The ischaemic penumbra

The case for neuregulin-1 as a clinical treatment for stroke

Ischemic stroke is the leading cause of serious long-term disability and the 5th leading cause of death in the United States. Revascularization of the occluded cerebral artery, either by thrombolysis or endovascular thrombectomy, is the only effective, clinically-approved stroke therapy. Several potentially neuroprotective agents, including glutamate antagonists, anti-inflammatory compounds and free radical scavenging agents were shown to be effective neuroprotectants in preclinical animal models of brain ischemia. However, these compounds did not demonstrate efficacy in clinical trials with human patients following stroke. Proposed reasons for the translational failure include an insufficient understanding on the cellular and molecular pathophysiology of ischemic stroke, lack of alignment between preclinical and clinical studies and inappropriate design of clinical trials based on the preclinical findings. Therefore, novel neuroprotective treatments must be developed based on a clearer understanding of the complex spatiotemporal mechanisms of ischemic stroke and with proper clinical trial design based on the preclinical findings from specific animal models of stroke. We and others have demonstrated the clinical potential for neuregulin-1 (NRG-1) in preclinical stroke studies. NRG-1 significantly reduced ischemia-induced neuronal death, neuroinflammation and oxidative stress in rodent stroke models with a therapeutic window of >13 h. Clinically, NRG-1 was shown to be safe in human patients and improved cardiac function in multisite phase II studies for heart failure. This review summarizes previous stroke clinical candidates and provides evidence that NRG-1 represents a novel, safe, neuroprotective strategy that has potential therapeutic value in treating individuals after acute ischemic stroke.

Presenting Symptoms and Diffusion-Weighted MRI Positivity by Time After Transient Neurologic Events: A Pooled Analysis of 3 Cohort Studies

BACKGROUND AND OBJECTIVE

The association between focal vs nonfocal presenting symptom and diffusion-weighted imaging (DWI) positivity in relation to onset-to-imaging time in patients with transient neurologic events remains unclear. We hypothesize that episodes consisting of focal symptoms would have proportionally higher DWI-positive imaging at later onset-to-imaging times.

METHODS

Patients with transient neurologic symptoms and a normal neurologic examination who had DWI in the combined data set of 3 cohort studies were included. We used logistic regression models to evaluate the association between each type of presenting symptom (motor weakness, speech impairment, sensory symptoms, vision loss, diplopia, gait instability, dizziness, headache, presyncope, and amnesia) and DWI positivity after adjusting for clinical variables (age, sex, history of stroke, dyslipidemia, coronary artery disease, atrial fibrillation, symptoms duration [<10, 10-59, ≥60 minutes, or unclear], and study source). We stratified the results by onset-to-imaging time categories (<6 hours, 6-23 hours, and ≥24 hours).

RESULTS

Of the total 2,411 patients (1,345 male, median age 68 years), DWI-positive lesions were detected in 598 patients (24.8%). The prevalence of DWI positivity was highest in those with motor weakness (34.7%), followed by speech impairment (33.5%). In a multivariable analysis, the presence of motor weakness, speech impairment, and sensory symptoms was associated with DWI positivity, while vision loss and headache were associated with lower odds of DWI positivity, but nevertheless had 13.6% and 15.3% frequency of DWI positive. The odds of being DWI positive varied by onset-to-imaging time categories for motor weakness, with greater odds of being DWI positive at later imaging time (<6 hours: odds ratio [OR] 1.25, 95% confidence interval [CI] 0.84-1.87; 6-23 hours: OR 2.24, 95% CI 1.47-3.42; and ≥24 hours: OR 2.42, 95% CI 1.74-3.36; interaction p = 0.033). Associations of other symptoms with DWI positivity did not vary significantly by time categories.

DISCUSSION

We found that onset-to-imaging time influences the relationship between motor weakness and DWI positivity in patients with transient neurologic events. Compared with motor, speech, and sensory symptoms, visual or nonfocal symptoms carry a lower but still a substantive association with DWI positivity.

Anti-neuroinflammatory effect of 3,4-dihydroxybenzaldehyde in ischemic stroke

BACKGROUND

Increasing evidence from human and animal studies suggests that cerebral ischemic diseases are associated with nerve dysfunction and neuroinflammation. Therefore, alleviating neuroinflammation is a potential way to treat ischemic stroke. Gastrodia elata Blume (GEB) is a traditional Chinese medicine used to treat central nervous system diseases and related conditions, such as vertigo, headache, epilepsy. We have previously shown that GEB has a protective effect in ischemic stroke, and that the underlying mechanism is related to anti-neuroinflammation. 3,4-Dihydroxybenzaldehyde (DBD) is a phenolic component of GEB and may be responsible for the neuroprotective effect of GEB; however, the detailed molecular mechanisms underlying the effects of DBD are unknown.

METHODS

The anti-neuroinflammatory effect of DBD and the potential mechanisms underlying it were assessed. We using a rat model of middle cerebral artery occlusion/reperfusion and lipopolysaccharide-treated BV2 microglial cells.

RESULTS

DBD (10 mg/kg) significantly decreased infarct volume. Additionally, it alleviated neurological deficits in the rats by inhibiting microglia activation. DBD (0.01, 0.1, and 1 μM) also significantly decreased the levels of inflammatory mediators and cytokines such as tumor necrosis factor-α, interleukin (IL)-1β, IL-6, prostaglandin E2. Furthermore, phenotypic analysis of the BV2 cells showed that DBD significantly down-regulated the expression of M1 marker but significantly up-regulated the expression of M2 marker. Moreover, it suppressed nuclear factor (NF)-κB activation and inhibited the phosphorylation of p38 mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase, and extracellular signal-regulated protein kinases 1/2.

