Combined neuroprotection and reperfusion therapy for stroke. Effect of lubeluzole and diaspirin cross-linked hemoglobin in experimental focal ischemia

T155g-Immortalized Kidney Cells Produce Growth Factors and Reduce Sequelae of Cerebral Ischemia

Fetal rat kidney cells produce high levels of glial-derived neurotrophic factor (GDNF) and exert neuroprotective effects when transplanted into the brain in animal models of Parkinson's disease and stroke. The purpose of the present experiment was to produce kidney cell lines that secrete GDNF. Genes encoding two truncated N-terminal fragments of SV40 large T antigen, T155g and T155c, which does not code for small t antigen, were used. T155g was transduced into E17 cultured fetal Sprague-Dawley rat kidney cortex cells using a plasmid vector, and T155c was transduced with a plasmid and a retroviral vector. Sixteen clones were isolated from cultures transfected with the T155g-expressing plasmid. No cell lines were obtained with T155c. Four clones produced GDNF at physiological concentrations ranging from 55 to 93 pg/ml of medium. These four clones were transplanted into the ischemic core or penumbra of rats that had undergone middle cerebral artery occlusion (MCAO). Three of the four clones reduced the volume of infarction and the behavioral abnormalities normally resulting from MCAO. Blocking experiments with antibodies to GDNF and platelet-derived growth factor (PDGF) suggested that these growth factors contributed only minimally to the reduction in infarct volume and behavioral abnormality. These cell lines may be useful for intracerebral transplantation in animal models of brain injury, stroke, or Parkinson's disease.

Pharmacological, Cell, and Gene Therapy Strategies to Promote Spinal Cord Regeneration

In this review, recent studies using pharmacological treatment, cell transplantation, and gene therapy to promote regeneration of the injured spinal cord in animal models will be summarized. Pharmacological and cell transplantation treatments generally revealed some degree of effect on the regeneration of the injured ascending and descending tracts, but further improvements to achieve a more significant functional recovery are necessary. The use of gene therapy to promote repair of the injured nervous system is a relatively new concept. It is based on the development of methods for delivering therapeutic genes to neurons, glia cells, or nonneural cells. Direct in vivo gene transfer or gene transfer in combination with (neuro)transplantation (ex vivo gene transfer) appeared powerful strategies to promote neuronal survival and axonal regrowth following traumatic injury to the central nervous system. Recent advances in understanding the cellular and molecular mechanisms that govern neuronal survival and neurite outgrowth have enabled the design of experiments aimed at viral vector-mediated transfer of genes encoding neurotrophic factors, growth-associated proteins, cell adhesion molecules, and antiapoptotic genes. Central to the success of these approaches was the development of efficient, nontoxic vectors for gene delivery and the acquirement of the appropriate (genetically modified) cells for neurotransplantation. Direct gene transfer in the nervous system was first achieved with herpes viral and E1-deleted adenoviral vectors. Both vector systems are problematic in that these vectors elicit immunogenic and cytotoxic responses. Adeno-associated viral vectors and lentiviral vectors constitute improved gene delivery systems and are beginning to be applied in neuroregeneration research of the spinal cord. Ex vivo approaches were initially based on the implantation of genetically modified fibroblasts. More recently, transduced Schwann cells, genetically modified pieces of peripheral nerve, and olfactory ensheathing glia have been used as implants into the injured spinal cord.

Haemodilution for acute ischaemic stroke

BACKGROUND

Ischaemic stroke interrupts the flow of blood to part of the brain. Haemodilution is thought to improve the flow of blood to the affected areas of the brain and thus reduce infarct size.

OBJECTIVES

To assess the effects of haemodilution in acute ischaemic stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (February 2014), the Cochrane Central Register of Controlled Trials (Issue 1, 2014), MEDLINE (January 2008 to October 2013) and EMBASE (January 2008 to October 2013). We also searched trials registers, scanned reference lists and contacted authors. For the previous version of the review, the authors contacted manufacturers and investigators in the field.

SELECTION CRITERIA

Randomised trials of haemodilution treatment in people with acute ischaemic stroke. We included only trials in which treatment was started within 72 hours of stroke onset.

DATA COLLECTION AND ANALYSIS

Two review authors assessed trial quality and one review author extracted the data.

MAIN RESULTS

We included 21 trials involving 4174 participants. Nine trials used a combination of venesection and plasma volume expander. Twelve trials used plasma volume expander alone. The plasma volume expander was plasma alone in one trial, dextran 40 in 12 trials, hydroxyethyl starch (HES) in five trials and albumin in three trials. Two trials tested haemodilution in combination with another therapy. Evaluation was blinded in 14 trials. Five trials probably included some participants with intracerebral haemorrhage. Haemodilution did not significantly reduce deaths within the first four weeks (risk ratio (RR) 1.10; 95% confidence interval (CI) 0.90 to 1.34). Similarly, haemodilution did not influence deaths within three to six months (RR 1.05; 95% CI 0.93 to 1.20), or death and dependency or institutionalisation (RR 0.96; 95% CI 0.85 to 1.07). The results were similar in confounded and unconfounded trials, and in trials of isovolaemic and hypervolaemic haemodilution. No statistically significant benefits were documented for any particular type of haemodiluting agents, but the statistical power to detect effects of HES was weak. Six trials reported venous thromboembolic events. There was a tendency towards reduction in deep venous thrombosis or pulmonary embolism or both at three to six months' follow-up (RR 0.68; 95% CI 0.37 to 1.24). There was no statistically significant increased risk of serious cardiac events among haemodiluted participants.

AUTHORS' CONCLUSIONS

The overall results of this review showed no clear evidence of benefit of haemodilution therapy for acute ischaemic stroke.These results are compatible with no persuasive beneficial evidence of haemodilution therapy for acute ischaemic stroke. This therapy has not been proven to improve survival or functional outcome.

The role of glutamate in neuronal ischemic injury: the role of spark in fire

Although being a physiologically important excitatory neurotransmitter, glutamate plays a pivotal role in various neurological disorders including ischemic neurological diseases. Its level is increased during cerebral ischemia with excessive neurological stimulation causing the glutamate-induced neuronal toxicity, excitotoxicity, and this is considered the triggering spark in the ischemic neuronal damage. The glutamatergic stimulation will lead to rise in the intracellular sodium and calcium, and the elevated intracellular calcium will lead to mitochondrial dysfunction, activation of proteases, accumulation of reactive oxygen species and release of nitric oxide. Interruption of the cascades of glutamate-induced cell death during ischemia may provide a way to prevent, or at least reduce, the ischemic damage. Various therapeutic options are suggested interrupting the glutamatergic pathways, e.g., inhibiting the glutamate synthesis or release, increasing its clearance, blocking of its receptors or preventing the rise in intracellular calcium. Development of these strategies may provide future treatment options in the management of ischemic stroke.

