Maternal IL-1beta production prevents lung injury in a mouse model of bronchopulmonary dysplasia

Hyperoxia Induced Bronchopulmonary Dysplasia-Like Inflammation via miR34a-TNIP2-IL-1β Pathway

Lung injury induced by oxygen is a key contributor to the pathogenesis of preterm infant bronchopulmonary dysplasia (BPD). To date, there are comprehensive therapeutic strategy for this disease, but the underlying mechanism is still in progress. By using lentivirus, we constructed microRNA34a (miR34a)-overexpressing or knockdown A549 cell lines, and exposure to hyperoxia to mimic oxygen induce lung injury. In this study, we investigated 4 proinflammatory cytokines, interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), angiopoietin-1 (Ang-1), and Cyclooxygenase-2 (COX-2) in the secreted sputum of infants who received mechanical ventilation, and found that IL-1β was substantially elevated in the first week after oxygen therapy and with no significant decrease until the fourth week, while TNF-α, Ang-1, and COX-2 were increased in the first week but decreased quickly in the following weeks. In addition, in vitro assay revealed that hyperoxia significantly increased the expression of miR-34a, which positively regulated the proinflammatory cytokine IL-1β in a time- and concentration-dependent manner in A549 cells. Overexpressing or knockdown miR34 would exacerbate or inhibit production of IL-1β and its upstream NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome signaling pathway. Mechanically, it's found that TNFAIP3 interacting protein 2 (TNIP2), an inhibitor of nuclear factor κB (NF-κB), is a direct target of miR34a, negatively regulated activation of NLRP3 inflammasome and the production of IL-1β. Overexpressing TNIP2 ameliorated hyperoxia-induced production of IL-1β and cell apoptosis. Our findings suggest that TNIP2 may be a potential clinical marker in the diagnosis of BPD.

IL-33-induced neutrophil extracellular traps degrade fibronectin in a murine model of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the leading cause of chronic lung disease in preterm neonates. Extracellular matrix (ECM) abnormalities reshape lung development, contributing to BPD progression. In the present study, we first discovered that the ECM component fibronectin was reduced in the pulmonary tissues of model mice with BPD induced by lipopolysaccharide (LPS) and hyper-oxygen. Meanwhile, interleukin-33 (IL-33) and other inflammatory cytokines were elevated in BPD lung tissues. LPS stimulated the production of IL-33 in alveolar epithelial cells via myeloid differentiation factor 88 (MyD88), protein 38 (p38), and nuclear factor-kappa B (NF-κB) protein 65 (p65). Following the knockout of either IL-33 or its receptor suppression of tumorigenicity 2 (ST2) in mice, BPD disease severity was improved, accompanied by elevated fibronectin. ST2 neutralization antibody also relieved BPD progression and restored the expression of fibronectin. IL-33 induced the formation of neutrophil extracellular traps (NETs), which degraded fibronectin in alveolar epithelial cells. Moreover, DNase-mediated degradation of NETs was protective against BPD. Finally, a fibronectin inhibitor directly decreased fibronectin and caused BPD-like disease in the mouse model. Our findings may shed light on the roles of IL-33-induced NETs and reduced fibronectin in the pathogenesis of BPD.

Anthropometry before Day 46 and Growth Velocity before 6 Months of Guatemalan Breastfed Infants Are Associated with Subclinical Mastitis and Milk Cytokines, Minerals, and Trace Elements

BACKGROUND

Subclinical mastitis (SCM) is an inflammatory condition of the mammary gland, but its association with human milk composition and infant growth is not well described.

OBJECTIVES

We investigated whether SCM, milk cytokines, and/or estimated intakes of milk minerals and trace elements were associated with infant anthropometry or growth velocity before 6 mo.

