Blockade of adenosine A 2A receptors prevents interleukin-1β-induced exacerbation of neuronal toxicity through a p38 mitogen-activated protein kinase pathway

Background and purpose: blockade of adenosine a 2a receptors (a 2ar) affords robust neuroprotection in a number of brain conditions,although the mechanisms are still unknown. a likely candidate mechanism for this neuroprotection is the control of neuroinflammation,which contributes to the amplification of neurodegeneration,mainly through the abnormal release of pro-inflammatory cytokines such as interleukin(il)-1β. we investigated whether a 2ar controls the signaling of il-1β and its deleterious effects in cultured hippocampal neurons.methods: hippocampal neuronal cultures were treated with il-1β and/or glutamate in the presence or absence of the selective a 2ar antagonist,sch58261 (50 nmol/l). the effect of sch58261 on the il-1β-induced phosphorylation of the mitogen-activated protein kinases (mapks) c-jun n-terminal kinase (jnk) and p38 was evaluated by western blotting and immunocytochemistry. the effect of sch58261 on glutamate-induced neurodegeneration in the presence or absence of il-1β was evaluated by nucleic acid and by propidium iodide staining,and by lactate dehydrogenase assay. finally,the effect of a 2ar blockade on glutamate-induced intracellular calcium,in the presence or absence of il-1β,was studied using single-cell calcium imaging.results: il-1β (10 to 100 ng/ml) enhanced both jnk and p38 phosphorylation,and these effects were prevented by the il-1 type 1 receptor antagonist il-1ra (5 μg/ml),in accordance with the neuronal localization of il-1 type 1 receptors,including pre-synaptically and post-synaptically. at 100 ng/ml,il-1β failed to affect neuronal viability but exacerbated the neurotoxicity induced by treatment with 100 μmol/l glutamate for 25 minutes (evaluated after 24 hours). it is likely that this resulted from the ability of il-1β to enhance glutamate-induced calcium entry and late calcium deregulation,both of which were unaffected by il-1β alone. the selective a 2ar antagonist,sch58261 (50 nmol/l),prevented both the il-1β-induced phosphorylation of jnk and p38,as well as the il-1β-induced deregulation of calcium and the consequent enhanced neurotoxicity,whereas it had no effect on glutamate actions.conclusions: these results prompt the hypothesis that the neuroprotection afforded by a 2ar blockade might result from this particular ability of a 2ar to control il-1β-induced exacerbation of excitotoxic neuronal damage,through the control of mapk activation and late calcium deregulation. © 2012 simões et al.; licensee biomed central ltd.