The Study Of The Antagonism Of Trichostatin A On Cisplatin Ototoxicity Via STAT6Signaling Pathway

Cisplatin is a chemotherapeutic agent used in the treatment of solid tumors likeovarian, testicular, cervical, lung, head and neck and bladder cancers. Dose limitingside effects of cisplatin include nephrotoxicity, neurotoxicity and ototoxicity. Whilenephrotoxicity can to some extent be reversed by increasing saline hydration as wellas mannitol diuresis, there are no known cures or preventative treatments available forototoxicity and neurotoxicity as the mechanism of Cisplatin-induced ototoxicity is notclarified definitely. Therefore, the further study of its molecular mechanism is needed.Cisplatin ototoxicity occurs primarily in the cochleae, especially in the outer haircells (OHCs) of the organ of Corti from the basal turn of the cochlea and the spiralganglion neurons, and increasing doses are associated with additional damage to theinner hair cells, supporting cells, and stria vascularis. Cisplatin could inducegeneration of proinflammatory cytokines in vitro and in vivo, and markedly induceproinflammatory cytokine release and production from auditory cells, resulting ininner hair cell apoptosis. Proinflammatory cytokines function as a major effector inthe pathogenesis of inner ear sensory hair cell damage.Trichostatin A (TSA) is produced by selected strains of Streptomyces platensis,Streptomyces hygroscopicus Y-50or Streptomyces sioyaensis. TSA can reversely andunselectively block histone deacetylase and regulate the diverse functions of proteinvia inhibiting the histone deacetylase, increasing the level of histone acetylation.Recently studies report that Trichostatin A exhibit pivotal effect on anti-inflammation,anti-tumor and anti-ototoxicity induced by drugs such as cisplatin and aminoglycosideantibiotics. The study presented here is focusing on the role of STAT6signalingpathway and the antagonism of Trichostatin A on cisplatin-induced hair cell loss.Aims:In this study, we are supposed to investigate the antagonism of Trichostatin A oncisplatin-induced hair cell loss in rats and how transcription factor-Signal transducer and activator of transcription-6signaling pathway affects the ototoxicity on cochleawhen treated with cisplatin plus TSA.Materials and methods：Basilar membranes are cultured and treated with various concentrations of TSA,cisplatin or cisplatin with TSA. The number of diminished hair cells is investigated byimmunofluorescent staining to investigate whether TSA affect hair cell and find theoptimal concentration of TSA. The protein location of STAT6and p-STAT6aremeasured by immunocytochemistry. IL-4and proinflammatory cytokines IL-6、IL-1βare measured by ELISA in order to study the role of inflammatory response incisplatin-induced ototoxicity. The protein expression of STAT6and p-STAT6aremeasured by western blot to assess the antagonism of TSA on cisplatin-inducedototoxicity.Results：1.TSA do not have negative effect on hair cell under certain concentration range.2.TSA could reduce cisplatin-induced hair cell loss, showing that the antagonismof TSA.3.TSA could lower the high expression of IL-4and inhibit the expression ofSTAT6and p-STAT6in downstream signaling pathway of IL-4.4.TSA could inhibit the expression of proinflammatory cytokines IL-1β、IL-6induced by cisplatin.Conclusion：These results indicate that proinflammatory cytokines such as IL-1β、IL-6andthe cytokines including STAT6、IL-4play a central role in the hair cell damage causedby cisplatin. TSA might inhibit the expression of STAT6and inflammation viaregulating cellular level of histone acetylation, then antagonizing cisplatin-inducedototoxicity.