Hypothermia and brain-derived neurotrophic factor reduce glutamate synergistically in acute stroke

Exploring the Therapeutic Effect of Neurotrophins and Neuropeptides in Neurodegenerative Diseases: at a Glance

Neurotrophins and neuropeptides are the essential regulators of peripheral nociceptive nerves that help to induce, sensitize, and maintain pain. Neuropeptide has a neuroprotective impact as it increases trophic support, regulates calcium homeostasis, and reduces excitotoxicity and neuroinflammation. In contrast, neurotrophins target neurons afflicted by ischemia, epilepsy, depression, and eating disorders, among other neuropsychiatric conditions. Neurotrophins are reported to inhibit neuronal death. Strategies maintained for "brain-derived neurotrophic factor (BDNF) therapies" are to upregulate BDNF levels using the delivery of protein and genes or compounds that target BDNF production and boosting BDNF signals by expanding with BDNF mimetics. This review discusses the mechanisms of neurotrophins and neuropeptides against acute neural damage as well as highlighting neuropeptides as a potential therapeutic agent against Parkinson's disease (PD), Huntington's disease (HD), Alzheimer's disease (AD), and Machado-Joseph disease (MJD), the signaling pathways affected by neurotrophins and their receptors in both standard and diseased CNS systems, and future perspectives that can lead to the potent application of neurotrophins and neuropeptides in neurodegenerative diseases (NDs).

Combining Growth Factor and Stem Cell Therapy for Stroke Rehabilitation, A Review

Stroke is a serious, life-threatening condition demanding vigorous search for new therapies. Recent research has focused on stem cell-based therapies as a viable choice following ischemic stroke, based on studies displaying that stem cells transplanted to the brain not only survive but also cause functional recovery. Growth factors defined as polypeptides that regulate the growth and differentiation of many cell types. Many studies have demonstrated that combined use of growth factors may increase results by the stimulation of endogenous neurogenesis, anti-inflammatory, neuroprotection properties, and enhancement of stem cell survival rates and so may be more effective than a single stem cell therapy. This paper reviews and discusses the most promising new stroke recovery research, including combination treatment.

Therapeutic Potential of Cytokines in Demyelinating Lesions After Stroke

White matter damage is a component of most human stroke and usually accounts for at least half of the lesion volume. Subcortical white matter stroke (WMS) accounts for 25% of all strokes and causes severe motor and cognitive dysfunction. The adult brain has a very limited ability to repair white matter damage. Pathological analysis shows that demyelination or myelin loss is the main feature of white matter injury and plays an important role in long-term sensorimotor and cognitive dysfunction. This suggests that demyelination is a major therapeutic target for ischemic stroke injury. An acute inflammatory reaction is triggered by brain ischemia, which is accompanied by cytokine production. The production of cytokines is an important factor affecting demyelination and myelin regeneration. Different cytokines have different effects on myelin damage and myelin regeneration. Exploring the role of cytokines in demyelination and remyelination after stroke and the underlying molecular mechanisms of demyelination and myelin regeneration after ischemic injury is very important for the development of rehabilitation treatment strategies. This review focuses on recent findings on the effects of cytokines on myelin damage and remyelination as well as the progress of research on the role of cytokines in ischemic stroke prognosis to provide a new treatment approach for amelioration of white matter damage after stroke.

Acute Injection of Omega-3 Triglyceride Emulsion Provides Very Similar Protection as Hypothermia in a Neonatal Mouse Model of Hypoxic-Ischemic Brain Injury

Therapeutic hypothermia (HT) is a currently accepted treatment for neonatal asphyxia and is a promising strategy in adult stroke therapy. We previously reported that acute administration of docosahexaenoic acid (DHA) triglyceride emulsion (tri-DHA) protects against hypoxic-ischemic (HI) injury in neonatal mice. We questioned if co-treatment with HT and tri-DHA would achieve synergic effects in protecting the brain from HI injury. Neonatal mice (10-day old) subjected to HI injury were placed in temperature-controlled chambers for 4 h of either HT (rectal temperature 31–32°C) or normothermia (NT, rectal temperature 37°C). Mice were treated with tri-DHA (0.375 g tri-DHA/kg bw, two injections) before and 1 h after initiation of HT. We observed that HT, beginning immediately after HI injury, reduced brain infarct volume similarly to tri-DHA treatment (~50%). Further, HT delayed 2 h post-HI injury provided neuroprotection (% infarct volume: 31.4 ± 4.1 vs. 18.8 ± 4.6 HT), while 4 h delayed HT did not protect against HI insult (% infarct volume: 30.7 ± 5.0 vs. 31.3 ± 5.6 HT). HT plus tri-DHA combination treatment beginning at 0 or 2 h after HI injury did not further reduce infarct volumes compared to HT alone. Our results indicate that HT offers similar degrees of neuroprotection against HI injury compared to tri-DHA treatment. HT can only be provided in tertiary care centers, requires intense monitoring and can have adverse effects. In contrast, tri-DHA treatment may be advantageous in providing a feasible and effective strategy in patients after HI injury.

Effects of Therapeutic Hypothermia Combined with Other Neuroprotective Strategies on Ischemic Stroke: Review of Evidence

Ischemic stroke is a major cause of death and disability globally, and its incidence is increasing. The only treatment approved by the US Food and Drug Administration for acute ischemic stroke is thrombolytic treatment with recombinant tissue plasminogen activator. As an alternative, therapeutic hypothermia has shown excellent potential in preclinical and small clinical studies, but it has largely failed in large clinical studies. This has led clinicians to explore the combination of therapeutic hypothermia with other neuroprotective strategies. This review examines preclinical and clinical progress towards developing highly effective combination therapy involving hypothermia for stroke patients.

