Decreased interleukin-10 in tracheal aspirates from preterm infants developing chronic lung disease

Chitin Derived Small Molecule AVR-48 Reprograms the Resting Macrophages to an Intermediate Phenotype and Decrease Pseudomonas aeruginosa Mouse Lung Infection

AVR-48 is a structural derivative of chitin previously shown by our laboratory to significantly decrease lung injury parameters in LPS, hyperoxia and sepsis-induced rodent models. The current study objectives are to determine the cellular mechanism of action and demonstrate efficacy in a mouse bacterial lung infection model. For in vitro receptor binding and macrophage polarization studies, C57Bl/6J mouse derived spleens and human peripheral blood mononuclear cells (hPBMCs) were treated with AVR-48 ± LPS or biotin conjugated AVR-48. Different macrophage types were determined using flow cytometry and secreted cytokines were measured using ELISA. In vivo, a CD-1 mouse Pseudomonas aeruginosa lung infection was treated with AVR-48, assessing bacterial colony forming unit (CFU), IL-10 and IL-17A levels in lung and blood samples. AVR-48 binds to both the toll-like receptor 4 (TLR4) and the CD163 receptor on mouse monocytes. In hPBMCs, frequency of intermediate macrophages increased upon AVR-48 treatment for 72 h. Increased bacterial phagocytosis/intracellular killing were observed in THP-1 cells and reduction in CFU in CD-1 mouse lungs. Binding of AVR-48 to both TLR4 and CD163 receptors bring the macrophages to an intermediary stage, resulting in increased phagocytosis and decreased inflammation, altogether providing an optimal immune balance for treating lung injury and infection.

Chronic Inflammatory Placental Lesions Correlate With Bronchopulmonary Dysplasia Severity in Extremely Preterm Infants

OBJECTIVE

Correlation of BPD with placental pathology is important for clarification of the multifactorial pathogenesis of BPD; however, previous reports have yielded varying results. We report placental findings in no/mild BPD compared to moderate/severe BPD, and with and without pulmonary hypertension (PH).

METHODS

Eligible infants were 23^0/7-27^6/7 weeks gestational age. BPD was defined by the need for oxygen at ≥28 days with severity based on need for respiratory support at ≥36 weeks. Acute and chronic inflammatory placental lesions and lesions of maternal and fetal vascular malperfusion were examined.

RESULTS

Of 246 eligible infants, 146 (59%) developed moderate/severe BPD. Thirty-four (23%) infants developed PH, all but 1 being in the moderate/severe BPD group. Chronic deciduitis (32% vs 16%, P = .003), chronic chorioamnionitis (23% vs 12%, P = .014), and ≥ 2 chronic inflammatory lesions (13% vs 3%, P = .007) were more frequent in the moderate/severe BPD group. Development of PH was associated with placental villous lesions of maternal vascular malperfusion (30% vs 15%, P = .047).

CONCLUSIONS

The association of chronic inflammatory placental lesions with BPD severity has not been previously reported. This supports the injury responsible for BPD as beginning before birth in some neonates, possibly related to cytokines associated with these chronic inflammatory lesions.

Pilot feasibility study to detect mesenchymal stem cell biomarkers of bronchopulmonary dysplasia in the tracheal aspirate fluid of preterm infants

OBJECTIVE

This study aimed to detect novel mesenchymal stem cell peptides/biomarkers of bronchopulmonary dysplasia (BPD) in the tracheal aspirate fluid (TAF) of preterm infants.

STUDY DESIGN

Participants included infants less than 32 weeks' gestational age or birth weight under 1500 grams who required endotracheal intubation and mechanical ventilation within first 24 hours of life. TAF sample collection was performed at the time of the first clinically indicated routine suctioning. Standardization curves for human levels of osteopontin (Opn), macrophage colony stimulating factor 1 (Csf1), transforming growth factor beta 1 (TGF-β1), and secretory immunoglobulin A (sIgA) were generated for 15 enrolled participants.

RESULTS

We demonstrated that stem cell biomarkers are secreted into the TAF of preterm infants and their concentrations can be easily measured during the first week of life.

CONCLUSIONS

Further studies are warranted to determine a causal relationship between these biomarkers and BPD development and severity.

CD11b(+) Mononuclear Cells Mitigate Hyperoxia-Induced Lung Injury in Neonatal Mice

Bronchopulmonary dysplasia (BPD) is a common consequence of life-saving interventions for infants born with immature lungs. Resident tissue myeloid cells regulate lung pathology, but their role in BPD is poorly understood. To determine the role of lung interstitial myeloid cells in neonatal responses to lung injury, we exposed newborn mice to hyperoxia, a neonatal mouse lung injury model with features of human BPD. In newborn mice raised in normoxia, we identified a CD45(+) F4/80(+) CD11b(+), Ly6G(lo-int) CD71(+) population of cells in lungs of neonatal mice present in significantly greater percentages than in adult mice. In response to hyperoxia, surface marker and gene expression in whole lung macrophages/monocytes was biased to an alternatively activated phenotype. Partial depletion of these CD11b(+) mononuclear cells using CD11b-diphtheria toxin (DT) receptor transgenic mice resulted in 60% mortality by 40 hours of hyperoxia exposure with more severe lung injury, perivascular edema, and alveolar hemorrhage compared with DT-treated CD11b-DT receptor-negative controls, which displayed no mortality. These results identify an antiinflammatory population of CD11b(+) mononuclear cells that are protective in hyperoxia-induced neonatal lung injury in mice, and suggest that enhancing their beneficial functions may be a treatment strategy in infants at risk for BPD.

