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Hyperoxia may cause pulmonary fibrosis in neonates and is characterized by the epithelial-to-mesenchymal transition (EMT) of alveolar epithelial cells. The placental growth factor (PLGF) gene is a member of the vascular endothelial growth factor family and is highly expressed in lung tissues that have been exposed to hyperoxia. The aim of the present study was to assess the role of PLGF in the EMT of lung tissue. Lung tissue exhibiting low PLGF expression was obtained by injecting rats exposed to hyperoxia with a PLGF-silencing lentiviral plasmid. Western blot analysis and immunohistochemistry revealed that expression levels of the EMT-related protein epithelial-cadherin were increased, whereas its inhibitor protein zinc-finger E-box binding homeobox 2 was decreased in these rats. These data demonstrated that PLGF silencing may significantly mitigate hyperoxia-induced EMT in rat lung tissue. Additionally, an increase in phosphorylated-p38 MAPK protein expression indicated that PLGF may be able to regulate hyperoxia-induced lung injury in rats via the p38 MAPK pathway. [ABSTRACT FROM AUTHOR]

Background A persistent increase in the number of lung fibroblasts (LFs) is found in the interstitium of the lungs of infants with bronchopulmonary dysplasia (BPD), which leads to lung fibrosis. P16 methylation plays an important role in the pathogenesis of BPD. 5-aza-2′-deoxycytidine (5-aza-CdR) is a major methyltransferase-specific inhibitor. This study investigated the effects of 5-aza-CdR on LFs in vitro from a hyperoxia-induced lung fibrosis model in newborn rats. Methods Methylation-specific polymerase chain reaction (PCR) and Western blotting were performed to determine P16 gene methylation status and protein expression after LFs were treated with 0 μmol/L, 0.5 μmol/L, 1.0 μmol/L, and 5.0 μmol/L 5-aza-CdR for 120 hours. Proliferation was assessed by an MTT assay after LFs were treated with 0 μmol/L, 0.5 μmol/L, 1.0 μmol/L, and 5.0 μmol/L 5-aza-CdR for 24 hours, 48 hours, 72 hours, 96 hours, and 120 hours. At the final time point, cells were also analyzed by flow cytometry to identify any change in their cell cycle profiles. Results A methylated P16 gene promoter was detected in hyperoxia LFs. Following treatment with 5-aza-CdR, partial methylation and demethylation was detected. The expression protein's level of the P16 gene was significantly higher in the 5.0 μmol/L 5-aza-CdR-treated group compared with that in the control group ( p < 0.01). The cell growth rate at each tested time point was lower in the 5-aza-CdR-treated group compared with that in the control group after 72 hours ( p < 0.01). Flow cytometry revealed that the cells in the 1.0 μmol/L and 5.0 μmol/L 5-aza-CdR-treated groups were apparently arrested in the G0/G1 phase and that the number of cells in the S phase was significantly lower than the control group ( p < 0.01). Conclusion 5-aza-CdR inhibits the growth of the LFs in hyperoxia-induced neonatal BPD rats in vitro by demethylating the P16 gene. [ABSTRACT FROM AUTHOR]

Life-saving mechanical ventilation can also cause lung injury through the overproduction of reactive oxygen species ( ROS), leading to bronchopulmonary dysplasia (BPD)-like symptoms in preterm infants. It is reported that the autophagic protein microtubule-associated protein-1 light chain (LC)-3B can confer protection against hyperoxia-induced DNA damage in lung alveolar epithelium. However, its role in the transdifferentiation of type II alveolar epithelial cells (AECIIs) to type I cells (AECIs) is unclear and requires further investigation. In this study, newborn Sprague-Dawley rats were exposed to 90% oxygen for up to 14 days to mimic BPD in human infants, with neonatal pups exposed to room air (21% oxygen) as controls. Primary rat AECIIs were cultured under hyperoxic conditions for up to 24 hours to further investigate the underlying mechanisms. This study found that hyperoxia promoted a significant and time-dependent increase of AECII marker surfactant protein (SP)-C in the lung. The increase of AECI marker T1α was repressed by hyperoxia during lung development. These results indicated an impaired AECII transdifferentiation. Pulmonary ROS concentration and expression of autophagic protein LC-3B were increased gradually in response to hyperoxia exposure. Furthermore, AECIIs produced more ROS when cultured under hyperoxic conditions in vitro. Both the LC3B expression and the conversion from LC3BI to LC3BII were enhanced in hyperoxic AECs. Interestingly, inhibition of LC3B either by ROS inhibitor N-acetyl- l-cysteine (NAC) or adenovirus-mediated LC3B shRNA could partly restore AECII transdifferentiation under hyperoxia condition. In summary, the current study reveals a novel role of activated LC3B induced by hyperoxia in AECII transdifferentiation. [ABSTRACT FROM AUTHOR]