A two-hour window for hypothermic modulation of early events that impact delayed opening of the rat blood-brain barrier after ischemia

Brain organoids for hypoxic-ischemic studies: from bench to bedside

Our current knowledge regarding the development of the human brain mostly derives from experimental studies on non-human primates, sheep, and rodents. However, these studies may not completely simulate all the features of human brain development as a result of species differences and variations in pre- and postnatal brain maturation. Therefore, it is important to supplement the in vivo animal models to increase the possibility that preclinical studies have appropriate relevance for potential future human trials. Three-dimensional brain organoid culture technology could complement in vivo animal studies to enhance the translatability of the preclinical animal studies and the understanding of brain-related disorders. In this review, we focus on the development of a model of hypoxic-ischemic (HI) brain injury using human brain organoids to complement the translation from animal experiments to human pathophysiology. We also discuss how the development of these tools provides potential opportunities to study fundamental aspects of the pathophysiology of HI-related brain injury including differences in the responses between males and females.

Nonphosphorylating Oxidation in Mitochondria and Related Processes

The mechanism of oxidative phosphorylation and its regulation remain one of the main problems of bioenergetics. Efficiency of the mitochondrial energization is determined by the relationship between the rate of generation of electrochemical potential of hydrogen ions and the rate of its expenditure on the synthesis of ATP and the use of ATP in endergonic reactions. Uncoupling (partial or complete), which occurs in the process of uncontrolled and controlled leakage of ions through the inner mitochondrial membrane, on the one hand leads to the decrease in the relative synthesis of ATP, and on the other, being consistent with the law of conservation of energy, leads to the formation of heat, generation of which is an essential function of the organism. In addition to increased thermogenesis, the increase of non-phosphorylating oxidation of various substrates is accompanied by the decrease in transmembrane potential, production of reactive oxygen species, and activation of oxygen consumption, water and carbon dioxide production, increase in the level of intracellular ADP and acidification of the cytosol. In this analysis, each of these factors will be considered separately for its role in regulating metabolism.

Comparison of Neuronal Death, Blood-Brain Barrier Leakage and Inflammatory Cytokine Expression in the Hippocampal CA1 Region Following Mild and Severe Transient Forebrain Ischemia in Gerbils

Transient ischemia in the brain causes blood-brain barrier (BBB) breakdown and dysfunction, which is related to ischemia-induced neuronal damage. Leakage of plasma proteins following transient ischemia is one of the indicators that is used to determine the extent of BBB dysfunction. In this study, neuronal damage/death, leakage of albumin and IgG, microgliosis, and inflammatory cytokine expression were examined in the hippocampal CA1 region, which is vulnerable to transient ischemia, following 5-min (mild) and 15-min (severe) ischemia in gerbils induced by transient common carotid arteries occlusion (tCCAo). tCCAo-induced neuronal damage/death occurred earlier and was more severe after 15-min tCCAo vs. after 5-min tCCAo. Significant albumin and IgG leakage (albumin and IgG immunoreactivity) took 1 or 2 days to begin, and immunoreactivity was markedly increased 5 days after 5-min tCCAo. While, albumin and IgG leakage began to increase 6 h after 15-min tCCAo and remained significantly higher over time than that seen in 5-min tCCAo. IgG immunoreactivity was observed in degenerating neurons and activated microglia after tCCAo, and microglia were activated to a greater extent after 15-min tCCAo than 5-min tCCAo. In addition, following 15-min tCCAo, pro-inflammatory cytokines [tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β)] immunoreactivity was significantly higher than that seen following 5-min tCCAo, whereas immunoreactivity of anti-inflammatory cytokines (IL-4 and IL-13) was lower in 15-min than 5-min tCCAo. These results indicate that duration of tCCAo differentially affects the timing and degree of neuronal damage or loss, albumin and IgG leakage and inflammatory cytokine expression in brain tissue. In addition, more severe BBB leakage is closely related to acceleration of neuronal damage through increased microglial activation and pro-inflammatory cytokine expression in the ischemic hippocampal CA1 region.

Hypoxic-ischemic-related cerebrovascular changes and potential therapeutic strategies in the neonatal brain

Perinatal hypoxic-ischemic (HI)-related brain injury is an important cause of morbidity and long-standing disability in newborns. The only currently approved therapeutic strategy available to reduce brain injury in the newborn is hypothermia. Therapeutic hypothermia can only be used to treat HI encephalopathy in full-term infants and survivors remain at high risk for a wide spectrum of neurodevelopmental abnormalities as a result of residual brain injury. Therefore, there is an urgent need for adjunctive therapeutic strategies. Inflammation and neurovascular damage are important factors that contribute to the pathophysiology of HI-related brain injury and represent exciting potential targets for therapeutic intervention. In this review, we address the role of each component of the neurovascular unit (NVU) in the pathophysiology of HI-related injury in the neonatal brain. Disruption of the blood-brain barrier (BBB) observed in the early hours after an HI-related event is associated with a response at the basal lamina level, which comprises astrocytes, pericytes, and immune cells, all of which could affect BBB function to further exacerbate parenchymal injury. Future research is required to determine potential drugs that could prevent or attenuate neurovascular damage and/or augment repair. However, some studies have reported beneficial effects of hypothermia, erythropoietin, stem cell therapy, anti-cytokine therapy and metformin in ameliorating several different facets of damage to the NVU after HI-related brain injury in the perinatal period.

Rhythmic light flicker rescues hippocampal low gamma and protects ischemic neurons by enhancing presynaptic plasticity

The complex relationship between specific hippocampal oscillation frequency deficit and cognitive dysfunction in the ischemic brain is unclear. Here, using a mouse two-vessel occlusion (2VO) cerebral ischemia model, we show that visual stimulation with a 40 Hz light flicker drove hippocampal CA1 slow gamma and restored 2VO-induced reduction in CA1 slow gamma power and theta-low gamma phase-amplitude coupling, but not those of the high gamma. Low gamma frequency lights at 30 Hz, 40 Hz, and 50 Hz, but not 10 Hz, 80 Hz, and arrhythmic frequency light, were protective against degenerating CA1 neurons after 2VO, demonstrating the importance of slow gamma in cognitive functions after cerebral ischemia. Mechanistically, 40 Hz light flicker enhanced RGS12-regulated CA3-CA1 presynaptic N-type calcium channel-dependent short-term synaptic plasticity and associated postsynaptic long term potentiation (LTP) after 2VO. These results support a causal relationship between CA1 slow gamma and cognitive dysfunctions in the ischemic brain.

