Adenosine A2A receptor stimulation potentiates nitric oxide release by activated microglia

The absence of adenosine A2A receptors, or its pharmacological inhibition, has neuroprotective effects. Experimental data suggest that glial A2A receptors participate in neurodegeneration induced by A 2A receptor stimulation. In this study we have investigated the effects of A2A receptor stimulation on control and activated glial cells. Mouse cortical mixed glial cultures (75% astrocytes, 25% microglia) were treated with the A2A receptor agonist CGS21680 alone or in combination with lipopolysaccharide (LPS). CGS21680 potentiated lipopolysaccharide-induced NO release and NO synthase-II expression in a time- and concentration-dependent manner. CGS21680 potentiation of lipopolysaccharide-induced NO release was suppressed by the A2A receptor antagonist ZM-241385 and did not occur on mixed glial cultures from A2A receptor-deficient mice. In mixed glial cultures treated with LPS + CGS21680, the NO synthase-II inhibitor 1400W abolished NO production, and NO synthase-II immunoreactivity was observed only in microglia. Binding experiments demonstrated the presence of A2A receptors on microglial but not on astroglial cultures. However, the presence of astrocytes was necessary for CGS21680 potentiating effect. In light of the reported neurotoxicity of microglial NO synthase-II and the neuroprotection of A2A receptor inhibition, these data suggest that attenuation of microglial NO production could contribute to the neuroprotection afforded by A2A receptor antagonists. © 2005 International Society for Neurochemistry.This work was supported by grants from Spanish Ministerio de Ciencia y Tecnología (SAF2001-2240 and Red CIEN to JS, SAF2002-03293 to RF and SAF2003-4864; GEN2003-20651-C06-02 to RM); from Spanish Fondo de Investigaciones Sanitarias (PI040778 to JS; RTA-G03/05 to RM); from Fundació Marató TV3 (01/012710 to RF) and Fundació la Caixa (2003 × 928 to RM and 02/056–00 to RF); from National Institute of Health (ES10804) to MS. AE is recipient of a pre-doctoral grant from IDIBAPSPeer Reviewe