Mouse Model Of Ischemic Stroke Research Articles

A novel genetic locus modulates infarct volume independently of the extent of collateral circulation

In the mouse model of permanent, middle cerebral artery occlusion, infarct volume varies widely across inbred strains but generally is inversely correlated with collateral vessel number. However, we also observed certain mouse strains that share similar collateral vessel anatomy but exhibit significantly different infarct volume. To identify genetic factors determining infarct volume in a collateral vessel-independent manner, we performed quantitative trait locus analysis on a F2 cross between C57BL/6J and C3H/HeJ strains. We mapped four novel loci (Civq4 through Civq7) that modulate infarct volume. Civq4, on chromosome 8, is the strongest locus (logarithm of the odds 9.8) that contributes 21% of the phenotypic variance of infarct volume in the cross. The Civq4 and Civq6 loci represent transgressive B6 alleles that render animals susceptible to larger infarcts. Based on genomic sequence and microarray analyses, we propose candidate genes for the Civq4 locus. By selecting inbred strains with similar collateral vessel anatomy but that vary significantly in infarct volume, we have mapped four loci determining infarct volume in a mouse model of ischemic stroke. Two of the loci appear to modulate infarct volume through a collateral vessel-independent mechanism. Based on strain-specific sequence variants and differences in transcript levels, Msr1 and Mtmr7 appear to be strong candidate genes for Civq4. Identifying the underlying genetic factors of these loci will elucidate the genetic architecture response to cerebral ischemia, shed new light on disease mechanisms of ischemic stroke, and identify potential therapeutic targets for clinical applications.

Carcinoembryonic Antigen–Related Cell Adhesion Molecule 1 Inhibits MMP-9–Mediated Blood–Brain–Barrier Breakdown in a Mouse Model for Ischemic Stroke

Blood-brain-barrier (BBB) breakdown and cerebral edema result from postischemic inflammation and contribute to mortality and morbidity after ischemic stroke. A functional role for the carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) in the regulation of reperfusion injury has not yet been demonstrated. We sought to identify and characterize the relevance of CEACAM1-expressing inflammatory cells in BBB breakdown and outcome after ischemic stroke in Ceacam1(-/-) and wild-type mice. Focal ischemia was induced by temporary occlusion of the middle cerebral artery with a microfilament. Using MRI and Evans blue permeability assays, we observed increased stroke volumes, BBB breakdown and edema formation, reduction of cerebral perfusion, and brain atrophy in Ceacam1(-/-) mice. This translated into poor performance in neurological scoring and high poststroke-associated mortality. Elevated neutrophil influx, hyperproduction, and release of neutrophil-related matrix metalloproteinase-9 in Ceacam1(-/-) mice were confirmed by immune fluorescence, flow cytometry, zymography, and stimulation of neutrophils. Importantly, neutralization of matrix metalloproteinase-9 activity in Ceacam1(-/-) mice was sufficient to alleviate stroke sizes and improve survival to the level of CEACAM1-competent animals. Immune histochemistry of murine and human poststroke autoptic brains congruently identified abundance of CEACAM1(+)matrix metalloproteinase-9(+) neutrophils in the ischemic hemispheres. CEACAM1 controls matrix metalloproteinase-9 secretion by neutrophils in postischemic inflammation at the BBB after stroke. We propose CEACAM1 as an important inhibitory regulator of neutrophil-mediated tissue damage and BBB breakdown in focal cerebral ischemia.

Abstract TP126: The Ketones Acetoacetate And Beta-hydroxybutyrate Alleviate Ischemic Injury Following Occlusion Of The Middle Cerebral Artery

