Protective effects of Ginkgo biloba extract on presbycusis in the rat model via autophagy pathway / 中成药

ABSTRACT

AIM To investigate the effects of Ginkgo biloba extract on hearing function,cochlear morphology and autophagy-related protein expression in a rat model of presbycusis.METHODS Forty-five rats were randomly divided into the control group,the model group and the low,medium and high dose G.biloba extract groups(10,20 and 30 mg/kg),with 9 rats in each group.The rat model of presbycusis was established by intraperitoneal injection of 500 mg/kg D-galactose(D-gal).Eight weeks after the corresponding administration,the rats had their changes of hearing threshold detected by the auditory brainstem evoked potential(ABR);their morphological changes of cochlear hair cells,stria vascularis(SV)and spiral ganglion cells observed by HE staining;their number of hair cells inside and outside the cochlea detected by immunofluorescence staining;their ultrastructure changes of cochlear hair cells observed by transmission electron microscopy;and their expression of autophagy-related proteins in cochlea tissue detected by Western blot.RESULTS Compared with the control group,the model group displayed increased ABR threshold(P<0.01);more severely damaged inner and outer hair cells,spiral ganglion cells and SV,decreased SV thickness and numbers of spiral ganglion cells,inner and outer hair cells and autophagosomes(P<0.01);decreased protein expressions of Beclin1 and LC3 Ⅱ and ratio of LC3 Ⅱ/LC3 Ⅰ in cochlear tissue(P<0.01),and higher P62 protein expression(P<0.01).Compared with the model group,the medium and high dose G.biloba extract groups shared decreased ABR thresholds(P<0.01);improved morphology of inner and outer hair cells and SV in the cochlea,normalized,morphology of spiral ganglion cells,and increased SV thickness and the numbers of spiral ganglion cells,inner and outer hair cells and autophagosomes(P<0.05,P<0.01);increased protein expressions of Beclin1 and LC3 Ⅱ and the ratio of LC3 Ⅱ/LC3 Ⅰ in the cochlea(P<0.01),and decreased P62 protein expression(P<0.01).CONCLUSION The protective effects G.biloba extract on hearing function and cochlear cells in the rat model of presbycusis may be associated with the up-regulated expression of Beclin1 and LC3 Ⅱ proteins and down-regulated P62 protein expression in cochlear tissues.