Effects of intermittent hypoxia and hyperoxia on angiogenesis and lung development in newborn mice

Caffeine: The Story beyond Oxygen-Induced Lung and Brain Injury in Neonatal Animal Models-A Narrative Review

Caffeine is one of the most commonly used drugs in intensive care to stimulate the respiratory control mechanisms of very preterm infants. Respiratory instability, due to the degree of immaturity at birth, results in apnea of prematurity (AOP), hyperoxic, hypoxic, and intermittent hypoxic episodes. Oxidative stress cannot be avoided as a direct reaction and leads to neurological developmental deficits and even a higher prevalence of respiratory diseases in the further development of premature infants. Due to the proven antioxidant effect of caffeine in early use, largely protective effects on clinical outcomes can be observed. This is also impressively observed in experimental studies of caffeine application in oxidative stress-adapted rodent models of damage to the developing brain and lungs. However, caffeine shows undesirable effects outside these oxygen toxicity injury models. This review shows the effects of caffeine in hyperoxic, hypoxic/hypoxic-ischemic, and intermittent hypoxic rodent injury models, but also the negative effects on the rodent organism when caffeine is administered without exogenous oxidative stress. The narrative analysis of caffeine benefits in cerebral and pulmonary preterm infant models supports protective caffeine use but should be given critical consideration when considering caffeine treatment beyond the recommended corrected gestational age.

Correlation Between HIF1-A Expression and Airway Remodeling in COPD

Background

Airway remodeling is a significant pathological characteristic of chronic obstructive pulmonary disease (COPD). In recent years, hypoxia-inducible factor 1-α (HIF-1α), a member of the hypoxia-inducible factor protein family, has gained attention. However, the potential correlation between HIF-1α and COPD airway remodeling remains unclear.

Objective

This study explored the expression patterns of HIF-1α in patients with COPD and its association with airway remodelling. This investigation aims to furnish novel insights for the clinical identification of prospective therapeutic targets for ameliorating COPD-related airway remodelling.

Patients and Methods

A total of 88 subjects were included, consisting of 28 controls and 60 COPD patients. Various staining methods were employed to observe the pathological changes in airway tissues. Immunohistochemistry was utilized to detect the expression of HIF-1α and MMP9 (matrix metalloproteinase 9) in airway tissues. Enzyme-linked immunosorbent assay (ELISA) was used to measure the concentration in serum of HIF-1α and MMP9. Computed tomography (CT) airway parameters were measured in all participants to assess airway remodeling. The relationship between serum HIF-1α and MMP9 concentrations and airway parameters was analyzed.

Results

Staining of airway structures in COPD patients revealed significant pathological changes associated with airway remodelling, including mixed cilia and subepithelial fibrosis. The expression of HIF-1α and MMP9 was significantly higher in both human airway tissue and serum compared to controls. Chest CT scans exhibited typical imaging features of airway remodeling and increased airway parameters.

Conclusion

The findings suggest a correlation between increased HIF-1α expression and COPD airway remodelling. This study provides novel evidence that HIF-1α may be a potential biomarker for airway remodelling in COPD patients.

Oxygen and mechanical stretch in the developing lung: risk factors for neonatal and pediatric lung disease

Chronic airway diseases, such as wheezing and asthma, remain significant sources of morbidity and mortality in the pediatric population. This is especially true for preterm infants who are impacted both by immature pulmonary development as well as disproportionate exposure to perinatal insults that may increase the risk of developing airway disease. Chronic pediatric airway disease is characterized by alterations in airway structure (remodeling) and function (increased airway hyperresponsiveness), similar to adult asthma. One of the most common perinatal risk factors for development of airway disease is respiratory support in the form of supplemental oxygen, mechanical ventilation, and/or CPAP. While clinical practice currently seeks to minimize oxygen exposure to decrease the risk of bronchopulmonary dysplasia (BPD), there is mounting evidence that lower levels of oxygen may carry risk for development of chronic airway, rather than alveolar disease. In addition, stretch exposure due to mechanical ventilation or CPAP may also play a role in development of chronic airway disease. Here, we summarize the current knowledge of the impact of perinatal oxygen and mechanical respiratory support on the development of chronic pediatric lung disease, with particular focus on pediatric airway disease. We further highlight mechanisms that could be explored as potential targets for novel therapies in the pediatric population.

