Sustained hyperoxia-induced NF-κB activation improves survival and preserves lung development in neonatal mice

Oxygen toxicity contributes to the pathogenesis of bronchopulmonary dysplasia (BPD). Neonatal mice exposed to hyperoxia develop a simplified lung structure that resembles BPD. Sustained activation of the transcription factor NF-kappa B and increased expression of protective target genes attenuate hyperoxia-induced mortality in adults. However, the effect of enhancing hyperoxia-induced NF-kappa B activity on lung injury and development in neonatal animals is unknown. We performed this study to determine whether sustained NF-kappa B activation, mediated through I kappa B beta overexpression, preserves lung development in neonatal animals exposed to hyperoxia. Newborn wild-type (WT) and I kappa B beta-overexpressing (AKBI) mice were exposed to hyperoxia (>95%) or room air from day of life (DOL) 0-14, after which all animals were kept in room air. Survival curves were generated through DOL 14. Lung development was assessed using radial alveolar count (RAC) and mean linear intercept (MLI) at DOL 3 and 28 and pulmonary vessel density at DOL 28. Lung tissue was collected, and NF-kappa B activity was assessed using Western blot for I kappa B degradation and NF-kappa B nuclear translocation. WT mice demonstrated 80% mortality through 14 days of exposure. In contrast, AKBI mice demonstrated 60% survival. Decreased RAC, increased MLI, and pulmonary vessel density caused by hyperoxia in WT mice were significantly attenuated in AKBI mice. These findings were associated with early and sustained NF-kappa B activation and expression of cytoprotective target genes, including vascular endothelial growth factor receptor 2. We conclude that sustained hyperoxia-induced NF-kappa B activation improves neonatal survival and preserves lung development. Potentiating early NF-kappa B activity after hyperoxic exposure may represent a therapeutic intervention to prevent BPD.