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.

Transcriptional profiling of lung macrophages identifies a predictive signature for inflammatory lung disease in preterm infants

Lung macrophages mature after birth, placing newborn infants, particularly those born preterm, within a unique window of susceptibility to disease. We hypothesized that in preterm infants, lung macrophage immaturity contributes to the development of bronchopulmonary dysplasia (BPD), the most common serious complication of prematurity. By measuring changes in lung macrophage gene expression in preterm patients at risk of BPD, we show here that patients eventually developing BPD had higher inflammatory mediator expression even on the first day of life. Surprisingly, the ex vivo response to LPS was similar across all samples. Our analysis did however uncover macrophage signature genes whose expression increased in the first week of life specifically in patients resilient to disease. We propose that these changes describe the dynamics of human lung macrophage differentiation. Our study therefore provides new mechanistic insight into both neonatal lung disease and human developmental immunology.

Tie-2 Cre-Mediated Deficiency of Extracellular Signal-Regulated Kinase 2 Potentiates Experimental Bronchopulmonary Dysplasia-Associated Pulmonary Hypertension in Neonatal Mice

Bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH) is a significant lung morbidity of infants, and disrupted lung angiogenesis is a hallmark of this disease. We observed that extracellular signal-regulated kinases (ERK) 1/2 support angiogenesis in vitro, and hyperoxia activates ERK1/2 in fetal human pulmonary microvascular endothelial cells (HPMECs) and in neonatal murine lungs; however, their role in experimental BPD and PH is unknown. Therefore, we hypothesized that Tie2 Cre-mediated deficiency of ERK2 in the endothelial cells of neonatal murine lungs would potentiate hyperoxia-induced BPD and PH. We initially determined the role of ERK2 in in vitro angiogenesis using fetal HPMECs. To disrupt endothelial ERK2 signaling in the lungs, we decreased ERK2 expression by breeding ERK2^flox/flox mice with Tie-Cre mice. One-day-old endothelial ERK2-sufficient (eERK2^+/+) or –deficient (eERK2^+/−) mice were exposed to normoxia or hyperoxia (FiO₂ 70%) for 14 d. We then performed lung morphometry, gene and protein expression studies, and echocardiography to determine the extent of inflammation, oxidative stress, and development of lungs and PH. The knockdown of ERK2 in HPMECs decreased in vitro angiogenesis. Hyperoxia increased lung inflammation and oxidative stress, decreased lung angiogenesis and alveolarization, and induced PH in neonatal mice; however, these effects were augmented in the presence of Tie2-Cre mediated endothelial ERK2 deficiency. Therefore, we conclude that endothelial ERK2 signaling is necessary to mitigate hyperoxia-induced experimental BPD and PH in neonatal mice. Our results indicate that endothelial ERK2 is a potential therapeutic target for the management of BPD and PH in infants.

Bioinformatic analysis of the molecular mechanism underlying bronchial pulmonary dysplasia using a text mining approach

Bronchopulmonary dysplasia (BPD) is a common disease of premature infants with very low birth weight. The mechanism is inconclusive. The aim of this study is to systematically explore BPD-related genes and characterize their functions.Natural language processing analysis was used to identify BPD-related genes. Gene data were extracted from PubMed database. Gene ontology, pathway, and network analysis were carried out, and the result was integrated with corresponding database.In this study, 216 genes were identified as BPD-related genes with P < .05, and 30 pathways were identified as significant. A network of BPD-related genes was also constructed with 17 hub genes identified. In particular, phosphatidyl inositol-3-enzyme-serine/threonine kinase signaling pathway involved the largest number of genes. Insulin was found to be a promising candidate gene related with BPD, suggesting that it may serve as an effective therapeutic target.Our data may help to better understand the molecular mechanisms underlying BPD. However, the mechanisms of BPD are elusive, and further studies are needed.

Antioxidants & bronchopulmonary dysplasia: Beating the system or beating a dead horse?

Preterm birth is a primary cause of worldwide childhood mortality. Bronchopulmonary dysplasia, characterized by impaired alveolar and lung vascular development, affects 25-50% of extremely low birth weight (BW; <1 kg) infants. Abnormalities in lung function persist into childhood in affected infants and are second only to asthma in terms of childhood respiratory disease healthcare costs. While advances in the medical care of preterm infants have reduced mortality, the incidence of BPD has not decreased in the past 10 years. Reactive oxygen intermediates play a key role in the development of lung disease but, despite promising preclinical therapies, antioxidants have failed to translate into meaningful clinical interventions to decrease the incidence of lung disease in premature infants. In this review we will summarize the state of the art research developments in regards to antioxidants and premature lung disease and discuss the limitations of antioxidant therapies in order to more fully comprehend the reasons why therapeutic antioxidant administration failed to prevent BPD. Finally we will review promising therapeutic strategies and targets.

Intraperitoneal injection of MSC-derived exosomes prevent experimental bronchopulmonary dysplasia

Mesenchymal stromal cell (MSC) derived exosomes mediate tissue protection and regeneration in many injuries and diseases by modulating cell protein production, protecting from apoptosis, inhibiting inflammation, and increasing angiogenesis. In the present study, daily intraperitoneal injection of MSC-derived exosomes protected alveolarization and angiogenesis in a newborn rat model of bronchopulmonary dysplasia (BPD) induced by 14 days of neonatal hyperoxia exposure (85% O₂). Exosome treatment during hyperoxia prevented disruption of alveolar growth, increased small blood vessel number, and inhibited right heart hypertrophy at P14, P21, and P56. In vitro, exosomes significantly increased tube-like network formation by HUVEC, in part through a VEGF mediated mechanism. In summary, daily intraperitoneal injection of exosomes increased blood vessel number and size in the lung through pro-angiogenic mechanisms. MSC-derived exosomes therefore have both anti-inflammatory and pro-angiogenic mechanism to protect the lung from hyperoxia induced lung and heart disease associated with BPD.

[Preventive effect of caffeine on bronchopulmonary dysplasia in preterm infants]

With the increase in the rescue success rate of critically ill preterm infants and extremely preterm infants, the incidence rate of bronchopulmonary dysplasia (BPD) is increasing year by year. BPD has a high mortality rate and high possibility of sequelae, which greatly affects the quality of life of preterm infants and brings a heavy burden to their families, and so the treatment of BPD is of vital importance. At present, no consensus has been reached on the treatment measures for BPD. However, recent studies have shown that early application of caffeine can prevent BPD. With reference to the latest studies on the effect of caffeine in the prevention of BPD, this article reviews the mechanism of action of caffeine in reducing pulmonary inflammation, improving morphological abnormalities of lung injury, reducing oxidative stress injury, and improving pulmonary function.

[Preventive effect of caffeine on bronchopulmonary dysplasia in preterm infants]

With the increase in the rescue success rate of critically ill preterm infants and extremely preterm infants, the incidence rate of bronchopulmonary dysplasia (BPD) is increasing year by year. BPD has a high mortality rate and high possibility of sequelae, which greatly affects the quality of life of preterm infants and brings a heavy burden to their families, and so the treatment of BPD is of vital importance. At present, no consensus has been reached on the treatment measures for BPD. However, recent studies have shown that early application of caffeine can prevent BPD. With reference to the latest studies on the effect of caffeine in the prevention of BPD, this article reviews the mechanism of action of caffeine in reducing pulmonary inflammation, improving morphological abnormalities of lung injury, reducing oxidative stress injury, and improving pulmonary function.

SOX2 Drives Bronchial Dysplasia in a Novel Organotypic Model of Early Human Squamous Lung Cancer

RATIONALE

Improving the early detection and chemoprevention of lung cancer are key to improving outcomes. The pathobiology of early squamous lung cancer is poorly understood. We have shown that amplification of sex-determining region Y-box 2 (SOX2) is an early and consistent event in the pathogenesis of this disease, but its functional oncogenic potential remains uncertain. We tested the impact of deregulated SOX2 expression in a novel organotypic system that recreates the molecular and microenvironmental context in which squamous carcinogenesis occurs.

