Mucosal tumor necrosis factor-alpha production and extensive disruption of sulfated glycosaminoglycans begin within hours of birth in neonatal respiratory distress syndrome

Vascular Endothelial Growth Factor as Molecular Target for Bronchopulmonary Dysplasia Prevention in Very Low Birth Weight Infants

Bronchopulmonary dysplasia (BPD) still represents an important burden of neonatal care. The definition of the disease is currently undergoing several revisions, and, to date, BPD is actually defined by its treatment rather than diagnostic or clinic criteria. BPD is associated with many prenatal and postnatal risk factors, such as maternal smoking, chorioamnionitis, intrauterine growth restriction (IUGR), patent ductus arteriosus (PDA), parenteral nutrition, sepsis, and mechanical ventilation. Various experimental models have shown how these factors cause distorted alveolar and vascular growth, as well as alterations in the composition and differentiation of the mesenchymal cells of a newborn's lungs, demonstrating a multifactorial pathogenesis of the disease. In addition, inflammation and oxidative stress are the common denominators of the mechanisms that contribute to BPD development. Vascular endothelial growth factor-A (VEGFA) constitutes the most prominent and best studied candidate for vascular development. Animal models have confirmed the important regulatory roles of epithelial-expressed VEGF in lung development and function. This educational review aims to discuss the inflammatory pathways in BPD onset for preterm newborns, focusing on the role of VEGFA and providing a summary of current and emerging evidence.

Anti-inflammatory effects of the new generation synthetic surfactant CHF5633 on Ureaplasma-induced cytokine responses in human monocytes

BACKGROUND

Synthetic surfactants represent a promising alternative to animal-derived preparations in the treatment of neonatal respiratory distress syndrome. The synthetic surfactant CHF5633 has proven biophysical effectiveness and, moreover, demonstrated anti-inflammatory effects in LPS-stimulated monocytes. With ureaplasmas being relevant pathogens in preterm lung inflammation, the present study addressed immunomodulatory features on Ureaplasma-induced monocyte cytokine responses.

METHODS

Ureaplasma parvum-stimulated monocytes were exposed to CHF5633. TNF-α, IL-1β, IL-8, IL-10, TLR2 and TLR4 expression were analyzed using qPCR and flow cytometry.

RESULTS

CHF5633 did not induce pro-inflammation, and did not aggravate Ureaplasma-induced pro-inflammatory cytokine responses. It suppressed U. parvum-induced intracellular TNF-α (p < 0.05) and IL-1β (p < 0.05) in neonatal monocytes and inhibited Ureaplasma-induced TNF-α mRNA (p < 0.05), TNF-α protein (p < 0.001), and IL-1β (p = 0.05) in adult monocytes. Ureaplasma-modulated IL-8, IL-10, TLR2 and TLR4 were unaffected.

CONCLUSION

CHF5633 does neither act pro-apoptotic nor pro-inflammatory in native and Ureaplasma-infected monocytes. Suppression of Ureaplasma-induced TNF-α and IL-1β underlines anti-inflammatory features of CHF5633.

Increased postnatal inflammation in mechanically ventilated preterm infants born to mothers with early-onset preeclampsia

BACKGROUND

Preeclampsia and preterm labor often underlie preterm birth, and are associated with maternal inflammation. In preterm infants, respiratory distress syndrome (RDS) and mechanical ventilation are associated with systemic inflammation.

OBJECTIVE

We aimed to study whether early-onset preeclampsia or preterm labor modulate the systemic inflammation affecting preterm infants with RDS.

METHODS

We recruited mechanically ventilated infants with gestational ages <32 weeks; 11 infants were born after early-onset preeclampsia and 25 after preterm labor. Blood was drawn during postnatal days 1-7, and the mean values of days 1-2, 3-4 and 5-6 were used. Phagocyte CD11b expression was analyzed with flow cytometry, and plasma C-reactive protein (CRP) concentrations with immunoturbidimetry.

RESULTS

As compared with infants born after preterm labor, infants born after early-onset preeclampsia had higher CD11b expression on days 1-6 on both neutrophils and monocytes. In addition, infants born after early-onset preeclampsia had higher CRP concentrations on days 2-6 (all p < 0.05).

