Fish Oil Improves Dysbiosis of Host-microbial Interaction and Maintains Remission in Colitis Mice / 中国生物化学与分子生物学报

n-3 polyunsaturated fatty acids (PUFAs) play an active role in controlling the progression of ulcerative colitis (UC), but its mechanism is not very clear. In this study, we compared the effects of fish oil (the main component is n-3 PUFAs) in the mouse model with acute and chronic colitis induced by dextran sulfate sodium (DSS). Male C57BL/6J mice were randomly divided into six groups, and each group had ten mice. The alleviating effect of fish oil on chronic colitis was significantly better than acute colitis as indicated by the following analysis: the weight loss of mice (P < 0. 05), decreased disease activity index (DAI) score (P<0. 05), colonic edema, colon length index and histopathological score (P < 0. 05), and serum pro-inflammatory factor levels like IL-1β, TNF-α, and IL-6 (P < 0. 01). Moreover, fish oil promoted the level of serum anti-inflammatory factor IL-10 (P<0. 05). The treatment of fish oil increased the n-3 PUFA concentration in the intestinal epithelium of mice (P < 0. 01), especially EPA (P<0. 05). 16S rRNA sequencing of feces revealed that fish oil significantly increased the relative abundance of butyrate-producing flora (Clostridiales) and probiotics (Bifidobacteriales) in the feces of the maintained remission model group, reduce the proportion of aerobic, parthenogenic anaerobic and pathogenic, and improved the disorder of glycan biosynthesis and metabolism and oxidative phosphorylation (P<0. 05). Compared with the induced remission fish oil group, fish oil treatment led to an elevated expression of mechanical barrier and energy metabolism pathway proteins in the maintained remission fish oil group. Our results showed that fish oil exerted a more potent inhibitory effect in the remission mice model, which may be related to effectively strengthening the mechanical barrier, improving the composition and function of intestinal microbiota and concentration of butyric acids and improving dysbiosis of host-microbial interaction.

Overexpression of miR-31 regulates TLR4/NF-κB signaling pathway and apoptotic protein in colitis model mice / 中国应用生理学杂志

To investigate the effects of miR-31 on TLR4/NF-κB signaling pathway and apoptosis-related proteins in dextran sulfate sodium (DSS) induced mouse colon colitis. Methods: ① Mouse model of colon colitis: 1% DSS was used to induce mouse ulcerative colitis (UC). Fourteen FVB non-transgenic mice were randomly divided into control group (n= 6), DSS group (n= 8), and 16 FVB miR-31 transgenic mice were randomly divided into miR-31 overexpression group (n= 8), miR-31 overexpression +DSS group (n= 8). DSS was dissolved in water and administered to mice by drinking water. The DSS group and miR-31+DSS group drank 1% DSS water in the first week, normal sterilized water in the second week, and 1% DSS water in the third week, after 5 weeks, the modeling was completed, then the colon tissues of the mice were collected. Western blot and IHC were used to detect the expressions of NF-κB p65, TLR4, Bax and Bcl-2 proteins in mouse colon tissue, TUNEL was used to detect apoptosis of mouse colon tissues. ② Cell culture experiments: Transfection of miR-31mimic and inhibitor by lipofectamine resulted in overexpression or knockdown of miR-31 in human colon epithelial cell line HCT 116 cells, each group was repeated three times and cells were collected 48 h later, Western blot was used to detect the expressions of NF-κB p65 and TLR4 protein. ① In animal experiments, compared with the control group, the expression levels of NF-κB p65, TLR4 protein and apoptotic cell index in the DSS group and miR-31 overexpression group in mouse colon tissue were significantly increased (P＜0.05 or P＜0.01), and the Bcl-2 / Bax ratio was significantly reduced (P＜0.05 or P＜0.01); and compared with the DSS group, the expression levels of NF-κB p65, TLR4 protein and apoptotic cell index in the miR-31+DSS group were significantly increased (P＜0.01), while the Bcl-2/Bax ratio was significantly decreased (P＜0.01). ② In cell experiments, compared with the control group, the expression levels of NF-κB p65 and TLR4 protein in the over-expressed miR-31 group of HCT 116 cells were significantly increased (P＜0.05 or P＜0.01), the expressions of NF-κB p65 and TLR4 protein in miR-31 knockdown group were decreased (P＜0.05). miR-31 promotes the development of colitis by promoting TLR4/NF-κB signaling pathway and mediating apoptosis of intestinal epithelial cells.

Induction of Indoleamine 2,3-dioxygenase by Pre-treatment with Poly(I:C) May Enhance the Efficacy of MSC Treatment in DSS-induced Colitis

Mesenchymal stem cells (MSCs) have been used experimentally for treating inflammatory disorders, partly owing to their immunosuppressive properties. The goal of the study was to determine whether TLR ligands can enhance the therapeutic efficacy of bone marrow-derived MSCs for the treatment of inflammatory bowel disease. Mice (C57BL6) were administered with 4% dextran sulfate sodium (DSS) in drinking water for 7 days and injected with MSCs on days 1 and 3 following DSS ingestion. Our results demonstrated that among various TLR ligands, MSCs treated with polyinosinic-polycytidylic acid [poly(I:C)], which is a TLR3 ligand, more profoundly induced IDO, which is a therapeutically relevant immunosuppressive factor, without any observable phenotype change in vitro. The poly(I:C)-treated MSCs attenuated the pathologic severity of DSS-induced murine colitis when injected i.p. but not i.v. In summary, preconditioning MSCs with poly(I:C) might improve their efficacy in treating DSS-induced colitis, and this effect at least partly depends on the enhancement of their immunosuppressive activity through increasing their production of IDO.

Trichinella spiralis Infection Suppressed Gut Inflammation with CD4+CD25+Foxp3+ T Cell Recruitment

In order to know the effect of pre-existing Trichinella spiralis infection on experimentally induced intestinal inflammation and immune responses, we induced colitis in T. spiralis-infected mice and observed the severity of colitis and the levels of Th1, Th2, and regulatory cytokines and recruitment of CD4+CD25+Foxp3+ T (regulatory T; Treg) cells. Female C57BL/6 mice were infected with 250 muscle larvae; after 4 weeks, induction of experimental colitis was performed using 3% dextran sulfate sodium (DSS). During the induction period, we observed severity of colitis, including weight loss and status of stool, and evaluated the disease activity index (DAI). A significantly low DAI and degree of weight loss were observed in infected mice, compared with uninfected mice. In addition, colon length in infected mice was not contracted, compared with uninfected mice. We also observed a significant increase in production of pro-inflammatory cytokines, IL-6 and IFN-gamma, in spleen lymphocytes treated with DSS; however, such an increase was not observed in infected mice treated with DSS. Of particular interest, production of regulatory cytokines, IL-10 and transforming growth factor (TGF)-beta, in spleen lymphocytes showed a significant increase in mice infected with T. spiralis. A similar result was observed in mesenteric lymph nodes (MLN). Subsets of the population of Treg cells in MLN and spleen showed significant increases in mice infected with T. spiralis. In conclusion, T. spiralis infection can inhibit the DSS-induced colitis in mice by enhancing the regulatory cytokine and Treg cells recruitment.