Neutrophil activation in preterm infants who have respiratory distress syndrome

Immunoinflammatory markers SIRI and NAR as predictors of respiratory distress syndrome and secondary infections in premature infants

Background

Premature infants are at high risk for neonatal respiratory distress syndrome (RDS) and secondary infections. This study aims to investigate the association between immunoinflammatory markers-the systemic immune inflammation index (SII), systemic inflammation response index (SIRI), and neutrophil-to-albumin ratio (NAR)-and the risk of developing RDS in premature infants.

Methods

A total of 2164 premature infants were enrolled in this retrospective study. The clinical records of these neonates (respiratory tract infections, adverse pregnancy history, placental abnormalities, birth weight, Apgar scores, and immunoinflammatory indices) were collected. Comparisons were made between infants with and without RDS. Logistic regression analysis was used to evaluate the relationship between SII, SIRI, NAR and RDS.

Results

Among the cohort, 962 infants developed RDS, while 1202 did not. The RDS group showed higher proportions of mothers with adverse pregnancy history, placental abnormalities, birth weight <2.5 kg, and lower Apgar scores at 1 and 5 minutes (all p<0.05). SII, SIRI, and NAR levels were significantly elevated in RDS infants (p<0.05). Logistic regression revealed that adverse pregnancy history (OR: 1.390, p=0.001), placental abnormalities (OR: 2.499, p<0.001), birth weight <2.5 kg (OR: 4.165, p<0.001), high SIRI (OR: 1.338, p=0.035), and high NAR (OR: 1.639, p<0.001) were significant predictors of RDS. Additionally, secondary infections, particularly pneumonia and sepsis, were significantly more common in the RDS group (p<0.001).

Conclusion

Adverse pregnancy history, placental abnormalities, low birth weight, elevated SIRI and NAR were associated with increased risk of RDS and secondary infections in premature infants. These findings suggest that SIRI and NAR could serve as useful markers for early identification and management of RDS and its complications in this vulnerable population.

Interrelation between miRNAs Expression Associated with Redox State Fluctuations, Immune and Inflammatory Response Activation, and Neonatal Outcomes in Complicated Pregnancy, Accompanied by Placental Insufficiency

Redox disbalance in placental cells leads to the hyperproduction of reactive oxygen species (ROS), it mediates the dysregulation of the maternal immune tolerance to a semi-allogenic fetus, inducing pro-inflammatory reactions, and it plays a central role in perinatal complications and neonatal disease programming. Microvesicles, which provide transplacental communication between a mother and fetus, contain microRNAs (miRNAs) that are sensitive to oxidative stress (OS) mediators and can control the balance of ROS production and utilization in target cells. In the context of this paradigm, we evaluated the markers of redox balance—MDA and 4-HNE for OS and GPx, and SOD, CAT, and GSH for the antioxidant system in the cord blood plasma of newborns diagnosed with fetal growth restriction (FGR)—by using polarography, spectrophotometry, and Western blotting. The expression of miRNAs associated with OS, immune and inflammatory responses in the blood plasma of newborns with intrauterine pneumonia (IP), neonatal sepsis (NS) and respiratory distress syndrome (RDS) was evaluated by a quantitative RT-PCR. Significant differences in the MDA level and reduced GPx and CAT activity were co-found for early-onset FGR (i.e., <34 gestational age). Significant correlations were found with a low birth weight by Apgar scores with reduced levels of antioxidant enzymes. Indeed, the level of OS markers increased in early-onset FGR in newborns with an extremely low body weight and high echogenicity of the periventricular zones, and reduced in late-onset FGR in newborns with IP, hyperbilirubinemia, intraventricular hemorrhage (IVH) and cerebral cysts. A prognostic model (AUC = 1; cutoff—0.5) was developed to assess the risk of IVH in newborns diagnosed with FGR based on the assessment of the OS markers (i.e., MDA + 4 HNE + CAT + GSH). A significant increase in the miR-127-3p expression was found in the plasma of newborns with NS (<32 GA; p ≤ 0.03 and >32 GA; p ≤ 0.009), IP (>32 GA; p ≤ 0.0001), and RDS (>32 GA; p ≤ 0.03). At the same time, the expression of miR-25-3p (p ≤ 0.03) was increased only in newborns with NS (>32 GA; p ≤ 0.03). The risk of developing IVH for premature newborns with IP (AUC = 0.8; cutoff—0.6) and NS (AUC = 0.68; cutoff—0.49) was assessed based on the miR-25-3p and miR-127-3p expression. Several key transcription factors were identified as the targets of studied miRNA since they are involved in the regulation of OS (NRF2), signaling and activation of the immune response (PRDM1, CCL26) and, also, inflammatory responses (NFKB1). The study of these miRNAs showed that they are involved in the modulation of processes leading to perinatal complications. Moreover, miR-127-3p is related to pro-inflammatory reactions and the formation of the macrophage phenotype in newborns with IP, NS, and RDS, while miR-25-3p is associated with an inhibition of macrophage migration and activation of antioxidant enzymes, which may prevent the development of oxidative damage in newborns with NS.

Evaluation of the neonatal sequential organ failure assessment and mortality risk in neonates with respiratory distress syndrome: A retrospective cohort study

BACKGROUND

Respiratory distress syndrome (RDS) is one of the leading causes of neonatal death in the neonatal intensive care unit (NICU). Previous studies have suggested that the development of neonatal RDS may be associated with inflammation and lead to organ dysfunction. The neonatal sequential organ failure assessment (nSOFA) scoring system is an operational definition of organ dysfunction, but whether it can be used to predict mortality in neonates RDS is unknown. The aim of this study was to clarify the performance of the nSOFA score in predicting mortality in patients with neonatal RDS, with the aim of broadening the clinical application of the nSOFA score.

METHODS

Neonates with RDS were identified from the Medical Information Mart for Intensive Care (MIMIC)-III database. Cox proportional hazards model were used to assess the association between nSOFA score and mortality. Propensity score matched analysis were used to assess the robustness of the analytical results.

