Decreased ZONAB expression promotes excessive transdifferentiation of alveolar epithelial cells in hyperoxia-induced bronchopulmonary dysplasia

Tat-P combined with GAPR1 releases Beclin1 to promote autophagy and improve Bronchopulmonary dysplasia model

Long-term exposure to hyperoxia can leading to the bronchopulmonary dysplasia (BPD). The progression of BPD is primarily driven by the apoptosis of alveolar epithelial cells, and the regulation of autophagy has an impact on apoptosis. This study aims to investigate the therapeutic potential and underlying mechanism of an autophagy-promoting peptide (Tat-P) in ameliorating BPD. In vitro experiments demonstrated that Tat-P promoted autophagy and partially prevented apoptosis caused by exposure to hyperoxia. Further investigation into the mechanism revealed that Tat-P competitively binds to GAPR1, displacing the Beclin1 protein and thereby inhibiting the apoptosis. In vivo experiments conducted on Sprague-Dawley pups exposed to high oxygen levels demonstrated that Tat-P promoted autophagy and reduced apoptosis in lung tissues and ameliorated BPD-related phenotypes. Our findings elucidate the underlying mechanisms and effects of Tat-P in enhancing autophagy and preventing apoptosis. This study presents an approach for the prevention and treatment of BPD.

Lef1 is transcriptionally activated by Klf4 and suppresses hyperoxia-induced alveolar epithelial cell injury

PURPOSE

Bronchopulmonary dysplasia (BPD) is a long-term respiratory condition. More than a quarter of extremely premature newborns are harmed by BPD. At present, there are no apparent effective drugs or treatments for the condition. In this study, we aimed to investigate the functional role and mechanism of lymphoid enhancer-binding factor 1 (Lef1) in BPD in vitro.

MATERIALS AND METHODS

Blood samples from BPD patients and healthy volunteers were gathered, and an in vitro model of BPD was developed in alveolar epithelial cells (AECs) MLE-12 induced by hyperoxia. Then expression of krüppel-like factor 4 (KLF4/Klf4) and LEF1/Lef1 were evaluated. After Lef1 overexpressing plasmid and the vector were transfected into hyperoxia-induced MLE-12 cells, cell proliferation assays were carried out. Cell apoptosis was investigated by a flow cytometry assay, and apoptosis related proteins Bcl-2, cleaved-caspase 3 and 9 were analyzed by a western blot assay. The binding between Klf4 and Lef1 promoter predicted on the JASPAR website was verified using luciferase and ChIP assays. For further study of the mechanism of Klf4 and Lef1 in BPD, gain-of-function experiments were performed.

RESULTS

The mRNA levels of KLF4/Klf4 and LEF1/Lef1 were diminished in clinical BPD serum samples and hyperoxia-induced MLE-12 cells. Overexpression of Lef1 stimulated AEC proliferation and suppressed AEC apoptosis induced by hyperoxia. Mechanically, Klf4 bound to Lef1's promoter region and aids transcription. Moreover, the results of gain-of-function experiments supported that Klf4 could impede AEC damage induced by hyperoxia via stimulating Lef1.

CONCLUSION

Klf4 and Lef1 expression levels were declined in hyperoxia-induced AECs, and Lef1 could be transcriptionally activated by Klf4 and protect against hyperoxia-induced AEC injury in BPD. As a result, Lef1 might become a prospective therapeutic target for BPD.