CONCLUSIONS

As compared with infants born after preterm labor to mothers without preeclampsia, infants born after early-onset preeclampsia presented with a stronger postnatal systemic inflammatory reaction. Antenatal exposure to preeclampsia may induce fetal leukocyte priming and regulation of inflammation, and thereby modify postnatal inflammatory reactions and morbidity.

Serum and glucocorticoid-inducible kinase in pulmonary tissue of preterm fetuses exposed to chorioamnionitis

OBJECTIVES

The interaction between inflammation and transepithelial Na(+) transport is poorly understood. Chorioamnionitis has been shown to be associated with preterm labor and postnatal pulmonary morbidity of preterm infants. The human isoform of serum and glucocorticoid-inducible kinase (SGK1) is upregulated by proinflammatory cytokines and stimulates epithelial Na(+) channel ENaC and the Na(+)/K(+)-ATPase activity, an effect presumably participating in the regulation of transepithelial Na(+) transport.

STUDY DESIGN

Lung tissue sections from 31 stillborn fetuses (range 21-41 weeks of gestational age) with or without chorioamnionitis were analyzed. Macrophages, neutrophils and lymphocytes were stained immunohistochemically. In addition, in situ hybridization for the detection of SGK1 mRNA was performed in fetal lung tissue. Positively labeled cells were compared by semiquantitative assessment.

RESULTS

A marked influx of macrophages into the pulmonary tissue of fetuses exposed to intrauterine inflammation when compared to fetuses without exposure to chorioamnionitis was observed (p < 0.05). There was also a tendency towards an increased density of neutrophils in fetuses exposed to chorioamnionitis. However, only small numbers of lymphocytes were detected in both groups. In fetuses exposed to chorioamnionitis, 6 of 8 fetuses did not express SGK1; however, in the group of fetuses without exposure to intrauterine inflammation 15 of 23 cases exhibited a profound SGK1 detection rate in lung tissue and airway epithelium, independent of the gestational age of the fetuses (p < 0.05).

CONCLUSIONS

Human serine threonine kinase SGK1 mRNA is observed in fetal lung tissue. On the basis of this study, we speculate that exposure to chorioamnionitis is associated with a downregulation of SGK1 in fetal lung tissue. The possible consequences of a decreased rate of SGK1 mRNA could be an impaired ability to clear the lungs from excessive fluid immediately after preterm birth.

[Chorioamnionitis and lung damage in the extremely low birth weight infant]

Some experimental work suggests that exposure to intrauterine infection is associated, not only, with lung maturation and a reduced risk of respiratory distress syndrome, but also, with delayed alveolarization and increased risk of bronchopulmonary dysplasia.

AIM

To evaluate the association between histological chorioamnionitis and lung disease in extremely low birth weight preterm infants.

METHODS

A retrospective chart review of 63 less than 1000 g birthweight, appropriated for gestational age neonates, delivered at three tertiary medical centers in the north of Portugal, between 2001 and 2002. The association between histological chorioamnionitis and lung damage (respiratory distress syndrome and bronchopulmonary dysplasia) was evaluated through the calculation of crude and adjusted odds ratio.

RESULTS

There were 32 newborns from mothers with histological chorioamnionitis and 31 without the condition. The association between histological chorioamnionitis and respiratory distress syndrome was OR 0.23 (95% CI 0.01 - 2.51). The association between chorioamnionitis and bronchopulmonary dysplasia was OR 1.61 (95% CI 0.38 - 6.97). The association between histological chorioamnionitis and bronchopulmonary dysplasia when adjusted for gestational age, multiple birth and C-section revealed no statistical significance: OR 2.66 (95% CI 0.36 - 19.60) for chorio- amnionitis without funisitis or vasculitis and OR 1.68 (95% CI 0.25 - 11.18) for funisitis and/or vasculitis.

