Low Dose of Cyanidin-3-O-Glucoside Alleviated Dextran Sulfate Sodium-Induced Colitis, Mediated by CD169+ Macrophage Pathway

Inflammatory bowel disease (IBD) is a chronic disease of the intestinal tract in which excessive activation of inflammatory response is correlated. Cyanidin-3-O-glucoside (C3G) is a powerful anti-inflammatory agent, widely existing in fruits and vegetables. However, the role of C3G has rarely been investigated in dextran sulfate sodium (DSS)-induced colitis. In an attempt to elucidate the possible mechanism of IBD and develop new efficient therapeutic methods for colitis, we evaluated the effects of C3G on DSS-induced colitis. DSS-induced colitic C57BL/6 mice were intraperitoneal injected with 1ug C3G or phosphate buffer every 2 days, a total of 3 times; the changes in macrophages and regular T cells were analyzed by flow cytometry and immunofluorescence. Cytokines and chemokines were measured by real-time quantitative polymerase chain reaction. The results showed that C3G treatment did not cause changes in body weight and colon length as much as those of DSS-treated mice only. Cytokine expression levels such as interleukin (IL)- 6, IL-1β, IL-18, tumor necrosis factor α, interferon γ (IFN γ) in colons and mesenteric lymph nodes (mLNs) from C3G-treated mice were lower than those from colitic mice. Meanwhile, C3G injection inhibited the decrease in CCL22 levels and Tregs induction in colitic mice. Furthermore, the activation of macrophages by LPS and increase of CD169+ cells induced by type I IFN could be inhibited by C3G directly in vitro. The study is the first to demonstrate strong effects of C3G to alleviate DSS-induced colonic damage in mice. The effect of C3G on DSS-induced colitis clearly showed a decrease of CD169+ macrophages in both the colon and mLNs. An increase of CD169+ cells induced by type I IFN could be inhibited by C3G. All these data suggest that the role of C3G in colitic inflammation was mediated at least partially by CD169+ cells and the type I IFN pathway.