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Synergistic expression of inducible nitric oxide synthase by phorbol ester and interferon-γ is mediated through NF-κB and ERK in microglial cells

Authors

  • Inn-Oc Han,

    1. Research Institute, National Cancer Center, Goyang, Gyeonggi, Republic of Korea
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  • Hee-Sun Kim,

    1. Department of Pharmacology, College of Medicine, Laboratory of Neurodegenerative Diseases, Ewha Institute of Neuroscience, Ewha Women's University, Seoul, Republic of Korea
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  • Hyoung-Chun Kim,

    1. Department of Pharmacy, College of Pharmacy, Kwangwon National University, Chunchon, Kwangwon-do, Republic of Korea
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  • Eun-Hye Joe,

    1. Department of Pharmacology, School of Medicine, Ajou University, Suwon, Kyoungki-do, Republic of Korea
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  • Won-Ki Kim

    Corresponding author
    1. Department of Pharmacology, College of Medicine, Laboratory of Neurodegenerative Diseases, Ewha Institute of Neuroscience, Ewha Women's University, Seoul, Republic of Korea
    • Laboratory of Neurodegenerative Diseases, Ewha Institute of Neuroscience, Tongdaemoon Hospital, Ewha Women's University, 70 Chongro-6-ga, Chongroku, Seoul 110-783, Republic of Korea
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Abstract

A proinflammatory cytokine IFN-γ stimulates microglia in the injured brain; however, signaling pathways for IFN-γ-mediated microglia activation are not well characterized. In the present study, a protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) acts in concert with IFN-γ to enhance nitric oxide (NO) production in murine microglial BV2 cells by synergistically increasing expression of inducible NO synthase (iNOS). The synergistic NO production by PMA was in part decreased by a PKC inhibitor Gö6976. PMA alone induced activation of nuclear factor-kappa B (NF-κB) and extracellular signal-regulated kinase (ERK) of mitogen-activated protein kinases (MAPKs) subtypes, whereas IFN-γ alone had little effect. PMA and IFN-γ synergistically enhanced activity of NF-κB, but not ERK. The inhibitors of NF-κB (pyrrolidine dithiocarbamate, PDTC) and ERK (1,4-diamino-2,3-dicyano-1,4 bis[2-aminophenylthio]butadiene; U0126) markedly decreased synergistic NO production in BV2 cells treated with IFN-γ and PMA in combination. We found further that co-treatment with IFN-γ and PMA synergistically induced interferon regulatory factor-1 (IRF-1), which is the major transcription factor for IFN-γ-mediated iNOS expression. The present results demonstrate the cooperative interaction of multiple signaling pathways in the induction of NO production in activated microglial cells, and suggest that the functional interplay of these pathways may be important for the onset of microglia-mediated inflammatory responses in brain. © 2003 Wiley-Liss, Inc.

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