Oxidative injury of the pulmonary circulation in the perinatal period: Short- and long-term consequences for the human cardiopulmonary system

Impact of Climate Change on Dietary Nutritional Quality and Implications for Asthma and Allergy

Asthma and allergic disorders are common in childhood with genetic and environmental determinants of disease that include prenatal nutritional exposures such as long-chain polyunsaturated fatty acids and antioxidants. Global climate change is implicated in asthma and allergic disorder morbidity with potential mechanisms including perturbations of ecosystems. There is support that environmental and climatic changes such as increasing global temperate and carbon dioxide levels affect aquatic and agricultural ecosystems with subsequent alterations in long-chain polyunsaturated fatty acid availability and nutrient quality and antioxidant capacity of certain crops, respectively. This article discusses asthma epidemiology and the influence of global climate change.

L-citrulline attenuates lipopolysaccharide-induced inflammatory lung injury in neonatal rats

BACKGROUND

Prenatal or postnatal lung inflammation and oxidative stress disrupt alveolo-vascular development leading to bronchopulmonary dysplasia (BPD) with and without pulmonary hypertension. L-citrulline (L-CIT), a nonessential amino acid, alleviates inflammatory and hyperoxic lung injury in preclinical models of BPD. L-CIT modulates signaling pathways mediating inflammation, oxidative stress, and mitochondrial biogenesis-processes operative in the development of BPD. We hypothesize that L-CIT will attenuate lipopolysaccharide (LPS)-induced inflammation and oxidative stress in our rat model of neonatal lung injury.

METHODS

Newborn rats during the saccular stage of lung development were used to investigate the effect of L-CIT on LPS-induced lung histopathology and pathways involved in inflammatory, antioxidative processes, and mitochondrial biogenesis in lungs in vivo, and in primary culture of pulmonary artery smooth muscle cells, in vitro.

RESULTS

L-CIT protected the newborn rat lung from LPS-induced: lung histopathology, ROS production, NFκB nuclear translocation, and upregulation of gene and protein expression of inflammatory cytokines (IL-1β, IL-8, MCP-1α, and TNF-α). L-CIT maintained mitochondrial morphology, increased protein levels of PGC-1α, NRF1, and TFAM (transcription factors involved in mitochondrial biogenesis), and induced SIRT1, SIRT3, and superoxide dismutases protein expression.

CONCLUSION

L-CIT may be efficacious in decreasing early lung inflammation and oxidative stress mitigating progression to BPD.

IMPACT

The nonessential amino acid L-citrulline (L-CIT) mitigated lipopolysaccharide (LPS)-induced lung injury in the early stage of lung development in the newborn rat. This is the first study describing the effect of L-CIT on the signaling pathways operative in bronchopulmonary dysplasia (BPD) in a preclinical inflammatory model of newborn lung injury. If our findings translate to premature infants, L-CIT could decrease inflammation, oxidative stress and preserve mitochondrial health in the lung of premature infants at risk for BPD.

Artesunate Alleviates Hyperoxia-Induced Lung Injury in Neonatal Mice by Inhibiting NLRP3 Inflammasome Activation

