Matrix metalloproteinases-2, -8, and -9 and TIMP-2 in tracheal aspirates from preterm infants with respiratory distress

Matrix Metalloproteinases on Severe COVID-19 Lung Disease Pathogenesis: Cooperative Actions of MMP-8/MMP-2 Axis on Immune Response through HLA-G Shedding and Oxidative Stress

Patients with COVID-19 predominantly have a respiratory tract infection and acute lung failure is the most severe complication. While the molecular basis of SARS-CoV-2 immunopathology is still unknown, it is well established that lung infection is associated with hyper-inflammation and tissue damage. Matrix metalloproteinases (MMPs) contribute to tissue destruction in many pathological situations, and the activity of MMPs in the lung leads to the release of bioactive mediators with inflammatory properties. We sought to characterize a scenario in which MMPs could influence the lung pathogenesis of COVID-19. Although we observed high diversity of MMPs in lung tissue from COVID-19 patients by proteomics, we specified the expression and enzyme activity of MMP-2 in tracheal-aspirate fluid (TAF) samples from intubated COVID-19 and non-COVID-19 patients. Moreover, the expression of MMP-8 was positively correlated with MMP-2 levels and possible shedding of the immunosuppression mediator sHLA-G and sTREM-1. Together, overexpression of the MMP-2/MMP-8 axis, in addition to neutrophil infiltration and products, such as reactive oxygen species (ROS), increased lipid peroxidation that could promote intensive destruction of lung tissue in severe COVID-19. Thus, the inhibition of MMPs can be a novel target and promising treatment strategy in severe COVID-19.

Azithromycin Treatment vs Placebo in Children With Respiratory Syncytial Virus-Induced Respiratory Failure: A Phase 2 Randomized Clinical Trial

IMPORTANCE

Despite a high disease burden, there is no effective treatment for respiratory syncytial virus (RSV) infection.

OBJECTIVES

To determine whether administration of azithromycin (AZM) to children with RSV-induced respiratory failure is safe and to define the effect of AZM therapy on nasal matrix metalloproteinase 9 (MMP-9) levels.

DESIGN, SETTING, AND PARTICIPANTS

This randomized, double-blind, placebo-controlled phase 2 trial was conducted at a single tertiary pediatric intensive care unit from February 2016 to February 2019. The study included children with RSV infection who were admitted to the pediatric intensive care unit and required respiratory support via positive pressure ventilation (invasive and noninvasive). A total of 147 children were screened; 90 were excluded for not meeting inclusion criteria, having an absent legal guardian, lacking pharmacy support, or having a language barrier and 9 declined participation, resulting in 48 patients enrolled in the study.

INTERVENTION

Receipt of standard dose AZM (10 mg/kg/d), high-dose AZM (20 mg/kg/d), or a matching placebo of normal saline intravenously for 3 days.

MAIN OUTCOMES AND MEASURES

Nasal and endotracheal samples were collected at baseline as well as at 24 hours and 48 hours after start of treatment. The secondary outcome was to determine treatment effect on clinical outcome measures, including days of positive pressure ventilation and length of hospital stay.

RESULTS

A total of 48 patients were enrolled in the trial, with a median (range) age at randomization of 12 (1 to 125) months; 36 participants (75.0%) were younger than 2 years. Overall, 26 participants (54.2%) were boys, and 29 (60.4%) had a comorbidity. A total of 16 patients were randomized into each trial group (ie, placebo, standard-dose AZM, and high-dose AZM). Baseline demographic characteristics were comparable among the 3 groups. Both doses of AZM were safe, with no adverse events observed. No difference in nasal MMP-9 levels were observed between treatment groups. Among those who required mechanical ventilation and received high-dose AZM, endotracheal active and total MMP-9 levels were lower on day 3. Compared with baseline, active and total MMP-9 levels in endotracheal aspirates were 1.0 log lower in the high-dose AZM group (active MMP-9: 99.8% CI, -1.28 to -0.64; P < .001; total MMP-9: 99.8% CI, -1.37 to -0.57; P < .001). Patients who received high-dose AZM had fewer median (interquartile range) hospital days compared with those receiving the placebo (8 [6-14] days vs 11 [8-20] days; mean ratio estimate, 0.57; 95% CI, 0.38-0.87; P = .01).

CONCLUSIONS AND RELEVANCE

In this phase 2 randomized clinical trial, both doses of AZM were safe. While nasal MMP-9 levels were unchanged among treatment groups, endotracheal MMP-9 levels were lower among those who received high-dose AZM. The positive secondary clinical outcome, while exploratory, provides insight for end points in a multicenter randomized trial.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02707523.

Ventilation with 18, 21, or 100% Oxygen during Cardiopulmonary Resuscitation of Asphyxiated Piglets: A Randomized Controlled Animal Trial

BACKGROUND

In previous piglet experiments of profound asphyxia and cardiac arrest, recovery was similar when 21 and 100% oxygen were used for positive pressure ventilation (PPV). There was no consistent reduction in inflammation and oxidative stress in piglets ventilated with 21 or 100% oxygen.

OBJECTIVES

We aimed to investigate hypoxic resuscitation, i.e., PPV with 18% oxygen, in profoundly asphyxiated piglets with cardiac arrest. We hypothesized that resuscitation with 18% oxygen would result in less inflammation and oxidative stress compared to 21 or 100% oxygen.

METHOD

Twenty-four piglets were exposed to 30 min of normocapnic hypoxia followed by asphyxia until asystole. The piglets were randomized to PPV with 18% oxygen (n = 8), 21% oxygen (n = 8), or 100% oxygen (n = 8), and resuscitated with chest compressions and intravenous epinephrine. Return of spontaneous circulation (ROSC) was defined as an unassisted heart rate ≥100 bpm for 15 s. Lactate, GSH (total glutathione), GSSG (oxidized glutathione), and GSSG/GSH ratio were measured in myocardial and frontoparietal cortex homogenates. Interleukin (IL)-8, IL-6, IL-1β and tumor necrosis factor α were measured in frontoparietal cortex homogenates.

RESULTS

There was no difference in time to ROSC or inflammation and oxidative stress in the 3 oxygen groups.

CONCLUSIONS

Resuscitation with 18% oxygen did not result in differences in inflammation and oxidative stress when compared to 21 or 100% oxygen.

Imbalance of Ly-6Chi and Ly-6Clo Monocytes/Macrophages Worsens Hyperoxia-Induced Lung Injury and Is Rescued by IFN-γ

Inflammation in response to oxygen exposure is a major contributing factor in neonatal lung injury leading to bronchopulmonary dysplasia. Although increased levels of proinflammatory cytokines are seen in airway samples and blood from bronchopulmonary dysplasia patients, the innate immune responses in this common neonatal lung condition have not been well characterized. We previously reported that depletion of murine CD11b-expressing mononuclear phagocytes at birth led to severe acute hyperoxia-induced lung injury (HILI) and significant mortality. In this study, we further define the mononuclear phagocyte populations that are present in the neonatal lung and characterize their responses to hyperoxia exposure. We used myeloid depleter mice (CD11b-DTR and CCR2-DTR) to contrast the effects of depleting different monocyte/macrophage subpopulations on the innate immune response to hyperoxia. Using RNA sequencing and subsequent data analysis, we identified an IFN-γ-mediated role for interstitial monocytes/macrophages in acute HILI, in which decreased IFN-γ expression led to increased disease severity and increased Mmp9 mRNA expression. Importantly, intranasal administration of rIFN-γ largely rescued CD11b-DTR⁺ mice from severe HILI and decreased Mmp9 mRNA expression in Ly-6C^lo and Ly-6C^hi interstitial monocyte/macrophages. We conclude that the proinflammatory effects of hyperoxia exposure are, at least in part, because of the modulation of effectors downstream of IFN-γ by pulmonary monocytes/macrophages.

