Efficacy of Alteplase in a Mouse Model of Acute Ischemic Stroke: A Retrospective Pooled Analysis.

BACKGROUND AND PURPOSE: The debate over the fact that experimental drugs proposed for the treatment of stroke fail in the translation to the clinical situation has attracted considerable attention in the literature. In this context, we present a retrospective pooled analysis of a large data set from preclinical studies, to examine the effects of early versus late administration of intravenous recombinant tissue-type plasminogen activator. METHODS: We collected data from 26 individual studies from 9 international centers (13 researchers; 716 animals) that compared recombinant tissue-type plasminogen activator with controls, in a unique mouse model of thromboembolic stroke induced by an in situ injection of thrombin into the middle cerebral artery. Studies were classified into early (<3 hours) versus late (≥3 hours) drug administration. Final infarct volumes, assessed by histology or magnetic resonance imaging, were compared in each study, and the absolute differences were pooled in a random-effect meta-analysis. The influence of time of administration was tested. RESULTS: When compared with saline controls, early recombinant tissue-type plasminogen activator administration was associated with a significant benefit (absolute difference, -6.63 mm(3); 95% confidence interval, -9.08 to -4.17; I(2)=76%), whereas late recombinant tissue-type plasminogen activator treatment showed a deleterious effect (+5.06 mm(3); 95% confidence interval, +2.78 to +7.34; I(2)=42%; Pint<0.00001). Results remained unchanged after subgroup analyses. CONCLUSIONS: Our results provide the basis needed for the design of future preclinical studies on recanalization therapies using this model of thromboembolic stroke in mice. The power analysis reveals that a multicenter trial would require 123 animals per group instead of 40 for a single-center trial.

Protective effects of angiopoietin-like 4 on cerebrovascular and functional damages in ischaemic stroke.

AIMS: Given the impact of vascular injuries and oedema on brain damage caused during stroke, vascular protection represents a major medical need. We hypothesized that angiopoietin-like 4 (ANGPTL4), a regulator of endothelial barrier integrity, might exert a protective effect during ischaemic stroke. METHODS AND RESULTS: Using a murine transient ischaemic stroke model, treatment with recombinant ANGPTL4 led to significantly decreased infarct size and improved behaviour. Quantitative characteristics of the vascular network (density and branchpoints) were preserved in ANGPTL4-treated mice. Integrity of tight and adherens junctions was also quantified and ANGPTL4-treated mice displayed increased VE-cadherin and claudin-5-positive areas. Brain oedema was thus significantly decreased in ANGPTL4-treated mice. In accordance, vascular damage and infarct severity were increased in angptl4-deficient mice thus providing genetic evidence that ANGPTL4 preserves brain tissue from ischaemia-induced alterations. Altogether, these data show that ANGPTL4 protects not only the global vascular network, but also interendothelial junctions and controls both deleterious inflammatory response and oedema. Mechanistically, ANGPTL4 counteracted VEGF signalling and thereby diminished Src-signalling downstream from VEGFR2. This led to decreased VEGFR2-VE-cadherin complex disruption, increased stability of junctions and thus increased endothelial cell barrier integrity of the cerebral microcirculation. In addition, ANGPTL4 prevented neuronal loss in the ischaemic area. CONCLUSION: These results, therefore, show ANGPTL4 counteracts the loss of vascular integrity in ischaemic stroke, by restricting Src kinase signalling downstream from VEGFR2. ANGPTL4 treatment thus reduces oedema, infarct size, neuronal loss, and improves mice behaviour. These results suggest that ANGPTL4 constitutes a relevant target for vasculoprotection and cerebral protection during stroke.

Targeting TXNIP in endothelial progenitors mitigates IL-8-induced neutrophil recruitment under metabolic stress.