CONCLUSIONS

The neuroprotective and anti-inflammatory effects of DBD are associated with selective modulation of microglia polarization and reduction in the production of inflammatory mediators and cytokines through inhibition of MAPK and NF-κB activation. These findings suggest that DBD may be a potential treatment for ischemic stroke and other neuroinflammatory diseases.

How reliable is cerebral blood flow to map changes in neuronal activity?

Neuroimaging techniques, such as functional MRI, map brain activity through hemodynamic-based signals, and are invaluable diagnostic tools in several neurological disorders such as stroke and dementia. Hemodynamic signals are normally precisely related to the underlying neuronal activity through neurovascular coupling mechanisms that ensure the supply of blood, glucose and oxygen to neurons at work. The knowledge of neurovascular coupling has greatly advanced over the last 30 years, it involves multifaceted interactions between excitatory and inhibitory neurons, astrocytes, and the microvessels. While the tight relationship between blood flow and neuronal activity forms a fundamental brain function, whether neurovascular coupling mechanisms are reliable across physiological and pathological conditions has been questioned. In this review, we interrogate the relationship between blood flow and neuronal activity during activation of different brain pathways: a sensory stimulation driven by glutamate, and stimulation of neuromodulatory pathways driven by acetylcholine or noradrenaline, and we compare the underlying neurovascular coupling mechanisms. We further question if neurovascular coupling mechanisms are affected by changing brain states, as seen in behavioral conditions of sleep, wakefulness, attention and in pathological conditions. Finally, we provide a short overview of how alterations of the brain vasculature could compromise the reliability of neurovascular coupling. Overall, while neurovascular coupling requires activation of common signalling pathways, alternate unique cascades exist depending on the activated pathways. Further studies are needed to fully elucidate the alterations in neurovascular coupling across brain states and pathological conditions.

Transcriptomic analysis of neuregulin-1 regulated genes following ischemic stroke by computational identification of promoter binding sites: A role for the ETS-1 transcription factor

Ischemic stroke is a major cause of mortality in the United States. We previously showed that neuregulin-1 (NRG1) was neuroprotective in rat models of ischemic stroke. We used gene expression profiling to understand the early cellular and molecular mechanisms of NRG1's effects after the induction of ischemia. Ischemic stroke was induced by middle cerebral artery occlusion (MCAO). Rats were allocated to 3 groups: (1) control, (2) MCAO and (3) MCAO + NRG1. Cortical brain tissues were collected three hours following MCAO and NRG1 treatment and subjected to microarray analysis. Data and statistical analyses were performed using R/Bioconductor platform alongside Genesis, Ingenuity Pathway Analysis and Enrichr software packages. There were 2693 genes differentially regulated following ischemia and NRG1 treatment. These genes were organized by expression patterns into clusters using a K-means clustering algorithm. We further analyzed genes in clusters where ischemia altered gene expression, which was reversed by NRG1 (clusters 4 and 10). NRG1, IRS1, OPA3, and POU6F1 were central linking (node) genes in cluster 4. Conserved Transcription Factor Binding Site Finder (CONFAC) identified ETS-1 as a potential transcriptional regulator of NRG1 suppressed genes following ischemia. A transcription factor activity array showed that ETS-1 activity was increased 2-fold, 3 hours following ischemia and this activity was attenuated by NRG1. These findings reveal key early transcriptional mechanisms associated with neuroprotection by NRG1 in the ischemic penumbra.

Regulation of inflammatory responses by neuregulin-1 in brain ischemia and microglial cells in vitro involves the NF-kappa B pathway

Background

We previously demonstrated that neuregulin-1 (NRG-1) was neuroprotective in rats following ischemic stroke. Neuroprotection by NRG-1 was associated with the suppression of pro-inflammatory gene expression in brain tissues. Over-activation of brain microglia can induce pro-inflammatory gene expression by activation of transcriptional regulators following stroke. Here, we examined how NRG-1 transcriptionally regulates inflammatory gene expression by computational bioinformatics and in vitro using microglial cells.

Methods

To identify transcriptional regulators involved in ischemia-induced inflammatory gene expression, rats were sacrificed 24 h after middle cerebral artery occlusion (MCAO) and NRG-1 treatment. Gene expression profiles of brain tissues following ischemia and NRG-1 treatment were examined by microarray technology. The Conserved Transcription Factor-Binding Site Finder (CONFAC) bioinformatics software package was used to predict transcription factors associated with inflammatory genes induced following stroke and suppressed by NRG-1 treatment. NF-kappa B (NF-kB) was identified as a potential transcriptional regulator of NRG-1-suppressed genes following ischemia. The involvement of specific NF-kB subunits in NRG-1-mediated inflammatory responses was examined using N9 microglial cells pre-treated with NRG-1 (100 ng/ml) followed by lipopolysaccharide (LPS; 10 μg/ml) stimulation. The effects of NRG-1 on cytokine production were investigated using Luminex technology. The levels of the p65, p52, and RelB subunits of NF-kB and IkB-α were determined by western blot analysis and ELISA. Phosphorylation of IkB-α was investigated by ELISA.

Results

CONFAC identified 12 statistically over-represented transcription factor-binding sites (TFBS) in our dataset, including NF-kBP65. Using N9 microglial cells, we observed that NRG-1 significantly inhibited LPS-induced TNFα and IL-6 release. LPS increased the phosphorylation and degradation of IkB-α which was blocked by NRG-1. NRG-1 also prevented the nuclear translocation of the NF-kB p65 subunit following LPS administration. However, NRG-1 increased production of the neuroprotective cytokine granulocyte colony-stimulating factor (G-CSF) and the nuclear translocation of the NF-kB p52 subunit, which is associated with the induction of anti-apoptotic and suppression of pro-inflammatory gene expression.

