Acute lung injury in preterm newborn infants: mechanisms and management

The respiratory consequences of preterm birth: from infancy to adulthood

Survival of preterm-born infants, especially at extremes of prematurity (less than 28 weeks gestation), is now common, particularly in the developed world. Despite advances in neonatal care, short-term respiratory morbidity, termed bronchopulmonary dysplasia (also called chronic lung disease of prematurity), remains an important clinical outcome. As survival during the neonatal period has improved, preterm-born individuals are now entering childhood, adolescence and adulthood in far greater numbers, and adverse longer-term respiratory outcomes following birth at an immature stage of lung development are becoming increasingly apparent. In this article, we shall review the background of the major respiratory complications in the neonatal period, bronchopulmonary dysplasia, and the current evidence regarding its prevention and management. In addition, we shall review the emerging literature on the respiratory morbidity experienced in childhood, adolescence, and adulthood by preterm-born survivors, with reduced lung function and a risk of developing chronic obstructive pulmonary disease in early adult life. As this population of preterm-born individuals increases, an understanding of the respiratory consequences of preterm birth will become increasingly important not only for neonatologists, paediatricians and paediatric pulmonologists but also for physicians and healthcare professionals involved in the care of adults who were born preterm.

Role of gasotransmitters in necroptosis

Gasotransmitters are endogenous gaseous signaling molecules that can freely pass through cell membranes and transmit signals between cells, playing multiple roles in cell signal transduction. Due to extensive and ongoing research in this field, we have successfully identified many gasotransmitters so far, among which nitric oxide, carbon monoxide, and hydrogen sulfide are best studied. Gasotransmitters are implicated in various diseases related to necroptosis, such as cardiovascular diseases, inflammation, ischemia-reperfusion, infectious diseases, and neurological diseases. However, the mechanisms of their effects on necroptosis are not fully understood. This review focuses on endogenous gasotransmitter synthesis and metabolism and discusses their roles in necroptosis, aiming to offer new insights for the therapeutic approaches to necroptosis-associated diseases.

Efficacy and safety of different inhaled corticosteroids for bronchopulmonary dysplasia prevention in preterm infants: A systematic review and meta-analysis

BACKGROUND

This systematic review and meta-analysis aimed to evaluate the efficacy and safety of inhaled corticosteroids (budesonide, beclomethasone, or fluticasone propionate) in preventing bronchopulmonary dysplasia (BPD) for premature infants.

METHOD

Electronic databases, including PubMed, EMBASE, Web of science, Scopus, and Cochrane library, were searched from databases inception to January 2022 for eligible randomized controlled trials. Clinical outcomes such as BPD, mortality, BPD or death, adverse events, and neurodevelopmental outcomes were assessed.

RESULTS

Overall, budesonide was significantly associated with a reduction in BPD at 36 weeks' postmenstrual age (RR 0.48; 95 % CI [0.38, 0.62]) and patent ductus arteriosus (PDA) (RR 0.75; 95 % CI [0.63, 0.89]) compared with control treatments. Early longer duration inhalation of budesonide alone was associated with a lower risk of BPD at 36 weeks' postmenstrual age and PDA compared with controls. Early shorter duration intratracheal instillation of budesonide with surfactant as vehicle was associated with a lower risk of BPD at 36 weeks' postmenstrual age and all-cause mortality compared with surfactant. There was no statistically significant difference between budesonide and control groups regarding neurodevelopmental impairment. Beclomethasone and fluticasone propionate did not show any superior or inferior effect on clinical outcomes compared to control treatments.

CONCLUSION

These findings suggest that budesonide, especially intratracheal instillation of budesonide using surfactant as a vehicle, is a safe and effective option in preventing BPD for preterm infants. More well-design large-scale trials with long-term follow-ups are necessary to verify the present findings.

Evidence of abnormality in glutathione metabolism in the airways of preterm born children with a history of bronchopulmonary dysplasia

Preterm-born children are at risk of long-term pulmonary deficits, including those who developed bronchopulmonary dysplasia (BPD) in infancy, however the underlying mechanisms remain poorly understood. We characterised the exhaled breath condensate (EBC) metabolome from preterm-born children, both with and without BPD. Following spirometry, EBC from children aged 7-12 years, from the Respiratory Health Outcomes in Neonates study, were analysed using Time-of-Flight Mass Spectrometry. Metabolite Set Enrichment Analysis (MSEA) linked significantly altered metabolites to biological processes. Linear regression models examined relationships between metabolites of interest and participant demographics. EBC was analysed from 214 children, 144 were born preterm, including 34 with BPD. 235 metabolites were detected, with 38 above the detection limit in every sample. Alanine and pyroglutamic acid were significantly reduced in the BPD group when compared to preterm controls. MSEA demonstrated a reduction in glutathione metabolism. Reduced quantities of alanine, ornithine and urea in the BPD group were linked with alteration of the urea cycle. Linear regression revealed significant associations with BPD when other characteristics were considered, but not with current lung function parameters. In this exploratory study of the airway metabolome, preterm-born children with a history of BPD had changes consistent with reduced antioxidant mechanisms suggesting oxidative stress.

Follow-up study of infants recruited to the randomised, placebo-controlled trial of azithromycin for the prevention of chronic lung disease of prematurity in preterm infants-study protocol for the AZTEC-FU study

Background

Preterm birth, especially at less than 30 weeks’ gestation, is significantly associated with respiratory, neurodevelopmental and growth abnormalities. The AZTEC study has recruited 799 infants born at < 30 weeks’ gestation to determine if a ten-day intravenous treatment with azithromycin improves survival without development of chronic lung disease of prematurity (CLD) at 36 weeks’ post menstrual age (PMA) when compared to placebo. The follow-up studies will compare respiratory, neurodevelopmental and growth outcomes up to 2 years of corrected age between infants who received azithromycin and those who received placebo in the early neonatal period.

Methods

Survivors at 36 weeks’ PMA from the main Azithromycin Therapy for Chronic Lung Disease of Prematurity (AZTEC) study with parental consent will continue to be followed up to discharge from the neonatal unit and to 2 years of corrected age. Length of stay, rates of home oxygen, length of supplemental oxygen requirement, hospital admissions, drug usage, respiratory illness, neurodevelopmental disability and death rates will be reported. Data is being collected via parentally completed respiratory and neurodevelopmental questionnaires at 1 and 2 years of corrected age respectively. Additional information is being obtained from various sources including hospital discharge and clinical letters from general practitioners and hospitals as well as from national databases including the National Neonatal Research Database and NHS Digital.

Discussion

The AZTEC-FU study will assess mortality and important neonatal morbidities including respiratory, neurodevelopmental and growth outcomes. Important safety data will also be collected, including the incidence of potential consequences of early macrolide use, primarily pyloric stenosis. This study may have implications on future neonatal care.

Trial registration

The study was retrospectively registered on ISRCTN (ISRCTN47442783).

Impaired exercise outcomes with significant bronchodilator responsiveness in children with prematurity-associated obstructive lung disease

INTRODUCTION

Preterm-born children have their normal in-utero lung development interrupted, thus are at risk of short- and long-term lung disease. Spirometry and exercise capacity impairments have been regularly reported in preterm-born children especially those who developed chronic lung disease of prematurity (CLD) in infancy. However, specific phenotypes may be differentially associated with exercise capacity. We investigated exercise capacity associated with prematurity-associated obstructive (POLD) or prematurity-associated preserved ratio of impaired spirometry (pPRISm) when compared to preterm- and term-controls with normal lung function.

MATERIALS AND METHODS

Preterm- and term-born children identified through home screening underwent in-depth lung function and cardiorespiratory exercise testing, including administration of postexercise bronchodilator, as part of the Respiratory Health Outcomes in Neonates (RHiNO) study.

