Abnormal endothelial proliferation and angiogenesis may contribute to brain arteriovenous malformation (BAVM) formation. G protein-coupled receptor 124 (GPR124) mediates embryonic CNS angiogenesis; thus we investigated the association of single nucleotide polymorphisms (SNPs) and haplotypes in GPR124 with risk of BAVM. Ten tagging SNPs spanning 39 kb of GPR124 were genotyped in 195 Caucasian BAVM patients and 243 Caucasian controls. SNP and haplotype association with risk of BAVM was screened using χ2 analysis. Associated variants were further evaluated using multivariable logistic regression, adjusting for age and sex. The minor alleles of 3 GPR124 SNPs adjacent to exon 2 and localized to a 16 kb region of high linkage disequilibrium were associated with reduced risk of BAVM (rs7015566 A, P=0.001; rs7823249 T, P=0.014; rs12676965 C, P=0.007). SNP rs7015566 (intron 1) remained associated after permutation testing (additive model P=0.033). Haplotype analysis revealed a significant overall association (χ2=12.55, 4 df, P=0.014); 2 haplotypes (ATCC, P=0.006 and GGCT, P=0.008) were associated with risk of BAVM. We genotyped a known synonymous SNP (rs16887051) in exon 2, however genotype frequency did not differ between cases and controls. Sequencing of conserved GPR124 regions revealed a novel indel polymorphism in intron 2. Immunohistochemistry confirmed GPR124 expression in the endothelium with no qualitative difference in expression between BAVM cases and controls. SNP rs7015566 mapping to intron 1 of GPR124 was associated with BAVM susceptibility among Caucasians. Future work is focused on investigating this gene region.
Angiogenesis; Genetics; Intracerebral hemorrhage; Risk factor; Vascular malformation
The human umbilical cord blood (HUCB) mononuclear cell (MNC) fraction is a mixed population of cells that induces functional repair in rodent models of stroke when injected intravenously (i.v.). The transplanted cells are found in the infarcted hemisphere and the spleen. The goal of this project was to determine the nature of the interaction between the HUCB MNCs cells and splenic immune cells. Male Sprague Dawley rats underwent permanent middle cerebral artery occlusion (MCAO) and received i.v. injection of either vehicle (MCAO only), HUCB MNCs or MNCs depleted of CD14+ monocytes, CD133+ stem cells or CD19+ B cells 48 hours post-stroke. At 72 hours post-MCAO, the animals were euthanized and the spleens and blood MNCs harvested for flow cytometry and mitogen proliferation assays. All HUCB cell preparations decreased the percentage of T cells in the spleen and monocytes in the blood (p < 0.05). MNCs depleted of CD14+ and CD19+ decreased the percentage of macrophage (p < 0.001), while CD133 depleted MNCs increased the percentage of macrophage in spleen (p < 0.001); MNC did not alter the macrophage population from the level observed after MCAO. Only HUCB MNC significantly decreased Concanavalin A (ConA)-induced T cell stimulation (p < 0.05). These results suggest that the effects of HUCB MNC in the spleen are not due to a single HUCB population, but the interaction of all the subpopulations together.
mononuclear cells; T cells; monocytes; macrophage; B cells; stroke
The use of accelerometry to monitor activity in human stroke patients has revealed strong correlations between objective activity measurements and subjective neurological findings. The goal of our study was to assess the applicability of accelerometry-based measurements in experimental animals undergoing surgically-induced cerebral ischemia. Using a nonhuman primate cortical stroke model, we demonstrate for the first time that monitoring locomotor activity prior to and following cerebrovascular ischemic injury using an accelerometer is feasible in adult male rhesus macaques and that the measured activity outcomes significantly correlate with severity of brain injury. The use of accelerometry as an unobtrusive, objective preclinical efficacy determinant could complement standard practices involving subjective neurological scoring and magnetic resonance imaging in nonhuman primates. Similar activity monitoring devices to those employed in this study are currently in use in human clinical studies, underscoring the feasibility of this approach for assessing the clinical potential of novel treatments for cerebral ischemia.