Differences in Brain-Derived Neurotrophic Factor and Matrix Metalloproteinase-9 between Appropriate Neonates between Normal Birth Weight and Intrauterine Growth Restriction

BACKGROUND:

Intrauterine Growth Restriction (IUGR) was defined as the growth of the fetus less than its normal potential growth due to genetic and environmental factors. One of the most widely believed causes of IUGR was impaired uteroplacental mechanism from mother to fetus. Furthermore, factor which was thought to affect placental growth was due to the influence of Brain-Derived Neurotrophic Factor (BDNF) and Matrix Metalloproteinase (MMP-9) which play an important role in angiogenesis.

AIM:

This study aims to determine differences in Brain-Derived Neurotrophic Factor (BDNF) and moderately mature Matrix Metalloproteinase (MMP-9) between normal birth weight and intrauterine growth restriction.

MATERIAL AND METHODS:

The study design was a cross-sectional study at four hospitals in Padang city from August 2017-January 2018. The sample of this study was umbilical cord blood of appropriate gestational age neonate with normal birth weight (31 neonates) and IUGR (31 neonates) by consecutive sampling, samples taken from mothers who meet inclusion criteria. BDNF and MMP-9 levels were analysed by ELISA. The differences between normal birth weight and IUGR test were followed by unpaired T-test.

RESULTS:

The results showed that BDNF levels in normal neonates was 1.58 ± 0.23 ng/ml and in IUGR neonates were 1.25 ± 0.35 ng/ml (p = 0.001). MMP-9 levels in normal neonates was 1.09 ± 0.20 ng/ml and in IUGR neonates were 1.25 ± 0.35 (p = 0.03).

CONCLUSION:

The conclusion of this study was BDNF of moderately mature neonates was significantly higher in normal birth weight compared to intrauterine growth restriction, and the moderately high MMP-9 neonates were significantly higher in intrauterine growth restriction compared with normal birth weight.

Club cell secretory protein (CC16) in gastric fluid at birth and subsequent lung disease in preterm infants

BACKGROUND

Club cell secretory protein (CC16) probably has a role in protecting the lung from inflammation.

AIM

To evaluate if low levels of CC16 in gastric fluid at birth, reflecting low levels of CC16 in the lung, would be associated with lung inflammation and respiratory morbidity.

METHODS

A study of 64 infants with mean gestational age 26.1 weeks. CC16 was analyzed in gastric fluid at birth. CC16, pro-inflammatory cytokines, and MMP-9 were analyzed in tracheal aspirate within 24 h from birth.

RESULTS

CC16 in gastric fluid increased with gestational age (P = 0.033). Lower concentrations of CC16 in gastric fluid at birth were associated with higher concentrations of IL-1β (P = 0.028), TNF-α (P = 0.034), and MMP-9 (P = 0.015) in tracheal aspirate. Infants who needed mechanical ventilation at 24 and 72 h of age had lower CC16 in gastric fluid than those not ventilated at these ages (P = 0.011 and P = 0.024, respectively). Lower CC16 in gastric fluid was associated with higher FiO₂ at 6 h (P = 0.009), higher PaCO₂ at 24 h (P = 0.03), more ventilator days (P = 0.012) and more days with supplemental oxygen (P = 0.03). Infants who had either died or were still treated with supplemental oxygen at 36 weeks postmenstrual age had lower CC16 in gastric fluid than infants with none of these outcomes (P = 0.049).

CONCLUSION

A low CC16 concentration in gastric fluid at birth was associated with increased inflammation in the trachea within the first 24 h of life and with more need for respiratory support in the neonatal period.

Reactive Oxygen Species, Biomarkers of Microvascular Maturation and Alveolarization, and Antioxidants in Oxidative Lung Injury

The lungs of extremely low gestational age neonates (ELGANs) are deficient in pulmonary surfactant and are incapable of efficient gas exchange necessary for successful transition from a hypoxic intrauterine environment to ambient air. To improve gas exchange and survival, ELGANs often receive supplemental oxygen with mechanical ventilation which disrupts normal lung developmental processes, including microvascular maturation and alveolarization. Factors that regulate these developmental processes include vascular endothelial growth factor and matrix metalloproteinases, both of which are influenced by generation of oxygen byproducts, or reactive oxygen species (ROS). ELGANs are also deficient in antioxidants necessary to scavenge excessive ROS. Thus, the accumulation of ROS in the preterm lungs exposed to prolonged hyperoxia, results in inflammation and development of bronchopulmonary dysplasia (BPD), a form of chronic lung disease (CLD). Despite advances in neonatal care, BPD/CLD remains a major cause of neonatal morbidity and mortality. The underlying mechanisms are not completely understood, and the benefits of current therapeutic interventions are limited. The association between ROS and biomarkers of microvascular maturation and alveolarization, as well as antioxidant therapies in the setting of hyperoxia-induced neonatal lung injury are reviewed in this article.

Intravitreal bevacizumab alters type IV collagenases and exacerbates arrested alveologenesis in the neonatal rat lungs

Purpose/Aim: Intravitreal bevacizumab (Avastin) is an irreversible vascular endothelial growth factor (VEGF) inhibitor used off-label to treat severe retinopathy of prematurity in extremely low gestational age neonates. VEGF and matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs) participate in lung maturation. We tested the hypothesis that intravitreal bevacizumab enters the systemic circulation and has long-lasting effects on lung MMPs.

MATERIALS AND METHODS

Neonatal rats were exposed to: (1) hyperoxia (50% O₂); (2) intermittent hypoxia (IH) (50% O₂ with brief episodes of 12% O₂); or (3) room air (RA) from birth (P0) to P14. At P14, the time of eye opening in rats, a single dose of Avastin (0.125 mg) was injected into the vitreous cavity of the left eye. A control group received equivalent volume saline. At P23 and P45, lung MMP-2 and MMP-9, and TIMP-1, and TIMP-2 were assessed in the lungs.

RESULTS

At P23, Avastin increased MMP-2, MMP-9, and TIMP-1 levels in the hyperoxia group but decreased TIMP-1 levels in the IH group. The ratios of MMP-2/TIMP-1 and MMP-9/TIMP-1 were significantly elevated at P23 in the IH group treated with Avastin. At P45, the levels of MMP-2 and MMP-9 remained elevated in the hyperoxia and IH groups treated with Avastin, while a rebound increase in TIMP-1 levels was noted in the IH group.

CONCLUSIONS

Avastin treatment in IH has lasting alterations in the balance between MMPs and their tissue inhibitors. These changes may lead to impaired alveologenesis and tissue damage consistent with bronchopulmonary dysplasia/chronic lung disease.

Moderate hyperoxia induces extracellular matrix remodeling by human fetal airway smooth muscle cells

BACKGROUND

Premature infants are at increased risk for airway diseases, such as wheezing and asthma, because of early exposure to risk factors including hyperoxia. As in adult asthma, airway remodeling and increased extracellular matrix (ECM) deposition is involved.

METHODS

We assessed the impact of 24-72 h of moderate hyperoxia (50%) on human fetal airway smooth muscle (fASM) ECM deposition through western blot, modified in-cell western, and zymography techniques.

RESULTS

Hyperoxia exposure significantly increased collagen I and collagen III deposition, increased pro- and cleaved matrix metalloproteinase 9 (MMP9) activity, and decreased endogenous MMP inhibitor, TIMP1, expression. Hyperoxia-induced change in caveolin-1 (CAV1) expression was assessed as a potential mechanism for the changes in ECM deposition. CAV1 expression was decreased following hyperoxia. Supplementation of CAV1 activity with caveolar scaffolding domain (CSD) peptide abrogated the hyperoxia-mediated ECM changes.

CONCLUSION

These results demonstrate that moderate hyperoxia enhances ECM deposition in developing airways by altering the balance between MMPs and their inhibitors (TIMPs), and by increasing collagen deposition. These effects are partly mediated by a hyperoxia-induced decrease in CAV1 expression. In conjunction with prior data demonstrating increased fASM proliferation with hyperoxia, these data further demonstrate that hyperoxia is an important instigator of remodeling in developing airways.

