Effect of allopurinol on brain adenosine levels during hypoxia in newborn piglets

Detailed statistical analysis plan for ALBINO: effect of Allopurinol in addition to hypothermia for hypoxic-ischemic Brain Injury on Neurocognitive Outcome - a blinded randomized placebo-controlled parallel group multicenter trial for superiority (phase III)

BACKGROUND

Despite therapeutic hypothermia (TH) and neonatal intensive care, 45-50% of children affected by moderate-to-severe neonatal hypoxic-ischemic encephalopathy (HIE) die or suffer from long-term neurodevelopmental impairment. Additional neuroprotective therapies are sought, besides TH, to further improve the outcome of affected infants. Allopurinol - a xanthine oxidase inhibitor - reduced the production of oxygen radicals and subsequent brain damage in pre-clinical and preliminary human studies of cerebral ischemia and reperfusion, if administered before or early after the insult. This ALBINO trial aims to evaluate the efficacy and safety of allopurinol administered immediately after birth to (near-)term infants with early signs of HIE.

METHODS/DESIGN

The ALBINO trial is an investigator-initiated, randomized, placebo-controlled, double-blinded, multi-national parallel group comparison for superiority investigating the effect of allopurinol in (near-)term infants with neonatal HIE. Primary endpoint is long-term outcome determined as survival with neurodevelopmental impairment versus death versus non-impaired survival at 2 years.

RESULTS

The primary analysis with three mutually exclusive responses (healthy, death, composite outcome for impairment) will be on the intention-to-treat (ITT) population by a generalized logits model according to Bishop, Fienberg, Holland (Bishop YF, Discrete Multivariate Analysis: Therory and Practice, 1975) and ."will be stratified for the two treatment groups.

DISCUSSION

The statistical analysis for the ALBINO study was defined in detail in the study protocol and implemented in this statistical analysis plan published prior to any data analysis. This is in accordance with the Declaration of Helsinki and the International Conference on Harmonization Good Clinical Practice guidelines.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03162653. Registered on 22 May 2017.

Advances in Therapies to Treat Neonatal Hypoxic-Ischemic Encephalopathy

Neonatal hypoxic-ischemic encephalopathy (HIE) is a condition that results in brain damage in newborns due to insufficient blood and oxygen supply during or after birth. HIE is a major cause of neurological disability and mortality in newborns, with over one million neonatal deaths occurring annually worldwide. The severity of brain injury and the outcome of HIE depend on several factors, including the cause of oxygen deprivation, brain maturity, regional blood flow, and maternal health conditions. HIE is classified into mild, moderate, and severe categories based on the extent of brain damage and resulting neurological issues. The pathophysiology of HIE involves different phases, including the primary phase, latent phase, secondary phase, and tertiary phase. The primary and secondary phases are characterized by episodes of energy and cell metabolism failures, increased cytotoxicity and apoptosis, and activated microglia and inflammation in the brain. A tertiary phase occurs if the brain injury persists, characterized by reduced neural plasticity and neuronal loss. Understanding the cellular and molecular aspects of the different phases of HIE is crucial for developing new interventions and therapeutics. This review aims to discuss the pathophysiology of HIE, therapeutic hypothermia (TH), the only approved therapy for HIE, ongoing developments of adjuvants for TH, and potential future drugs for HIE.

Non-canonical pathways in the pathophysiology and therapeutics of bipolar disorder

Bipolar disorder (BD) is characterized by extreme mood swings ranging from manic/hypomanic to depressive episodes. The severity, duration, and frequency of these episodes can vary widely between individuals, significantly impacting quality of life. Individuals with BD spend almost half their lives experiencing mood symptoms, especially depression, as well as associated clinical dimensions such as anhedonia, fatigue, suicidality, anxiety, and neurovegetative symptoms. Persistent mood symptoms have been associated with premature mortality, accelerated aging, and elevated prevalence of treatment-resistant depression. Recent efforts have expanded our understanding of the neurobiology of BD and the downstream targets that may help track clinical outcomes and drug development. However, as a polygenic disorder, the neurobiology of BD is complex and involves biological changes in several organelles and downstream targets (pre-, post-, and extra-synaptic), including mitochondrial dysfunction, oxidative stress, altered monoaminergic and glutamatergic systems, lower neurotrophic factor levels, and changes in immune-inflammatory systems. The field has thus moved toward identifying more precise neurobiological targets that, in turn, may help develop personalized approaches and more reliable biomarkers for treatment prediction. Diverse pharmacological and non-pharmacological approaches targeting neurobiological pathways other than neurotransmission have also been tested in mood disorders. This article reviews different neurobiological targets and pathophysiological findings in non-canonical pathways in BD that may offer opportunities to support drug development and identify new, clinically relevant biological mechanisms. These include: neuroinflammation; mitochondrial function; calcium channels; oxidative stress; the glycogen synthase kinase-3 (GSK3) pathway; protein kinase C (PKC); brain-derived neurotrophic factor (BDNF); histone deacetylase (HDAC); and the purinergic signaling pathway.

