RESUMO
Objective To investigate the NAD+ - dependent protein deacetylase SIRT1 expression in the cochlea of C57BL/6 mice ,a mouse model of age - related hearing loss(AHL) .Methods A total of 46 C57BL/6 mice were used ,and were divided into 2 groups ;according the age ,there were young group (1 ~ 2 months old ,23 mice) and old group (12 ~ 16 months old ,23 mice) .ABR measurements were performed on young and old C57BL/6 mice . The expression of SIRT1 in the cochlea was detected by qRT - PCR and immunofluorescence .Results The ABR thresholds in the old mice(4 kHz :82 .7 ± 7 .32 dB SPL ,8 kHz :80 .9 ± 7 .8 dB SPL ,16 kHz :89 .3 ± 5 .5 dB SPL ,32 kHz :89 .9 ± 4 dB SPL) were significantly higher than those in the young C57BL/6 mice(4 kHz :52 .1 ± 8 .3 dB SPL ,8 kHz :40 .5 ± 6 .1 dB SPL ,16 kHz :50 .7 ± 9 .4 dB SPL ,32 kHz :57 .6 ± 11 .9 dB SPL)(P < 0 .001) .SIRT1 mRNA expression was significantly decreased in the cochlea of old C57BL/6 mice in comparison with young mice ( P <0 .01) .SIRT1 protein was abundantly expressed in the inner hair cells ,outer hair cells ,supporting cells ,strial marginal cells ,strial intermediated cells ,and spiral ganglion neurons .The positive area and the average flourescence intensity of SIRT1 protein were reduced in old C57BL/6 mice(P< 0 .001) .Conclusion The down - regulation of SIRT1 mRNA and protein expression in the older C57BL/6 mouse cochlea may be correlated with the pathogenesis of AHL .