The Effect Of Mannan From The Wall Of Saccharomyces Cerevisiae On DSS Induced Colitis In Mice

BackgroundInflammatory bowel disease(IBD)is a chronic non-infectious gastrointestinal inflammatory disease,including ulcerative colitis(UC)and Crohn’s disease(CD),and its main clinical symptom is pus stool and bloody stool.The incidence of IBD has been on the rise for many years and there is no radical cure for IBD,which bring great pain and economic burden to the patients.The exact pathogenesi of IBD is not clear after many years of research.but scholars generally believe that the unbalanced microbiota and dysfunctional immune play an important role in the pathogenesis of IBD.Intestinal microbiota includes bacteria,fungi,viruses,etc.Researchs on intestinal microbiota mainly focuse on bacteria and its metabolites at present,but there are few studies on the role of fungi in IBD.Many researchs indicate that fungi are closely related to IBD.Saccharomyces cerevisiae,a member of fungus,is widely used in our production and life.Recent studies have found that Saccharomyces cerevisiae will not induce Th17 differentiation in the co-culture of dendritic cells(DDR)and CD4~+T cells,the mannan in the cell wall can also induce CD4~+T differentiate into regulatory T cell(Treg).Treg plays an important anti-inflammatory role in IBD,so it is worth of investigating whether the mannan in the cell wall of Saccharomyces cerevisiae can inhibit inflammation by promoting the differentiation of Treg in colitis.ObjectiveThe DSS solution was free acess to Balb/c mice to establish a colitis model,the mannan in the cell wall of Saccharomyces cerevisiae was used to intervene the colitis model.Evaluate the degree of inflammation by disease activity index and histological injury score and detect the expression of Foxp3 and RORγt in the colon tissue to explore whether mannan in cell wall of Saccharomyces cerevisiae can improve colon inflammation and regulate the differentiation of Th17 cells and Treg cells in the colonic mucosa.Methods(1)Grouping of experimental animals:48 male SPB male Balb/c mice were randomly divided into normal control group,DSS model group,DSS+mannan group and mannan group,with 12 rats in each group.(2)Experimental treatment:1.normal control group:free access to water,no special treatment.2.DSS model group:Free access to distilled water for 7 days,replace with 2.75%DSS solution on the 8th day,and replace the DSS solution every two days.3.DSS+mannan group:Free access to distilled water for 7 days,replace with 2.75%DSS solution on the 8th day,and replace the DSS solution every two days,while administering mannan 50mg/kg/d to the stomach.4.Mannan group:Free access to water,while administering mannan50mg/kg/d.(3)Monitor the body weight and activity of mouse daily,observe stool characteristics,and record data.(4)When the DSS model group began to show significant weight loss and bloody stools,the mice were sacrificed,serum and colon tissue were collected.(5)Evaluate the DAI according to the change of body weight,stool characteristics and whether there is bloody stool,observe pathological changes and histological damage index(Histological index)by HE staining of colon tissue,detect the expressions of IL-10 and IL-17A in serum,and the expression of Foxp3 and RORγt in colon tissue.(6)Data processing:All data were statistically analyzed by using SPSS 21.0 software.The measurement data were expressed as mean±standard deviation.The data of each group were analyzed by one-way ANOVA,and the comparison test level wasα=0.05,It is considered statistically significant when P<0.05.Results(1)Disease activity scores of mice in each group:Compared with the normal control group,DSS group showed significant weight loss,stools and bloody stools;DSS+mannan group showed less weight loss than DDS group,and inflammation showed lighter.The DAI score of the DSS group was higher than the normal control group.The DAI score of the DSS+mannan group was lower than the DSS group,and the difference were statistically significant(P<0.05).There was no significant difference between the mannan group and the normal control group.(2)HI scores of mice in each group:Compared with the normal control group,the colonic mucosa of the DSS group showed glandular disappearance,epithelial cell damage,crypt destruction and inflammatory cell infiltration.The inflammation in the DSS+mannan group was smaller than that in the DDS group,The HI score of the DSS group was higher than that of the normal control group.The HI score of the DSS+mannan group was lower than that of the DSS group,and the difference were statistically significant(P<0.05).There was no significant difference between the mannan group and the normal control group.(3)The expression of IL-10 and IL-17A in serum of each group:The level of IL-10 in serum of DSS+mannan group was higher than that of DSS group,the difference was statistically significant(P<0.05).The serum IL-17A level in the DSS group was higher than that in the DSS+mannan group,and the difference was statistically significant(P<0.05).There was no difference between the mannan group and the normal group.(4)The levels of Foxp3 in the colon tissue of DSS+mannan group were higher than those in the DSS group.The difference was statistically significant(P<0.05).There was no significant difference between the normal group and the mannan group.The levels of RORγt in the DSS group was higher than that in the DSS+mannan group,and the difference was statistically significant(P<0.05).There was no difference between the mannan group and the normal group.Conclusions(1)Mannan in the cell wall of Saccharomyces cerevisiae can alleviate DSS-induced colitis in mice;(2)Mannan in the cell wall of Saccharomyces cerevisiae can induce Treg cell differentiation and inhibit Th17 cell differentiation.