The Regulatory Role Of Ca²⁺/Calpain/CDK5Pathway In Cochlear Hair Cells Death Induced By Ototoxic Drug

Objective：To explore CDK5/P35expression in cochlear tissue pattern，observe whetherthe ototoxicity drugs such as kanamycin sulfate lead to the damage of rat’s cochlear haircells and deafness by activating CDK5pathway, and the interference of this pathway.Method：Immunofluorescence histochemistry, Western Blot, PCR confirm the expressionof CDK5and its activator P35in the rat cochlea hair cells; the acute hair cells in vitroadministration detect whether sulfate kanamycin causing upregulation of the calciumconcentration in the hair cells and calcium overload using cochlear hair cells in vitroculturing ototoxic damage model, in vitro culture four days after birth neonatal rat cochleaseparation, randomly divided into three groups: control, KM, KM+Roscovitine; fostering8h, then PI staining, detecting the death level. Western Blot detect the variety of apoptosisupstream molecules Calpain in each experimental group.Results:1. In rat cochlear inner hair cells, the result of Immunofluorescencehistochemistry, Western Blot, PCR and in vitro kinase assay show the expression ofCDK5/P35in Corti’s;2. In vitro acute administration of KM lead to a significantly increase of the concentrationof calcium within the cochlea hair cells, and in a time-dependent changes, activatingCa²⁺/Calpain/CDK5pathway; 3. KM treats in vitro culture hair cells, the expression of CDK5unchanged, Calpain andP25increased, P35decreased; after the treatment of CDK5inhibitor Roscovitine, thenumber of dead hair cells decreases when comparing with the KM treating group.Conclusion：1. There are CDK5/P35expression in cochlear hair cells, and CDK5has its kinasesactivity;2. Ototoxic drugs activate Ca²⁺/Calpain/CDK5pathway in cochlear hair cells;3. CDK5inhibitor intervene hair cell death induced by ototoxic drug by regulatingCa²⁺/Calpain/CDK5pathway.