BACKGROUND: This study explores the potential role of Thioredoxin-interacting protein (TXNIP) silencing in endothelial colony-forming cells (ECFCs) within the scope of age-related comorbidities and impaired vascular repair. We aim to elucidate the effects of TXNIP silencing on vasculogenic properties, paracrine secretion, and neutrophil recruitment under conditions of metabolic stress. METHODS: ECFCs, isolated from human blood cord, were transfected with TXNIP siRNA and exposed to a high glucose and ß-hydroxybutyrate (BHB) medium to simulate metabolic stress. We evaluated the effects of TXNIP silencing on ECFCs' functional and secretory responses under these conditions. Assessments included analyses of gene and protein expression profiles, vasculogenic properties, cytokine secretion and neutrophil recruitment both in vitro and in vivo. The in vivo effects were examined using a murine model of hindlimb ischemia to observe the physiological relevance of TXNIP modulation under metabolic disorders. RESULTS: TXNIP silencing did not mitigate the adverse effects on cell recruitment, vasculogenic properties, or senescence induced by metabolic stress in ECFCs. However, it significantly reduced IL-8 secretion and consequent neutrophil recruitment under these conditions. In a mouse model of hindlimb ischemia, endothelial deletion of TXNIP reduced MIP-2 secretion and prevented increased neutrophil recruitment induced by age-related comorbidities. CONCLUSIONS: Our findings suggest that targeting TXNIP in ECFCs may alleviate ischemic complications exacerbated by metabolic stress, offering potential clinical benefits for patients suffering from age-related comorbidities.

Soluble endoglin reduces thrombus formation and platelet aggregation via interaction with αIIbß3 integrin.

BACKGROUND: The circulating form of human endoglin (sEng) is a cleavage product of membrane-bound endoglin present on endothelial cells. Because sEng encompasses an RGD motif involved in integrin binding, we hypothesized that sEng would be able to bind integrin αIIbß3, thereby compromising platelet binding to fibrinogen and thrombus stability. METHODS: In vitro human platelet aggregation, thrombus retraction, and secretion-competition assays were performed in the presence of sEng. Surface plasmon resonance (SPR) binding and computational (docking) analyses were carried out to evaluate protein-protein interactions. A transgenic mouse overexpressing human sEng (hsEng+) was used to measure bleeding/rebleeding, prothrombin time (PT), blood stream, and embolus formation after FeCl3-induced injury of the carotid artery. RESULTS: Under flow conditions, supplementation of human whole blood with sEng led to a smaller thrombus size. sEng inhibited platelet aggregation and thrombus retraction, interfering with fibrinogen binding, but did not affect platelet activation. SPR binding studies demonstrated that the specific interaction between αIIbß3 and sEng and molecular modeling showed a good fitting between αIIbß3 and sEng structures involving the endoglin RGD motif, suggesting the possible formation of a highly stable αIIbß3/sEng. hsEng+ mice showed increased bleeding time and number of rebleedings compared to wild-type mice. No differences in PT were denoted between genotypes. After FeCl3 injury, the number of released emboli in hsEng+ mice was higher and the occlusion was slower compared to controls. CONCLUSIONS: Our results demonstrate that sEng interferes with thrombus formation and stabilization, likely via its binding to platelet αIIbß3, suggesting its involvement in primary hemostasis control.

Induction of P-glycoprotein and Bcrp at the rat blood-brain barrier following a subchronic morphine treatment is mediated through NMDA/COX-2 activation.

