Brain cell death following ischemia and reperfusion: a proposed biochemical sequence

Beyond Pharmacology: The Biological Mechanisms of Remote Ischemic Conditioning in Cerebrovascular Disease

Cerebrovascular diseases (CVDs), comprising predominantly ischemic stroke and chronic cerebral hypoperfusion (CCH), are a significant threat to global health, often leading to disability and mortality. Remote ischemic conditioning (RIC) has emerged as a promising, non-pharmacological strategy to combat CVDs by leveraging the body's innate defense mechanisms. This review delves into the neuroprotective mechanisms of RIC, categorizing its effects during the acute and chronic phases of stroke recovery. It also explores the synergistic potential of RIC when combined with other therapeutic strategies, such as pharmacological treatments and physical exercise. Additionally, this review discusses the pathways through which peripheral transmission can confer central neuroprotection. This review concludes by addressing the challenges regarding and future directions for RIC, emphasizing the need for standardized protocols, biomarker identification, and expanded clinical trials to fully realize its therapeutic potential.

Region-specific protective effects of monomethyl fumarate in cerebellar and hippocampal organotypic slice cultures following oxygen-glucose deprivation

To date, apart from moderate hypothermia, there are almost no adequate interventions available for neuroprotection in cases of brain damage due to cardiac arrest. Affected persons often have severe limitations in their quality of life. The aim of this study was to investigate protective properties of the active compound of dimethyl fumarate, monomethyl fumarate (MMF), on distinct regions of the central nervous system after ischemic events. Dimethyl fumarate is an already established drug in neurology with known anti-inflammatory and antioxidant properties. In this study, we chose organotypic slice cultures of rat cerebellum and hippocampus as an ex vivo model. To simulate cardiac arrest and return of spontaneous circulation we performed oxygen-glucose-deprivation (OGD) followed by treatments with different concentrations of MMF (1-30 μM in cerebellum and 5-30 μM in hippocampus). Immunofluorescence staining with propidium iodide (PI) and 4',6-diamidine-2-phenylindole (DAPI) was performed to analyze PI/DAPI ratio after imaging with a spinning disc confocal microscope. In the statistical analysis, the relative cell death of the different groups was compared. In both, the cerebellum and hippocampus, the MMF-treated group showed a significantly lower PI/DAPI ratio compared to the non-treated group after OGD. Thus, we showed for the first time that both cerebellar and hippocampal slice cultures treated with MMF after OGD are significantly less affected by cell death.

Effect of Dl-3-n-butylphthalide on mitochondrial Cox7c in models of cerebral ischemia/reperfusion injury

Several studies have demonstrated the protective effect of dl-3-n-Butylphthalide (NBP) against cerebral ischemia, which may be related to the attenuation of mitochondrial dysfunction. However, the specific mechanism and targets of NBP in cerebral ischemia/reperfusion remains unclear. In this study, we used a chemical proteomics approach to search for targets of NBP and identified cytochrome C oxidase 7c (Cox7c) as a key interacting target of NBP. Our findings indicated that NBP inhibits mitochondrial apoptosis and reactive oxygen species (ROS) release and increases ATP production through upregulation of Cox7c. Subsequently, mitochondrial respiratory capacity was improved and the HIF-1α/VEGF pathway was upregulated, which contributed to the maintenance of mitochondrial membrane potential and blood brain barrier integrity and promoting angiogenesis. Therefore, our findings provided a novel insight into the mechanisms underlying the neuroprotective effects of NBP, and also proposed for the first time that Cox7c exerts a critical role by protecting mitochondrial function.

Cryptotanshinone reduces neurotoxicity induced by cerebral ischemia-reperfusion injury involving modulation of microglial polarization

BACKGROUND

The diterpenoid cryptotanshinone (CTS) has wide biological functions, including inhibition of tumor growth, inflammation and apoptosis. The present study aimed to explore the possible effect of CTS on cerebral ischemia/reperfusion (I/R) injury and the underlying mechanisms.

METHODS

Male C57BL/6J mice underwent transient middle cerebral artery occlusion (tMCAO) and murine microglia BV2 cells were challenged by Oxygen/glucose deprivation, to mimic I/R and ischemic/hypoxic and reperfusion (H/R) injury, respectively. CTS was administered 0.5 h (10 mg/kg) after the onset of MCAO or 2 h (20μM) post OGD. Infarct volume and neurological deficit were measured. Immunofluorescence, qPCR, and western blot, were performed to detect the expression of cytokines, apoptotic marker, and M1/M2 phenotype-specific genes. Flow cytometry was applied for M1/M2 subpopulation or Annexin V/PI apoptosis assessment.