RESULTS

In this study of 1,281 patients with RDS of which 57.2% were male, death occurred in 40 cases (3.1%). Patients with high nSOFA scores had a higher mortality rate of 10.7% compared with low nSOFA scores at 0.3%. After adjusting for confounding, multivariate Cox proportional risk analysis showed that an increase in nSOFA score was significantly associated with increased mortality in patients with RDS [adjusted Hazards Ratio (aHR): 1.48, 95% Confidence Interval (CI): 1.32-1.67; p < 0.001]. Similarly, the High nSOFA group was significantly associated with higher mortality in RDS patients (aHR: 19.35, 95% CI: 4.41-84.95; p < 0.001) compared with the low nSOFA group.

CONCLUSION

The nSOFA score was positively associated with the risk of mortality in cases of neonatal RDS in the NICU, where its use may help clinicians to quickly and accurately identify high risk neonates and implement more aggressive intervention.

Extracellular Vesicles Protect the Neonatal Lung from Hyperoxic Injury through the Epigenetic and Transcriptomic Reprogramming of Myeloid Cells

Rationale: Mesenchymal stem/stromal cell (MSC)-small extracellular vesicle (MEx) treatment has shown promise in experimental models of neonatal lung injury. The molecular mechanisms by which MEx afford beneficial effects remain incompletely understood. Objectives: To investigate the therapeutic mechanism of action through assessment of MEx biodistribution and impact on immune cell phenotypic heterogeneity. Methods: MEx were isolated from the conditioned medium of human umbilical cord Wharton's jelly-derived MSCs. Newborn mice were exposed to hyperoxia (HYRX, 75% O2) from birth and returned to room air at Postnatal Day 14 (PN14). Mice received either a bolus intravenous MEx dose at PN4 or bone marrow-derived myeloid cells (BMDMy) pretreated with MEx. Animals were killed at PN4, PN7, PN14, or PN28 to characterize MEx biodistribution or for assessment of pulmonary parameters. The therapeutic role of MEx-educated BMDMy was determined in vitro and in vivo. Measurements and Main Results: MEx therapy ameliorated core histological features of HYRX-induced neonatal lung injury. Biodistribution and mass cytometry studies demonstrated that MEx localize in the lung and interact with myeloid cells. MEx restored the apportion of alveolar macrophages in the HYRX-injured lung and concomitantly suppressed inflammatory cytokine production. In vitro and ex vivo studies revealed that MEx promoted an immunosuppressive BMDMy phenotype. Functional assays demonstrated that the immunosuppressive actions of BMDMy are driven by phenotypically and epigenetically reprogrammed monocytes. Adoptive transfer of MEx-educated BMDMy, but not naive BMDMy, restored alveolar architecture, blunted fibrosis and pulmonary vascular remodeling, and improved exercise capacity. Conclusions: MEx ameliorate hyperoxia-induced neonatal lung injury though epigenetic and phenotypic reprogramming of myeloid cells.

Perinatal Inflammation: Could Partial Blocking of Cell Adhesion Molecule Function Be a Solution?

In spite of the great advances made in recent years in prenatal and perinatal medicine, inflammation can still frequently result in injury to vital organs and often constitutes a major cause of morbidity. It is today well established that in neonates—though vulnerability to infection among neonates is triggered by functional impairments in leukocyte adhesion—the decreased expression of cell adhesion molecules also decreases the inflammatory response. It is also clear that the cell adhesion molecules, namely, the integrins, selectins, and the immunoglobulin (Ig) gene super family, all play a crucial role in the inflammatory cascade. Thus, by consolidating our knowledge concerning the actions of these vital cell adhesion molecules during the prenatal period as well as regarding the genetic deficiencies of these molecules, notably leukocyte adhesion deficiency (LAD) I, II, and III, which can provoke severe clinical symptoms throughout the first year of life, it is anticipated that intervention involving blocking the function of cell adhesion molecules in neonatal leukocytes has the potential to constitute an effective therapeutic approach for inflammation. A promising perspective is the potential use of antibody therapy in preterm and term infants with perinatal inflammation and infection focusing on cases in which LAD is involved, while a further important scientific advance related to this issue could be the combination of small peptides aimed at the inhibition of cellular adhesion.

Role of oxidative stress in neonatal respiratory distress syndrome

Respiratory distress syndrome is the commonest respiratory disorder in preterm infants. Although it is well known that preterm birth has a key role, the mechanisms of lung injury have not been fully elucidated. The pathogenesis of this neonatal condition is based on the rapid formation of the oxygen reactive species, which surpasses the detoxification capacity of anti-oxidative defense system. The high reactivity of free radical leads to damage to a variety of molecules and may induce respiratory cell death. There is evidence that the oxidative stress involved in the physiopathology of this disease, is particularly related to oxygen supplementation, mechanical ventilation, inflammation/infection and diabetes. This narrative review summarizes what is known regarding the connection between oxidative stress and respiratory distress syndrome.

Association between interleukin-10 genetic variant (-1082G>A) with detection and severity of respiratory distress syndrome in preterm neonates

BACKGROUND

Abnormal cytokine production derived from specific polymorphisms can have effect on development of respiratory distress syndrome (RDS). Therefore, the present study aimed to determine whether polymorphisms of IL10 in preterm newborn are associated with RDS.

METHODS

A total of one hundred and one venous blood samples were collected from preterm neonates, and they were classified as 51 with no RDS and 50 with RDS. Grading of RDS, history of surfactant administration or ventilator was assessed in the diseased group. Genetic variant of IL10-1082G/A (rs1800896) was genotyped by PCR-RFLP.

RESULTS

The RDS group showed a higher prevalence of IL10-1082 AA and lower prevalence of IL10-1082 GG (p < .001). We found that the incidence of the allele G in the IL10-1082 polymorphism was lower in the RDS group (24%) than the non-RDS group (51%) (p < .001). Allele model (A vs. G): OR = 0.304, 95% CI: 0.166-0.554, p ≤ .001; Dominant model (AA vs. AG + GG): OR = 0 0.470, 95% CI: 0.282-0.783, p = .04. More severe grades of RDS, need for surfactant and mechanical ventilation, were significantly associated with AA genotype when compared to AG + GG genotypes. IL10 (AG + GG) genotypes were considered as an independent predictor for lower risk of RDS within preterm neonates.

CONCLUSION

IL10-1082 A/A genotype associated with increased susceptibility to RDS. Also, A allele has been associated with increase severity of RDS in preterm neonates. Regression analysis revealed that IL10 AG + GG genotypes were considered as independent predictors for lower risk development of RDS within preterm neonates.

Examining the utility of the CD64 index compared with other conventional indices for early diagnosis of neonatal infection

As specific clinical manifestations and detection tools for early neonatal infections are lacking, early detection and treatment are ongoing challenges. The present study aimed to investigate the role and clinical significance of the CD64 index in comparison with conventional examination indices (WBC, PCT and CRP) for the early diagnosis of neonatal infection. Of 74 in-patient newborns, non-sepsis (non-specific infection but free of sepsis), sepsis and control [newborns with ABO hemolytic disease of the newborn (ABOHDN) but without infection] groups involved 32, 16 and 26 cases, respectively. Peripheral blood WBC, PCT, CRP and CD64 indices were acquired for all groups. The sepsis group showed significantly higher WBC, PCT and CRP levels than the control group. Compared with the non-sepsis group, the sepsis group demonstrated significant increases in PCT but not in WBC or CRP. Compared with the control group, the non-sepsis and sepsis groups had higher CD64 indices. Combined, compared with the WBC, PCT and CRP indices, the CD64 index is unique in its capacity to diagnose neonatal infections early. The CD64 index combined with other conventional indices may lay a basis for the future early diagnosis and effective treatment of neonatal infections.

Association between Interleukin-10-1082 G/A and Tumor Necrosis Factor- 308 G/A Gene Polymorphisms and Respiratory Distress Syndrome in Iranian Preterm Infants

Cytokine polymorphisms may contribute to the prevalence of respiratory distress syndrome. The present study was done to investigate the frequency of interleukin- (IL-) 10 and tumor necrosis factor- (TNF-) α gene polymorphisms and their association with the risk of RDS in preterm infants. One-hundred and nineteen patients with RDS and 119 healthy preterm infants were enrolled. PCR restriction fragment length polymorphism was used to determine the frequency of IL-10 and TNF-α genotypes at -1082 A and -308 A, respectively. One-hundred and nineteen out of 238 infants had RDS (50%). The age of the mothers and gestational age ranged 17–45 (mean: 28.6 ± 5.3) years and 24–34 (mean: 34.3 ± 2.38) weeks, respectively. Totally, 23 deaths were recorded in the RDS group. Incidence of TNF-α-308 A/A and TNF-α-308 G/A was 84% and 16%, respectively. TNF-a-308 G/G was not found in both groups. Prevalence of IL-10-1082 G/G and IL-10-1082 G/A variants was 65.5% and 34.5%, respectively. IL-10-1082 A/A was not found in both groups. The incidence of the allele G in the IL-10-1082 polymorphism was lower in RDS group (P < 0.05). We found that the risk of RDS was correlated to sex, gestational age, and IL-10-1082.

The Importance of Human Milk for Immunity in Preterm Infants

The immune system of preterm infants is immature, placing them at increased risk for serious immune-related complications. Human milk provides a variety of immune protective and immune maturation factors that are beneficial to the preterm infant's poorly developed immune system. The most studied immune components in human milk include antimicrobial proteins, maternal leukocytes, immunoglobulins, cytokines and chemokines, oligosaccharides, gangliosides, nucleotides, and long-chain polyunsaturated fatty acids. There is growing evidence that these components contribute to the lower incidence of immune-related conditions in the preterm infant. Therefore, provision of these components in human milk, donor milk, or formula may provide immunologic benefits.

Interaction of Streptococcus agalactiae and Cellular Innate Immunity in Colonization and Disease

Streptococcus agalactiae (Group B streptococcus, GBS) is highly adapted to humans, where it is a normal constituent of the intestinal and vaginal flora. Yet, GBS has highly invasive potential and causes excessive inflammation, sepsis, and death at the beginning of life, in the elderly and in diabetic patients. Thus, GBS is a model pathobiont that thrives in the healthy host, but has not lost its potential virulence during coevolution with mankind. It remains incompletely understood how the innate immune system contains GBS in the natural niches, the intestinal and genital tracts, and which molecular events underlie breakdown of mucocutaneous resistance. Newborn infants between days 7 and 90 of life are at risk of a particularly striking sepsis manifestation (late-onset disease), where the transition from colonization to invasion and dissemination, and thus from health to severe sepsis is typically fulminant and not predictable. The great majority of late-onset sepsis cases are caused by one clone, GBS ST17, which expresses HvgA as a signature virulence factor and adhesin. In mice, HvgA promotes the crossing of both the mucosal and the blood–brain barrier. Expression levels of HvgA and other GBS virulence factors, such as pili and toxins, are regulated by the upstream two-component control system CovR/S. This in turn is modulated by acidic epithelial pH, high glucose levels, and during the passage through the mouse intestine. After invasion, GBS has the ability to subvert innate immunity by mechanisms like glycerinaldehyde-3-phosphate-dehydrogenase-dependent induction of IL-10 and β-protein binding to the inhibitory phagocyte receptors sialic acid binding immunoglobulin-like lectin 5 and 14. On the host side, sensing of GBS nucleic acids and lipopeptides by both Toll-like receptors and the inflammasome appears to be critical for host resistance against GBS. Yet, comprehensive models on the interplay between GBS and human immune cells at the colonizing site are just emerging.

