Emerging therapies for acute ischemic stroke: new therapies on trial

Intranasal wnt3a Attenuates Neuronal Apoptosis through Frz1/PIWIL1a/FOXM1 Pathway in MCAO Rats

After ischemic stroke, apoptosis of neurons is a primary factor in determining outcome. Wnt3a is a naturally occurring protein that has been shown to have protective effects in the brain for traumatic brain injury. Although wnt3a has been investigated in the phenomena of neurogenesis, anti-apoptosis, and anti-inflammation, it has never been investigated as a therapy for stroke. We hypothesized that the potential neuroprotective agent wnt3a would reduce infarction and improve behavior following ischemic stroke by attenuating neuronal apoptosis and promoting cell survival through the Frizzled-1/PIWI1a/FOXM1 pathway in middle cerebral artery occlusion (MCAO) rats. A total of 229 Sprague Dawley rats were assigned to male, female, and 9-month-old male MCAO or sham groups followed by reperfusion 2 h after MCAO. Animals assigned to MCAO were either given wnt3a or its control. To explore the downstream signaling of wnt3a, the following interventions were given: Frizzled-1 siRNA, PIWI1a siRNA, and PIWI1a-clustered regularly interspaced short palindromic repeats, along with the appropriate controls. Post-MCAO assessments included neurobehavioral tests, infarct volume, Western blot, and immunohistochemistry. Endogenous levels of wnt3a and Frizzled-1/PIWI1a/FOXM1 were lowered after MCAO. The administration of intranasal wnt3a, 1 h after MCAO, increased PIWIL1a and FOXM1 expression through Frizzled-1, reducing brain infarction and neurological deficits at 24 and 72 h. Frizzled-1 and PIWI1a siRNAs reversed the protective effects of wnt3a after MCAO. Restoration of PIWI1a after knockdown of Frizzled-1 increased FOXM1 survival protein and reduced cleaved caspase-3 levels. In summary, wnt3a decreases neuronal apoptosis and improves neurological deficits through Frizzled-1/PIWI1a/FOXM1 pathway after MCAO in rats. Therefore, wnt3a is a novel intranasal approach to decrease apoptosis after stroke.SIGNIFICANCE STATEMENT Only 5% of patients receive recombinant tissue plasminogen activator after stroke, and few qualify for mechanical thrombectomy. No neuroprotective agents have been successfully translated to promote neuronal survival in stroke. Thus, using a clinically relevant rat model of stroke, middle cerebral artery occlusion, we explored a novel intranasal administration of wnt3a. wnt3a naturally occurs in the body and crosses the blood-brain barrier, supporting the clinically translatable approach of intranasal administration. Significant neuronal apoptosis occurs during stroke, and wnt3a shows promise due to its antiapoptotic effects. We investigated whether wnt3a mediates its poststroke effects via Frizzled-1 and the impact on its downstream signaling molecules, PIWI1a and FOXM1, in apoptosis. Elucidating the mechanism of wnt3a will identify additional pharmacological targets and further understanding of stroke.

Acute Ischaemic Stroke: Management, Recent Advances and Controversies

Acute ischaemic stroke is a major cause of death and disability. It may become an enormous burden to the patients themselves, their families as well as the health care systems. Patients at risk of airway, breathing and circulatory compromise should receive prompt resuscitation. Vital parameters and neurological status should be closely monitored. Attentions to blood pressure, temperature and sugar profile are important. The significance of early and correct diagnosis and subsequent treatment cannot be over-emphasised. There have been tremendous recent advances in different treatment modalities in acute stroke management. Various recanalisation modalities include intravenous and/or intra-arterial thrombolysis, acute defibrinogenation, anti-platelet treatment and anticoagulation. Carotid endarterectomy and endovascular strategies are recommended in selected patients. Advanced neuro-imaging techniques and neuroprotectants are being evaluated. Multidisciplinary stroke teams have been shown to improve patient survival and functional outcome. Pre-defined algorithms and protocols should be in place to expedite smooth and effective delivery of stroke service. Future directions should be aimed at exploring safer recanalisation modalities and extending the limit of the current 3-hour treatment window for thrombolysis.

Docosahexaenoic acid attenuates hyperglycemia-enhanced hemorrhagic transformation after transient focal cerebral ischemia in rats

Hemorrhagic transformation (HT) is a feared complication of cerebral ischemic infarction, especially following the use of thrombolytic therapy. In this study, we examined whether docosahexaenoic acid (DHA; 22:6n-3), an omega-3 essential fatty acid family member, can protect the brain from injury and whether DHA can decrease the risk of HT enhanced by hyperglycemia after focal ischemic injury. Male Sprague-Dawley rats were injected with 50% dextrose (6ml/kg intraperitoneally) to induce hyperglycemia 10min before 1.5h of filament middle cerebral artery occlusion (MCAO) was performed. Treatment with DHA (10mg/kg) 5min before reperfusion reduced HT and further improved the 7-day neurological outcome. It also reduced infarct volume, which is consistent with the restricted DWI and T2WI hyperintensive area. Reduced Evans Blue extravasation and increased expression of collagen IV indicated the improved integrity of the blood-brain barrier (BBB) in DHA-treated rats. Moreover, DHA reduced the expression of the intercellular adhesion molecule-1 (ICAM-1) in the ischemic injured brain. Therefore, we conclude that DHA attenuated hyperglycemia-enhanced HT and improved neurological function by preserving the integrity of BBB and reducing inflammation.

Thrombolysis for acute ischaemic stroke

BACKGROUND

Most strokes are due to blockage of an artery in the brain by a blood clot. Prompt treatment with thrombolytic drugs can restore blood flow before major brain damage has occurred and improve recovery after stroke in some people. Thrombolytic drugs, however, can also cause serious bleeding in the brain, which can be fatal. One drug, recombinant tissue plasminogen activator (rt-PA), is licensed for use in selected patients within 4.5 hours of stroke in Europe and within three hours in the USA. There is an upper age limit of 80 years in some countries, and a limitation to mainly non-severe stroke in others. Forty per cent more data are available since this review was last updated in 2009.

OBJECTIVES

To determine whether, and in what circumstances, thrombolytic therapy might be an effective and safe treatment for acute ischaemic stroke.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (last searched November 2013), MEDLINE (1966 to November 2013) and EMBASE (1980 to November 2013). We also handsearched conference proceedings and journals, searched reference lists and contacted pharmaceutical companies and trialists.

SELECTION CRITERIA

Randomised trials of any thrombolytic agent compared with control in people with definite ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two review authors applied the inclusion criteria, extracted data and assessed trial quality. We verified the extracted data with investigators of all major trials, obtaining additional unpublished data if available.