Therapeutic potential of mesenchymal stem cells for pulmonary complications associated with preterm birth

Preterm infants frequently suffer from pulmonary complications resulting in significant morbidity and mortality. Physiological and structural lung immaturity impairs perinatal lung transition to air breathing resulting in respiratory distress. Mechanical ventilation and oxygen supplementation ensure sufficient oxygen supply but enhance inflammatory processes which might lead to the establishment of a chronic lung disease called bronchopulmonary dysplasia (BPD). Current therapeutic options to prevent or treat BPD are limited and have salient side effects, highlighting the need for new therapeutic approaches. Mesenchymal stem cells (MSCs) have demonstrated therapeutic potential in animal models of BPD. This review focuses on MSC-based therapeutic approaches to treat pulmonary complications and critically compares results obtained in BPD models. Thereby bottlenecks in the translational systems are identified that are preventing progress in combating BPD. Notably, current animal models closely resemble the so-called "old" BPD with profound inflammation and injury, whereas clinical improvements shifted disease pathology towards a "new" BPD in which arrest of lung maturation predominates. Future studies need to evaluate the utility of MSC-based therapies in animal models resembling the "new" BPD though promising in vitro evidence suggests that MSCs do possess the potential to stimulate lung maturation. Furthermore, we address the mode-of-action of MSC-based therapies with regard to lung development and inflammation/fibrosis. Their therapeutic efficacy is mainly attributed to an enhancement of regeneration and immunomodulation due to paracrine effects. In addition, we discuss current improvement strategies by genetic modifications or precondition of MSCs to enhance their therapeutic efficacy which could also prove beneficial for BPD therapies.

Anti-inflammatory actions of endogenous and exogenous interleukin-10 versus glucocorticoids on macrophage functions of the newly born

OBJECTIVE

To determine whether specific macrophage immune functions of the newly born are insensitive to the actions of therapeutic levels of dexamethasone (DEX), previously measured in infants with bronchopulmonary dysplasia (BPD), compared with betamethasone (BETA) and exogenous or endogenous interleukin-10 (IL-10).

STUDY DESIGN

Macrophages were differentiated from cord blood monocytes (N=18). A serial dose-response (around 10(-8 )M), in vitro study was used to examine the effect of DEX, BETA and IL-10, on proinflammatory (PI) cytokine release, phagocytosis and respiratory burst.

RESULT

Exogenous IL-10 (10(-8 )M) significantly (P<0.05) inhibited the endotoxin-stimulated release of IL-6, IL-8 and tumor necrosis factor by 63 to 82% with no significant effect by DEX and BETA. There was no inhibition by these three agents at 10(-8 )M on phagocytosis and respiratory burst. Inhibition of endogenous IL-10 with a monoclonal antibody significantly increased endotoxin-stimulated cytokine release by at least fourfold.

CONCLUSION

Macrophages were relatively insensitive to therapeutic levels of DEX and BETA with regard to PI cytokine release. This study provides rationale for translational and preclinical research using airway instillation of IL-10 for the treatment of BPD.

Reduced IL-10 production in fetal type II epithelial cells exposed to mechanical stretch is mediated via activation of IL-6-SOCS3 signaling pathway

An imbalance between pro-inflammatory and anti-inflammatory cytokines is a key factor in the lung injury of premature infants exposed to mechanical ventilation. Previous studies have shown that lung cells exposed to stretch produces reduced amounts of the anti-inflammatory cytokine IL-10. The objective of these studies was to analyze the signaling mechanisms responsible for the decreased IL-10 production in fetal type II cells exposed to mechanical stretch. Fetal mouse type II epithelial cells isolated at embryonic day 18 were exposed to 20% stretch to simulate lung injury. We show that IL-10 receptor gene expression increased with gestational age. Mechanical stretch decreased not only IL-10 receptor gene expression but also IL-10 secretion. In contrast, mechanical stretch increased release of IL-6. We then investigated IL-10 signaling pathway-associated proteins and found that in wild-type cells, mechanical stretch decreased activation of JAK1 and TYK2 and increased STAT3 and SOCS3 activation. However, opposite effects were found in cells isolated from IL-10 knockout mice. Reduction in IL-6 secretion by stretch was observed in cells isolated from IL-10 null mice. To support the idea that stretch-induced SOCS3 expression via IL-6 leads to reduced IL-10 expression, siRNA-mediated inhibition of SOCS3 restored IL-10 secretion in cells exposed to stretch and decreased IL-6 secretion. Taken together, these studies suggest that the inhibitory effect of mechanical stretch on IL-10 secretion is mediated via activation of IL-6-STAT3-SOCS3 signaling pathway. SOCS3 could be a therapeutic target to increase IL-10 production in lung cells exposed to mechanical injury.

Gene expression profile of endotoxin-stimulated leukocytes of the term new born: control of cytokine gene expression by interleukin-10

Introduction

Increasing evidence now supports the association between the fetal inflammatory response syndrome (FIRS) with the pathogenesis of preterm labor, intraventricular hemorrhage and bronchopulmonary dysplasia. Polymorphonuclear leukocyte (PMNs) and mononuclear cell (MONOs) infiltration of the placenta is associated with these disorders. The aim of this study was to reveal cell-specific differences in gene expression and cytokine release in response to endotoxin that would elucidate inflammatory control mechanisms in the newly born.

