Glucocorticoid hormone treatment enhances the cytokine production of regulatory T cells by upregulation of Foxp3 expression

Objective: Despite the fact that glucocorticoids (GC) are important therapeutic tools, their effects on regulatory " cells (Treg) are not well defined. The aim of our work was to investigate how GCs influence in vivo the thymi (tTreg) and peripheral Treg (pTreg) differentiation, survival and cytokine production. Methods: Tregs were detected with flow cytometry in lymphatic organs of 4-6 weeks old BALB/c mice afte repeated (2-4 days), high-dose in vivo GC treatment using CD4/CD25 cell surface and Foxp3/IL-10/TGF beta glucocorticoid receptor (GR) intracellular staining. Cytokine, Foxp3, and GR mRNA levels of sorte CD4(+)CD25(high) T cells were analyzed using RT-PCR. Foxp3 and GR localization in Treg cells was investigate with confocal microscopy. Results: GC treatment of mice resulted in increased relative tTreg frequency in the thymus, which was due t decreased total thymocyte numbers with unchanged absolute tTreg cell count. In contrast the relative pTreg ce ratio in secondary lymphatic organs decreased or showed no changes after GC treatment, while the absolut number of pTregs decreased. Elevated intracellular IL-10(+) and TGF beta(+) tTreg and pTreg ratios were measured i GC-treated animals, accompanied with elevated Foxp3 mRNA expression. In addition, GC treatment cause increased TGF beta and IL-35 mRNA expression in CD4(+)CD25(high+) splenic and elevated IL-10 mRNA level i thymic tTregs. GR expression of thymic tTreg cells was lower than in pTregs. GC treatment caused an opposit change in GR levels, elevating GR in tTregs but decreasing it in pTregs. We observed a nuclear localization of G] in both tTregs and pTregs, which showed high colocalization (similar to 60%) with Foxp3 transcription factor. Thes data suggest an interaction of these two transcription factors with further increase due to GC treatment in spleni pTregs. Conclusion: Our data show selective survival of tTregs and elevated production of immunosuppressive cytokine by Treg cells after GC treatment, which may contribute to the immunosuppressive effects of GCs.