Abstract 5428: Nuclear Factor Kappa B Mediates Postnatal Alveolarization by Promoting Pulmonary Angiogenesis via Vascular Endothelial Growth Factor Receptor-2 Regulation
Vascular development drives alveolarization via vascular endothelial growth factor receptor-2 (VEGFR-2) signaling. Chronic lung disease of infancy, bronchopulmonary dysplasia (BPD) results from arrested alveolar and vascular development. However, the transcription factors that control alveolarization are unknown. Recent data identified a novel, developmentally regulated, anti-inflammatory role for the transcription factor nuclear factor kappa B (NFκB) in the neonatal lung, as opposed to its recognized, pro-inflammatory role in the mature lung. Thus, we hypothesized that NFκB is essential for alveolarization. To test this hypothesis, neontal mice were treated with the NFκB inhibitor, BAY 11–7082 (BAY), or vehicle (PBS). At 8h, lung was procured for gene and protein expression. At 24h, lungs were fixed at 25 cm H2O pressure for morphometric analysis, determination of apoptosis (TUNEL), and immunohistochemistry (IHC) to detect proliferating cell nuclear antigen (PCNA) and capillary density (CD31). Chromatin immunoprecipitation (ChIP) was performed on lung tissue to evaluate if the NFκB subunit, p65, binds the VEGFR2 promoter. Pulmonary endothelial cells (EC) were isolated using CD31 coated beads to determine VEGFR2 expression and VEGF-mediated survival and proliferation. At 8h, NFκB blockade (BAY) decreased VEGFR2 mRNA and protein in the lung (p<0.01, versus PBS). At 24h, lungs of BAY treated mice had increased alveolar area (p<0.05) and decreased radial alveolar counts (p<0.01), in association with decreased capillary density (p<0.01), reduced proliferation (p<0.001), and increased apoptosis (p<0.05). ChIP demonstrated that, in control lungs, p65 binds the VEGFR2 promoter. Furthermore, NFκB blockade with BAY caused a dose-dependent reduction of VEGFR2 mRNA and protein in pulmonary EC, and impaired VEGF mediated EC survival and proliferation. In summary, NFκB blockade disrupts postnatal alveolarization by decreasing VEGFR2, demonstrating that NFκB promotes alveologenesis through VEGFR2 mediated pulmonary EC survival and proliferation. We speculate that during lung development:
NFκB promotes lung angiogenesis; and
impaired NFκB activity may play a causal role in the arrest of alveolar formation characteristic of BPD.
This research has received full or partial funding support from the American Heart Association, National Center.