Subchronic morphine treatment induces P-glycoprotein (P-gp) up-regulation at the blood-brain barrier. This study investigates the rate and extent to which P-gp and breast cancer-resistance protein (Bcrp) increase at the rat blood-brain barrier following subchronic morphine treatment. Rats were given increasing doses of morphine (10-40 mg/kg) or saline i.p. twice daily for 5 days. The brain cortex large vessels and microvessels were then mechanical isolated 6, 9, 12, 24, and 36 h after the last injection. The gene and protein expression of P-gp and Bcrp in morphine-treated and control rats were compared by qRT-PCR and western blotting. The levels of Mdr1a and Bcrp mRNAs were not significantly modified 6 h post morphine, but the Mdr1a mRNA increased 1.4-fold and Bcrp mRNA 2.4-fold at 24 h. P-gp and Bcrp protein expression in brain microvessels was unchanged 6 h post morphine and increased 1.5-fold at 24 h. This effect was more pronounced in large vessels than in microvessels. However, extracellular morphine concentrations of 0.01-10 µM did not modify the expressions of the MDR1 and BCRP genes in hCMEC/D3 human endothelial brain cells in vitro. MK-801 (NMDA antagonist) and meloxicam (cyclo-oxygenase-2 inhibitor) given after morphine treatment completely blocked P-gp and Bcrp up-regulation. Interestingly, misoprostol and iloprost, two well-known agonists of prostaglandin E2 receptors induced both MDR1 and BCRP mRNA levels in hCMEC/D3. Thus, morphine does not directly stimulate P-gp and Bcrp expression by the brain endothelium, but glutamate released during morphine withdrawal may do so by activating the NMDA/cyclo-oxygenase-2 cascade.

Neuroblast survival depends on mature vascular network formation after mouse stroke: role of endothelial and smooth muscle progenitor cell co-administration.

Pro-angiogenic cell-based therapies constitute an interesting and attractive approach to enhancing post-stroke neurogenesis and decreasing neurological deficit. However, most new stroke-induced neurons die during the first few weeks after ischemia, thus impairing total recovery. Although the neovascularization process involves different cell types and various growth factors, most cell therapy protocols are based on the biological effects of single-cell-type populations or on the administration of heterogeneous populations of progenitors, namely human cord blood-derived CD34(+) cells, with scarce vascular progenitor cells. Tight cooperation between endothelial cells and smooth muscle cells/pericytes is critical for the development of functional neovessels. We hypothesized that neuroblast survival in stroke brain depends on mature vascular network formation. In this study, we injected a combination of endothelial progenitor cells (EPCs) and smooth muscle progenitor cells (SMPCs), isolated from human umbilical cord blood, into a murine model of permanent focal ischemia induced by middle cerebral artery occlusion. The co-administration of SMPCs and EPCs induced enhanced angiogenesis and vascular remodeling in the peri-infarct and infarct areas, where vessels exhibited a more mature phenotype. This activation of vessel growth resulted in the maintenance of neurogenesis and neuroblast migration to the peri-ischemic cortex. Our data suggest that a mature vascular network is essential for neuroblast survival after cerebral ischemia, and that co-administration of EPCs and SMPCs may constitute a novel therapeutic strategy for improving the treatment of stroke.

Simvastatin in traumatic brain injury: effect on brain edema mechanisms.

OBJECTIVES: Traumatic brain injury causes deleterious brain edema, leading to high mortality and morbidity. Brain edema exacerbates neurologic deficits and may be attributable to the breakdown of endothelial cell junction protein, leukocyte infiltration, and matrix metalloproteinase activation. These all contribute to loss of blood-brain barrier integrity. The pleiotropic effects of statins, hydroxymethylglutaryl-coenzyme A reductase inhibitors, may inhibit posttraumatic brain edema. We therefore investigated the effect of acute simvastatin on neurologic deficits, cerebral edema, and its origins. DESIGN: Randomized laboratory animal study. SETTINGS: University-affiliated research laboratory. SUBJECTS: Male Sprague-Dawley rats. INTERVENTIONS: Rats were subjected to lateral fluid percussion traumatic brain injury. Our preliminary dose-effect study indicated that 37.5 mg/kg simvastatin, administered orally 1 hr and 6 hrs after traumatic brain injury, has the greatest anti-edematous effect. This dose was used to study its effects on brain edema and on its mechanisms. MEASUREMENTS AND MAIN RESULTS: We first assessed the effects of simvastatin 24 hrs after traumatic brain injury on brain edema, brain claudin-5 expression, and the vascular endothelial-cadherin (pTyr731)/total vascular endothelial-cadherin ratio, matrix metalloproteinase-9 activity, intercellular adhesion molecule-1 expression, and polymorphonuclear neutrophil infiltration. We also evaluated blood-brain barrier permeability by measuring Evans blue and fluorescein sodium salt extravasation into the cerebral parenchyma. We then investigated whether simvastatin reduces neurologic deficits, edema, and blood-brain barrier permeability earlier than 24 hrs; these effects were evaluated 6 hrs after traumatic brain injury. The anti-edematous effect of simvastatin 24 hrs after traumatic brain injury was associated with increased claudin-5 and decreased intercellular adhesion molecule-1, polymorphonuclear neutrophil infiltration, and blood-brain barrier permeability, with no effect on matrix metalloproteinase-9 activity or vascular endothelial-cadherin phosphorylation. Earlier, 6-hrs after traumatic brain injury, simvastatin reduced neurologic deficits, cerebral edema, and blood-brain barrier permeability. CONCLUSIONS: Simvastatin could be a new therapy for reducing posttraumatic edema by preventing damage to tight junctions and neutrophil infiltration into the parenchyma, thus preserving blood-brain barrier integrity.