RESULTS

CTS significantly reduced cerebral infarct volume, neurologic deficit scores, pro-inflammatory cytokine production (IL-6, TNF-α, and IL-1β), apoptotic protein expression (cleaved caspase-3) of mice after tMCAO challenge. Furthermore, CTS attenuated CD16+ M1-type and elevated CD206+ M2-type microglia in vivo or in vitro.

CONCLUSIONS

We propose that the neuroprotective effect of CTS in the I/R or H/R context are explained modulation of microglial polarization, suggesting therapeutic potential for cerebral ischemic stroke.

The impact of intra-arrest hypothermia

PURPOSE OF REVIEW

To address the impact of therapeutic hypothermia induced already during cardiopulmonary resuscitation (i.e. intra-arrest cooling) and its association with neurologic functional outcome.

RECENT FINDINGS

Intra-arrest cooling is superior than post-ROSC cooling to mitigate brain injuries in experimental models of cardiac arrest. The delayed initiation of hypothermia in human studies may not have adequately addressed the underlying pathophysiology of ischemia and reperfusion. The assessment of early initiation of cooling has been complicated by increased rate of hemodynamic adverse events caused by infusion of cold intravenous fluids. These adverse events have been more deleterious in patients with initial shockable rhythms. A recent randomized study shows that an alternative intra-arrest cooling method using trans-nasal evaporative cooling was well tolerated and effective to shorten time to target temperature. However, the neurologic outcomes (CPC 1-2 at 90 days) in favor of intra-arrest cooling compared to hospital cooling (34.8% vs 25.9%, P = 0.11) in patients with initial shockable rhythms did not reach statistical significance.

SUMMARY

Therapeutic intra-arrest hypothermia can be initiated safely at the scene of the arrest using transnasal evaporative cooling. The potential beneficial effect of intra-arrest cooling on neurologic recovery in patients with initial shockable rhythms should be explored further.

Role of Regular Physical Activity in Neuroprotection against Acute Ischemia

One of the major obstacles that prevents an effective therapeutic intervention against ischemic stroke is the lack of neuroprotective agents able to reduce neuronal damage; this results in frequent evolution towards a long-term disability with limited alternatives available to aid in recovery. Nevertheless, various treatment options have shown clinical efficacy. Neurotrophins such as brain-derived neurotrophic factor (BDNF), widely produced throughout the brain, but also in distant tissues such as the muscle, have demonstrated regenerative properties with the potential to restore damaged neural tissue. Neurotrophins play a significant role in both protection and recovery of function following neurological diseases such as ischemic stroke or traumatic brain injury. Unfortunately, the efficacy of exogenous administration of these neurotrophins is limited by rapid degradation with subsequent poor half-life and a lack of blood-brain-barrier permeability. Regular exercise seems to be a therapeutic approach able to induce the activation of several pathways related to the neurotrophins release. Exercise, furthermore, reduces the infarct volume in the ischemic brain and ameliorates motor function in animal models increasing astrocyte proliferation, inducing angiogenesis and reducing neuronal apoptosis and oxidative stress. One of the most critical issues is to identify the relationship between neurotrophins and myokines, newly discovered skeletal muscle-derived factors released during and after exercise able to exert several biological functions. Various myokines (e.g., Insulin-Like Growth Factor 1, Irisin) have recently shown their ability to protects against neuronal injury in cerebral ischemia models, suggesting that these substances may influence the degree of neuronal damage in part via inhibiting inflammatory signaling pathways. The aim of this narrative review is to examine the main experimental data available to date on the neuroprotective and anti-ischemic role of regular exercise, analyzing also the possible role played by neurotrophins and myokines.

[The spinal catheter in aortic surgery : Implications for anesthesia]

During surgical repair of aortic pathologies (e.g. dissection, aneurysms), cross-clamping of the aorta or overstenting of critical segmental arteries can lead to ischemia- and edema-related spinal cord damage with subsequent paraplegia. By regulating cerebrospinal fluid pressure, the spinal catheter is an effective method for prophylaxis and treatment of spinal cord ischemia. Due to the high complication rate of the spinal catheter a detailed risk-benefit assessment is obligatory: besides cerebrospinal fluid leakage, postpuncture headaches and local infections, feared complications, such as intracranial bleeding, meningitis and neuraxial hematomas can also occur, sometimes with a significant latent period after termination of the procedure. Adequate training of personnel in the perioperative handling of spinal catheters and meticulous adherence to drainage parameters are important components for increasing procedural safety. This is particularly true since the clinical aspects of catheter-associated complications only slightly differ from that of ischemic spinal cord injury.