Bronchopulmonary dysplasia (BPD) is a chronic respiratory disease in preterm infants that may cause persistent lung injury. Artesunate exhibits excellent anti-inflammatory in lung injury caused by various factors. This study aimed to investigate the effect of the artesunate on hyperoxia-induced lung injury in neonatal mice and its mechanism. A BPD model of hyperoxic lung injury in neonatal mice was established after hyperoxia (75% oxygen) exposure for 14 days, and part of the mice received intraperitoneal injections of the artesunate. H&E staining was used to observe the pathology of lung tissue, and the degree of oxidative stress in the lung tissue was determined by commercial kits. The levels of inflammatory cytokines in the serum and lung tissues of neonatal mice were detected by an enzyme-linked immunosorbent assay. Immunohistochemical experiments were performed to further evaluate the expression of IL-1β. The real-time quantitative polymerase chain reaction was used to determine the mRNA level of the NLRP3 inflammasome. The western blot assay was used to measure the levels of NLRP3 inflammasome and NF-κB pathway-related proteins. Artesunate ameliorated weight loss and lung tissue injury in neonatal mice induced by hyperoxia. The level of malondialdehyde was decreased, while the activity of superoxide dismutase and the level of glutathione increased after artesunate treatment. Artesunate reduced the level of inflammation cytokines TNF-α, IL-6, and IL-1β in the serum and lung. Moreover, artesunate inhibited the mRNA expression and protein levels of NLRP3, ASC, and caspase-1, as well as the phosphorylation of the NF-κB and IκBα. Our findings suggest that artesunate treatment can attenuate hyperoxia-induced lung injury in BPD neonatal mice by inhibiting the activation of NLRP3 inflammasome and the phosphorylation of the NF-κB pathway.

Exercise and hypoxia unmask pulmonary vascular disease and right ventricular dysfunction in a 10- to 12-week-old swine model of neonatal oxidative injury

Prematurely born young adults who experienced neonatal oxidative injury (NOI) of the lungs have increased incidence of cardiovascular disease. Here, we investigated the long-term effects of NOI on cardiopulmonary function in piglets at the age of 10-12 weeks. To induce NOI, term-born piglets (1.81 ± 0.06 kg) were exposed to hypoxia (10-12%F iO 2 ${F}_{{\rm{iO}}_{\rm{2}}}$ ), within 2 days after birth, and maintained for 4 weeks or until symptoms of heart failure developed (range 16-28 days), while SHAM piglets were normoxia raised. Following recovery (>5 weeks), NOI piglets were surgically instrumented to measure haemodynamics during hypoxic challenge testing (HCT) and exercise with modulation of the nitric-oxide system. During exercise, NOI piglets showed a normal increase in cardiac index, but an exaggerated increase in pulmonary artery pressure and a blunted increase in left atrial pressure - suggesting left atrial under-filling - consistent with an elevated pulmonary vascular resistance (PVR), which correlated with the duration of hypoxia exposure. Moreover, hypoxia duration correlated inversely with stroke volume (SV) during exercise. Nitric oxide synthase inhibition and HCT resulted in an exaggerated increase in PVR, while the PVR reduction by phosphodiesterase-5 inhibition was enhanced in NOI compared to SHAM piglets. Finally, within the NOI piglet group, prolonged duration of hypoxia was associated with a better maintenance of SV during HCT, likely due to the increase in RV mass. In conclusion, duration of neonatal hypoxia appears an important determinant of alterations in cardiopulmonary function that persist further into life. These changes encompass both pulmonary vascular and cardiac responses to hypoxia and exercise. KEY POINTS: Children who suffered from neonatal oxidative injury, such as very preterm born infants, have increased risk of cardiopulmonary disease later in life. Risk stratification requires knowledge of the mechanistic underpinning and the time course of progression into cardiopulmonary disease. Exercise and hypoxic challenge testing showed that 10- to 12-week-old swine that previously experienced neonatal oxidative injury had increased pulmonary vascular resistance and nitric oxide dependency. Duration of neonatal oxidative injury was a determinant of structural and functional cardiopulmonary remodelling later in life. Remodelling of the right ventricle, as a result of prolonged neonatal oxidative injury, resulted in worse performance during exercise, but enabled better performance during the hypoxic challenge test. Increased nitric oxide dependency together with age- or comorbidity-related endothelial dysfunction may contribute to predisposition to pulmonary hypertension later in life.

Supplemental oxygen strategies in infants with bronchopulmonary dysplasia after the neonatal intensive care unit period: study protocol for a randomised controlled trial (SOS BPD study)

INTRODUCTION

Supplemental oxygen is the most important treatment for preterm born infants with established bronchopulmonary dysplasia (BPD). However, it is unknown what oxygen saturation levels are optimal to improve outcomes in infants with established BPD from 36 weeks postmenstrual age (PMA) onwards. The aim of this study is to compare the use of a higher oxygen saturation limit (≥95%) to a lower oxygen saturation limit (≥90%) after 36 weeks PMA in infants diagnosed with moderate or severe BPD.