MAIN RESULTS

We included 27 trials, involving 10,187 participants, testing urokinase, streptokinase, rt-PA, recombinant pro-urokinase or desmoteplase. Four trials used intra-arterial administration, while the rest used the intravenous route. Most data come from trials that started treatment up to six hours after stroke. About 44% of the trials (about 70% of the participants) were testing intravenous rt-PA. In earlier studies very few of the participants (0.5%) were aged over 80 years; in this update, 16% of participants are over 80 years of age due to the inclusion of IST-3 (53% of participants in this trial were aged over 80 years). Trials published more recently utilised computerised randomisation, so there are less likely to be baseline imbalances than in previous versions of the review. More than 50% of trials fulfilled criteria for high-grade concealment; there were few losses to follow-up for the main outcomes.Thrombolytic therapy, mostly administered up to six hours after ischaemic stroke, significantly reduced the proportion of participants who were dead or dependent (modified Rankin 3 to 6) at three to six months after stroke (odds ratio (OR) 0.85, 95% confidence interval (CI) 0.78 to 0.93). Thrombolytic therapy increased the risk of symptomatic intracranial haemorrhage (OR 3.75, 95% CI 3.11 to 4.51), early death (OR 1.69, 95% CI 1.44 to 1.98; 13 trials, 7458 participants) and death by three to six months after stroke (OR 1.18, 95% CI 1.06 to 1.30). Early death after thrombolysis was mostly attributable to intracranial haemorrhage. Treatment within three hours of stroke was more effective in reducing death or dependency (OR 0.66, 95% CI 0.56 to 0.79) without any increase in death (OR 0.99, 95% CI 0.82 to 1.21; 11 trials, 2187 participants). There was heterogeneity between the trials. Contemporaneous antithrombotic drugs increased the risk of death. Trials testing rt-PA showed a significant reduction in death or dependency with treatment up to six hours (OR 0.84, 95% CI 0.77 to 0.93, P = 0.0006; 8 trials, 6729 participants) with significant heterogeneity; treatment within three hours was more beneficial (OR 0.65, 95% CI 0.54 to 0.80, P < 0.0001; 6 trials, 1779 participants) without heterogeneity. Participants aged over 80 years benefited equally to those aged under 80 years, particularly if treated within three hours of stroke.

AUTHORS' CONCLUSIONS

Thrombolytic therapy given up to six hours after stroke reduces the proportion of dead or dependent people. Those treated within the first three hours derive substantially more benefit than with later treatment. This overall benefit was apparent despite an increase in symptomatic intracranial haemorrhage, deaths at seven to 10 days, and deaths at final follow-up (except for trials testing rt-PA, which had no effect on death at final follow-up). Further trials are needed to identify the latest time window, whether people with mild stroke benefit from thrombolysis, to find ways of reducing symptomatic intracranial haemorrhage and deaths, and to identify the environment in which thrombolysis may best be given in routine practice.

Neuroprotective activity of gossypin from Hibiscus vitifolius against global cerebral ischemia model in rats

OBJECTIVES

The objective of this study is to evaluate the neuroprotective effect of gossypin (isolated from Hibiscus vitifolius) against global cerebral ischemia/reperfusion (I/R) injury-induced oxidative stress in rats.

MATERIALS AND METHODS

Sprague Dawlet rats of wither gender were used in the study. Evaluation of cerbroprotective activity of bioflavonoid gossypin (in 5, 10 and 20 mg/kg oral doses) isolated from H. vitifolius was carried out by using the global cerebral I/R model by bilateral carotid artery occlusion for 30 min, followed by 24 h reperfusion. The antioxidant enzymatic and non-enzymatic levels were estimated along with histopathological studies.

RESULT

Gossypin showed dose-dependent neuroprotective activity by significant decrease in lipid peroxidation (P < 0.001) and increase in the superoxide dismutase, catalase, glutathione and total thiol levels in gossypin treated groups when compared to control group. Cerebral infarction area was markedly reduced in gossypin treated groups when compared to control group.

CONCLUSION

Gossypin showed potent neuroprotective activity against global cerebral I/R injury-induced oxidative stress in rats.

Elevation of plasma oxidized LDL in acute stroke patients is associated with ischemic lesions depicted by DWI and predictive of infarct enlargement

Oxidized low-density lipoprotein (OxLDL) plays a major role in atherosclerosis. We undertook the present study to clarify the relationship between plasma OxLDL and the ischemic volume. We used ELISA to determine plasma OxLDL levels, and performed diffusion- and perfusion-weighted MRI (DWI, PWI) to measure the ischemic volume in 44 ischemic stroke patients. Based on the location of the ischemic lesion, they were divided into three groups: Group I (GI, n = 21) had cortical lesions, Group II (GII, n = 17) had lesions in the basal ganglia or brain stem, and Group III (GIII, n = 6) had massive lesions that involved one entire hemisphere. In GI, but not GII and GIII, plasma OxLDL was significantly higher than in 19 age-matched controls (p < 0.01) and was significantly correlated with the initial ischemic volume visualized on DWI (p = 0.01), PWI (p < 0.01), and the DWI-PWI mismatch (p < 0.05). A persistent increase in plasma OxLDL was associated with enlargement of the ischemic lesion in the early phase after the insult. These findings suggest that elevated plasma OxLDL levels are associated with moderate ischemic damage in patients with cortical lesions (GI), but not those with massive hemispheric lesions (GIII), which may be irreversible. In addition, elevated plasma OxLDL may represent a predictor of enlargement of the ischemic lesion.

Pharmacokinetics of Arundic Acid, an Astrocyte Modulating Agent, in Acute Ischemic Stroke

Arundic acid is an astrocyte modulating agent that improves neurological outcome in experimental acute stroke models. The pharmacokinetics of arundic acid in patients with acute ischemic stroke was investigated in a randomized, double-blind study. Six groups of 8 to 9 patients each received 2, 4, 6, 8, 10, or 12 mg/kg/h of arundic acid for a daily 1-hour infusion until completion of 7 doses. Maximum plasma concentrations of arundic acid increased with increasing dose; however, the systemic exposure was less than dose proportional at higher doses. The mean terminal half-life was approximately 2 to 3 hours. There was no excessive accumulation in plasma. Although systemic exposure in elderly patients was 30% greater than that in younger patients, the plasma concentration returned to nearly or below the limit of quantification prior to next administration. The pharmacokinetics of arundic acid in acute stroke patients assessed in this study were similar to that in healthy adults.

Systemic administration of guanosine promotes functional and histological improvement following an ischemic stroke in rats

Previously we have found that extracellular guanosine (Guo) has neuroprotective properties in in vitro and in vivo. Moreover, extracellular Guo significantly increased in the ipsilateral hemisphere within 2h following focal stroke in rats, and remained elevated for one week. Therefore, we hypothesized that Guo could be a potential candidate for a non-toxic neuroprotective agent. In the present study, we examined the effects of Guo on rats following permanent middle cerebral artery occlusion (MCAO). We also determined whether Guo can precondition neurons by modulating endoplasmic reticulum (ER) stress proteins. As most therapies employ a combination treatment regimen, we optimized the neuroprotection by combining pre- and post-MCAO treatments with Guo, attempting to reduce both ischemic cell death and improve functional recovery. A combination of 4mg/kg Guo given 30min pre-stroke and 8mg/kg Guo given 3, 24 and 48h post-stroke exerted the most significant decrease in infarct volume and sustainable improvement in neurological function. Moreover, these effects are not attributable to Guo metabolites. Measurements taken 6h post-MCAO from animals pre-treated with Guo did not reveal any significant changes in ER stress proteins (GRP 78 and 94) or HSP 70, but did reveal significantly increased levels of m-calpain. Thus, our data indicate that there is a treatment regimen for Guo as a neuroprotectant following ischemic stroke. The mechanism by which Guo confers neuroprotection may involve an increase in m-calpain, possibly resulting from a mild increase in intracellular calcium. M-calpain may be involved in the preconditioning response to ischemia by upregulating endogenous pro-survival mechanisms in neurons.

