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

Objective To investigate the role of purinergic P2Z receptors for apoptosis of human leukemic lymphocytes mediated by extracellular adenosine triphosp hate (ATP). Methods A total of 13 B-chronic lymphocytic leukemia (CLL) patients were st udied. 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), agar ose gel electrophoresis, and the quantitative assay-TdT assay. Results Apoptosis was detected only in leukemic lymphocytes with P2Z recept ors. Using a quantitative assay, ATP-induced DNA strand breaks were found t o 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 recent ly 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-isoquinoli nesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine (KN-62) was found to inh ibit the ATP-induced apoptosis. Furthermore, choline, an inhibitor of phosp holipase D (PLD), is first shown to partially inhibit ATP-induced apoptosis . Conclusion These data indicate that P2Z receptors on lymphocytes play an im portant role in the apoptosis induced by ATP in vitro.