Gadolinium-Based Neuroprognostic Magnetic Resonance Imaging Agents Suppress COX-2 for Prevention of Reperfusion Injury after Stroke

Advancements in recanalization therapies have rendered reperfusion injury an important challenge for stroke management. It is essential to work toward effective therapeutics that protect the ischemic brain from reperfusion injury. Here, we report a new concept of neuroprognostic agents, which combine molecular diagnostic imaging and targeted neuroprotection for treatment of reperfusion injury after stroke. These neuroprognostic agents are inflammation-targeted gadolinium compounds conjugated with nonsteroidal anti-inflammatory drugs (NSAIDs). Our results demonstrated that gadolinium-based MRI contrast agents conjugated with NSAIDs suppressed the increase in cyclooxygenase-2 (COX-2) levels, ameliorated glial activation, and neuron damage that are phenotypic for stroke by mitigating neuroinflammation, which prevented reperfusion injury. In addition, this study showed that the neuroprognostic agents are promising T₁ molecular MRI contrast agents for detecting precise reperfusion injury locations at the molecular level. Our results build on this new concept of neuroprognostics as a novel management strategy for ischemia-reperfusion injury, combining neuroprotection and molecular diagnostics.

Inhibition of microRNA-199a-5p ameliorates oxygen-glucose deprivation/reoxygenation-induced apoptosis and oxidative stress in HT22 neurons by targeting Brg1 to activate Nrf2/HO-1 signalling

MicroRNAs (miRNAs) have emerged as critical regulators of neuronal survival during cerebral ischaemia/reperfusion injury. Accumulating evidence has shown that miR-199a-5p plays a crucial role in regulating apoptosis and survival in various cell types. However, whether miR-199a is involved in regulating neuronal survival during cerebral ischaemia/reperfusion injury remains unknown. In this study, we aimed to explore the biological role of miR-199a-5p in regulating neuronal injury induced by oxygen-glucose deprivation/reoxygenation (OGD/R), an in vitro cellular model of cerebral ischaemia and reperfusion injury. We found that miR-199a-5p expression was significantly altered in neurons in response to OGD/R treatment. Overexpression of miR-199a-5p facilitated OGD/R-induced apoptosis and reactive oxygen species (ROS) production, whereas miR-199a-5p inhibition alleviated OGD/R-induced apoptosis and ROS production. Notably, our results identified Brahma-related gene 1 (Brg1) as a target gene of miR-199a-5p. Moreover, inhibition of miR-199a-5p promoted the activation of nuclear factor-erythroid-2-related factor-2 (Nrf2)/heme oxygenase-1 (HO-1) signalling via targeting Brg1. However, silencing of Brg1 markedly reversed the miR-199a-5p inhibition-mediated neuroprotective effect. Taken together, our results suggest that downregulation of miR-199a-5p protects neurons from OGD/R-induced neuronal injury through upregulating Brg1 to activate Nrf2/HO-1 signalling. The miR-199a-5p/Brg1/Nrf2/HO-1 regulation axis may play an important role in regulating neuronal survival during cerebral ischaemic/reperfusion injury in vivo.

Bilirubin and Ischemic Stroke: Rendering the Current Paradigm to Better Understand the Protective Effects of Bilirubin

Novel and innovative methods are critical in fostering new treatments and improving clinical outcomes in patients who suffer from ischemic stroke. Bilirubin has long been considered metabolic waste that can be harmful to the body; however, it is now becoming recognized as one of the body's most potent antioxidant, anti-inflammatory, and neuroprotective molecules. These properties facilitate bilirubin's anti-atherogenic effects to impede and prevent the formation of thrombi in ischemic stroke. These functions allow for protection from neuronal injury during an ischemic state and suggest that elevated bilirubin levels may be linked to a lower rate of morbidity and mortality. Therefore, here we discuss the pathophysiology of stroke and the molecular properties of bilirubin to better understand their beneficial relationship. We outline clinical studies looking at the relationship between serum bilirubin levels and ischemic stroke prevalence. At this time, few studies have rigorously looked at the relationship between bilirubin and ischemic stroke, whether it is positive or negative. Thus, rigorous research is needed to provide evidence supporting the current studies, expand on these studies, and facilitate their translation to bedside therapy for patients who suffer from ischemic stroke.