Anemia and red blood cell transfusion in neurocritical care

INTRODUCTION

Anemia is one of the most common medical complications to be encountered in critically ill patients. Based on the results of clinical trials, transfusion practices across the world have generally become more restrictive. However, because reduced oxygen delivery contributes to 'secondary' cerebral injury, anemia may not be as well tolerated among neurocritical care patients.

METHODS

The first portion of this paper is a narrative review of the physiologic implications of anemia, hemodilution, and transfusion in the setting of brain-injury and stroke. The second portion is a systematic review to identify studies assessing the association between anemia or the use of red blood cell transfusions and relevant clinical outcomes in various neurocritical care populations.

RESULTS

There have been no randomized controlled trials that have adequately assessed optimal transfusion thresholds specifically among brain-injured patients. The importance of ischemia and the implications of anemia are not necessarily the same for all neurocritical care conditions. Nevertheless, there exists an extensive body of experimental work, as well as human observational and physiologic studies, which have advanced knowledge in this area and provide some guidance to clinicians. Lower hemoglobin concentrations are consistently associated with worse physiologic parameters and clinical outcomes; however, this relationship may not be altered by more aggressive use of red blood cell transfusions.

CONCLUSIONS

Although hemoglobin concentrations as low as 7 g/dl are well tolerated in most critical care patients, such a severe degree of anemia could be harmful in brain-injured patients. Randomized controlled trials of different transfusion thresholds, specifically in neurocritical care settings, are required. The impact of the duration of blood storage on the neurologic implications of transfusion also requires further investigation.

Imidazole derivatives as antioxidants and selective inhibitors of nNOS

The reperfusion of ischemic tissue often delays its physiological and functional recovery; this paradoxical effect is ascribed to increased release of free radicals including O(2)(-) and NO. For these reasons, scavenging reactive oxygen species or inhibition the NO synthesis has been shown to result in an enhanced neuronal survival after cerebral ischemia. Many authors believe that therapy for stroke patients would be a cocktail of drugs with various mechanisms of action. Combination therapy is a difficult and complicated avenue for drug development because of the possibility of drug-drug interactions. An alternative approach would be to combine multiple activities within the same compound. In consideration of the free-radical scavenging and inhibitory effect on NOS of various natural and synthetic compounds, the aim of this study was to analyze the antioxidant properties of some imidazole derivatives previously synthesized in our laboratory. Results obtained in the present study provide evidence that tested compounds exhibit interesting antioxidant properties, expressed either by their capacity to scavenge free radicals or their ability to reduce lipid peroxidation. In particular, compounds A and B represent chemical structures which can be easily modified to improve the observed antioxidant properties and to provide new therapeutic strategies focused on multiple downstream events.

Salvage of focal cerebral ischemic damage by transfusion of high O2-affinity recombinant hemoglobin polymers in mouse

Cell-free hemoglobin solutions with high oxygen affinity might be beneficial for selectively delivering oxygen to ischemic tissue. A recombinant hybrid hemoglobin molecule was designed using the human alpha-subunit and the bovine beta-subunit, with placement of surface cysteines to permit disulfide bond polymerization of the tetramers. The resulting protein generated from an Escherichia coli expression system had a molecular mass >1 MDa, a P50 of approximately 3 Torr, and a cooperativity of n = 1.0. Anesthetized mice were transfused during 2-h occlusion of the middle cerebral artery. Compared with transfusion with 5% albumin, cerebral infarct volume was reduced by 41% with transfusion of a 3% solution of the high oxygen-affinity hemoglobin polymer and by 50% with transfusion of a 6% solution of the polymer. Transfusion of a 6% solution of a 500-kDa polymer possessing a P50 of 17 Torr and a cooperativity of n = 2.0 resulted in a 66% reduction of infarct volume. These results indicate that cell-free Hb polymers with P50 values much lower than that of red blood cell hemoglobin are highly capable of salvaging ischemic brain. The assumption that the P50 of blood substitutes should be similar to that of blood might not be warranted when used during ischemic conditions.

Catalpol prevents the loss of CA1 hippocampal neurons and reduces working errors in gerbils after ischemia-reperfusion injury

Catalpol, an iridoid glycoside, contained richly in the roots of Rehmannia glutinosa, was found for the first time to be of neuroprotection in gerbils subjected to transient global cerebral ischemia. Catalpol (1 mg/kg ip) used immediately after reperfusion and repeatedly at 12, 24, 48 and 72 h significantly rescued neurons in hippocampal CA1 subfield and reduced working errors during behavioral testing. The neuroprotective efficacy of catalpol became more evident when the doses of catalpol were increased to 5 and 10mg/kg. In addition, it was exciting that the significant neuroprotection by catalpol was also evident when catalpol was applied up to 3 h after ischemia. But the neuroprotective efficacy of catalpol became weak when catalpol was given at 6h after ischemia. Of great encouragement was the finding that the neuroprotection of catalpol could be seen not only in a short post-ischemic period (12 days) but also in a long period (35 days). All these indicated that catalpol was truly neuroprotective rather than simply delayed the onset of neuronal damage and might be of therapeutic value for the treatment of global cerebral ischemia.

Role of nitric oxide after brain ischaemia

Ischaemic stroke is the second or third leading cause of death in developed countries. In the last two decades substantial research and efforts have been made to understand the biochemical mechanisms involved in brain damage and to develop new treatments. The evidence suggests that nitric oxide (NO) can exert both protective and deleterious effects depending on factors such as the NOS isoform and the cell type by which NO is produced or the temporal stage after the onset of the ischaemic brain injury. Immediately after brain ischaemia, NO release from eNOS is protective mainly by promoting vasodilation; however, after ischaemia develops, NO produced by overactivation of nNOS and, later, NO release by de novo expression of iNOS contribute to the brain damage. This review article summarizes experimental and clinical data supporting the dual role of NO in brain ischaemia and the mechanisms by which NO is regulated after brain ischaemia. We also review NO-based therapeutic strategies for stroke treatment, not only those directly linked with the NO pathway such as NO donors and NOS inhibitors but also those partially related like statins, aspirin or lubeluzole.