New possibilities for neuroprotection in neonatal hypoxic-ischemic encephalopathy

Around 0.75 million babies worldwide suffer from moderate or severe hypoxic-ischemic encephalopathy (HIE) each year resulting in around 400,000 babies with neurodevelopmental impairment. In 2010, neonatal HIE was associated with 2.4% of the total Global Burden of Disease. Therapeutic hypothermia (TH), a treatment that is now standard of care in high-income countries, provides proof of concept that strategies that aim to improve neurodevelopment are not only possible but can also be implemented to clinical practice. While TH is beneficial, neonates with moderate or severe HIE treated with TH still experience devastating complications: 48% (range: 44-53) combined death or moderate/severe disability. There is a concern that TH may not be effective in low- and middle-income countries. Therapies that further improve outcomes are desperately needed, and in high-income countries, they must be tested in conjunction with TH. We have in this review focussed on pharmacological treatment options (e.g. erythropoietin, allopurinol, melatonin, cannabidiol, exendin-4/exenatide). Erythropoietin and allopurinol show promise and are progressing towards the clinic with ongoing definitive phase 3 randomised placebo-controlled trials. However, there remain global challenges for the next decade. Conclusion: There is a need for more optimal animal models, greater industry support/sponsorship, increased use of juvenile toxicology, dose-ranging studies with pharmacokinetic-pharmacodynamic modelling, and well-designed clinical trials to avoid exposure to harmful medications or abandoning putative treatments. What is Known: • Therapeutic hypothermia is beneficial in neonatal hypoxic-ischemic encephalopathy. • Neonates with moderate or severe hypoxic-ischemic encephalopathy treated with therapeutic hypothermia still experience severe sequelae. What is New: • Erythropoietin, allopurinol, melatonin, cannabidiol, and exendin-4/exenatide show promise in conjunction with therapeutic hypothermia. • There is a need for more optimal animal models, greater industry support/sponsorship, increased use of juvenile toxicology, dose-ranging studies with pharmacokinetic-pharmacodynamic modelling, and well-designed clinical trials.

CeRebrUm and CardIac Protection with ALlopurinol in Neonates with Critical Congenital Heart Disease Requiring Cardiac Surgery with Cardiopulmonary Bypass (CRUCIAL): study protocol of a phase III, randomized, quadruple-blinded, placebo-controlled, Dutch multicenter trial

Background

Neonates with critical congenital heart disease (CCHD) undergoing cardiac surgery with cardiopulmonary bypass (CPB) are at risk of brain injury that may result in adverse neurodevelopment. To date, no therapy is available to improve long-term neurodevelopmental outcomes of CCHD neonates. Allopurinol, a xanthine oxidase inhibitor, prevents the formation of reactive oxygen and nitrogen species, thereby limiting cell damage during reperfusion and reoxygenation to the brain and heart. Animal and neonatal studies suggest that allopurinol reduces hypoxic-ischemic brain injury and is cardioprotective and safe. This trial aims to test the hypothesis that allopurinol administration in CCHD neonates will result in a 20% reduction in moderate to severe ischemic and hemorrhagic brain injury.

Methods

This is a phase III, randomized, quadruple-blinded, placebo-controlled, multicenter trial. Neonates with a prenatal or postnatal CCHD diagnosis requiring cardiac surgery with CPB in the first 4 weeks after birth are eligible to participate. Allopurinol or mannitol-placebo will be administered intravenously in 2 doses early postnatally in neonates diagnosed antenatally and 3 doses perioperatively of 20 mg/kg each in all neonates. The primary outcome is a composite endpoint of moderate/severe ischemic or hemorrhagic brain injury on early postoperative MRI, being too unstable for postoperative MRI, or mortality within 1 month following CPB. A total of 236 patients (n = 188 with prenatal diagnosis) is required to demonstrate a reduction of the primary outcome incidence by 20% in the prenatal group and by 9% in the postnatal group (power 80%; overall type 1 error controlled at 5%, two-sided), including 1 interim analysis at n = 118 (n = 94 with prenatal diagnosis) with the option to stop early for efficacy. Secondary outcomes include preoperative and postoperative brain injury severity, white matter injury volume (MRI), and cardiac function (echocardiography); postnatal and postoperative seizure activity (aEEG) and regional cerebral oxygen saturation (NIRS); neurodevelopment at 3 months (general movements); motor, cognitive, and language development and quality of life at 24 months; and safety and cost-effectiveness of allopurinol.

Discussion

This trial will investigate whether allopurinol administered directly after birth and around cardiac surgery reduces moderate/severe ischemic and hemorrhagic brain injury and improves cardiac function and neurodevelopmental outcome in CCHD neonates.

Trial registration

EudraCT 2017-004596-31. Registered on November 14, 2017. ClinicalTrials.gov NCT04217421. Registered on January 3, 2020

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06098-y.