Acute ischemic stroke is treated with thrombolysis but therapeutic benefits are modest. One potential reason for the limited clinical improvement is the apoptotic, delayed cell death that occurs prominently in the periphery of the ischemic core, the penumbra, despite successful reperfusion. Apoptotic cell death has been attributed to glutamate excitotoxicity, a consequence of ischemic energy depletion as well as a cause of persistent mitochondrial dysfunction that perpetuates energetic failure. We have previously shown that glutamate excitotoxicity and mitochondrial dysfunction are alleviated by the ketones acetoacetate and beta-hydroxybutyrate, a combination of physiological compounds produced by liver during calorie restriction to sustain cellular energy requirements. Ketones enhance mitochondrial respiration driven by complex I of the electron transport chain, decrease oxidative stress and increase ATP synthesis. Here, we investigated the effects of ketones in 3 month-old mice subjected to middle cerebral artery (MCA) occlusion with a filament for 90 min. Ketones (50 mg/kg) were administered intraperitoneally 30 min after the onset of ischemia and significantly improved outcomes. MCA occlusion caused significant neuronal loss 24 hours later in the subcortical and cortical regions of the ipsilateral hemisphere. Damage was most severe in the subcortical region and was quite evident on a 7 Tesla MRI. The results were confirmed by non-invasive imaging of apoptosis with the fluorescent indicator Annexin Vivo 750 using a Xenogen IVIS Spectrum (Caliper). Treating mice with ketones significantly decreased neuronal damage based on histology, MRI and fluorescence imaging of apoptosis with Annexin Vivo 750. Furthermore, ketones improved motor activity on the Rotarod and Open Field tests. Untreated mice exhibited evident decreases in the times they remained on the rods whereas ketone-treated mice were almost back to baseline. Consistently, untreated animals were less active in the open field. In sum, our data show that a combination of physiological ketones previously shown to enhance mitochondrial activity and alleviate glutamate excitotoxicity decreases cellular loss and improves motor function in a mouse model of ischemic stroke.

Following experimental stroke, the recovering brain is vulnerable to lipoxygenase‐dependent semaphorin signaling

Recovery from stroke is limited, in part, by an inhibitory environment in the postischemic brain, but factors preventing successful remodeling are not well known. Using cultured cortical neurons from mice, brain endothelial cells, and a mouse model of ischemic stroke, we show that signaling from the axon guidance molecule Sema3A via eicosanoid second messengers can contribute to this inhibitory environment. Either 90 nM recombinant Sema3A, or the 12/15-lipoxygenase (12/15-LOX) metabolites 12-HETE and 12-HPETE at 300 nM, block axon extension in neurons compared to solvent controls, and decrease tube formation in endothelial cells. The Sema3A effect is reversed by inhibiting 12/15-LOX, and neurons derived from 12/15-LOX-knockout mice are insensitive to Sema3A. Following middle cerebral artery occlusion to induce stroke in mice, immunohistochemistry shows both Sema3A and 12/15-LOX are increased in the cortex up to 2 wk. To determine whether a Sema3A-dependent damage pathway is activated following ischemia, we injected recombinant Sema3A into the striatum. Sema3A alone did not cause injury in normal brains. But when injected into postischemic brains, Sema3A increased cortical damage by 79%, and again, this effect was reversed by 12/15-LOX inhibition. Our findings suggest that blocking the semaphorin pathway should be investigated as a therapeutic strategy to improve stroke recovery.

Small molecule-induced cytosolic activation of protein kinase Akt rescues ischemia-elicited neuronal death

Elevating Akt activation is an obvious clinical strategy to prevent progressive neuronal death in neurological diseases. However, this endeavor has been hindered because of the lack of specific Akt activators. Here, from a cell-based high-throughput chemical genetic screening, we identified a small molecule SC79 that inhibits Akt membrane translocation, but paradoxically activates Akt in the cytosol. SC79 specifically binds to the PH domain of Akt. SC79-bound Akt adopts a conformation favorable for phosphorylation by upstream protein kinases. In a hippocampal neuronal culture system and a mouse model for ischemic stroke, the cytosolic activation of Akt by SC79 is sufficient to recapitulate the primary cellular function of Akt signaling, resulting in augmented neuronal survival. Thus, SC79 is a unique specific Akt activator that may be used to enhance Akt activity in various physiological and pathological conditions.