OBJECTIVES

(1) To develop an in vitro model of bronchial dysplasia that recapitulates key molecular and phenotypic characteristics of the human disease; (2) to test the hypothesis that SOX2 deregulation is a key early event in the pathogenesis of bronchial dysplasia; and (3) to use the model for studies on pathogenesis and chemoprevention.

METHODS

We engineered the inducible activation of oncogenes in immortalized bronchial epithelial cells. We used three-dimensional tissue culture to build an organotypic model of bronchial dysplasia.

MEASUREMENTS AND MAIN RESULTS

We recapitulated human bronchial dysplasia in vitro. SOX2 deregulation drives dysplasia, and loss of tumor promoter 53 is a cooperating genetic event that potentiates the dysplastic phenotype. Deregulated SOX2 alters critical genes implicated in hallmarks of cancer progression. Targeted inhibition of AKT prevents the initiation of the dysplastic phenotype.

CONCLUSIONS

In the appropriate genetic and microenvironmental context, acute deregulation of SOX2 drives bronchial dysplasia. This confirms its oncogenic potential in human cells and affords novel insights into the impact of SOX2 deregulation. This model can be used to test therapeutic agents aimed at chemoprevention.

MicroRNAs in Lung Development and Disease

MicroRNAs (miRNAs) are small (∼22 nucleotides), non-coding RNA molecules that regulate gene expression post-transcriptionally by inhibiting target mRNAs. Research into the roles of miRNAs in lung development and disease is at the early stages. In this review, we discuss the role of miRNAs in pediatric respiratory disease, including cystic fibrosis, asthma, and bronchopulmonary dysplasia.

Airway Microbial Community Turnover Differs by BPD Severity in Ventilated Preterm Infants

Preterm birth exposes the developing lung to an environment with direct exposure to bacteria, often facilitated by endotracheal intubation. Despite evidence linking bacterial infections to the pathogenesis of bronchopulmonary dysplasia (BPD), systematic studies of airway microbiota are limited. The objective was to identify specific patterns of the early respiratory tract microbiome from tracheal aspirates of mechanically ventilated preterm infants that are associated with the development and severity of BPD. Infants with gestational age ≤34 weeks, and birth weight 500-1250g were prospectively enrolled. Mechanically ventilated infants had tracheal aspirate samples collected at enrollment, 7, 14, and 21 days of age. BPD was determined by modified NIH criteria with oxygen reduction tests; infants without BPD were excluded due to low numbers. Aspirates were processed for bacterial identification by 16S rRNA sequencing, and bacterial load by qPCR. Cross-sectional analysis was performed using 7 day samples and longitudinal analysis was performed from subjects with at least 2 aspirates. Microbiome analysis was performed on tracheal aspirates from 152 infants (51, 49, and 52 with mild, moderate, and severe BPD, respectively). Seventy-nine of the infants were included in the cross-sectional analysis and 94 in the longitudinal. Shannon Diversity, bacterial load, and relative abundance of individual taxa were not strongly associated with BPD status. Longitudinal analysis revealed that preterm infants who eventually developed severe BPD exhibited greater bacterial community turnover with age, acquired less Staphylococcus in the first days after birth, and had higher initial relative abundance of Ureaplasma. In conclusion, longitudinal changes in the airway microbial communities of mechanically ventilated preterm infants may be associated with BPD severity, whereas cross-sectional analysis of airway ecology at 7 days of age did not reveal an association with BPD severity. Further evaluation is necessary to determine whether the observed longitudinal changes are causal or in response to clinical management or other factors that lead to BPD.

[Decreased SIRT1 expression is related to bronchopulmonary dysplasia in premature infants after oxygen exposure]

Objective To observe silent information regulator 1 (SIRT1) expression in the peripheral blood mononuclear cells (PBMCs), and explore the relationship between SIRT1 expression and bronchopulmonary dysplasia (BPD) in premature infants after oxygen exposure. Methods Premature infants with 28 to 30 weeks' gestation were divided into three groups according to the fraction of inspiration O2 (FiO₂): low-oxygen group with FiO₂<30%, medium-oxygen group with FiO₂ being 30%~40%, and high-oxygen group with FiO₂≥40%; other premature infants with 28 to 30 weeks' gestation and without inspiration O₂ served as a control group. The children's clinical data and residual blood samples obtained from the routine examination of 0, 7, 14 and 28 days of hospitalization were collected, and PBMCs were isolated and cryopreserved in -80DegreesCelsius refrigerator. Twenty children diagnosed with BPD were enrolled as a BPD group, and other sex-matched 20 children without BPD were randomly chosen as a non-BPD group. The children's clinical data were retrospectively analyzed, and SIRT1 expression in the PBMCs of each group was measured by Western blotting. Furthermore, the role of SIRT1 expression in the occurrence and development of BPD in premature infants was also analyzed. Results Compared with the control group, SIRT1 expression in the medium-oxygen group and the high-oxygen group significantly decreased with the increase of FiO₂, and the expression in the low-oxygen group and the control group was almost at a similar level. Compared with the non-BPD group, SIRT1 expression in the BPD group of 14 and 28 days was significantly reduced. Conclusion There is a certain relationship between the decreased SIRT1 expression in PBMCs and the occurrence of BPD in premature infants after continuous and high-concentration oxygen exposure.

Genetic predisposition to bronchopulmonary dysplasia

The objective of this study is to review the candidate gene and genome-wide association studies relevant to bronchopulmonary dysplasia, and to discuss the emerging understanding of the complexities involved in genetic predisposition to bronchopulmonary dysplasia and its outcomes. Genetic factors contribute much of the variance in risk for BPD. Studies to date evaluating single or a few candidate genes have not been successful in yielding results that are replicated in GWAS, perhaps due to more stringent p-value thresholds. GWAS studies have identified only a single gene (SPOCK2) at genome-wide significance in a European White and African cohort, which was not replicated in two North American studies. Pathway gene-set analysis in a North American cohort confirmed involvement of known pathways of lung development and repair (e.g., CD44 and phosphorus oxygen lyase activity) and indicated novel molecules and pathways (e.g., adenosine deaminase and targets of miR-219) involved in genetic predisposition to BPD. The genetic basis of severe BPD is different from that of mild/moderate BPD, and the variants/pathways associated with BPD vary by race/ethnicity. A pilot study of whole exome sequencing identified hundreds of genes of interest, and indicated the overall feasibility as well as complexity of this approach. Better phenotyping of BPD by severity and pathophysiology, and careful analysis of race/ethnicity is required to gain a better understanding of the genetic basis of BPD. Future translational studies are required for the identification of potential genetic predispositions (rare variants and dysregulated pathways) by next-generation sequencing methods in individual infants (personalized genomics).

Biomarkers, Early Diagnosis, and Clinical Predictors of Bronchopulmonary Dysplasia

The pathogenesis of bronchopulmonary dysplasia (BPD) is multifactorial, and the clinical phenotype of BPD is extremely variable. Several clinical and laboratory biomarkers have been proposed for the early identification of infants at higher risk of BPD and for determination of prognosis of infants with a diagnosis of BPD. The authors review available literature on prediction tools and biomarkers of BPD, using clinical variables and biomarkers based on imaging, lung function measures, and measurements of various analytes in different body fluids that have been determined to be associated with BPD either in a targeted manner or by unbiased omic profiling.

Surfactant protein B gene polymorphisms is associated with risk of bronchopulmonary dysplasia in Chinese Han population

OBJECTIVE

To investigate the relationship between Surfactant protein B (SP-B) gene polymorphisms and bronchopulmonary dysplasia (BPD) development in preterm infants of China Han ethnic population.

