Blood brain barrier permeability in acute liver necrosis of mice

The roles of tumor necrosis factor-alpha in colon tight junction protein expression and intestinal mucosa structure in a mouse model of acute liver failure

Background

Spontaneous bacterial peritonitis (SBP) is a common clinical disease and one of the most severe complications of acute liver failure (ALF). Although the mechanism responsible for SBP is unclear, cytokines play an important role. The aim of this study was to investigate the effects of tumor necrosis factor-alpha (TNF-α) on the structure of the intestinal mucosa and the expression of tight junction (Zona Occludens 1; ZO-1) protein in a mouse model of ALF.

Methods

We induced ALF using D-galactosamine/lipopolysaccharide (GalN/LPS) or GalN/TNF-α and assessed the results using transmission electron microscopy, immunohistochemistry, Western blotting, ELISA and real-time quantitative PCR. The effects of administration of anti-TNF-α IgG antibody or anti-TNF-α R1 antibody before administration of GalN/LPS or GalN/TNF-α, respectively, on TNF-α were also assessed.

Results

Morphological abnormalities in the intestinal mucosa of ALF mice were positively correlated with serum TNF-α level. Electron microscopic analysis revealed tight junction (TJ) disruptions, epithelial cell swelling, and atrophy of intestinal villi. Gut bacteria invaded the body at sites where TJ disruptions occurred. Expression of ZO-1 mRNA was significantly decreased in both ALF models, as was the level of ZO-1 protein. Prophylactic treatment with either anti-TNF-α IgG antibody or anti-tumor necrosis factor-a receptor1 (anti-TNF-α R1) antibody prevented changes in intestinal tissue ultrastructure and ZO-1 expression.

Conclusion

TNF-α affects the structure of the intestinal mucosa, decreases expression of ZO-1, and affects the morphology of the colon in a mouse model of ALF. It also may participate in the pathophysiological mechanism of SBP complicated to ALF.

Tumor necrosis factor-alpha induces apoptosis of enterocytes in mice with fulminant hepatic failure

AIM: To explore the alterations of intestinal mucosa morphology, and the effects of tumor necrosis factor α (TNFα) on enterocyte apoptosis in mice with fulminant hepatic failure (FHF).

METHODS: Liver damage was induced by lipopolysaccharide (LPS)/TNF-α in D-galactosamine (GalN) sensitized BALB/c mice. There were 40 mice in normal saline (NS)-treated group, 40 mice in LPS-treated group, 40 mice in GalN-treated group, 120 mice in GalN/ LPS-treated group and 120 mice in GalN/ TNFα-treated group. Each group was divided into five subgroups of eight mice each. Serum samples and liver, intestinal tissues were respectively obtained at 2, 6, 9, 12 and 24 h after administration. Anti-TNFα monoclonal antibody was injected intravenously into GalN/LPS-treated mice. Serum TNFα levels were determined by enzyme-linked immunosorbent assays (ELISA). Serum ALT levels were determined using an automatic analyzer. The intestinal tissues were studied under light microscope and electron microscope at 2, 6, 9, 12 and 24 h in mice with fulminant hepatic failure, respectively. Enterocyte apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) method. The expression of tumor necrosis factor receptor 1 (TNFR1) in intestinal tissue was tested by immunohistochemistry Envision Two Steps.

RESULTS: Gut mucosa was morphologically normal at all time points in all groups, but typical apoptotic cells could be seen in all experimental groups under electron micro-scope. Apoptosis rate of gut mucosal epithelial cells were significantly increased at 6, 9 and 12 h, peaked at 12 h in mice with fulminant hepatic failure. TNFα induced apoptosis of enterocytes in mice with FHF. The integrated OD (IOD) levels of TNFα receptor 1 protein expressed in the intestine of mice with GalN/LPS and GalN/ TNFα-induced FHF at 2, 6, 9, 12 and 24 h after GalN/LPS and GalN/TNFα administration were 169.54±52.62/905.79±111.84, 11350.67±2133.26/28160.37±4601.67, 25781.00±2277.75/122352.30±49412.40, 5241.53±3007.24/49157.93±9804.88, 7086.13±1031.15/3283.45±127.67, respectively, compared with those in control groups (with NS, LPS and GalN administration, respectively). IOD level of TNFR1 changed significantly at 6, 9 and 12 h after GalN/LPS and GalN/TNFα administration. The expression of TNFR1 protein was significantly higher at 9 h after GalN/LPS and GalN/TNFα administration than that in control groups. Protein expression of TNFR1 was positively correlated with enterocyte apoptosis.

CONCLUSION: TNFα can induce apoptosis of enterocytes in mice with FHF. Anti-TNFα IgG can inhibit this role.