Macrophages prevent hemorrhagic infarct transformation in murine stroke models

Inflammation is increasingly viewed as a new therapeutic target in subacute stages of brain infarction. However, apart from causing secondary damage, inflammation could equally promote beneficial lesion remodeling and repair. Distinct subpopulations of monocytes/macrophages (MOs/MPs) may critically determine the outcome of lesion-associated inflammation. We addressed the role of bone marrow-derived MOs/MPs in 2 different mouse models of ischemic stroke using a combined cell-specific depletion, chemokine receptor knockout, bone marrow chimeric, and pharmacological approach. Starting within 24 hours of stroke onset, immature Ly6c(hi) monocytes infiltrated into the infarct border zone and differentiated into mature Ly6c(lo) phagocytes within the lesion compartment. MO/MP infiltration was CCR2-dependent, whereas we did not obtain evidence for additional recruitment via CX3CR1. Depletion of circulating MOs/MPs or selective targeting of CCR2 in bone marrow-derived cells caused delayed clinical deterioration and hemorrhagic conversion of the infarctions. Bleeding frequently occurred around thin-walled, dilated neovessels in the infarct border zone and was accompanied by decreased expression of transforming growth factor (TGF)-β1 and collagen-4, along with diminished activation of Smad2. Injection of TGF-β1 into the lesion border zone greatly reduced infarct bleeding in MO/MP-depleted mice. Bone marrow-derived MOs/MPs recruited via CCR2 and acting via TGF-β1 are essential for maintaining integrity of the neurovascular unit following brain ischemia. Future therapies should be aimed at enhancing physiological repair functions of CCR2(+) MOs/MPs rather than blocking their hematogenous recruitment.

Abstract 197: Post-stroke Inhibition of TGF-β-activated Kinase by 5Z-7-oxozeaenol Improves Histological and Behavioral Outcomes in a Mouse Model of Ischemic Stroke

Background: Transforming growth factor-β activated kinase 1 (TAK1) activates several intracellular signaling cascades, affecting cell proliferation, inflammation, and apoptosis. It is also a putative kinase for adenosine monophosphate protein kinase (AMPK). 5Z-7-oxozeaenol is a selective inhibitor of TAK1. We and others have previously reported that this drug reduced infarct volume and levels of activated TAK1when administered prior to ischemia in a mouse model of ischemic stroke. We investigated the possible clinical utility of the drug by administering it after ischemia and measuring infarct volumes and behavioral outcomes at 7 days. We also explored the relationship between TAK1 and AMPK by examining outcomes of TAK1 inhibition in AMPK knockout (KO) mice. Methods: Stroke was induced by 90 minutes of reversible middle cerebral artery occlusion (MCAO) in male mice. In one cohort, wild-type (WT) and AMPK KO mice were treated with drug or vehicle via intraperitoneal (IP) injection 2 hours after stroke onset and stroke severity was measured by tissue staining at 24 hours. In a second cohort, WT and AMPK KO mice were treated with drug or vehicle 3.5 hours after stroke onset and stroke severity was measured using the novel-object recognition test (NORT) and by tissue staining at 7 days. Proteins were analyzed by western blot in a third cohort of mice that were sacrificed 4 hours after onset of ischemia. Results: IP injection of 5.0 mg/kg of drug 2 hours after onset of MCAO resulted in a significant reduction in whole-hemisphere infarct volume after 24 hours of reperfusion (49.18±4.18% vehicle vs.17.81±5.86% drug, p=0.001, n=7 vehicle, 8 drug) and after 7 days of reperfusion (57.16±2.38% vehicle vs. 38.35±8.97% drug, p=0.049, n=8 vehicle, 8 drug), and significantly increased the percentage of time that the mice spent exploring a novel object (59.85 ± 3.62% drug vs. 33.15 ± 5.04% vehicle, p=0.001, n=7 vehicle, 7 drug). In AMPK KO mice, there was also a reduction in whole-hemisphere infarct volume. The drug reduced levels of the TAK1 target JNK as well as the JNK target c-Jun. Conclusions: Post-stroke inhibition of TAK1 was neuroprotective and this effect was sustained for 7 days. It was also associated with improvement in the NORT, suggesting preservation of memory function. Together, these findings suggest that 5Z-7-oxozeaenol may have clinical utility for patients suffering ischemic stroke. 5Z-7-oxozeaenol reduced levels of the TAK1 target JNK and its target, c-Jun, suggesting that the benefits of inhibition are due to decreased levels of the transcription factor complex AP-1, of which c-Jun is a major component. The sustained protective effect in AMPK KO mice suggests that AMPK is not important to the mechanism of neuroprotection following TAK1 inhibition.

