Rationale: The NF-E2 related factor 2 (Nrf2)-antioxidant response element (ARE) pathway is essential for protection against oxidative injury and inflammation including hyperoxia-induced acute lung injury. Microarray expression profiling revealed that lung peroxisome proliferator activated receptor g (PPARg) induction is suppressed in hyperoxia-susceptible Nrf2-deficient (Nrf2 2/2 ) mice compared with wild-type (Nrf2 1/1 ) mice. PPARg has pleiotropic beneficial effects including antiinflammation in multiple tissues. Objectives: We tested the hypothesis that PPARg is an important determinant of pulmonary responsivity to hyperoxia regulated by Nrf2. Methods: A computational bioinformatic method was applied to screen potential AREs in the Pparg promoter for Nrf2 binding. The functional role of a potential ARE was investigated by in vitro promoter analysis. A role for PPARg in hyperoxia-induced acute lung injury was determined by temporal silencing of PPARg via intranasal delivery of PPARg-specific interference RNA and by administration of a PPARg ligand 15-deoxy-D 12,14 -prostaglandin J 2 in mice. Measurements and Main Results: Deletion or site-directed mutagenesis of a potential ARE spanning -784/-764 sequence significantly attenuated hyperoxia-increased Pparg promoter activity in airway epithelial cells overexpressing Nrf2, indicating that the -784/-764 ARE is critical for Nrf2-regulated PPARg expression. Mice with decreased lung PPARg by specific interference RNA treatment had significantly augmented hyperoxia-induced pulmonary inflammation and injury. 15 Deoxy-D 12,14 -prostaglandin J 2 administration significantly reduced hyperoxia-induced lung inflammation and edema in Nrf2 1/1 , but not in Nrf2 2/2 mice. Conclusions: Results indicate for the first time that Nrf2-driven PPARg induction has an essential protective role in pulmonary oxidant injury. Our observations provide new insights into the therapeutic potential of PPARg in airway oxidative inflammatory disorders.

Aims: Nrf2 is an essential transcription factor for protection against oxidant disorders. However, its role in organ development and neonatal disease has received little attention. Therapeutically administered oxygen has been considered to contribute to bronchopulmonary dysplasia (BPD) in prematurity. The current study was performed to determine Nrf2-mediated molecular events during saccular-to-alveolar lung maturation, and the role of Nrf2 in the pathogenesis of hyperoxic lung injury using newborn Nrf2-deficient (Nrf2 -/ -) and wild-type (Nrf2) mice. Results: Pulmonary basal expression of cell cycle, redox balance, and lipid/carbohydrate metabolism genes was lower while lymphocyte immunity genes were more highly expressed in Nrf2 -/ -neonates than in Nrf2neonates. Hyperoxia-induced phenotypes, including mortality, arrest of saccular-to-alveolar transition, and lung edema, and inflammation accompanying DNA damage and tissue oxidation were significantly more severe in Nrf2 -/ -neonates than in Nrf2 +/+ neonates. During lung injury pathogenesis, Nrf2 orchestrated expression of lung genes involved in organ injury and morphology, cellular growth/proliferation, vasculature development, immune response, and cell-cell interaction. Bioinformatic identification of Nrf2 binding motifs and augmented hyperoxia-induced inflammation in genetically deficient neonates supported Gpx2 and Marco as Nrf2 effectors. Innovation: This investigation used lung transcriptomics and gene targeted mice to identify novel molecular events during saccular-to-alveolar stage transition and to elucidate Nrf2 downstream mechanisms in protection from hyperoxia-induced injury in neonate mouse lungs. Conclusion: Nrf2 deficiency augmented lung injury and arrest of alveolarization caused by hyperoxia during the newborn period. Results suggest a therapeutic potential of specific Nrf2 activators for oxidative stress-associated neonatal disorders including BPD.

The estrogen-related receptor alpha gene encodes a nuclear receptor protein, ERR alpha, whose structure is closely related to the estrogen receptors. ERR alpha modulates estrogen receptor (ER)-mediated signaling pathways both positively and negatively. It is selectively expressed in a variety of cell types during development and in adult tissues. We have previously shown that estrogen stimulates the expression of the ERR alpha gene in mouse uterus. In this study, we found that the ERR alpha gene is stimulated by estrogen in mouse uterus and heart but not in liver. Estrogen also stimulates the expression of ERR alpha in the human breast and endometrial cell lines. The human ERR alpha gene promoter contains multiple Sp1 binding sites, and the Sp1 protein is required for the promoter activity. The major estrogen response is mediated by a 34-bp DNA element that contains multiple steroid hormone response element half-sites (MHREs) that are conserved between the human and mouse ERR alpha gene promoters. Mutations made at a single or multiple sites of the MHREs abolished the ER-mediated transcription of the element in transient transfection experiments. By chromatin immunoprecipitation assay, we demonstrated the interaction between ER alpha and MHREs of the endogenous ERR alpha gene promoter in MCF-7 cells. Estrogen treatment further enhanced the association of ER alpha and MHREs in vivo. The present study demonstrated that the ERR alpha gene is a downstream target of ER alpha.