Therapeutic Hypothermia and Neuroprotection in Acute Neurological Disease

Therapeutic hypothermia has consistently been shown to be a robust neuroprotectant in many labs studying different models of neurological disease. Although this therapy has shown great promise, there are still challenges at the clinical level that limit the ability to apply this routinely to each pathological condition. In order to overcome issues involved in hypothermia therapy, understanding of this attractive therapy is needed. We review methodological concerns surrounding therapeutic hypothermia, introduce the current status of therapeutic cooling in various acute brain insults, and review the literature surrounding the many underlying molecular mechanisms of hypothermic neuroprotection. Because recent work has shown that body temperature can be safely lowered using pharmacological approaches, this method may be an especially attractive option for many clinical applications. Since hypothermia can affect multiple aspects of brain pathophysiology, therapeutic hypothermia could also be considered a neuroprotection model in basic research, which would be used to identify potential therapeutic targets. We discuss how research in this area carries the potential to improve outcome from various acute neurological disorders.

Association between the simultaneous decrease in the levels of soluble vascular cell adhesion molecule-1 and S100 protein and good neurological outcomes in cardiac arrest survivors

OBJECTIVE

This study aimed to determine whether simultaneous decreases in the serum levels of cell adhesion molecules (intracellular cell adhesion molecule-1 [ICAM-1], vascular cell adhesion molecule-1 [VCAM-1], and E-selectin) and S100 proteins within the first 24 hours after the return of spontaneous circulation were associated with good neurological outcomes in cardiac arrest survivors.

METHODS

This retrospective observational study was based on prospectively collected data from a single emergency intensive care unit (ICU). Twenty-nine out-of-hospital cardiac arrest survivors who were admitted to the ICU for post-resuscitation care were enrolled. Blood samples were collected at 0 and 24 hours after ICU admission. According to the 6-month cerebral performance category (CPC) scale, the patients were divided into good (CPC 1 and 2, n=12) and poor (CPC 3 to 5, n=17) outcome groups.

RESULTS

No difference was observed between the two groups in terms of the serum levels of ICAM-1, VCAM-1, E-selectin, and S100 at 0 and 24 hours. A simultaneous decrease in the serum levels of VCAM-1 and S100 as well as E-selectin and S100 was associated with good neurological outcomes. When other variables were adjusted, a simultaneous decrease in the serum levels of VCAM-1 and S100 was independently associated with good neurological outcomes (odds ratio, 9.285; 95% confidence interval, 1.073 to 80.318; P=0.043).

CONCLUSION

A simultaneous decrease in the serum levels of soluble VCAM-1 and S100 within the first 24 hours after the return of spontaneous circulation was associated with a good neurological outcome in out-of-hospital cardiac arrest survivors.

Effect of Adipose-Derived Mesenchymal Stem Cell Administration and Mild Hypothermia Induction on Delayed Neuronal Death After Transient Global Cerebral Ischemia

OBJECTIVES

Global cerebral ischemia is a cause of poor prognosis after resuscitation from cardiac arrest. Various attempts have been made to minimize global cerebral ischemia but none been more effective than mild hypothermia induction. A few studies have shown the effect of mesenchymal stem cells on global cerebral ischemia, but no studies have compared this effect with mild hypothermia or assessed any possible interaction. We aimed to show the effect of mesenchymal stem cells on delayed neuronal death after global cerebral ischemia and to compare this effect with mild hypothermia.

DESIGN

Experimental study.

SETTING

Animal research laboratory.

SUBJECTS

Adult male Sprague-Dawley rats weighing 250-300 g.

INTERVENTIONS

Rats were subjected to 7 minutes of transient global cerebral ischemia and randomized into four groups: control, mild hypothermia, injection of human adipose-derived mesenchymal stem cells, and combined application of mild hypothermia and mesenchymal stem cells, along with four sham groups treated identically. Rats were euthanized 7 days after global cerebral ischemia.

MEASUREMENTS AND MAIN RESULTS

Degree of neuronal death in hippocampus was significantly higher in control than in other groups. The number of activated microglia was higher in control group than in other groups and was higher in mild hypothermia than shams, mesenchymal stem cells, mild hypothermia/mesenchymal stem cells. Degree of blood-brain barrier disruption and the count of infiltrated neutrophils were significantly higher in control than in other groups. Degree of oxidative injury was significantly higher in control than other groups. It was higher in mild hypothermia than sham groups, mesenchymal stem cells, mild hypothermia/mesenchymal stem cells and was higher in mesenchymal stem cells group than sham groups. Significantly, worse functional results were found in control than in other groups.

CONCLUSIONS

Administration of mesenchymal stem cells after transient global cerebral ischemia has a prominent protective effect on delayed neuron death, even compared with mild hypothermia.

Mild hypothermia alleviates brain oedema and blood-brain barrier disruption by attenuating tight junction and adherens junction breakdown in a swine model of cardiopulmonary resuscitation

Mild hypothermia improves survival and neurological recovery after cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). However, the mechanism underlying this phenomenon is not fully elucidated. The aim of this study was to determine whether mild hypothermia alleviates early blood-brain barrier (BBB) disruption. We investigated the effects of mild hypothermia on neurologic outcome, survival rate, brain water content, BBB permeability and changes in tight junctions (TJs) and adherens junctions (AJs) after CA and CPR. Pigs were subjected to 8 min of untreated ventricular fibrillation followed by CPR. Mild hypothermia (33°C) was intravascularly induced and maintained at this temperature for 12 h, followed by active rewarming. Mild hypothermia significantly reduced cortical water content, decreased BBB permeability and attenuated TJ ultrastructural and basement membrane breakdown in brain cortical microvessels. Mild hypothermia also attenuated the CPR-induced decreases in TJ (occludin, claudin-5, ZO-1) and AJ (VE-cadherin) protein and mRNA expression. Furthermore, mild hypothermia decreased the CA- and CPR-induced increases in matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF) expression and increased angiogenin-1 (Ang-1) expression. Our findings suggest that mild hypothermia attenuates the CA- and resuscitation-induced early brain oedema and BBB disruption, and this improvement might be at least partially associated with attenuation of the breakdown of TJ and AJ, suppression of MMP-9 and VEGF expression, and upregulation of Ang-1 expression.

Therapeutic hypothermia protocols

The application of targeted temperature management has become common practice in the neurocritical care setting. It is important to recognize the pathophysiologic mechanisms by which temperature control impacts acute neurologic injury, as well as the clinical limitations to its application. Nonetheless, when utilizing temperature modulation, an organized approach is required in order to avoid complications and minimize side-effects. The most common clinically relevant complications are related to the impact of cooling on hemodynamics and electrolytes. In both instances, the rate of complications is often related to the depth and rate of cooling or rewarming. Shivering is the most common side-effect of hypothermia and is best managed by adequate monitoring and stepwise administration of medications specifically targeting the shivering response. Due to the impact cooling can have upon pharmacokinetics of commonly used sedatives and analgesics, there can be significant delays in the return of the neurologic examination. As a result, early prognostication posthypothermia should be avoided.