Intermittent Hypoxia-Hyperoxia and Oxidative Stress in Developing Human Airway Smooth Muscle

Premature infants are frequently and intermittently administered supplemental oxygen during hypoxic episodes, resulting in cycles of intermittent hypoxia and hyperoxia. The relatively hypoxic in utero environment is important for lung development while hyperoxia during the neonatal period is recognized as detrimental towards the development of diseases such as bronchopulmonary dysplasia and bronchial asthma. Understanding early mechanisms that link hypoxic, hyperoxic, and intermittent hypoxic-hyperoxic exposures to altered airway structure and function are key to developing advanced therapeutic approaches in the clinic. Changes in oxygen availability can be detrimental to cellular function and contribute to oxidative damage. Here, we sought to determine the effect of oxygen on mitochondria in human fetal airway smooth muscle cells exposed to either 5% O₂, 21% O₂, 40% O₂, or cycles of 5% and 40% O₂ (intermittent hypoxia-hyperoxia). Reactive oxygen species production, altered mitochondrial morphology, and changes in mitochondrial respiration were assessed in the context of the antioxidant N-acetylcysteine. Our findings show developing airway smooth muscle is differentially responsive to hypoxic, hyperoxic, or intermittent hypoxic-hyperoxic exposure in terms of mitochondrial structure and function. Cycling O₂ decreased mitochondrial branching and branch length similar to hypoxia and hyperoxia in the presence of antioxidants. Additionally, hypoxia decreased overall mitochondrial respiration while the addition of antioxidants increased respiration in normoxic and O₂-cycling conditions. These studies show the necessity of balancing oxidative damage and antioxidant defense systems in the developing airway.

Intrauterine Hypoxia and Epigenetic Programming in Lung Development and Disease

Clinically, intrauterine hypoxia is the foremost cause of perinatal morbidity and developmental plasticity in the fetus and newborn infant. Under hypoxia, deviations occur in the lung cell epigenome. Epigenetic mechanisms (e.g., DNA methylation, histone modification, and miRNA expression) control phenotypic programming and are associated with physiological responses and the risk of developmental disorders, such as bronchopulmonary dysplasia. This developmental disorder is the most frequent chronic pulmonary complication in preterm labor. The pathogenesis of this disease involves many factors, including aberrant oxygen conditions and mechanical ventilation-mediated lung injury, infection/inflammation, and epigenetic/genetic risk factors. This review is focused on various aspects related to intrauterine hypoxia and epigenetic programming in lung development and disease, summarizes our current knowledge of hypoxia-induced epigenetic programming and discusses potential therapeutic interventions for lung disease.

Intratracheal administration of mesenchymal stem cell-derived extracellular vesicles reduces lung injuries in a chronic rat model of bronchopulmonary dysplasia

Early therapeutic effect of intratracheally (IT)-administered extracellular vesicles secreted by mesenchymal stem cells (MSC-EVs) has been demonstrated in a rat model of bronchopulmonary dysplasia (BPD) involving hyperoxia exposure in the first 2 postnatal weeks. The aim of this study was to evaluate the protective effects of IT-administered MSC-EVs in the long term. EVs were produced from MSCs following GMP standards. At birth, rats were distributed in three groups: (a) animals raised in ambient air for 6 weeks (n = 10); and animals exposed to 60% hyperoxia for 2 weeks and to room air for additional 4 weeks and treated with (b) IT-administered saline solution (n = 10), or (c) MSC-EVs (n = 10) on postnatal days 3, 7, 10, and 21. Hyperoxia exposure produced significant decreases in total number of alveoli, total surface area of alveolar air spaces, and proliferation index, together with increases in mean alveolar volume, mean linear intercept and fibrosis percentage; all these morphometric changes were prevented by MSC-EVs treatment. The medial thickness index for <100 µm vessels was higher for hyperoxia-exposed/sham-treated than for normoxia-exposed rats; MSC-EV treatment significantly reduced this index. There were no significant differences in interstitial/alveolar and perivascular F4/8-positive and CD86-positive macrophages. Conversely, hyperoxia exposure reduced CD163-positive macrophages both in interstitial/alveolar and perivascular populations and MSC-EV prevented these hyperoxia-induced reductions. These findings further support that IT-administered EVs could be an effective approach to prevent/treat BPD, ameliorating the impaired alveolarization and pulmonary artery remodeling also in a long-term model. M2 macrophage polarization could play a role through anti-inflammatory and proliferative mechanisms.

