Inhibition of Regulatory-Associated Protein of Mechanistic Target of Rapamycin Prevents Hyperoxia-Induced Lung Injury by Enhancing Autophagy and Reducing Apoptosis in Neonatal Mice

Am J Respir Cell Mol Biol. 2016 Nov;55(5):722-735. doi: 10.1165/rcmb.2015-0349OC.


Administration of supplemental oxygen remains a critical clinical intervention for survival of preterm infants with respiratory failure. However, prolonged exposure to hyperoxia can augment pulmonary damage, resulting in developmental lung diseases embodied as hyperoxia-induced acute lung injury and bronchopulmonary dysplasia (BPD). We sought to investigate the role of autophagy in hyperoxia-induced apoptotic cell death in developing lungs. We identified increased autophagy signaling in hyperoxia-exposed mouse lung epithelial-12 cells, freshly isolated fetal type II alveolar epithelial cells, lungs of newborn wild-type mice, and human newborns with respiratory distress syndrome and evolving and established BPD. We found that hyperoxia exposure induces autophagy in a Trp53-dependent manner in mouse lung epithelial-12 cells and in neonatal mouse lungs. Using pharmacological inhibitors and gene silencing techniques, we found that the activation of autophagy, upon hyperoxia exposure, demonstrated a protective role with an antiapoptotic response. Specifically, inhibiting regulatory-associated protein of mechanistic target of rapamycin (RPTOR) in hyperoxia settings, as evidenced by wild-type mice treated with torin2 or mice administered (Rptor) silencing RNA via intranasal delivery or Rptor+/-, limited lung injury by increased autophagy, decreased apoptosis, improved lung architecture, and increased survival. Furthermore, we identified increased protein expression of phospho-beclin1, light chain-3-II and lysosomal-associated membrane protein 1, suggesting altered autophagic flux in the lungs of human neonates with established BPD. Collectively, our study unveils a novel demonstration of enhancing autophagy and antiapoptotic effects, specifically through the inhibition of RPTOR as a potentially useful therapeutic target for the treatment of hyperoxia-induced acute lung injury and BPD in developing lungs.

Keywords: bronchopulmonary dysplasia; cell death; newborn; oxygen; pulmonary.

MeSH terms

  • Acute Lung Injury / etiology*
  • Acute Lung Injury / metabolism
  • Acute Lung Injury / pathology*
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Alveolar Epithelial Cells / metabolism
  • Animals
  • Animals, Newborn
  • Apoptosis* / drug effects
  • Autophagy* / drug effects
  • Bronchopulmonary Dysplasia / complications
  • Bronchopulmonary Dysplasia / metabolism
  • Bronchopulmonary Dysplasia / pathology
  • Cell Line
  • Female
  • Humans
  • Hyperoxia / complications*
  • Hyperoxia / metabolism
  • Hyperoxia / pathology*
  • Hypertension, Pulmonary / complications
  • Hypertension, Pulmonary / pathology
  • Hypertrophy, Right Ventricular / complications
  • Hypertrophy, Right Ventricular / pathology
  • Infant, Newborn
  • Lung / metabolism
  • Lung / pathology
  • Mice
  • Microtubule-Associated Proteins / metabolism
  • Naphthyridines / pharmacology
  • Phenotype
  • Regulatory-Associated Protein of mTOR
  • Time Factors
  • Tumor Suppressor Protein p53 / metabolism


  • 9-(6-aminopyridin-3-yl)-1-(3-(trifluoromethyl)phenyl)benzo(h)(1,6)naphthyridin-2(1H)-one
  • Adaptor Proteins, Signal Transducing
  • MAP1LC3A protein, human
  • Microtubule-Associated Proteins
  • Naphthyridines
  • Regulatory-Associated Protein of mTOR
  • Rptor protein, mouse
  • Tumor Suppressor Protein p53