Methods

PMNs and MONOs were separately isolated from the same cord blood sample. A genome-wide microarray screened for gene expression and related pathways at 4 h of LPS stimulation (n = 5). RT-qPCR and ELISA were performed for selected cytokines at 4 h and 18 h of LPS stimulation.

Results

Compared to PMNs, MONOs had a greater diversity and more robust gene expression that included pro-inflammatory (PI) cytokines, chemokines and growth factors at 4 h. Only MONOs had genes changing expression (all up regulated including interleukin-10) that were clustered in the JAK/STAT pathway. Pre-incubation with IL-10 antibody, for LPS-stimulated MONOs, led to up regulated PI and IL-10 gene expression and release of PI cytokines after 4 h.

Discussion

The present study suggests a dominant role of MONO gene expression in control of the fetal inflammatory response syndrome at 4 hrs of LPS stimulation. LPS-stimulated MONOs but not PMNs of the newborn have the ability to inhibit PI cytokine gene expression by latent IL-10 release.

Early postnatal surge of serum Clara cell secretory protein in newborn infants

BACKGROUND

Clara cell secretory protein (CCSP) is an anti-inflammatory mediator, but its role in neonatal lung adaptation and diseases is uncertain.

OBJECTIVE

To characterize postnatal changes in serum CCSP in relation to gestation, respiratory disease (RDS) and bronchopulmonary dysplasia (BPD) in comparison with other anti-inflammatory cytokines (IL-4, -10 and -13).

METHODS

Blood was collected from 76 infants (26 of 23-29 weeks' gestation, 33 of 30-36 weeks' gestation and 17 term infants) at birth (preterm cord blood); on admission; at 12, 24 and 48 h; and on days 3-4 and 7 of life. CCSP was assayed by ELISA and cytokines by Bio-Plex.

RESULTS

Median serum CCSP in extremely and moderately preterm infants rose from a baseline of 13.6 and 15.9 to 33.4 ng/ml (p = 0.04) and 59.8 ng/ml (p = 0.03) at 12 h of age, respectively. CCSP levels were highest in term infants (80.7 ng/ml at 12 h). CCSP then decreased to 22.5 ng/ml on days 3-4 (p = 0.001). CCSP of 37 RDS infants fell to a lower baseline on days 4 and 7 than that of the 22 non-RDS preterms. The 8 infants who developed BPD had persistently low serum CCSP (12.7 ng/ml at 12 h). In contrast, early postnatal changes were not seen in IL-4, -10 and -13 levels, but low IL-10 and -13 levels were found on day 7 in BPD infants.

CONCLUSIONS

Serum CCSP levels were characterized by an early postnatal surge. This apparent gestation-influenced surge may represent an initiation of a protective cascade against postnatal lung injury during extrauterine adaptation.

IL-10 inhibits inflammatory cytokines released by fetal mouse lung fibroblasts exposed to mechanical stretch

BACKGROUND

Mechanical ventilation plays an important role in the pathogenesis of bronchopulmonary dysplasia. However, the molecular mechanisms by which excessive stretch induces lung inflammation are not well characterized.

OBJECTIVES

In this study, we investigated in vitro the contribution of lung mesenchymal cells to the inflammatory response mediated by mechanical stretch and the potential protective role of IL-10.

METHODS

Fetal mouse lung fibroblasts isolated during the saccular stage of lung development were exposed to 20% cyclic stretch to simulate mechanical injury. The phenotype of cultured fibroblasts was investigated by red oil O and alpha-smooth muscle actin (α-SMA) staining. Cell necrosis, apoptosis, and inflammation were analyzed by lactate dehydrogenase release, cleaved caspase-3 activation and release of cytokines and chemokines into the supernatant, respectively.

RESULTS

First, we characterized the phenotype of the cultured fibroblasts and found an absence of red oil O staining and 100% positive staining for α-SMA, indicating that cultured fibroblasts were myofibroblasts. Mechanical stretch increased necrosis and apoptosis by two- and three-fold, compared to unstretched samples. Incubation of monolayers with IL-10 prior to stretch did not affect necrosis but significantly decreased apoptosis. Mechanical stretch increased release of pro-inflammatory cytokines and chemokines IL-1β, MCP-1, RANTES, IL-6, KC and TNF-α into the supernatant by 1.5- to 2.5-fold, and administration of IL-10 before stretch blocked that release.

CONCLUSIONS

Our data demonstrate that lung interstitial cells may play a significant role in the inflammatory cascade triggered by mechanical stretch. IL-10 protects fetal fibroblasts from injury secondary to stretch. Pediatr. Pulmonol. 2011; 46:640-649. © 2011 Wiley-Liss, Inc.

Intratracheal Clara cell secretory protein (CCSP) administration in preterm infants with or at risk of respiratory distress syndrome

BACKGROUND

Clara cell secretary protein (CCSP) is an immune-modulating and anti-inflammatory agent. CCSP is available synthetically as recombinant human Clara cell protein (rhCC10). It has been shown in animal models to reduce lung injury, improve pulmonary compliance and oxygenation, decrease systemic inflammation and up-regulate surfactant protein and vascular endothelial growth factor expression. These properties makes intratracheally administered CCSP a potential agent in prevention of chronic lung disease (CLD).