Chronic lung disease in the preterm infant. Lessons learned from animal models

Neonatal chronic lung disease, also known as bronchopulmonary dysplasia (BPD), is the most common complication of premature birth, affecting up to 30% of very low birth weight infants. Improved medical care has allowed for the survival of the most premature infants and has significantly changed the pathology of BPD from a disease marked by severe lung injury to the "new" form characterized by alveolar hypoplasia and impaired vascular development. However, increased patient survival has led to a paucity of pathologic specimens available from infants with BPD. This, combined with the lack of a system to model alveolarization in vitro, has resulted in a great need for animal models that mimic key features of the disease. To this end, a number of animal models have been created by exposing the immature lung to injuries induced by hyperoxia, mechanical stretch, and inflammation and most recently by the genetic modification of mice. These animal studies have 1) allowed insight into the mechanisms that determine alveolar growth, 2) delineated factors central to the pathogenesis of neonatal chronic lung disease, and 3) informed the development of new therapies. In this review, we summarize the key findings and limitations of the most common animal models of BPD and discuss how knowledge obtained from these studies has informed clinical care. Future studies should aim to provide a more complete understanding of the pathways that preserve and repair alveolar growth during injury, which might be translated into novel strategies to treat lung diseases in infants and adults.

Differential expression of antimicrobial polypeptides in cord blood samples of preterm and term infants

AIM

To determine levels of antimicrobial polypeptides (AMP) in cord blood of term and preterm neonates and to investigate influencing factors.

METHODS

In a single-centre study, n = 139 preterm infants and n = 36 term infants were included. AMP levels were analysed in supernatants of whole cord blood cultures with a standardised concentration of 5 × 10(6) white blood cells/mL via enzyme-linked immunosorbent assay (ELISA).

RESULTS

Lactoferrin, human neutrophil peptides (HNP) 1-3 and bacterial permeability-increasing protein (BPI) expression in cord blood of preterm infants were influenced by the cause of preterm delivery, that is increased levels in infants with clinical amniotic infection. AMP levels also weakly correlated with white blood cell and neutrophil count at birth. In the whole cohort, no association between gestational age or birthweight with AMP levels was found. In the subgroup of infants without clinical amniotic infection (n = 77 preterm infants, n = 36 healthy term infants), we noted a weak correlation between gestational age and lactoferrin, calprotectin and HNP1-3 levels. In addition to that, we observed higher levels of lactoferrin and HNP1-3 in large-for-gestational-age infants.

CONCLUSION

Our study confirms that several factors influence cord blood AMP levels which underlines the difficulties of using AMP levels as biomarkers of immunological response.

Physiologic underpinnings for clinical problems in moderately preterm and late preterm infants

This article highlights some of the important developmental characteristics that underpin common problems seen in moderate and late preterm infants. Preterm birth is associated with an increased prevalence of clinical problems caused by functional immaturities in a wide variety of organ systems, acquired problems, and problems associated with inadequate monitoring and/or follow-up plans. There are variations in the degree of maturation among infants of similar gestational ages because the developmental process is nonlinear. Therefore, different organ systems mature at rates and trajectories that are specific to their functions. A better understanding of these principles can help guide optimal treatment strategies.

Low monocyte HLA-DR expression as an indicator of immunodepression in very low birth weight infants

BACKGROUND

As a protective response to an inflammatory stimulus, the antigen-presenting molecules (human leukocyte antigen-DR (HLA-DR)) on monocytes are downregulated. If severe, the response may lead to immunodepression or immunoparalysis, associated with an increased rate of morbidity and mortality in adults. In very low birth weight (VLBW) infants, birth and intensive care present major immunological challenges.

METHODS

We measured monocyte HLA-DR expression by flow cytometry and determined 13 plasma cytokines in 56 VLBW infants (gestational age (GA): 23.7-31.8 wk) and 25 controls (GA: 34.1-41.4 wk).

RESULTS

HLA-DR expression decreased postnatally both in VLBW and in control infants. In VLBW infants, GA and respiratory distress syndrome (RDS) both showed associations with HLA-DR nadir on day 3, when 45% of them met the criteria of immunodepression. HLA-DR expression was lower in those infants subsequently developing infection (74 vs. 49% (day 3) and 85 vs. 68% (day 7); both P = 0.002). Interleukin (IL)-6 on day 1 was a predictor of the HLA-DR nadir.

CONCLUSION

VLBW infants are in a state of immunodepression postnatally. This immunodepression correlated with GA and was a predisposing factor for late infections. The downregulation of HLA-DR during RDS probably indicates an RDS-induced antigen load on the immune system.

High tissue factor in lungs and plasma associates with respiratory morbidity in preterm infants

AIM

In preterm infants, inflammation and intra-alveolar fibrin formation characterize respiratory distress syndrome (RDS). Tissue factor (TF) is a link between inflammation and coagulation pathways. We investigated the relationship between TF and cytokines in preterm infants to gain information of the role of TF in the inflammatory response.

METHODS

We measured TF in plasma and in tracheal aspirates and analysed TF on monocytes by flow cytometry and 13 cytokines from plasma, in 56 preterm infants (birthweight 600-1500 g) during their first week.

RESULTS

Plasma TF increased and peaked on day 3 and correlated with both RDS and inversely with paO2/FIO2. On day 1, TF in tracheal aspirates was 10-fold higher than in plasma and correlated with plasma TF (4888 vs. 506 pg/mL, R = 0.692, p = 0.013, n = 12). Of main pro-inflammatory cytokines, plasma TF correlated post-natally with IL-8 and IL-6 but not with IL-1 or TNF-α.

CONCLUSIONS

Respiratory morbidity associates with high TF in lungs and plasma. In sick newborn infants, upregulation of TF may be mediated by IL-6 and IL-8. High TF and pro-inflammatory cytokines may together participate in the pathogenesis of pulmonary and extrapulmonary injury in preterm infants through pro-inflammatory mechanisms.

Poractant alfa (Curosurf®) increases phagocytosis of apoptotic neutrophils by alveolar macrophages in vivo

BACKGROUND

Clearance of apoptotic neutrophils in the lung is an essential process to limit inflammation, since they could become a pro-inflammatory stimulus themselves. The clearance is partially mediated by alveolar macrophages, which phagocytose these apoptotic cells. The phagocytosis of apoptotic immune cells by monocytes in vitro has been shown to be augmented by several constituents of pulmonary surfactant, e.g. phospholipids and hydrophobic surfactant proteins. In this study, we assessed the influence of exogenous poractant alfa (Curosurf®) instillation on the in vivo phagocytosis of apoptotic neutrophils by alveolar macrophages.

