Mariangela Longini

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.

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.

Activation of autophagy and Akt/CREB signaling play an equivalent role in the neuroprotective effect of rapamycin in neonatal hypoxia-ischemia

We have previously shown that in neonatal rats subjected to hypoxia-ischemia (HI) rapamycin administration increases autophagy, decreases apoptosis and significantly reduces brain damage. After HI, when autophagy is blocked neuronal cells rapidly progress toward necrotic cell death. The present study was undertaken to assess the potential role of activation of autophagic and phosphatidylinositol 3-kinase (PI3K)/Akt kinase pathways in the neuroprotective effect of rapamycin. Rapamycin administration caused a significant reduction of 70 kDa S6 kinase (p70S6K) phosphorylation and a significant increase of the autophagic proteins beclin 1 and microtubule-associated protein 1 light chain 3 (LC3), as of monodansylcadaverine (MDC) labelling in the lesioned side. The phosphorylation of Akt and cAMP response element binding protein (CREB) was increased in neuronal cells, and both p-Akt and p-CREB co-localized with beclin 1. Wortmannin (WT) administration significantly reduced Akt and CREB phosphorylation as well as the neuroprotective effect of rapamycin but did not affect the phosphorylation of p70S6K, the expression of beclin 1 and LC3, and MDC labelling. In contrast, 3-methyladenine (3MA) reduced the increased beclin 1 expression, the MDC labelling and the neuroprotective effect of rapamycin without affecting Akt phosphorylation. However, both compounds significantly increased necrotic cell death. Taken together, these data indicate that in neonatal HI autophagy can be part of an integrated pro-survival signalling which includes the PI3K-Akt-mammalian target of rapamycin (mTOR) axis. When the autophagic or the PI3K-Akt-mTOR pathways are interrupted cells undergo necrotic cell death.

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.

Maternal Allopurinol During Fetal Hypoxia Lowers Cord Blood Levels of the Brain Injury Marker S-100B

BACKGROUND: Fetal hypoxia is an important determinant of neonatal encephalopathy caused by birth asphyxia, in which hypoxia-induced free radical formation plays an important role. HYPOTHESIS: Maternal treatment with allopurinol, will cross the placenta during fetal hypoxia (primary outcome) and reduce S-100B and free radical formation (secondary outcome). METHODS: In a randomized, double-blind feasibility study, 53 pregnant women in labor (54 fetuses) with a gestational age of >36 weeks and fetal hypoxia, as indicated by abnormal/nonreassuring fetal heart rate tracing or fetal scalp pH of <7.20, received 500 mg of allopurinol or placebo intravenously. Severity of fetal hypoxia, brain damage and free radical formation were assessed by arterial cord blood lactate, S-100B and non-protein-bound-iron concentrations, respectively. At birth, maternal and cord blood concentrations of allopurinol and its active metabolite oxypurinol were determined. RESULTS: Allopurinol and oxypurinol concentrations were within the therapeutic range in the mother (allopurinol > 2 mg/L and/or oxypurinol > 4 mg/L) but not always in arterial cord blood. We therefore created 3 groups: a placebo (n = 27), therapeutic allopurinol (n = 15), and subtherapeutic allopurinol group (n = 12). Cord lactate concentration did not differ, but S-100B was significantly lower in the therapeutic allopurinol group compared with the placebo and subtherapeutic allopurinol groups (P < .01). Fewer therapeutic allopurinol cord samples had measurable non–protein-bound iron concentrations compared with placebo (P < .01). CONCLUSIONS: Maternal allopurinol/oxypurinol crosses the placenta during fetal hypoxia. In fetuses/newborns with therapeutic allopurinol/oxypurinol concentrations in cord blood, lower plasma levels of the brain injury marker protein S-100B were detected. A larger allopurinol trial in compromised fetuses at term seems warranted. The allopurinol dosage must be adjusted to achieve therapeutic fetal allopurinol/oxypurinol concentrations.

Glutathione recycling and antioxidant enzyme activities in erythrocytes of term and preterm newborns at birth.

