Objective: Critical illness is associated with tissue damage, inflammation and the development of immune dysfunction. Leukocyte reprogramming occurs leading to insufficient production of pro-inflammatory cytokines upon subsequent stimulation. Cellular nucleotides released during tissue damage act via purinergic receptors to modulate immune function. We hypothesized that extracellular nucleotides in concentrations similar to those found near injured and ischemic tissues will modulate cytokine secretion.
Design and participants: Bench study in 28 healthy human volunteers using standardized lipopolysaccharide (LPS) stimulated ex vivo whole blood cultures (ILCS).
Setting: The Nepean Hospital Laboratories, University of Sydney.
Interventions: Nucleotides ATP, ADP and other P2 purinergic receptor agonists ATPgammaS, BzATP, UTP and P1 agonist CV1808 were injected into the ILCS, and cultured for 6, 12 and 24 h as indicated.
Measurements and results: ATP (100 muM) reduced the LPS stimulated secretion of TNFalpha at 6 and 12 h, as well as IL-12(p70) and IFNgamma at 24 h of incubation. ADP, ATPgammaS, BzATP, and CV1808, but not UTP displayed IL-12(p70) and IFNgamma reducing effect similar to ATP. Higher ATP concentration (500 muM) had even more pronounced immunosuppressive effect. Nucleotides had variable effect on stimulated IL-10 secretion.
Conclusions: ATP and ADP at high-micromolar concentrations reduce secretion of the main Th1 cytokines TNFalpha, IL-12(p70) and IFNgamma in LPS stimulated human blood. As immune dysfunction associated with critical illness is characterized by decreased TNFalpha, IL-12 and IFNgamma production by leukocytes, extracellular nucleotides might contribute to its pathogenesis [corrected]