Serafina Perrone

Oxidative stress in preterm neonates at birth and on the seventh day of life.

Previous studies have demonstrated increased oxidative damage to proteins and increased lipid peroxidation products in the plasma of hypoxic newborns at birth. We tested the hypothesis that hypoxic preterm newborns are at increased risk for oxidative stress in the first week of life. Heparinized blood samples of 34 hypoxic and 15 control preterm newborns were obtained at birth from the umbilical vein immediately after delivery and from a peripheral vein on postnatal d 7. Plasma levels of hypoxanthine, total hydroperoxide (TH), and advanced oxidation protein products (AOPP) were measured in cord blood and blood drawn on d 7. Hypoxanthine, TH, and AOPP levels were significantly higher in cord and d 7 blood samples of hypoxic newborn than control infants. Statistically significant correlations were observed between AOPP and hypoxanthine and between AOPP and TH plasma levels on d 7. AOPP and TH plasma levels significantly increased from cord to d 7 blood in neonates without hypoxia. These findings show that the oxidative stress observed in cord blood of hypoxic preterm newborns is still higher than control infants on d 7. The significant increase in TH and AOPP levels in nonhypoxic preterm newborns at the end of the first postnatal week indicates that damage caused by free radicals also occurs in nonhypoxic babies with normal clinical course. In summary, TH and AOPP production is prolonged for several days after birth in hypoxic preterm babies. The risk of free radical damage is lower but still exists in preterm neonates with normal clinical course.

Oxygen toxicity: chemistry and biology of reactive oxygen species

Oxygen has a central role in the evolution of complex life on Earth mainly because of the biochemical symmetry of oxygenic photosynthesis and aerobic respiration that can maintain homeostasis within our planet biosphere. Oxygen can also produce toxic molecules, reactive oxygen species (ROS). ROS is a collective term that includes both oxygen radicals and certain oxidizing agents that are easily converted into radicals. They can be produced from both endogenous and exogenous substances. ROS play a dual role in biological systems, since they can be either harmful or beneficial to living systems. They can be considered a double-edged sword because on the one hand oxygen-dependent reactions and aerobic respiration have significant advantages but, on the other, overproduction of ROS has the potential to cause damage.

Total hydroperoxide and advanced oxidation protein products in preterm hypoxic babies.

Previous studies have shown that plasma lipoproteins are a common target of free radical-induced oxidative stress in hypoxic newborn infants. In contrast to lipids, the reaction of proteins with various oxidants during hypoxia has not been extensively studied. We tested the hypothesis that tissue hypoxia results in increased production of protein oxidation in cord blood of preterm newborns. Heparinized blood samples of 39 hypoxic and 16 control preterm newborns were obtained from the umbilical vein, after cord clamping immediately after delivery. Plasma levels of total hydroperoxide (TH), advanced oxidation protein products (AOPP), hypoxanthine (Hx), xanthine (Xa), and uric acid (UA) were measured. Higher Hx, Xa, UA, TH, and AOPP levels were found in hypoxic newborn infants than in controls. Statistically significant correlations were observed between: TH and Hx (r = 0.54, p = 0.003, n = 28), AOPP and Hx (r = 0.64, p = 0.0001, n = 27), and TH and AOPP plasma levels (r = 0.50, p = 0.02, n = 21). In summary, TH, AOPP, Hx, Xa, and UA production is increased in fetal blood during hypoxia. The more severe the hypoxia, the higher the lipid and protein damage by free radicals.

Effect of Multisensory Stimulation on Analgesia in Term Neonates: A Randomized Controlled Trial