Study of the interaction of lubeluzole with cardiac sodium channels

The effects of lubeluzole on sodium currents were examined in guinea-pig isolated cardiac myocytes by use of the whole-cell patch clamp technique. Lubeluzole (0.01-100 microM) reduced peak Na+ current (INa) obtained at a holding potential of -80 mV with an IC50 value of 9.5 (3.5-21.9) microM and a Hill coefficient of 1.1. These effects were rapid and reversible. Lubeluzole (10 microM) produced a shift in the inactivation curve to hyperpolarized potentials (by -9.7 mV, P < 0.05), but produced no change in the voltage-dependence of activation. Lubeluzole (10 microM) produced significant tonic block of INa obtained at a holding potential of -120 mV (2.7 +/- 1.4% and 27.5 +/- 5.8% for control and lubeluzole, respectively; n = 6; P < 0.05). Use-dependent block of INa was also observed. Recovery from block was delayed by lubeluzole (10 microM; tau1=4.4 +/- 6.2, tau2=22.7 +/- 1.5 milliseconds for control and tau1=311 +/- 144, tau2 = 672 +/- 23 milliseconds for lubeluzole; n = 6; P < 0.001) confirming use-dependency of block. The results indicate that lubeluzole produces both tonic and use-dependent block of cardiac sodium channels at concentrations similar to those that block neuronal sodium channels, due mainly to interaction of the drug with channels in the inactivated state.

Neuroprotective effects of NS-7, voltage-gated Na+/Ca2+ channel blocker in a rodent model of transient focal ischaemia

The aim of the present study was to characterize neuroprotective activity of NS- 7, a mixed voltage-gated sodium and calcium channel blocker in a model of transient focal ischaemia in rats. Ischaemia was induced by a 75 min reversible occlusion of middle cerebral artery (MCAo) using a nylon filament. NS-7 (0.5 mg/kg i.v.) or 0.9% NaCl (1 ml/kg i.v.) were infused over 3 min. starting 30 min after the MCAo. Infarct analysis was performed 72 h after ischaemia. Application of NS- 7 produced significant protection seen in neurological tests and diminished brain damage by 37% in total infarct (17.7+/- 3.0% vs. 27.9 +/- 3.2% control; [p < 0.01]; t-test), 47.8% in cortical infarct size by (8.5 +/- 2.4% vs. 16.2 +/- 2.4% control; [p < 0.01]), and by 21.5% in striatal infarction (9.2 +/- 0.8% vs. 11.7 +/- 0.9% control; [p < 0.05]). The results indicate that NS- 7 has potential for neuroprotection against transient ischaemic insult.

Synthesis and structure-activity relationships of 6,7-benzomorphan derivatives as use-dependent sodium channel blockers for the treatment of stroke

We have synthesized a series of 6,7-benzomorphan derivatives and determined their ability to bind to voltage-dependent sodium channels. We have also compared the functional consequences of this blockade in vitro and in vivo. The ability of the compounds to displace [(3)H]batrachotoxin from voltage-dependent sodium channels was compared with their ability to inhibit [(3)H]glutamate release in rat brain slices and block convulsions in the maximal electroshock test in mice. We found that the hydroxyl function in the 4'-position is crucial for improving the sodium channel blocking properties. Moreover, the stereochemistry and the topology of the N-linked side chain also influence this interaction. Indeed, the affinity is improved by an aromatic substitution in the side chain. By modifying the N substituent and the substitution pattern of the hydroxyl function, we were able to discover (2R)-[2alpha,3(S),6alpha]-1,2,3,4,5,6-hexahydro-6,11,11-tri-methyl-3-[2-(phenylmethoxy)propyl]-2,6-methano-3-benzazocin-10-ol hydrochloride. This compound was chosen as the best candidate for further pharmacological investigations.

Cerebral ischemia and trauma-different etiologies yet similar mechanisms: neuroprotective opportunities

Cerebral ischemia leads to brain damage caused by pathogenetic mechanisms that are also activated by neurotrauma. These mechanisms include among others excitotoxicity, over production of free radicals, inflammation and apoptosis. Furthermore, cerebral ischemia and trauma both trigger similar auto-protective mechanisms including the production of heat shock proteins, anti-inflammatory cytokines and endogenous antioxidants. Neuroprotective therapy aims at minimizing the activation of toxic pathways and at enhancing the activity of endogenous neuroprotective mechanisms. The similarities in the damage-producing and endogenous auto-protective mechanisms may imply that neuroprotective compounds found to be active against one of these conditions may indeed be also protective in the other. This review summarizes the pathogenetic events of ischemic and traumatic brain injury and reviews the neuroprotective strategies employed thus far in each of these conditions with a special emphasize on their clinical relevance and on future directions in the field of neuronal protection.

Lubeluzole pretreatment does not provide neuroprotection against transient global cerebral ischemia in fetal sheep near term

The aim of the present study was to test the neuroprotective effect of the novel benzothiazol compound lubeluzole on neuronal cell damage in fetal sheep arising from global cerebral ischemia. Thirteen fetal sheep were prepared at a mean gestational age of 127 +/- 1 d (term is at 147 d). Six fetuses were treated with lubeluzole (0.33 mg/kg estimated body weight) before induction of global cerebral ischemia (-90, -60, and -30 min), while the remainder (n = 7) received solvent. Cerebral ischemia was induced by occluding both carotid arteries for 30 min. Cerebral blood flow was measured by injecting radio-labeled microspheres before (-90 min), during (+3 min and +27 min), and after (+40 min, +3 h, and +72 h) cerebral ischemia. Neuronal cell damage was assessed in the cerebrum and deeper brain structures by light microscopy. Values are given as means +/- SD. In control fetuses, blood flow to the cerebrum was reduced from 100 +/- 25 mL.100 g(-1) min(-1) to less than 20 mL.100 g(-1) min(-1) during ischemia. Shortly after ischemia, hyperperfusion occurred (217 +/- 66 mL.100 g(-1)min(-1)) followed by a tendency toward hypoperfusion (72 +/- 17 mL.100 g(-1) min(-1)) later on (+3 h). Significant differences in blood flow to the various brain structures between the control and study groups could not be observed. Neuronal cell damage was concentrated in the parasagittal regions of the cerebrum. Preischemic application of lubeluzole did not have any effect on the extent of neuronal cell damage. From these results, we conclude that pretreatment with lubeluzole fails to protect the brain of fetal sheep near term from injury after transient global cerebral ischemia. However, because the observation period lasted only 3 d, a possible effect of lubeluzole on pathophysiological mechanisms inducing delayed neuronal cell death cannot be fully excluded.

Regional cerebral blood flow in cats with cross-linked hemoglobin transfusion during focal cerebral ischemia

The beneficial effect of hemodilution on cerebral blood flow (CBF) during focal cerebral ischemia is mitigated by reduced arterial oxygen content (CaO2). In anesthetized cats subjected to permanent middle cerebral artery occlusion, the time course of regional CBF was evaluated after isovolemic exchange transfusion with either albumin or a tetrameric hemoglobin-based oxygen carrier. The transfusion started 30 min after arterial occlusion. We tested the hypothesis that bulk oxygen transport (CBF x CaO2) to ischemic tissue is increased by hemoglobin transfusion at a hematocrit of 18% compared with albumin-transfused cats at a hematocrit of 18% or control cats at a hematocrit of 30% and equivalent arterial pressure. In the nonischemic hemisphere, CBF increased selectively after albumin transfusion, and oxygen transport was similar among groups. In the ischemic cortex, albumin transfusion increased CBF, but oxygen transport was not increased above that of the control group. Hemoglobin transfusion increased both CBF and oxygen transport in the ischemic cortex above values in the control group, but the increase was delayed until 4 h of ischemia. Consequently, acute injury volume measured at 6 h of ischemia was not significantly attenuated. In contrast to the cortex, CBF in the ischemic caudate nucleus was not substantially increased by either albumin or hemoglobin transfusion. Therefore, in a large animal model of permanent focal ischemia in which transfusion starts 30 min after ischemia, tetrameric cross-linked hemoglobin transfusion can augment oxygen transport to the ischemic cortex, but the increase can be delayed and not necessarily provide protection. Moreover, an end-artery region such as the caudate nucleus is less likely to benefit from hemodilution.

