Glycine antagonist (GV150526) in acute stroke: a multicentre, double-blind placebo-controlled phase II trial

Smoothened is a therapeutic target for reducing glutamate toxicity in ischemic stroke

[Figure: see text].

The Hazard of Negative (Not Neutral) Trials on Treatment of Acute Stroke: A Review

Importance

While there are a limited number of beneficial treatments for acute stroke (eg, stroke units, reperfusion, aspirin, hemicraniectomy), there are more negative (as opposed to neutral) interventions spanning multiple different mechanisms of action. To reduce the risk of future negative studies, it is vital to understand why previous interventions appeared to cause harm.

Observations

The limited number of beneficial treatments for acute ischemic stroke are far outnumbered by negative (not neutral) interventions that worsened outcomes in randomized clinical trials (RCTs), including those with putative neuroprotectant, anticoagulant, anti-inflammatory, free radical-scavenging, hemorrhagic, or vasoactive activity. Other agents reduced thrombolytic efficiency or exhibited neuropsychiatric or cardiac toxicity. In intracerebral hemorrhage, platelet transfusion was hazardous. Although reperfusion treatments should be given as soon as possible, very early intervention with other strategies may instead be hazardous, as has been seen with physical therapy and vasodepressors.

Conclusions and Relevance

The lessons learned from negative stroke RCTs are vital for designing future studies. Multicenter preclinical studies are necessary, and animals that die must be included in analyses. Randomized clinical trials must assess multiple neurological, vascular, cardiac, and general safety effects, whether these are on target or off target. All preclinical trials and RCTs must be published in full. Learning from the past will help to reduce the number of negative stroke RCTs in the future.

Treatment duration affects cytoprotective efficacy of positive allosteric modulation of α7 nAChRs after focal ischemia in rats

To minimize irreversible brain injury after acute ischemic stroke (AIS), the time to treatment (i.e., treatment delay) should be minimized. However, thus far, all cytoprotective clinical trials have failed. Analysis of literature identified short treatment durations (≤72 h) as a common motif among completed cytoprotective clinical trials. Here, we argue that short cytoprotective regimens even if given early after AIS may only slow down the evolution of ischemic brain injury and fail to deliver sustained long-term solutions leading to relapses that may be misinterpreted for conceptual failure of cytoprotection. In this randomized blinded study, we used young adult male rats subjected to transient 90 min suture middle cerebral artery occlusion (MCAO) and treated with acute vs. sub-chronic regimens of PNU120596, a prototypical positive allosteric modulator of α7 nicotinic acetylcholine receptors with anti-inflammatory cytoprotective properties to test the hypothesis that insufficient treatment durations may reduce therapeutic benefits of otherwise efficacious cytoprotectants after AIS. A single acute treatment 90 min after MCAO significantly reduced brain injury and neurological deficits 24 h later, but these effects vanished 72 h after MCAO. These relapses were avoided by utilizing sub-chronic treatments. Thus, extending treatment duration augments therapeutic efficacy of PNU120596 after MCAO. Furthermore, sub-chronic treatments could offset the negative effects of prolonged treatment delays in cases where the acute treatment window after MCAO was left unexploited. We conclude that a combination of short treatment delays and prolonged treatment durations may be required to maximize therapeutic effects of PNU120596, reduce relapses and ensure sustained therapeutic efficacy after AIS. Similar concepts may hold for other cytoprotectants including those that failed in clinical trials.

Oncostatin M Confers Neuroprotection against Ischemic Stroke

Cell-surface receptors provide potential targets for the translation of bench-side findings into therapeutic strategies; however, this approach for the treatment of stroke is disappointing, at least partially due to an incomplete understanding of the targeted factors. Previous studies of oncostatin M (OSM), a member of the gp130 cytokine family, have been limited, as mouse models alone may not strongly resemble the human condition enough. In addition, the precise function of OSM in the CNS remains unclear. Here, we report that human OSM is neuroprotective in vivo and in vitro by recruiting OSMRβ in the setting of ischemic stroke. Using gain- and loss-of-function approaches, we demonstrated that decreased neuronal OSMRβ expression results in deteriorated stroke outcomes but that OSMRβ overexpression in neurons is cerebroprotective. Moreover, administering recombinant human OSM to mice before the onset of I/R showed that human OSM can be protective in rodent models of ischemic stroke. Mechanistically, OSM/OSMRβ activate the JAK2/STAT3 prosurvival signaling pathway. Collectively, these data support that human OSM may represent a promising drug candidate for stroke treatment.

SIGNIFICANCE STATEMENT

OSM, a member of the gp130 cytokine family, regulates neuronal function and survival. OSM engages a second receptor, either LIFRα or OSMRβ, before recruiting gp130. However, it is not clear whether OSM/OSMRβ signaling is involved in neuroprotection in the setting of ischemic stroke. Recent studies show that, compared with mouse disease models, the OSM receptor system in rats more closely resembles that in humans. In the present study, we use genetic manipulations of OSMRβ in both mouse and rat stroke models to demonstrate that OSMRβ in neurons is critical for neuronal survival during cerebral ischemic/reperfusion. Interestingly, administration of human OSM also leads to improved stroke outcomes. Therefore, OSM may represent a promising drug candidate for stroke treatment.

