Oxygen-glucose deprivation-induced enhancement of extracellular ATP-P2Y purinoceptors signaling for the propagation of astrocytic calcium waves

Abstract

Waves of elevated intracellular free Ca 2+ that propagate between neighboring astrocytes (Ca 2+ waves) are important for the communication among astrocytes. We have previously revealed that focal photolysis of a caged calcium ionophore results in an increase in the concentration of intracellular Ca 2+ in the target astrocytes, then the increase propagates to neighboring astrocytes through gap junctions. The extracellular ATP-purinoceptors signaling pathways are not primarily responsible for the propagation of the photolytic flash-induced Ca 2+ waves. Here we examined whether and if so how the dynamics of Ca 2+ waves changed after treatment with sublethal simulated ischemia; oxygen-glucose deprivation (OGD). OGD treatment increased the astrocytic expression of P2Y 1 and P2Y 2 receptors early during reperfusion, resulting in an increase in the propagating waves speed. In contrast, the expression of a gap junction protein was not changed significantly by the OGD suggesting that the extracellular ATP-P2Y receptors signaling pathways were preferentially enhanced after OGD. The present method to induce Ca 2+ waves by focal photolysis of a caged calcium ionophore may provide a valuable tool with which to analyze glial Ca 2+ waves under not only normal but also pathologic conditions.