Immunomodulatory effects of Lactobacillus rhamnosus Gorbach Goldin on alcoholic liver injury

Objective To study the effects of Lactobacillus rhamnosus Gorbach Goldin (LGG) on the balance of regulatory cell (Treg)/T helper cell 17 (Th17) and the expression changes of Toll-like receptor (TLR) signaling pathway in alcoholic liver injury. Methods After an acclimatizing period, 10-week male C57/BL6 mice were randomized into control group, alcohol group and treatment group with six mice in each group. The mice in alcohol group were fed with 5% alcohol-containing Lieber-DeCarli diet for 10 days, followed by gavage of a single dose of 40% alcohol at 5g/kg by weight. The mice in control group were pair-fed the control isocaloric diets in which ethanol was replaced with maltose-dextrin; the mice in treatment group were given LGG in the liquid diet in which one mouse consumed 1 mL/d LGG. Blood and tissue samples were collected for stained with hematoxylin-eosin (HE) or Oil red O. Serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were detected. mRNA levels of ZO-1, claudin-1, and ccluding were analyzed by real-time polymerase chain reaction (RT-PCR). The expressions of TLR4, myeloid differentiation factor 88 (MyD88), interleukin-1 receptor-associated kinase-1 (IRAK-1), nuclear factor (NF)-κB, and tumor necrosis factor (TNF)-α were analyzed by Western blot. Flow cytometry was used to analyze the balance of Treg/Th17 cells in the spleen. One-way analysis of variance (ANOVA) and multiple comparison analysis were performed for multi-groups comparison. Results Compared with control group, HE and Oil red O staining demonstrated that LGG supplementation significantly reduced the number of lipid droplets. Serum ALT and AST levels in alcohol group ([147.0±42.1] U/L and [373.5±169.7] U/L, respectively) were more elevated than control group ([56.8±15.3] U/L and [211.5±57.8] U/L, respectively), and LGG supplementation decreased the serum levels of ALT and AST ([75.3±150.2] U/L and [211.7±36.3] U/L, respectively) with statistical significant difference (F=19.474 and 4.702, respectively; P=0.000 and 0.026, respectively). The mRNA expression of tight junction proteins including ZO-1, ccluding and claudin-1 were significantly decreased by alcohol feeding, which were reversed by LGG supplementation (F=149.219, 145.561 and 154.237, respectively; all P=0.000). The hepatic protein level of Escherichia coli in the LGG supplementation group was decreased compared with alcohol group (F=130.317, P=0.000). The expressions of critical proteins such as TLR4, MyD88, IRAK-1, NF-κB, and TNF-α in the TLR4 signaling pathway in alcohol group were higher than the control group. The changes were reversed by the supplementation of LGG. The number of Treg was decreased by alcohol exposure, which was ameliorated by the supplementation of LGG administration. The number of Th17 was increased by alcohol exposure, while supplementation of LGG administration decreased Th17 counts. Conclusion LGG is effective in protecting alcohol-induced hepatic injury, by balancing Treg/Th17 and inhibiting the upregulation of TLR4 signaling pathway, which could be a potential therapeutic target in alcohol liver disease. Key words: Lactobacillus rhamnosus; Liver diseases, alcoholic; Toll-like receptors; T-lymphocytes, regulatory; Th17 cells