CURCUMIN IMPROVES EXPERIMENTALLY INDUCED COLITIS IN MICE BY REGULATING FOLLICULAR HELPER T CELLS AND FOLLICULAR REGULATORY T CELLS BY INHIBITING INTERLEUKIN-21

To determine whether curcumin (Cur) can treat mice with experimentally-induced colitis by regulating follicular helper T cells (Tfh) and follicular regulatory T cells (Tfr) by inhibiting interleukin (IL)-21. In this study, 40 male C57BL/6 mice were randomly grouped into four groups, i.e., normal, trinitrobenzene sulfonic acid (TNBS), TNBS + curcumin, and TNBS + antiIL-21. Mice with experimental colitis were induced by 100 mg/kg TNBS. The mice in the TNBS + Cur group were treated with 100 mg/kg curcumin for seven days, and mice in the TNBS + anti-IL-21 group were treated with anti-IL-21 (150 mu g/mouse) once per week, intraperitoneally, starting on the second day after establishing the experimental colitis model. On day eight, the therapeutic effect of curcumin was evaluated by colon mucosa damage index (CMDI), histological examination, and disease activity index (DAI). Furthermore, the number of CD4 + CXCR5 + PD-1 + Tfh and CD4 + CXCR5 + FoxP3 + Tfr cells were measured by flow cytometry. The mRNA and protein expression of IL-21, Bcl-6, FOXP3, ICOS, and PD-1 in colonic mucosa was detected by reverse transcription polymerase chain reaction and the Western blot technique. Compared with the TNBS group, the DAI, CMDI, histological score, the number of CD4 + CXCR5 + PD-1 + Tfh cells, the expression of IL-21, Bcl-6, ICOS, and PD-1 were significantly decreased in the TNBS + curcumin group and TNBS + antiIL-21 group; body weight, number of CD4 + CXCR5 + FoxP3 + Tfr cells, and the expression of FoxP3 were observably elevated in the TNBS + curcumin group (all P < 0.05). Curcumin may have a potential therapeutic effect on mice with colitis treated experimentally through regulation of the balance of Tfh and Tfr cells via inhibiting the synthesis of IL-21.