Correlation of free oxygen radical-induced lipid peroxidation with outcome in very low birth weight infants

Pathogenesis of Bronchopulmonary Dysplasia: Role of Oxidative Stress from 'Omics' Studies

Bronchopulmonary dysplasia (BPD) remains the most common respiratory complication of prematurity as younger and smaller infants are surviving beyond the immediate neonatal period. The recognition that oxidative stress (OS) plays a key role in BPD pathogenesis has been widely accepted since at least the 1980s. In this article, we examine the interplay between OS and genetic regulation and review 'omics' data related to OS in BPD. Data from animal models (largely models of hyperoxic lung injury) and from human studies are presented. Epigenetic and transcriptomic analyses have demonstrated several genes related to OS to be differentially expressed in murine models that mimic BPD as well as in premature infants at risk of BPD development and infants with established lung disease. Alterations in the genetic regulation of antioxidant enzymes is a common theme in these studies. Data from metabolomics and proteomics have also demonstrated the potential involvement of OS-related pathways in BPD. A limitation of many studies includes the difficulty of obtaining timely and appropriate samples from human patients. Additional 'omics' studies could further our understanding of the role of OS in BPD pathogenesis, which may prove beneficial for prevention and timely diagnosis, and aid in the development of targeted therapies.

Early versus late parenteral nutrition in term and late preterm infants: study protocol for a randomised controlled trial

BACKGROUND

Despite the wide use of parenteral nutrition (PN) in neonatal intensive care units (NICU), there is limited evidence regarding the optimal time to commence PN in term and late preterm infants. The recommendations from the recently published ESPGHAN/ESPEN/ESPR/CPEN and NICE guidelines are substantially different in this area, and surveys have reported variations in clinical practice. The aim of this randomised controlled trial (RCT) is to evaluate the benefits and risks of early versus late PN in term and late preterm infants.

METHODS/DESIGN

This study is a single-centre, non-blinded RCT in the NICU of Perth Children's Hospital, Western Australia.A total of 60 infants born ≥34 weeks of gestation who have a high likelihood of intolerance to enteral nutrition (EN) for at least 3-5 days will be randomised to early (day 1 or day 2 of admission) or late commencement (day 6 of admission) of PN after informed parental consent. In both groups, EN will be commenced as early as clinically feasible. Primary outcomes are plasma phenylalanine and plasma F2-isoprostane levels on Day 4 and Day 8 of admission. Secondary outcomes are total and individual plasma amino acid profiles, plasma and red blood cell fatty acid profiles, in-hospital all-cause mortality, hospital-acquired infections, length of hospital/NICU stay, z scores and changes in z scores at discharge for weight, height and head circumference, time to full EN, duration of respiratory (mechanical, non-invasive) support, duration of inotropic support, the incidence of hyper and hypoglycaemia, incidence of metabolic acidosis, liver function, blood urea nitrogen, and C-reactive protein (CRP).

DISCUSSION

This RCT will examine the effects of early versus late PN in term and late preterm infants by comparing key biochemical and clinical outcomes and has the potential to identify underlying pathways for beneficial or harmful effects related to the timing of commencement of PN in such infants.

TRIAL REGISTRATION

ANZCTR; ACTRN12620000324910 (3rd March 2020).

Association of maternal dietary patterns during pregnancy with small-for-gestational-age infants: Korean Mothers and Children's Environmental Health (MOCEH) study

BACKGROUND

Nutrients that support the desired growth and development of the fetus (i.e., micronutrients like folate, iron, and zinc) have been associated with birth outcomes, such as gestational age at delivery and birth weight.

OBJECTIVES

We characterized the maternal dietary patterns that explain the maximum variation in folate, iron, and zinc intakes in pregnant Korean women using reduced-rank regression (RRR) and investigated the association of these patterns with small-for-gestational-age (SGA) risk.

METHODS

A total of 1158 pregnant Korean women at 12-28 weeks of gestation and their newborns were recruited for the Mothers and Children's Environmental Health (MOCEH) study between 2006 and 2010. A semiquantitative FFQ was collected from the women, and RRR was used to derive their dietary patterns. Log-transformed maternal intakes of folate, iron, and zinc were selected as the intermediate response variables to extract dietary patterns. Infant birth outcome measurements were obtained from hospital records. Associations were assessed by logistic regression with adjustment for confounding factors.

RESULTS

Three dietary patterns were identified. Pattern 1, characterized by high intakes of grains, green/yellow and light-colored vegetables, kimchi, legumes, fruits, meat, eggs, fish, seaweeds, tofu/soymilk, yogurt, and nuts, was associated with a lower risk of SGA in the highest quartile than in the lowest quartile (OR: 0.36; 95% CI: 0.14, 0.94). Especially, maternal dietary pattern 1 was negatively related to high-sensitivity C-reactive protein in the blood and malondialdehyde concentrations in the urine. No association was observed between other dietary patterns and SGA.

CONCLUSION

Among pregnant Korean women, adherence to a dietary pattern characterized by high intakes of grains, green/yellow and light-colored vegetables, kimchi, legumes, fruits, meat, eggs, fish, seaweeds, tofu/soymilk, yogurt, and nuts is associated with a lower risk of delivering SGA infants.

Inflammatory biomarkers in very preterm infants during early intravenous paracetamol administration

BACKGROUND

Paracetamol promotes early closure of patent ductus arteriosus (PDA), and it may affect inflammation after preterm birth.

OBJECTIVE

The aim of this study was to evaluate the association between paracetamol treatment and serum inflammatory biomarkers in very preterm infants with respiratory distress.

STUDY DESIGN

The infants were randomly assigned to intravenous paracetamol or placebo during the first 4 days of life, and others received a lower dose of paracetamol unblinded. Serum samples were used for the analysis of 10 cytokines, C-reactive protein (CRP) and malondialdehyde (MDA). The impact of paracetamol on the biomarkers was evaluated, based on the levels during the early (<60 h) and the later (60-120 h) postnatal age.

RESULTS

Altogether, 296 serum samples from 31 paracetamol and 25 placebo group infants were analysed. Paracetamol had no effect on cytokine levels during the first 60 h when most induced PDA contractions took place. Later paracetamol treatment was associated with lower serum levels of several cytokines, including interleukin (IL-) 10, interferon gamma-induced protein (IP-) 10, and monocyte chemoattractant protein-1. CRP levels were lower in the paracetamol group during the early treatment. Amongst the infants who had severe morbidities, MDA was higher (p = .045), regardless of paracetamol treatment.

CONCLUSION

No significant differences in the cytokine levels were evident between the treatment and placebo groups. However, during early treatment, CRP levels were lower in the paracetamol group. To clarify whether this was due to a decrease in cardiopulmonary distress, or a distinct anti-inflammatory effect, requires further studies.

Combination Antioxidant/NSAID Therapies and Oral/Topical Ocular Delivery Modes for Prevention of Oxygen-Induced Retinopathy in a Rat Model

Given the complexity of oxygen-induced retinopathy (OIR), we tested the hypothesis that combination therapies and modes of administration would synergistically optimize efficacy for prevention of OIR. Newborn rats were exposed to neonatal intermittent hypoxia (IH) from the first day of life (P0) until P14 during which they received: (1) oral glutathione nanoparticles (nGSH) with topical ocular phosphate buffered saline (PBS); (2) nGSH with topical ocular Acuvail (ACV); (3) oral coenzyme Q10 (CoQ10) + ACV; (4) oral omega 3 polyunsaturated fatty acids (n-3 PUFAs) + ACV; (5) CoQ10 + n-3 PUFAs + PBS; or (6) CoQ10 + n-3 PUFAs + ACV. Treated groups raised in room air (RA) served as controls. At P14, pups were placed in RA with no treatment until P21. Retinal vascular pathology, ocular angiogenesis biomarkers, histopathology, and morphometry were determined. All combination treatments in IH resulted in the most beneficial retinal outcomes consistent with suppression of angiogenesis growth factors during reoxygenation/reperfusion and no significant adverse effects on somatic growth. nGSH + PBS also reversed IH-induced retinopathy, but had negative effects on growth. Simultaneously targeting oxidants, inflammation, and poor growth mitigates the damaging effects of neonatal IH on the developing retina. Therapeutic synergy with combination delivery methods enhance individual attributes and simultaneously target multiple pathways involved in complex diseases such as OIR.

Parenteral nutrition and oxidant stress in the newborn: A narrative review

There is strong evidence that oxidant molecules from various sources contaminate solutions of parenteral nutrition following interactions between the mixture of nutrients and some of the environmental conditions encountered in clinical practice. The continuous infusion of these organic and nonorganic peroxides provided us with a unique opportunity to study in cells, in vascular and animal models, the mechanisms involved in the deleterious reactions of oxidation in premature infants. Potential clinical impacts of peroxides infused with TPN include: a redox imbalance, vasoactive responses, thrombosis of intravenous catheters, TPN-related hepatobiliary complications, bronchopulmonary dysplasia and mortality. This is a narrative review of published data.

Oxidative Stress and Bronchopulmonary Dysplasia: Evidences From Microbiomics, Metabolomics, and Proteomics

Bronchopulmonary dysplasia is a major issue affecting morbidity and mortality of surviving premature babies. Preterm newborns are particularly susceptible to oxidative stress and infants with bronchopulmonary dysplasia have a typical oxidation pattern in the early stages of this disease, suggesting the important role of oxidative stress in its pathogenesis. Bronchopulmonary dysplasia is a complex disease where knowledge advances as new investigative tools become available. The explosion of the "omics" disciplines has recently affected BPD research. This review focuses on the new evidence coming from microbiomics, metabolomics and proteomics in relation to oxidative stress and pathogenesis of bronchopulmonary dysplasia. Since the pathogenesis is not yet completely understood, information gained in this regard would be important for planning an efficacious prevention and treatment strategy for the future.

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

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

Co-Enzyme Q10 and n-3 Polyunsaturated Fatty Acid Supplementation Reverse Intermittent Hypoxia-Induced Growth Restriction and Improved Antioxidant Profiles in Neonatal Rats

Neonatal intermittent hypoxia (IH) increases the risk for many morbidities in extremely low birth weight/gestational age (ELBW/ELGA) neonates with compromised antioxidant systems and poor growth. We hypothesized that supplementation with coenzyme Q10 (CoQ10, ubiquinol) or n-3 polyunsaturated fatty acids (PUFAs) during neonatal IH improves antioxidant profiles and somatic growth in neonatal rats. Newborn rats were exposed to two IH paradigms at birth (P0): (1) 50% O₂ with brief hypoxic episodes (12% O₂); or (2) room air (RA) with brief hypoxia, until P14 during which they received daily oral CoQ10 in olive oil, n-3 PUFAs in fish oil, or olive oil only from P0 to P14. Pups were studied at P14 or placed in RA until P21 for recovery from IH (IHR). Body weight and length; organ weights; and serum antioxidants and growth factors were determined at P14 and P21. Neonatal IH resulted in sustained reductions in somatic growth, an effect that was reversed with n-3 PUFAs. Improved growth was associated with higher serum growth factors. CoQ10 decreased superoxide dismutase (SOD) and glutathione, but increased catalase, suggesting reduced oxidative stress. Further studies are needed to determine the synergistic effects of CoQ10 and n-3 PUFA co-administration for the prevention of IH-induced oxidative stress and postnatal growth deficits.

Randomized trial of early erythropoietin supplementation after preterm birth: Iron metabolism and outcome

BACKGROUND

Excess of iron and oxidant injury shortly after birth may be associated with neonatal morbidities in preterm infants.

AIMS

The aim was to determine whether administration of erythropoietin without iron supplementation decreases iron load and morbidity.

STUDY DESIGN AND SUBJECTS

In a randomized trial, we administered erythropoietin (EPO 250IU/kg daily during the first 6days of life) or placebo to 39 preterm infants (BW 700-1500g, GA≤30.0weeks).

OUTCOME MEASURES

The iron status, postnatal morbidities and follow-up at the age of two years were investigated.

RESULTS

In all, 21 EPO- and 18 placebo-treated infants were recruited. A requirement of red blood cell transfusions during first 28days was similar between the study groups. EPO treatment decreased total serum iron concentration (p=0.035). EPO supplementation had no significant effect on serum transferrin receptors or reactive non-protein-bound iron. There were no differences in neonatal morbidity or in survival without major neurological abnormality at two years of age.

CONCLUSIONS

A 6-day course of EPO decreased the iron load in preterm infants. There was no change in reactive, non-protein bound iron plasma levels and no influence on the outcomes during early childhood. Whether the neurocognitive effects of early EPO treatment can be detectable later in childhood remained to be verified.

Emerging Clinical Benefits of New-Generation Fat Emulsions in Preterm Neonates

Soybean oil-based intravenous fat emulsions (IVFEs) have been the predominant parenteral nutrition IVFE used in the United States for neonates over the past 45 years. Even though this emulsion has proven useful in supplying infants with energy for growth and essential fatty acids, there have been concerns over its composition in the development of several morbidities, ranging from sepsis to liver disease, bronchopulmonary dysplasia, and impaired neurodevelopment and growth. The exact mechanisms that drive these morbidities in preterm infants are multifactorial, but potential contributors include high ω-6 (n-6) fatty acid composition, low docosahexaenoic acid and antioxidant supplementation, and the presence of potentially harmful nonnutritive components (eg, phytosterols). To address these issues, new-generation IVFEs with various types and amounts of fat have been developed containing greater amounts of the medium-chain fatty acids, long-chain polyunsaturated fatty acid, docosahexaenoic acid, lower concentrations of ω-6 polyunsaturated fatty acids, supplemental vitamin E, and low or negligible amounts of phytosterols. This review examines the clinical outcomes associated with different morbidities of parenteral nutrition in neonates who have received either soybean oil-based or new-generation IVFEs and addresses whether the proposed benefits of new-generation IVFEs have improved outcomes in the neonatal population.

Oxygen Saturation Targeting and Bronchopulmonary Dysplasia

Oxygen saturation targeting is widely used in neonatal intensive care, but the optimal target range in very preterm infants has been uncertain and is the subject of recent debate and research. This review briefly discusses the technology of oxygen monitoring and the role of oxygen toxicity in preterm infants. The background to the recent trials of oxygen saturation targeting in acute and continuing care of very preterm infants is reviewed, and the findings and implications of the recent trials, particularly with respect to bronchopulmonary dysplasia, are discussed.

Effects of supplemental oxygen on urinary 8-hydroxy-2'-deoxyguanosine levels in extremely low birth weight infants

As the effects of supplementary oxygen on urinary excretion of 8-hydroxy-2'-deoxyguanosine (8-OHdG) are poorly understood, urinary 8-OHdG levels (ng/mg creatinine) were determined longitudinally on the postnatal day (PND) 1, 3, and 30 in 16 neonates with birth weight < 1000 g. No supplementary oxygen was required in 9 neonates during the first 24 h of life. Urinary 8-OHdG level on PND 1 was inversely correlated with birth weight in these 9 neonates (P = 0.0323) and was higher in four with birth weight < 750 g than five with birth weight > 750 g (41.0 ± 6.9 vs. 5.6 ± 2.7, respectively, P = 0.0200). Median urinary 8-OHdG on PND 1 of these 9 neonates was significantly lower than that of 7 neonates with oxygen (9.3 vs. 60.2, respectively), although there were no significant differences in clinical background, such as birth weight, between the two groups. Five of the 9 did not require supplemental oxygen at all during the first 30 days of life. Median urinary 8-OHdG levels were consistently significantly lower in the 5 neonates than in 11 neonates with oxygen transiently or persistently (9.3 vs. 54.6, 19.1 vs. 61.4, and 28.3 vs. 145 on PND 1, 3, and 30, respectively), although there were no differences in clinical background, such as birth weight, between the two groups. Urinary 8-OHdG on PND 30 was significantly positively correlated with supplemental oxygen dose on PND 30 (P < 0.0001), but not with birth weight in the 16 neonates. These results suggest that higher supplemental oxygen tension caused higher urinary 8-OHdG in this population.

Adduct of malondialdehyde to hemoglobin: a new marker of oxidative stress that is associated with significant morbidity in preterm infants

Preterm infants (PT) are particularly exposed to oxidative stress (OS), and a blood-sparing marker, the malondialdehyde adduct to hemoglobin (MDA-Hb), may be useful to accurately assess OS-related neonatal morbidity. In a prospective study, MDA-Hb concentrations were assessed in two groups of PT, one with and one without severe neonatal morbidity as estimated by a composite index of severe morbidity (ISM). All PT born in a single tertiary care NICU (<32 weeks and birth weight <1500 g) were consecutively included. MDA-Hb and blood glutathione (GSH) concentrations were measured by liquid chromatography-mass spectrometry during the first 6 weeks of life. Linear regressions and a multilevel model were fitted to study the relationship between MDA-Hb or GSH and ISM. Of the 83 PT (mean ± SD: 28.3 ± 2 weeks, 1089 ± 288 g), 21% presented severe neonatal morbidity. In the multivariate model, MDA-Hb concentrations were significantly higher in the ISM+ group than in the ISM– group during the first 6 weeks of life (P = 0.009). No significant difference in GSH concentrations was observed between groups (P = 0.180). MDA-Hb is a marker of interest for estimating oxidative stress in PT and could be useful to evaluate the impact of strategies to improve perinatal outcomes.

