Abstract Rationale Bronchopulmonary dysplasia (BPD), a complication of prematurity, increases long-term pulmonary and neuro-developmental impairments. BPD occurs when premature saccular stage lung is utilized to support gas exchange, leading to alveolar and vascular growth arrest. The mechanisms leading to shared developmental impairments in the lung and brain of BPD infants is unknown. This knowledge is critical to development of novel therapies to decrease these co-morbidities. We previously found downregulation of liver kinase B1-AMP Kinase (LKB1-AMPK) signaling in the lung in a mouse model of BPD induced by neonatal exposure to hyperoxia. We hypothesized that this shared mechanism underlies decreased angiogenesis and neuronal growth in critical brain regions in hyperoxia. Methods We exposed newborn mouse litters from postnatal day 1 (P1) to P10 to either 21% or 75% O2 (hyperoxia) followed by recovery in 21% O2 from P11 to P21. We administered pups either 25mg/Kg of metformin in saline or control saline intraperitoneally from P1 to P10. Pups in both groups then returned to 21% O2 to recover from P11 to P21. All pups were euthanized at P21, and lungs and brain were harvested for histology and western blots. Paraffin embedded formalin fixed sections were used for immunofluorescent staining of markers for cell proliferation (Ki67), growth arrest (P53) and angiogenesis (VE-Cadherin). Data from at least 5 pups were included and compared by ANOVA and Tukey’s test with P 0.05 taken as significant difference. Results Hyperoxia decreased expression of LKB1, p-AMPK, mitochondrial transcription factor PGC1α and SOD2 in lung samples. Metformin increased the levels of LKB1, p-AMPK PGC-1α and SOD2 in lung samples. Hyperoxia increased mean linear intercept (MLI) and decreased radial alveolar count (RAC) which persisted to P21. Metformin increased RAC and decreased MLI in lungs. Hyperoxia markedly increased the expression of P53, and decreased Ki67 and SOD2 levels and VE-Cadherin positive capillaries in posterior parietal brain. Metformin reversed these changes with increases in Ki67 and VE-Cadherin positive vessel count and decrease in P53 levels in brain sections. Conclusions Decreased LKB1-AMPK signaling in hyperoxia leads to decreased lung alveolar and vascular growth. Hyperoxia decreased the endothelial proliferation and vessel density and increased endothelial growth arrest in the posterior parietal brain in mouse pups. Our novel studies show that metformin reverses these changes and improves lung and brain angiogenesis together in a hyperoxia model of BPD in mouse pups. This abstract is funded by: Advancing Healthier Wisconsin Endowment
Konduri et al. (Fri,) studied this question.