accelerometer; actigraphy; ischemia; nonhuman primate; rhesus macaque; stroke
Cell loss immediately adjacent to an intracerebral hemorrhage may be mediated in part by the toxicities of extracellular hemoglobin (Hb) and thrombin. However, at low concentrations, these proteins induce tolerance to hemin and iron that may limit further peri-hematomal injury as erythrocyte lysis progresses. The mechanisms mediating these preconditioning effects have not been completely defined, but increased expression of both heme oxygenase (HO)-1 and iron binding proteins likely contributes. In the present study, we hypothesized that iron chelator therapy would attenuate this protective response. Pretreatment of cortical glial cultures (> 90 % GFAP+) with 3 μM methemoglobin (metHb) or 5 units/ml thrombin for 24 h was nontoxic per se, and increased HO-1 and ferritin expression. When challenged with a toxic concentration of hemin, the increase in cellular redox-active iron was attenuated in preconditioned cultures and cell survival was increased. However, if cultures were pretreated with metHb or thrombin plus deferoxamine or 2,2′-bipyridyl, ferritin induction was prevented and cellular redox-active iron increased with hemin treatment. Preconditioning-mediated cytoprotection was consistently reduced by deferoxamine, while 2,2′-bipyridyl had a variable effect. Neither chelator altered HO-1 expression. A cytoprotective response was preserved when chelator therapy was limited to 11 hours of the 24 h preconditioning interval. These results suggest a potentially deleterious effect of continuous iron chelator therapy after ICH. Intermittent therapy may remove peri-hematomal iron without negating the benefits of exposure to low concentrations of Hb or thrombin.
Heme; Intracerebral hemorrhage; Iron; Ischemia; Stroke; Subarachnoid hemorrhage
Greater impairment in autoregulation is seen in male versus female piglets following fluid percussion injury (FPI). This is partially mediated by a greater upregulation of extracellular signal-related kinase mitogen-activated protein kinase (ERK MAPK). We hypothesized that these trends would be reflected by the pressure reactivity index (PRx), a clinical measure of autoregulation. We further hypothesized that PRx values would correlate well with pial artery dilatory responses to hypotension. Male and female piglets were subjected to FPI and treated with a vehicle or ERK MAPK antagonist U 0126 (1 mg/kg IV) 30 min post-injury. FPI led to upregulation of CSF ERK MAPK in untreated piglets of both sexes, however significantly higher PRx values were seen in male versus female piglets. Following administration of U 0126, elevation of ERK MAPK levels was blocked in both sexes and PRx values were significantly improved in the male. A strong correlation was seen between the PRx and pial artery vasomotor activity. These data support previous observations that male piglets demonstrate reversible ERK MAPK-mediated impairment in autoregulation following FPI, which is reflected by the PRx. The strong correlation between the PRx and pial artery vasomotor activity supports the practice of continuously monitoring cerebrovascular autoregulation in patients using this index.
Pressure reactivity index; ERK MAPK; Sex; Autoregulation; Pediatric traumatic brain injury
Female sex steroids, particularly estrogens, contribute to the sexually dimorphic response observed in cerebral ischemic outcome, with females being relatively protected compared to males. Using a mouse model of cardiac arrest and cardiopulmonary resuscitation (CA/CPR), we previously demonstrated that estrogen neuroprotection is mediated in part by the estrogen receptor β, with no involvement of estrogen receptor α. In this study we examined the neuroprotective effect of the novel estrogen receptor, G-protein coupled estrogen receptor 1 (GPER1/GPR30). Male mice administered the GPR30 agonist G1 exhibited significantly reduced neuronal injury in the hippocampal CA1 region and striatum. The magnitude of neuroprotection observed in G1 treated mice was indistinguishable from estrogen treated mice, implicating GPR30 in estrogen neuroprotection. Real-time quantitative RT-PCR indicates that G1 treatment increases expression of the neuroprotective ion channel, small conductance calcium-activated potassium channel 2. We conclude that GPR30 agonists show promise in reducing brain injury following global cerebral ischemia.
Cardiac arrest; GPR30/GPER1; SK2; cerebral ischemia; G1
Removing the spleen prior to ischemic stroke abrogates immunologic response to brain injury and reduces cerebral infarction. However, the effectiveness of splenectomy for neuroprotection after stroke has not been established. Moreover, the risks of the surgical splenectomy in stroke patients create a major obstacle to removing the spleen’s inflammatory response. We hypothesized that acute splenic irradiation will ablate splenic cells and thereby will diminish stroke progression.