RESULTS

From 241 invited children, aged 7-12 years, 202 underwent exercise testing including 18 children with POLD (percent predicted (%)FEV₁ and FEV₁ /FVC < LLN); 12 pPRISm (%FEV₁  < LLN and FEV₁ /FVC ≥ LLN), 106 preterm-controls (PT_c , %FEV₁  ≥ LLN) and 66 term-controls (T_c , %FEV₁  > 90%). POLD children had reduced relative workload, peak O₂ uptake, CO₂ production, and minute ventilation compared to T_c , and used a greater proportion of their breathing reserve compared to both control groups. pPRISm and PT_c children also had lower O₂ uptake compared to T_c . POLD children had the greatest response to postexercise bronchodilator, improving their %FEV₁ by 19.4% (vs 6.3%, 6% 6.3% in pPRISm PT_c, T_c , respectively; p < .001).

CONCLUSION

Preterm-born children with obstructive airway disease had the greatest impairment in exercise capacity, and significantly greater response to postexercise bronchodilators. These classifications can be used to guide treatment in children with POLD.

Lung mechanics and respiratory morbidities in school-age children born moderate-to-late preterm

BACKGROUND

Late and moderate prematurity may have an impact on pulmonary function during childhood. The present study aimed to investigate lung mechanics in school-age children born moderate-to-late preterm (MLPT).

METHODS

Children aged 5-10 years were enrolled in this case-control study. Lung function and bronchodilator response were assessed by impulse oscillometry (IOS) at two hospital-based specialized clinics. A structured questionnaire was employed to assess respiratory morbidities.

RESULTS

A total of 123 children was divided into two groups: case (MLPT) n = 52 and control (children born at term) n = 71. The results showed no difference between groups in mean baseline IOS variables: R5 0.80 ± 0.20 vs 0.82 ± 0.22 kPa/L/s, p = 0.594, R20 0.54 ± 0.13 vs 0.55 ± 0.13 kPa/L/s, p = 0.732, R5-R20 0.26 ± 0.12 vs 0.27 ± 0.15 kPa/L/s, p = 0.615, X5 -0.29 ± 0.01 vs -0.29 ± 0.1 kPa/L/s, p = 0.990, Fres 21.1 ± 3.3 vs 21.7 ± 3.1 L/s, p = 0.380, and AX 2.7 ± 3.36 vs 2.5 ± 1.31 kPa/L/s, p = 0.626. Bronchodilator response and the occurrence of respiratory morbidities after birth were also similar between groups.

CONCLUSIONS

This study found lung mechanics parameters to be similar in school-age children born MLPT and those born at term, suggesting that pulmonary plasticity continues to occur in children up to school age.

IMPACT

Late and moderate prematurity is associated with an increased risk of reduced pulmonary function during childhood. Follow-up reports in adolescents and adults born MLPT are scarce but have indicated pulmonary plasticity with normalization of airway function. Our results show that the lung function in school-age children born MLPT is similar to that of children born at term.

Integrated Network Pharmacology and Experimental Validation Approach to Investigate the Therapeutic Effects of Capsaicin on Lipopolysaccharide-Induced Acute Lung Injury

An integrated method combining network pharmacology and in vivo experiment was performed to investigate the therapeutic mechanism of capsaicin (Cap) against acute lung injury. The potential key genes and signaling pathways involved in the therapeutic effect of Cap were predicted by the network pharmacology analyses. Additionally, the histological assessment, ELISA, and RT-qPCR were performed to confirm the therapeutic effect and the potential mechanism action involved. Our findings showed that TNF, IL-6, CXCL1, CXCL2, and CXCL10 were part of the top 50 genes. Enrichment analysis revealed that those potential genes were enriched in the TNF signaling pathway and IL-17 signaling pathway. In vivo experiment results showed that Cap alleviated histopathological changes, decreased inflammatory infiltrated cells and inflammatory cytokines, and improved antioxidative enzyme activities in the bronchoalveolar lavage fluid (BALF). Furthermore, Cap treatment effectively downregulated TNF, IL-6, NF-κB, CXCL1, CXCL2, and CXCL10 in lung tissue. Thus, our findings demonstrated that Cap has the therapeutic effect on LPS-induced acute lung injury in neonatal rats via suppression of the TNF signaling pathway and IL-17 signaling pathway.

Lipocalin-2 silencing suppresses inflammation and oxidative stress of acute respiratory distress syndrome by ferroptosis via inhibition of MAPK/ERK pathway in neonatal mice

Neonatal acute respiratory distress syndrome (ARDS) has high morbidity and mortality rates worldwide, but there is a lack of pharmacologic treatment and clinical targeted therapies. In this study, we aimed to explore the effects of Lipocalin-2 (LCN2) on ferroptosis-mediated inflammation and oxidative stress in neonatal ARDS and the potential mechanism. In this study, we established an in vivo ARDS mouse model and an in vitro ARDS cell model by LPS (Lipopolysaccharide) stimulation. Lung tissue injury was evaluated by wet/dry ratios and histopathological examination. LCN2 expression was detected by qRT-PCR and Western blot. Inflammatory factors, oxidative stress and apoptosis were also detected. Ferroptosis was identified by detection of Fe²⁺ level and ferroptosis-associated protein expressions. Mitogen-activated protein kinases (MAPK)/extracellular signal-regulated kinase (ERK) pathway signaling was examined by Western blot analysis. The data revealed that LCN2 expression was significantly upregulated in neonatal mice with ARDS. Interference with LCN2 protected LPS-induced lung in neonatal mouse by reducing the radio of wet/dry and alleviating pathological damages. In addition, LCN2 silencing repressed LPS-induced inflammation, oxidative stress in vivo and in vitro, as well as apoptosis. Meanwhile, decreased level of Fe²⁺ and transferrin while increased levels of ferritin heavy chain 1 (FTH1) and glutathione peroxidase 4 (GPX4) were observed. The expression MAPK/ERK pathway was inhibited by depletion of LCN2. The present results suggest that LCN2 knockdown protected LPS-induced ARDS model via inhibition of ferroptosis-related inflammation and oxidative stress by inhibiting the MAPK/ERK pathway, thereby presenting a novel target for the treatment of ARDS.

Association of Early Life Factors with Prematurity-Associated Lung Disease: Prospective Cohort Study

Background

Although bronchopulmonary dysplasia (BPD) is associated with lung function deficits in childhood, many who develop BPD have normal lung function in childhood and many without BPD, including those born at 33–34 weeks of gestation, have lung dysfunction in childhood. Since the predictability of BPD for future lung deficits is increasingly doubted, we prospectively recruited preterm-born children to identify early-life factors associated with lung function deficits after preterm birth.

Methods

From 767 children aged 7–12 years who had their respiratory symptoms assessed, and had spirometry before and after a bronchodilator in our Respiratory Health Outcomes in Neonates (RHiNO) study, 739 (544 preterm-born at ≤34 weeks of gestation and 195 term-born) had satisfactory lung function. Data were analysed using multivariable logistic regression and mediation.

Results

When preterm-born children were classified according to their lung function, low lung function (prematurity-associated lung disease (PLD)) was associated with BPD, gestation and intra-uterine growth restriction (IUGR) on univariable logistic regression analyses. However, on multivariable logistic regression analyses, gestation (β= –0.153, se 0.051; p=0.003) and IUGR (OR 1.783, 95% CI 1.06–3.00; p=0.029) remained significantly associated with later deficits of lung function, but BPD (OR 0.99, 95% CI 0.52–1.89; p=0.974) did not. Mediation analyses confirmed these results.

Conclusions

Although traditionally BPD has been associated with low lung function in later life, the data show that gestation and IUGR are significantly associated with PLD in childhood, but BPD is not. By identifying children with PLD, we can better understand the underlying mechanisms and develop optimal therapies.

