Resistance of rat hepatocytes against bile acid-induced apoptosis in cholestatic liver injury is due to nuclear factor-kappa B activation.
OBJECTIVE
To examine the extent and mechanisms of apoptosis in cholestatic liver injury and to explore the role of the transcription factor nuclear factor-kappa B in protection against bile acid-induced apoptosis.


METHODS
Cholestatic liver injury was induced by bile duct ligation in Wistar rats. Furthermore, primary cultures of rat hepatocytes were exposed to glycochenodeoxycholic acid (GCDCA), tauroursodeoxycholic acid (TUDCA), taurochenodeoxycholic acid (TCDCA) and to cytokines. Apoptosis was determined by TUNEL-staining, active caspase-3 staining, activation of caspase-8, -9 and -3.


RESULTS
Limited hepatocyte apoptosis and an increased expression of NF-kappaB-regulated anti-apoptotic genes A1 and cIAP2 were detected in cholestatic rat livers. Bcl-2 expression was restricted to bile duct epithelium. In contrast to TCDCA and TUDCA, GCDCA induced apoptosis in a Fas-associated protein with death domain (FADD)-independent pathway in hepatocytes. Although bile acids do not activate NF-kappaB, NF-kappaB activation by cytokines (induced during cholestasis) protected against GCDCA-induced apoptosis in vitro by upregulating A1 and cIAP2.


CONCLUSIONS
GCDCA induces apoptosis in a mitochondria-controlled pathway in which caspase-8 is activated in a FADD-independent manner. However, bile acid-induced apoptosis in cholestasis is limited. This could be explained by cytokine-induced activation of NF-kappaB-regulated anti-apoptotic genes like A1 and cIAP2.
Schoemaker
Marieke H
MH
Center for Liver, Digestive and Metabolic Diseases, Groningen, The Netherlands. m.h.schoemaker@med.rug.nl
Gommans
Willemijn M
WM
Conde de la Rosa
Laura
L
Homan
Manon
M
Klok
Pieter
P
Trautwein
Christian
C
van Goor
Harry
H
Poelstra
Klaas
K
Haisma
Hidde J
HJ
Jansen
Peter L M
PL
Moshage
Han
H
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D002779:Cholestasis / Q000378:metabolism* / Q000473:pathology*; D016207:Cytokines / Q000235:genetics; D004195:Disease Models, Animal; D053200:Fas-Associated Death Domain Protein; D015870:Gene Expression; D005999:Glycochenodeoxycholic Acid / Q000494:pharmacology; D022781:Hepatocytes / Q000378:metabolism / Q000473:pathology*; D008297:Male; D016328:NF-kappa B / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013047:Specific Pathogen-Free Organisms; D013655:Taurochenodeoxycholic Acid / Q000494:pharmacology
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D016207:Cytokines; C505535:Fadd protein, rat; D053200:Fas-Associated Death Domain Protein; D016328:NF-kappa B; D013655:Taurochenodeoxycholic Acid; C031655:ursodoxicoltaurine; D005999:Glycochenodeoxycholic Acid