The effects of the antioxidant α-tocopherol succinate on cisplatin-induced ototoxicity in HEI-OC1 auditory cells.
CONCLUSIONS
D-α-tocopherol succinate significantly reduced a cisplatin-induced hair cell loss in HEI-OC1 cell lines. These effects were mediated by its scavenging activity against reactive oxygen species (ROS) and inhibition of apoptosis.


OBJECTIVE
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 D-α-tocopherol succinate 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 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 D-α-tocopherol succinate protected HEI-OC1 auditory cells against cisplatin-induced cytotoxicity. D-α-tocopherol succinate significantly reduced the cisplatin-induced increase in ROS. D-α-tocopherol succinate treatment induced a 15% reduction of ROS and 50% decrease in necrosis and late apoptosis as compared to cisplatin treatment. D-α-tocopherol succinate also decreased the activation of caspase-3 and reduced levels of cleaved poly-ADP-ribose polymerase (PARP).
Department of Otolaryngology-Head and Neck Surgery, Korea University College of Medicine, Inchon-ro 73, Seongbuk-Gu, Seoul, Republic of Korea.
Sung Kyun
SK
Kim
Department of Otolaryngology-Head and Neck Surgery, Korea University College of Medicine, Inchon-ro 73, Seongbuk-Gu, Seoul, Republic of Korea.
Gi Jung
GJ
Im
Department of Otolaryngology-Head and Neck Surgery, Jesaeng Hospital, Seohyeon-ro 20, Bundang-Gu, Seognam, Gyeonggi, Republic of Korea.
Yun Suk
YS
An
Department of Otolaryngology-Head and Neck Surgery, Korea University College of Medicine, Inchon-ro 73, Seongbuk-Gu, Seoul, Republic of Korea.
Se Hee
SH
Lee
Department of Otolaryngology-Head and Neck Surgery, Korea University College of Medicine, Inchon-ro 73, Seongbuk-Gu, Seoul, Republic of Korea.
Hak Hyun
HH
Jung
Department of Otolaryngology-Head and Neck Surgery, Wonju College of Medicine, Yonsei University, 162 Ilsan-dong, Wonju 220-701, Republic of Korea. Electronic address: sangyoo3@yonsei.ac.kr.
Sang Yoo
SY
Park
D000970:Antineoplastic Agents / Q000633:toxicity*; D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000633:toxicity*; D006198:Hair Cells, Auditory / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D017382:Reactive Oxygen Species / Q000378:metabolism; D024502:alpha-Tocopherol / Q000494:pharmacology*
D000970:Antineoplastic Agents; D000975:Antioxidants; D017382:Reactive Oxygen Species; D024502:alpha-Tocopherol; D002945:Cisplatin
Alpha-tocopherol; Antioxidants; Cisplatin; Ototoxicity; Reactive oxygen species