METHODS

SP-B gene polymorphisms were studied in 134 neonates who were born at <32 weeks of gestation, with the diagnosis of BPD and in a control group of 168 preterm infants without BPD. Genotyping for SP-B was performed by polymerase chain reaction (PCR) and gene sequencing.

RESULTS

In this study, three of the SNP genotypes, -18C/A, 1580C/T and 4564T/C were common identified in SP-B gene. The -18C/A genotype was found to be significantly associated with BPD (χ2=10.741, P<0.01), with P<0.01 for the dominant model (OR=1.712, 95% CI=1.228-2.3894) and the allelic model (OR=1.787, 95% CI=1.276-2.502). The 1580C/T genotype was found to be associated with BPD (χ2=7.014, P<0.05), with P<0.05 for the dominant model (OR=0.752, 95% CI=0.593-0.954) and P<0.01 for the allelic model (OR=0.706, 95% CI=0.548-0.909). The 4564T/C genotypes and alleles were found not to be associated with BPD (χ2=3.399 and 3.227, P>0.05).

CONCLUSION

SP-B -18C/A and 1580C/T polymorphisms are associated with BPD. The 1580C/T polymorphism was protective while the -18C/A polymorphism increased the risk for BPD. SP-B 4564T/C polymorphism is not associated with BPD.

Surfactant protein-D-encoding gene variant polymorphisms are linked to respiratory outcome in premature infants

OBJECTIVE

Associations between the genetic variation within or downstream of the surfactant protein-D-encoding gene (SFTPD), which encodes the collectin surfactant protein-D (SP-D) and may lead to respiratory distress syndrome or bronchopulmonary dysplasia, recently were reported. Our aim was to investigate whether SFTPD variations affect serum SP-D levels in infants and pulmonary outcome in premature infants.

STUDY DESIGN

Serum SP-D levels were measured in 211 mature and 202 premature infants, and 7 SFTPD single-nucleotide polymorphisms (SNPs) were genotyped. SNP analysis and haplotype analysis were used to associate genetic variation to SP-D, respiratory distress (RD), oxygen requirement, and respiratory support.

RESULTS

The 5'-upstream SFTPD SNP rs1923534 and the 3 structural SNPs rs721917, rs2243639, and rs3088308 were associated with the SP-D level. The same SNPs were associated with RD, a requirement for supplemental oxygen, and a requirement for respiratory support. Haplotype analyses identified 3 haplotypes that included the minor alleles of rs1923534, rs721917, and rs3088308 that exhibited highly significant associations with decreased SP-D levels and decreased ORs for RD, oxygen supplementation, and respiratory support.

CONCLUSION

These findings extend and validate previous observations of SFTPD association with the risk of respiratory outcomes and suggest SFTPD as an essential factor affecting pulmonary adaptation in premature infants.

[Assessing the impact of risk factors and polymorphisms GST genes on the development of bronchopulmonary dysplasia in premature infants]

An increasing incidence of bronchopulmonary dysplasia (BPD) in premature infants has been reported in recent years. In the present study we analyzed the risk factors for BPD. It was revealed that the most significant factors are the low gestational age and birth weight, as well as prolonged use of mechanical ventilation and late neonatal infection. Polymorphism of studied genes and various combinations of polymorphic variants did not affect the risk of BPD developing. The influence of genetic polymorphisms on the duration of mechanical ventilation, the occurrence of late neonatal infection. For proper evaluation of the contribution of genetic polymorphism is necessary to conduct a preliminary analysis of all possible clinical and laboratory parameters to identify strong independent predictors and then analyze the indirect effects of genetic factors. Further research and development of new approaches to ventilation mode in preterm infants, based on the genetic polymorphism, will create a set of preventive measures and reduce the incidence of BPD.

Lipopolysaccharide induces up-regulation of TGF-α through HDAC2 in a rat model of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is characterized by alveolar simplification with decreased alveolar number and increased airspace. Previous studies suggested that transforming growth factor-α (TGF-α) may contribute to arrested alveolar development in BPD. Histone deacetylases (HDACs) control cellular signaling and gene expression. HDAC2 is crucial for suppression of inflammatory gene expression. Here we investigated whether HDAC2 was involved in the arrest of alveolarization, as well as the ability of HDAC2 to regulate TGF-α expression in a rat model of BPD induced by intra-amniotic injection of lipopolysaccharide (LPS). Results showed that LPS exposure led to a suppression of both HDAC1 and HDAC2 expression and activity, induced TGF-α expression, and disrupted alveolar morphology. Mechanistic studies showed that overexpression of HDAC2, but not HDAC1, suppressed LPS-induced TGF-α expression. Moreover, the HDAC inhibitor TSA or downregulation of HDAC2 by siRNA both significantly increased TGF-α expression in cultured myofibroblasts. Finally, preservation of HDAC activity by theophylline treatment improved alveolar development and attenuated TGF-α release. Together, these findings indicate that attenuation of TGF-α-mediated effects in the lung by enhancing HDAC2 may have a therapeutic effect on treating BPD.

Reduction of microRNA-206 contributes to the development of bronchopulmonary dysplasia through up-regulation of fibronectin 1

OBJECTIVE

To characterize microRNA-206 (miR-206) in the development of bronchopulmonary dysplasia (BPD).

DESIGN/METHODS

We assessed the expression of miR-206 in BPD mouse lung tissues and blood samples of BPD patients by quantitative real-time PCR. Then, the role of miR-206 in regulating cell biology were examined by XTT assay, flow cytometry, transwell invasion assay, wound healing assay and adhesion assay in vitro. Furthermore, luciferase reporter assay, real-time PCR, western blot and Immunofluorescence staining were performed to figure out the target gene of miR-206.

RESULTS

A reduction in expression of miR-206 was observed in BPD mice compared with controls and in BPD patients compared with controls. miR-206 overexpression significantly induced cell apoptosis, reduced cell proliferation, migration and adhesion abilities, whereas the inhibition of miR-206 expression had the opposite effect. Fibronectin 1 (FN1) is a direct target of miR-206, and fn 1 can be transcriptionally and translationally regulated by miR-206. Down-regulation of miR-206 modulates biological functions of the cells, at least in part, by increasing the level of fn 1. Furthermore, fn 1 expression levels were increased in the BPD mice and BPD patients.

CONCLUSIONS

The expression of miR-206 and its target gene, fn 1, may contribute to the progression of BPD.

TNF-238 polymorphism may predict bronchopulmonary dysplasia among preterm infants in the Egyptian population

Bronchopulmonary dysplasia (BPD) remains as a major and increasing burden in Egypt.

RATIONALE

To determine whether alleles of TNFα-238G > A affect the risk of BPD or the severity of BPD in preterm infants in Egypt.

STUDY DESIGN

We prospectively genotyped 220 premature neonates (birth weight <1,500 g and gestational age 26-32 weeks) for the -238 polymorphism, and assessed the clinical risk factors for BPD in our study populations. Infants with BPD were mechanically ventilated.

RESULTS

Infants who developed BPD (n = 120) had a younger gestational age (31.0 ± 2.1 weeks vs. 34.3 ± 1.5 weeks) and lower birth weight (1,490 ± 360 g vs. 1,880 ± 520 g) than infants who did not develop BPD (n = 100). Results of antenatal steroid supplementation, surfactant therapy, or sepsis might affect the genetic modulation of BPD. The -238G > A polymorphism was associated with a twofold risk of BPD (OR = 2.86; 95% confidence interval, 1.35-3.83). Despite the dominance of the G allele in the Egyptian population, the -238A allele was more common among infants with BPD (23%) than among infants without BPD (15%). The A allele occurred less often in infants with mild BPD (9%) than in infants with severe (39%) or moderate (52%). The AA genotype occurred in 15% of cases but in none of the controls.