Conclusions

Neuroprotective and anti-inflammatory effects of NRG-1 are associated with the differential regulation of NF-kB signaling pathways in microglia. Taken together, these findings suggest that NRG-1 may be a potential therapeutic treatment for treating stroke and other neuroinflammatory disorders.

Lipoic acid and bone marrow derived cells therapy induce angiogenesis and cell proliferation after focal brain injury

Abstract Introduction: Traumatic brain injury is a main cause of disability and death in developed countries, above all among children and adolescents. The intrinsic inability of the central nervous system to efficiently repair traumatic injuries renders transplantation of bone marrow-derived cells (BMDC) a promising approach towards repair of brain lesions. On the other hand, many studies have reported the beneficial effect of Lipoic acid (LA), a potent antioxidant promoting cell survival, angiogenesis and neuroregeneration.

METHODS

In this study, the cortex of adult mice was cryo-injured in order to mimic local traumatic brain injury. Vehicle or freshly prepared BMDC were grafted in the cerebral penumbra area 24 hours after unilateral local injury alone or combined with intra-peritoneal LA administration as a new regenerative strategy.

RESULTS

Differences were found in the process of cell proliferation, angiogenesis and glial scar formation after local injury depending of the applied treatment, either LA or BMDC alone or in combination.

CONCLUSION

The data presented here suggest that transplantation of BMDC is a good alternative and valid strategy to treat a focal brain injury when LA could not be prescribed due to its non-desired secondary effects.

The significance of matrix metalloproteinase (MMP)-2 and MMP-9 in the ischemic stroke

There is a continuous urgent need to explore the pathogenesis and biochemical changes within the infarcted area during acute ischemic stroke (IS). Matrix metalloproteinases (MMPs), prevailing extracellular endopeptideses, can digest proteins located extracellulary, e.g. collagen, proteoglycans, elastin or fibronectin. Among MMPs, gelatinases (MMP-2 and MMP-9) are the most investigated enzymes. Gelatinases possess the ability to active numerous pro-inflammatory agents as chemokine CXCL-8, interleukin 1β or tumor necrosis factor α. Moreover, due to digestion of collagen type IV (the component of basal membranes) and tight junction proteins (TJPs) they facilitate to cross the endothelium by leukocytes. Due to the significant role of gelatinases during brain ischemia, their selective inhibition seems to be an interesting kind of treatment of acute stroke. The synthetic inhibitors of gelatineses decrease the infarct volume in animal models of IS. In clinical practice statins, the lipid-lowering drugs possess the ability to inhibit the activity of MMP-9 during acute IS. This review briefly provides the most important information about the involvement of MMP-2 and MMP-9 in the pathogenesis of brain ischemia.

Interventional neuroradiology of stroke, still not dead

Since the National Institute of Neurological Disorders and Stroke trial, intravenous thrombolysis has been gaining wide acceptance as the modality of treatment for acute embolic stroke, with a current therapeutic window of up to 4.5 h. Both imaging [with either magnetic resonance imaging (MRI) or computed tomography (CT)] and interventional techniques (thrombolysis and/or thrombectomy) have since improved and provided us with additional imaging of the penumbra using CT or MRI and more advanced thrombolysis or thrombectomy strategies that have been embraced in many centers dealing with patients with acute cerebral ischemia. These techniques, however, have come under scrutiny due to their accrued healthcare costs and have been questioned following major recent studies. These studies basically showed that interventional techniques were not superior to the traditional intravenous thrombolysis techniques and that penumbra imaging could not determine what patients would benefit from more aggressive (i.e., interventional) treatment. We discuss this in the light of the latest developments in both diagnostic and interventional neuroradiology and point out why further studies are needed in order to define the right choices for patients with acute stroke. Indeed, these studies were in part conducted with suboptimal patient recruitment strategies and did not always use the latest interventional techniques available today. So, while these studies may have raised some relevant questions, at the same time, definitive answers have not been given, in our opinion.

Magnetic resonance diffusion-perfusion mismatch in acute ischemic stroke: An update

The concept of magnetic resonance perfusion-diffusion mismatch (PDM) provides a practical and approximate measure of the tissue at risk and has been increasingly applied for the evaluation of hyperacute and acute stroke in animals and patients. Recent studies demonstrated that PDM does not optimally define the ischemic penumbra; because early abnormality on diffusion-weighted imaging overestimates the infarct core by including part of the penumbra, and the abnormality on perfusion weighted imaging overestimates the penumbra by including regions of benign oligemia. To overcome these limitations, many efforts have been made to optimize conventional PDM. Various alternatives beyond the PDM concept are under investigation in order to better define the penumbra. The PDM theory has been applied in ischemic stroke for at least three purposes: to be used as a practical selection tool for stroke treatment; to test the hypothesis that patients with PDM pattern will benefit from treatment, while those without mismatch pattern will not; to be a surrogate measure for stroke outcome. The main patterns of PDM and its relation with clinical outcomes were also briefly reviewed. The conclusion was that patients with PDM documented more reperfusion, reduced infarct growth and better clinical outcomes compared to patients without PDM, but it was not yet clear that thrombolytic therapy is beneficial when patients were selected on PDM. Studies based on a larger cohort are currently under investigation to further validate the PDM hypothesis.