Oxygen or cooling, to make a decision after acute ischemia stroke

The presence of a salvageable penumbra, a region of ischemic brain tissue with sufficient energy for short-term survival, has been widely agreed as the premise for thrombolytic therapy with tissue plasminogen activator (tPA), which remains the only United States Food and Drug Administration (FDA) approved treatment for acute ischemia stroke. However, the use of tPA has been profoundly constrained due to its narrow therapeutic time window and the increased risk of potentially deadly hemorrhagic transformation (HT). Blood brain barrier (BBB) damage within the thrombolytic time window is an indicator for tPA-induced HT and both normobaric hyperoxia (NBO) and hypothermia have been shown to protect the BBB from ischemia/reperfusion injury. Therefore, providing the O₂ as soon as possible (NBO treatment), freezing the brain (hypothermia treatment) to slow down ischemia-induced BBB damage or their combined use may extend the time window for the treatment of tPA. In this review, we summarize the protective effects of NBO, hypothermia or their use combined with tPA on ischemia stroke, based on which, the combination of NBO and hypothermia may be an ideal early stroke treatment to preserve the ischemic penumbra. Given this, there is an urge for large randomized controlled trials to address the effect.

White matter injury in ischemic stroke

Stroke is one of the major causes of disability and mortality worldwide. It is well known that ischemic stroke can cause gray matter injury. However, stroke also elicits profound white matter injury, a risk factor for higher stroke incidence and poor neurological outcomes. The majority of damage caused by stroke is located in subcortical regions and, remarkably, white matter occupies nearly half of the average infarct volume. Indeed, white matter is exquisitely vulnerable to ischemia and is often injured more severely than gray matter. Clinical symptoms related to white matter injury include cognitive dysfunction, emotional disorders, sensorimotor impairments, as well as urinary incontinence and pain, all of which are closely associated with destruction and remodeling of white matter connectivity. White matter injury can be noninvasively detected by MRI, which provides a three-dimensional assessment of its morphology, metabolism, and function. There is an urgent need for novel white matter therapies, as currently available strategies are limited to preclinical animal studies. Optimal protection against ischemic stroke will need to encompass the fortification of both gray and white matter. In this review, we discuss white matter injury after ischemic stroke, focusing on clinical features and tools, such as imaging, manifestation, and potential treatments. We also briefly discuss the pathophysiology of WMI and future research directions.

Prolonged hypothermia exposure diminishes neuroprotection for severe ischemic-hypoxic primary neurons

This study aimed to identify optimal mild hypothermic (MH) condition that would provide the best protection for neuronal cells undergoing severe ischemia and hypoxia. We also sought to determine if longer exposure to mild hypothermia would confer greater protection to severe ischemia and hypoxia in these cells. We designed a primary neuronal cell model for severe glucose and oxygen deprivation/reoxygenation (OGD/R) to simulate the hypoxic-ischemic condition of patients with severe stroke, trauma, or hypoxic-ischemic encephalopathy. We evaluated the viability of these neurons following 3 h of OGD/R and variable MH conditions including different temperatures and durations of OGD/R exposure. We further explored the effects of the optimal MH condition on several parts which are associated with mitochondrial apoptosis pathway: intracellular calcium, reactive oxygen species (ROS), and mitochondrial transmembrane potential (MTP). The results of this study showed that the apoptosis proportion (AP) and cell viability proportion (CVP) after OGD/R significantly varied depending on which MH condition cells were exposed to (p < 0.001). Further, our findings showed that prolonged MH reduced the neuroprotection to AP and CVP. We also determined that the optimal MH conditions (34 °C for 4.5 h) reduced intracellular calcium, ROS, and recovered MTP. These findings indicate that there is an optimal MH treatment strategy for severely hypoxia-ischemic neurons, prolonged duration might diminish the neuroprotection, and that MH treatment likely initiates neuroprotection by inhibiting the mitochondrial apoptosis pathway.

The Glutamate-Glutamine Cycle in Epilepsy

Epilepsy is a complex, multifactorial disease characterized by spontaneous recurrent seizures and an increased incidence of comorbid conditions such as anxiety, depression, cognitive dysfunction, and sudden unexpected death. About 70 million people worldwide are estimated to suffer from epilepsy, and up to one-third of all people with epilepsy are expected to be refractory to current medications. Development of more effective and specific antiepileptic interventions is therefore requisite. Perturbations in the brain's glutamate-glutamine cycle, such as increased extracellular levels of glutamate, loss of astroglial glutamine synthetase, and changes in glutaminase and glutamate dehydrogenase, are frequently encountered in patients with epilepsy. Hence, manipulations of discrete glutamate-glutamine cycle components may represent novel approaches to treat the disease. The goal of his review is to discuss some of the glutamate-glutamine cycle components that are altered in epilepsy, particularly neurotransmitters and metabolites, enzymes, amino acid transporters, and glutamate receptors. We will also review approaches that potentially could be used in humans to target the glutamate-glutamine cycle. Examples of such approaches are treatment with glutamate receptor blockers, glutamate scavenging, dietary intervention, and hypothermia.

Therapeutic hypothermia applicable to cardiac surgery

OBJECTIVE

To review the beneficial and adverse effects of therapeutic hypothermia (TH) applicable to cardiac surgery with cardiopulmonary bypass (CPB) in the contexts of various temperature levels and techniques for achieving TH.

DATABASES USED

Multiple electronic literature searches were performed using PubMed and Google for articles published from June 2012 to December 2014. Relevant terms (e.g. 'hypothermia', 'cardiopulmonary bypass', 'cardiac surgery', 'neuroprotection') were used to search for original articles, letters and reviews without species limitation. Reviews were included despite potential publication bias. References from the studies identified were also searched to find other potentially relevant citations. Abstracts, case reports, conference presentations, editorials and expert opinions were excluded.

CONCLUSIONS

Therapeutic hypothermia is an essential measure of neuroprotection during cardiac surgery that may be achieved most effectively by intravascular cooling using hypothermic CPB. For most cardiac surgical procedures, mild to modest (32-36 °C) TH will be sufficient to assure neuroprotection and will avoid most of the adverse effects of hypothermia that occur at lower body core temperatures.

Therapeutic hypothermia for stroke: Where to go?

Ischemic stroke is a major cause of death and long-term disability worldwide. Thrombolysis with recombinant tissue plasminogen activator is the only proven and effective treatment for acute ischemic stroke; however, therapeutic hypothermia is increasingly recognized as having a tissue-protective function and positively influencing neurological outcome, especially in cases of ischemia caused by cardiac arrest or hypoxic-ischemic encephalopathy in newborns. Yet, many aspects of hypothermia as a treatment for ischemic stroke remain unknown. Large-scale studies examining the effects of hypothermia on stroke are currently underway. This review discusses the mechanisms underlying the effect of hypothermia, as well as trends in hypothermia induction methods, methods for achieving optimal protection, side effects, and therapeutic strategies combining hypothermia with other neuroprotective treatments. Finally, outstanding issues that must be addressed before hypothermia treatment is implemented at a clinical level are also presented.