CONCLUSION

In this study we could not confirm a decreased risk of respiratory distress syndrome nor an increased risk of bronchopulmonary dysplasia in extremely low birth weight preterm neonates with histological chorioamnionitis

The Respiratory System

One of the most critical events of birth is the conversion of the fluid-filled lung, unimportant to fetal intrauterine existence, into a hollow organ distended with air and capable of gaseous exchange sufficient to support life. Indeed, it has been argued that the major determinant of perinatal survival is respiratory function (Wigglesworth and Desai 1982).

The failure to make this conversion adequately may lead, directly or indirectly, to infant death, and the pathologist often needs to assess the contribution made by respiratory inadequacy to the sequence of events leading to death. In the preterm infant, problems are mainly related to pulmonary immaturity and associated therapy. In the mature infant, birth asphyxia primarily results in cerebral damage but can engender significant respiratory complications when associated with aspiration of meconium. Even in stillbirths, where primary pulmonary pathology is rarely a cause of death, lung pathology may provide clues to antecedent events. Poor lung growth and maturation may point to the presence of pathology elsewhere. Consequently, adequate pathological investigation of the fetal or infant respiratory system is critical in any perinatal autopsy.

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'.

Pulmonary inflammation and bronchopulmonary dysplasia

Various pre- and postnatal risk factors, which act additively or synergistically induce an injurious inflammatory response in the airways and the pulmonary interstitium of preterm infants with bronchopulmonary dysplasia. This inflammatory response is characterized by an accumulation of neutrophils and macrophages as well as an arsenal of proinflammatory mediators that affect the endothelium and alveolar-capillary integrity. Besides proinflammatory cytokines and toxic oxygen radicals, lipid mediators as well as potent proteases may be responsible for acute lung injury. There is increasing evidence that an imbalance between pro- and anti-inflammatory factors, which should protect the alveoli and lung tissue, are key features in the pathogenesis of bronchopulmonary dysplasia. In addition, a subnormal generation of growth factors may affect alveolarization and vascular development in preterm infants with bronchopulmonary dysplasia. In this condensed review article, the current concepts on the possible role of inflammation in the evolution of bronchopulmonary dysplasia will be summarized.

Bronchopulmonary dysplasia

Bronchopulmonary dysplasia is a chronic lung disease that affects premature babies and contributes to their morbidity and mortality. Improved survival of very immature infants has led to increased numbers of infants with this disorder. This increase puts a heavy burden on health resources since these infants need frequent re-admission to hospital in the first 2 years after birth and, even as adolescents, have lung-function abnormalities and persistent respiratory symptoms. Unlike the original description of the disease in 1967, premature infants can develop chronic oxygen dependency without severe, acute respiratory distress; this "new bronchopulmonary dysplasia" could be the result of impaired postnatal lung growth. Whether such infants subsequently have catch-up lung growth, especially if given corticosteroids postnatally, is unknown. No safe and effective preventive therapy has been identified, but promising new treatments directed either at reducing lung injury or improving lung growth are under study.

Onset of mechanical ventilation is associated with rapid activation of circulating phagocytes in preterm infants

OBJECTIVE

In preterm infants with respiratory distress syndrome (RDS), circulating neutrophils are activated. Kinetics and effects of surfactant therapy on this activation are unknown. Therefore, we studied activation of circulating neutrophils and monocytes in newborn preterm infants with and without RDS.

PATIENTS AND METHODS

Preterm infants with RDS who were mechanically ventilated and received surfactant ("ventilated infants": n = 38; mean gestational age +/- SD: 28.3 +/- 2.2 weeks; mean birth weight +/- SD: 1086 +/- 353 g) and preterm infants who received nasal continuous positive airway pressure (n = 8) or no ventilatory support (n = 17) ("control infants": mean gestational age +/- SD: 32.1 +/- 1.2 weeks; mean birth weight +/- SD: 1787 +/- 457 g) were recruited. Blood samples were taken from ventilated infants at birth, before surfactant treatment, at 1 and 2 hours after surfactant, and at 12 to 24 hours of age. Blood samples were taken from control infants at birth, at 2 to 6 hours, and at 12 to 24 hours of age. Phagocyte CD11b expression was analyzed by flow cytometry.

