Anti-oxidant strategies

Combination treatment with ethyl pyruvate and IGF-I exerts neuroprotective effects against brain injury in a rat model of neonatal hypoxic-ischemic encephalopathy

Neonatal hypoxic-ischemic (HI) brain injury causes severe brain damage in newborns. Following HI injury, rapidly accumulating oxidants injure neurons and interrupt ongoing developmental processes. The antioxidant, sodium pyruvate, has been shown to reduce neuronal injury in neonatal rats under conditions of oxygen glucose deprivation (OGD) and HI injury. In this study, we evaluated the effects of ethyl pyruvate (EP) and insulin-like growth factor-I (IGF-I) alone or in combination in a similar setting. For this purpose, we used an in vitro model involving primary neonatal rat cortical neurons subjected to OGD for 2.5 h and an in vivo model involving unilateral carotid ligation in rats on post-natal day 7 with exposure to 8% hypoxia for 2.5 h. The cultured neurons were examined by lactate dehydrogenase (LDH) and cell viability assays. For the in vivo experiments, behavioral development was evaluated by the foot fault test at 4 weeks of recovery. 2,3,5-Triphenyltetrazolium chloride monohydrate and cresyl violet staining were used to evaluate HI injury. The injured neurons were Fluoro-Jade B-labeled, new neuroprecursors were double labeled with bromodeoxyuridine (BrdU) and doublecortin, new mature neurons were BrdU-labeled and neuronal nuclei were labeled by immunofluorescence. Under conditions of OGD, the LDH levels increased and neuronal viability decreased. Treatment with 0.5 mM EP or 25 ng/ml IGF-I protected the neurons (P<0.05), exerting additive effects. Similarly, either the early administration of EP or delayed treatment with IGF-I protected the neonatal rat brains against HI injury and improved neurological performance and these effects were also additive. This effect may be the result of reduced neuronal injury, and enhanced neurogenesis and maturation. On the whole, our findings demonstrate that the combination of the early administration of EP with delayed treatment with IGF-I exerts neuroprotective effects against HI injury in neonatal rat brains.

Melatonin reduces oxidative stress and improves vascular function in pulmonary hypertensive newborn sheep

Pulmonary hypertension of the newborn (PHN) constitutes a critical condition with severe cardiovascular and neurological consequences. One of its main causes is hypoxia during gestation, and thus, it is a public health concern in populations living above 2500 m. Although some mechanisms are recognized, the pathophysiological facts that lead to PHN are not fully understood, which explains the lack of an effective treatment. Oxidative stress is one of the proposed mechanisms inducing pulmonary vascular dysfunction and PHN. Therefore, we assessed whether melatonin, a potent antioxidant, improves pulmonary vascular function. Twelve newborn sheep were gestated, born, and raised at 3600 meters. At 3 days old, lambs were catheterized and daily cardiovascular measurements were recorded. Lambs were divided into two groups, one received daily vehicle as control and another received daily melatonin (1 mg/kg/d), for 8 days. At 11 days old, lung tissue and small pulmonary arteries (SPA) were collected. Melatonin decreased pulmonary pressure and resistance for the first 3 days of treatment. Further, melatonin significantly improved the vasodilator function of SPA, enhancing the endothelial- and muscular-dependent pathways. This was associated with an enhanced nitric oxide-dependent and nitric oxide independent vasodilator components and with increased nitric oxide bioavailability in lung tissue. Further, melatonin reduced the pulmonary oxidative stress markers and increased enzymatic and nonenzymatic antioxidant capacity. Finally, these effects were associated with an increase of lumen diameter and a mild decrease in the wall of the pulmonary arteries. These outcomes support the use of melatonin as an adjuvant in the treatment for PHN.

Effects of L-proline on the Growth Performance, and Blood Parameters in Weaned Lipopolysaccharide (LPS)-challenged Pigs

This trail was conducted to study the effect of L-proline on the growth performance, and blood parameter in the weaned lipopolysaccharide (LPS)-challenged pigs. Thirty six pigs (9.13±0.85 kg) were assigned randomly to dietary treatments in a 2×3 factorial arrangement in a 20-d growth assay. Factors were intraperitoneal injection with saline or LPS, and three dietary L-proline supplement levels (0%, 0.5%, or 1.0%). On d 10, blood samples were collected at 3 h after LPS (100 μg LPS/kg body weight [BW]) or saline injection. On d 20 of the trial, all pigs were orally administrated D-xylose (0.1 g/kg BW) at 2 h, and blood samples were collected at 3 h after LPS or saline injection. As a result, dietary supplementation with 0.5% proline had a tendency to increase average daily gain (ADG) in piglets during d 10 to 20 (p = 0.088). Without LPS challenge, dietary supplementation with 1.0% proline had no effect on growth hormone (GH) concentrations on d 10 (p>0.05), but decreased it after LPS challenge (p<0.05). There was LPS challenge×proline interaction for GH concentrations on d 10 (p<0.05). Dietary supplementation with 1.0% proline decreased glucagon concentration on d 10 after LPS challenge (p<0.05). In addition, dietary supplementation with proline increased superoxide dismutase (SOD) activity significantly on d 10 and 20 (p<0.05), and 1.0% proline increased heat shock proteins-70 concentration on d 10 (p<0.05). Moreover, proline supplementation increased diamine oxidase (DAO) concentrations after LPS challenge (p<0.05). There was LPS challenge×proline interaction for DAO (p<0.05). Furthermore, dietary supplementation with 1.0% proline increased the D-xylose level when no LPS challenge (p<0.05). These results indicate that proline supplementation could improve growth performance, increase SOD activities, and has a positive effect on the gastrointestinal tract digestibility in early weaned pigs.