Many attempts have been made to obtain safe and effective analgesia in newborns. Oral glucose-water has been found to have analgesic properties in neonates. We investigated whether other sensory stimulation added to oral glucose provided more effective analgesia than oral glucose alone. In a randomized prospective double-blind trial, we studied 120 term newborns during heel prick. The babies were divided randomly into six groups of 20, and each group was treated with a different procedure during heel prick:A) control;B) 1 mL 33% oral glucose given 2 min before the heel prick;C) sucking;D) 1 mL 33% oral glucose plus sucking;E) multisensory stimulation including 1 mL 33% oral glucose (sensorial saturation);F) multisensory stimulation without oral glucose. Sensorial saturation consisted in massage, voice, eye contact, and perfume smelling during heel prick. Each heel prick was filmed and assigned a point score according to the Douleur Aiguë du Nouveau-né (DAN) neonatal acute pain scale. Camera recording began 30 s before the heel prick, so it was impossible for the scorers to distinguish procedure A (control) from B (glucose given 2 min before), C (sucking water) from D (sucking glucose), and E (multisensory stimulation and glucose) from F (multisensory stimulation and water) from the video. Procedure E (multisensory stimulation and glucose) was found to be the most effective procedure, and the analgesia was even more effective than that produced by procedure D (sucking glucose). We conclude that sensorial saturation is an effective analgesic technique that potentiates the analgesic effect of oral sugar. It can be used for minor painful procedures on newborns.

Melatonin protects from the long-term consequences of a neonatal hypoxic-ischemic brain injury in rats

Abstract:  Among the main factors responsible for perinatal brain injury, inflammation, hypoxia‐ischemia and formation of free radicals (FR) appear to play key roles. Melatonin, an endogenously produced indoleamine formed in higher amounts in adults than in neonates, is a potent FR scavenger as well as an indirect antioxidant. Herein, we examined whether melatonin provides significant protection against brain damage and its long‐term consequences in a neonatal model of hypoxia‐ischemia (HI). Seven day‐old rats were subjected to permanent legation of the right common carotid artery followed to 2.5 hrs hypoxia 3 hrs later (HI). The neuroprotective effect of melatonin was evaluated 7 days after HI, or when rats reached adulthood, using behavioral and histological analyses. A beneficial effect was observed with 5 mg/kg melatonin administered before HI. The same dose repeated three times reduced further injury. A significant protective effect was found when 15 mg/kg melatonin was given 30 min before HI or when the same dose was given after HI and administration repeated after 24 and 48 hrs. The latter schedule of administration was used to assess the long‐term protective effects. Melatonin did not affect growth rate and behavior at adulthood, but significantly improved the behavioral asymmetry and learning deficits induced by HI. Consistently, brain injury was significantly attenuated in the melatonin‐treated ischemic group. The present study demonstrates that melatonin administration before or after HI in immature rats has an excellent and long‐lasting benefit on ischemic outcomes suggesting that the drug could represent a potentially safe approach to perinatal brain damage in humans.

Nucleated red blood cell count at birth as an index of perinatal brain damage

OBJECTIVE The prognostic value of the nucleated red blood cell count at birth with respect to perinatal brain damage and neonatal outcome was assessed in infants at high risk of having neurologic damage. STUDY DESIGN The nucleated red blood cell count at birth, pulsed Doppler ultrasonography in the cerebral arteries, cranial fontanelle sonograms, and neurodevelopmental status were evaluated in 337 newborn infants. RESULTS The nucleated red blood cell count at birth was significantly higher (1) in neonates with abnormal Doppler ultrasonographic parameters for the cerebral arteries at 48 to 72 hours after birth than in healthy neonates, (2) in 6-month-old infants with sequelae of hypoxic-ischemic encephalopathy than in healthy infants, and (3) in 3-year-old children with abnormal developmental status than in those with no abnormalities at follow-up. Significant correlations were observed between the nucleated red blood cell count and gestational age, Apgar score at 1 and 5 minutes, pH, base deficit, fraction of inspired oxygen, blood oxygen content, and birth weight. CONCLUSIONS The nucleated red blood cell count at birth not only reflects a response of the infant to perinatal hypoxia but is also a reliable index of perinatal brain damage.

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.

Intraerythrocyte nonprotein-bound iron and plasma malondialdehyde in the hypoxic newborn

Intraerythrocyte nonprotein-bound iron (INPBI), malondialdehyde (MDA), and hypoxanthine plasma levels (HxPL), were determined by high-pressure liquid chromatography in 138 randomly selected newborn infants with gestational ages ranging from 23 to 42 weeks at birth and on fourth day of life. MDA plasma levels were significantly higher in cord and fourth-day blood samples of preterm babies than term infants as well as babies born by emergency Caesarean section than babies born by vaginal delivery and in intubated than in nonintubated newborns. Highly significant correlations both in cord blood and fourth-day blood samples were observed between MDA plasma levels and gestational age, birth weight, Apgar score at 1 min and 5 min, HxPL, pH, base deficit, and INPBI content. Multiple regression analysis identified HxPL as the best single predictor of MDA plasma levels in cord blood, and INPBI content in fourth-day blood as the best single predictor of MDA plasma levels in fourth-day blood. The results indicate that red cells and plasma lipoproteins are a common target of free radical-induced oxidative stress during hypoxia.

Free iron, total F2‐isoprostanes and total F4‐neuroprostanes in a model of neonatal hypoxic–ischemic encephalopathy: neuroprotective effect of melatonin

Abstract:  Oxidative stress due to free radical formation and initiation of abnormal oxidative reactions is involved in several diseases of newborns, such as hypoxic–ischemic encephalopathy. Melatonin, an endogenously produced indoleamine primarily formed in the pineal gland, is a potent free radical scavenger as well as an indirect antioxidant. The present study was conducted to evaluate the formation of oxidative damage mediators and the possible effect of melatonin treatment in a model of hypoxic–ischemic encephalopathy in 7‐day‐old rats. Pups were subjected to permanent ligation of the right common carotid artery and exposed for 2.5 hr to a nitrogen–oxygen mixture (92% and 8%, respectively) (hypoxia–ischemia, HI). Melatonin was injected intraperitoneally to a group of rats at the dose of 15 mg/kg 30 min before starting the ischemic procedure (HI–Melatonin). After 24 hr of treatment, in homogenized cerebral cortex, desferoxamine (DFO)‐chelatable free iron, total F2‐isoprostanes and total F4‐neuroprostanes, originating from the free radical‐catalyzed peroxidation of arachidonic and docosahexaenoic acids, respectively, were determined. HI induced a significant increase in DFO‐chelatable iron, total F2‐isoprostanes and F4‐neuroprostanes in both right and left side of the cerebral cortex. In HI–Melatonin‐treated animals the levels of free iron, F2‐isoprostanes, and F4‐neuroprostanes were significantly lower than that in HI rats and the values were similar to controls. These data show the important neuroprotective role of melatonin in reducing oxidative damage resulting from HI. Melatonin could represent a potential safe approach to perinatal brain damage in humans.

The Timing of Neonatal Brain Damage

Although neonatal morbidity and mortality are less than in the past, the risk of pre-natal and neonatal brain damage has not been eliminated. In order to optimize pre-natal, perinatal and neonatal care, it is necessary to detect factors responsible for brain damage and obtain information about their timing. Knowledge of the timing of asphyxia, infections and circulatory abnormalities would enable obstetricians and neonatologists to improve prevention in pre-term and full-term neonates. Cardiotocography has been criticized as being too indirect a sign of fetal condition and as having various technical pitfalls, though its reliability seems to be improved by association with pulse oximetry, fetal blood pH and electrocardiography. Neuroimaging is particularly useful to determine the timing of hypoxic-ischemic brain damage. Cranial ultrasound has been used to determine the type and evolution of brain damage. Magnetic resonance has also been used to detect antenatal, perinatal and neonatal abnormalities and timing on the basis of standardized assessment of brain maturation. Advances in the interpretation of neonatal electroencephalograms have also made this technique useful for determining the timing of brain lesions. Nucleated red blood cell count in cord blood has been recognized as an important indication of the timing of pre-natal hypoxia, and even abnormal lymphocyte and thrombocyte counts may be used to establish pre-natal asphyxia. Cord blood pH and base excess are well-known markers of fetal hypoxia, but are best combined with heart rate and blood pressure. Other markers of fetal and neonatal hypoxia useful for determining the timing of brain damage are assays of lactate and markers of oxidative stress in cord blood and neonatal blood. Cytokines in blood and amniotic fluid may indicate chorioamnionitis or post-natal infections. The determination of activin and protein S100 has also been proposed. Obstetricians and neonatologists can therefore now rely on various methods for monitoring the risk of brain damage in the antenatal and post-natal periods.