Simona Negro

Oxidative stress and antioxidant strategies in newborns

Oxidative stress (OS) is defined as an unbalance between prooxidant and antioxidant factors that can lead to cellular and tissue damage.The newborn, especially if preterm, is highly prone to OS and to the toxic effect of free radicals (FR). At birth, the newborn is exposed to a relatively hyperoxic environment caused by an increased oxygen bioavailability with greatly enhanced generation of FR. Additional sources (inflammation, hypoxia, ischemia, glutamate, and free iron release) occur magnifying OS. In the preterm baby, the perinatal transition is accompanied by the immaturity of the antioxidant systems and the reduced ability to induce efficient homeostatic mechanisms designed to control overproduction of cell-damaging FR. Improved understanding of the pathophysiological mechanism involved in perinatal brain lesions helps to identify potential targets for neuroprotective interventions, and the knowledge of these mechanisms has enabled scientists to develop new therapeutic strategies that have confirmed their neuroprotective effects in animal studies. Considering the growing role of OS in preterm newborn morbidity in respect to the higher risk of FR damage in these babies, a strict control of oxygen administration, lutein, melatonin, and hypothermia show great promise as potential neuroprotectans. This review provides an overview of the pathogenesis of free radical-mediated diseases of the newborn and the antioxidant strategies for now tested to reduce the OS and its damaging effects.

The use of melatonin in hypoxic-ischemic brain damage: an experimental study

Objective: Oxidative stress (OS) plays a key role in perinatal brain damage. The aim of this study is to evaluate the effectiveness of melatonin as a neuroprotective drug by investigating the influence of melatonin on OS and inflammation biomarkers in an animal model of cerebral hypoxia-ischemia. Methods: Five minutes after hypoxic-ischemic (HI) injury melatonin was administered to 28 rats (HI-Mel group). At the same time, 28 hypoxic-ischemic rats were vehicle-treated (V-HI group). Five rats were used as sham operated controls (CTL). OS biomarkers: isoprostanes (IsoPs), neuroprostanes (NPs) and neurofurans (NFs), and microglial activation markers (glial fibrillary acidic protein [GFAP] and monoclonal antirat CD68 [ED1]) were measured in the cerebral cortex of the two lobes. Results: A significant increase of IsoPs on the left lobe was observed in V-HI after 1 hour (h) from HI injury (p < 0.001); a significant increase of NPs on both side (p < 0.05) and a significant increase of NFs on the left (p < 0.05) were also observed in V-HI after 24 h. A significant increase of IsoPs on the left (p < 0.05) and of NPs on both lobes (p < 0.05) were observed in HI-Mel after 48 h. The ED1 and GFAP expression was lower in the HI-Mel brain tissue. Conclusions: Melatonin reduces OS and inflammatory cells recruitment and glial cells activation in cerebral cortex after neonatal HI damage. These results lay the groundwork for future clinical studies in infants.

May oxidative stress biomarkers in cord blood predict the occurrence of necrotizing enterocolitis in preterm infants

Introduction: Oxidative stress (OS) is strongly involved in the pathogenesis of many preterm newborn diseases; this is due to the low efficiency of neonatal antioxidant systems unable to counteract the harmful effects of free radicals (FRs). Hypoxic-ischemic events and inflammation, involved in necrotizing enterocolitis (NEC) pathogenesis, are responsible of the overproduction of FRs, generating OS. Aim: To test the hypotesis that OS markers levels in cord blood may early identify the newborns at high risk to develop NEC. Materials and methods: 332 preterm newborns of gestational age (GA) between 24 and 33 week and birth weight (BW) between 460 and 2540 g were consecutively recruited in three european neonatal intensive care units. Markers of potential OS risk: non-protein bound iron (NPBI), and markers of FRs damage: advanced oxidation protein products (AOPP) and total hydroperoxides (TH), were measured in the cord blood. Associations between NEC and OS markers were checked through inferential analysis. Results: Out of 332 preterm babies, 29 developed NEC. Babies with NEC had a BW and a GA significantly lower than healthy babies. AOPP, TH and NPBI cord blood levels were significantly higher in babies with NEC than in babies without (respectively mean AOPP = 28.05 ± 21 vs 15.80 ± 7.14; p < 0.05; TH = 154.48 ± 84.67 vs 107.40 ± 61.01; p < 0.05; NPBI = 2.21 ± 3.98 vs 0.95 ± 1.59; p < 0.05). Conclusions: The determination of OS biomarkers in cord blood can be useful in identifying babies at high risk for NEC and in devising new strategies to ameliorate perinatal outcome.