Interleukin-24 as a Pulmonary Target Cytokine in Bronchopulmonary Dysplasia

The proliferation of fetal alveolar type II cells (FATIICs) was impaired in bronchopulmonary dysplasia (BPD), which is modulated by hyperoxia and inflammatory response. Interleukin 24 (IL-24), a cytokine produced by certain cell types, plays an essential role in inflammation and host protection against infection. However, the ability of FATIICs to produce IL-24 remains unclear, and the role of IL-24 in BPD progression is yet to be determined. With reverse transcription quantitative polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay, the authors evaluated whether FATIICs produce IL-24 in physiological conditions. The authors quantified IL-24 expression in the lungs of newborn rat pups exposed to hyperoxia (70% oxygen) and in FATIICs isolated on embryonic day 19 that were exposed to 95% oxygen or lipopolysaccharide (LPS). The role of IL-24 in FATIICs, cell proliferation, cell apoptosis, and cell cycle were further evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and flow cytometric analysis. Also, they assessed caspase-3 and SOCS3 mRNA in IL-24 siRNA-treated cells by using RT-qPCR. During culture, IL-24 mRNA and protein levels in FATIICs gradually decreased with FATIIC differentiation. IL-24 expression increased significantly in rat lungs exposed to hyperoxia and FATIICs exposed to oxygen or LPS. Recombinant IL-24 enhanced cell proliferation by decreasing the proportion of apoptotic cells and increasing the proportion of cells in the S phase. The IL-24 siRNA-treated cells expressed more caspase-3 mRNA. Furthermore, suppressor of cytokine signaling 3 (SOCS3) mRNA was significantly decreased in rats and FATIICs exposed to oxygen, whereas it dramatically increased in FATIICs exposed to LPS. The IL-24 siRNA-treated cells expressed more SOCS3 mRNA. These studies suggest IL-24 is a pulmonary target cytokine in BPD, and may possibly regulate SOCS3 in oxidative stress and inflammation of the lung.

Recent advances in our understanding of the mechanisms of lung alveolarization and bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common cause of morbidity and mortality in preterm infants. A key histopathological feature of BPD is stunted late lung development, where the process of alveolarization-the generation of alveolar gas exchange units-is impeded, through mechanisms that remain largely unclear. As such, there is interest in the clarification both of the pathomechanisms at play in affected lungs, and the mechanisms of de novo alveoli generation in healthy, developing lungs. A better understanding of normal and pathological alveolarization might reveal opportunities for improved medical management of affected infants. Furthermore, disturbances to the alveolar architecture are a key histopathological feature of several adult chronic lung diseases, including emphysema and fibrosis, and it is envisaged that knowledge about the mechanisms of alveologenesis might facilitate regeneration of healthy lung parenchyma in affected patients. To this end, recent efforts have interrogated clinical data, developed new-and refined existing-in vivo and in vitro models of BPD, have applied new microscopic and radiographic approaches, and have developed advanced cell-culture approaches, including organoid generation. Advances have also been made in the development of other methodologies, including single-cell analysis, metabolomics, lipidomics, and proteomics, as well as the generation and use of complex mouse genetics tools. The objective of this review is to present advances made in our understanding of the mechanisms of lung alveolarization and BPD over the period 1 January 2017-30 June 2019, a period that spans the 50th anniversary of the original clinical description of BPD in preterm infants.

Bronchopulmonary Dysplasia: An Update on Experimental Therapeutics

Bronchopulmonary dysplasia (BPD) is a chronic inflammatory lung disease that affects thousands of newborns and infants every year. Although it is accepted that BPD results from lung damage and inflammation triggered by mechanical ventilation and hyperoxia, the causes and molecular events leading to lung damage and arrested development remain unknown. While recent advances in neonatal care have improved the survival of very low-weight infants, the rates of BPD have not improved accordingly. This is mainly due to our limited understanding of the disease’s pathogenesis and the effective therapeutic options available. Current therapeutics for BPD involve ventilation management, steroid treatment, and administration of various agents, such as pulmonary surfactant, caffeine, vitamin A, nitric oxide, and stem cells. However, the efficacy of these agents in preventing and ameliorating BPD symptoms varies depending on the populations studied and the disease stage. As the field moves towards personalised therapeutic approaches, this review summarises clinical and experimental studies conducted in various models, aiming to increase understanding of the cellular and molecular mechanisms by which these agents can prevent or treat BPD. Due to the increasing number of extremely premature infants, it is imperative that we continue to work towards understanding the mechanisms of BPD pathogenesis and generating more effective therapeutic options.