METHODS

Breast milk was collected from Mam-Mayan mothers (n = 114) at both early (2-46 d) and established (4-6 mo) lactation. Concentrations of 9 elements (sodium, potassium, calcium, magnesium, copper, iron, manganese, selenium, zinc) analyzed by inductively-coupled plasma mass spectrometry were used to estimate infants' daily intakes. Concentrations of 4 cytokines were measured. Milk concentrations and infants' estimated elemental intakes and anthropometric measurements during early and established lactation were compared by SCM status. Multiple regression was used to identify factors associated with infant growth attainment (<46 d) for infant weight- (WAZ), length- (LAZ), and head circumference-for-age (HCAZ) and weight-for-length (WLZ) z scores and with growth velocity (expressed as Δ/d) from early to established lactation.

RESULTS

SCM prevalence was higher in early (30%) than established (10%) lactation. Breast milk of SCM mothers had higher cytokine concentrations and higher magnesium in early and higher selenium concentrations in both early and established lactation (Padj < 0.0121). At day 46, regression models showed inverse associations of SCM with WLZ and IL-1β with LAZ (Padj < 0.0150). In contrast, linear growth velocity was positively associated with IL-1β measured in early lactation (Padj < 0.0124), whereas cranial growth velocity was positively associated with IL-8 measured during established lactation ( Padj < 0.0124).

CONCLUSIONS

Despite a high prevalence of inadequate intakes, only infants' intake of milk magnesium during early lactation was associated with linear growth velocity in breastfed infants <6 mo. Evidence shows that SCM, breast-milk cytokines, and infants' estimated intakes of select elements are independently associated with growth attainment and growth velocity during lactation.

Impact of different stages of intrauterine inflammation on outcome of preterm neonates: Gestational age-dependent and -independent effect

Objective

To investigate the impact of different stages of intrauterine inflammation (IUI) on neonatal outcomes, before and after adjusting for gestational age (GA) and other perinatal confounders.

Methods

This was an observational, prospective, single-center cohort study including all eligible neonates with GA < 35 weeks and/or birth weight ≤ 1500 g born at a 3^rd level Neonatal Intensive Care Unit between 2011 and 2014. Pathological patterns of placenta, membranes and cord were classified according to Redline’s criteria. Multivariable linear and logistic regression models were applied, either including or not GA among the covariates.

Results

Of the 807 enrolled neonates, 134 (16.6%) had signs of IUI: among these, 54.5% showed just histological chorioamnionitis (HCA), 25.4% had HCA + funisitis (FUN) stage 1, and 20.1% had HCA + FUN stage 2–3. At univariate analysis, HCA increased the risk for retinopathy of prematurity (ROP) and bronchopulmonary dysplasia, while FUN (any stage) had a deleterious impact on all outcomes investigated. After adjustment for covariates not including GA, HCA was a risk factor only for ROP (OR = 2.8, CI: 1–7.8), while FUN (any stage) was still associated with increased ORs for all outcomes (p <0.01). Upon inclusion of GA in the regression model, the results differed remarkably. HCA was associated with lower risk for mechanical ventilation (OR = 0.3, CI: 0.1–0.7) and need for surfactant (OR = 0.5, CI: 0.2–0.9), while FUN (any stage) worsened clinical conditions at birth (p <0.05), increased the risk for early-onset sepsis (p <0.01), and increased the length of mechanical ventilation (FUN stage 2–3 only, RC = 6.5 days, CI: 2–11). No other outcome was affected.

Conclusions

IUI, especially FUN, negatively impact most neonatal morbidities, but its effect is partially reverted adjusting for GA. Considered that GA is an intermediate variable interposed between prenatal causes of prematurity and outcomes, the appropriateness of adjusting for GA may be questionable.

Gene expression profile in newborn rat lungs after two days of recovery of mechanical ventilation

BACKGROUND

Preterm infants having immature lungs often require respiratory support, potentially leading to bronchopulmonary dysplasia (BPD). Conventional BPD rodent models based on mechanical ventilation (MV) present outcome measured at the end of the ventilation period. A reversible intubation and ventilation model in newborn rats recently allowed discovering that different sets of genes modified their expression related to time after MV. In a newborn rat model, the expression profile 48 h after MV was analyzed with gene arrays to detect potentially interesting candidates with an impact on BPD development.