Whole Body Hypothermia and Oxidative Stress in Babies With Hypoxic-Ischemic Brain Injury

According to increasing evidence, hypothermia can significantly improve outcomes in term neonates manifesting asphyxic insult and hypoxic-ischemic encephalopathy. Oxidative stress plays a key role in hypoxic-ischemic and inflammatory brain injuries. We investigated the impact of hypothermia on oxidative stress in babies with hypoxic-ischemic encephalopathy. Term infants were randomly selected for treatment with moderate whole body hypothermia or standard care on normothermia, after perinatal asphyxia. Total hydroperoxides as biochemical markers of oxidative stress, and C-reactive protein as a marker of inflammation, were assayed in blood samples drown at 6, 12, 24, 48, and 72 postnatal hours. In both hypothermic and normothermic groups, total hydroperoxides and C-reactive protein exhibited a continuous increase in the first days after birth. Nevertheless, a tendency was evident for slower and smaller elevations of total hydroperoxides and C-reactive protein in hypothermic compared with normothermic infants. A significant correlation was observed between total hydroperoxides and C-reactive protein in all patients, indicating an association between inflammation and oxidative stress during asphyxia. The slower increase and lower peaks of total hydroperoxides in the hypothermic group support the hypothesis that postasphyxic oxidative stress may be reduced by hypothermia.

Resuscitating preterm infants with 100% oxygen is associated with higher oxidative stress than room air.

The starting fraction of inspired oxygen for preterm resuscitation is a matter of debate, and the use of room air in full‐term asphyxiated infants reduces oxidative stress. This study compared oxidative stress in preterm infants randomised for resuscitation with either 100% oxygen or room air titrated to internationally recommended levels of preductal oxygen saturations.

Is newborn melatonin production influenced by magnetic fields produced by incubators

BACKGROUND During permanence in most incubators, newborns are very close to the electric engine, which represents a source of electromagnetic fields (EMF). Previous studies demonstrated a decrease in melatonin production in adults and animals exposed to EMF. AIMS To assess melatonin production in a group of newborns exposed to EMF, and to evaluate whether removing the babies from the source of MF can affect melatonin production. STUDY DESIGN AND SUBJECTS We have recruited 28 babies (study group), who had spent at least 48 h in incubator where we had previously assessed the presence of significant EMF. We have measured their mean 6-hydroxy-melatonin-sulfate (6OHMS) urine excretion at the end of their permanence in the incubators, and compared it with their mean 6OHMS excretion after having been put in cribs, where EMF are below the detectable limit (<0.1mG). We have also measured urine 6OHMS twice, with an interval of 48h, in a control group of 27 babies who were not exposed to EMF during both samples. RESULTS Mean 6OHMS/cr values were respectively 5.34±4.6 and 7.68±5.1ng/mg (p=0.026) when babies were exposed to EMF in incubators, and after having been put in the crib. In the control group, mean 6OHMS/cr values in the first and in the second sample were respectively 5.91±5.41 vs 6.17±3.94ng/mg (p=0.679). CONCLUSIONS The transitory increase in melatonin production soon after removing newborns from incubators demonstrates a possible influence of EMF on melatonin production in newborns. Further studies are needed to confirm these data.

Nitric oxide in neonatal hypoxemic respiratory failure

Nitric oxide (NO) is a cellular signaling molecule and a powerful vasodilator. NO modulates basal pulmonary vascular tone and it is important to reduce blood pressure and to treat hypoxemic respiratory failure, such as persistent pulmonary hypertension (PPHN) in newborns. PPHN is defined as a failure of normal pulmonary vascular adaptation at or soon after birth, resulting in a persisting high pulmonary vascular resistance. iNO therapy decreases the need of extracorporeal membrane oxygenation (ECMO) although it did not reduce mortality of these patients. Severe meconial aspiration syndrome is associated with PPHN, resulting in severe hypoxemia; iNO administration combined with HFV results in ameliorate oxygenation. The cause of hypoxemic respiratory failure in patients with congenital diaphragmatic hernia (CDH) is complex. CDH patients experienced oxygenation improvement after iNO therapy, but they can be often considered iNO poor responders. In some cases iNO therapy can reduce the need of ECMO in presurgical stabilization. The pathophysiology of respiratory failure and the potential risks differ substantially in preterm infants. Pulmonary hypertension can complicate respiratory failure in preterm babies. Current evidence does not support use of iNO in early routine, early rescue or layer rescue regimens in the care of preterm infants.