[First Brazilian consensus for the management of the acute phase of cerebral vascular accidents]

The cerebrovascular diseases have a high incidence, and they cause an enormous social and economic burden. With the increasing knowledge of the pathophysiology of the ischemic insult, and the possibility of the thrombolysis in the acute phase, the management of the stroke patients is considered an emergency. This consensus is the result of a recent meeting to establish a better approach to these patients. This is the official guideline for the management of patients with acute stroke of the Brazilian Cerebrovascular Disease Society.

Neuroprotective effect of treatment with human albumin in permanent focal cerebral ischemia: histopathology and cortical perfusion studies

In recent experimental studies, we demonstrated a highly beneficial neuroprotective effect of moderate- to high-dose human albumin treatment of transient focal cerebral ischemia, but we did not define the effect of albumin therapy in permanent focal cerebral ischemia. In this study, anesthetized Sprague-Dawley rats were subjected to permanent middle cerebral artery occlusion by retrograde insertion of an intraluminal nylon suture coated with poly-L-lysine. Albumin was administered i.v. at 2 h after onset of middle cerebral artery occlusion, in doses of either 1.25 (n=8) or 2.5 g/kg (n=6). In a separate group of animals, albumin (2.5 g/kg) was given 1 h after middle cerebral artery occlusion (n=6). Vehicle-treated rats (n=6) received 0.9% saline in equivalent volumes. Neurological status was evaluated during and 24 h after middle cerebral artery occlusion. One day after middle cerebral artery occlusion, infarct volumes and brain edema were determined. In a separate group of animals, cortical perfusion was assessed by Laser-Doppler perfusion imaging. Albumin (1.25 g/kg; n=3) or vehicle (sodium chloride 0.9%; n=3) was administered at 2 h after onset of middle cerebral artery occlusion. Higher-dose albumin therapy (2.5 g/kg) significantly improved the neurological score compared to vehicle rats at 24 h, when administered at either 1 or 2 h after middle cerebral artery occlusion. Total infarct volume was reduced by albumin (2.5 g/kg given at 2 h) by 32% compared with vehicle-treated rats. Both albumin doses (1.25 and 2.5 g/kg) significantly reduced cortical and striatal infarct areas at several coronal levels when administered at 2 h after middle cerebral artery occlusion. Brain swelling was not affected by albumin treatment. Cortical perfusion declined during middle cerebral artery occlusion in both groups. Treatment with albumin led to 48% increases in cortical perfusion (P<0.002), but saline caused no change. These results support a beneficial effect of albumin therapy in permanent focal cerebral ischemia.

Rat middle cerebral artery occlusion: Correlations between histopathology, T2-weighted magnetic resonance imaging, and behavioral indices

During attempts to develop the intraluminal suture model of transient middle cerebral artery occlusion (MCAO) in the Sprague Dawley strain of rats, we noticed a wide variability in lesion size seen with T2-weighed magnetic resonance imaging (MRI) or histopathology, as well as in scores for behavioral indices. It was our intent to examine the results of the study carefully and determine whether there were strong point-to-point correlations between the degree of lesion size determined from T2-weighted MRI or histopathology and intermediate or long-term neurologic/behavioral assessments. Baseline behavioral scores for forelimb dexterity (staircase test) were obtained on all animals in the period before receiving 60 minutes of transient MCAO. After MCAO, animals were tested at specified intervals from 1 to 21 days for composite neurologic deficits. T2-weighted MRI was taken at 2 and 7 days post-MCAO. At 30 and 60 days post-MCAO, animals were retested in the staircase test with subsequent histopathologic examination of the brains. Indeed, there were highly significant correlations between lesion size determined by MRI and histopathology. The damage observed in the T2-weighted MRI, as well as the size of the histopathologic lesions, were in turn highly correlated to deficiencies observed in the composite neurologic assessments, as well as to deficits at 30 and 60 days post-MCAO for skilled use of the contralateral forepaw (damaged side). In the latter test, the correlations were somewhat less significant for the ability of rats to reach for food with the ipsilateral forepaw (undamaged side).

The failure of neuronal protective agents versus the success of thrombolysis in the treatment of ischemic stroke. The predictive value of animal models

Agents claimed to be neuroprotective in animal stroke models have all failed in human trials. Thrombolysis has been reported as beneficial in animal and human stroke. We explore the reasons for this disparity, using a review of published results of agents tested both in animal stroke models and in human stroke trials. In animals the effect of neuroprotective agents and of thrombolytic agents on infarct size is time-dependent: early initiation of treatment works best; and benefit is progressively--and eventually totally--lost with increasing delay of time of first treatment. The animal data also show that, overall, the beneficial effects of the neuroprotective agents are weaker, and are totally lost sooner, than those of thrombolytics. The human data show that the failed trials of the neuroprotective agents had entry windows that went far beyond the windows of (any) success seen in tests of these agents in animals. By contrast, human thrombolysis trials uniformly restricted time of entry to windows in which these agents have shown beneficial effect in animals. In clinical stroke trials, neuroprotective agents failed to produce benefit because their effects at best are too weak, and they were used at times predictable from the animal models as too late. Thrombolytic therapy, which has a stronger effect than neuroprotective agents in animal models, was used clinically during the early window of optimal effectiveness, and produced beneficial results. "Too little/too late" is the recipe for failure in the treatment of ischemic stroke.

Trophic factor secreting kidney cell lines: in vitro characterization and functional effects following transplantation in ischemic rats

Several kidney cell lines were investigated for their ability to produce glial cell line-derived neurotrophic factor (GDNF). Cell line-conditioned medium was analyzed using ELISA and two cell lines were identified which produce GDNF in physiologically active concentrations. ELISA analyses revealed that conditioned medium from these two cell lines also contained PDGF, bFGF, TGFbeta1 and TGFbeta2. Both of these cell lines were then transplanted into the striatal penumbra of rats, 1 h following middle cerebral artery occlusion. Behavioral testing revealed that both cell lines reduced the deficit associated with cerebral ischemia and reduced the infarct volume relative to controls. Reduction of infarct volume was likely achieved by the action of GDNF and/or other growth factors produced by the cells.