Cell-Permeable Peptide Targeting the Nrf2-Keap1 Interaction: A Potential Novel Therapy for Global Cerebral Ischemia

The current study examined efficacy of a small Tat (trans-activator of transcription)-conjugated peptide activator of the Nrf2 (nuclear factor-E2-related factor-2) antioxidant/cell-defense pathway as a potential injury-specific, novel neuroprotectant against global cerebral ischemia (GCI). A competitive peptide, DEETGE-CAL-Tat, was designed to facilitate Nrf2 activation by disrupting interaction of Nrf2 with Keap1 (kelch-like ECH-associated protein 1), a protein that sequesters Nrf2 in the cytoplasm and thereby inactivates it. The DEETGE-CAL-Tat peptide contained the critical sequence DEETGE for the Nrf2-Keap1 interaction, the cell transduction domain of the HIV-Tat protein, and the cleavage sequence of calpain, which is sensitive to Ca(2+) increase and allows injury-specific activation of Nrf2. Using an animal model of GCI, we demonstrated that pretreatment with the DEETGE-CAL-Tat peptide markedly decreased Nrf2 interaction with Keap1 in the rat hippocampal CA1 region after GCI, and enhanced Nrf2 nuclear translocation and DNA binding. The DEETGE-CAL-Tat peptide also induced Nrf2 antioxidant/cytoprotective target genes, reduced oxidative stress, and induced strong neuroprotection and marked preservation of hippocampal-dependent cognitive function after GCI. These effects were specific as control peptides lacked neuroprotective ability. Intriguingly, the DEETGE-CAL-Tat peptide effects were also injury specific, as it had no effect upon neuronal survival or cognitive performance in sham nonischemic animals. Of significant interest, peripheral, postischemia administration of the DEETGE-CAL-Tat peptide from days 1-9 after GCI also induced robust neuroprotection and strongly preserved hippocampal-dependent cognitive function. Based on its robust neuroprotective and cognitive-preserving effects, and its unique injury-specific activation properties, the DEETGE-CAL-Tat peptide represents a novel, and potentially promising new therapeutic modality for the treatment of GCI.

SIGNIFICANCE STATEMENT

The current study demonstrates that DEETGE-CAL-Tat, a novel peptide activator of a key antioxidant gene transcription pathway in the hippocampus after global cerebral ischemia, can exert robust neuroprotection and preservation of cognitive function. A unique feature of the peptide is that its beneficial effects are injury specific. This feature is attractive as it targets drug activation specifically in the site of injury, and likely would lead to a reduction of undesirable side effects if translatable to the clinic. Due to its injury-specific activation, robust neuroprotection, and cognitive-preserving effects, this novel peptide may represent a much-needed therapeutic advance that could have efficacy in the treatment of global cerebral ischemia.

Cornel iridoid glycoside reduces infarct size measured by magnetic resonance imaging and improves neurological function after focal cerebral ischemia in rats

OBJECTIVE

To investigate the effect of cornel iridoid glycoside (CIG), an ingredient extracted from traditional Chinese herb Cornus offificinalis, on neurological function and infarct size in rats as measured by magnetic resonance imaging (MRI) after ischemic stroke.

METHODS

Sprague-Dawley rats were divided into three group: control (n=11), model (n=20) and CIG (n=16) groups. Rats in the model and CIG groups underwent 90-min middle cerebral artery occlusion (MCAO) followed by reperfusion. Their neurological defect was measured by using a modified neurological severity score (mNSS). T2-weighted MRI (T2-MRI) of the brain was performed in vivo from 2 to 28 days after MCAO. The infarct volume in the brain was also measured using 2,3,5-triphenyltetrazolium chloride (TTC) staining 28 days after stroke.

RESULTS

CIG, 60 mg/(kg day), administered by oral gavage starting from 6 h after the onset of MCAO improved neurological function at 7, 14, 21, and 28 days post occlusion (P<0.05 orP<0.01) and decreased mortality. The infarct volumes computed from the T2-MR images were reduced in the CIG-treated group compared with the model group at 7, 14 and 28 days after MCAO (P<0.05); and the rate at which the infarct volume decreased from 2 to 28 days was higher in the CIG-treated group than that in the model group (P<0.05). The infarct volumes measured by TTC staining were also decreased 28 days after stroke (P<0.05).

CONCLUSION

CIG treatment, starting from 6 h after MCAO, reduced infarct size in the brain as measured by MRI and improved neurological function 2-28 days after focal cerebral ischemia in rats, suggesting that CIG could be a clinical application in improving stroke treatment.

Adipose-derived mesenchymal stem cells reduce neuronal death after transient global cerebral ischemia through prevention of blood-brain barrier disruption and endothelial damage

Global cerebral ischemia (GCI) is the leading cause of a poor prognosis even after successful resuscitation from cardiac arrest. Therapeutic induction of hypothermia (TH) is the only proven therapy-and current standard care-for GCI after cardiac arrest; however, its application has been significantly limited owing to technical difficulties. Mesenchymal stem cells (MSCs) are known to suppress neuronal death after cerebral ischemia. The prevention of blood-brain barrier (BBB) disruption has not been suggested as a mechanism of MSC treatment but has for TH. We evaluated the therapeutic effect of MSC administration on BBB disruption and neutrophil infiltration after GCI. To evaluate the therapeutic effects of MSC treatment, rats were subjected to 7 minutes of transient GCI and treated with MSCs immediately after reperfusion. Hippocampal neuronal death was evaluated at 7 days after ischemia using Fluoro-Jade B (FJB). BBB disruption, endothelial damage, and neutrophil infiltration were evaluated at 7 days after ischemia by immunostaining for IgG leakage, Rat endothelial antigen-1, and myeloperoxidase (MPO). Rats treated with MSCs showed a significantly reduced FJB+ neuron count compared with the control group. They also showed reduced IgG leakage, endothelial damage, and MPO+ cell counts. The present study demonstrated that administration of MSCs after transient GCI provides a dramatic protective effect against hippocampal neuronal death. We hypothesized that the neuroprotective effects of MSC treatment might be associated with the prevention of BBB disruption and endothelial damage and a decrease in neutrophil infiltration.

The importance of temperature on the neurovascular unit

Therapeutic hypothermia is the only treatment that has been shown to be of benefit to infant's ≥ 36 weeks of gestation with hypoxic-ischemic encephalopathy. The evidence for the benefit is based on multiple, well-designed randomized clinical trials. Based on this data, the use of therapeutic hypothermia has been widely disseminated throughout the neonatal community. An important concept in hypoxic-ischemic brain injury is the functioning of the neurovascular unit which links neurons, non-neuronal cellular elements and the capillary endothelial cells to promote optimal barrier maintenance between the brain and systemic circulation, regulation of blood flow and neuro-immunologic functioning. Hypoxic-ischemic injury can trigger increased permeability of the blood-brain-barrier via molecular events within the neurovascular unit and initiate pathways to brain injury. In addition, exposure of the brain to cellular elements from the systemic circulation can further propagate the neuro-inflammatory response. The influence of temperature on injury to the neurovascular unit has received relatively little attention. This review will focus on one component of the neurovascular unit, the blood-brain barrier and its constituents. Specifically, this review will address the effects of hypoxia-ischemia and temperature on the neurovascular unit and potential knowledge gaps which may serve as areas for further investigation.

