Effects of healthy ear compound of traditional Chinese medicine against age-induced apoptosis on cochlear spiral ganglion neurons in C57BL/6J mice and research on mechanisms by regulating caspase-3 / 中华老年医学杂志

ABSTRACT

Objective To explore the damage of spiral ganglion neurons(SGNs),the protective effects of different dosages of healthy ear compound (HEC)from traditional Chinese medicine(TCM) against age-induced SGNs degeneration and its possible mechanism in spiral ganglion neurons(SGNs)of C57BL/6J mice.Methods Totally 36 C57BL/6J mice just after ablactation were randomly divided into four groups.Normal control group (n =6)drank tap water daily from ablactation to 2 months old.Ageing-related SGNs apoptosis control group(n=12)drank tap water daily from ablactation to 7 months old.High dose TCM group(n=12)at drank 3.65 g/kg/d of HEC from ablactation to 7 months old.Low dose TCM group(n=6)drank 0.91 g/kg/d of HEC from ablactation to 7 months old.The animal cochleae were immediately removed at the termination of the experiment.In each group,the cochleae of 6 animals were used for paraffin embedding,slicing and toluidine blue staining to observe neuronal morphological changes.The caspase-3 mRNA expression study was performed by real-time PCR technique in 6 cochleae of High dose TCM group and ageing-related SGNs apoptosis control group.Results The morphological structure of cochlear SGNs represented healthy and normal density in normal control group at 2 months old.In contrast,amount or density of SGNs in cochlear basilar part was significantly damaged and reduced in ageing-related SGNs apoptosis control group at 7 months old(P＜ 0.001).But the high dose TCM group at 7 months of age was similar to the normal control group at 2 months old in morphological structure,amount or density of SGNs(P＞0.05).The low dose TCM group was significantly different from other 3 groups in amount or density of SGNs (P＜0.001).However,SGNs in the middle part and apical part showed integrity in each group.In addition,the expression level of caspase-3 in the cochlea of high dose TCM group was also obviously different with age-related SGNs apoptosis control group(P＜0.01) Conclusions Ageing-related damage of SGNs in C57BL/6J mice begins from the base of cochlea and progresses towards the apex.The HEC of TCM could significantly protect SGNs against age-induced apoptosis in SGNs.The efficacy of the high dose TCM is better than that of the low dose TCM.Its SGNs protective mechanisms might be related to involving the caspase-mediated cell apoptotic pathway.