Effect Of Cisplatin On Expression Of Calpain In Mouse Cochlea

ObjectiveTo establish a mouse model of cisplatin-induced ototoxicity, and toinvestigate the effect of cisplatin on expression of calpain in mouse cochlea,and to explore the possible role of calpain in cisplatin-induced hearing loss, soas to provide experimental evidence for the therapy of cisplation ototoxicity.Methods65healthy BALB/c mice were randomly assigned to control group,cisplatin2.5mg/kg group, cisplatin3.5mg/kg group, cisplatin4.5mg/kg groupand cisplatin5.5mg/kg group, each group was13mice. Mice were injectedintraperitoneally for5days, and once a day. Immunofluorescent staining andimaging analysis technique and western blotting were used to detect theexpression of calpain1and calpain2in mouse cochlea. At the same time,auditory brainstem response (ABR) was measured to observe the change ofhearing.Results1. After injected intraperitoneally for5days, the weights of mice in controlgroup were increased slightly, while the weights of mice in different dose ofcisplatin groups were decreased significantly from the third day as comparedwith control group (P<0.05, P<0.01), and the weight loss of mice was greaterremarkably with the more cisplatin injected (P<0.05，P<0.01).2. After injected intraperitoneally for5days, ABR threshold shifts indifferent dose of cisplatin groups were significantly amplified at eachstimulating frequency as compared with control group (P<0.01), and increased remarkably with more injected cisplatin (P<0.01). It showed that there was adose-effect relationship between them.3. The results of immunofluorescent staining and imaging analysisshowed that calpain1and calpain2were both pale expression in outer haircell, spiral ganglion and stria vascularis of cochlea in control group. Theexpressions of calpain1and calpain2in above positions in different dose ofcisplatin groups were greater than that in control group (P<0.05, P<0.01).However, the expression of calpain1was no obvious difference amongcisplatin groups, while the expression of calpain2was increased remarkablywith more injected cisplatin (P<0.01).4. The results of western blotting and semi-quantitative analysis showedthat the protein expression levels of calpain1and calpain2were very low incontrol group. The protein expression levels of calpain1and calpain2indifferent dose of cisplatin groups were greater than those in control group(P<0.01). However, the protein expression level of calpain1was no significantdifference among cisplatin groups, while the protein expression level of calpain2were greater remarkably with more injected cisplatin (P<0.01).ConclusionsA model of cisplatin-induced ototoxicity could be established byadministration of adult BALB/c mouse. There was a little expression of calpainin the cochlea of normal mouse. Cisplatin could increase the expressions ofcalpain1and calpain2in mouse cochlea, and the expression of calpain2gradually increased with more concentration of cisplatin. These suggested thatcalpain1and calpain2might be involved in cisplatin-induced ototoxicity, andcalpain2might play a leading role in cisplatin-induced ototoxic injury.