Peroxynitrite anion stimulates arginine release from cultured rat astrocytes

Abstract

The biosynthesis of the physiological messenger nitric oxide (·NO) in neuronal cells is thought to depend on a glial-derived supply of the ·NO synthase substrate arginine. To expand our knowledge of the mechanism responsible for this glial-neuronal interaction, we studied the possible roles of peroxynitrite anion (ONOO-), superoxide anion (O2·-), ·NO, and H2O2 in L-[3H]arginine release in cultured rat astrocytes. After 5 min of incubation at 37°C, initial concentrations of 0.05-2 mM ONOO- stimulated the release of arginine from astrocytes in a concentration-dependent way; this effect was maximum from 1 mM ONOO- and proved to be ~400% as compared with control cells. ONOO--mediated arginine release was prevented by arginine transport inhibitors, such as L-lysine and N(G)-monomethyl-L- arginine, suggesting an involvement of the arginine transporter in the effect of ONOO-. In situ xanthine/xanthine oxidase-generated O2·- (20 nmol/min) stimulated arginine release to a similar extent to that found with 0.1 mM ONOO-, but this effect was not prevented by arginine transport inhibitors ·NO donors, such as sodium nitroprusside, S-nitroso-N-acetylpenicillamine, or 1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate, and H2O2 did not significantly modify arginine release. As limited arginine availability for neuronal ·NO synthase activity may be neurotoxic due to ONOO- formation, our results suggest that ONOO--mediated arginine release from astrocytes may contribute to replenishing neuronal arginine, hence avoiding further generation of ONOO- within these cells.