RESUMEN
Objective To establish a culture protocol for Th17 cells in vitro and evaluate the effect of curcumin on the differentiation and functions of Th17 cells and explore the related mechanisms. Methods Splenic CD4+CD25- T cells of C57BL/6 mice were isolated and purified with magnetic bead methods, and were co-cultured with plate-bound anti-CD3 and anti-CD28 antibodies and with transforming growth factor (TGF)-β, interleukin (IL)-6, IL-23, anti-interferon-γ antibody and anti-IL-2 antibody for Th17-polarization. The cultured Th17 cells were allocated into four groups: the control group, in which T cells were cultured on the basis of the above protocol; the low-concentration curcumin (CM-L, 5 μmol/L) and high-concentration (CM-H, 25 μmol/L) curcumin groups, and sirolimus (SRL, 100 ng/ml) group. The proportion of Th17 cells was detected with flow cytometry, and the mRNA expression of retinoic acid-related orphan receptor (ROR)γt, IL-17A, IL-21 was examined with real-time quantitative polymerase chain reaction. Finally, the protein expression of RORγt and the phosphorylation levels of signal transducer and activator of transcription (STAT) 3 were measured using western blotting analysis. Results The proportion of Th17 cells in the freshly isolated CD4+CD25- T cells was (3.1 ±0.4)%, whereas the proportion of the cells cultured with the protocol could get [(54.1±3.4)%, P0.05). Moreover, the mRNA levels of RORγt, IL-17A and IL-21, the protein expression of RORγt and the phosphorylation levels of STAT 3 in CM-L, CM-H and SRL groups were also lower than those in the control group (IL-17A mRNA: CM-L 0.81±0.05, CM-H 0.61±0.05, SRL 0.58±0.05, Control 1.01 ±0.11, t=4.81, 8.52, 8.89; IL-21 mRNA: CM-L 0.73±0.06, CM-H 0.49±0.03,SRL 0.59±0.03, Control 1.12±0.11, t=5.98, 9.22, 7.95, P<0.01). The mRNA level of IL-21 in the CM-H group was lower than that in the SRL group (P<0.05). Conclusion In vitro, curcumin can inhibit the differentiaton of splenic CD4+CD25- T cells into Th17 cells in the setting of Th 17-polarization and inhibit the expression of IL-17A and IL-21 mRNA, which is associated with the inhibitive effect of curcumin on RORγt expression and STAT 3 phosphorylation.