ABSTRACT
Objective To investigate the effect of histone deacetylase 2(HDAC2) expression by aminophylline on glucocorticoid sensitivity of guinea pigs with lipopolysaccharide -induced sudden hearing loss .Methods Fifty guinea pigs were randomly divided into five groups :control/artificial perilymph(AP) group (n=10) in which both the ears were administrated 5μl sterile artificial perilymph fluid by means of drilling the scala tympani of the cochle‐ar basal turn ;whereas 5 μl of 5 mg/ml LPS was transferred into the cochlea of both the ears of other groups in the same way ,which were model(LPS) group(n=10) ,lipopolysaccharide+ dexamethasone(LPS+ DEX) group(n=10) ,lipopolysaccharide+ aminophylline(LPS+ AMI) group(n= 10) ,and lipopolysaccharide+ dexamethasone+aminophylline(LPS+DEX+AMI) group(n=10) .Guinea pigs with normal hearing tested by auditory brain stem response (ABR) before treatment were included in this study .ABRs were recorded in all guinea pigs 48 hours after surgery .The immunofluorescence staining was used to detect for the HDAC2 in the inner ear .The HDAC2 levels in the cochlea of guinea pigs were detected by ELISA test .Results ABR results showsed that hearing loss in AP group was mild ,the threshold shifts were less than 10 dB at 4 kHz ,8 kHz ,16 kHz frequencies ,at 32 kHz the threshold shift was 11 .50 dB ,respectively .However ,the hearing loss was obvious in LPS group ,especially at the high frequency (the threshold shift was 60 .75 ± 6 .02 dB SPL) .Compared to AP group ,hearing loss in LPS group was statistically significant at all frequencies (P<0 .01) .The hearing improvement was obvious at frequeniies of 16 kHz and 32 kHz in group of LPS+DEX and LPS+AMI (P<0 .05) .The LPS+DEX+ AMI treatment for LPS -induced acute hearing loss was the most remarkable at all frequencies compared with glucocorticoid or aminophylline treatment alone ,especially at 16 kHz (P<0 .05) .The immunofluorescence staining showed positive expression of HDAC2 in the cochlea in the inner and outer hair cells ,stria vascularis ,spiral ganglion and spiral ligament .The correlation analysis showed negative correlations between the expression of HDAC2 and threshold shift of ABR at 8 kHz ,16 kHz ,and 32 kHz (P<0 .05) .Conclusion It is effective for dexamethasone and aminophylline treatment in induced hearing loss in guinea pigs .Aminophylline can elevate HDAC2 expression and improve the effect of glu‐cocorticoid .In conclusion ,HDAC2 plays a critical role in restoring glucocorticoid sensitivity in the inner ear .