Extracorporeal methods of blood glutamate scavenging: a novel therapeutic modality

Pathologically elevated glutamate concentrations in the brain's extracellular fluid are associated with several acute and chronic brain insults. Studies have demonstrated that by decreasing the concentration of glutamate in the blood, thereby increasing the concentration gradient between the brain and the blood, the rate of brain-to-blood glutamate efflux can be increased. Blood glutamate scavengers, pyruvate and oxaloacetate have shown great promise in providing neuroprotection in many animal models of acute brain insults. However, glutamate scavengers' potential systemic toxicity, side effects and pharmacokinetic properties may limit their use in clinical practice. In contrast, extracorporeal methods of blood glutamate reduction, in which glutamate is filtered from the blood and eliminated, may be an advantageous adjunct in treating acute brain insults. Here, we review the current evidence for the glutamate-lowering effects of hemodialysis, peritoneal dialysis and hemofiltration. The evidence reviewed here highlights the need for clinical trials.

Combination of therapeutic hypothermia and other neuroprotective strategies after an ischemic cerebral insult

Abrupt deprivation of substrates to neuronal tissue triggers a number of pathological events (the “ischemic cascade”) that lead to cell death. As this is a process of delayed neuronal cell death and not an instantaneous event, several pharmacological and non-pharmacological strategies have been developed to attenuate or block this cascade. The most promising neuroprotectant so far is therapeutic hypothermia and its beneficial effects have inspired researchers to further improve its protective benefit by combining it with other neuroprotective agents. This review provides an overview of all neuroprotective strategies that have been combined with therapeutic hypothermia in rodent models of focal cerebral ischemia. A distinction is made between drugs interrupting only one event of the ischemic cascade from those mitigating different pathways and having multimodal effects. Also the combination of therapeutic hypothermia with hemicraniectomy, gene therapy and protein therapy is briefly discussed. Furthermore, those combinations that have been studied in a clinical setting are also reviewed.

Combination of mild hypothermia with neuroprotectants has greater neuroprotective effects during oxygen-glucose deprivation and reoxygenation-mediated neuronal injury

Co-treatment of neuroprotective reagents may improve the therapeutic efficacy of hypothermia in protecting neurons during ischemic stroke. This study aimed to find promising drugs that enhance the neuroprotective effect of mild hypothermia (MH). 26 candidate drugs were selected based on different targets. Primary cultured cortical neurons were exposed to oxygen-glucose deprivation and reoxygenation (OGD/R) to induce neuronal damage, followed by either single treatment (a drug or MH) or a combination of a drug and MH. Results showed that, compared with single treatment, combination of MH with brain derived neurotrophic factor, glibenclamide, dizocilpine, human urinary kallidinogenase or neuroglobin displayed higher proportion of neuronal cell viability. The latter three drugs also caused less apoptosis rate in combined treatment. Furthermore, co-treatment of those three drugs and MH decreased the level of reactive oxygen species (ROS) and intracellular calcium accumulation, as well as stabilized mitochondrial membrane potential (MMP), indicating the combined neuroprotective effects are probably via inhibiting mitochondrial apoptosis pathway. Taken together, the study suggests that combined treatment with hypothermia and certain neuroprotective reagents provide a better protection against OGD/R-induced neuronal injury.

Allopregnanolone and its precursor progesterone do not reduce injury after experimental stroke in hypertensive rats - role of postoperative temperature regulation?

Allopregnanolone is a neurosteroid synthesized from progesterone in brain. It increases inhibition through modulation of the gamma-aminobutyric acid type A (GABA-A) receptor. Both agents are putative neuroprotectants after ischemic stroke. We sought to confirm their effectiveness in a hypertensive rat stroke model, with intra- and post-operative temperature regulation. The primary study compared allopregnanolone, progesterone or vehicle control treatments, administered 105 minutes after induction of temporary middle cerebral artery occlusion in spontaneously hypertensive rats. Temperature was controlled intraoperatively and a heat mat used in the 6 hours postoperatively to permit animal temperature self-regulation. The primary outcome was infarct volume and secondary outcomes were tests of sensory and motor function. There was no significant effect of treatment on any outcome measure. Given prior reports of GABA-A receptor agonists causing hypothermia, follow-up experiments were conducted to examine postoperative temperature regulation. These did not reveal a difference in postoperative temperature in neurosteroid-treated animals compared to control. However, in all rats maintained postoperatively in ambient temperature, moderate hypothermia was observed. This was in contrast to rats maintained over a heat mat. The lowest mean postoperative temperature was between 34.4-34.9°C in all 3 groups. These data do not support a neuroprotective effect of allopregnanolone or progesterone in ischemic stroke in hypertensives in the setting of normothermia. Given previous evidence of synergy between neuroprotective agents and hypothermia, demonstration of neuroprotective effect of these agents in the absence of postoperative hypothermia would be prudent before consideration of these agents for further clinical investigation.

Potential therapeutic effects of neurotrophins for acute and chronic neurological diseases

The neurotrophins (NTs) nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), NT-3, and NT-4/5 are proteins that regulate cell proliferation, differentiation, and survival in both the developing and mature central nervous system (CNS) by binding to two receptor classes, Trk receptors and p75 NTR. Motivated by the broad growth- and survival-promoting effects of these proteins, numerous studies have attempted to use exogenous NTs to prevent the death of cells that are associated with neurological disease or promote the regeneration of severed axons caused by mechanical injury. Indeed, such neurotrophic effects have been repeatedly demonstrated in animal models of stroke, nerve injury, and neurodegenerative disease. However, limitations, including the short biological half-lives and poor blood-brain permeability of these proteins, prevent routine application from treating human disease. In this report, we reviewed evidence for the neuroprotective efficacy of NTs in animal models, highlighting outstanding technical challenges and discussing more recent attempts to harness the neuroprotective capacity of endogenous NTs using small molecule inducers and cell transplantation.

