Extracellular signal-regulated kinase activation delays hyperoxia-induced epithelial cell death in conditions of Akt downregulation.
Hyperoxia (fraction of inspired oxygen = 95%) induces death of lung epithelial cells. The duration of cell survival in the setting of hyperoxia depends on hyperoxia-induced activation of intracellular survival pathways. Two survival pathways with known effects on lung epithelial cells are the propidium iodide 3-kinase/Akt and extracellular signal-regulated kinase (ERK)/mitogen-activated protein (MAP) kinase pathways. We investigated the effect of hyperoxia on activity of both the Akt and ERK pathways in the A549 lung epithelial cell line. Hyperoxia-exposed cells show progressive loss of Akt activation and total Akt protein. Hyperoxia decreases Akt mRNA, consistent with the loss of total Akt. In addition, hyperoxia induces ERK activation. Inhibition of ERK with the MAP kinase kinase 1/2 inhibitor, U0126, shortens the survival time of cells in hyperoxia, suggesting that increased ERK activity partially compensates for the hyperoxia-induced Akt downregulation. Our findings show, for the first time, that hyperoxia has divergent effects on two survival pathways (Akt and ERK), and that ERK activity compensates for the loss of the Akt survival effects, delaying the death of hyperoxia-exposed lung epithelial cells.
Truong
Son V
SV
Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
Monick
Martha M
MM
Yarovinsky
Timur O
TO
Powers
Linda S
LS
Nyunoya
Toru
T
Hunninghake
Gary W
GW
D017209:Apoptosis / Q000187:drug effects; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D002467:Cell Nucleus / Q000473:pathology; D015536:Down-Regulation / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006801:Humans; D008168:Lung / Q000166:cytology; D009336:Necrosis / Q000139:chemically induced; D010100:Oxygen / Q000494:pharmacology*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011419:Propidium / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
D061945:Caspase Inhibitors; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D011419:Propidium; D011065:Poly(ADP-ribose) Polymerases; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D020169:Caspases; D010100:Oxygen