From positron emission tomography to cell analysis of the 18-kDa Translocator Protein in mild traumatic brain injury.

Traumatic brain injury (TBI) leads to a deleterious neuroinflammation, originating from microglial activation. Monitoring microglial activation is an indispensable step to develop therapeutic strategies for TBI. In this study, we evaluated the use of the 18-kDa translocator protein (TSPO) in positron emission tomography (PET) and cellular analysis to monitor microglial activation in a mild TBI mouse model. TBI was induced on male Swiss mice. PET imaging analysis with [18F]FEPPA, a TSPO radiotracer, was performed at 1, 3 and 7 days post-TBI and flow cytometry analysis on brain at 1 and 3 days post-TBI. PET analysis showed no difference in TSPO expression between non-operated, sham-operated and TBI mice. Flow cytometry analysis demonstrated an increase in TSPO expression in ipsilateral brain 3 days post-TBI, especially in microglia, macrophages, lymphocytes and neutrophils. Moreover, microglia represent only 58.3% of TSPO+ cells in the brain. Our results raise the question of the use of TSPO radiotracer to monitor microglial activation after TBI. More broadly, flow cytometry results point the lack of specificity of TSPO for microglia and imply that microglia contribute to the overall increase in TSPO in the brain after TBI, but is not its only contributor.

Antioxidant Activity and Toxicity Study of Cerium Oxide Nanoparticles Stabilized with Innovative Functional Copolymers.

Oxidative stress, which is one of the main harmful mechanisms of pathologies including ischemic stroke, contributes to both neurons and endothelial cell damages, leading to vascular lesions. Although many antioxidants are tested in preclinical studies, no treatment is currently available for stroke patients. Since cerium oxide nanoparticles (CNPs) exhibit remarkable antioxidant capacities, the objective is to develop an innovative coating to enhance CNPs biocompatibility without disrupting their antioxidant capacities or enhance their toxicity. This study reports the synthesis and characterization of functional polymers and their impact on the enzyme-like catalytic activity of CNPs. To study the toxicity and the antioxidant properties of CNPs for stroke and particularly endothelial damages, in vitro studies are conducted on a cerebral endothelial cell line (bEnd.3). Despite their internalization in bEnd.3 cells, coated CNPs are devoid of cytotoxicity. Microscopy studies report an intracellular localization of CNPs, more precisely in endosomes. All CNPs reduces glutamate-induced intracellular production of reactive oxygen species (ROS) in endothelial cells but one CNP significantly reduces both the production of mitochondrial superoxide anion and DNA oxidation. In vivo studies report a lack of toxicity in mice. This study therefore describes and identifies biocompatible CNPs with interesting antioxidant properties for ischemic stroke and related pathologies.

Behavioral tests that reveal long-term deficits after permanent focal cerebral ischemia in mouse.

