Regulatory Effect Of Lactobacillus Gasseri JM1 On The Intestinal Barrier In Colitis Mice

Ulcerative colitis is a chronic and recurrent inflammatory disease that affects the intestines and occurs in the lining of the rectum and colon.UC and Crohn's disease(CD)are both inflammatory bowel diseases(IBD).With the continuous development of industrialization and urbanization,its incidence rates had gradually increased,and the relationship betweenn intestinal microbes and IBD has been studied.Lactobacillus gassseri,a kind of important intestinal symbiotic bacteria,plays an important role in relieving diarrhea,reducing colonization of pathogenic bacteria and maintaining intestinal balance of nature,also widely used in food fermentation,industry,medicine and other fields.In the current research,the relieving effect of L. gasseri on UC is rarely reported and the specific mechanism is unknown.Therefore,more in-depth researches on the mechanism of L. gasseri in relieving ulcerative colitis are needed.In this study,8 strains of Lactobacillus stored in the laboratory were evaluated for their adhesion ability in vitro by autoaggregation,surface hydrophobicity,and adhesion with Caco-2 cells.Lactobacillus gasseri JM1 with the strongest adhesion ability was selected as the research object.Secondly,we constructed the ulcerative colitis mouse model and studied effects of L. gasseri JM1 on intestinal mucosal injury,the intestinal barrier and metabolites in ulcerative colitis mice.Secondly,a mouse model of ulcerative colitis was constructed to study the effects of L. gasseri JM1 on intestinal mucosal damage,intestinal barrier and intestinal metabolites in UC mice,and to explore the mechanism of L. gasseri JM1 to relieve ulcerative colitis.The results of the above research are as follows:(1)L. gasseri JM1 had a strong in vitro adhesion ability.The adhesive ability of 8 strains of Lactobacillus was evaluated by screening in vitro,and it was found that 8 strains had the different adhesive ability.Among them,the autoaggregation ability of L. gasseri JM1 reached 51.08%,the surface hydrophobicity was 88.67%,and the adhesion ability to Caco-2 cells was 75.7%.Combining the three indicators,it shows a strong in vitro adhesion ability,so this topic selects L. gasseri JM1 as the follow-up research object.(2)DSS was used to successfully establish the ulcerative colitis mouse model,and the intestinal inflammation relieved index of the strain was evaluated.The results showed that drinking water for7 days with 3% DSS caused significant decrease of body weight and colon length,an increase in DAI index,spleen index and MPO activity,and serious damage to the colon tissue.However,under the different doses of L. gasseri JM1,the above situation can be effectively alleviated,especially the medium and high doses of L. gasseri JM1 have better effects.(3)L. gasseri JM1 could effectively improve the tight junction structure and protect the mucus layer in mice with colitis.The gene expression level of tight junction protein was detected by realtime PCR technology.After treatment with L. gasseri JM1,it could significantly reduce the transcription level of Claudin-2,increase the transcription level of Claudin-3,Occludin,and ZO-1,but no significant dose-dependent changes were observed.Staining results showed that medium and high doses of L. gasseri JM1 could significantly increase the number of goblet cells(p<0.01)and the secretion of intestinal mucin.Different doses of L. gasseri JM1 could increase the ratio of acidic mucin after intervention;medium and high doses of L. gasseri JM1 could also significantly upregulate the expression of MUC2 gene(p<0.01)and protect the integrity of intestinal mucous layer.(4)L. gasseri JM1 could regulate the expression of immune cytokines in colitis mice.Changes in cytokines in colon tissue were detected by ELISA.Pro-inflammatory cytokines TNF-?,IL-6 and IL-1? significantly increased in the inflammatory status of mice(p<0.01).Under the intervention of L. gasseri JM1,it effectively decreased the content of pro-inflammatory cytokines and significantly increased the content of IL-10(p<0.01),which played a role in immune regulation and reduced intestinal inflammation in mice.And presents a dose-dependent.(5)L. gasseri JM1 could regulate the diversity of intestinal microbes to a certain extent.L. gasseri JM1 could increase the Alpha diversity index.Beta diversity results show that the intestinal flora of different groups of mice has obvious differences,and L. gasseri JM1 effectively reduced the abundance of pathogenic bacteria Shigella,Turicibacter,Enterococcus,increased the abundance of Bacteroides,Mucispirillum,Oscillospira,Clostridiaceae?Clostridium,Parabacteroides,Alistipes and Ruminococcus to regulate the imbalance of intestinal flora destroyed by DSS,then increase the diversity of bacterial flora.(6)High-dose L. gasseri JM1 could increase the concentration of short-chain fatty acids to a certain extent.Changes in the content of SCFAs in the contents of the cecum were measured by gas chromatography.Low and medium doses of L. gasseri JM1 have no significant effect on SCFAs.High-dose L. gasseri JM1 could significantly increase the concentration of propionic acid,isobutyric acid,and isovaleric acid(p<0.05),and increase the concentration of acetic acid and butyric acid,but has no effect on valeric acid,played a role in regulating intestinal metabolic products.Initial speculation is that L. gasseri JM1 alleviates DSS-induced colitis by regulating intestinal barrier function,improvingg intestinal flora abundance and metabolite levels.