Maternal and fetal indicators of oxidative stress in various obstetric complications

The present study demonstrates the incidence of increased lipid peroxidation and protein oxidation in both maternal and fetal erythrocytes as markers of oxygen radical activity in different complications of pregnancy. In fetuses born after premature rupture of membranes, lipid peroxidation was significantly elevated as indicated by increased malondialdehyde levels (p<0.05) as compared to controls. Proteolytic activity in the erythrocytes of mothers in this group was also significantly high (p<0.01). In patients delivered by lower segment cesarian section, lipid peroxidation and proteolytic activity in maternal erythrocytes were significantly high (p<0.05 and p<0.001 respectively). In patients with prolonged second stage of labour, lipid peroxidation and proteolytic activity in maternal erythrocytes was significantly higher than in controls (p<0.001 and p<0.05 respectively). In this group, endogenous protein damage due to oxidative stress was significantly high both in the mother and the fetus (p<0.001 and p<0.05 respectively).

Maternal and fetal indicators of oxidative stress during intrauterine growth retardation (IUGR)

The present study demonstrates the possibility of increased lipid peroxidation and protein oxidation in both maternal and fetal erythrocytes as markers of oxygen radical activity during intrauterine growth retardation. The erythrocyte MDA levels were significantly elevated in mothers of IUGR babies when compared to controls (p<0.01). The endogenous protein damage due to oxidative stress was significantly higher in IUGR mothers when compared to controls (p<0.05). Similarly the proteolytic activity in erythrocyte lysates against oxidatively damaged hemoglobin was significantly increased in mothers of IUGR babies compared to controls (p<0.001).In fetuses born with IUGR, both lipid peroxidation and proteolytic activity were significantly increased when compared to normal newborns (p<0.01).The result of this study indicates that oxidative stress was induced both in IUGR babies and their mothers which is manifested as increased lipid peroxidation and protein oxidant damage.

Breath pentane as a potential biomarker for survival in hepatic ischemia and reperfusion injury--a pilot study

Background

Exhaled pentane, which is produced as a consequence of reactive oxygen species-mediated lipid peroxidation, is a marker of oxidative stress. Propofol is widely used as a hypnotic agent in intensive care units and the operating room. Moreover, this agent has been reported to inhibit lipid peroxidation by directly scavenging reactive oxygen species. In this study, using a porcine liver ischemia-reperfusion injury model, we have evaluated the hypothesis that high concentrations of breath pentane are related to adverse outcome and that propofol could reduce breath pentane and improve liver injury and outcome in swine in this situation.

Methodology/Principal Findings

Twenty male swine were assigned to two groups: propofol (n = 10) and chloral hydrate groups (n = 10). Hepatic ischemia was induced by occluding the portal inflow vessels. Ischemia lasted for 30 min, followed by reperfusion for 360 min. Exhaled and blood pentane concentrations in the chloral hydrate group markedly increased 1 min after reperfusion and then decreased to baseline. Breath and blood pentane concentrations in the propofol group increased 1 min after reperfusion but were significantly lower than in the chloral hydrate group. A negative correlation was found between breath pentane levels and survival in the chloral hydrate group. The median overall survival was 251 min after reperfusion (range 150–360 min) in the chloral hydrate group. All of the swine were alive in the propofol group.

Conclusions

Monitoring of exhaled pentane may be useful for evaluating the severity of hepatic ischemia-reperfusion injury and aid in predicting the outcome; propofol may improve the outcome in this situation.

Lipid peroxidation in all-in-one admixtures for preterm neonates: impact of amount of lipid, type of lipid emulsion and delivery condition

AIM

To evaluate the effect of lipid emulsion composition and delivery condition on lipid peroxidation in typical all-in-one parenteral admixtures for preterm neonates.

METHODS

Malonedialdehyde (MDA) concentrations were assessed in different all-in-one admixtures. We evaluated the effects of fat blend (three lipid emulsions) and the amount of lipids, as well as the effects of protecting bags and/or tubing from ambient light and storage for 72 h. MDA was measured by liquid chromatography/mass spectrometry.

RESULTS

Three hundred and sixty samples were collected from 114 admixtures. Neither the type of lipid (p = 0.43) nor the interaction between light and type of lipid (p = 0.49) had any influence on final MDA concentrations, but the increase in MDA concentration at 24 h (T(24)) was related to light exposure (p < 0.001). The increase in MDA concentration was related to the increase in lipid amount in the admixture at T(0) (r = 0.77) and T(24) (r = 0.86). MDA concentrations in solutions stored for 72 h showed no significant increase, with no difference between the three lipid emulsions (p = 0.69).

CONCLUSION

All-in-one admixtures may be interesting for the parenteral nutrition of preterm neonates. Protection from light and restricting the amount of lipid to what is required for appropriate energy provision are essential to limit lipid peroxidation.

Identification of a radical formed in the reaction mixture of rat brain homogenate with a ferrous ion/ascorbic acid system using HPLC–EPR and HPLC–EPR–MS

Identification of a free radical is performed for the reaction mixture of rat brain homogenate with a ferrous ion/ascorbic acid system using EPR, high performance liquid chromatography-electron paramagnetic resonance spectrometry (HPLC-EPR) and high performance liquid chromatography-electron paramagnetic resonance-mass spectrometry (HPLC-EPR-MS). EPR measurements of the reaction mixtures showed prominent signals with hyperfine coupling constants (alpha(N) = 1.58 mT and alpha(H)beta = 0.26 mT). No EPR spectrum was detectable without rat brain homogenate, suggesting that the radical is derived from rat brain homogenate. An HPLC-EPR analysis of the reaction mixture showed a peak with retention time of 33.7 min. An HPLC-EPR-MS analysis of the peak gave two ions at m/z 224 and 137, suggesting that alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN)/ethyl radical adduct forms in the reaction mixture.

Resuscitation of preterm infants with reduced oxygen results in less oxidative stress than resuscitation with 100% oxygen

The objective of this study was to determine the effects of the level of inhaled oxygen during resuscitation on the levels of free radicals and anti-oxidative capacity in the heparinized venous blood of preterm infants. Forty four preterm infants <35 weeks of gestation with mild to moderate neonatal asphyxia were randomized into two groups. The first group of infants were resuscitated with 100% oxygen (100% O(2) group), while in the other group (reduced O(2) group), the oxygen concentration was titrated according to pulse oximeter readings. We measured total hydroperoxide (TH) and redox potential (RP) in the plasma within 60 min of birth. The integrated excessive oxygen ( summation operator(FiO(2)-0.21) x Time(min)) was higher in the 100% O(2) group than in the reduced O(2) group (p<0.0001). TH was higher in the 100% O(2) group than in the reduced O(2) group (p<0.0001). RP was not different between the 100% O(2) and reduced O(2) groups (p = 0.399). RP/TH ratio was lower in the 100% O(2) group than in the reduced O(2) group (p<0.01). We conclude that in the resuscitation of preterm infants with mild to moderate asphyxia, oxidative stress can be reduced by lowering the inspired oxygen concentration using a pulse oximeter.