Welfare Risks of Repeated Application of On-Farm Killing Methods for Poultry

Simple Summary

During poultry production, some birds are killed humanely on farm, usually because they are ill or injured. Recent European Union (EU) legislation has restricted the number of birds that can be killed by manual neck dislocation to 70 birds per person per day. We examined whether this limit is meaningful by investigating the effects of repeated application of two methods of killing (neck dislocation and a percussive method, the CashPoultry Killer). Twelve male stockworkers each killed 100 birds (broilers, laying hens, or turkeys) at a fixed rate with each method. Both methods were highly successful, and reflex and behaviour measures confirmed they caused rapid loss of brain function. Importantly, there was no evidence of reduced performance with time/bird number up to 100 birds with either method. The Cash Poultry Killer caused a more rapid death, but it was prone to technical difficulties with repeated use. Neck dislocation has the important advantage that it can be performed immediately with no equipment, which may make it preferable in some situations. We present the first evidence that, at the killing rates tested, there was no evidence to justify the current EU number limit for performance of neck dislocation to kill poultry on farm.

Abstract

Council Regulation (EC) no. 1099/2009 on the protection of animals at the time of killing restricts the use of manual cervical dislocation in poultry on farms in the European Union (EU) to birds weighing up to 3 kg and 70 birds per person per day. However, few studies have examined whether repeated application of manual cervical dislocation has welfare implications and whether these are dependent on individual operator skill or susceptibility to fatigue. We investigated the effects of repeated application (100 birds at a fixed killing rate of 1 bird per 2 min) and multiple operators on two methods of killing of broilers, laying hens, and turkeys in commercial settings. We compared the efficacy and welfare impact of repeated application of cervical dislocation and a percussive killer (Cash Poultry Killer, CPK), using 12 male stockworkers on three farms (one farm per bird type). Both methods achieved over 96% kill success at the first attempt. The killing methods were equally effective for each bird type and there was no evidence of reduced performance with time and/or bird number. Both methods of killing caused a rapid loss of reflexes, indicating loss of brain function. There was more variation in reflex durations and post-mortem damage in birds killed by cervical dislocation than that found using CPK. High neck dislocation was associated with improved kill success and more rapid loss of reflexes. The CPK caused damage to multiple brain areas with little variation. Overall, the CPK was associated with faster abolition of reflexes, with fewer birds exhibiting them at all, suggestive of better welfare outcomes. However, technical difficulties with the CPK highlighted the advantages of cervical dislocation, which can be performed immediately with no equipment. At the killing rates tested, we did not find evidence to justify the current EU limit on the number of birds that one operator can kill on–farm by manual cervical dislocation.

Limb Remote Ischemic Conditioning: Mechanisms, Anesthetics, and the Potential for Expanding Therapeutic Options

Novel and innovative approaches are essential in developing new treatments and improving clinical outcomes in patients with ischemic stroke. Remote ischemic conditioning (RIC) is a series of mechanical interruptions in blood flow of a distal organ, following end organ reperfusion, shown to significantly reduce infarct size through inhibition of oxidation and inflammation. Ischemia/reperfusion (I/R) is what ultimately leads to the irreversible brain damage and clinical picture seen in stroke patients. There have been several reports and reviews about the potential of RIC in acute ischemic stroke; however, the focus here is a comprehensive look at the differences in the three types of RIC (remote pre-, per-, and postconditioning). There are some limited uses of preconditioning in acute ischemic stroke due to the unpredictability of the ischemic event; however, it does provide the identification of biomarkers for clinical studies. Remote limb per- and postconditioning offer a more promising treatment during patient care as they can be harnessed during or after the initial ischemic insult. Though further research is needed, it is imperative to discuss the importance of preclinical data in understanding the methods and mechanisms involved in RIC. This understanding will facilitate translation to a clinically feasible paradigm for use in the hospital setting.

Free Radical Damage in Ischemia-Reperfusion Injury: An Obstacle in Acute Ischemic Stroke after Revascularization Therapy

Acute ischemic stroke is a common cause of morbidity and mortality worldwide. Thrombolysis with recombinant tissue plasminogen activator and endovascular thrombectomy are the main revascularization therapies for acute ischemic stroke. However, ischemia-reperfusion injury after revascularization therapy can result in worsening outcomes. Among all possible pathological mechanisms of ischemia-reperfusion injury, free radical damage (mainly oxidative/nitrosative stress injury) has been found to play a key role in the process. Free radicals lead to protein dysfunction, DNA damage, and lipid peroxidation, resulting in cell death. Additionally, free radical damage has a strong connection with inducing hemorrhagic transformation and cerebral edema, which are the major complications of revascularization therapy, and mainly influencing neurological outcomes due to the disruption of the blood-brain barrier. In order to get a better clinical prognosis, more and more studies focus on the pharmaceutical and nonpharmaceutical neuroprotective therapies against free radical damage. This review discusses the pathological mechanisms of free radicals in ischemia-reperfusion injury and adjunctive neuroprotective therapies combined with revascularization therapy against free radical damage.

