Although survival rate of infants born prematurely has been raised by supplemental oxygen treatment, it is followed by high morbidity of hyperoxia-induced bronchopulmonary dysplasia. In this study, the effect of resveratrol on the lung injury was evaluated in hyperoxia-exposed rats of preterm birth. The results demonstrated that hyperoxia led to thickened alveolar wall, simplified alveolar architecture and fibrosis. In addition, elevated methane dicarboxylic aldehyde level, decreased glutathione level and superoxide dismutase activity were also found in hyperoxic lungs, as well as the increased tumor necrosis factor-α, interleukin-1β and interleukin-6 in the bronchoalveolar lavage fluid. Fibrotic-associated proteins transforming growth factor-β1, α-smooth muscle actin, collagen I and fibronectin deposition were also found in interstitial substance of lungs. Furthermore, Wnt/β-catenin signalling was found to be active in hyperoxia-induced lungs. In addition, expression of SP-C was increased and T1α was decreased in hyperoxia-exposed lungs. Resveratrol intraperitoneal administration alleviated hyperoxia-induced histological injury of lungs, regulated redox balance, decreased pro-inflammatory cytokine release, and down-regulated expression of fibrotic-associated proteins. Furthermore, Wnt/β-catenin signalling was also suppressed by resveratrol, as represented by diminished expression of lymphoid enhancer factor-1, Wnt induced signalling protein-1 and cyclin D1. In addition, the increase of SP-C and decrease of T1α expression was prevented as well. The present study showed that resveratrol could protect lungs from hyperoxia-induced injury through its antioxidant, anti-inflammatory and anti-fibrotic effects. The transdifferentiation of alveolar epithelial type II cells to alveolar epithelial type I cells promotion and Wnt/β-catenin signalling suppression are also involved in the protective effect.

Septic shock with low cardiac output is very common in children. However, the mechanism underlying myocardial depression is unclear. The role of β₃-AR in the development of myocardial depression in sepsis is unknown. In the present study, we generated an adolescent rat model of hypodynamic septic shock induced by lipopolysaccharide (LPS). Neonatal cardiomyocytes were also treated with LPS to mimic myocardial depression in sepsis, which was confirmed via an in vivo left ventricular hemodynamic study, and measurements of contractility and the Ca²⁺ transient in isolated adolescent and neonatal cardiomyocytes. After 16 h of LPS treatment, cultured neonatal cardiomyocytes showed a diminished Ca²⁺ transient amplitude associated with an increase in the β₃-AR level. With the addition of a β₃-AR agonist, the Ca²⁺ transient in LPS-treated neonatal rat cardiomyocytes gradually decreased over time; such a change was absent in cells treated with nitric oxide synthase (NOS) inhibitors prior to treatment with a β₃-AR agonist. In adolescent rats with septic myocardial depression, cardiac function declined as indicated by decreased MAP, dP/dt_max, and dP/dt_mix for 6 h after LPS injection; however, the β₃-AR level first increased 2 h after LPS treatment and then decreased 6 h after LPS treatment in the absence of exogenous catecholamines. The results indicate that, in vitro, at the cellular level β₃-AR may be involved in the development of myocardial depression (Ca²⁺ transient depression) in sepsis through NOS signaling pathways; however, in vivo, a complicated mechanism for modulating β₃-AR may exist.

Transdifferentiation of alveolar epithelial type II cells (AECIIs) to type I cells (AECIs) is critical for reestablishment and maintenance of an intact alveolar epithelium. However, this process is frequently destroyed by hyperoxia treatment, which is commonly used in respiratory distress syndrome therapy in preterm infants. Wnt5a is considered to participate in this physiopathologic process, but the clear mechanisms still need to be further investigated. In this study, preterm rats and primary rat AECIIs were exposed to hyperoxia. Hematoxylin and eosin staining was used to examine the histological changes of the lungs. Real-time PCR and western blotting were used to examine Wnt5a expression and biomarkers of AECII and AECI expression. Immunohistochemistry and immunofluorescence were also used to determine the expression and location of selected biomarkers. Furthermore, AECIIs transfected with Wnt5a gene and exogenous Wnt5a were used to examine whether Wnt5a contributes to the transdifferentiation of AECIIs to AECIs. Results showed that hyperoxia inhibited the transdifferentiation of AECIIs to AECIs in vitro, which is represented by biomarkers of two types of cell that remained unchanged. In addition, Wnt5a protein expression was found to be decreased after hyperoxia exposure in vitro and in vivo. Furthermore, both the overexpression of Wnt5a and exogenous Wnt5a addition blocked the inhibitory effect of hyperoxia in vitro. In conclusion, our results suggest that the transdifferentiation of AECIIs to AECIs is impaired by hyperoxia, and this process may be associated with Wnt5a downregulation. Targeting Wnt5a may have the potential for the therapy of lung injury in preterm infants induced by hyperoxia.

ArticlePremature newborns often suffer from hypoxemia and acute respiratory failure. Supplemental oxygen is one of the most treatments for preterm respiratory support. It has been reported that prolonged exposure to hyperoxia results in oxidative stress-induced tissue damage in the lung, such as acute lung injury and bronchopulmonary dysplasia (BPD) (Kugelman and Durand 2011). BPD is a clinical syndrome of chronic respiratory, which can lead to hypoxemic respiratory failure and death. Advance in mechanical ventilation increases the percentage of infants surviving delivery earlier in gestation but also results in a high morbidity of BPD (Merritt et al. 2009).In animal models, retarded lung alveolization and differentiation of alveolar epithelial type II cells (AECIIs), fewer and larger alveoli, and enlarged airspace area were found in hyperoxia-exposed lungs (Dauger et al. 2003;Wang et al. 2005;Woyda et al. 2009). These damages were considered the result of the decreased proliferation of alveolar epithelium. Alveoli are lined by two morphologically and functionally different types of cells, type I alveolar epithelial cells (AECIs) and type II alveolar epithelial cells (AECIIs) (Crapo et al. 1982). AECIs cover 95% to 99% of the alveolar surface area and are responsible for gas, ions, SummaryThe aim of this study is to investigate the effect of Wnt3a in the transdifferentiation of type II alveolar epithelial cells (AECIIs) to type I alveolar epithelial cells (AECIs) under hyperoxia condition. In the in vivo study, preterm rats were exposed in hyperoxia for 21 days. In the in vitro study, primary rat AECIIs were subjected to a hyperoxia and normoxia exposure alternatively every 24 hr for 7 days. siRNA-mediated knockout of Wnt3a and exogenous Wnt3a were used to investigate the effect of Wnt3a on transdifferentiation of AECIIs to AECIs. Wnt5a-overexpressed AECIIs were also used to investigate whether Wnt3a could counteract the effect of Wnt5a. The results showed that hyperoxia induced alveolar damage in the lung of preterm born rats, as well as an increased expression of Wnt3a and nuclear accumulation of β-catenin. In addition, Wnt3a/β-catenin signaling was activated in isolated AECIIs after hyperoxia exposure. Wnt3a knockout blocked the inhibition of the transdifferentiation induced by hyperoxia, and Wnt3a addition exacerbated this inhibition. Furthermore, Wnt3a addition blocked the transdifferentiation-promoting effect of Wnt5a in hyperoxia-exposed Wnt5a-overexpressed AECIIs. In conclusion, our results demonstrate that the activated Wnt3a/β-catenin signal may be involved in the hyperoxiainduced inhibition of AECIIs' transdifferentiation to AECIs. (J Histochem Cytochem 63:879-891, 2015)