Rapamycin alleviates brain edema after focal cerebral ischemia reperfusion in rats

Brain edema is a major consequence of cerebral ischemia reperfusion. However, few effective therapeutic options are available for retarding the brain edema progression after cerebral ischemia. Recently, rapamycin has been shown to produce neuroprotective effects in rats after cerebral ischemia reperfusion. Whether rapamycin could alleviate this brain edema injury is still unclear. In this study, the rat stroke model was induced by a 1-h left transient middle cerebral artery occlusion using an intraluminal filament, followed by 48 h of reperfusion. The effects of rapamycin (250 μg/kg body weight, intraperitoneal; i.p.) on brain edema progression were evaluated. The results showed that rapamycin treatment significantly reduced the infarct volume, the water content of the brain tissue and the Evans blue extravasation through the blood-brain barrier (BBB). Rapamycin treatment could improve histological appearance of the brain tissue, increased the capillary lumen space and maintain the integrity of BBB. Rapamycin also inhibited matrix metalloproteinase 9 (MMP9) and aquaporin 4 (AQP4) expression. These data imply that rapamycin could improve brain edema progression after reperfusion injury through maintaining BBB integrity and inhibiting MMP9 and AQP4 expression. The data of this study provide a new possible approach for improving brain edema after cerebral ischemia reperfusion by administration of rapamycin.

Non-pharmaceutical therapies for stroke: mechanisms and clinical implications

Stroke is deemed a worldwide leading cause of neurological disability and death, however, there is currently no promising pharmacotherapy for acute ischemic stroke aside from intravenous or intra-arterial thrombolysis. Yet because of the narrow therapeutic time window involved, thrombolytic application is very restricted in clinical settings. Accumulating data suggest that non-pharmaceutical therapies for stroke might provide new opportunities for stroke treatment. Here we review recent research progress in the mechanisms and clinical implications of non-pharmaceutical therapies, mainly including neuroprotective approaches such as hypothermia, ischemic/hypoxic conditioning, acupuncture, medical gases and transcranial laser therapy. In addition, we briefly summarize mechanical endovascular recanalization devices and recovery devices for the treatment of the chronic phase of stroke and discuss the relative merits of these devices.

The mechanisms and treatment of asphyxial encephalopathy

Acute post-asphyxial encephalopathy occurring around the time of birth remains a major cause of death and disability. The recent seminal insight that allows active neuroprotective treatment is that even after profound asphyxia (the “primary” phase), many brain cells show initial recovery from the insult during a short “latent” phase, typically lasting approximately 6 h, only to die hours to days later after a “secondary” deterioration characterized by seizures, cytotoxic edema, and progressive failure of cerebral oxidative metabolism. Although many of these secondary processes are potentially injurious, they appear to be primarily epiphenomena of the “execution” phase of cell death. Animal and human studies designed around this conceptual framework have shown that moderate cerebral hypothermia initiated as early as possible but before the onset of secondary deterioration, and continued for a sufficient duration to allow the secondary deterioration to resolve, has been associated with potent, long-lasting neuroprotection. Recent clinical trials show that while therapeutic hypothermia significantly reduces morbidity and mortality, many babies still die or survive with disabilities. The challenge for the future is to find ways of improving the effectiveness of treatment. In this review, we will dissect the known mechanisms of hypoxic-ischemic brain injury in relation to the known effects of hypothermic neuroprotection.

Delayed administration of zingerone mitigates the behavioral and histological alteration via repression of oxidative stress and intrinsic programmed cell death in focal transient ischemic rats

The neuronal mitochondria succumb to ischemia-reperfusion injury and release huge amount of reactive oxygen species and ultimately lead the neurons to intrinsic pathway of programmed cell death (iPCD). The present study was undertaken to elucidate the ischemia-reperfusion-induced oxidative stress and molecular events in iPCD 24 h post ischemia-reperfusion injury and plausible mitigation by zingerone, a potent antioxidant of ginger rhizome. The right middle cerebral artery was occluded for 2 h followed by reperfusion for 22 hours. A maximum infarct volume (43.29%) and mitochondrial injury (56.99%) was observed in middle cerebral artery occlusion (MCAO) group. However, zingerone administration (50 and 100 mg/kg b.wt. orally twice) at 5 h and 12 h from initiation of MCAO showed a significant reduction in infarct volume and mitochondrial injury (p<0.001). Zingerone treatment significantly improved behavioral outputs (p<0.05) and histological architecture (p<0.001) by reducing lipid peroxidation (p<0.01), augmenting the reduced glutathione content (p<0.01) and restoring Na(+)-K(+) ATPase and superoxide dismutase activities (p<0.01) in MCAO brain. Zingerone successfully reduced the caspase-3 and -9 activities in MCAO group (p<0.05) and succeeded in lowering the expressions of pro-apoptotic proteins - Apaf-1 and Bax (p<0.001). The present study suggests that zingerone is a potent antioxidant that salvaged the ischemic penumbral zone neurons by inhibiting iPCD and oxidative stress.

Fundamental research progress of mild hypothermia in cerebral protection

Through the years, the clinical application of mild hypothermia has been carried out worldwide and is built from the exploration and cognition of neuroprotection mechanisms by hypothermia. However, within the last decade, extensive and fundamental researches in this area have been conducted. In addition to aspects of the previous findings, scholars have discovered several new contents and uncertain results. This article reviews and summarizes this decade’s progression of mild hypothermia in lowering the cerebral oxygen metabolism, protecting the blood–brain-barrier, regulating the inflammatory response, regulating the excessive release of neurotransmitters, inhibiting calcium overload, and reducing neuronal apoptosis. In many aspects, particularly in regulating inflammatory reverse reaction, various results have been reported and therefore guide scholars to conduct more detailed analysis and investigation in order to discover the inherent theories surrounding the effect of mild hypothermia, and for better clinical services.

Safety of intravenous administration of hydrogen-enriched fluid in patients with acute cerebral ischemia: initial clinical studies

BACKGROUND

Most of the results regarding hydrogen (H2) therapy for acute cerebral ischemia are derived from in vitro studies and animal experiments, with only a few obtained from human trials with a limited number of subjects. Thus, there is a paucity of information regarding both the beneficial therapeutic effects as well as the side effects of H2 on acute cerebral ischemia in humans. We designed a pilot study to investigate single dose intravenous H2-administration in combination with edaravone, aiming to provide an initial estimate of the possible risks and benefits in select patients presenting with acute ischemic stroke.

