Curcumin Improves Experimental Colitis In Mice By Regulating Follicular Helper T Cells And Follicular Regulatory T Cells Via Inhibiting IL-21

Objectives:To observe the inhibitory effect of curcumin on IL-21 secretion and the regulation of follicular helper T cells and follicular regulatory T cells in TNBS induced experimental colitis model mice,and to investigate the mechanisms of curcumin alleviating experimental colitis in mice.Methods:40 male C57BL/6 mice were randomly divided into normal control group;TNBS group;TNBS+curcumin group(TNBS+Cur);TNBS+anti-IL-21 group;Each group was 10,The experimental colitis model was prepared by 100 mg/kg trinitrobenzene sulfonic acid(TNBS)ethanol solution enema,Normal group received the same volume of 50%ethanol solution enema;Mice of TNBS+Cur group were treated by 100 mg/kg curcumin solution each day from the second day after establishing IBD model;Mice in normal control、TNBS and TNBS+anti-IL-21 group were administered with the same dose of5%DMSO solutionintragastrically for 7 days;Mice of TNBS+anti-IL-21 group were treated withanti-IL-21(150ug/mouse),once per weekintraperitoneallyfrom the second day after establishing experimental colitis model;The normal control group,TNBS group and TNBS+curcumin group were given the same volume of 0.9%Sodium Chloride Solution,once per weekintraperitoneally;Daily evaluation of disease activity index(DAI)changes in all groups of mice;Each mouse was anesthetized with 4%chloral hydrate(7mL/kg)after 8 days,and the specimens of abdominal aorta blood,spleen and colon tissue were collected;the therapeutic effect of Cur was evaluated by visual assessment and histological examination;The expression of IL-21(interleukin-21)in the serum of all mice was detected by ELISA;while Changes of the number of CD4~+CXCR5~+PD-1~+Tfhand CD4~+CXCR5~+FoxP3~+Tfr cells in spleen of mice were measured by flow cytometry;The expression levels of IL-21 and Tfh cell related molecules bcl-6,ICOS,PD-1 and Tfr cell transcription factor FoxP3protein in colonic mucosa tissue were detected by Western blot.Results:Compared with normal control group,The DAI、histological score、The expression levels of IL-21 in the serum、the percentage of CD4~+CXCR5~+PD-1~+Tfhcells in the spleen and the protein levels of IL-21 and Tfh cell related molecules bcl-6,ICOS,PD-1 in colonic mucosa of TNBS group were significantly elevated,while the percentage of CD4~+CXCR5~+FoxP3~+Tfr cells in the spleen and the protein level of Tfr cell transcription factor FoxP3 in colonicmucosaofTNBSgoupweredecreasedsignificantly(all P<0.05);Compared with TNBS goup,The DAI、histological score、The expression levels of IL-21 in the serum、the percentage of CD4~+CXCR5~+PD-1~+Tfhcells in the spleen and the protein levels of IL-21 and Tfh cell related molecules bcl-6,ICOS,PD-1 in colonic mucosa of TNBS+Cur group and TNBS+anti-IL-21goup were decreased significantly,while the percentage of CD4~+CXCR5~+FoxP3~+Tfr cells in the spleen and the protein level of Tfr cell transcription factor FoxP3 in colonic mucosa of TNBS+Cur group and TNBS+anti-IL-21goupwere elevated remarkably(all P<0.05);Conclusion:The development of TNBS-induced experimental colitis may be associated with abnormal IL-21 secretion and the abnormal proportion of Tfh/Tfr cells;Curcumin may have an obvious therapeutic effect on TNBS-induced experimental colitis by regulating the balance of Tfh cells and Tfr cells through inhibiting the synthesis of IL-21.