Male adult Sprague Dawley rats were subjected to 2-hour middle cerebral artery occlusion (MCAO), then CT scanned for spleen localization and irradiated to the lateral splenic region with 8Gy of Cobalt 60 at 3, 4, 6 or 8 hrs after start of cerebral ischemia. Untreated controls underwent the same procedures except that sham irradiation was applied. At 2 or 7 days after ischemia the rats were euthanized, and brains recovered for the assessment of brain injury and the extent of neuroinflammation.
Irradiation at 3 hrs reduced spleen weight and lymphocyte blood levels after stroke. Splenic irradiation at 3 and 4 hrs after start of ischemia significantly reduced cerebral infarction volumes measured at 48 hrs and 7 days, respectively. The histological analysis on day 7 revealed reduced counts of microglia, infiltrating T cells, and apoptotic neurons in the rats irradiated at 4 hrs.
The noninvasive single-dose procedure of splenic irradiation performed within a time interval of up to 4 hours offers neuroprotection against ischemic stroke possibly by abrogating deployment of splenic cells to the brain.
cerebral ischemia; spleen; Cobalt-60; lymphocyte; neuroinflammation; rats
The recent explosion of interest in epigenetics and chromatin biology has made a significant impact on our understanding of the pathophysiology of cerebral ischemia and led to the identification of new treatment strategies for stroke, such as those that employ histone deacetylase inhibitors. These are key advances; however, the rapid pace of discovery in chromatin biology and innovation in the development of chromatin-modifying agents implies there are emerging classes of drugs that may also have potential benefits in stroke. Herein, we discuss how various chromatin regulatory factors and their recently identified inhibitors may serve as drug targets and therapeutic agents for stroke, respectively. These factors primarily include members of the repressor element-1 silencing transcription factor (REST)/neuron-restrictive silencer factor macromolecular complex, polycomb group (PcG) proteins, and associated chromatin remodeling factors, which have been linked to the pathophysiology of cerebral ischemia. Further, we suggest that, because of the key roles played by REST, PcG proteins and other chromatin remodeling factors in neural stem and progenitor cell (NSPC) biology, chromatin-modifying agents can be utilized not only to mitigate ischemic injury directly but also potentially to promote endogenous NSPC-mediated brain repair mechanisms.
Cerebral ischemia; Chromatin-modifying agent; Epigenetic reprogramming; Histone modification; Polycomb group; Neural stem cell; REST/NRSF; Stroke
Reperfusion therapy for ischemic stroke can cause secondary brain injury, especially under hyperglycemic (HG) conditions. Here we investigated the effect of acute treatment with rosiglitazone, a peroxisome proliferator-activated receptor-gamma (PPAR-γ) agonist, prior to postischemic reperfusion, on stroke outcome during HG stroke. Male Wistar rats that were either normoglycemic (NG) or HG by STZ (50 mg/kg; for 5-6 days) underwent middle cerebral artery occlusion (MCAO) for 2 hours with 2 hours of reperfusion. Animals were treated i.v. with rosiglitazone (1mg/kg; n=16), rosiglitazone (1mg/kg) + the free radical scavenger Tempol (50mg/kg; n=10) or vehicle (n=16) ten minutes prior to reperfusion and infarct volume, edema formation and cerebral blood flow (CBF) were measured. Compared to NG, HG stroke significantly increased infarct volume from 5.2±3.0% vs. 14.7±3.6% (p<0.05). Rosiglitazone prevented the increased infarct volume induced by HG that was only 6.9±2.0% (p<0.05 vs. HG) but did not have any effect on edema formation that was increased by 3.0% in both HG vehicle and rosiglitazone-treated ipsilateral vs. contralateral hemispheres (p<0.05). Combined treatment of rosiglitazone + Tempol did not significantly change brain water content that remained 2.2% greater than contralateral (p<0.05), but reversed the neuroprotective properties of rosiglitazone in HG MCAO animals such that infarct volume was 14.3±4.4% (p>0.05 vs. vehicle). The lack of an effect of combined treatment of rosiglitazone + Temple may be due to a decrease in reperfusion CBF that was only 60% of baseline (p<0.01) compared to 82% and 89% for HG vehicle and rosiglitazone treated animals (p>0.05). In conclusion, acute rosiglitazone treatment prior reperfusion was neuroprotective but not vascular protective during HG stroke.