We previously demonstrated a high susceptibility of neonatal red blood cells (RBC) to oxidative stress at birth. The aim of this study was to compare the RBC antioxidant capacity and redox cycle enzyme activities as well as glutathione (GSH) recycling in full-term and preterm infants at birth and in normal adults. GSH and GSH disulfide (GSSG) concentrations, GSH/GSSG ratio, and the activities of glucose-6-phosphate dehydrogenase (G-6-PDH), GSH peroxidase, GSH reductase (GR), catalase (CAT), superoxide dismutase (SOD), and hexokinase (HK) were measured in RBC of 25 healthy adults and 56 newborns (23 term, 33 preterm) at birth. The GSH recycling was measured in adult and newborn RBC exposed to oxidative stress (1 mM tert-butylhydroperoxide). The RBC of term and preterm babies showed higher GSH, GSSG, G-6-PDH, GR, and HK levels/activities and lower GSH/GSSG ratios and higher GSH-recycling rates than those of adults. In preterm babies significant correlations were found between G-6-PDH and CAT, GSH, GSH/GSSG ratio, and GSSG (r = –0.67, r = 0.71, r = –0.66, p < 0.01; r = 0.71, p < 0.05, respectively). In term newborns, statistically significant correlations were observed between G-6-PDH and CAT, SOD, and GSH (r = –0.65, r = –0.65, r = –0.69, p < 0.01, respectively). The results indicate the central role of the G-6-PDH activity in antioxidant defenses. We speculate that preterm babies have prompter involvement of antioxidant defenses than term babies.

Resuscitation with supplementary oxygen induces oxidative injury in the cerebral cortex

Isoprostanes, neuroprostanes, isofurans, and neurofurans have all become attractive biomarkers of oxidative damage and lipid peroxidation in brain tissue. Asphyxia and subsequent reoxygenation cause a burst of oxygen free radicals. Isoprostanes and isofurans are generated by free radical attacks of esterified arachidonic acid. Neuroprostanes and neurofurans are derived from the peroxidation of docosahexanoic acid, which is abundant in neurons and could therefore more selectively represent oxidative brain injury. Newborn piglets (age 12-36 h) underwent hypoxia until the base excess reached -20 mmol/L or the mean arterial blood pressure dropped below 15 mm Hg. They were randomly assigned to receive resuscitation with 21, 40, or 100% oxygen for 30 min and then ventilation with air. The levels of isoprostanes, isofurans, neuroprostanes, and neurofurans were determined in brain tissue (ng/g) isolated from the prefrontal cortex using gas chromatography-mass spectrometry (GC/MS) with negative ion chemical ionization (NICI) techniques. A control group underwent the same procedures and observations but was not submitted to hypoxia or hyperoxia. Hypoxia and reoxygenation significantly increased the levels of isoprostanes, isofurans, neuroprostanes, and neurofurans in the cerebral cortex. Nine hours after resuscitation with 100% oxygen for 30 min, there was nearly a 4-fold increase in the levels of isoprostanes and isofurans compared to the control group (P=0.007 and P=0.001) and more than a 2-fold increase in neuroprostane levels (P=0.002). The levels of neuroprostanes and neurofurans were significantly higher in the piglets that were resuscitated with supplementary oxygen (40 and 100%) compared to the group treated with air (21%). The significance levels of the observed differences in neuroprostanes for the 21% vs 40% comparison and the 21% vs 100% comparison were P<0.001 and P=0.001, respectively. For neurofurans, the P values of the 21% vs 40% comparison and the 21% vs 100% comparison were P=0.036 and P=0.025, respectively. Supplementary oxygen used for the resuscitation of newborns increases lipid peroxidation in brain cortical neurons, a result that is indicative of oxidative brain damage. These novel findings provide new knowledge regarding the relationships between oxidative brain injury and resuscitation with oxygen.

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.

Effects of Lutein on Oxidative Stress in the Term Newborn: A Pilot Study

Background: Oxidative stress (OS) plays a crucial role in pathological conditions during the early neonatal period. The newborns are susceptible to oxidative damage due to high metabolic rate and low levels of antioxidant enzymes. Lutein has been found to have protective functions in adult humans as antioxidant. Aim: To evaluate the effects of lutein on OS in newborns. We tested the hypothesis that lutein would act both by increasing antioxidant capacity and inhibiting OS. Methods: This was a randomized, double-blind, placebo-controlled, single-center study. 20 healthy term newborns were assigned to receive lutein or placebo (lutein and control group, respectively) at 12 and 36 h after birth. Total hydroperoxides (TH), as marker of OS, and biological antioxidant potential (BAP), as marker of antioxidant power, were detected on cord blood and at 48 h of life in all babies. Results: TH significantly increased from birth to 48 h in the control group (p = 0.02), but not in the lutein group. In the lutein group, BAP significantly increased after 48 h (p = 0.02), showing a strengthening of antioxidant activity due to lutein. At 48 h of life, compared with those in the control group, neonates assigned to receive lutein had significantly lower TH levels (p = 0.04) and higher BAP levels (p = 0.028). Conclusions: Lutein administration in newborns increases the levels of BAP decreasing TH. The enhancement of antioxidant activity in plasma clearly results in protecting newborn from perinatal OS. These preliminary results, adding a new contribution in antioxidant strategies, strongly require to be confirmed by RCT.