Brain self-protection: the role of endogenous neural progenitor cells in adult brain after cerebral cortical ischemia

Convincing evidence has shown that brain ischemia causes the proliferation of neural stem cells/neural progenitor cells (NSCs/NPCs) in both the subventricular zone (SVZ) and the subgranular zone (SGZ) of adult brain. The role of brain ischemia-induced NSC/NPC proliferation, however, has remained unclear. Here we have determined whether brain ischemia-induced amplification of the NSCs/NPCs in adult brain is required for brain self-protection. The approach of intracerebroventricular (ICV) infusion of cytosine arabinoside (Ara-C), an inhibitor for cell proliferation, for the first 7days after brain ischemia was used to block ischemia-induced NSC/NPC proliferation. We observed that ICV infusion of Ara-C caused a complete blockade of NSC/NPC proliferation in the SVZ and a dramatic reduction of NSC/NPC proliferation in the SGZ. Additionally, as a result of the inhibition of ischemia-induced NSC/NPC pool amplification, the number of neurons in the hippocampal CA1 and CA3 was significantly reduced, the infarction size was significantly enlarged, and neurological deficits were significantly worsened after focal brain ischemia. We also found that an NSC/NPC-conditioned medium showed neuroprotective effects in vitro and that adult NSC/NPC-released brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) are required for NSC/NPC-conditioned medium-induced neuroprotection. These data suggest that NSC/NPC-generated trophic factors are neuroprotective and that brain ischemia-triggered NSC/NPC proliferation is crucial for brain protection. This study provides insights into the contribution of endogenous NSCs/NPCs to brain self-protection in adult brain after ischemia injury.

Human neural stem cell transplantation attenuates apoptosis and improves neurological functions after cerebral ischemia in rats

BACKGROUND

Neuroprotection is a major therapeutic approach for ischemic brain injury. We investigated the neuroprotective effects induced by transplantation of human embryonic neural stem cells (NSCs) into the cortical penumbra 24 h after focal cerebral ischemia.

METHODS

NSCs were prepared from human embryonic brains obtained at 8 weeks of gestation. Focal cerebral ischemia was induced in adult rats by permanent occlusion of the middle cerebral artery. Animals were randomly divided into two groups: NSCs-grafted group and medium-grafted group (control). Infarct size was assessed 28 days after transplantation by hematoxylin and eosin staining. Neurological severity scores were evaluated before ischemia and at 1, 7, 14, and 28 days after transplantation. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay and immunohistochemical analysis of Bcl-2 and Bax were performed at 7, 14, and 28 days after transplantation.

RESULTS

Physiological parameters of the two groups were comparable, but not significantly different. NSC transplantation significantly improved neurological function (P<0.05) but did not reduce the infarct size significantly (P>0.05). Compared with the control, NSC transplantation significantly reduced the number of TUNEL- and Bax-positive cells in the penumbra at 7 days. Interestingly, the number of Bcl-2-positive cells in the penumbra after NSC transplantation was significantly higher than that after medium transplantation (P<0.05).

CONCLUSIONS

The results indicate that NSC transplantation has anti-apoptotic activity and can improve the neurological function; these effects are mediated by the up-regulation of Bcl-2 expression in the penumbra.

Transplanted human embryonic neural stem cells survive, migrate, differentiate and increase endogenous nestin expression in adult rat cortical peri-infarction zone

Transplantation of stem cells is a potential therapeutic strategy for stroke damage. The survival, migration, and differentiation of transplanted human embryonic neural stem cells in the acute post-ischemic environment were characterized and endogenous nestin expression after transplantation was investigated. Human embryonic neural stem cells obtained from the temporal lobe cortex were cultured and labeled with fluorescent 1,1'-dioctadecy-6,6'-di (4-sulfopheyl)-3,3,3',3'-tetramethylindocarbocyanin (DiI) in vitro. Labeled cells were transplanted into cortical peri-infarction zones of adult rats 24 h after permanent middle cerebral artery occlusion. Survival, migration, and differentiation of grafted cells were quantified in immunofluorescence-stained sections from rats sacrificed at 7, 14, and 28 days after transplantation. Endogenous nestin-positive cells in the cortical peri-infarction zone were counted at serial time points. The cells transplanted into the cortical peri-infarction zone displayed the morphology of living cells and became widely located around the ischemic area. Moreover, some of the transplanted cells expressed nestin, GFAP, or NeuN in the peri-infarction zone. Furthermore, compared with the control group, endogenous nestin-positive cells in the peri-infarction zone had increased significantly 7 days after cell transplantation. These results confirm the survival, migration, and differentiation of transplanted cells in the acute post-ischemic environment and enhanced endogenous nestin expression within a brief time window. These findings indicate that transplantation of neural stem cells into the peri-infarction zone may be performed as early as 24 h after ischemia.

Comparing two methods for assessment of perfusion-diffusion mismatch in a rodent model of ischaemic stroke: a pilot study

This stroke experiment was designed to define the mismatch between perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI) in MRI by applying early or instantly acquired PWI. Eight rats were induced with stroke through photothrombotic occlusion of the middle cerebral artery and scanned serially between 1 h and day 3 after induction using DWI and PWI with a 1.5 T MR scanner. The relative lesion volumes (rLV) on MRI and triphenyl tetrazolium chloride-stained specimens were defined as the proportion of lesion volume over brain volume. Discrepancies in the rLV between PWI- and DWI-derived apparent diffusion coefficient (ADC) maps were expressed by subtraction of the ADC from PWI, resulting in three possible patterns: (i) (PWI-ADC > 10% of PWI) denoting a mismatch; (ii) (-(10% of PWI) <or= PWI-ADC <or= 10% of PWI) denoting a match; and (iii) (PWI-ADC < -(10% of PWI)) denoting a reverse mismatch. The differences were compared with the minuend being either early PWI (ePWI) or instant PWI (iPWI) and the subtrahend being instant ADC (iADC). The occurrence and evolution of PWI-ADC patterns were analysed. Over time, PWI-ADC discrepancies evolved from mismatch, through to match, to reversed mismatch. The PWI-ADC mismatch still existed 3 days after MCA occlusion in one to three of the eight cases. The rLVs and mismatch incidences between the ePWI-iADC and iPWI-iADC models were linear correlated. A higher mismatch rate occurred in iPWI-iADC within day 1 and in ePWI-iADC at day 3. Both ePWI and iPWI proved useful to define PWI-ADC patterns within day 1. At day 3, iPWI appeared more adequate.

