[Kirenol relieves dextran sulfate sodium-induced ulcerative colitis in mice by inhibiting inflammatory cytokines and inducing CD4+ T lymphocyte apoptosis]

Abstract

Objective: To investigate whether kirenol, the major pharmacologically active compound of the Chinese medicinal herb Herba Siegesbeckiae, can protect mice from dextran sulfate sodium (DSS)-induced ulcerative colitis (UC).

Methods: C57BL/6 mice with or without kirenol pretreatment were treated with DSS in drinking water for 7 days to induce UC. The symptoms of UC including weight loss, diarrhea and bloody stool were observed daily and graded using the disease activity index (DAI). Colon injury of the mice was assessed by measuring the length of the colon and HE staining of the colon tissue. The levels of inflammatory cytokines produced by the mesenteric lymph nodes (MLNs) lymphocytes were measured using enzyme-linked immunosorbent assay; the apoptosis of the lymphocytes and CD4⁺ T cells was analyzed using flow cytometry.

Results: The mice receiving pretreatment with kirenol showed obviously ameliorated symptoms of UC and milder pathological changes in the colon as compared with the control mice. Kirenol treatment significantly down-regulated the secretion of IFN-γ, IL-17A, IL-6 and TNF-α by the MLNs lymphocytes and increased the apoptosis of lymphocytes, especially CD4⁺ T cells in the DSS-treated mice.

Conclusion: Kirenol can protect against T cell-mediated colon injury in DSS-treated mice possibly by suppressing the secretion of inflammatory mediators and inducing apoptosis of the inflammatory lymphocytes.

Keywords: apoptosis; kirenol; lymphocytes; ulcerative colitis.

1

Kirenol relieves DSS-induced ulcerative colitis in mice. A: Chemical structure of kirenol; B: DAI scores of the UC model mice and kirenol-treated mice (*P < 0.05, **P < 0.005, n=8).

2

Gross observation of the colon samples from UC model and kirenol-treated mice. A: A representative image of colons in the two groups; B, C: Statistical analysis of the colon length and colon length/body weight ratio, respectively (*P < 0.05, **P < 0.005, n=8).

3

Kirenol attenuates the severity of colon injury in DSS-treated mice. A, B: Representative image of the colons in UC model and kirenol-treated groups, respectively (HE staining, × 100); C: Comparison of histopathological scores between the two groups (*P < 0.05, n=8).

4

Kirenol inhibits secretion of inflammatory cytokines by activated MLNs lymphocytes. The lymphocytes were obtained from the MLNs of UC mice on day 7 and cultured in the presence of anti-CD3 +anti-CD28 for 48 h. IFN-γ (A), IL-17A (B) IL-6 (C) and TNF-α (D) secretion by activated lymphocytes in the supernatants was determined by ELISA assay. The results are presented as Means±SD (*P < 0.05, **P < 0.005, ***P < 0.005, n=8).

5

Kirenol induces apoptosis of lymphocytes and CD4⁺T cells from the MLNs of UC mice. A: Representative data of AV⁺ PI⁺ cells analyzed by flow cytometry; B: Quantification of the proportion of AV⁺PI⁺ cells (*P < 0.05, n=8); C: Representative data of CD4⁺AV⁺ cells analyzed by flow cytometry; D: Quantification of the proportion of CD4⁺AV⁺ cells (*P < 0.05, n=8).