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.

Oxidative stress in perinatal asphyxia

Oxygen free radicals may cause tissue injury in perinatal asphyxia. We measured plasma and cerebrospinal fluid levels of malondialdehyde and plasma levels of glutathione peroxidase, catalase, and superoxide dismutase in 50 term newborns with perinatal asphyxia and eight newborns without asphyxia. Neonates with sepsis, major congenital malformations, and hemolytic disease were excluded. The levels of plasma and cerebrospinal fluid malondialdehyde, as well as of plasma glutathione peroxidase, catalase, and superoxide dismutase, were significantly higher in newborns with perinatal asphyxia, and demonstrated a progressive increase with greater severity of hypoxic ischemic encephalopathy. Higher levels of plasma and cerebrospinal fluid malondialdehyde and plasma catalase were documented in newborns who died from hypoxic ischemic encephalopathy, compared with those who survived, but no such difference was found in plasma levels of glutathione peroxidase and superoxide dismutase. The data of the present study suggest that, despite the increased activities of antioxidant enzymes in perinatal asphyxia, these neonates experience higher degrees of oxidative stress, as evidenced by increased levels of plasma and cerebrospinal fluid malondialdehyde. Hence, oxygen free radicals can be considered to play a significant role in the pathophysiology of perinatal asphyxia.

[Oxidative stress in the neonatal lung disease]

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

Fluidity and oxidative stress in erythrocytes from very low birth weight infants during their first 7 days of life

OBJECTIVE

To study the evolution of lipid peroxidation, enzymatic antioxidants response, lipid profile and membrane fluidity in erythrocytes from very low birth weight (VLBW) infants during their first 7 days of extra-uterine life.

STUDY DESIGN

One hundred and twenty infants were selected and divided in two groups according to their weight and gestational age. Hydroperoxides, fatty-acid profile, fluidity (DPH and TMA-DPH) and catalase, SOD and GPx activities were measured in erythrocytes.

RESULTS

VLBW group showed higher concentration of hydroperoxides and lower membrane fluidity during the first 72 h, lower SOD activity during the first 3 h and higher GPx activity during the first 7 days of life. Also, this group showed lower n-3 polyunsaturated fatty-acids percentage with respect to the term group.

CONCLUSION

Erythrocytes from VLBW infants showed higher oxidative damage and lower fluidity in their membranes, at least during the first 3 days of extra-uterine life, which may cause alterations in their functions and flexibility.

Lipid peroxidation in cord blood and neonatal outcome

BACKGROUND

Periventricular-intraventricular hemorrhage, necrotizing enterocolitis, chronic lung disease and retinopathy of prematurity have been referred to as oxygen radical diseases (ORD) because they are thought to be related to excess oxidant stress relative to anti-oxidant defenses in premature infants. 8-Isoprostane is a product of lipid peroxidation that can be used as a measure of free radical exposure or injury. The aim of the present study was to determine whether fetal oxidant stress is associated with adverse effects in preterm infants.

METHODS

Mothers delivering at gestational age <37 weeks were recruited. Umbilical arterial and venous cord blood samples were collected and 8-isoprostane levels measured. Levels of 8-isoprostane in cord blood were correlated with maternal and perinatal variables, neonatal mortality, and the development of one or more ORD.

RESULTS

Umbilical cord venous, but not arterial, 8-isoprostane levels were associated with mortality and the development of one or more of the ORD. After controlling for gestational age, for each unit change in the log value of 8-isoprostane in venous cord blood the odds of mortality were 12 (95% confidence interval [CI]: 1-223) and oxygen radical disease were 2.7 (95%CI: 1-7.2). Isoprostane levels were not related to gender, method of delivery, use of maternal magnesium or steroids, pregnancy-induced hypertension, or delivery room resuscitation.

CONCLUSION

Oxidant stress in utero may be an important determinant of mortality and morbidity in preterm infants. Elevated umbilical venous isoprostane levels suggest that oxidative injury to maternal and placental tissues predispose to adverse neonatal outcomes.

Retinopatía del prematuro y estrés oxidativo

INTRODUCTION

There is some evidence that retinopathy of prematurity is due to excessive oxidative stress on the developing retina caused by high free radical production or reduced ability to eliminate these radicals.

OBJECTIVE

To determine the relationship between high levels of oxidative stress and retinopathy of prematurity.

MATERIAL AND METHODS

A prospective cohort study was designed. Fifty premature infants of less than 33 weeks' gestational age were included. Serum lipoperoxide levels were determined as a measure of oxidative stress. Samples were taken once a week for 1 month, starting from the first week of life. The results of all four samples were compared between infants who developed any degree of retinopathy of prematurity and those without it. Ophthalmological examinations were performed after the fourth week of life.

RESULTS

The incidence of retinopathy of prematurity was 22 % (11/50). The mean values of all the samples showed a significant difference between infants who developed retinopathy of prematurity (5.44 +/- 1.30 nmol/ml) and those who did not (2.94 +/- 0.89 nmol/ml, p = 0.0001). The relative risk of developing retinopathy of prematurity with high serum lipoperoxide levels was 5.15, 5.63, 4.15 and 12.70 for each of the weekly samples.

CONCLUSIONS

There is an association between high serum lipoperoxide levels, as a measure of oxidative stress, and the incidence of retinopathy of prematurity.