QEEG prognostic value in acute stroke

The objective of our study is to determine the predictive value of QEEG in patients suffering from an acute ischemic cerebral stroke. Twenty-eight patients were studied within the first 72 hours of clinical evolution of middle cerebral artery territory ischemic stroke. Thirty-seven QEEG recordings were obtained: 13 in the first 24 hours after cerebral stroke onset, 9 between 24-48 hours and 15 between 48-72 hours. Absolute Energies (AE) were the QEEG selected variables for statistical analysis: first, AE Z values were calculated using the Cuban QEEG norms, then the maximum and minimum AE Z values were selected within each frequency band and total power. The medians of the five neighboring Z values were also chosen. Regression models were estimated using the RANKIN scores as dependent variables and the selected QEEG variables as independent, then outcome predictions at hospital discharge and 3 months later were calculated. Percentages of concordance and errors between the estimated and real outcome scores were obtained. Alpha and theta AE were the best predictor for short-term outcome and delta AE for long-term outcome. We conclude that QEEG performed within the first 72 hours of ischemic stroke might be a powerful tool predicting short- and long-term outcome.

A3 adenosine receptor antagonists delay irreversible synaptic failure caused by oxygen and glucose deprivation in the rat CA1 hippocampus in vitro

The role of adenosine A3 receptor activation during ischaemia-like conditions produced by oxygen and glucose deprivation (OGD) was evaluated with extracellular recordings from the CA1 region of rat hippocampal slices. In all, 7 min of OGD evoked tissue anoxic depolarisation (AD, peak at approximately 7 min from OGD start, n=20) and were invariably followed by irreversible loss of electrically evoked field epsps (fepsps, n=42).The selective adenosine A3 antagonists 3-propyl-6-ethyl-5[(ethylthio)carbonyl]-2-phenyl-4-propyl-3-pyridinecarboxylate (MRS 1523, 1-100 nM, n=31), N-[9-chloro-2-(2-furanyl)[1,2,4]-triazolo[1,5-c]quinazolin-5-yl]benzeneacetamide (MRS 1220, 100 nM, n=7), N-(2-methoxyphenyl)-N'-[2-(3-pyrindinyl)-4-quinazolinyl]-urea, (VUF 5574, 100 nM, n=3) and 5-[[(4-pyridyl)amino]carbonyl]amino-8-methyl-2-(2-furyl)-pyrazolo[4,3-e]1,2,4-triazolo[1,5-c]pyrimidine hydrochloride (1 nM, n=4), prevented the irreversible failure of neurotransmission induced by 7 min OGD (n=45) and the development of AD in 20 out of 22 monitored slices. When tested on OGD episodes of longer duration (8-10 min, n=18), 100 nM MRS 1523 prevented or delayed the appearance of AD and exerted a protective effect on neurotransmission for episodes of up to 9 min duration. In the absence of AD, the fepsp recovery was almost total, regardless of OGD episode duration. These findings support the notion that A3 receptor stimulation is deleterious during ischaemia and suggest that selective A3 receptor block may substantially increase the resistance of the CA1 hippocampal region to ischaemic damage.

Extended therapeutic window and functional recovery after intraarterial administration of neuregulin-1 after focal ischemic stroke

We have previously shown that neuregulin-1 (NRG-1) protects neurons from ischemic brain injury if administered before focal stroke. Here, we examined the therapeutic window and functional recovery after NRG-1 treatment in rats subjected to 90 mins of middle cerebral artery occlusion (MCAO) and 24 h of reperfusion. Neuregulin-1 (2.5 microg/kg [corrected] bolus, 1.25 microg/kg/min [corrected] infusion) reduced infarct volume by 89.2%+/-41.9% (mean+/-s.d.; n=8; P<0.01) if administered immediately after the onset of reperfusion. Neuroprotection was also evident if NRG-1 was administered 4 h (66.4%+/-52.6%; n=7; P<0.01) and 12 h (57.0%+/-20.8%; n=8; P<0.01) after reperfusion. Neuregulin-1 administration also resulted in a significant improvement of functional neurologic outcome compared with vehicle-treated animals (32.1%+/-5.7%; n=9; P<0.01). The neuroprotective effect of the single administration of NRG-1 was seen as long as 2 weeks after treatment. Neurons labeled with the neurodegeneration marker dye Fluoro-JadeB were observed after MCAO in the cortex, but the numbers were significantly reduced after NRG-1 treatment. These results indicate that NRG-1 is a potent neuroprotective compound with an extended therapeutic window that has practical therapeutic potential in treating individuals after ischemic brain injury.