OBJECTIVES

To determine the effect of intratracheal CCSP administration compared to placebo or no treatment on morbidity and mortality in preterm infants with or at risk of respiratory distress syndrome (RDS).

SEARCH STRATEGY

We searched CENTRAL (The Cochrane Library, October 2010), MEDLINE and PREMEDLINE (1950 to October 2010), EMBASE (1980 to October 2010) and CINAHL (1982 to October 2010). We searched proceedings of scientific meetings, Google Scholar and reference lists of identified studies, and contacted expert informants and surfactant manufacturers.

SELECTION CRITERIA

Published, unpublished and ongoing randomised controlled, cluster-randomised or quasi-randomised trials of intratracheal CCSP administration, compared to placebo or no treatment on morbidity and mortality in preterm infants at risk of RDS.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies for eligibility and quality, and extracted data.

MAIN RESULTS

One pilot study was identified and included. This study enrolled 22 preterm infants 700 to 1300g with established RDS who required ventilation for surfactant administration. Infants received one intratracheal dose of placebo (n = 7), 1.5 mg/kg (n = 8) or 5 mg/kg (n = 7) rhCC10 within four hours of surfactant treatment. At either dose of rhCC10, no significant difference was reported in CLD (36 weeks postmenstrual age or 28 days), mortality, intraventricular haemorrhage, periventricular leukomalacia, patent ductus arteriosus, necrotising enterocolitis, sepsis or days supplemental oxygen compared to placebo. A significant increase in days mechanical ventilation was reported for infants receiving rhCC10 5mg/kg (mean difference 12.00, 95% confidence interval 0.39 to 23.61) but not at the lower dose. The study reported that a single intratracheal dose of rhCC10 was well tolerated and resulted in a significant reduction in tracheal aspirate neutrophil and total cell count, and lung protein concentration. There was no significant difference reported in tracheal aspirate cytokine levels between groups.

AUTHORS' CONCLUSIONS

There are insufficient data to determine the role of rhCC10 in clinical practice. Further studies are required to determine if rhCC10 reduces lung inflammation in infants at risk of CLD, and to determine dose and dosing strategy.

Correlation between serum caffeine levels and changes in cytokine profile in a cohort of preterm infants

OBJECTIVE

To determine changes in cytokine levels associated with caffeine treatment in a cohort of preterm infants.

STUDY DESIGN

For this observational prospective study, we collected clinical data from 26 preterm infants (≤ 30 weeks gestational age). In addition to caffeine levels, cytokine profiles in peripheral blood (PB) and tracheal aspirates (TA) were determined with enzyme-linked immunosorbent assay at birth, before and after (at 24 hours and 1 week) initiation of caffeine. Non-parametric statistics were applied.

RESULTS

Included infants were 26.9 ± 1.7 weeks gestational age and weighed 985 ± 202 g. At birth, all cytokine concentrations were significantly greater in TA than PB. Serum caffeine levels were 11.1 μg/mL (interquartile range, 1.85) at approximately 24 hours post-load and 16.4 (8.7) μg/mL at 1 week on treatment. At approximately 24 hours post-load, interleukin (IL)-10 levels decreased by 47.5% (P = .01) in PB and 38.5% (P = .03) in TA, whereas other cytokine levels remained unchanged. At 1 week, caffeine levels were correlated (U-shaped) with changes in proinflammatory tumor necrosis factor-α (R(2) = 0.65; P = .0008), interleukin (IL)-1β (R(2) = 0.73; P = .0007), and IL-6 (R(2) = 0.59; P = .003), whereas inversely correlated (linear) with the anti-inflammatory IL-10 (R(2) = 0.64; P = .0008). Altogether, caffeine, at serum levels ≥ 20 μg/mL, was associated with a proinflammatory profile after 1 week of treatment.

CONCLUSIONS

Caffeine treatment for apnea of prematurity correlates with changes in cytokine profile. Caffeine levels ≥ 20 μg/mL are associated with a proinflammatory profile in our cohort of preterm infants.

Placental IL-10 dysregulation and association with bronchopulmonary dysplasia risk

Cytokine profiles in amniotic fluid, cord serum, and tracheal aspirate of premature infants suggest a shift toward a proinflammatory state. Cytokines also contribute to the pathogenesis of bronchopulmonary dysplasia (BPD). We hypothesize that the initiating events for BPD are reflected in the placenta and propose that placental expression of cytokines provide a blueprint of events leading to BPD. This is a retrospective, case-controlled study of placental cytokines of premature infants with (n = 49) and without (n = 49) BPD, matched for gender, birth weight, and year of birth at Women and Infants Hospital between 2003 and 2005. Cytokine expression, including IL-6 and IL-10, was determined by immunohistochemistry in membrane rolls, umbilical cords, and placentas. IL-6 was similarly expressed in all tissues of infants with and without BPD. In contrast, anti-inflammatory cytokine IL-10 was less prominent in the placenta of patients with BPD compared with those without BPD. IL-10 expression in the villous trophoblast layer was associated with a reduced odds ratio of developing BPD (adjusted OR 0.08, 95% CI 0.01-0.70, p = 0.02). These results suggest that a placental balance between inflammatory and anti-inflammatory cytokines is crucial to normal lung organogenesis. Importantly, IL-10 seems to be protective against the development of BPD.

