Oxidative stress and bronchopulmonary dysplasia

The Role of Sphingolipid Signaling in Oxidative Lung Injury and Pathogenesis of Bronchopulmonary Dysplasia

Premature infants are born with developing lungs burdened by surfactant deficiency and a dearth of antioxidant defense systems. Survival rate of such infants has significantly improved due to advances in care involving mechanical ventilation and oxygen supplementation. However, a significant subset of such survivors develops the chronic lung disease, Bronchopulmonary dysplasia (BPD), characterized by enlarged, simplified alveoli and deformed airways. Among a host of factors contributing to the pathogenesis is oxidative damage induced by exposure of the developing lungs to hyperoxia. Recent data indicate that hyperoxia induces aberrant sphingolipid signaling, leading to mitochondrial dysfunction and abnormal reactive oxygen species (ROS) formation (ROS). The role of sphingolipids such as ceramides and sphingosine 1-phosphate (S1P), in the development of BPD emerged in the last decade. Both ceramide and S1P are elevated in tracheal aspirates of premature infants of <32 weeks gestational age developing BPD. This was faithfully reflected in the murine models of hyperoxia and BPD, where there is an increased expression of sphingolipid metabolites both in lung tissue and bronchoalveolar lavage. Treatment of neonatal pups with a sphingosine kinase1 specific inhibitor, PF543, resulted in protection against BPD as neonates, accompanied by improved lung function and reduced airway remodeling as adults. This was accompanied by reduced mitochondrial ROS formation. S1P receptor1 induced by hyperoxia also aggravates BPD, revealing another potential druggable target in this pathway for BPD. In this review we aim to provide a detailed description on the role played by sphingolipid signaling in hyperoxia induced lung injury and BPD.

Protective Effects of 18β-Glycyrrhetinic Acid on Neonatal Rats with Hyperoxia Exposure

Bronchopulmonary dysplasia (BPD) is a common devastating pulmonary complication in preterm infants. Supplemental oxygen is a lifesaving therapeutic measure used for premature infants with pulmonary insufficiency. However, oxygen toxicity is a significant trigger for BPD. Oxidative stress disrupts lung development, accompanied by increased pro-inflammatory cytokines and chemokines expression and immune cells infiltration in lung tissue. Licorice, a typical traditional herbal medicine, is commonly used in the medicine and food industries. 18β-Glycyrrhetinic acid (18β-GA), a primary active ingredient of licorice, has powerful anti-oxidative and anti-inflammatory effects. This study aimed to determine whether 18β-GA has a protective effect on neonatal rats with hyperoxia exposure. Newborn Sprague-Dawley rats were kept in either 21% (normoxia) or 80% O₂ (hyperoxia) continuously from postnatal day (PN) 1 to 14. 18β-GA was injected intragastrically at 50 or 100 mg/kg body weight once a day from PN 1 to 14. We examined the body weight and alveolar development and measured ROS level and the markers of pulmonary inflammation. Mature-IL-1β and NF-κB pathway proteins, and the NLRP3 inflammasome, were assessed; concurrently, caspase-1 activity was measured. Our results indicated that hyperoxia resulted in alveolar simplification and decreased bodyweight of neonatal rats. Hyperoxia increased ROS level and pulmonary inflammation and activated NF-κB and the NLRP3 inflammasome. 18β-GA treatment inhibited the activation of NF-κB and the NLRP3 inflammasome, decreased ROS level and pulmonary inflammation, improved alveolar development, and increased the bodyweight of neonatal rats with hyperoxia exposure. Our study demonstrates that 18β-GA has a protective effect on neonatal rats with hyperoxia exposure.

The protective effects of apocynin in hyperoxic lung injury in neonatal rats

AIM

Inflammation and oxidate stress are significant factors in the pathogenesis of bronchopulmonary dysplasia (BPD). The aim of this study is to investigate the efficacy of apocynin (APO), an anti-inflammatory, antioxidant, and antiapoptotic drug, in the prophylaxis of neonatal hyperoxic lung injury.

METHOD

This experimental study included 40 neonatal rats divided into the control, APO, BPD, and BPD + APO groups. The control and APO groups were kept in a normal room environment, while the BPD and BPD + APO groups were kept in a hyperoxic environment. The rats in the APO and BPD + APO groups were administered intraperitoneal APO, while the control and BPD rats were administered ordinary saline. At the end of the trial, lung tissue was evaluated with respect to the degree of histopathological injury, apoptosis, oxidant and antioxidant capacity, and severity of inflammation.

RESULT

The BPD and BPD + APO groups exhibited higher mean histopathological injury and alveolar macrophage scores compared to the control and APO groups. Both scores were lower in the BPD + APO group in comparison to the BPD group. The BPD + APO group had a significantly lower average of TUNEL positive cells than the BPD group. The lung tissue examination indicated significantly higher levels of mean malondialdehyde (MDA), total oxidant status (TOS), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) in the BPD group compared to the control and APO groups. While the TNF-α and IL-1β levels of the BPD + APO group were similar to that of the control group, the MDA and TOS levels were higher compared to the controls and lower compared to the BPD group. The BPD group demonstrated significantly lower levels/activities of mean total antioxidant status, glutathione reductase, superoxide dismutase, glutathione peroxidase in comparison to the control and APO groups. While the mean antioxidant enzyme activity of the BPD + APO group was lower than the control group, it was significantly higher compared to the BPD group.

CONCLUSION

This is the first study in the literature to reveal through an experimental neonatal hyperoxic lung injury that APO, an anti-inflammatory, antioxidant, and antiapoptotic drug, exhibits protective properties against the development of BPD.

Co-expression network analysis for identification of novel biomarkers of bronchopulmonary dysplasia model

BACKGROUND

Bronchopulmonary dysplasia (BPD) is the most common neonatal chronic lung disease. However, its exact molecular pathogenesis is not understood. We aimed to identify relevant gene modules that may play crucial roles in the occurrence and development of BPD by weighted gene co-expression network analysis (WGCNA).

METHODS

We used RNA-Seq data of BPD and healthy control rats from our previous studies, wherein data from 30 samples was collected at days 1, 3, 7, 10, and 14. Data for preprocessing analysis included 17,613 differentially expressed genes (DEGs) with false discovery rate <0.05.

RESULTS

We grouped the highly correlated genes into 13 modules, and constructed a network of mRNA gene associations, including the 150 most associated mRNA genes in each module. Lgals8, Srpra, Prtfdc1, and Thap11 were identified as the key hub genes. Enrichment analyses revealed Golgi vesicle transport, coated vesicle, actin-dependent ATPase activity and endoplasmic reticulum pathways associated with these genes involved in the pathological process of BPD in module.

CONCLUSIONS

This is a study to analyze data obtained from BPD animal model at different time-points using WGCNA, to elucidate BPD-related susceptibility modules and disease-related genes.

The CD146-HIF-1α axis regulates epithelial cell migration and alveolar maturation in a mouse model of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common challenge in preterm neonates. Retardation of alveolar development characterizes the pulmonary pathology in BPD. In the present study, we explored the roles of the CD146-HIF-1α axis in BPD. We demonstrated that the levels of reactive oxygen species (ROS) and soluble CD146 (sCD1146) were increased in the peripheral blood of preterm neonates with BPD. In alveolar epithelial cells, hyperoxia promoted the expression of HIF-1α and CD146, which reinforced each other. In a mouse model of BPD, by exposing pups to 65% hyperoxia, HIF-1α and CD146 were increased in the pulmonary tissues. Mechanistically, CD146 hindered the migration of alveolar epithelial cells; in contrast, movement was significantly enhanced in CD146-knockout alveolar epithelial cells. As expected, CD146-knockout ameliorated alveolarization and improved BPD disease severity. Taken together, our findings imply that the CD146-HIF-1α axis contributes to alveolarization and that CD146 may be a novel candidate in BPD therapy.

