Synaptic P2X7 and oxygen/glucose deprivation in organotypic hippocampal cultures

The P2X(7) receptor for extracellular ATP is the main candidate, among P2 receptors, inducing cell death in the immune system. Here, we demonstrate the direct participation of this receptor to cell damage induced by oxygen/glucose deprivation, in the ex vivo model of organotypic hippocampal cultures. By pharmacological and immunological approaches, we show that P2X(7) is rapidly and transiently up regulated in hippocampal areas eliciting metabolism impairment. Moreover, the P2 antagonists 2',3',-dialdehyde ATP and reactive blue 2 prevent both up regulation of this receptor and hypoxic/hypoglycernic damage. By confocal laser microscopy, we show that P2X(7) is present at the synaptic level of fibers extending : a from the CA 1-2 pyramidal cell layer throughout the strata oriens and radiatum, but absent on oligodendrocytes, astrocytes or neuronal cell bodies. Colocalization of P2X(7), is obtained with neurofilament-L protein and with synaptophysin, not with myelin basic protein. glial fibrillary acidic protein or a market for neuronal nuclei. P2X(7) up regulation and diffuse cellular damage are also induced by 3'-O-(4-benzoyl) benzoyl-ATP an agonist selective but not exclusive for P2X(7). In summary, our study demonstrates that P2X(7) not only directly participates to the hypoxic/hypoglycemic process, but also owns specific phenotypic localization. We do not exclude that it might serve as a sensor of dysregulated neuronal activity and ATP release, both occurring during oxygen/glucose deprivation.