Background: Bronchopulmonary dysplasia is an inflammatory lung disease that afflicts preterm infants requiring supplemental oxygen and is associated with impaired pulmonary angiogenesis. We tested the hypothesis that there is a critical threshold of inspired O2 (FiO2) that alters pulmonary angiogenesis.
Methods: Within 2-6 h of birth, rat pups were exposed to 10%, 21%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100% FiO2 for 2 h. Mixed arterial-venous blood gases, serum and pulmonary levels of vascular endothelial growth factor (VEGF) and soluble VEGF receptor-1, and pulmonary angiogenesis gene profiles were determined.
Results: PO2 increased with hyperoxia from 35.6 ± 5.0 (range: 31.5-39.8) at 10% O2 to 108.5 ± 25.0 (range: 82.2-134.8) at 100% O2. PO2 at 21% O2 was 42.4 ± 7.3 (range: 36.8-48.1). Lung VEGF levels declined at 40%-100%. The critical PO2 associated with decreased lung VEGF was 66 mm Hg, achieved with a FiO2 of 0.4. PO2 was inversely correlated with VEGF levels in the lungs (R = -0.377; P < 0.008). Antiangiogenesis genes were robustly upregulated at 70%, predominantly in males. Data are reported as mean ± SD.
Conclusions: A critical threshold of FiO2 affecting angiogenesis exists in immature lungs. Exposure of preterm lungs to >40% inspired O2, even for 2 h, may result in abnormal expression of biomarkers regulating lung angiogenesis.