Hyperoxia stimulates an Nrf2-ARE transcriptional response via ROS-EGFR-PI3K-Akt/ERK MAP kinase signaling in pulmonary epithelial cells.
Nuclear factor erythroid 2-related factor (Nrf2) confers protection against cell death induced by hyperoxia and other proapoptotic stimuli. Because phosphoinositide-3-kinase (PI3K)/Akt signaling promotes cell survival, the significance of this pathway in mediating reactive oxygen species (ROS)-dependent hyperoxia-induced Nrf2 activation was investigated in the murine pulmonary epithelial cell line, C10. Inhibition of the PI3K pathway markedly attenuated hyperoxia-induced Nrf2 translocation and ARE (antioxidant response element)-mediated transcription. Consistent with this, hyperoxia markedly stimulated the activation of PI3K pathway, while an NADPH oxidase inhibitor and an antioxidant prevented such activation. The inhibition of Akt activity using a pharmacological inhibitor markedly attenuated Nrf2 translocation and ARE-driven expression. Moreover, overexpression of a dominant-negative Akt mutant attenuated the transcription, whereas a constitutively active mutant stimulated it. These results suggest that PI3K/Akt signaling regulates Nrf2 activation by hyperoxia. Inhibition of the PI3K pathway prevented hyperoxia-stimulated Akt and ERK1/2 kinase activation, which is critical for Nrf2-mediated transcription. Likewise, the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, AG1478, blocked hyperoxia-stimulated Akt and ERK1/2 phosphorylation, Nrf2 nuclear accumulation, and ARE-driven transcription. Consistent with this result, an NADPH oxidase inhibitor blocked hyperoxia- stimulated EGFR phosphorylation, which was correlated with the attenuation of Akt and ERK activation. Collectively, our data suggest that EGFR-PI3K signaling through Akt and ERK kinases regulates ROS-dependent, hyperoxia-induced Nrf2 activation in pulmonary epithelial cells.
Department of Environmental Health Sciences, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, Maryland, USA.
Srinivas
S
Papaiahgari
Qin
Q
Zhang
Steven R
SR
Kleeberger
Hye-Youn
HY
Cho
Sekhar P
SP
Reddy
D000818:Animals; D002460:Cell Line; D066246:ErbB Receptors / Q000502:physiology*; D018496:Hyperoxia / Q000503:physiopathology* / Q000517:prevention & control; D007150:Immunohistochemistry; D020935:MAP Kinase Signaling System / Q000502:physiology*; D051379:Mice; D008954:Models, Biological; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000502:physiology*; D020545:Respiratory Mucosa / Q000502:physiology*; D014158:Transcription, Genetic
D051267:NF-E2-Related Factor 2; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt