Bleomycin initiates apoptosis of lung epithelial cells by ROS but not by Fas/FasL pathway

Am J Physiol Lung Cell Mol Physiol. 2006 Apr;290(4):L790-L796. doi: 10.1152/ajplung.00300.2004. Epub 2005 Nov 23.

Abstract

Epithelial cells are considered to be a main target of bleomycin-induced lung injury, which leads to fibrosis in vivo. We studied the characteristics of in vitro bleomycin-induced apoptosis in a mouse lung epithelial (MLE) cell line. Bleomycin caused an increase of reactive oxygen species (ROS) resulting in oxidative stress, mitochondrial leakage, and apoptosis. These were associated with elevated caspase-8 and resultant caspase-9 activity and with upregulation of Fas expression. Glutathione and inhibitors of caspase-8 or caspase-9, but not of FasL, inhibited these effects, suggesting their dependence on ROS, caspase-8 and -9, in a Fas/FasL-independent pathway. However, postbleomycin-exposed MLE cells were more sensitive to Fas-mediated apoptosis. These results demonstrate that the initial bleomycin-induced oxidative stress causes a direct apoptotic effect in lung epithelial cells involving a regulatory role of caspase-8 on caspase-9. Fas represents an amplification mechanism, and not a direct trigger of bleomycin-induced epithelial cell apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antimetabolites, Antineoplastic / administration & dosage
  • Antimetabolites, Antineoplastic / pharmacology*
  • Apoptosis / drug effects*
  • Bleomycin / administration & dosage
  • Bleomycin / pharmacology*
  • Caspase 8
  • Caspase 9
  • Caspase Inhibitors
  • Caspases / metabolism
  • Cell Death / drug effects
  • Cell Line
  • Dose-Response Relationship, Drug
  • Enzyme Activation / drug effects
  • Enzyme Inhibitors / pharmacology
  • Epithelial Cells / physiology
  • Fas Ligand Protein
  • Glutathione / pharmacology
  • Lung / cytology
  • Lung / physiology*
  • Membrane Glycoproteins / metabolism*
  • Membrane Potentials / drug effects
  • Mice
  • Mitochondria / physiology
  • Reactive Oxygen Species / metabolism*
  • Tumor Necrosis Factors / metabolism*
  • Up-Regulation
  • fas Receptor / metabolism*

Substances

  • Antimetabolites, Antineoplastic
  • Caspase Inhibitors
  • Enzyme Inhibitors
  • Fas Ligand Protein
  • Fasl protein, mouse
  • Membrane Glycoproteins
  • Reactive Oxygen Species
  • Tumor Necrosis Factors
  • fas Receptor
  • Bleomycin
  • Casp8 protein, mouse
  • Casp9 protein, mouse
  • Caspase 8
  • Caspase 9
  • Caspases
  • Glutathione