BCAT1 binds the RNA-binding protein ZNF423 to activate autophagy via the IRE1-XBP-1-RIDD axis in hypoxic PASMCs

Abnormal functional changes in pulmonary artery smooth muscle cells are the main causes of many lung diseases. Among, autophagy plays a crucial role. However, the specific molecular regulatory mechanism of autophagy in PASMCs remains unclear. Here, we first demonstrate that BCAT1 played a key role in the autophagy of hypoxic PASMCs and hypoxic model rats. BCAT1-induced activation and accumulation of the autophagy signaling proteins BECN1 and Atg5 by the endoplasmic reticulum (ER) stress pathway. Interestingly, we discovered that BCAT1 bound IRE1 on the ER to activate expression of its downstream pathway XBP-1-RIDD axis to activate autophagy. More importantly, we identified an RNA-binding protein, zinc finger protein 423, which promoted autophagy by binding adenylate/uridylate (AU)-rich elements in the BCAT1 mRNA 3′-untranslated region. Overall, our results identify BCAT1 as a potential therapeutic target for the clinical treatment of lung diseases and reveal a novel posttranscriptional regulatory mechanism and signaling pathway in hypoxia-induced PASMC autophagy.

Fatty Acid Oxidation Protects against Hyperoxia-induced Endothelial Cell Apoptosis and Lung Injury in Neonatal Mice

In neonates, hyperoxia or positive pressure ventilation causes continued lung injury characterized by simplified vascularization and alveolarization, which are the hallmarks of bronchopulmonary dysplasia. Although endothelial cells (ECs) have metabolic flexibility to maintain cell function under stress, it is unknown whether hyperoxia causes metabolic dysregulation in ECs, leading to lung injury. We hypothesized that hyperoxia alters EC metabolism, which causes EC dysfunction and lung injury. To test this hypothesis, we exposed lung ECs to hyperoxia (95% O₂/5% CO₂) followed by air recovery (O₂/rec). We found that O₂/rec reduced mitochondrial oxidative phosphorylation without affecting mitochondrial DNA copy number or mitochondrial mass and that it specifically decreased fatty acid oxidation (FAO) in ECs. This was associated with increased ceramide synthesis and apoptosis. Genetic deletion of carnitine palmitoyltransferase 1a (Cpt1a), a rate-limiting enzyme for carnitine shuttle, further augmented O₂/rec-induced apoptosis. O₂/rec-induced ceramide synthesis and apoptosis were attenuated when the FAO was enhanced by l-carnitine. Newborn mice were exposed to hyperoxia (>95% O₂) between Postnatal Days 1 and 4 and were administered l-carnitine (150 and 300 mg/kg, i.p.) or etomoxir, a specific Cpt1 inhibitor (30 mg/kg, i.p.), daily between Postnatal Days 10 and 14. Etomoxir aggravated O₂/rec-induced apoptosis and simplified alveolarization and vascularization in mouse lungs. Similarly, arrested alveolarization and reduced vessel numbers were further augmented in EC-specific Cpt1a-knockout mice compared with wild-type littermates in response to O₂/rec. Treatment with l-carnitine (300 mg/kg) attenuated O₂/rec-induced lung injury, including simplified alveolarization and decreased vessel numbers. Altogether, enhancing FAO protects against hyperoxia-induced EC apoptosis and lung injury in neonates.