Pitfalls, problems, and progress in bronchopulmonary dysplasia

Bronchopulmonary dysplasia is a chronic lung disease associated with premature birth and characterized by early lung injury. In this review we discuss some pitfalls, problems, and progress in this condition over the last decade, focusing mainly on the last 5 years, limited to studies in human neonates. Changes in the definition, pathogenesis, genetic susceptibility, and recent biomarkers associated with bronchopulmonary dysplasia will be discussed. Progress in current management strategies, along with novel approaches/therapies, will be critically appraised. Finally, recent data on long-term pulmonary and neurodevelopmental outcomes of infants with bronchopulmonary dysplasia will be summarized.

A single recruitment maneuver in ventilated critically ill children can translocate pulmonary cytokines into the circulation

INTRODUCTION

Recruitment maneuvers (RMs) are advocated to prevent pulmonary collapse during low tidal volume ventilation and improve oxygenation. However, convincing clinical evidence for improved outcome is lacking. Recent experimental studies demonstrate that RMs translocate pulmonary inflammatory mediators into the circulation. To determine whether a single RM in ventilated children affects pulmonary and systemic cytokine levels, we performed a prospective intervention study.

METHODS

Cardiorespiratory stable ventilated patients (0.5-45 months, n = 7) with acute lung injury were subjected to an RM determining opening and closing pressures (peak inspiratory pressure < or =45 cmH(2)O, positive end expiratory pressure (PEEP) < or =30 cmH(2)O). Before and after RM, cardiorespiratory parameters and ventilator settings were recorded, blood gas analysis performed, and bronchoalveolar lavage fluid and plasma TNF-alpha, IL-1beta, IL-6, IL-8, and IL-10 concentrations were determined.

RESULTS

Fifteen minutes after the RM, an increase was observed in plasma tumor necrosis factor-alpha (400% +/- 390% of baseline, P = .04), IL-6 (120% +/- 35%, P = .08), and IL-1beta (520% +/- 535%, P = .04), which decreased at T = 60 minutes, hence indicative of translocation. Recruitment maneuver did not change the plasma levels of the anti-inflammatory IL-10 (105% +/- 12%, P = .5). Apart from a nonsignificant increase of IL-8 after 360 minutes (415% +/- 590%,P = .1), bronchoalveolar cytokine levels were not influenced by the RM. No increase in oxygenation or improvement of lung kinetics was observed.

CONCLUSIONS

A single RM can translocate pro-inflammatory cytokines from the alveolar space into the systemic circulation in ventilated critically ill children.

Pulmonary Biomarkers of Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia, or BPD, is a chronic pulmonary disorder of premature infants, commonly defined as having an oxygen requirement at 36 weeks postmenstrual age. It is an important source of morbidity and mortality in premature neonates. Its' etiology appears to be multifactorial with the most common associations being prematurity, need for mechanical ventilation, and oxygen exposure. Implied in the pathogenesis of BPD is the role of cytokines which are immune mediators produced by most cell types. This is evidenced by studies in which there exist alterations in the levels of "pro-inflammatory" and "anti-inflammatory" cytokines. The imbalance of these cytokines have either heralded the onset or predicted the presence of BPD, or indicated a decreased propensity to developing this chronic respiratory disorder of preterm infants. Many other pulmonary markers have been shown to be altered in patients with BPD. These include markers indicative of altered lung repair processes, decreased endothelial integrity, oxidative damage and abnormal fibrinolytic activity, all of which are thought to be mechanisms contributing to the development of BPD.In this review, we will discuss the physiologic role of specific biomarkers in the pulmonary tract of the human premature neonate, the perturbations that enable them to be deranged, and their proposed association with BPD.

The oxygenation ratio during mechanical ventilation in children: the role of tidal volume and positive end-expiratory pressure

OBJECTIVE

The objective of this study is to analyze the role of tidal volume (Vt) and positive end-expiratory pressure on the oxygenation ratio (OR) (Pao(2)/Fio(2)) during mechanical ventilation (MV) in children with a normal pulmonary gas exchange on admission.

METHODS

A retrospective cohort study of children with an admission OR greater than 300 mm Hg and duration of MV greater than 48 hours (n = 96) was done. We analyzed Vt, Fio(2), Pao(2), and positive end-expiratory pressure and calculated Vt (mL/kg) and Pao(2)/Fio(2) based on the measured Vt and weight. Patients were divided into group 1, Vt less than 9 mL/kg (n = 24); 2, Vt 9 to 12 mL/kg (n = 58); and 3, Vt 12 mL/kg or higher (n = 14).

RESULTS

Baseline characteristics and OR were comparable. Forty-one percent of patients developed OR less than 300 mm Hg. The proportion of patients developing an OR less than 300 mm Hg was lowest in group 1 and highest in group 3, and differences became more pronounced with longer MV duration: 56%, 58%, and 89% on day 5; 29%, 65%, and 100% on day 7 (P = .05); 0%, 40%, and 100% on day 10 (P = .03). In patients maintaining an OR greater than 300 mm Hg during 10 days of MV, Vt was 9.3 +/- 1.0 vs 12.7 +/- 4.8 mL/kg in patients developing an OR less than 300 mm Hg (P = .05). Mechanical ventilation duration was longer in children developing OR less than 300 mm Hg (P < .01). Positive end-expiratory pressure levels were not significantly different between groups.

CONCLUSION

In ventilated children, Vt was greater than 9 mL/kg were associated with increased development of an OR less than 300 mm Hg and longer duration of MV.