Efforts are still needed regarding the research of therapeutics for ischemic stroke. While in experimental studies the protective effect of pharmacological agents is often highlighted by a reduction of the lesion size evaluated in the short term (days), in clinical studies a functional recovery of patients suffering from stroke is expected on the long-term (months and years). Long-term functional preclinical studies are highly recommended to evaluate potential neuroprotective agents for stroke, rather than an assessment of the infarction size at a short time point. The present study thus aimed to select among various behavioral tests those able to highlight long-term deficits (3 months) after cerebral ischemia in mice. Permanent focal cerebral ischemia was carried out in male Swiss mice by intraluminal occlusion of the left middle cerebral artery (MCA). Fourteen behavioral tests were assessed from 7 days to 90 days after ischemia (locomotor activity, neurological score, exit circle test, grip and string tests, chimney test, adhesive removal test, pole test, beam-walking tests, elevated plus maze, marble burying test, forced swimming test, novel object recognition test). The present study clearly identified a battery of behavioral tests able to highlight deficits up to 3 months in our mouse model of permanent MCA occlusion (locomotor activity, neurological score, adhesive removal test, pole test, beam-walking tests, elevated plus maze, marble burying test, forced swimming test and novel object recognition test). This battery of behavioral tests highlighting long-term deficits is useful to study future neuroprotective strategies for stroke treatment.

Reduction of hemorrhagic transformation by PJ34, a poly(ADP-ribose)polymerase inhibitor, after permanent focal cerebral ischemia in mice.

Hemorrhagic transformation is an aggravating event that occurs in 15 to 43% of patients suffering from ischemic stroke. This phenomenon due to blood-brain barrier breakdown appears to be mediated in part by matrix metalloproteinases (MMPs) among which MMP-2 and MMP-9 could be particularly involved. Recent experimental studies demonstrated that post-ischemic MMP-9 overexpression is regulated by poly(ADP-ribose)polymerase (PARP). In this context, our study aimed to evaluate the effect of PJ34 (N-(6-oxo-5,6-dihydrophenanthridin-2-yl)-2-(N,N-dimethylamino)acetamide), a potent PARP inhibitor, on MMP-2 and MMP-9 levels and on hemorrhagic transformations in a model of permanent focal cerebral ischemia in mice. PJ34 (6.25-12.5 mg/kg, i.p.) was given at the time of ischemia onset and 4 h later. Hemorrhagic transformations, divided into microscopic and macroscopic hemorrhages, were counted 48 h after ischemia on 12 coronal brain slices. Microscopic and macroscopic hemorrhages were respectively reduced by 38% and 69% with 6.25 mg/kg PJ34. The anti-hemorrhagic effect of PJ34 was associated with a 57% decrease in MMP-9 overexpression assessed by gelatin zymography. No increase in MMP-2 activity was observed after ischemia in our model. The vascular protection achieved by PJ34 was associated with a reduction in the motor deficit (P<0.05) and in infarct volume (-31%, P<0.01). In conclusion, our study demonstrates for the first time that PJ34 reduces hemorrhagic transformations after cerebral ischemia. Thus this PARP inhibitor exhibits both anti-hemorrhagic and neuroprotective effects that may be of valuable interest for the treatment of stroke.

Improved Reperfusion and Vasculoprotection by the Poly(ADP-Ribose)Polymerase Inhibitor PJ34 After Stroke and Thrombolysis in Mice.