RESULTS

In ventilated infants, phagocyte CD11b expression increased from birth to the first postnatal samples. It increased further by 12 to 24 hours of age. Control infants with or without nasal continuous positive airway pressure showed no significant increase after birth. At 12 to 24 hours of age, phagocyte CD11b expression was higher in ventilated infants than in control infants. In ventilated infants, neutrophil CD11b expression at 1 and 2 hours after surfactant correlated positively with gestational age.

CONCLUSIONS

In preterm infants with RDS, significant activation of circulating phagocytes occurs within 1 to 3 hours of the onset of mechanical ventilation, independent of surfactant administration, which indicates that mechanical ventilation may be the inducer of this systemic inflammatory response.

Increase of interleukin-6 in tracheal aspirate at birth: a predictor of subsequent bronchopulmonary dysplasia in preterm infants

AIM

We tested whether interleukin-6 (IL-6) in tracheal aspirate (TA) at birth, as a marker of fetal pulmonary inflammation, can be a predictor of bronchopulmonary dysplasia (BPD) in preterm infants.

METHODS

A total of 75 preterm (< or = 32 wk) infants who were intubated in the delivery room were prospectively enrolled. Multivariate logistic regression analysis was done to determine whether IL-6 in TA at birth is an independent risk factor for BPD, and a receiver-operating characteristic curve was constructed to determine the accuracy of IL-6 in TA for predicting the risk of BPD.

RESULTS

IL-6 in TA at birth was an independent risk factor for BPD. Fetal pulmonary inflammation defined as IL-6 in TA at birth > or = 316 pg/ml together with patent ductus arteriosus (PDA) additively predicted the risk of BPD. The sensitivity, specificity, and positive and negative predictive values of fetal pulmonary inflammation for the identification of BPD were 73%, 71%, 58% and 83%, respectively.

CONCLUSION

IL-6 in TA at birth can be used as a predictor of BPD in combination with the presence of PDA.

Nuclear Factor-Kappa B Expression in Alveolar Macrophages of Mechanically Ventilated Neonates with Respiratory Distress Syndrome

BACKGROUND

Inflammatory reaction and injury in mature lungs are associated with activation of nuclear factor-kappaB (NF-kappaB) to trigger proinflammatory cytokine release. In preterm infants with immature lungs, this mechanism is not yet fully understood, therefore we investigated this mechanism in mechanically ventilated neonates with respiratory distress syndrome (RDS).

METHODS

Serial samples of the airway aspirates (AA) were obtained during mechanical ventilation from 21 preterm infants with RDS, of which 12 were survivors (birth weight 1.48 +/- 0.32 kg and gestational age 31 +/- 1.5 weeks) and 9 nonsurvivors (1.34 +/- 0.31 kg and 30 +/- 2 weeks). Seven neonates matched for age and birth weight without respiratory disorders served as controls. Alveolar macrophages (AM) of AA were isolated by differential adherence, some were cultured with lipopolysaccharide (LPS) for 1 h. Then, nuclear extracts of AM were analyzed by electrophoretic mobility shift assay for NF-kappaB expression. The NF-kappaB inhibitor (IkappaB-alpha protein) in cytoplasmic extracts was detected by Western blot, and concentrations of IL-1beta and IL-8 in AA by enzyme-linked immunosorbent assay (ELISA).

RESULTS

On day 2 NF-kappaB expression in AM was significantly increased in the survivors and nonsurvivors at 33.3 +/- 9 and 54.8 +/- 10.2 relative density units (RDU) compared to control infants (11.1 +/- 6.7; p < 0.01). Expression of IkappaB-alpha was significantly higher in controls than that in the survivors and nonsurvivors on days 2 and 4. Moreover, in the nonsurvivors of RDS, expression of NF-kappaB was decreased following LPS stimulation in vitro on day 4. IL-1beta and IL-8 levels in the AA supernatant were higher in the survivors than in controls on days 2 and 4, but lower than those of the nonsurvivors on day 2. There were close correlations between the expression of NF-kappaB and levels of IL-1beta (r = 0.78, p < 0.01), and IL-8 (r = 0.81, p < 0.01) in AA.

CONCLUSION

There were alterations in NF-kappaB activity in the AM of mechanically ventilated preterm neonates with RDS, mediated by decreased synthesis and increased degradation of IkappaB.

