Nucleotide responses of human neutrophils

Since human polymorphonuclear neutrophils (PMN) exposed to ATP or its poorly hydrolyzable analogue, adenosine-5'-O-(3-thiotriphosphate) (ATP gamma S), respond with increases in intracellular calcium and enhanced O2- responses to the chemotactic peptide N'-formyl-Met-Leu-Phe (fMLP), we systematically evaluated responses of PMN to various nucleotides. The P2X and P2Y receptor agonists, 2-methylthioadenosine triphosphate and beta, gamma-methyleneadenosine triphosphate, failed to induce increases in intracellular calcium and did not desensitize PMN to increases in intracellular calcium induced by ATP gamma S. Since it has been suggested that P2Z receptor occupancy with the ATP4- species caused nonselective increases in cell permeability, the ability of ATP to induce increases in intracellular calcium was evaluated in the presence and absence of extracellular Ca2+ and Mg2+. In the presence of these cations, 5-fold greater concentrations of ATP were required. The effects of ATP4- were not associated with changes in cell membrane permeability. This suggests that ATP4- is the active species but that its effect on PMN is not linked to a nonselective increase in permeability of the cell membrane. With respect to responses of PMN to purine and pyrimidine nucleotides as defined by increases in intracellular calcium, the rank order of potency for the nucleotides was ATP = UTP greater than ATP gamma S greater than or equal to ITP greater than GTP greater than or equal to CTP. These responses were blocked by pretreatment of PMN with pertussis toxin. Prior exposure of PMN to ATP gamma S blocked cellular responses (calcium increases) to these nucleotides but not to fMLP. Likewise, exposure of PMN to any nucleotides blocked subsequent cellular responses to ATP gamma S but not to fMLP. These data support the concept that nucleotide responses of PMN utilize either a common receptor or a common signal transduction pathway involving a guanine nucleotide binding protein in events leading to elevations in intracellular calcium. Nucleotide interaction with PMN does not follow the established pattern of responses associated with P2X or P2Y purinergic receptor occupancy.