Lethal hepatic apoptosis mediated by tumor necrosis factor receptor, unlike Fas-mediated apoptosis, requires hepatocyte sensitization in mice.
OBJECTIVE
Tumor necrosis factor a (TNF-alpha) and Fas ligand are apoptotic cell-death mediators that act by binding to their responsive receptors. The aims of this study were to assess the differences between liver cell deaths induced by TNF-alpha and anti-Fas antibody, and to investigate the mechanism by which GalN sensitizes the hepatocyte to injury by TNF-alpha.


METHODS
TNF-alpha or anti-Fas antibody was injected into BALB/c mice sensitized or unsensitized by D-galactosamine (GalN). Liver injury was assessed biochemically and histologically. The expressions of TNF receptor (TNFR)1 and TNFR2 mRNA in the liver were determined by Northern blot analysis. Nuclear factor-kappaB (NF-kappaB) DNA binding activity was determined by gel shift assay.


RESULTS
In GalN-sensitized mice, hepatocyte apoptosis and liver failure were observed after TNF-alpha injection, but neither occurred in unsensitized mice. Microscopically, GalN preceding TNF-alpha caused massive hemorrhagic liver damage with fragmented hepatocyte nuclei resembling effects of anti-Fas antibody, but GalN largely failed to sensitize to injury by this antibody. TNFR1 mRNA expression in the liver was upregulated within 3 h after GalN administration, and anti-TNFR1 antibody protected GalN-sensitized mice from hepatotoxic effects of TNF-alpha. GalN treatment failed to affect TNF-alpha-induced NF-kappaB activation.


CONCLUSIONS
Unlike Fas-related apoptosis, TNFR-mediated apoptosis requires hepatocyte sensitization involving TNFR1 upregulation.
Nagaki
M
M
First Department of Internal Medicine, Gifu University School of Medicine, Japan.
Sugiyama
A
A
Osawa
Y
Y
Naiki
T
T
Nakashima
S
S
Nozawa
Y
Y
Moriwaki
H
H
D000818:Animals; D000906:Antibodies / Q000276:immunology; D017209:Apoptosis; D053222:Fas Ligand Protein; D008099:Liver / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D016328:NF-kappa B / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism*; D019014:fas Receptor / Q000276:immunology / Q000378:metabolism
D000906:Antibodies; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D018124:Receptors, Tumor Necrosis Factor; D019014:fas Receptor