[Elafin-expressing probiotic Escherichia coli Nissle 1917 protects against experimental colitis]

Objective: To construct the gene modified probiotic Escherichia coli nissle1917 (EcN) which can express human Elafin protein and to explore its protective effect on the acute colitis in mice. Methods: The recombinant plasmid with human Elafin gene was constructed and then transferred to EcN. Western blot results confirmed that the engineered probiotic expressed Elafin successfully in vitro. C57/BL6J mouse was used in this study and were randomly divided into 4 groups according to different treatment: PBS gavage (PBS group); DSS administrated (DSS group); DSS administrated with wild-type EcN (EcN-WT) gavage (EcN-WT group); DSS administrated with EcN-Elafin gavage (EcN-Elafin group). Body weight and disease activity index (DAI) were measured every day. The length of mice colons in each group were measured after euthanasia. The degree of inflammation of intestinal mucosa in each group was measured through histopathological scoring. The proportion of neutrophils and macrophages infiltrated into colon lamina propria was detected by flow cytometry. The protein expression levels of pro-inflammatory cytokines TNF-α, IL-6 and chemokine CXCL-1 in colonic tissue were quantified by enzyme-linked immunosorbent assay. Results: Elafin protein could be detected in the supernatant of EcN-Elafin culture medium and EcN-Elafin homogenates. Compared with DSS group, the weight loss and DAI score of EcN-Elafin group and EcN-WT group were both significantly improved. The colon length of EcN-Elafin group was significantly longer than that of DSS group. The histological score of colitis in EcN-Elafin group was significantly lower than that in DSS group (5.3±2.3 vs 9.3±1.4, P<0.05). In EcN-Elafin group, the proportion of neutrophils[(8.65±1.49)% vs (17.60±2.16)%, P<0.01]and macrophages[(3.79±0.26)% vs (5.73±0.45)%, P<0.01]infiltrated into the colon lamina propria was significantly decreased compared with DSS group. The protein expression levels of TNF-α, IL-6 and CXCL-1 in EcN-Elafin group and EcN-WT group were significantly lower than those in DSS group. Conclusion: Elafin-expressing EcN can protect against DSS-induced acute colitis in mice and may have provided an effective and cost-efficient method for the treatment of IBD.