Although traditionally bronchopulmonary dysplasia is thought to be associated with longer term lung function deficits, this study shows that gestation and fetal growth restriction are better predictors of lung function deficits in prematurely born childrenhttps://bit.ly/3obSdSz

Efficacy of intratracheal budesonide-surfactant combined therapy in surfactant-insufficient rat lungs with lipopolysaccharide insult

BACKGROUND

Intratracheal steroid therapy for lipopolysaccharide (LPS)-induced acute lung injury (ALI) remains challenging particularly in surfactant-insufficient lungs, a common problem of neonatal or pediatric ALI. Surfactant has been used as a vehicle for intratracheal steroid in the treatment of other types of ALI. This study investigated the efficacy of intratracheal budesonide (BUD) delivered by two concentrations of surfactant in the treatment of LPS-induced ALI in surfactant-insufficient rat lungs.

METHODS

Male adult rats were anesthetized and ventilated. Our ALI model was established by repeated saline lavage to produce surfactant insufficiency, followed by intratracheal LPS instillation. Five study groups (n = 5 for each) with different intratracheal treatments following ALI were used: control (no treatment), BUD (NS-BUD; BUD in saline), DS-BUD (BUD in diluted surfactant), FS-BUD (BUD in full-strength surfactant), FS (full-strength surfactant). Cardiopulmonary variables were monitored 4 hours post injury. Histological and immunohistochemical assessments of the lungs were performed.

RESULTS

The FS-BUD and FS groups presented better gas exchange, less metabolic acidosis, less oxygen index, and more stable hemodynamic changes than the DS-BUD, NS-BUD, and control groups. The total lung injury scores assessed by histological examination were ordered as follows: FS-BUD < DS-BUD or FS < NS-BUD < control. The immunostaining intensities of lung myeloperoxidase showed the following order: NS-BUD, DS-BUD, or FS-BUD < control or FS. Only the FS-BUD group displayed a smaller immunostaining intensity of lung tumor necrosis factor (TNF)-α than the control group.

CONCLUSION

Among our therapeutic strategies, intratracheal BUD delivered by full-strength surfactant confers an optimal protection against LPS-induced ALI in surfactant-insufficient rat lungs.

Narciclasine attenuates LPS-induced acute lung injury in neonatal rats through suppressing inflammation and oxidative stress

Acute lung injury (ALI) is a life-threatening disorder related to serious pulmonary inflammation. Narciclasine exhibits strong anti-inflammation activity and attenuates the reactive oxygen species (ROS) production. The present study aims to investigate the underlying mechanism related to the effect of narciclasine on the pathogenesis of neonatal acute lung injury (ALI). Narciclasine attenuated LPS-induced pathological injury and pulmonary edema. In addition, narciclasine suppressed the secretion of inflammatory cytokines, including necrosis factor-α (TNF-α), Interleukin (IL-6), IL-1β, monocyte chemotactic protein-1 (MCP-1) in serum, and inhibited the expressions of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in lung tissues of neonatal ALI rats. Furthermore, narciclasine alleviated oxidative stress and apoptosis in lung tissues. Importantly, narciclasine exerted an inhibition effect on NF-κB nuclear translocation and activation of Toll-like Receptor 4 (TLR4)/Nuclear factor (NF)-κB/Cyclooxygenase 2 (Cox2) signaling pathway. Taken together, narciclasine protected against lung injury via inhibition effect on excessive inflammation, oxidative stress and apoptosis, hence, narciclasine may be considered as an effective and novel agent for clinical therapeutic strategy of ALI Treatment.

MicroRNA-490-3p inhibits inflammatory responses in LPS-induced acute lung injury of neonatal rats by suppressing the IRAK1/TRAF6 pathway

Acute lung injury (ALI) is a main reason for neonatal death. Studying the molecular mechanism behind neonatal ALI is critical for the development of therapeutic strategies. The present study explored microRNA (miR)-490-3p-mediated regulatory effects on lipopolysaccharide (LPS)-induced neonatal ALI. Initially, LPS (10 mg/kg body weight) was injected to 3-8 day old neonatal SD rats to induce ALI, and LPS (100 ng/ml) was used to treat lung epithelial cells to construct an ALI model in vitro. Next, miR-490-3p, pro-inflammatory factors (that included IL-1β, IL-6 and TNFα), interleukin 1 receptor associated kinase 1 (IRAK1) and TNF receptor associated factor 6 (TRAF6) mRNA expression levels in lung tissues and epithelial cells were assessed via reverse transcription-quantitative PCR. In addition, miR-490-3p mimics were adopted to construct its overexpressed cell model, and Cell Counting Kit-8 and BrdU assays were conducted to assess cell viability. Furthermore, the miR-490-3p target, IRAK was predicted by bioinformatics analysis and verified via Dual-luciferase reporter gene assay. The results revealed that miR-490-3p was markedly downregulated in an LPS-induced rat ALI model, while IL-1β, IL-6, TNFα, IRAK1 and TRAF6 were all upregulated and negatively correlated with miR-490-3p expression. Moreover, overexpressed miR-490-3p significantly inhibited LPS-induced lung epithelial cell injury and inflammatory response. Mechanistically, miR-490-3p targeted and attenuated IRAK1 expression, which thus inactivated the LPS-mediated TRAF6/NF-κB pathway. Overall, the present study indicated that miR-490-3p overexpression significantly inhibited LPS-induced ALI and inflammatory responses by restricting the IRAK1/TRAF6 pathway.

Study protocol: azithromycin therapy for chronic lung disease of prematurity (AZTEC) - a randomised, placebo-controlled trial of azithromycin for the prevention of chronic lung disease of prematurity in preterm infants

INTRODUCTION

Chronic lung disease of prematurity (CLD), also known as bronchopulmonary dysplasia (BPD), is a cause of significant respiratory morbidity in childhood and beyond. Coupled with lung immaturity, infections (especially by Ureaplasma spp) are implicated in the pathogenesis of CLD through promotion of pulmonary inflammation. Azithromycin, which is a highly effective against Ureaplasma spp also has potent anti-inflammatory properties. Thus, azithromycin therapy may improve respiratory outcomes by targeting infective and inflammatory pathways. Previous trials using macrolides have not been sufficiently powered to definitively assess CLD rates. To address this, the azithromycin therapy for chronic lung disease of prematurity (AZTEC) trial aims to determine if a 10-day early course of intravenous azithromycin improves rates of survival without CLD when compared with placebo with an appropriately powered study.

METHODS AND ANALYSIS

796 infants born at less than 30 weeks' gestational age who require at least 2 hours of continuous respiratory support within the first 72 hours following birth are being enrolled by neonatal units in the UK. They are being randomised to receive a double-blind, once daily dose of intravenous azithromycin (20 mg/kg for 3 days, followed by 10 mg/kg for a further 7 days), or placebo. CLD is being assessed at 36 weeks' PMA. Whether colonisation with Ureaplasma spp prior to randomisation modifies the treatment effect of azithromycin compared with placebo will also be investigated. Secondary outcomes include necrotising enterocolitis, intraventricular/cerebral haemorrhage, retinopathy of prematurity and nosocomial infections, development of antibiotic resistance and adverse reactions will be monitored.

ETHICS AND DISSEMINATION

Ethics permission has been granted by Wales Research Ethics Committee 2 (Ref 18/WA/0199), and regulatory permission by the Medicines and Healthcare Products Regulatory Agency (Clinical Trials Authorisation reference 21323/0050/001-0001). The study is registered on ISRCTN (ISRCTN11650227). The study is overseen by an independent Data Monitoring Committee and an independent Trial Steering Committee. We shall disseminate our findings via national and international peer-reviewed journals, and conferences. A summary of the findings will also be posted on the trial website.

