Reactive oxygen species are required for hyperoxia-induced Bax activation and cell death in alveolar epithelial cells.
Exposure of animals to hyperoxia results in respiratory failure and death within 72 h. Histologic evaluation of the lungs of these animals demonstrates epithelial apoptosis and necrosis. Although the generation of reactive oxygen species (ROS) is widely thought to be responsible for the cell death observed following exposure to hyperoxia, it is not clear whether they act upstream of activation of the cell death pathway or whether they are generated as a result of mitochondrial membrane permeabilization and caspase activation. We hypothesized that the generation of ROS was required for hyperoxia-induced cell death upstream of Bax activation. In primary rat alveolar epithelial cells, we found that exposure to hyperoxia resulted in the generation of ROS that was completely prevented by the administration of the combined superoxide dismutase/catalase mimetic EUK-134 (Eukarion, Inc., Bedford, MA). Exposure to hyperoxia resulted in the activation of Bax at the mitochondrial membrane, cytochrome c release, and cell death. The administration of EUK-134 prevented Bax activation, cytochrome c release, and cell death. In a mouse lung epithelial cell line (MLE-12), the overexpression of Bcl-XL protected cells against hyperoxia by preventing the activation of Bax at the mitochondrial membrane. We conclude that exposure to hyperoxia results in Bax activation at the mitochondrial membrane and subsequent cytochrome c release. Bax activation at the mitochondrial membrane requires the generation of ROS and can be prevented by the overexpression of Bcl-XL.
Buccellato
Leonard J
LJ
Division of Pulmonary and Critical Care Medicine, Northwestern University, Chicago, Illinois 60611, USA.
Tso
May
M
Akinci
Ozkan I
OI
Chandel
Navdeep S
NS
Budinger
G R Scott
GR
D000818:Animals; D020169:Caspases / Q000378:metabolism; D016923:Cell Death; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000166:cytology*; D005978:Glutathione / Q000378:metabolism; D000860:Hypoxia; D015151:Immunoblotting; D007425:Intracellular Membranes / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008168:Lung / Q000166:cytology; D051379:Mice; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D009942:Organometallic Compounds / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species; D012190:Retroviridae / Q000235:genetics; D012459:Salicylates / Q000494:pharmacology; D013482:Superoxide Dismutase / Q000378:metabolism; D013997:Time Factors; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
C494827:Bax protein, mouse; C494828:Bax protein, rat; C494812:Bcl2l1 protein, mouse; C494813:Bcl2l1 protein, rat; C433928:EUK-134; D009942:Organometallic Compounds; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D012459:Salicylates; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D045304:Cytochromes c; D007770:L-Lactate Dehydrogenase; D013482:Superoxide Dismutase; D020169:Caspases; D005978:Glutathione; D010100:Oxygen