Angiopoietin 2 concentrations in infants developing bronchopulmonary dysplasia: attenuation by dexamethasone

OBJECTIVES

To study the association between angiopoietin 2 (Ang2) concentrations in tracheal aspirates (TAs) and adverse outcome (bronchopulmonary dysplasia (BPD)/death) in ventilated premature infants (VPIs) and modulation of Ang2 concentrations with dexamethasone (Dex) use.

STUDY DESIGN

Serial TA samples were collected on days 1, 3, 5 and 7, and Ang2 concentrations were measured. Ang2 TA concentrations were compared prior to and after 48 to 72 h of using Dex.

RESULT

A total of 151 TA samples were collected from 60 VPIs. BPD was defined as the oxygen requirement at 36 weeks postmenstrual age (PMA). Twelve infants (mean+/-s.d.) (gestational age (GA) 26.5+/-2.1 weeks, birth weight (BW) 913+/-230 g) had no BPD, 32 infants (GA 25.8+/-1.4 weeks, BW 768+/-157 g) developed BPD and 16 infants (GA 24.5+/-1.1 weeks, BW 710+/-143 g) died before 36 weeks PMA. Ang2 concentrations were significantly lower in infants with no BPD (median, 25th and 75th percentile) (157, 16 and 218 pg mg(-1)) compared with those who developed BPD (234, 138 and 338 pg mg(-1), P=0.03) or BPD and/or death (234, 157 and 347 pg mg(-1), P=0.017), in the first week of life. Twenty-six VPIs (BW 719+/-136 g, GA 25.1+/-1.3 weeks) received 27 courses of Dex. Ang2 concentrations before starting Dex were 202, 137 and 278 pg mg(-1) and significantly decreased to 144, 0 and 224 pg mg(-1) after therapy (P=0.007).

CONCLUSIONS

Higher Ang2 concentrations in TAs are associated with the development of BPD or death in VPIs. Dex use suppressed Ang2 concentrations.

Interleukin-10 protects cultured fetal rat type II epithelial cells from injury induced by mechanical stretch

Mechanical ventilation plays a central role in the pathogenesis of bronchopulmonary dysplasia. However, the mechanisms by which excessive stretch of fetal or neonatal type II epithelial cells contributes to lung injury are not well defined. In these investigations, isolated embryonic day 19 fetal rat type II epithelial cells were cultured on substrates coated with fibronectin and exposed to 5% or 20% cyclic stretch to simulate mechanical forces during lung development or lung injury, respectively. Twenty percent stretch of fetal type II epithelial cells increased necrosis, apoptosis, and proliferation compared with control, unstretched samples. By ELISA and real-time PCR (qRT-PCR), 20% stretch increased secretion of IL-8 into the media and IL-8 gene expression and inhibited IL-10 release. Interestingly, administration of recombinant IL-10 before 20% stretch did not affect cell lysis but significantly reduced apoptosis and IL-8 release compared with stretched samples without IL-10. Collectively, our studies suggest that IL-10 may play an important role in protection of fetal type II epithelial cells from injury secondary to stretch.

TNF-a and IL-10 levels in tracheobronchial lavage of ventilated preterm infants and subsequent lung function

The role of airway inflammation in ventilated preterm newborns and the risk factors associated with the development of chronic lung disease are not well understood. Our objective was to analyze the association of the airway inflammatory response in ventilated preterm infants by serial measurements of TNF-alpha and IL-10 in tracheobronchial lavage (TBL) with perinatal factors and lung function measured early in life. A series of TBL samples were collected from ventilated preterm infants (less than 32 weeks of gestational age) and concentrations of TNF-alpha and IL-10 were measured by ELISA. Pulmonary function tests were performed after discharge by the raised volume rapid compression technique. Twenty-five subjects were recruited and 70 TBL samples were obtained. There was a significant positive association between TNF-alpha and IL-10 levels and length of time between the rupture of the amniotic membranes and delivery (r = 0.65, P = 0.002, and r = 0.57, P < 0.001, respectively). Lung function was measured between 1 and 22 weeks of corrected age in 10 patients. Multivariable analysis with adjustment for differences in lung volume showed a significant negative association between TNF-alpha levels and forced expiratory flow (FEF(50); r = -0.6; P = 0.04), FEF(75) (r = -0.76; P = 0.02), FEF(85) (r = -0.75; P = 0.03), FEF(25-75) (-0.71; P = 0.02), and FEV(0.5) (r = -0.39; P = 0.03). These data suggest that TNF-alpha levels in the airways during the first days of life were associated with subsequent lung function abnormalities measured weeks or months later.

Interleukin-10 production after pro-inflammatory stimulation of neutrophils and monocytic cells of the newborn. Comparison to exogenous interleukin-10 and dexamethasone levels needed to inhibit chemokine release

BACKGROUND

Neutrophils followed by monocytic cells are recruited into the lung during the early development of bronchopulmonary dysplasia (BPD).

OBJECTIVES

We determined: (1) the capacity of polymorphonuclear leukocytes (PMNs) and peripheral blood monocytic cells (PBMCs) of the newborn to produce and release the anti-inflammatory cytokine, interleukin (IL)-10, after stimulation by lipopolysaccharide (LPS) or tumor necrosis factor (TNF), and (2) the levels of exogenous IL-10 and/or dexamethasone (DEX) needed to inhibit the release of the pro-inflammatory chemokine IL-8 from stimulated cells.

METHODS

PMNs and PBMCs were isolated from cord blood of healthy term infants. RT-PCR and ELISA were used to detect mRNA and cytokine levels from culture media, respectively.