Excitotoxicity and stroke: identifying novel targets for neuroprotection

Excitotoxicity, the specific type of neurotoxicity mediated by glutamate, may be the missing link between ischemia and neuronal death, and intervening the mechanistic steps that lead to excitotoxicity can prevent stroke damage. Interest in excitotoxicity began fifty years ago when monosodium glutamate was found to be neurotoxic. Evidence soon demonstrated that glutamate is not only the primary excitatory neurotransmitter in the adult brain, but also a critical transmitter for signaling neurons to degenerate following stroke. The finding led to a number of clinical trials that tested inhibitors of excitotoxicity in stroke patients. Glutamate exerts its function in large by activating the calcium-permeable ionotropic NMDA receptor (NMDAR), and different subpopulations of the NMDAR may generate different functional outputs, depending on the signaling proteins directly bound or indirectly coupled to its large cytoplasmic tail. Synaptic activity activates the GluN2A subunit-containing NMDAR, leading to activation of the pro-survival signaling proteins Akt, ERK, and CREB. During a brief episode of ischemia, the extracellular glutamate concentration rises abruptly, and stimulation of the GluN2B-containing NMDAR in the extrasynaptic sites triggers excitotoxic neuronal death via PTEN, cdk5, and DAPK1, which are directly bound to the NMDAR, nNOS, which is indirectly coupled to the NMDAR via PSD95, and calpain, p25, STEP, p38, JNK, and SREBP1, which are further downstream. This review aims to provide a comprehensive summary of the literature on excitotoxicity and our perspectives on how the new generation of excitotoxicity inhibitors may succeed despite the failure of the previous generation of drugs.

Ion channels as drug targets in central nervous system disorders

Ion channel targeted drugs have always been related with either the central nervous system (CNS), the peripheral nervous system, or the cardiovascular system. Within the CNS, basic indications of drugs are: sleep disorders, anxiety, epilepsy, pain, etc. However, traditional channel blockers have multiple adverse events, mainly due to low specificity of mechanism of action. Lately, novel ion channel subtypes have been discovered, which gives premises to drug discovery process led towards specific channel subtypes. An example is Na(+) channels, whose subtypes 1.3 and 1.7-1.9 are responsible for pain, and 1.1 and 1.2 - for epilepsy. Moreover, new drug candidates have been recognized. This review is focusing on ion channels subtypes, which play a significant role in current drug discovery and development process. The knowledge on channel subtypes has developed rapidly, giving new nomenclatures of ion channels. For example, Ca(2+)s channels are not any more divided to T, L, N, P/Q, and R, but they are described as Ca(v)1.1-Ca(v)3.3, with even newer nomenclature α1A-α1I and α1S. Moreover, new channels such as P2X1-P2X7, as well as TRPA1-TRPV1 have been discovered, giving premises for new types of analgesic drugs.

Guidelines for the early management of patients with acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association

BACKGROUND AND PURPOSE

The authors present an overview of the current evidence and management recommendations for evaluation and treatment of adults with acute ischemic stroke. The intended audiences are prehospital care providers, physicians, allied health professionals, and hospital administrators responsible for the care of acute ischemic stroke patients within the first 48 hours from stroke onset. These guidelines supersede the prior 2007 guidelines and 2009 updates.

METHODS

Members of the writing committee were appointed by the American Stroke Association Stroke Council's Scientific Statement Oversight Committee, representing various areas of medical expertise. Strict adherence to the American Heart Association conflict of interest policy was maintained throughout the consensus process. Panel members were assigned topics relevant to their areas of expertise, reviewed the stroke literature with emphasis on publications since the prior guidelines, and drafted recommendations in accordance with the American Heart Association Stroke Council's Level of Evidence grading algorithm.

RESULTS

The goal of these guidelines is to limit the morbidity and mortality associated with stroke. The guidelines support the overarching concept of stroke systems of care and detail aspects of stroke care from patient recognition; emergency medical services activation, transport, and triage; through the initial hours in the emergency department and stroke unit. The guideline discusses early stroke evaluation and general medical care, as well as ischemic stroke, specific interventions such as reperfusion strategies, and general physiological optimization for cerebral resuscitation.

CONCLUSIONS

Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke remains urgently needed.

Stroke intervention pathways: NMDA receptors and beyond

Despite abundant evidence from basic/preclinical research that excessive NMDAR (N-methyl-d-aspartate receptor) stimulation is a crucial step required for brain damage following a stroke, clinical trials for NMDAR blockers have all ended with disappointments. The past decade of stroke research has revealed distinct NMDAR subpopulations and many specific effectors downstream of these receptors that are differentially responsible for neuronal survival and death. These new advancements provide promising targets for the development of novel NMDAR-based neuroprotective stroke therapies that could have greater therapeutic windows and reduced side effects. In this review, we discuss these advancements with a particular emphasis on the identification of novel signaling effectors downstream of proneuronal death NMDARs and the potential implications of these findings for the development of stroke therapeutics.

Middle cerebral artery occlusion model in rodents: methods and potential pitfalls

A variety of animal models have been developed for modeling ischemic stroke. The middle cerebral artery occlusion (MCAO) model has been utilized extensively, especially in rodents. While the MCAO model provides stroke researchers with an excellent platform to investigate the disease, controversial or even paradoxical results are occasionally seen in the literature utilizing this model. Various factors exert important effects on the outcome in this stroke model, including the age and sex of the animal examined. This paper discusses emerging information on the effects of age and sex on ischemic outcomes after MCAO, with an emphasis on mouse models of stroke.