Benefits from thrombolysis with recombinant tissue plasminogen activator (rt-PA) after ischemic stroke remain limited due to a narrow therapeutic window, low reperfusion rates, and increased risk of hemorrhagic transformations (HT). Experimental data showed that rt-PA enhances the post-ischemic activation of poly(ADP-ribose)polymerase (PARP) which in turn contributes to blood-brain barrier injury. The aim of the present study was to evaluate whether PJ34, a potent PARP inhibitor, improves poor reperfusion induced by delayed rt-PA administration, exerts vasculoprotective effects, and finally increases the therapeutic window of rt-PA. Stroke was induced by thrombin injection (0.75 UI in 1 µl) in the left middle cerebral artery (MCA) of male Swiss mice. Administration of rt-PA (0.9 mg kg-1) or saline was delayed for 4 h after ischemia onset. Saline or PJ34 (3 mg kg-1) was given intraperitoneally twice, just after thrombin injection and 3 h later, or once, 3 h after ischemia onset. Reperfusion was evaluated by laser Doppler, vascular inflammation by immunohistochemistry of vascular cell adhesion molecule-1 (VCAM-1) expression, and vasospasm by morphometric measurement of the MCA. Edema, cortical lesion, and sensorimotor deficit were evaluated. Treatment with PJ34 improved rt-PA-induced reperfusion and promoted vascular protection including reduction in vascular inflammation (decrease in VCAM-1 expression), HT, and MCA vasospasm. Additionally, the combined treatment significantly reduced brain edema, cortical lesion, and sensorimotor deficit. In conclusion, the combination of the PARP inhibitor PJ34 with rt-PA after cerebral ischemia may be of particular interest in order to improve thrombolysis with an extended therapeutic window.

Recombinant tissue plasminogen activator enhances microparticle release from mouse brain-derived endothelial cells through plasmin.

Thrombolysis with recombinant tissue plasminogen activator (rt-PA) is currently the only approved pharmacological strategy for acute ischemic stroke. However, rt-PA exhibits vascular toxicity mainly due to endothelial damage. To investigate the mechanisms underlying rt-PA-induced endothelial alterations, we assessed the role of rt-PA in the generation of endothelial microparticles (EMPs), emerging biological markers and effectors of endothelial dysfunction. The mouse brain-derived endothelial cell line bEnd.3 was used. Cells were treated with rt-PA at 20, 40 or 80µg/ml for 15 or 24h, and EMPs were quantified in the culture media using Annexin-V staining coupled with flow cytometry. Rt-PA enhanced EMP release from bEnd.3 cells with a maximal increase at the 40µg/ml dose for 24h (+78% compared to controls). Using tranexamic acid and aprotinin we demonstrated that plasmin is responsible for rt-PA-induced EMP release. The p38 MAPK inhibitor SB203580 and the poly(ADP-ribose)polymerase (PARP) inhibitor PJ34 also reduced rt-PA-induced EMP production, suggesting that p38 MAPK and PARP are downstream intracellular effectors of rt-PA/plasmin. Rt-PA also altered through plasmin the morphology and the confluence of bEnd.3 cells. By contrast, these changes did not implicate p38 MAPK and PARP. This study demonstrates that rt-PA induces the production of microparticles by cerebral endothelial cells, through plasmin, p38 MAPK and PARP pathways. Determining the phenotype of these EMPs to clarify their role on the endothelium in ischemic conditions could thus be of particular interest.

Induction of type 2 iodothyronine deiodinase in astrocytes after transient focal cerebral ischemia in the rat.

This study investigated the expression of deiodinases of thyroid hormones in the rat brain after transient occlusion of the middle cerebral artery. The activity of type 2 deiodinase (D2), which catalyzes the deiodination of thyroxine into the more active thyroid hormone 3,5,3'-triiodothyronine, was strongly increased by cerebral ischemia at 6 and 24 hours in the striatum and at 24 hours in the cerebral cortex. The activity of type 3 deiodinase, which catalyzes the inactivation of thyroid hormones, was not affected by ischemia. In situ hybridization showed, as soon as 6 hours, an upregulation of the expression of D2 mRNA in the ipsilateral striatum, which disappeared at 24 hours. In the ipsilateral cortex, the induction of D2 mRNA started at 6 hours, was increased at 24 hours and finally declined at 72 hours. These results were confirmed by reverse transcription-PCR for D2 mRNA in the striatum and cerebral cortex. The upregulation of D2 mRNA after ischemia was mainly localized in astrocytic cell bodies. These results show that D2 is rapidly induced in astrocytes after ischemic stroke. Future work will include the exploration of the role of the upregulation of this enzyme, responsible for local 3,5,3'-triiodothyronine production as a neuroprotective mechanism in the brain.