CONCLUSION

The TNFα -238G > A polymorphism-particularly the presence of an A allele-should be evaluated as a biomarker to predict the clinical outcome of preterm infants with BPD in Egypt. Even the presence of one copy of this mutant allele appears to be sufficient to influence the severity of disease.

Association of surfactant protein B gene polymorphisms (C/A-18, C/T1580, intron 4 and A/G9306) and haplotypes with bronchopulmonary dysplasia in chinese han population

This study aimed to investigate the association between surfactant protein B (SP-B) polymorphisms and bronchopulmonary dysplasia (BPD) in Chinese Han infants. We performed a casecontrol study including 86 infants with BPD and 156 matched controls. Genotyping was performed by sequence specific primer-polymerase chain reaction (PCR) and haplotypes were reconstructed by the fastPHASE software. The results showed that significant differences were detected in the genotype distribution of C/A-18 and intron 4 polymorphisms of SP-B gene between cases and controls. No significant differences were detected in the genotype distribution of C/T1580 or A/G9306 between the two groups. Haplotype analysis revealed that the frequency of A-del-C-A haplotype was higher in case group (0.12 to 0.05, P=0.003), whereas the frequency of C-inv-C-A haplotype was higher in control group (0.19 to 0.05, P=0.000). In addition, a significant difference was observed in the frequency of C-inv-T-A haplotype between the two groups. It was concluded that the polymorphisms of SP-B intron 4 and C/A-18 could be associated with BPD in Chinese Han infants, and the del allele of intron 4 and A allele of C/A-18 might be used as markers of susceptibility in the disease. Haplotype analysis indicated that the gene-gene interactions would play an important part in determining susceptibility to BPD.

A generalized Defries-Fulker regression framework for the analysis of twin data

Twin studies compare the similarity between monozygotic twins to that between dizygotic twins in order to investigate the relative contributions of latent genetic and environmental factors influencing a phenotype. Statistical methods for twin data include likelihood estimation and Defries-Fulker regression. We propose a new generalization of the Defries-Fulker model that fully incorporates the effects of observed covariates on both members of a twin pair and is robust to violations of the Normality assumption. A simulation study demonstrates that the method is competitive with likelihood analysis. The Defries-Fulker strategy yields new insight into the parameter space of the twin model and provides a novel, prediction-based interpretation of twin study results that unifies continuous and binary traits. Due to the simplicity of its structure, extensions of the model have the potential to encompass generalized linear models, censored and truncated data; and gene by environment interactions.

Genetic basis of apnoea of prematurity and caffeine treatment response: role of adenosine receptor polymorphisms: genetic basis of apnoea of prematurity

AIM

Caffeine treatment reduces the frequency of apnoea of prematurity (AOP) and eliminates the need for mechanical ventilation by acting as a nonspecific inhibitor of adenosine A1 and adenosine 2A receptors. Patients with AOP have demonstrated variant responses to caffeine therapy. We proposed to investigate the role of A1 and 2A polymorphisms in the development of AOP and individual differences in caffeine response. Secondly, we aimed to determine whether these polymorphisms have any effect on bronchopulmonary dysplasia (BPD) development.

METHODS

Cord blood samples were collected from infants born with gestational ages between 24 and 34 weeks. Two groups were defined: patients without apnoea (n = 60) and patients with apnoea (n = 55). Patients with apnoea were divided into two subgroups: a caffeine-responsive group (n = 30) and an unresponsive group (n = 25). Six single-nucleotide polymorphisms were chosen for genotyping.

RESULTS

Patients with apnoea over 28 weeks of gestational age who responded to the caffeine treatment were found to carry the rs16851030 C/C genotype rather than the C/T or T/T genotype. Logistic regression analysis showed a significant correlation between rs35320474-C/T and T/T genotypes and apnoea and BPD development.

CONCLUSION

Our results indicate a role for adenosine receptor gene polymorphisms in susceptibility to AOP and BPD and in interindividual variability to caffeine response.

Genetic susceptibility to neonatal lung diseases

Advances in molecular genetics have enabled improvement of knowledge in pathogenesis and diagnosis of either monogenic or multifactorial neonatal lung diseases. Variants in genes regulating surfactant function and metabolism are implicated in some rare and common respiratory diseases. Congenital surfactant deficiencies are rare diseases due to mutations in genes encoding surfactant proteins and cause significant and often lethal respiratory failure in newborns and interstitial lung disease in older children. Diagnosis is made by molecular analysis and eventually confirmed by histological analysis of lung tissue. A multifactorial contribution, resulting from interaction between multiple genes and environmental factors, has been supposed for respiratory distress syndrome (RDS) and bronchopulmonary dysplasia (BPD). Several potential candidate genes, especially regarding surfactant proteins and cytokines, have been shown in association with these diseases. Genetic variants predisposing to RDS or BPD are usually polymorphisms which are not causative, but can increase susceptibility to the disease. Identification of infants at risk of disease can be useful to provide them individualized therapies. (www.actabiomedica.it).

Hyperoxia impairs alveolar formation and induces senescence through decreased histone deacetylase activity and up-regulation of p21 in neonatal mouse lung

Alveolar development comprises the transition of lung architecture from saccules to gas-exchange units during late gestation and early postnatal development. Exposure to hyperoxia disrupts developmental signaling pathways and causes alveolar hypoplasia as seen in bronchopulmonary dysplasia affecting preterm human newborns. Expanding literature suggests that epigenetic changes caused by environmental triggers during development may lead to heritable changes in gene expression. Given recent data on altered histone deacetylase (HDAC) activity in lungs of humans and animal models with airspace enlargement/emphysema, we hypothesized that alveolar hypoplasia from hyperoxia exposure in neonatal mice is a consequence of cell cycle arrest and reduced HDAC activity and up-regulation of the cyclin-dependent kinase inhibitor, p21. We exposed newborn mice to hyperoxia and compared lung morphologic and epigenetic changes to room air controls. Furthermore, we pretreated a subgroup of animals with the macrolide antibiotic azithromycin (AZM), known to possess antiinflammatory properties. Our results showed that hyperoxia exposure resulted in alveolar hypoplasia and was associated with decreased HDAC1 and HDAC2 and increased p53 and p21 expression. Furthermore, AZM did not confer protection against hyperoxia-induced alveolar changes. These findings suggest that alveolar hypoplasia caused by hyperoxia is mediated by epigenetic changes affecting cell cycle regulation/senescence during lung development.

[The use of microarrays for gene expression analysis in premature children--new strategy of searching for genetic basis of late complications of prematurity--preliminary research]

Progress achieved in the development of medical care for children born prematurely has resulted in increased survival of the smallest and most immature infants. At the same time increased incidence of the late complications of prematurity such as bronchopulmonary dysplasia (BPD) and retinopathy of prematurity (ROP) has become a growing problem. The aim of the study was to identify groups of genes potentially involved in the development of long-term complications of prematurity, by conducting genome wide microarray expression analysis. The prospective cohort study was conducted, 52 premature babies were included. At the 5th, 14th and 28th day of life samples of the peripheral blood were taken from the study participants. Subsequently, total RNA was extracted and microarray experiment, with the use of GeneChip Human Gene 1.0 ST Array (Affymetrix), was performed. The analysis of the results was carried out in the separate cohorts of prematures. Within 52 infants 2 groups were distinguished--children without BPD (n = 25) and children with BPD (n = 27). Significant difference in the expression of 251 genes was observed. Additionally, a group of 20 participants of the study, in whom ROP was diagnosed, was compared with the group of the remaining 32 children without proven retinopathy. The analysis revealed a significant difference in the expression between the analyzed groups with regard to 752 genes. Further study is needed to verify the obtained results. The impact of the over- and underexpressed genes should be studied, as well as detailed analysis of the metabolic pathways should be performed.