HIF活性化・Akt活性化を標的とした新規脳保護薬の開発

We here presented two new neuroprotective agents; a HIF activator and an Akt activator. Hypoxia inducible factor (HIF) plays a pivotal role in the adaptation to ischemic conditions, and its activity is modulated by an oxygen-dependent hydroxylation of proline residues by prolyl hydroxylases (PHD). We discovered a unique compound TM6008, which inhibited PHD and stabilized HIF activity in vitro. Oral administration of TM6008 protected neurons in forebrain as well as focal ischemia. The protection was associated with amelioration of apoptosis but independent of enhanced angiogenesis. Next, elevating Akt activation is an obvious clinical strategy to prevent progressive neuronal death in neurological diseases. We identified a small molecule SC79 that inhibits Akt membrane translocation, but paradoxically activates Akt in the cytosol. SC79 specifically binds to the PH domain of Akt. SC79-bound Akt adopts a conformation favorable for phosphorylation by upstream protein kinases. In a hippocampal neuronal culture system and a mouse model for ischemic stroke, the cytosolic activation of Akt by SC79 is sufficient to recapitulate the primary cellular function of Akt signaling, resulting in augmented neuronal survival. Thus, HIF and Akt activators may be the new therapeutic strategy against cerebral infarction, and be expanded the therapeutic time window for hemolysis.

Warfarin Anticoagulation Exacerbates the Risk of Hemorrhagic Transformation after rt-PA Treatment in Experimental Stroke: Therapeutic Potential of PCC

BackgroundOral anticoagulant therapy (OAT) with warfarin is the standard of stroke prevention in patients with atrial fibrillation. Approximately 30% of patients with cardioembolic strokes are on OAT at the time of symptom onset. We investigated whether warfarin exacerbates the risk of thrombolysis-associated hemorrhagic transformation (HT) in a mouse model of ischemic stroke.Methods62 C57BL/6 mice were used for this study. To achieve effective anticoagulation, warfarin was administered orally. We performed right middle cerebral artery occlusion (MCAO) for 3 h and assessed functional deficit and HT blood volume after 24 h.ResultsIn non-anticoagulated mice, treatment with rt-PA (10 mg/kg i.v.) after 3 h MCAO led to a 5-fold higher degree of HT compared to vehicle-treated controls (4.0±0.5 µl vs. 0.8±0.1, p<0.001). Mice on warfarin revealed larger amounts of HT after rt-PA treatment in comparison to non-anticoagulated mice (9.2±3.2 µl vs. 2.8±1.0, p<0.05). The rapid reversal of anticoagulation by means of prothrombin complex concentrates (PCC, 100 IU/kg) at the end of the 3 h MCAO period, but prior to rt-PA administration, neutralized the exacerbated risk of HT as compared to sham-treated controls (3.8±0.7 µl vs. 15.0±3.8, p<0.001).ConclusionIn view of the vastly increased risk of HT, it seems to be justified to withhold tPA therapy in effectively anticoagulated patients with acute ischemic stroke. The rapid reversal of anticoagulation with PCC prior to tPA application reduces the risk attributed to warfarin pretreatment and may constitute an interesting therapeutic option.

Lutein enhances survival and reduces neuronal damage in a mouse model of ischemic stroke

IntroductionStroke is one of the leading causes of death worldwide. Protective agents that could diminish the injuries induced by cerebral ischemia/reperfusion (I/R) are crucial to alleviate the detrimental outcome of stroke. The aim of this study is to investigate the protective roles of lutein in cerebral I/R injury. MethodsTwo-hour cerebral ischemia was induced by unilateral middle cerebral artery occlusion (MCAo) in mice. Either lutein (0.2mg/kg) or vehicle was given to mice intraperitoneally 1h after MCAo and 1h after reperfusion. Neurological deficits were evaluated at 22h after reperfusion while survival rate was assessed daily until 7days after reperfusion. Brains were cut into 2mm-thick coronal slices and stained with 2% 2,3,5-triphenyltetrazolium chloride to determine the infarct size after MCAo. Paraffin-embedded brain sections were prepared for TUNEL assay and immunohistochemistry. Protein lysate was collected for Western blotting experiments. ResultsHigher survival rate, better neurological scores, smaller infarct area and smaller infarct volume were noted in the lutein-treated group. Immunohistochemistry data showed a decrease of immunoreactivity of nitrotyrosine, poly(ADP-ribose) and NFκB in the lutein-treated brains. Western blotting data showed decreased levels of Cox-2, pERK, and pIκB, but increased levels of Bcl-2, heat shock protein 70 and pAkt in the lutein-treated brains. ConclusionsPost-treatment of lutein protected the brain from I/R injury, probably by its anti-apoptotic, anti-oxidative and anti-inflammatory properties. These suggest that lutein could diminish the deleterious outcomes of cerebral I/R and may be used as a potential treatment for stroke patients.

