Bleomycin initiates apoptosis of lung epithelial cells by ROS but not by Fas/FasL pathway.
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.
Wallach-Dayan
Shulamit B
SB
Lung Cellular and Molecular Laboratory, Inst. of Pulmonology, Hadassah Univ. Hospital, POB 12000, Jerusalem, Israel. wallach-dayan@hadassah.org.il
Izbicki
Gabriel
G
Cohen
Pazit Y
PY
Gerstl-Golan
Regina
R
Fine
Alan
A
Breuer
Raphael
R
D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001761:Bleomycin / Q000008:administration & dosage / Q000494:pharmacology*; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000502:physiology; D053222:Fas Ligand Protein; D005978:Glutathione / Q000494:pharmacology; D008168:Lung / Q000166:cytology / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008928:Mitochondria / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D048069:Tumor Necrosis Factors / Q000378:metabolism*; D015854:Up-Regulation; D019014:fas Receptor / Q000378:metabolism*
D000964:Antimetabolites, Antineoplastic; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008562:Membrane Glycoproteins; D017382:Reactive Oxygen Species; D048069:Tumor Necrosis Factors; D019014:fas Receptor; D001761:Bleomycin; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D005978:Glutathione