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 alpha (TNFalpha) on enterocyte apoptosis in mice with fulminant hepatic failure (FHF).
METHODS: Liver damage was induced by lipopolysaccharide (LPS)/TNF-alpha 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/TNFalpha-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-TNFalpha monoclonal antibody was injected intravenously into GalN/LPS-treated mice. Serum TNFalpha 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. TNFalpha induced apoptosis of enterocytes in mice with FHF. The integrated OD (IOD) levels of TNFalpha receptor 1 protein expressed in the intestine of mice with GalN/LPS and GalN/ TNFalpha-induced FHF at 2, 6, 9, 12 and 24 h after GalN/LPS and GalN/TNFalpha administration were 169.54+/-52.62/905.79+/-111.84, 11,350.67+/-2 ,133.26/28,160.37+/-4,601.67, 25,781.00 +/-2,277.75/122,352.30+/-49,412.40, 5,241.53+/-3,007.24/49,157.93+/-9,804.88, 7,086.13+/-1,031.15/3,283.45+/-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/TNFalpha administration. The expression of TNFR1 protein was significantly higher at 9 h after GalN/LPS and GalN/TNFalpha administration than that in control groups. Protein expression of TNFR1 was positively correlated with enterocyte apoptosis.
CONCLUSION: TNFalpha can induce apoptosis of enterocytes in mice with FHF. Anti-TNFalpha IgG can inhibit this role.