Overexpression of IL22 by adeno-associated virus effectively ameliorates dextran sulfate sodium-induced colitis in mice

Abstract

Objective To investigate the effects of interleukin22 (IL22) in acute colitis induced by dextran sulfate sodium salt (DSS) in mice and its underlying mechanism. Methods Three IL22 knockout mice (IL22-/-) and 3 control mice (IL22+/+) of 8-week-old males were subjected from the same litter, and then had free-choice drinking of 2.5% DSS water for 6 d followed by normal water for 2 d to construct a mouse model of acute colitis. The changes in body mass weight and disease activity index (DAI) were measured and calculated. After the intervention of 8 d, mouse enteroscopy was performed, and the length of colon and the organ index of major immune organs were measured in both groups. Protein levels of pro-inflammatory cytokines, such as IL1α, IL1β, IL6 and TNFα were detected by Western blotting. Adeno-associated virus (AAV) transfection model was established in 8-week-old male C57BL/6 mice, which were then treated by 2.5%DSS drinking. The mice were randomly divided into PBS group (n=5), AAV-mock+DSS group (n=5) and AAV-IL22+DSS group (n=5). The expression levels of colonic closed small loop protein 1 (ZO-1) and calcium adhesion protein (E-claudin) in different groups were detected by immunofluorescence assay. The protein levels of IL22, Occludin, Stat3 and p-Stat3 were detected by Western blotting. Results Compared with the IL22+/+ group, the mice in the IL22-/- group had significantly decreased body weight on day 8 (P<0.05), obviously increased DAI score (P<0.01), endoscopy score (P<0.05) and pathological score (P<0.01) after DSS induction, and notable up-regulation of pro-inflammatory cytokines including IL1α, IL1β, cleaved-IL1β, IL6, and TNFα in the colon tissues (P<0.05). While AAV-IL22 transfection reversed DSS-induced colitis. Significantly reduced inflammation in colonic tissues (P<0.05), enhanced E-claudin expression (P<0.05) and up-regulation of p-Stat3 and Occludin (P<0.01) were observed in the AAV-IL22+DSS group than the AAV-mock+DSS group. Conclusion IL22 deficiency aggravates DSS-induced colitis in mice, and its overexpression by AAV-IL22 alleviates DSS enteritis by enhancing colonic tight junction proteins and reducing inflammatory infiltration, which may be related to the activation of Jak/Stat3 pathway.

Keywords

• il22
• adeno-associated virus
• inflammatory bowel disease
• dextran sulfate sodium
• jak/stat3 pathway