Lactobacillus Inhibits Dss-Induced Ulcerative Colitis In Mice

Lactobacillus belongs to the normal flora of the intestine and participates in regulating the immune response in order to maintain the balance of the intestinal microflora.More and more studies have found that Lactobacillus has a variety of immunomodulatory activities as a probiotic.However,there are few studies on the regulation of intestinal inflammation by Lactobacillus strains in vivo.This subject pre-experimental study of DSS action time,the construction of DSSinduced mouse enteritis model.Divided into four groups,each group recorded changes in body weight and life status,the DAI score comparison,measurement of changes in mouse colon length and spleen weight,and combined with the mouse colon tissue pathological structure analysis(HE staining),Determine the severity of intestinal inflammation in mice.In the latter experiment,the mortality rate of the mice was observed.Combined with HE analysis,a DSS-induced enteritis model was established.The immunosuppressive effects of L.paracasei M5-L,L.casei Q8-L and LGG on DSS-induced mouse enteritis,DAI scores indicate that the three Lactobacillus strains can reduce the symptoms of mice to varying degrees.Through the weight of the organ in the mouse and the length of the colon,DSS can cause enteritis,and all three Lactobacillus strains can improve the degree of colonic shortening of spleen due to enteritis.After hematoxylin-eosin staining of the mouse colon,histological scoring and histological scoring were performed to confirm that L.casei Q8-L,L.paracasei M5-L,and LGG could alleviate the histological damage caused by enteritis in varying degrees.The occurrence of inflammation will lead to the increase of free radicals in the body.Superoxide dismutase(SOD)can scavenge free radicals.Therefore,the content of SOD and the severity of inflammation show a negative feedback trend.Experiments have shown that L.paracasei M5-L and L.casei Q8-L LGG strains can increase SOD content and reduce inflammation.The MPO of mice's colon in the MPO kit was measured,and the levels of IL-6 and TNF-? in the serum of mice were determined by ELISA.It was found that L.casei Q8-L,L.paracasei M5-L,and LGG can both down-regulate DSS.The content of MPO,IL-6 and TNF-? produced by the stimulated mice up-regulated IL-10 content.Among them,L.casei Q8-L group had the most obvious regulation effect.Experiments showed that IL-6 content in L.casei Q8-L group was reduced to 52.37 pg/m L,and IL-10 content was increased to 20.07 pg/m L.Lactobacillus acts on I?B-? kinase to decrease its phosphorylation,weaken the activation of P65-P50 dimer,and down-regulate inflammation by down-regulating the expression of P65,P50 protein in NF-?B signaling pathway.And by using RT-PCR to determine the gene expression levels of TLR4 and TLR9,we found that IL-6 and TNF-? levels were down-regulated.Three strains of Lactobacillus could inhibit the secretion of TNF-? by mice stimulated by DSS.And TLR4 and TLR9 receptors play a key role in the regulation of intestinal inflammation by Lactobacillus.These results indicate that selected Lactobacillus strains can significantly modulate enteritis in vivo and have a potential modulatory effect on mouse enteritis.