Oxidative stress and bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the major cause of pulmonary disease in infants. The pathophysiology and management of BPD changed with the improvement of neonatal intensive care unit (NICU) management and with the increase of survival rates. Despite the improvements made, BPD is still a public health concern, resulting in frequent hospitalizations with high rates of mortality, impaired weight and height growth, and neurodevelopmental disorders. Lung injury in the neonatal period has multiple etiologic factors - genetic, hemodynamic, metabolic, nutritional, mechanical, and infectious mechanisms - act in a cumulative and synergic way. Free radical (FR) generation is largely recognized as the major cause of lung damage. Oxidative stress (OS) is the final common endpoint for a complex convergence of events, some genetically determined and some triggered by in utero stressors. Inflammatory placental disorders and chorioamnionitis also play an important role due to the coexistence of inflammatory and oxidative lesions. In addition, the contribution of airway inflammation has been extensively studied. The link between inflammation and OS injury involves the direct activation of inflammatory cells, especially granulocytes, which potentiates the inflammatory reaction. Individualized interventions to support ventilation, minimize oxygen exposure, minimize apnea, and encourage growth should decrease both the frequency and severity of BPD. Future perspectives suggest supplementation with enzymatic and/or non-enzymatic antioxidants. The use of antioxidants in preterm newborns particularly exposed to OS and at risk for BPD represents a logical strategy to ameliorate FRs injury, but further studies are needed to support this hypothesis.

Pharmacologic neuroprotective strategies in neonatal brain injury

This article explains the mechanisms underlying choices of pharmacotherapy for hypoxic-ischemic insults of both preterm and term babies. Some preclinical data are strong enough that clinical trials are now underway. Challenges remain in deciding the best combination therapies for each age and insult.

G-protein-coupled receptor 91 and succinate are key contributors in neonatal postcerebral hypoxia-ischemia recovery

OBJECTIVE

Prompt post-hypoxia-ischemia (HI) revascularization has been suggested to improve outcome in adults and newborn subjects. Other than hypoxia-inducible factor, sensors of metabolic demand remain largely unknown. During HI, anaerobic respiration is arrested resulting in accumulation of carbohydrate metabolic intermediates. As such succinate readily increases, exerting its biological effects via a specific receptor, G-protein-coupled receptor (GPR) 91. We postulate that succinate/GPR91 enhances post-HI vascularization and reduces infarct size in a model of newborn HI brain injury.

APPROACH AND RESULTS

The Rice-Vannucci model of neonatal HI was used. Succinate was measured by mass spectrometry, and microvascular density was evaluated by quantification of lectin-stained cryosection. Gene expression was evaluated by real-time polymerase chain reaction. Succinate levels rapidly increased in the penumbral region of brain infarcts. GPR91 was foremost localized not only in neurons but also in astrocytes. Microvascular density increased at 96 hours after injury in wild-type animals; it was diminished in GPR91-null mice leading to an increased infarct size. Stimulation with succinate led to an increase in growth factors implicated in angiogenesis only in wild-type mice. To explain the mode of action of succinate/GPR91, we investigated the role of prostaglandin E2-prostaglandin E receptor 4, previously proposed in neural angiogenesis. Succinate-induced vascular endothelial growth factor expression was abrogated by a cyclooxygenase inhibitor and a selective prostaglandin E receptor 4 antagonist. This antagonist also abolished succinate-induced neovascularization.

CONCLUSIONS

We uncover a dominant metabolic sensor responsible for post-HI neurovascular adaptation, notably succinate/GPR91, acting via prostaglandin E2-prostaglandin E receptor 4 to govern expression of major angiogenic factors. We propose that pharmacological intervention targeting GPR91 could improve post-HI brain recovery.

Comparative effects of respiratory stimulants on hypoxic neuronal cell injury in SH-SY5Y cells and in hippocampal slice cultures from rat pups

BACKGROUND

This study was conducted to clarify whether respiratory stimulants used to treat apnea of prematurity (AOP) attenuate or aggravate hypoxia-induced neuronal damage.

METHODS

A human neuroblastoma cell line, SH-SY5Y cells, and hippocampal slice cultures from rat pups were exposed to hypoxia to induce cell injury. The effects of respiratory stimulants on cell injury were evaluated.

RESULTS

Theophylline and doxapram did not have any effects against cell injury induced by hypoxia in SH-SY5Y cells and hippocampal slice cultures of rat pups, while caffeine protected these cells and the slice cultures from hypoxia. The protective effects of caffeine in SH-SY5Y cells disappeared with co-treatment by the adenosine A2A receptor agonist, CGS21680, and were mimicked by the adenosine A2A R antagonist, SCH58261. Meanwhile, co-treatment with phosphatidylinositol 3-kinase/AKT pathway inhibitors did not affect the protective effects of caffeine. Hydroxy radical scavenging activity of caffeine were not observed at the concentrations that produced cytoprotective activity, and radical scavengers did not have any effects on the cell injury induced by hypoxia in SH-SY5Y cells.

CONCLUSIONS

Caffeine significantly attenuated cell injury induced by hypoxia in SH-SY5Y cells and hippocampal slice cultures of rat pups, at least partly through A2A R antagonism. Caffeine can protect neuronal cells from injury induced by hypoxemia, and may be a beneficial treatment for AOP with neuroprotective potential.

Neuroprotective effect of melatonin: a novel therapy against perinatal hypoxia-ischemia

One of the most common causes of mortality and morbidity in children is perinatal hypoxia-ischemia (HI). In spite of the advances in neonatology, its incidence is not diminishing, generating a pediatric population that will require an extended amount of chronic care throughout their lifetime. For this reason, new and more effective neuroprotective strategies are urgently required, in order to minimize as much as possible the neurological consequences of this encephalopathy. In this sense, interest has grown in the neuroprotective possibilities of melatonin, as this hormone may help to maintain cell survival through the modulation of a wide range of physiological functions. Although some of the mechanisms by which melatonin is neuroprotective after neonatal asphyxia remain a subject of investigation, this review tries to summarize some of the most recent advances related with its use as a therapeutic drug against perinatal hypoxic-ischemic brain injury, supporting the high interest in this indoleamine as a future feasible strategy for cerebral asphyctic events.