Regulated hypoxia/reperfusion-dependent modulation of ERK1/2, cPLA2, and Bcl-2/Bax: a potential mechanism of neuroprotective effect of penehyclidine hydrochloride

The activation of event-related kinase 1/2 (ERK1/2) and cytosolic phospholipaseA2 (cPLA2), which can aggravate hypoxia/reoxygenation (H/R) damage related to their downstream Bcl-2/Bax and Caspase-3 pathway, plays a key role in H/R. The M1 receptors could be responsible for activation of ERK1/2. Thus, it seems that the regulation of M1 receptors mediated the ERK1/2; cPLA2-mediated Bcl-2/Bax pathway may be a significant responsive signal in H/R. Penehyclidine hydrochloride (PHC) is an anticholinergic agent with high degree of selectivity for M1 and M3 receptor subtypes, it is reported that PHC has a protective effect against H/R damage. Here we hypothesize and demonstrate that PHC could downregulate the expression of pERK1/2, cPLA2, and Caspase-3, increased the ratio of Bcl-2/Bax. This study may widen the application of PHC and therapeutic agents of stroke.

[Implementation of thrombolysis in acute stroke--10-year results of the Innsbruck stroke registry]

BACKGROUND

Randomized controlled trials have yielded evidence for the efficacy and safety of intravenous alteplase in the therapy of acute ischemic stroke. A large patient registry has recently confirmed the safe implementation of this therapy in the clinical routine setting.

METHODS

Between January 1998 and December 2007 302 stroke patients were treated with 0.9 mg/kg rt-PA at the stroke unit of the Innsbruck University Hospital. Severity and circumstances of the stroke event, indicators of pre- and intrahospital management as well as safety and outcome at three months were prospectively assessed in the local thrombolysis database.

RESULTS

The number of patients receiving intravenous thrombolysis increased continuously from 2 patients in 1998 to 67 in 2007 and 87 patients in 2008. 43% of our patients were females. The median age and NIHSS-score on admission was 67 and 16, respectively. The mean onset-to-needle time decreased from 171 min to 110 min--mainly due to a substantial shortening of the door-to-needle time from 105 min to 45 min. A proportion of 41% of our patients were treated in the main working time while 59% received rt-PA during night and weekend service. A total of 38% of our patients were functionally independent at three months (mRS 0-2). Once considering the high initial stroke severity in our patient series and correcting the NIHSS scores to levels usually seen in randomized control trials and patient registries, 56% of our patients would reach a good outcome (mRS 0-2). The rate of symptomatic intracranial bleedings was low at 6.3%.

CONCLUSION

Our data reinforce that intravenous thrombolysis is safe in the treatment of acute ischemic stroke in clinical routine setting. Establishment of modern stroke services and the implementation of structural operating procedures have contributed to an increase in the number of treated patients and a parallel decrease in door-to-needle time at our hospital. Widespread educational programs in the general community, introduction of optimized pre-hospital triage algorithms as well as the potential extension of the 3-hour window to 4.5 hours all are suitable measures to further extend the benefit of i.v. thrombolysis to large proportion of stroke patients.

Thrombolysis for acute ischaemic stroke

BACKGROUND

The majority of strokes are due to blockage of an artery in the brain by a blood clot. Prompt treatment with thrombolytic drugs can restore blood flow before major brain damage has occurred and could improve recovery after stroke. Thrombolytic drugs, however, can also cause serious bleeding in the brain, which can be fatal. One drug, recombinant tissue plasminogen activator (rt-PA), is licensed for use in highly selected patients within three hours of stroke.

OBJECTIVES

To assess the safety and efficacy of thrombolytic agents in patients with acute ischaemic stroke.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched October 2008), MEDLINE (1966 to October 2008) and EMBASE (1980 to October 2008). We contacted researchers and pharmaceutical companies, attended relevant conferences and handsearched pertinent journals.

SELECTION CRITERIA

Randomised trials of any thrombolytic agent compared with control in patients with definite ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two review authors applied the inclusion criteria and extracted data. We assessed trial quality. We verified the extracted data with the principal investigators of all major trials. We obtained both published and unpublished data if available.

MAIN RESULTS

We included 26 trials involving 7152 patients. Not all trials contributed data to each outcome. The trials tested urokinase, streptokinase, recombinant tissue plasminogen activator, recombinant pro-urokinase or desmoteplase. Four trials used intra-arterial administration, the rest used the intravenous route. Most data come from trials that started treatment up to six hours after stroke; three trials started treatment up to nine hours and one small trial up to 24 hours after stroke. About 55% of the data (patients and trials) come from trials testing intravenous tissue plasminogen activator. Very few of the patients (0.5%) were aged over 80 years. Many trials had some imbalances in key prognostic variables. Several trials did not have complete blinding of outcome assessment. Thrombolytic therapy, mostly administered up to six hours after ischaemic stroke, significantly reduced the proportion of patients who were dead or dependent (modified Rankin 3 to 6) at three to six months after stroke (odds ratio (OR) 0.81, 95% confidence interval (CI) 0.73 to 0.90). Thrombolytic therapy increased the risk of symptomatic intracranial haemorrhage (OR 3.49, 95% CI 2.81 to 4.33) and death by three to six months after stroke (OR 1.31, 95% CI 1.14 to 1.50). Treatment within three hours of stroke appeared more effective in reducing death or dependency (OR 0.71, 95% CI 0.52 to 0.96) with no statistically significant adverse effect on death (OR 1.13, 95% CI 0.86 to 1.48). There was heterogeneity between the trials in part attributable to concomitant antithrombotic drug use (P = 0.02), stroke severity and time to treatment. Antithrombotic drugs given soon after thrombolysis may increase the risk of death.

AUTHORS' CONCLUSIONS

Overall, thrombolytic therapy appears to result in a significant net reduction in the proportion of patients dead or dependent in activities of daily living. This overall benefit was apparent despite an increase both in deaths (evident at seven to 10 days and at final follow up) and in symptomatic intracranial haemorrhages. Further trials are needed to identify which patients are most likely to benefit from treatment and the environment in which thrombolysis may best be given in routine practice.