Neuroprotective effect of low dose riluzole in gerbil model of transient global ischemia

Riluzole is a neuroprotective agent the efficacy of which was proven in amyotrophic lateral sclerosis in human and in animal models of cerebral ischemia. However, the dosage used in animal experiments was much higher than that in human. We investigated the efficacy of low dose riluzole, which was similar to the dose used in human trials, in animal model of global ischemia. Global ischemia was induced in male Mongolian gerbils for 5min under monitoring of rectal temperature. Riluzole (0.8 mg/kg) were injected intraperitoneally 30min before ischemia. Seven days after ischemia, animals were decapitated and surviving nerve cells in hippocampal CA1 area were quantified. The number of surviving cells was compared between in riluzole-treated and control groups and the former showed statistically significant better survivals than the latter (P<0.001).

The future of stroke treatment

The concept of the therapeutic window of opportunity in ischemic neuronal injury and understanding the necessity of well organized stroke services revolutionized the management of acute ischemic stroke during the last years of the second millennium. Thrombolysis with IV rt-PA within 3 hours from the onset of symptoms is an established therapy for selected patients. The challenge of stroke therapy at the outset of this millennium is how to translate basic pathophysiologic evidence of ischemic neuronal injury into novel neuroprotective therapies either independently or combined with thrombolysis. Great hopes are placed in identification of pivotal molecular events in ischemic brain tissue and design of effective pharmacological interventions to target them. Aggressive, invasive procedures are also being developed and therapies such as intra-arterial clot lysis, hemicraniectomy and mild hypothermia may improve the bleakest outcomes associated with the most severe forms of ischemic stroke, but their role must be rigorously evaluated. There is, however, no need to wait for future breakthroughs. The existing evidence strongly implies that good care of patients with stroke starts with organization of the entire stroke chain; from the prehospital scene, through the emergency room, to the stroke unit. Without structured stroke services no pharmacological or intervening therapy is likely to improve the outcome of the patient with a stroke.

Usefulness of postischemic thrombolysis with or without neuroprotection in a focal embolic model of cerebral ischemia

OBJECT

Recent studies have shown that the use of thrombolysis in the setting of acute stroke is associated with an increased risk of cerebral hemorrhage. The time of onset of symptoms to initiation of medication and the dose levels of the thrombolytic agents are important determinants for the risk of cerebral hemorrhage. The authors evaluated the time course of thrombolysis-related hemorrhages in experimental settings and tested whether the addition of neuroprotective medication augments the efficacy of thrombolysis and reduces the incidence of hemorrhages.

METHODS

Male Wistar rats were subjected to right middle cerebral artery embolization with an autologous thrombus and were then randomly assigned to one of the following groups: Group 1, saline-treated (2 hours after ischemic insult) animals as controls; Groups 2 to 4, high-dose urokinase (5,000 U/kg) at 2, 3, and 6 hours after the insult; Group 5, low-dose urokinase (2,500 U/kg) at 2 hours after the insult; Group 6, 20 mg/kg topiramate (TPM) at 2 hours after the insult; Group 7, a combination of 20 mg/kg TPM at 2 hours and low-dose urokinase (2,500 U/kg) at 6 hours after the insult; and Group 8, 20 mg/kg TPM (20 mg/kg) at 2 hours and high-dose urokinase (5,000 U/kg) at 2 hours after the insult. Neurological behavior and the infarct volume in the brain were assessed following cerebral embolism and the various treatments. All animals in the single therapy and low-dose combination groups survived surgery. Three of eight animals treated with high-dose urokinase alone at 6 hours and three of six animals in the combined high-dose urokinase and TPM group developed fatal intracerebral hemorrhages. There was a significantly better neurological outcome at 24 hours in the animals treated with either medication compared with controls. The volume of the infarct in the saline-treated group was 54.2 +/- 9%. The use of TPM at 2 hours led to a decrease in the infarct to 20.1 +/- 11.2% (p < 0.01). Treatment with urokinase at 6 hours after the occlusion showed a trend toward protection; the infarct volume was 31.9 +/- 14.1% (p < 0.05). The addition of TPM to low- or high-dose urokinase achieved better neuroprotection (8.2 +/- 6% and 11.9 +/- 10.7%, respectively; both p < 0.01).

CONCLUSIONS

In this study the authors show that the volume of the infarct can be significantly decreased with 2 to 6-hour delayed intraarterial thrombolysis with urokinase and that the efficacy of thrombolysis may be enhanced by combining neuroprotective agents like TPM. It is also shown that low-dose combination therapy may decrease the likelihood of cerebral hemorrhage.

Enhanced neuroprotection and reduced hemorrhagic incidence in focal cerebral ischemia of rat by low dose combination therapy of urokinase and topiramate

Thrombolysis is increasingly being used in treating acute ischemic stroke but it is also accompanied with a serious complication of cerebral hemorrhage in a dose-dependent fashion. As a lower dose may result in decreased effectiveness, we tested the efficacy of combining a neuroprotective agent, topiramate (TPM), with lower doses of intra-arterial urokinase in an embolic stroke model. Focal ischemia was produced by introduction of an autogenous thrombus into the right middle cerebral artery. Urokinase was infused via the ipsilateral internal carotid artery and neuroprotective agent, TPM, was administrated intra-peritoneally 2 h following ischemic insult. The animals were assigned to five groups: (1) control group (n=6); (2) urokinase 5000 units/kg (n=8); (3) urokinase at 2500 units/kg (n=8); (4) topiramate at 20 mg/kg (n=8); (5) urokinase at 2500 units/kg and topiramate at 20 mg/kg (n=8). Neurobehavioral outcome and the degree of brain infarct volume were assessed at 24 h. Three animals in the group treated by high dose urokinase developed intracranial hemorrhage but none in other groups. Animals in all medication-groups showed significant improvement in neurobehavioral score. Post-ischemia treatment with urokinase or TPM alone significantly attenuated brain infarct volume (low-dose urokinase, 39.1+/-13.0%, p<0.05; high-dose, 18.4+/-8.5%, p<0.001; TPM, 20. 1+/-11.2%, p<0.001) when compared to the control (54.2+/-9.04%). Addition of TPM to low dose urokinase achieved better neuroprotection (8.2+/-6.0%) than any single-drug-treated groups. Our data suggests that combination of low dose urokinase with a neuroprotective agent may benefit ischemic stroke treatment by improving neurologic recovery, attenuating infarction size, and reducing the risk of cerebral hemorrhage.

