Induction of COX-2 and reactive gliosis by P2Y receptors in rat cortical astrocytes is dependent on ERK1/2 but independent of calcium signalling.
The present study has been aimed at characterizing the ATP/P2 receptor (and transductional pathways) responsible for the morphological changes induced in vitro by alphabetamethyleneATP on rat astrocytes obtained from cerebral cortex, a brain area highly involved in neurodegenerative diseases. Exposure of cells to this purine analogue resulted in elongation of cellular processes, an event reproducing in vitro a major hallmark of in vivo reactive gliosis. alphabetamethyleneATP-induced gliosis was prevented by the P2X/P2Y blocker pyridoxalphosphate-6-azophenyl-2'-4'-disulfonic acid, but not by the selective P2X antagonist 2',3'-O-(2,4,6-trinitrophenyl)-ATP, ruling out a role for ligand-gated P2X receptors. Conversely, the Gi/Go protein inactivator pertussis toxin completely prevented alphabetamethyleneATP-induced effects. No effects were induced by alphabetamethyleneATP on intracellular calcium concentrations. RT-PCR and western blot analysis showed that alphabetamethyleneATP-induced gliosis involves up-regulation of cyclooxygenase-2 (but not lipooxygenase). Also this effect was fully prevented by pyridoxalphosphate-6-azophenyl-2'-4'-disulfonic acid. Experiments with inhibitors of mitogen-activated protein kinases (MAPK) suggest that extracellular signal regulated protein kinases (ERK)1/2 mediate both cyclooxygenase-2 induction and the associated in vitro gliosis. These findings suggest that purine-induced gliosis involves the activation of a calcium-independent G-protein-coupled P2Y receptor linked to ERK1/2 and cyclooxygenase-2. Based on the involvement of cyclooxygenase-2 and inflammation in neurodegenerative diseases, these findings open up new avenues in the identification of novel biological targets for the pharmacological manipulation of neurodegeneration.
Brambilla
Roberta
R
Department of Pharmacological Sciences, University of Milan School of Pharmacy, Milan, Italy.
Neary
Joseph T
JT
Cattabeni
Flaminio
F
Cottini
Lorenzo
L
D'Ippolito
Gianluca
G
Schiller
Paul C
PC
Abbracchio
Maria P
MP
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D051546:Cyclooxygenase 2; D004790:Enzyme Induction / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000378:metabolism; D005911:Gliosis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D007527:Isoenzymes / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects
D007527:Isoenzymes; D018048:Receptors, Purinergic P2; D000255:Adenosine Triphosphate; D001094:Arachidonate 5-Lipoxygenase; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D019204:GTP-Binding Proteins; C002630:alpha,beta-methyleneadenosine 5'-triphosphate