A Dynamic Pharmacophore Drives the Interaction between Psalmotoxin-1 and the Putative Drug Target Acid-Sensing Ion Channel 1a

Acid-sensing ion channel 1a (ASIC1a) is a primary acid sensor in the peripheral and central nervous system. It has been implicated as a novel therapeutic target for a broad range of pathophysiological conditions including pain, ischemic stroke, depression, and autoimmune diseases such as multiple sclerosis. The only known selective blocker of ASIC1a is π-TRTX-Pc1a (PcTx1), a disulfide-rich 40-residue peptide isolated from spider venom. π-TRTX-Pc1a is an effective analgesic in rodent models of acute pain and it provides neuroprotection in a mouse model of ischemic stroke. Thus, understanding the molecular basis of the π-TRTX-Pc1a-ASIC1a interaction should facilitate development of therapeutically useful ASIC1a blockers. We therefore developed an efficient bacterial expression system to produce a panel of π-TRTX-Pc1a mutants for probing structure-activity relationships as well as isotopically labeled toxin for determination of its solution structure and dynamics. We demonstrate that the toxin pharmacophore resides in a β-hairpin loop that was revealed to be mobile over a wide range of time scales using molecular dynamics simulations in combination with NMR spin relaxation and relaxation dispersion measurements. The toxin-receptor interaction was modeled by in silico docking of the toxin structure onto a homology model of rat ASIC1a in a restraints-driven approach that was designed to take account of the dynamics of the toxin pharmacophore and the consequent remodeling of side-chain conformations upon receptor binding. The resulting model reveals new insights into the mechanism of action of π-TRTX-Pc1a and provides an experimentally validated template for the rational design of therapeutically useful π-TRTX-Pc1a mimetics.

Thrombin Mutant W215A/E217A Treatment Improves Neurological Outcome and Reduces Cerebral Infarct Size in a Mouse Model of Ischemic Stroke

Treatment of ischemic stroke by activation of endogenous plasminogen using tissue plasminogen activator is limited by bleeding side effects. In mice, treatment of experimental ischemic stroke with activated protein C improves outcomes; however, activated protein C also has bleeding side effects. In contrast, activation of endogenous protein C using thrombin mutant W215A/E217A (WE) is antithrombotic without hemostasis impairment in primates. Therefore, we investigated the outcome of WE-treated experimental ischemic stroke in mice. The middle cerebral artery was occluded with a filament for 60 minutes to induce ischemic stroke. Vehicle, recombinant WE, or tissue plasminogen activator was administered during middle cerebral artery occlusion or 2 hours after middle cerebral artery occlusion. Neurological performance was scored daily. Intracranial bleeding and cerebral infarct size, defined by 2,3,5-triphenyltetrazolium chloride exclusion, were determined on autopsy. Hemostasis was evaluated using tail bleeding tests. WE improved neurological performance scores, increased laser Doppler flowmetry-monitored post-middle cerebral artery occlusion reperfusion of the parietal cortex, and reduced 2,3,5-triphenyltetrazolium chloride-defined cerebral infarct size versus vehicle controls. However, unlike tissue plasminogen activator, WE did not increase tail bleeding or intracranial hemorrhage. WE treatment is neuroprotective without hemostasis impairment in experimental acute ischemic stroke in mice and thus may provide an alternative to tissue plasminogen activator for stroke treatment.