METHODS AND ANALYSIS

This non-blinded, multicentre, randomised controlled trial will recruit 198 preterm born infants with moderate or severe BPD between 36 and 38 weeks PMA. Infants will be randomised to either a lower oxygen saturation limit of 95% or to a lower limit of 90%; supplemental oxygen and/or respiratory support will be weaned based on the assigned lower oxygen saturation limit. Adherence to the oxygen saturation limit will be assessed by extracting oxygen saturation profiles from pulse oximeters regularly, until respiratory support is stopped. The primary outcome is the weight SD score at 6 months of corrected age. Secondary outcomes include anthropometrics collected at 6 and 12 months of corrected age, rehospitalisations, respiratory complaints, infant stress, parental quality of life and cost-effectiveness.

ETHICS AND DISSEMINATION

Ethical approval for the trial was obtained from the Medical Ethics Review Committee of the Erasmus University Medical Centre, Rotterdam, the Netherlands (MEC-2018-1515). Local approval for conducting the trial in the participating hospitals has been or will be obtained from the local institutional review boards. Informed consent will be obtained from the parents or legal guardians of all study participants.

TRIAL REGISTRATION NUMBER

NL7149/NTR7347.

Prematurity and Pulmonary Vein Stenosis: The Role of Parenchymal Lung Disease and Pulmonary Vascular Disease

Pulmonary vein stenosis (PVS) has emerged as a critical problem in premature infants with persistent respiratory diseases, particularly bronchopulmonary dysplasia (BPD). As a parenchymal lung disease, BPD also influences vascular development with associated pulmonary hypertension recognized as an important comorbidity of both BPD and PVS. PVS is commonly detected later in infancy, suggesting additional postnatal factors that contribute to disease development, progression, and severity. The same processes that result in BPD, some of which are inflammatory-mediated, may also contribute to the postnatal development of PVS. Although both PVS and BPD are recognized as diseases of inflammation, the link between them is less well-described. In this review, we explore the relationship between parenchymal lung diseases, BPD, and PVS, with a specific focus on the epidemiology, clinical presentation, risk factors, and plausible biological mechanisms in premature infants. We offer an algorithm for early detection and prevention and provide suggestions for research priorities.

Simvastatin Inhibits NLRP3 Inflammasome Activation and Ameliorates Lung Injury in Hyperoxia-Induced Bronchopulmonary Dysplasia via the KLF2-Mediated Mechanism

Bronchopulmonary dysplasia (BPD) is a chronic lung disease commonly found in premature infants. Excessive inflammation and oxidative stress contribute to BPD occurrence and development. Simvastatin, as an inhibitor of HMG-CoA reductase, has been reported to have antioxidative and anti-inflammatory effects. However, its effect and possible mechanisms in hyperoxia-induced lung injury are rarely reported. In this study, in vivo and in vitro experiments were conducted to investigate whether simvastatin could ameliorate hyperoxia-induced lung injury and explore its potential mechanism. For the in vivo study, simvastatin could improve alveolar development after hyperoxic lung injury and reduce hyperoxic stress and inflammation. The in vitro study revealed that simvastatin can reduce inflammation in A549 cells after high-oxygen exposure. Simvastatin suppressed NLRP3 inflammasome activation and played anti-inflammatory and antioxidant roles by increasing KLF2 (Krüppel-like factor 2) expression. In vitro experiments also revealed that these effects of simvastatin were partially reversed by KLF2 shRNA, indicating that KLF2 was involved in simvastatin effects. In summary, our findings indicate that simvastatin could downregulate NLRP3 inflammasome activation and attenuate lung injury in hyperoxia-induced bronchopulmonary dysplasia via KLF2-mediated mechanism.