Ischemic postconditioning as a novel avenue to protect against brain injury after stroke

Ischemic postconditioning initially referred to a stuttering reperfusion performed immediately after reperfusion, for preventing ischemia/reperfusion injury in both myocardial and cerebral infarction. It has evolved into a concept that can be induced by a broad range of stimuli or triggers, and may even be performed as late as 6 h after focal ischemia and 2 days after transient global ischemia. The concept is thought to be derived from ischemic preconditioning or partial/gradual reperfusion, but in fact the first experiment for postconditioning was carried out much earlier than that of preconditioning or partial/gradual reperfusion, in the research on myocardial ischemia. This review first examines the protective effects and parameters of postconditioning in various cerebral ischemic models. Thereafter, it provides insights into the protective mechanisms of postconditioning associated with reperfusion injury and the Akt, mitogen-activated protein kinase (MAPK), protein kinase C (PKC), and ATP-sensitive K+ (K(ATP)) channel cell signaling pathways. Finally, some open issues and future challenges regarding clinical translation of postconditioning are discussed.

Postconditioning with isoflurane reduced ischemia-induced brain injury in rats

BACKGROUND

Preexposure of brain to isoflurane, a commonly used anesthetic, induces ischemic tolerance. This phenomenon is called isoflurane preconditioning. However, it is not known whether isoflurane application after ischemia provides neuroprotection.

METHODS

Corticostriatal slices (400 microm) freshly prepared from adult male Sprague-Dawley rats were subjected to a 15-min oxygen-glucose deprivation (OGD; to simulate ischemia in vitro). Isoflurane was applied after OGD. Brain slices were harvested 2 h after OGD for measuring 2,3,5-triphenyltetrazolium chloride (TTC) conversion to quantify cell injury. Adult male Sprague-Dawley rats were also subjected to middle cerebral arterial occlusion for 90 min and then treated with or without 2% isoflurane for 60 min started at the onset of reperfusion. The infarct volumes, neurologic deficit scores, and performance on rotarod were evaluated at 24 h after the onset of reperfusion.

RESULTS

Isoflurane applied immediately after the 15-min OGD for 30 min dose-dependently reversed the OGD-induced decrease of TTC conversion. The TTC conversion was 34 +/- 16% and 58 +/- 28% of the control, respectively, for OGD alone and OGD plus 2% isoflurane (P < 0.05, n = 12). Application of 2% isoflurane for 30 min started at 10 min after the OGD also reduced the OGD-decreased TTC conversion. The presence of 0.3 microm glibenclamide, a general adenosine 5'-triphosphate-sensitive potassium channel blocker, or 500 microm 5-hydroxydecanoic acid, a mitochondrial adenosine 5'-triphosphate-sensitive potassium channel blocker, during the application of 2% isoflurane abolished the isoflurane preservation of TTC conversion. Application of isoflurane during reperfusion also improved neurologic outcome after brain ischemia.

CONCLUSIONS

The results suggest that isoflurane administrated after OGD or brain ischemia provides neuroprotection. Mitochondrial adenosine 5'-triphosphate-sensitive potassium channels may be involved in this protection.

Protein-energy malnutrition increases activation of the transcription factor, nuclear factor kappaB, in the gerbil hippocampus following global ischemia

Protein-energy malnutrition (PEM) exacerbates functional impairment caused by brain ischemia. This is correlated with reactive gliosis, which suggests an increased inflammatory response. The objective of the current study was to investigate if PEM increases hippocampal activation of nuclear factor kappaB (NFkappaB), a transcription factor that amplifies the inflammatory response involved in ischemic brain injury. Mongolian gerbils (11-12 weeks old) were randomly assigned to control diet (12.5% protein) or protein-deficient diet (2%) for 4 weeks. The 2% protein group had a 15% decrease in voluntary food intake (P<.001; unpaired t test), resulting in PEM. Body weight after 4 weeks was 20% lower in the PEM group (P<.001). Gerbils were then exposed to sham surgery or global ischemia induced by 5-min bilateral common carotid artery occlusion. PEM independently increased hippocampal NFkappaB activation detected by electrophoretic mobility shift assay at 6 h after surgery (P=.014; 2-factor ANOVA). Ischemia did not significantly affect NFkappaB activation nor was there interaction between diet and ischemia. Serum glucose and cortisol concentrations at 6 h postischemia were unaltered by diet or ischemia. A second experiment using gerbils of the same age and feeding paradigm demonstrated that PEM also increases hippocampal NFkappaB activation in the absence of surgery. These findings suggest that PEM, which exists in 16% of elderly patients at admission for stroke, may worsen outcome by increasing activation of NFkappaB. Since PEM increased NFkappaB activation independent of ischemia or surgery, the data also have implications for the inflammatory response of the many individuals affected globally by PEM.

2,3-Benzodiazepine-type AMPA receptor antagonists and their neuroprotective effects

AMPA receptors are fast ligand-gated members of glutamate receptors in neuronal and many types of non-neuronal cells. The heterotetramer complexes are assembled from four subunits (GluR1-4) in region-, development- and function-selective patterns. Each subunit contains three extracellular domains (a large amino terminal domain, an agonist-binding domain and a transducer domain), and three transmembrane segments with a loop (pore forming domain), as well as the intracellular carboxy terminal tail (traffic and conductance regulatory domain). The binding of the agonist (excitatory amino acids and their derivatives) initiates conformational realignments, which transmit to the transducer domain and membrane spanning segments to gate the channel permeable to Na+, K+ and more or less to Ca2+. Several 2,3-benzodiazepines act as non-competitive antagonists of the AMPA receptor (termed also negative allosteric modulators), which are thought to bind to the transducer domains and inhibit channel gating. Analysing their effects in vitro, it has been possible to recognize a structure-activity relationship, and to describe the critical parts of the molecules involved in their action at AMPA receptors. Blockade of AMPA receptors can protect the brain from apoptotic and necrotic cell death by preventing neuronal excitotoxicity during pathophysiological activation of glutamatergic neurons. Animal experiments provided evidence for the potential usefulness of non-competitive AMPA antagonists in the treatment of human ischemic and neurodegenerative disorders including stroke, multiple sclerosis, Parkinson's disease, periventricular leukomalacia and motoneuron disease. 2,3-benzodiazepine AMPA antagonists can protect against seizures, decrease levodopa-induced dyskinesia in animal models of Parkinson's disease demonstrating their utility for the treatment of a variety of CNS disorders.

Ischemia-Induced Neurogenesis: Role of Growth Factors

The neurogenic response in ischemic brain to growth factors is the net result of cell division and cell survival in specific regions of the brain. To increase the cell number, these physiologic processes should be active. Hence, when growth factors are infused into the brain, they might stimulate survival, cell division, or both to enhance neurogenesis. The end result is the interplay of all the endogenous factors with the infused exogenous factors. It is essential to understand the growth factors and their regulators that are expressed after ischemia if one is to pharmacologically enhance neurogenesis. It seems that a combinational therapy of factors or their inhibitors may provide powerful therapeutic potential for enhancing stroke-induced neurogenesis and restoring the damaged tissue to function.