Intraarterial transplantation of human umbilical cord blood mononuclear cells is more efficacious and safer compared with umbilical cord mesenchymal stromal cells in a rodent stroke model

INTRODUCTION

Stroke is the second leading cause of death worldwide, claims six lives every 60 seconds, and is a leading cause of adult disability across the globe. Tissue plasminogen activator, the only United States Food and Drug Administration (FDA)-approved drug currently available, has a narrow therapeutic time window of less than 5 hours. In the past decade, cells derived from the human umbilical cord (HUC) have emerged as a potential therapeutic alternative for stroke; however, the most effective HUC-derived cell population remains unknown.

METHODS

We compared three cell populations derived from the human umbilical cord: cord blood mononuclear cells (cbMNCs); cord blood mesenchymal stromal cells (cbMSCs), a subpopulation of cbMNCs; and cord matrix MSCs (cmMSCs). We characterized these cells in vitro with flow cytometry and assessed the cells' in vivo efficacy in a 2-hour transient middle cerebral artery occlusion (MCAo) rat model of stroke. cbMNCs, cbMSCs, and cmMSCs were each transplanted intraarterially at 24 hours after stroke.

RESULTS

A reduction in neurologic deficit and infarct area was observed in all three cell groups; however, this reduction was significantly enhanced in the cbMNC group compared with the cmMSC group. At 2 weeks after stroke, human nuclei-positive cells were present in the ischemic hemispheres of immunocompetent stroke rats in all three cell groups. Significantly decreased expression of rat brain-derived neurotrophic factor mRNA was observed in the ischemic hemispheres of all three cell-treated and phosphate-buffered saline (PBS) group animals compared with sham animals, although the decrease was least in cbMNC-treated animals. Significantly decreased expression of rat interleukin (IL)-2 mRNA and IL-6 mRNA was seen only in the cbMSC group. Notably, more severe complications (death, eye inflammation) were observed in the cmMSC group compared with the cbMNC and cbMSC groups.

CONCLUSIONS

All three tested cell types promoted recovery after stroke, but cbMNCs showed enhanced recovery and fewer complications compared with cmMSCs.

Brain to blood glutamate scavenging as a novel therapeutic modality: a review

It is well known that abnormally elevated glutamate levels in the brain are associated with secondary brain injury following acute and chronic brain insults. As such, a tight regulation of brain glutamate concentrations is of utmost importance in preventing the neurodegenerative effects of excess glutamate. There has been much effort in recent years to better understand the mechanisms by which glutamate is reduced in the brain to non-toxic concentrations, and in how to safely accelerate these mechanisms. Blood glutamate scavengers such as oxaloacetate, pyruvate, glutamate-oxaloacetate transaminase, and glutamate-pyruvate transaminase have been shown to reduce blood glutamate concentrations, thereby increasing the driving force of the brain to blood glutamate efflux and subsequently reducing brain glutamate levels. In the past decade, blood glutamate scavengers have gained increasing international interest, and its uses have been applied to a wide range of experimental contexts in animal models of traumatic brain injury, ischemic stroke, subarachnoid hemorrhage, epilepsy, migraine, and malignant gliomas. Although glutamate scavengers have not yet been used in humans, there is increasing evidence that their use may provide effective and exciting new therapeutic modalities. Here, we review the laboratory evidence for the use of blood glutamate scavengers. Other experimental neuroprotective treatments thought to scavenge blood glutamate, including estrogen and progesterone, beta-adrenergic activation, hypothermia, insulin and glucagon, and hemodialysis and peritoneal dialysis are also discussed. The evidence reviewed here will hopefully pave the way for future clinical trials.

Genetic deficiency of β2-containing nicotinic receptors attenuates brain injury in ischemic stroke

One of the major consequences of stroke is brain injury caused by glutamate-mediated excitotoxicity. Glutamate-mediated excitatory activities are partially driven by β2-containing nicotinic acetylcholine receptors (β2-nAChRs). In examining the role of β2-nAChRs in cerebral ischemic injury, excitotoxicity and stroke outcome, we found that deficiency of β2-nAChRs attenuated brain infarction and neurological deficit at 24 and 72 h after transient middle cerebral artery occlusion (MCAO). Genetic deletion of β2-nAChRs associated with reduced terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL(+)) and cleaved caspase-3(+) cells after MCAO, together with a reduction of extracellular glutamate and oxygen-glucose deprivation-induced increase of excitatory inputs in cortical neurons. Pharmacologic pretreatment with a selective β2-nAChRs antagonist reduced brain infarction, neurological deficit, and MCAO-induced glutamate release. These findings suggest that deficiency of β2-nAChRs, also achievable by pharmacological blockade, can decrease brain infarction and improve the neurological status in ischemic stroke. The improved outcome is associated with reduced extracellular glutamate level and lower excitatory inputs into ischemic neurons, suggesting a reduction of glutamate-mediated excitotoxicity in the mechanisms of neuroprotection.

The role of hypothermia in the regulation of blood glutamate levels in naive rats

BACKGROUND

The exact mechanism of hypothermia-induced neuroprotection has not been determined yet; however, we hypothesized that it may be mediated by a blood glutamate-scavenging effect. Here, we examine the effect of hypothermic conditions (mild, moderate, and deep) on blood glutamate levels in naive rats. To identify the mechanism of hypothermia-induced glutamate reduction, we also measured concentrations of glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT), the primary regulators of glutamate concentration in blood.

METHODS

Rats were anesthetized with isoflurane, and their rectal temperature was maintained for 6 hours at 36 to 37°C, 33 to 36°C, 30 to 32°C, 18 to 22°C, or was not maintained artificially. At 6 hours, active cooling was discontinued and rats were allowed to rewarm. There were 12 rats in each group for a total of 60 rats. Blood samples were drawn at 0, 3, 6, 12, 24, and 48 hours for the determination of blood glutamate, GOT, and GPT levels.

RESULTS

A strong correlation between body temperature and blood glutamate levels was observed (P<0.001). Mild (33 to 36°C) and moderate (30 to 32°C) hypothermia led to reduced blood glutamate levels (P<0.001). Deep hypothermia (18 to 22°C) was associated with significant elevations in blood glutamate levels (P<0.001). Hypothermia, irrespective of the degree, led to elevations in GOT in plasma (P<0.001).