Apoptotic cell death progression after photothrombotic focal cerebral ischaemia: effects of the lipophilic iron chelator 2,2'-dipyridyl

Two different forms of cell death have been distinguished morphologically following cerebral ischaemia: necrotic and apoptotic cell death. The aim of this study was to investigate the contribution of apoptosis to ischaemic damage by carefully depicting the temporal and spatial neuronal death following focal ischaemia. For this purpose, rats were subjected to chemical photothrombosis, and histological and biochemical analyses were performed over a period of 24 h after the onset of ischaemia. In addition, the effects of the lipophilic antioxidant iron chelator 2,2'-dipyridyl (DP) were evaluated 24 h after photothrombosis when the lesion volume was maximal. Our results showed two separate waves of neuronal death. In the first wave, shrunken dark neurons were massively present as early as 2 h after photothrombosis in the infarct core. From this initial neuronal abnormal population, progressive and time-dependent changes of both necrotic and apoptotic cell death were observed, leading to ghost neurons and apoptotic bodies after 24 h. The extension of the lesion coincided with a second wave of cell death. Massive and rapid neuronal loss occurred at the infarct border, which appeared as a sharply demarcated pale region. Procaspase and poly(ADP-ribose) polymerase-1 (PARP-1) cleavages were also detected in the infarct core and surrounding damaged tissue. DP treatment markedly blocked the enlargement of the lesion, the infarct border being rescued from infarction. Furthermore, a large decrease of apoptotic bodies was associated with a significant drop of caspase and PARP-1 cleavages, suggesting that the protective effect of DP closely correlates with limitation of apoptosis expansion.

Apnea testing for the diagnosis of brain death

OBJECTIVES

A review is given on various methods, preconditions and pitfalls of apnea testing for the diagnosis of brain death.

MATERIALS AND METHODS

An extensive medical data base search was implemented by information gathered from books and our own experience with more than 2000 apnea tests.

RESULTS

While testing for apnea (AT) is considered indispensable worldwide, recommendations and handling differ. Rather than relying on elapsed time, a specific target value for the partial arterial pressure of carbon dioxide (PaCO2) should be aimed at being the maximum physiological stimulus for respiration. Methodological points are elaborated upon in detail for apneic oxygenation and hypoventilation.

CONCLUSION

AT is an indispensable element of diagnosing brain death. Although with proper handling and adequate precautions AT is safe, it should be performed as a last resort. An international agreement on target values for the PaCO2 is desirable.

Neuroprotection by neuregulin-1 following focal stroke is associated with the attenuation of ischemia-induced pro-inflammatory and stress gene expression

Neuregulins are a family of growth factors with potent neuroprotective properties. We recently demonstrated that neuregulin-1 blocked delayed neuronal death following focal ischemic stroke in the rat. Focal ischemia results in the release of pro-inflammatory cytokines that produce profound changes in gene expression and contribute to cell death associated with stroke. Inflammatory and stress mediators are involved in the pathogenesis of focal ischemic brain damage. We examined whether neuregulin-1 can influence inflammatory and stress gene expression in the rat brain following transient middle cerebral artery occlusion (MCAO). In this study, we compared gene expression profiles in animals treated with neuregulin-1beta (NRG-1) or vehicle followed by MCAO. We used the Affymetrix GeneChip system to analyze gene expression in focal ischemia of the rat brain. Several inflammatory and stress genes were significantly induced following MCAO compared to sham controls including heat shock protein-70 (HSP70), interleukin-1beta, and macrophage chemotattractant protein-1 (JE/MCP-1). Treatment with NRG-1 attenuated the expression of many of these genes by 50% or more. In vitro studies demonstrated that NRG-1 suppressed inflammatory gene expression in activated macrophages. NRG-1 also prevented neuronal death induced by oxygen-glucose deprivation in a rat neuroblastoma cell line, suggesting that NRG-1 may have both direct and indirect neuroprotective capacity. These results demonstrate that NRG-1 can regulate inflammatory and stress gene expression and may give new insight to the molecular mechanisms involved in the neuroprotective role of neuregulins in stroke.

Prion protein accumulation and neuroprotection in hypoxic brain damage

The function of the normal conformational isoform of prion protein, PrP(C), remains unclear although lines of research have suggested a role in the cellular response to oxidative stress. Here we investigate the expression of PrP(C) in hypoxic brain tissues to examine whether PrP(C) is in part regulated by neuronal stress. Cases of adult cerebral ischemia and perinatal hypoxic-ischemic injury in humans were compared with control tissues. PrP(C) immunoreactivity accumulates within neuronal processes in the penumbra of hypoxic damage in adult brain, and within neuronal soma in cases of perinatal hypoxic-ischemic injury, and in situ hybridization analysis suggests an up-regulation of PrP mRNA during hypoxia. Rodents also showed an accumulation of PrP(C) in neuronal soma within the penumbra of ischemic lesions. Furthermore, the infarct size in PrP-null mice was significantly greater than in the wild type, supporting the proposed role for PrP(C) in the neuroprotective adaptive cellular response to hypoxic injury.

Treatment of Bipolar, Seizure, and Sleep Disorders and Migraine Headaches Utilizing a Chiropractic Technique

OBJECTIVE

To discuss the use of an upper cervical technique in the case of a 23-year-old male patient with rapid-cycling bipolar disorder, sleep disorder, seizure disorder, neck and back pain, and migraine headaches.

CLINICAL FEATURES

The patient participated in a high school track meet at age 17, landing on his head from a height of 10 ft while attempting a pole vault. Prior to the accident, no health problems were reported. Following the accident, the patient developed numerous neurological disorders. Symptoms persisted over the next 6 years, during which time the patient sought treatment from many physicians and other health care practitioners.

INTERVENTION AND OUTCOME

At initial examination, evidence of a subluxation stemming from the upper cervical spine was found through thermography and radiography. Chiropractic care using an upper cervical technique was administered to correct and stabilize the patient's upper neck injury. Assessments at baseline, 2 months, and 4 months were conducted by the patient's neurologist. After 1 month of care, the patient reported an absence of seizures and manic episodes and improved sleep patterns. After 4 months of care, seizures and manic episodes remained absent and migraine headaches were reduced from 3 per week to 2 per month. After 7 months of care, the patient reported the complete absence of symptoms. Eighteen months later, the patient remains asymptomatic.