Dissimilarity of the gut-lung axis and dysbiosis of the lower airways in ventilated preterm infants

BACKGROUND

Chronic lung disease of prematurity (CLD), also called bronchopulmonary dysplasia, is a major consequence of preterm birth, but the role of the microbiome in its development remains unclear. Therefore, we assessed the progression of the bacterial community in ventilated preterm infants over time in the upper and lower airways, and assessed the gut-lung axis by comparing bacterial communities in the upper and lower airways with stool findings. Finally, we assessed whether the bacterial communities were associated with lung inflammation to suggest dysbiosis.

METHODS

We serially sampled multiple anatomical sites including the upper airway (nasopharyngeal aspirates), lower airways (tracheal aspirate fluid and bronchoalveolar lavage fluid) and the gut (stool) of ventilated preterm-born infants. Bacterial DNA load was measured in all samples and sequenced using the V3-V4 region of the 16S rRNA gene.

RESULTS

From 1102 (539 nasopharyngeal aspirates, 276 tracheal aspirate fluid, 89 bronchoalveolar lavage, 198 stool) samples from 55 preterm infants, 352 (32%) amplified suitably for 16S RNA gene sequencing. Bacterial load was low at birth and quickly increased with time, but was associated with predominant operational taxonomic units (OTUs) in all sample types. There was dissimilarity in bacterial communities between the upper and lower airways and the gut, with a separate dysbiotic inflammatory process occurring in the lower airways of infants. Individual OTUs were associated with increased inflammatory markers.

CONCLUSIONS

Taken together, these findings suggest that targeted treatment of the predominant organisms, including those not routinely treated, such as Ureaplasma spp., may decrease the development of CLD in preterm-born infants.

Ibudilast, a Phosphodiesterase-4 Inhibitor, Ameliorates Acute Respiratory Distress Syndrome in Neonatal Mice by Alleviating Inflammation and Apoptosis

Background

Acute respiratory distress syndrome (ARDS) is a sudden and serious disease with increasing morbidity and mortality rates. Phosphodiesterase 4 (PDE4) is a novel target for inflammatory disease, and ibudilast (IBU), a PDE4 inhibitor, inhibits inflammatory response. Our study investigated the effect of IBU on the pathogenesis of neonatal ARDS and the underlying mechanism related to it.

Material/Methods

Western blotting was performed to analyze the expression levels of PDE4, CXCR4, SDF-1, CXCR5, CXCL1, inflammatory cytokines, and proteins related to cell apoptosis. Hematoxylin-eosin staining was performed to observe the pathological morphology of lung tissue. Pulmonary edema score was used to assess the degree of lung water accumulation after pulmonary injury. Enzyme-linked immunosorbent assay (ELISA) was used to assess levels of inflammatory factors (TNF-α, IL-1β, IL-6, and MCP-1) in serum. TUNEL assay was used to detect apoptotic cells.

Results

Increased expression of PDE4 was observed in an LPS-induced neonatal ARDS mouse model, and IBU ameliorated LPS-induced pathological manifestations and pulmonary edema in lung tissue. In addition, IBU attenuated the secretion of inflammatory cytokines by inactivating the chemokine axis in the LPS-induced neonatal ARDS mouse model. Finally, IBU significantly reduced LPS-induced cell apoptosis in lung tissue.

Conclusions

IBU, a PDE4 inhibitor, protected against ARDS by interfering with pulmonary inflammation and apoptosis. Our findings provide a novel and promising strategy to regulate pulmonary inflammation in ARDS.

Preterm prelabor rupture of membranes prior to early preterm delivery elevates the risk of later respiratory-related hospitalizations in the offspring

OBJECTIVE

Preterm prelabor rupture of membranes (PPROM) precedes 30%-40% of all preterm births. Early preterm delivery (<34 gestation weeks) is a well-established risk factor for short- and long-term respiratory morbidity in the offspring. We aimed to ascertain whether the presence of PPROM, before early preterm delivery, independently impacts long-term respiratory hospitalizations in the offspring.

STUDY DESIGN

A population-based retrospective cohort analysis was performed including all singleton early preterm deliveries. Exposure was defined as the presence of PPROM. Hospitalizations of the offspring up to the age of 18 years involving respiratory-related morbidity were evaluated. A Kaplan-Meier survival curve and multivariable Cox regression model were used to assess the association.

RESULTS

During the study period, 3309 early preterm deliveries met the inclusion criteria. In 22.4% of cases (n = 742), PPROM was documented. Rates of respiratory-related hospitalizations of the offspring up to the age of 18 years were significantly higher in the exposed group (12.5% vs 9.4% in the unexposed group, P = .023). The survival curve demonstrated significantly higher cumulative incidence of respiratory hospitalizations in the exposed group (logrank P = .018). In the Cox regression model controlled for gestational age, and other clinically relevant confounders - PPROM before early preterm deliveries was independently associated with an increased risk for long-term childhood respiratory-related hospitalizations in the offspring (adjusted hazard ratio 1.40, 95% confidence interval, 1.05-1.87, P = .021).

CONCLUSION

Fetal exposure to PPROM before early preterm delivery was associated with an increased risk for long-term respiratory hospitalizations in the offspring.

Thearubigin regulates the production of Nrf2 and alleviates LPS-induced acute lung injury in neonatal rats

This study was undertaken to investigate the effect of natural bioactive compound thearubigin on neonatal acute lung injury (ALI) using LPS-induced ALI as a model. We also attempted to understand the possible underlying mechanism. The effect of thearubigin on lung wet-to-dry weight ratio, the activity of LDH, lung histopathology, BALF protein levels, the activity of MPO, production and extravasation of cytokines and oxidative stress were studied. The results showed that thearubigin caused a significant reduction in lung inflammation as evident from lung wet-to-dry weight ratio, BALF protein levels and MPO activity and histopathological analysis. It was further observed that the attenuation in inflammation happened due to a significant reduction in cytokine levels in alveolar cavities. Thearubigin also showed strong antioxidant properties as evidenced by reduced levels of oxygen species such as H₂O₂, MDA and OH ion. Additionally, the antioxidant response element nuclear factor erythroid-2-related factor 2 (Nrf2) pathway was found to be activated in thearubigin-treated group. These results provided a possible mechanism of antioxidant activity of thearubigin in neonatal ALI. Overall, this study showed that thearubigin can be a natural alternative for the treatment of neonatal ALI. However, further studies are required to understand its mechanism antioxidant and anti-inflammatory action.

Carbon Monoxide Attenuates Lipopolysaccharides (LPS)-Induced Acute Lung Injury in Neonatal Rats via Downregulation of Cx43 to Reduce Necroptosis

Background

Acute lung injury (ALI) is one of major causes of death in newborns, making it urgent to improve therapy. Administration of low dose carbon monoxide (CO) plays a protective role in ALI but the mechanisms are not fully understood. This study was designed to test the therapeutic effect of monoxide-releasing molecule 3 (MORM3) in lipopolysaccharide (LPS) induced neonatal ALI and the possibly associated molecular mechanisms.

Material/Methods

For this study, 3- to 8-day old Newborn Sprague-Dawley rats were subjected to intraperitoneal injection of 3 mg/kg LPS to induce ALI. Then animals received intraperitoneal injection of carbon monoxide-releasing molecules 3 (CORM3) (8 mg/kg) or inactive CORM3 (iCORM3) for 7 consecutive days. Lung tissues were collected for histological examination and total cell counts and protein content in bronchoalveolar lavage fluid (BALF) were measured. Expression of Cx43 and necroptosis-related markers were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot.