METHODS

Poractant alfa (200 mg/kg) was instilled intratracheally in the lungs of three months old adult male C57/Black 6 mice, followed by apoptotic neutrophil instillation. Bronchoalveloar lavage was performed and alveolar macrophages and neutrophils were counted. Phagocytosis of apoptotic neutrophils was quantified by determining the number of apoptotic neutrophils per alveolar macrophages.

RESULTS

Exogenous surfactant increased the number of alveolar macrophages engulfing apoptotic neutrophils 2.6 fold. The phagocytosis of apoptotic neutrophils was increased in the presence of exogenous surfactant by a 4.7 fold increase in phagocytosed apoptotic neutrophils per alveolar macrophage.

CONCLUSIONS

We conclude that the anti-inflammatory properties of surfactant therapy may be mediated in part by increased numbers of alveolar macrophages and increased phagocytosis of apoptotic neutrophils by alveolar macrophages.

Total serum bilirubin level in umbilical cord blood and respiratory distress syndrome in very low birth weight infants

AIMS

To explore the association between total serum bilirubin (TSB) level in umbilical cord blood (UCB) and the occurrence and/or severity of respiratory distress syndrome (RDS) in very low birth weight (VLBW) infants.

METHODS

We performed a prospective study of 579 VLBW infants. The mean TSB level in UCB (1.8 mg/dL) was used to divide the cohort into two groups: neonates with levels <1.8 mg/dL and those with levels >1.8 mg/dL. Demographic and clinical characteristics of the 2 groups, including diagnosis of RDS, need for ventilation, peak fraction of inspired oxygen (FiO2), oxygenation index (OI), and duration of respiratory support, were compared.

RESULTS

Three hundred and twenty-four infants were included in the low-TSB group and 255 infants were included in the high-TSB group. RDS was less frequent in the high TSB group than in the low one (46.3% vs. 56.6%, P=0.01). A negative association between TSB level in UCB and the occurrence of RDS [odds ratio (OR)=0.620; 95% confidence interval (CI) 0.440-0.873, P=0.006] was observed. However, lower TSB in UCB was not associated with the maximum FiO2, OI, or duration of mechanical ventilation.

CONCLUSIONS

VLBW infants with low TSB levels in UCB were more likely to develop RDS. However, in conjunction with surfactant replacement therapy, no correlation was found between TSB levels in UCB and the severity of RDS. The negative association between high TSB in UCB and RDS warrants further investigation.

Hematologic profile of the fetus with systemic inflammatory response syndrome

OBJECTIVE

The fetal inflammatory response syndrome (FIRS) is associated with impending onset of preterm labor/delivery, microbial invasion of the amniotic cavity and increased perinatal morbidity. FIRS has been defined by an elevated fetal plasma interleukin (IL)-6, a cytokine with potent effects on the differentiation and proliferation of hematopoietic precursors. The objective of this study was to characterize the hematologic profile of fetuses with FIRS.

STUDY DESIGN

Fetal blood sampling was performed in patients with preterm prelabor rupture of membranes and preterm labor with intact membranes (n=152). A fetal plasma IL-6 concentration ≥ 11 pg/mL was used to define FIRS. Hemoglobin concentration, platelet count, total white blood cell (WBC) count, differential count, and nucleated red blood cell (NRBC) count were obtained. Since blood cell count varies with gestational age, the observed values were corrected for fetal age by calculating a ratio between the observed and expected mean value for gestational age.

RESULTS

1) The prevalence of FIRS was 28.9% (44/152); 2) fetuses with FIRS had a higher median corrected WBC and corrected neutrophil count than those without FIRS (WBC: median 1.4, range 0.3-5.6, vs. median 1.1, range 0.4-2.9, P=0.001; neutrophils: median 3.6, range 0.1-57.5, vs. median 1.8, range 0.2-13.9, P<0.001); 3) neutrophilia (defined as a neutrophil count >95th centile of gestational age) was significantly more common in fetuses with FIRS than in those without FIRS (71%, 30/42, vs. 35%, 37/105; P<0.001); 4) more than two-thirds of fetuses with FIRS had neutrophilia, whereas neutropenia was present in only 4.8% (2/42); 5) FIRS was not associated with detectable changes in hemoglobin concentration, platelet, lymphocyte, monocyte, basophil or eosinophil counts; and 6) fetuses with FIRS had a median corrected NRBC count higher than those without FIRS. However, the difference did not reach statistical significance (NRBC median 0.07, range 0-1.3, vs. median 0.04, range 0-2.3, P=0.06).

CONCLUSION

The hematologic profile of the human fetus with FIRS is characterized by significant changes in the total WBC and neutrophil counts. The NRBC count in fetuses with FIRS tends to be higher than fetuses without FIRS.

Predictive values of neutrophil CD64 expression compared with interleukin-6 and C-reactive protein in early diagnosis of neonatal sepsis

BACKGROUND

Despite major advances in the management of newborn infants, neonatal sepsis (NS) remain important causes of neonatal morbidity and mortality in the newborn, mainly among preterm and low birth weight infants.

OBJECTIVE

The aim of this study was to investigate the usefulness of neutrophil CD64 expression alone and together with other infection markers in NS.

METHODS

Peripheral blood samples were taken from 109 neonates, who were categorized into three groups: proven or clinical sepsis (n=35); disease without infection (n=42); and healthy controls (n=32). Complete blood count with differential, interleukin-6 (IL-6), C-reactive protein (CRP), and cell surface expression of CD64 on neutrophils have been evaluated in a prospective manner as a diagnostic aid for NS.

RESULTS

Expression of CD64 was significantly enhanced in neonates with sepsis compared with newborns with disease without infection and healthy controls (P=0.001 and P=0.001, respectively). Cutoff values of IL-6, CRP, CD64(MFI), and CD64(i) were 24.9  pg/ml, 4.05  mg/l, 87.7, and 4.39, respectively. Sensitivity-negative predictive values of IL-6, CRP, and CD64(MFI)/CD64(i) were 80.0-90.6%, 80.0-88.8%, and 88.6-94.0%, respectively. Combining all three tests increased the sensitivity to 100%; however, specificity and positive predictive value decreased to 62.1 and 55.5%, respectively.