Pre- and postnatal inflammatory mechanisms in chronic lung disease of preterm infants

Epidemiological data suggest a strong association between chorioamnionitis and the development of chronic lung disease in preterm infants. Increased concentrations of proinflammatory cytokines present in the amniotic fluid and the systemic fetal circulation seem to be important mediators in the early inflammatory response by recruiting and activating inflammatory cells and by inducing pathways of lung injury. As a consequence vascular cell adhesion molecules are upregulated and a marked infiltration of neutrophils and macrophages as well as an increased expression of interleukin-8 mRNA in the bronchoalveolar epithelium and in the interstitial tissue takes place. These antenatal events may prime the lungs such that various injurious factors in the postnatal period provoke an excessive inflammatory response: oxygen toxicity, mechanical ventilation, inappropriate resuscitation, pulmonary and systemic infections, persistent ductus arteriosus. Besides proinflammatory cytokines, toxic oxygen radicals, lipid mediators and potent proteases may be responsible for acute and chronic lung injury. In general, an imbalance between pro- and anti-inflammatory factors can be considered as a hallmark of lung injury, and may considerably affect normal alveolarisation and pulmonary vascular development by inducing growth arrest of the immature lung.

Pulmonary trypsin-2 in the development of bronchopulmonary dysplasia in preterm infants

OBJECTIVES

In the preterm infant, lung injury can lead to irreversible tissue destruction and abnormal lung development. We examined whether pulmonary trypsin, a potent matrix-degrading serine proteinase and proteinase-cascade activator, is associated with the development of bronchopulmonary dysplasia (BPD) in preterm infants.

METHODS

Samples of tracheal aspirate fluid were collected from 32 intubated preterm infants during their first 2 postnatal weeks. The presence and molecular forms of trypsin in tracheal aspirate fluid samples were analyzed by zymography and Western blotting. The concentrations of trypsinogen-1 and -2 and tumor-associated trypsin inhibitor were measured by immunofluorometry. For examining the expression of trypsin-2 in lung tissue, immunohistochemistry was performed on autopsy specimens of fetuses, of preterm infants who died from respiratory distress syndrome or BPD, and of term infants without lung injury.

RESULTS

In infants who subsequently developed BPD (n = 18), we detected significantly higher concentrations of trypsinogen-2 during postnatal days 5 to 10 compared with those who survived without it. There was no difference in trypsinogen-1 concentrations. Tumor-associated trypsin inhibitor concentrations were significantly lower in infants who needed mechanical ventilation for >1 week. Immunohistochemistry demonstrated that trypsin-2 was predominantly expressed in bronchial and bronchiolar epithelium. In 2 preterm infants who died from prolonged respiratory distress syndrome, trypsin-2 was also expressed in vascular endothelium.

CONCLUSIONS

The levels of trypsinogen-2 are higher during postnatal days 5 to 10 in infants who subsequently develop BPD. The results suggest that high levels of pulmonary trypsin-2 may be associated with the development of BPD. This raises the possibility that therapy with exogenous proteinase inhibitors might prevent the development of BPD in preterm infants with respiratory distress.

Inflammation and bronchopulmonary dysplasia

Pulmonary inflammation is a key feature in the pathogenesis of bronchopulmonary dysplasia (BPD). This inflammatory process, induced by multiple risk factors, is characterized by the presence of inflammatory cells, cytokines and an arsenal of additional humoral mediators in the airways and pulmonary tissue of preterm infants with the condition. Several mediators have a direct detrimental effect on pulmonary structures by affecting cell integrity and inducing apoptosis. An imbalance between pro-inflammatory and anti-inflammatory factors can generally be considered to be a hallmark of lung injury. Intrauterine exposure to pro-inflammatory cytokines or antenatal infection may prime the fetal lung such that minimally injurious postnatal events provoke an excessive pulmonary inflammatory response that most certainly affects normal alveolization and pulmonary vascular development in preterm infants with BPD.