Modulation of neuroprotective effect of ischemic post-conditioning by dichlorobenzamil a Na(+)/Ca(2+) exchanger inhibitor in mice

The present study has been designed to investigate the modulatory role of dichlorobenzamil a Na(+)/Ca(2+) exchanger inhibitor in ischemic post-conditioning-induced neuroprotection in mice. Bilateral carotid artery occlusion followed by reperfusion, produced a significant rise in cerebral infarct size along with impairment of memory and motor coordination. Ischemic post-conditioning involving three episodes of 10 s carotid artery occlusion with intermittent reperfusion of 10 s proceeding prolonged ischemic insult of 12 min, produced a significant decrease in cerebral infarct size along with reversal of ischemia-reperfusion-induced impairment of memory and motor coordination. Ischemic post-conditioning-induced neuroprotective effects were significantly abolished by pretreatment with dichlorobenzamil (DBZ 0.5, 1 mg/kg, intraperitoneal) a Na(+)/Ca(2+) exchange inhibitor. It may be concluded that Na(+)/Ca(2+) exchanger possibly plays an important role in ischemic post-conditioning-induced neuroprotection.

Neuroprotective strategies for intracerebral hemorrhage: trials and translation

Intracerebral hemorrhage is a devastating neurological illness with few treatment options. In the past 10 years, 6 clinical trials have been completed examining the potential role that putative neuroprotective agents might play in improving outcome. Although each of these trials failed to show a benefit, animal research continues to supply the translational pipeline and 5 clinical trials evaluating neuroprotective agents in intracerebral hemorrhage are currently ongoing. Despite initial failures, neuroprotective agents continue to show promise in the treatment of intracerebral hemorrhage, but improvements in clinical trial design and more accurate predictive outcome models are necessary.

Should data monitoring committees assess efficacy when considering safety in trials in acute stroke?

BACKGROUND

The primary role of a trial's data monitoring committee (DMC) is to ensure the safety of enrolled patients. In stroke trials, safety is monitored typically by comparing death and stroke-specific events between treatment groups. DMCs may also have the remit for monitoring efficacy depending on the aims of the trial. We hypothesised that functional outcome at the end of follow-up, a measure of efficacy, is also a powerful measure of safety and tested this in a systematic review.

METHODS

Acute stroke trials with a negative outcome or which were stopped prematurely on the grounds of safety were sought systematically from searches of electronic databases and published reviews. Information on early and late death, impairment and functional outcome, and the presence of a DMC, were recorded for each trial. The results for each outcome measure were ranked within each trial to determine which was most statistically efficient in detecting hazard.

RESULTS

Fourteen trials were included. The most efficient outcomes for detecting hazard were late death or disability, six trials; early death, four trials (two of which tested thrombolysis); late death, three trials and late death or impairment, one trial. Early death was insensitive to hazard in all six trials where late death or dependency was most sensitive. Two trials (both phase II) did not report the presence of a DMC.

CONCLUSIONS

Functional outcome at end of follow-up can be sensitive to hazard and should be included in all assessments of safety in stroke trials, whether or not efficacy itself is being assessed.

Guidelines for the Early Management of Adults With Ischemic Stroke

Purpose— Our goal is to provide an overview of the current evidence about components of the evaluation and treatment of adults with acute ischemic stroke. The intended audience is physicians and other emergency healthcare providers who treat patients within the first 48 hours after stroke. In addition, information for healthcare policy makers is included.

Methods— Members of the panel were appointed by the American Heart Association Stroke Council’s Scientific Statement Oversight Committee and represented different areas of expertise. The panel reviewed the relevant literature with an emphasis on reports published since 2003 and used the American Heart Association Stroke Council’s Levels of Evidence grading algorithm to rate the evidence and to make recommendations. After approval of the statement by the panel, it underwent peer review and approval by the American Heart Association Science Advisory and Coordinating Committee. It is intended that this guideline be fully updated in 3 years.

Results— Management of patients with acute ischemic stroke remains multifaceted and includes several aspects of care that have not been tested in clinical trials. This statement includes recommendations for management from the first contact by emergency medical services personnel through initial admission to the hospital. Intravenous administration of recombinant tissue plasminogen activator remains the most beneficial proven intervention for emergency treatment of stroke. Several interventions, including intra-arterial administration of thrombolytic agents and mechanical interventions, show promise. Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke is needed.

Guidelines for the early management of adults with ischemic stroke: a guideline from the American Heart Association/American Stroke Association Stroke Council, Clinical Cardiology Council, Cardiovascular Radiology and Intervention Council, and the Atherosclerotic Peripheral Vascular Disease and Quality of Care Outcomes in Research Interdisciplinary Working Groups: the American Academy of Neurology affirms the value of this guideline as an educational tool for neurologists

PURPOSE

Our goal is to provide an overview of the current evidence about components of the evaluation and treatment of adults with acute ischemic stroke. The intended audience is physicians and other emergency healthcare providers who treat patients within the first 48 hours after stroke. In addition, information for healthcare policy makers is included.

METHODS

Members of the panel were appointed by the American Heart Association Stroke Council's Scientific Statement Oversight Committee and represented different areas of expertise. The panel reviewed the relevant literature with an emphasis on reports published since 2003 and used the American Heart Association Stroke Council's Levels of Evidence grading algorithm to rate the evidence and to make recommendations. After approval of the statement by the panel, it underwent peer review and approval by the American Heart Association Science Advisory and Coordinating Committee. It is intended that this guideline be fully updated in 3 years.

