Effect of tobacco extract on surfactant synthesis and its reversal by retinoic acid-role of cell-cell interactions in vitro

Abnormal Fetal Lung of Hoxa1-/- Piglets Is Rescued by Maternal Feeding with All-Trans Retinoic Acid

Neonatal Hoxa1-/- piglets were characterized by dyspnea owing to the Hoxa1 mutation, and maternal administration with ATRA alleviated the dyspnea of neonatal Hoxa1-/- piglets. The purpose of this experiment was to explore how maternal ATRA administration rescued the abnormal fetal lungs of Hoxa1-/- piglets. Samples of the lungs were collected from neonatal Hoxa1-/- and non-Hoxa1-/- piglets delivered by sows in the control group, and from neonatal Hoxa1-/- piglets born by sows administered with ATRA at 4 mg/kg body weight on dpc 12, 13, or 14, respectively. These were used for the analysis of ELISA, histological morphology, immunofluorescence staining, immunohistochemistry staining, and quantitative real-time PCR. The results indicate that the Hoxa1 mutation had adverse impacts on the development of the alveoli and pulmonary microvessels of Hoxa1-/- piglets. Maternal administration with ATRA at 4 mg/kg body weight on dpc 14 rescued the abnormal lung development of Hoxa1-/- piglets by increasing the IFN-γ concentration (p < 0.05), airspace area (p < 0.01) and pulmonary microvessel density (p < 0.01); increasing the expression of VEGFD (p < 0.01), PDGFD (p < 0.01), KDR (p < 0.01), ID1 (p < 0.01), and NEDD4 (p < 0.01); and decreasing the septal wall thickness (p < 0.01) and the expression of SFTPC (p < 0.01) and FOXO3 (p < 0.01). Maternal administration with ATRA plays a vital role in rescuing the abnormal development of lung of Hoxa1-/- fetal piglets.

Molecular Impact of Conventional and Electronic Cigarettes on Pulmonary Surfactant

The alveolar epithelium is covered by a non-cellular layer consisting of an aqueous hypophase topped by pulmonary surfactant, a lipo-protein mixture with surface-active properties. Exposure to cigarette smoke (CS) affects lung physiology and is linked to the development of several diseases. The macroscopic effects of CS are determined by several types of cell and molecular dysfunction, which, among other consequences, lead to surfactant alterations. The purpose of this review is to summarize the published studies aimed at uncovering the effects of CS on both the lipid and protein constituents of surfactant, discussing the molecular mechanisms involved in surfactant homeostasis that are altered by CS. Although surfactant homeostasis has been the topic of several studies and some molecular pathways can be deduced from an analysis of the literature, it remains evident that many aspects of the mechanisms of action of CS on surfactant homeostasis deserve further investigation.

SENP1 has an important role in lung development and influences the differentiation of alveolar type 2 cells

Post-translational modification via small ubiquitin-like modifier (SUMO) is involved in the regulation of various important cellular processes. SUMO modification can be regulated at the level of conjugation, and can also be reversed by the SUMO-specific proteases (SENPs). However, current studies of the regulation and function of SENP in lung development remain limited. In this study, the expression levels of SENP1 and SUMO1 were assessed during lung development in rats. SUMO1 modification occurred during lung development and changes in SENP1 expression were consistent with the changes in the presence of free SUMO1. In order to investigate the function of SENP1, alveolar type (AT) 2 cells were transfected with SENP1-targeting small interfering RNA, and the proliferation, apoptosis and differentiation function of AT2 cells was subsequently evaluated. Marked upregulation of conjugated SUMO1 was observed following SENP1 inhibition. Furthermore, depletion of SENP1 resulted in increased apoptosis, decreased proliferation and impaired differentiation status of AT2 cells. Thus, the results support that SENP1 is an essential regulator of the balance between SUMOylation and deSUMOylation during lung development, specifically affecting the proliferation and differentiation status of AT2 cells.

Anti-inflammatory Effects of Resveratrol on Hypoxia/Reoxygenation-Induced Alveolar Epithelial Cell Dysfunction

Reducing oxidative stress is crucial to prevent hypoxia-reoxygenation (H/R)-induced lung injury. Resveratrol has excellent antioxidant and anti-inflammatory effects, and this study investigated its role in H/R-induced type II pneumocyte dysfunction. H/R conditions increased expression of inflammatory cytokines including interleukin (IL)-1β (142.3 ± 21.2%, P < 0.05) and IL-6 (301.9 ± 35.1%, P < 0.01) in a type II alveolar epithelial cell line (A549), while the anti-inflammatory cytokine IL-10 (64.6 ± 9.8%, P < 0.05) and surfactant proteins (SPs) decreased. However, resveratrol treatment effectively inhibited these effects. H/R significantly activated an inflammatory transcription factor, nuclear factor (NF)-κB, while resveratrol significantly inhibited H/R-induced NF-κB transcription activities. To the best of our knowledge, this is the first study showing resveratrol-mediated reversal of H/R-induced inflammatory responses and dysfunction of type II pneumocyte cells in vitro. The effects of resveratrol were partially mediated by promoting SP expression and inhibiting inflammation with NF-κB pathway involvement. Therefore, our study provides new insights into mechanisms underlying the action of resveratrol in type II pneumocyte dysfunction.

Retinoic acid promotes primary fetal alveolar epithelial type II cell proliferation and differentiation to alveolar epithelial type I cells

Retinoic acid (RA) plays an important role in lung development and maturation. Many stimuli can induce alveolar epithelial cell damage which will result in the injury of lung parenchyma. The aim of this study was to observe the effect of RA on the proliferation and differentiation of primary fetal alveolar epithelial type II cells (fAECIIs). Primary fAECIIs were isolated from fetal rats at 19 d of gestation and purified by a differential centrifugation and adhesion method. The cells were randomly divided into control (dimethyl sulfoxide, DMSO) and RA groups. Cell proliferation, viability, apoptosis, cycle, and expression of target protein were examined at 24, 48, and 72 h. We found that the proliferation and viability of cells in the RA-exposed group significantly increased compared with the DMSO control group. The proportion (%) of cells in the G2 and S phases in the RA group was significantly higher than that in control group cells. The proportion (%) of both early apoptotic cells and late apoptotic cells decreased significantly in cells exposed to RA compared with cells exposed to DMSO. RA significantly enhanced the expression of aquaporin 5 (AQP5). The expression level of pulmonary surfactant C (SPC) was elevated after cells were exposed to RA for 24 and 72 h but was inhibited when cells were exposed to RA for 48 h. These results suggest that RA promotes fAECII proliferation by improving cell viability, promoting S phase entry and inhibiting apoptosis and RA promotes fAECIIs differentiation to alveolar epithelial type I cells (AECIs).