Lack of EC-SOD worsens alveolar and vascular development in a neonatal mouse model of bleomycin-induced bronchopulmonary dysplasia and pulmonary hypertension

BACKGROUND: Pulmonary arterial hypertension (PAH) worsens clinical outcomes in former preterm infants with bronchopulmonary dysplasia (BPD). Oxidant stress disrupts alveolar and vascular development in models of BPD. Bleomycin causes oxidative stress and induces BPD and PAH in neonatal rats. Disruption in the VEGF and nitric oxide signaling pathways contributes to BPD. We hypothesized that loss of EC-SOD would worsen PAH associated with BPD in a neonatal mouse model of bleomycin-induced BPD by disrupting the VEGF/NO signaling pathway. METHODS: Neonatal wild-type mice (WT), and mice lacking EC-SOD (EC-SOD KO) received intraperitoneal bleomycin (2 units/kg) or PBS three times weekly and were evaluated at week 3 or 4. RESULTS: Lack of EC-SOD impaired alveolar development and resulted in PH (elevated right ventricular systolic pressures, right ventricular hypertrophy (RVH)), decreased vessel density and an increased small vessel muscularization. Exposure to bleomycin further impaired alveolar development, worsened RVH and vascular remodeling. Lack of EC-SOD and bleomycin treatment decreased lung total and phosphorylated VEGFR2 and eNOS protein expression. CONCLUSION: EC-SOD is critical in preserving normal lung development and loss of EC-SOD results in disrupted alveolar development, PAH and vascular remodeling at baseline, which is further worsened with bleomycin and associated with decreased activation of VEGFR2.