CONCLUSION

The onset of the symptoms following the patient's accident, the immediate reduction in symptoms correlating with the initiation of care, and the complete absence of all symptoms within 7 months of care suggest a link between the patient's headfirst fall, the upper cervical subluxation, and his neurological conditions. Further investigation into upper cervical trauma as a contributing factor to bipolar disorder, sleep disorder, seizure disorder, and migraine headaches should be pursued.

Pediatric perfusion imaging using pulsed arterial spin labeling

PURPOSE

To test the feasibility of pediatric perfusion imaging using a pulsed arterial spin labeling (ASL) technique at 1.5 T.

MATERIALS AND METHODS

ASL perfusion imaging was carried out on seven neurologically normal children and five healthy adults. The signal-to-noise ratio (SNR) of the perfusion images along with T1, M(0), arterial transit time, and the temporal fluctuation of the ASL image series were measured and compared between the two age groups. In addition, ASL perfusion magnetic resonance (MR) was performed on three children with neurologic disorder.

RESULTS

In the cohort of neurologically normal children, a 70% increase in the SNR of the ASL perfusion images and a 30% increase in the absolute cerebral blood flow compared to the adult data were observed. The measures of ASL SNR, T1, and M(0) were found to decrease linearly with age. Transit time and temporal fluctuation of the ASL perfusion image series were not significantly different between the two age groups. The feasibility of ASL in the diagnosis of pediatric neurologic disease was also illustrated.

CONCLUSION

ASL is a promising tool for pediatric perfusion imaging given the unique and reciprocal benefits in terms of safety and image quality.

A critical role of neural-specific JNK3 for ischemic apoptosis

c-Jun N-terminal kinase (JNK) signaling is an important contributor to stress-induced apoptosis, but it is unclear whether JNK and its isoforms (JNK1, JNK2, and JNK3) have distinct roles in cerebral ischemia. Here we show that JNK1 is the major isoform responsible for the high level of basal JNK activity in the brain. In contrast, targeted deletion of Jnk3 not only reduces the stress-induced JNK activity, but also protects mice from brain injury after cerebral ischemia-hypoxia. The downstream mechanism of JNK3-mediated apoptosis may include the induction of Bim and Fas and the mitochondrial release of cytochrome c. These results suggest that JNK3 is a potential target for neuroprotection therapies in stroke.

Topography and Temporal Evolution of Hypoxic Viable Tissue Identified by 18 F-Fluoromisonidazole Positron Emission Tomography in Humans After Ischemic Stroke

Background and Purpose— We sought to characterize the spatial and temporal evolution of human cerebral infarction. Using a novel method of quantitatively mapping the distribution of hypoxic viable tissue identified by 18 F-fluoromisonidazole ( 18 F-FMISO) PET relative to the final infarct, we determined its evolution and spatial topography in human stroke.

Methods— Patients with acute middle cerebral artery territory stroke were imaged with 18 F-FMISO PET (n=19; <6 hours, 4; 6 to 16 hours, 4; 16 to 24 hours, 5; 24 to 48 hours, 6). The hypoxic volume (HV) comprised voxels with significant ( P <0.05; >1 mL) uptake on statistical parametric mapping compared with 15 age-matched controls. Central, peripheral, and external zones of the corresponding infarct on the anatomically coregistered delayed CT were defined according to voxel distance from the infarct center and subdivided into 24 regions by coronal, sagittal, and axial planes. Maps (“penumbragrams”) displaying the percentage of HV in each region were generated for each time epoch.

Results— Higher HV was observed in the central region of the infarct in patients studied within 6 hours of onset (analysis of covariance [ANCOVA]; P <0.05) compared with those studied later, in whom the HV was mainly in the periphery or external to the infarct. HV was maximal in the superior, mesial, and posterior regions of the infarct (ANCOVA; P <0.05).

Conclusions— These observations suggest that infarct expansion occurs at the expense of hypoxic tissue from the center to the periphery of the ischemic region in humans, similar to that seen in experimental animal models. These findings have important pathophysiological and therapeutic implications.

Delayed administration of interleukin-1 receptor antagonist protects against transient cerebral ischaemia in the rat

The cytokine interleukin-1 (IL-1) has been implicated in ischaemic, excitotoxic and traumatic brain damage in rodents. The naturally occurring IL-1 receptor antagonist (IL-1ra) markedly reduces neuronal injury in these conditions. However, the effects of IL-1ra on focal, transient cerebral ischaemia in the rat, which is of major clinical relevance, have not been reported. The objectives of this study were to test the effects of IL-1ra on cell death after temporary cerebral ischaemia, and to investigate the therapeutic time window for IL-1ra treatment. Ischaemia was induced by temporary (60 min) occlusion of the middle cerebral artery (MCAO) in rats, via surgical insertion (and subsequent removal) of a thread into the internal carotid artery. Damage was quantified at various times after MCAO to investigate the temporal progression of damage and establish an appropriate time to assess the effects of IL-1ra on cell death. Cell death was complete 18-24 h after temporary MCAO. Intracerebroventricular injection of IL-1ra (10 microg) at the time of MCAO and 60 min later reduced the lesion volume measured 24 h (57% reduction) or 48 h (52% reduction) after MCAO. Cell death was also significantly reduced when IL-1ra (20 microg) was administered as a single injection, 1 h (47%), 2 h (57%) or 3 h (46%) after MCAO, when compared to vehicle. These data show that IL-1ra markedly reduces cell death even when administration is delayed until 3 h after induction of reversible, focal cerebral ischaemia in the rat, and support our proposal that IL-1ra may be of therapeutic benefit in stroke.