Intermittent hypoxia and bronchial hyperreactivity

The premature neonate is at high risk for childhood airway hyperreactivity and episodes of wheezing. Intermittent hypoxic events are frequently observed during the first weeks and months of life in these infants. Intermittent hypoxemia has been associated with adverse outcomes in extremely premature infants; including the diagnosis of bronchopulmonary dysplasia, reported wheezing, and use of prescription asthma medications. We review the incidence of intermittent hypoxia, their potential role in short and longer term respiratory morbidity, and the translational newborn models now being used to investigate common pathways by which intermittent hypoxia contributes to respiratory disease.

Rodent models of respiratory control and respiratory system development-Clinical significance

The newborn infant's respiratory system must rapidly adapt to extra-uterine life. Neonatal rat and mouse models have been used to investigate early development of respiratory control and reactivity in both health and disease. This review highlights several rodent models of control of breathing and respiratory system development (including pulmonary function), discusses their translational strengths and limitations, and underscores the importance of creating clinically relevant models applicable to the human infant.

Effect of intermittent hypoxia or hyperoxia on lung development in preterm rat neonates during constant oxygen therapy

Impaired lung development is a major negative factor in the survival of preterm neonates. The present study was aimed to investigate the impact of constant oxygen, intermittent hyperoxia, and hypoxia on the lung development in preterm rat neonates. Neonatal rats were exposed to 40% O₂ with or without brief hyperoxia episodes (95% O₂ ) or brief hypoxia episodes (10% O₂ ) from day 0 to day 14, or to room air. The body weight, radical alveolar count (RAC), and total antioxidant capacity (TAOC) were significantly lower whereas the lung coefficient and malondialdehyde (MDA) were significantly higher in the hyperoxia and hypoxia groups than the air control and constant oxygen group at day 7, day 14, and day 21 after birth. The lung function indexes were reduced by intermittent hyperoxia and hypoxia. In contrast, the constant oxygen therapy increased the lung function. HIF-1α and VEGF expression were significantly increased by hypoxia and decreased by hyperoxia. The constant oxygen therapy only decreased the HIF-1α expression at day 14 and 21. In summary, the constant oxygen treatment promoted lung function without affecting the antioxidative capacity in preterm rat neonates. While intermittent hyperoxia and hypoxia inhibited lung development, decreased antioxidative capacity, and dysregulated HIF-1α/VEGF signaling in preterm rat neonates.

Bronchopulmonary dysplasia: what are its links to COPD?

Emerging evidence suggests that adverse early life events can affect long-term health trajectories throughout life. Preterm birth, in particular, is a significant early life event that affects approximately 10% of live births. Worldwide, prematurity is the number one cause of death in children less than 5 years of age and has been shown to disrupt normal lung development with lasting effects into adult life. Along with impaired lung development, interventions used to support gas exchange and other sequelae of prematurity can lead to the development of bronchopulmonary dysplasia (BPD). BPD is a chronic respiratory disease of infancy characterized by alveolar simplification, small airways disease, and pulmonary vascular changes. Although many survivors of BPD improve with age, survivors of BPD often have chronic lung disease characterized by airflow obstruction and intermittent pulmonary exacerbations. Long-term lung function trajectories as measured by FEV1 can be lower in children and adults with a history BPD. In this review, we discuss the epidemiology and manifestations of BPD and its long-term consequences throughout childhood and into adulthood. Available evidence suggests that disrupted lung development, genetic susceptibility and subsequent environment and infectious events that occur in prenatal and postnatal life likely increase the predisposition of children with BPD to develop early onset chronic obstructive pulmonary disease (COPD). The reviews of this paper are available via the supplemental material section.