Semi-mechanistic Modeling of Hypoxanthine, Xanthine, and Uric Acid Metabolism in Asphyxiated Neonates

BACKGROUND AND OBJECTIVE

Previously, we developed a pharmacokinetic-pharmacodynamic model of allopurinol, oxypurinol, and biomarkers, hypoxanthine, xanthine, and uric acid, in neonates with hypoxic-ischemic encephalopathy, in which high initial biomarker levels were observed suggesting an impact of hypoxia. However, the full pharmacodynamics could not be elucidated in our previous study. The current study included additional data from the ALBINO study (NCT03162653) placebo group, aiming to characterize the dynamics of hypoxanthine, xanthine, and uric acid in neonates with hypoxic-ischemic encephalopathy.

METHODS

Neonates from the ALBINO study who received allopurinol or placebo mannitol were included. An extended population pharmacokinetic-pharmacodynamic model was developed based on the mechanism of purine metabolism, where synthesis, salvage, and degradation via xanthine oxidoreductase pathways were described. The initial level of the biomarkers was a combination of endogenous turnover and high disease-related amounts. Model development was accomplished by nonlinear mixed-effects modeling (NONMEM^®, version 7.5).

RESULTS

In total, 20 neonates treated with allopurinol and 17 neonates treated with mannitol were included in this analysis. Endogenous synthesis of the biomarkers reduced with 0.43% per hour because of precursor exhaustion. Hypoxanthine was readily salvaged or degraded to xanthine with rate constants of 0.5 1/h (95% confidence interval 0.33-0.77) and 0.2 1/h (95% confidence interval 0.09-0.31), respectively. A greater salvage was found in the allopurinol treatment group consistent with its mechanism of action. High hypoxia-induced initial levels of biomarkers were quantified, and were 1.2-fold to 2.9-fold higher in neonates with moderate-to-severe hypoxic-ischemic encephalopathy compared with those with mild hypoxic-ischemic encephalopathy. Half-maximal xanthine oxidoreductase inhibition was achieved with a combined allopurinol and oxypurinol concentration of 0.68 mg/L (95% confidence interval 0.48-0.92), suggesting full xanthine oxidoreductase inhibition during the period studied.

CONCLUSIONS

This extended pharmacokinetic-pharmacodynamic model provided an adequate description of the complex hypoxanthine, xanthine, and uric acid metabolism in neonates with hypoxic-ischemic encephalopathy, suggesting a positive allopurinol effect on these biomarkers. The impact of hypoxia on their dynamics was characterized, underlining higher hypoxia-related initial exposure with a more severe hypoxic-ischemic encephalopathy status.

Pharmacokinetic/Pharmacodynamic Modelling of Allopurinol, its Active Metabolite Oxypurinol, and Biomarkers Hypoxanthine, Xanthine and Uric Acid in Hypoxic-Ischemic Encephalopathy Neonates

Background

Allopurinol, an xanthine oxidase (XO) inhibitor, is a promising intervention that may provide neuroprotection for neonates with hypoxic-ischemic encephalopathy (HIE). Currently, a double-blind, placebo-controlled study (ALBINO, NCT03162653) is investigating the neuroprotective effect of allopurinol in HIE neonates.

Objective

The aim of the current study was to establish the pharmacokinetics (PK) of allopurinol and oxypurinol, and the pharmacodynamics (PD) of both compounds on hypoxanthine, xanthine, and uric acid in HIE neonates. The dosage used and the effect of allopurinol in this population, either or not undergoing therapeutic hypothermia (TH), were evaluated.

Methods

Forty-six neonates from the ALBINO study and two historical clinical studies were included. All doses were administered on the first day of life. In the ALBINO study (n = 20), neonates received a first dose of allopurinol 20 mg/kg, and, in the case of TH (n = 13), a second dose of allopurinol 10 mg/kg. In the historical cohorts (n = 26), neonates (all without TH) received two doses of allopurinol 20 mg/kg in total. Allopurinol and oxypurinol population PK, and their effects on inhibiting conversions of hypoxanthine and xanthine to uric acid, were assessed using nonlinear mixed-effects modelling.

Results

Allopurinol and oxypurinol PK were described by two sequential one-compartment models with an autoinhibition effect on allopurinol metabolism by oxypurinol. For allopurinol, clearance (CL) was 0.83 L/h (95% confidence interval [CI] 0.62–1.09) and volume of distribution (V_d) was 2.43 L (95% CI 2.25–2.63). For metabolite oxypurinol, CL and V_d relative to a formation fraction (f_m) were 0.26 L/h (95% CI 0.23–0.3) and 11 L (95% CI 9.9–12.2), respectively. No difference in allopurinol and oxypurinol CL was found between TH and non-TH patients. The effect of allopurinol and oxypurinol on XO inhibition was described by a turnover model of hypoxanthine with sequential metabolites xanthine and uric acid. The combined allopurinol and oxypurinol concentration at the half-maximal XO inhibition was 0.36 mg/L (95% CI 0.31–0.42).