RESULTS

We found that PMNs did not produce IL-10 mRNA or release IL-10 but did produce IL-8 mRNA by 1 h. PBMCs did produce IL-10 mRNA after 4 h (with IL-8 mRNA expression by 1 h). LPS-stimulated PBMCs released IL-10 to a maximum of 1,038 pg/ml/5 million cells (56 femtomolar). Equimolar doses of exogenous IL-10 or DEX produced up to 83% inhibition of IL-8 from PMNs. Exogenous IL-10 was more potent than DEX, on an equimolar basis, with regard to IL-8 release from PBMCs (90 vs. 33% respectively at a 10 nanomolar level). No inhibition of IL-8 release by IL-10 or DEX was observed at 100 femtomolar level. IL-10 and DEX did not have an additive inhibitory effect on IL-8 release.

CONCLUSIONS

We conclude that for the newborn: (1) PBMCs produce IL-10 far below the level needed to inhibit a submaximal release of IL-8 from PMNs or PBMCs, and (2) exogenous IL-10 was equipotent or more potent than therapeutic levels of DEX on inhibition of IL-8 from these cells. Further studies are needed to determine if exogenous IL-10 may be useful in the treatment of BPD or other inflammatory disorders of the newborn.

Diminished response to interleukin-10 and reduced antibody-dependent cellular cytotoxicity of cord blood monocyte-derived macrophages

Monocyte-derived macrophage (MPhi) subsets are generated by antagonistic induction pathways. A helper MPhi-type (Mh-MPhi) is induced by interferon gamma (IFN-gamma), whereas a cytotoxic MPhi-type (Mc-MPhi), induced by interleukin-10 (IL-10), is a potent mediator of antibody-dependent cellular cytotoxicity (ADCC). Compared with MPhi from healthy adults [peripheral blood monocyte-derived macrophages (PBMPhi)], cord blood MPhi (CBMPhi) were found less capable of generating Mh-MPhi. Here we tested the hypothesis that their generation of Mc-MPhi via IL-10 is also impaired. MPhi surface markers were phenotyped. IL-10 protein and mRNA production were detected after stimulation [alphaCD3 monoclonal antibody (mAb)]. CBMPhi or PBMPhi were co-cultured with MPhi-depleted mononuclear cells of adults and CD4-targeting antibodies as models for ADCC were added. In cord blood, we found diminished alphaCD3-induced IL-10 protein and mRNA production (p < 0.05 versus adults). Basal CD16 and HLA-DR expressions on CBMPhi of preterm and full-term neonates were lower (p < 0.05 versus PBMPhi). IL-10 had reduced effects on CD16 up- and HLA-DR down-modulation on CBMPhi (p < 0.05 versus PBMPhi). CD4-directed receptor modulation and deletion were reduced in the presence of CBMPhi (p < 0.05 versus PBMPhi). IL-10 failed to enhance their ADCC capacity, which was in contrast to PBMPhi (p < 0.05). These data suggest that CBMPhi have an impaired cytotoxic capacity via lower sensitivity toward IL-10.

Glutamine modulates LPS-induced IL-8 production through IkappaB/NF-kappaB in human fetal and adult intestinal epithelium

The intestinal epithelium may serve as a nidus for inflammation that can cause local and systemic organ dysfunction. Relative to the adult, the immature intestine is exquisitely sensitive to inflammatory agents. Glutamine (Gln), an amino acid that is rapidly depleted during critical illness, modulates intestinal inflammation in vitro and in vivo. Here we relate Gln status to activation of the inhibitor of kappaB (IkappaB)/nuclear factor (NF)-kappaB signaling pathway in fetal-derived (H4) and adult (Caco-2) enterocytes. In the absence of Gln with or without LPS, H4 cells expressed more interleukin (IL)-8) than Caco-2 cells. Gln supplementation partially prevented the LPS-induced elevation of IL-8 in both cell types. IkappaBalpha was significantly decreased in both H4 and Caco-2 cells with Gln deprivation, and this was followed by an increase in NF-kappaB p65 in the nucleus. DNA binding of NF-kappaB was increased in both H4 and Caco-2 cells with Gln deprivation. IkappaBalpha phosphorylation was not altered by Gln status in either H4 or Caco-2 cells. Proteasomal inhibition after Gln depletion in Caco-2 cells was associated with an increase in the IkappaB-ubiquitin complex, but a decrease in complex formation in H4 cells, indicating that Gln deprivation alters IkappaBalpha through a pathway that differs from Caco-2 cells. We speculate that a reduced capacity of the immature enterocyte (H4) to respond to Gln deprivation with increased synthesis of IkappaBalpha rather than increased proteolysis as seen in the Caco-2 cells is the underlying mechanism.

Association between environmental tobacco smoke and diminished dendritic cell interleukin 10 production during infancy

BACKGROUND

Diminished interleukin 10 (IL-10) production has been documented in children and adults with asthma and atopy. Environmental tobacco smoke (ETS) is recognized as a risk factor for the development of childhood asthma.

OBJECTIVE

To determine whether there is an association between ETS and dendric cell (DC) IL-10 production during infancy.

METHODS

ETS was evaluated by questionnaire, and blood samples were obtained at 2 weeks, 3 months, and 5 months of age in 37 healthy infants. DCs were cultured and stimulated, and supernatants were assayed for IL-10 by enzyme immunoassay.

