Differential activation of subtype purinergic receptors modulates Ca2+ mobilization and COX-2 in human microglia

Authors

  • Hyun B. Choi,

    1. Department of Pharmacology and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
    2. Division of Neurology, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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  • Seok H. Hong,

    1. Department of Pharmacology and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
    2. Brain Disease Research Center, Ajou University, Suwon, Korea
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  • Jae K. Ryu,

    1. Department of Pharmacology and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
    2. Division of Neurology, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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  • Seung U. Kim,

    1. Division of Neurology, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
    2. Brain Disease Research Center, Ajou University, Suwon, Korea
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  • James G. McLarnon

    Corresponding author
    1. Department of Pharmacology and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
    • Department of Pharmacology and Therapeutics, University of British Columbia, 2176 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
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Abstract

We have studied modulation of purinergic receptors (P2Y and P2X subtypes) on changes in intracellular Ca2+ [Ca2+]i and expression and production of COX-2 in human microglia. Measurements using Ca2+-sensitive spectrofluorometry showed adenosine triphosphate (ATP) to cause rapid transient increases in [Ca2+]i. Application of ATP plus the P2X antagonist, pyridoxal-phosphate-6-azophenyl-2′,4′-disulfonic acid (PPADS), or treatment with adenosine diphosphate-β-S (ADP-β-S), a selective P2Y agonist, led to a considerable prolongation in [Ca2+]i responses compared with ATP. The prolonged time courses were consistent with sustained activation of store-operated channels (SOC) since SKF96365, an inhibitor of SOC, blocked this component of the response. RT-PCR data showed that microglia expressed no COX-2 either constitutively or following treatment of cells with ATP (100 μM for 8 h). However, treatment using ATP plus PPADS or with ADP-β-S led to marked expression of COX-2. The enhanced COX-2 with ATP plus PPADS treatment was absent in the presence of SKF96365 or using Ca2+-free solution. Immunocytochemistry, using a specific anti-COX-2 antibody, also revealed a pattern of purinergic modulation whereby lack of P2X activation enhanced the production of COX-2 protein. These results suggest that modulation of subtypes of purinergic receptors regulates COX-2 in human microglia with a link involving SOC-mediated influx of Ca2+. © 2003 Wiley-Liss, Inc.

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