Mesenchymal Stem Cell-Derived Extracellular Vesicles for the Treatment of Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is the most common chronic respiratory disease in premature infants. However, there is a lack of effective treatment. Mesenchymal stromal cells derived extracellular vesicles (MSC-EVs), as nano- and micron-sized heterogeneous vesicles secreted by MSCs, are the main medium for information exchange between MSCs and injured tissue and organ, playing an important role in repairing tissue and organ injury. EVs include exosomes, microvesicles and so on. They are rich with various proteins, nucleic acids, and lipids. Now, EVs are considered as a new way of cell-to-cell communication. EVs mainly induce regeneration and therapeutic effects in different tissues and organs through the biomolecules they carry. The surface membrane protein or loaded protein and nucleic acid molecules carried by EVs, can activate the signal transduction of target cells and regulate the biological behavior of target cells after binding and cell internalization. MSC-EVs can promote the development of pulmonary vessels and alveoli and reduce pulmonary hypertension (PH) and inflammation and play an important role in the repair of lung injury in BPD. The regeneration potential of MSC-EVs is mainly due to the regulation of cell proliferation, survival, migration, differentiation, angiogenesis, immunoregulation, anti-inflammatory, mitochondrial activity and oxidative stress. As a new type of cell-free therapy, MSC-EVs have non-immunogenic, and are small in size and go deep into most tissues. What's more, it has good biological stability and can be modified and loaded with drugs of interest. Obviously, MSC-EVs have a good application prospect in the treatment of lung injury and BPD. However, there are still many challenges to make MSC-EVs really enter clinical application.

Urinary biomarkers for the early prediction of bronchopulmonary dysplasia in preterm infants: A pilot study

BACKGROUND

This study investigated whether 8-hydroxy-2'-deoxyguanosine (8-OHdG) and N-terminal pro-brain natriuretic peptide (NT-proBNP) concentrations in the urine could predict bronchopulmonary dysplasia (BPD) in preterm infants.

METHODS

This prospective cohort study enrolled 165 preterm infants, of whom 70 developed BPD. We measured urinary 8-OHdG and NT-proBNP concentrations from day of life (DOL) 7 to 28. Then, we evaluated the prediction efficiency by receiver operating characteristic curves and assessed correlations between the two biomarkers. Finally, we identified the predictive risk factors for BPD by multivariable logistic regression.

RESULTS

8-OHdG and NT-proBNP levels were significantly higher from DOL 7 to 28 in the BPD group than in the control group (P < 0.05). Additionally, the 8-OHdG level was positively correlated with the NT-proBNP level (r: 0.655-0.789, P < 0.001), and the 8-OHdG and NT-proBNP levels were positively correlated with mechanical ventilation duration and oxygen exposure time (r: 0.175-0.505, P < 0.05) from DOL 7 to 28. Furthermore, the 8-OHdG (DOL 14-28) and NT-proBNP (DOL 7-28) levels were significantly associated with BPD development (P < 0.05).

CONCLUSION

The urine 8-OHdG concentrations from DOL 14 to 28 and NT-proBNP concentrations from DOL 7 to 28 may be practical non-invasive predictors of BPD development in preterm infants.

Non-reassuring fetal status and anesthetic impact on cesarean section-delivered very-low-birthweight infants

BACKGROUND

There is limited evidence concerning the impact on neonatal outcomes of different types of anesthesia used for cesarean delivery due to non-reassuring fetal status (NRFS). We aimed to assess the impact of NRFS and general anesthesia (GA) on neonatal outcomes in very-low-birthweight (VLBW) infants delivered by cesarean section.

METHODS

Data were collected relating to VLBW infants admitted to our institution. Infants were grouped into no-NRFS and NRFS groups and further subcategorized into GA and regional anesthesia (RA) subgroups. Neonatal outcomes were evaluated based on the presence of NRFS and the type of anesthesia.

RESULTS

A total of 356 infants were included. The GA subgroup in the no-NRFS group had higher requirements for respiratory support. However, GA was not associated with adverse neonatal outcomes based on the multivariable logistic regression analysis except for 5 min Apgar score <5. On the other hand, NRFS was associated with an increased risk of 5 min Apgar score <5 [adjusted odds ratio (aOR) 2.062, 95% confidence interval (CI) 1.064-3.997], use of high-frequency ventilation (aOR: 2.891, 95% CI: 1.477-5.658), and pulmonary hypertension (aOR: 2.890, 95% CI: 1.436-5.819).

CONCLUSIONS

In our cohort of VLBW infants, NRFS was a significant risk factor for a low 5 min Apgar score, increased respiratory support requirement, and pulmonary hypertension. Accurate assessment of fetal well-being, timely delivery, and presence of a resuscitation team fully aware of perinatal conditions and anesthetic impact is important.

Carboxyhaemoglobin levels and free-radical-related diseases in prematurely born infants

BACKGROUND

Carboxyhaemoglobin (COHb) levels may reflect the level of early oxidative stress which plays a role in mediating free-radical-related diseases in prematurely born infants.

AIM

To assess the relationship of COHb levels in the first seven days of after birth to the development of bronchopulmonary dysplasia (BPD) and other free-radical-related diseases.

STUDY DESIGN

Retrospective analysis of routinely performed COHb via blood gas samples of infants born at less than 30 weeks of gestation admitted to a tertiary neonatal intensive care unit was undertaken.

SUBJECTS

One hundred and four infants were included with a median (range) gestational age of 27.4 (22.4-29.9) weeks and a birthweight of 865 (395-1710) grams.

OUTCOMES

The maximum COHb per infant per day was recorded for the first 28 days and BPD and other free-radical-related diseases including intraventricular haemorrhage (IVH) were noted. The severity of BPD, requirement for home oxygen on discharge and survival to discharge were also recorded.

RESULTS

Infants who developed BPD (n = 76) had significantly higher COHb levels in the first seven days [1.7% (0.3-6.8)] compared to those that did not develop BPD [1.6% (0.9-3.8); p = 0.001]. Higher COHb levels in the first seven days after birth were also observed in infants with grade three/four IVH [n = 20; 1.9% (1.0-6.8)] compared to those without [1.6% (0.3-5.6); p < 0.001]. COHb levels, however, were not associated with the duration of ventilation, BPD severity or survival to discharge.

CONCLUSION

Higher COHb levels in prematurely born infants were associated with the development of BPD and IVH.

Increased Impact of Air Pollution on Lung Function in Preterm versus Term Infants: The BILD Study

Rationale: Infants born prematurely have impaired capacity to deal with oxidative stress shortly after birth. Objectives: We hypothesize that the relative impact of exposure to air pollution on lung function is higher in preterm than in term infants. Methods: In the prospective BILD (Basel-Bern Infant Lung Development) birth cohort of 254 preterm and 517 term infants, we investigated associations of particulate matter ⩽10 μm in aerodynamic diameter (PM₁₀) and nitrogen dioxide with lung function at 44 weeks' postconceptional age and exhaled markers of inflammation and oxidative stress response (fractional exhaled nitric oxide [Fe_NO]) in an explorative hypothesis-driven study design. Multilevel mixed-effects models were used and adjusted for known confounders. Measurements and Main Results: Significant associations of PM₁₀ during the second trimester of pregnancy with lung function and Fe_NO were found in term and preterm infants. Importantly, we observed stronger positive associations in preterm infants (born 32-36 wk), with an increase of 184.9 (95% confidence interval [CI], 79.1-290.7) ml/min [Formula: see text]e per 10-μg/m³ increase in PM₁₀, than in term infants (75.3; 95% CI, 19.7-130.8 ml/min) (p_{prematurity × PM10 interaction} = 0.04, after multiple comparison adjustment p_adj = 0.09). Associations of PM₁₀ and Fe_NO differed between moderate to late preterm (3.4; 95% CI, -0.1 to 6.8 ppb) and term (-0.3; 95% CI, -1.5 to 0.9 ppb) infants, and the interaction with prematurity was significant (p_{prematurity × PM10 interaction} = 0.006, p_adj = 0.036). Conclusions: Preterm infants showed significantly higher susceptibility even to low to moderate prenatal air pollution exposure than term infants, leading to increased impairment of postnatal lung function. Fe_NO results further elucidate differences in inflammatory/oxidative stress response when comparing preterm infants with term infants.