METHODS

Rat pups were injected P4-5 with 2 mg/kg lipopolysaccharide (LPS). One day later, MV with 21 or 60% oxygen was applied during 6 h. Animals were sacrified 48 h after end of ventilation. Affymetrix gene arrays assessed the total gene expression profile in lung tissue.

RESULTS

In fully treated animals (LPS + MV + 60% O(2)) vs. controls, 271 genes changed expression significantly. All modified genes could be classified in six pathways: tissue remodeling/wound repair, immune system and inflammatory response, hematopoiesis, vasodilatation, and oxidative stress. Major alterations were found in the MMP and complement system.

CONCLUSION

MMPs and complement factors play a central role in several of the pathways identified and may represent interesting targets for BPD treatment/prevention.Bronchopulmonary dysplasia (BPD) is a chronic lung disease occurring in ~30% of preterm infants born less than 30 wk of gestation (1). Its main risk factors include lung immaturity due to preterm delivery, mechanical ventilation (MV), oxygen toxicity, chorioamnionitis, and sepsis. The main feature is an arrest of alveolar and capillary formation (2). Models trying to decipher genes involved in the pathophysiology of BPD are mainly based on MV and oxygen application to young mammals with immature lungs of different species (3). In newborn rodent models, analyses of lung structure and gene and protein expression are performed for practical reasons directly at the end of MV (4,5,6). However, later appearing changes of gene expression might also have an impact on lung development and the evolution towards BPD and cannot be discovered by such models. Recently, we developed a newborn rat model of MV using an atraumatic (orotracheal) intubation technique that allows the weaning of the newborn animal off anesthesia and MV, the extubation to spontaneous breathing, and therefore allows the evaluation of effects of MV after a ventilation-free period of recovery (7). Indeed, applying this concept of atraumatic intubation by direct laryngoscopy, we recently were able to show significant differences between gene expression changes appearing directly after MV compared to those measured after a ventilation-free interval of 48 h. Immediately after MV, inflammation-related genes showed a transitory modified expression, while another set of more structurally related genes changed their expression only after a delay of 2 d (7). Lung structure, analyzed by conventional 2D histology and also by 3D reconstruction using synchrotron x-ray tomographic microscopy revealed, 48 h after end of MV, a reduced complexity of lung architecture compared to the nonventilated rat lungs, similar to the typical findings in BPD. To extend these observations about late gene expression modifications, we performed with a similar model a full gene expression profile of lung tissue 48 h after the end of MV with either room air or 60% oxygen. Essentially, we measured changes in the expression of genes related to the MMPs and complement system which played a role in many of the six identified mostly affected pathways.

Prenatal interventions to prevent bronchopulmonary dysplasia in animal models: a systematic review

OBJECTIVE

The objective of this study is to identify and systematically review in vivo animal studies on antenatal medical interventions to prevent bronchopulmonary dysplasia.

METHODS

An automated literature search was conducted using MEDLINE (Pubmed) and Embase including all studies using Medical Subject Headings (MeSH) and keywords following a step-by-step approach. All in vivo prenatal intervention studies in animal models mimicking key aspects of the pathophysiology of bronchopulmonary dysplasia were included. In view of relevance of the findings, an additional criterion was that outcomes at 48 h of life or beyond were available. The PRISMA statement concerning systemic reviews was applied and a quality checklist developed by the CAMARADES group was used.

RESULTS

In total, 518 abstracts were identified yet only eight studies were eligible for further analysis. Four studies involved administration of glucocorticoids, the other studies described therapy with epidermal growth factor, interleukin 1b, beta-naphthoflavone, or vitamin D. Outcomes were survival, pulmonary histology, lung function, and/or biochemical analysis.

CONCLUSIONS

Though many in vivo experimental studies in animal models for bronchopulmonary dysplasia have been done, only few have looked into the effect of prenatal interventions and measured outcomes after at least 48 h of life. Most involve the use of antenatal glucocorticoids, although still only four.

