Decreased apoptosis during CAR-mediated hepatoprotection against lithocholic acid-induced liver injury in mice

Toxicol Lett. 2009 Jul 10;188(1):38-44. doi: 10.1016/j.toxlet.2009.03.005. Epub 2009 Mar 20.

Abstract

Myeloid cell leukemia-1 (Mcl-1) is an anti-apoptotic protein that is regulated by the constitutive androstane receptor (CAR). Activation of CAR can protect the liver against bile acid-induced toxicity and it may have a role in cell death via apoptosis by altering expression of Bcl-2 family proteins such as myeloid cell leukemia-1 (Mcl-1). Our aim was to determine if activation of CAR reduces hepatocellular apoptosis during cholestasis as a mechanism of hepatoprotection. CAR(+/+) (WT) and CAR(-/-) (CAR-null) mice were pre-treated with compounds known to activate CAR prior to induction of intrahepatic cholestasis using the secondary bile acid lithocholic acid (LCA). Pre-treatment with the CAR activators phenobarbital (PB) and TCPOBOP (TC), as well as the non-CAR activator pregnenolone 16alpha-carbontrile (PCN), protected against LCA-induced liver injury in WT mice, whereas liver injury was more extensive without CAR (CAR-null). Unexpectedly, expression of anti-apoptotic Mcl-1 and Bcl-x(L) was not increased in hepatoprotected mice. Compared to unprotected groups, apoptosis was decreased in hepatoprotected mice as evidenced by the absence of cleaved caspase 3 (cCasp3). In contrast to the cytoplasmic localization in the injured livers (LCA and oltipraz), Mcl-1 protein was localized in the nucleus of hepatoprotected livers to potentially promote cell survival. This study demonstrates that although apoptosis is reduced in hepatoprotected mice pre-treated with CAR and non-CAR activators; hepatoprotection is not directly a result of CAR-induced Mcl-1 expression.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Apoptosis / drug effects*
  • Caspase 3 / metabolism
  • Cholestasis, Intrahepatic / chemically induced
  • Cholestasis, Intrahepatic / metabolism
  • Cholestasis, Intrahepatic / pathology
  • Cholestasis, Intrahepatic / prevention & control*
  • Constitutive Androstane Receptor
  • Cytoprotection
  • Disease Models, Animal
  • Lithocholic Acid
  • Liver / drug effects*
  • Liver / metabolism
  • Liver / pathology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Myeloid Cell Leukemia Sequence 1 Protein
  • Phenobarbital / pharmacology*
  • Pregnenolone Carbonitrile / pharmacology*
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Pyrazines / pharmacology*
  • Pyridines / pharmacology*
  • RNA, Messenger / metabolism
  • Receptors, Cytoplasmic and Nuclear / agonists*
  • Receptors, Cytoplasmic and Nuclear / genetics
  • Receptors, Cytoplasmic and Nuclear / metabolism
  • Thiones
  • Thiophenes
  • Transcription Factors / agonists*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • bcl-X Protein / metabolism

Substances

  • Constitutive Androstane Receptor
  • Mcl1 protein, mouse
  • Myeloid Cell Leukemia Sequence 1 Protein
  • Proto-Oncogene Proteins c-bcl-2
  • Pyrazines
  • Pyridines
  • RNA, Messenger
  • Receptors, Cytoplasmic and Nuclear
  • Thiones
  • Thiophenes
  • Transcription Factors
  • bcl-X Protein
  • Pregnenolone Carbonitrile
  • Lithocholic Acid
  • oltipraz
  • 1,4-bis(2-(3,5-dichloropyridyloxy))benzene
  • Casp3 protein, mouse
  • Caspase 3
  • Phenobarbital