Mechanism of Adipose-Derived Mesenchymal Stem Cell-Derived Extracellular Vesicles Carrying miR-21-5p in Hyperoxia-Induced Lung Injury

Hyperoxia-induced lung injury (HILI) tends to develop bronchopulmonary dysplasia. Adipose-derived mesenchymal stem cell (ADMSC)-derived extracellular vesicles (EVs) hold great promise in alleviating lung injury. This study explored the mechanism of ADMSC-EVs in HILI. ADMSC-EVs were isolated and identified. The murine and cell models of HILI were established. HILI mice and cells were pre-treated with ADMSC-EVs. The lung dry/wet ratio, pathological structure, apoptosis, and inflammation of HILI mice were measured. The viability, apoptosis, and oxidative stress of HILI cells were measured. The internalization of EVs in lung and cells was observed by fluorescence labeling. The binding relationships between miR-21-5p and SKP2, and Nr2f2 and C/EBPα were analyzed. The binding of SKP2 and Nr2f2 and the Nr2f2 ubiquitination level were detected. ADMSC-EVs exerted preventive effects on HILI mice, evidenced by reduced lung dry/wet ratio, inflammation, and apoptosis in HILI mice. In vitro, EVs enhanced HILI cell viability and reduced apoptosis, inflammation, and oxidative stress. EVs carried miR-21-5p into lung cells to upregulate miR-21-5p expression and thereby target SKP2. SKP2 bound to Nr2f2 and promoted its ubiquitination degradation. EVs inhibited the binding of Nr2f2 and C/EBPα and further suppressed C/EBPα transcription. Collectively, ADMSC-EVs carrying miR-21-5p alleviated HILI via the SKP2/Nr2f2/C/EBPα axis. Role and mechanism of adipose-derived mesenchymal stem cell-derived extracellular vesicles in hyperoxia-induced lung injury. ADMSC-EVs upregulated miR-21-5p expression in cells by carrying miR-21-5p into lung cells, thereby promoting the binding of miR-21-5p and SKP2 mRNA, inhibiting the expression of SKP2, reducing the ubiquitination level of Nr2f2, increasing the expression of Nr2f2, promoting the binding of Nr2f2 and the C/EBPα promoter, upregulating C/EBPα mRNA level, and eventually alleviating HILI.

Increased mitochondrial oxygen consumption in adult survivors of preterm birth

BACKGROUND

Premature birth affects roughly 10% of live births and is associated with long-term increased risk for multiple comorbidities. Although many comorbidities are associated with increased oxidative stress, the potential late impact of extreme premature birth on mitochondrial function has not previously been assessed. We hypothesized that mitochondrial function would be impaired in adult survivors of premature birth.

METHODS

Mitochondrial function in peripheral blood mononuclear cells from young adults born moderately to extremely preterm was measured using a Seahorse XF Analyzer at baseline and in response to acute oxidative stress, and compared to age-matched term-born adults. Adult pulmonary function was also obtained.

RESULTS

Young adults born preterm (average gestational age 29 weeks) had increased mitochondrial oxygen consumption at baseline, particularly with respect to basal and non-ATP-linked respiration. Maximal and spare capacities were also higher, even in response to acute oxidative stress. Lung function was lower in adults born preterm, and the degree of airflow obstruction correlated only modestly with mitochondrial function.

CONCLUSIONS

In conclusion, adults born preterm have higher basal and non-ATP-linked mitochondrial respiration. Similar mitochondrial profiles have previously been documented in diabetics, and may support the increased risk for cardiometabolic disease in adults born preterm.

IMPACT

Adults born preterm have higher maximal but also higher basal and non-ATP-linked mitochondrial respiration. Similar mitochondrial profiles have previously been documented in diabetics, and may support the increased risk for cardiometabolic disease in adults born preterm. Prior studies demonstrate a link between perinatal mitochondrial function and risk for development of bronchopulmonary dysplasia. Here, maximal mitochondrial respiration correlates modestly with adult lung function. Peripheral blood mononuclear cell mitochondrial function may be a biomarker of both early lung function and late cardiometabolic risk after preterm birth.

Oxidative Stress and Respiratory Diseases in Preterm Newborns

Premature infants are exposed to increased generation of reactive oxygen species, and on the other hand, they have a deficient antioxidant defense system. Oxidative insult is a salient part of lung injury that begins as acute inflammatory injury in respiratory distress disease and then evolves into chronic and structural scarring leading to bronchopulmonary dysplasia. Oxidative stress is also involved in the pathogenesis of pulmonary hypertension in newborns through the modulation of the vascular tone and the response to pulmonary vasodilators, with consequent decrease in the density of the pulmonary vessels and thickening of the pulmonary arteriolar walls. Oxidative stress has been recognized as both a trigger and an endpoint for several events, including inflammation, hypoxia, hyperoxia, drugs, transfusions, and mechanical ventilation, with impairment of pulmonary function and prolonged lung damage. Redoxomics is the most fascinating new measure to address lung damage due to oxidative stress. The new challenge is to use omics data to discover a set of biomarkers useful in diagnosis, prognosis, and formulating optimal and individualized neonatal care. The aim of this review was to examine the most recent evidence on the relationship between oxidative stress and lung diseases in preterm newborns. What is currently known regarding oxidative stress-related lung injury pathogenesis and the available preventive and therapeutic strategies are also discussed.

Oxidative Stress in Preterm Newborns

Preterm babies are highly susceptible to oxidative stress (OS) due to an imbalance between the oxidant and antioxidant systems. The generation of free radicals (FR) induces oxidative damage to multiple body organs and systems. OS is the main factor responsible for the development of typical premature infant diseases, such as bronchopulmonary dysplasia, retinopathy of prematurity, necrotizing enterocolitis, intraventricular hemorrhage, periventricular leukomalacia, kidney damage, eryptosis, and also respiratory distress syndrome and patent ductus arteriosus. Many biomarkers have been detected to early identify newborns at risk of developing a free radical-mediated disease and to investigate new antioxidant strategies. This review reports the current knowledge on OS in the preterm newborns and the newest findings concerning the use of OS biomarkers as diagnostic tools, as well as in implementing antioxidant therapeutic strategies for the prevention and treatment of these diseases and their sequelae.

Stability of glutathione added as a supplement to parenteral nutrition

BACKGROUND

Most very premature newborns (< 32 weeks of gestation) receive parenteral nutrition (PN) that is inherently contaminated with peroxides. Oxidative stress induced by PN is associated with bronchopulmonary dysplasia, a main pathological complication in these babies who have weak antioxidant capacity to detoxify peroxides because of their glutathione deficiency. In animals, glutathione supplementation of PN prevented oxidative stress and alveolar loss (the main characteristic of bronchopulmonary dysplasia). Of its two forms - disulfide (GSSG) and free thiol (GSH) - GSSG was used because of its better stability in PN. However, a 30% loss of GSSG in PN is observed. The potentially high therapeutic benefits of GSSG supplementation on the health of very premature babies makes the study of its stability highly important.

MATERIALS AND METHODS

GSSG was incubated in combination with the following components of PN: dextrose, multivitamins, Primene, Travasol, as well as with cysteine, cystine and peroxides for 24h. Total glutathione in these solutions was measured 0-24h after the addition of GSSG.

RESULTS

The combination of cysteine and multivitamins caused the maximum loss of glutathione. The stability of GSSG was not affected by multivitamins. The cysteine was responsible for about 20% of the loss of GSSG, in presence of multivitamins the loss reached more than 70%. Removing the cysteine prevented the degradation of glutathione.

CONCLUSION

GSSG reacts with cysteine to form cysteine-glutathione disulfide, another suitable glutathione substrate for preterm neonates. The study confirms that GSSG added to PN can potentially provide a precursor to de novo synthesis of glutathione in vivo. This article is protected by copyright. All rights reserved.

