Epidermal growth factor receptor regulates Beclin-1 in hyperoxic acute lung injury.

BACKGROUND: While delivery of supplemental oxygen is a life-saving therapy, exposure to high oxygen, called hyperoxia, leads to increased intensive care unit mortality. Hyperoxia induces oxidant-mediated acute lung injury (ALI) and pulmonary cell death, called hyperoxic ALI (HALI). Elucidating molecular mechanisms in HALI could identify therapeutic targets in ALI. METHODS: In the current study, we examined in vivo effects of HALI on Beclin-1 (BCN1), which regulates autophagy, and modulation of BCN1 by epidermal growth factor receptor (EGFR). Effects of HALI on BCN1 and autophagy were examined in mice with genetically decreased EGFR (EGFR(Wa5/+)). Wildtype (WT) and EGFR(Wa5/+) mice were exposed to 100% oxygen for 24-72 hours along with normoxia controls (eight groups; n=4-6/group), and analysis of pulmonary BCN1 and autophagy was completed. RESULTS: In WT, HALI led to increased BCN1 (59% increased total BCN1/β-Actin; p<0.01) in lung and alveolar epithelium (484% increased H-score; p<0.001). HALI led to decreased microtubule-associated protein 1B-light chain (LC3B)-II/-I ratios (43% decrease; p<0.05) and increased p62 (93% increase; p<0.05), suggesting reduced autophagic flux. In human alveolar type-II cells derived from induced pluripotent stem cells (AT2s(iPSC)), HALI caused increased LDH release (130% increase; p<0.0001) and decreased LC3B-II/-I ratios (32% decrease; p<0.05). We previously showed that EGFR(Wa5/+) mice are protected in HALI. In the current study, EGFR(Wa5/+) mice showed increased pulmonary BCN1 (122% increase; p<0.05), reduced phosphorylated-(p-)/total BCN1 (47% decrease; p<0.05) and decreased LC3B-II/-I ratios (70% decrease; p<0.01) in HALI compared with WT. In addition, wortmannin (1 mg/kg), which decreases BCN1-mediated autophagy, increased mortality in HALI compared with vehicle control (n=10/group; 18% decreased hours survived; p<0.001). CONCLUSIONS: These data delineate a novel cell death pathway in HALI involving BCN1 and EGFR with therapeutic potential.