Association of polymorphisms in the human surfactant protein-D (SFTPD) gene and postnatal pulmonary adaptation in the preterm infant

BACKGROUND

Surfactant protein-D (SP-D) is a member of the collagenous subfamily of calcium-dependent lectins (collectins). Associations between single nucleotide polymorphisms (SNPs) of the human gene coding surfactant protein-D (SFTPD) and infectious pulmonary diseases have been established by several groups. As the outcome of very preterm infants is mainly determined by pulmonary morbidity, the aim of the present study was to investigate the potential association between sequence variations within the SFTPD gene and pulmonary morbidity in preterm infants below 32 weeks of gestational age (GA).

MATERIALS AND RESULTS

Four validated SNPs were genotyped with sequence-specific probes (TaqMan 7000) in 284 newborn infants below 32 weeks of GA. An association between the SNP rs1923537 and the development of respiratory distress syndrome (RDS) in the study population was found with a lower prevalence of RDS in infants having homozygous a minor allele genotype (odds ratio = 1.733, 95% confidence interval 1.139-2.636, adjusted p = 0.0408). Consecutively, the indicated polymorphism was found to be associated with a lower number of repetitive surfactant doses, and with a lower prevalence for the requirement of oxygen supplementation on day 28, as well as the use of diuretics.

CONCLUSION

The finding of an association of a variant of the SFTPD gene, that has previously been shown to be associated with increased SP-D serum levels in adult patients with acute respiratory failure, i.e. RDS in preterm infants, may provide a basis for the initial risk assessment of RDS and modification of surfactant treatment strategies. A role for SP-D in neonatal pulmonary adaptation has to be postulated.

Matrix metalloproteinase gene polymorphisms and bronchopulmonary dysplasia: identification of MMP16 as a new player in lung development

BACKGROUND

Alveolarization requires coordinated extracellular matrix remodeling, a process in which matrix metalloproteinases (MMPs) play an important role. We postulated that polymorphisms in MMP genes might affect MMP function in preterm lungs and thus influence the risk of bronchopulmonary dysplasia (BPD).

METHODS AND FINDINGS

Two hundred and eighty-four consecutive neonates with a gestational age of <28 weeks were included in this prospective study. Forty-five neonates developed BPD. Nine single-nucleotide polymorphisms (SNPs) were sought in the MMP2, MMP14 and MMP16 genes. After adjustment for birth weight and ethnic origin, the TT genotype of MMP16 C/T (rs2664352) and the GG genotype of MMP16 A/G (rs2664349) were found to protect from BPD. These genotypes were also associated with a smaller active fraction of MMP2 and with a 3-fold-lower MMP16 protein level in tracheal aspirates collected within 3 days after birth. Further evaluation of MMP16 expression during the course of normal human and rat lung development showed relatively low expression during the canalicular and saccular stages and a clear increase in both mRNA and protein levels during the alveolar stage. In two newborn rat models of arrested alveolarization the lung MMP16 mRNA level was less than 50% of normal.

CONCLUSIONS

MMP16 may be involved in the development of lung alveoli. MMP16 polymorphisms appear to influence not only the pulmonary expression and function of MMP16 but also the risk of BPD in premature infants.

[Relationship between reduced expression of surfactant protein B and neonatal respiratory distress syndrome in twenty Han ethnic group neonates in China]

OBJECTIVE

To investigate possible relationship between expression of surfactant protein B (SP-B) gene product and neonatal respiratory distress syndrome (NRDS) in Han ethnic group.

METHOD

Unrelated 20 cases with NRDS of Han ethnic group were selected as NRDS group while unrelated 20 diseases cases of Han ethnic group with diseases were selected as control group. The cases in the control group had congenital heart disease or bronchopulmonary dysplasia or persistent pulmonary hypertension. Blood sample was taken from every case. Lung tissues were taken from the patients who died half an hour after death in the two groups. Expression of SP-B in lung tissue was determined with immunohistochemical tecnique. Genetic deficiency variant of SP-B intron IV was screened with polymerase chain reaction (PCR).

RESULTS

Two cases at gestational age 26 weeks and one case at gestational age 34 weeks and two cases at gestational age 42 weeks of NRDS groups had lower level expression of SP-B in lung tissue than those at the same age of NRDS. Expression of SP-B in lung tissue of control group increased with gestational age, but no such phenomenon was found in NRDS group. Further, two cases at gestational age 42 weeks of NRDS group had genetic deficiency variant of SP-B intron IV with gene analysis of five cases who had lower expression of SP-B. Clinical data suggest that patients at 42 weeks of gestational age had severe illness.

CONCLUSIONS

Decrease of SP-B expression may participate in occurrence of NRDS, genetic deficiency variant of SP-B intron IV exists in the NRDS cases of Han ethnic group of China.

Dysplasia: a review

Bronchopulmonary dysplasia (BPD) is a common perinatal complication of very low birth weight preterm infants with a significant risk of long-term disability and morbidity. While clinical conditions such as prematurity and mechanical ventilation are its major risk factors, studies suggest that there is an individual susceptibility to BPD. This comprehensive review summarizes data collected about the implication of genetic polymorphisms in BPD and in its risk factors. Some studies have directly related the risk of BPD to genotype. Indeed, carrier states of genetic variants of cytokines (IFNgamma T+874A), adhesion molecules (L-selectin-Pro213Ser), elements of renin-angiotensin system (ACE-I/D), antioxidant enzymes (GST-P1 Val105Ile), and surfactant proteins (SPA1, SPB intron 4) has been identified as risk factors to BPD. Other studies investigated the role of genotype in BPD risk factors. Premature birth has been linked to carrier states of genetic variants with an impact on immune status (such as IL-6 G(-174)C, MBL2 54G/A, VEGF G+405C, HSP72 A+1267G genes) and matrix metalloproteases. Fetal inflammatory response syndrome, a major determinant of BPD is also affected by genotype (including LTalpha A+250G). Disturbed intrauterine lung development and vascularization may also contribute to BPD; these processes may be impaired in the presence of some rare genetic mutations. Furthermore, there is also a genetic component in the susceptibility to other perinatal adaptational disturbances such as respiratory distress syndrome that are associated with an increased need for mechanical ventilation, and, hence, with lung damage. The genetic variants presented in this article may help to identify infants at risk for BPD.

Association of polymorphisms in the mannose-binding lectin gene and pulmonary morbidity in preterm infants

Deficiency in the collectin mannose-binding lectin (MBL) increases the risk for pulmonary and systemic infections and its complications in children and adults. The aim of this prospective cohort study was to determine the genetic association of sequence variations within the MBL gene with systemic infections and pulmonary short- and long-term complications in preterm infants below 32 weeks gestational age (GA). Three single-nucleotide polymorphisms (SNPs) in the coding region and one SNP in the promotor region of MBL2 were genotyped by direct sequencing and with sequence-specific probes in 284 newborn infants <32 weeks GA. Clinical variables were comprehensively monitored. An association was found between two SNPs and the development of bronchopulmonary dysplasia (BPD), defined as persistent oxygen requirement at 36 weeks postmenstrual age, adjusting for covariates GA, grade of respiratory distress syndrome and days on mechanical ventilation (rs1800450 (exon 1 at codon 54, B variant): odds ratio dominant model (OR)=3.59, 95% confidence interval (CI)=1.62-7.98; rs7096206 (-221, X variant): OR=2.40, 95% CI=1.16-4.96). Haplotype analyses confirmed the association to BPD, and a single haplotype (frequency 56%) including all SNPs in their wild-type form showed a negative association with the development of BPD. We detected no association between the MBL gene variations and the development of early-onset infections or further pulmonary complications. Frequent variants of the MBL gene, leading to low MBL concentrations, are associated with the diagnosis of BPD in preterm infants. This provides a basis for potential therapeutic options and further genetic and proteomic analysis of the function of MBL in the resistance against pulmonary long-term complications in preterm infants.