On Farm Evaluation of a Novel Mechanical Cervical Dislocation Device for Poultry

Urgent development of alternative on-farm killing methods for poultry is required following the number restrictions placed on the use of traditional manual cervical dislocation by European Legislation (EU 1099/2009). Alternatives must be proven to be humane and, crucially, practical in commercial settings with multiple users. We assessed the performance and reliability of a novel mechanical cervical dislocation device (NMCD) compared to the traditional manual cervical dislocation (MCD) method. NMCD was based on a novel device consisting of a thin supportive glove and two moveable metal finger inserts designed to aid the twisting motion of cervical dislocation. We employed a 2 × 2 factorial design, with a total of eight stockworkers from broiler and layer units (four per farm) each killing 70 birds per method. A successful kill performance was defined as immediate absence of rhythmic breathing and nictitating membrane reflex; a detectable gap in the vertebrae and only one kill attempt (i.e., one stretch and twist motion). The mean stockworker kill performance was significantly higher for MCD (98.4 ± 0.5%) compared to NMCD (81.6 ± 1.8%). However, the MCD technique normally used by the stockworkers (based previous in-house training received) affected the performance of NMCD and was confounded by unit type (broilers), with the majority of broiler stockworkers trained in a non-standard technique, making adaption to the NMCD more difficult. The consistency of trauma induced by the killing methods (based on several post-mortem parameters) was higher with NMCD demonstrated by "gold standard" trauma achieved in 30.2% of birds, compared to 11.4% for MCD (e.g., dislocation higher up the cervical region of the spine i.e., between vertebrae C0-C1, ≥1 carotid arteries severed), suggesting it has the potential to improve welfare at killing. However, the results also suggest that the NMCD method requires further refinement and training optimization in order for it to be acceptable as an alternative across poultry industry, irrespective of previous MCD technique and training.

Neuron-autonomous transcriptome changes upon ischemia/reperfusion injury

Ischemic stroke and the following reperfusion, an acute therapeutic intervention, can cause irreversible brain damages. However, the underlying pathological mechanisms are still under investigation. To obtain a comprehensive, real-time view of the cell-autonomous mechanisms involved in ischemic stroke and reperfusion, we applied the next-generation sequencing (NGS) technology to characterize the temporal changes in gene expression profiles using primarily cultured hippocampal neurons under an oxygen-glucose deprivation/reperfusion (OGD/R) condition. We first identified the differentially expressed genes (DEGs) between normal cultured neurons, neurons with OGD, and neurons with OGD followed by reperfusion for 6 h, 12 h, and 18 h, respectively. We then performed bioinformatics analyses, including gene ontological (GO) and pathway analysis and co-expression network analysis to screen for novel key pathways and genes involved in the pathology of OGD/R. After we confirmed the changes of selected key genes in hippocampal cultures with OGD/R, we further validated their expression changes in an in vivo ischemic stroke model (MCAO). Finally, we demonstrated that prevention of the up-regulation of a key gene (Itga5) associated with OGD/R promoted hippocampal neuronal survival. Our research thereby provided novel insights into the molecular mechanisms in ischemic stroke pathophysiology and potential targets for therapeutic intervention after ischemic stroke.

Hepatocyte growth factor inhibits hypoxia/reoxygenation-induced activation of xanthine oxidase in endothelial cells through the JAK2 signaling pathway