Animal models of bronchopulmonary dysplasia. The term mouse models

The etiology of bronchopulmonary dysplasia (BPD) is multifactorial, with genetics, ante- and postnatal sepsis, invasive mechanical ventilation, and exposure to hyperoxia being well described as contributing factors. Much of what is known about the pathogenesis of BPD is derived from animal models being exposed to the environmental factors noted above. This review will briefly cover the various mouse models of BPD, focusing mainly on the hyperoxia-induced lung injury models. We will also include hypoxia, hypoxia/hyperoxia, inflammation-induced, and transgenic models in room air. Attention to the stage of lung development at the timing of the initiation of the environmental insult and the duration of lung injury is critical to attempt to mimic the human disease pulmonary phenotype, both in the short term and in outcomes extending into childhood, adolescence, and adulthood. The various indexes of alveolar and vascular development as well as pulmonary function including pulmonary hypertension will be highlighted. The advantages (and limitations) of using such approaches will be discussed in the context of understanding the pathogenesis of and targeting therapeutic interventions to ameliorate human BPD.

Perinatal inflammation and lung injury

Bronchopulmonary dysplasia (BPD) remains the major morbidity of extreme preterm birth. The incidence of BPD has remained stable despite recent efforts to reduce postnatal exposures to volutrauma and hyperoxia. This review will focus on recent clinical and experimental insights that provide support for the concept that the 'new BPD' is the result of inflammation-mediated injury and altered lung development during a window of vulnerability in genetically susceptible infants that is modified by maternal and postnatal exposures.

Developmental stage is a major determinant of lung injury in a murine model of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a common inflammatory lung disease in premature infants. To study the hypothesis that the sensitivity of the lung to inflammatory injury depends on the developmental stage, we studied postnatal lung development in transgenic mice expressing human IL-1β (hIL-1β) in the lungs during the late canalicular-early saccular, saccular, or late saccular-alveolar stage. Overexpression of hIL-1β in the saccular stage caused arrest in alveolar development, airway remodeling, and goblet cell hyperplasia in the lungs as well as poor growth and survival of infant mice. Overexpression of hIL-1β during the late canalicular-early saccular stage did not adversely affect lung development, growth, or survival of the pups. Mice expressing hIL-1β from the late saccular to alveolar stage had smaller alveolar chord length, thinner septal walls, less airway remodeling and mucus metaplasia, and better survival than mice expressing hIL-1β during the saccular stage. Human IL-1β overexpression in the saccular stage was sufficient to cause a BPD-like illness in infant mice, whereas the lung was more resistant to hIL-1β-induced injury at earlier and later developmental stages.

Mechanisms of inflammatory lung injury in the neonate: lessons from a transgenic mouse model of bronchopulmonary dysplasia

The role of inflammation in the pathogenesis of bronchopulmonary dysplasia (BPD) is not well understood. By using a transgenic mouse expressing the inflammatory cytokine interleukin (IL)-1beta in the lung, we have shown that perinatal expression of IL-1beta causes a BPD-like illness in infant mice. We have used this model to identify mechanisms by which inflammation causes neonatal lung injury. Increased matrix metalloproteinase (MMP)-9 activity is associated with BPD. MMP-9 deficiency worsens alveolar hypoplasia in IL-1beta-expressing newborn mice, suggesting that MMP-9 has a protective role in neonatal inflammatory lung injury. The beta6 integrin subunit, an activator of transforming growth factor-beta, is involved in adult lung disease. Absence of the beta6 integrin subunit improves alveolar development in IL-1beta-expressing mice, suggesting that the beta6 integrin subunit is a pathogenetic factor in inflammatory lung disease in the newborn. The authors of clinical studies who have examined maternal inflammation as a risk factor for BPD have found variable results. We have shown that maternal IL-1beta production preceding fetal IL-1beta production prevents lung inflammation, alveolar hypoplasia, and airway remodeling in newborn IL-1beta-expressing mice. Thus, maternal inflammation may protect the newborn lung against subsequent inflammatory injury. In contrast, when maternal and fetal production of IL-1beta are induced simultaneously, the development of IL-1beta-induced lung disease in the newborn is not prevented.