Abstract： Objective To investigate the impact of tumor necrosis factor-α (TNF-α) on intestinal mucosa permeability and the protective effect of probiotics in mice with acute liver failure (ALF).Methods Thirty male BALB/c mice aged 6-8 weeks were randomly divided into normal control,ALF and intervention groups (10 for each group).Mice in intervention group were fed with live combined bifidobacterium and lactobacillus (900 mg · kg-1 · d-1) by gavage,while those in normal control and ALF groups were fed with normal saline (9 mL · kg-1 · d-1).After two weeks,mice in ALF and intervention groups were given an intraperitoneal injection of D-galactosamine (3.0 g/kg) to induce liver failure,and all mice were sacrificed 9 h after the injection.Biochemical markers were tested,expressions of TNF-α mRNA in liver tissues and zonula occluden-1 (ZO-1) mRNA in ileum tissues were detected by real-time PCR,and the expression of ZO-1 protein in ileum tissues was detected by Western blotting.One-way analysis of variance or Kraskal-Wallis test was performed to explore the differences in biochemical markers,TNF-α mRNA,ZO-1 mRNA and ZO-1 protein expressions among groups,and Pearson test was used to analyze the correlations between the expression of ZO-1 protein in ileum tissues and serum level of TNF-α or plasma levels of endotoxins.Results Serum alanine aminotransferase (ALT),aspartate aminotransferase (AST),TNF-α and plasma level of endotoxins in ALF group were significantly higher than those in normal control group (P ＜0.01) ; while compared with ALF group,the above biomarkers were significantly decreased in the intervention group (P ＜ 0.01).The expression of TNF-α mRNA in liver tissues in ALF group was higher than that in the normal control group (Z =4.038,P ＜ 0.01) ; while compared with ALF group,it was decreased in intervention group (Z =3.780,P ＜ 0.01).The expressions of ZO-1 mRNA and ZO-1 protein in ileum tissues in ALF group were lower than those in normal control group (P ＜ 0.01) ; while compared with ALF group,those in intervention group were increased (P ＜ 0.01).Pearson analysis showed that the expression of ZO-1 protein in ileum tissues was negatively correlated with serum level of TNF-α level and plasma level of endotoxin (r =-0.946 and-0.919,both P ＜ 0.01).Conclusions TNF-α may be involved in the increased permeability of intestinal mucosa in mice with ALF.Live combined bifidobacterium and lactobacillus may relieve liver damages through inhibiting endotoxin synthesis and release,and ameliorate the permeability of intestinal mucosa through up-regulating ZO-1 protein expression.