RESULTS

Management of patients with acute ischemic stroke remains multifaceted and includes several aspects of care that have not been tested in clinical trials. This statement includes recommendations for management from the first contact by emergency medical services personnel through initial admission to the hospital. Intravenous administration of recombinant tissue plasminogen activator remains the most beneficial proven intervention for emergency treatment of stroke. Several interventions, including intra-arterial administration of thrombolytic agents and mechanical interventions, show promise. Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke is needed.

Comparison of ischemic lesion evolution in embolic versus mechanical middle cerebral artery occlusion in Sprague Dawley rats using diffusion and perfusion imaging

BACKGROUND AND PURPOSE

Differences among models in the temporal evolution of ischemia after middle cerebral artery occlusion (MCAO) in rats may considerably influence the results of experimental stroke research. Using diffusion and perfusion imaging, we compared the spatiotemporal evolution of ischemia in Sprague Dawley rats after permanent suture MCAO (sMCAO; n=8) and embolic MCAO (eMCAO; n=8).

METHODS

Serial measurements of quantitative cerebral blood flow (CBF) and the apparent diffusion coefficient (ADC) were performed up to 180 minutes after MCAO. ADC and CBF values within 5 different brain regions were analyzed. ADC and CBF lesion volumes were calculated by using previously established viability thresholds and correlated with infarct volume defined by 2,3,5-triphenyltetrazolium chloride staining 24 hours after MCAO.

RESULTS

Compared with sMCAO animals, the threshold-derived CBF lesion volume was significantly larger in eMCAO at all time points (P<0.01), remained relatively constant over time, and was highly correlated with the 2,3,5-triphenyltetrazolium chloride-defined infarct size. The ADC lesion volume did not differ between models at any time point. A diffusion/perfusion mismatch was present significantly longer in eMCAO animals (P<0.05), and these rats demonstrated larger absolute mismatch volumes that were statistically significant at 30, 60, and 90 minutes (P<0.05). In both models, CBF and ADC declines were highly correlated.

CONCLUSIONS

This study demonstrated substantial differences in acute ischemic lesion evolution between the eMCAO and sMCAO models.

Hydrogen Sulfide Is a Mediator of Cerebral Ischemic Damage

BACKGROUND AND PURPOSE

We observed recently that elevated plasma cysteine levels are associated with poor clinical outcome in acute stroke patients. In a rat stroke model, cysteine administration increased the infarct volume apparently via its conversion to hydrogen sulfide (H2S). We therefore investigated the effects of H2S and the inhibition of its formation on stroke.

METHODS

Cerebral ischemia was studied in a rat stroke model created by permanent occlusion of the middle cerebral artery (MCAO). The resultant infarct volume was measured 24 hours after occlusion.

RESULTS

Administration of sodium hydrosulfide (NaHS, an H2S donor) significantly increased the infarct volume after MCAO. The NaHS-induced increase in infarct volume was abolished by the administration of dizolcilpine maleate (an N-methyl-d-aspartate receptor channel blocker). MCAO caused an increase in H2S level in the lesioned cortex as well as an increase in the H2S synthesizing activity. Administration of 4 different inhibitors of H2S synthesis reduced MCAO-induced infarct volume dose dependently. The potency of these inhibitors in effecting neuroprotection in vivo appeared to parallel their potency as inhibitors of H2S synthesis in vitro. It also appeared that most of the H2S synthesizing activity in the cortex results from the action of cystathionine beta-synthase.

CONCLUSIONS

The present results strongly suggest that H2S plays a part in cerebral ischemic damage after stroke. Inhibition of H2S synthesis should be investigated for its potential as a novel neuroprotective stroke therapy.

Significant variation in mortality and functional outcome after acute ischaemic stroke between Western countries: data from the tinzaparin in acute ischaemic stroke trial (TAIST)

BACKGROUND

The medical care of patients with acute stroke varies considerably between countries. This could lead to measurable differences in mortality and functional outcome.

OBJECTIVE

To compare case mix, clinical management, and functional outcome in stroke between 11 countries.

METHODS

All 1484 patients from 11 countries who were enrolled into the tinzaparin in acute ischaemic stroke trial (TAIST) were included in this substudy. Information collected prospectively on demographics, risk factors, clinical features, measures of service quality (for example, admission to a stroke unit), and outcome were assessed. Outcomes were adjusted for treatment assignment, case mix, and service relative to the British Isles.

RESULTS

Differences in case mix (mostly minor) and clinical service (many of prognostic relevance) were present between the countries. Significant differences in outcome were present between the countries. When assessed by geographical region, death or dependency were lower in North America (odds ratio (OR) adjusted for treatment group only = 0.52 (95% confidence interval, 0.39 to 0.71) and north west Europe (OR = 0.54 (0.37 to 0.78)) relative to the British Isles; similar reductions were found when adjustments were made for 11 case mix variables and five service quality measures. Similarly, case fatality rates were lower in North America (OR = 0.44 (0.30 to 0.66)) and Scandinavia (OR = 0.50 (0.33 to 0.74)) relative to the British Isles, whether crude or adjusted for case mix and service quality.

CONCLUSIONS

Both functional outcome and case fatality vary considerably between countries, even when adjusted for prognostic case mix variables and measures of good stroke care. Differing health care systems and the management of patients with acute stroke may contribute to these findings.

NXY-059 for acute ischemic stroke

BACKGROUND

NXY-059 is a free-radical-trapping agent that is neuroprotective in animal models of stroke. We tested whether it would reduce disability in humans after acute ischemic stroke.