The therapeutic effect of Apocynin against hyperoxy and Inflammation-Induced lung injury

Lung damage due to hyperoxia and inflammation are important causes of bronchopulmonary dysplasia (BPD). We aimed to investigate the beneficial effects of Apocynin (Apo) on rat pups exposed to hyperoxia and inflammation. Forty-eight rat pups were randomly divided into 3 groups as hyperoxia (95% O₂) + lipopolysaccharide (LPS), hyperoxia + LPS + Apo treated and control (21% O₂). Rat pups in the Apo group received Apo at a daily dose of 40 mg/kg. Histopathological (Hematoxylin-Eosin, Masson trichrome), immunochemical (surfactant B and C protein staining) evaluations and biochemical studies incluiding, total antioxidant status (TAS), total oxidant status (TOS), OSI (oxidant stress index), AOPP (advanced protein degradation product), Lipid hydroperoxide (LPO), 8-OHdG, NADPH oxidase activity (NOX), superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), myeloperoxidase (MPO), tumor necrosis factor-alpha (TNF- α), interleukin-1 beta (IL-1β), IL-18, IL-6, caspase-1 and 3, nuclear factor erythroid 2-related factor 2 (NFR2), Nod-like receptor pyrin domain-containing 3 (NLRP3) activities were studied. After Apo treatment, AOPP, LPO, 8-OHdG, NOX, TOS, OSI levels decreased; SOD, CAT, GSH and TAS levels increased (P < 0.05). Apo reduced inflammatory cell infiltration and proinflammatory cytokines with reduction in NLRP3 inflammasome in addition to increased Nrf2 levels. Moreover, caspase-1 and 3 levels decreased with Apo (P < 0.05). Apo was found to provide preventive and therapeutic effects by reducing oxidant stress, blocking inflammation and increasing antioxidant status. Beyond anti-oxidative effects, Apo also have anti-inflammatory effects by suppressing NLRP3 inflammasome activation and inducing Nrf2 as well. Therefore, Apo might be a potential option in the treatment of BPD.

Does Chrysin prevent severe lung damage in Hyperoxia-Induced lung injury Model?

BACKGROUND

Oxidative stress and inflammation play a critical role in the etiopathogenesis of bronchopulmonary dysplasia (BPD). The aim of this study was to evaluate the preventive effect of Chrysin (CH), an antioxidant, antiinflammatory, antiapoptotic and antifibrotic drug, on hyperoxia-induced lung injury in a neonatal rat model.

METHODS

Forty infant rats were divided into four groups labeled the Control, CH, BPD, and BPD + CH. The control and CH groups were kept in a normal room environment, while the BPD and BPD + CH groups were kept in a hyperoxic (90-95%) environment. At the end of the study, lung tissue was evaluated with respect to apoptosis, histopathological damage and alveolar macrophage score as well as oxidant capacity, antioxidant capacity, and inflammation.

RESULTS

Compared to the BPD + CH and control groups, the lung tissues of the BPD group displayed substantially higher levels of MDA, TOS, TNF-α, and IL-1β (p < 0.05). While the BPD + CH group showed similar levels of TNF-α and IL-1β as the control group, MDA and TOS levels were higher than the control group, and significantly lower than the BPD group (p < 0.05). The BPD group exhibited considerably lower levels of TAS, SOD, GSH, and GSH-Px in comparison to the control group (p < 0.05). The BPD and BPD + CH groups exhibited higher mean scores of histopathological damage and alveolar macrophage when compared to the control and CH groups (p ≤ 0.0001). Both scores were found to be lower in the BPD + CH group in comparison to the BPD group (p ≤ 0.0001). The BPD + CH group demonstrated a significantly lower average of TUNEL and caspase-3 positive cells than the BPD group.

CONCLUSION

We found that prophylaxis with CH results in lower histopathological damage score and reduces apoptotic cell count, inflammation and oxidative stress while increasing anti-oxidant capacity.

Role of the SENP1-SIRT1 pathway in hyperoxia-induced alveolar epithelial cell injury

Bronchopulmonary dysplasia (BPD) is a common complication in preterm infants, and its main pathogenesis partly involves oxidative stress. A large number of studies have shown that silent information regulator 1 (SIRT1) plays a protective role in oxidative stress. SUMO-specific protease 1 (SENP1) is vital in the nucleoplasmic distribution of SIRT1 under stress. However, whether the SENP1-SIRT1 pathway is involved in the hyperoxic lung injury is unknown. Therefore, this study aimed to explore the role and related mechanisms of the SENP1-SIRT1 pathway in hyperoxic lung injury. Peripheral blood mononuclear cells (PBMCs) from infants with BPD and SENP1-silenced alveolar epithelial cells were used as research models. PBMCs were isolated from the peripheral blood of premature infants. Next, the SENP1-silenced human alveolar epithelial cells were used to verify the role of the SENP1-SIRT1 pathway in vitro. The results indicated that the ROS level and the mRNA and protein expression of SENP1 increased in PBMCs of infants with BPD, but the expression of SIRT1 decreased in the nucleus and increased in the cytoplasm, and then the expression of acetyl-p53 (Ac-p53) increased. In the hyperoxic alveolar epithelial cell injury model, it seemed that hyperoxia could induce the same variation trend in the SENP1-SIRT1 pathway as in infants with BPD and then increased the expression of Ac-p53 and BAX, and cell apoptosis. Furthermore, silencing SENP1 could alleviate these hyperoxia-induced changes. These results suggested that SENP1 played an important role in hyperoxia-induced lung injury. It could regulate the expression and nucleoplasmic distribution of SIRT1 to inhibit its deacetylase activity, and then promoted cell apoptosis. Hence, SENP1 may become a potential intervention target of BPD in the future.

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.

Comparison of coenzyme Q10 or fish oil for prevention of intermittent hypoxia-induced oxidative injury in neonatal rat lungs

BACKGROUND

Neonatal intermittent hypoxia (IH) results in oxidative distress in preterm infants with immature antioxidant systems, contributing to lung injury. Coenzyme Q10 (CoQ10) and fish oil protect against oxidative injury. We tested the hypothesis that CoQ10 is more effective than fish oil for prevention of IH-induced lung injury in neonatal rats.

METHODS

Newborn rats were exposed to two clinically relevant IH paradigms at birth (P0): (1) 50% O₂ with brief hypoxia (12% O₂); or (2) room air (RA) with brief hypoxia (12% O₂), until P14 during which they were supplemented with daily oral CoQ10, fish oil, or olive oil from P0 to P14. Pups were studied at P14 or placed in RA until P21 with no further treatment. Lungs were assessed for histopathology and morphometry; biomarkers of oxidative stress and lipid peroxidation; and antioxidants.

RESULTS

Of the two neonatal IH paradigms 21%/12% O₂ IH resulted in the most severe outcomes, evidenced by histopathology and morphometry. CoQ10 was effective for preserving lung architecture and reduction of IH-induced oxidative stress biomarkers. In contrast, fish oil resulted in significant adverse outcomes including oversimplified alveoli, hemorrhage, reduced secondary crest formation and thickened septae. This was associated with elevated oxidants and antioxidants activities.

CONCLUSIONS

Data suggest that higher FiO₂ may be needed between IH episodes to curtail the damaging effects of IH, and to provide the lungs with necessary respite. The negative outcomes with fish oil supplementation suggest oxidative stress-induced lipid peroxidation.

Effects of Hyperoxia on Mitochondrial Homeostasis: Are Mitochondria the Hub for Bronchopulmonary Dysplasia?

Mitochondria are involved in energy metabolism and redox reactions in the cell. Emerging data indicate that mitochondria play an essential role in physiological and pathological processes of neonatal lung development. Mitochondrial damage due to exposure to high concentrations of oxygen is an indeed important factor for simplification of lung structure and development of bronchopulmonary dysplasia (BPD), as reported in humans and rodent models. Here, we comprehensively review research that have determined the effects of oxygen environment on alveolar development and morphology, summarize changes in mitochondria under high oxygen concentrations, and discuss several mitochondrial mechanisms that may affect cell plasticity and their effects on BPD. Thus, the pathophysiological effects of mitochondria may provide insights into targeted mitochondrial and BPD therapy.

