Abstract
Ulcerative colitis (UC) is a chronic and nonspecific intestinal inflammatory disease, which may increase the risk of colon cancer. Andrographolide is a main active component of Andrographis paniculata. The anti-inflammatory ability of andrographolide suggested its potential therapeutic effect against UC. In the present study, elevated serum concentrations of proinflammatory factors, including (TNF)-α, interleukin (IL)-1β, IL-6 and IL-23, as well as increased percentages of Th17 cells (IL-17+CD4+ cells) in CD4+ cells were detected in UC patients compared to that in healthy donors. These data suggested that Th17 immune responses may involve in the pathogenesis of UC. Experimental colitis mouse model was then established. The results of hematoxylin and eosin staining demonstrated the therapeutic effect of andrographolide on colitis. Enzyme-linked immunosorbent assay (ELISA), flow cytometry and western blotting analyses showed that andrographolide could decreased the levels of proinflammatory factors TNF-α, IL-1β, IL-6 and IL-17A in the serum and in the colon tissues, reduced the percentages of Th17 cells in CD4+ cells, and suppressed the levels of IL-23, IL-17A, ROR-γt (key transcription factor of Th17 cells) and p-STAT3 in the colon tissues. Further, peripheral blood mononuclear cells (PBMCs) were isolated from UC patients and treated with various concentrations of andrographolide (0, 10, 20 and 30 μg/ml). Andrographolide also showed inhibitory effects on the levels of proinflammatory factors, the percentages of Th17 cells and the expression of relative proteins. Similar results were obtained in lipopolysaccharide-treated normal PBMCs. These data suggested that andrographolide may inhibit Th17 immune response via STAT3 signaling. In conclusion, we demonstrated that andrographolide inhibited the activity of IL-23/IL-17 axis and down-stream pro-inflammatory factors so as to suppress inflammation response, resulting in the relieving of UC.