METHODS

We conducted a randomized, double-blind, placebo-controlled trial involving 1722 patients with acute ischemic stroke who were randomly assigned to receive a 72-hour infusion of placebo or intravenous NXY-059 within 6 hours after the onset of the stroke. The primary outcome was disability at 90 days, as measured according to scores on the modified Rankin scale for disability (range, 0 to 5, with 0 indicating no residual symptoms and 5 indicating bedbound, requiring constant care).

RESULTS

Among the 1699 subjects included in the efficacy analysis, NXY-059 significantly improved the overall distribution of scores on the modified Rankin scale, as compared with placebo (P=0.038 by the Cochran-Mantel-Haenszel test). The common odds ratio for improvement across all categories of the scale was 1.20 (95 percent confidence interval, 1.01 to 1.42). Mortality and rates of serious and nonserious adverse events were each similar in the two groups. NXY-059 did not improve neurologic functioning as measured according to the National Institutes of Health Stroke Scale (NIHSS): the difference between the two groups in the change from baseline scores was 0.1 point (95 percent confidence interval, -1.4 to 1.1; P=0.86). Likewise, no improvement was observed according to the Barthel index (P=0.14). In a post hoc analysis of patients who also received alteplase, NXY-059 was associated with a lower incidence of any hemorrhagic transformation (P=0.001) and symptomatic intracranial hemorrhage (P=0.036).

CONCLUSIONS

The administration of NXY-059 within six hours after the onset of acute ischemic stroke significantly improved the primary outcome (reduced disability at 90 days), but it did not significantly improve other outcome measures, including neurologic functioning as measured by the NIHSS score. Additional research is needed to confirm whether NXY-059 is beneficial in ischemic stroke. (ClinicalTrials.gov number, NCT00119626.).

N-Methyl-D-aspartate receptors as a target for improved antipsychotic agents: novel insights and clinical perspectives

RATIONALE

Activation of "co-agonist" N-methyl-D-aspartate (NMDA) and Glycine(B) sites is mandatory for the operation of NMDA receptors, which play an important role in the control of mood, cognition and motor function.

OBJECTIVES

This article outlines the complex regulation of activity at Glycine(B)/NMDA receptors by multiple classes of endogenous ligand. It also summarizes the evidence that a hypoactivity of Glycine(B)/NMDA receptors contributes to the pathogenesis of psychotic states, and that drugs which enhance activity at these sites may possess antipsychotic properties.

RESULTS

Polymorphisms in several genes known to interact with NMDA receptors are related to an altered risk for schizophrenia, and psychotic patients display changes in levels of mRNA encoding NMDA receptors, including the NR1 subunit on which Glycine(B) sites are located. Schizophrenia is also associated with an overall decrease in activity of endogenous agonists at Glycine(B)/NMDA sites, whereas levels of endogenous antagonists are elevated. NMDA receptor "open channel blockers," such as phencyclidine, are psychotomimetic in man and in rodents, and antipsychotic agents attenuate certain of their effects. Moreover, mice with genetically invalidated Glycine(B)/NMDA receptors reveal similar changes in behaviour. Finally, in initial clinical studies, Glycine(B) agonists and inhibitors of glycine reuptake have been found to potentiate the ability of "conventional" antipsychotics to improve negative and, albeit modestly, cognitive and positive symptoms. In contrast, therapeutic effects of clozapine are not reinforced, likely since clozapine itself enhances activity at NMDA receptors.

CONCLUSIONS

Reduced activity at NMDA receptors is implicated in the aetiology of schizophrenia. Correspondingly, drugs that (directly or indirectly) increase activity at Glycine(B) sites may be of use as adjuncts to other classes of antipsychotic agent. However, there is an urgent need for broader clinical evaluation of this possibility, and, to date, there is no evidence that stimulation of Glycine(B) sites alone improves psychotic states.

Stroke in the female: role of biological sex and estrogen

Women are protected from stroke relative to men until the years of menopause. Because stroke is the leading cause of serious, long-term disability in the United States, modeling sex-specific mechanisms and outcomes in animals is vital to research. Important research questions are focused on the effects of hormone replacement therapy, age, reproductive status, and identification of sex-specific risk factors. Available research relevant to stroke in the female has almost exclusively utilized rodent models. Gender-linked stroke outcomes are more detectable in experimental studies than in clinical trials and observational studies. Various estrogens have been extensively studied as neuroprotective agents in women, animals, and a variety of in vitro models of neural injury and degeneration. Most data in animal and cell models are based on 17 beta estradiol and suggest that this steroid is neuroprotective in injury from ischemia/reperfusion. However, current evidence for the clinical benefits of hormone replacement therapy is unclear. Future research in this area will need to expand into stroke models utilizing higher order, gyrencephalic animals such as nonhuman primates if we are to improve extrapolation to the human scenario and to direct and enhance the design of ongoing and future clinical studies and trials.

