title: Cathepsin B contributes to bile salt-induced apoptosis of rat hepatocytes.
abstract: OBJECTIVE
  Bile salt-induced apoptosis is mediated by a trypsin-like nuclear protease. The aims of this study were to identify this protease and to elucidate its mechanistic role in bile salt-induced hepatocyte apoptosis.
  
  
  METHODS
  Rats, isolated rat hepatocytes, and a rat hepatoma cell line stably transfected with a bile salt transporter (McNtcp.24) were used for this study.
  
  
  RESULTS
  In the bile duct-ligated rat, a threefold increase in apoptosis and a fourfold increase in trypsin-like nuclear protease activity were observed. The nuclear protease activity was purified from bile duct-ligated rats and identified as cathepsin B. Specific, structurally dissimilar cathepsin B inhibitors blocked glycochenodeoxycholate (GCDC)-induced apoptosis in cultured rat hepatocytes. Furthermore, stable transfection of McNtcp.24 cells with the complementary DNA for cathepsin B in the antisense orientation reduced cathepsin B activity and GCDC-induced apoptosis by >75%. Next, cathepsin B cellular localization during apoptosis was determined by immunoblot analysis of nuclear cell fractions, immunocytochemistry, and by determining the compartmentation of expressed cathepsin B fused to green fluorescent protein. All three approaches showed translocation of cathepsin B from the cytoplasm to the nucleus during GCDC-induced apoptosis.
  
  
  CONCLUSIONS
  The data suggest that translocation of cathepsin B from the cytoplasm to the nucleus is a mechanism contributing to bile salt-induced apoptosis of hepatocytes.
authors.affiliation: Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: L R
authors.initials: LR
authors.lastname: Roberts
authors.forename: H
authors.initials: H
authors.lastname: Kurosawa
authors.forename: S F
authors.initials: SF
authors.lastname: Bronk
authors.forename: P J
authors.initials: PJ
authors.lastname: Fesmier
authors.forename: L B
authors.initials: LB
authors.lastname: Agellon
authors.forename: W Y
authors.initials: WY
authors.lastname: Leung
authors.forename: F
authors.initials: F
authors.lastname: Mao
authors.forename: G J
authors.initials: GJ
authors.lastname: Gores
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001647:Bile Acids and Salts / Q000633:toxicity*; D001692:Biological Transport; D002401:Cathepsin B / Q000502:physiology*; D002467:Cell Nucleus / Q000201:enzymology; D002478:Cells, Cultured; D008099:Liver / Q000187:drug effects* / Q000473:pathology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D001647:Bile Acids and Salts; D002401:Cathepsin B