Genetic variants of surfactant proteins A, B, C, and D in bronchopulmonary dysplasia

BPD_28D (O₂ dependency at 28 days of life) and BPD_36W (O₂ dependency at 36 wks post-menstrual age) are diseases of prematurely born infants exposed to mechanical ventilation and/or oxygen supplementation. In order to determine whether genetic variants of surfactant proteins (SPs-A, B, C, and D) and SP-B-linked microsatellite markers are risk factors in BPD, we performed a family based association study using a Greek study group of 71 neonates (<30 wks gestational age) from 60 families with, 52 BPD_28D and 19 BPD_36W, affected infants. Genotyping was performed using newly designed pyrosequencing assays and previously published methods. Associations between genetic variants of SPs and BPD subgroups were determined using Transmission Disequilibrium Test (TDT) and Family Based Association Test (FBAT). Significant associations (p ≤ 0.01) were observed for alleles of SP-B and SP-B-linked microsatellite markers, and haplotypes of SP-A, SP-D, and SP-B. Specifically, allele B-18_C associated with susceptibility in BPD_36W. Microsatellite marker AAGG_6 associated with susceptibility in BPD_28D/36W group. Haplotype analysis revealed ten susceptibility and one protective haplotypes for SP-B and SP-B-linked microsatellite markers and two SP-A-SP-D protective haplotypes. The data indicate that SP loci are linked to BPD. Studies in different study groups and/or of larger sample size are warranted to confirm these observations and delineate genetic background of BPD subgroups.

Bronchopulmonary dysplasia: where have all the vessels gone? Roles of angiogenic growth factors in chronic lung disease

Bronchopulmonary dysplasia and emphysema are significant global health problems at the extreme stages of life. Both are characterized by arrested alveolar development or loss of alveoli, respectively. Both lack effective treatment strategies. Knowledge about the genetic control of branching morphogenesis in mammals derives from investigations of the respiratory system in Drosophila, but mechanisms that regulate alveolar development remain poorly understood. Even less is known about regulation of the growth and development of the pulmonary vasculature. Understanding how alveoli and the underlying capillary network develop, and how these mechanisms are disrupted in disease states, are critical for developing effective therapies for lung diseases characterized by impaired alveolar structure. Recent observations have challenged old notions that the development of the blood vessels in the lung passively follows that of the airways. Rather, increasing evidence suggests that lung blood vessels actively promote alveolar growth during development and contribute to the maintenance of alveolar structures throughout postnatal life. Our working hypothesis is that disruption of angiogenesis impairs alveolarization, and that preservation of vascular growth and endothelial survival promotes growth and sustains the architecture of the distal airspace. Furthermore, the explosion of interest in stem cell biology suggests potential roles for endothelial progenitor cells in the pathogenesis or treatment of lung vascular disease. In this Pulmonary Perspective, we review recent data on the importance of the lung circulation, specifically examining the relationship between dysmorphic vascular growth and impaired alveolarization, and speculate on how these new insights may lead to novel therapeutic strategies for bronchopulmonary dysplasia.

Association of interferon gamma T+874A and interleukin 12 p40 promoter CTCTAA/GC polymorphism with the need for respiratory support and perinatal complications in low birthweight neonates

BACKGROUND

Data support the role of interferon (IFN)gamma and interleukin (IL)12 in perinatal complications. IFNgamma T(+874)A and IL12 p40 promoter CTCTAA/GC polymorphisms may have an effect on cytokine production.

METHODS

DNA was extracted from dried blood samples of 153 low birthweight (LBW) infants and 172 healthy term infants. IFNgamma and IL12 genetic polymorphisms were determined to investigate the association between polymorphisms and ventilation characteristics, bronchopulmonary dysplasia (BPD) and other perinatal disorders.

RESULTS

The IFNgamma(+874)A allele was over-represented in LBW infants. Carriers of the IFNgamma(+874)T allele required mechanical ventilation and oxygen supplementation for time periods 41% and 35%, respectively, shorter than those required by those not carrying the IFNgamma(+874)T allele. Stepwise logistic regression analysis showed that carriers of the IFNgamma(+874)T allele were protected against BPD (odds ratio (OR) 0.35 (95% confidence interval (CI) (0.12 to 0.99))) and patent ductus arteriosus (OR 0.43 (95% CI 0.19 to 0.97)), whereas carriers of the IFNgamma(+874)A allele were at higher risk of severe hypotension (OR 3.40 (95% CI 1.01 to 11.52)) and respiratory distress syndrome (OR 4.03 (95% CI 1.30 to 12.50)). Carriers of the IL12 GC allele were protected against pneumonia (OR 0.32 (95% CI 0.14 to 0.75)). Carriers of the IL12 CTCTAA allele were at higher risk of developing necrotising enterocolitis (NEC; OR 2.37 (95% CI 1.01 to 5.53)).

CONCLUSIONS

Carrier state of the IFNgamma(+874)A allele presents an increased risk for premature birth and lung damage, as well as other perinatal complications. The risks of pneumonia and NEC are higher in heterozygotic carriers of the IL12 CTCTAA/GC polymorphism. Further studies are needed to determine whether these associations are the result of altered cytokine-producing capacity in infants carrying the tested alleles.

Single nucleotide polymorphisms of tumor necrosis factor-alpha and the susceptibility to bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease of infancy. A "New" BPD has been characterized in preterm infants that may begin in utero, and then progress post-natally, resulting in arrested lung development and alveolar hypoplasia. Foundations for this "New" BPD may be derived from pro-inflammatory genes including tumor necrosis factor-alpha (TNFalpha). The hypothesis of the current study is that single nucleotide polymorphisms (SNPs) of the pro-inflammatory TNFalpha gene place preterm infants at increased risk for BPD. Preterm infants (105 in number) with birthweights <or=1 kg, who survived to at least 36 weeks postmenstrual age (PMA) or discharge were enrolled into this study. They were stratified for BPD according to their need for supplemental oxygen at 28 days and at 36 weeks PMA (non-, mild-, moderate-, or severe-BPD). DNA was extracted from these infants and subjected to analyses for the TNFalpha SNPs: -1,031, -863, -857, -308, and -238. The PHASE software (version 2.1) was used to reconstruct haplotypes and estimate their frequencies within the study population. Differences in birth weight (P < 0.001) and gestational age (P < 0.001), but not in racial distribution between the groups were found. Haplotype-specific analysis revealed no significant association between BPD severity and any of the 5-marker common haplotypes with 10 or more copies in this study population. Additionally, no significant association was observed in any three SNP haplotypes at -1,031, -863, and -857, and two SNP haplotypes at -308 and -238. We observed no association between BPD severity and the five TNFalpha SNPs investigated.

Genetic analysis of the dystroglycan gene in bronchopulmonary dysplasia affected premature newborns

BACKGROUND

Dystroglycan (DG) is an extracellular matrix receptor that serves as an adhesion molecule and is essential for the stability of the plasma membrane. DG is highly expressed within the epithelial cell layer where it supports morphogenesis, adhesion and wound repair. Mechanically ventilated newborns often develop bronchopulmonary dysplasia (BPD), characterized by a progressive impairment of wound repair capacity in their lung.

METHODS

To verify if the susceptibility to BPD might be linked to genetic abnormalities in the DG gene (DAG1), we searched for possible mutations in 33 premature newborns with gestational age<34 weeks with risk of developing BPD. DAG1 genotype was determined in 11 premature newborns with BPD as compared to 22 premature infants without lung complications.