RESULTS

Sixteen infants had no history of exposure to ETS, and 21 infants had a history of ETS exposure. The frequency of subjects with detectable IL-10 levels was similar in both groups at 2 weeks and 3 months but significantly different at 5 months (P < .001). In those without ETS exposure, the frequency with detectable IL-10 levels increased during the observation period (25% at 2 weeks, 20% at 3 months, and 36% at 5 months; P = .03 vs 2 weeks). In contrast, in those with ETS exposure, the frequency with detectable IL-10 levels decreased during the observation period (33% at 2 weeks, 19% at 3 months; P = .02 vs 2 weeks; and 7% at 5 months; P < .001 vs 2 weeks).

CONCLUSIONS

Our study results demonstrate an association between ETS and diminished DC IL-10 production during infancy. Future studies need to expand on these sample sizes and explore whether diminished DC IL-10 production is the mechanism by which ETS predisposes patients to the development of asthma and/or atopy.

Developmentally regulated IkappaB expression in intestinal epithelium and susceptibility to flagellin-induced inflammation

Necrotizing enterocolitis is a devastating inflammatory condition of the intestine that occurs almost exclusively in premature newborns. Although its exact pathogenesis is unclear, we have postulated that it may result from a predisposition of the immature intestine to mount an unusually robust and damaging response to microbial infection. In support of this idea, we report that the IL-8 response of an immature human enterocyte cell line to bacterial infection was significantly higher than that of a mature enterocyte cell line. The response in both cell lines was flagellin-dependent. Corresponding to the difference in IL-8 production, the immature enterocytes expressed appreciably lower levels of specific IkappaB genes when compared with the mature enterocytes. Similar developmentally regulated differences in cytokine response and IkappaB expression were also seen in primary rat enterocytes, indicating that these observations were not peculiarities of the cell lines. Furthermore, when the level of IkappaBalpha expression was increased in the immature cell line by transfection, the flagellin-dependent IL-8 response was attenuated. Thus, we have demonstrated a previously undescribed developmental regulation of IkappaB expression in the intestine involved in modulating the IL-8 response to bacterial infection, which may contribute to the pathogenesis of age-specific inflammatory bowel diseases such as necrotizing enterocolitis.

High Tidal Volume Ventilation Causes Different Inflammatory Responses in Newborn versus Adult Lung

We investigated the effect of high VT ventilation on adult and newborn rats by examining pulmonary injury and cytokine messenger RNA (mRNA). On the basis of compliance, edema formation, and histology, ventilation with 25 ml.kg(-1) was more injurious to adult rats than newborns. Ventilation with 40 ml kg(-1) minimally affected compliance in newborns but caused death in adults. Ventilation of adults for 30 minutes at 25 ml kg(-1) upregulated the mRNA expression of interleukin (IL)-1beta, IL-6, tumor necrosis factor-alpha (TNF-alpha), macrophage inflammatory protein-2 (MIP-2), and IL-10, whereas in newborns such ventilation only increased mRNA expression of MIP-2 and IL-10. When VT was raised to 40 ml kg(-1) in newborns, IL-1beta mRNA levels were additionally increased at 30 minutes, whereas ventilation for 3 hours additionally increased IL-6 and TNF-alpha mRNA. In newborns, the addition of 100% oxygen (O2) to 30 minutes of ventilation blunted the high VT induction of IL-1beta, IL-10, and MIP-2 mRNA expressions, whereas at 3 hours, 100% O2 concentration synergistically increased the mRNAs for TNF-alpha and IL-6. Overall, adult rats are more susceptible to high VT-induced lung injury compared with newborns. In newborns, the inflammatory response is dependent on VT, duration, and supplemental O2. Thus, recommendations for VT limitation based on adult data may be inappropriate for newborns.

Interleukin-16 in tracheal aspirate fluids of newborn infants

BACKGROUND

It is currently unknown if interleukin (IL)-16 exists in the lungs of ventilated infants, and because the predominant cells in the airways of infants with CLD are CD4+ macrophages, we hypothesized that IL-16 plays a role as a pro-inflammatory mediator in lung inflammation.

AIMS

To examine if IL-16, a chemoattractant for CD4+ cells, is detectable in airway secretions of ventilated newborns. Its presence may be associated with lung inflammatory responses.

STUDY DESIGN

Cohort cross-sectional study.

SUBJECTS

Thirty-four mechanically ventilated newborn infants.

MAIN OUTCOME MEASURES

Tracheal fluid (TF) specimens collected during the first month of life were examined for cell differentials determined from cytospin slides and supernatant was analyzed by ELISA for IL-16.

RESULTS

Eighty-three cross-sectional tracheal fluid (TF) specimens were analyzed. Eleven of the 27 preterm but none of the 7 term infants developed chronic lung disease (CLD). IL-16, ranging from 203 to 42,073 pg/ml, was detected in 16 of the 46 specimens obtained from CLD infants, 1 of the 30 specimens from 16 non-CLD preterm and 2 of the 7 specimens from 7 term infants (p<0.001). Leukocyte counts (median 16.6 vs. 2.0 x 10(-9)/l, p<0.0001) and percentage neutrophils (median 93% vs. 73%, p<0.001) were higher in IL-16 positive specimens.

CONCLUSION

IL-16 is detectable within the airway secretions of ventilated newborn infants and its presence is associated with a neutrophilic infiltration. Further studies are required to investigate its role in chronic inflammation in CLD.