Early activation of inflammation and clotting in the preterm lamb with neonatal RDS: comparison of conventional ventilation and high frequency oscillatory ventilation

In neonatal respiratory distress syndrome activation of inflammation and clotting is demonstrated. High frequency oscillatory ventilation (HFOV) is considered to be less damaging to the human preterm lung, resulting in less activation of inflammation and clotting compared with conventional ventilation (CV). To assess the sequence of events of activation of inflammation and clotting and to compare the impact of HFOV to CV, we ventilated preterm lambs delivered by cesarean section at 132 d gestational age (term 145 d) for 8 h by CV (n = 10) or HFOV (n = 11). Fifteen minutes after birth and at 2-h intervals thereafter blood samples, from umbilical catheters, were analyzed for AP50 (complement activation), number of polymorphonuclear leukocytes, beta-glucuronidase, platelet function, activated partial thromboplastin time, thrombin time and thrombin inhibition, and bronchoalveolar lavage fluid was analyzed for elastase, thrombin and protein. We found complement activation, low number of polymorphonuclear leukocytes and high levels of beta-glucuronidase already at 15 min after birth. Within 2 to 4 h after birth platelet function deteriorated, activated partial thromboplastin time prolonged, and thrombin inhibition decreased. Activation of inflammation and clotting in the lungs was demonstrated by increased levels of elastase and thrombin in bronchoalveolar lavage fluid. In the HFOV group, AP50 remained significantly higher than in the CV group, reflecting less complement activation, and platelet function analysis remained significantly lower, reflecting better platelet function. We conclude that systemic activation of inflammation can be found in the ventilated preterm lamb with respiratory distress syndrome within 15 min after birth. Afterward, or due to activation of inflammation, clotting is activated. HFOV possibly attenuates activation of inflammation.

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

OBJECTIVES

Matrix metalloproteinases (MMPs) are a family endoproteinases that act in degradation of extracellular matrix and basement membranes. The development of bronchopulmonary dysplasia (BPD) is characterized by early pulmonary inflammation, increased microvascular permeability, and subsequently by disordered repair. The aims of our study were to characterize the presence and molecular weight forms of MMP-2, -8, and -9 and their specific inhibitor, tissue inhibitor of metalloproteinases (TIMP)-2, in lungs of preterm infants during the early postnatal period and to determine whether levels of these MMPs and TIMP-2 in tracheal aspirate fluid (TAF) are associated with acute or chronic lung morbidity of the preterm infant.

METHODS

TAF samples were collected from 16 intubated preterm infants (gestational age 27.0 +/- 2.0 weeks; birth weight 875 +/- 246 g) during their first 5 postnatal days. The presence and molecular weight forms of MMPs and TIMP-2 were identified by Western immunoblotting, and their levels were evaluated by densitometric scanning.

RESULTS

MMP-8 in TAF was higher in infants who needed treatment with surfactant (25.4 +/- 6.3 vs 10.6 +/- 1.5 arbitrary unit/secretory component of immunoglobulin A [AU/SC]) and in whom BPD developed (N = 6; 27.6 +/- 5.2 vs 15.1 +/- 5.0 AU/SC). TIMP-2 levels were lower in infants with initial arterial to alveolar oxygen tension ratios <0.22 (2.7 +/- 1.1 vs 16.8 +/- 7.4 AU/SC) and in infants needing mechanical ventilation for >1 week (5.2 +/- 2.1 vs 22.8 +/- 11.7 AU/SC).

CONCLUSIONS

In preterm infants, an imbalance between pulmonary MMP-8 and TIMP-2 participates in the acute inflammatory process in respiratory distress syndrome and may contribute to the development of chronic lung injury.

Type I collagenases in bronchoalveolar lavage fluid from preterm babies at risk of developing chronic lung disease

OBJECTIVE

To assess whether increased collagenolysis precedes severe chronic lung disease (CLD).

METHODS

Matrix metalloproteinase-1 (MMP-1) and MMP-8 (enzymes that degrade type I collagen, the main structural protein of lung extracellular matrix) were measured by enzyme linked immunosorbent assay in 100 bronchoalveolar lavage samples taken during the first 6 postnatal days from 45 ventilated preterm babies < 33 weeks gestation. The median value for each baby was calculated. CLD was defined as an oxygen requirement after the 36th week after conception.

