Modified apple polysaccharide prevents colitis through modulating IL-22 and IL-22BP expression

Chronic intestinal inflammation enhances cell proliferation, angiogenesis, and migration, then promotes the development of colorectal cancer (CRC). Many ingredients of apples have been proven to have anti-inflammatory properties, and show benefits for colitis treatment. In our previous studies, we found modified apple polysaccharide (MAP) could prevent colitis associated colorectal carcinogenesis effectively. Herein, we further our study to observe the effect of MAP on dextran sodium sulfate (DSS)-induced colitis and to investigate the possible mechanisms. IL-22 has both pathogenic and protective effects during intestinal tissue damage. It could be neutralized by the soluble IL-22 receptor, known as the IL-22 binding protein (IL-22BP). A DSS-induced colitis mouse model, a mouse CRC cell line MCA-38 and a mouse dendritic cell line DC2.4 were treated with MAP. Western blot, ELISA, BrdU staining and a co-culture system were used to detect the expression of IL-22 and IL-22BP. MAP significantly protected ICR mice against DSS-induced colitis, and inhibited the growth of MCA-38 cells. The mechanisms may be that MAP down-regulated IL-22 level and up-regulated expression of IL-22BP. These data may provide another molecular basis for understanding how apples act to prevent colitis and suggest that MAP has a potential to treat colitis and prevent CRC.