Murine Neonatal Oxidant Lung Injury: NRF2-Dependent Predisposition to Adulthood Respiratory Viral Infection and Protection by Maternal Antioxidant

NRF2 protects against oxidant-associated airway disorders via cytoprotective gene induction. To examine if NRF2 is an important determinant of respiratory syncytial virus (RSV) susceptibility after neonate lung injury, Nrf2-deficient (Nrf2−/−) and wild-type (Nrf2+/+) mice neonatally exposed to hyperoxia were infected with RSV. To investigate the prenatal antioxidant effect on neonatal oxidative lung injury, time-pregnant Nrf2−/−and Nrf2+/+mice were given an oral NRF2 agonist (sulforaphane) on embryonic days 11.5–17.5, and offspring were exposed to hyperoxia. Bronchoalveolar lavage and histopathologic analyses determined lung injury. cDNA microarray analyses were performed on placenta and neonatal lungs. RSV-induced pulmonary inflammation, injury, oxidation, and virus load were heightened in hyperoxia-exposed mice, and injury was more severe in hyperoxia-susceptible Nrf2−/− mice than in Nrf2+/+ mice. Maternal sulforaphane significantly alleviated hyperoxic lung injury in both neonate genotypes with more marked attenuation of severe neutrophilia, edema, oxidation, and alveolarization arrest in Nrf2−/− mice. Prenatal sulforaphane altered different genes with similar defensive functions (e.g., inhibition of cell/perinatal death and inflammation, potentiation of angiogenesis/organ development) in both strains, indicating compensatory transcriptome changes in Nrf2−/− mice. Conclusively, oxidative injury in underdeveloped lungs NRF2-dependently predisposed RSV susceptibility. In utero sulforaphane intervention suggested NRF2-dependent and -independent pulmonary protection mechanisms against early-life oxidant injury.

miR-184 mediates hyperoxia-induced injury by targeting cell death and angiogenesis signalling pathways in the developing lung

MicroRNAs (miRs) have been shown to disrupt normal lung development and function by interrupting alveolarization and vascularisation leading to development of bronchopulmonary dysplasia (BPD). Here we report that miR-184 has a critical role in the induction of BPD phenotype characterised by abnormal alveolarization and pulmonary angiogenesis in the developing lung. We observed an increased expression of miR-184 in BPD clinical specimens: tracheal aspirates (TA), human neonatal lungs with BPD and in fetal human lung Type II alveolar epithelial cells (TIIAECs) exposed to hyperoxia. Consistent with this, we also detected an upregulated miR-184-3p expression in whole lungs, in freshly isolated TIIAECs from lungs of hyperoxia-induced experimental BPD mice and in fetal mice lung TIIAECs exposed to hyperoxia. We demonstrate that overexpression of miR-184-3p exacerbates the BPD pulmonary phenotype, while downregulation of miR-184-3p expression ameliorated the BPD phenotype and also improved respiratory function. We identified miR-184 specific targets: platelet-derived growth factor-beta (Pdgf-β) and friend of Gata 2 (Fog2), also known as zinc finger protein family member (Zfpm2), and show that they are critically involved in pulmonary alveolarization and angiogenesis. Using cell-based luciferase analysis, downregulation of miR-184-3p expression and gene knockdown of miR-184-3p targets Pdgf-β and Fog2 in lung TIIAECs and endothelial cells, we mechanistically show that inhibition of miR-184-3p expression improves pulmonary alveolarization by regulating PDGF-β/AKT/Foxo3/Bax, Bcl2 signalling and enhances angiogenesis by Fog2/VEGF-A/Angiopoietin-1/2 pathway. Collectively, these data suggest that the use of miR-184-3p specific inhibitors may act as novel therapeutic interventions to control the adverse effects of hyperoxia on lung development and function.