Hypoxia-ischemia alters nucleotide and nucleoside catabolism and Na+,K+-ATPase activity in the cerebral cortex of newborn rats

It is well known that the levels of adenosine in the brain increase dramatically during cerebral hypoxic-ischemic (HI) insults. Its levels are tightly regulated by physiological and pathophysiological changes that occur during the injury acute phase. The aim of the present study was to examine the effects of the neonatal HI event on cytosolic and ecto-enzymes of purinergic system--NTPDase, 5'-nucleotidase (5'-NT) and adenosine deaminase (ADA)--in cerebral cortex of rats immediately post insult. Furthermore, the Na(+)/K(+)-ATPase activity, adenosine kinase (ADK) expression and thiobarbituric acid reactive species (TBARS) levels were assessed. Immediately after the HI event the cytosolic NTPDase and 5'-NT activities were increased in the cerebral cortex. In synaptosomes there was an increase in the ecto-ADA activity while the Na(+)/K(+) ATPase activity presented a decrease. The difference between ATP, ADP, AMP and adenosine degradation in synaptosomal and cytosolic fractions could indicate that NTPDase, 5'-NT and ADA were differently affected after insult. Interestingly, no alterations in the ADK expression were observed. Furthermore, the Na(+)/K(+)-ATPase activity was correlated negatively with the cytosolic NTPDase activity and TBARS content. The increased hydrolysis of nucleotides ATP, ADP and AMP in the cytosol could contribute to increased adenosine levels, which could be related to a possible innate neuroprotective mechanism aiming at potentiating the ambient levels of adenosine. Together, these results may help the understanding of the mechanism by which adenosine is produced following neonatal HI injury, therefore highlighting putative therapeutical targets to minimize ischemic injury and enhance recovery.

Effect of therapeutic hypothermia on oxidative stress and outcome in term neonates with perinatal asphyxia: a randomized controlled trial

OBJECTIVES

To evaluate in term babies with perinatal asphyxia, the effect of therapeutic hypothermia (TH) on oxidative stress and neurological outcome at discharge.

METHODS

Babies who satisfied inclusion criteria were randomized to TH, with cooling gel packs to a target temperature of 33-34°C for 72 h or normothermia. Blood sample was collected before and after TH for oxidative stress assessment: total antioxidant status (TAS) and malondialdehyde (MDA).

RESULTS

Of 116 babies randomized, there was no statistically significant difference in the baseline TAS and MDA. After 72 h of TH, TAS was significantly higher (p = <0.001) (761.69 ± 114.01 vs. 684.16 ± 88.86) and MDA was significantly lower (p = <0.001) in TH group (1.73 ± 0.66 vs. 5.2 ± 1.06). Risk of developing deficit was lower (p < 0.001) in TH group with relative risk of 0.49 and 95 % confidence interval: 0.29-0.68.

CONCLUSION

TH reduces oxidative stress and improves neurological outcome in perinatal asphyxia.

TRIAL REGISTRATION NUMBER

CTRI/2011/12/002196.

Influence of allopurinol on evoked cortical afterdischarges during early ontogenesis

The aim of our study was to test the hypothesis, whether repeated allopurinol pre-treatment (in dose of 135 mg/kg s.c.) can influence changes of brain excitability caused by long-term hypoxia exposition in young immature rats. Rat pups were exposed together with their mother in to an intermittent hypobaric hypoxia (simulated altitude of 7 000 m) since the day of birth till the 11th day (youngest experimental group) or 17th day for 8 hours a day. Allopurinol was administered daily immediately before each hypoxia exposition. The duration of evoked afterdischarges (ADs) and the shape of evoked graphoelements were evaluated in 12, 18, 25 and 35-day-old freely moving male pups. Hypobaric hypoxia prolonged the duration of ADs in 12, 18 and 25-day-old rats. The ADs were prolonged in 35-day-old rats only after the first stimulation. Allopurinol shorted the duration of ADs only in 12-day-old pups. In older experimental group the effect of allopurinol treatment was less pronounced.

Changes in carotid blood flow after unilateral perinatal arterial ischemic stroke

INTRODUCTION

Little is known about changes in carotid blood flow after perinatal arterial ischemic stroke (PAIS). The aim of this study was to assess the blood flow in the internal carotid arteries (ICAs) after unilateral PAIS.

METHODS

The carotid flow (ml/min) was measured noninvasively by means of two-dimensional phase-contrast magnetic resonance angiography (2D PC-MRA) in 25 full-term infants who had unilateral PAIS within 10 d after birth. In 17 infants a second 2D PC-MRA was carried out at the age of 3 mo. Asymmetry of carotid blood flow was calculated at both time points, and the circle of Willis (CoW) was assessed with a three-dimensional (3D) time-of-flight MRA.

RESULTS

On the early magnetic resonance imaging (MRI), a significant increase in ipsilateral blood flow was observed (7.7%, 95% confidence interval (CI) 3.0-14.9%), which persisted after correcting for CoW configuration. At 3 mo, this asymmetry was no longer observed. No relationship was found between the asymmetry in blood flow and either stroke size or postnatal age at scan.

DISCUSSION

A higher blood flow in the ipsilateral ICA was observed during the acute phase after unilateral PAIS, and this disappeared after 3 mo. Further research into the role of hyperperfusion after PAIS may suggest new approaches to neuroprotection.

Hypothermia attenuates the severity of oxidative stress development in asphyxiated newborns

PURPOSE

This retrospective case-control study aimed to examine the development of oxidative stress in asphyxiated infants delivered at more than 37 weeks of gestation.

MATERIAL AND METHODS

Thirty-seven neonates were stratified into 3 groups: the first group experienced hypothermia (n = 6); the second received hypothermia cooling cup treatment for 3 days, normothermia (n = 16); and the third was the control group (n = 15). Serum total hydroperoxide (TH), biological antioxidant potential, and oxidative stress index (OSI) (calculated as TH/biological antioxidant potential) were measured within 3 hours after birth.

RESULTS

Serum TH and OSI levels gradually increased after birth in hypothermia and normothermia cases. At all time points, serum TH and OSI levels were higher in hypothermia and normothermia cases than in control cases. Serum TH and OSI levels were higher in normothermia cases than in hypothermia cases at days 3, 5, and 7.

CONCLUSION

This study demonstrated that hypothermia attenuated the development of systemic oxidative stress in asphyxiated newborns.

