The Role Of Lactobacillus In Liver Inflammation And Hepatocellular Carcinogenesis

Part I The role of Lactobacillus Pro15 in carbon tetrachloride-induced acute liver injuryObjective:Our lab isolated a lactic acid bacteria strain of probiotics named Pro15. The protective effect of probiotics was reported in various diseases, so we studied the role of Pro15 strain in mice acute liver injury model, and explored the mechanism invovled.Methods:Mice were divided into three groups, including the Pro15 strain experimental group, Lctobacillus rharmosus GG (LGG) strain control group and PBS control group. On day 1,3,5 and 7, mice were gavaged with 100ul Pro15 strains (109 cells), LGG (109 cells) or PBS. And on day 8, mice were injected intraperitoneally with 50% carbon tetrachloride solution to establish acute liver injury model. We injected mice with 5.5 ml/kg carbon tetrachloride solution to observe the survival of mice. And we also treated mice with 2 ml/kg carbon tetrachloride solution and the mice were sacrificed after 24 hours. We detected the levels of alanine aminotransferase(A LT) and aspertate aminotransferase(AST) in mice serum and analyzed the immune cell types of mice by flow cytometry. Intracellular staining was ued to determine the TNF- and IFN-.-.production by CD8+ T, CD4+T and NK cells.Results:Compared with PBS control group, Pro15 strain could alleviate acute liver injury:(1) Pro15 strain significantly prolonged the survival time of mice; (2) Pro15 strain reduced the level of aspertate aminotransferase (AST) in serum; (3) Pro15 strain significantly reduced mice liver damage. Flow cytometry analysis showed that Pro15 strain inhibited CD8+ T and NK cells activation; Pro15 strain reduced the proportion of Th1 cells and IFN-.-.expression of CD8+ T cells; Pro15 strain promoted TNF-expression by splenocytes and liver; TNFR2 decifiency increased the mortality of mice after CCl4 administration.Conclusion:Pro15 strain can alleviate the acute liver injury induced by carbon tetrachloride, and Pro15 strain protected mice from liver inflammation possibly by inhibiting NK and CD8+ T cells activation and promoting the expression of TNF-which activated TNFR2 signaling pathway.Part Ⅱ The role of Lactobacillus Pro15 in the development of hepatocellular carcinomaObjective:Pro15 strain exerted a protective effect on acute liver injury. Since liver inflammation is closely related to hepatocellular carcinoma (HCC), we studied the role of Pro15 strain in hepatocellular carcinoma development and explored the mechanism invovled.Methods:Mice were divided into three groups, including the Pro15 strain experimental group, LGG strain control group and PBS control group. On day 1,3,5 and 7, mice were gavaged with 100ul Pro15 strains (109 cells), LGG (109 cells) or PBS. And on day 8, hepa1-6 cells were injected to livers of mice to establish orthotopic HCC model. Mice were sacrificed and the tumor volume was measured two weeks after tumor cells injection. We analyzed the percents of immune cell types in mice liver and spleen by flow cytometry. Intracellular staining was ued to determine cytokine productions by immune cells, including IFN-.;.TNF- and IL-17A.Results:Our results showed that Pro15 strain promoted HCC development. Flow cytometry analysis showed that Pro15 strain increased the percentage and cell number of MDSC.Conclusion:Pro15 strains contributed to the development of HCC possibly by increasing MDSC infiltration to promote tumor growth.