Vascular endothelial cells (ECs) appear to be one of the primary targets of hypoxia/reoxygenation (H/R) injury. In our previous study, we demonstrated that hepatocyte growth factor (HGF) exhibited a protective effect in cardiac microvascular endothelial cells (CMECs) subjected to H/R by inhibiting xanthine oxidase (XO) by reducing the cytosolic Ca2+ concentration increased in response to H/R. The precise mechanisms through which HGF inhibits XO activation remain to be determined. In the present study, we examined the signaling pathway through which HGF regulates Ca2+ concentrations and the activation of XO during H/R in primary cultured rat CMECs. CMECs were exposed to 4 h of hypoxia and 1 h of reoxygenation. The protein expression of XO and the activation of the phosphoinositide 3-kinase (PI3K), janus kinase 2 (JAK2) and p38 mitogen-activated protein kinase (p38 MAPK) signaling pathways were detected by western blot analysis. Cytosolic calcium (Ca2+) concentrations and reactive oxygen species (ROS) levels were measured by flow cytometry. The small interfering RNA (siRNA)‑mediated knockdown of XO inhibited the increase in ROS production induced by H/R. LY294002 and AG490 inhibited the H/R-induced increase in the production and activation of XO. The PI3K and JAK2 signaling pathways were activated by H/R. The siRNA‑mediated knockdown of PI3K and JAK2 also inhibited the increase in the production of XO protein. HGF inhibited JAK2 activation whereas it had no effect on PI3K activation. The siRNA-mediated knockdown of JAK2 prevented the increase in cytosolic Ca2+ induced by H/R. Taken together, these findings suggest that H/R induces the production and activation of XO through the JAK2 and PI3K signaling pathways. Furthermore, HGF prevents XO activation following H/R primarily by inhibiting the JAK2 signaling pathway and in turn, inhibiting the increase in cytosolic Ca2+.

Maternal seizures can affect the brain developing of offspring

To elucidate the impact of maternal seizures in the developing rat brain, pregnant Wistar rats were subjected to the pilocarpine-induced seizures and pups from different litters were studied at different ages. In the first 24 h of life, blood glucose and blood gases were analyzed. (14)C-leucine [(14)C-Leu] incorporation was used to analyze protein synthesis at PN1, and Western Blot method was used to analyze protein levels of Bax, Bcl-2 and Poly(ADP-ribose) polymerase-1 (PARP-1) in the hippocampus (PN3-PN21). During the first 22 days of postnatal life, body weight gain, length, skull measures, tooth eruption, eye opening and righting reflex have been assessed. Pups from naive mothers were used as controls. Experimental pups showed a compensated metabolic acidosis and hyperglycemia. At PN1, the [(14)C-Leu] incorporation into different studied areas of experimental pups was lower than in the control pups. During development, the protein levels of Bax, Bcl-2 and PARP-1 in the hippocampus of experimental pups were altered when compared with control pups. A decreased level of pro- and anti-apoptotic proteins was verified in the early postnatal age (PN3), and an increased level of pro-apoptotic proteins concomitant with a reduced level of anti-apoptotic protein was observed at the later stages of the development (PN21). Experimental pups had a delay in postnatal growth and development beyond disturb in protein synthesis and some protein expression during development. These changes can be result from hormonal alterations linked to stress and/or hypoxic events caused by maternal epileptic seizures during pregnancy.

Revisiting Cerebral Postischemic Reperfusion Injury: New Insights in Understanding Reperfusion Failure, Hemorrhage, and Edema

Cerebral postischemic reperfusion injury is defined as deterioration of ischemic brain tissue that parallels and antagonizes the benefits of restoring cerebral circulation after therapeutic thrombolysis for acute ischemic stroke. To understand the paradox of injury caused by treatment, we first emphasize the phenomenon in which recanalization of an occluded artery does not lead to tissue reperfusion. Additionally, no-reflow after recanalization may be due to injury of the neurovascular unit, distal microthrombosis, or both, and certainly worsens outcome. We examine the mechanism of molecular and sub-cellular damage in the neurovascular unit, notably oxidative stress, mitochondrial dysfunction, and apoptosis. At the level of the neurovascular unit, which mediates crosstalk between the damaged brain and systemic responses in blood, we summarize emerging evidence demonstrating that individual cell components play unique and cumulative roles that lead to damage of the blood–brain barrier and neurons. Furthermore, we review the latest developments in establishing a link between the immune system and microvascular dysfunction during ischemic reperfusion. Progress in assessing reperfusion injury has also been made, and we review imaging studies using various magnetic resonance imaging modalities. Lastly, we explore potential treatment approaches, including ischemic preconditioning, postconditioning, pharmacologic agents, and hypothermia.

Upregulation of ICAM-1 in diabetic rats after transient forebrain ischemia and reperfusion injury

Background

Hyperglycemia exacerbates brain damage caused by cerebral ischemia. Neuroinflammation may play a role in mediating such enhanced damage. The objectives of this study were to examine the mRNA and protein levels and cell type distribution of ICAM-1 after cerebral ischemia in normo-and diabetic hyperglycemic rats.