Ischemic stroke; hyperglycemia; infarct volume; edema; cerebral blood flow; rosiglitazone
Although inflammatory immune cells clearly contribute to the development of middle cerebral artery occlusion (MCAO) in mice, the failure to block neutrophil-associated injury in clinical stroke trials has discouraged further development of immunotherapeutic approaches. However, there is renewed interest in a possible protective role for regulatory T- and B-cells that can suppress inflammation and limit central nervous system damage induced by infiltrating pro-inflammatory cells. Our failure to implicate CD4+FoxP3+ T-cells in limiting brain lesion volume after MCAO turned our focus towards regulatory B-cells known to mediate protection against other inflammatory CNS conditions. Our results clearly demonstrated that B-cell deficient mice developed larger infarct volumes, higher mortality and more severe functional deficits compared to wild-type mice, and had increased numbers of activated T-cells, macrophages, microglial cells, and neutrophils in the affected brain hemisphere. These MCAO-induced changes were completely prevented in B-cell-restored mice after transfer of highly purified WT B-cells but not IL-10-deficient B-cells. Our novel observations are the first to implicate IL-10-secreting B-cells as a major regulatory cell type in stroke and suggest that enhancement of regulatory B-cells might have application as a novel therapy for this devastating neurologic condition.
Experimental stroke; Bregs; IL-10; PD-1; immunotherapy
The goal of this study was to develop an in vivo sonothrombolysis model for stroke research. The rabbit carotid artery has average vessel diameters similar to human M1/M2 segments and allows generation of a thrombotic occlusion using various kinds of thrombus material as well as thrombus placement under visual control. It further allows real-time monitoring of flow and clot mechanics during the sonothrombolysis procedure using high-frequency diagnostic ultrasound. In the present study, the model will be introduced and first results to show feasibility using diagnostic as well as high-intensity focused ultrasound will be presented.
Transcranial; Rabbit; Carotid artery; High-intensity focused ultrasound; Sonothrombolysis; Stroke
Quantitative measurement of blood–brain barrier (BBB) permeability using MRI and its application to cerebral ischemia are reviewed. Measurement of BBB permeability using MRI has been employed to evaluate ischemic damage during acute and subacute phases of stroke and to predict hemorrhagic transformation. There is also an emerging interest on the development and use of MRI to monitor vascular structural changes and angiogenesis during stroke recovery. In this review, we describe MRI BBB permeability and susceptibility-weighted MRI measurements and its applications to evaluate ischemic damage during the acute and subacute phases of stroke and vascular remodeling during stroke recovery.
Blood–brain barrier permeability; Blood-to-brain transfer constant; Hemorrhage; Angiogenesis; Vascular remodeling; Ischemia; Dynamic contrast-enhanced MRI; MRI
Intraventricular hemorrhage (IVH) is a cause of significant morbidity and mortality and is an independent predictor of a worse outcome in intracerebral hemorrhage (ICH) and germinal matrix hemorrhage (GMH). IVH may result in both injuries to the brain as well as hydrocephalus. This paper reviews evidence on the mechanisms and potential treatments for IVH-induced hydrocephalus. One frequently cited theory to explain hydrocephalus after IVH involves obliteration of the arachnoid villi by microthrombi with subsequent inflammation and fibrosis causing CSF outflow obstruction. Although there is some evidence to support this theory, there may be other mechanisms involved, which contribute to the development of hydrocephalus. It is also unclear whether the causes of acute and chronic hydrocephalus after hemorrhage occur via different mechanisms; mechanical obstruction by blood in the former, and inflammation and fibrosis in the latter. Management of IVH and strategies for prevention of brain injury and hydrocephalus are areas requiring further study. A better understanding of the pathogenesis of hydrocephalus after IVH, may lead to improved strategies to prevent and treat post-hemorrhagic hydrocephalus.
Immunotherapy represents an active area of biomedical research to treat cancer, autoimmune diseases, and neurodegenerative disorders. In stroke, recanalization therapy is effective in reducing brain tissue damage after acute ischemic stroke. However, the narrow time window restricts its application for the majority of stroke patients. There is an urgent need to develop adjuvant therapies such as immunotherapy, stem cell replacement, and neuroprotective drugs. A number of molecules have been targeted for immunotherapy in stroke management, including myelin-associated proteins and their receptors, N-methyl-d-aspartic acid receptors, cytokines, and cell adhesion molecules. Both active vaccination and passive antibodies were tested in animal models of acute ischemic stroke. However, the mechanisms underlying the efficacy of immunotherapy are different for each target protein. Blocking myelin-associated proteins may enhance neuroplasticity, whereas blocking adhesion molecules may yield neuroprotection by suppressing the immune response after stroke. Although results from animal studies are encouraging, clinical trials using therapeutic antibodies failed to improve stroke outcome due to severe side effects. It remains a challenge to generate specific therapeutic antibodies with minimal side effects on other organs and systems.
