Modulatory Mechanism Of Lactobacillus Casei On The Inflammatory Signaling Pathways In RAW264.7 Macrophages And Balb/c Mice

Enterotoxigenic Escherichia coli is one of the main pathogenic bacteria of enteritis,which often causes diarrhea,dehydration and even death and dose serious harm to the development of animal husbandry.A large number of studies have found that lactic acid bacteria can improve the intestinal micro-ecological environment and improve the barrier function of intestinal epithelial cells,and regulate cytokines to prevent or reduce inflammation.In order to study the immune mechanism of Lactobacillus in the prevention of bacterial enteritis,in this experiment,Lactobacillus caseiATCC393 was used to interfere with the inflammatory response of RAW264.7 cells,which induced by LPS in vitro.This study used 106 CFU/mL L.caseiATCC39,107 CFU/mL L.caseiATCC39,108 CFU/mL L.caseiATCC393 affect RAW264.7 cell 6 hours,then addition of 0.1 ?g/ml LPS to induce cell inflammation.In vivo,we used continuous 7 days lavage L.casei ATCC393 intervention ETEC K88 colitis model in mice by means of ELISA,fluorescence quantitative PCR,Western-blot and Flow cytometry detected the change of groups of TLR,nf-kappaB,MAPK,inflammatory factor and so on to study the effect of Lactobacillus casei to enteritis on TLR/nf-kappaB and TLR/MAPK signaling pathways,the influence of the inflammatory factors.This study laid a foundation for further research on the antibacterial mechanism of L.casei.The result indicated the contents of TLR4,NF-? B,MAPK,TNF-?,IL-1?,IL-6,IL-8,NO and PGE2 were increased in LPS cell culture supernatant and the difference was very significant(p<0.01).The content of TLR4,NF-?B,MAPK,TNF-?,IL-1?,IL-6,IL-8,NO,PGE2 decreased significantly after the intervention of L.caseiATCC393 in the inflammation induced by LPS.The difference of L.case ATCC393 intervention group was not significant between different concentrations.This shows that L.casei ATCC393 has preventive effect on the inflammation induced by LPS.In vivo: The ETEC K88 mice showed food intake decrease,depression,stool soft and fecal occult blood and other symptoms.The expression of IL-1,IL-8,NO,PGE2,TNF-?,TLR2,TLR4,MyD88,NF-?B,and MAPK were significantly enhanced compared with the control group(p<0.05).ETEC K88 + L.casei mice showed an improved mental state and increased food intake;faecal occult blood was not present.The expression of IL-1,IL-8,NO,PGE2,TNF-?,TLR4,MyD88,NF-?B,and MAPK were significantly decreased compared with the The ETEC K88 group(p<0.05).The TLR2 levels in the peripheral blood of the ETEC K88 + L.casei group were significantly increased(p<0.05).Therefore,Lactobacillus reduces the release of inflammatory cytokines and takes effect in the intervention of enteritis in mice by inhibiting the activation of signalling pathway of TLR4/NF-?B and TLR4/MAPK.The results of this study provide experimental basis for further study on the anti inflammatory effect of Lactobacillus.