Therapeutic time window of neuroprotection by non-competitive AMPA antagonists in transient and permanent focal cerebral ischemia in rats

EGIS-8332 and GYKI 53405 are selective, non-competitive AMPA (2-amino-3[3-hydroxy-5-methyl-4-isoxazolyl] propionic acid) antagonists that effectively protected against tissue injury caused by global and focal cerebral ischemia in laboratory animals. This study evaluated the therapeutic time window of neuroprotection by EGIS-8332 and GYKI 53405 in permanent and transient middle cerebral artery occlusion (MCAO) in Sprague-Dawley rats. Infarct size was measured by TTC staining 48 h after permanent MCAO (electrocoagulation), and 24 h after reperfusion following a 1-h transient MCAO carried out using the intraluminal filament technique. Treatment with EGIS-8332 (10 mg/kg, i.p.) 60 or 120 min after permanent MCAO, decreased infarct size by 30% and 36%, respectively, and the effect of GYKI 53405 (10 mg/kg, i.p.) was similar (30% and 33%, respectively; p<0.01 all). Neither compound was effective if administered 180 or 240 min after permanent MCAO. Both EGIS-8332 and GYKI 53405 (20 mg/kg, i.p.) reduced the core and total (core plus penumbra) volumes of tissue injury in the whole brain and the cerebral cortex when administered 120 or 180 min after transient MCAO. The compounds did not alter tissue damage in the striatum. No neuroprotective effect was obtained at 240 min after transient MCAO. In conclusion, the therapeutic time window of neuroprotection by EGIS-8332 and GYKI 53405 was 2 h in permanent and 3 h in transient focal cerebral ischemia in rats. The results suggest that treatment with non-competitive AMPA antagonists can only be expected to produce a neuroprotective action in humans if administered shortly after the appearance of stroke symptoms.

Interrupting reperfusion as a stroke therapy: ischemic postconditioning reduces infarct size after focal ischemia in rats

Cerebral ischemic preconditioning protects against stroke, but is clinically feasible only when the occurrence of stroke is predictable. Reperfusion plays a critical role in cerebral injury after stroke; we tested the hypothesis that interrupting reperfusion lessens ischemic injury. We found for the first time that such postconditioning with a series of mechanical interruptions of reperfusion significantly reduces ischemic damage. Focal ischemia was generated by permanent distal middle cerebral artery (MCA) occlusion plus transient bilateral common carotid artery (CCA) occlusion. After 30 secs of CCA reperfusion, ischemic postconditioning was performed by occluding CCAs for 10 secs, and then allowing for another two cycles of 30 secs of reperfusion and 10 secs of CCA occlusion. Infarct size was measured 2 days later. Cerebral blood flow (CBF) was measured in animals subjected to permanent MCA occlusion plus 15 mins of bilateral CCA occlusion, which demonstrates that postconditioning disturbed the early hyperemia immediately after reperfusion. Postconditioning dose dependently reduced infarct size in animals subjected to permanent MCA occlusion combined with 15, 30, and 60 mins of bilateral CCA occlusion, by reducing infarct size approximately 80%, 51%, and 17%, respectively. In addition, postconditioning blocked terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling-positive staining, a marker of apoptosis, in the penumbra 2 days after stroke. Furthermore, in situ superoxide detection using hydroethidine suggested that postconditioning attenuated superoxide products during early reperfusion after stroke. In conclusion, postconditioning reduced infarct size, most plausibly by blocking apoptosis and free radical generation. With further study it may eventually be clinically applicable for stroke treatment.

Cardiac glycosides provide neuroprotection against ischemic stroke: discovery by a brain slice-based compound screening platform

We report here the results of a chemical genetic screen using small molecules with known pharmacologies coupled with a cortical brain slice-based model for ischemic stroke. We identified a small-molecule compound not previously appreciated to have neuroprotective action in ischemic stroke, the cardiac glycoside neriifolin, and demonstrated that its properties in the brain slice assay included delayed therapeutic potential exceeding 6 h. Neriifolin is structurally related to the digitalis class of cardiac glycosides, and its putative target is the Na(+)/K(+)-ATPase. Other cardiac glycoside compounds tested also showed neuroprotective activity, although with lower apparent potencies. In subsequent whole-animal studies, we found that neriifolin provided significant neuroprotection in a neonatal model of hypoxia/ischemia and in a middle cerebral artery occlusion model of transient focal ischemia. The neuroprotective potential of Na(+)/K(+)-ATPase is of particular interest because of its known "druggability"; indeed, Food and Drug Administration-approved, small-molecule compounds such as digitoxin and digoxin have been in clinical usage for congestive heart failure and arrhythmias for several decades. Thus, an existing cardiac glycoside or closely related compound could provide an accelerated path toward clinical trial testing for ischemic stroke. Our findings underscore the important role that hypothesis-neutral, high-content, tissue-based screens can play in the identification of new candidate drugs and drug targets for the treatment of diseases for which validated therapeutic pathways are not currently available.

The FOOD Trial Collaboration: Nutritional Supplementation Strategies and Acute Stroke Outcome

Results from three large, randomized, multicenter FOOD (Feed or Ordinary Food) Collaboration Trials showed no reduction in death or poor outcome with routine oral protein-energy supplementation of stroke patients who were primarily well nourished upon admission to the hospital. Nasogastric tube feeding was favored over percutaneous endoscopic gastrostomy as the early route of feeding in dysphagic stroke patients.

Lipids and lipidomics in brain injury and diseases

Lipidomics is systems-level analysis and characterization of lipids and their interacting moieties. The amount of information in the genomic and proteomic fields is greater than that in the lipidomics field, because of the complex nature of lipids and the limitations of tools for analysis. The main innovation during recent years that has spurred advances in lipid analysis has been the development of new mass spectroscopic techniques, particularly the "soft ionization" techniques electrospray ionization and matrix-assisted laser desorption/ionization. Lipid metabolism may be of particular importance for the central nervous system, as it has a high concentration of lipids. The crucial role of lipids in cell signaling and tissue physiology is demonstrated by the many neurological disorders, including bipolar disorders and schizophrenia, and neurodegenerative diseases such as Alzheimer's, Parkinson's, and Niemann-Pick diseases, that involve deregulated lipid metabolism. Altered lipid metabolism is also believed to contribute to cerebral ischemic (stroke) injury. Lipidomics will provide a molecular signature to a certain pathway or a disease condition. Lipidomic analyses (characterizing complex mixtures of lipids and identifying previously unknown changes in lipid metabolism) together with RNA silencing, using small interfering RNA (siRNA), may provide powerful tools to elucidate the specific roles of lipid intermediates in cell signaling and open new opportunities for drug development.

