P2Z purinoceptor, a special receptor for apoptosis induced by ATP in human leukemic lymphocytes

Abstract

Objective: To investigate the role of purinergic P2Z receptors for apoptosis of human leukemic lymphocytes mediated by extracellular adenosine triphosphate (ATP).

Methods: A total of 13 B-chronic lymphocytic leukemia (CLL) patients were studied. Exposure of leukemic lymphocytes with (n = 8) or without (n = 5) P2Z receptors to ATP, benzoylbenzoic-ATP (BzATP), 2-methylthio-ATP (2MeSATP), adenosine-5' [gamma-thio] triphosphate (ATP-gamma S), and other nucleosides for 8 h in vitro. Apoptosis was detected by electron microscopy (EM), agarose gel electrophoresis, and the quantitative assay-TdT assay.

Results: Apoptosis was detected only in leukemic lymphocytes with P2Z receptors. Using a quantitative assay, ATP-induced DNA strand breaks were found to occur specifically with BzATP, ATP and 2MeSATP, but not for analogue ATP-gamma S nor other nucleosides. Meanwhile, ATP-induced DNA fragmentation was fully blocked by pretreatment with oxidized ATP (OxATP), a compound recently shown to block P2Z receptors. Also, it is shown that the Ca2+/calmodulin complex plays a role in the regulation of the apoptosis induced by ATP on CLL cells, because an antagonist of this complex, 1-[N, O-bis (5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine (KN-62) was found to inhibit the ATP-induced apoptosis. Furthermore, choline, an inhibitor of phospholipase D (PLD), is first shown to partially inhibit ATP-induced apoptosis.

Conclusion: These data indicate that P2Z receptors on lymphocytes play an important role in the apoptosis induced by ATP in vitro.