Indigo Naturalis ameliorates murine dextran sodium sulfate-induced colitis via aryl hydrocarbon receptor activation.

BACKGROUND: Indigo Naturalis (IN) is used as a traditional herbal medicine for ulcerative colitis (UC). However, the mechanisms of action of IN have not been clarified. We aimed to evaluate the efficacy of IN for ameliorating colonic inflammation. We further investigated the mechanisms of action of IN. METHODS: Colitis severity was assessed in dextran sodium sulfate-induced colitis and trinitrobenzene sulfonic acid-induced colitis models with or without the oral administration of IN or indigo, which is a known major component of IN. Colonic lamina propria (LP) mononuclear cells isolated from IN-treated mice were analyzed with quantitative reverse transcription polymerase chain reaction (qRT-PCR) and flow cytometry. LP and splenic mononuclear cells cultured in vitro with IN or indigo were also analyzed. The role of the candidate receptor for indigo, the aryl hydrocarbon receptor (AhR), was analyzed using Ahr-deficient mice. RESULTS: Colitis severity was significantly ameliorated in the IN and indigo treatment groups compared with the control group. The mRNA expression levels of interleukin (Il)-10 and Il-22 in the LP lymphocytes were increased by IN treatment. The treatment of splenocytes with IN or indigo increased the expression of anti-inflammatory cytokines and resulted in the expansion of IL-10-producing CD4+ T cells and IL-22-producing CD3-RORγt+ cells, but not CD4+Foxp3+ regulatory T cells. The amelioration of colitis by IN or indigo was abrogated in Ahr-deficient mice, in association with diminished regulatory cytokine production. CONCLUSIONS: IN and indigo ameliorated murine colitis through AhR signaling activation, suggesting that AhR could be a promising therapeutic target for UC.

Vitamin K deficiency leads to exacerbation of murine dextran sulfate sodium-induced colitis.

BACKGROUND: Patients with inflammatory bowel disease (IBD) often exhibit vitamin K deficiency. Vitamin K has been shown to inhibit inflammation via interleukin (IL)-6 suppression. This study aimed to evaluate the effect of vitamin K in a murine model of colitis. METHODS: Colitis was induced using dextran sulfate sodium (DSS) in mice fed either a vitamin K-deficient (K-def) or a vitamin K-supplemented (K-sup) diet. The clinical and histological severity of colitis was assessed, and levels of cytokine production from the spleen and colonic lamina propria were measured by enzyme-linked immunosorbent assay and quantitative real-time reverse transcription polymerase chain reaction. Cytokine expression levels in CD4(+), CD11b(+), and CD19(+) cells in the presence and absence of vitamin K [menatetrenone (MK-4)] were measured in vitro and apoptosis was determined by caspase 3/7 activity and Annexin V staining. RESULTS: DSS administration resulted in significantly more severe body weight loss, shorter colon length, and higher histological scores in mice fed a K-def diet than those fed a K-sup diet. IL-6 expression in lamina propria mononuclear cells was significantly higher in the K-def group than in the K-sup group. IL-6 expression was significantly decreased in the presence of MK-4 in CD19(+) cells, but not in the CD4(+) and CD11b(+) subpopulations. Apoptotic cell population in CD19(+) cells was increased in the presence of MK-4 in vitro and in vivo. CONCLUSIONS: Vitamin K exerts a protective effect against DSS colitis; this effect is associated with IL-6 downregulation. Vitamin K could be a potential treatment target for IBD.