Function of DNA methyltransferase 3a in lead (Pb2+)-Induced Cyclooxygenase-2 gene

Authors

  • Yao-Ting Tsai,

    1. Department of Clinical Pharmacy, School of Pharmacy, Taipei Medical University, Taipei, Taiwan
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    • both YT Tsai and CM Chang contributed equally to this work.

  • Che-Mai Chang,

    1. Department of Clinical Pharmacy, School of Pharmacy, Taipei Medical University, Taipei, Taiwan
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    • both YT Tsai and CM Chang contributed equally to this work.

  • Jaw-Yuan Wang,

    1. Cancer Center, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
    2. Division of Gastrointestinal and General Surgery, Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
    3. Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
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  • Ming-Feng Hou,

    1. Cancer Center, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
    2. Division of Gastrointestinal and General Surgery, Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
    3. Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
    4. Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
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  • Ju-Ming Wang,

    1. Institute of Bioinformatics and Biosignal Transduction, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, Taiwan
    2. Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan
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  • Robert Shiurba,

    1. Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, Tokyo, Japan
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  • Wen-Chang Chang,

    1. Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan
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  • Wei-Chiao Chang

    Corresponding author
    1. Department of Clinical Pharmacy, School of Pharmacy, Taipei Medical University, Taipei, Taiwan
    2. Cancer Center, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
    3. Department of Pharmacy, Taipei Medical University-Wanfang Hospital, Taipei, Taiwan
    4. Master Program for Clinical Pharmacogenomics and Pharmacoproteomics, School of Pharmacy, Taipei Medical University, Taipei, Taiwan
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ABSTRACT

Lead ions (Pb2+) are toxic industrial pollutants associated with chronic inflammatory diseases in humans and animals. Previously, we found that Pb2+ ions induce COX-2 gene expression via the EGF receptor/nuclear factor-κB signal transduction pathway in epidermoid carcinoma cell line A431. In this study, to see whether Pb2+ ions affect COX-2 expression by epigenetic mechanisms, we looked at the mRNAs of DNA methyltransferases (DNMTs) using real-time PCR of total RNA from these cells. Cells exposed to Pb2+ had low levels of DNMT3a mRNA, whereas the levels of DNMT1 and DNMT3b mRNAs remained unchanged. Pretreatment of cells with DNMT inhibitor 5-aza-2'-deoxycytidine (5 μM) followed by Pb2+ (1 μM) significantly increased levels of COX-2 mRNA compared with cells treated with Pb2+ alone. Overexpression of tumor suppressor gene Rb correlated with an increase in COX-2 mRNA and a decrease in DNMT3a mRNA. Conversely, overexpression of transcription factor E2F1 correlated with a decrease in COX-2 mRNA and an increase in DMNT3a mRNA. Pretreatment with EGFR inhibitors AG1478 and PD153035 significantly limited Pb2+-induced reduction in DNMT3a mRNA. In addition, gene knockdown of DNMT3a with short hairpin RNA correlated with increased COX-2 mRNA induced by Pb2+. Our findings suggest Pb2+ ions induce COX-2 expression indirectly by reducing DNMT3a methylation of the COX-2 promoter via transcription factors Rb and E2F1. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 1024–1032, 2015.

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