Oxidative Stress as a Physiological Pain Response in Full-Term Newborns

This research paper aims to investigate if oxidative stress biomarkers increase after a painful procedure in term newborns and if nonpharmacological approaches, or sex, influence pain degree, and the subsequent OS. 83 healthy term newborns were enrolled to receive 10% oral glucose or sensorial saturation (SS) for analgesia during heel prick (HP). The ABC scale was used to score the pain. Advanced oxidation protein products (AOPP) and total hydroperoxides (TH) as biomarkers of OS were measured at the beginning (early-sample) and at the end (late-sample) of HP. The early-sample/late-sample ratio for AOPP and TH was used to evaluate the increase in OS biomarkers after HP. Higher levels of both AOPP and TH ratio were observed in high degree pain (4–6) compared with low degree pain score (0–3) (AOPP: p = 0.049; TH: p = 0.001). Newborns receiving SS showed a significantly lower pain score (p = 0.000) and AOPP ratio levels (p = 0.021) than those without. Males showed higher TH levels at the end of HP (p = 0.005) compared to females. The current study demonstrates that a relationship between pain degree and OS exists in healthy full-term newborns. The amount of OS is gender related, being higher in males. SS reduces pain score together with pain-related OS in the newborns.

Early Prediction of Hypoxic-Ischemic Brain Injury by a New Panel of Biomarkers in a Population of Term Newborns

This research paper is aimed at evaluating the predictive role of a default panel of oxidative stress (OS) biomarkers for the early identification of infants at high risk of HIE and their validation through the correlation with MRI findings. A multicenter prospective observational study was performed between March 2012 and April 2015 in two European tertiary NICUs. Eighty-four term infants at risk for HIE (pH < 7, BE < −13 mmol/L, and 5′ Apgar < 5) were enrolled. Three were excluded for chromosomal abnormalities and one due to lack of blood samples. The final population was divided according to the severity of perinatal hypoxia into 2 groups: mild/moderate HIE and severe HIE. Advanced oxidation protein products (AOPP), non-protein-bound iron (NPBI), and F2-isoprostanes (F2-IsoPs) were measured in blood samples at P1 (4–6 hours), P2 (24–72 hours), and P3 (5 days), in both groups. MRIs were scored for the severity of brain injury, using a modified Barkovich score. The mean GA was 39.8 weeks (SD 1.4) and the mean birth weight 3538 grams (SD 660); 37 were females and 43 males. Significantly lower 5′ Apgar score, pH, and BE and higher Thompson score were found in group II compared to group I at birth. Group II showed significantly higher AOPP and NPBI levels than group I (mean (SD) AOPP: 15.7 (15.5) versus 34.1 (39.2), p = 0.033; NPBI 1.1 (2.5) versus 3.9 (4.4), p = 0.013) soon after birth (P1). No differences were observed in OS biomarker levels between the two groups at P2 and P3. A regression model, including adjustment for hypothermia treatment, gender, and time after birth, showed that AOPP levels and male gender were both risk factors for higher brain damage scores (AOPP: OR 3.6, 95% CI (1.1–12.2) and gender: OR 5.6, 95% CI (1.2–25.7), resp.). Newborns with severe asphyxia showed higher OS than those with mild asphyxia at birth. AOPP are significantly associated with the severity of brain injury assessed by MRI, especially in males.

PS-113 The Association Between Electrical Brain Activity And Arterial Spin Labelling Perfusion Mri In Neonates With Hypoxic-ischaemic Encephalopathy (hie)

Background and aims (a)EEG predicts outcome in full-term infants with HIE. Recently, increased perfusion in the basal ganglia, detected with arterial spin labelling (ASL), was shown to be related to brain injury1. Our aim was to investigate the relationship between (a)EEG and brain tissue perfusion. Methods 20 subjects with HIE, eligible for hypothermia, were enrolled. Four 1-hour periods were selected from the (a)EEG: P1 (4–6 h), P2 (20–24 h), P3 (32–36 h) and P4 (44–48 h). Burst-rate (number of burst/min) and IBI (interburst interval) from the rawEEG, minimum (MIN) amplitude (µV) and the% of time <5 µV (% < 5 µV) of the aEEG, were included in the analysis. Mean perfusion in the basal ganglia and thalami (BGT-CBF) was measured using ASL-MRI. Results In P1 a relation was found for suppressed aEEG signal (% <5 µV: p = 0.015; R = 0.709; MIN: p = 0.028; R = -0.659) and increased BGT-CBF. Concomitantly, a negative correlation was found between burst-rate and BGT-CBF, MIN in P2–3–4 (p < 0.05), whereas suppressed background pattern expressed by% <5 µV and IBI correlated positively with higher BGT-CBF (p < 0.05). In the multivariable regression, corrected for sedatives and anti-epileptic medication, the association between EEG parameters and BGT-CBF persisted (p < 0.05), with the exception of burst-rate in P1. Conclusion A depressed cortical activity in the first 48 h after birth, secondary to hypoxic-ischemia, is related to an abnormally increased brain perfusion. Using both techniques together might be of additional value to predict neurodevelopmental outcome. References Wintermark P et al. Am J Neuroradiol 2011;32:2023–29