Disruption of the serotonergic system after neonatal hypoxia-ischemia in a rodent model

Identifying which specific neuronal phenotypes are vulnerable to neonatal hypoxia-ischemia, where in the brain they are damaged, and the mechanisms that produce neuronal losses are critical to determine the anatomical substrates responsible for neurological impairments in hypoxic-ischemic brain-injured neonates. Here we describe our current work investigating how the serotonergic network in the brain is disrupted in a rodent model of preterm hypoxia-ischemia. One week after postnatal day 3 hypoxia-ischemia, losses of serotonergic raphé neurons, reductions in serotonin levels in the brain, and reduced serotonin transporter expression are evident. These changes can be prevented using two anti-inflammatory interventions; the postinsult administration of minocycline or ibuprofen. However, each drug has its own limitations and benefits for use in neonates to stem damage to the serotonergic network after hypoxia-ischemia. By understanding the fundamental mechanisms underpinning hypoxia-ischemia-induced serotonergic damage we will hopefully move closer to developing a successful clinical intervention to treat neonatal brain injury.

Oxidative Stress in Critically Ill Children with Sepsis

Sepsis is one of the leading causes of death in critically ill patients in the intensive care unit. Sepsis accounts for significant morbidity and mortality in critically ill children as well. The pathophysiology of sepsis is characterized by a complex systemic inflammatory response, endothelial dysfunction, and alterations in the coagulation system, which lead to perturbations in the delivery of oxygen and metabolic substrates to the tissues, end-organ dysfunction, and ultimately death. Oxidative stress plays a crucial role as both a promoter and mediator of the systemic inflammatory response, suggesting potential targets for the treatment of critically ill children with the sepsis syndrome. Herein, we will provide a brief review of the role of oxidative and nitrosative stress in the pathophysiology of sepsis.

Hypoxic Ischemic Encephalopathy: Pathophysiology and Experimental Treatments

Hypoxic ischemic encephalopathy (HIE) is a serious birth complication affecting full term infants: 40-60% of affected infants die by 2 years of age or have severe disabilities. The majority of the underlying pathologic events of HIE are a result of impaired cerebral blood flow and oxygen delivery to the brain with resulting primary and secondary energy failure. In the past, treatment options were limited to supportive medical therapy. Currently, several experimental treatments are being explored in neonates and animal models to ameliorate the effects of secondary energy failure. This review discusses the underlying pathophysiologic effects of a hypoxic-ischemic event and experimental treatment modalities being explored to manage infants with HIE. Further research is needed to better understand if the long-term impact of the experimental treatments and whether the combinations of experimental treatments can improve outcomes in infants with HIE.

Striatal neuroprotection from neonatal hypoxia-ischemia in piglets by antioxidant treatment with EUK-134 or edaravone

Striatal neurons are highly vulnerable to hypoxia-ischemia (HI) in term newborns. In a piglet model of HI, striatal neurons develop oxidative stress and organelle disruption by 3-6 h of recovery and ischemic cytopathology over 6-24 h of recovery. We tested the hypothesis that early treatment with the antioxidants EUK-134 (a manganese-salen derivative that acts as a scavenger of superoxide, hydrogen peroxide, nitric oxide or NO and peroxynitrite) or edaravone (MCI-186, a scavenger of hydroxyl radical and NO) protects striatal neurons from HI. Anesthetized newborn piglets were subjected to 40 min of hypoxia and 7 min of airway occlusion. At 30 min after resuscitation, the piglets received vehicle, EUK-134 or edaravone. Drug treatment did not affect arterial blood pressure, blood gases, blood glucose or rectal temperature. At 4 days of recovery, the density of viable neurons in the putamen of vehicle-treated piglets was 12 ± 6% (±SD) of sham-operated control density. Treatment with EUK-134 increased viability to 41 ± 17%, and treatment with edaravone increased viability to 39 ± 19%. In the caudate nucleus, neuronal viability was increased from 54 ± 11% in the vehicle group to 78 ± 15% in the EUK-134 group and to 73 ± 13% in the edaravone group. Antioxidant drug treatment accelerated recovery from neurologic deficits and decreased oxidative and nitrative damage to nucleic acids. Treatment with EUK-134 reduced the HI-induced formation of protein carbonyl groups and tyrosine nitration at 3 h of recovery. We conclude that systemic administration of antioxidant agents by 30 min after resuscitation from HI can reduce oxidative stress and salvage neurons in the highly vulnerable striatum in a large-animal model of neonatal HI. Therefore, oxidative stress is an important mechanism for this injury, and antioxidant therapy is a rational, mechanism-based approach to neuroprotection in the newborn brain.

Normoxic versus hyperoxic resuscitation in pediatric asphyxial cardiac arrest: effects on oxidative stress

OBJECTIVE

To determine the effects of normoxic vs. hyperoxic resuscitation on oxidative stress in a model of pediatric asphyxial cardiac arrest.

DESIGN

Prospective, interventional study.

SETTING

University research laboratory.

SUBJECTS

Postnatal day 16-18 rats (n = 5 per group).

INTERVENTIONS

Rats underwent asphyxial cardiac arrest for 9 min. Rats were randomized to receive 100% oxygen, room air, or 100% oxygen with polynitroxyl albumin (10 mL·kg⁻¹ intravenously, 0 and 30 min after resuscitation) for 1 hr from the start of cardiopulmonary resuscitation. Shams recovered in 100% oxygen or room air after surgery.

