[Anti-inflammatory effect of interleukin-35 in mice with colitis and its mechanism].

Objective: To investigate the anti-inflammatory effect and mechanisms of interleukin-35 (IL-35) in inflammatory bowel disease.

Methods: BALB/c mice were divided into three groups with 10 mice in each group:control group, model group (oral administration of 4% glucan sodium sulfate for 7 d) and IL-35-treated group (oral administration of 4% glucan sodium sulfate for 7 d, intraperitoneal injection of 2 μg IL-35 at d2-5). Disease activity index (DAI) was scored every day. After 7 d, the mice were sacrificed, and the serum and intestinal tissue samples were collected. The gross morphology of the colon was observed; HE staining was used to observe the pathological changes of colon tissue; flow cytometry was employed to detect the change of macrophage polarization ratio in colon tissue; the mRNA expression levels of cytokines IL-6, TNF-α, IFN-γ, IL-10 and SHIP1 in colon tissue were determined by real-time quantitative RT-PCR; the expression and distribution of SHIP1 in colon tissue was measured by immunohistochemistry; Western blotting was adopted to detect the expression level of SHIP1 protein in colonic intestinal tissues of each group.

Results: The DAI scores of the mice in the model group were higher than those in the control group, while the DAI scores in the IL-35-treated group were lower than those in the model group (all <0.01). Compared with the control group, the colon length was significantly shortened in the model group (<0.05), while the colon length of the IL-35-treated group had an increasing trend compared with the model group, but the difference was not statistically significant (>0.05). Compared with the model group, microscopic inflammatory infiltration score was decreased and microscopic crypt destruction and score was significantly lower in IL-35-treated group (all <0.05). The relative expression of proinflammatory cytokines IL-6, TNF-α and IFN-γ in the colon tissue of IL-35-treated group was decreased compared with the model group, while the relative expression of IL-10 mRNA was higher than that of the model group (all <0.05). Compared with the control group, the proportion of M1 macrophages in the model group increased (<0.05), while the proportion of M1 macrophages in the IL-35-treated group was lower than that in the model group (<0.05). The relative expression of SHIP1 mRNA and protein in the colon tissue of IL-35-treated group was higher than that in the model group (all <0.05).

Conclusions: IL-35 can inhibit the polarization of M1 macrophages and regulate inflammatory cytokines to promote anti-inflammatory effect on mice with colitis.