A paradoxical method to enhance compensatory lung growth: Utilizing a VEGF inhibitor

Exogenous vascular endothelial growth factor (VEGF) accelerates compensatory lung growth (CLG) in mice after unilateral pneumonectomy. In this study, we unexpectedly discovered a method to enhance CLG with a VEGF inhibitor, soluble VEGFR1. Eight-week-old C57BL/6 male mice underwent left pneumonectomy, followed by daily intraperitoneal (ip) injection of either saline (control) or 20 μg/kg of VEGFR1-Fc. On post-operative day (POD) 4, mice underwent pulmonary function tests (PFT) and lungs were harvested for volume measurement and analyses of the VEGF signaling pathway. To investigate the role of hypoxia in mediating the effects of VEGFR1, experiments were repeated with concurrent administration of PT-2385, an inhibitor of hypoxia-induced factor (HIF)2α, via orogastric gavage at 10 mg/kg every 12 hours for 4 days. We found that VEGFR1-treated mice had increased total lung capacity (P = 0.006), pulmonary compliance (P = 0.03), and post-euthanasia lung volume (P = 0.049) compared to control mice. VEGFR1 treatment increased pulmonary levels of VEGF (P = 0.008) and VEGFR2 (P = 0.01). It also stimulated endothelial proliferation (P < 0.0001) and enhanced pulmonary surfactant production (P = 0.03). The addition of PT-2385 abolished the increase in lung volume and endothelial proliferation in response to VEGFR1. By paradoxically stimulating angiogenesis and enhancing lung growth, VEGFR1 could represent a new treatment strategy for neonatal lung diseases characterized by dysfunction of the HIF-VEGF pathway.

Recent advances in the pathogenesis of BPD

Bronchopulmonary dysplasia (BPD) continues to be one of the most common complications of preterm birth and is characterized histopathologically by impaired lung alveolarization. Extremely preterm born infants remain at high risk for the development of BPD, highlighting a pressing need for continued efforts to understand the pathomechanisms at play in affected infants. This brief review summarizes recent progress in our understanding of the how the development of the newborn lung is stunted, highlighting recent reports on roles for growth factor signaling, oxidative stress, inflammation, the extracellular matrix and proteolysis, non-coding RNA, and fibroblast and epithelial cell plasticity. Additionally, some concerns about modeling BPD in experimental animals are reviewed, as are new developments in the in vitro modeling of pathophysiological processes relevant to impaired lung alveolarization in BPD.

Hypoxia Delays Oligodendrocyte Progenitor Cell Migration and Myelin Formation by Suppressing Bmp2b Signaling in Larval Zebrafish

Hypoxia in newborns tends to result in developmental deficiencies in the white matter of the brain. As previous studies of the effects of hypoxia on neuronal development in rodents and human infants have been unable to use in vivo imaging, insight into the dynamic development of oligodendrocytes (OLs) in the central nervous system under hypoxia is limited. Here, we developed a visual model to study OL development using sublethal postnatal hypoxia in zebrafish larvae. We observed that hypoxia significantly suppressed OL progenitor cell migration toward the dorsum using in vivo imaging. Further, we found that hypoxia affected myelination, as indicated by thinner myelin sheaths and by a downregulation of myelin basic protein expression. Bmp2b protein expression was also significantly downregulated following hypoxia onset. Using gain of function and loss of function experiments, we demonstrated that the Bmp2b protein was associated with the regulation of OL development. Thus, our work provides a visual hypoxia model within which to observe OL development in vivo, and reveals the underlying mechanisms involved in these processes.

Effects of hypoxia and hyperoxia on the differential expression of VEGF-A isoforms and receptors in Idiopathic Pulmonary Fibrosis (IPF)

Dysregulation of VEGF-A bioavailability has been implicated in the development of lung injury/fibrosis, exemplified by Idiopathic Pulmonary Fibrosis (IPF). VEGF-A is a target of the hypoxic response via its translational regulation by HIF-1α. The role of hypoxia and hyperoxia in the development and progression of IPF has not been explored. In normal lung (NF) and IPF-derived fibroblasts (FF) VEGF-A_xxxa protein expression was upregulated by hypoxia, mediated through activation of VEGF-A_xxxa gene transcription. VEGF-A receptors and co-receptors were differentially expressed by hypoxia and hyperoxia. Our data supports a potential role for hypoxia, hyperoxia and VEGF-A_xxxa isoforms as drivers of fibrogenesis.

