The effects of the antioxidant α-tocopherol on cisplatin-induced ototoxicity in HEI-OC1 auditory cells

Abstract

Objectives

Alpha-tocopherol is a class of methylated phenols, known as fat-soluble antioxidants, and is a different form of vitamin E, which reduces free radicals and acts as an antioxidant. We hypothesized that the antioxidative effect of α-tocopherol could protect against cisplastin-induced cytotoxicity, and thus evaluated its effects on cisplatin-induced ototoxicity in HEI-OC1 auditory cells.

Methods

HEI-OC1 cells were pretreated with α-tocopherol at a concentration of 10 μM for 24 h, and then exposed to 15 μM cisplatin for 48 h. The cellular viability was measured by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. The intracellular reactive oxygen species (ROS) level was measured by using a fluorescent dye, 2′,7′-dichlorofluorescein diacetate (DCFH-DA). Both Annexin V-FITC and propidium iodide (PI) staining were performed to analyze the pattern of apoptosis. The enzymatic activity of caspase-3 was assayed with caspase3/CPP32 fluorometric assay kit. Also, it was assessed by immunoblotting technique of poly-ADP-ribose polymerase (PARP).

Results

Pretreatment with 10 μM α-tocopherol protected HEI-OC1 auditory cells against cisplatin-induced cytotoxicity. Alpha-tocopherol significantly reduced the cisplatin-induced increase in ROS. Alpha-tocopherol treatment induced a 15% reduction of ROS and 50% decrease in necrosis and late apoptosis as compared to cisplatin treatment. Alpha-tocopherol also decreased the activation of caspase-3 and reduced levels of PARP.

Conclusion

This study was investigated the protective effects of α-tocopherol on cisplatin-induced ototoxicity in an auditory cell line. Tocopherol significantly reduced a cisplatin-induced increase in ROS, thereby inhibiting cisplatin-induced cytotoxicity.