Protective effect of tanshinone IIA against radiation-induced ototoxicity in HEI-OC1 cells

Radiotherapy is a highly efficient treatment method for nasopharyngeal carcinoma that is often accompanied by significant ototoxic side-effects. The inner ear hair cells are particularly prone to serious injury following radiotherapy. Tanshinone IIA is a transcription factor inhibitor that is extracted from the traditional herbal medicine, Salvia miltiorrhiza Bunge. The present study investigated the effects of tanshinone IIA treatment on radiation-induced toxicity in the HEI-OC1 hair cell line. Using an MTT assay and flow cytometry, the radiation-induced weakening of the cells was observed to be alleviated when the cells were pre-treated with tanshinone IIA. Radiation exposure promoted p65/nuclear factor (NF)-kappa B nuclear translocation and activated the p53/p21 pathway, two processes which play a significant role in radiation-induced cell apoptosis. However, pre-treatment of the cells with tanshinone IIA inhibited p65/NF-kappa B nuclear translocation and p53/p21 pathway activation. These results demonstrate that tanshinone IIA is capable of protecting cochlear cells from radiation-induced injury through the suppression of p65/NF-kappa B nuclear translocation and the p53/p21 signaling pathway.