| [Background]Cisplatin is a potent anticancer drug that produces reactive oxygen species(ROS),such as superoxide anions,which deplete antioxidant protective molecules in the cochlea.These processes lead to the death of cochlear hair cells by inducing apoptosis.Oxidative stress is a pathological condition.Oxidative stress through the action of free radicals is directly or indirectly involved in the pathogenesis of many diseases,including inner ear diseases.Oxidative damage activates a variety of intracellular stress signal transduction pathways,including mitogen-activated protein kinase(MAPK)family,tumor protein 53,AKT/PKB pathway,nf-Kb,Janus kinase(JAK)and other members.As a common clinical drug,Mison has a preventive effect on the production of reactive oxygen species in cells.Dexamethasone can inhibit Lipid peroxidation response,decrease MDA content in cochlear tissue,increase the activity of Superoxide dismutase,improve the ability of inner ear cells to scavenge oxygen free radicals,and alleviate oxidative stress induced by cisplatin,to protect the inner ear.It has been proved that Shh Gene and GLI1 gene exist in the colliculus of lateral line of zebrafish,which shows that Shh Signal Pathway participates in the development of colliculus of lateral line of zebrafish and has the maintenance function to its.Shh signaling pathway is reactivated in the process of regeneration of side-line hair cells in zebrafish after cisplatin injury,and inhibition of its activity can reduce the regeneration of side-line hair cells,it is suggested that Shh signaling pathway plays a positive role in the regeneration of zebrafish lateral hair cells after cisplatin injury.On this basis,we established a dexamethasone-zebrafish ototoxicity model,to investigate the protective effect of Mison on cisplatin-induced injury of colliculus hair cells in zebrafish lateral line and the effect of dexamethasone on the expression of SHH signal pathway.[Objective]To investigate the protective effect of dexamethasone on cisplatin induced injury of zebrafish lateral colliculus hair cells and the effect of dexamethasone on the expression of Shh signaling pathway genes.[Method](1)The 5-day postfertilization(dpf)zebrafish larvae were divided into control group,cisplatin group and cisplatin+dexamethasone group.They were treated with different drugs for 24 hours,and FM1-43FX was used to observe the number of hair cells at different times after withdrawal.(2)The oxidative stress model of zebrafish was established by cisplatin and dexamethasone.After removing cisplatin for 6h,ROS and MDA in the larvae of three groups of zebrafish were measured by DCFH-DA and DPPP fluorescent molecular probes.(3)The expression levels of antioxidant enzyme genes sodl,catl and gstr were detected by real-time fluorescent quantitative PCR(qPCR).(4)In situ hybridization was used to detect the expression of Shh signaling pathway in the lateral hair cell of zebrafish in control group,cisplatin group and cisplatin+dexamethasone group.[Result](1)Compared with the control group,the number of hair cells in cisplatin group and cisplatin+dexamethasone group was significantly decreased at 6,12 and 24h after cisplatin removal,while compared with cisplatin group,dexamethasone pretreatment group could alleviate the decrease of hair cell number(P<0.05);However,48 hours after cisplatin removal,there was no significant difference among the three groups.(2)The contents of ROS and MDA in cisplatin group were significantly higher than control group(P<0.05),and the content of ROS in the cisplatin+dexamethasone group was significantly lower than that in the cisplatin group(P<0.05).(3)The expression level of catl gene in zebrafish of cisplatin group and cisplatin+dexamethasone group was significantly lower than that of control group(P<0.05).(4)Compared with the control group,the gene expression of Shh and Gli1 in zebrafish lateral line hair cells in cisplatin group was significantly decreased after 6 hours of cisplatin removal,while the gene expression in cisplatin+dexamethasone group was relatively increased compared with cisplatin group.[Conclusion](1)Cisplatin can damage zebrafish lateral hair cells,but dexamethasone pretreatment can improve the damage of zebrafish hair cells induced by cisplatin.(2)Cisplatin could increase the content of ROS and MDA in the lateral hair cells of zebrafish,while dexamethasone could effectively improve the increase of ROS caused by cisplatin,which further indicated that dexamethasone could decrease the oxidative stress level of zebrafish larvae.(3)Cisplatin can reduce the gene level of partial antioxidant enzymes in zebrafish lateral hair cells,and dexamethasone increased the activity of some antioxidant enzyme genes when DDP induced hair cell injury,in order to protect the zebrafish juvenile hair cells from the impact of oxidative stress.(4)Dexamethasone plays a positive role in regulating Shh signaling pathway. |
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