Thrombolysis and neuroprotection in cerebral ischemia

Stroke is a major cause of death and disability worldwide. The resulting burden on society grows with the increase in the incidence of stroke. The term brain attack was introduced to describe the acute presentation of stroke and emphasize the need for urgent action to remedy the situation. Though a large number of therapeutic agents, like thrombolytics, NMDA receptor antagonists, calcium channel blockers and antioxidants, have been used or are being evaluated, there is still a large gap between the benefits of these agents and the properties of an ideal drug for stroke. So far, only thrombolysis with rtPA within a 3-hour time window has been shown to improve the outcome of patients with ischemic stroke. Understanding the mechanisms of injury and neuroprotection in these diseases is important to target news sites for treating ischemia. Better evaluation of the drugs and increased similarity between the results of animal experimentation and in the clinical setting requires critical assessment of the selection of animal models and the parameters to be evaluated. Our laboratory has employed a rat embolic stroke model to investigate the combination of rtPA with citicoline as compared to monotherapy alone and investigated whether neuroprotection should be provided before or after thrombolysis in order to achieve a greater reduction of ischemic brain damage.

NF-kappaB protects neurons from ischemic injury after middle cerebral artery occlusion in mice

Knowledge about the molecular mechanisms of neuronal survival following ischemia is crucial to the development of therapeutic interventions for victims of stroke. Previous research in our laboratory has implicated nuclear factor-kappaB (NF-kappaB) as contributing to neuronal survival in response to toxic or ischemic brain insult, with in vivo models having focused on the rat. To take advantage of genetic alterations available in the mouse, we utilized a murine transient endovascular middle cerebral artery occlusion (MCAO) model to examine the influence of NF-kappaB on neuronal survival. When brains were immunostained for the nuclear localization sequence (NLS) of the p50 subunit of NF-kappaB, a unilateral increase in immunoreactivity was seen, especially in pyramidal cell layers of the ipsilateral (stroked) hippocampus. When transgenic mice lacking p50 were compared with non-transgenic counterparts using Fluoro-Jade, a marker for neurodegeneration, both the hippocampus and striatum showed enhanced neurodegeneration at various survival times after 1 h of MCAO. In the hippocampus specifically, there was an eightfold increase in Fluoro-jade staining in the p50 knockout group vs. the non-transgenic group. Sections double stained for Fluoro-Jade and NF-kappaB activity (using a mouse engineered with a NF-kappaB responsive promoter driving a LacZ gene to produce beta galactosidase) demonstrated neuronal degeneration only in regions sparsely showing NF-kappaB activity, and those demonstrating NF-kappaB activity failed to degenerate. These data provide evidence that NF-kappaB participates in survival signaling following temporary focal ischemia, and thus may represent an attractive target for pharmacologic activation in the treatment of stroke.

Acute effects of 17beta-estradiol on the extracellular concentration of excitatory amino acids and energy metabolites during transient cerebral ischemia in male rats

Elevation of extracellular levels of amino acids has been implicated in the pathogenesis of stroke. The failure of brain energy metabolism due to the lack of oxygen and glucose contributes also to cell loss. Estrogen has been shown to protect brain cells against ischemia by a still unclear mechanism. We used intracerebral microdialysis to monitor the effects of acute 17beta-estradiol treatment on the release of glutamate and aspartate and on the levels of the energy metabolites glucose and lactate. In male rats subjected to 90 min of transient middle cerebral artery occlusion followed by 24-h reperfusion, acute treatment with 17beta-estradiol (0.8 mg/kg, i.v.) at the time of occlusion reduced the ischemic infarct by about 50%. In these treated rats, the ischemia-induced increases of extracellular levels of glutamate and aspartate were significantly and rapidly reduced. The reduction of glucose level during occlusion was not affected by 17beta-estradiol treatment; however, the increase of extracellular lactate was reduced during occlusion and reperfusion, probably due to the reduced glutamate-driven astrocytic glycolysis. These data suggest that acute treatment with 17beta-estradiol at the onset of occlusion significantly reduces the ischemia-induced excitotoxicity in the cortex, a mechanism that may participate in the neuroprotective effect on cellular survival.

Multimodal MR examination in acute ischemic stroke

In recent years, combined diffusion-weighted imaging (DWI) with perfusion imaging (PI) has become an important investigational tool in the acute phase of ischemic stroke, as it may differentiate reversible from irreversible brain tissue damage. We consecutively examined 20 subjects within 12 h of stroke onset using a multiparametric magnetic resonance (MR) examination consisting of DWI, mean transit time (MTT) as PI parameter, and MR angiography (MRA). T2-weighted and fluid-attenuated inversion recovery (FLAIR) on day 7 were also acquired in order to obtain final infarct volume. The following MR parameters were considered: volumetric measures of lesion growth and MTT abnormalities, quantification of regional apparent diffusion coefficient (ADC) and visual inspection of MRA findings. Our results showed: (1) an acute DWI lesion was not predictive of lesion growth and the DWI abnormality did not represent the irreversibly infarcted tissue; (2) ADC values in the ischemic penumbra could not predict tissue at risk; (3) the DWI-PI mismatch did not predict lesion growth, and the PI abnormality overestimated the amount of tissue at risk; and (4) patients with proximal middle cerebral artery occlusion had greater initial and final infarct volumes. This study did not demonstrate the prognostic value of a multimodal MR approach in early ischemic stroke; MRA alone provided predictive information about the volumetric evolution of the lesion.

Neuroprotective effects of a postischemic treatment with a bradykinin B2 receptor antagonist in a rat model of temporary focal cerebral ischemia

Bradykinin, an endogenous nonapeptide produced by activation of the kallikrein-kinin system, promotes neuronal tissue damage as well as disturbances in blood-brain barrier function through activation of B2 receptors. In a rat model of focal cerebral ischemia, blockade of B2 receptors before initiation of ischemia with the B2 receptor antagonist, LF 16-0687 Ms, afforded substantial neuroprotection. In order to assess the potential clinical value of this approach, we evaluated the effect of LF 16-0687 Ms given at reperfusion following focal cerebral ischemia on local cerebral blood flow (LCBF), neurological outcome, and infarct size. Sprague-Dawley rats were subjected to MCA occlusion for 90 min by an intraluminal filament. Animals were assigned to one of four treatment arms (n = 7 each): (1) vehicle, (2) LF 16-0687 Ms (1.0 mg/kg/day), (3) LF 16-0687 Ms (3.0 mg/kg/day), or (4) LF 16-0687 Ms (10.0 mg/kg/day) given at reperfusion and repetitively over 2 days. Neurological recovery was examined daily, and infarct volume was assessed histologically on day 7 after ischemia. Physiological parameters and local CBF were not influenced by the treatment. Significant improvement of neurological outcome was observed on postischemic day 3 in animals receiving 1.0 and 3.0 mg/kg/day of LF 16-0687 Ms (P < 0.05). Inhibition of B2 receptors significantly reduced infarct volume in all treated animals predominantly in the cortex. B2 receptor blockade with LF 16-0687 Ms showed neuroprotective effectiveness even when therapy was initiated upon reperfusion, i.e. 90 min after induction of ischemia. Therefore, blockade of B2 receptors seems to be a promising therapeutic approach after focal cerebral ischemia, which deserves further experimental and clinical evaluation.

