Maturation of human dendritic cells as sulfasalazine target

Aim. Sulfasalazine, a nonsteroidal anti-inflammatory drug, is effective in treating some autoimmune diseases, but its mechanism of action is unclear. To determine whether dendritic cells could be a possible target of the drug , we studied the effects of sulfasalazine and its metabolites, aminosalicyl ate and sulfapyridine, on in vitro maturation (terminal differentiation) of human myeloid dendritic cells. Methods. We prepared immature dendritic cells by incubating CD14-positive c ells in the presence of granulocyte-macrophage colony-stimulating factor an d interleukin (IL)-4. The cells were matured by addition of tumor necrosis factor (TNF)-a, IL-1 beta, and prostaglandin E-2 in the presence of sulfasa lazine or its metabolites - aminosalicylate and sulfapyridine, or their com binations. We quantified the effect of drugs on the dendritic cell characte ristics, such as stimulation of autologous and allogeneic pan-T cell prolif eration, surface marker phenotype, IL-12 p40 subunit secretion, and activat ion of nuclear transcription factor (NF)-kappaB. Results. Dendritic cells treated with sulfasalazine (1.25 mu mol/L or 2.5 m u mol/L) could not stimulate T cells (p < 0.028, two-sided paired t-test). In distinction to drug-free maturing dendritic cells, 2.5 mu mol/L sulfasal azine upregulated the levels of CD14 and CD68 and downregulated the levels of CD40, CD80, and CD83 (for all CD markers, p < 0.03 for difference betwee n measurements in the absence and the presence of sulfasalazine). From conc entration-dependent changes in CD83 expression, we found an apparent ID50 a pproximate to 1.5 mu mol/L sulfasalazine. The apparent ID50 value for amino salicylate-inhibited maturation was 4 mu mol/L. Sulfapyridine had no effect . At 1.25 mu mol/L, sulfasalazine largely inhibited NF-kappaB activation in dendritic cells. Conclusion. Maturing human dendritic cells are hundred-fold more sensitive to sulfasalazine than T cells and NK cells and the most sensitive human cel ls described so far. Thus, dendritic cell maturation is an important target of sulfasalazine. Because of the role of dendritic cells in (auto)immunity , inhibition of their maturation might provide a target for further optimiz ation of sulfasalazine therapy.