Early inhaled nitric oxide improves oxidative balance in very preterm infants

Inhaled nitric oxide (iNO) improves oxygenation in premature infants, but concern has been raised about its potential oxidative toxicity. We designed this study to assess the oxidative balance in premature infants who were exposed to low dose iNO and the relationship with their clinical outcome on day 28 of life. A total of 274 infants who were <32 wk gestation were randomized at birth to receive 5 ppm of iNO if they presented with hypoxemic respiratory failure. Nonhypoxemic infants were studied as the reference group. Blood samples were withdrawn 24 h apart, within the first 4 d of life, to assess malondialdehyde (MDA) concentration as oxidative stress marker and total plasmatic glutathione (GSH), intraerythrocyte GSH peroxidase, and GSH reductase activities as antioxidant defenses. After 24 h, the rise in MDA was blunted in the iNO group compared with controls and was close to the reference infants. Conversely, GSH was more stable in the iNO group, when there was no difference for the GSH peroxidase and GSH reductase activities. On day 28, Oxygen dependence was linked with a higher increase in MDA as was the risk for death, whereas intraventricular hemorrhage was associated with a higher initial drop in GSH. Early low-dose iNO in hypoxemic preterm infants improves oxidative balance and seems to be clinically beneficial up to day 28 of life.

Antioxidant defenses in the preterm lung: role for hypoxia-inducible factors in BPD?

Pulmonary antioxidants and their therapeutic implications have been extensively studied during past decades. The purpose of this review is to briefly summarize the key findings of these studies as well as to elaborate on some novel approaches with respect to potential preventive treatments for neonatal chronic lung disease bronchopulmonary dysplasia (BPD). Such new ideas include, for example, modification of transcription factors governing the hypoxic response pathways, important in angiogenesis, cell survival, and glycolytic responses. The fundamental strategy behind that approach is that fetal lung normally develops under hypoxic conditions and that this hypoxic, growth-favoring environment is interrupted by a premature birth. Importantly, during fetal lung development, alveolar development appears to be dependent on vascular development. Therefore, enhancement of signaling factors that occur during hypoxic fetal life ('continued fetal life ex utero'), including angiogenic responses, could potentially lead to improved lung growth and thereby alleviate the alveolar and vascular hypoplasia characteristic of BPD.

The effect of gestational age and labour on markers of lipid and protein oxidation in cord plasma

There are many potential sources of reactive oxidants around the time of birth and pre-term infants are considered to be particularly vulnerable to oxidative injury. To gain insight into these processes, we have measured biomarkers of lipid and protein oxidation in umbilical cord plasma and related concentrations to mode of delivery and gestational age. Protein carbonyls were measured by ELISA and malondialdehyde (MDA) by HPLC after reaction with thiobarbituric acid, for 54 pre-term (< or = 36 weeks gestational age) and 43 term infants. Protein carbonyls were significantly lower in pre-term (median for < 32 weeks gestational age 0.048nmol/mg protein) than in term infants (0.105 nmol/mg, p = 0.004), and were unrelated to mode of delivery. In contrast, MDA concentrations were higher in the very pre-term (<32 weeks gestation) group (2.47 compared with 1.83 microM for term infants, p < 0.0001). MDA concentrations were higher in infants who were born with labour compared with elective caesarean section. Pre-eclampsia in the mother was associated with higher cord blood MDA concentrations. The MDA results are consistent with other studies of this marker and could be interpreted as indicating increased oxidative stress associated with prematurity and labour. However, the lower protein carbonyls in pre-term infants would lead to an opposite interpretation. More information is needed on the source and fate of these and other biomarkers before drawing strong conclusions on how they reflect oxidative stress in this and other clinical situations.

Pulmonary antioxidant concentrations and oxidative damage in ventilated premature babies

OBJECTIVE

To determine the relation between lipid peroxidation and the antioxidants ascorbate, urate, and glutathione in epithelial lining fluid in ventilated premature babies, and to relate the biochemical findings to clinical outcome.

DESIGN

A cohort study conducted between January 1999 and June 2001.

SETTING

A NHS neonatal intensive care unit.

PATIENTS

An opportunity sample of 43 ventilated babies of less than 32 weeks gestation.

MAIN OUTCOME MEASURES

The duration of supplementary oxygen according to the definition of bronchopulmonary dysplasia (BPD; oxygen dependency at 36 weeks gestational age).

METHODS

Epithelial lining fluid was sampled by bronchoalveolar lavage. Ascorbate, urate, glutathione, and malondialdehyde (a marker of lipid peroxidation) were measured.

RESULTS

Babies who developed BPD had significantly lower initial glutathione concentrations (mean (SEM) 1.89 (0.62) v 10.76 (2.79) microM; p = 0.043) and higher malondialdehyde concentrations (mean (SEM) 1.3 (0.31) v 0.345 (0.09) microM; p < 0.05) in the epithelial lining fluid than those who were not oxygen dependent. These variables were poor predictors of the development of BPD. Gestational age, endotracheal infection, and septicaemia had good predictive power. The level of oxidative damage was associated with the presence of endotracheal infection/septicaemia rather than inspired oxygen concentration.

CONCLUSIONS

Endotracheal infection, septicaemia, and gestational age, rather than antioxidant concentrations, are the most powerful predictors of the development of BPD.

