We found that Keap1f/wt pups (bearing heterozygous “floxed” allele) were also protected from experimental BPD in a manner similar to Keap1f/f mice with homozygous “floxed” alleles (Fig. 9), indicating that even modest levels of Nrf2 target gene expression may be sufficient to block the detrimental effects of supplemental oxygen on lung development. This evidence concerns the gene NFE2L2 and bronchopulmonary dysplasia.