Progress in the identification of stroke-related genes: emerging new possibilities to develop concepts in stroke therapy

Stroke is a very complex disease influenced by many risk factors: genetic, environmental and comorbidities, such as hypertension, diabetes mellitus, obesity and having had a previous stroke. Neuroprotective therapies that have been found to be successful in laboratory animals have failed to produce the same benefits in clinical trials. Currently, a re-analysis of the clinical trial failures is underway and new therapeutic approaches using the growing knowledge from neurogenesis and neuroinflammation studies, combined with the information from gene expression studies, are taking place. This review focuses on possible ways to identify therapeutic targets using the new discoveries in neuroinflammation and intrinsic regenerative mechanisms of the brain. Molecular events associated with ischaemia trigger an environment for inflammation. Within the ischaemic region and its penumbra, a battery of chemokines and cytokines are released, which have both detrimental and beneficial effects, depending on the specific timepoint after injury and the current activation status of microglia/macrophages. Preventive therapies and treatments for stroke may be established by identifying the genes that are responsible for the induction of those phenotypic changes of microglia/macrophages that switch them to become players in tissue repair and regeneration processes. To aid in the establishment of new target sources for novel therapeutic agents, animal stroke models should closely mimic stroke in humans. To do so, these models should take into account the various risk factors for stroke. For example, hypertensive animals have a more vulnerable blood-brain barrier that in turn may trigger a greater degree of damage after stroke. Furthermore, in aged animals an accelerated astrocytic and microglial reaction has been observed and the regenerative capacity of aged brains is not as high as young brains. Improvements in animal models may also help to ensure better success rates of potential therapies in clinical studies. Inflammation in the brain is a double-edged sword--characterised by the deleterious effect of nerve cell damage and nerve cell death, as well as the beneficial influence on regeneration. The major challenge to develop successful stroke therapies is to broaden the knowledge regarding the underlying pathologic processes and the intrinsic mechanisms of the brain to drive regenerative and plasticity-related changes. On this basis, new concepts can be created leading to better stroke therapy.

New Goals in Ischemic Stroke Therapy: The Experimental Approach – Harmonizing Science with Practice

Undeniable advances have been made in clinical and experimental investigation into the pathophysiology, diagnosis, and treatment of cerebral ischemia. However, with the exception of intravenous thrombolysis and some neuroprotectors, such as citicoline, the majority of the drugs successfully tested in experimental studies have failed in clinical trials. Valuable lessons for the improvement of research methodology and appropriate coordination of experimental and clinical research can be learnt from the analysis of discrepancies between the laboratory and clinic, which will allow us to increase the power and cost-effectiveness of the studies. In addition, this progress has opened the way for the investigation of very promising new therapeutic strategies, such as combined pharmacological and mechanical thrombolysis, thrombolysis and neuroprotection, or the combination of various neuroprotectors, antiapoptotic therapies, and neurorestoration therapies, such as stem cell transplants.

Protein-energy malnutrition impairs functional outcome in global ischemia

We investigated whether protein-energy malnutrition (PEM) exacerbates brain injury in global ischemia. It was hypothesized that PEM would increase secondary brain damage by worsening ischemia-induced depletion of glutathione (GSH) and increasing oxidative stress. Adult male gerbils were fed an adequate protein (12.5%; C) or low protein (2%; PEM) diet for 4 weeks and subjected to 5 min of bilateral carotid artery occlusion (Ischemia) or sham surgery (Sham). At 12 h post-ischemia, GSH and markers of oxidative stress were measured in hippocampus and neocortex. The remaining gerbils were tested in the open field on days 3, 7, and 10, with viable hippocampal CA1 neurons assessed on day 10. Although the habituation of C-Ischemia gerbils in the open field was normal by day 7, PEM-Ischemia gerbils failed to habituate even by day 10 and spent greater time in the outer zone (P < 0.05). Mean (+/-SEM) total number of viable CA1 neurons at 10 days post-ischemia were C-Sham = 713 (13), C-Ischemia = 264 (48), PEM-Sham = 716 (12), and PEM-Ischemia = 286 (66). Although PEM did not increase CA1 neuron loss caused by ischemia, a subset (4/12) of PEM-Ischemia gerbils showed dramatic reactive gliosis accompanied by extensive neuronal loss. Hippocampal protein thiols were decreased by PEM and ischemia. Although the mechanism is yet to be established, the finding that PEM worsens functional outcome following global ischemia is clinically relevant since 16% of elderly are nutritionally compromised at the time of admission for stroke.

Effect of endothelin antagonist (TAK-044) on cerebral ischemic volume, oxidative stress markers and neurobehavioral parameters in the middle cerebral artery occlusion model of stroke in rats

Stroke causes brain injury in millions of people world wide each year. Despite the enormity of problem, currently there is no established therapy, which can restore the blood flow at infracted area and also improve the neurological deficit. The present study was carried out to investigate the effect of an endothelin antagonist (TAK-044) in middle cerebral artery (MCA) occlusion model of acute ischemic stroke in rats. Male Wistar rats were pretreated with TAK-044 (5 mg/kg, i.p.) for 7 days and thereafter subjected to focal ischemia by occlusion of MCA using intraluminal thread for two hours. 30 min after reperfusion the animals were subjected to diffusion-weighted imaging (DWI) for assessment of protective effect. Twenty-four hours later the motor performance was tested and subsequently the animals were sacrificed for estimation of markers of oxidative stress; malondialdehyde (MDA), glutathione (GSH) and superoxide dismutase (SOD). Control group received vehicle (saline) and similar experimental protocol was followed. In the TAK-044 pretreated group, percent hemispheric lesion area (% HLA) in DWI was significantly attenuated 17.5 +/- 0.5% as compared to control group 61.2 +/- 5.9%. Significant motor impairment, with significant elevated levels of MDA, decrease in GSH and SOD were observed in the vehicle treated MCA occluded rats. Pretreatment with TAK-044 prevented the motor impairment and significantly reversed the changes in markers of oxidative stress (MDA, GSH and SOD). In addition to well-known vasodilatory effect, TAK-044 has recently been documented to have antioxidant and anti-inflammatory properties. These effects can contribute to the protection afforded by TAK-044 in the present study.

Cytidine 5'-diphosphocholine (CDP-choline) in stroke and other CNS disorders

Brain phosphatidylcholine (PC) levels are regulated by a balance between synthesis and hydrolysis. Pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1alpha/beta) activate phospholipase A(2) (PLA(2)) and PC-phospholipase C (PC-PLC) to hydrolyze PC. PC hydrolysis by PLA(2) releases free fatty acids including arachidonic acid, and lyso-PC, an inhibitor of CTP-phosphocholine cytidylyltransferase (CCT). Arachidonic acid metabolism by cyclooxygenases/lipoxygenases is a significant source of reactive oxygen species. CDP-choline might increase the PC levels by attenuating PLA(2) stimulation and loss of CCT activity. TNF-alpha also stimulates proteolysis of CCT. TNF-alpha and IL-1beta are induced in brain ischemia and may disrupt PC homeostasis by increasing its hydrolysis (increase PLA(2) and PC-PLC activities) and inhibiting its synthesis (decrease CCT activity). The beneficial effects of CDP-choline may result by counteracting TNF-alpha and/or IL-1 mediated events, integrating cytokine biology and lipid metabolism. Re-evaluation of CDP-choline phase III stroke clinical trial data is encouraging and future trails are warranted. CDP-choline is non-xenobiotic, safe, well tolerated, and can be considered as one of the agents in multi-drug treatment of stroke.