METHODS

An open-label, prospective, non-randomized study of intravenous H2-administration was performed in 38 patients hospitalized for acute ischemic stroke. All patients received an H2-enriched intravenous solution in addition to edaravone immediately after the diagnosis of acute ischemic stroke. Acute stroke patients within 3 h of onset received intravenous tissue plasminogen activator (t-PA) (0.6 mg/kg) treatment, and patients receiving t-PA had to commence the administration of the H2-enriched intravenous solution and edaravone before or at the same time as the t-PA was infused.

RESULTS

Complications were observed in 2 patients (5.3%), which consisted of diarrhea in 1 patient (2.6%) and cardiac failure in 1 patient (2.6%). No deterioration in laboratory tests, urinary tests, ECG, or chest X-ray radiograms occurred in any patient in this study. In all patients, the mean National Institutes of Health Stroke Scale (NIHSS) scores at baseline, and 7, 30, and 90 d after admission were 8.2 ± 7.5, 5.6 ± 7.1, 4.9 ± 6.5, and 4.5 ± 6.3, respectively. The early recanalization was identified in 4 of 11 patients (36.4%) who received intravenous t-PA administration. Hemorrhagic transformation was observed in 2 patients (18.2%). None of the patients in this study that were treated with t-PA developed symptomatic intracranial hemorrhage.

CONCLUSIONS

Data from the current study indicate that an H2-enriched intravenous solution is safe for patients with acute cerebral infarction, including patients treated with t-PA.

Azadirachta indica mitigates behavioral impairments, oxidative damage, histological alterations and apoptosis in focal cerebral ischemia-reperfusion model of rats

Azadirachta indica Linn. (Meliaceae) has been used from ancient times as a remedy for various ailments. The present study was designed to investigate the antioxidant and anti-apoptotic properties of A. indica seed extract (ASE) in transient middle cerebral artery occlusion (MCAO) rat model. Antioxidant potential of ASE was determined in vitro. Further, ASE was evaluated against neurological deficits, histological alterations (TTC, CV and H&E) and oxidative damage (TBARS, GSH and nitrite) in MCAO rats. Moreover, caspase-3 and -9 were analyzed to evaluate the anti-apoptotic activity of ASE. ASE has shown potent in vitro reducing power (126.2 mg AsAE/g extract) and free radical scavenging activities (DPPH 171.0 and NO 176.0 μg/ml). Furthermore, ASE inhibited oxidative stress and decreased the activities of caspase-3 (26.7 %, p < 0.05) and caspase-9 (31.2 %, p < 0.01) thus, reduced neuronal loss in MCAO rats. Our data revealed that ASE has potent antioxidant and anti-apoptotic properties, and may be explored for its active constituents against neurodegenerative diseases.

Effect of hydrogen gas on the survival rate of mice following global cerebral ischemia

Global cerebral ischemia and reperfusion (I/R) often result in high mortality. Free radicals have been reported to play an important role in global cerebral I/R, and therefore, reduction of these might improve the outcome. Here, we investigated the effect of hydrogen gas (H2) (a strong free radical scavenger) on the survival rate of mice following global cerebral I/R. We further examined the histopathological outcome and also the brain water content (as a possible determinant of mortality). Male C57BL/6J mice were subjected to global cerebral I/R by means of 45-min bilateral common carotid artery occlusion (BCCAO). A total of 160 mice were divided into three groups: sham surgery (sham group), BCCAO without H2 (BCCAO group), and BCCAO treated with 1.3% H2 (BCCAO + H2 group). We observed that H2 treatment significantly (P = 0.0232) improved the 7-day survival rate of mice, from 8.3% (BCCAO group, n = 12) to 50% (BCCAO + H2 group, n = 10). Histopathological analysis revealed that H2 treatment significantly attenuated neuronal injury and autophagy in the hippocampal cornu ammonis 1 sector and also brain edema, after 24 h of reperfusion. The beneficial effects of H2 treatment on brain injury were associated with significantly lower levels of oxidative stress markers (8-hydroxy-2'-deoxyguanosine and malondialdehyde) in the brain tissue. Thus, we believe that H2 may be an effective treatment for global cerebral I/R.

NADPH oxidase mediates striatal neuronal injury after transient global cerebral ischemia

Medium spiny neurons (MSNs) constitute most of the striatal neurons and are known to be vulnerable to ischemia; however, the mechanisms of the vulnerability remain unclear. Activated forms of nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase (NOX), which require interaction between cytosolic and membrane-bound subunits, are among the major sources of superoxide in the central nervous system. Although increasing evidence suggests that NOX has important roles in neurodegenerative diseases, its roles in MSN injury after transient global cerebral ischemia (tGCI) have not been elucidated. To clarify this issue, C57BL/6 mice were subjected to tGCI by bilateral common carotid artery occlusion for 22 minutes. Western blot analysis revealed upregulation of NOX subunits and recruitment of cytosolic subunits to the cell membrane at early (3 to 6 hours) and late (72 hours) phases after tGCI. Taken together with immunofluorescent studies, this activation arose in MSNs and endothelial cells at the early phase, and in reactive microglia at the late phase. Pharmacological and genetic inhibition of NOX attenuated oxidative injury, microglial activation, and MSN death after tGCI. These findings suggest that NOX has pivotal roles in MSN injury after tGCI and could be a therapeutic target for brain ischemia.

Cerebral reactive oxygen species assessed by electron spin resonance spectroscopy in the initial stage of ischemia-reperfusion are not associated with hypothermic neuroprotection

Using an in vivo L-band electron spin resonance (ESR) system, we determined changes in reactive oxygen species (ROS) levels during the early stage (within 60 minutes) of global cerebral ischemia-reperfusion (IR) under normothermic and hypothermic conditions in rats. To confirm the neuroprotective role of hypothermia in this IR model, we immunohistochemically evaluated the levels of active caspase-3 in the hippocampal CA1 sector. ROS levels increased within the first 15 minutes following IR under both normothermic and hypothermic conditions; however, the ROS levels did not differ significantly between normothermic and hypothermic conditions. In the later periods of IR, there were no significant changes in ROS levels for either normothermic or hypothermic conditions relative to the control. As expected, normothermia increased the number of active caspase-3 immunoreactive nuclei in the IR model. However, this induction was prevented by hypothermia. These results suggest that the neuroprotective role of hypothermia does not correlate with the early ROS-induced oxidative stress following IR as measured by ESR.