MEASUREMENTS AND MAIN RESULTS

Physiological variables were recorded at baseline to 1 hr after resuscitation. At 6 hrs after asphyxial cardiac arrest, levels of reduced glutathione and protein-thiols (fluorescent assay), activities of total superoxide dismutase and mitochondrial manganese superoxide dismutase (cytochrome c reduction method), manganese superoxide dismutase expression (Western blot), and lipid peroxidation (4-hydroxynonenal Michael adducts) were evaluated in brain tissue homogenates. Hippocampal 3-nitrotyrosine levels were determined by immunohistochemistry 72 hrs after asphyxial cardiac arrest. Survival did not differ among groups. At 1 hr after resuscitation, Pao2, pH, and mean arterial pressure were decreased in room air vs. 100% oxygen rats (59 ± 3 vs. 465 ± 46 mm Hg, 7.36 ± 0.05 vs. 7.42 ± 0.03, 35 ± 4 vs. 45 ± 5 mm Hg; p < .05). Rats resuscitated with 100% oxygen had decreased hippocampal reduced glutathione levels vs. sham (15.3 ± 0.4 vs. 20.9 ± 4.1 nmol·mg protein⁻¹; p < .01). Hippocampal manganese superoxide dismutase activity was significantly increased in 100% oxygen rats vs. sham (14 ± 2.4 vs. 9.5 ± 1.6 units·mg protein⁻¹, p < .01), with no difference in protein expression of manganese superoxide dismutase. Room air and 100% oxygen plus polynitroxyl albumin groups had hippocampal reduced glutathione and manganese superoxide dismutase activity levels comparable with sham. Protein thiol levels were unchanged across groups. Compared with all other groups, rats receiving 100% oxygen had increased immunopositivity for 3-nitrotyrosine in the hippocampus and increased lipid peroxidation in the cortex.

CONCLUSIONS

Resuscitation with 100% oxygen leads to increased oxidative stress in a model that mimics pediatric cardiac arrest. This may be prevented by using room air or giving an antioxidant with 100% oxygen resuscitation.

Early biochemical effects after unilateral hypoxia-ischemia in the immature rat brain

Perinatal hypoxia-ischemia (HI) gives rise to inadequate substrate supply to the brain tissue, resulting in damage to neural cells. Previous studies at different time points of development, and with different animal species, suggest that the HI insult causes oxidative damage and changes Na+, K+-ATPase activity, which is known to be very susceptible to free radical-related lipid peroxidation. The aim of the present study was to establish the onset of the oxidative damage response in neonatal Wistar rats subjected to brain HI, evaluating parameters of oxidative stress, namely nitric oxide production, lipoperoxidation by thiobarbituric acid reactive substances (TBA-RS) production and malondialdehyde (MDA) levels, reactive species production by DCFH oxidation, antioxidant enzymatic activities of catalase, glutathione peroxidase, superoxide dismutase as well as Na+, K+-ATPase activity in hippocampus and cerebral cortex. Rat pups were subjected to right common carotid ligation followed by exposure to a hypoxic atmosphere (8% oxygen and 92% nitrogen) for 90 min. Animals were sacrificed by decapitation 0, 1 and 2 h after HI and both hippocampus and cerebral cortex from the right hemisphere (ipsilateral to the carotid occlusion) were dissected out for further experimentation. Results show an early decrease of Na+, K+-ATPase activity (at 0 and 1 h), as well as a late increase in MDA levels (2 h) and superoxide dismutase activity (1 and 2 h after HI) in the hippocampus. There was a late increase in both MDA levels and DCFH oxidation (1 and 2 h) and an increase in superoxide dismutase activity (2 h after HI) in cortex; however Na+, K+-ATPase activity remained unchanged. We suggest that neonatal HI induces oxidative damage to both hippocampus and cortex, in addition to a decrease in Na+, K+-ATPase activity in hippocampus early after the insult. These events might contribute to the later morphological damage in the brain and indicate that it would be essential to pursue neuroprotective strategies, aimed to counteract oxidative stress, as early as possible after the HI insult.

Isoprostane levels in urine of preterm newborns treated with ibuprofen for patent ductus arteriosus closure

Patent ductus arteriosus (PDA) is the most common cardiovascular abnormality of the preterm infant usually treated with ibuprofen (IBU). PDA is strictly related to oxidative stress (OS) in neonates. This study tests the hypothesis that OS occurs in neonates with PDA and that IBU treatment reduces OS. Forty-three preterm babies with gestational age (GA) <33 weeks were studied prospectively. Three urine samples were collected: at time 0 (before starting treatment), time 1 (after pharmacological PDA closure), and time 2 (7 days after the end of treatment) in all patients. OS was studied by measuring urinary isoprostane (IPs) levels. The results showed significant changes in urinary IP levels from time 0 to time 2 (Kruskal-Wallis, p=0.047). Time trend showed a significant decrease in IPs from time 0 to time 1 after IBU therapy (p=0.0067). This decrease was followed by an increase in IPs levels 7 days after treatment. IBU therapy for PDA closure reduced the risk of OS related to free-radical (FR) generation. This antioxidant effect of IBU may be beneficial in preterm babies with PDA who are at high risk for OS.

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.

Effects of spray-dried animal plasma on serous and intestinal redox status and cytokines of neonatal piglets

The study investigated the effects of dietary supplementation with spray-dried animal plasma (SDAP) on growth performance, intestinal morphology, as well as serum and intestinal cytokines and antioxidant indicators of artificially reared neonatal piglets. Three diets, 1) control (a fish meal basal diet), 2) SDAP (containing 10% SDAP), and 3) autoclaved SDAP (auSDAP; containing 10% auSDAP), were fed to 36 weaned piglets (3 d old), which were randomly allotted to 3 groups. At 21 d of age, blood and intestinal mucosal samples were collected from all piglets after they were slaughtered. Compared with the control, both SDAP and auSDAP improved ADFI and duodenal villus height of piglets (P < 0.05), whereas SDAP increased ADG and duodenal villus height to crypt depth ratio (P < 0.05). Piglets fed SDAP and auSDAP had reduced malondialdehyde (MDA) content in mucosa (P < 0.05). The concentration of serum MDA was decreased and mucosal catalase (CAT) activities were increased in piglets fed SDAP diet than those fed the control diet (P < 0.05). In the mucosa, both SDAP and auSDAP decreased tumor necrosis factor α, IL-6, transforming growth factor β, and soluble IL-2 receptor contents (P < 0.05). Mucosal IL-1β was decreased in SDAP compared with auSDAP and control groups (P < 0.05). The SDAP and control groups had increased mucosal IL-2 compared with auSDAP group (P < 0.05). The cytokines in serum were not affected by SDAP and auSDAP. The results indicate that both SDAP and auSDAP improved the growth performance of neonatal piglets, whereas the SDAP had a greater effect. The benefits of SDAP probably resulted from the promotion of the intestinal development, which were accompanied by the increased antioxidant capacity and the decreased production of inflammatory factors in the intestinal mucosa.