Absinthin attenuates LPS-induced ALI through MIP-1α-mediated inflammatory cell infiltration

Acute lung injury (ALI) is characterized by severe lung inflammation, and anti-inflammatory treatment is proposed to be a pertinent therapeutic strategy for the disease. Absinthin is a triterpene, extracted from a Chinese herb, with anti-inflammatory properties. The aim of this study was to evaluate whether absinthin can attenuate ALI in a mouse model of lung injury. Mice were treated with various concentrations (20 mg/kg, 40 mg/kg, and 80mg/kg) of absinthin, and lipopolysaccharide (LPS) to induce ALI. We found that the administration of absinthin relieved LPS-induced acute lung injury, as suggested by reduced histological scores, wet-to-dry ratio, myeloperoxidase activity, and accumulation of inflammatory cells in lung bronchoalveolar lavage fluid. Moreover, we demonstrated that absinthin significantly enhanced the expression of matrix metalloproteinase-8 (MMP-8); this effect could inhibit the accumulation of inflammatory cells in lung tissues through a mechanism dependent on MMP-8-mediated inactivation of macrophage inflammatory protein-1α. Therefore, we propose that absinthin is a promising novel therapeutic candidate for the treatment of ALI.

Novel 5-Hydroxy, 5-Substituted Benzenesulfonamide Pyrimidine-2,4,6-Triones Attenuate Lipopolysaccharide-Induced Acute Lung Injury via Inhibition of the Gelatinases, MMP-2 and MMP-9

Preclinical Research A novel series of ten 5-hydroxy, 5-substituted benzene sulfonamide pyrimidine-2,4,6-triones were synthesized and their structures ascertained using (1) H-NMR, (13) C-NMR, mass and elemental analysis. These compounds were subsequently tested for inhibition of MMP-2 and MMP-9 where most exhibited activity with compound 5i being the most potent against MMP-2 and MMP-9 with IC50 values of 2.35 nM and 8.24 nM, respectively. Compound 5i was further analyzed in a mouse LPS-induced acute lung injury model where it had protective activity. Histochemical studies indicated that 5i improved the vascular integrity of the lung. Drug Dev Res 77 : 251-257, 2016. © 2016 Wiley Periodicals, Inc.

Biomarkers in Pediatric ARDS: Future Directions

Acute respiratory distress syndrome (ARDS) is common among mechanically ventilated children and accompanies up to 30% of all pediatric intensive care unit deaths. Though ARDS diagnosis is based on clinical criteria, biological markers of acute lung damage have been extensively studied in adults and children. Biomarkers of inflammation, alveolar epithelial and capillary endothelial disruption, disordered coagulation, and associated derangements measured in the circulation and other body fluids, such as bronchoalveolar lavage, have improved our understanding of pathobiology of ARDS. The biochemical signature of ARDS has been increasingly well described in adult populations, and this has led to the identification of molecular phenotypes to augment clinical classifications. However, there is a paucity of data from pediatric ARDS (pARDS) patients. Biomarkers and molecular phenotypes have the potential to identify patients at high risk of poor outcomes, and perhaps inform the development of targeted therapies for specific groups of patients. Additionally, because of the lower incidence of and mortality from ARDS in pediatric patients relative to adults and lack of robust clinical predictors of outcome, there is an ongoing interest in biological markers as surrogate outcome measures. The recent definition of pARDS provides additional impetus for the measurement of established and novel biomarkers in future pediatric studies in order to further characterize this disease process. This chapter will review the currently available literature and discuss potential future directions for investigation into biomarkers in ARDS among children.

The Extracellular Matrix in Bronchopulmonary Dysplasia: Target and Source

Bronchopulmonary dysplasia (BPD) is a common complication of preterm birth that contributes significantly to morbidity and mortality in neonatal intensive care units. BPD results from life-saving interventions, such as mechanical ventilation and oxygen supplementation used to manage preterm infants with acute respiratory failure, which may be complicated by pulmonary infection. The pathogenic pathways driving BPD are not well-delineated but include disturbances to the coordinated action of gene expression, cell-cell communication, physical forces, and cell interactions with the extracellular matrix (ECM), which together guide normal lung development. Efforts to further delineate these pathways have been assisted by the use of animal models of BPD, which rely on infection, injurious mechanical ventilation, or oxygen supplementation, where histopathological features of BPD can be mimicked. Notable among these are perturbations to ECM structures, namely, the organization of the elastin and collagen networks in the developing lung. Dysregulated collagen deposition and disturbed elastin fiber organization are pathological hallmarks of clinical and experimental BPD. Strides have been made in understanding the disturbances to ECM production in the developing lung, but much still remains to be discovered about how ECM maturation and turnover are dysregulated in aberrantly developing lungs. This review aims to inform the reader about the state-of-the-art concerning the ECM in BPD, to highlight the gaps in our knowledge and current controversies, and to suggest directions for future work in this exciting and complex area of lung development (patho)biology.

Low levels of tissue inhibitor of metalloproteinase-2 at birth may be associated with subsequent development of bronchopulmonary dysplasia in preterm infants

Purpose

Bronchopulmonary dysplasia (BPD) is characterized by inflammation with proteolytic damage to the lung extracellular matrix. The results from previous studies are inconsistent regarding the role of proteinases and antiproteinases in the development of BPD. The aim of the present study was to investigate whether matrix metalloproteinase (MMP)-8, MMP-9, tissue inhibitor of metalloproteinase (TIMP)-2, and TIMP-1 levels in the serum of preterm infants at birth are related to the development of BPD.

Methods

Serum was collected from 62 preterm infants at birth and analyzed for MMP-8, MMP-9, TIMP-2, and TIMP-1 by using enzyme-linked immunosorbent assay. MMPs and TIMPs were compared in BPD (n=24) and no BPD groups (n=38). Clinical predictors of BPD (sex, birth weight, gestational age, etc.) were assessed for both groups. The association between predictors and outcome, BPD, was assessed by using multivariate logistic regression.

Results

Sex, birth weight, and mean gestational age were similar between the groups. BPD preterm infants had significantly lower TIMP-2 levels at birth compared with no BPD preterm infants (138.1±23.0 ng/mL vs. 171.8±44.1 ng/mL, P=0.027). No significant difference was observed in MMP-8, MMP-9, and TIMP-1 levels between the two groups. Multivariate logistic regression analysis indicated that the TIMP-2 levels were predictive of BPD after adjusting for sex, birth weight, gestational age, proteinuric preeclampsia, and intraventricular hemorrhage (β=-0.063, P=0.041).

Conclusion

Low TIMP-2 serum levels at birth may be associated with the subsequent development of BPD in preterm infants.

Matrix Metalloproteinase-9 Mediates RSV Infection in Vitro and in Vivo

Respiratory Syncytial Virus (RSV) is an important human pathogen associated with substantial morbidity and mortality. The present study tested the hypothesis that RSV infection would increase matrix metalloproteinase (MMP)-9 expression, and that MMP-9 inhibition would decrease RSV replication both in vitro and in vivo. RSV A2 infection of human bronchial epithelial cells increased MMP-9 mRNA and protein release. Cells transfected with siRNA against MMP-9 following RSV infection had lower viral titers. In RSV infected wild-type (WT) mice, MMP-9, airway resistance and viral load peaked at day 2 post infection, and remained elevated on days 4 and 7. RSV infected MMP-9 knockout (KO) mice had decreased lung inflammation. On days 2 and 4 post inoculation, the RSV burden was lower in the MMP-9 KO mice compared to WT controls. In conclusion, our studies demonstrate that RSV infection is a potent stimulus of MMP-9 expression both in vitro and in vivo. Reduction of MMP-9 (via siRNA knockdown, and in MMP-9 KO mice) resulted in decreased viral replication. Our findings suggest MMP-9 is a potential therapeutic target for RSV disease.