Results

Compared to normoglycemic ischemia animals, diabetes aggravated neuronal death, decreased Nissl body staining, and increased ICAM-1 mRNA and protein levels in the frontal cortex. The increased ICAM-1 was located not only in vascular endothelial cells but also in cortical neurons.

Conclusions

Our results suggest that exacerbated neuro-inflammation in the brain may mediate the detrimental effects of diabetes on the ischemic brain.

Temporal changes in hepatic antioxidant enzyme activities after ischemia and reperfusion in a rat liver ischemia model

This study investigated the hypothesis that administration of tilapia fish oil diet would attenuate warm liver ischemia/reperfusion injury (IRI) and whether fish oil modulates prooxidant/antioxidant status. Male Wistar rats were subjected to 30 min of approximately 70% hepatic ischemia followed by 1, 12, and 24 h reperfusion. Rats were randomly divided into three groups: sham-operated group (SO), control–warm hepatic ischemia (WI) group, and Oil–WI group given tilapia oil for 3 weeks followed by liver IRI. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were measured in the plasma. Levels of thiobarbituric acid reactive substances (TBARS) and antioxidant enzymes as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities were measured in liver fractions.

In the sham group, there was no enzymatic or histological change. I/R caused significant increase in serum AST, ALT, and tissue TBARS levels. As compared to the control group, animals treated with tilapia oil experienced a significant decrease ( p < 0.05) in AST and ALT levels in reperfusion periods. Tissue TBARS levels in Oil–WI group were significantly ( p < 0.05) reduced as compared to control group at 60 min after reperfusion. After ischemia, 1, 12, and 24 h of reperfusion, CAT, SOD, and GPx values were the lowest in the Oil–WI group and highest in the control group and were statistically significant ( p < 0.05). Histological analysis also revealed that fish oil provided some protection compared with the control group.

Tilapia oil exerts a protective effect during the early phase of reperfusion, and it modulates prooxidant/antioxidant status of rat liver subjected to warm IRI.

Resveratrol inhibits oxygen-glucose deprivation-induced MMP-3 expression and cell apoptosis in primary cortical cells via the NF-κB pathway

Resveratrol (Res) or trans-3,4',5-trihydroxystilbene, has been proven to exert neuroprotective effects in cerebral ischemia. The aim of the present study was to investigate whether Res has neuroprotective effects in primary cortical neurons subjected to transient oxygen-glucose deprivation (OGD) via inhibiting the expression of the gene encoding stromelysin-1, also known as matrix metalloproteinase-3 (MMP-3), and via inhibiting cell apoptosis. Primary cortical cells were exposed to OGD, followed by reoxygenation to induce transient ischemia. Res (50 µM) was added into the culture medium during transient ischemia in the presence or absence of the nuclear factor (NF)-κB inhibitor pyrrolidine dithiocarbamate (PDTC; 10 µM) or 500 µM of the nitric oxide (NO) donor NOC-18. Cell viability was assessed using the tetrazolium reduction (MTT) assay. Cell apoptosis was evaluated by flow cytometry. MMP-3 expression was analyzed by western blot and reverse transcription-polymerase chain reaction (RT-PCR), while the levels of inducible NO synthase (iNOS), NF-κB, caspase-3, cleaved caspase-3, B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax) were assayed by western blot. NO was detected using a spectrophotometric method. We found that the cellular viability was significantly reduced by transient OGD and that this effect was reversed by Res treatment. In addition, OGD was shown to induce cell apoptosis, the expression of Bax and the activation of caspase-3, and inhibit the expression of Bcl-2, and these effects were also reversed by Res treatment. Res treatment significantly reduced the level of MMP-3 that was induced by transient OGD, via inhibition of NF-κB expression. In addition, Res inhibited iNOS expression and NO synthesis that were induced by OGD. MMP-3 expression induced by NO was attenuated by Res treatment and was partially restored by exogenous NO using NOC-18. Taken together, these findings indicate that OGD induces apoptosis through canonical apoptosis signaling and by modulating the expression of MMP-3; Res can reverse the OGD-induced MMP-3 expression and cell apoptosis via the NF-κB-iNOS/NO pathway. Therefore, Res may be a promising agent for the treatment of neuronal injury associated with stroke.