Reconvene and reconnect the antioxidant hypothesis in human health and disease

The antioxidants are essential molecules in human system but are not miracle molecules. They are neither performance enhancers nor can prevent or cure diseases when taken in excess. Their supplemental value is debateable. In fact, many high quality clinical trials on antioxidant supplement have shown no effect or adverse outcomes ranging from morbidity to all cause mortality. Several Chochrane Meta-analysis and Markov Model techniques, which are presently best available statistical models to derive conclusive answers for comparing large number of trials, support these claims. Nevertheless none of these statistical techniques are flawless. Hence, more efforts are needed to develop perfect statistical model to analyze the pooled data and further double blind, placebo controlled interventional clinical trials, which are gold standard, should be implicitly conducted to get explicit answers. Superoxide dismutase (SOD), glutathione peroxidase and catalase are termed as primary antioxidants as these scavenge superoxide anion and hydrogen peroxide. All these three enzymes are inducible enzymes, thereby inherently meaning that body increases or decreases their activity as per requirement. Hence there is no need to attempt to manipulate their activity nor have such efforts been clinically useful. SOD administration has been tried in some conditions especially in cancer and myocardial infarction but has largely failed, probably because SOD is a large molecule and can not cross cell membrane. The dietary antioxidants, including nutrient antioxidants are chain breaking antioxidants and in tandem with enzyme antioxidants temper the reactive oxygen species (ROS) and reactive nitrogen species (RNS) within physiological limits. Since body is able to regulate its own requirements of enzyme antioxidants, the diet must provide adequate quantity of non-enzymic antioxidants to meet the normal requirements and provide protection in exigent condition. So far, there is no evidence that human tissues ever experience the torrent of reactive species and that in chronic conditions with mildly enhanced generation of reactive species, the body can meet them squarely if antioxidants defense system in tissues is biochemically optimized. We are not yet certain about optimal levels of antioxidants in tissues. Two ways have been used to assess them: first by dietary intake and second by measuring plasma levels. Lately determination of plasma/serum level of antioxidants is considered better index for diagnostic and prognostic purposes. The recommended levels for vitamin A, E and C and beta carotene are 2.2-2.8 μmol/l; 27.5-30 μmol/l; 40-50 μmol/l and 0.4-0.5 μmol/l, respectively. The requirement and recommended blood levels of other dietary antioxidants are not established. The resolved issues are (1) essential to scavenge excess of radical species (2) participants in redox homeostasis (3) selective antioxidants activity against radical species (4) there is no universal antioxidant and 5) therapeutic value in case of deficiency. The overarching issues are (1) therapeutic value as adjuvant therapy in management of diseases (2) supplemental value in developing population (3) selective interactivity of antioxidant in different tissues and on different substrates (4) quantitative contribution in redox balance (5) mechanisms of adverse action on excess supplementation (6) advantages and disadvantages of prooxidant behavior of antioxidants (7) behavior in cohorts with polymorphic differences (8) interaction and intervention in radiotherapy, diabetes and diabetic complications and cardiovascular diseases (9) preventive behavior in neurological disorders (10) benefits of non-nutrient dietary antioxidants (11) markers to assess optimized antioxidants status (12) assessment of benefits of supplementation in alcoholics and heavy smokers. The unresolved and intriguing issues are (1) many compounds such as vitamin A and many others possessing both antioxidant and non-antioxidant properties contribute to both the activities in vivo or exclusively only to non-antioxidant activity and (2) since human tissues do not experience the surge of FR, whether there is any need to develop stronger synthetic antioxidants. Theoretically such antioxidants may do more harm than good.

The problem of the eukaryotic genome size

The current state of knowledge concerning the unsolved problem of the huge interspecific eukaryotic genome size variations not correlating with the species phenotypic complexity (C-value enigma also known as C-value paradox) is reviewed. Characteristic features of eukaryotic genome structure and molecular mechanisms that are the basis of genome size changes are examined in connection with the C-value enigma. It is emphasized that endogenous mutagens, including reactive oxygen species, create a constant nuclear environment where any genome evolves. An original quantitative model and general conception are proposed to explain the C-value enigma. In accordance with the theory, the noncoding sequences of the eukaryotic genome provide genes with global and differential protection against chemical mutagens and (in addition to the anti-mutagenesis and DNA repair systems) form a new, third system that protects eukaryotic genetic information. The joint action of these systems controls the spontaneous mutation rate in coding sequences of the eukaryotic genome. It is hypothesized that the genome size is inversely proportional to functional efficiency of the anti-mutagenesis and/or DNA repair systems in a particular biological species. In this connection, a model of eukaryotic genome evolution is proposed.

Ascorbic acid protects the newborn rat brain from hypoxic-ischemia

Ascorbic acid (AA) is a potent antioxidant, and its neuroprotective effect has not been established yet. Using the Rice-Vannucci model, we examined the effect of AA on hypoxic-ischemic (HI) injury in the immature rat brain. Under isoflurane anesthesia, 7-day-old rat pups received 750 mg/kg of AA by intraperitoneal injection just before hypoxic exposure; 8% oxygen for 90 min. Vehicle controls received an equal volume of saline. AA decreased a macroscopic brain injury score at 48 and 168 h post-HI compared with vehicle controls (48 h post-HI, AA 1.38+/-0.45 vs. controls 2.94+/-0.24, p<0.05; 168 h post-HI, 1.13+/-0.44 vs. 2.50+/-0.25, p<0.05). AA injection significantly decreased the number of both necrotic and apoptotic cells in cortex, caudate putamen, thalamus and hippocampus, and also seemed to reduce the number of TUNEL-positive cells. Western blot analysis showed that AA significantly suppressed 150/145 kDa subunits of alpha-fodrin breakdown products (FBDP) in cortex, striatum, thalamus and hippocampus at 24 and 48 h post-HI, and also 120 kDa subunit of FBDP in all examined regions except for thalamus, which indicated that AA injection inhibited both calpain and caspase-3 activation. Western blot analysis of nitrotyrosine failed to show inhibition of free radical production by AA, however, our results show that AA inhibits both necrotic and apoptotic cell death and that AA is neuroprotective after HI in immature rat brain.