Antioxidant strategies in the treatment of stroke.

Excessive production of free radicals is known to lead to cell injury in a variety of diseases, such as cerebral ischemia. In this review, we describe some of the numerous studies that have examined this oxidative stress and the efficiency of antioxidant strategies in focal cerebral ischemia. Besides using genetically modified mice, these strategies can be divided into three groups: (1) inhibition of free radical production, (2) scavenging of free radicals, and (3) increase of free radical degradation by using agents mimicking the enzymatic activity of endogenous antioxidants. Finally, the clinical trials that have tested or are currently testing the efficiency of antioxidants in patients suffering from stroke are reviewed. The results presented here lead us to consider that antioxidants are very promising drugs for the treatment of ischemic stroke.

Time course of oxidative stress, lesion and edema after intrastriatal injection of malonate in rat: effect of alpha-phenyl-N-tert-butylnitrone.

The aim of this study was to characterize the model of oxidative stress consisting in the infection of malonate (3 mumol), an inhibitor of mitochondrial complex II, in the rat striatum. The striatal concentrations of both the reduced and oxidized forms of glutathione (the major endogenous antioxidant) were determined at various times after malonate injection (1-4 h) in order to evaluate the evolution of oxidative stress. The progression of lesion size and edema was also determined up to 24 h after malonate administration. Finally, the effect of alpha-phenyl-N-tert-butylnitrone (PBN), an antioxidant nitrone, was studied. The levels of reduced glutathione (GSH) progressively decreased after malonate injection up to 40% of those of sham animals at 4 h. An increase in the concentrations of oxidized glutathione (GSSG) was also observed as early as 1 h after malonate administration which was maintained up to 4 h. The size of the lesion was maximal within 2 h of malonate injection, whereas edema continued to increase between 2 and 24 h. Injection of PBN at 100 mg/kg i.p. 30 min before and 2 h after malonate administration abolished the GSSG increase caused by malonate but did not modify the drop in GSH. This moderate antioxidant effect of PBN was associated with a slight decrease of the lesion area at two levels (10.7 and 10.2 mm anterior to the interaural line), but the lesion volume remained unchanged. By contrast, PBN reduced edema by 30%. Taken together, these results show that malonate induced a severe oxidative stress leading to the rapid development of the lesion. PBN demonstrates anti-edematous properties that are not sufficient to reduce the lesion.

LF 16-0687 Ms, a bradykinin B2 receptor antagonist, reduces ischemic brain injury in a murine model of transient focal cerebral ischemia.

1. Bradykinin promotes neuronal damage and brain edema through the activation of the B(2) receptor. The neuroprotective effect of LF 16-0687 Ms, a B(2) receptor antagonist, has been described when given prior to induction of transient focal cerebral ischemia in rat, but there are no data regarding the consequence of a treatment when given after injury. Therefore, in a murine model of transient middle cerebral artery occlusion (MCAO), we evaluated the effect of LF 16-0687 Ms given prior to and/or after the onset of ischemia on neurological deficit, infarct volume and inflammatory responses including cerebral edema, blood-brain barrier (BBB) disruption and neutrophil accumulation. 2. LF 16-0687 Ms (1, 2 and 4 mg kg(-1)) administered 0.5 h before and, 1.25 and 6 h after MCAO, decreased the infarct volume by a maximum of 33% and significantly improved the neurological recovery. 3. When given at 0.25 and 6.25 h after MCAO, LF 16-0687 Ms (1.5, 3 and 6 mg kg(-1)) decreased the infarct volume by a maximum of 25% and improved the neurological score. 4. Post-treatment with LF 16-0687 Ms (1.5 mg kg(-1)) significantly decreased brain edema (-28%), BBB disruption (-60%) and neutrophil accumulation (-65%) induced by ischemia. Physiological parameters were not modified by LF 16-0687 Ms. 5. These data emphasize the role of bradykinin B(2) receptor in the development of infarct lesion, neurological deficit and inflammatory responses resulting from transient focal cerebral ischemia. Therefore, B(2) receptor antagonist might represent a new therapeutic approach in the pharmacological treatment of stroke.