Stem-Cell Therapy for Bronchopulmonary Dysplasia (BPD) in Newborns

Premature newborns are at a higher risk for the development of respiratory distress syndrome (RDS), acute lung injury (ALI) associated with lung inflammation, disruption of alveolar structure, impaired alveolar growth, lung fibrosis, impaired lung angiogenesis, and development of bronchopulmonary dysplasia (BPD) with severe long-term developmental adverse effects. The current therapy for BPD is limited to supportive care including high-oxygen therapy and pharmacotherapy. Recognizing more feasible treatment options to improve lung health and reduce complications associated with BPD is essential for improving the overall quality of life of premature infants. There is a reduction in the resident stem cells in lungs of premature infants with BPD, which strongly suggests a critical role of stem cells in BPD pathogenesis; this warrants the exploration of the potential therapeutic use of stem-cell therapy. Stem-cell-based therapies have shown promise for the treatment of many pathological conditions including acute lung injury and BPD. Mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles (EVs) including exosomes are promising and effective therapeutic modalities for the treatment of BPD. Treatment with MSCs and EVs may help to reduce lung inflammation, improve pulmonary architecture, attenuate pulmonary fibrosis, and increase the survival rate.

Revisited Hyperoxia Pathophysiology in the Perioperative Setting: A Narrative Review

The widespread use of high-dose oxygen, to avoid perioperative hypoxemia along with WHO-recommended intraoperative hyperoxia to reduce surgical site infections, is an established clinical practice. However, growing pathophysiological evidence has demonstrated that hyperoxia exerts deleterious effects on many organs, mainly mediated by reactive oxygen species. The purpose of this narrative review was to present the pathophysiology of perioperative hyperoxia on surgical wound healing, on systemic macro and microcirculation, on the lungs, heart, brain, kidneys, gut, coagulation, and infections. We reported here that a high systemic oxygen supply could induce oxidative stress with inflammation, vasoconstriction, impaired microcirculation, activation of hemostasis, acute and chronic lung injury, coronary blood flow disturbances, cerebral ischemia, surgical anastomosis impairment, gut dysbiosis, and altered antibiotics susceptibility. Clinical studies have provided rather conflicting results on the definitions and outcomes of hyperoxic patients, often not speculating on the biological basis of their results, while this review highlighted what happens when supranormal PaO₂ values are reached in the surgical setting. Based on the assumptions analyzed in this study, we may suggest that the maintenance of PaO₂ within physiological ranges, avoiding unnecessary oxygen administration, may be the basis for good clinical practice.

Recent Advances in ROS-Sensitive Nano-Formulations for Atherosclerosis Applications

Over the past decade, ROS-sensitive formulations have been widely used in atherosclerosis applications such as ROS scavenging, drug delivery, gene delivery, and imaging. The intensified interest in ROS-sensitive formulations is attributed to their unique self-adaptive properties, involving the main molecular mechanisms of solubility switch and degradation under the pathological ROS differences in atherosclerosis. This review outlines the advances in the use of ROS-sensitive formulations in atherosclerosis applications during the past decade, especially highlighting the general design requirements in relation to biomedical functional performance.

Bronchopulmonary Dysplasia and Pulmonary Hypertension. The Role of Smooth Muscle adh5