Antibody; Stroke; Immunotherapy
Emerging evidence suggests sex and apolipoprotein E (APOE) genotype separately modify outcomes after intracerebral hemorrhage (ICH). We test the hypothesis that an interaction exists between sex and APOE polymorphism in modifying outcomes after ICH and is altered by administration of exogenous apoE-mimetic peptide. To define the effects of sex and APOE polymorphism in ICH, we created collagenase-induced ICH in male and female APOETR mice (targeted replacement mice homozygous for APOE3 or APOE4 alleles; n=12/group) and assessed performance on Rotarod (RR) and Morris water maze (MWM). To evaluate hematoma formation, we used hematoxylin and eosin staining at 24 h after injury (n=8/group). Using separate cohorts (n=12/group), apoE-mimetic peptide (COG1410 at 2 mg/kg) was administered after ICH, and mice were assessed by RR and MWM. Female mice outperformed male mice via RR and MWM by over 190% improvement through 7 days (RR) and 32 days (MWM) of testing after ICH (p<0.01). Female APOE3TR mice demonstrated improved function compared with all other groups (p<0.05) without any difference in hematoma volume at 24 h after injury in any group. Administration of a therapeutic apoE-mimetic peptide improved RR latencies through 7 days after ICH in male and female APOE4TR mice and MWM latencies over days 28–32 after ICH in male APOE4TR mice (p<0.05). Sex and APOE polymorphism influence functional outcomes in our murine model of ICH. Moreover, administration of exogenous apoE-mimetic peptide after injury differentially modifies the interaction between sex and APOE polymorphism.
Apolipoprotein E; Sex differences; Murine; Intracerebral hemorrhage; Female
Neonatal stroke occurs in one in 4,000 live births and leads to significant morbidity and mortality. Approximately two thirds of the survivors have long-term sequelae including seizures and neurological deficits. However, the pathophysiological mechanisms of recovery after neonatal stroke are not clearly understood, and preventive measures and treatments are nonexistent in the clinical setting. In this study, we investigated the effect of vascular endothelial growth factor (VEGF) treatment on histological recovery and angiogenic response to the developing brain after an ischemic insult. Ten-day-old Sprague–Dawley rats underwent right middle cerebral arterial occlusion (MCAO) for 1.5 h. Diffusion-weighted MRI during occlusion confirmed focal ischemia that was then followed by reperfusion. On group of animals received 5-bromo-2-deoxyuridine and sacrificed at postnatal day (P)18 or P25. A second group of animals was treated with VEGF (1.5 µg/kg, icv) or phosphate-buffered saline (PBS) at P18 and perfusion fixed at P25. Based on Nissl and iron staining, a single VEGF injection reduced the injury score, compared to the animals that underwent MCAO and PBS injection. Furthermore, neurodegeneration represented by neuronal nuclei staining was markedly diminished. In addition, animals treated with VEGF revealed a positive trend in endothelial proliferation and a significant increase in total vessel volume in the peri-infarct region of the caudate. The number of Iba1-positive microglial cells was significantly reduced after a single VEGF injection, and myelin basic protein expression was enhanced in the caudate after ischemia without an effect of VEGF treatment. In conclusion, delayed treatment with VEGF ameliorates injury, promotes endothelial cell proliferation, and increases total vascular volume following neonatal stroke. These results suggest that VEGF has a neuroprotective effect, in part by enhancing endogenous angiogenesis. These data contribute to a better understanding of neonatal stroke.