Results

LPS exposure induced significant lung injury indicated by histological damage, increased lung wet/dry weight ratio (W/D) and increased total cell counts and protein concentration in BALF. These changes were significantly ameliorated by administration of CORM3 but not iCORM3. LPS also increased necroptosis-related markers RIP1, RIP3, and MLKL and their elevation was blocked by CORM3. CORM3 administration ameliorated LPS induced elevation of Cx43 expression and adenoviral overexpression of Cx43 abolished lung protective effect of CORM3. CORM3 administration attenuated LPS induced activation of extracellular-signal-regulated kinase (ERK) and its protection against necroptosis was abolished by ERK inhibitor U0126.

Conclusions

CORM3 attenuates LPS-Induced ALI in neonatal rats and its lung protective effect might be through downregulation of Cx43 to attenuate ERK signaling and ameliorate necroptosis, suggesting CORM3 as a potential therapeutic drug for ALI in neonates.

Protective effects of propofol on experimental neonatal acute lung injury

The present study aimed to investigate the effects of propofol on neonatal acute lung injury (ALI) in a rat model and to examine the molecular mechanisms underlying propofol function. A rat model of ALI was established by intraperitoneal injection of lipopolysaccharides (LPS). The neonatal rats were treated with various concentrations of propofol and a lung injury score was assessed. The protein expression levels of pro‑inflammatory cytokines was detected using ELISA. In the present study, oxidative stress was determined by measuring the level of malondialdehyde (MDA) and the activity of superoxide dismutase (SOD) in lung tissues. Reverse transcription quantitative‑polymerase chain reaction and western blot analysis were used to examine the mRNA and protein expression levels of the factors downstream to LPS signaling pathway. Treatment with propofol significantly alleviated LPS‑induced lung injury in neonatal rats as suggested by the decreased lung injury score, increased partial pressure of oxygen and decreased lung wet‑dry weight ratio. LPS promoted the upregulation of tumor necrosis factor α (TNF‑α), interleukin (IL)‑6 and IL‑1β in lung tissues and bronchoalveolar lavage fluid from neonatal rats exhibiting ALI. Notably, treatment with propofol decreased the expression levels of these factors. Additionally, LPS caused an increase in the levels of MDA, and a decrease in SOD activity, and treatment with propofol suppressed these effects in a dose‑dependent manner. Furthermore, LPS induced the upregulation of phosphorylated (p‑)p38, nuclear factor κ‑light‑chain‑enhancer of activated B cells (NF‑κB), p‑p65, NLR family pyrin domain containing 3 (NLRP3), apoptosis‑associated speck‑like protein containing CARD and caspase‑1 in lung tissues of neonatal rats, and treatment with propofol was able to downregulate these factors in a dose‑dependent manner. Propofol alleviated lung injury in neonatal rats with LPS‑induced ALI by preventing inflammation and oxidative stress via the regulation of the activity of the p38 mitogen‑activated protein kinase/NF‑κB signaling pathway and the expression levels of the NLRP3 inflammasome.

Comparison of the Associations of Early-Life Factors on Wheezing Phenotypes in Preterm-Born Children and Term-Born Children

Although respiratory symptoms, including wheezing, are common in preterm-born subjects, the natural history of the wheezing phenotypes and the influence of early-life factors and characteristics on phenotypes are unclear. Participants from the Millennium Cohort Study who were born between 2000 and 2002 were studied at 9 months and at 3, 5, 7, and 11 years. We used data-driven methods to define wheezing phenotypes in preterm-born children and investigated whether the association of early-life factors and characteristics with wheezing phenotypes was similar between preterm- and term-born children. A total of 1,049/1,502 (70%) preterm-born children and 12,307/17,063 (72%) term-born children had recent wheeze data for 3 or 4 time points. Recent wheeze was more common at all time points in the preterm-born group than in term-born group. Four wheezing phenotypes were defined for both groups: no/infrequent, early, persistent, and late. Early-life factors and characteristics, especially antenatal maternal smoking, atopy, and male sex, were associated with increased rates for all phenotypes in both groups, and breastfeeding was protective in both groups, except late wheeze in the preterm group. Preterm-born children had similar phenotypes to term-born children. Although early-life factors and characteristics were similarly associated with the wheezing phenotypes in both groups, the preterm-born group had higher rates of early and persistent wheeze. However, a large proportion of preterm-born children had early wheeze that resolved with time.

Terbutaline alleviates the lung injury in the neonatal rats exposed to endotoxin: Potential roles of epithelial sodium channels

Intrauterine inflammation generates inflammatory mediators that damage the developing bronchoalveolar epithelium, resulting in neonatal lung injury. Lung fluid transport disorders are the main reasons for the development of pulmonary edema, an important pathology of lung injury. Previous studies suggested that epithelial sodium channels (ENaCs) play an important role in lung fluid transport. Here, we investigated whether changes in the expression of ENaCs were observed when neonatal rat lung injury was induced by maternal exposure to endotoxin. We also examined the therapeutic effect of terbutaline nebulizer inhalation on this injury. The results showed that maternal exposure to endotoxin increased the levels of TNF-α and IL-1β in bronchoalveolar lavage fluid, suppressed α-, β-, γ-ENaC in the neonatal rat lung, and resulted in the formation of pulmonary edema on postnatal days 1 and 7. Terbutaline up-regulated the expression of β- and γ-ENaC in the distal lung after 7 days of treatment. The potential signal molecules cAMP, PKA, and CREB expressions were increased after terbutaline treatment. In summary, maternal exposure to endotoxin decreased the expression of ENaCs in neonatal rats which, in turn, may exacerbate pulmonary edema. Inhalation of the β2-adrenergic receptor agonist terbutaline improved lung liquid clearance. By increasing the expression of sodium ion channels, the effective removal of alveolar fluid provides a new way for the prevention and treatment of neonatal lung injury.

Efficacy and safety of systemic hydrocortisone for the prevention of bronchopulmonary dysplasia in preterm infants: a systematic review and meta-analysis

Early lung inflammation has been implicated in the pathogenesis of bronchopulmonary dysplasia (BPD). We aimed to establish the efficacy and safety of systemic hydrocortisone for the prevention of BPD. A systematic review and meta-analysis were undertaken, with a detailed electronic literature search. Trials involving preterm infants were included if they were randomised to receive systemic hydrocortisone or a placebo. The primary outcome was the composite of survival without BPD at 36-week postmenstrual age (PMA). Results are presented as relative risk (RR) or risk difference (RD) with 95% confidence intervals (CIs), along with numbers needed to treat (NNT) or harm (NNH). After filtering, 12 studies using early (within 1 week of birth) and two using late hydrocortisone were identified. Early systemic hydrocortisone significantly increased the chances of survival without BPD (RR 1.13, 95% CI [1.01, 1.26], NNT 18), and survival without moderate-to-severe neurodevelopmental impairment (1.13 [1.02, 1.26], NNT 14). Infants who received hydrocortisone had a higher risk of intestinal perforation (1.69 [1.07, 2.68], NNH 30), primarily with concurrent treatment for patent ductus arteriosus.Conclusion: Early systemic hydrocortisone is a modestly effective therapy for the prevention of BPD in preterm infants, although some safety concerns remain. No conclusions could be drawn for late hydrocortisone due to the paucity of studies. What is Known: • Preterm infants are at high risk of developing bronchopulmonary dysplasia (BPD) and early lung inflammation plays a significant role in its pathogenesis. • Both early and late systemic dexamethasone seems to reduce the incidence of BPD, but its use is associated with serious neurodevelopmental impairment at follow-up. What is New: • Early systemic hydrocortisone significantly improved survival without BPD at 36 weeks and survival without moderate to severe neurodevelopmental impairment on follow up. • Incidence of gastrointestinal perforation associated with concurrent treatment for PDA was significantly higher, although early systemic hydrocortisone reduced the need for treatment of PDAs.