Plasma 8-isoprostane is increased in preterm infants who develop bronchopulmonary dysplasia or periventricular leukomalacia

Our aim was to assess the plasma free 8-epi-prostaglandin F(2alpha) (8-isoprostane) and ascorbyl radical as risk indicators for oxidative damage in extremely low birth weight infants (ELBWIs) and the effect of N-acetylcysteine (NAC) on these markers. Plasma samples were collected on days 3 and 7 of life from infants who were enrolled in a randomized, controlled trial in which i.v. NAC or placebo was administered to ELBWIs during the first week of life, with the aim of preventing bronchopulmonary dysplasia (BPD). Plasma 8-isoprostane was analyzed in 83 infants using an enzyme immunoassay kit. Ascorbyl radical concentration was measured in 61 infants with electron spin resonance spectroscopy. The 8-isoprostane concentrations were similar in the NAC and placebo groups. In infants who later developed BPD or died (n = 29), the median (range) 8-isoprostane concentration was significantly higher (p = 0.001) on day 3 and day 7 [50.0 pg/mL (19-360) and 57.0 pg/mL (14-460), respectively] than in survivors without BPD [n = 54; 34.5 pg/mL (5-240) and 39.5 pg/mL (7-400), respectively]. The 8-isoprostane levels increased significantly more (p < 0.05) in infants who later developed periventricular leukomalacia. NAC treatment or the later development of BPD was not related to the ascorbyl radical levels. The ascorbyl radical level decreased significantly in all groups from day 3 to day 7, but the difference between the groups was not significant. The mean (SD) ascorbyl radical level on day 3 was significantly higher (p < 0.01) in infants who later developed periventricular leukomalacia [287 (124) versus 194 (90)]. These data suggest that plasma 8-isoprostane could serve as a marker in assessing the risk for BPD development in ELBWIs.

Suppressive effects of breast milk on oxidative DNA damage in very low birthweight infants

BACKGROUND

Human milk contains many kinds of antioxidant and is considered to prevent diseases mediated by oxygen free radicals in very low birthweight (VLBW) infants.

AIMS

To examine the antioxidant effects of breast milk in VLBW infants by determining urinary 8-hydroxydeoxyguanosine (8-OHdG) excretion, which is known to be a non-invasive marker for in vivo oxidative DNA damage.

METHODS

Urinary 8-OHdG concentrations were measured in 15 breast fed and 14 formula fed VLBW infants at 2, 7, 14, and 28 days of age.

RESULTS

Urinary 8-OHdG excretion at 14 and 28 days of age was significantly lower than at 2 and 7 days of age in the breast fed group, and significantly lower than in the formula fed group.

CONCLUSION

This is the first direct evidence of the antioxidant action of human milk in VLBW infants.

Role of redox in fetal development and neonatal diseases

In the cell, reducing and oxidizing molecules modulate the redox state. In embryonic and fetal growth, increased oxidative stress may be detrimental, but an oxidized state can also be beneficial. This is because redox may also affect key transcription factors that can alter gene expression during development. In addition, redox may impact on placentation and amniotic membrane integrity during pregnancy. Lastly, diseases of prematurity, such as necrotizing enterocolitis, retinopathy of prematurity, and chronic lung disease, may be modulated by redox in the premature. Because antioxidant therapies have not necessarily modified the outcome of these diseases, some debate exists as to this. Nonetheless, sufficient evidence suggests a role for redox throughout embryonic, fetal, and postnatal development. This evidence will be explored here.

N-acetylcysteine does not prevent bronchopulmonary dysplasia in immature infants: a randomized controlled trial

OBJECTIVE

To evaluate whether N-acetylcysteine (NAC) infusion during the first week of life reduces the risk of death or bronchopulmonary dysplasia (BPD) in infants with extremely low birth weight. Study design In a Nordic multicenter, double-blind trial, infants (n=391) weighing 500 to 999 g and on ventilator or nasal continuous positive airway pressure were randomized before the age of 36 hours to receive NAC 16 to 32 mg/kg/d (n=194) or placebo (n=197) intravenously for 6 days. Primary end points were death or BPD, defined as supplementary oxygen requirement at 36 weeks' gestational age.

RESULTS

There was no difference in the combined incidence of the primary end points death or BPD, 51% vs. 49%, between the NAC group and control group. Also similar was the incidence of BPD in survivors at 36 weeks' gestational age, 40% vs. 40%, and the mean oxygen requirement at the age of 28 days, 31.2% vs. 30.7%, respectively. The severity of BPD was similar in both groups.

CONCLUSIONS

A 6-day course of intravenous N-acetylcysteine at the dosage used does not prevent BPD or death in infants with extremely low birth weight.

New biomarkers of fetal-neonatal hypoxic stress

The complex pathophysiological mechanisms underlying perinatal hypoxia make it difficult to define early markers of severe hypoxia-ischemia encephalopathy. However, as progress in the development of neuroprotective therapeutic measures continues, the early identification of neonates at risk of severe hypoxic-ischemic encephalopathy is an important goal for appropriate decision making. Although the timing of perinatal hypoxic brain damage may vary and is sometimes unknown, high levels of non-protein-bound iron and high nucleated red blood cell counts in cord blood indicate an antepartum origin of neurological impairment, because they can occur only as a consequence of a pre-existing asphyxic event.

CONCLUSION

The combined assessment of nucleated red blood cells and non-protein-bound iron at birth seems extremely useful for the early identification of newborns at high risk of brain damage. Activin A also seems to be a reliable marker of perinatal hypoxia. Prospective long-term follow-up studies are needed to verify their predictive role.

Pulmonary outcome at 1 year corrected age in premature infants treated at birth with recombinant human CuZn superoxide dismutase

OBJECTIVE

To examine whether treatment of premature infants with intratracheal recombinant human CuZn superoxide dismutase (r-h CuZnSOD) reduces bronchopulmonary dysplasia and improves pulmonary outcome at 1 year corrected age.

DESIGN

Three hundred two premature infants (600-1200 g birth weight) treated with exogenous surfactant at birth for respiratory distress syndrome were randomized to receive either intratracheal r-h CuZnSOD (5 mg/kg in 2 mL/kg saline) or placebo every 48 hours (as long as intubation was required) for up to 1 month of age. Short-term, as well as longer-term pulmonary outcome was assessed.

RESULTS

There were no differences between groups in the incidence of death or the development of bronchopulmonary dysplasia (oxygen requirement with an Edwards chest radiograph score of >or=3) at 28 days of life or 36 weeks' postmenstrual age. r-h CuZnSOD was well-tolerated and not associated with significant increases in any adverse event. At a median of 1 year corrected age, health assessments and physical examinations were performed on 209 (80%) surviving infants, with complete data available on 189 infants. Thirty-seven percent of placebo-treated infants had repeated episodes of wheezing or other respiratory illness severe enough to require treatment with asthma medications such as bronchodilators and/or corticosteroids compared with 24% of r-h CuZnSOD-treated infants, a 36% reduction. In infants <27 weeks' gestation, 42% treated with placebo received asthma medications compared with 19% of r-h CuZnSOD-treated infants, a 55% decrease. Infants <27 weeks' gestation who received r-h CuZnSOD also had a 55% decrease in emergency department visits and a 44% decrease in subsequent hospitalizations. Growth measurements and the results of physical examinations were comparable between groups.