CONCLUSIONS

Mild and moderate hypothermia led to a reduction in blood glutamate levels in rats, whereas deep hypothermia was associated with a significant elevation in blood glutamate levels. We further demonstrated an elevation of GOT and GPT levels, supporting their involvement in reducing blood glutamate by the conversion of glutamate to 2-ketoglutarate. We suggest that the neuroprotective properties of hypothermia may be partially because of a blood glutamate-scavenging mechanism.

Associations of BDNF genotype and promoter methylation with acute and long-term stroke outcomes in an East Asian cohort

Background

Brain derived neurotrophic factor (BDNF) has been shown to play an important role in poststroke recovery. BDNF secretion is influenced by genetic and epigenetic profiles. This study aimed to investigate whether BDNF val66met polymorphism and promoter methylation status were associated with outcomes at two weeks and one year after stroke.

Methods and Findings

A total of 286 patients were evaluated at the time of admission and two weeks after stroke, and 222 (78%) were followed one year later in order to evaluate consequences of stroke at both acute and chronic stages. Stroke outcomes were dichotomised into good and poor by the modified Rankin Scale. Stroke severity (National Institutes of Health Stroke Scale), physical disability (Barthel Index), and cognitive function (Mini-Mental State Examination) were measured. Associations of BDNF genotype and methylation status on stroke outcomes and assessment scale scores were investigated using logistic regression, repeated measures ANOVA and partial correlation tests. BDNF val66met polymorphism was independently associated with poor outcome at 2 weeks and at 1 year, and with worsening physical disability and cognitive function over that period. Higher BDNF promoter methylation status was independently associated with worse outcomes at 1 year, and with the worsening of physical disability and cognitive function. No significant genotype-methylation interactions were found.

Conclusions

A role for BDNF in poststroke recovery was supported, and clinical utility of BDNF genetic and epigenetic profile as prognostic biomarkers and a target for drug development was suggested.

Ischemic stroke and neuroprotection

Stroke is a major cause of morbidity and mortality in both developed and developing countries of the world. Greater understanding of the pathophysiology of neuronal damage in ischemic stroke has generated interest in neuroprotection as a management strategy. This paper aims to review the current concept and place of neuroprotection in ischemic stroke. An extensive search of all materials related to the topic was made using library sources including Pubmed and Medline searches. Current research findings were also included. The findings are as presented. Neuroprotection is an increasingly recognized management strategy in ischemic stroke that promises to assist clinicians in reducing stroke mortality rates and improving the quality of life of survivors.

Neuroprotective effects of bilobalide are accompanied by a reduction of ischemia-induced glutamate release in vivo

Neuroprotective properties of bilobalide, a specific constituent of Ginkgo extracts, were tested in a mouse model of stroke. After 24h of middle cerebral artery occlusion (MCAO), bilobalide reduced infarct areas in the core region (striatum) by 40-50% when given at 10mg/kg 1h prior to MCAO. Neuroprotection was also observed at lower doses, or when the drug was given 1h past stroke induction. Sensorimotor function in mice was improved by bilobalide as shown by corner and chimney tests. When brain metabolism in situ was monitored by microdialysis, MCAO caused a rapid disappearance of extracellular glucose in the striatum which returned to baseline levels after reperfusion. Extracellular levels of glutamate were increased by more than ten-fold in striatal tissue, and by four- to fivefold in hippocampal tissue (penumbra). Bilobalide did not affect glucose levels but strongly attenuated glutamate release in both core and penumbra regions. Bilobalide was equally active when given locally via the microdialysis probe and also reduced ischemia-induced glutamate release in vitro in brain slices. We conclude that bilobalide is a strong neuroprotectant in vivo at doses that can be used therapeutically in humans. The mechanism of action evidently involves reduction of glutamate release, thereby reducing excitotoxicity.

Therapeutic applications of hypothermia in cerebral ischaemia

There is considerable experimental evidence that hypothermia is neuroprotective and can reduce the severity of brain damage after global or focal cerebral ischaemia. However, despite successful clinical trials for cardiac arrest and perinatal hypoxia-ischaemia and a number of trials demonstrating the safety of moderate and mild hypothermia in stroke, there are still no established guidelines for its use clinically. Based upon a review of the experimental studies we discuss the clinical implications for the use of hypothermia as an adjunctive therapy in global cerebral ischaemia and stroke and make some suggestions for its use in these situations.

Therapeutic hypothermia: critical review of the molecular mechanisms of action

Therapeutic hypothermia (TH) is nowadays one of the most important methods of neuroprotection. The events that occur after an episode of ischemia are multiple and hypothermia can affect the various steps of this cascade. The mechanisms of action of TH are varied and the possible explanation for the benefits of this therapy is probably the multiple mechanisms of action blocking the cascade of ischemia on many levels. TH can affect many metabolic pathways, reactions of inflammation, apoptosis processes, and promote neuronal integrity. To know the mechanisms of action of TH will allow a better understanding about the indications for this therapy and the possibility of searching for other therapies when used in conjunction with hypothermia will provide a therapeutic synergistic effect.

Hypothermia as a cytoprotective strategy in ischemic tissue injury

Hypothermia is a well established cytoprotectant, with remarkable and consistent effects demonstrated across multiple laboratories. At the clinical level, it has recently been shown to improve neurological outcome following cardiac arrest and neonatal hypoxia-ischemia. It is increasingly being embraced by the medical community, and could be considered an effective neuroprotectant. Conditions such as brain injury, hepatic encephalopathy and cardiopulmonary bypass seem to benefit from this intervention. It's role in direct myocardial protection is also being explored. A review of the literature has demonstrated that in order to appreciate the maximum benefits of hypothermia, cooling needs to begin soon after the insult, and maintained for relatively long period periods of time. In the case of ischemic stroke, cooling should ideally be applied in conjunction with the re-establishment of cerebral perfusion. Translating this to the clinical arena can be challenging, given the technical challenges of rapidly and stably cooling patients. This review will discuss the application of hypothermia especially as it pertains to its effects neurological outcome, cooling methods, and important parameters in optimizing hypothermic protection.

The c-Jun N-terminal kinase (JNK) inhibitor XG-102 enhances the neuroprotection of hyperbaric oxygen after cerebral ischaemia in adult rats

AIM

Both hyperbaric oxygenation (HBO) and inhibition of the c-Jun N-terminal kinases (JNKs) by the peptide inhibitor XG-102 (D-JNKI-1) are efficient protective strategies against ischaemia-induced neurodegeneration. The present study investigated whether the combination of HBO and JNK inhibitor, XG-102, provides additive neuroprotection against cerebral ischaemia.