Bronchopulmonary dysplasia (BPD) is characterized by alveolar simplification, airway hyperreactivity, and pulmonary hypertension. In our BPD model, we have investigated the metabolism of the bronchodilator and pulmonary vasodilator GSNO (S-nitrosoglutathione). We have shown the GSNO catabolic enzyme encoded by adh5 (alcohol dehydrogenase-5), GSNO reductase, is epigenetically upregulated in hyperoxia. Here, we investigated the distribution of GSNO reductase expression in human BPD and created an animal model that recapitulates the human data. Blinded comparisons of GSNO reductase protein expression were performed in human lung tissues from infants and children with and without BPD. BPD phenotypes were evaluated in global (adh5^-/-) and conditional smooth muscle (smooth muscle/adh5^-/-) adh5 knockout mice. GSNO reductase was prominently expressed in the airways and vessels of human BPD subjects. Compared with controls, expression was greater in BPD smooth muscle, particularly in vascular smooth muscle (2.4-fold; P = 0.003). The BPD mouse model of neonatal hyperoxia caused significant alveolar simplification, airway hyperreactivity, and right ventricular and vessel hypertrophy. Global adh5^-/- mice were protected from all three aspects of BPD, whereas smooth muscle/adh5^-/- mice were only protected from pulmonary hypertensive changes. These data suggest adh5 is required for the development of BPD. Expression in the pulmonary vasculature is relevant to the pathophysiology of BPD-associated pulmonary hypertension. GSNO-mimetic agents or GSNO reductase inhibitors, both of which are currently in clinical trials for other conditions, could be considered for further study in BPD.

Red cell distribution width as a predictor for bronchopulmonary dysplasia in premature infants

Bronchopulmonary dysplasia (BPD) is the most common morbidity complicating preterm birth. Red blood cell distribution width (RDW), a measure of the variation of red blood cell size, could reflect oxidative stress and chronic inflammation in many diseases such as cardiovascular, pulmonary, and other diseases. The objectives of the present study were to evaluate perinatal factors affecting RDW and to validate whether RDW could be a potential biomarker for BPD. A total of 176 preterm infants born at < 30 weeks were included in this study. They were categorized into BPD (n = 85) and non-BPD (n = 91) infants. RDW at birth and 14 days and 28 days of life (DOL 14, DOL 28) were measured. Clinical data were obtained from all subjects at Fukushima Medical University (Fukushima, Japan). The mean RDW at birth, DOL 14 and DOL 28 were 16.1%, 18.6%, 20.1%, respectively. Small for gestational age (SGA), chorioamnionitis (CAM), hypertensive disorders of pregnancy (HDP), gestational age and birth weight were significantly associated with RDW at birth. SGA, BPD and red blood cell (RBC) transfusion before DOL 14 were associated with RDW at DOL 14. BPD and RBC transfusion before DOL 14 were associated with RDW at DOL 28. Compared with non-BPD infants, mean RDW at DOL 14 (21.1% vs. 17.6%, P < 0.001) and DOL 28 (22.2% vs. 18.2%, P < 0.001) were significantly higher in BPD infants. Multivariate analysis revealed that RDW at DOL 28 was significantly higher in BPD infants (P = 0.001, odds ratio 1.63; 95% CI 1.22–2.19). Receiver operating characteristic analysis for RDW at DOL 28 in infants with and without BPD yielded an area under the curve of 0.87 (95% CI 0.78–0.91, P < 0.001). RDW at DOL 28 with mild BPD (18.1% vs. 21.3%, P < 0.001), moderate BPD (18.1% vs. 21.2%, P < 0.001), and severe BPD (18.1% vs. 24.0%, P < 0.001) were significantly higher than those with non-BPD, respectively. Furthermore, there are significant differences of RDW at DOL 28 among mild, moderate, and severe BPD. In summary, we conclude that RDW at DOL 28 could serve as a biomarker for predicting BPD and its severity. The mechanism by which RDW at DOL 28 is associated with the pathogenesis of BPD needs further elucidation.