RESULTS

Eight polymorphisms were found, four of them being new DAG1 single nucleotide polymorphisms (SNPs). Only one significant association was found with BPD positive infants: the N494H homozygous genotype (p=0.033). The same polymorphism was found significantly associated with BPD when allelic frequencies were considered (p=0.0015).

CONCLUSIONS

Our data enrich the list of DAG1 SNPs and could be useful to trigger further genetic studies about the involvement of DG in human diseases.

Selectin polymorphisms and perinatal morbidity in low-birthweight infants

BACKGROUND

Studies have shown an association between altered expression of selectins and premature birth, early sepsis and bronchopulmonary dysplasia.

AIM

To investigate the possible link between functional polymorphisms of the E-, P- and L-selectin genes and perinatal morbidity.

METHODS

We compared the genotype distribution of the E-selectin Ser128Arg, P-selectin Thr715Pro and L-selectin Pro213Ser polymorphisms in 125 low-birthweight singleton infants with those of 156 healthy term neonates. We also analysed the association of genotype with risk of sepsis and bronchopulmonary dysplasia.

RESULTS

We found no association between E-selectin or P-selectin polymorphisms and premature birth, nor did we find any association between E-selectin or P-selectin and early postnatal sepsis or bronchopulmonary dysplasia. Carriers of the 213Ser L-selectin allele were found to be more prevalent in low-birthweight infants, particularly in those with bronchopulmonary dysplasia. We found no association between the L-selectin polymorphism and early postnatal sepsis.

CONCLUSION

Our results underline the importance of L-selectin in perinatal pathology, but further studies are needed to evaluate the alteration of L-selectin levels in carriers of the 213Ser allele and their possible contribution to premature birth and bronchopulmonary dysplasia.

Antenatal inflammation induced TGF-beta1 but suppressed CTGF in preterm lungs

Chorioamnionitis is frequently associated with preterm birth and increases the risk of adverse outcomes such as bronchopulmonary dysplasia (BPD). Transforming growth factor (TGF)-beta1 is a key regulator of lung development, airway remodeling, lung fibrosis, and regulation of inflammation, and all these processes contribute to the development of BPD. Connective tissue growth factor (CTGF) is a downstream mediator of some of the profibrotic effects of TGF-beta1, vascular remodeling, and angiogenesis. TGF-beta1-induced CTGF expression can be blocked by TNF-alpha. We asked whether chorioamnionitis-associated antenatal inflammation would regulate TGF-beta1, the TGF-beta1 signaling pathway, and CTGF in preterm lamb lungs. Fetal sheep were exposed to 4 mg of intra-amniotic endotoxin or saline for 5 h, 24 h, 72 h, or 7 days before preterm delivery at 125 days gestation (full term = 150 days). Intra-amniotic endotoxin increased lung TGF-beta1 mRNA and protein expression. Elevated TGF-beta1 levels were associated with TGF-beta1-induced phosphorylation of Smad2. CTGF was selectively expressed in lung endothelial cells in control lungs, and intra-amniotic endotoxin caused CTGF expression to decrease to 30% of control values and TNF-alpha protein to increase. The antenatal inflammation-induced TGF-beta1 expression and Smad signaling in the fetal lamb lung may contribute to impaired lung alveolarization and reduced lung inflammation. Decreased CTGF expression may inhibit vascular development or remodeling and limit lung fibrosis during remodeling. These effects may contribute to the impaired alveolar and pulmonary vascular development that is the hallmark of the new form of BPD.

The genetics of bronchopulmonary dysplasia

Over the last 15 years, neonatal morbidity and mortality has changed little for very low birth weight babies despite significant technological and therapeutic advances. Bronchopulmonary dysplasia (BPD) continues to be a major problem despite antenatal steroid use, surfactant replacement therapy, gentle noninvasive ventilation techniques, permissive hypercarbia, and judicious use of oxygen. Current evidence supports multiple contributing factors. Prematurity is the cardinal factor; others include pulmonary baro/volutrauma, hyperoxia, and inflammation. BPD is an end product of pulmonary inflammatory response and lung repair with impaired alveolarization and vascularization in response to lung injury. These sequences involve multiple morphoregulatory molecules, which have a range of activities largely determined by genetic variability. A clearer understanding of genetic susceptibility for BPD has recently emerged. Twin studies have shown that the BPD status of one twin, even after correcting for contributing factors, is a highly significant predictor of BPD in the second twin. After controlling for covariates, genetic factors account for 53% (P = 0.004, 95% CI = 16%-89%) of the variance in liability for BPD. Incremental improvements will likely depend on identification of these genetic components for targeting specific therapies.

Familial and genetic susceptibility to major neonatal morbidities in preterm twins

BACKGROUND

Intraventricular hemorrhage, necrotizing enterocolitis, and bronchopulmonary dysplasia remain significant causes of morbidity and mortality in preterm newborns.

OBJECTIVES

Our goal was to assess the familial and genetic susceptibility to intraventricular hemorrhage, necrotizing enterocolitis, and bronchopulmonary dysplasia.

METHODS

Mixed-effects logistic-regression and latent variable probit model analysis were used to assess the contribution of several covariates in a multicenter retrospective study of 450 twin pairs born at < or =32 weeks of gestation. To determine the genetic contribution, concordance rates in a subset of 252 monozygotic and dizygotic twin pairs were compared.

RESULTS

The study population had a mean gestational age of 29 weeks and birth weight of 1286 g. After controlling for effects of covariates, the twin data showed that 41.3%, 51.9%, and 65.2%, respectively, of the variances in liability for intraventricular hemorrhage, necrotizing enterocolitis, and bronchopulmonary dysplasia could be accounted for by genetic and shared environmental factors. Among the 63 monozygotic twin pairs, the observed concordance for bronchopulmonary dysplasia was significantly higher than the expected concordance; 12 of 18 monozygotic twin pairs with > or =1 affected member had both members affected versus 3.69 expected. After controlling for covariates, genetic factors accounted for 53% of the variance in liability for bronchopulmonary dysplasia.

CONCLUSIONS

Twin analyses show that intraventricular hemorrhage, necrotizing enterocolitis, and bronchopulmonary dysplasia are familial in origin. These data demonstrate, for the first time, the significant genetic susceptibility for bronchopulmonary dysplasia in preterm infants.

Pathogenesis of bronchopulmonary dysplasia: the role of interleukin 1beta in the regulation of inflammation-mediated pulmonary retinoic acid pathways in transgenic mice

BACKGROUND

Pulmonary inflammation, increased production of the inflammatory cytokine interleukin-1beta (IL-1beta), and vitamin A deficiency are risk factors for the development of bronchopulmonary dysplasia (BPD) in premature infants. To determine the mechanisms by which IL-1beta influences lung development, we have generated transgenic mice in which human IL-1beta is expressed in the lung epithelium with a doxycycline-inducible system controlled by the Clara cell secretory protein promoter. Perinatal IL-1beta production in these mice causes a phenotype that is strikingly similar to BPD. Pulmonary pathology in the mice shows inflammation, lack of alveolar septation, and impaired vascular development of the lung, similar to the histological characteristics of BPD. Retinoic acid (RA), one of the most biologically active derivatives of vitamin A, increases septation. Proteins involved in mediating the cellular responses to RA include the cellular retinoic acid binding proteins CRABP-I and CRABP-II and the nuclear retinoic acid receptors RAR-alpha, RAR-beta, and RAR-gamma.

OBJECTIVE

To test the hypothesis that IL-1beta inhibits the expression of proteins involved in mediating the cellular response to RA.

