Time-dependent effects of ATP and its degradation products on inflammatory markers in human blood ex vivo

We recently reported that adenosine 5'-triphosphate (ATP) modulates cytokine release in lipopolysaccharide (LPS)-phytohemagglutinin (PHA)-stimulated blood. ATP inhibited tumor necrosis factor-alpha (TNF-alpha) release via activation of the P2Y(11) receptor and increased interleukin (IL)-10 release via stimulation of the P2Y(12) receptor. Because ATP is known to be broken down by various ecto-enzymes, we determined the degradation profile of ATP in time in LPS-PHA-stimulated blood. ATP slowly metabolized with 14% remaining after 6h. Simultaneously, adenosine 5'-diphosphate (ADP), adenosine 5'-monophosphate (AMP) and hypoxanthine were formed. Subsequently, we investigated the time-dependent effects of ATP and its metabolites on inflammatory markers. Results showed that ATP decreased the rise in concentrations of TNF-alpha, interferon-gamma (IFN-gamma) and IL-1beta, but increased concentrations of IL-8 and IL-10. Metabolites of ATP showed either no, similar or opposite effects on cytokine release, compared to ATP. In conclusion, ATP has rapid immunomodulatory effects on a variety of cytokines in stimulated whole blood that persist until 24h.