Clusterin Deficiency Exacerbates Hyperoxia-Induced Acute Lung Injury

Exposure to high oxygen concentrations leads to generation of excessive reactive oxygen species, causing cellular injury and multiple organ dysfunctions and is associated with a high mortality rate. Clusterin (CLU) is a heterodimeric glycoprotein that mediates several intracellular signaling pathways, including cell death and inflammation. However, the role of CLU in the pathogenesis of hyperoxic acute lung injury (HALI) is unknown. Wild-type (WT) and CLU-deficient mice and cultured human airway epithelial cells were used. Changes in cell death- and inflammation-related molecules with or without hyperoxia exposure in cells and animals were determined. Hyperoxia induced an increase in CLU expression in mouse lungs and human airway epithelial cells. Mice lacking CLU had increased HALI and mortality rate compared with WT mice. In vitro, CLU-disrupted cells showed enhanced release of cytochrome c, Bax translocation, cell death and inflammatory cytokine expression. However, treatment with recombinant CLU attenuated hyperoxia-induced apoptosis. Moreover, the Kyoto Encyclopedia of Genes and Genomes and Gene Ontology analyses revealed metabolic pathways, hematopoietic cell lineage, response to stress and localization and regulation of immune system that were differentially regulated between WT and CLU-/- mice. These results demonstrate that prolonged hyperoxia-induced lung injury is associated with CLU expression and that CLU replenishment may alleviate hyperoxia-induced cell death.

Lower oxygen saturation targets in preterm infants are not associated with increased rates of pulmonary hypertension

BACKGROUND

The optimal oxygen saturation target in preterm infants is not known. In this study, we aimed to assess the effect of lower oxygen saturation targets on the rate of bronchopulmonary dysplasia (BPD), retinopathy of prematurity (ROP), and pulmonary hypertension (PH) in preterm infants.

METHODS

Retrospective cohort study comparing BPD, ROP, and PH incidence among two cohorts of infants born at≤32 weeks gestation with different oxygen saturation targets at≥34 weeks post-menstrual age (PMA): cohort 1, 94-98% (n = 126); cohort 2, 92-97% (n = 121). Groups compared by Chi-square test, t-test, and multivariable logistic regression.

RESULTS

When comparing cohort 1 (average gestational age 29.8 weeks, average birth weight 1271g) with cohort 2 (average gestational age 29.6 weeks, average birth weight 1299g), there was no difference in rate of BPD (24% vs. 19%, p = 0.38), ROP (4% vs. 3%, p = 0.49), or PH (2% vs. 4%, p = 0.44).

CONCLUSION

An oxygen saturation target of 92-97% at≥34 weeks PMA was not associated with a higher rate of PH or lower rate of BPD or ROP when compared with a higher target of 94-98%.

Hyperoxia-induced bronchopulmonary dysplasia: better models for better therapies

Bronchopulmonary dysplasia (BPD) is a chronic lung disease caused by exposure to high levels of oxygen (hyperoxia) and is the most common complication that affects preterm newborns. At present, there is no cure for BPD. Infants can recover from BPD; however, they will suffer from significant morbidity into adulthood in the form of neurodevelopmental impairment, asthma and emphysematous changes of the lung. The development of hyperoxia-induced lung injury models in small and large animals to test potential treatments for BPD has shown some success, yet a lack of standardization in approaches and methods makes clinical translation difficult. In vitro models have also been developed to investigate the molecular pathways altered during BPD and to address the pitfalls associated with animal models. Preclinical studies have investigated the efficacy of stem cell-based therapies to improve lung morphology after damage. However, variability regarding the type of animal model and duration of hyperoxia to elicit damage exists in the literature. These models should be further developed and standardized, to cover the degree and duration of hyperoxia, type of animal model, and lung injury endpoint, to improve their translational relevance. The purpose of this Review is to highlight concerns associated with current animal models of hyperoxia-induced BPD and to show the potential of in vitro models to complement in vivo studies in the significant improvement to our understanding of BPD pathogenesis and treatment. The status of current stem cell therapies for treatment of BPD is also discussed. We offer suggestions to optimize models and therapeutic modalities for treatment of hyperoxia-induced lung damage in order to advance the standardization of procedures for clinical translation.

SIRT1-Related Signaling Pathways and Their Association With Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic and debilitating disease that can exert serious and overwhelming effects on the physical and mental health of premature infants, predominantly due to intractable short- and long-term complications. Oxidative stress is one of the most predominant causes of BPD. Hyperoxia activates a cascade of hazardous events, including mitochondrial dysfunction, uncontrolled inflammation, reduced autophagy, increased apoptosis, and the induction of fibrosis. These events may involve, to varying degrees, alterations in SIRT1 and its associated targets. In the present review, we describe SIRT1-related signaling pathways and their association with BPD. Our intention is to provide new insights into the molecular mechanisms that regulate BPD and identify potential therapeutic targets for this debilitating condition.

Lymphocyte-Specific Biomarkers Associated With Preterm Birth and Bronchopulmonary Dysplasia

Many premature babies who are born with neonatal respiratory distress syndrome (RDS) go on to develop Bronchopulmonary Dysplasia (BPD) and later Post-Prematurity Respiratory Disease (PRD) at one year corrected age, characterized by persistent or recurrent lower respiratory tract symptoms frequently related to inflammation and viral infection. Transcriptomic profiles were generated from sorted peripheral blood CD8+ T cells of preterm and full-term infants enrolled with consent in the NHLBI Prematurity and Respiratory Outcomes Program (PROP) at the University of Rochester and the University at Buffalo. We identified outcome-related gene expression patterns following standard methods to identify markers for oxygen utilization and BPD as outcomes in extremely premature infants. We further identified predictor gene sets for BPD based on transcriptomic data adjusted for gestational age at birth (GAB). RNA-Seq analysis was completed for CD8+ T cells from 145 subjects. Among the subjects with highest risk for BPD (born at <29 weeks gestational age (GA); n=72), 501 genes were associated with oxygen utilization. In the same set of subjects, 571 genes were differentially expressed in subjects with a diagnosis of BPD and 105 genes were different in BPD subjects as defined by physiologic challenge. A set of 92 genes could predict BPD with a moderately high degree of accuracy. We consistently observed dysregulation of TGFB, NRF2, HIPPO, and CD40-associated pathways in BPD. Using gene expression data from both premature and full-term subjects (n=116), we identified a 28 gene set that predicted the PRD status with a moderately high level of accuracy, which also were involved in TGFB signaling. Transcriptomic data from sort-purified peripheral blood CD8+ T cells from 145 preterm and full-term infants identified sets of molecular markers of inflammation associated with independent development of BPD in extremely premature infants at high risk for the disease and of PRD among the preterm and full-term subjects.

Heat Shock Protein-70 Levels Are Associated With a State of Oxidative Damage in the Development of Bronchopulmonary Dysplasia

Background: Heat shock protein-70 (Hsp-70) exhibits cytoprotective effects against oxidative stress-induced airway injury. This study aimed to examine Hsp-70 and 8-hydroxy-2'-deoxyguanosine (8-OHdG) from tracheal aspirates (TA) in very low-birth weight (VLBW) preterm infants to predict the development of bronchopulmonary dysplasia (BPD). Methods: This birth cohort study enrolled 109 VLBW preterm infants, including 32 infants who developed BPD. Hsp-70 and 8-OHdG concentrations from TA were measured by immunoassay. The apoptosis of TA epithelial cells obtained on Day 28 after birth was measured using annexin-V staining assay. Results: Hsp-70 and 8-OHdG levels in TA fluid were persistently increased from Day 1 to Day 28 of life in the BPD group. Multiple linear regression analysis demonstrated that BPD was significantly associated with gestational age, respiratory distress syndrome, and TA Hsp-70 and 8-OHdG levels on post-natal Day 28. The TA Hsp-70 level positively correlated with TA 8-OHdG level on the Day 1 (r = 0.47) and Day 28 of life (r = 0.68). Incubation of recombinant Hsp-70 with primary epithelial cells derived from TA of patients decreased hydrogen peroxide-induced epithelial cell death. Conclusions: Hsp-70 levels are associated with a state of oxidative injury in the development of BPD.