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

RATIONALE

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

OBJECTIVES

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

METHODS

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

MAIN RESULTS

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

CONCLUSIONS

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

Cigarette smoke enhances proliferation and extracellular matrix deposition by human fetal airway smooth muscle

Cigarette smoke is a common environmental insult associated with increased risk of developing airway diseases such as wheezing and asthma in neonates and children. In adults, asthma involves airway remodeling characterized by increased airway smooth muscle (ASM) cell proliferation and increased extracellular matrix (ECM) deposition, as well as airway hyperreactivity. The effects of cigarette smoke on remodeling and contractility in the developing airway are not well-elucidated. In this study, we used canalicular-stage (18-20 wk gestational age) human fetal airway smooth muscle (fASM) cells as an in vitro model of the immature airway. fASM cells were exposed to cigarette smoke extract (CSE; 0.5-1.5% for 24-72 h), and cell proliferation, ECM deposition, and intracellular calcium ([Ca(2+)]i) responses to agonist (histamine 10 μM) were used to evaluate effects on remodeling and hyperreactivity. CSE significantly increased cell proliferation and deposition of ECM molecules collagen I, collagen III, and fibronectin. In contrast, [Ca(2+)]i responses were not significantly affected by CSE. Analysis of key signaling pathways demonstrated significant increase in extracellular signal-related kinase (ERK) and p38 activation with CSE. Inhibition of ERK or p38 signaling prevented CSE-mediated changes in proliferation, whereas only ERK inhibition attenuated the CSE-mediated increase in ECM deposition. Overall, these results demonstrate that cigarette smoke may enhance remodeling in developing human ASM through hyperplasia and ECM production, thus contributing to development of neonatal and pediatric airway disease.

Expression of cathepsin K in periodontitis and in gingival fibroblasts

OBJECTIVE

To study non-osteoclastic sources of cathepsin K in periodontitis.

MATERIALS AND METHODS

Tissue samples were obtained from 10 otherwise healthy periodontitis pati-ents during routine periodontal flap operations and 10 systemically and periodontally healthy individuals who underwent extraction operations for retained third molars. Methods used were immunohistochemistry, image analysis, immunofluorescence double-staining, gingival fibroblast culture, tumour necrosis factor-α (TNF-α) stimulation and Western blotting.

RESULTS

Macrophage-like cells, fibroblast-like cells, vascular endothelial cells and gingival epithelial cells were more intensively stained for cathepsin K and also more frequent in periodontitis than in controls (665 ± 104 vs 258 ± 40 cells mm(-2) , P < 0.01). Some cathepsin K(+) cells in periodontal tissues were CD68(+) , but some were CD68(-) and probably fibroblasts. Indeed, in gingival fibroblast culture, resting fibroblasts released cathepsin K, more 43 kD procathepsin K than 29 kD active cathepsin K. TNF-α increased the release of the activated cathepsin K 4- to 5-fold.

CONCLUSIONS

Results suggest that GCF-cathepsin K is not only osteoclast-derived, but in periodontitis, also other cells contribute to it. GCF-cathepsin K, perhaps together with intracellular, lysosomal collagenolytically active cathepsin K in fibroblasts, macrophages and gingival epithelial cells, can contribute to the loss of attachment and destruction of the periodontal ligament.

Maternal dietary docosahexaenoic acid supplementation attenuates fetal growth restriction and enhances pulmonary function in a newborn mouse model of perinatal inflammation

The preterm infant is often exposed to maternal and neonatal inflammatory stimuli and is born with immature lungs, resulting in a need for oxygen therapy. Nutritional intervention with docosahexaenoic acid (DHA; 6.3 g/kg of diet) has been shown to attenuate inflammation in various human diseases. Previous studies demonstrated that maternal DHA supplementation during late gestation and lactation attenuated hyperoxic lung injury in newborn mouse pups. In the present studies, we tested the hypothesis that DHA supplementation to the dam would reduce hyperoxic lung injury and growth deficits in a more severe model of systemic maternal inflammation, including lipopolysaccharide (LPS) and neonatal hyperoxia exposure. On embryonic day 16, dams were placed on DHA (6.3 g DHA/kg diet) or control diets and injected with saline or LPS. Diets were maintained through weaning. At birth, pups were placed in room air or hyperoxia for 14 d. Improvements in birth weight (P < 0.01), alveolarization (P ≤ 0.01), and pulmonary function (P ≤ 0.03) at 2 and 8 wk of age were observed in pups exposed to perinatal inflammation and born to DHA-supplemented dams compared with control diet-exposed pups. These improvements were associated with decreases in tissue macrophage numbers (P < 0.01), monocyte chemoattractant protein-1 expression (P ≤ 0.05), and decreases in soluble receptor for advanced glycation end products concentrations (P < 0.01) at 2 and 8 wk. Furthermore, DHA supplementation attenuated pulmonary fibrosis, which was associated with the reduction of matrix metalloproteinases 2, 3, and 8 (P ≤ 0.03) and collagen mRNA (P ≤ 0.05), and decreased collagen (P < 0.01) and vimentin (P ≤ 0.03) protein concentrations. In a model of severe inflammation, maternal DHA supplementation lessened inflammation and improved lung growth in the offspring. Maternal supplementation with DHA may be a therapeutic strategy to reduce neonatal inflammation.

Pulmonary matrix metalloproteinase-9 activity in mechanically ventilated children with respiratory syncytial virus

Respiratory syncytial virus (RSV) infection is a potent stimulus for airway epithelial expression of matrix metalloproteinase (MMP)-9. MMP-9 activity in vivo is a predictor of disease severity in children with RSV-induced respiratory failure. Human airway epithelial cells were infected with RSV A2 strain and analysed for MMP-9 and tissue inhibitor of metalloproteinase (TIMP)-1 (a natural inhibitor of MMP-9) release. In addition, endotracheal samples from children with RSV-RF and controls (non-RSV pneumonia and nonlung disease controls) were analysed for MMP-9, TIMP-1, human neutrophil elastase and myeloperoxidase activity. RSV infection of airway epithelia was sufficient to rapidly induce MMP-9 transcription and protein release. Pulmonary MMP-9 activity peaked at 48 h in infants with RSV-induced respiratory failure. In the RSV group, MMP-9 activity and MMP-9/TIMP-1 ratio imbalance predicted higher oxygen requirement and worse paediatric risk of mortality scores. The highest levels of human neutrophil elastase and myeloperoxidase activity were measured in the RSV cohort; however, unlike MMP-9, these neutrophil markers failed to predict disease severity. These results support the hypothesis that RSV is a potent stimulus for MMP-9 expression and release from human airway epithelium, and that MMP-9 is an important biomarker of disease severity in mechanically ventilated children with RSV lung infection.

The relationship between the first episode of wheezing and matrix metalloproteinases-9 and MMP-2 and tissue inhibitors of MMP-1 levels in preterm infants

AIMS

Matrix metalloproteinases (MMP) have been associated with neonatal lung morbidity and MMP dysregulation contributes to the pathology of chronic and acute lung disorders. Most of the previous studies were performed in the 1(st) weeks of life of the preterm newborns. There are no data on the serum levels of MMP-2, MMP-9 or tissue inhibitors of matrix metalloproteinases (TIMP-1) from preterm infants recovering from lung morbidities. We aimed to compare MMP-2, MMP-9 and TIMP-1 levels in preterm and term infants hospitalized with their first episode of wheezing.

METHODS

We prospectively evaluated 18 preterm infants with a history of chronic lung disease, respiratory distress syndrome or oxygen therapy and 14 age- and sex-matched term infants who were admitted for a first episode of wheezing. We quantified total serum concentrations of MMP-2, MMP-9 and TIMP-1 to assess whether these serum markers levels were associated with the first episode of wheezing in infants with a history of oxygen therapy during the neonatal period.

RESULTS

Upon hospitalization, MMP-2 and TIMP-1 levels were higher in preterm infants than in term infants. In contrast, there was no significant relationship between MMP-9 levels or the MMP-9/TIMP-1 ratio between preterm and term infants. The area under the receiver operating characteristic curve for MMP-2 was 0.70 (95% confidence interval [CI] 0.51-0.89). The area under the curve for TIMP-1 was 0.78 (95% CI 0.61-0.94). MMP-9, MMP-2 and TIMP-1 levels did not correlate with gestational age, gender or severity of wheezing.

CONCLUSION

The negative proportion of MMP-9 to TIMP-1 that we detected in term infants was not present in preterm infants. The balance of MMP-9 to TIMP-1 may have been disrupted by lung damage in the premature infants. Overproduction of MMP-2 and TIMP-1 in the serum may be associated with the pathogenesis of wheezing in preterm infants.

