Reactive oxygen species and extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase mediate hyperoxia-induced cell death in lung epithelium.
Therapy with high oxygen concentrations (hyperoxia) is often necessary to treat patients with respiratory failure. However, hyperoxia may exacerbate the development of acute lung injury, perhaps by increasing lung epithelial cell death. Therefore, interrupting lung epithelial cell death is an important protective and therapeutic strategy. In the present study, hyperoxia (95% O(2)) results in murine lung epithelium cell death by DNA-laddering, terminal deoxynucleotidyltransferase dUTP nick end labeling, and Annexin V-fluorescein isothiocyanate flow cytometry assay. We show that hyperoxia increases superoxide production, as assessed by nicotinamide adenine dinucleotide phosphate reduced (NADPH) oxidase activity and flow cytometric assay, and increases phospho-extracellular signal-regulated kinase (ERK)1/2 by Western blot analysis. These processes are inhibited by a reactive oxygen species inhibitor, diphenylene iodonium (DPI), and by an inhibitor of the mitogen-activated protein (MAP) or ERK kinase (MEK)/ERK1/2 pathway, PD98059. ERK1/2 activation in hyperoxia is also inhibited by DPI. Hyperoxia-induced cell death is associated with cytochrome c release, subsequent caspase 9 and 3 activation, and poly (ADP-ribosyl) polymerase cleavage, which can all be suppressed by DPI and PD98059. However, the broad caspase inhibitor z-VAD-FMK protects cells from death without affecting superoxide generation and ERK1/2 activation. Taken together, our data suggest that hyperoxia, by virtue of activating NADPH oxidase, generates reactive oxygen species (ROS), which mediates cell death of lung epithelium via ERK1/2 MAPK activation, and functions upstream of caspase activation in lung epithelial cells.
Zhang
Xuchen
X
Section of Pulmonary and Critical Care Medicine, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
Shan
Peiying
P
Sasidhar
Madhu
M
Chupp
Geoffrey L
GL
Flavell
Richard A
RA
Choi
Augustine M K
AM
Lee
Patty J
PJ
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D020169:Caspases / Q000378:metabolism; D016923:Cell Death; D002461:Cell Line, Transformed; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003576:Electron Transport Complex IV / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000201:enzymology*; D005419:Flavonoids / Q000494:pharmacology; D018496:Hyperoxia / Q000473:pathology*; D008168:Lung / Q000473:pathology*; D051379:Mice; D018345:Mice, Knockout; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019255:NADPH Oxidases / Q000378:metabolism; D009861:Onium Compounds / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction
D000590:Amino Acid Chloromethyl Ketones; D015853:Cysteine Proteinase Inhibitors; D004791:Enzyme Inhibitors; D005419:Flavonoids; D009861:Onium Compounds; D017382:Reactive Oxygen Species; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C007517:diphenyleneiodonium; D019255:NADPH Oxidases; D003576:Electron Transport Complex IV; D011065:Poly(ADP-ribose) Polymerases; D020928:Mitogen-Activated Protein Kinases; D020169:Caspases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one