Curcumin Attenuates Pulmonary Inflammation in Lipopolysaccharide Induced Acute Lung Injury in Neonatal Rat Model by Activating Peroxisome Proliferator-Activated Receptor γ (PPARγ) Pathway

Background

This study aimed to investigate the therapeutic effect of curcumin in lipopolysaccharide (LPS) induced neonatal acute lung injury (ALI) and the possibly associated molecular mechanisms.

Material/Methods

ALI neonatal animal model was established by using LPS. Curcumin and/or peroxisome proliferator-activated receptor γ (PPARγ) inhibitor BADGE (bisphenol A diglycidyl ether) were administrated to animals. Lung edema was evaluated by PaO₂ and lung wet/dry weight ratio (W/D) measurements. EMSA was used to determine the PPARγ activity. Levels of high-mobility group box 1 (HMGB1), secretory receptor for advanced glycation end products (RAGE), tumor necrosis factor α (TNFα), interleukin 6 (IL6), and transforming growth factor β1 (TGFβ1) in bronchoalveolar lavage fluid (BALF) were examined by ELISA. Western blotting was used to evaluate the expression levels of HMGB1, RAGE, heme oxygenase 1 (HO1), TNFα, IL6, and TGFβ1 in lung tissue.

Results

Curcumin administration significantly improved lung function by increasing PaO₂ and decreasing W/D in neonatal ALI rats. Curcumin treatment upregulated the PPARγ activity and expression level of HO1 which were suppressed in lung tissue of neonatal ALI rats. Elevated levels of HMGB1, RAGE, TNFα, IL6, and TGFβ1 in both lung tissue and BALF from neonatal ALI rats were decreased dramatically by curcumin treatment. PPARγ inhibitor BADGE administration impaired curcumin’s alleviation on lung edema, inhibitory effects on inflammatory cytokine expression and recovery of PPARγ/HO1 signaling activation.

Conclusions

Curcumin alleviated lung edema in LPS-induced ALI by inhibiting inflammation which was induced by PPARγ/HO1 regulated-HMGB1/RAGE pro-inflammatory pathway.

Effect of fetal and infant growth on respiratory symptoms in preterm-born children

OBJECTIVES

Fetal growth and rapid postnatal weight gain are associated with adverse respiratory outcomes in childhood. However, the preterm-born population is less well studied. We assessed if the increased respiratory symptoms associated with altered fetal growth and infant weight gain were mediated by early factors.

STUDY DESIGN

We used data from our cohort of preterm- and term-born (n = 4284 and 2865) children, aged 1-10 years. Respiratory outcomes obtained from a respiratory questionnaire were regressed on measures of fetal growth and infant weight gain, defined as >0.67 SD change in fetal measurement or weight between birth and nine months of age, then adjusted for covariates. We used mediation analysis to investigate which variables were effect modifiers.

RESULTS

Accelerated fetal growth between the 1st trimester and birth (OR 2.01; 95%CI 1.25, 2.32), and between the 2nd trimester and birth (1.60; 1.15, 2.22) was associated with increased wheeze-ever in preterm-born children. Rapid infant weight gain was associated with increased wheeze-ever (1.22; 1.02, 1.45); children born ≤32 weeks' gestation exhibiting rapid weight gain had fivefold higher risk of wheeze-ever compared to term-born without weight gain. Current maternal smoking and gestational age were identified as candidate mediating effects.

CONCLUSIONS

Our study suggested that antenatal and postnatal growth rates are important for future respiratory health in preterm-born children, and that their effects may be mediated by modifiable factors. Minimizing exposure to environmental pollutants, especially maternal tobacco smoking, may improve outcomes.

Postnatal steroids in extreme preterm infants: Intra-tracheal instillation using surfactant as a vehicle

Chronic Lung Disease (CLD) is a common respiratory morbidity in survivors following extreme preterm birth, and is associated with adverse neurodevelopment in the long term. Besides demographics, multiple risk factors are implicated in the pathogenesis of CLD. However, early lung inflammation appears to be the common pathway that leads to the pathological and clinical changes observed in CLD. Postnatal use of systemic steroids has been successful in reducing the incidence of CLD but resulted in unacceptable adverse neurodevelopmental outcomes. The efficacy of inhaled steroids is not yet established. We review the evidence of tracheal instillation of steroids using surfactant as a lipid vehicle, including published data on drug distribution, in vitro physical studies, and clinical trials in animals and human infants.

Multifrequency Oscillatory Ventilation in the Premature Lung: Effects on Gas Exchange, Mechanics, and Ventilation Distribution

BACKGROUND

Despite the theoretical benefits of high-frequency oscillatory ventilation (HFOV) in preterm infants, systematic reviews of randomized clinical trials do not confirm improved outcomes. The authors hypothesized that oscillating a premature lung with multiple frequencies simultaneously would improve gas exchange compared with traditional single-frequency oscillatory ventilation (SFOV). The goal of this study was to develop a novel method for HFOV, termed "multifrequency oscillatory ventilation" (MFOV), which relies on a broadband flow waveform more suitable for the heterogeneous mechanics of the immature lung.

METHODS

Thirteen intubated preterm lambs were randomly assigned to either SFOV or MFOV for 1 h, followed by crossover to the alternative regimen for 1 h. The SFOV waveform consisted of a pure sinusoidal flow at 5 Hz, whereas the customized MFOV waveform consisted of a 5-Hz fundamental with additional energy at 10 and 15 Hz. Per standardized protocol, mean pressure at airway opening ((Equation is included in full-text article.)) and inspired oxygen fraction were adjusted as needed, and root mean square of the delivered oscillatory volume waveform (Vrms) was adjusted at 15-min intervals. A ventilatory cost function for SFOV and MFOV was defined as (Equation is included in full-text article.), where Wt denotes body weight.

RESULTS

Averaged over all time points, MFOV resulted in significantly lower VC (246.9 ± 6.0 vs. 363.5 ± 15.9 ml mmHg kg) and (Equation is included in full-text article.)(12.8 ± 0.3 vs. 14.1 ± 0.5 cm H2O) compared with SFOV, suggesting more efficient gas exchange and enhanced lung recruitment at lower mean airway pressures.

CONCLUSION

Oscillation with simultaneous multiple frequencies may be a more efficient ventilator modality in premature lungs compared with traditional single-frequency HFOV.

Common respiratory conditions of the newborn

KEY POINTS

Respiratory distress is a common presenting feature among newborn infants.Prompt investigation to ascertain the underlying diagnosis and appropriate subsequent management is important to improve outcomes.Many of the underlying causes of respiratory distress in a newborn are unique to this age group.A chest radiograph is crucial to assist in diagnosis of an underlying cause.

EDUCATIONAL AIMS

To inform readers of the common respiratory problems encountered in neonatology and the evidence-based management of these conditions.To enable readers to develop a framework for diagnosis of an infant with respiratory distress. The first hours and days of life are of crucial importance for the newborn infant as the infant adapts to the extra-uterine environment. The newborn infant is vulnerable to a range of respiratory diseases, many unique to this period of early life as the developing fluid-filled fetal lungs adapt to the extrauterine environment. The clinical signs of respiratory distress are important to recognise and further investigate, to identify the underlying cause. The epidemiology, diagnostic features and management of common neonatal respiratory conditions are covered in this review article aimed at all healthcare professionals who come into contact with newborn infants.

Respiratory Microbiome of New-Born Infants

The respiratory tract, once believed to be sterile, harbors diverse bacterial communities. The role of microorganisms within health and disease is slowly being unraveled. Evidence points to the neonatal period as a critical time for establishing stable bacterial communities and influencing immune responses important for long-term respiratory health. This review summarizes the evidence of early airway and lung bacterial colonization and the role the microbiome has on respiratory health in the short and long term. The challenges of neonatal respiratory microbiome studies and future research directions are also discussed.