Hyperoxia exposure arrests alveolarization in neonatal rats via PTEN‑induced putative kinase 1‑Parkin and Nip3‑like protein X‑mediated mitophagy disorders

Bronchopulmonary dysplasia (BPD), also known as chronic lung disease, is one of the most common respiratory diseases in premature new‑born humans. Mitochondria are not only the main source of reactive oxygen species but are also critical for the maintenance of homeostasis and a wide range of biological activities, such as producing energy, buffering cytosolic calcium and regulating signal transduction. However, as a critical quality control method for mitochondria, little is known about the role of mitophagy in BPD. The present study assessed mitochondrial function in hyperoxia‑exposed alveolar type II (AT‑II) cells of rats during lung development. New‑born Sprague‑Dawley rats were divided into hyperoxia (85% oxygen) and control (21% oxygen) groups. Histopathological and morphological properties of the lung tissues were assessed at postnatal days 1, 3, 7 and 14. Ultrastructural mitochondrial alteration was observed using transmission electron microscopy and the expression of the mitophagy proteins putative kinase (PINK)1, Parkin and Nip3‑like protein X (NIX) in the lung tissues was evaluated using western blotting. Immunofluorescence staining was used to determine the co‑localisation of PINK1 and Parkin. Real‑time analyses of extracellular acidification rate and oxygen consumption rate were performed using primary AT‑II cells to evaluate metabolic changes. Mitochondria in hyperoxia‑exposed rat AT‑II cells began to show abnormal morphological and physiological features. These changes were accompanied by decreased mitochondrial membrane potential and increased expression levels of PINK1‑Parkin and NIX. Increased binding between a mitochondria marker (cytochrome C oxidase subunit IV isoform I) and an autophagy marker (microtubule‑associated protein‑1 light chain‑3B) was observed in primary AT‑II cells and was accompanied by decreased mitochondrial metabolic capacity in model rats. Thus, mitophagy mediated by PINK1, Parkin and NIX in AT‑II cells occurred in hyperoxia‑exposed new‑born rats. These findings suggested that the accumulation of dysfunctional mitochondria may be a key factor in the pathogenesis of BPD and result in attenuated alveolar development.

Tetrandrine attenuates hyperoxia-induced lung injury in newborn rats via NF-κB p65 and ERK1/2 pathway inhibition

Background

Bronchopulmonary dysplasia (BPD) is an important cause of respiratory illness in preterm newborns that results in significant morbidity and mortality. Hyperoxia is a critical factor in the pathogenesis of BPD, hyperoxia-induced lung injury model has similar pathological manifestations as human BPD. Tetrandrine (Tet) is known to suppress oxidative stress, apoptosis and inflammation. Thus it has been used to prevent organ injuries. However, the protective effect of Tet against hyperoxia-induced lung injury in newborn rats has not been reported.

Methods

A hyperoxia-induced lung injury model was established using newborn rats exposed to high O₂ levels. The models were treated with various concentrations of Tet, and a lung function test was conducted. Then, the lung tissues and blood were collected to detect the effect of Tet on cell apoptosis, inflammatory response, and fibrosis. The effect of Tet on nuclear factor-kappa B (NF-κB) and extracellular signal-regulated kinase1/2 (ERK1/2) pathways was also determined.

Results

Lung function was decreased in hyperoxia-induced rats, and Tet could reverse this inhibiting effect. For oxidative stress, Tet caused an increase in the levels of antioxidant enzymes. The apoptosis rate and apoptosis-related proteins were decreased in hyperoxia-induced rats after Tet treatment. Additionally, Tet treatment could reduce inflammatory factor levels, while increasing CD4⁺IFN-γ⁺ T cell levels and decreasing CD4⁺IL-4⁺ T cell levels. Tet treatment was also able to inhibit the expression of fibrosis-related markers and NF-κB and ERK1/2 pathways.

Conclusions

Tet demonstrated potent activity against hyperoxia-induced lung injury in newborn rats through NF-κB and ERK1/2 pathway inhibition.

Prevention of Oxygen-Induced Inflammatory Lung Injury by Caffeine in Neonatal Rats

Background

Preterm birth implies an array of respiratory diseases including apnea of prematurity and bronchopulmonary dysplasia (BPD). Caffeine has been introduced to treat apneas but also appears to reduce rates of BPD. Oxygen is essential when treating preterm infants with respiratory problems but high oxygen exposure aggravates BPD. This experimental study is aimed at investigating the action of caffeine on inflammatory response and cell death in pulmonary tissue in a hyperoxia-based model of BPD in the newborn rat. Material/Methods. Lung injury was induced by hyperoxic exposure with 80% oxygen for three (P3) or five (P5) postnatal days with or without recovery in ambient air until postnatal day 15 (P15). Newborn Wistar rats were treated with PBS or caffeine (10 mg/kg) every two days beginning at the day of birth. The effects of caffeine on hyperoxic-induced pulmonary inflammatory response were examined at P3 and P5 immediately after oxygen exposure or after recovery in ambient air (P15) by immunohistological staining and analysis of lung homogenates by ELISA and qPCR.

Results

Treatment with caffeine significantly attenuated changes in hyperoxia-induced cell death and apoptosis-associated factors. There was a significant decrease in proinflammatory mediators and redox-sensitive transcription factor NFκB in the hyperoxia-exposed lung tissue of the caffeine-treated group compared to the nontreated group. Moreover, treatment with caffeine under hyperoxia modulated the transcription of the adenosine receptor (Adora)1. Caffeine induced pulmonary chemokine and cytokine transcription followed by immune cell infiltration of alveolar macrophages as well as increased adenosine receptor (Adora1, 2a, and 2b) expression.

Conclusions

The present study investigating the impact of caffeine on the inflammatory response, pulmonary cell degeneration and modulation of adenosine receptor expression, provides further evidence that caffeine acts as an antioxidative and anti-inflammatory drug for experimental oxygen-mediated lung injury. Experimental studies may broaden the understanding of therapeutic use of caffeine in modulating detrimental mechanisms involved in BPD development.

Intratracheal Transplantation of Amnion-Derived Mesenchymal Stem Cells Ameliorates Hyperoxia-Induced Neonatal Hyperoxic Lung Injury via Aminoacyl-Peptide Hydrolase

Background and Objectives

Bronchopulmonary dysplasia (BPD) has major effects in premature infants. Although previous literature has indicated that mesenchymal stem cells (MSCs) can alleviate lung pathology in BPD newborns and improve the survival rate, few research have been done investigating significantly differentially expressed genes in the lungs before and after MSCs therapy. The aim of this study is to identify differentially expressed genes in lung tissues before and after hAD-MSC treatment.

Methods and Results

Human amnion-derived MSCs (hAD-MSCs) were cultured and met the MSCs criteria for cell phenotype and multidirectional differentiation. Then we confirmed the size of hAD-MSCs-EXOs and their expressed markers. An intratracheal drip of living cells showed the strongest effect on NHLI compared to cellular secretions or exosomes, both in terms of ameliorating pulmonary edema and reducing inflammatory cell infiltration. Through gene chip hybridization, PCR, and western blotting, acylaminoacyl-peptide hydrolase (APEH) expression was found to be significantly decreased under hyperoxia, and significantly increased after hAD-MSC treatment.

Conclusions

The intratracheal transplantation of hAD-MSCs ameliorated NHLI in neonatal rats through APEH.

Mechanism of oxidative stress and Keap-1/Nrf2 signaling pathway in bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease common in premature infants and is one of the leading causes of disability and death in newborns. The Keap-1/Nrf2 signaling pathway plays an important role in antioxidant and anti-inflammatory.Ten clean-grade, healthy pregnant Sprague-Dawley rats (purchased from Experimental Animal Center of Peking university, China) naturally gave birth to 55 neonatal rats from which 40 were selected and randomly divided into a hyperoxia group and a control group (N = 20, each). Thirty-two BPD patient samples are from Neonatal Department of the second Hospital of Jilin University from November 30, 2016 to May 1 2019.In present study, we observed that lung tissues of the control group did not undergo obvious pathological changes, whereas in the hyperoxia group, lung tissues had disordered structures. With increased time of hyperoxia exposure, the alveolar wall became attenuated. Under hypoxia conditions, the activity of oxidative stress-related enzymes (CAT, GSH-Px, SOD) in lung samples was significantly lower than that before treatment. The expression level of Keap1 mRNA and protein in the hyperoxia group was slightly lower than that of control group. The expression of Nrf2 and HO-1 mRNA and protein in the hyperoxia group was significantly higher than that of control group. For the infants with BPD, we found that the activity of SOD, GSH-Px, and CAT was significantly different from those of control group.We constructed a premature BPD animal model and found the abnormal of oxidative stress in different groups and the expression levels of Keap1/Nrf2 signaling pathway-related molecules, and we validated the results in premature infants with 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.

