The 55-kD tumor necrosis factor receptor and CD95 independently signal murine hepatocyte apoptosis and subsequent liver failure.
BACKGROUND
Activation of either the 55-kD tumor necrosis factor receptor (TNF-R1) or CD95 (Fas/Apo-1) causes apoptosis of cells and liver failure in mice, and has been associated with human liver disorders. The aim of this study was first to clarify the association between CD95 activation, hepatocyte apoptosis, and fulminant liver failure. Next, we investigated whether TNF-R1 and CD95 operate independently of each other in the induction of hepatocyte apoptosis.


METHODS
Using both mice and primary liver cell cultures deficient in either TNF-R1 or functional CD95, the induction of apoptosis and hepatocyte death following activation of TNF-R1 or CD95 were studied in vitro and in various in vivo models of acute liver failure.


RESULTS
In vivo or in vitro stimulation of CD95 caused apoptosis of wild-type (wt) murine hepatocytes which had not been sensitized by blocking transcription. Time course studies showed that DNA fragmentation and chromatin condensation preceded, respectively, membrane lysis in vitro and necrosis in vivo. Similar results were obtained after CD95 activation in hepatocytes or livers lacking TNF-R1. Conversely, hepatocytotoxicity due to endogenous or exogenous TNF was not affected in animals or liver cell cultures lacking the expression of functional CD95.


CONCLUSIONS
TNF-R1 and CD95 are independent and differentially regulated triggers of murine apoptotic liver failure.
Faculty of Biology, University of Konstanz, Germany.
M
M
Leist
F
F
Gantner
G
G
Künstle
I
I
Bohlinger
G
G
Tiegs
H
H
Bluethmann
A
A
Wendel
D000410:Alanine Transaminase / Q000097:blood / Q000378:metabolism; D000818:Animals; D000906:Antibodies / Q000276:immunology / Q000494:pharmacology; D017209:Apoptosis / Q000235:genetics*; D002478:Cells, Cultured; D003208:Concanavalin A / Q000494:pharmacology; D004249:DNA Damage / Q000187:drug effects / Q000235:genetics; D003609:Dactinomycin / Q000494:pharmacology; D004587:Electrophoresis, Agar Gel; D005688:Galactosamine / Q000494:pharmacology; D015870:Gene Expression / Q000235:genetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000293:injuries / Q000378:metabolism*; D008233:Lymphotoxin-alpha / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D008954:Models, Biological; D010100:Oxygen / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000172:deficiency / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D019014:fas Receptor / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology
D000906:Antibodies; D008233:Lymphotoxin-alpha; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; D003208:Concanavalin A; D003609:Dactinomycin; D005688:Galactosamine; D007770:L-Lactate Dehydrogenase; D000410:Alanine Transaminase; D010100:Oxygen