The expanding interleukin-1 family and its receptors: do alternative IL-1 receptor/signaling pathways exist in the brain?

Interleukin-1 (IL-1) has been implicated in neuroimmune responses and has pleiotropic actions in the brain. Compelling evidence has shown that IL-1 is a major mediator of inflammation and the progression of cell death in response to brain injury and cerebral ischemia. Its expression is strongly increased in these pathological conditions, and central administration of exogenous IL-1 significantly exacerbates ischemic brain damage. In contrast, inhibiting IL-1 actions (by intracerebroventricular [icv] injection of IL-1ra, neutralizing antibody to IL-1 or caspase-1 inhibitor) significantly reduces ischemic brain damage. IL-1 acts by binding to the IL-1 type-I receptor (IL-1RI), which is to date, the only known functional receptor for IL-1. However, our recent investigations suggest that IL-1 can act independently of IL-1RI, raising the possibility that additional, as yet undiscovered, receptor(s) for IL-1 exist in the brain. The recent characterization of putative, new IL-1 ligands and new IL-1 receptor-related molecules leads to the hypothesis that there might be alternative IL-1 signaling pathway(s) in the central nervous system (CNS).

Matching gene expression with hypometabolism after cerebral ischemia in the nonhuman primate

To correlate brain metabolic status with the molecular events during cerebral ischemia, a cDNA array was performed after positron emission tomography scanning in a model of focal cerebral ischemia in baboons. Cluster analysis for the expression of 74 genes allowed the identification of 4 groups of genes. In each of the distinct groups, the authors observed a marked inflection in the pattern of gene expression when the CMRo was reduced by 48% to 66%. These patterns of coordinated modifications in gene expression could define molecular checkpoints for the development of an ischemic infarct and a molecular definition of the penumbra.

Ischaemic penumbra: highlights

The ischaemic penumbra was described for the first time in the late 1970s as a ring of hypoperfused zone surrounding the region of complete infarction. The penumbral zone is a functionally silent tissue which is able to regain its function if promptly reperfused. This implies that the ischaemic penumbra is not a static but a "dynamic" and "time-dependent" concept. In this paper we describe the role of neuroimmaging tecniques such as single photon emission tomography (SPET), positron emission tomography (PET), and diffusion-weighted and perfusion-weighted magnetic resonance imaging (DWI and PWI) in the study of ischaemic penumbra. These functional imaging techniques have the advantage of giving "in vivo" quantitative estimate of cerebral blood flow (CBF) as well as information on how the ischaemic tissue metabolic changes develop. It follows that, as therapeutic options for treating acute stroke evolve, neuroimaging strategies are assuming an increasingly important role in the initial evaluation and management of the acute ischaemic patient. In this regard, a wide range of therapeutic approaches have been investigated for either ameliorating the perfusion, or interfering with the pathobiochemical cascade leading to ischaemic neuronal damage, or improving endogenous neuroprotection pathways. The "time windows" required for these treatments to be effective varies being rather short for reperfusion and longer for neuroprotection. Salvaging more penumbra would enhance recovery and thereby allow the most appropriate candidate for therapeutic trials to be selected.

Inducible nitric oxide synthase expression in the ischemic core and penumbra after transient focal cerebral ischemia in mice

The present observations examined the hypothesis that the iNOS expression in the ischemic penumbra after a transient focal ischemic insult is involved in the recruitment of penumbra into infarction. The middle cerebral artery in mice was occluded for 2 h by an intraluminal filament and then recirculated. The measurement of iNOS activity, iNOS protein formation and NO concentration in the ischemic core and penumbra, and the determination of infarct volume were performed at 6, 12, 24 and 48 h after reperfusion. iNOS protein and iNOS enzymatic activity appeared at 6 h, peaked at 24 h, and declined at 48 h in the penumbra after reperfusion. iNOS protein was not detectable in contralateral area and in sham-operated brains. The time course of iNOS protein, enzymatic activity and NO concentration in the penumbra but not in the core matched the process of infarct maturation. Treatment with iNOS inhibitor aminoguanidine (100 mg.kg(-1), i.p.) at 6 and 12 h after reperfusion inhibited iNOS activity by 88.0 +/- 10.4% and reduced NO concentration by 48.5 +/- 8.3% in the penumbra, and lessened infarct size by 48.8 +/- 7.2%. The iNOS activity and NO level in the core were not affected by the administration of aminoguanidine. These results suggest that iNOS expression in the ischemic penumbra is involved in the recruitment of penumbra into infarction and thereby contributing to the enlargement of infarct.

Pre-treatment with melatonin reduces volume of cerebral infarction in a permanent middle cerebral artery occlusion stroke model in the rat

We investigated whether pre-treatment with melatonin, a potent free radical scavenger and antioxidant, would protect against permanent focal cerebral ischemia without reperfusion in a rat middle cerebral artery occlusion (MCAO) model. A single dose of melatonin at 5, 15, or 50 mg/kg or the vehicle alone was given via an intraperitoneal injection at 0.5 h before permanent MCAO. Relative infarction volumes on day 3 were significantly reduced in the groups treated with melatonin at 5 (mean+/-SEM, 17.0+/-6.5%), 15 (18.1+/-5.8%), or 50 (20.6+/-5.0%) mg/kg when compared with the vehicle-treated group (37.1+/-2.8%) and so melatonin treatment achieved a relative reduction in infarct volume by 54.2, 51.2 and 44.5%, respectively. Melatonin did not affect the hemodynamic parameters. Thus, pre-treatment with melatonin at a dose between 5 and 50 mg/kg protects against focal cerebral ischemia without reperfusion.