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

The objective of lung development is to generate an organ of gas exchange that provides both a thin gas diffusion barrier and a large gas diffusion surface area, which concomitantly generates a steep gas diffusion concentration gradient. As such, the lung is perfectly structured to undertake the function of gas exchange: a large number of small alveoli provide extensive surface area within the limited volume of the lung, and a delicate alveolo-capillary barrier brings circulating blood into close proximity to the inspired air. Efficient movement of inspired air and circulating blood through the conducting airways and conducting vessels, respectively, generates steep oxygen and carbon dioxide concentration gradients across the alveolo-capillary barrier, providing ideal conditions for effective diffusion of both gases during breathing. The development of the gas exchange apparatus of the lung occurs during the second phase of lung development-namely, late lung development-which includes the canalicular, saccular, and alveolar stages of lung development. It is during these stages of lung development that preterm-born infants are delivered, when the lung is not yet competent for effective gas exchange. These infants may develop bronchopulmonary dysplasia (BPD), a syndrome complicated by disturbances to the development of the alveoli and the pulmonary vasculature. It is the objective of this review to update the reader about recent developments that further our understanding of the mechanisms of lung alveolarization and vascularization and the pathogenesis of BPD and other neonatal lung diseases that feature lung hypoplasia.

Diagnostic Approach to Pulmonary Hypertension in Premature Neonates

Bronchopulmonary dysplasia (BPD) is a form of chronic lung disease in premature infants following respiratory distress at birth. With increasing survival of extremely low birth weight infants, alveolar simplification is the defining lung characteristic of infants with BPD, and along with pulmonary hypertension, increasingly contributes to both respiratory morbidity and mortality in these infants. Growth restricted infants, infants born to mothers with oligohydramnios or following prolonged preterm rupture of membranes are at particular risk for early onset pulmonary hypertension. Altered vascular and alveolar growth particularly in canalicular and early saccular stages of lung development following mechanical ventilation and oxygen therapy, results in developmental lung arrest leading to BPD with pulmonary hypertension (PH). Early recognition of PH in infants with risk factors is important for optimal management of these infants. Screening tools for early diagnosis of PH are evolving; however, echocardiography is the mainstay for non-invasive diagnosis of PH in infants. Cardiac computed tomography (CT) and magnetic resonance are being used as imaging modalities, however their role in improving outcomes in these patients is uncertain. Follow-up of infants at risk for PH will help not only in early diagnosis, but also in appropriate management of these infants. Aggressive management of lung disease, avoidance of hypoxemic episodes, and optimal nutrition determine the progression of PH, as epigenetic factors may have significant effects, particularly in growth-restricted infants. Infants with diagnosis of PH are managed with pulmonary vasodilators and those resistant to therapy need to be worked up for the presence of cardio-vascular anomalies. The management of infants and toddlers with PH, especially following premature birth is an emerging field. Nonetheless, combination therapies in a multi-disciplinary setting improves outcomes for these infants.

Pathophysiology, screening and diagnosis of pulmonary hypertension in infants with bronchopulmonary dysplasia - A review of the literature

Bronchopulmonary dysplasia (BPD) is a common complication of extreme prematurity, which has increased over the last 20 years. BPD is associated with increased morbidities and mortality. It has been increasingly recognized that BPD affects overall lung development including the pulmonary vasculature. More recent studies have demonstrated an increased awareness of pulmonary arterial hypertension (PH) in BPD patients and recent international guidelines have advocated for better screening. This review will describe the current understanding of the pathophysiology of PH in infants with BPD, the in-depth assessment of the available literature linking PH and BPD, and propose an approach of screening and diagnosis of PH in infants with BPD.

Long-term effects of recurrent intermittent hypoxia and hyperoxia on respiratory system mechanics in neonatal mice

BACKGROUND

Premature infants are at increased risk for wheezing disorders. Clinically, these neonates experience recurrent episodes of apnea and desaturation often treated by increasing the fraction of inspired oxygen (FIO₂). We developed a novel paradigm of neonatal intermittent hypoxia with subsequent hyperoxia overshoots (CIH_O/E) and hypothesized that CIH_O/E elicits long-term changes on pulmonary mechanics in mice.