CONCLUSIONS

CD64 might be used either alone or combined with IL-6 and CRP for early diagnosis of NS. The advantages of CD64 when compared with IL-6 and CRP are rapid quantitation, very small blood volume required, and easy handling.

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.

Neonatal respiratory distress syndrome: an inflammatory disease?

Surfactant substitution has been a major breakthrough in the treatment of neonatal respiratory distress syndrome (RDS), primarily caused by a lack of pulmonary surfactant; it has significantly reduced mortality and acute pulmonary morbidity in preterm infants. Some very immature infants, however, have a poor response to surfactant replacement or an early relapse. This brief article is based on the hypothesis that neonatal RDS has a complex and multifactorial pathogenesis characterized by an injurious inflammatory sequence in the immature lung. Fetal exposure to chorioamnionitis has been shown to initiate an inflammatory reaction beginning in utero. A 'low-grade' inflammatory stimulus in utero may 'prime' the fetal lung for accelerated maturation of the surfactant system, especially in conjunction with prenatal steroids, and may protect the preterm infant from developing moderate to severe RDS. Depending on the severity of inflammatory injury to the alveolar-capillary unit, however, serum proteins will leak into the airways and induce surfactant inactivation. Following this intrauterine 'first hit', the immature infant may develop severe RDS and have a poor response to surfactant substitution. Secondary insults such as traumatic stabilization techniques, oxygen toxicity, initiation of mechanical ventilation and others injure the immature lung immediately after birth and perpetuate and may aggravate the inflammatory process. Observational studies in preterm infants and animal experiments support this concept. Whenever surfactant inactivation is suspected, higher or repetitive doses of natural surfactant may help to overcome surfactant inactivation and to restore lung function.

Biomarkers for late-onset neonatal sepsis: cytokines and beyond

Acute phase reactants, pro and antiinflammatory mediators including chemokines and cytokines, and cell-surface antigens are nonspecific biomarkers that have been extensively studied for the diagnosis and management of late-onset neonatal sepsis (LONS) and necrotizing enterocolitis. It is expected that the next generation of biomarkers and tests will be more specific, will pinpoint the precise disease entity, and will provide crucial information on the exact pathogen or category of microorganism and its antibiotic profile within hours of clinical presentation. Research on molecular pathogen detection and proteomic profiling has shown promising results. Academic-industry partnerships are vital for successful development of new diagnostic biomarkers for LONS, which are sensitive, inexpensive, fully automated, and easy to measure, allowing a quick turnaround time for clinical decision making.

Pathophysiology and treatment of septic shock in neonates

Neonatal septic shock is a devastating condition associated with high morbidity and mortality. Definitions for the sepsis continuum and treatment algorithms specific for premature neonates are needed to improve studies of septic shock and assess benefit from clinical interventions. Unique features of the immature immune system and pathophysiologic responses to sepsis, particularly those of extremely preterm infants, necessitate that clinical trials consider them as a separate group. Keen clinical suspicion and knowledge of risk factors will help to identify those neonates at greatest risk for development of septic shock. Genomic and proteomic approaches, particularly those that use very small sample volumes, will increase our understanding of the pathophysiology and direct the development of novel agents for prevention and treatment of severe sepsis and shock in the neonate. Although at present antimicrobial therapy and supportive care remain the foundation of treatment, in the future immunomodulatory agents are likely to improve outcomes for this vulnerable population.

Role of innate host defenses in susceptibility to early-onset neonatal sepsis

Neonatal sepsis continues to take a devastating toll globally. Although adequate to protect against invasive infection in most newborns, the distinct function of neonatal innate host defense coupled with impairments in adaptive immune responses increases the likelihood of acquiring infection early in life, with subsequent rapid dissemination and death. Unique differences exist between neonates and older populations with respect to the capacity, quantity, and quality of innate host responses to pathogens. Recent characterization of the age-dependent maturation of neonatal innate immune function has identified novel translational approaches that may lead to improved diagnostic, prophylactic, and therapeutic modalities.

Induction and termination of inflammatory signaling in group B streptococcal sepsis

SUMMARY

Group B streptococcus (GBS) is part of the normal genital and gastrointestinal flora in healthy humans. However, GBS is a major cause of sepsis and meningitis in newborn infants in the Western world and an important pathogen in many developing countries. The dissection of the host response to GBS may increase the general understanding of innate immunity in sepsis, because newborn infants lack a sufficient adaptive response. Inflammatory signal induction in macrophages by GBS seems largely preserved in newborn infants, as shown both in vitro and in vivo. The engagement of Toll-like receptor 2 (TLR2) by lipoproteins and a myeloid differentiation factor 88 (MyD88)--dependent pathway induced by GBS cell wall are both important in this context. TLR2 activation of microglia by GBS induces neuronal damage, which might account for the high morbidity of GBS meningitis. At the same time, TLR2 mediates activation-induced cell death (AICD), a process involved in the containment of inflammation. In newborn infants, AICD and anti-bacterial polymorphonuclear leukocyte activity appears to be compromised. Accordingly, neonatal aberrations in the pathogen-specific negative control of inflammatory signaling are likely to contribute to excessive inflammation and neurological sequelae in GBS sepsis and meningitis.

