ATP releases ATP or other nucleotides from human peripheral blood leukocytes through purinergic P2 receptors

Aims: Almost every eukaryotic cell releases ATP under certain conditions. The idea that ATP induces the release of ATP has been scantly investigated. Methods: We explored this possibility by assessing the rate of exogenous ATP breakdown (measured by phosphates production) by human peripheral blood leukocytes. The role of P2Y and P2X receptors was evaluated pharmacologically, by patch clamp, or by flow cytometry. Key findings: In mononuclear and/or polymorphonuclear cells, ATP increased phosphates formation in a time- and concentration-dependent manner. Uncoupling of P2Y receptors with N-ethylmaleimide and antagonism of P2Y and P2X receptors through suramin reduced phosphate formation after 500 mu M ATP, suggesting that part of the phosphate production was due to activation of P2 receptors, with subsequent release of ATP or other nucleotides. Similar results were obtained with UTP and ATP gamma S. Gadolinium(connexins inhibitor) also significantly reduced the ATP-induced phosphate production. Blockade of P2X receptors with SKF 96365 or NF023 did not modify the phosphate production. Inmonocytes, 500 mu MATP induced inward currents suggestive of P2X(1) activation, but higher concentrations (1-5mM) induced inward currents suggestive of P2X(7) activation. We discarded a role of adenosine in the ATP-evoked nucleotides release. Flow cytometry identified that almost all mononuclear and polymorphonuclear cells expressed P2Y(1,2,4,6,11) receptors. Significance: 500 mu M ATP induced the release of ATP or other nucleotides through activation of P2Y(2,4,6,11) receptors in human leukocytes, and probably via P2X receptors at higher concentrations. This ATP-induced nucleotides release constitutes a potential mechanism leading to amplification of ATP signaling. (C) 2015 Elsevier Inc. All rights reserved.