METHODS

Rat middle cerebral artery was occluded (MCAO) for 90 min. XG-102 [2 mg/kg, intraperitoneally] or HBO (3 ATA, 60 min) was applied 3 h after the onset of MCAO. For the combination treatment, HBO was started 10 min after the injection of XG-102. Twenty-four hours after MCAO, the infarct area, the neurological score and the immunohistochemistry staining in brain slices for cleaved-PARP, transferase-mediated biotinylated UTP nick end labelling, c-Jun and phosphorylated (activated) c-Jun were observed.

RESULTS

XG-102 or HBO alone reduced the total infarct area by 43% and 63%, respectively. The combination diminished total infarct area by 78%, improved the neurological function and reduced brain oedema. Co-application of HBO and XG-102 also significantly reduced the cleavage of PARP, by 96% and 91% in cortical penumbra and ischaemic core, respectively. Moreover, cotreatment significantly attenuated the number of cells labelled with transferase-mediated biotinylated UTP nick end labelling and phosphorylated c-Jun.

CONCLUSION

Our study demonstrates that HBO reinforces the efficiency of neuroprotective drugs such as XG-102 and vice versa. Both treatments, physical HBO and pharmacological XG-102, are already in phase I/II studies and promising strategies for clinical use.

Neuroprotective effects of group II metabotropic glutamate receptor agonist DCG-IV on hippocampal neurons in transient forebrain ischemia

Activation of group II metabotropic glutamate receptor (mGluR) inhibits the excessive release of glutamate that may be crucial in the pathogenesis of cerebral ischemia. This study investigated the protective effects of the group II mGluR agonist (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG-IV), against cerebral ischemia by examining extracellular glutamate concentration ([Glu]e) and neuronal damage in a rat model of transient forebrain ischemia. Cerebral ischemia was induced by 5 min of bilateral carotid artery occlusion and hypotension. DCG-IV (10, 100, or 250 pmol) was administered into the lateral ventricle four times every 12 h from 36 h before the start of ischemia, or administered intraperitoneally (40 micromol/kg) 24 h before ischemia, and the effect of the group II mGluR antagonist (LY341495) was also examined. [Glu]e in the CA1 subfield was measured by microdialysis during the peri-ischemic period, and the survival rate of CA1 neurons was evaluated 5 days after ischemia. [Glu]e increased significantly after cerebral ischemia and reached the maximum at 1 min after reperfusion, then gradually decreased and returned to the preischemic level in the vehicle group. The intraventricular injection of DCG-IV (250 pmol) significantly attenuated the [Glu]e increase and significantly increased the survival rate of CA1 neurons. Co-injection of LY341495 reversed the protective effects of DCG-IV. These results suggest that pretreatment with DCG-IV has neuroprotective effects against ischemic neuronal injuries through the inhibition of the glutamate release via the activation of group II mGluR.

Early brain temperature elevation and anaerobic metabolism in human acute ischaemic stroke

Early after acute ischaemic stroke, elevation of brain temperature might augment tissue metabolic rate and conversion of ischaemic but viable tissue to infarction. This might explain the observed link between pyrexia, severe stroke and poor outcome. We tested this hypothesis by measuring brain temperature and lactate concentration with multi-voxel magnetic resonance spectroscopic imaging across the acute ischaemic stroke lesion and normal brain as determined on diffusion imaging. We compared patterns of lactate concentration (reported in 'institutional units') and temperature elevation in diffusion lesion core, potential penumbra, ipsilateral and contralateral normal brain and with stroke severity. Amongst 40 patients with moderate to severe acute stroke imaged up to 26 h after onset, lactate concentration was highest in the ischaemic lesion core (42 versus 26 units in potential penumbra, P < 0.05), whereas temperature was highest in the potential penumbra (37.7 versus 37.3 degrees C in lesion core, P < 0.05). Neither sub-regional temperature nor lactate concentration correlated with stroke severity. With increasing time after stroke, ipsilateral brain temperature did not change, but contralateral hemisphere temperature was higher in patients scanned at later times; lactate remained elevated in the lesion core, but declined in potential penumbral and ipsilateral normal tissue at later times. We conclude that early brain temperature elevation after stroke is not directly related to lactate concentration, therefore augmented metabolism is unlikely to explain the relationship between early pyrexia, severe stroke and poor outcome. Early brain temperature elevation may result from different mechanisms to those which raise body temperature after stroke. Further studies are required to determine why early brain temperature elevation is highest in potential penumbral tissue.

Preliminary evidence of cannabinoid effects on brain-derived neurotrophic factor (BDNF) levels in humans

BACKGROUND

Acute and chronic exposure to cannabinoids has been associated with cognitive deficits, a higher risk for schizophrenia and other drug abuse. However, the precise mechanism underlying such effects is not known. Preclinical studies suggest that cannabinoids modulate brain-derived neurotrophic factor (BDNF). Accordingly, we hypothesized that Delta(9)-tetrahydrocannabinol (Delta(9)-THC), the principal active component of cannabis, would alter BDNF levels in humans.

MATERIALS AND METHODS

Healthy control subjects (n = 14) and light users of cannabis (n = 9) received intravenous administration of (0.0286 mg/kg) Delta(9)-THC in a double-blind, fixed order, placebo-controlled, laboratory study. Serum sampled at baseline, after placebo administration, and after Delta(9)-THC administration was assayed for BDNF using ELISA.

RESULTS

Delta(9)-THC increased serum BDNF levels in healthy controls but not light users of cannabis. Further, light users of cannabis had lower basal BDNF levels. Delta(9)-THC produced psychotomimetic effects, perceptual alterations, and "high" and spatial memory impairments.

IMPLICATIONS

The effects of socially relevant doses of cannabinoids on BDNF suggest a possible mechanism underlying the consequences of exposure to cannabis. This may be of particular importance for the developing brain and also in disorders believed to involve altered neurodevelopment such as schizophrenia. Larger studies to investigate the effects of cannabinoids on BDNF and other neurotrophins are warranted.

