title: Nitric oxide inhibits the secretion of T-helper 1- and T-helper 2-associated cytokines in activated human T cells.
abstract: Mechanisms regulating the balance of T-helper 1 (Th1) and T-helper 2 (Th2) immune responses are of great interest as they may determine the outcome of allergic and infectious diseases. Recently, in mice, nitric oxide (NO), a powerful modulator of inflammation, has been reported to preferentially down-regulate Th1-mediated immune responses. In the present study, we investigated the effect of NO on the production of Th1- and Th2-associated cytokines by activated human T cells and human T-cell clones. Cytokine secretion was measured in the presence of the NO-donating agents 3-morpholinosydnonimine (SIN-1) and S-nitroso-N-acetylpenicillamine (SNAP). Both NO-donors markedly inhibited the release of interferon-gamma (IFN-gamma), interleukin-2 (IL-2), IL-5, IL-10 and IL-4 by anti-CD3 activated T cells. A preferential inhibition of Th1-associated cytokines was not observed. Neither was nitrite found in the supernatants of activated T cells, nor was specific mRNA for inducible and constitutive NO synthase detectable, indicating that T cells themselves did not contribute to the observed effect of the NO donors. Costimulation with anti-CD28 monoclonal antibodies (mAb) prevented SIN-1/SNAP-mediated down-regulation of cytokine production only in part. In contrast, when T cells were stimulated by phorbol-ester and ionomycin, they were refractory to SIN-1-induced inhibition of cytokine production. When SIN-1 was added after the onset of anti-CD3 stimulation, the inhibitory effect was found to be less pronounced, indicating that SIN-1 may interfere with early signal transduction events. The addition of superoxide dismutase (SOD) and catalase did not restore the effects of SIN-1, demonstrating that the inhibition of cytokines was due to NO and not to oxygen intermediates. Furthermore, 8-Br-cGMP-mediated increase of intracellular cGMP caused the same pattern of cytokine inhibition as observed with SIN-1 and SNAP. Using a single cell assay, these agents were shown to reduce the frequency of IFN-gamma-producing T cells, suggesting that not all T cells are susceptible to SIN-1/SNAP. However, cytokine production by purified T-cell subpopulations (CD4+, CD8+, CD45RA+, and CD45RO+) was equally impaired by NO donors. In conclusion, in contrast to the murine system, our results do not provide evidence that NO preferentially inhibits Th1-cytokine secretion of activated human T cells in vitro.
authors.affiliation: Department of Dermatology, Göttingen University, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Bauer
authors.forename: T
authors.initials: T
authors.lastname: Jung
authors.forename: D
authors.initials: D
authors.lastname: Tsikas
authors.forename: D O
authors.initials: DO
authors.lastname: Stichtenoth
authors.forename: J C
authors.initials: JC
authors.lastname: Frölich
authors.forename: C
authors.initials: C
authors.lastname: Neumann
mesh_terms: D017252:CD3 Complex / Q000276:immunology; D018929:Cell Culture Techniques; D002455:Cell Division / Q000187:drug effects; D016207:Cytokines / Q000096:biosynthesis*; D006801:Humans; D008213:Lymphocyte Activation / Q000187:drug effects; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology; D009569:Nitric Oxide / Q000276:immunology*; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D026423:S-Nitroso-N-Acetylpenicillamine; D015398:Signal Transduction / Q000187:drug effects; D018417:Th1 Cells / Q000187:drug effects / Q000276:immunology*; D018418:Th2 Cells / Q000187:drug effects / Q000276:immunology*
chemical_list: D017252:CD3 Complex; D016207:Cytokines; D009569:Nitric Oxide; C002385:linsidomine; D026423:S-Nitroso-N-Acetylpenicillamine; D008981:Molsidomine; D010396:Penicillamine