ATP released from β-amyloid-stimulated microglia induces reactive oxygen species production in an autocrine fashion

Present study demonstrated that fibrillar beta-amyloid peptide (fA beta(1-42)) induced ATP release, which in turn activated NADPH oxidase via the P2X(7) receptor (P2X(7)R). Reactive oxygen species (ROS) production in fA beta(1-42)-treated microglia appeared to require Ca2+ influx from extracellular sources, because ROS generation was abolished to control levels in the absence of extracellular Ca2+. Considering previous observation of superoxide generation by Ca2+ influx through P2X(7)R in microglia, we hypothesized that ROS production in fA beta-stimulated microglia might be mediated by ATP released from the microglia. We therefore examined whether fAp(1-42)-induced Ca2+ influx was mediated through P2X(7)R activation. In serial experiments, we found that microglial pretreatment with the P2X(7)R antagonists Pyridoxal-phosphate-6-azophenyl-2',4'-disulfonate (100 mu M) or oxidized ATP (100 mu M) inhibited fA beta-induced Ca2+ influx and reduced ROS generation to basal levels. Furthermore, ATP efflux from fA beta(1-42)-stimulated microglia was observed, and apyrase treatment decreased the generation of ROS. These findings provide conclusive evidence that fA beta-stimulated ROS generation in microglial cells is regulated by ATP released from the microglia in an autocrine manner.