VEGF; Neuroprotection; Angiogenesis; Neonatal stroke
Blood-brain-barrier disruption occurs with a high incidence after traumatic brain injury, and is an important contributor to many pathological processes, including brain edema, inflammation, and neuronal cell death. Therefore, blood-brain-barrier integrity is an important potential therapeutic target in the treatment of the acute phase of brain trauma. In this short communication, we report our data showing that neuregulin-1 (NRG1), a growth factor with diverse functions in the CNS, ameliorates pathological increases in endothelial permeability and in BBB permeability in experimental models of injury. For in-vitro studies, rat brain endothelial cells were incubated with the inflammatory cytokine IL-1β, which caused an increase in permeability of the cell layer. Co-incubation with NRG1 ameliorated this permeability increase. For in-vivo studies, C57Bl mice were subjected to controlled cortical impact (CCI) under anesthesia, and BBB permeability was assessed by measuring the amount of Evans blue dye extravasation at 2h. NRG1 administered by tail-vein injection 10 minutes after CCI resulted in a decrease in Evans blue dye extravasation by 35%. Since Evans blue extravasation may result from an increase in BBB permeability or from bleeding due to trauma, hemoglobin ELISA was also performed at the same time point. There was a trend towards lower levels of hemoglobin extravasation in the NRG1 group, but the results did not reach statistical significance. MMP-9 activity was not different between groups at 2h. These data suggest that NRG1 has beneficial effects on endothelial permeability and BBB permeability following experimental trauma, and may have neuroprotective potential during CNS injury.
neuregulin-1; endothelial; blood-brain barrier; brain trauma; IL-1β; permeability
Inflammation cell infiltration and cytokine expression are seen in the vascular walls and intervening stroma of resected brain arteriovenous malformation (bAVM) specimens, even in unruptured and previously untreated lesions. Macrophages may play a critical role in bAVM progression to rupture, and could serve as a marker for rupture risk. We assessed feasibility of imaging macrophages within the bAVM nidus using ferumoxytol-enhanced MRI in four patients with already diagnosed bAVMs using iron-sensitive imaging (ISI; T2*-GE-MRI sequence). Patients were imaged at baseline and at either 1 day (n=2) or 5 days (n=2) after infusion of 5mg/kg of ferumoxytol. Residual intravascular ferumoxytol obscured evaluation for uptake in bAVM vascular walls and stroma at the 1-day time point. The two cases imaged at 5 days showed less intravascular tracer but had signal loss in the nidal region consistent with ferumoxytol localization. One case underwent surgical resection; there was prominent vascular wall CD68 staining. Ferumoxytol-enhanced-MRI for assessing bAVM inflammatory cell burden appears feasible and has the potential to be developed as a biomarker to study lesional inflammatory events.
Arteriovenous malformations; Inflammation; Magnetic resonance imaging; Ferumoxytol; USPIO
Ischemic preconditioning (IPC) provides protection against subsequent severe ischemic injury. A recent study found that cerebral IPC prolongs bleeding time. In this study, we examined whether IPC protects against intra-cerebral hemorrhage (ICH)-induced brain edema formation and whether IPC affects blood coagulation. There were three sets of experiments in this study. In the first set, male Sprague–Dawley rats were preconditioned with either 15 min of left middle cerebral artery occlusion, an IPC stimulus, or a sham operation. Three days later, rats received an infusion of autologous whole blood in the ipsilateral or contralateral caudate. Rats were killed 24 h later for brain water content measurement. In the second set, rats underwent 15 min of IPC or a sham operation. Three days later, rats were used for bleeding and thrombin clotting time tests. In the third set, the levels of p44/42 mitogen-activated protein kinases (MAPKs), heme oxygenase-1 (HO-1), transferrin (Tf), and transferrin receptor (TfR) in the brain 24 or 72 h after IPC were examined. We found that IPC reduced ICH-induced brain edema when blood was injected into the ipsilateral caudate but it did not when blood was injected into the contralateral caudate. IPC resulted in prolongation of bleeding time and thrombin clotting time. IPC also induced the activation of p44/42 MAPKs and upregulation of HO-1, Tf, and TfR levels in the ipsilateral caudate. These results suggest that IPC protects against ICH-induced brain edema formation and decreases blood coagulation. The protection of IPC against ICH is mainly due to local factors in the brain and may be related to activation of p44/42 MAPKs and upregulation of HO-1, Tf, and TfR.