Perinatal factors in neonatal and pediatric lung diseases

Wheezing and asthma are significant clinical problems for infants and young children, particularly following premature birth. Recurrent wheezing in infants can progress to persistent asthma. As in adults, altered airway structure (remodeling) and function (increased bronchoconstriction) are also important in neonatal and pediatric airway diseases. Accumulating evidence suggests that airway disease in children is influenced by perinatal factors including perturbations in normal fetal lung development, postnatal interventions in the intensive care unit (ICU) and environmental and other insults in the neonatal period. Here, in addition to genetics, maternal health, environmental processes, innate immunity and impaired lung development/function can all influence pathogenesis of airway disease in children. We summarize current understanding of how prenatal and postnatal factors can contribute to development of airway diseases in neonates and children. Understanding these mechanisms will help identify and develop novel therapies for childhood airway diseases.

Effect of hydrocortisone therapy on severe leaky lung syndrome in ventilated preterm infants

BACKGROUND

The aim of this study was (i) to determine the incidence and risk factors of severe leaky lung syndrome (sLLS), persistent pulmonary edema characterized by massive tracheal secretions and resistance to surfactant therapy, in extremely low gestational age newborns requiring ventilatory support; and (ii) to evaluate the effects of hydrocortisone (HC) therapy for sLLS on tracheal aspirate fluid (TAF) volume and β2-microglobulin levels in TAF.

METHODS

Infants born at <28 weeks gestation requiring ventilation beyond day of life (DOL) 7 were included. Daily TAF volume changes were assessed using a TAF scoring system. Levels of TAF β2-microglobulin, an indicator of capillary leakage, were measured at DOL0, 7, before, and 4 days after starting HC therapy (started at 4 mg/kg/day; tapered for 1-3 weeks).

RESULTS

Of the 54 infants enrolled, 24 (44%) were diagnosed with sLLS. Lower gestational age, lower birthweight, and higher TAF β2-microglobulin levels at DOL7 were independent risk factors for sLLS. Seventeen infants with sLLS received HC therapy starting at DOL17 (median), with subsequent decreases in TAF volume and β2-microglobulin levels.

CONCLUSIONS

The incidence of sLLS, as defined in this study, was 44% in extremely low gestational age newborns requiring ventilator support beyond a week. HC therapy effectively reduced TAF volume and β2-microglobulin levels, suggesting suppression of increased permeability of pulmonary capillaries in infants with sLLS.

Cathepsin K deficiency aggravates lung injury in hyperoxia-exposed newborn mice

Cathepsin K (CatK) is a potent collagenase and elastase and may be involved in the development of neonatal bronchopulmonary dysplasia. The authors evaluated the effects of CatK deletion on neonatal lung development and response to prolonged hyperoxic challenge. CatK deficiency resulted in thinner alveolar walls than wild-type littermates on postnatal day (PN) 7. However, no morphological difference could be detected between CatK-deficient and control groups on PN 14. Exposure to 90% oxygen for 7 days after birth caused intensive CatK expression in the bronchial epithelium and alveolar macrophages of wild-type mice. Hyperoxia caused fatal respiratory distress in both groups of mice. However, whereas ∼20% of wild-type mice survived for 2 weeks in hyperoxia, all CatK-deficient mice died within the first 9 postnatal days. Hyperoxia-exposed lungs of CatK-deficient mice contained high number of macrophages and multinucleated giant cells and had increased content of reduced glutathione, indicating intensified pulmonary oxidative stress. These results suggest that CatK is involved in pulmonary development and it may be an important host-defence protease in the oxygen-stressed newborn lung.

Differential expression of MMP-2 and -9 and their inhibitors in fetal lung cells exposed to mechanical stretch: regulation by IL-10

STUDY OBJECTIVES

Abnormal remodeling of the extracellular matrix (ECM) has been implicated in the pathogenesis of bronchopulmonary dysplasia. However, the contribution of lung parenchymal cells to ECM remodeling after mechanical injury is not well defined. The objective of these studies was to investigate in vitro the release of MMP-2 and -9 and their respective inhibitors TIMP-2 and -1, and to explore potential regulation by IL-10.

DESIGN

Mouse fetal epithelial cells and fibroblasts isolated on E18-19 of gestation were exposed to 20% cyclic stretch to simulate lung injury. MMP-2 and MMP-9 activity were investigated by zymography and ELISA. TIMP-1 and TIMP-2 abundance were analyzed by Western blot.

RESULTS

We found that mechanical stretch increased MMP-2 and decreased TIMP-2 in fibroblasts, indicating that excessive stretch promotes MMP-2 activation, expressed as the MMP-2/TIMP-2 ratio. Incubation with IL-10 did not change MMP-2 activity. In contrast, mechanical stretch of epithelial cells decreased MMP-9 activity and the MMP-9/TIMP-1 ratio by 60-70%. When IL-10 was added, mechanical stretch increased the MMP-9/TIMP-1 ratio by 50%.

CONCLUSIONS

We conclude that mechanical stretch differentially affects MMP-2/9 and their inhibitors in fetal lung cells. IL-10 modulates MMP-9 activity through a combination of effects on MMP-9 and TIMP-1 levels.

A role for matrix metalloproteinase 9 in IFNγ-mediated injury in developing lungs: relevance to bronchopulmonary dysplasia

We noted a marked increase in IFNγ mRNA in newborn (NB) murine lungs after exposure to hyperoxia. We sought to evaluate the role of IFNγ in lung injury in newborns. Using a unique triple-transgenic (TTG), IFNγ-overexpressing, lung-targeted, externally regulatable NB murine model, we describe a lung phenotype of impaired alveolarization, resembling human bronchopulmonary dysplasia (BPD). IFNγ-mediated abnormal lung architecture was associated with increased cell death and the upregulation of cell death pathway mediators caspases 3, 6, 8, and 9, and angiopoietin 2. Moreover, an increase was evident in cathepsins B, H, K, L, and S, and in matrix metalloproteinases (MMPs) 2, 9, 12, and 14. The IFNγ-mediated abnormal lung architecture was found to be MMP9-dependent, as indicated by the rescue of the IFNγ-induced pulmonary phenotype and survival during hyperoxia with a concomitant partial deficiency of MMP9. This result was concomitant with a decrease in caspases 3, 6, 8, and 9 and angiopoietin 2, but an increase in the expression of angiopoietin 1. In addition, NB IFNγ TTG mice exhibited significantly decreased survival during hyperoxia, compared with littermate controls. Furthermore, as evidence of clinical relevance, we show increased concentrations of the downstream targets of IFNγ chemokine (C-X-C motif) ligands (CXCL10 and CXCL11) in baboon and human lungs with BPD. IFNγ and its downstream targets may contribute significantly to the final common pathway of hyperoxia-induced injury in the developing lung and in human BPD.

Active matrix metalloproteinase-2 upregulation in the abdominal skin of patients with direct inguinal hernia

BACKGROUND

Prior studies suggest impaired collagen metabolism involving the whole abdominal wall including the skin in patients with abdominal hernia. We compared expression patterns of matrix metalloproteinase-2 (MMP-2) and its modulators membrane type-1-matrix metalloproteinase (MT-1 MMP) and tissue inhibitor of metalloproteinase-2 (TIMP-2) in the skin of patients with and without primary inguinal hernia.

MATERIALS AND METHODS

Skin biopsy specimens from abdominal wall incisions were obtained during surgery from patients with direct inguinal hernia, indirect inguinal hernia or without hernia (controls). MMP-2, MT-1 MMP and TIMP-2 expression were determined using immunocytochemistry and immunoblotting in intact tissue and in cultured fibroblasts isolated from the biopsies. The degradation activity of MMP-2 was semiquantitatively determined using zymography.

RESULTS

Significantly greater active MMP-2 expression was observed in skin fibroblasts obtained from patients with direct hernia compared with controls. MT1-MMP expression was directly correlated with MMP-2 expression with most intense staining produced in patients with direct or indirect inguinal hernia. TIMP-2, was maximally expressed in the control group, with significantly diminished expression levels recorded in the hernia groups.