Post-ischemic RSR13 amplifies the effect of dizocilpine on outcome from transient focal cerebral ischemia in the rat

In a recent study of focal cerebral ischemia in rats, pre-ischemic administration of the synthetic allosteric hemoglobin modifier RSR13 (2-[4-[[3,5-dimethylanilino) carbonyl] methyl] phenoxy]-2-methylproprionic acid) reduced cerebral infarct size when combined with the NMDA receptor antagonist dizocilpine (MK-801) but not when given alone. We hypothesized that post-ischemic RSR13 administration would enhance neuroprotection afforded by NMDA receptor antagonism in a rat model of transient middle cerebral artery occlusion (MCAO). Fasted normothermic Wistar rats underwent 75 min of temporary MCAO. At onset of reperfusion, rats randomly received: (1) 0.9% NaCl (vehicle) i.v. alone (n=16); (2) 0.9% NaCl+dizocilpine (0.25 mg/kg) i.v. (n=16); or (3) RSR13 (150 mg/kg)+dizocilpine (0.25 mg/kg) i.v. (n=17). Seven days later, neurologic deficit and cerebral infarct size were determined. Dizocilpine alone compared to vehicle reduced mean+/-S.D. subcortical (52+/-24 mm(3) vs. 122+/-64 mm(3), P=0.003) and cortical (35+/-35 mm(3) vs. 125+/-72 mm(3), P=0.00074) infarct volumes. When compared to dizocilpine alone, the combination of RSR13+dizocilpine further reduced subcortical (37+/-14 mm(3) vs. 52+/-24 mm(3), P=0. 034) and cortical (8+/-19 mm(3) vs. 35+/-35 mm(3), P=0.018) infarct size. RSR13+dizocilpine improved neurologic scores vs. either dizocilpine alone (P=0.0014) or vehicle (P=10(-7)). The combination of NMDA receptor antagonism and a RSR13 mediated rightward shift of the oxy-hemoglobin dissociation curve improved outcome from MCAO. Because this occurred after reperfusion, our results suggest that the post-ischemic brain continues to suffer from hypoperfusion defects, which are amenable to therapy by enhanced O(2) delivery. The results also support the concept that neuroprotective strategies, which combine drugs with different mechanisms of action, may yield cumulative benefits.

Haemodilution for acute ischaemic stroke

BACKGROUND

Ischaemic stroke interrupts the flow of blood to part of the brain. Haemodilution is thought to improve the flow of blood to the affected areas of the brain.

OBJECTIVES

The objective of this review was to assess the effects of haemodilution in acute ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group trials register, Medline and conference abstracts. We contacted manufactures and investigators in the field.

SELECTION CRITERIA

Randomised trials of haemodilution treatment in people with acute ischaemic stroke. Only trials where treatment was started within 72 hours of stroke onset were included.

DATA COLLECTION AND ANALYSIS

Two reviewers assessed trial quality and independently extracted the data.

MAIN RESULTS

Sixteen trials were included. A combination of venesection and plasma volume expander was used in eight trials. Eight trials used plasma volume expander alone. The plasma volume expander was dextran 40 in 11 trials, hydroxyethyl starch in four trials and albumin in one trial. Two trials tested haemodilution in combination with another therapy. Evaluation was blinded in 11 trials. Five trials probably included some patients with intracerebral haemorrhage. Haemodilution did not significantly reduce deaths within seven to 28 days (odds ratio 1.12, 95% confidence interval 0.88 to 1.43). Similarly, haemodilution did not influence deaths within three to six months (odds ratio 1.02, 95% confidence interval 0.85 to 1.23), or death and dependency or institutionalisation (odds ratio 1.01, 95% confidence interval 0.86 to 1.19). The results were similar in confounded and unconfounded trials, in trials of isovolaemic and hypervolaemic haemodilution, and in trials using different types of hemodiluting agents. Six trials reported venous thromboembolic events. There was a tendency towards reduction in deep venous thrombosis and/or pulmonary embolism at three to six months follow-up (odds ratio 0.59, 95% confidence interval 0.33 to 1.06).

REVIEWER'S CONCLUSIONS

The overall results of this review are compatible both with a modest benefit and a moderate harm of haemodilution therapy for acute ischaemic stroke. As used in the randomised trials, this therapy has not been proven to improve survival or functional outcome.

Clinical trials with neuroprotective drugs in acute ischaemic stroke: are we doing the right thing?

Ischaemic stroke is a leading cause of death and long-lasting disability. Several neuroprotective drugs have been developed that have the potential to limit ischaemic brain damage and improve outcome for patients. While promising results with these drugs have been achieved in animal stroke models, all Phase III trials conducted so far indicate that these drugs have failed to live up to their promise. Despite the limits of animal models, which cannot mimic the clinical situation, the disappointing results of neuroprotective trials might largely be due to methodological problems. Future trials with neuroprotective drugs should be performed in stroke (care) units, after sufficient information regarding therapeutic time window, dosage, duration of therapy and safety has been gathered from pilot studies, and a better selection of target patients has been made. Much of this information can now be obtained by techniques that visualize the penumbra, such as combined diffusion-weighted and perfusion MRI. Consideration should also be given to clinical trials with well-designed combinations of treatments.

Combination treatment for acute ischemic stroke: A ray of Hope?

BACKGROUND

With the implementation of thrombolysis, a large number of distinct pharmacological agents are now under consideration for the treatment of acute ischemic stroke, with disappoiting early results. Because the processes that ultimately lead to ischemic cell death involve a variety of pathophysiologic pathways, it is likely that combinations of agents may be necessary to positively affect neurological outcome. We review the general strategies under consideration for reduction of ischemic injury in the central nervous system, the types of possible interactions between compounds, and the experimental evidence showing effective combination therapies.

SUMMARY OF REVIEW

Reduction of ischemic injury has been attempted by the following pharmacologic mechanisms: thrombolysis, neuroprotection, and perfusion/reperfusion enhancers. There is experimental evidence that the combination of thrombolytic therapy with a neuroprotective agent is additive in some ischemic models, as is the combination of a thrombolytic with an agent that facilitates reperfusion (thromboxane A(2) receptor antagonist and neutrophil adhesion/activation inhibition). Combinations of neuroprotective agents such as glutamate antagonists and calcium channel antagonists may be additive, and other combinations of neuroprotective agents, such as a glutamate antagonist with a gamma-aminobutyric acid (GABA) agonist, have even shown synergism in a rat stroke model. It has also been suggested that lower doses of toxic drugs may be used together to yield a positive neurologic outcome. Successful demonstration of additive or synergistic effects of pharmacologic agents in ischemia will depend on (1) the model used (well below a maximal "ceiling effect"); (2) the timing of drug administration; (3) the doses of the drugs used; and (4) the primary neurologic endpoint used. (Infarction size requires prolonged survival.)

CONCLUSIONS

It appears from preclinical studies that some combinations of pharmacotherapeutic agents may be beneficial in cerebral ischemia, but rigorous evaluation is needed before initiating clinical trials.