Adrenomedullin regulated by miRNA-574-3p protects premature infants with bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease (CLD) in premature infants. The present study was designed to elucidate the regulation of miRNA-547-3p on adrenomedullin (ADM) during the pathogenesis of BPD. We used Agilent Human 4x44K Gene Expression Microarrays v2 and miRCURY LNA™ microRNA Array to identify the differently expressed miRNA and its potential target genes, and certified them again by luciferase reporter gene analysis. We only retained target genes that met the following two conditions: first, coexisting in two databases, and second, expressing differences, and then identifying target genes by luciferase reporter gene analysis. Thus, we selected miRNA-574-3p and its target gene ADM for further research. We used real-time q-PCR to determine the expression of miRNA-574-3p and its target gene ADM in premature infants with BPD. We used microarray expression to analyze BPD samples and non-BPD samples and found that there were 516 differently expressed probes between them. The 516 differently expressed probes included 408 up-regulated probes and 108 down-regulated probes. The blood samples of BPD infants were detected by real-time q-PCR and found that the expression of miRNA-574-3p was decreased, while the expression of ADM was significantly increased. Luciferase reporter gene analysis showed that hsa-miR-574-3p can regulate the expression of luciferase with ADM 3′UTR, and decrease it by 61.84%. It has been reported in the literature that ADM can protect the premature infants with BPD. The target gene ADM of miRNA-574-3p may contribute to the prevention and treatment of BPD.

Caffeine prevents hyperoxia-induced lung injury in neonatal mice through NLRP3 inflammasome and NF-κB pathway

Background

Bronchopulmonary dysplasia (BPD) is a common chronic lung disease in premature infants and hyperoxia exposure is a major cause. In hyperoxic lung injury animal model, alveolar simplification and pro-inflammatory cells infiltration are the main pathophysiologic changes. Caffeine is a drug used to treat apnea in premature infants. Early use of caffeine can decrease the rate and the severity of BPD while the mechanisms are still unclear. The purpose of this study was to evaluate the effects of caffeine on inflammation and lung development in neonatal mice with hyperoxic lung injury and to explore the possible mechanism.

Methods

Following 14 d of 75% oxygen exposure in newborn mouse, the BPD model was established. Caffeine at a dose of 1 g/L was added in drinking water to nursing mouse. We measured the concentration of caffeine in serum and oxidative stress in lung by commercially available kits. Adenosine 2A receptor (A_2AR) expression and lung inflammation were measured by Immunohistochemistry and western blotting. Apoptosis and surfactant protein-C (SFTPC) levels were measured by immunofluorescence. The inflammasome and NF-κB pathway proteins were assessed by western blotting.

Results

We found that the caffeine concentration in plasma at present dose significantly decreased the expression of A_2AR protein in mice lung. Caffeine treatment significantly reduced oxidative stress, improved weight gain, promoted alveolar development, attenuated inflammatory infiltration and lung injury in hyperoxia-induced lung injury mice. Moreover, caffeine decreased the cell apoptosis in lung tissues, especially the Type II alveolar epithelial cell. The expression of NLRP3 inflammasome protein and NF-κB pathway were significantly inhibited by caffeine treatment.

Conclusion

Caffeine treatment can protect hyperoxia-induced mice lung from oxidative injury by inhibiting NLRP3 inflammasome and NF-κB pathway.

Oxygen injury in neonates: which is worse? hyperoxia, hypoxia, or alternating hyperoxia/hypoxia

Premature birth results in an increased risk of respiratory distress and often requires oxygen therapy. While the supplemental oxygen has been implicated as a cause of bronchopulmonary dysplasia (BPD), in clinical practice this supplementation usually only occurs after the patient's oxygen saturation levels have dropped. The effect of hyperoxia on neonates has been extensively studied. However, there is an unanswered fundamental question: which has the most impact-hyperoxia, hypoxia or fluctuating oxygen levels? In this review, we will summarize the reported effect of hypoxia, hyperoxia or a fluctuation of oxygen levels (hypoxia/hyperoxia cycling) in preterm neonates, with special emphasis on the lungs.