Airway inflammatory cell responses to intra-amniotic lipopolysaccharide in a sheep model of chorioamnionitis

Chorioamnionitis, a risk factor for bronchopulmonary dysplasia in preterm infants, causes an influx of inflammatory cells into the fetal lung. Using a fetal sheep model, we evaluated the time course of activation, functional maturity, and apoptosis of the leukocytes recruited to the fetal air spaces by lipopolysaccharide (LPS). Time-mated sheep were given intra-amniotic injections with 10 mg of Escherichia coli LPS or saline 2 or 7 days before preterm delivery at 124 days of gestation (term is 150 days). Both neutrophils and monocytes in bronchoalveolar lavage fluid (BALF) had activated NF-kappaB after 2- and 7-day LPS exposures. These neutrophils and monocytes expressed the activation factor CD11b and the maturation factor PU.1 at 2 days, and increased PU.1 expression was detected in macrophages at 7 days. Leukocyte oxidative burst activity was greatest at 7 days. BALF lipid peroxidation increased fivefold at 2 days, while protein carbonyls increased eightfold at 7 days. Nitrative stress was not detected in the BALF, but leukocytes in the lung expressed nitric oxide synthase (NOS)II (inducible NOS). BALF leukocytes expressed the antioxidant peroxiredoxin V. Lung glutathione peroxidase was also increased with LPS exposure. There was minimal apoptosis of airway and lung leukocytes assessed by caspase-3 activation. Intra-amniotic LPS recruits leukocytes to the fetal air space that have a persistent activation. These results have implications for the pathogenesis of lung inflammatory disorders in the preterm.

Increased heme oxygenase-1 expression in premature infants with respiratory distress syndrome

Oxidative stress is known to play an important role in the pathogenesis of certain severe illnesses in preterm infants. The enzyme heme oxygenase-1 (HO-1) participates in cytoprotection against oxygen radical injury. We have previously described the role of HO-1 in physiologic adaptation by demonstrating the induction of HO-1 in healthy mature neonates and asymptomatic preterm infants. Our current aim was to investigate the HO-1 expression in preterm infants with respiratory distress syndrome (RDS). We collected venous blood samples from 28 preterm infants with RDS on the 1st, 3rd and 5th days after birth. The HO-1 mRNA expression was determined by means of a competitive reverse transcriptase PCR technique, and a quantitative blood count was performed on the residual blood sample. A significant increase in HO-1 expression was found in the preterm infants with RDS as compared with both the healthy mature and the asymptomatic premature groups. The elevation was approximately eight-fold. The platelet count displayed a significant negative association with the HO-1 expression, and in the RDS prematures with thrombocytopenia the HO-1 induction was significantly greater than in those with a normal platelet count. In conclusion, the RDS of prematures is accompanied by an elevated HO-1 expression during the first 5 days of life, consistent with the inflammatory and oxidative characteristics of the disease.

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.

Biomarkers in neonatal infection

Infected newborn infants are often difficult to differentiate from patients suffering from noninfective diseases. Whilst delaying treatment with antibiotics of infected infants may be fatal, widespread indiscriminate use in all cases with suspected bacterial infection could lead to both drug-induced complications and the development of multidrug-resistant organisms. Conventional biomarkers, such as blood cell counts and morphology, have serious limitations. Investigators in this area of research have, therefore, made strenuous efforts to discover more reliable biomarkers with superior diagnostic utilities and clinically relevant characteristics to help neonatal clinicians differentiate between infected and noninfected infants. The major classes of biomarkers in neonatal infection of recent interest will be discussed, including: acute phase reactants, cytokines, chemokines and leukocyte surface antigens. The application of these biomarkers to derive prognostic information useful to neonatal clinicians will also be considered.

Cytokine gene polymorphisms in Italian preterm infants: association between interleukin-10 -1082 G/A polymorphism and respiratory distress syndrome

In this study, we determined the genotype frequencies of polymorphisms of cytokine genes and investigated their association with the risk of respiratory distress syndrome (RDS) in preterm infants. Genetic polymorphisms in the cytokines interleukin (IL)-10, IL-8, and tumor necrosis factor (TNF) alpha, were studied in 342 white Italian newborns (112 without RDS, 66 prematurely born with RDS, and 164 infants born at term who were included as healthy controls). The polymorphisms were analyzed by polymerase chain reaction (PCR) restriction fragment length polymorphism (RFLP). The IL-10 mRNA levels were analyzed according to genotype by quantitative real-time PCR (QRT-PCR) in Epstein-Barr virus-transformed lymphoblastoid cell lines (EBV-LCLs) of 42 full-term healthy infants. Logistic regression analysis demonstrated the risk of RDS to be significantly lower in preterm infants with an IL-10 -1082 GG/GA genotype than in those with an AA genotype [odds ratio (OR) = 0.48, 95% confidence interval (CI): 0.24-0.95, p = 0.03]. QRT-PCR analyses showed that the IL-10 mRNA levels were significantly higher in 27 IL-10 -1082 GG/GA carriers compared with 15 IL-10 -1082 AA carriers (p = 0.03). We conclude that the IL-10 -1082 GG/GA polymorphism may have a role in RDS development in premature infants.

Lung epithelial cell apoptosis during acute lung injury in infancy

CONTEXT

Apoptosis of lung epithelial cells is implicated in the pathogenesis of acute lung injury. Most research on this subject has focused on adults. Very little is known about a potential interaction of this process with lung development in children.

OBJECTIVE

To summarize the current literature on lung epithelial cell apoptosis and common causes of acute lung injury in infants and young children and to identify new areas of research.

DESIGN

A Medline-based literature search.

RESULTS AND CONCLUSIONS

Few studies have focused on lung epithelial cell apoptosis during common causes of acute lung injury in children. Nevertheless, the limited literature suggests that this may be an important mechanism during respiratory distress syndrome of infants and viral respiratory tract infection. Apoptosis is an essential process during lung development and maturation. Insufficient attention has been paid to potential consequences of this for the short- and long-term outcomes of acute lung injury.

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'.

The innate immune system and its relevance to neonatal sepsis

PURPOSE OF REVIEW

The advent of human Toll-like receptors has revolutionized our understanding of innate immunity. This review summarizes recent discoveries about the role of Toll-like receptors and innate immunity in neonatal sepsis with a particular emphasis on the paradigmatic organism S. agalactiae.