Oxidative stress biomarkers in the perinatal period: Diagnostic and prognostic value

Perinatal oxidative stress (OS) is involved in the physiopathology of many pregnancy-related disorders and is largely responsible for cellular, tissue and organ damage that occur in the perinatal period especially in preterm infants, leading to the so-called "free-radicals related diseases of the newborn". Reliable biomarkers of lipid, protein, DNA oxidation and antioxidant power in the perinatal period have been demonstrated to show specificity for the disease, to have prognostic power or to correlate with disease activity. Yet potential clinical applications of oxidative stress biomarkers in neonatology are still under study. Overcoming the technical and economic difficulties that preclude the use of OS biomarkers in the clinical practice is a challenge that needs to be overcome to identify high-risk subjects and to predict their short- and long-term outcome. Cord blood, urine and saliva represent valid and ethically acceptable biological samples for investigations in the perinatal period.

PaO2 greater than 300 mmHg promotes an inflammatory response during extracorporeal circulation in a rat extracorporeal membrane oxygenation model

Background

Extracorporeal membrane oxygenation (ECMO) is being increasingly used for mechanical support of respiratory and cardio-circulatory failure. An excessive systemic inflammatory response is observed during sepsis and after cardiopulmonary bypass (CPB) with similar clinical features. We hypothesized that hyperoxia condition encourages the systemic inflammatory response and organ disorder during ECMO. To prove this hypothesis correct, we investigated the systemic inflammatory responses at normal and high levels of arterial oxygen pressure (PaO₂) in the rat ECMO model.

Methods

Rats were randomly assigned to one of the following groups depending on the value of PaO₂ during ECMO: A group (n=11, PaO₂ 100–199 mmHg), B group (n=10, PaO₂ 200–299 mmHg), C group (n=8, PaO₂ 300–399 mmHg), and D group (n=11, PaO₂ >400 mmHg). Serum cytokine levels [tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10)] were measured before, 60, and 120 min after the initiation of ECMO. The wet-to-dry weight (W/D) ratio of the left lung was also measured, and dihydroethidium (DHE) staining, reflecting superoxide generation, of lung and liver tissues was performed 120 min after ECMO initiation.

Results

In the C and D groups, the pro-inflammatory cytokines (TNF-α and IL-6) significantly increased during ECMO compared with the other groups. On the other hand, the increase in anti-inflammatory cytokines (IL-10) was more suppressed in the C and D groups than in the other groups. The W/D ratio increased significantly more in the C and D groups than in the other groups. In addition, DHE fluorescence had a tendency to increase as the PaO₂ rose.

Conclusions

These data demonstrate that it is better to avoid administration of too much oxygen during ECMO to attenuate lung injury linked to generation of superoxide and the systemic inflammatory response.

Effects of hyperoxia exposure on the expression of Nrf2 and heme oxygenase-1 in lung tissues of premature rats

Bronchopulmonary dysplasia (BPD) is a chronic lung disease with long-term sequelae including neurodevelopmental delay. Although the precise mechanism of BPD is not well defined, oxidative stress is thought to be involved in the pathogenesis process of BPD. Nrf2 (Nuclear factor erythroid 2-related factor 2)-Keap1 (Kelch-like ECH associated protein 1)-ARE (Antioxidant Reaction Elements) signaling pathway is one of the main protective mechanisms of BPD, which can induce cytoprotective gene expression, such as heme oxygenase-1 (HO-1), nicotinamide quinone oxidoreductase 1 (NQO1) and so on. We exposed premature rats to hyperoxia and identified lung developmental retardation in preterm rats, with similar pathological changes as BPD. The expression of Nrf2 and HO-1 in premature rats was significantly higher after hyperoxia exposure. To explore the changes of Nrf2 and HO-1 in premature rats and enhance their beneficial functions may provide new treatment strategies for infants at risk of BPD.

Perspectives on Probiotics and Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic respiratory disease of preterm infants, associated with high morbidity and hospitalization expenses. With the revolutionary advances in microbiological analysis technology, increasing evidence indicates that children with BPD are affected by lung microbiota dysbiosis, which may be related to the illness occurrence and progression. However, dysbiosis treatment in BPD patients has not been fully investigated. Probiotics are living microorganisms known to improve human health for their anti-inflammatory and anti-tumor effects, and particularly by balancing gut microbiota composition, which promotes gut-lung axis recovery. The aim of the present review is to examine current evidence of lung microbiota dysbiosis and explore potential applications of probiotics in BPD, which may provide new insights into treatment strategies of this disease.

The expression of miR-125b in Nrf2-silenced A549 cells exposed to hyperoxia and its relationship with apoptosis

Bronchopulmonary dysplasia (BPD) is a chronic lung disease that affects the quality of life of infants. At present, premature exposure to hyperoxia for extended periods of time is believed to affect the development of lung tissue and vascularity, resulting in BPD. The oxidative stress caused by hyperoxia exposure is an important risk factor for BPD in premature infants. Nuclear factor E2‐related factor 2 (Nrf2) is an important regulator of antioxidant mechanisms. As a microRNA, microRNA‐125b (miR‐125b) plays an important role in cell proliferation, differentiation and apoptosis. Although the Nrf2/ARE pathway has been extensively studied, little is known about the regulatory role of microRNAs in Nrf2 expression. In this study, the expression levels of Nrf2 and miR‐125b in the lung tissues of premature Sprague Dawley (SD) rats and A549 cells exposed to hyperoxia were detected by quantitative real‐time polymerase chain reaction (qRT‐PCR), and the apoptosis of A549 cells was detected by flow cytometry. The results showed that Nrf2 and miRNA‐125b in the lung tissues of premature rats increased significantly upon exposure to hyperoxia and played a protective role. Nrf2 was suppressed by small interfering RNA (siRNA) in A549 cells, miR‐125b was similarly inhibited, and apoptosis was significantly increased. These results suggest that miR‐125b helps protect against BPD as a downstream target of Nrf2.

Autologous cord blood cell infusion in preterm neonates safely reduces respiratory support duration and potentially preterm complications

Preterm birth and its complications are the leading cause of neonatal death. The main underlying pathological mechanisms for preterm complications are disruption of the normal maturation processes within the target tissues, interrupted by premature birth. Cord blood, as a new and convenient source of stem cells, may provide new, promising options for preventing preterm complications. This prospective, nonrandomized placebo controlled study aimed at investigating the effect of autologous cord blood mononuclear cells (ACBMNC) for preventing preterm associated complications. Preterm infants less than 35 weeks gestational age were assigned to receive ACBMNC (5 × 10⁷ cells/kg) intravenous or normal saline within 8 hours after birth. Preterm complication rates were compared between two groups to demonstrate the effect of ACBMNC infusion in reducing preterm complications. Fifteen preterm infants received ACBMNC infusion, and 16 infants were assigned to the control group. There were no significant differences when comparing mortality and preterm complication rates before discharge. However, ACBMNC infusion demonstrated significant decreases in duration of mechanical ventilation (3.2 days vs 6.41 days, P = .028) and oxygen therapy (5.33 days vs 11.31 days, P = .047). ACBMNC infusion was effective in reducing respiratory support duration in very preterm infants. Due to the limited number of patients enrolled, powered randomized controlled trials are needed to better define its efficacy.

The effects of bosentan on hyperoxia-induced lung injury in neonatal rats

BACKGROUND

Bronchopulmonary dysplasia (BPD) remains an important cause of morbidity and mortality in premature infants. There is currently no proven effective treatment modality for BPD, and inflammation and oxidative injury play an important role in the pathogenesis of this disease. This study investigated the histopathological and biochemical effects of bosentan, which is a non-specific endothelin receptor antagonist with known antioxidant and anti-inflammatory properties, on hyperoxia-induced lung injury (HILI) in neonatal rats.

METHODS

The experiment was performed on newborn rats from the 3rd to the 13th postnatal day. The rats were randomly divided into six groups: Group 1 (air-exposed + saline, n = 6); Group 2 (HILI, n = 8); Group 3 (air-exposed + bosentan, n = 7); Group 4 (HILI + saline, n = 7); Group 5 (HILI + early bosentan-treated group, n = 6), and Group 6 (HILI + late bosentan-treated group, n = 7). Bosentan was administered (30 mg/kg/day) intraperitoneally. The histopathological effects of bosentan on lung tissue were assessed by their alveolar surface area, fibrosis, and smooth muscle actin (SMA) scores, and the biochemical effects on lung tissue were assessed by interleukin-1 beta (IL-1β), IL-6, IL-10, and tumor necrosis factor-alpha (TNF-α).