Antagonist, CP-101,606, Enhances the Functional Recovery The NMDA NR2B Subunit-Selective Receptor and Reduces Brain Damage after Cortical Compression-Induced Brain Ischemia

Using a novel in vivo model for cerebral ischemia produced by short-lasting compression of a well-defined brain area of sensorimotor cortex we studied neuroprotective effects of the NMDA NR2B subunit selective antagonist, CP-101,606, in Sprague-Dawley rats. Cortical compression for 30 min produced a consistent and highly reproducible functional impairment, that is paresis of contralateral hind and fore limbs. The neurological deficit was accompanied by marked brain damage in cerebral cortex, hippocampus and thalamus as identified by Fluoro-Jade, a marker of general neuronal cell death. Using a daily performed beam walking test it was shown that untreated animals recovered from their functional impairment within 5-7 days following surgery. Intravenous administration of increasing doses (1, 5, 10, 20 mg/kg) of the NMDA NR2B subunit receptor specific antagonist, CP-101,606, dose-dependently improved the rate of functional recovery and protected against the ischemic brain damage in cerebral cortex, hippocampus, and thalamus as identified 2 days after the ischemic insult. Based upon these results, we conclude that NMDA NR2B receptor subunits represent potential targets to reduce not only the functional deficits, but also neuronal death in cortex and several midbrain regions produced by moderate, transient, cerebral ischemia.

Intracerebral injection of AMPA causes axonal damage in vivo

Brain injury following acute and chronic neurological conditions can involve both neuronal perikaryal and axonal damage, yet considerably less is known about the mechanisms of axonal damage. Oligodendrocytes and myelin are highly vulnerable to AMPA receptor-mediated excitotoxicity. In vitro studies using isolated white matter preparations have shown that AMPA receptor-mediated excitotoxicity results in axonal damage. The effect of AMPA on axons in vivo remains to be determined. We established an in vivo model to determine if axons were vulnerable to AMPA-mediated toxicity, and furthermore, to examine if axonal damage occurred through an AMPA receptor-mediated mechanism. Adult rats received stereotaxic injection of AMPA (2.5 or 25 nmol) or vehicle (PBS) into the external capsule. Axonal damage was detected in the external capsule and cortex in sections immunostained for cytoskeletal components microtubule associated protein-5 (MAP 5), the 200 kDa neurofilament subunit (NF 200) and non-phosphorylated neurofilament-H (SMI 32). Quantification of axonal damage in the external capsule of MAP 5-immunostained sections showed that AMPA caused a significant, dose-dependent increase in axonal damage compared to the vehicle-treated controls. AMPA also induced a dose-dependent increase in myelin and neuronal perikaryal damage. Systemic administration of the AMPA receptor antagonist SPD 502 significantly reduced the amount of AMPA-induced axonal, myelin and neuronal damage. These data suggest that AMPA induces structural damage to the cytoskeleton of axons in vivo, as well as neuronal and myelin damage, and that this occurs through AMPA receptor-mediated mechanisms. AMPA receptor antagonism may have therapeutic potential to salvage both axons and neuronal perikarya in a number of neurological disorders.

Neuroprotection by the stable nitroxide 3-carbamoyl-proxyl during reperfusion in a rat model of transient focal ischemia

OBJECT

Nitroxides mimic superoxide dismutase (SOD) biochemically and may prevent free radical oxidative injury in settings in which endogenous SOD is overwhelmed. The authors have previously shown the efficacy of a nitroxide, Tempol, in reducing stroke infarct size. Of the nitroxides, 3-carbamoyl-proxyl (3-CP) is especially promising for clinical use, because it does not cause hypotension in animals. Its efficacy in brain ischemia, however, is untested. The goal of this study was to ascertain whether 3-CP would reduce brain damage in a rat ischemia-reperfusion model.

METHODS

The authors performed a blinded, dose-response study of the effect of different amounts of 3-CP (1, 10, and 100 mg/kg) on infarct size at 24 hours after focal ischemia and reperfusion. The 3-CP was given intravenously during reperfusion, which followed 1 hour of reversible ischemia induced by a thread placed intraluminally in the middle cerebral artery of rats. Brain infarcts, measured with 2,3,5-triphenyltetrazolium chloride staining in six 3-CP groups, were compared with those measured in controls (animals given an equal volume of saline). Edema-corrected infarct sizes (mean +/- standard deviation) were as follows: 146 +/- 64 mm3 in controls; 107 +/- 18 mm3 in rats given 1 mg/kg 3-CP; 40 +/- 20 mm3 in those given 10 mg/kg 3-CP; and 44 +/- 17 mm3 in those given 100 mg/kg 3-CP. A statistically significant reduction in infarct size was achieved in the 10- and 100-mg/kg 3-CP-treated groups (p < 0.01). A reduction in infarct size was also seen in the 1 mg/kg 3-CP-treated group, but this did not reach statistical significance. The authors observed no effects of 3-CP on blood pressure or brain temperature.

CONCLUSIONS

Given at reperfusion, 3-CP significantly decreases brain infarct size at doses of 10 and 100 mg/kg without causing hypotension. The authors found that 3-CP is well suited for further laboratory and clinical use in brain ischemia and reperfusion.

Excitatory amino acid antagonists for acute stroke

BACKGROUND

Focal cerebral ischaemia causes release of excitatory amino acid (EAA) neurotransmitters, principally glutamate, with resultant over-stimulation of EAA receptors and downstream pathways. Excess glutamate release is a pivotal event in the evolution of irreversible ischaemic damage in animal models of ischaemia, and drugs that modulate glutamate action either by inhibiting its release, or blocking post-synaptic receptors, are potent neuroprotective agents. Many clinical trials with EAA modulating drugs have been conducted, none individually demonstrating efficacy.

OBJECTIVES

To synthesise all the available data on all different classes of EAA modulators and to evaluate evidence of effects on outcome systematically.

SEARCH STRATEGY

Relevant trials were identified in the Specialised Register of Controlled Trials (last searched May 2001). In addition, MEDLINE and EMBASE online searches for the terms "neuroprotection" (and its variants), "neuroprotective agent", for all individual drugs and drug classes included in the review, hand searches of conference proceedings from European, International, American Heart Association and Princeton conferences on Stroke, American Neurological Association and American Academy of Neurology meetings from 1992-2001, and direct contact with individual investigators and pharmaceutical companies.

