Ascorbic acid ameliorates oxidative stress and inflammation in dextran sulfate sodium-induced ulcerative colitis in mice

Abstract

Ascorbic acid (AA) has been shown to exert beneficial effects, including mitigating oxidative stress and inhibiting inflammation. However, the preventative effect of vitamin C in chronic inflammatory diseases such as inflammatory bowel disease (IBD) remains unclear. In our study, we investigated the anti-inflammatory effects of AA and possible mechanism involved in inhibiting dextran sulfate sodium (DSS)-induced ulcerative colitis in mice. Male C57BL/6 mice were randomly divided to three groups: control group, DSS group, and DSS plus ascorbic acid treated group. Several clinical and inflammatory parameters as well as oxidative stress were evaluated. The results demonstrated that ascorbic acid significantly reduced clinical signs, inflammatory cytokines, myeloperoxidase (MPO) and malonaldehyde (MDA) activities, whereas the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were increased in DSS-induced mice. In addition, ascorbic acid was capable of inhibiting NF-κB, COX-2 and iNOS expression in the colonic. Taken together, these findings suggest that ascorbic acid contributes to the reduction of oxidative stress and inflammatory response in DSS-induced colitis and exerts the potential to prevent and clinical treatment of inflammatory bowel disease.

Keywords: Ascorbic acid; NF-κB; experimental colitis; oxidative stress.

Figure 1

Ascorbic acid alleviated DSS-induced experimental colitis. (A) Body weight changes after DSS induction of colitis. (B) Disease activity index (DAI). *P < 0.05; **P < 0.01, versus DSS-treated group. (C) Macroscopic appearances and (D) the length of colons. E. Spleen weight. Data are presented as mean ± SEM of 6 mice in each group. *P < 0.05; **P < 0.01, versus control group and #P < 0.05 versus DSS-treated group.

Figure 2

Ascorbic acid treatment protected against DSS-induced colon damage in mice. A. Colon tissues were stained with hematoxylin and eosin (H&E). B. Histopathological scores were analyzed from slides. C. MPO activity. Data are presented as means ± SEM. *P < 0.05 compared with control group; #P < 0.05 compared with DSS-treated group.

Figure 3

Ascorbic acid decreased the levels of oxidative stress in DSS-induced colitis mice. A. MDA content. B. SOD activity. C. CAT activity. D. GPx activity in the colonic tissue. Data represent the means ± SEM. *P < 0.05 compared with control group; #P < 0.05 compared with DSS-treated group.

Figure 4

Ascorbic acid decreased pro-inflammatory mediators production and mRNA levels in DSS-induced colitis mice. TNF-α (A), IL-1β (B), IL-6 (C) and IL-17 (D) in colon were determined by ELISA, respectively. The mRNA levels of TNF-α (E), IL-1β (F), IL-6 (G) and IL-17 (H) in colonic tissue were determined by RT-PCR. Data represent the means ± SEM. *P < 0.05 compared with control group; #P < 0.05 compared with DSS-treated group.

Figure 5

Ascorbic acid inhibited the activation of NF-κB and decreased inflammatory proteins expression. A. One representative image of p-p65 and p65 expression is shown. B, C. Quantification of the protein expression was performed by densitometric analysis of the blots. D. A representative immunoblot of COX-2 and iNOS. E, F. Quantification of the protein expression. The results are expressed as a percentage of the control, which is set at 100%. Data were expressed as means ± SEM of three independent experiments. *P < 0.05 compared with control group; #P < 0.05 compared with DSS-treated group.