BN 80933, a dual inhibitor of neuronal nitric oxide synthase and lipid peroxidation: a promising neuroprotective strategy

Nitric oxide (NO) and reactive oxygen species (ROS) act independently as well as cooperatively to induce neuronal death in acute neurological disorders. Inhibition of neuronal nitric oxide synthase (nNOS) and inhibition of lipid peroxidation induced by ROS have both been proposed as neuroprotective strategies in stroke and trauma. Recently, in our laboratory, the combination of the two strategies was found to be synergistic in reducing neuronal damage. Here, we report that BN 80933 [(S)-N-[4-[4-[(3,4-dihydro-6-hydroxy-2, 5,7, 8-tetramethyl-2H-1-benzopyran-2-yl)carbonyl]-1-piperazinyl]phenyl]-2- thiophenecarboximidamide], a compound that combines potent antioxidant and selective nNOS inhibitory properties in vitro, affords remarkable neuronal protection in vivo. Intravenous administration of BN 80933 significantly reduced brain damage induced by head trauma in mice, global ischemia in gerbils, and transient focal ischemia in rats. Treatment with BN 80933 (0.3-10 mg/kg) significantly reduced infarct volume (>60% protection) and enhanced behavioral recovery in rats subjected to transient (2-h) middle cerebral artery occlusion and 48-h or 7-day reperfusion. Furthermore, treatment with BN 80933 commencing up to 8 h after the onset of ischemia resulted in a significant improvement of neurological outcome. All these results indicate that BN 80933 represents a class of potentially useful therapeutic agents for the treatment of stroke or trauma and possibly neurodegenerative disorders that involve both NO and ROS.

Effects of RSR13, a synthetic allosteric modifier of hemoglobin, alone and in combination with dizocilpine, on outcome from transient focal cerebral ischemia in the rat

This study examined the effect of a pharmacologically induced rightward shift in the partial pressure of oxygen at which 50% of hemoglobin is saturated (P50) on outcome from transient focal cerebral ischemia in the rat. Halothane anesthetized rats (n=20 per group) were given saline or a single 15-min infusion of 150 mg/kg RSR13 (2-[4-[[3,5-dimethylanilino) carbonyl]methyl]phenoxy]-2-methylproprionic acid) intravenously before or 30 min after onset of 75 min of middle cerebral artery filament occlusion (MCAO). Seven days later, severity of hemiparesis and cerebral infarct size were examined. RSR13 alone did not significantly improve outcome. Conscious normothermic rats (n=12 per group) were also given RSR13 (150 mg/kg) or 0.9% NaCl intravenously and subjected to 75 min of MCAO with 7 days of recovery. Again, RSR13 alone did not significantly reduce infarct size or improve neurologic score. A dose-response curve for dizocilpine (MK-801) was then constructed in conscious normothermic rats subjected to 75 min of MCAO. Dizocilpine (0.5 mg/kg i.v.) caused a 90% reduction in mean infarct size while 0.25 mg/kg reduced infarct size by 48%. Other rats were then subjected to 75 min of MCAO after being given dizocilpine (0.25 mg/kg i.v.; n=18) or RSR13 (150 mg/kg i.v. )+dizocilpine (0.25 mg/kg i.v.; n=15). RSR13+dizocilpine resulted in smaller cortical infarct volume (8+/-14 mm3 vs. 34+/-37 mm3, p<0.02) and total cerebral infarct volume (46+/-28 mm3 vs. 81+/-60 mm3, p<0. 05) compared to dizocilpine alone, respectively. We conclude that a pre-ischemic peak increase in P50 of approximately 25 mmHg alone is insufficient to reduce focal ischemic injury, but may be advantageous when used in conjunction with other neuroprotective agents.

Neuroprotective effects of lamotrigine enhanced by flunarizine in gerbil global ischemia

We examined whether the anti-ischemic effect of lamotrigine (LTG), which inhibits the presynapic sodium channel, could be enhanced by the calcium channel blocker-flunarizine (FNR) in cerebral ischemia. Global ischemia was induced in Mongolian gerbils for 5 min under the monitoring of scalp temperature. LTG and FNR were administered intraperitoneally 1 h before ischemia. After 7 days, animals were killed and viable neurons in CA1 area were counted. LTG treated group showed significant protective effects compared to control group (P < 0.01). These effects were more prominent in group treated with LTG and FNR (P = 0.01). Combination of two drugs did not increase the mortality rate compared to single-treated group. These results show that a synergistic reduction of neuronal death can be achieved by combination of LTG and FNR without serious adverse reaction.

Superoxide anion production during reperfusion is reduced by an antineutrophil antibody after prolonged cerebral ischemia

Neutrophils may be involved in the pathophysiology of reperfusion injury following cerebral ischemia. One potential mechanism of reperfusion injury by neutrophils is through production of the superoxide anion. We hypothesized that, due to progressive endothelial damage during ischemia, neutrophil activation would be more prominent after longer periods of ischemia prior to reperfusion. Thus, neutrophils would contribute more to pathological processes such as superoxide anion formation after longer than after shorter periods of ischemia. A reversible middle cerebral artery occlusion model in rats was employed and superoxide anion concentration was measured with a cytochrome c coated electrode placed on the cortical penumbral region. Occlusion times were varied from 60 min to 2 h, and neutrophils were inhibited with an antiCD18 antibody administered prior to occlusion. Neutrophil accumulation and reduction with antibody treatment was confirmed immunohistochemically. Superoxide anion (O2*-) concentration was detected during the hours following 60 min of occlusion, and increased further with 2 h of occlusion. Treatment with the antiCD18 antibody had no effect on O2*- concentration during reperfusion in the 60-90 min occlusion groups, but O2*- concentration was significantly lower in the antiCD18 antibody treated group than in the control group during reperfusion after 120 min of ischemia. The antibody also reduced cortical neutrophil accumulation in the 120 min ischemia group. These results indicate for the first time that superoxide production by neutrophils becomes more important with longer periods of ischemia, and other quantitatively less important sources of superoxide predominate with shorter periods of ischemia. This phenomenon may explain some of the variation seen between different models of ischemia with different durations of ischemia when targeting reactive oxygen species, and supports an approach to combination therapy to extend the therapeutic window and reduce the deleterious effects of reperfusion.

The importance of voltage-dependent sodium channels in cerebral ischaemia

Strategies for the treatment of thromboembolic stroke are based on restoring the blood flow as soon as possible and protecting the neurons from the deleterious consequences of cerebral ischaemia. Interest has focused on blockers of voltage-dependent Na+ channels as potential neuroprotective agents because they prevent neuronal death in various experimental models of cerebral ischaemia and act cytoprotectively in models of white matter damage. Although several Na+ blockers are currently being tested in various phases of clinical development, most of these agents are relatively weak and unspecific. I therefore consider it worthwhile to search for molecules which specifically block voltage-dependent Na+ channels for the treatment of cerebral ischaemia.

