Extracellular ATP triggers tumor necrosis factor-alpha release from rat microglia.
Brain microglia are a major source of inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha), which have been implicated in the progression of neurodegenerative diseases. Recently, microglia were revealed to be highly responsive to ATP, which is released from nerve terminals, activated immune cells, or damaged cells. It is not clear, however, whether released ATP can regulate TNF-alpha secretion from microglia. Here we demonstrate that ATP potently stimulates TNF-alpha release, resulting from TNF-alpha mRNA expression in rat cultured brain microglia. The TNF-alpha release was maximally elicited by 1 mM ATP and also induced by a P2X(7) receptor-selective agonist, 2'- and 3'-O-(4-benzoylbenzoyl)adenosine 5'-triphosphate, suggesting the involvement of P2X(7) receptor. ATP-induced TNF-alpha release was Ca(2+)-dependent, and a sustained Ca(2+) influx correlated with the TNF-alpha release in ATP-stimulated microglia. ATP-induced TNF-alpha release was inhibited by PD 098059, an inhibitor of extracellular signal-regulated protein kinase (ERK) kinase 1 (MEK1), which activates ERK, and also by SB 203580, an inhibitor of p38 mitogen-activated protein kinase. ATP rapidly activated both ERK and p38 even in the absence of extracellular Ca(2+). These results indicate that extracellular ATP triggers TNF-alpha release in rat microglia via a P2 receptor, likely to be the P2X(7) subtype, by a mechanism that is dependent on both the sustained Ca(2+) influx and ERK/p38 cascade, regulated independently of Ca(2+) influx.
Department of Pharmacology, Institute of Pharmaceutical Sciences, Hiroshima University School of Medicine, Japan. ihide@hiroshima-u.ac.jp
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Hide
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Tanaka
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Inoue
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Nakajima
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Kohsaka
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Inoue
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Nakata
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D007093:Imidazoles / Q000494:pharmacology; D007700:Kinetics; D048369:MAP Kinase Kinase 1; D017628:Microglia / Q000187:drug effects / Q000502:physiology*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D058910:Purinergic P2 Receptor Agonists; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D058486:Receptors, Purinergic P2X7; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics* / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases
D004791:Enzyme Inhibitors; D005419:Flavonoids; D007093:Imidazoles; C546470:P2rx7 protein, rat; D058910:Purinergic P2 Receptor Agonists; D011725:Pyridines; D058486:Receptors, Purinergic P2X7; D014409:Tumor Necrosis Factor-alpha; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D002118:Calcium