OBJECTIVETo study the role of tumor necrosis factor-alpha (TNFalpha) on enterocyte apoptosis in the experimental model of fulminant hepatic failure (FHF).

METHODSLiver damage was induced by lipopolysaccharide (LPS)/TNFalpha in D-galactosamine (GalN) sensitized BALB/c mice. Serum TNFalpha levels were determined by enzyme-linked immunosorbent assays (ELISA). The intestinal tissues were studied micro- and ultra-microscopically at 2 h, 6 h, 9 h, 12 h and 24 h time points in mice with fulminant hepatic failure. Enterocyte apoptosis was determined by TUNEL method. The TNFR I expression in the intestinal tissue was tested by immunohistochemistry.

RESULTS(1) Gut mucosa was morphologically normal at every time point in all groups, but typical apoptotic cells could be seen in the experimental groups under the electron microscope. Apoptosis rate of gut mucosal epithelial cells was significantly increased at 6 h (large intestine: 6.47e(-3)+/-2.91e(-4); small intestine: 6.64e(-3)+/-3.78e(-4)), 9 h (large intestine: 6.81e(+4)+/-7.41e(+3); small intestine: 2.58e(+4)+/-2.28e(+3)) and 12 h (large intestine: 4.92e(+4)+/-9.80e(+3); small intestine: 5.24e(+4)+/-3.01e(+3)), and peaked at 12 h in mice with FHF. (2) TNFalpha induced apoptosis of enterocytes in mice with FHF. Anti-TNFalpha inhibited this effect. (3) The integrated OD (IOD) levels of TNFalpha receptor I protein expressed differently in the intestine of mice with GalN/LPS and GalN/ TNFalpha-induced FHF at 9 h after GalN/LPS and GalN/ TNFalpha administration, in comparison with those of the control groups. IOD level of TNFRI changed significantly at 6 h (large intestine: 2.82e(+4)+/-4.60e(+3); small intestine: 1.14e(+4)+/-2.13e(+3)), 9 h (large intestine: 6.81e(+4)+/-7.41e(+3); small intestine: 2.58e(+4)+/-2.28e(+3)) and 12 (large intestine: 4.92e(+4)+/-9.80e(+3); small intestine: 5.24e(+4)+/-3.01e(+3)) hours after GalN/LPS and GalN/ TNFa administration. The expression of TNFR1 protein was significantly higher at 9 and 12 h after GalN/LPS and GalN/TNFa administration than other time points. Protein expression of TNFR1 was positively correlated with enterocyte apoptosis.

CONCLUSIONTNFa can induce enterocyte apoptosis in mice with FHF. Anti- TNFalpha IgG can inhibit this role. Excessive TNFRI expression of enterocyte in fulminant hepatic failure can be induced by TNFa, which suggests that TNFalpha can induce apoptosis of enterocyte by up-regulation of TNFRI protein expression.