Cytokine regulation of pro- and anti-apoptotic genes in rat hepatocytes: NF-kappaB-regulated inhibitor of apoptosis protein 2 (cIAP2) prevents apoptosis.
OBJECTIVE
In acute liver failure, hepatocytes are exposed to various cytokines that activate both cell survival and apoptotic pathways. NF-kappaB is a central transcription factor in these responses. Recent studies indicate that blocking NF-kappaB causes apoptosis, indicating the existence of NF-kappaB-regulated anti-apoptotic genes. In the present study the relationship between NF-kappaB activation and apoptosis has been investigated in hepatocytes.


METHODS
Primary rat hepatocytes were exposed to a cytokine mixture of tumor necrosis factor alpha, interleukin-1beta, interferon-gamma and lipopolysaccharide. Modulation of signalling pathways was performed by using dominant negative adenoviral constructs. Apoptosis and NF-kappaB activation were determined by caspase-3 activity, Hoechst staining and electrophoretic mobility shift assay, respectively. Furthermore, expression and regulation of apoptosis-related genes were investigated.


RESULTS
(1) Inhibition of NF-kappaB activation results in apoptosis. (2) Inhibitor of apoptosis protein (IAP) family members, inhibitor of apoptosis protein1 (cIAP1), and X-chromosome-linked IAP, are expressed in rat hepatocytes. cIAP2 is induced by cytokines in an NF-kappaB-dependent manner and overexpression of cIAP2 inhibits apoptosis. (3) The anti-apoptotic Bcl-2 family member A1/Bfl-1 and the pro-apoptotic members Bak and Bid are induced by cytokines and NF-kappaB-dependent. (4) Nitric oxide inhibits caspase-3 activity in hepatocytes.


CONCLUSIONS
In inflammatory conditions, hepatocyte survival is dependent on NF-kappaB activation and cIAP2 contributes significantly to this protection.
Schoemaker
Marieke H
MH
Center for Liver, Digestive and Metabolic Diseases, University Hospital Groningen, PO Box 30.001, 9700 RB, Groningen, The Netherlands. m.h.schoemaker@med.rug.nl
Ros
Jenny E
JE
Homan
Manon
M
Trautwein
Christian
C
Liston
Peter
P
Poelstra
Klaas
K
van Goor
Harry
H
Jansen
Peter L M
PL
Moshage
Han
H
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3; D061945:Caspase Inhibitors; D016207:Cytokines / Q000378:metabolism / Q000494:pharmacology*; D015870:Gene Expression; D006505:Hepatitis / Q000378:metabolism; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007371:Interferon-gamma / Q000378:metabolism / Q000494:pharmacology; D007375:Interleukin-1 / Q000378:metabolism / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D016328:NF-kappa B / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology
D000970:Antineoplastic Agents; D061945:Caspase Inhibitors; D016207:Cytokines; D007375:Interleukin-1; D008070:Lipopolysaccharides; D016328:NF-kappa B; D011506:Proteins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; C505410:Casp3 protein, rat; D053148:Caspase 3