CONCLUSIONS

Our findings indicate active MMP-2 upregulation in the abdominal skin of patients with direct inguinal hernia. This metalloproteinase plays a role in matrix degradation, weakening the abdominal wall. Skin disorders and previously described transversalis fascia defects in these patients could point to a systemic collagen metabolism abnormality as a risk factor for direct hernia.

Hyperoxia-derived lung damage in preterm infants

Hyperoxia-induced lung injury is characterized by an influx of inflammatory cells, increased pulmonary permeability, endothelial and epithelial cell death. This review highlights the mechanistic aspects of inflammation, vascular leak and cell death. The focus will be on agents that contribute to hyperoxia-induced lung injury in developmentally appropriate animal models, and those that have been detected in human premature neonates.

Relationship of proteinases and proteinase inhibitors with microbial presence in chronic lung disease of prematurity

BACKGROUND

A proteolytic imbalance has been implicated in the development of "classical" chronic lung disease of prematurity (CLD). However, in "new" CLD this pattern has changed. This study examines the longitudinal relationship between neutrophil proteinases and their inhibitors in ventilated preterm infants and their relationship to microbial colonisation.

METHODS

Serial bronchoalveolar lavage fluid was obtained from ventilated newborn preterm infants. Neutrophil elastase (NE) activity, cell counts, metalloproteinase (MMP)-9, MMP-9/TIMP-1 complex, SerpinB1 concentration and percentage of SerpinB1 and alpha(1)-antitrypsin (AAT) in complex with elastase were measured. The presence of microbial genes was examined using PCR for 16S rRNA genes.

RESULTS

Statistically more infants who developed CLD had NE activity in at least one sample (10/20) compared with infants with resolved respiratory distress syndrome (RDS) (2/17). However, NE activity was present in a minority of samples, occurring as episodic peaks. Peak levels of MMP-9, MMP-9/TIMP-1 complex, percentage of AAT and SerpinB1 in complex and cell counts were all statistically greater in infants developing CLD than in infants with resolved RDS. Peak values frequently occurred as episodic spikes and strong temporal relationships were noted between all markers. The peak values for all variables were significantly correlated to each other. The presence of bacterial 16S rRNA genes was associated with the development of CLD and with elevated elastase and MMP-9.

CONCLUSION

NE activity and MMP-9 appear to be important in the development of "new" CLD with both proteinase and inhibitor concentrations increasing episodically, possibly in response to postnatal infection.

The importance of intra-amniotic inflammation in the subsequent development of atypical chronic lung disease

OBJECTIVE

To examine whether the intra-amniotic inflammation is a risk factor for the development of atypical chronic lung disease (CLD).

STUDY DESIGN

A retrospective cohort study was undertaken in 72 patients who delivered preterm neonates (gestational age: 24-32 weeks) within 5 days of amniocentesis and whose neonates subsequently developed CLD. Atypical CLD was defined as CLD without respiratory distress syndrome (RDS). Intra-amniotic inflammation was defined as an elevated amniotic fluid (AF) concentration of matrix metalloproteinase-8 (MMP-8) (>23 ng/ml).

RESULTS

(1) Atypical CLD was identified in 54.2% (39/72) of cases with CLD; (2) there were no significant differences in the median gestational age at birth and the rate of antenatal corticosteroid use between infants with atypical CLD and CLD with RDS; (3) preterm newborns with atypical CLD had a significantly higher median AF MMP-8 concentration (median 373.1 ng/ml vs. 8.6 ng/ml, p = 0.003) and median AF white blood cell count (median 450.0/mm(3)vs. 5.5/mm(3), p = 0.009), and a higher rate of intra-amniotic inflammation (74.4%vs. 45.5%, p = 0.012) than those with CLD with RDS.

CONCLUSION

Intra-amniotic inflammation confers a greater risk for atypical CLD than for typical CLD with initial RDS. This novel observation strengthens the importance of prenatal inflammation as a mechanism of lung injury.

Effects of MMP-9 inhibition by doxycycline on proteome of lungs in high tidal volume mechanical ventilation-induced acute lung injury

Background

Although mechanical ventilation (MV) is a major supportive therapy for patients with acute respiratory distress syndrome, it may result in side effects including lung injury. In this study we hypothesize that MMP-9 inhibition by doxycycline might reduce MV-related lung damage. Using a proteomic approach we identified the pulmonary proteins altered in high volume ventilation-induced lung injury (VILI). Forty Wistar rats were randomized to an orally pretreated with doxycycline group (n = 20) or to a placebo group (n = 20) each of which was followed by instrumentation prior to either low or high tidal volume mechanical ventilation. Afterwards, animals were euthanized and lungs were harvested for subsequent analyses.

Results

Mechanical function and gas exchange parameters improved following treatment with doxycycline in the high volume ventilated group as compared to the placebo group. Nine pulmonary proteins have shown significant changes between the two biochemically analysed (high volume ventilated) groups. Treatment with doxycycline resulted in a decrease of pulmonary MMP-9 activity as well as in an increase in the levels of soluble receptor for advanced glycation endproduct, apoliporotein A-I, peroxiredoxin II, four molecular forms of albumin and two unnamed proteins. Using the pharmacoproteomic approach we have shown that treatment with doxycycline leads to an increase in levels of several proteins, which could potentially be part of a defense mechanism.

Conclusion

Administration of doxycycline might be a significant supportive therapeutic strategy in prevention of VILI.

Matrix metalloproteinase-8 inactivates macrophage inflammatory protein-1 alpha to reduce acute lung inflammation and injury in mice

To determine the role of matrix metalloproteinase-8 (MMP-8) in acute lung injury (ALI), we delivered LPS or bleomycin by the intratracheal route to MMP-8(-/-) mice versus wild-type (WT) mice or subjected the mice to hyperoxia (95% O(2)) and measured lung inflammation and injury at intervals. MMP-8(-/-) mice with ALI had greater increases in lung polymorphonuclear neutrophils (PMNs) and macrophage counts, measures of alveolar capillary barrier injury, lung elastance, and mortality than WT mice with ALI. Bronchoalveolar lavage fluid (BALF) from LPS-treated MMP-8(-/-) mice had more MIP-1alpha than BALF from LPS-treated WT mice, but similar levels of other pro- and anti-inflammatory mediators. MIP-1alpha(-/-) mice with ALI had less acute lung inflammation and injury than WT mice with ALI, confirming that MIP-1alpha promotes acute lung inflammation and injury in mice. Genetically deleting MIP-1alpha in MMP-8(-/-) mice reduced the increased lung inflammation and injury and mortality in MMP-8(-/-) mice with ALI. Soluble MMP-8 cleaved and inactivated MIP-1alpha in vitro, but membrane-bound MMP-8 on activated PMNs had greater MIP-1alpha-degrading activity than soluble MMP-8. High levels of membrane-bound MMP-8 were detected on lung PMNs from LPS-treated WT mice, but soluble, active MMP-8 was not detected in BALF samples. Thus, MMP-8 has novel roles in restraining lung inflammation and in limiting alveolar capillary barrier injury during ALI in mice by inactivating MIP-1alpha. In addition, membrane-bound MMP-8 on activated lung PMNs is likely to be the key bioactive form of the enzyme that limits lung inflammation and alveolar capillary barrier injury during ALI.

Bronchoalveolar lavage fluid peptidomics suggests a possible matrix metalloproteinase-3 role in bronchopulmonary dysplasia

BACKGROUND

Bronchoalveolar lavage fluid (BALF) is an important diagnostic source to investigate molecular changes occurring in lung disorders. The objective of this study was to assess and compare the peptidomic profiles of BALF from premature neonates with and without bronchopulmonary dysplasia (BPD).

METHODS

Samples were obtained on the 3rd day of life from 34 neonates with gestational age <or=32 weeks. Two pools of samples from patients with and without BPD were analyzed by high performance liquid chromatography. Several differentially expressed peptides were collected and sequenced. Moreover, samples from single donors were analyzed by liquid chromatography-electrospray ionization mass spectrometry to define the molecular mass values of various peptides and to quantify their expression. Levels of some matrix metalloproteinases and their tissue inhibitors were also determined in single samples.

