could be detected hardly in the group receiving Amk plus EGCG.The image analysis showed that the percentage of the positive SGNs in the group receiving Amk was significantly higher than that in the control group,and the percentage of the positive SGNs in the group receiving Amk plus EGCG was significantly lower than that in the group receiving Amk(P0.01).Conclusions Tunel-staining demonstrated Amk-induced SGNs apoptosis in the rat cochlea.EGCG effectively suppressed amikacin-induced spiral ganglion neuron apoptosis.