Expression of autotaxin and lysophosphatidic acid receptors 1 and 3 in the developing rat lung and in response to hyperoxia

We sought to evaluate lysophosphatidic acid (LPA) signaling improvement in lung development by assessing the expression of autotaxin and LPA receptor 1 and 3 (LPAR1 and LPAR3) in the neonatal rat lung during normal perinatal development and in response to hyperoxia. In the developmental study, rats were sacrificed on days 17, 19, and 21 of gestation; on postnatal days 1, 4, and 7; and at adulthood (postnatal 9 weeks). In the hyperoxia study, 42 postnatal 4-day-old rat pups were divided into seven groups and exposed to either 85% O2 for 24, 72, or 120 h or room air for 0, 24, 72, or 120 h. The rats were then euthanized after 0, 24, 72, and 120 h of exposure. Immunofluorescence demonstrated that autotaxin, LPAR1, and LPAR3 proteins were broadly colocalized in airway epithelial cells, but mainly distributed in vascular endothelial and mesenchymal cells during the first postnatal week. The expression of autotaxin, LPAR1, and LPAR3 were increased during late gestation and then decreased after birth. Autotaxin expression and enzymatic activity were significantly increased at 72 and 120 h after exposure to hyperoxia. LPAR1 and LPAR3 expression was also increased after 120 h of hyperoxic exposure. These findings suggest that LPA-associated molecules were upregulated at birth and induced by hyperoxia in the developing rat lung. Therefore, the LPA pathway may be involved in normal lung development, including vascular development, as well as wound-healing processes of injured neonatal lung tissue, which is at risk of neonatal hyperoxic acute lung injury.

Neurally adjusted ventilator assist in very low birth weight infants: Current status

Continuous improvements in perinatal care have resulted in increased survival of premature infants. Their immature lungs are prone to injury with mechanical ventilation and this may develop into chronic lung disease (CLD) or bronchopulmonary dysplasia. Strategies to minimize the risk of lung injury have been developed and include improved antenatal management (education, regionalization, steroids, and antibiotics), exogenous surfactant administration and reduction of barotrauma by using exclusive or early noninvasive ventilatory support. The most frequently used mode of assisted ventilation is pressure support ventilation that may lead to patient-ventilator asynchrony that is associated with poor outcome. Ventilator-induced diaphragmatic dysfunction or disuse atrophy of diaphragm fibers may also occur. This has led to the development of new ventilation modes including neurally adjusted ventilatory assist (NAVA). This ventilation mode is controlled by electrodes embedded within a nasogastric catheter which detect the electrical diaphragmatic activity (Edi) and transmit it to trigger the ventilator in synchrony with the patient’s own respiratory efforts. This permits the patient to control peak inspiratory pressure, mean airway pressure and tidal volume. Back up pressure control (PC) is provided when there is no Edi signal and no pneumatic trigger. Compared with standard conventional ventilation, NAVA improves blood gas regulation with lower peak inspiratory pressure and oxygen requirements in preterm infants. NAVA is safe mode of ventilation. The majority of studies have shown no significant adverse events in neonates ventilated with NAVA nor a difference in the rate of intraventricular hemorrhage, pneumothorax, or necrotizing enterocolitis when compared to conventional ventilation. Future large size randomized controlled trials should be established to compare NAVA with volume targeted and pressure controlled ventilation in newborns with mature respiratory drive. Most previous studies and trials were not sufficiently large and did not include long-term patient oriented outcomes. Multicenter, randomized, outcome trials are needed to determine whether NAVA is effective in avoiding intubation, facilitating extubation, decreasing time of ventilation, reducing the incidence of CLD, decreasing length of stay, and improving long-term outcomes such as the duration of ventilation, length of hospital stay, rate of pneumothorax, CLD and other major complications of prematurity. In order to prevent barotrauma, next generations of NAVA equipment for neonatal use should enable automatic setting of ventilator parameters in the backup PC mode based on the values generated by NAVA. They should also include an upper limit to the inspiratory time as in conventional ventilation. The manufacturers of Edi catheters should produce smaller sizes available for extreme low birth weight infants. Newly developed ventilators should also include leak compensation and high frequency ventilation. A peripheral flow sensor is also essential to the proper delivery of all modes of conventional ventilation as well as NAVA.

Effect of preterm birth on exercise capacity: A systematic review and meta-analysis

BACKGROUND

Survivors of preterm-birth have increased prevalence of respiratory, cardiovascular, and neurological diseases in later life however, the overall impact of prematurity on cardiorespiratory exercise capacity is unclear.

OBJECTIVE

We, therefore, systematically reviewed the literature on cardiorespiratory exercise capacity in survivors of preterm birth.

METHODOLOGY

Relevant studies up to March 2013 were searched using eight electronic health databases. Studies reporting exercise capacity in participants born preterm (<37 weeks) were included. The main outcome of interest was oxygen uptake (V˙O2max⁡) at maximal exercise. Data were categorized into four groups: (i) preterm-born subjects including those with or without bronchopulmonary dysplasia (BPD) but excluding study groups biased towards BPD; (ii) preterm-born subjects (BPD excluded); (iii) preterm-born subjects who had BPD28 (defined as oxygen dependency at 28 days of life) in infancy; (iv) preterm born subjects with BPD36 (oxygen dependency at 36 weeks post menstrual age) in infancy.

RESULTS

From 9,341 abstracts, 22 included publications reported V˙O2max⁡ in ml/kg/min from 685 preterm and 680 term-born subjects. Overall 20 studies reported results for preterm-born subjects including BPD; 14 studies for the preterm group excluding BPD; 10 studies for the BPD28 group; and 8 studies for BPD36 group. The mean differences (95% CI) for the four groups were -2.20 (-3.70, -0.70) ml/kg/min; -2.26 (-4.44, -0.07 ml/kg/min; -3.04 (-5.48, -0.61) ml/kg/min, and -3.05 (-5.93, -0.18) ml/kg/min, respectively.

CONCLUSION

Despite marked deficits in spirometry, preterm-born children have a marginally decreased V˙O2max⁡, which is unlikely to be of great clinical significance. Pediatr Pulmonol. 2015; 50:293-301. © 2014 Wiley Periodicals, Inc.

Role of serine proteases in the regulation of interleukin-877 during the development of bronchopulmonary dysplasia in preterm ventilated infants

RATIONALE

The chemokine interleukin-8 is implicated in the development of bronchopulmonary dysplasia in preterm infants. The 77-amino acid isoform of interleukin-8 (interleukin-877) is a less potent chemoattractant than other shorter isoforms. Although interleukin-877 is abundant in the preterm circulation, its regulation in the preterm lung is unknown.

OBJECTIVES

To study expression and processing of pulmonary interleukin-877 in preterm infants who did and did not develop bronchopulmonary dysplasia.

METHODS

Total interleukin-8 and interleukin-877 were measured in bronchoalveolar lavage fluid from preterm infants by immunoassay. Neutrophil serine proteases were used to assess processing. Neutrophil chemotaxis assays and degranulation of neutrophil matrix metalloproteinase-9 were used to assess interleukin-8 function.