RESULTS

Neonates of the BPD group (N = 16) showed significantly lower mean gestational age and birth weight with respect to the no-BPD group (N = 18; P < 0.0001). Levels of six peptides were significantly higher in BPD patients (P < 0.05). Two of them were identified as the albumin fragments 1-21 (2,428 Da) and 399-406 (956 Da). Levels of matrix metalloproteinase-3 (MMP-3) enzyme probably involved in albumin fragment generation were also significantly higher in the BPD group compared to the no-BPD group (P < 0.05), whereas the levels of tissue inhibitor of metalloproteinases-1 were significantly lower (P < 0.05). Levels of albumin fragments and MMP-3 showed a significant correlation (P < 0.05).

CONCLUSIONS

This study shows that proteomic techniques can be applied to investigate the involvement of proteolytic enzymes on the airways of mechanically ventilated premature infants.

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.

Matrix metalloproteinase activity in pediatric acute lung injury

Pediatric Acute Lung Injury (ALI) is associated with a high mortality and morbidity, and dysregulation of matrix metalloproteinases (MMPs) may play an important role in the pathogenesis and evolution of ALI. Here we examined MMP expression and activity in pediatric ALI compared with controls. MMP-8, -9, and to a lesser extent, MMP-2, -3, -11 and -12 were identified at higher levels in lung secretions of pediatric ALI patients compared with controls. Tissue Inhibitor of Matrix metalloproteinase-1 (TIMP-1), a natural inhibitor of MMPs was detected in most ALI samples, but MMP-9:TIMP-1 ratios were high relative to controls. In subjects who remained intubated for >or=10 days, MMP-9 activity decreased, with > 80% found in the latent form. In contrast, almost all MMP-8 detected at later disease course was constitutively active. Discriminating MMP-9:TIMP-1 ratios were found in those who had a prolonged ALI course. These results identify a specific repertoire of MMP isoforms in the lung secretions of pediatric ALI patients, and demonstrate inverse changes in MMPs -8 and -9 with protracted disease.

Effect of covalent antithrombin-heparin complex on developmental mechanisms in the lung

We have developed a potent antithrombin (AT)-heparin conjugate (ATH) that is retained in the lung to prevent pulmonary thrombosis associated with respiratory distress in premature newborns. During continuing maturation, pulmonary angiogenesis in premature infants would be a crucial process in lung development. A naturally occurring latent form of antithrombin (L-AT) has antiangiogenic effects on lung vascularization. However, impact of latent ATH (L-ATH) on developing lung vascularization is unknown. Thus, effects of L-AT and L-ATH on fetal murine lung development were compared. Lung buds from embryonic day 11.5 (E11.5) Tie2-LacZ mouse embryos were incubated in DMEM plus FBS supplemented with PBS, AT, L-AT, heparin, ATH, or L-ATH. Vasculature of cultured explants was quantified by X-galactosidase staining. RNA was analyzed with murine gene probes for angiopoietin (Ang)-1, Ang-2, fibroblast growth factor 2 (FGF2), platelet endothelial cell adhesion molecule (PECAM), and vascular endothelial growth factor (VEGF). FGF2-supplemented medium was used to test contribution to effects of L-AT and L-ATH on angiogenesis. Epithelial branching morphogenesis was inhibited by L-AT (P = 0.003) and heparin (P < 0.001). L-AT and heparin decreased relative vascular area compared with PBS, ATH, and L-ATH. Expressions of all genes studied were downregulated by L-AT. However, L-AT and L-ATH inhibited branching morphogenesis and vasculature with added FGF2. These findings indicate that covalent linkage of AT to heparin negates disruptive effects of these moieties on lung morphology, vascularization, and growth factor gene expression. ATH may have enhanced safety as an anticoagulant during vascular development.

Inflammatory mediators in the immunobiology of bronchopulmonary dysplasia

Inflammation is important in the development of bronchopulmonary dysplasia (BPD). Polymorphonuclear cells and macrophages and proinflammatory cytokines/chemokines denote early inflammation in clinical scenarios such as in utero inflammation with chorioamnionitis or initial lung injury associated with respiratory distress syndrome or ventilator-induced lung injury. The persistence and non-resolution of lung inflammation contributes greatly to BPD, including altering the lung's ability to repair, contributing to fibrosis, and inhibiting secondary septation, alveolarization, and normal vascular development. Further understanding of the role of inflammation in the pathogenesis of BPD, in particular, during the chronic inflammatory period, offers us the opportunity to develop inflammation-related prevention and treatment strategies of this disease that has long-standing consequences for very premature infants.

Role of matrix metalloprotease-9 in hyperoxic injury in developing lung

Matrix metalloprotease-9 (MMP-9) is increased in lung injury following hyperoxia exposure in neonatal mice, in association with impaired alveolar development. We studied the role of MMP-9 in the mechanism of hyperoxia-induced functional and histological changes in neonatal mouse lung. Reduced alveolarization with remodeling of ECM is a major morbidity component of oxidant injury in developing lung. MMP-9 mediates oxidant injury in developing lung causing altered lung remodeling. Five-day-old neonatal wild-type (WT) and MMP-9 (-/-) mice were exposed to hyperoxia for 8 days. The lungs were inflation fixed, and sections were examined for morphometry. The mean linear intercept and alveolar counts were evaluated. Immunohistochemistry for MMP-9 and elastin was performed. MMP-2, MMP-9, type I collagen, and tropoelastin were measured by Western blot analysis. Lung quasistatic compliance was studied in anaesthetized mice. MMP-2 and MMP-9 were significantly increased in lungs of WT mice exposed to hyperoxia compared with controls. Immunohistochemistry showed an increase in MMP-9 in mesenchyme and alveolar epithelium of hyperoxic lungs. The lungs of hyperoxia-exposed WT mice had less gas exchange surface area and were less compliant compared with room air-exposed WT and hyperoxia-exposed MMP-9 (-/-) mice. Type I collagen and tropoelastin were increased in hyperoxia-exposed WT with aberrant elastin staining. These changes were ameliorated in hyperoxia-exposed MMP-9 (-/-) mice. MMP-9 plays an important role in the structural changes consequent to oxygen-induced lung injury. Blocking MMP-9 activity may lead to novel therapeutic approaches in preventing bronchopulmonary dysplasia.

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.

[Oxidative stress in the neonatal lung disease]

Oxidative stress is a risk factor for bronchopulmonary dysplasia in the preterm newborn. Antioxidant defense is impaired in the preterm newborn. Oxidative stress is also involved in cell growth and development. The relationship between oxidative stress and cell growth needs to be understood before antioxidant therapy can be routinely introduced. Several antioxidant therapies have been unsuccessfully tried until now. This review highlights the importance of oxygen free radicals in the pathogenesis of bronchopulmonary dysplasia.

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.

Pepsin, a marker of gastric contents, is increased in tracheal aspirates from preterm infants who develop bronchopulmonary dysplasia

OBJECTIVE

The objective of this study was to study the association between pepsin in tracheal aspirate samples and the development of bronchopulmonary dysplasia in preterm infants.

METHODS

Serial tracheal aspirate samples were collected during the first 28 days from mechanically ventilated preterm neonates. Bronchopulmonary dysplasia was defined as the need for supplemental oxygen at 36 weeks' postmenstrual age. An enzymatic assay with a fluorescent substrate was used to detect pepsin. Total protein was measured by the Bradford assay to correct for the dilution during lavage. Immunohistochemistry using antibody against human pepsinogen was performed in 10 lung tissue samples from preterm infants.