METHODS

The mRNA expression of CRABP-I, CRABP-II, RAR-alpha1, RAR-beta2, RAR-beta4, and RAR-gamma2 was studied with real-time RT-PCR on gestational day 18, and postnatal days 0, 1, 5, and 7 in IL-1beta-expressing mice and their control littermates. In addition, immunohistochemistry for CRABP-I was performed.

RESULTS

IL-1beta decreased the mRNA expression and protein production of CRABP-I as well as the mRNA expression of RAR-gamma2. In contrast, no differences between IL-1beta-expressing and control mice were detected in the expression of CRABP-II, RAR-alpha1, RAR-beta2, or RAR-beta4.

CONCLUSION

The present study demonstrates for the first time a link between inflammation and the retinoic acid pathway. Inhibition of CRABP-I and RAR-gamma2 expression may be one mechanism by which inflammation prevents alveolar septation. The therapeutic potential of RA in promoting septation in the setting of perinatal lung inflammation deserves further investigation.

The genetic basis for bronchopulmonary dysplasia

While the 'original' bronchopulmonary dysplasia (BPD) was attributed to the iatrogenic effects of oxygen and barotrauma on the preterm lung, analyses of the 'new' BPD suggests that these environmental effects may contribute to arrested pulmonary development, and that there may also be genetic foundations for the susceptibility to BPD. Twinning, family and population studies implicate heritable factors in the evolution of BPD. The candidate genes examined for their potential role in BPD include surfactant apoprotein and inflammatory genes. With the identification and mapping of single nucleotide polymorphisms (SNPs), an explosion of testing for these genetic components that may contribute to a number of complex, multigenic disease conditions-including BPD-have been initiated. Sophisticated multiplex analyses are now available to link candidate SNPs to conditions such as BPD. However, there continues to be wide variation in the expression of BPD throughout neonatal units. Differentiating the effects caused by environmental and environmental-genetic interactions from isolated genetic etiologies is still problematic and will require carefully designed genetic analyses of preterm infant groups and their families.

G protein-coupled receptor for asthma susceptibility associates with respiratory distress syndrome

BACKGROUND

Respiratory distress syndrome (RDS) and bronchopulmonary dysplasia (BPD) have some common features with asthma.

AIM

To study whether G protein-coupled receptor for asthma susceptibility (GPRA) contributes to RDS or BPD.

METHODS

A haplotype association study was performed in a case-control setting of 521 Finnish infants (including 176 preterm neonates with RDS and 37 with BPD). Immunoreactivity of GPRA isoforms A and B was determined in pulmonary samples of fetuses, term infants and preterm infants with RDS or BPD. GPRA mRNA expression was determined by quantitative real-time polymerase chain reaction (PCR) in samples from nasal respiratory epithelium of adults, term infants and preterm infants.

RESULTS

In infants with RDS born at 32-35 weeks of gestation, GPRA haplotype H1 was significantly underrepresented in RDS, whereas haplotype H4/H5 was associated with an increased risk. As in asthma, GPRA B isoform was induced in bronchial smooth muscle cells in RDS and BPD. In nasal respiratory epithelium, relative GPRA mRNA expression was strong in adults, weak in preterm and slightly higher in term samples.

CONCLUSIONS

The results suggest that near-term RDS and asthma share the same susceptibility and protective GPRA haplotypes. Altered GPRA expression may play a role in the pathogenesis of RDS and BPD in preterm infants.

Deletion allele of angiotensin-converting enzyme is associated with increased risk and severity of bronchopulmonary dysplasia

OBJECTIVE

To explore whether the deletion (D) allele of angiotensin-converting enzyme (ACE) is associated with the risk or severity of bronchopulmonary dysplasia (BPD) among very low birth weight (BW) infants.

STUDY DESIGN

Infants with a BW < or = 1250 g were prospectively recruited. The D and I (insertion) alleles of ACE were determined using a polymerase chain reaction followed by restriction fragment length polymorphism analysis.

RESULTS

Infants with DD/DI genotype of ACE had a (mean +/- SD) birth weight (938 +/- 204 g vs 925 +/- 196 g) and gestational age (28 +/- 3 weeks vs 28 +/- 2 weeks), similar to infants with II genotype of ACE (P > .05). Infants with DD/DI genotype of ACE were more likely to have BPD than infants with II genotype (47% vs 22%, P = .025). Among infants with BPD, ACE DD/DI genotype was more common among infants with moderate or severe BPD compared with infants with mild BPD (74% vs 26%, P = .012). The number of D alleles of ACE correlated directly and positively with the severity of BPD (R = 0.23, P = .045).

CONCLUSION

The D allele of ACE is associated with an increased risk and severity of BPD among preterm infants.

No association between TAP1 DpnII polymorphism and bronchopulmonary dysplasia

The possibility that a family history of asthma may have a role in susceptibility to bronchopulmonary dysplasia (BPD) had been raised in several reports, and there was evidence of a strong association between transporter associated with antigen processing (TAP1) polymorphism and asthma in Taiwanese population. To test whether TAP polymorphism has a role in the BPD, we investigated the association between TAP1 polymorphism and BPD by analyzing the results of genotype distribution. The study included 224 ventilated preterm infants (<30 weeks) who had respiratory distress syndrome (RDS) and needed intermittent mandatory ventilation (IMV) during Jan. 1999 to July 2003. The typing of TAP1 polymorphism was performed by polymerase chain reaction (PCR)-based restriction analysis. The demography between two groups of these ventilated preterm infants was not different. We observed no significant differences in genotype distribution or allele frequency of the TAPI polymorphisms between BPD and their respective control infants. There was also no significant difference in genotype distribution of the TAP1 polymorphism with duration of IMV. Therefor, we conclude that TAP1 polymorphism is not a useful marker for predicting the susceptibility or severity to BPD for Taiwanese.

Interleukin-10 -1082 G/A polymorphism and risk of death or bronchopulmonary dysplasia in ventilated very low birth weight infants

IL-10 is an anti-inflammatory cytokine that may have a protective role in acute lung injury. IL-10 expression is affected by a single-nucleotide polymorphism (SNP) located at position -1082 (G to A). The A allele is associated with lower IL-10 production. Low IL-10 production has been linked to the development of BPD. Thus, the IL-10 -1082 SNP may be a genetic risk factor for the development of BPD in the premature newborn. The IL-10 -1082 SNP was determined in 294 (235 African American, 56 Caucasian, and 3 Hispanic) mechanically ventilated very low birth weight (VLBW) infants and compared to outcome (death and/or development of BPD). Differences in groups were analyzed using ANOVA (continuous variables) or chi square (proportions). The frequency of the A allele in our population was 0.62. Thirty-nine (13.3%) infants were homozygous GG, 146 (49.7%) were heterozygous GA, and 109 (37.0%) were homozygous AA. There were no significant differences between genotype groups with respect to ethnic origin, gender, need for surfactant replacement therapy, and isolation of Ureaplasma urealyticum or Mycoplasma hominis from tracheal aspirates at birth. However, AA infants were slightly more mature and of greater birth weight than GA infants (26.9 +/- 0.2 weeks vs. 26.3 +/- 0.2 weeks, P < 0.05, and 940 +/- 22 g vs. 882 +/- 18 g, P < 0.05, respectively). There was no significant effect of the IL-10 -1082 SNP on mortality or the development of BPD (O2 on 28 days or 36 weeks postconceptional age). However, when considered together, the IL-10 -1082 AA/GA genotypes (lower IL-10 production) were associated with a trend toward reduction in risk for the combined outcome of BPD or death (18/39 vs. 80/255, respectively; P = 0.068). The incidence of other complications of prematurity (retinopathy of prematurity, intraventricular hemorrhage, or periventricular leukomalacia) was not different between groups. In conclusion, the IL-10 -1082 G/A SNP does not have a major influence on mortality or the development of BPD in ventilated VLBW infants.