RESULTS

MMP-8 levels in bronchoalveolar lavage fluid were higher (median 13 ng/ml) in 20 babies who developed CLD than in 25 without CLD (median 2 ng/ml). No MMP-1 was detected in any sample.

CONCLUSIONS

MMP-8 can be detected in bronchoalveolar lavage fluid from preterm babies, and higher levels are found in those who later develop CLD. MMP-8 may contribute to lung injury that occurs as a prelude to CLD.

A pilot study of N-acetyl glucosamine, a nutritional substrate for glycosaminoglycan synthesis, in paediatric chronic inflammatory bowel disease

BACKGROUND

The breakdown of glycosaminoglycans is an important consequence of inflammation at mucosal surfaces, and inhibition of metalloprotease activity may be effective in treating chronic inflammation.

AIM

To report an alternative approach, using the nutriceutical agent N-acetyl glucosamine (GlcNAc), an amino-sugar directly incorporated into glycosaminoglycans and glycoproteins, as a substrate for tissue repair mechanisms.

METHODS

GlcNAc (total daily dose 3-6 g) was administered orally as adjunct therapy to 12 children with severe treatment-resistant inflammatory bowel disease (10 Crohn's disease, 2 ulcerative colitis). Seven of these children suffered from symptomatic strictures. In addition, similar doses were administered rectally as sole therapy in nine children with distal ulcerative colitis or proctitis resistant to steroids and antibiotics. Where pre- and post-treatment biopsies were available (nine cases), histochemical assessment of epithelial and matrix glycosaminoglycans and GlcNAc residues was made.

FINDINGS

Eight of the children given oral GlcNAc showed clear improvement, while four required resection. Of the children with symptomatic Crohn's stricture, only 3 of 7 have required surgery over a mean follow-up of > 2.5 years, and endoscopic or radiological improvement was detected in the others. Rectal administration induced remission in two cases, clear improvement in three and no effect in two. In all cases biopsied there was evidence of histological improvement, and a significant increase in epithelial and lamina propria glycosaminoglycans and intracellular GlcNAc.

CONCLUSIONS

GlcNAc shows promise as an inexpensive and nontoxic treatment in chronic inflammatory bowel disease, with a mode of action which is distinct from conventional treatments. It may have the potential to be helpful in stricturing disease. However, controlled trials and an assessment of enteric-release preparations are required to confirm its efficacy and establish indications for use.

Infection, neutrophils, and hematopoietic growth factors in the pathogenesis of neonatal chronic lung disease

Continued definition of the biochemical and molecular mechanisms underlying the development of chronic lung disease (CLD) has persuaded investigators that inflammatory cells and mediators are key factors in the pathophysiology of the disease. High numbers of inflammatory cells and their products are present in the airways of ventilated neonates with respiratory distress syndrome and precede the development of CLD. This article reviews the mechanisms underlying neutrophil recruitment in the lungs of ventilated preterm infants with respiratory distress syndrome and the injurious effects that these cells can produce on lung parenchyma with special emphasis on the development of CLD. The role of granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor is stressed as a pivotal mechanism of neutrophil recruitment and activation.

The effect of selenium supplementation on outcome in very low birth weight infants: a randomized controlled trial. The New Zealand Neonatal Study Group

BACKGROUND

Low selenium (SE) status has been documented in preterm infants and has been suggested to be a risk factor for chronic lung disease.

METHODS

A total of 534 infants with birth weight <1500 g were enrolled in 8 New Zealand centers in a double-blind placebo-controlled randomized trial of SE supplementation from week 1 of life until 36 weeks' postmenstrual age or discharge home. Supplemented infants received 7 microg/kg/d of SE when fed parenterally and 5 microg/kg/d when fed orally. Plasma SE and glutathione peroxidase concentrations were measured in mothers after delivery and in infants before randomization and at 28 days and 36 weeks' postmenstrual age. Primary outcome measures were oxygen dependency at 28 days and total days oxygen dependency.

