Differential crosstalk between P2X7 and arachidonic acid in activation of mitogen-activated protein kinases

Neurochem Int. 2008 Dec;53(6-8):255-62. doi: 10.1016/j.neuint.2008.05.001. Epub 2008 Sep 19.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / analogs & derivatives
  • Adenosine Triphosphate / metabolism
  • Adenosine Triphosphate / pharmacology
  • Affinity Labels / pharmacology
  • Animals
  • Animals, Newborn
  • Arachidonic Acid / metabolism*
  • Astrocytes / metabolism*
  • Cell Line
  • Cells, Cultured
  • Dose-Response Relationship, Drug
  • Drug Synergism
  • Encephalitis / metabolism*
  • Encephalitis / physiopathology
  • Humans
  • MAP Kinase Signaling System / drug effects
  • MAP Kinase Signaling System / physiology*
  • Mitogen-Activated Protein Kinase 3 / drug effects
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Phosphorylation
  • Purinergic P2 Receptor Agonists
  • Rats
  • Receptor Cross-Talk / physiology*
  • Receptors, Purinergic P2 / genetics
  • Receptors, Purinergic P2 / metabolism*
  • Receptors, Purinergic P2X7
  • Transfection

Substances

  • Affinity Labels
  • P2RX7 protein, human
  • P2rx7 protein, rat
  • Purinergic P2 Receptor Agonists
  • Receptors, Purinergic P2
  • Receptors, Purinergic P2X7
  • Arachidonic Acid
  • 3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate
  • Adenosine Triphosphate
  • Mitogen-Activated Protein Kinase 3