RESULTS

A total of 256 tracheal aspirate samples were collected from 59 preterm neonates. Pepsin was detected in 234 (91.4%) of 256 of the tracheal aspirate samples. Twelve infants had no bronchopulmonary dysplasia, 31 infants developed bronchopulmonary dysplasia, and 16 infants died before 36 weeks' postmenstrual age. The mean pepsin concentration was significantly lower in infants with no bronchopulmonary dysplasia compared with those who developed bronchopulmonary dysplasia or developed bronchopulmonary dysplasia/died before 36 weeks' postmenstrual age. Moreover, the mean pepsin level was significantly higher in infants with severe bronchopulmonary dysplasia compared with moderate bronchopulmonary dysplasia. The mean pepsin level in tracheal aspirate samples from the first 7 days was also lower in infants with no bronchopulmonary dysplasia compared with those who developed bronchopulmonary dysplasia or developed bronchopulmonary dysplasia/died before 36 weeks' postmenstrual age. Pepsinogen was not localized in the lung tissues by immunohistochemistry.

CONCLUSION

The concentration of pepsin was increased in the tracheal aspirate of preterm infants who developed bronchopulmonary dysplasia or died before 36 weeks' postmenstrual age. Recovery of pepsin in tracheal aspirate samples is secondary to gastric aspiration, not by hematogenous spread or local synthesis in the lungs. Chronic aspiration of gastric contents may contribute in the pathogenesis of bronchopulmonary dysplasia.

Maternal betamethasone and chorioamnionitis induce different collagenases during lung maturation in fetal sheep

BACKGROUND

Fetal lung maturation occurs after both maternal corticosteroid administration and chorioamnionitis. The effectors of this antenatally-induced lung maturation are not understood. Matrix metalloproteinases (MMPs) 2 and 9 are type-IV collagenases that can degrade alveolar basement membranes.

OBJECTIVES

We hypothesized that the structural changes of lung maturation by both antenatal corticosteroid treatment and chorioamnionitis would be associated with increases in these MMPs.

METHODS

64 pregnant ewes were randomly assigned to one of four treatment groups: intra-amniotic injection of 10 mg endotoxin, maternal intramuscular injection of 0.5 mg/kg betamethasone, both treatments combined or saline-treated controls. We quantified MMP-2 which is derived from connective tissue and MMP-9 which is predominantly derived from neutrophils in fetal lung fluid of lambs after maternal corticosteroid therapy and induction of chorioamnionitis and the combination of both therapies given at 109-111 days' gestational age with delivery 1, 5 or 15 days later.

RESULTS

Betamethasone, endotoxin and the combined treatments increased both surfactant pool size, lung gas volume and reduced alveolar wall thickness at 15 days. MMP-2 concentration was increased after betamethasone. MMP-9 concentration increased after endotoxin-induced chorioamnionitis but decreased by the combined treatments.

CONCLUSION

Lung maturation via different pathways may use different forms of collagenases for remodelling lung structure.

Matrix metalloproteinase-3 (stromelysin-1) in acute inflammatory tissue injury

Mice lacking matrix metalloproteinase-3 (MMP-3; stromelysin-1) demonstrated significantly less injury than their normal counterparts following the formation of IgG-containing immune complexes in the alveolar wall or in the wall of the peritoneum. Likewise, mice lacking MMP-3 demonstrated less lung injury following intra-tracheal instillation of the chemotactic cytokine macrophage inhibitory protein-2 (MIP-2) than did mice with MMP-3. There was a relationship between tissue injury (evidenced histologically) and accumulation of anti-laminin 111 immunoreactive material in the bronchoalveolar lavage (BAL) or peritoneal lavage (PL) fluid. There was also a relationship between tissue injury and influx of neutrophils into the BAL or PL fluid. Taken together, these data demonstrate an important role for MMP-3 in acute inflammatory tissue injury.

Matrix metalloprotease-9 dysregulation in lower airway secretions of cystic fibrosis patients

Matrix metalloproteases (MMPs) are proteolytic enzymes that regulate extracellular matrix turnover and aid in restoring tissue architecture following injury. There is an emerging role for extracellular matrix destruction in the pathogenesis of chronic neutrophilic lung diseases. In this study, we examined the expression and activity profiles of MMPs in lower airway secretions from cystic fibrosis (CF) patients, patients with acute respiratory failure (ARF), and normal controls. A discrete repertoire of MMP isoforms was found in the CF samples, with robust MMP-9 expression compared with normal controls and ARF. CF samples possessed increased levels of active MMP-9, as well as decreased amounts of tissue inhibitor of metalloprotease-1 (TIMP-1), a natural inhibitor of MMP-9. The CF inpatient samples demonstrated fully active MMP-9 activity compared with CF outpatients, ARF, and normal controls. CF samples also demonstrated increased human neutrophil elastase (HNE) levels compared with ARF and normal controls. To examine potential mechanisms for the protease dysregulation seen in the CF clinical samples, in vitro studies demonstrated that HNE could activate pro-MMP-9 and also degrade TIMP-1; this HNE-based activation, however, was not seen with MMP-8. A strong correlation was seen between HNE and MMP-9 activity in CF inpatient samples. Finally, the dysregulated MMP-9 activity seen in CF inpatient sputum samples could be significantly reduced by the use of MMP-9 inhibitors. Collectively, these findings further emphasize the proposed protease/antiprotease imbalance in chronic neutrophilic lung disease, providing a potential mechanism contributing to this proteolytic dysregulation.

Up-regulation of trypsin and mesenchymal MMP-8 during development of hyperoxic lung injury in the rat

Acute lung injury is marked by damage to alveolar-capillary barrier. High pulmonary levels of matrix-degrading serine proteinase trypsin and matrix metalloproteinases (MMP)-2, -8, and -9 have been shown in preterm infants with respiratory distress syndrome (RDS). We studied expression of trypsin and MMP-2, -8, and -9 in rats exposed to >95% oxygen for 24, 48, or 60 h. As demonstrated by zymography and Western immunoblotting, levels of trypsin and MMP-2, -8, and -9 in bronchoalveolar lavage fluid (BALF) sharply increased after 48 h of hyperoxia relative to normoxia controls. This coincided with increase in alveolar-capillary permeability, as indicated by increased protein concentration in BALF. Both neutrophil-derived 80-kD and mesenchymal cell-derived 60-kD MMP-8 isoforms were detected in BALF. Of them, mesenchymal-type MMP-8 predominated. In immunohistochemistry, alveolar epithelium showed strong trypsin expression at 48 and 60 h of hyperoxia, whereas it was predominantly negative in controls. MMP-8 was mostly expressed in macrophages. Marked up-regulation of trypsin and MMP-8 early during hyperoxic lung injury suggests that these enzymes play a role in the pathogenesis of acute lung injury and may therefore be potential targets for therapy of lung injury.

Cathepsin K expression is diminished in infants with bronchopulmonary dysplasia

The expression of a potent collagenolytic enzyme, cathepsin K, was measured in repeated tracheal aspirate samples from premature infants with and without a chronic lung disorder, bronchopulmonary dysplasia (BPD). At 9--13 d, but not before, cathepsin K expression was significantly lower in the lungs of premature infants developing BPD.

CONCLUSION

Insufficient pulmonary cathepsin K in BPD may predispose premature lungs to pulmonary fibrosis.

Inflammation and bronchopulmonary dysplasia: a continuing story

Increasing evidence indicates that bronchopulmonary dysplasia (BPD) results, at least in part, from an imbalance between pro-inflammatory and anti-inflammatory mechanisms, with a persistent imbalance that favours pro-inflammatory mechanisms. The inflammatory response is characterised by an accumulation of neutrophils and macrophages in the airways and pulmonary tissue of preterm infants and, moreover, by an arsenal of pro-inflammatory mediators which affect the alveolar capillary unit and tissue integrity. As well as pro-inflammatory cytokines and toxic oxygen radicals, various lipid mediators as well as potent proteases may be responsible for acute lung injury. During the last decade it has become evident that multiple pre- and postnatal events contribute to the development of BPD in preterm infants. Chorioamnionitis and cytokine exposure in utero, plus sequential lung injury caused by postnatal resuscitation, oxygen toxicity, volu-, barotrauma and infection all lead to a pulmonary inflammatory response which is most probably associated with aberrant wound healing and an inhibition of alveolarisation as well as vascular development in the immature lungs of very preterm infants, causing the 'new BPD'.