RESULTS

No significant differences were seen between the groups with respect to primary or secondary outcome measures, with the exception that fewer supplemented infants had an episode of sepsis after the first week of life (P <.038). Mean plasma SE concentrations were 0.33 micromol/L before randomization in both groups and at 28 days had risen in the supplemented group (0.56 micromol/L) but fallen in the control group (0.29 micromol/L) (P <.0001). There was no association between outcome measures and SE concentrations at 28 days or 36 weeks' postmenstrual age. However, lower maternal and infant prerandomization SE concentrations were associated with increased respiratory morbidity.

CONCLUSIONS

Postnatal SE supplementation in very low birth weight infants did not improve neonatal outcome. Further investigation of SE supplementation of mothers from the second half of pregnancy is warranted.

Natural porcine surfactant (Curosurf) down-regulates mRNA of tumor necrosis factor-alpha (TNF-alpha) and TNF-alpha type II receptor in lipopolysaccharide-stimulated monocytes

We have previously shown that Curosurf, a natural porcine surfactant, and its phospholipids effectively suppressed secretion of tumor necrosis factor (TNF-alpha) by resting and through lipopolysaccharide (LPS)-stimulated human monocytes. In this study the effect of Curosurf on monocyte mRNA for TNF-alpha and TNF-alpha type II-receptor (TNF-alpha-RII) were analyzed to evaluate the cellular mechanisms involved in the modulation of TNF-alpha expression. LPS-stimulated monocytes simultaneously exposed to Curosurf (500 microg/mL for 24 h) expressed approximately 70% less TNF-alpha mRNA when compared with control subjects (p < 0.05). In addition, 86% less TNF-alpha RII mRNA was found in monocytes exposed to Curosurf (p < 0.001). Decreased mRNA expression was clearly associated with significantly reduced secretion of TNF-alpha protein (Curosurf-exposed LPS-stimulated monocytes 3628 +/- 1873 pg/mL TNF, LPS-stimulated monocytes 31,376 +/- 2524 pg/mL TNF; mean +/- SEM, p < 0.001). The activation of the transcription factor nuclear factor-kappaB upon LPS stimulation is not affected by Curosurf incubation. This excludes that the decrease in mRNA and protein levels of TNF-alpha and TNF-alpha-RII is due to an inhibition of nuclear factor-kappaB activation by Curosurf. We conclude that Curosurf affects TNF-alpha release of LPS-stimulated monocytes at a pretranslational site by down-regulating both mRNA for TNF-alpha and TNF-alpha-RII, therefore acting as an anti-inflammatory agent within alveolar space.

Early production of macrophage inflammatory protein-1 alpha occurs in respiratory distress syndrome and is associated with poor outcome

Although progression to pulmonary fibrosis in preterm infants with respiratory distress syndrome (RDS) is related to the inflammatory response, the nature of this response remains controversial. We have therefore performed sequential bronchoalveolar lavages in 30 infants with RDS (13 of whom developed bronchopulmonary dysplasia) and 7 ventilated control infants, characterizing the cells obtained by immunohistochemical analysis of lineage-specific markers and assaying macrophage-associated chemokines and cytokines in supernatant fluid. At all ages from birth, lavage supernatants demonstrated highly significant increase over controls of the beta-chemokine macrophage inflammatory protein (MIP)-1 alpha, although not of regulated upon activation, normal T cell expressed and secreted (RANTES), of the cytokines tumor necrosis factor (TNF)-alpha and IL-1 beta, and of elastase/alpha-1 antitrypsin. Significantly higher concentrations of MIP-1 alpha in particular were associated with the later development of fibrosis. Increased numbers of macrophages expressing the activation marker RM/3-1 were found at all ages in bronchopulmonary dysplasic infants, whereas neutrophil numbers were increased from d 3. Dexamethasone administered to 10 infants induced rapid decrease in inflammatory cell numbers and concentrations of MIP-1 alpha, tumor necrosis factor-alpha, IL-1 beta, and elastase/alpha-1 antitrypsin. The inflammatory response in neonatal RDS begins within the first day of life. Long-term outcome is associated with the magnitude of this early response, in particular production of MIP-1 alpha. The early introduction of specific therapy is thus likely to be beneficial.