MAIN RESULTS

Peak total interleukin-8 and interleukin-877 concentrations were increased in infants who developed bronchopulmonary dysplasia compared to those who did not. Shorter forms of interleukin-8 predominated in the preterm lung (96.3% No-bronchopulmonary dysplasia vs 97.1% bronchopulmonary dysplasia, p>0.05). Preterm bronchoalveolar lavage fluid significantly converted exogenously added interleukin-877 to shorter isoforms (p<0.001). Conversion was greater in bronchopulmonary dysplasia infants (p<0.05). This conversion was inhibited by α-1 antitrypsin and antithrombin III (p<0.01). Purified neutrophil serine proteases efficiently converted interleukin-877 to shorter isoforms in a time- and dose-dependent fashion; shorter interleukin-8 isoforms were primarily responsible for neutrophil chemotaxis (p<0.001). Conversion by proteinase-3 resulted in significantly increased interleukin-8 activity in vitro (p<0.01).

CONCLUSIONS

Shorter, potent, isoforms interleukin-8 predominate in the preterm lung, and are increased in infants developing bronchopulmonary dysplasia, due to conversion of interleukin-877 by neutrophil serine proteases and thrombin. Processing of interleukin-8 provides an attractive therapeutic target to prevent development of bronchopulmonary dysplasia.

The role of genetic polymorphisms in antioxidant enzymes and potential antioxidant therapies in neonatal lung disease

SIGNIFICANCE

Oxidative stress is involved in the development of newborn lung diseases, such as bronchopulmonary dysplasia and persistent pulmonary hypertension of the newborn. The activity of antioxidant enzymes (AOEs), which is impaired as a result of prematurity and oxidative injury, may be further affected by specific genetic polymorphisms or an unfavorable combination of more of them.

RECENT ADVANCES

Genetic polymorphisms of superoxide dismutase and catalase were recently demonstrated to be protective or risk factors for the main complications of prematurity. A lot of research focused on the potential of different antioxidant strategies in the prevention and treatment of lung diseases of the newborn, providing promising results in experimental models.

CRITICAL ISSUES

The effect of different genetic polymorphisms on protein synthesis and activity has been poorly detailed in the newborn, hindering to derive conclusive results from the observed associations with adverse outcomes. Therapeutic strategies that aimed at enhancing the activity of AOEs were poorly studied in clinical settings and partially failed to produce clinical benefits.

FUTURE DIRECTIONS

The clarification of the effects of genetic polymorphisms on the proteomics of the newborn is mandatory, as well as the assessment of a larger number of polymorphisms with a possible correlation with adverse outcome. Moreover, antioxidant treatments should be carefully translated to clinical settings, after further details on optimal doses, administration techniques, and adverse effects are provided. Finally, the study of genetic polymorphisms could help select a specific high-risk population, who may particularly benefit from targeted antioxidant strategies.

Acute lung injury in preterm fetuses and neonates: mechanisms and molecular pathways

Acute lung injury (ALI) results in high morbidity and mortality among preterm neonates and efforts have therefore been devoted to both antenatal and postnatal prevention of the disease. ALI is the result of an inflammatory response which is triggered by a variety of different mechanisms. It mostly affects the fetal lung and, in particular, causes damage to the integrity of the lung's alveolar-capillary unit while weakening its cellular linings. Chemotactic activity and inflammatory products, such as proinflammatory cytokines TNF-α, IL-1, IL-6, IL-11, VEGF,TGF-α and TGF-β, provoke serious damage to the capillary endothelium and the alveolar epithelium, resulting in hyaline membrane formation and leakage of protein-rich edema fluid into the alveoli. Chorioamnionitis plays a major part in triggering fetal lung inflammation, while mechanical ventilation, the application of which is frequently necessary in preterm neonates, also causes ALI by inducing proinflammatory cytokines. Many different ventilation-strategies have been developed in order to reduce potential lung injury. Furthermore, tissue injury may occur as a result of injurious oxygen by-products (Reactive Oxygen Species, ROS), secondary to hyperoxia. Knowledge of the inflammatory pathways that connect intra-amniotic inflammation and ALI can lead to the formulation of novel interventional procedures. Future research should concentrate on the pathophysiology of ALI in preterm neonates and οn possible pharmaceutical interventions targeting prevention and/or resolution of ALI.

Role of interleukin-6, its receptor and soluble gp130 in chronic lung disease of prematurity

BACKGROUND

Interleukin-6 (IL-6) signalling involves the interplay between IL-6, soluble IL-6 receptor (sIL-6R) and soluble gp130 (sgp130). IL-6 activity is modulated by the soluble receptors to produce both pro- and anti-inflammatory effects in human diseases and animal models. The expression and functional activity of these molecules in lungs of preterm ventilated infants is unknown.

OBJECTIVES

We investigated this pathway in preterm infants who were at risk of developing chronic lung disease of prematurity (CLD).

METHODS

Cytokines and soluble receptors were measured in bronchoalveolar lavage fluid (BALF) from ventilated preterm infants ≤32 weeks of gestation who did or did not develop CLD. B9 cells, which specifically proliferate to IL-6, were used to assess BALF IL-6 functional activity.

RESULTS

Inflammatory cells, IL-8 and monocyte chemotactic protein-1 were increased in BALF from the CLD group when compared to the No CLD group (p < 0.05). BALF IL-6 and sIL-6R were similar in both groups. In contrast, BALF sgp130 and sgp130/sIL-6R were greater in the CLD group when compared to the No CLD group (p = 0.01 and p = 0.02, respectively). However, the increased BALF sgp130 did not appear to modulate the BALF IL-6 functional activity.

CONCLUSION

Lung inflammation was observed in the CLD group. Increased BALF sgp130 was noted in the CLD group but it did not appear to modulate the pulmonary IL-6 bioactivity. Further research is needed to investigate the potential modulatory activity of sgp130 in the preterm lung.

Impaired surfactant production by alveolar epithelial cells in a SCID-hu lung mouse model of congenital human cytomegalovirus infection

Human cytomegalovirus (HCMV) is the leading viral cause of birth defects and life-threatening lung-associated diseases in premature infants and immunocompromised children. Although the fetal lung is a major target organ of the virus, HCMV lung pathogenesis has remained unexplored, possibly as a result of extreme host range restriction. To overcome this hurdle, we generated a SCID-hu lung mouse model that closely recapitulates the discrete stages of human lung development in utero. Human fetal lung tissue was implanted into severe combined immunodeficient (CB17-scid) mice and inoculated by direct injection with the VR1814 clinical isolate of HCMV. Virus replication in the fetal lung was assessed by the quantification of infectious virus titers and HCMV genome copies and the detection of HCMV proteins by immunohistochemistry and Western blotting. We show that HCMV efficiently replicated in the lung implants during a 2-week period, forming large viral lesions. The virus productively infected alveolar epithelial and mesenchymal cells, imitating congenital infection of the fetal lung. HCMV replication triggered apoptosis near and within the viral lesions and impaired the production of surfactant proteins in the alveolar epithelium. Our findings highlight that congenital and neonatal HCMV infection can adversely impact lung development, leading to pneumonia and acute lung injury. We have successfully developed a small-animal model that closely recapitulates fetal and neonatal lung development and provides a valuable, biologically relevant tool for an understanding of the lung pathogenesis of HCMV as well as other human respiratory viruses. Additionally, this model would greatly facilitate the development and testing of new antiviral therapies for HCMV along with select human pulmonary pathogens.

Long term respiratory outcomes of late preterm-born infants

In recent years, the rate of preterm births has risen in many industrialised countries with late preterm births forming a substantial proportion of the preterm births. Late preterm infants are delivered at the immature saccular stage of lung development when surfactant and antioxidant systems are still developing. It is now increasingly recognised that late preterm infants have increased respiratory morbidity in the neonatal period. In addition, late preterm infants are at an increased risk of lower respiratory tract infections in infancy from respiratory viruses such as respiratory syncytial virus. There is a paucity of data reporting lung function in infancy and childhood in late preterm born children. The available data suggest that children born late preterm may be at risk of decreased lung function in later life. However, further studies are required to assess the medium and long term respiratory consequences of late preterm birth.