Nanoparticle-mediated delivery of superoxide dismutase to the brain: an effective strategy to reduce ischemia-reperfusion injury

Excessive production of reactive oxygen species (ROS) after cerebral ischemia and reperfusion is implicated in brain damage through different cellular and molecular mechanisms, and it is further aggravated by impaired cellular antioxidant defense systems under ischemic conditions. Therapeutic strategies based on exogenous delivery of the native form of superoxide dismutase (SOD), a free radical scavenger, are limited because of its short half-life (approximately 6 min) in vivo and poor permeability across the blood-brain-barrier (BBB). We encapsulated SOD in biodegradable poly(D,L-lactide co-glycolide) nanoparticles (SOD-NPs) and tested their efficacy in a rat focal cerebral ischemia-reperfusion injury model. We hypothesized that localized brain delivery of SOD-NPs would sustain the protective effect of SOD by neutralizing the deleterious effects of ROS formed following ischemia-reperfusion. SOD-NPs were administered at the time of reperfusion via the intracarotid route to maximize their localization in the brain. Animals receiving SOD-NPs (10,000 U of SOD/kg) demonstrated a 65% reduction in infarct volume, whereas an equivalent dose of SOD in solution (SOD-Sol) increased it by 25% over saline control (P<0.001; data at 6 h following reperfusion). Control NPs alone or mixed with SOD-Sol were ineffective in reducing infract volume, with results similar to saline control, indicating the protective effect of the encapsulated enzyme. SOD-NPs maintained BBB integrity, thereby preventing edema, reduced the level of ROS formed following reperfusion, and protected neurons from undergoing apoptosis. Animals treated with SOD-NPs demonstrated greater survival than those with saline control (75% vs. 0% at 28 days) and later regained most vital neurological functions. SOD-NPs may be an effective treatment option in conjunction with a thrombolytic agent for stroke patients.

Antioxidant therapy and neuroprotection in the newborn

Injury to the perinatal brain is a leading cause of childhood mortality and lifelong disability. Despite recent improvements in neonatal care, no effective treatment for perinatal brain lesions is available. The newborn, especially if preterm, is highly prone to oxidative stress (OS) and to the toxic effect of free radicals (FRs). At birth, the newborn is exposed to a relatively hyperoxic environment caused by an increased oxygen bioavailability with greatly enhanced generation of FRs. Additional sources (e.g., 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 FRs. 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, erythropoietin, allopurinol, melatonin and hypothermia demonstrate great promise as potential neuroprotectans. This article provides an overview of the pathogenesis of FR-mediated diseases of the newborn and the antioxidant strategies now tested in order to reduce OS and its damaging effects.

Neuroprotection in infant heart surgery

Neonatal hypoxic-ischemic encephalopathy, prematurity, sepsis-meningitis, and serious forms of complex congenital heart disease requiring infant heart surgery are just a few examples of disorders that share high mortality and morbidity rates. Newborn heart surgery represents a period of planned and deliberate ischemia-reperfusion injury, which is obliged to occur to cure or palliate complex forms of congenital heart disease. Advances in cardiothoracic surgical and anesthetic techniques, including cardiopulmonary bypass and deep hypothermic circulatory arrest, have substantially decreased mortality, expanding the horizon to address functional neurologic and cardiac outcomes in long-term survivors. Interest in the functional status of survivors now stretches beyond the newborn period to childhood, adolescence, and adulthood.

Effect of erythropoietin on oxygen-induced brain injury in the newborn rat

The developing nervous system is sensitive to supraphysiological oxygen concentrations. Recent studies showed that exposure to hyperoxia in infant rats leads to extensive apoptotic degeneration in the cortex and white matter of the developing brain. A wide variety of experimental studies have shown that erythropoietin exerts a remarkable neuroprotection in both cell cultures and in animal models of nervous system disorders. In the present study, we investigated the effect of erythropoietin against hyperoxia-induced neurodegeneration in the developing brain. Eighteen Wistar rat pups were divided into three groups: control group, hyperoxia+saline-treated group and hyperoxia+erythropoietin-treated group. Hyperoxia groups were exposed to 80% oxygen (n=12) in a plexiglas chamber in which the oxygen concentration was monitored twice daily from birth until postnatal day 5. Hyperoxia exposure was 24h/day for 5 days. The hyperoxia+erythropoietin group received an intraperitoneal injection of recombinant human erythropoietin at a dose of 1000U/(kgday). At postnatal day 5, all animals were sacrificed. Neuronal cell death and apoptosis were evaluated. Histopathological examination showed that erythropoietin significantly diminished apoptosis in the CA1 region and dentate gyrus of hippocampus and parietal cortex in hyperoxia+erythropoietin-treated group. Regarding the safety profile of erythropoietin in premature and mature infants, this agent may be potentially beneficial in preventing hyperoxic brain injury.

Oxygen free radicals: effects in the newborn period

Free radical production occurs continuously in all cells as a by-product of cell metabolism. In tandem, the human body has developed endogenous antioxidant systems as well as taken advantage of dietary exogenous antioxidants to process and detoxify free radicals appropriately. However, certain conditions may increase free radical production beyond the body's endogenous and exogenous antioxidant systems. The neonatal period is a vulnerable time for free radical damage and injury, particularly for preterm infants whose antioxidant defense systems have not fully matured. Endogenous and passively acquired exogenous antioxidant defense systems do not accelerate in maturation until late in the third trimester. To explore the complexities of these concepts, this article includes a description, an evolutionary perspective of oxygen, and a basic background on free radical chemistry in biology. In addition, this chemistry is applied to the etiology of many of the most common diseases seen in the neonatal period. Finally, the current research addressing clinical strategies in this area is critically appraised. Implications for practice and directions for further research are presented with an emphasis on strategies that support the prudent use of oxygen therapies.

[An endogenous dithiol with antioxidant properties: alpha-lipoic acid, potential uses in cardiovascular diseases]

Alpha-Lipoic acid (ALA) is a natural compound, chemically named 1,2-dithiolane-3-pentanoic acid, also referred to as thioctic acid. In humans, ALA is synthetized by the liver and other tissues with high metabolic activity: heart, kidney. ALA is both water and fat soluble and therefore, is widely distributed in both cellular membranes and cytosol. Recently, a greater deal of attention has been given to antioxidant function for ALA and its reduced formed: dihydrolipoic acid (DHLA). ALA scavenges hydroxyl radicals, hypochlorous acid and singlet oxygen. It may also exert antioxidant effects in biological systems through transitional metal chelation. Dihydrolipoic acid has been shown to have antioxidant but also pro-oxidant properties in systems in which hydroxyl radical was generated. ALA/DHLA ratio has the capacity to recycle endogenous antioxidants such as vitamin E. A number of experimental as well as clinical studies point to the usefulness of ALA as a therapeutic agent for such diverse conditions as diabetes, atherosclerosis, insulin resistance, neuropathy, neurodegenerative diseases and ischemia-reperfusion injury. ALA represents a potential agent on the vascular endothelium, recording to ALA/DHLA redox couple is one of the most powerful biological antioxidant systems.

Low endogenous G-protein-coupled receptor kinase 2 sensitizes the immature brain to hypoxia-ischemia-induced gray and white matter damage

Hypoxic-ischemic brain injury is regulated in part by neurotransmitter and chemokine signaling via G-protein-coupled receptors (GPCRs). GPCR-kinase 2 (GRK2) protects these receptors against overstimulation by inducing desensitization. Neonatal hypoxic-ischemic brain damage is preceded by a reduction in cerebral GRK2 expression. We determined the functional importance of GRK2 in hypoxic-ischemic brain damage. Nine-day-old wild-type and GRK2(+/-) mice with a approximately 50% reduction in GRK2 protein were exposed to unilateral carotid artery occlusion and hypoxia. In GRK2(+/-) animals, gray and white matter damage was aggravated at 3 weeks after hypoxia-ischemia. In addition, cerebral neutrophil infiltration was increased in GRK2(+/-) animals. Neutrophil depletion reduced brain damage, but neuronal loss was still more pronounced in GRK2(+/-) animals. Onset of neuronal loss was advanced in GRK2(+/-) animals regardless of neutrophil depletion. White matter injury was advanced in GRK2(+/-) animals and was not affected by neutrophil depletion. Activation/infiltration of microglia/macrophages was stronger in GRK2(+/-) brains but only occurred 24 h after hypoxia-ischemia and is therefore not the primary cause of increased damage. During hypoxia, cerebral blood flow was reduced to the same extent in both genotypes. In vitro, GRK2(+/-) hippocampal slices and cerebellar granular neurons were more sensitive to glutamate-induced death. We propose the novel concept that the kinase GRK2 regulates onset and magnitude of hypoxic-ischemic brain damage. Increased gray and white matter damage in GRK2(+/-) animals was not dependent on infiltrating neutrophils and occurred before microglia/macrophage activation was detected. Collectively, our data suggest that cerebral GRK2 has an important endogenous neuroprotective role in ischemic cerebral damage.

Genetic and pharmacologic manipulation of oxidative stress after neonatal hypoxia-ischemia

Oxidative stress is a critical component of the injury response to hypoxia-ischemia (HI) in the neonatal brain, and this response is unique and at times paradoxical to that seen in the mature brain. Previously, we showed that copper-zinc superoxide-dismutase (SOD1) over-expression is not beneficial to the neonatal mouse brain with HI injury, unlike the adult brain with ischemic injury. However, glutathione peroxidase 1 (GPx1) over-expression is protective to the neonatal mouse brain with HI injury. To further test the hypothesis that an adequate supply of GPx is critical to protection from HI injury, we crossed SOD1 over-expressing mice (hSOD-tg) with GPx1 over-expressing mice (hGPx-tg). Resulting litters contained wild-type (wt), hGPx-tg, hSOD-tg and hybrid hGPx-tg/hSOD-tg pups, which were subjected to HI at P7. Confirming previous results, the hGPx-tg mice had reduced injury compared to both Wt and hSOD-tg littermates. Neonatal mice over-expressing both GPx1 and SOD1 also had less injury compared to wt or hSOD-tg alone. A result of oxidative stress after neonatal HI is a decrease in the concentration of reduced (i.e. antioxidant-active) glutathione (GSH). In this study, we tested the effect of systemic administration of alpha-lipoic acid on levels of GSH in the cortex after HI. Although GSH levels were restored by 24h after HI, injury was not reduced compared to vehicle-treated mice. We also tested two other pharmacological approaches to reducing oxidative stress in hSOD-tg and wild-type littermates. Both the specific inhibitor of neuronal nitric oxide synthase, 7-nitroindazole (7NI), and the spin-trapping agent alpha-phenyl-tert-butyl-nitrone (PBN) did not reduce HI injury, however. Taken together, these results imply that H2O2 is a critical component of neonatal HI injury, and GPx1 plays an important role in the defense against this H2O2 and is thereby neuroprotective.

Characterization and expression of Peroxiredoxin 1 in the neonatal tammar wallaby (Macropus eugenii)

Peroxiredoxin 1 (PRDX1) is a ubiquitously expressed antioxidant with vital roles in basal metabolic functions. In addition PRDX1 is involved in cell differentiation and proliferation, apoptosis and innate immunity. In this study, we have characterized PRDX1 from the tammar wallaby (Macropus eugenii). Tammar PRDX1 has high conservation of functional residues and motifs, and demonstrates a close homology with eutherian and vertebrate orthologues. Stimulation of adult tammar leukocytes with lipopolysaccharide and lipoteichoic acid suggests a role for PRDX1 in innate immune defences. PRDX1 expression in the organs of tammar pouch young was mildly elevated early in life possibly reflecting its role in basal metabolic processes. Later increases in PRDX1 expression correlated with functional maturation of several immune organs or with preparation for increased oxidative stress of emergence. The findings of the study are reflections of the complex integrated roles that PRDX1 has in regulation of oxidative stress, apoptosis, cell differentiation and proliferation, and innate immunity.