Conclusion

The PK and PD of allopurinol, oxypurinol, hypoxanthine, xanthine, and uric acid in neonates with HIE were described. The dosing regimen applied in the ALBINO trial leads to the targeted XO inhibition in neonates treated with or without TH.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40262-021-01068-0.

Allopurinol for fibromyalgia pain in adults: A randomized controlled trial

BACKGROUND

Allopurinol is a potent inhibitor of the enzyme xanthine oxidase used in the treatment of hyperuricemia and gout. Because it is well known that purines exert multiple affects on pain transmission, we hypothesized that the inhibition of xanthine oxidase by allopurinol could be a valid strategy to treat pain in humans. This study aimed to compare the analgesic efficacy of oral allopurinol versus placebo as an adjuvant therapy in patients displaying fibromyalgia.

METHODS

This randomized, double-blinded, placebo-controlled study included 60 women with the diagnosis of fibromyalgia. Patients were randomly assigned to receive either oral allopurinol 300 mg (n = 31) or placebo (n = 29) twice daily during 30 days. The patients were submitted to evaluation for pain sensitivity, anxiety, depression, and functional status before treatment, and 15 and 30 days thereafter.

RESULTS

Oral administration of allopurinol 300 mg twice daily was ineffective in improving pain scores measured by several tools up to 30 days of treatment (P > 0.05). Additionally, no significant effects of allopurinol over anxiety, depressive symptoms, and functional status of fibromyalgia patients were observed in the present study.

CONCLUSIONS

Although previous findings indicated that allopurinol could present intrinsic analgesic effects in both animals and humans, this study showed no benefit of the use of oral allopurinol as an adjuvant strategy during 30 days in women displaying fibromyalgia. However, considering previous promising results, new prospective studies are still valid to further investigate allopurinol and more selective purine derivatives in the management of pain syndromes.

Intracellular Signaling Cascades in Bipolar Disorder

Bipolar spectrum disorders carry a significant public health burden. Disproportionately high rates of suicide, incarceration, and comorbid medical conditions necessitate an extraordinary focus on understanding the intricacies of this disease. Elucidating granular, intracellular details seems to be a necessary preamble to advancing promising therapeutic opportunities. In this chapter, we review a wide range of intracellular mechanisms including mitochondrial energetics, calcium signaling, neuroinflammation, the microbiome, neurotransmitter metabolism, glycogen synthase kinase 3-beta (GSK3β), protein kinase C (PKC) and diacylglycerol (DAG), and neurotrophins (especially BDNF), as well as the glutamatergic, dopaminergic, purinergic, and neurohormonal systems. Owing to the relative lack of understanding and effective therapeutic options compared to the rest of the spectrum, special attention is paid in the chapter to the latest developments in bipolar depression. Likewise, from a therapeutic standpoint, special attention should be paid to the pervasive mechanistic actions of lithium as a means of amalgamating numerous, disparate cascades into a digestible cognitive topology.

Excess Iron Enhances Purine Catabolism Through Activation of Xanthine Oxidase and Impairs Myelination in the Hippocampus of Nursing Piglets

BACKGROUND

Few studies have addressed the risk of nutritional iron overexposure in infancy. We previously found that excess dietary iron in nursing piglets resulted in iron overload in the liver and hippocampus and diminished socialization with novel conspecifics in a test for social novelty preference.

OBJECTIVES

This experiment aimed to identify metabolites and metabolic pathways affected by iron overload in the liver and hippocampus of nursing piglets.

METHODS

Liver and hippocampal tissues collected from 22-d-old piglets (Hampshire × Yorkshire crossbreed; 5.28 ± 0.53 kg body weight; 50% male) that received orally 0 (NI group) or 50 mg iron/(d · kg body weight) (HI group) from postnatal day (PD) 2 to PD21 were analyzed for mRNA and protein expression and enzyme activity of xanthine oxidase (XO). Untargeted metabolomics was performed using GC-MS. Expression of myelin basic protein (MBP) in the hippocampus was determined using western blot.

RESULTS

There were 108 and 126 metabolites identified in the hippocampus and liver, respectively. Compared with NI, HI altered 15 metabolites (P < 0.05, q < 0.2) in the hippocampus, including a reduction in myo-inositol (0.86-fold) and N-acetylaspartic acid (0.84-fold), 2 metabolites important for neuronal function and myelination. Seven metabolites involved in purine and pyrimidine metabolism (e.g., hypoxanthine, xanthine, and β-alanine) were coordinately changed in the hippocampus (P < 0.05, q < 0.2), suggesting that iron excess enhanced purine catabolism. The mRNA expression (2.3-fold) (P < 0.05) and activity of XO, a rate-limiting enzyme in purine degradation, was increased. Excess iron increased hippocampal lipid peroxidation by 74% (P < 0.05) and decreased MBP by 44% (P = 0.053). The hepatic metabolome was unaffected.

CONCLUSIONS

In nursing piglets, excess iron enhances hippocampal purine degradation through activation of XO, which may induce oxidative stress and alter energy metabolism in the developing brain.

Effect of allopurinol in addition to hypothermia treatment in neonates for hypoxic-ischemic brain injury on neurocognitive outcome (ALBINO): study protocol of a blinded randomized placebo-controlled parallel group multicenter trial for superiority (phase III)

Background

Perinatal asphyxia and resulting hypoxic-ischemic encephalopathy is a major cause of death and long-term disability in term born neonates. Up to 20,000 infants each year are affected by HIE in Europe and even more in regions with lower level of perinatal care. The only established therapy to improve outcome in these infants is therapeutic hypothermia. Allopurinol is a xanthine oxidase inhibitor that reduces the production of oxygen radicals as superoxide, which contributes to secondary energy failure and apoptosis in neurons and glial cells after reperfusion of hypoxic brain tissue and may further improve outcome if administered in addition to therapeutic hypothermia.

Methods

This study on the effects of ALlopurinol in addition to hypothermia treatment for hypoxic-ischemic Brain Injury on Neurocognitive Outcome (ALBINO), is a European double-blinded randomized placebo-controlled parallel group multicenter trial (Phase III) to evaluate the effect of postnatal allopurinol administered in addition to standard of care (including therapeutic hypothermia if indicated) on the incidence of death and severe neurodevelopmental impairment at 24 months of age in newborns with perinatal hypoxic-ischemic insult and signs of potentially evolving encephalopathy. Allopurinol or placebo will be given in addition to therapeutic hypothermia (where indicated) to infants with a gestational age ≥ 36 weeks and a birth weight ≥ 2500 g, with severe perinatal asphyxia and potentially evolving encephalopathy. The primary endpoint of this study will be death or severe neurodevelopmental impairment versus survival without severe neurodevelopmental impairment at the age of two years. Effects on brain injury by magnetic resonance imaging and cerebral ultrasound, electric brain activity, concentrations of peroxidation products and S100B, will also be studied along with effects on heart function and pharmacokinetics of allopurinol after iv-infusion.

Discussion

This trial will provide data to assess the efficacy and safety of early postnatal allopurinol in term infants with evolving hypoxic-ischemic encephalopathy. If proven efficacious and safe, allopurinol could become part of a neuroprotective pharmacological treatment strategy in addition to therapeutic hypothermia in children with perinatal asphyxia.

Trial registration

NCT03162653, www.ClinicalTrials.gov, May 22, 2017.

Current and Emerging Therapies in the Management of Hypoxic Ischemic Encephalopathy in Neonates

Neonatal hypoxic ischemic encephalopathy (HIE) presents a significant clinical burden with its high mortality and morbidity rates globally. Therapeutic hypothermia (TH) is now standard of care for infants with moderate to severe HIE, but has not definitively changed outcomes in severe HIE. In this review, we discuss newer promising markers that may help the clinician identify severity of HIE. Therapies that are beneficial and agents that hold promise for neuroprotection are described, both for use either alone or as adjuncts to TH. These include endogenous pathway modifiers such as erythropoietin and analogues, melatonin, and remote ischemic post conditioning. Stem cells have therapeutic potential in this condition, as in many other neonatal conditions. Of the agents listed, only erythropoietin and analogues are currently being evaluated in large randomized controlled trials (RCTs). Exogenous therapies such as argon and xenon, allopurinol, monosialogangliosides, and magnesium sulfate continue to be investigated. The recognition of tertiary mechanisms of brain damage has opened up new research into therapies not only to attenuate brain damage but also to promote cell repair and regeneration in a developmentally disorganized brain long after the perinatal insult. These alternative modalities may be especially important in mild HIE and in areas of the world where there is limited access to expensive hypothermia equipment and services.

Neuroprotection with hypothermia and allopurinol in an animal model of hypoxic-ischemic injury: Is it a gender question?

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) is one of the most important causes of neonatal brain injury. Therapeutic hypothermia (TH) is the standard treatment for term newborns after perinatal hypoxic ischemic injury (HI). Despite this, TH does not provide complete neuroprotection. Allopurinol seems to be a good neuroprotector in several animal studies, but it has never been tested in combination with hypothermia. Clinical findings show that male infants with (HI) fare more poorly than matched females in cognitive outcomes. However, there are few studies about neuroprotection taking gender into account in the results. The aim of the present study was to evaluate the potential additive neuroprotective effect of allopurinol when administrated in association with TH in a rodent model of moderate HI. Gender differences in neuroprotection were also evaluated.

METHODS

P10 male and female rat pups were subjected to HI (Vannucci model) and randomized into five groups: sham intervention (Control), no treatment (HI), hypothermia (HIH), allopurinol (HIA), and dual therapy (hypothermia and allopurinol) (HIHA). To evaluate a treatment's neuroprotective efficiency, 24 hours after the HI event caspase3 activation was measured. Damaged area and hippocampal volume were also measured 72 hours after the HI event. Negative geotaxis test was performed to evaluate early neurobehavioral reflexes. Learning and spatial memory were assessed via Morris Water Maze (MWM) test at 25 days of life.

RESULTS

Damaged area and hippocampal volume were different among treatment groups (p = 0.001). The largest tissue lesion was observed in the HI group, followed by HIA. There were no differences between control, HIH, and HIHA. When learning process was analyzed, no differences were found. Females from the HIA group had similar results to the HIH and HIHA groups. Cleaved caspase 3 expression was increased in both HI and HIA. Despite this, in females cleaved caspase-3 was only differently increased in the HI group. All treated animals present an improvement in short-term (Negative geotaxis) and long-term (WMT) functional tests. Despite this, treated females present better long-term outcome. In short-term outcome no sex differences were observed.

CONCLUSIONS

Our results suggest that dual therapy confers great neuroprotection after an HI event. There were functional, histological, and molecular improvements in all treated groups. These differences were more important in females than in males. No statistically significant differences were found between HIHA and HIH; both of them present a great improvement. Our results support the idea of different regulation mechanisms and pathways of cell death, depending on gender.

Role of Antioxidants in Neonatal Hypoxic-Ischemic Brain Injury: New Therapeutic Approaches

Hypoxic-ischemic brain damage is an alarming health and economic problem in spite of the advances in neonatal care. It can cause mortality or detrimental neurological disorders such as cerebral palsy, motor impairment and cognitive deficits in neonates. When hypoxia-ischemia occurs, a multi-faceted cascade of events starts out, which can eventually cause cell death. Lower levels of oxygen due to reduced blood supply increase the production of reactive oxygen species, which leads to oxidative stress, a higher concentration of free cytosolic calcium and impaired mitochondrial function, triggering the activation of apoptotic pathways, DNA fragmentation and cell death. The high incidence of this type of lesion in newborns can be partly attributed to the fact that the developing brain is particularly vulnerable to oxidative stress. Since antioxidants can safely interact with free radicals and terminate that chain reaction before vital molecules are damaged, exogenous antioxidant therapy may have the potential to diminish cellular damage caused by hypoxia-ischemia. In this review, we focus on the neuroprotective effects of antioxidant treatments against perinatal hypoxic-ischemic brain injury, in the light of the most recent advances.

Neuroprotective agents for neonatal hypoxic-ischemic brain injury

Hypoxic-ischemic (H-I) brain injury in newborns is a major cause of morbidity and mortality that claims thousands of lives each year. In this review, we summarize the promising neuroprotective agents tested on animal models and pilot clinical studies of neonatal H-I brain injury according to the different phases of the disease. These agents target various phases of injury including the early phase of excitotoxicity, oxidative stress and apoptosis as well as late-phase inflammatory reaction and neural repair. We analyze the cell survival and cell death pathways modified by these agents in neonatal H-I brain injury. We aim to 'build a bridge' between animal trials of neuroprotective agents and potential candidate treatments for future clinical applications against H-I encephalopathy.

New antioxidant drugs for neonatal brain injury

The brain injury concept covers a lot of heterogeneity in terms of aetiology involving multiple factors, genetic, hemodynamic, metabolic, nutritional, endocrinological, toxic, and infectious mechanisms, acting in antenatal or postnatal period. Increased vulnerability of the immature brain to oxidative stress is documented because of the limited capacity of antioxidant enzymes and the high free radicals (FRs) generation in rapidly growing tissue. FRs impair transmembrane enzyme Na⁺/K⁺-ATPase activity resulting in persistent membrane depolarization and excessive release of FR and excitatory aminoacid glutamate. Besides being neurotoxic, glutamate is also toxic to oligodendroglia, via FR effects. Neuronal cells die of oxidative stress. Excess of free iron and deficient iron/binding metabolising capacity are additional features favouring oxidative stress in newborn. Each step in the oxidative injury cascade has become a potential target for neuroprotective intervention. The administration of antioxidants for suspected or proven brain injury is still not accepted for clinical use due to uncertain beneficial effects when treatments are started after resuscitation of an asphyxiated newborn. The challenge for the future is the early identification of high-risk babies to target a safe and not toxic antioxidant therapy in combination with standard therapies to prevent brain injury and long-term neurodevelopmental impairment.

Allopurinol for mania: a randomized trial of allopurinol versus placebo as add-on treatment to mood stabilizers and/or antipsychotic agents in manic patients with bipolar disorder

OBJECTIVE

An emerging body of evidence supports a role for dysfunctional purinergic neurotransmission in mood disorders. Adenosine agonists have been shown to have properties similar to those of dopamine antagonists; there is a well-characterized interaction between adenosine and dopamine receptors in the ventral striatum, and increasing adenosinergic transmission has been demonstrated to reduce the affinity of dopamine agonists for dopamine receptors. Allopurinol increases adenosine levels in the brain, and hence is hypothesized to reduce the symptoms of mania. Two randomized, placebo-controlled trials administering add-on allopurinol to manic patients showed significantly greater improvements in Young Mania Rating Scale (YMRS) scores for drug compared to placebo, while a more recent, relatively small, add-on study showed negative results. Based on these data, our objective was to examine the efficacy of allopurinol as add-on treatment to mood stabilizers and/or antipsychotic agents in manic patients with bipolar disorder.

METHODS

We performed a large, well-powered, multicenter, six-week, randomized, placebo-controlled trial of allopurinol added to mood stabilizers and/or antipsychotic agents in 180 patients with bipolar disorder in an acute manic episode.

RESULTS

Both groups showed improvement on the YMRS (effect size of 1.5 for placebo and 1.6 for allopurinol), with no difference observed between groups on YMRS scores (t = 0.28, p = 0.78). There was no difference in the proportion of patients who responded to treatment (defined as showing at least 50% improvement in YMRS score) between the two groups (p = 0.92), or in dropout rates (p = 0.84).

LIMITATIONS

None of our patients received lithium. However, the side effects of lithium and its narrow therapeutic index made the use of lithium less common and, therefore, our study results reflect common current clinical practice. In the present study, we used a variety of antipsychotic and/or mood stabilizing treatments, to which we added allopurinol; one might hypothesize that add-on allopurinol has a different effect in combination with different antipsychotic agents or mood stabilizers.

CONCLUSIONS

The findings of this large, well-powered study do not support add-on allopurinol as a treatment for acute mania. This study did not test the efficacy of allopurinol as monotherapy.

Neuroprotective therapies after perinatal hypoxic-ischemic brain injury

Hypoxic-ischemic (HI) brain injury is one of the main causes of disabilities in term-born infants. It is the result of a deprivation of oxygen and glucose in the neural tissue. As one of the most important causes of brain damage in the newborn period, the neonatal HI event is a devastating condition that can lead to long-term neurological deficits or even death. The pattern of this injury occurs in two phases, the first one is a primary energy failure related to the HI event and the second phase is an energy failure that takes place some hours later. Injuries that occur in response to these events are often manifested as severe cognitive and motor disturbances over time. Due to difficulties regarding the early diagnosis and treatment of HI injury, there is an increasing need to find effective therapies as new opportunities for the reduction of brain damage and its long term effects. Some of these therapies are focused on prevention of the production of reactive oxygen species, anti-inflammatory effects, anti-apoptotic interventions and in a later stage, the stimulation of neurotrophic properties in the neonatal brain which could be targeted to promote neuronal and oligodendrocyte regeneration.

A randomized controlled trial of allopurinol vs. placebo added on to antipsychotics in patients with schizophrenia or schizoaffective disorder

Adenosine agonists produce behavioral effects similar to dopamine antagonists, hence increasing adenosine levels might improve symptoms of schizophrenia. This hypothesis is supported by three single-site studies indicating that allopurinol, which increases adenosine levels, improved symptoms in patients with schizophrenia. We performed a multi-center, 8-week RCT of allopurinol vs. placebo added to anti-psychotic medications in 248 patients with schizophrenia or schizoaffective disorder. Both groups showed improvement in the PANSS (effect size 1.13) and in clinical and cognitive measures. No difference was observed between groups in primary (t=0.01, p=0.992) or secondary outcome measures. These findings do not support allopurinol as a treatment for schizophrenia.

Allopurinol augmentation in the outpatient treatment of bipolar mania: a pilot study

BACKGROUND

Allopurinol promotes the salvage of purines, possibly increasing endogenous adenosine levels. Recent studies suggest that adenosine has neuroprotective and inhibitory effects. Two previous inpatient trials demonstrated that allopurinol has anti-manic activity. Our objective was to test allopurinol as an adjunct to standard medications in bipolar disorder manic outpatients.

METHODS

In this double-blind, placebo-controlled trial, 27 subjects who met DSM-IV criteria for bipolar disorder and scored ≥ 14 on the Young Mania Rating Scale (YMRS) were randomized to augmentation with allopurinol or placebo for six weeks. The primary efficacy measure was the YMRS. The primary safety measure was the Treatment Emergent Symptom Scale.

RESULTS

The effect of allopurinol augmentation in decreasing mean YMRS scores was modest, with an overall effect size of -0.25 (Cohen's d). Allopurinol-treated individuals who abstained from caffeine (n = 4) had a greater decrease in YMRS scores (-15.3 ± 1.8) than subjects using caffeine (n = 5) (-9.6 ± 3.4, p = 0.219), with an effect size of -0.86.

CONCLUSION

In this small outpatient pilot study, allopurinol augmentation did not show a statistically significant improvement over placebo in attenuating manic symptoms. Subjects with restricted caffeine use showed a greater effect size compared to caffeine users. This finding may be interpreted as corroborating the hypothesized mechanism of action of allopurinol's anti-manic effect in previous studies.

Placental transfer and pharmacokinetics of allopurinol in late pregnant sows and their fetuses

At present no standard pharmacological intervention strategy is available to reduce these adverse effects of birth asphyxia. In the present study we aimed to evaluate placental transfer of allopurinol, an inhibitor of XOR. For this purpose, fetal catheterization of the jugular vein was conducted in five late pregnant sows (one fetus per sow). At 24-48 h after surgery, sows received allopurinol (15 mg/kg body weight; i.v.) and pharmacokinetics of allopurinol and its active metabolite oxypurinol were measured in both late pregnant sows and fetuses. Maternal and fetal blood samples were collected during and after allopurinol administration. Maternal C(max) values averaged 41.90 microg/mL (allopurinol) and 3.68 microg/mL (oxypurinol). Allopurinol crossed the placental barrier as shown by the average fetal C(max) values of 5.05 microg/mL at 1.47 h after allopurinol administration to the sow. In only one fetus low plasma oxypurinol concentrations were found. Incubations of subcellular hepatic fractions of sows and 24-h-old piglets confirmed that allopurinol could be metabolized into oxypurinol. In conclusion, we demonstrated that allopurinol can cross the placental barrier, a prerequisite for further studies evaluating the use of allopurinol as a neuroprotective agent to reduce the adverse effects following birth asphyxia in neonatal piglets.

Anti-nociceptive properties of the xanthine oxidase inhibitor allopurinol in mice: role of A1 adenosine receptors

BACKGROUND AND PURPOSE

Allopurinol is a potent inhibitor of the enzyme xanthine oxidase, used primarily in the treatment of hyperuricemia and gout. It is well known that purines exert multiple effects on pain transmission. We hypothesized that the inhibition of xanthine oxidase by allopurinol, thereby reducing purine degradation, could be a valid strategy to enhance purinergic activity. The aim of this study was to investigate the anti-nociceptive profile of allopurinol on chemical and thermal pain models in mice.

EXPERIMENTAL APPROACH

Mice received an intraperitoneal (i.p.) injection of vehicle (Tween 10%) or allopurinol (10-400 mg kg(-1)). Anti-nociceptive effects were measured with intraplantar capsaicin, intraplantar glutamate, tail-flick or hot-plate tests.

KEY RESULTS

Allopurinol presented dose-dependent anti-nociceptive effects in all models. The opioid antagonist naloxone did not affect these anti-nociceptive effects. The non-selective adenosine-receptor antagonist caffeine and the selective A(1) adenosine-receptor antagonist, DPCPX, but not the selective A(2A) adenosine-receptor antagonist, SCH58261, completely prevented allopurinol-induced anti-nociception. No obvious motor deficits were produced by allopurinol, at doses up to 200 mg kg(-1). Allopurinol also caused an increase in cerebrospinal fluid levels of purines, including the nucleosides adenosine and guanosine, and decreased cerebrospinal fluid concentration of uric acid.

CONCLUSIONS AND IMPLICATIONS

Allopurinol-induced anti-nociception may be related to adenosine accumulation. Allopurinol is an old and extensively used compound and seems to be well tolerated with no obvious central nervous system toxic effects at high doses. This drug may be useful to treat pain syndromes in humans.

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.

The effect of infusing hypoxanthine or xanthine on hypoxic–ischemic brain injury in rabbits

Xanthine oxidase (XO), an enzyme that converts hypoxanthine to xanthine and xanthine to uric acid, is thought to contribute to hypoxic-ischemic brain injury by generating oxygen-free radicals during reperfusion. This is based largely on the observation that inhibition of XO reduces brain damage, but the precise mechanism by which the enzyme contributes to cerebral ischemic injury has not been specifically evaluated. We examined the role of XO in generating oxygen-free radicals that cause brain injury, hypothesizing that if XO generated a significant amount of free radicals during hypoxia-ischemia and reperfusion, providing additional substrate at the time of injury should increase brain damage. Anesthetized rabbits were first subjected to 8 min of cerebral hypoxia by breathing 3% oxygen and then to 8 min of ischemia by raising intracranial pressure equal to mean arterial pressure with an artificial CSF. In order to promote oxygen-free radical generation, hypoxanthine (n=9) or xanthine (n=9), XO substrates, or the vehicle (n=8) was infused intravenously beginning 30 min before and continuing until 30 min after the insult. Animals were sacrificed after 4 h of reperfusion. Neither hypoxanthine nor xanthine infusion increased brain damage. However, administration of hypoxanthine significantly improved somatosensory evoked potential recovery and preserved neurofilament 68 kDa protein, a neuronal structural protein. This study does not support free radical generation by XO as a major cause of damage in cerebral hypoxia-ischemia. Infusion of hypoxanthine reduced cerebral injury suggesting that another mechanism may explain why inhibition of XO reduces brain damage.