Prognostic Value of Oxidative Stress Markers in Patients with Pulmonary Arterial or Chronic Thromboembolic Pulmonary Hypertension

Oxidative stress is regarded to play a crucial role in the pathophysiology of pulmonary arterial hypertension (PAH) and inoperable chronic thromboembolic pulmonary hypertension (CTEPH). This study evaluated the prognostic value of serum oxidative stress markers (malondialdehyde (MDA), total antioxidant capacity (TAC), catalase activity (CAT), and superoxide activity (SOD)) in patients with PAH and CTEPH (n = 45). During 13 months of follow-up (median 9 months), clinical deterioration occurred in 14 patients (including 2 deaths). On the Cox regression analysis, MDA, TAC, and CAT were associated with clinical deterioration (p = 0.0068, HR = 1.42, 95% CI: 1.10-1.82; p = 0.0038, HR = 0.033, 95% CI: 0.0032-0.33; and p = 0.046, HR = 0.20, 95% CI: 0.04-0.98, respectively). There was no significant difference in SOD (p = 0.53, HR = 0.97, 95% CI: 0.87-1.08). The cut-off value derived from ROC curve analysis was 3.79 μM (p = 0.0048, AUC = 0.76, 95% CI: 0.62-0.91) for MDA, 0.49 mM (p = 0.027, AUC = 0.71, 95% CI: 0.18-0.47) for TAC, and 1.34 U/L (p = 0.029, AUC = 0.71, 95% CI: 0.55-0.86) for CAT. MDA in the group with deterioration was higher (p = 0.0041), while TAC as well as CAT were lower (p = 0.027 and p = 0.028, respectively) when compared to stable patients. Survival without clinical deterioration was significantly longer in patients with lower MDA (p = 0.037, HR = 0.37, 95% CI: 0.12-1.14, log-rank), higher TAC (p = 0.0018, HR = 0.19, 95% CI: 0.06-0.60, log-rank), and higher CAT (p = 0.044, HR = 0.31 95% CI: 0.11-0.88, log-rank). Markers of oxidative stress such as MDA, TAC, and CAT were associated with adverse clinical outcomes in patients with PAH and inoperable or residual CTEPH.

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.

Autophagy in pulmonary hypertension: Emerging roles and therapeutic implications

Autophagy is an important mechanism for cellular self-digestion and basal homeostasis. This gene- and modulator-regulated pathway is conserved in cells. Recently, several studies have shown that autophagic dysfunction is associated with pulmonary hypertension (PH). However, the relationship between autophagy and PH remains controversial. In this review, we mainly introduce the effects of autophagy-related genes and some regulatory molecules on PH and the relationship between autophagy and PH under the conditions of hypoxia, monocrotaline injection, thromboembolic stress, oxidative stress, and other drugs and toxins. The effects of other autophagy-related drugs, such as chloroquine, 3-methyladenine, rapamycin, and other potential therapeutic drugs and targets, in PH are also described.

Changes in the nitric oxide pathway of the pulmonary vasculature after exposure to hypoxia in swine model of neonatal pulmonary vascular disease

Neonatal pulmonary vascular disease (PVD) is increasingly recognized as a disease that complicates the cardiopulmonary adaptations after birth and predisposes to long-term cardiopulmonary disease. There is growing evidence that PVD is associated with disruptions in the nitric oxide (NO)-cGMP-phosphodiesterase 5 (PDE5) pathway. Examination of the functionality of different parts of this pathway is required for better understanding of the pathogenesis of neonatal PVD. For this purpose, the role of the NO-cGMP-PDE5 pathway in regulation of pulmonary vascular function was investigated in vivo, both at rest and during exercise, and in isolated pulmonary small arteries in vitro, in a neonatal swine model with hypoxia-induced PVD. Endothelium-dependent vasodilatation was impaired in piglets with hypoxia-induced PVD both in vivo at rest and in vitro. Moreover, the responsiveness to the NO-donor SNP was reduced in hypoxia-exposed piglets in vivo, while the relaxation to SNP and 8-bromo-cyclicGMP in vitro were unaltered. Finally, PDE5 inhibition-induced pulmonary vasodilatation was impaired in hypoxia-exposed piglets both in vitro and in vivo at rest. During exercise, however, the pulmonary vasodilator effect of PDE5 inhibition was significantly larger in hypoxia-exposed as compared to normoxia-exposed piglets. In conclusion, the impaired endothelium-dependent vasodilatation in piglets with hypoxia-induced PVD was accompanied by reduced responsiveness to NO, potentially caused by altered sensitivity and/or activity of soluble guanylyl cyclase (sGC), resulting in an impaired cGMP production. Our findings in a newborn animal model for neonatal PVD suggests that sGC stimulators/activators may be a novel treatment strategy to alleviate neonatal PVD.