SELECTION CRITERIA

Trials were included if they were randomised, controlled studies giving agents with pharmacological properties that included modification of release of EAAs, or blockade of EAA receptors, in stroke within 24h of onset. Efficacy analysis was restricted to trials with a parallel group design: dose escalation studies were excluded. Intention-to-treat analyses were performed on all data. Outcome had to be reported in terms of death or dependence 1-12 months after the acute event.

DATA COLLECTION AND ANALYSIS

Data were available for 36 of 41 relevant trials identified, involving 11,209 subjects. Data were unavailable for 632 participants (517 in trials fulfilling criteria for efficacy analysis). Seven trials did not report disability data, which were available for 29 trials involving 10,802 subjects. Twenty one of these trials, involving 10,342 subjects, were parallel group studies included in the primary efficacy analysis. Efficacy analysis included data derived from 9 trials not primarily designed to assess efficacy (1022 subjects). The primary (efficacy) end-point was the proportion of patients dead or disabled at final follow-up (defined by Barthel Index<60 at 3 months by preference). Mortality was a secondary end-point. Drugs were considered as individual agents, and also grouped principally into categories of ion channel modulators (glutamate release inhibition) and NMDA antagonists.

MAIN RESULTS

There was no significant heterogeneity of outcome amongst individual drugs, or of drug classes either for the primary efficacy analysis (death or dependence) or for mortality at final follow-up. For the primary efficacy analysis, odds of death or dependence were 1.03 [95% confidence interval 0.96-1.12], and for mortality 1.02 [0.92-1.12]. Neither ion channel modulators (death or dependence 1.02 [0.90-1.16]) nor NMDA antagonists (death or dependence 1.05 [0.95-1.16]) differed from the principal analysis including all compounds. Trends for increased mortality with three NMDA antagonists were seen - selfotel (OR 1.19 [0.81-1.74]), aptiganel (OR 1.32 [0.91-1.93]) and gavestinel (OR 1.12 [0.95-1.32]) - but this did not achieve significance for the NMDA antagonists considered as a class (1.09 [0.96-1.23]). Aptiganel was also associated with a trend towards worse functional outcome (OR 1.20 [0.88-1.65]) although this was not the case for either of the other two compounds. No statistically significant detriment of psychotomimetic NMDA antagonists was found, although a trend towards higher mortality in this sub-group was seen (OR 1.25 [0.96-1.64]).

REVIEWER'S CONCLUSIONS

There was no evidence of significant benefit or harm from drugs modulating excitatory amino acid action. Reductio]).

REVIEWER'S CONCLUSIONS

There was no evidence of significant benefit or harm from drugs modulating excitatory amino acid action. Reduction of death or dependence by 8% or more has been excluded for gavestinel and lubeluzole, which contribute most of the data for this review. However, mechanistic understanding of neuroprotection is too poor to extrapolate from these two failed development plans to all glutamate modulators. Further clinical trials of neuroprotective agents remain justified, since confidence limits around estimates of effect remain wide for most agents, and cannot reliably exclude benefit. Although numbers of patients are too small to confirm or refute a trend towards increased mortality with some NMDA antagonists, further commercial development of these agents is exceedingly unlikely.

The selective glycine antagonist gavestinel lacks phencyclidine-like behavioral effects

Gavestinel [GV150526A; ( E)-3[(phenylcarbamoil)ethenyl]-4,6-dichloroindole-2-carboxylic acid sodium salt] is a selective antagonist at the strychnine-insensitive glycine site of the -methyl-D-aspartate (NMDA) receptor. It was tested for its ability to substitute for phencyclidine (PCP) in rats and rhesus monkeys trained to discriminate PCP from saline, under a two-lever fixed-ratio (FR) food reinforcement schedule, and for its ability to maintain responding in rhesus monkeys trained to self-administer PCP under a FR reinforcement schedule. No PCP-lever responding was observed after gavestinel (1-56 mg/kg i.p.) administration to rats discriminating PCP (2.0 mg/kg i.p.) from saline. The highest dose of gavestinel (100 mg/kg i.p.) tested eliminated responding. Likewise, no PCP-lever responding was observed after gavestinel (1-30 mg/kg s.c.) administration to rhesus monkeys discriminating PCP (0.08 or 0.1 mg/kg i.m.) from saline; the highest dose of gavestinel (30 mg/kg s.c.) tested reduced response rates to approximately 50% of those observed after its vehicle ( -cyclodextrin in 0.9% saline). Gavestinel (0.1-1 mg/kg per i.v. infusion) was not self-administered by rhesus monkeys that reliably self-administered PCP (0.0056 or 0.01 mg/kg per i.v. infusion). Infusion rates at the highest dose were typically lower than those for vehicle or saline, suggesting behavioral activity. Together, these results suggest that at behaviorally active doses gavestinel is not PCP-like and is likely to have low abuse liability.