Increased Risk of Hemorrhagic Transformation in Ischemic Stroke Occurring During Warfarin Anticoagulation

The prevalence of long-term oral anticoagulant therapy is rising. Treatment options for patients who have an ischemic stroke under oral anticoagulant therapy are limited, and clinical data on the risk of hemorrhagic transformation (HT) in this condition are scarce. We therefore aimed to establish a mouse model of ischemic stroke occurring during oral anticoagulant therapy to assess the frequency and characteristics of HT. C57BL/6 mice (n=59) were pretreated with warfarin. Untreated mice (n=32) served as controls. We performed a 3-hour transient filament occlusion of the right middle cerebral artery. In a first set of animals, ischemic lesion size and HT were evaluated macroscopically at 24 hours after middle cerebral artery occlusion. In a second set of mice, quantitative analysis of HT was performed at different time points after middle cerebral artery occlusion and in animals with different international normalized ratio levels using a photometric hemoglobin assay. Oral anticoagulant therapy at the onset of ischemia led to HT in all anticoagulated mice, whereas only 14% of the control mice showed HT. Mean HT blood volume 24 hours after middle cerebral artery occlusion was 0.3±0.4 μL in controls, 4.2±1.7 μL in mice anticoagulated to a mean international normalized ratio of 1.9±0.5 (P<0.05 versus controls), and 5.2±2.7 μL in mice with an international normalized ratio of 2.9±0.9 (P<0.001 versus controls). Anticoagulated mice euthanized at the time point of reperfusion had less HT than mice euthanized after 21 hours of reperfusion (1.6±0.5 μL versus 5.9±3.6 μL, P<0.05). We present a mouse model of ischemic stroke occurring during oral anticoagulant therapy. Warfarin pretreatment dramatically increases the risk of HT 24 hours after middle cerebral artery occlusion. Reperfusion injury seems to be a critical component in this condition.

Granulocyte Colony-Stimulating Factor Enhances Arteriogenesis and Ameliorates Cerebral Damage in a Mouse Model of Ischemic Stroke

Enhancing collateral artery growth is a potent therapeutic approach to treat cardiovascular ischemic disease from occlusive artery. Granulocyte-macrophage colony-stimulating factor (GM-CSF) has gained attention for its ability to promote arteriogenesis, ameliorating brain damage, by the mechanisms involving monocyte upregulation. However, the recent clinical study testing its efficacy in myocardial ischemia has raised the question about its safety. We tested alternative colony-stimulating factors for their effects on collateral artery growth and brain protection. Brain hypoperfusion was produced by occluding the left common carotid artery in C57/BL6 mice. After the surgery, granulocyte colony-stimulating factor, macrophage colony-stimulating factor, or GM-CSF (100 μg/kg/day) was administered daily for 5 days. The angioarchitecture for leptomeningeal anastomoses and the circle of Willis were visualized after the colony-stimulating factor treatment. Circulating blood monocytes and Mac-2-positive cells in the dorsal surface of the brain were determined. A set of animals underwent subsequent ipsilateral middle cerebral artery occlusion and infarct volume was assessed. Granulocyte colony-stimulating factor as well as GM-CSF promoted leptomeningeal collateral growth after common carotid artery occlusion. Both granulocyte colony-stimulating factor and GM-CSF increased circulating blood monocytes and Mac-2-positive cells in the dorsal brain surface, suggesting the mechanisms coupled to monocyte upregulation might be shared. Infarct volume after middle cerebral artery occlusion was reduced by granulocyte colony-stimulating factor, similarly to GM-CSF. Macrophage colony-stimulating factor showed none of theses effects. Granulocyte colony-stimulating factor enhances collateral artery growth and reduces infarct volume in a mouse model of brain ischemia, similarly to GM-CSF.

Systemic Neutrophil Activation in a Mouse Model of Ischemic Stroke and Reperfusion

