Naringin Exhibited Therapeutic Effects against DSS-Induced Mice Ulcerative Colitis in Intestinal Barrier-Dependent Manner

Abstract

Naringin is a kind of multi-source food additive which has been explored broadly for its various biological activities and therapeutic potential. In the present study, the protective effect and mechanism of naringin on dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) in mice were investigated. The results showed that naringin significantly alleviated DSS-induced colitis symptoms, including disease activity index (DAI), colon length shortening, and colon pathological damage. The tissue and serum secretion of inflammatory cytokines, as well as the oxidative stress, were decreased accordingly upon naringin intervention. Naringin also decreased the proteins involved in inflammation and increased the expression of tight junction (TJ) proteins. Moreover, naringin increased the relative abundance of Firmicutes/Bacteroides and reduced the content of Proteobacteria to improve the intestinal flora disorder caused by DSS, which promotes the intestinal health of mice. It was concluded that naringin can significantly ameliorate the pathogenic symptoms of UC through inhibiting inflammatory response and regulating intestinal microbiota, which might be a promising natural therapeutic agent for the dietary treatment of UC and the improvement of intestinal symbiosis.

Keywords: inflammation; intestinal microbiota; naringin; ulcerative colitis.

Figure 1

Naringin could alleviate the symptoms of DSS-induced colitis in mice. (A) Changes in body weight of mice during the experiment. (B) DAI score. (C) Appearances of the colon tissues. (D) Weights of colon in different groups. (E) Lengths of colon in different groups. Data are presented as means ± SD (n = 10 per group). ## p < 0.01 and ### p < 0.001, compared with the control group; * p < 0.05, ** p < 0.01 and *** p < 0.001, compared with the model group.

Figure 2

Histopathological changes of colons in ulcerative colitis mice were improved by naringin. (A) The colons of each group were processed for histological evaluation (H&E staining, 50×). (B) Histopathological scores of each group were evaluated. Data are presented as means ± SD (n = 6). ### p < 0.001, compared with the control group; * p < 0.05 and ** p < 0.01, compared with the DSS model group.

Figure 3

Effect of naringin on the expression of inflammatory cytokines in ulcerative colitis mice. (A) TNF-α, IL-6 and IL-1β distribution in the colons of each group (immunofluorescence analysis, 200×). (B) Concentration of TNF-α in the blood serum. (C) Concentration of IL-6 in the blood serum. Data are presented as means ± SD (n = 3). ## p < 0.01, compared with the control group; * p < 0.05 and ** p < 0.01, compared with the model group.

Figure 4

Effects of naringin on oxidative stress levels in mice with colitis. The level of MAD (A), GSH (B) and SOD (C) were detected in the colon tissues of each group. Data are presented as means ± SD (n = 3). ## p < 0.01 and ### p < 0.001, compared with the control group. * p < 0.05, ** p < 0.01 and *** p < 0.001, compared with the model group.

Figure 5

Expression of related proteins in tissues of ulcerative colitis mice. (A) The protein expressions of iNOS, COX-2, Occludin and ZO-1 were detected by Western blotting. GAPDH was used as an internal control. The gray density scanning analysis of iNOS (B), COX-2 (C) and occludin (D) and ZO-1 (E). Data are presented as means ± SD (n = 3). # p < 0.05 and ### p < 0.001, compared with the control group; * p < 0.05 and *** p < 0.001, compared with the model group.

Figure 6

Naringin regulated on the disturbed gut microbiota in DSS-induced colitis mice. (A) Rank-Abundance curves of the OUT level. (B) Shannon dilution curves. (C) Venn diagram of species in the three groups. (D) Histogram of intestinal microbial community structure at the phylum level. (E) Community heatmap analysis in the phylum levels. (F) Circos of samples and species in the phylum levels.

Figure 7

Species difference analysis on the gut microbiota in DSS-induced colitis mice. (A) Cluster dendrogram of the three groups on OUT level. (B) PCA analysis of variation on phylum level. (n = 5). (C) The Kruskal-Wallis H test was used to compare the species of intestinal flora in different groups. This figure is the result at the level of phylum classification. * p < 0.05 and ** p < 0.01, compared with the control group. (D) The LEfSe dendrogram showed the phylogenetic distribution of associated colonic microorganisms in three groups of mice.