title: Differential crosstalk between P2X7 and arachidonic acid in activation of mitogen-activated protein kinases.
abstract: Accumulating evidence indicates that astroglial syncytium plays key role in normal and pathological brain functions. Astrocytes both in vitro and in situ respond to extracellular adenine-based nucleotides via the activation of P2 receptors. Massive release of ATP from neurons and glial cells occurs as a result of pathological conditions of the brain leading to neuroinflammation and involving P2X7 receptors. In this study, we investigated whether P2X7 stimulation on cultured cortical astrocytes promoted a differential activation of mitogen-activated protein kinases (MAPKs), and whether the second messenger arachidonic acid (AA), which is also a key modulator of neuroinflammation, affected the P2X7-mediated MAPK phosphorylation. The results show that the synthetic P2X7 receptor agonist 2',3'-O-(4-benzoyl)benzoyl-ATP (BzATP), induced a concentration-dependent phosphorylation of MAPK ERK1/2, JNK and p38. Stimulation of ERK1/2, JNK and p38 phosphorylation was also obtained by pathophysiological levels of extracellularly applied AA. Interestingly, a robust potentiation of ERK1/2 phosphorylation was elicited by co-application of BzATP and AA, whereas no differences were observed in JNK or p38 phosphosignals. The kinases activation showed a differential dependence on the presence of extracellular Ca(2+). The potentiation of BzATP-mediated ERK1/2 phosphorylation was also observed in human embryonic kidney cells (HEK293) stably transfected with rat P2X7, but not in HEK cells expressing truncated P2X7 receptor lacking the full cytoplasmic carboxy-terminal or in those carrying the structurally related rat P2X2. AA and BzATP synergism in ERK1/2 activation was abolished by cyclo-oxygenase and lipoxygenase pathway inhibitors. The result that ERK1/2-mediated transduction pathway is synergistically modulated by ATP and AA signalling depicts possible novel pharmacological targets for interfering with pathological activation of astroglial cells.
authors.affiliation: Institute of Biophysics, CNR, Via De Marini, 6 - 16149 Genoa, Italy.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Barbieri
authors.forename: Susanna
authors.initials: S
authors.lastname: Alloisio
authors.forename: Stefano
authors.initials: S
authors.lastname: Ferroni
authors.forename: Mario
authors.initials: M
authors.lastname: Nobile
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D000345:Affinity Labels / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D016718:Arachidonic Acid / Q000378:metabolism*; D001253:Astrocytes / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004660:Encephalitis / Q000378:metabolism* / Q000503:physiopathology; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3 / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation; D058910:Purinergic P2 Receptor Agonists; D051381:Rats; D020239:Receptor Cross-Talk / Q000502:physiology*; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7; D014162:Transfection
chemical_list: D000345:Affinity Labels; C546468:P2RX7 protein, human; C546470:P2rx7 protein, rat; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D016718:Arachidonic Acid; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D048052:Mitogen-Activated Protein Kinase 3