Enhanced post-ischemic neurogenesis in aging rats

Hippocampal neurogenesis persists in adult mammals, but its rate declines dramatically with age. Evidence indicates that experimentally-reduced levels of neurogenesis (e.g., by irradiation) in young rats has profound influence on cognition as determined by learning and memory tests. In the present study we asked whether in middle-aged, 10- to 13-months-old rats, cell production can be restored toward the level present in young rats. To manipulate neurogenesis we induced bilateral carotid occlusion with hypotension. This procedure is known to increase neurogenesis in young rats, presumably in a compensatory manner, but until now, has never been tested in aging rats. Cell production was measured at 10, 35, and 90 days after ischemia. The results indicate that neuronal proliferation and differentiation can be transiently restored in middle-aged rats. Furthermore, the effects are more pronounced in the dorsal as opposed to ventral hippocampus thus restoring the dorso-ventral gradient seen in younger rats. Our results support previous findings showing that some of the essential features of the age-dependent decline in neurogenesis are reversible. Thus, it may be possible to manipulate neurogenesis and improve learning and memory in old age.

A novel quantification of blood-brain barrier damage and histochemical typing after embolic stroke in rats

Treatment strategies in acute ischemic stroke are still limited. Considering numerous translation failures, research is tending to a preferred use of human-like animal models, and a more-complex perspective of tissue salvaging involving endothelial, glial and neuronal components according to the neurovascular unit (NVU) concept. During ischemia, blood-brain barrier (BBB) alterations lead to brain edema and hemorrhagic transformation affecting NVU components. The present study aims on a novel quantification method of BBB damage and affected tissue following experimental cerebral ischemia, closely to the human condition. Wistar rats underwent embolic middle cerebral artery occlusion, followed by an intravenous application of fluorescein isothiocyanate (FITC)-tagged albumin (≈70kDa) and/or biotinylated rat IgG (≈150kDa) as BBB permeability markers. Both fluorescent agents revealed similar leakage and allow quantification of BBB permeability by fluorescence microscopy, and after immunohistochemical conversion into a permanent diaminobenzidine label at light-microscopical level. The following markers were identified for sufficient detection of NVU components: Rat endothelial cell antigen-1 (RECA) and laminin for vessels, Lycopersicon esculentum and Griffonia simplicifolia agglutinin for vessels and microglial subpopulations, ionized calcium binding adaptor molecule 1 (Iba1), CD68 and CD11b for macrophages, activated microglia, monocytes and neutrophils, S100β for astroglia, as well as NeuN and HuC/D for neurons. This is the first report confirming the usefulness of simultaneously applied FITC-albumin and biotinylated rat IgG as BBB permeability markers in experimental stroke, and, specifying antibodies and lectins for multiple fluorescence labeling of NVU components. Newly elaborated protocols might facilitate a more-complex outcome measurement in drug development for cerebral ischemia.

Mild hypothermia (33 degrees C) reduces intracranial hypertension and improves functional outcome after subarachnoid hemorrhage in rats

OBJECTIVE

After a subarachnoid hemorrhage (SAH), the primary cause of mortality is secondary brain injury occurring within the first 48 hours after the initial bleeding. Because of the unknown pathophysiology of these early events, therapeutic approaches are scarce. Because mild hypothermia (33 degrees C) is among the strongest neuroprotectants known so far, the aim of this study was to investigate acute and delayed effects of hypothermia if applied after SAH.

METHODS

Male Sprague-Dawley rats were subjected to SAH and randomly assigned to the following groups: 1) SAH under normothermia, 2) SAH followed by 2 hours of hypothermia starting 1 hour after the bleeding, and 3) SAH followed by 2 hours of hypothermia starting 3 hours after the bleeding. Cerebral blood flow and intracranial pressure were continuously measured up to 6 hours after SAH. Mortality, neurological deficits, and body weight were assessed from postoperative day 1 to day 7. Brain water content and morphological brain damage were quantified 24 hours and 7 days after SAH, respectively.

RESULTS

Mild hypothermia reduced intracranial pressure (P < 0.001) and posthemorrhagic neurological deficits (P < 0.05) and improved postoperative weight gain significantly (P < 0.05). Mortality, cerebral blood flow, and the formation of cerebral edema were not significantly influenced by mild hypothermia.

CONCLUSION

The current results show that mild hypothermia (33 degrees C) exhibits sustained neuroprotection if applied up to 3 hours after SAH. Overall, mild hypothermia seems to be an effective neuroprotective strategy after SAH and should therefore be evaluated as a treatment option for SAH in patients.

Importance of normothermia control in investigating delayed neuronal injury in a mouse global ischemia model

This study aims to establish a mouse global cerebral ischemia model in which the physiological parameter measurements and neuronal injury evaluations are conducted in the same group of animals and to identify the effect of post-ischemic core temperature (CT) on the outcome of neuronal injury. Global ischemia was induced by 12-min bilateral common carotid artery occlusion followed by 7 days of reperfusion in C57BL/6 mice. Immediately after occlusion, mice were randomly assigned to be kept in environments of different temperatures [25 degrees C (room temperature, group 1), 33-34 degrees C for 2h (group 2), and 33-34 degrees C for 24h (group 3)] before being returned to their home cages. We found that in group 1, CT declined to approximately 32 degrees C after ischemia and then recovered at 24h post-ischemia; in group 2, CT remained at the pre-ischemia level during the first 2h, declined after the mice were returned to room temperature, and recovered at 24h post-ischemia; and in group 3, CT remained constant at the pre-ischemia level throughout the reperfusion period. The number of surviving neurons in a sector of the hippocampal CA1 region was significantly lower in all ischemic groups than in the sham controls, but the number was significantly higher in group 1 than that in groups 2 or 3 (P<0.05). We observed that CT declines initially but recovers spontaneously at 24h post-ischemia. Early post-ischemic hypothermia impacts the delayed neuronal injury, suggesting that tight temperature control immediately following ischemia is important to obtain the most reproducible neuronal damage in mouse models of cerebral global ischemia.

Intraoperative hypothermia during vascular neurosurgical procedures

Increasing evidence in animal models and clinical trials for stroke, hypoxic encephalopathy for children, and traumatic brain injury have shown that mild hypothermia may attenuate ischemic damage and improve neurological outcome. However, it is less clear if mild intraoperative hypothermia during vascular neurosurgical procedures results in improved outcomes for patients. This review examines the scientific evidence behind hypothermia as a treatment and discusses factors that may be important for the use of this adjuvant technique, including cooling temperature, duration of hypothermia, and rate of rewarming.