Polymorphonuclear neutrophils contribute to infarction and oxidative stress in the cortex but not in the striatum after ischemia-reperfusion in rats.

The present work examined whether polymorphonuclear neutrophil (PMN) infiltration contributes to cortical and striatal brain damage and oxidative stress in a model of transient focal cerebral ischemia. A 2-h occlusion of the left middle cerebral artery and ipsilateral common carotid artery was performed in rats. Administration of the neutropenic agent vinblastine (0.5 mg/kg, i.v.) resulted in a profound decrease in circulating PMNs which was associated with a 80% decrease in myeloperoxidase activity, a marker of PMN infiltration, in both the cortex and the striatum. In the cortex, vinblastine-treated animals exhibited a 44% decrease in the infarct volume and also reduced the oxidative stress (evaluated by the decrease in glutathione concentrations). By contrast, in the striatum, neutropenia modified neither the lesion size nor the oxidative stress. These results indicate that PMN contribution to postischemic injury and oxidative stress is dependent on the brain structure.

Changes in oxidative stress, iNOS activity and neutrophil infiltration in severe transient focal cerebral ischemia in rats.

Oxidative stress, inducible nitric oxide synthase (iNOS) and neutrophils all contribute to post-ischemic brain damage. This study has determined the time courses of these three phenomena after ischemia in parallel with histological and functional outcomes. Ischemia was produced in rats by occluding the left middle cerebral artery and both common carotid arteries for 20 min. Regional cerebral blood flow (rCBF) rapidly decreased to 20% of its preischemic value during occlusion and stabilized at 60% following reperfusion. The striatal infarction was maximal 15 h after reperfusion (50+/-3 mm(3)), whereas the cortical infarction reached its maximum at 48 h (183+/-10 mm(3)). This drastic decrease in rCBF followed by incomplete reperfusion and massive infarction is, thus, extremely severe. The cortical infarction was strongly correlated with the neurologic deficit and loss of body weight. Oxidative stress, evaluated by the decrease in glutathione concentrations, appeared in the striatum at 6 h after reperfusion and in the cortex at 15 h. Calcium-independent NOS activity, considered as inducible NOS activity, was significantly enhanced at 24 h in the striatum and at 48 h in the cortex. Myeloperoxidase activity, a marker of neutrophil infiltration, was significantly increased at 48 h in both the striatum and cortex. These time courses show that the delayed iNOS activity and neutrophil infiltration that occur after the maturation of infarction in severe ischemia may not contribute to ischemic brain damage. By contrast, early oxidative stress may well be implicated in cerebral injury.

Biphasic modulation by nitric oxide of caspase activation due to malonate injection in rat striatum.

The present study examined caspase activation and its modulation by nitric oxide (NO) in a model of oxidative stress induced by injection of malonate (3 micromol), a mitochondrial toxin, into rat striatum. Caspase-3-like enzymatic activity was maximal 6 h after malonate while NO production evaluated by its metabolites nitrites and nitrates was increased at 3 h. The neuronal NO-synthase inhibitor 7-nitroindazole reduced malonate induced-NO production by 50% at 25 mg/kg and enhanced by 32% caspase activation. This result suggests that a moderate production of NO potentiates caspase activation, an effect counterbalanced by NO itself at higher concentrations. Accordingly, complete inhibition of NO production by 7-nitroindazole at 50 mg/kg did not modify malonate-induced caspase activity. Thus NO production by the neuronal isoform of NO-synthase is not the major event leading to caspase activation due to malonate. However, NO seems to have pro- and anti-caspase effects that neutralize each other.