Nitric oxide mediates TNF-α–induced apoptosis in the auditory cell line

Authors

  • Hun Yi Park MD,

    1. Department of OtolaryngologyAjou University School of Medicine, Suwon, South Korea
    2. Center for Cell Death Regulating Biodrug, Ajou University School of Medicine, Suwon, South Korea
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  • Mi Hye Lee,

    1. Department of OtolaryngologyAjou University School of Medicine, Suwon, South Korea
    2. Center for Cell Death Regulating Biodrug, Ajou University School of Medicine, Suwon, South Korea
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  • Sung Un Kang,

    1. Department of OtolaryngologyAjou University School of Medicine, Suwon, South Korea
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  • Hye Sook Hwang,

    1. Department of OtolaryngologyAjou University School of Medicine, Suwon, South Korea
    2. Center for Cell Death Regulating Biodrug, Ajou University School of Medicine, Suwon, South Korea
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  • Keehyun Park MD, PhD,

    1. Department of OtolaryngologyAjou University School of Medicine, Suwon, South Korea
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  • Yun-Hoon Choung MD, PhD,

    1. Department of OtolaryngologyAjou University School of Medicine, Suwon, South Korea
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  • Chul-Ho Kim MD, PhD

    Corresponding author
    1. Department of OtolaryngologyAjou University School of Medicine, Suwon, South Korea
    2. Center for Cell Death Regulating Biodrug, Ajou University School of Medicine, Suwon, South Korea
    • Department of Otolaryngology, Ajou University, School of Medicine, San 5, Wonchon-Dong, Yeongtong-Gu, Suwon, 442-749, South Korea
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Abstract

Objectives/Hypothesis:

Tumor necrosis factor-alpha (TNF-α) is released in a variety of pathological states in the inner ear. Inducible nitric oxide synthase (iNOS) can be induced by cytokines and other inflammatory factors, and is generally thought to be associated with inflammation and other pathological processes in the cochlea. The purpose of the present study was to reveal that TNF-α could induce apoptosis in the auditory cell line and to investigate the role of nitric oxide (NO) in TNF-α–induced auditory cell death.

Study Design:

Experimental study.

Methods:

UB-OC1 cells and zebrafish were exposed to TNF-α. Flow cytometry, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) assay, assay of mitochondrial membrane potential (MMP), and electron microscopy were used to show that TNF-α could induce apoptosis. Western blot was used to measure iNOS expression and mitogen-activated protein kinase pathway.

Results:

Flow cytometric analysis, TUNEL assay, MMP, and electron microscopy all demonstrated that TNF-α could induce apoptosis in UB-OC1 cells. TNF-α significantly increased NO generation and iNOS expression. Pretreatment with iNOS blocker NG-methyl-L-arginine (NMA) attenuated TNF-α–induced cell death and caspase-3 activation. Also, TNF-α treatment increased p-p38 and p-ERK, and pretreatment of NMA reduced this increased expression of p-p38 and p-ERK.

Conclusions:

TNF-α can induce apoptosis in the auditory cell line, and NO production in response to TNF-α is essential for apoptosis. Laryngoscope, 2012

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