Post-ischemic hypothermia attenuates loss of the vascular basement membrane proteins, agrin and SPARC, and the blood-brain barrier disruption after global cerebral ischemia

Vascular basement membrane (BM) stabilizes brain vessels and inhibits endothelial cell cycle. Cerebral ischemia causes BM breakdown with the loss of structural BM components including collagens and laminins. In this study, the expression changes of the BM proteoglycan agrin, and the non-structural BM constituent SPARC (BM-40, osteonectin), were studied in brain vessels after global cerebral ischemia. A transient 20-min forebrain ischemia followed by 1, 6 or 24 h of reperfusion was induced in adult Sprague-Dawley rats by combined bilateral common carotid artery occlusion and hypotension (42-45 mm Hg). In a separate group of animals, a mild (32 degrees C) post-ischemic hypothermia was induced for 6 h, starting immediately after ischemia. RNA from approximately 500 brain vessels (20-100 microm) extracted by laser-capture microdissection (LCM) microscopy was used to determine the expression of proteoglycans agrin and SPARC mRNAs by quantitative PCR (Q-PCR). Protein expression was determined by immunohistochemistry in adjacent tissue sections. The BBB permeability was assessed using (3)H-sucrose as an in vivo tracer and by examining fibrinogen immunoreactivity in tissue sections. A transient global brain ischemia resulted in a significant (ANOVA, p<0.05; 6 animals/group) reduction in agrin and SPARC mRNAs in LCM-captured brain vessels 24 h after reperfusion. A time-dependent loss of agrin and SPARC from the BM during reperfusion was also observed by immunochemistry. A 6-h post-ischemic hypothermia reduced SPARC and agrin mRNA and protein losses, BBB transfer constant for (3)H-sucrose as well as fibrinogen extravasation 24 h after reperfusion. It is conluded that a transient post-ischemic hypothermia stabilizes brain vessels and reduces BBB disruption in part by preventing proteolytic degradation of regulatory BM constituents, SPARC and agrin.

Blood-brain barrier permeability to manganese and to Gd-DOTA in a rat model of transient cerebral ischaemia

Loss of integrity of the blood-brain barrier (BBB) and brain swelling is a potentially lethal complication of reperfusion in human stroke. To assess the time course of BBB modifications, we performed angiography, diffusion-weighted imaging, T1-weighted (T1 W) imaging and T1 mapping, and monitored acute changes after middle cerebral artery occlusion and recanalization in rats (n = 27). The animals were grouped according to the duration of occlusion: 30 min (group A, n = 8), 1 h 30 min (group B, n = 9), and 2 h 30 min (group C, n = 10). For 17 animals (four in group A, six in group B, and seven in group C), MnCl2 and dimeglumine gadoterate (Gd-DOTA) were injected at 13 min and 34 min after recanalization, respectively. The 10 remaining animals (control groups) underwent the same acquisition protocols, but no contrast agents were injected. Cell damage was determined 1 h after recanalization on haematoxylin and eosin-stained sections. Our results indicate that in the middle cerebral artery occlusion model in the rat, changes in BBB permeability assessed by contrast agent extravasation occur within the first hour of reperfusion, even after an occlusion period not exceeding 30 min. No differences between BBB permeability to Gd-DOTA and Mn2+ were detected in our experimental conditions. The reduction in apparent diffusion coefficient during occlusion appears to be a good predictor of BBB modifications after reperfusion in this model.

General versus specific actions of mild-moderate hypothermia in attenuating cerebral ischemic damage

Mild or moderate hypothermia is generally thought to block all changes in signaling events that are detrimental to ischemic brain, including ATP depletion, glutamate release, Ca(2+) mobilization, anoxic depolarization, free radical generation, inflammation, blood-brain barrier permeability, necrotic, and apoptotic pathways. However, the effects and mechanisms of hypothermia are, in fact, variable. We emphasize that, even in the laboratory, hypothermic protection is limited. In certain models of permanent focal ischemia, hypothermia may not protect at all. In cases where hypothermia reduces infarct, some studies have overemphasized its ability to maintain cerebral blood flow and ATP levels, and to prevent anoxic depolarization, glutamate release during ischemia. Instead, hypothermia may protect against ischemia by regulating cascades that occur after reperfusion, including blood-brain barrier permeability and the changes in gene and protein expressions associated with necrotic and apoptotic pathways. Hypothermia not only blocks multiple damaging cascades after stroke, but also selectively upregulates some protective genes. However, most of these mechanisms are addressed in models with intraischemic hypothermia; much less information is available in models with postischemic hypothermia. Moreover, although it has been confirmed that mild hypothermia is clinically feasible for acute focal stroke treatment, no definite beneficial effect has been reported yet. This lack of clinical protection may result from suboptimal criteria for patient entrance into clinical trials. To facilitate clinical translation, future efforts in the laboratory should focus more on the protective mechanisms of postischemic hypothermia, as well as on the effects of sex, age and rewarming during reperfusion on hypothermic protection.

The NMDA and AMPA/KA receptors are involved in glutamate-induced alterations of occludin expression and phosphorylation in brain endothelial cells

Glutamate levels increase dramatically in cerebral ischemia and stroke. This may lead to opening of the blood-brain barrier (BBB) and induce further brain damage. Because endothelial tight junctions are critical elements of the BBB integrity, the aim of this study was to investigate the mechanisms of glutamate-induced alterations of the tight-junction protein occludin in cultured brain microvascular endothelial cells (BMECs). Transient exposure to glutamate resulted in cellular redistribution of occludin, followed by a decrease in the total level of this protein and diminished barrier function of BMECs. Inhibition of the N-methyl-D-aspartate (NMDA) or alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate/kainate (AMPA/KA) receptors attenuated glutamate-induced changes in occludin redistribution but not in the total protein levels. Treatment with glutamate also increased tyrosine phosphorylation and decreased threonine phosphorylation of occludin. Inhibition of the NMDA receptors by MK-801 partially protected against glutamate-induced elevation of occludin tyrosine phosphorylation. In addition, pretreatment with MK-801-attenuated glutamate-mediated disruption of endothelial barrier function. Blocking of the AMPA/KA receptors by 6,7-dinitroquinoxaline-2.3-dione (DNQX) protected against hypophosphorylation of threonine residues of occludin; however, it did not affect disruption of endothelial integrity. These findings indicate the opposite effects of the NMDA and AMPA/KA receptors on occludin phosphorylation and disruption of the BBB functions.

Critical role of microvasculature basal lamina in ischemic brain injury

Cerebral vascular system can be divided into two categories: the macrovessels and microvessels. The microvessels consist of arterioles, capillaries and venules. There are three basic components in the microvasculature: endothelial cells, basal lamina and end-feet of astrocytes. The basal lamina is situated between the endothelial cells and the end-feet of astrocytes, and connects these two layers together. Damage to the basal lamina causes the dismantlement of microvascular wall structures, which in turn results in increase of microvascular permeability, hemorrhagic transformation, brain edema and compromise of the microcirculation. The present article reviews microvascular changes during ischemic brain injury, with emphasis on basal lamina damage.

A review of progress in understanding the pathophysiology and treatment of brain edema

Object

Brain edema resulting from traumatic brain injury (TBI) or ischemia if uncontrolled exhausts volume reserve and leads to raised intracranial pressure and brain herniation. The basic types of edema—vasogenic and cytotoxic—were classified 50 years ago, and their definitions remain intact.

Methods

In this paper the author provides a review of progress over the past several decades in understanding the pathophysiology of the edematous process and the success and failures of treatment. Recent progress focused on those manuscripts that were published within the past 5 years.