As a natural response to injury and disease, neutrophils activate, adhere to the microvasculature, migrate into brain tissue, and release toxic substances such as reactive oxygen species and proteases. This neutrophil response occurs when blood flow is returned to brain tissue (reperfusion) after ischemic stroke. Thus, the presence of activated systemic neutrophils increases the potential for tissue injury during reperfusion after ischemic stroke. Although experiments in rat models suggest that activated neutrophils play a pivotal role in cerebral ischemia reperfusion injury, little is known about systemic neutrophil activation during reperfusion following ischemic stroke in a mouse model. The purpose of this study was to characterize systemic leukocyte responses and neutrophil CD11b expression 15-min and 24-hr post-reperfusion in a mouse model of ischemic stroke. The intraluminal filament method of transient middle cerebral artery occlusion (tMCAO) with reperfusion or a sham procedure was performed in male C57Bl/6 mice. Automated leukocyte counts and manual white blood cell (WBC) differential counts were measured. Flow cytometry was used to assess systemic neutrophil surface CD11b expression. The data suggest that the damaging potential of systemic neutrophil activation begins as early as 15 min and remains evident at 24 hr after the initiation of reperfusion. In addition, because transgenic mouse models, bred on a C57Bl/6 background, are increasingly used to elucidate single mechanisms of reperfusion injury after ischemic stroke, findings from this study are foundational for future investigations examining the damaging potential of neutrophil responses post-reperfusion after ischemic stroke in genetically altered mouse models within this background strain.

No effectiveness of synthetic anti-inflammatory tetrapeptides in a mouse model of ischemic stroke

Background. Inflammation plays an important role in the pathophysiology of ischemic stroke and may contri-bute to secondary damage following ischemic stroke. Recently, it has been shown that synthetic oligopeptides related to human chorionic gonadotropin (hCG) and various other synthetic oligopeptides may have immuno-modulatory effects. We aimed to investigate the effects of two promising synthetic anti-inflammatory tetrapeptides, namely the hCG-related peptide AQGV and the p53-related peptide EPPE on infarct volume and on inflammatory gene expres-sion in a mouse model of focal cerebral ischemia. Methods. In a randomized single-blinded fashion, mice received two intravenous injections of either AQGV (30 mg/kg bodyweight) or EPPE (30mg/kg bodyweight) or phosphate buffered saline. The first dose was adminis-tered directly before 90-minutes middle cerebral artery occlusion, and the second dose was injected directly af-ter reperfusion. Infarct volume and gene expression levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), E-selectin and intercellular adhesion molecule-I (ICAM-1) were measured 24 hours after reperfusion. Results. We found no significant effect of either AQGV (108.7 +/- 12.1 mm3 versus PBS 114.9 +/- 23.9 mm3; P=0.7) or EPPE (131.8 +/-12.8 mm3 versus PBS 114.9 +/- 23.9 mm3 Conclusion. AQGV and EPPE did not show any beneficial effects in this mouse model of acute ischemic stroke. Further studies are needed to investigate the nature and dynamics of the immunomodulatory effects of synthetic oligopeptides in acute ischemic stroke. ; P=0.1) on direct lesion volume. All three experimental groups displayed similar mRNA expression levels of TNF-α, IL-6, E-selectin and ICAM-1 at 24 hours after the ischemic insult.

Neuroprotective effect of Fn14 deficiency is associated with induction of the granulocyte-colony stimulating factor (G-CSF) pathway in experimental stroke and enhanced by a pathogenic human antiphospholipid antibody

Using a transgenic mouse model of ischemic stroke we checked for a possible interaction of antiphospholipid antibodies (aPL) which often cause thromboses as well as central nervous system (CNS) involvement under non-thrombotic conditions and the TWEAK/Fn14 pathway known to be adversely involved in inflammatory and ischemic brain disease. After 7days, infarct volumes were reduced in Fn14 deficient mice and were further decreased by aPL treatment. This was associated with strongest increase of the endogenous neuroprotective G-CSF/G-CSF receptor system. This unexpected beneficial action of aPL is an example for a non-thrombogenic action and the double-edged nature of aPL.

Mannose binding lectin modulates cerebral injury after ischemic stroke and reperfusion

Complement proteins mediate reperfusion injury via cytolysis, opsonin, and inflammatory processes. The presence of mannose binding lectin (MBL), necessary for lectin pathway complement activation, is known to increase tissue damage in murine models of myocardial, intestinal, and renal ischemia-reperfusion injury. We investigated the potential protective role of MBL deficiency in cerebral injury after ischemic stroke and reperfusion. Congenic mice with targeted mutations to MBL genes (MBL−/−) or the C57Bl/6 strain (MBL+/+) were subjected to sixty minutes of cerebral ischemia and 24 hours of reperfusion using the intraluminal filament method. After twenty-four hours of reperfusion, the brains were removed, sliced in 2mm sections, and stained with 1% triphenyltetrazolium chloride for analysis of cerebral infarct volume and hemispheric edema. MBL deficiency significantly decreased cerebral infarct volume in the striatum (p < 0.05) but not in the cortex or total hemisphere. MBL deficiency reduced hemispheric edema by 44%. These results indicate that in a mouse model of ischemic stroke and reperfusion 1) MBL deficiency protects brain striatum and 2) MBL may play a role in edema formation. Elucidating mechanisms of MBL mediated striatal neuroprotection and reduced hemispheric edema will add to the understanding of complement-mediated reperfusion injury after stroke. Supported by NIH NRSA 1F31 NR010658-01 (Morrison)