Tenoxicam Exerts a Neuroprotective Action after Cerebral Ischemia in Rats

In this study we investigated the effects of Tenoxicam, a type 2 cyclooxygenase (COX-2) inhibitor, on brain damage induced by ischemia-reperfusion. Male Wistar rats (18-month old average) were anesthetized and submitted to ischemia occlusion of both common carotid arteries (BCAO) for 45 min. After 24 h of reperfusion, rats were decapitated and hippocampi removed for further assays. Animals were divided into sham-operated, ischemia, ischemia + Tenoxicam 2.5 mg/kg, and ischemia + Tenoxicam 10 mg/kg groups. Tenoxicam was administered intraperitoneally immediately after BCAO. Histological analyses show that ischemia produced significant striatal as well as hippocampal lesions which were reversed by the Tenoxicam treatment. Tenoxicam also significantly reduced, to control levels, the increased myeloperoxidase activity in hippocampus homogenates observed after ischemia. However, nitrite concentrations showed only a tendency to decrease in the ischemia + Tenoxicam groups, as compared to that of ischemia alone. On the other hand, hippocampal glutamate and aspartate levels were not altered by Tenoxicam. In conclusion, we showed that ischemia is certainly related to inflammation and to increased free radical production, and selective COX-2 inhibitors might be neuroprotective agents of potential benefit in the treatment of cerebral brain ischemia.

Three-dimensional structural changes in cerebral microvessels after transient focal cerebral ischemia in rats: scanning electron microscopic study of corrosion casts

Pathological changes of cerebral microvessels in transient ischemia were investigated by scanning electron microscopy of vascular corrosion casts. Wistar rats were treated with middle cerebral artery (MCA) occlusion for 30 min, 1 h, 3 h, 4 h, 5 h or 7 h and subsequent reperfusion for 2 h. The ultrastructures of the cast were observed and computer-aided montage micrographs were obtained for visualization of the whole microvasculature in the ischemic brain hemisphere. Avascular areas representing ischemic areas were detected in the frontotemporal cortex and caudate putamen in the groups from 30 min to 5 h occlusion. Extravasation of the resin, which probably corresponded to the leakage of plasma or hemorrhage, was seen as spheroidal, conglomerative, large massive and worm-like types. The spheroidal type, which probably indicated a small leakage or minor hemorrhage, began to appear in the 30-min occlusion group. The conglomerative type, which probably indicated a larger leakage or moderate hemorrhage, appeared in the 3- to 5-h occlusion groups. The large massive and worm-like types, which probably indicated a significant hemorrhage, appeared in the 4- and 5-h occlusion groups. The number of these extravasations increased significantly in the 4-h occlusion group. Arterioles near the avascular area frequently showed vasospastic appearances, such as corrugations, fusiform indentations of endothelial nuclei, continuous circulatory constrictions and severe narrowing with interrupted branches. Arteriolar vasospasm possibly caused prolonged hypoperfusion even if reperfusion was achieved. The capillaries had a thin stringy appearance in the 4- and 5-h occlusion groups. These changes seemed to relate closely with increased intracranial pressure by brain edema or hemorrhage. The present study suggested that the risk of brain edema or hemorrhagic infarction increased beyond 3 h of MCA occlusion, and vasospasm of the arterioles might participate in stroke pathophysiology.

Applications of diffusion/perfusion magnetic resonance imaging in experimental and clinical aspects of stroke

The acute evaluation of stroke patients has undergone dramatic advances in the recent past. The increasing availability of novel magnetic resonance imaging (MRI) techniques, such as diffusion and perfusion MRI, provides a plethora of information to clinicians evaluating patients suspected of having an acute stroke. This review focuses on recent advances with experimental and clinical applications of perfusion and diffusion imaging and their utility in identifying potentially salvageable ischemic tissue in rat stroke model and stroke patients.

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

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

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

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

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

Inhibition of release of taurine and excitatory amino acids in ischemia and neuroprotection

Volume regulated anion channels (VRAC) have been extensively studied in purified single cell systems like cell cultures where they can be activated by cell swelling. This provides a convenient way of analyzing mechanisms and will likely lead to the holy grails of the field, namely the nature or natures of the volume sensor and the nature or natures of VRACs. Important reasons for such an understanding are that these channels are ubiquitous and have important physiological functions which under pathological conditions convert to deleterious effects. Here we summarize data showing the involvement of VRACs in ischemia-induced release of excitatory amino acids (EAAs) in a rat model of global ischemia. Using microdialysis studies we found that reversal of the astrocytic glutamate transporter and VRACs contribute about equally to the large initial release of EAAs and together account for around 80% of the total release. We used the very potent VRAC blocker, tamoxifen, to see if such inhibition of EAA release via VRACs led to significant neuroprotection. Treatment in the focal rat MCA occlusion model led to around 80% reduction in infarct size with an effective post initiation of ischemia therapeutic window of three hours. However, the common problem of other effects for even the most potent inhibitors pertains here, as tamoxifen has other, potentially neuroprotective, effects. Thus it inhibits nitrotyrosine formation, likely due to its inhibition of nNOS and reduction of peroxynitrite formation. Although tamoxifen cannot therefore be used as a test of the "VRAC-excitotxicity" hypothesis it may prove successful for translation of basic stroke research to the clinic because of its multiple targets.

Outcome of acutely ischemic brain tissue in prolonged middle cerebral artery occlusion: a serial positron emission tomography investigation in the baboon

Thrombolysis within 3 to 6 hours of symptom onset is recommended therapy for acute middle cerebral artery (MCA) stroke, but recent imaging studies in humans suggest that the penumbra may last much longer in some patients. It is therefore important to study the events that take place with occlusions that last longer than 6 hours. Based upon positron emission tomography (PET), the tissue with high oxygen extraction fraction (OEF) is at risk of infarction. In a previous sequential PET study in anesthetized baboons, we documented that when reperfusion was initiated at 6 hours after MCA occlusion, the region with the acutely highest OEF was not incorporated within the final magnetic resonance imaging (MRI)-defined infarct, suggesting reperfusion prevented such demise. In agreement with this hypothesis, we report here using the same sequential PET paradigm with final chronic-stage volume MRI that a 20-hour MCA occlusion resulted in, on average, 36% of the highest OEF area being recruited into the final infarct. We also found that the portion of the highest OEF area that went on to infarct had at the earliest time-point significantly lower cerebral blood flow and cerebral oxygen metabolism (mean reductions relative to unoccluded side, 56% and 32%, respectively) than the portion that did not (41% and 11%, respectively) and that some reperfusion occurred in the latter at second time-point, that is, before recanalization. Thus, apart from duration of occlusion, the fate of the at-risk tissue is predicated by the initial severity of the ischemia as well as by early secondary events such as partial spontaneous reperfusion.