METHODS

Neonatal C57BL/6 mice received CIH_O/E, which consisted of 10% O2 (1 min) followed by a transient exposure to 50% FIO₂, on 10-min repeating cycles 24 h/d from birth to P7. Baseline respiratory mechanics, methacholine challenge, RT-PCR for pro and antioxidants, radial alveolar counts, and airway smooth muscle actin were assessed at P21 after 2-wk room air recovery. Control groups were mice exposed to normoxia, chronic intermittent hyperoxia (CIH_E), and chronic intermittent hypoxia (CIH_O).

RESULTS

CIH_O/E and CIH_E increased airway resistance at higher doses of methacholine and decreased baseline compliance compared with normoxia mice. Lung mRNA for NOX2 was increased by CIH_O/E. Radial alveolar counts and airway smooth muscle actin was not different between groups.

CONCLUSION

Neonatal intermittent hypoxia/hyperoxia exposure results in long-term changes in respiratory mechanics. We speculate that recurrent desaturation with hyperoxia overshoot may increase oxidative stress and contribute to wheezing in former preterm infants.

The injury of fine particulate matter from cooking oil fumes on umbilical cord blood vessels in vitro

Cooking oil fumes (COFs) derived PM_2.5 is the major source of indoor air pollution in Asia. For this, a pregnant rat model within different doses of cooking oil fumes (COFs) derived PM_2.5 was established in pregnancy in our research. Our previous studies have showed that exposure to COFs-derived PM_2.5 was related to adverse pregnancy outcomes. However, the mechanisms of signaling pathways remain unknown. Therefore, this study aimed to investigate the underlying mechanisms induced by COFs-derived PM2.5 injury on umbilical cord blood vessels (UCs) in vitro. Exposure to COFs-derived PM_2.5 resulted in changing the expression of eNOS, ET-1, ETRA, and ETRB. In additions, western blot analysis indicated that the HIF-1α/iNOS/NO signaling pathway and VEGF/VEGFR1/iNOS signaling pathway were involved in UCs injury triggered by COFs-derived PM_2.5. In conclusion, our data suggested that exposure to COFs-derived PM_2.5 resulted in increasing of oxidative stress and inflammation, as well as dysfunction of UCs.

Intermittent hypoxia during recovery from neonatal hyperoxic lung injury causes long-term impairment of alveolar development: A new rat model of BPD

Bronchopulmonary dysplasia (BPD) is a chronic lung injury characterized by impaired alveologenesis that may persist into adulthood. Rat models of BPD using varying degrees of hyperoxia to produce injury either cause early mortality or spontaneously recover following removal of the inciting stimulus, thus limiting clinical relevance. We sought to refine an established rat model induced by exposure to 60% O₂ from birth by following hyperoxia with intermittent hypoxia (IH). Rats exposed from birth to air or 60% O₂ until day 14 were recovered in air with or without IH (FI_O2 = 0.10 for 10 min every 6 h) until day 28 Animals exposed to 60% O₂ and recovered in air had no evidence of abnormal lung morphology on day 28 or at 10-12 wk. In contrast, 60% O₂-exposed animals recovered in IH had persistently increased mean chord length, more dysmorphic septal crests, and fewer peripheral arteries. Recovery in IH also increased pulmonary vascular resistance, Fulton index, and arterial wall thickness. IH-mediated abnormalities in lung structure (but not pulmonary hypertension) persisted when reexamined at 10-12 wk, accompanied by increased pulmonary vascular reactivity and decreased exercise tolerance. Increased mean chord length secondary to IH was prevented by treatment with a peroxynitrite decomposition catalyst [5,10,15,20-Tetrakis(4-sulfonatophenyl)-21H,23H-porphyrin iron (III) chloride, 30 mg/kg/day, days 14-28], an effect accompanied by fewer inflammatory cells. We conclude that IH during recovery from hyperoxia-induced injury prevents recovery of alveologenesis and leads to changes in lung and pulmonary vascular function lasting into adulthood, thus more closely mimicking contemporary BPD.