Global Long Noncoding RNA and mRNA Expression Changes between Prenatal and Neonatal Lung Tissue in Pigs

Lung tissue plays an important role in the respiratory system of mammals after birth. Early lung development includes six key stages, of which the saccular stage spans the pre- and neonatal periods and prepares the distal lung for alveolarization and gas-exchange. However, little is known about the changes in gene expression between fetal and neonatal lungs. In this study, we performed transcriptomic analysis of messenger RNA (mRNA) and long noncoding RNA (lncRNA) expressed in the lung tissue of fetal and neonatal piglets. A total of 19,310 lncRNAs and 14,579 mRNAs were identified and substantially expressed. Furthermore, 3248 mRNAs were significantly (FDR-adjusted p value ≤ 0.05, FDR: False Discovery Rate) differentially expressed and were mainly enriched in categories related to cell proliferation, immune response, hypoxia response, and mitochondrial activation. For example, CCNA2, an important gene involved in the cell cycle and DNA replication, was upregulated in neonatal lungs. We also identified 452 significantly (FDR-adjusted p value ≤ 0.05) differentially expressed lncRNAs, which might function in cell proliferation, mitochondrial activation, and immune response, similar to the differentially expressed mRNAs. These results suggest that differentially expressed mRNAs and lncRNAs might co-regulate lung development in early postnatal pigs. Notably, the TU64359 lncRNA might promote distal lung development by up-regulating the heparin-binding epidermal growth factor-like (HB-EGF) expression. Our research provides basic lung development datasets and will accelerate clinical researches of newborn lung diseases with pig models.

Identification of microRNAs changed in the neonatal lungs in response to hyperoxia exposure

Bronchopulmonary dysplasia (BPD) is a multifactorial chronic lung disease of premature infants. BPD can be attributed to the dysregulation of normal lung development due to ventilation and oxygen toxicity, resulting in pathologic complications of impaired alveolarization and vascularization. MicroRNAs (miRNA) are small noncoding RNAs that regulate gene expression posttranscriptionally and are implicated in diverse biological processes and diseases. The objectives of this study are to identify the changed miRNAs and their target genes in neonatal rat lungs in response to hyperoxia exposure. Using miRNA microarray and real-time PCR analyses, we found downregulation of five miRNAs, miR-342, miR-335, miR-150, miR-126*, and miR-151*, and upregulation of two miRNAs, miR-21 and miR-34a. Some of these miRNAs had the highest expression during embryonic and early postnatal development. DNA microarray analysis yielded several genes with conserved binding sites for these altered miRNAs. Glycoprotein nonmetastatic melanoma protein b (GPNMB) was experimentally verified as a target of miR-150. In summary, we identified seven miRNAs that were changed in hyperoxia-exposed neonatal lungs. These results provide a basis for deciphering the mechanisms involved in the spatial and temporal regulation of proteins that contribute to the pathogenesis of BPD.

Alveolar Macrophages in Neonatal Mice Are Inherently Unresponsive to Pneumocystis murina Infection

ABSTRACTPneumocystispneumonia was first diagnosed in malnourished children and has more recently been found in children with upper respiratory symptoms. We previously reported that there is a significant delay in the immune response in newborn mice infected withPneumocystiscompared to adults (Garvy BA, Harmsen AG, Infect. Immun. 64:3987–3992, 1996, and Garvy BA, Qureshi M, J. Immunol. 165:6480–6486, 2000). This delay is characterized by the failure of neonatal lungs to upregulate proinflammatory cytokines and attract T cells into the alveoli. Here, we report that regardless of the age at which we infected the mice, they failed to mount an inflammatory response in the alveolar spaces until they were 21 days of age or older. Anti-inflammatory cytokines had some role in dampening inflammation, since interleukin-10 (IL-10)-deficient pups clearedPneumocystisfaster than wild-type pups and the neutralization of transforming growth factor beta (TGF-β) with specific antibody enhanced T cell migration into the lungs at later time points. However, the clearance kinetics were similar to those of control pups, suggesting that there is an intrinsic deficiency in the ability of innate immunity to controlPneumocystis. We found, using an adoptive transfer strategy, that the lung environment contributes to association ofPneumocystisorganisms with alveolar macrophages, implying no intrinsic deficiency in the binding ofPneumocystisby neonatal macrophages. Using bothin vivoandin vitroassays, we found thatPneumocystisorganisms were less able to stimulate translocation of NF-κB to the nucleus of alveolar macrophages from neonatal mice. These data indicate that there is an early unresponsiveness of neonatal alveolar macrophages toPneumocystisinfection that is both intrinsic and related to the immunosuppressive environment found in neonatal lungs.