Results

Perhaps the most exciting new findings that speak to both the control of production and resolution of edema in both trauma and ischemia are the recent studies that have focused on the newly described “water channels” or aquaporins. Other important findings relate to the predominance of cellular edema in TBI.

Conclusions

Significant new findings have been made in understanding the pathophysiology of brain edema; however, less progress has been made in treatment. Aquaporin water channels offer hope for modulating and abating the devastating effects of fulminating brain edema in trauma and stroke.

Effect of mild hypothermia on angiogenesis in rats with focal cerebral ischemia

In the present study, we investigated the effect of mild hypothermia on infarct volume, angiogenesis and brain-derived neurotrophic factor (BDNF) level after stroke. After permanent middle cerebral artery occlusion, mild hypothermia was induced immediately and maintained for 24h. 2,3,5-Triphenyltetrazolium chloride (TTC) staining, laser scanning confocal microscopy (LSCM) and ELISA were performed to assay infarct volume, angiogenesis and BDNF level in the ischemic boundary zone (IBZ), respectively. Compared with normothermic group, mild hypothermia reduced total infarct volume and increased endogenous BDNF level. And the microvessel diameter, the number of vascular branch points and the vessel surface area were significantly increased in the mild hypothermia group. These findings suggest that mild hypothermia enhances angiogenesis in ischemic brain, which might be enhanced in part via BDNF.

Effects of crocin on reperfusion-induced oxidative/nitrative injury to cerebral microvessels after global cerebral ischemia

This paper studied the effects of crocin, a pharmacologically active component of Crocus sativus L., on ischemia/reperfusion (I/R) injury in mice cerebral microvessels. Transient global cerebral ischemia (20 min), followed by 24 h of reperfusion, significantly promoted the generation of nitric oxide (NO) and malondialdehyde (MDA) in cortical microvascular homogenates, as well as markedly reduced the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-px) and promoted the activity of nitric oxide synthase (NOs). Reperfusion for 24 h led to serous edema with substantial microvilli loss, vacuolation, membrane damage and mitochondrial injuries in cortical microvascular endothelial cells (CMEC). Furthermore, enhanced phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and decreased expression of matrix metalloproteinase-9 (MMP-9) were detected in cortical microvessels after I (20 min)/R (24 h). Reperfusion for 24 h also induced membrane (functional) G protein-coupled receptor kinase 2 (GRK2) expression, while it reduced cytosol GRK2 expression. Pretreatment with crocin markedly inhibited oxidizing reactions and modulated the ultrastructure of CMEC in mice with 20 min of bilateral common carotid artery occlusion (BCCAO) followed by 24 h of reperfusion in vivo. Furthermore, crocin inhibited GRK2 translocation from the cytosol to the membrane and reduced ERK1/2 phosphorylation and MMP-9 expression in cortical microvessels. We propose that crocin protects the brain against excessive oxidative stress and constitutes a potential therapeutic candidate in transient global cerebral ischemia.

Effect of duration of osmotherapy on blood-brain barrier disruption and regional cerebral edema after experimental stroke

Osmotherapy is the cornerstone of medical management for cerebral edema associated with large ischemic strokes. We determined the effect of duration of graded increases in serum osmolality with mannitol and hypertonic saline (HS) on blood-brain barrier (BBB) disruption and regional cerebral edema in a well-characterized rat model of large ischemic stroke. Halothane-anesthetized adult male Wistar rats were subjected to transient (2-h) middle cerebral artery occlusion (MCAO) by the intraluminal occlusion technique. Beginning at 6 h after MCAO, rats were treated with either no intravenous fluids or a continuous intravenous infusion (0.3 mL/h) of 0.9% saline, 20% mannitol, 3% HS, or 7.5% HS for 24, 48, 72, and 96 h. In the first series of experiments, BBB permeability was quantified by the Evans blue (EB) extravasation method. In the second series of experiments, water content was assessed by comparing wet-to-dry weight ratios in six predetermined brain regions. Blood-brain barrier disruption was maximal in rats treated with 0.9% saline for 48 h, but did not correlate with increases in serum osmolality or treatment duration with osmotic agents. Treatment with 7.5% HS attenuated water content in the periinfarct regions and all subregions of the contralateral nonischemic hemisphere to a greater extent than mannitol did with no adverse effect on survival rates. These data show that (1) BBB integrity is not affected by the duration and degree of serum osmolality with osmotic agents, and (2) attenuation of increases in brain water content with HS to target levels >350 mOsm/L may have therapeutic implications in the treatment of cerebral edema associated with ischemic stroke.

Astrocyte-endothelial interactions at the blood-brain barrier

The blood-brain barrier, which is formed by the endothelial cells that line cerebral microvessels, has an important role in maintaining a precisely regulated microenvironment for reliable neuronal signalling. At present, there is great interest in the association of brain microvessels, astrocytes and neurons to form functional 'neurovascular units', and recent studies have highlighted the importance of brain endothelial cells in this modular organization. Here, we explore specific interactions between the brain endothelium, astrocytes and neurons that may regulate blood-brain barrier function. An understanding of how these interactions are disturbed in pathological conditions could lead to the development of new protective and restorative therapies.

Characterization of vascular protein expression patterns in cerebral ischemia/reperfusion using laser capture microdissection and ICAT‐nanoLC‐MS/MS

Cerebral ischemia rapidly initiates structural and functional changes in brain vessels, including blood-brain barrier disruption, inflammation, and angiogenesis. Molecular events that accompany these changes were investigated in brain microvessels extracted using laser-capture microdissection (LCM) from Sprague-Dawley rats subjected to a 20 min transient global cerebral ischemia followed by 1, 6, or 24 h reperfusion. Proteins extracted from approximately 300 LCM captured microvessels (20-100 microm) were ICAT-labeled and analyzed by nanoLC-MS. In-house software was used to identify paired ICAT peaks, which were then sequenced by nanoLC-MS/MS. Pattern analyses using k-means clustering method classified 57 differentially expressed proteins in 7 distinct dynamic patterns. Protein function was assigned using Panther Classification system. Early reperfusion (1 h) was characterized by down-regulation of ion pumps, nutrient transporters, and cell structure/motility proteins, and up-regulation of transcription factors, signal transduction molecules and proteins involved in carbohydrate metabolism. The up-regulation of inflammatory cytokines and proteins involved in the extracellular matrix remodeling and anti-oxidative defense was observed in late reperfusion (6-24 h). The up-regulation of IL-1beta and TGF-1beta in ischemic brain vessels was confirmed by ELISA, quantitative PCR, and/or immunohistochemistry. A biphasic postischemic (1 and 24 h) BBB opening for (3)H-sucrose was evident in the same model. Differentially expressed proteins identified in brain vessels during reperfusion are likely involved in orchestrating functional vascular responses to ischemia, including the observed BBB disruption.