Combination therapy with hypothermia for treatment of cerebral ischemia

Mild hypothermia is an established neuroprotectant in the laboratory, showing remarkable and consistent effects across multiple laboratories and models of brain injury. At the clinical level, mild hypothermia has shown benefits in patients who have suffered cardiac arrest and in some pediatric populations suffering hypoxic brain insults. However, a review of the literature has demonstrated that in order to appreciate the maximum benefits of hypothermia, brain cooling needs to begin soon after the insult, maintained for relatively long period periods of time, and, in the case of ischemic stroke, should be applied in conjunction with the re-establishment of cerebral perfusion. Translating this to the clinical arena can be challenging, especially rapid cooling and the re-establishment of perfusion. The addition of a second neuroprotectant could potentially (1) enhance overall protection, (2) prolong the temporal therapeutic window for hypothermia, or (3) provide protection where hypothermic treatment is only transient. Combination therapies resulting in recanalization following ischemic stroke would improve the likelihood of a good outcome, as the experimental literature suggests more consistent neuroprotection against ischemia with reperfusion, than ischemia without. Since recombinant tissue plasiminogen activator (rt-PA) is the only FDA approved treatment for acute ischemic stroke, and acts to recanalize occluded vessels, it is an obvious initial strategy to combine with hypothermia. However, the effects of thrombolytics are also temperature dependent, and the risk of hemorrhage is significant. The experimental data nevertheless seem to favor a combinatorial approach. Thus, in order to apply hypothermia to a broader range of patients, combination strategies should be further investigated.

Delay to Diagnosis in Acute Pediatric Arterial Ischemic Stroke

Background and Purpose— For the clinician, the diagnosis of arterial ischemic stroke (AIS) in children is a challenge. Prompt diagnosis of pediatric AIS within 6 hours enables stroke-specific thrombolytic and neuroprotective strategies.

Methods— We conducted a retrospective study of prospectively enrolled consecutive cohort of children with AIS, admitted to The Hospital for Sick Children, Toronto, from January 1992 to December 2004. The data on clinical presentation, symptom onset, emergency department arrival, neuroimaging and stroke diagnosis were recorded. The putative predictors of delayed diagnosis were selected a priori for analysis.

Results— A total of 209 children with AIS were studied. The median interval from symptom onset to AIS diagnosis was 22.7 hours (interquartile range: 7.1 to 57.7 hours), prehospital delay (symptom onset to hospital arrival) was 1.7 hours (interquartile range: 49 minutes to 8.1 hours), and the in-hospital delay (presentation to diagnosis) was 12.7 hours (interquartile range: 4.5 to 33.5 hours). The initial assessment was completed in 16 minutes and initial neuroimaging in 8.8 hours. The diagnosis of AIS was suspected on initial assessment in 79 (38%) children and the initial neuroimaging diagnosed AIS in 47%. The parent’s help seeking action, nonabrupt onset of symptoms, altered consciousness, milder stroke severity, posterior circulation infarction and lack of initial neuroimaging at a tertiary hospital were predictive delayed AIS diagnosis.

Conclusion— In the diagnosis of AIS, significant prehospital and in-hospital delays exist in children. Several predictors of the delayed AIS diagnosis were identified in the present study. Efforts to target these predictors can reduce diagnostic delays and optimize the management of AIS in children.

Continuous decrease in serum brain-derived neurotrophic factor (BDNF) levels in a neuropsychiatric syndrome of systemic lupus erythematosus patient with organic brain changes

In the present study, the authors reported on a case in neuropsychiatric syndromes of systemic lupus erythematosus (NPSLE) with irreversible organic brain changes. The authors also longitudinally investigated serum brain-derived neurotrophic factor (BDNF) levels in the patient. We found that serum BDNF levels in the NPSLE patient with irreversible organic brain change were consistently low, independent of the severity of psychiatric symptoms. Thus, the longitudinal measurement of serum BDNF levels might be useful in predicting the prognosis of NPSLE.

A broadly neuroprotective derivative of curcumin

The plant polyphenolic curcumin alters the response of nerve cells to some forms of toxic stress. The steroid-like compound, cyclohexyl bisphenol A, has broad neuroprotective properties that are very distinct from those of curcumin. To incorporate both families of biological activities into a single molecule, a pyrazole derivative of curcumin, called CNB-001, was synthesized. CNB-001 acquires a new activity and is far superior in neuroprotection assays to either parental molecule, but retains some of the properties of both. It is neuroprotective in cell culture assays for trophic factor withdrawal, oxidative stress, excitotoxicity, and glucose starvation, as well as toxicity from both intracellular and extracellular amyloid. While the creation of CNB-001 was based upon an uncommon approach to drug design, it has the potential of a lead drug candidate for treating multiple conditions involving nerve cell death.

BDNF plasma levels in acute stroke

The transport of brain derived neurotrophic factor (BDNF) across the blood-brain barrier (BBB) is negligible in normal conditions. However, BDNF might pass through the BBB when BBB is disrupted by a pathological condition such as stroke. This migration of BDNF through the BBB might be important during post-ischemic phase since BDNF can exert a protective action in the site of lesion. This study aimed to investigate plasma levels of BDNF in the acute phase of stroke in humans. Serial venous blood samples were taken in ten patients with acute stroke at the admission to the Stroke Unit and on the following 4 days. In the same samples we also evaluated the plasma levels of S100beta protein, a marker of BBB disruption. There was no significant change in BDNF plasma levels in our patients, even in the presence of a pronounced BBB dysfunction, as demonstrated by a significant increase of S100beta protein concentrations at days 2 and 3 after stroke. Our data, though indirectly, suggest that there is no significant increase in endogenous extracellular BDNF after a stroke in humans.

Apoptosis: Future Targets for Neuroprotective Strategies

Focal permanent or transient cerebral artery occlusion produces massive cell death in the central core of the infarction, whereas in the peripheral zone (penumbra) nerve cells are subjected to various determining survival and death signals. Cell death in the core of the infarction and in the adult brain is usually considered a passive phenomenon, although events largely depend on the partial or complete disruption of crucial metabolic pathways. Cell death in the penumbra is currently considered an active process largely dependent on the activation of cell death programs leading to apoptosis. Yet cell death in the penumbra includes apoptosis, necrosis, intermediate and other forms of cell death. A rather simplistic view implies poor prospects regarding cell survival in the core of the infarction and therapeutic expectations in the control of cell death and cell survival in the penumbra. However, the capacity for neuroprotection depends on multiple factors, primarily the use of the appropriate agent, at the appropriate time and during the appropriate interval. Understanding the mechanisms commanding cell death and survival area is as important as delimiting the therapeutic time window and the facility of a drug to effectively impact on specific targets. Moreover, the detrimental effects of homeostasis and the activation of multiple pathways with opposing signals following ischemic stroke indicate that better outcome probably does not depend on a single compound but on several drugs acting in combination at the optimal time in a particular patient.

