The Role Of IL-35 Expressing Escherichia Coli In Meliorates Experimental Colitis In Mice

Background:Ulcerative colitis(UC)is a type of inflammatory bowel disease(IBD)characterized by chronic inflammation of colon.It is commonly believed that the imbalance of immune system and overwhelming production of cytokines are involved in the pathogenesis of UC.Recent studies demonstrated that interleukin-35(IL-35),a key player in the regulation of inflammation,has been identified as potential therapeutic target to treat UC.However,conventional intravenous administration is costly and inconvenient.The present study was designed to establish a novel IL-35delivery system and investigate its therapeutic effects on dextran sulfate sodium(DSS)-induced experimental colitis in mice for the first time.Objective:An engineered Escherichia coli(E.coli/IL-35)expressing IL-35 was constructed.We induced experimental colitis by dextran sulfate sodium(DSS).Investigating the role of Escherichia Coli expressing IL-35 in meliorates experimental colitis in mice.Methods:(1)The IL-35 segment subcloned into pET-28a(+)vector linearized to construct pET-28a(+)-IL35 recombinant plasmid,which was transformed into E.coli strain BL21(DE3)to get E.coli/IL-35.(2)Adult male BALB/c mice randomly got the oral administration of E.coli/IL-35,empty plasmid-transformed E.coli(E.coli0)or PBS for treatment following ingestion of 3%DSS solution for five days.Normal mice were used as control group.Colonic and splenic tissues were collected on day 10post-DSS-induction.Clinical signs,disease activity index(DAI),pathological and immunohistological changes,cytokine profiles and cell populations were evaluated.Results:(1)Construction of pET28a(+)-IL-35 and detection of IL-35 expression in E.coli/IL-35 in vitro and vivo.(2)Intragastric administration of E.coli/IL-35 effectively protected the colitis mice from DSS assimilation including weight loss and colon shortening.Pathological analysis showed significantly lower DAI score and much less intra-colon infiltration of neutrophils and CD3~+cells in the IL-35 treated group.Moreover,E.coli/IL-35-treated mice demonstrated much less CD4~+IL-17A~+Th17 cells and a higher level of CD4~+CD25~+Foxp3~+Tregs in spleen and mesenteric lymph nodes,as well as increased colon and serum level of IL-10 and IL-35 and decreased levels of IL-6.Conclusions:Our study showed that E.coli/IL-35 as a novel oral IL-35 delivery system alleviated inflammatory damage of colonic tissue in the colitic mice.Genetic therapeutic strategies using engineered E.coli encoding immunoregulatory cytokines may provide a potential approach for the treatment of IBD.