P2X7 nucleotide receptor activation enhances IFNγ-induced type II nitric oxide synthase activity in BV-2 microglial cells

Under normal and pathological conditions, brain cells release nucleotides that regulate a wide range of cellular responses due to activation of P2 nucleotide receptors. In this study, the effect of extracellular nucleotides on IFNgamma-induced NO release in murine BV-2 microglial cells was investigated. BV-2 cells expressed mRNA for metabotropic P2Y and ionotropic P2X receptors. Among the P2 receptor agonists tested, ATP, ADP, 2',3'-O-(4-benzoylbenzoyl)-ATP ( BzATP), and 2-methylthio-ATP (2-MeSATP), but not UTP, enhanced IFNgamma-induced iNOS expression and NO production, suggesting that the uridine nucleotide receptors P2Y(2) and P2Y(6) are not involved in this response. U0126, an antagonist for MEK1/2, a kinase that phosphorylates the extracellular signal-regulated kinases ERK1/2, decreased IFNgamma-induced NO production. BzATP, a potent P2X(7) receptor agonist, was more effective than ATP, ADP, or 2-MeSATP at enhancing IFNgamma-induced ERK1/2 phosphorylation. Consistent with activation of the P2X(7) receptor, periodate-oxidized ATP, a P2X(7) receptor antagonist, and suramin, a non-specific P2 receptor antagonist, inhibited the effect of ATP or BzATP on IFNgamma-induced NO production, whereas pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid ( PPADS), an antagonist of several P2X receptor subtypes, was ineffective. These results suggest that activation of P2X(7) receptors may contribute to inflammatory responses in microglial cells seen in neurodegenerative diseases.