title: Bi-functional effects of ATP/P2 receptor activation on tumor necrosis factor-alpha release in lipopolysaccharide-stimulated astrocytes.
abstract: Neuroinflammation is associated with a variety of CNS pathologies. Levels of tumor necrosis factor-alpha (TNF-alpha), a major proinflammatory cytokine, as well as extracellular ATP, are increased following various CNS insults. Here we report on the relationship between ATP/P2 purinergic receptor activation and lipopolysaccharide (LPS)-induced TNF-alpha release from primary cultures of rat cortical astrocytes. Using ELISA, we confirmed that treatment with LPS stimulated the release of TNF-alpha in a concentration and time dependent manner. ATP treatment alone had no effect on TNF-alpha release. LPS-induced TNF-alpha release was attenuated by 1 mm ATP, a concentration known to activate P2X7 receptors. Consistent with this, 3'-O-(4-Benzoyl)benzoyl-ATP (BzATP), a P2X7 receptor agonist, also attenuated LPS-induced TNF-alpha release. This reduction in TNF-alpha release was not due to loss of cell viability. Adenosine and 2-chloroadenosine were ineffective, suggesting that attenuation of LPS-induced TNF-alpha release by ATP was not due to ATP breakdown and subsequent activation of adenosine/P1 receptors. Interestingly, treatment of astrocyte cultures with 10 microm or 100 microm ATP potentiated TNF-alpha release induced by a submaximal concentration of LPS. UTP and 2methylthioADP (2-MeSADP), P2Y receptor agonists, also enhanced this LPS-induced TNF-alpha release. Our observations demonstrate opposing effects of ATP/P2 receptor activation on TNF-alpha release, i.e. P2X receptor activation attenuates, whereas P2Y receptor activation potentiates TNF-alpha release in LPS-stimulated astrocytes. These observations suggest a mechanism whereby astrocytes can sense the severity of damage in the CNS via ATP release from damaged cells and can modulate the TNF-alpha mediated inflammatory response depending on the extracellular ATP concentration and corresponding type of astrocyte ATP/P2 receptor activated.
authors.affiliation: Research Service, Miami Veterans Affairs Medical Center, 1201 NW 16th Street, Miami, FL 33125, USA.
authors.forename: Brandon M
authors.initials: BM
authors.lastname: Kucher
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Neary
mesh_terms: D000244:Adenosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D008070:Lipopolysaccharides / Q000494:pharmacology*; D058910:Purinergic P2 Receptor Agonists; D051381:Rats; D011916:Rats, Inbred F344; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058469:Receptors, Purinergic P2X; D058486:Receptors, Purinergic P2X7; D013268:Stimulation, Chemical; D013873:Thionucleotides / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D008070:Lipopolysaccharides; C546470:P2rx7 protein, rat; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D058486:Receptors, Purinergic P2X7; D013873:Thionucleotides; D014409:Tumor Necrosis Factor-alpha; C002480:methylthio-ADP; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate