Xanthine oxidase-derived hydrogen peroxide contributes to ischemia reperfusion-induced edema in gerbil brains

The Role of Potential Oxidative Biomarkers in the Prognosis of Acute Ischemic Stroke and the Exploration of Antioxidants as Possible Preventive and Treatment Options

Ischemic strokes occur when the blood supply to a part of the brain is interrupted or reduced due to arterial blockage, and it often leads to damage to brain cells or death. According to a myriad of experimental studies, oxidative stress is an important pathophysiological mechanism of ischemic stroke. In this narrative review, we aimed to identify how the alterations of oxidative stress biomarkers could suggest a severity-reflecting diagnosis of ischemic stroke and how these interactions may provide new molecular targets for neuroprotective therapies. We performed an eligibility criteria-based search on three main scientific databases. We found that patients with acute ischemic stroke are characterized by increased oxidative stress markers levels, such as the total antioxidant capacity, F2-isoprostanes, hydroxynonenal, total and perchloric acid oxygen radical absorbance capacity (ORACTOT and ORACPCA), malondialdehyde (MDA), myeloperoxidase, and urinary 8-oxo-7,8-dihydro-2′-deoxyguanosine. Thus, acute ischemic stroke is causing significant oxidative stress and associated molecular and cellular damage. The assessment of these molecular markers could be useful in diagnosing ischemic stroke, finding its causes, predicting its severity and outcomes, reducing its impact on the cellular structures of the brain, and guiding preventive treatment towards antioxidant-based therapy as novel therapeutic alternatives.

Brain Energy Metabolism in Ischemic Stroke: Effects of Smoking and Diabetes

Proper regulation of energy metabolism in the brain is crucial for maintaining brain activity in physiological and different pathophysiological conditions. Ischemic stroke has a complex pathophysiology which includes perturbations in the brain energy metabolism processes which can contribute to worsening of brain injury and stroke outcome. Smoking and diabetes are common risk factors and comorbid conditions for ischemic stroke which have also been associated with disruptions in brain energy metabolism. Simultaneous presence of these conditions may further alter energy metabolism in the brain leading to a poor clinical prognosis after an ischemic stroke event. In this review, we discuss the possible effects of smoking and/or diabetes on brain glucose utilization and mitochondrial energy metabolism which, when present concurrently, may exacerbate energy metabolism in the ischemic brain. More research is needed to investigate brain glucose utilization and mitochondrial oxidative metabolism in ischemic stroke in the presence of smoking and/or diabetes, which would provide further insights on the pathophysiology of these comorbid conditions and facilitate the development of therapeutic interventions.

In vivo dynamics of acidosis and oxidative stress in the acute phase of an ischemic stroke in a rodent model

Ischemic cerebral stroke is one of the leading causes of death and disability in humans. However, molecular processes underlying the development of this pathology remain poorly understood. There are major gaps in our understanding of metabolic changes that occur in the brain tissue during the early stages of ischemia and reperfusion. In particular, it is generally accepted that both ischemia (I) and reperfusion (R) generate reactive oxygen species (ROS) that cause oxidative stress which is one of the main drivers of the pathology, although ROS generation during I/R was never demonstrated in vivo due to the lack of suitable methods. In the present study, we record for the first time the dynamics of intracellular pH and H2O2 during I/R in cultured neurons and during experimental stroke in rats using the latest generation of genetically encoded biosensors SypHer3s and HyPer7. We detect a buildup of powerful acidosis in the brain tissue that overlaps with the ischemic core from the first seconds of pathogenesis. At the same time, no significant H2O2 generation was found in the acute phase of ischemia/reperfusion. HyPer7 oxidation in the brain was detected only 24 h later. Comparison of in vivo experiments with studies on cultured neurons under I/R demonstrates that the dynamics of metabolic processes in these models significantly differ, suggesting that a cell culture is a poor predictor of metabolic events in vivo.

Role of Uric Acid Metabolism-Related Inflammation in the Pathogenesis of Metabolic Syndrome Components Such as Atherosclerosis and Nonalcoholic Steatohepatitis

Uric acid (UA) is the end product of purine metabolism and can reportedly act as an antioxidant. However, recently, numerous clinical and basic research approaches have revealed close associations of hyperuricemia with several disorders, particularly those comprising the metabolic syndrome. In this review, we first outline the two molecular mechanisms underlying inflammation occurrence in relation to UA metabolism; one is inflammasome activation by UA crystallization and the other involves superoxide free radicals generated by xanthine oxidase (XO). Importantly, recent studies have demonstrated the therapeutic or preventive effects of XO inhibitors against atherosclerosis and nonalcoholic steatohepatitis, which were not previously considered to be related, at least not directly, to hyperuricemia. Such beneficial effects of XO inhibitors have been reported for other organs including the kidneys and the heart. Thus, a major portion of this review focuses on the relationships between UA metabolism and the development of atherosclerosis, nonalcoholic steatohepatitis, and related disorders. Although further studies are necessary, XO inhibitors are a potentially novel strategy for reducing the risk of many forms of organ failure characteristic of the metabolic syndrome.

Targeting oxidative stress for the treatment of ischemic stroke: Upstream and downstream therapeutic strategies

Excessive oxygen and its chemical derivatives, namely reactive oxygen species (ROS), produce oxidative stress that has been known to lead to cell injury in ischemic stroke. ROS can damage macromolecules such as proteins and lipids and leads to cell autophagy, apoptosis, and necrosis to the cells. This review describes studies on the generation of ROS, its role in the pathogenesis of ischemic stroke, and recent development in therapeutic strategies in reducing oxidative stress after ischemic stroke.

Plasma Oxidants and Antioxidants in Acute Ischaemic Stroke

Plasma levels of the oxidants xanthine oxidase, nitric oxide and malondialdehyde and the antioxidants superoxide dismutase, glutathione peroxidase and glutathione reductase, together with total superoxide scavenger activity and non-enzymatic superoxide scavenger activity, were determined in 19 patients with acute ischaemic stroke and 20 controls. Compared with controls, superoxide dismutase, total superoxide scavenger activity, glutathione peroxidase and glutathione reductase activities were significantly lower, and nitric oxide and malondialdehyde levels significantly higher, in acute stroke patients. Xanthine oxidase showed a slight but non-significant increase in stroke patients compared with controls. There was no significant difference in non-enzymatic superoxide scavenger activity between the two groups. There was a positive correlation between glutathione reductase levels and Glasgow Coma Scale scores, and a negative correlation between malondialdehyde levels and non-enzymatic superoxide scavenger activity. These findings suggest that oxidative stress in patients with acute ischaemic stroke may be the result of an imbalance in oxidant/antioxidant homeostasis.

[Phospholipids metabolism disorders in acute stroke]

The disturbances of cerebral circulation results in the violation of phospholipid metabolism. Activation of lipid peroxidation and protein kinase C and release of intracellular calcium leads to disruption of the homeostasis of phosphatidylcholine. The use of cytidine-5-diphosphocholine, which is used as an intermediate compound in the biosynthesis of phospholipids of the cell membrane, helps to stabilize cell membranes, and reduce the formation of free radicals.

Reperfusion injury and reactive oxygen species: The evolution of a concept

Reperfusion injury, the paradoxical tissue response that is manifested by blood flow-deprived and oxygen-starved organs following the restoration of blood flow and tissue oxygenation, has been a focus of basic and clinical research for over 4-decades. While a variety of molecular mechanisms have been proposed to explain this phenomenon, excess production of reactive oxygen species (ROS) continues to receive much attention as a critical factor in the genesis of reperfusion injury. As a consequence, considerable effort has been devoted to identifying the dominant cellular and enzymatic sources of excess ROS production following ischemia-reperfusion (I/R). Of the potential ROS sources described to date, xanthine oxidase, NADPH oxidase (Nox), mitochondria, and uncoupled nitric oxide synthase have gained a status as the most likely contributors to reperfusion-induced oxidative stress and represent priority targets for therapeutic intervention against reperfusion-induced organ dysfunction and tissue damage. Although all four enzymatic sources are present in most tissues and are likely to play some role in reperfusion injury, priority and emphasis has been given to specific ROS sources that are enriched in certain tissues, such as xanthine oxidase in the gastrointestinal tract and mitochondria in the metabolically active heart and brain. The possibility that multiple ROS sources contribute to reperfusion injury in most tissues is supported by evidence demonstrating that redox-signaling enables ROS produced by one enzymatic source (e.g., Nox) to activate and enhance ROS production by a second source (e.g., mitochondria). This review provides a synopsis of the evidence implicating ROS in reperfusion injury, the clinical implications of this phenomenon, and summarizes current understanding of the four most frequently invoked enzymatic sources of ROS production in post-ischemic tissue.

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Reperfusion injury is implicated in a variety of human diseases and disorders.

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Evidence implicating ROS in reperfusion injury continues to grow.

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Several enzymes are candidate sources of ROS in post-ischemic tissue.

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Inter-enzymatic ROS-dependent signaling enhances the oxidative stress caused by I/R.

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Neferine, a bisbenzylisoquinoline alkaloid, offers protection against cobalt chloride-mediated hypoxia-induced oxidative stress in muscle cells

Background

Neferine, a bisbenzylisoquinoline alkaloid, isolated from Nelumbo nucifera has a wide range of biological activities. Cobalt chloride (CoCl₂) was known to mimic hypoxic condition. In the present study, we assessed the cytoprotective effect of neferine against CoCl₂-induced oxidative stress in muscle cells.

Methods

Rhabdomyosarcoma cells were exposed to different concentrations of CoCl₂, and the IC₅₀ value was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Lactate dehydrogenase and NO assays were performed in order to determine the cytotoxic effect of CoCl₂. Reactive oxygen species generation and cellular antioxidant status were determined for evaluating oxidative stress. For analyzing the effect of neferine on CoCl₂-induced apoptosis, propidium iodide staining was performed.

Results

The results of the present study indicate that CoCl₂ induces cell death in a dose-dependent manner. Neferine pretreatment at 700 nM concentration offers better cytoprotection in the cells exposed to CoCl₂. Lactate dehydrogenase and NO release in the culture medium were restored after neferine pretreatment. CoCl₂ triggers time-dependent reactive oxygen species generation in muscle cells. Further, results of propidium iodide staining, mitochondrial membrane potential, and intracellular calcium accumulation confirm that neferine offers protection against CoCl₂-induced hypoxic injury. Depleted activities of antioxidants such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase due to CoCl₂ exposure were also reinstated in the group that received neferine pretreatment.

Conclusion

Our study suggests that neferine from N. nucifera offers protection to muscle cells by counteracting the oxidative stress induced by CoCl₂.

Vitamin B-complex initiates growth and development of human embryonic brain cells in vitro

We studied a combined effect of subcomponents of vitamin B complex on the growth, development, and death of human embryonic brain-derived cells (E90) cultured using a modified method of Matson. Cell death was detected by trypan blue staining. According to our results, vitamin B-complex in low-doses promote the development, maturation, and enlargement of human embryonic brain cells, on the one hand, and increases the percent of cell death, which attests to accelerated maturation and metabolism, on the other.

The neuroprotection of oxymatrine in cerebral ischemia/reperfusion is related to nuclear factor erythroid 2-related factor 2 (nrf2)-mediated antioxidant response: role of nrf2 and hemeoxygenase-1 expression

Cerebral ischemia-reperfusion (CI/R) injury remains a major medical problem due to the lack of effective therapies. Previous studies have shown that increasing the activity of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and gene targets in cell culture and stroke animal models is highly neuroprotective. Oxymatrine is the major quinolizidine alkaloid extracted from the root of Sophora flavescens AIT, and has been proved to be protective after ischemia in recent studies. The present study was designed to investigate the potential effect of oxymatrine in ischemia-reperfusion injury in rat's brain and to explore the possible role of oxymatrine in Nrf2 pathway. The results indicated that the ischemic infarct and edema were significantly reduced in rats that received oxymatrine, with a corresponding improvement in neurological function after CI/R. In immunohistochemistry and Western blotting analyses, Nrf2 and hemeoxygenase-1 (HO-1) were up-regulated in ischemic cortex, beginning at 6 h, peaking at 48 h and declining at 72 h after CI/R. Intraperitoneal injection of oxymatrine inhibited the production of lipid peroxidation and increased the activities of Nrf2 and HO-1 in rats brain after CI/R. Taken together, these results suggest that oxymatrine administered systemically protected brain against focal ischemia-reperfusion damage at the early stage of stroke, and that activating Nrf2/HO-1 pathway may contribute to the neuroprotective action of oxymatrine in rat focal brain ischemia-reperfusion model. Thus, treatment of stroke with oxymatrine may prevent severe consequences after brain attack.

The chemopreventive effect of dimethylthiourea against carmustine-induced myelotoxicity in rats

The possible chemopreventive role of dimethylthiourea (DMTU) against carmustine (1,3-bis(2-chloroethyl)-1-nitrosourea, BCNU)-induced myelotoxicity was assessed through evaluation of apoptosis, lipid peroxidation, glutathione (GSH) content and some antioxidant enzymes activities in bone marrow cells of rats. Thirty-six rats were randomly classified into four groups. The first group was injected i.p. with ethanol and served as a control. The second group was treated with BCNU. The third group was given DMTU, while the fourth group was co-administered with DMTU prior to BCNU administration. BCNU treatment in a single dose of 30 mg/kg significantly decreased the normal counts of RBCs, WBCs and platelets as well as hemoglobin level. In addition, BCNU exhibited marked apoptotic effect associated with significant alterations in the oxidative cascade parameters. Treatment of animals with DMTU in a single dose of 500 mg/kg 1h before BCNU injection, followed by 125 mg/kg twice daily for 5 consecutive days significantly mitigated the induced changes in the hematological parameters. The induced alterations in the oxidant and antioxidant parameters as well as apoptosis were also improved. Conclusively, DMTU treatment exhibited marked chemopreventive effect against BCNU-induced myelotoxicity; an effect which may be partially attributed to its inherently antioxidant potential.

Hydrogen peroxide is the major oxidant product of xanthine oxidase

Xanthine oxidase (XO) is a critical source of reactive oxygen species (ROS) in inflammatory disease. Focus, however, has centered almost exclusively on XO-derived superoxide (O(2)(*-)), whereas direct H(2)O(2) production from XO has been less well investigated. Therefore, we examined the relative quantities of O(2)(*-) and H(2)O(2) produced by XO under a range (1-21%) of O(2) tensions. At O(2) concentrations between 10 and 21%, H(2)O(2) accounted for approximately 75% of ROS production. As O(2) concentrations were lowered, there was a concentration-dependent increase in H(2)O(2) formation, accounting for 90% of ROS production at 1% O(2). Alterations in pH between 5.5 and 7.4 did not affect the relative proportions of H(2)O(2) and O(2)(*-) formation. Immobilization of XO, by binding to heparin-Sepharose, further enhanced relative H(2)O(2) production by approximately 30%, under both normoxic and hypoxic conditions. Furthermore, XO bound to glycosaminoglycans on the apical surface of bovine aortic endothelial cells demonstrated a similar ROS production profile. These data establish H(2)O(2) as the dominant (70-95%) reactive product produced by XO under clinically relevant conditions and emphasize the importance of H(2)O(2) as a critical factor when examining the contributory roles of XO-catalyzed ROS in inflammatory processes as well as cellular signaling.

POSTCAROTID ENDARTERECTOMY CEREBRAL HYPERPERFUSION CAN BE PREVENTED BY MINIMIZING INTRAOPERATIVE CEREBRAL ISCHEMIA AND STRICT POSTOPERATIVE BLOOD PRESSURE CONTROL UNDER CONTINUOUS SEDATION

OBJECTIVE

Cerebral hyperperfusion syndrome is a major complication after carotid endarterectomy (CEA). We investigated whether our strategy of minimizing intraoperative cerebral ischemia and strict postoperative blood pressure control under continuous sedation prevented postoperative hyperperfusion.

METHODS

Eighty consecutive patients undergoing CEA were studied. A shunt was used in all patients during CEA. All patients were managed postoperatively under continuous sedation for as long as 48 hours on the basis of the regional cerebral blood flow (rCBF) measured immediately after CEA. Postoperative hyperperfusion was assessed, on the basis of the cerebral blood flow study under sedation (propofol) after CEA, either as a greater than 30% increase in rCBF compared with the contralateral side, or a greater than 100% increase in the corrected rCBF (calculated from percentage reduction of the contralateral rCBF induced by propofol) compared with preoperative values.

RESULTS

No patient developed cerebral hyperperfusion syndrome. Postoperative hyperperfusion was found at very low rates (2.5% in the middle cerebral artery territory and 1.3% in the anterior cerebral artery territory by definition 1, and 0% in both territories by definition 2). Ratios of regional oxygen saturation after internal carotid artery clamping to preclamp baseline values were greater than 0.9 in 78 of 80 patients, indicating very mild intraoperative cerebral ischemia. Parameters related to cerebral ischemia during CEA, such as regional oxygen saturation, internal carotid artery cross-clamping duration, and stump pressure (index), did not affect the incidence of postoperative hyperperfusion.

CONCLUSION

The present study suggests that minimizing intraoperative cerebral ischemia using a shunt, followed by strict postoperative blood pressure control under continuous sedation, can prevent post-CEA hyperperfusion.

Regulation of endothelial barrier function by reactive oxygen and nitrogen species

Excessive generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS), by activated neutrophils and endothelial cells, has been implicated in the pathophysiology of endothelial barrier dysfunction. Disruption of the integrity of this barrier markedly increases permeability to fluids, solutes and inflammatory cells and is the hallmark of many disorders such as acute lung injury (ALI) and sepsis. There has been considerable progress in our understanding of the sequence of molecular and structural events that mediate the response of endothelial cells to oxidants and nitrosants. In addition, substantial experimental evidence demonstrates improvement of endothelial barrier dysfunction with antioxidant strategies. However, no significant benefits have been observed, so far, in clinical trials of antioxidants for the treatment of endothelial barrier dysfunction. This article will review the available evidence implicating ROS and RNS in endothelial barrier dysfunction, explore potential underlying mechanisms, and identify areas of further research.

Postresuscitation N-acetylcysteine treatment reduces cerebral hydrogen peroxide in the hypoxic piglet brain

OBJECTIVE

Reactive oxygen species have been implicated in the pathogenesis of hypoxia-reoxygenation injury. However, little information is known regarding the temporal profile of cerebral hydrogen peroxide (HPO) production and its response to N-acetylcysteine (an antioxidant) administration during neonatal hypoxia-reoxygenation. Using an acute swine model of neonatal hypoxia-reoxygenation, we examined the short-term neuroprotective effects of N-acetylcysteine on cerebral HPO production and oxidative stress in the brain.

DESIGN

Controlled, block-randomized animal study.

SETTING

University animal research laboratory.

SUBJECTS

Newborn piglets (1-3 days, 1.7-2.1 kg).

INTERVENTIONS

At 5 min after reoxygenation, piglets were given either saline or N-acetylcysteine (20 or 100 mg/kg/h) in a blinded, randomized fashion.

MEASUREMENTS AND RESULTS

Newborn piglets were block-randomized into a sham-operated group (without hypoxia-reoxygenation, n = 5) and three hypoxic-reoxygenated groups (2 h of normocapnic alveolar hypoxia followed by 2h of reoxygenation, n = 7/group). Heart rate, mean arterial pressure, cortical HPO concentration, amino acid levels in cerebral microdialysate, and cerebral tissue glutathione and lipid hydroperoxide levels were examined. Hypoxic piglets were hypotensive and acidotic, and they recovered similarly in all hypoxic-reoxygenated groups. In hypoxic-reoxygenated control piglets, the cortical HPO concentration gradually increased during reoxygenation. Both doses of N-acetylcysteine abolished the increased HPO concentration and oxidized glutathione levels and tended to reduce the glutathione ratio and lipid hydroperoxide levels in the cerebral cortex (p = 0.08 and p = 0.1 vs. controls, respectively). N-acetylcysteine at 100mg/kg/h also increased the cerebral extracellular taurine levels.

CONCLUSION

In newborn piglets with hypoxia-reoxygenation, postresuscitation administration of N-acetylcysteine reduces cerebral HPO production and oxidative stress, probably through a taurine-related mechanism.

Preoperative cerebral hemodynamic impairment and reactive oxygen species produced during carotid endarterectomy correlate with development of postoperative cerebral hyperperfusion

BACKGROUND AND PURPOSE

The purpose of the present study was to determine whether preoperative cerebral hemodynamic impairment and reactive oxygen species produced during carotid endarterectomy (CEA) correlate with development of postoperative cerebral hyperperfusion.

METHODS

Concentrations of malondialdehyde-modified low-density lipoprotein (MDA-LDL), a biochemical marker of oxidative damage, were measured in serum samples obtained from 90 patients undergoing CEA for ipsilateral ICA stenosis (>70%). Serum samples were obtained from a venous catheter inserted into the ipsilateral jugular bulb before clamping of the internal carotid artery (ICA), 10 minutes after clamping of the ICA, and 5 and 20 minutes after declamping of the ICA. Cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) to acetazolamide were also measured using single-photon emission computed-tomography before CEA. In addition, CBF was measured postoperatively.

RESULTS

Hyperperfusion (CBF increase >100% compared with preoperative values) was observed immediately after CEA in 12 patients (13%). Logistic regression analysis demonstrated that reduced preoperative CVR (95% CIs, 1.053 to 1.453; P=0.0097) and an increase in MDA-LDL (calculated as a percentage of the preclamp values) after ICA declamping (95% CIs, 0.862 to 0.980; P=0.0098) were significantly associated with development of postoperative cerebral hyperperfusion among the variables tested. Ten of 11 patients with reduced preoperative CVR and increased MDA-LDL after ICA declamping developed post-CEA hyperperfusion, and 2 of these patients developed cerebral hyperperfusion syndrome.

CONCLUSIONS

Both preoperative cerebral hemodynamic impairment and reactive oxygen species produced during surgery correlate with development of cerebral hyperperfusion after CEA.

Pyruvate protects mitochondria from oxidative stress in human neuroblastoma SK-N-SH cells

Oxidative stress is implicated in neurodegenerative diseases including stroke, Alzheimer's disease and Parkinson's disease, and has been extensively studied as a potential target for therapeutic intervention. Pyruvate, a natural metabolic intermediate and energy substrate, exerts antioxidant effects in brain and other tissues susceptible to oxidative stress. We tested the protective effects of pyruvate on hydrogen peroxide (H(2)O(2)) toxicity in human neuroblastoma SK-N-SH cells and the mechanisms underlying its protection. Hydrogen peroxide insult resulted in 85% cell death, but co-treatment with pyruvate dose-dependently attenuated cell death. At concentrations of >or=1 mM, pyruvate totally blocked the cytotoxic effects of H(2)O(2). Pyruvate exerted its protective effects even when its administration was delayed up to 2 h after H(2)O(2) insult. As a scavenger of reactive oxygen species (ROS), pyruvate dose-dependently attenuated H(2)O(2)-induced ROS formation, assessed from 2,7-dichlorofluorescein diacetate fluorescence. Furthermore, pyruvate suppressed superoxide production by submitochondrial particles, and attenuated oxidative stress-induced collapse of the mitochondrial membrane potential. Collectively, these results suggest that pyruvate protects neuronal cells through its antioxidant actions on mitochondria.

Cerebral hyperperfusion after carotid endarterectomy is associated with preoperative hemodynamic impairment and intraoperative cerebral ischemia

The aim of this study was to investigate whether postoperative hyperperfusion is associated with preoperative cerebral hemodynamic impairment due to chronic ischemia and with acute cerebral ischemia during clamping of the internal carotid artery (ICA) during carotid endarterectomy (CEA). Transcranial cerebral oxygen saturation (SO2) was monitored intraoperatively using near-infrared spectroscopy in 89 patients undergoing CEA for ipsilateral ICA stenosis (>70%). Cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) to acetazolamide were also measured using single photon emission computed tomography (SPECT) before CEA. In addition, CBF was measured immediately after CEA and on the third postoperative day. Hyperperfusion (CBF increase>100% compared with preoperative values) was observed immediately after CEA in 10 of 18 patients (56%) with reduced preoperative CVR. Also, post-CEA hyperperfusion was observed in nine of 16 patients (56%) whose SO2 during clamping of the ICA decreased to less than 90% of the preclamping value. Logistic regression analysis showed that reduced preoperative CVR and reduced SO2 during ICA clamping were significant independent predictors of the development of hyperperfusion immediately after CEA. In fact, all patients with reduced preoperative CVR and reduced SO2 during ICA clamping developed post-CEA hyperperfusion, and two of these patients developed cerebral hyperperfusion syndrome. These data suggest that development of cerebral hyperperfusion after CEA is associated with preoperative hemodynamic impairment and intraoperative cerebral ischemia.

Therapeutic effects of xanthine oxidase inhibitors: renaissance half a century after the discovery of allopurinol

The prototypical xanthine oxidase (XO) inhibitor allopurinol, has been the cornerstone of the clinical management of gout and conditions associated with hyperuricemia for several decades. More recent data indicate that XO also plays an important role in various forms of ischemic and other types of tissue and vascular injuries, inflammatory diseases, and chronic heart failure. Allopurinol and its active metabolite oxypurinol showed considerable promise in the treatment of these conditions both in experimental animals and in small-scale human clinical trials. Although some of the beneficial effects of these compounds may be unrelated to the inhibition of the XO, the encouraging findings rekindled significant interest in the development of additional, novel series of XO inhibitors for various therapeutic indications. Here we present a critical overview of the effects of XO inhibitors in various pathophysiological conditions and also review the various emerging therapeutic strategies offered by this approach.

Antioxidant supplementation enhances antioxidant capacity and mitigates oxidative damage following acute ischaemic stroke

OBJECTIVE

To test whether supplementary antioxidants immediately following acute ischaemic stroke will enhance antioxidant capacity and mitigate oxidative damage.

DESIGN

A randomised controlled trial.

SETTING

A university teaching hospital.

SUBJECTS

A total of 48 acute ischaemic stroke patients within 12 h of symptom onset.

INTERVENTION

Daily oral 800 IU (727 mg) of alpha-tocopherol and 500 mg of vitamin C (n = 24), or no treatment (n = 24) for 14 days. Treatment group and controls were matched for stroke subtype and age.

MAIN OUTCOME MEASURES

alpha-Tocopherol, ascorbic acid, total antioxidant capacity (TAOC), plasma malondialdehyde (MDA) and C-reactive protein (CRP) before treatment, at day 7 and day 14 following recruitment.

RESULTS

In all, 14 days of vitamin supplementation significantly improved plasma alpha-tocopherol and ascorbic concentrations in the treatment group compared with the decrease seen in the control group (P < 0.005 for difference in cumulative changes). TAOC increased significantly in the treatment group compared with controls (P < 0.003). There was a significant reduction in plasma MDA concentration in the treatment group, in contrast to the increase seen in the control group (P < 0.002). After adjusting for clinical complications CRP concentrations within 90 days postinfarct were significantly lower in the treatment group compared with controls.

CONCLUSION

Supplementation with antioxidant vitamins within 12 h of onset of acute ischaemic stroke increased antioxidant capacity, reduced lipid peroxidation products and may have an anti-inflammatory effect.

SPONSORSHIP

Sheffield Teaching Hospital NHS Trust.

Effect of allopurinol in focal cerebral ischemia in rats: an experimental study

BACKGROUND

Allopurinol is a xanthine oxidase inhibitor that prevents the generation of free radicals and may play a role in the protection of the cells during cerebral ischemia.

METHODS

We evaluated the protective and therapeutic effect of allopurinol on reversible focal cerebral ischemia-reperfusion model in rats. Cerebral blood flow to the left hemisphere of adult Sprague-Dawley rats (n = 40) was temporarily interrupted by middle cerebral artery (MCA) and bilateral common carotid artery (CCA) occlusion for 3 hours in 5 groups of 8 rats each. Allopurinol (50 mg/kg) was given intraperitoneally 2 hours and immediately before ischemia and immediately and 2 hours after reperfusion in 4 different groups of rats, respectively. Animals were kept alive 24 hours after reperfusion. After sacrifice, infarction volumes and ratios of the brain slices were calculated, and the results were compared with those of the control group.

RESULTS

The difference between the allopurinol-administered group and the control group 2 hours before for both infarction volumes and infarction ratios achieved statistical significance. Regarding the allopurinol-administered group immediately before ischemia, infarction volumes and infarction ratios were diminished, but there was no statistically significant difference. The difference between allopurinol-administered and control group immediately after and 2 hours after reperfusion for both infarction volumes and infarction ratios achieved no statistical significance.

CONCLUSION

This study showed that allopurinol has a protective effect, but not a therapeutic effect, on cerebral ischemia.

Oxidants, antioxidants and the ischemic brain

Despite numerous defenses, the brain is vulnerable to oxidative stress resulting from ischemia/reperfusion. Excitotoxic stimulation of superoxide and nitric oxide production leads to formation of highly reactive products, including peroxynitrite and hydroxyl radical, which are capable of damaging lipids, proteins and DNA. Use of transgenic mutants and selective pharmacological antioxidants has greatly increased understanding of the complex interplay between substrate deprivation and ischemic outcome. Recent evidence that reactive oxygen/nitrogen species play a critical role in initiation of apoptosis, mitochondrial permeability transition and poly(ADP-ribose) polymerase activation provides additional mechanisms for oxidative damage and new targets for post-ischemic therapeutic intervention. Because oxidative stress involves multiple post-ischemic cascades leading to cell death, effective prevention/treatment of ischemic brain injury is likely to require intervention at multiple effect sites.

B-group vitamin supplementation mitigates oxidative damage after acute ischaemic stroke

Evidence shows that there is a rapid increase in the production of markers of oxidative damage immediately following acute stroke and that endogenous antioxidant defences are rapidly depleted, thus permitting further tissue damage. Several studies point to an antioxidant effect of B-group vitamins and a pro-oxidant effect of elevated plasma tHcy (total homocysteine). In the present study, we assessed whether supplementary B-group vitamins during this critical period will enhance antioxidant capacity and mitigate oxidative damage. Forty-eight patients with acute ischaemic stroke within 12 h of symptom onset were assigned to receive daily oral supplements of B-group vitamins comprising 5 mg of folate, 5 mg of vitamin B2, 50 mg of vitamin B6 and 0.4 mg of vitamin B12 (n=24) or no supplements (n=24) for 14 days. The treatment group and controls were matched for stroke subtype and age. Blood samples were obtained before intervention and also at 7 and 14 days post-recruitment for measurement of the following biomarkers: red cell folate (whole blood folate corrected with haematocrit), erythrocyte glutathione reductase activity coefficient (EGRAC; measure of vitamin B2 status), plasma pyridoxal phosphate (vitamin B6 status), plasma vitamin B12, plasma alpha-tocopherol, plasma ascorbic acid, plasma TAOC (total antioxidant capacity), plasma MDA (malondialdehyde), plasma tHcy and CRP (C-reactive protein). Supplementation for 14 days with B-group vitamins significantly increased the plasma concentrations of pyridoxal phosphate and red blood cell folate and improved a measure of B2 status compared with the control group (P<0.05). Plasma tHcy decreased in both groups albeit less in the control group, but differences in cumulative changes were not significant. There was, however, a decrease in plasma MDA concentration in the treatment group, in contrast with the increase seen in the control group and these differences were significant (P=0.05). CRP concentration, a marker of tissue inflammation, was significantly lower in the treatment group compared with controls (P<0.05). In conclusion, B-group vitamin supplementation immediately post-infarct may have antioxidant and anti-inflammatory effects in stroke disease independent of a homocysteine-lowering effect.

Pretreatment with the Free Radical Scavenger Edaravone Prevents Cerebral Hyperperfusion after Carotid Endarterectomy

OBJECTIVE:

Cerebral hyperperfusion syndrome after carotid endarterectomy (CEA) is a rare but potentially devastating complication. The purpose of the present study, which was not a randomized controlled trial but a case cohort study with historical control, was to determine whether pretreatment with a novel free radical scavenger, edaravone, could prevent occurrence of cerebral hyperperfusion after CEA.

METHODS:

Fifty patients with ipsilateral internal carotid artery stenosis (≥70%) underwent CEA with administration of edaravone before internal carotid artery clamping. Preoperative cerebral blood flow and cerebrovascular reactivity (CVR) to acetazolamide were assessed with single-photon emission computed tomography (SPECT). Cerebral blood flow also was measured immediately after CEA and on the 3rd postoperative day.

RESULTS:

Cerebral hyperperfusion (cerebral blood flow increase ≥100% compared with preoperative values) was revealed by SPECT performed immediately after CEA in only one patient (2%), who also exhibited reduced preoperative CVR. The incidence of post-CEA hyperperfusion as revealed by SPECT in the control group (51 CEA patients without administration of edaravone) was significantly higher (16%) (P= 0.0310, control versus treatment group). In addition, in a subgroup of patients with reduced preoperative CVR, the incidence of post-CEA hyperperfusion as revealed by SPECT in the edaravone group (7%) was significantly lower than that in the control group (67%) (P= 0.0029). Logistic regression analysis demonstrated that reduced preoperative CVR and absence of pretreatment with edaravone were significant independent predictors of post-CEA hyperperfusion as revealed by SPECT.

CONCLUSION:

Pretreatment with edaravone can prevent occurrence of cerebral hyperperfusion after CEA.

Neuroprotective effect of peroxynitrite decomposition catalyst and poly(adenosine diphosphate—ribose) polymerase inhibitor alone and in combination in rats with focal ischemia

Object. The authors evaluated the neuroprotective effect of 5,10,15,20-tetrakis(N-methyl-4′-pyridyl)porphyrinatoiron(III) (FeTMPyP), a peroxynitrite decomposition catalyst, and 1,5-isoquinolinediol (ISO), a poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) inhibitor, alone and in combination in rats with focal cerebral ischemia induced by middle cerebral artery occlusion (MCAO).

Methods. Male Sprague—Dawley rats were subjected to 2 hours of MCAO followed by 22 hours of reperfusion. Cerebral infarction and neurological deficits were estimated after ischemia. Intraperitoneal injections of FeTMPyP (1 and 2 mg/kg) and ISO (0.05 and 0.1 mg/kg) were administered alone or in combination in ischemic animals. The PARP activity in vehicle- and drug-treated groups was estimated using anti—poly(ADP-ribose) antibody in immunofluorescence and immunoblotting studies.

Two hours of MCAO and 22 hours of reperfusion produced significant cerebral infarction and neurological deficits. Treatment with FeTMPyP (1 and 2 mg/kg) and ISO (0.05 and 0.1 mg/kg) produced a significant reduction in cerebral infarction and neurological deficits. Combination therapy (2 mg/kg FeTMPyP and 0.1 mg/kg ISO) enhanced the inhibition of ischemic volume (77.81 ± 0.86%) compared with monotherapies (FeTMPyP 54.07 ± 5.6% and ISO 53.06 ± 3.88%). Immunoblotting and immunofluorescence studies showed PARP activation after ischemia, which was reduced by drug treatment.

Conclusions. Neuroprotection observed with FeTMPyP and ISO alone and in combination may be attributed to inhibition of the peroxynitrite—PARP cascade of cerebral ischemia/reperfusion injury.

Differential MnSOD and HO-1 expression in cerebral endothelial cells in response to sublethal oxidative stress

The two inducible enzymes, manganese superoxide dismutase (MnSOD) and heme-oxygenase-1 (HO-1) may participate in the cellular defense of brain endothelium against oxidative stress. The time-dependent expression of MnSOD and HO-1 mRNAs and proteins was investigated in vitro in rat cerebral endothelial cells (CEC) subjected to sublethal mild or moderate hydroxyl radical-induced oxidative stress. Mild oxidative stress induced increases in both MnSOD and HO-1 mRNA and protein expression. Moderate oxidative stress resulted in a significant reduction in HO-1 mRNA and protein expression, whereas MnSOD expression pattern was similar to that observed after mild oxidative stress. A profound protein loss of both MnSOD and HO-1 was detected 24 h after exposure of CEC to a moderate oxidative stress. The data indicate that cerebral endothelial cells respond by increasing the expression of antioxidant defense enzymes in a manner dependent on the oxidative stress intensity.

Effects of alpha-phenyl-N-tert-butyl nitrone (PBN)on brain cell membrane function and energy metabolism during transient global cerebral hypoxia-ischemia and reoxygenation-reperfusion in newborn piglets

We sought to know whether a free radical spin trap agent, alpha-phenyl-N-tert-butyl nitrone (PBN) influences brain cell membrane function and energy metabolism during and after transient global hypoxia-ischemia (HI) in the newborn piglets. Cerebral HI was induced by temporary complete occlusion of bilateral common carotid arteries and simultaneous breathing with 8% oxygen for 30 min, followed by release of carotid occlusion and normoxic ventilation for 1 hr (reoxygenation-reperfusion,RR). PBN (100 mg/kg) or vehicle was administered intravenously just before the induction of HI or RR. Brain cortex was harvested for the biochemical analyses at the end of HI or RR. The level of conjugated dienes significantly increased and the activity of Na+, K+ -ATPase significantly decreased during HI,and they did not recover during RR. The levels of ATP and phosphocreatine (PCr)significantly decreased during HI, and recovered during RR. PBN significantly decreased the level of conjugated dienes both during HI and RR, but did not influence the activity of Na+, K+ -ATPase and the levels of ATP and PCr. We demonstrated that PBN effectively reduced brain cell membrane lipid peroxidation, but did not reverse ongoing brain cell membrane dysfunction nor did restore brain cellular energy depletion, in our piglet model of global hypoxic-ischemic brain injury.

Nutritional iron deprivation attenuates kainate-induced neurotoxicity in rats: implications for involvement of iron in neurodegeneration

There is evidence suggesting that oxidative stress contributes to kainate neurotoxicity. Since iron promotes oxidative stress, the present study explores how change in nutritional iron content modulates kainate-induced neurotoxicity. Rats received an iron-deficient diet (ID) from 22 days of age for 4 weeks. One control group received the same diet supplemented with iron and another control group received standard rodent diet. Cellular damage after subcutaneous kainate (10 mg/kg) was assessed by silver impregnation and gliosis by staining microglia. ID reduced cellular damage in piriform and entorhinal cortex, in thalamus, and in hippocampal layers CA1-3. ID also attenuated gliosis, except in the hippocampal CA1 layer. Given involvement of zinc in hippocampal neurotransmission and in oxidative stress, we tested for a possible interaction of nutritional iron with nutritional zinc. Rats were made iron-deficient and then assigned to supplementation with iron, zinc, or iron + zinc. Controls were continued on ID diet. After 2 weeks, rats were treated with kainate. Iron supplementation abolished the protective effect of ID in piriform and entorhinal cortex. In hippocampal CA1 and dorsal thalamus, neither iron nor zinc supplementation alone abolished the protective effect of ID against cellular damage. Iron + zinc supplementation abolished ID protection in dorsal thalamus, but not in reuniens nucleus. Kainate-induced gliosis in CA1 remained unaffected by nutritional treatments. Thus, in piriform and entorhinal cortex, nutritional iron has a major impact on cellular damage and gliosis. In hippocampal CA1, gliosis may associate with synaptic plasticity not modulated by nutritional iron, while cellular damage is sensitive to nutritional iron and zinc.

Application of in vivo ESR spectroscopy to measurement of cerebrovascular ROS generation in stroke

This study used an in vivo ESR spectroscopy/spin probe technique to measure directly the generation of reactive oxygen species (ROS) in the brain after cerebral ischemia-reperfusion. Transient middle cerebral artery occlusion (MCAO) was induced in rats by inserting a nylon thread into the internal carotid artery for 1 h. The in vivo generation of ROS and its location in the brain were analyzed from the enhanced ESR signal decay data of three intra-arterially injected spin probes with different membrane permeabilities. The ESR signal decay of the probe with intermediate permeability was significantly enhanced 30 min after reperfusion following MCAO, whereas no enhancement was observed with the other probes or in the control group. The enhanced in vivo signal decay was significantly suppressed by superoxide dismutase (SOD). Brain damage was barely discernible until 3 h of reperfusion, and was clearly suppressed with the probe of intermediate permeability. The antioxidant MCI-186 completely suppressed the enhanced in vivo signal decay after transient MCAO. These results clearly demonstrate that ROS are generated at the interface of the cerebrovascular cell membrane when reperfusion follows MCAO in rats, and that the ROS generated during the initial stages of transient MCAO cause brain injury.

Protective effects of sesamin and sesamolin on hypoxic neuronal and PC12 cells

Reactive oxygen species (ROS) are important mediators of a variety of pathological processes, including inflammation and ischemic injury. The neuroprotective effects of sesame antioxidants, sesamin and sesamolin, against hypoxia or H2O2-induced cell injury were evaluated by cell viability or lactate dehydrogenase (LDH) activity. Sesamin and sesamolin reduced LDH release of PC12 cells under hypoxia or H2O2-stress in a dose-dependent manner. Dichlorofluorescein (DCF)-sensitive ROS production was induced in PC12 cells by hypoxia or H2O2-stress but was diminished in the presence of sesamin and sesamolin. We evaluated further the role of mitogen-activated protein kinases (MAPKs) and caspase-3 in hypoxia-induced PC12 cell death. Extracellular signal-regulated protein kinase (ERK) 1, c-jun N-terminal kinase (JNK), and p38 MAPKs of signaling pathways were activated during hypoxia. We found that the inhibition of MAPKs and caspase-3 by sesamin and sesamolin correlated well with the reduction in LDH release under hypoxia. Furthermore, the hypoxia-induced apoptotic-like cell death in cultured cortical cells as detected by a fluorescent DNA binding dye was reduced significantly by sesamin and sesamolin. Taken together, these results suggest that the protective effect of sesamin and sesamolin on hypoxic neuronal and PC12 cells might be related to suppression of ROS generation and MAPK activation.

Alterations of cullin-5 mRNA levels in the rat central nervous system following hemorrhagic shock

Hemorrhagic shock is a clinical syndrome that manifests as hypoperfusion, hypoxia, and ischemia initiating various cellular stress responses involved in the synthesis and release of an assortment of pro-inflammatory molecules, cytokines, chemokines, and reactive oxidant species (ROS). The ROS have been shown to oxidize and damage proteins making them targets for ubiquitination and proteasomal degradation. Cullin-5 (cul-5), an E3 ligase that binds ubiquitin to proteins targeted for degradation via the proteasome, was investigated for its gene expression during hemorrhagic shock. Male Long-Evans rats were subjected to volume controlled (27 ml kg-1) hemorrhage over 10 min and kept in shock for 60 min. Quantitative realtime polymerase chain reaction showed cul-5 mRNA levels were significantly increased in the brainstem and cerebellum, and decreased in the hypothalamus of rats as a result of hemorrhagic shock (n = 6) compared to sham-treated rats (n = 6). Cul-5 mRNA levels in the cerebral cortex, small intestine, kidney, liver, lung, or pituitary gland did not significantly change after hemorrhagic shock. This is the first report of cul-5 mRNA regulation by hemorrhagic shock. Evidence indicates this protein may have a regulatory role in ubiquitin-proteasomal protein degradation in response to hemorrhagic shock.

Oxypurinol administration fails to prevent hypoxic-ischemic brain injury in neonatal rats

The purpose of the present study was to determine whether oxypurinol, a xanthine oxidase inhibitor, reduces free radicals and brain injury in the rat pup hypoxic-ischemia (HI) model. Seven-day-old rat pups had right carotid arteries ligated followed by 2.5h of hypoxia (8% oxygen). Oxypurinol or vehicle was administered by i.p. injection at 5 min after reoxygenation and once daily for 3 days. Brain damage was evaluated by weight deficit of the right hemisphere at 22 days following hypoxia. Oxypurinol treatments did not reduce weight loss in the right hemisphere. Brain weight loss in the right hemisphere were -26.2+/-3.6, -15.2+/-6.9, -21.7+/-4.4, -15.8+/-5.1, and -16.7+/-3.4% in vehicle (n=33), 10 (n=17), 20 (n=16), 40 (n=15), and 135 mg/kg (n=13) oxypurinol-treated groups (p>0.05), respectively. Brain thiobarbituric acid-reacting substances (TBARS) were assessed 3 and 6h after reoxygenation. Concentrations of TBARS rose 1.5-fold due to HI. Oxypurinol did not significantly reduce an HI-induced increase in brain TBARS. Thus, xanthine oxidase may not be the primary source of oxy-radicals in pup brain and as such oxypurinol does not prevent free radical-mediated lipid peroxidation or protect against brain injury in the neonatal rat HI model.

Allopurinol for the treatment of aggressive behaviour in patients with dementia

Aggressive behaviour is commonly observed in patients with dementia, and current pharmacological treatments are still deficient in terms of efficacy and tolerability. Allopurinol is an inhibitor of the enzyme xanthine oxidase, with previously suggested anti-aggressive effects. After successful treatment of aggression in two patients, we performed a case-series study with allopurinol 300 mg a day orally for 6 weeks (increasing 300 mg every 2 weeks if the response was less than 50%) in six patients with dementia associated with prominent aggressive behaviour who failed to respond to two previous treatment strategies. Five patients were considerably responsive to allopurinol (four with 300 mg within 2 weeks and one with 600 mg), apparently without side-effects, which is in accordance with its well-established safety and tolerability profile. The observed therapeutic effect of allopurinol might be due to the inhibition of the enzyme xanthine oxidase, possibly decreasing production of oxygen-free radicals or promoting the accumulation of purines. Controlled studies are warranted to confirm these preliminary observations.

Protective effect of Nardostachys jatamansi in rat cerebral ischemia

The protective effect of Nardostachys jatamansi (NJ) on neurobehavioral activities, thiobarbituric acid reactive substance (TBARS), reduced glutathione (GSH), thiol group, catalase and sodium-potassium ATPase activities was studied in middle cerebral artery (MCA) occlusion model of acute cerebral ischemia in rats. The right MCA of male Wistar rats was occluded for 2 h using intraluminal 4-0 monofilament and reperfusion was allowed for 22 h. MCA occlusion caused significant depletion in the contents of glutathione and thiol group and a significant elevation in the level of TBARS. The activities of Na(+)K(+) ATPase and catalase were decreased significantly by MCA occlusion. The neurobehavioral activities (spontaneous motor activity and motor coordination) were also decreased significantly in MCA occlusion group. All the alternations induced by ischemia were significantly attenuated by 15 days pretreatment of NJ (250 mg/kg po) and correlated well with histopathology by decreasing the neuronal cell death following MCA occlusion and reperfusion. The study provides first evidence of effectiveness of NJ in focal ischemia most probably by virtue of its antioxidant property.

Nicotinamide therapy protects against both necrosis and apoptosis in a stroke model

BACKGROUND AND PURPOSE

Nicotinamide protects against brain damage in ischemia-reperfusion. However, the dosage and time of treatment require clarification. It is also not clear if nicotinamide can protect against both necrosis and apoptosis.

METHODS

Dose-response and time-effect studies were designed. Transient focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) for 90 min. Different doses of nicotinamide were injected upon reperfusion. In time-effect studies, 500 mg/kg nicotinamide was administered at different times after the onset of reperfusion. Neurological finding scores were recorded. Infarct volumes were measured.

RESULTS

In contrast to controls, neurological deficit scores and infarct volumes were greatly reduced by treatment with nicotinamide. The ED(50) of nicotinamide was 239+/-79 mg/kg (P=.95). It was found that nicotinamide injected during the first 6 h of reperfusion could effectively inhibit the development of brain damage. The optimal dose of nicotinamide was 500 mg/kg and gave a maximal response.

CONCLUSIONS

Poly(ADP-ribose) polymerase (PARP) plays a key role in DNA repair in stroke. Excessive PARP activity consumes NAD leading to energy depletion and neuronal damage. As an inhibitor of PARP, nicotinamide promotes the supply of energy. The results suggest that early application of nicotinamide at a suitable dosage significantly ameliorates necrotic and apoptotic brain injury after focal ischemia-reperfusion.

Effects of anti-intercellular adhesion molecule-1 antibody on reperfusion injury induced by late reperfusion in the rat middle cerebral artery occlusion model

OBJECTIVE

Inflammatory processes have been implicated in the mechanisms of reperfusion injury. The migration of leukocytes into ischemic tissue on reperfusion, which involves binding to the intercellular adhesion molecule (ICAM) of the endothelial cell, is thought to exacerbate tissue injury. The aim of the present study was to assess the effects of an anti-ICAM-1 antibody on reperfusion-induced injury after late reperfusion in a rat middle cerebral artery occlusion (MCAO) suture model.

METHODS

The animals were divided into four groups: 1) Group 1 (n = 7), 6 hours of permanent MCAO; 2) Group 2 (n = 7), 3 hours of MCAO followed by 3 hours of reperfusion; 3) Group 3 (n = 6), 6 hours of permanent MCAO and treatment with anti-ICAM-1 antibody (designated 1A29, 1 mg/kg) at 2 hours after onset of MCAO; and 4) Group 4 (n = 6), 3 hours of MCAO followed by 3 hours of reperfusion and 1A29 treatment. During the experiment, regional cerebral blood flow was measured by a laser Doppler flowmetric scanning technique. At the 6-hour time point, all rats were killed, and the results of leukocyte infiltration by myeloperoxidase activity and histological analysis using 2,3,5-triphenyltetrazolium chloride staining were examined.

RESULTS

Regional cerebral blood flow values before and after MCAO were not significantly different among the four groups. Regional cerebral blood flow values after reperfusion were not significantly different in the two reperfused groups. The percentage brain injury volumes in both the total and cortical areas and the myeloperoxidase activity in the latter were significantly larger in Group 2 (the reperfused group) than in the other groups (P < 0.05) but were decreased by anti-ICAM-1 antibody treatment (Group 2 versus Group 4, P < 0.05). However, there were no differences between Groups 1 and 3 without reperfusion. Myeloperoxidase activities correlated positively with infarct volumes (P < 0.01).

CONCLUSION

The findings of this study demonstrate that the anti-ICAM antibody treatment is effective at inhibiting early inflammatory processes and reperfusion-induced injury caused by late arterial recanalization, which would contribute to widening the therapeutic window of thrombolytic therapy.

Ischaemic brain oedema

Ischaemic brain oedema appears to involve two distinct processes, the relative contribution and time course of which depend on the duration and severity of ischaemia, and the presence of reperfusion. The first process involves an increase in tissue Na+ and water content accompanying increased pinocytosis and Na+, K+ ATPase activity across the endothelium. This is apparent during the early phase of infarction and before any structural damage is evident. This phenomenon is augmented by reperfusion. A second process results from a more indiscriminate and delayed BBB breakdown that is associated with infarction of both the parenchyma and the vasculature itself. Although, tissue Na+ level still seems to be the major osmotic force for oedema formation at this second stage, the extravasation of serum proteases is an additional potentially deleterious factor. The relative importance of protease action is not yet clear, however, degradation of the extracellular matrix conceivably leads to further BBB disruption and softening of the tissue, setting the stage for the most pronounced forms of brain swelling. A number of factors mediate or modulate ischaemic oedema formation, however, most current information comes from experimental models, and clinical data on this microcosmic level is lacking. Clinically significant brain oedema develops in a delayed fashion after large hemispheric strokes and is a cause of substantial mortality. Neurological signs appear to be at least as good as direct ICP measurement and neuroimaging in detecting and gauging the secondary damage produced by stroke oedema. The neuroimaging characteristics of the stroke, specifically the early involvement of greater than half of the MCA territory, are, however, highly predictive of the development of severe oedema over the subsequent hours and days. None of the available medical therapies provide substantial relief from the oedema and raised ICP, or at best, they are temporizing in most cases. Hemicraniectomy appears most promising as a method of avoiding death from brain compression, but the optimum timing and manner of patient selection are currently being investigated. All approaches to massive ischaemic brain swelling are clouded by the potential for survival with poor functional outcome. It is possible to manage blood pressure, serum osmolarity by way of selective fluid administration, and a number of other systemic factors that exaggerate brain oedema. Broad guidelines for treatment of stroke oedema can therefore be given at this time.

Rude unhinging of the machinery of life: metabolic approaches to hemorrhagic shock

In 1862, Samuel Gross described shock as the "rude unhinging" of the machinery of life. As noted above, adequate oxygen delivery and metabolism are essential to the maintenance of cellular energy stores. Failure of adequate tissue oxygen delivery and utilization during shock can lead to organ dysfunction and death. Hemorrhagic shock after trauma can result in inherent mitochondrial dysfunction as manifested by decoupling. This pathologic condition has been recently termed cytopathic hypoxia. Since mitochondria are the ultimate consumer of oxygen in cells, mitochondria might indeed be the machinery of life rudely unhinged by shock. Yet, therapeutic strategies have been recently developed to support mitochondrial function in shock and related states. If these therapeutic interventions directed towards organelle and cellular resuscitation are proven to enhance human organ function and improve survival, then these strategies could augment current therapeutic regimens directed exclusively towards hemodynamic and ventilatory homeostasis.

Allopurinol neurocardiac protection trial in infants undergoing heart surgery using deep hypothermic circulatory arrest

OBJECTIVE

This pharmacologic protection trial was conducted to test the hypothesis that allopurinol, a scavenger and inhibitor of oxygen free radical production, could reduce death, seizures, coma, and cardiac events in infants who underwent heart surgery using deep hypothermic circulatory arrest (DHCA).

DESIGN

This was a single center, randomized, placebo-controlled, blinded trial of allopurinol in infant heart surgery using DHCA. Enrolled infants were stratified as having hypoplastic left heart syndrome (HLHS) and all other forms of congenital heart disease (non-HLHS). Drug was administered before, during, and after surgery. Adverse events and the clinical efficacy endpoints death, seizures, coma, and cardiac events were monitored until infants were discharged from the intensive care unit or 6 weeks, whichever came first.

RESULTS

Between July 1992 and September 1997, 350 infants were enrolled and 348 subsequently randomized. A total of 318 infants (131 HLHS and 187 non-HLHS) underwent heart surgery using DHCA. There was a nonsignificant treatment effect for the primary efficacy endpoint analysis (death, seizures, and coma), which was consistent over the 2 strata. The addition of cardiac events to the primary endpoint resulted in a lack of consistency of treatment effect over strata, with the allopurinol treatment group experiencing fewer events (38% vs 60%) in the entire HLHS stratum, compared with the non-HLHS stratum (30% vs 27%). In HLHS surgical survivors, 40 of 47 (85%) allopurinol-treated infants did not experience any endpoint event, compared with 27 of 49 (55%) controls. There were fewer seizures-only and cardiac-only events in the allopurinol versus placebo groups. Allopurinol did not reduce efficacy endpoint events in non-HLHS infants. Treated and control infants did not differ in adverse events.

CONCLUSIONS

Allopurinol provided significant neurocardiac protection in higher-risk HLHS infants who underwent cardiac surgery using DHCA. No benefits were demonstrated in lower risk, non-HLHS infants, and no significant adverse events were associated with allopurinol treatment.congenital heart defects, hypoplastic left heart syndrome, induced hypothermia, ischemia-reperfusion injury, neuroprotective agents, allopurinol, xanthine oxidase, free radicals, seizures, coma.