RESULTS

The alveolar surface area and fibrosis scores were found to be significantly higher in HILI groups compared with Group 1 (P < 0.01). The SMA scores in HILI groups were also significantly higher than Group 1 (P < 0.01). Bosentan treatment, especially late therapy, reduced all of these histopathological scores and the levels of IL-6 and TNF-α in the hyperoxia groups (P < 0.01).

CONCLUSION

This experimental study showed that bosentan had a protective effect on hyperoxic lung injury through its anti-inflammatory properties.

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.

Biomarkers of oxidative stress in the fetus and in the newborn

The dynamic field of perinatology entails ever-increasing search for molecular mechanisms of neonatal diseases, especially in the domain of fetal growth and neurodevelopmental outcome. There is an urgent need for new molecular biomarkers, to early identify newborn at high risk for developing diseases and to provide new treatment targets. The interest in biomarkers of oxidative stress in perinatal period have begun to grow in the last century, when it was evidenced the importance of the free radicals generation underlying the various disease conditions. To date, interesting researches have been carried out, representing milestones for implementation of oxidative stress biomarkers in perinatal medicine. Use of a panel of "oxidative stress biomarkers", particularly non protein bound iron, advanced oxidative protein products and isoprostanes, may provide valuable information regarding functional pathways underlying free radical mediated diseases of newborns and their early identification and prevention. Here, we will review recent advances and the current knowledge on the application of biomarkers of oxidative stress in neonatal/perinatal medicine including novel biomarker discovery, defining yet unrecognized biologic therapeutic targets, and linking of oxidative stress biomarkers to relevant standard indices and long-term outcomes.

Sex-differences in LPS-induced neonatal lung injury

Being of the male sex has been identified as a risk factor for multiple morbidities associated with preterm birth, including bronchopulmonary dysplasia (BPD). Exposure to inflammatory stress is a well-recognized risk factor for developing BPD. Whether there is a sex difference in pulmonary innate immune TLR4 signaling, lung injury and subsequent abnormal lung development is unknown. Neonatal (P0) male and female mice (ICR) were exposed to systemic LPS (5 mg/kg, IP) and innate immune signaling, and the transcriptional response were assessed (1 and 5 hours), along with lung development (P7). Male and female mice demonstrated a similar degree of impaired lung development with decreased radial alveolar counts, increased surface area, increased airspace area and increased mean linear intercept. We found no differences between male and female mice in the baseline pulmonary expression of key components of TLR4-NFκB signaling, or in the LPS-induced pulmonary expression of key mediators of neonatal lung injury. Finally, we found no difference in the kinetics of LPS-induced pulmonary NFκB activation between male and female mice. Together, these data support the conclusion that the innate immune response to early postnatal LPS exposure and resulting pulmonary sequelae is similar in male and female mice.

Lipoxin A4 reduces hyperoxia-induced lung injury in neonatal rats through PINK1 signaling pathway

Bronchopulmonary dysplasia (BPD) is a common chronic lung disease in premature infants and is mainly caused by hyperoxia exposure and mechanical ventilation. Alveolar simplification, pulmonary vascular abnormalities and pulmonary inflammation are the main pathological changes in hyperoxic lung injury animals. Lipoxin A4 (LXA4) is an important endogenous lipid that can mediate the regression of inflammation and plays a role in acute lung injury and asthma. The purpose of this study was to evaluate the effects of LXA4 on inflammation and lung function in neonatal rats with hyperoxic lung injury and to explore the mechanism of the PINK1 pathway. After 85% oxygen exposure in newborn rats for 7 days, the BPD model was established. We found that LXA4 could significantly reduce cell and protein infiltration and oxidative stress in rat lungs, improve pulmonary function and alveolar simplification, and promote weight gain. LXA4 inhibited the expression of TNF-α, MCP-1 and IL-1β in serum and BALF from hyperoxic rats. Moreover, we found that LXA4 could reduce the expression of the PINK1 gene and down-regulate the expression of PINK1, Parkin, BNIP3L/Nix and the autophagic protein LC3B.These protective effects of LXA4 could be partially reversed by addition of BOC-2.Thus, we concluded that LXA4 can alleviate the airway inflammatory response, reduce the severity of lung injury and improve lung function in a hyperoxic rat model of BPD partly through the PINK1 signaling pathway.

Antioxidative effects of caffeine in a hyperoxia-based rat model of bronchopulmonary dysplasia

Background

While additional oxygen supply is often required for the survival of very premature infants in intensive care, this also brings an increasing risk of progressive lung diseases and poor long-term lung outcomes. Caffeine is administered to neonates in neonatal intensive care for the prevention and treatment of apneas and has been shown to reduce BPD incidence and the need for mechanical ventilation, although it is still unclear whether this is due to a direct pulmonary action via antagonism of adenosine receptors and/or an indirect action. This experimental study aims to investigate the action of caffeine on the oxidative stress response in pulmonary tissue in a hyperoxia-based model of bronchopulmonary dysplasia in newborn rats.

Methods

Newborn Wistar rats were exposed to 21% or 80% oxygen for 3 (P3) or 5 (P5) postnatal days with or without recovery on room air until postnatal day 15 (P15) and treated with vehicle or caffeine (10 mg/kg) every 48 h beginning on the day of birth. The lung tissue of the rat pups was examined for oxidative stress response at P3 and P5 immediately after oxygen exposure or after recovery in ambient air (P15) by immunohistological staining and analysis of lung homogenates by ELISA and qPCR.

Results

Lungs of newborn rats, corresponding to the saccular stage of lung development and to the human lung developmental stage of preterms, showed increased rates of total glutathione and hydrogen peroxide, oxidative damage to DNA and lipids, and induction of second-phase mediators of antioxidative stress response (superoxide dismutase, heme oxygenase-1, and the Nrf2/Keap1 system) in response to hyperoxia. Caffeine reduced oxidative DNA damage and had a protective interference with the oxidative stress response.

Conclusion

In addition to the pharmacological antagonism of adenosine receptors, caffeine appears to be a potent antioxidant and modulates the hyperoxia-induced pulmonary oxidative stress response and thus protective properties in the BPD-associated animal model. Free-radical-induced damage caused by oxidative stress seems to be a biological mechanism progress of newborn diseases. New aspects of antioxidative therapeutic strategies to passivate oxidative stress-related injury should be in focus of further investigations.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-1063-5) contains supplementary material, which is available to authorized users.

Celecoxib Protects Hyperoxia-Induced Lung Injury via NF-κB and AQP1

Objective: There is an increasing incidence of bronchopulmonary dysplasia (BDP) in preterm infants in China, which is the key issue affecting their survival rate and life quality. This study was performed to better understand the mechanism of protective effect of celecoxib on hyperoxia induced injury. Methods: Hyperoxia BPD model was established using newborn Sprague-Dawley (SD) rats exposed to high O₂ level (85%). Celecoxib treatment was also conducted. Histology of lung tissue samples were analyzed. Functional studies were systematically performed using the lung tissues and A549 cells. Results: Hyperoxia disrupted lung development in SD rats. Celecoxib alleviated the damaged lung development. NF-κB and Aquaporin (AQP) 1 were identified as the pathways in the hyperoxia-induced lung injury. We have shown that hyperoxia activated NF-κB pathway through increased nucleus translocation and repressed AQP1 expression. On the contrary, celecoxib inhibited NF-κB phosphorylation and nucleus translocation and increased AQP1 expression through inhibiting COX2 activity. Additionally, celecoxib also rescued apoptosis induced by hyperoxia. Conclusion: Our study identified NF-κB and AQP1 as the pathways in the hyperoxia-induced lung injury in the hyperoxia BPD model SD rats and it provided a better understanding of the protective effect of celecoxib. It suggests NF-κB and AQP1 may be as potential targets for treating newborns with BPD.

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.