No effectiveness of synthetic anti-inflammatory tetrapeptides in a mouse model of ischemic stroke

Background. Inflammation plays an important role in the pathophysiology of ischemic stroke and may contri-bute to secondary damage following ischemic stroke. Recently, it has been shown that synthetic oligopeptides related to human chorionic gonadotropin (hCG) and various other synthetic oligopeptides may have immuno-modulatory effects. We aimed to investigate the effects of two promising synthetic anti-inflammatory tetrapeptides, namely the hCG-related peptide AQGV and the p53-related peptide EPPE on infarct volume and on inflammatory gene expres-sion in a mouse model of focal cerebral ischemia. Methods. In a randomized single-blinded fashion, mice received two intravenous injections of either AQGV (30 mg/kg bodyweight) or EPPE (30mg/kg bodyweight) or phosphate buffered saline. The first dose was adminis-tered directly before 90-minutes middle cerebral artery occlusion, and the second dose was injected directly af-ter reperfusion. Infarct volume and gene expression levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), E-selectin and intercellular adhesion molecule-I (ICAM-1) were measured 24 hours after reperfusion. Results. We found no significant effect of either AQGV (108.7 +/- 12.1 mm3 versus PBS 114.9 +/- 23.9 mm3; P=0.7) or EPPE (131.8 +/-12.8 mm3 versus PBS 114.9 +/- 23.9 mm3 Conclusion. AQGV and EPPE did not show any beneficial effects in this mouse model of acute ischemic stroke. Further studies are needed to investigate the nature and dynamics of the immunomodulatory effects of synthetic oligopeptides in acute ischemic stroke. ; P=0.1) on direct lesion volume. All three experimental groups displayed similar mRNA expression levels of TNF-α, IL-6, E-selectin and ICAM-1 at 24 hours after the ischemic insult.

Activation of cannabinoid 2 receptors protects against cerebral ischemia by inhibiting neutrophil recruitment

Activation of the cannabinoid 2 receptor (CB(2)) reduces ischemic injury in several organs. However, the mechanisms underlying this protective action are unclear. In a mouse model of ischemic stroke, we show that the CB(2) agonist JWH-133 (1 mg . kg(-1) . d(-1)) decreases the infarct size measured 3 d after onset of ischemia. The neuroprotective effect of JWH-133 was lost in CB(2)-deficient mice, confirming the specificity of JWH-133. Analysis of bone marrow chimeric mice revealed that bone marrow-derived cells mediate the CB(2) effect on ischemic brain injury. CB(2) activation reduced the number of neutrophils in the ischemic brain as shown by FACS analysis and by measuring the levels of the neutrophil marker enzyme myeloperoxidase. Indeed, we found in vitro that CB(2) activation inhibits adherence of neutrophils to brain endothelial cells. JWH-133 (1 microM) also interfered with the migration of neutrophils induced by the endogenous chemokine CXCL2 (30 ng/ml) through activation of the MAP kinase p38. This effect on neutrophils is likely responsible for the neuroprotection mediated by JWH-133 because JWH-133 was no longer protective when neutrophils were depleted. In conclusion, our data demonstrate that by activating p38 in neutrophils, CB(2) agonists inhibit neutrophil recruitment to the brain and protect against ischemic brain injury.-Murikinati, S., Jüttler, E., Keinert, T., Ridder, D. A., Muhammad, S., Waibler, Z., Ledent, C., Zimmer, A., Kalinke, U., Schwaninger, M. Activation of cannabinoid 2 receptors protects against cerebral ischemia by inhibiting neutrophil recruitment.