Toward a Multimodal Neuroprotective Treatment of Stroke

Background and Purpose— Stroke remains a common medical problem with importance attributable to the demographic changes in industrialized societies.

Summary of Review— After years of setbacks, acute stroke therapy has finally emerged, including thrombolysis with tissue plasminogen activator (t-PA). However, t-PA treatment is limited by a narrow time window and side effects, so that only 3% of all stroke patients receive thrombolysis. Unimodal targeting of key events in stroke pathophysiology was not effective in providing long-term benefits, leading to negative results in previous clinical neuroprotective stroke trials. A successful future stroke therapy should approach multiple pathophysiological mechanisms besides revascularization at once, including reduction of t-PA–related side effects, prevention of cell death, stimulation of neuroregeneration, and plasticity.

Conclusions— Strategies targeting these processes include multiple combination therapies as well as treatment with multimodal drugs that interact with these mechanisms. Here, we review such combination approaches, and outline how this concept could be developed into future stroke treatment.

Intraventricular nerve growth factor infusion: a possible treatment for neurological deficits following hypoxic-ischemic brain injury in infants

OBJECTIVE AND IMPORTANCE

Hypoxic-ischemic brain injuries in childhood are associated with poor neurological outcome. Unfortunately, no new therapeutic approaches have been proposed. Recently, animal studies show that nerve growth factor (NGF) can reduce neurological deficits following hypoxic-ischemic brain injuries. The objective of this study is to demonstrate the therapeutic effects of intraventricular NGF infusion in severe post-ischemic damage.

CLINICAL PRESENTATION

Two infants, aged 9 and 8 months, with hypoxic-ischemic brain damage, secondary to prolonged cardiorespiratory arrest and stabilized after the conventional treatment, were treated with intraventricular NGF infusion. Before the therapy both infants were comatose with asymmetrical tetraparesis; their Glasgow Coma Scale (GCS) was 4 and 5, respectively. One month after the treatment, their GCS was 8 and 9, respectively. EEG examinations performed after the NGF infusion showed an increased alpha/theta ratio. MRI showed a reduction of malacic areas in the brain. A SPECT study, performed only in one infant, demonstrated that the NGF treatment resulted in an improvement of regional cerebral perfusion in right temporal and occipital cortices.

INTERVENTION

The drug utilized was 2.5S NGF purified and lyophilized from male mouse submaxillary glands. NGF infusion was started about 30 days after the hypoxic-ischemic brain injury. 0.1 mg NGF was administered via the external drainage catheter into the right cerebral ventricle once a day for 10 days consecutively.

CONCLUSION

Our observations are interesting, but further studies are necessary to confirm the effects of NGF in hypoxic-ischemic brain injuries in infants.

Neuroprotective effect of N-acetyl-aspartyl-glutamate in combination with mild hypothermia in the endothelin-1 rat model of focal cerebral ischaemia

Previously we showed that treatment with mild hypothermia (34 degrees C for 2 h) after a focal cerebral infarct was neuroprotective by reducing apoptosis in the penumbra (cortex), but not in the core (striatum) of the infarct. In this study we examined whether administration of N-acetyl-aspartyl-glutamate (NAAG) in combination with mild hypothermia could improve striatal neuroprotection in the endothelin-1 rat model. NAAG (10 mg/kg i.p.) was injected under normothermic (37 degrees C) or mild hypothermic conditions, either 40 min before or 20 min after the insult. NAAG reduced caspase 3 immunoreactivity in the striatum, irrespective of the time of administration and brain temperature. This neuroprotective effect could be explained, at least partially, by decreased nitric oxide synthase activity in the striatum and was blocked by the group II metabotropic glutamate receptor antagonist, LY341495. Hypothermia applied together with NAAG reduced both cortical and striatal caspase 3 immunoreactivity, as well as the overall ischaemic damage in these areas. However, no pronounced improvement was seen in total damaged brain volume. Extracellular glutamate levels did not correlate with the observed protection, whatever treatment protocol was applied. We conclude that treatment with NAAG causes the same degree of neuroprotection as treatment with hypothermia. Combination of the two treatments, although reducing apoptosis, does not considerably improve ischaemic damage.

Local brain hypothermia for neuroprotection in stroke treatment and aneurysm repair

Hypothermia is well known to provide neuroprotection following various brain insults in experimental animals. Two recently completed clinical trials of whole body hypothermia in out-of-hospital cardiac arrest patients' demonstrated significantly improved survival rates and neurologic outcomes. These results provide new excitement and encouragement for clinical application of hypothermia in cerebrovascular disease. However, the intensive care challenges and adverse events (e.g. prolonged times to target temperatures, shivering and sedation, pneumonia) during the management of hypothermia, dampen enthusiasm for widespread application especially in elderly stroke patients. In this manuscript, we review recent hypothermia trials for stroke. We describe an alternate approach, i.e. local brain cooling, and discuss this new technique with reference to the extensive literature on the marked efficacy of hypothermia. We describe a new technology, the ChillerPad(TM) and ChillerStrip(TM) Systems developed by Seacoast Technologies, Inc. (Portsmouth, NH, USA). The latter device has received FDA approval and will be employed in a trial of local hypothermia for cerebral aneurysm repair. We present our experimental findings that profound local hypothermia does not damage cortical neurons. We also report that local hypothermia protects the blood-brain barrier and markedly reduces vasogenic edema development in an experimental intracerebral hemorrhage model. Lastly, we review potential mechanisms through which hypothermia provides blood-brain barrier protection and reduces edema formation. Clearly, hypothermia has a bright future for cerebrovascular disease treatment if brain cooling can be delivered in a manner that does not compromise the patient or the neurosurgical and intensive care settings. Local brain cooling may be just that new treatment approach.