RECENT FINDINGS

S. agalactiae stimulates phagocytes to excessive formation of inflammatory cytokines such as tumor necrosis factor, and Toll-like receptors are essential for this response both in vivo and in vitro. On the molecular level, distinct signaling pathways are engaged by released S. agalactiae toxins such as lipoteichoic acid (Toll-like receptor-2 dependent) and cell-bound toxins (Toll-like receptor-2 independent). In contrast, complement receptors and Fc receptors, but not Toll-like receptors, are directly involved in phagocytosis and therefore elimination of S. agalactiae. Notably, neonatal phagocytes potently activate cytokines in response to S. agalactiae but are deficient in S. agalactiae uptake and killing. Interference with the Toll-like receptor-dependent mitogen activated protein kinase cJun N-terminal Kinase improves outcome in a neonatal model of S. agalactiae sepsis by inhibiting cytokine formation but preserving clearance of S. agalactiae.

SUMMARY

Recent progress in the understanding of S. agalactiae recognition and phagocytic signaling in neonatal sepsis suggests intermediates in the Toll-like receptor pathways as valuable targets for adjunctive sepsis therapy.

Diagnostic markers for neonatal sepsis

PURPOSE OF REVIEW

To review the current evidence on the use of infection markers for diagnostic evaluation of sepsis in neonates.

RECENT FINDINGS

Recent research in immunology has led to the discovery of cell surface antigens, chemokines, cytokines and acute phase proteins that can potentially be used to 'rule in' or 'rule out' sepsis. The diagnostic utilities of key inflammatory mediators, including CD11b, CD64, interleukin-6 and interleukin-8, are promising and likely to become increasingly used as markers of infection for both diagnostic and prognostic purposes.

SUMMARY

Serial measurements and use of combinations of markers have been reported to improve sensitivity and negative predictive value of these tests. Current markers are not infallible, however, and do not permit neonatologists to withhold antibiotics in sick infants with suspected infection. Thus, many have emerged as useful indicators for early discontinuation of unnecessary antimicrobial therapy. Some infection markers are also useful for identifying infants with severe infection and adverse prognosis. Advances in flow cytometry have allowed simultaneous measurement of key markers using only minimal blood volume. Judicious selection of a panel of markers with complementary properties could greatly increase the ability of neonatologists to diagnose infection and discern valuable prognostic information.

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.

CD64 (Fcgamma receptor I) cell surface expression on maturing neutrophils from preterm and term newborn infants

BACKGROUND

The expression of CD64 (FcgammaRI) is increased from an almost negligible to a marked level on neutrophils in patients with bacterial infections. CD64 expression on neutrophils might therefore be a potential candidate for the diagnosis of bacterial infections in infants.

AIM

This study was performed to monitor changes of neutrophil expression of CD64 during the postpartum period to further evaluate the usefulness of this analysis. The possible influence on the expression of this receptor by other factors was also investigated, including respiratory distress syndrome (RDS) and preterm rupture of the membranes (PROM).

METHODS

Cell surface expression of CD64 on neutrophils from preterm and term newborn infants and healthy adults was analysed by flow cytometry. The expression of the other Fcgamma receptors, CD32 and CD16, and the complement receptors CD11b/CD18 and CD35 was also analysed for comparison.

RESULTS

Neutrophils from preterm newborn infants showed a moderately increased level of CD64 expression that, during their first month of life, was reduced to the level observed on neutrophils from term newborn infants and adults. In contrast, the level of neutrophil expression of CD32 and CD16 was significantly lower in preterm than term newborn infants and adults. Neutrophils from all groups indicated similar levels of CD11b expression, but the expression on neutrophils from newborn infants increased after birth.

CONCLUSION

Our results showed that neutrophil expression of CD64 is moderately increased in preterm newborn infants at birth. It seems not to be influenced by RDS, PROM or other factors related to preterm birth but by bacterial infection.

High cord blood IL-10 levels in preterm newborns with respiratory distress syndrome

BACKGROUND

The development of respiratory distress syndrome (RDS) is closely related to fetal immaturity, although the participation of inflammatory mechanisms also seems to be likely. We previously reported high interleukin-10 (IL-10) levels in cord blood from preterm infants. In the present study, we investigate the possible role of IL-10 and IL-12 in preterm newborns with RDS, a disease that is also closely related to gestational age.

PATIENTS AND METHODS

Cord blood levels of IL-10 and IL-12 (p70 + p40) were determined by ELISA in 20 preterm infants who later developed RDS, in 21 preterm infants without RDS and in 31 full term newborns. In 11 patients follow-up samples could be also obtained between 2 and 14 days of life.

RESULTS

Preterm infants with RDS showed higher IL-10 (27 vs 10.8 pg/mL; p: 0.0003) and lower IL-12 (188 vs 384; p: 0.002) levels in cord blood than premature infants without RDS and full term newborns (IL-10: 3.2 pg/mL, p: 0.0001; IL-12: 352 pg/mL; p: 0.002). The differences remained statistically significant after correction for the effect of gestational age between both preterm groups.

CONCLUSIONS

The results obtained may be related to an immature cytokine response in premature infants, but the IL-12/IL-10 imbalance found in our patients also supports the hypothesis that inflammation plays a role in RDS.

Labor promotes neonatal neutrophil survival and lipopolysaccharide responsiveness

Labor is a mild proinflammatory state that is associated with fetal leukocytosis. Elective cesarean section has been linked with increased neonatal morbidity, which may be partially immune mediated. We hypothesized that labor may alter neutrophil phenotype and thereby decrease neonatal complications. We characterized neutrophil function and survival in normal neonates after either uncomplicated vaginal delivery (VD) or elective cesarean section (CS) without labor. Spontaneous neutrophil apoptosis is delayed in cord blood neutrophils of neonates after normal labor (VD) compared with CS, as assessed by propidium iodide DNA incorporation using flow cytometry. This demonstrates their ability to maintain an inflammatory response. CD11b expression on neonatal neutrophils after CS is decreased, providing further evidence of altered activation or priming. Lipopolysaccharide responsiveness, characterized by CD11b and apoptosis, is similar in VD and adults, but CS-derived neutrophils are unresponsive. Baseline TLR-4 levels are elevated in CS in contrast to the other groups, although expression is not up-regulated by lipopolysaccharide co-incubation. Neonatal neutrophil survival and function are altered by labor and may increase antibacterial function and neutrophilia. This suggests that labor of any duration may be immunologically beneficial to the normal term neonate.

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.