Determination of the dose proportionality of single intravenous doses (5, 10, and 15 mg) of lubeluzole in healthy volunteers

The dose proportionality of lubeluzole, a drug in clinical development for the treatment of acute ischemic stroke, was evaluated in a Phase I, single-center, open-label, randomized-dosing-sequence, three-way crossover clinical trial in 12 healthy adults. An equal number of male and female volunteers were enrolled in the trial, with a mean weight (+/- SD) of 73.2 +/- 11.9 kg, mean height (+/- SD) of 66.8 +/- 4.6 inches, and a mean age of 36.1 +/- 5.2 years. Subjects received intravenous infusions of 5 (A), 10 (B), and 15 mg (C) of lubeluzole over 1 hour on three separate occasions, with a minimum washout period of 2 weeks. The treatment sequences were A-B-C; A-C-B; B-A-C; B-C-A; C-A-B; and C-B-A. One male and one female were assigned to each sequence. After the 5-, 10-, and 15-mg doses, maximum concentration (Cmax) was 58.1, 113, and 138 microg/L, respectively, and the area under the curve from 0 to (AUC(0-infinity)) was 771, 1384, and 2025 microg x h/L. There were no statistically significant differences among the groups in mean terminal half-life, steady-state volume of distribution, total plasma clearance, or dose-normalized AUC(0-infinity). Dose-normalized values of Cmax differed significantly between the groups. No serious adverse events were reported, and no changes were observed in cardiac function, as judged by the QT(c) interval. The pharmacokinetics of lubeluzole appear to be linear at intravenous infusion doses of 5, 10, and 15 mg, and these doses are well tolerated by healthy adults.

Ischemic stroke

Acute ischemic stroke is a neurological emergency that requires ultra-rapid intervention. Stroke teams and stroke protocols can be devised to expediate evaluation and treatment. In carefully selected patients, thrombolytic therapy offers a significant benefit but must be initialized within 3 hours of stroke onset. Emerging alternative strategies for reperfusion and neuroprotection must also be initiated during the hyperacute period. The role of more traditional therapies, such as antiplatelet agents and anticoagulants, have been better defined through several recent major clinical trials.

Lubeluzole protects hippocampal neurons from excitotoxicity in vitro and reduces brain damage caused by ischemia

Previously reported effects of lubeluzole, such as inhibition of glutamate release, inhibition of nitric oxide (NO) synthesis and blockage of voltage-gated Na+- and Ca2+-ion channels, suggest a neuroprotective action of this drug. Here we report about the effects of lubeluzole and its R-isomer on glutamate-induced neuronal cell death in mixed hippocampal cultures. In addition, we studied the effect of lubeluzole in focal cerebral ischemia models in mice and rats. In hippocampal cultures exposed to 500 nM glutamate for 1 h, lubeluzole (0.1-100 nM), but not the R-isomer (1-100 nM), reduced the percentage of damaged neurons from 42 +/- 8% to 18 +/- 7% (P < 0.01). In mice and rats, lubeluzole reduced ischemic brain damage, when administered immediately after middle cerebral artery occlusion. Interestingly, the protective effect (reduction of the infarct volume in rats to 77% of control; P < 0.01) was also found when the lubeluzole treatment (2.5 mg/kg) was started 3 h after ischemia. Especially this latter effect suggests that lubeluzole will be a useful drug for stroke therapy.

MRI study on delayed ancrod therapy of focal cerebral ischaemia in rats

The therapeutic window for efficient post-treatment of focal cerebral ischaemia with the fibrinogen lowering agent ancrod was studied by magnetic resonance imaging (MRI) in spontaneously hypertensive rats (SHR). Ancrod or vehicle solution (0.9% NaCl) were i.v. infused (0.12 IU/kg per min) via implanted mini pumps starting 0.5, 1.5, 3 or 6 h after permanent proximal middle cerebral artery occlusion and lasting until brain mapping by multislice T2-weighted magnetic resonance imaging in vivo 24 h after middle cerebral artery occlusion. Plasma fibrinogen concentrations were measured before middle cerebral artery occlusion, before pump implantation and after magnetic resonance imaging. Total brain lesion volumes as determined by magnetic resonance imaging 24 h after middle cerebral artery occlusion were 131 +/- 36 (188 +/- 28)*, 151 +/- 39 (194 +/- 39)*, 147 +/- 44 (207 +/- 33)* and 209 +/- 60 (214 +/- 42) mm3 in rats with 0.5, 1.5, 3 and 6 h, respectively, delay of ancrod treatment (means +/- S.D., 8-11 animals/group, corresponding control groups in parentheses, *P < 0.05). Continuous i.v. ancrod infusions reduced plasma fibrinogen levels significantly (P < 0.05) in all ancrod-treated groups as compared to vehicle-treated controls until the end of the experiments 24 h after middle cerebral artery occlusion. In conclusion, significant cerebroprotection was achieved even when the onset of ancrod therapy for lowering of the plasma fibrinogen level was delayed for up to 3 h. To the best of our knowledge no drug efficacy has been reported so far with a therapeutic window of 3 h after permanent middle cerebral artery occlusion in spontaneously hypertensive rats suggesting that ancrod may provide an efficient therapy of acute human stroke.

Reperfusion injury: demonstration of brain damage produced by reperfusion after transient focal ischemia in rats

During reperfusion after ischemia, deleterious biochemical processes can be triggered that may antagonize the beneficial effects of reperfusion. Research into the understanding and treatment of reperfusion injury (RI) is an important objective in the new era of reperfusion therapy for stroke. To investigate RI, permanent and reversible unilateral middle cerebral artery/common carotid artery (MCA/CCA) occlusion (monitored by laser Doppler) of variable duration in Long-Evans (LE) and spontaneously hypertensive (SH) rats and unilateral MCA and bilateral CCA occlusion in selected LE rats was induced. In LE rats, infarct volume after 24 hours of permanent unilateral MCA/CCA occlusion was 31.1 +/- 34.6 mm3 and was only 28% of the infarct volume after 120 to 300 minutes of reversible occlusion plus 24 hours of reperfusion, indicating that 72% of the damage of ischemia/reperfusion is produced by RI. When reversible ischemia was prolonged to 480 and 1080 minutes, infarct volume was 39.6 mm3 and 16.6 mm3, respectively, being indistinguishable from the damage produced by permanent ischemia and significantly smaller than damage after 120 to 300 minutes of ischemia. Reperfusion injury was not seen in SH rats or with bilateral CCA occlusion in LE rats, in which perfusion is reduced more profoundly. Reperfusion injury was ameliorated by the protein synthesis inhibitor cycloheximide or spin-trap agent N-tert-butyl-alpha-phenylnitrone pretreatment.