CONCLUSIONS

These data indicate that treatment at birth with r-h CuZnSOD may reduce early pulmonary injury, resulting in improved clinical status when measured at 1 year corrected age. r-h CuZnSOD appears to be a safe and effective therapy that improves pulmonary outcome in high-risk premature infants.

3-Chlorotyrosine as a marker of protein damage by myeloperoxidase in tracheal aspirates from preterm infants: association with adverse respiratory outcome

Oxidative injury is implicated in the development of chronic lung disease in preterm infants with respiratory distress. However, direct evidence of a causal role is limited and the source of reactive oxidants has not been identified. We have previously shown that protein carbonyl levels in tracheal aspirates correlate positively with myeloperoxidase, suggesting that neutrophil oxidants could be the source of this protein injury. We have extended these observations by measuring 3-chlorotyrosine, a specific biomarker of the neutrophil oxidant, hypochlorous acid, in tracheal aspirate proteins (144 samples) from 69 infants with birth weight <1500 g. 3-Chlorotyrosine levels were higher in these infants than in larger infants without respiratory distress (median 83 compared with 13 micromol/mol tyrosine). They correlated strongly with myeloperoxidase activity (correlation coefficient 0.75, p < 0.0001) and to a lesser extent with protein carbonyls. 3-Chlorotyrosine levels (at 1 wk after birth) correlated negatively with birth weight or gestational age. They were significantly higher in infants who developed chronic lung disease (oxygen requirement at 36 wk postmenstrual age) than in those who did not (median 88 and 49 micromol/mol tyrosine, respectively) and correlated with days of supplemental oxygen. 3-Chlorotyrosine was also significantly higher in infants who had lung infection or were Ureaplasma urealyticum positive. Our results are the first evidence that chlorinated proteins are produced in the lungs of premature infants and that they are higher in infection. The higher 3-chlorotyrosine levels in infants who develop chronic lung disease suggest that neutrophil oxidants contribute to the pathology of this disease.

Bronchopulmonary dysplasia-oxidative stress and antioxidants

There is increasing evidence that oxidative stress is implicated in the development of bronchopulmonary dysplasia. Several important factors contribute to augmented oxidative stress in the newborn and especially the preterm infant: first, because of its immaturity, the lung of preterm infants is frequently exposed to oxygen therapy and hyperoxia. Second, the antioxidant defense and its ability to be induced during an hyperoxic challenge are impaired. Third, the preterm infant has an increased susceptibility to infection and inflammation, which increases oxidative stress. Fourth, free iron, which catalyzes the production of toxic reactive oxygen species, can be detected in preterm infants. The molecular and cellular mechanisms for free radical-induced injury are now understood in more detail, and it is clear that oxidative stress plays an important role in triggering apoptosis, in serving as second messenger and in signal transduction. This new insight might lead to novel and efficient therapies. So far, there has been no significant breakthrough regarding antioxidant therapies. Care should, however, be exercised in supplementing the preterm infant with antioxidants since this may affect growth and development.

Antioxidants as therapy in the newborn: some words of caution

Reactive oxygen and nitrogen species are considered to play a major role in the pathogenesis of a wide range of human disorders. This may be a particularly important pathogenetic mechanism in the newborn nursery. The phrase "oxygen radical disease of prematurity" has been coined to collectively describe a wide range of neonatal disorders based on the belief that premature newborns are deficient in antioxidant defenses at a time when they are subjected to acute and chronic oxidant stresses. This belief has led to a number of clinical trials of antioxidant therapies being undertaken in neonatal patients. The realization that reactive oxygen species play a critical role in neonatal illnesses has only recently been paralleled by an increased understanding of their physiologic roles. A major concern is that effective scavenging of reactive oxygen species, to attenuate their toxic effects, will also inhibit essential cellular functions such as growth in potential target organs such as lung, brain, intestine, and retina.

Oxidative stress and increased type-IV collagenase levels in bronchoalveolar lavage fluid from newborn babies

Oxidative stress may increase lung permeability by up-regulation of matrix-metalloproteinase-9 (MMP-9), a type-IV collagenase that can disrupt alveolar basement membranes. We have compared a marker of oxidative stress (protein carbonyl residues) with levels of MMP-9 and its inhibitor, tissue inhibitor of metalloproteinase-1 (TIMP-1), in bronchoalveolar lavage samples from newborn babies. Bronchoalveolar lavage samples (n = 87, two from each time point) were taken in the first 6 postnatal days from 41 ventilated babies: 18 of <29 wk gestation, 10 of 29-36 wk, 9 term with persistent fetal circulation, and 4 term without lung disease. Respiratory disease severity at the time of bronchoalveolar lavage was assessed using the arterial-alveolar oxygen tension ratio. One sample from each time point was used for the measurement of MMP-9 by zymography and TIMP-1 by ELISA. The second sample was used to measure carbonyl group concentrations, also using an ELISA. Correlations were calculated between protein carbonyls, arterial-alveolar oxygen tension ratio, and MMP-9 and TIMP-1 concentrations. Significant correlations were found between carbonyl concentrations and arterial-alveolar oxygen tension ratio (r = -0.325, p = 0.0031, n = 81), MMP-9 (r = 0.331, p < 0.0029, n = 79), and TIMP-1 (r = 0.436, p < 0.0001, n = 87). Worsening respiratory disease in newborn babies is associated with increased carbonyl concentrations in neonatal bronchoalveolar lavage fluid, and these correlated with MMP-9 and TIMP-1 levels. Increased oxidative stress may damage the lung by increasing type-IV collagenase activity, causing disruption of the extracellular matrix.