Long-term pulmonary vascular consequences of perinatal insults

Development of the pulmonary circulation is a critical component of fetal lung development, and continues throughout infancy and childhood, marking an extended window of susceptibility to vascular maldevelopment and maladaptation. Perinatal vascular insults may result in abnormal vascular structure or function, including decreased angiogenic signaling and vascular endowment, impaired vasoreactivity through increased pulmonary artery endothelial dysfunction and remodeling, or enhanced genetic susceptibility to pulmonary vascular disease through epigenetic modifications or germline mutations. Although some infants develop early onset pulmonary hypertension, due to the unique adaptive capabilities of the immature host many do not have clinically evident early pulmonary vascular dysfunction. These individuals remain at increased risk for development of late-onset pulmonary hypertension, and may be particularly susceptible to secondary insults. This review will address the role of perinatal vascular insults in the development of late pulmonary vascular dysfunction with an effort to highlight areas of critical research need.

Long-term pulmonary and cardiovascular morbidities of neonatal hyperoxia exposure in mice

Pulmonary hypertension (PH) frequently occurs in infants with bronchopulmonary dysplasia (BPD), causing increased mortality and right ventricular (RV) dysfunction that persists into adulthood. A first step in developing better therapeutic options is identifying and characterizing an appropriate animal model. Previously, we characterized the short-term morbidities of a model in which C57BL/6J wild-type (WT) mice were exposed to 70% O2 (hyperoxia) during the neonatal period. Here, we aimed to determine the long-term morbidities using lung morphometry, echocardiography (Echo), and cardiac magnetic resonance imaging (cMRI). The major highlight of this study is the use of the state-of-the art imaging technique, cMRI, in mice to characterize the long-term cardiac effects of neonatal hyperoxia exposure. To this end, WT mice were exposed to 21% O2 (normoxia) or hyperoxia for two weeks of life, followed by recovery in normoxia for six weeks. Alveolarization, pulmonary vascularization, pulmonary hypertension, and RV function were quantified at eight weeks. We found that hyperoxia exposure resulted in persistent alveolar and pulmonary vascular simplification. Furthermore, the Echo and cMRI studies demonstrated that hyperoxia-exposed mice had signs of PH and RV dysfunction as indicated by increased RV pressure, mass, and end-systolic and -diastolic volumes, and decreased RV stroke volume and ejection fractions. Taken together, our results demonstrate that neonatal hyperoxia exposure in mice cause cardiopulmonary morbidities that persists into adulthood and provides evidence for the use of this model to develop novel therapies for BPD infants with PH.

Oxidative stress and its possible relation to lower urinary tract functional pathology

Oxidative stress is considered to reflect an imbalance between the systemic manifestation of reactive oxygen and nitrogen species (RONS) and a biological system's ability to readily detoxify the reactive intermediates or to repair the resulting damage. RONS are not only harmful agents that cause oxidative damage in pathologies; they also have important roles as regulatory agents in a range of biological phenomena. They are normally generated as by-products of oxygen metabolism; however, environmental stressors (i.e., ultraviolet radiation, ionizing radiations, pollutants, heavy metal, and xenobiotics) contribute to greatly increase RONS production. Several antioxidants have been exploited in recent years for their actual or supposed beneficial effect against oxidative stress, but to date, none has been approved for any indication because they have not met the criteria of efficacy for drug approval. The present review discusses the concept of oxidative stress, how to measure it, how to prevent it, and its occurrence in different organ systems with special reference to the lower urinary tract.