Toxic bile salts induce rodent hepatocyte apoptosis via direct activation of Fas

J Clin Invest. 1999 Jan;103(1):137-45. doi: 10.1172/JCI4765.

Abstract

Cholestatic liver injury appears to result from the induction of hepatocyte apoptosis by toxic bile salts such as glycochenodeoxycholate (GCDC). Previous studies from this laboratory indicate that cathepsin B is a downstream effector protease during the hepatocyte apoptotic process. Because caspases can initiate apoptosis, the present studies were undertaken to determine the role of caspases in cathepsin B activation. Immunoblotting of GCDC-treated McNtcp.24 hepatoma cells demonstrated cleavage of poly(ADP-ribose) polymerase and lamin B1 to fragments that indicate activation of effector caspases. Transfection with CrmA, an inhibitor of caspase 8, prevented GCDC-induced cathepsin B activation and apoptosis. Consistent with these results, an increase in caspase 8-like activity was observed in GCDC-treated cells. Examination of the mechanism of GCDC-induced caspase 8 activation revealed that dominant-negative FADD inhibited apoptosis and that hepatocytes isolated from Fas-deficient lymphoproliferative mice were resistant to GCDC-induced apoptosis. After GCDC treatment, immunoprecipitation experiments demonstrated Fas oligomerization, and confocal microscopy demonstrated DeltaFADD-GFP (Fas-associated death domain-green fluorescent protein, aggregation in the absence of detectable Fas ligand mRNA. Collectively, these data suggest that GCDC-induced hepatocyte apoptosis involves ligand-independent oligomerization of Fas, recruitment of FADD, activation of caspase 8, and subsequent activation of effector proteases, including downstream caspases and cathepsin B.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Apoptosis / drug effects*
  • Bile Acids and Salts / pharmacology*
  • Caspases / metabolism*
  • Cathepsin B / metabolism*
  • Cell Line
  • Cysteine Proteinase Inhibitors / pharmacology
  • DNA Fragmentation / drug effects
  • Enzyme Activation / drug effects
  • Glycochenodeoxycholic Acid / pharmacology
  • Kinetics
  • Lamin Type B*
  • Lamins
  • Liver / drug effects*
  • Liver / metabolism
  • Mice
  • Nuclear Proteins / metabolism
  • Oligopeptides / metabolism
  • Poly(ADP-ribose) Polymerases / metabolism
  • RNA, Messenger / genetics
  • Rats
  • Receptors, Tumor Necrosis Factor / genetics
  • Serpins / genetics
  • Viral Proteins*
  • fas Receptor / metabolism*

Substances

  • Bile Acids and Salts
  • Cysteine Proteinase Inhibitors
  • Lamin Type B
  • Lamins
  • Nuclear Proteins
  • Oligopeptides
  • RNA, Messenger
  • Receptors, Tumor Necrosis Factor
  • Serpins
  • Viral Proteins
  • fas Receptor
  • lamin B1
  • Glycochenodeoxycholic Acid
  • interleukin-1beta-converting enzyme inhibitor
  • Poly(ADP-ribose) Polymerases
  • Caspases
  • Cathepsin B