PI3K-AKT Signaling via Nrf2 Protects against Hyperoxia-Induced Acute Lung Injury, but Promotes Inflammation Post-Injury Independent of Nrf2 in Mice

PLoS One. 2015 Jun 15;10(6):e0129676. doi: 10.1371/journal.pone.0129676. eCollection 2015.


Lung epithelial and endothelial cell death accompanied by inflammation contributes to hyperoxia-induced acute lung injury (ALI). Impaired resolution of ALI can promote and/or perpetuate lung pathogenesis, including fibrosis. Previously, we have shown that the transcription factor Nrf2 induces cytoprotective gene expression and confers protection against hyperoxic lung injury, and that Nrf2-mediated signaling is also crucial for the restoration of lung homeostasis post-injury. Although we have reported that PI3K/AKT signaling is required for Nrf2 activation in lung epithelial cells, significance of the PI3K/AKT-Nrf2 crosstalk during hyperoxic lung injury and repair remains unclear. Thus, we evaluated this aspect using Nrf2 knockout (Nrf2(-/-)) and wild-type (Nrf2(+/+)) mouse models. Here, we show that pharmacologic inhibition of PI3K/AKT signaling increased lung inflammation and alveolar permeability in Nrf2(+/+) mice, accompanied by decreased expression of Nrf2-target genes such as Nqo1 and Hmox1. PI3K/AKT inhibition dampened hyperoxia-stimulated Nqo1 and Hmox1 expression in lung epithelial cells and alveolar macrophages. Contrasting with its protective effects, PI3K/AKT inhibition suppressed lung inflammation in Nrf2(+/+) mice during post-injury. In Nrf2(-/-) mice exposed to room-air, PI3K/AKT inhibition caused lung injury and inflammation, but it did not exaggerate hyperoxia-induced ALI. During post-injury, PI3K/AKT inhibition did not augment, but rather attenuated, lung inflammation in Nrf2(-/-) mice. These results suggest that PI3K/AKT-Nrf2 signaling is required to dampen hyperoxia-induced lung injury and inflammation. Paradoxically, the PI3K/AKT pathway promotes lung inflammation, independent of Nrf2, during post-injury.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Acute Lung Injury / etiology*
  • Acute Lung Injury / metabolism*
  • Acute Lung Injury / pathology
  • Alveolar Epithelial Cells / metabolism
  • Animals
  • Cell Line
  • Chromones / pharmacology
  • Disease Models, Animal
  • Gene Knockdown Techniques
  • Hyperoxia / complications*
  • Macrophages, Alveolar / metabolism
  • Mice
  • Mice, Knockout
  • Morpholines / pharmacology
  • NF-E2-Related Factor 2 / genetics
  • NF-E2-Related Factor 2 / metabolism*
  • Neutrophil Infiltration
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphoinositide-3 Kinase Inhibitors
  • Proto-Oncogene Proteins c-akt / antagonists & inhibitors
  • Proto-Oncogene Proteins c-akt / metabolism*
  • Signal Transduction* / drug effects


  • Chromones
  • Morpholines
  • NF-E2-Related Factor 2
  • Phosphoinositide-3 Kinase Inhibitors
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • Proto-Oncogene Proteins c-akt