Purine and pyrimidine nucleotides potentiate activation of NADPH oxidase and degranulation by chemotactic peptides and induce aggregation of human neutrophils via G proteins

Abstract

Whereas the chemotactic peptide, N‐formyl‐l‐methionyl‐l‐leucyl‐l‐Phenylalanine (fMet‐Leu‐Phe), induced NADPH‐oxidase‐catalyzed superoxide (O₂⁻) formation in human neutrophils, purine and pyrimidine nucleotides per se did not stimulate NADPH oxidase but enhanced O₂⁻ formation induced by submaximally and maximally stimulatory concentrations of fMet‐Leu‐Phe up to fivefold. On the other hand, fMet‐Leu‐Phe primed neutrophils to generate O₂⁻ upon exposure to nucleotides. At a concentration of 100 μM, purine nucleotides enhanced O₂⁻ formation in the effectiveness order adenosine 5′‐O‐[3‐thio]triphosphate (ATP[γS]) > ITP > guanosine 5′‐O‐[3‐thio]triphosphate (GTP[γS]) > ATP = adenosine 5′‐O, ‐[2‐thio]triphosphate (Sp‐diastereomer) = GTP = guanosine 5′‐O, [2‐thio]diphosphate (GDP[βS] = ADP > adenosine 5′‐[β,γ‐imido]triphosphate = adenosine 5′‐O‐[2‐thio]triphosphate] (Rp‐diastereomer). Pyrimidine nucleotides stimulated fMet‐Leu‐Phe‐induced O₂⁻ formation in the effectiveness order uridine 5′‐O‐[3‐thio]triphosphate (UTP[γS]) > uridine 5′‐O‐[2‐thio]diphosphate (UDP[βS]) = uridine 5′‐O[2‐thio]triphosphate (Rp‐diastereomer) (Rp)‐UTP[βS]) = UTP > CTP. Uracil nucleotides were similarly effective potentiators of O₂⁻ formation as the corresponding adenine nucleotides. GDP[βS] and UDP[βS] synergistically enhanced the stimulatory effects of ATP[γS], GTP[γS] and UTP[γS]. Purine and pyrimidine nucleotides did not induce degranulation in neutrophils but potentiated fMet‐Leu‐Phe‐induced release of β‐glucuronidase with similar nucleotide specificities as for O₂⁻ formation. In contrast, nucleotides per se induced aggregation of neutrophils. Treatment with pertussis toxin prevented aggregation induced by both nucleotides and fMet‐Leu‐Phe. Our results suggest that purine and pyrimidine nucleotides act via nucleotide receptors, the nucleotide specificity of which is different from nucleotide receptors in other cell types. Neutrophil nucleotide receptors are coupled to guanine‐nucleotide‐binding proteins. As nucleotides are released from cells under physiological and pathological conditions, they may play roles as intercellular signal molecules in neutrophil activation.