Brain edema; Ischemic preconditioning; p44/42 mitogen activated protein kinases; Heme oxygenase-1; Transferrin; Transferrin receptor; Intracerebral hemorrhage
Intracerebral hemorrhage (ICH) is a devastating disease lacking an effective treatment. While the initial injury occurs within minutes, an inflammatory response contributes to ongoing tissue damage over hours to days. Relatively little is known about leukocyte trafficking into the brain in the hours after ICH onset. Understanding these events may lead to identification of new therapeutic targets. Using the blood injection mouse model of ICH, the numbers of leukocytes in the ipsilateral and contralateral brain were quantified by flow cytometry 12 hours after surgery. Perihematomal inflammation was confirmed by histology and chemokines and cytokines in the brain quantified by multiplex ELISA. Few neutrophils were detected in the brain 12 hours after ICH. The majority of leukocytes consisted of inflammatory macrophages (CD45.1hiCD3−Ly6G−CD11c−CD11b+Gr1+ cells) and inflammatory dendritic cells (CD45.1hiCD3−Ly6G−CD11cintCD11b+Gr1+ cells). Microglia numbers did not differ between the hemispheres. These results indicate that blood-derived monocyte populations traffic into brain early after ICH and outnumber neutrophils at 12 hours.
Intracerebral Hemorrhage; Inflammation; Stroke; Macrophages; Dendritic cells; Neutrophils; Neuroinflammation
Brain edema is a major contributor to poor outcome following ischemic and hemorrhagic stroke. In animal models, edema has historically been quantified as a change in % brain water content (water content/wet weight). As described in this communication, this number can be misleading, as ‘small’ changes in % brain water content actually reflect much bigger changes in brain swelling. Using either water content, expressed as g/g dry weight, or a measure of brain swelling, better reflect the impact of edema after stroke and brain injury.
Brain edema; swelling; water content; cerebral hemorrhage; cerebral ischemia
To assess whether phospholipase A2 (PLA2) plays a role in the pathogenesis of spinal cord injury (SCI), we compared lesions either induced by PLA2 alone or by a contusive SCI. At 24-h post-injury, both methods induced a focal hemorrhagic pathology. The PLA2 injury was mainly confined within the ventrolateral white matter, whereas the contusion injury widely affected both the gray and white matter. A prominent difference between the two models was that PLA2 induced a massive demyelination with axons remaining in the lesion area, whereas the contusion injury induced axonal damage and myelin breakdown. At 4 weeks, no cavitation was found within the PLA2 lesion, and numerous axons were myelinated by host-migrated Schwann cells. Among them, 45% of animals had early transcranial magnetic motor-evoked potential (tcMMEP) responses. In contrast, the contusive SCI induced a typical centralized cavity with reactive astrocytes forming a glial border. Only 15% of rats had early tcMMEP responses after the contusion. BBB scores were similarly reduced in both models. Our study indicates that PLA2 may play a unique role in mediating secondary SCI likely by targeting glial cells, particularly those of oligodendrocytes. This lesion model could also be used for studying demyelination and remyelination in the injured spinal cord associated with PLA2-mediated secondary SCI.
Phospholipase A2; Spinal cord injury; Demyelination; Axonal degeneration; Schwann cells
The sole Food and Drug Administration-approved treatment for acute stroke is tissue-type plasminogen activator (tPA), but tPA aggravates impairment of cerebrovasodilation during hypotension in a newborn pig photothrombotic model of stroke. Coupling to carrier red blood cells (RBC) enhances thrombolytic effects of tPA, while reducing its side effects. ATP- and Ca-sensitive K channels (Katp and Kca) are important regulators of cerebrovascular tone and mediate cerebrovasodilation during hypotension. Mitogen-activated protein kinase, a family of at least three kinases, ERK, p38, and c-Jun-N-terminal kinase (JNK), is upregulated after photothrombosis. This study examined the effect of photothrombosis on Katp- and Kca-induced cerebrovasodilation and the roles of tPA and JNK during/after injury. Photothrombosis blunted vasodilation induced by the Katp agonists cromakalim, calcitonin gene-related peptide, and the Kca agonist NS 1619, which was aggravated by injection of tPA. In contrast, both pre- or post-injury thrombosis injection of RBC-tPA and JNK antagonist SP 600125 prevented impairment of Katp- and Kca-induced vasodilation. Therefore, JNK activation in thrombosis impairs K channel-mediated cerebrovasodilation. Standard thrombolytic therapy of central nervous system ischemic disorders using free tPA poses the danger of further dysregulation of cerebrohemodynamics by impairing cation-mediated control of cerebrovascular tone, whereas RBC-coupled tPA both restores reperfusion and normalizes cerebral hemodynamics.
Cerebral circulation; Newborn; Plasminogen activators; Signal transduction; Ischemia