Nitric oxide regulation of human peripheral blood mononuclear cells: critical time dependence and selectivity for cytokine versus chemokine expression

NO is antiproliferative for T cells and other immune cells, but there is debate over whether it influences cytokine expression and if so whether it shows cytokine selectivity. Furthermore, the NO effect may depend on exposure time. To address these issues, we precultured human PBMC with the NO donors S-nitrosoglutathione (a natural storage form of NO) or S-nitroso-N-acetyl-D-penicillamine for up to 48 h before cell activation and then monitored proliferation and cytokine and chemokine expression. S-nitrosoglutathione or S-nitroso-N-acetyl-D-penicillamine, but not their non-NO-releasing analogues, inhibited proliferation induced by PHA or IL-2, the effect declining progressively from 48 to 0 h pre-exposure to the mitogen. This was accompanied by reduced PHA-induced IL-2 release and reduced IL-2, IFN-gamma, and IL-13 mRNA expression. In contrast, NO did not influence PHA-induced expression of mRNA for the chemokines lymphotactin, RANTES, IFN-gamma-inducible protein, macrophage-inhibitory protein-1alpha, macrophage-inhibitory protein-1beta, macrophage chemoattractant protein-1, and IL-8 or release of RANTES or IL-8. The NO effects were not toxic and were not accompanied by changes in PHA-induced CD25 expression. We conclude that exposure time to NO is critical to altered PBMC responsiveness and that NO inhibits expression of both Th1 and Th2 cytokines but not chemokines.