Grey matter and white matter ischemic damage is reduced by the competitive AMPA receptor antagonist, SPD 502

Protection of both grey and white matter is important for improvement in stroke outcome. In the present study the ability of a competitive alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) antagonist to protect axons, oligodendrocytes, and neuronal perikarya, was examined in a rodent model of transient focal cerebral ischemia. SPD 502 (8-methyl-5-(4-( -dimethylsulfamoyl)phenyl)-6,7,8,9-tetrahydro-1H-pyrrolo[3,2h]-isoquinoline-2,3-dione-3-o(4-hydroxybutyricacid-2-yl)oxime) was administered as an intravenous bolus (16 mg/kg) 15 minutes before transient (3-hour) middle cerebral artery (MCA) occlusion, followed by an intravenous infusion (16 mg kg(-1) hr(-1)) of the drug for 4 hours. Twenty-one hours after ischemia, axonal damage was reduced by 45% (P = 0.006) in the SPD 502-treated group compared with the vehicle. The anatomic extent of ischemically damaged oligodendrocytes, determined by Tau1 immunoreactivity, was reduced in the cerebral cortex by 53% (P = 0.024) in SPD 502-treated rats compared with vehicle-treated rats, but there was minimal effect in the subcortex. The volume of neuronal perikaryal damage after MCA occlusion was significantly reduced by SPD 502 in the cerebral cortex (by 68%; P = 0.005), but there was minimal change in the subcortex with drug treatment. The AMPA receptor antagonist significantly reduced the anatomic extent of lipid peroxidation (assessed as the volume of 4-hydroxynonenol immunoreactivity), and this may have contributed to its ability to protect multiple cell types in ischemia. The data demonstrate that AMPA blockade protects both grey and white matter from damage induced by transient focal ischemia.

Toward wisdom from failure: lessons from neuroprotective stroke trials and new therapeutic directions

BACKGROUND

Neuroprotective drugs for acute stroke have appeared to work in animals, only to fail when tested in humans. With the failure of so many clinical trials, the future of neuroprotective drug development is in jeopardy. Current hypotheses and methodologies must continue to be reevaluated, and new strategies need to be explored. Summary of Review- In part 1, we review key challenges and complexities in translational stroke research by focusing on the "disconnect" in the way that neuroprotective agents have traditionally been assessed in clinical trials compared with animal models. In preclinical studies, determination of neuroprotection has relied heavily on assessment of infarct volume measurements (instead of functional outcomes), short-term (instead of long-term) end points, transient (instead of permanent) ischemia models, short (instead of extended) time windows for drug administration, and protection of cerebral gray matter (instead of both gray and white matter). Clinical trials have often been limited by inappropriately long time windows, insufficient statistical power, insensitive outcome measures, inclusion of protocol violators, failure to target specific stroke subtypes, and failure to target the ischemic penumbra. In part 2, we explore new concepts in ischemic pathophysiology that should encourage us also to think beyond the hyperacute phase of ischemia and consider the design of trials that use multiagent therapy and exploit the capacity of the brain for neuroplasticity and repair.

CONCLUSIONS

By recognizing the strengths and limitations of animal models of stroke and the shortcomings of previous clinical trials, we hope to move translational research forward for the development of new therapies for the acute and subacute stages after stroke.

High rate of recanalization of middle cerebral artery occlusion during 2-MHz transcranial color-coded Doppler continuous monitoring without thrombolytic drug

BACKGROUND AND PURPOSE

Experimental evidence indicates that ultrasound can accelerate thrombolysis. We report our findings on early recanalization during transcranial color-coded Doppler (TCCD) continuous monitoring in acute stroke patients with middle cerebral artery (MCA) main stem occlusion.

METHODS

We performed continuous TCCD monitorings in 6 consecutive patients with acute MCA main stem occlusion using a 2-MHz transducer. Patients were not treated with recombinant tissue plasminogen activator.

RESULTS

Partial recanalization, defined as blunted waveforms, occurred during monitoring in 5 patients (83%). The mean time to beginning of recanalization was 17.2+/-9.6 minutes. Complete recanalization at 24 hours occurred in only 1 patient. The mean National Institutes of Health Stroke Scale score in the patients who recanalized during monitoring was 21.2+/-4.1 at baseline, 19.2+/-5 at 2 hours, and 15.6+/-3.4 at 24 hours (P=0.1).

CONCLUSIONS

In this short series of patients with acute MCA main stem occlusion, not treated with recombinant tissue plasminogen activator, we found a high rate of early partial recanalization during continuous exposure to 2-MHz ultrasound.

Combination therapy for ischemic stroke: potential of neuroprotectants plus thrombolytics

Thrombolysis improves clinical outcome in patients with acute ischemic stroke. However, only a small fraction of patients receive thrombolytic therapy due to the narrow therapeutic time window available for the treatment in patients with ischemic stroke. A better understanding of the mechanisms underlying ischemic injury may lead to the development of novel therapeutic strategies to reduce brain damage after stroke. Cerebral ischemia triggers a number of pathophysiological and biochemical changes in the brain that present potential targets for therapeutic intervention. Candidate pathways include those regulating cellular calcium influx, excitatory neurotransmitter uptake, and generation of reactive oxygen species, as well as activation of enzymes including kinases, proteases, and lipases. The end result of these pathophysiological pathways may be apoptosis (programmed cell death) or necrosis. The activation of inflammatory cascades following ischemia also contributes to brain injury. Several neuroprotective agents which block cell death pathways have been proposed to have therapeutic potential in patients with stroke including calcium channel antagonists, glutamate receptor antagonists, free radical scavengers, anti-inflammatory strategies, inhibitors for nitric oxide synthase, and growth factors. Although results from clinical trials to date have been disappointing, there is reason to believe that combination therapy involving both thrombolytics and neuroprotectants holds promise for stroke treatment and warrants further investigation.