Resveratrol protects primary cortical neuron cultures from transient oxygen-glucose deprivation by inhibiting MMP-9

It was recently shown that resveratrol exerts neuroprotective effects against cerebral ischemia in mice. The aim of the present study was to further confirm these effects in in vitro primary cortical neuron cultures with transient oxygen-glucose deprivation (OGD), and to investigate whether these effects are due to the inhibition of matrix metalloproteinase-9 (MMP-9) and of cell apoptosis. Neuronal primary cultures of cerebral cortex were prepared from BALB/c mice embryos (13-15 days). Cells from 14- to 16-day cultures were subjected to OGD for 3 h, followed by 21 h of reoxygenation to simulate transient ischemia. Different doses of resveratrol were added into the culture medium during the simulation of transient ischemia. The effect of the extracellular signal-regulated kinase (ERK) inhibitor U0126 was studied by adding U0126 (5 µg/µl, 4 µl) into the culture medium during transient ischemia; as a control, we used treatment of cells with 50 µM of resveratrol. Cell viability was investigated using the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) reduction assay. Cell apoptosis was assessed by flow cytometry. The effects of resveratrol on the expression of MMP-9 were analyzed by western blotting and reverse transcription-polymerase chain reaction (RT-PCR), while the levels of ERK, phosphorylated (p)-ERK, cleaved caspase-3, Bax and Bcl-2 were measured by western blotting. The results of the MTT assay showed that cell viability is significantly reduced by transient OGD. OGD induced cell apoptosis, the expression of Bax and the activation of caspase-3 and ERK, inhibited the expression of Bcl-2 and increased the expression of MMP-9, while these effects were reversed by treatment with resveratrol. The therapeutic efficacy of resveratrol was shown to be dose-dependent, with the most suitable dose range determined at 50-100 µM. Treatment with U0126 inhibited MMP-9 and Bax expression and caspase-3 activation, while it further promoted the expression of the anti-apoptotic molecule Bcl-2, suggesting that resveratrol inhibits MMP-9 expression and cell apoptosis by attenuating the activation of ERK1/2. In conclusion, OGD can induce apoptosis through canonical apoptotic signals and by regulating the expression of MMP-9; the anti-apoptotic activity of resveratrol and its inhibitory effect on MMP-9 expression contribute in the reduced activation of ERK.

Exclusion criteria for intravenous thrombolysis in stroke mimics: an observational study

BACKGROUND

Stroke mimics (SMs) are frequent in emergency departments (EDs), but are treated infrequently with intravenous recombinant tissue plasminogen activator (rt-PA) thrombolysis. We aimed at identifying the factors that lead to the exclusion of SMs from thrombolytic therapy.

METHODS

Consecutive patients presenting to the ED between December 2004 and March 2011 with symptoms that suggested acute ischemic stroke were included.

RESULTS

Eight hundred forty-two patients were included in this study; 113 (13.4%) were considered SMs; these patients were younger (P = .01), more frequently diabetic (P = .001), arrived later to the ED (P = .03), had lower National Institutes of Health Stroke Scale scores (P < .001), and higher frequencies of negative diffusion-weighted imaging studies (P = .002). The most common causes of cases of SM were toxic metabolic disorders (n = 34 [30.1%]) and seizures (n = 22 [19.5%]). The most frequent cause of consultation was aphasia (n = 43 [37.6%]). SM patients had a total of 152 contraindications for rt-PA, with 34 (30%) patients having >1 contraindication. The most frequent of these were being beyond the therapeutic window for thrombolysis (n = 96) and having deficits not measurable by the National Institutes of Health Stroke Scale or very mild symptoms before the start of rt-PA (n = 37). Twenty-four (21.2%) patients had both contraindications simultaneously. Two patients (1.76%) in the SM group were candidates for rt-PA but did not receive this treatment because they or their family rejected it. Of 729 stroke patients, 87 (11.9%) did receive rt-PA.

CONCLUSIONS

SM patients frequently had exclusion criteria for systemic thrombolysis, the most frequent being presenting beyond the established thrombolytic window.

2-vessel occlusion/hypotension: a rat model of global brain ischemia

Cardiac arrest followed by resuscitation often results in dramatic brain damage caused by ischemia and subsequent reperfusion of the brain. Global brain ischemia produces damage to specific brain regions shown to be highly sensitive to ischemia (1). Hippocampal neurons have higher sensitivity to ischemic insults compared to other cell populations, and specifically, the CA1 region of the hippocampus is particularly vulnerable to ischemia/reperfusion (2). The design of therapeutic interventions, or study of mechanisms involved in cerebral damage, requires a model that produces damage similar to the clinical condition and in a reproducible manner. Bilateral carotid vessel occlusion with hypotension (2VOH) is a model that produces reversible forebrain ischemia, emulating the cerebral events that can occur during cardiac arrest and resuscitation. We describe a model modified from Smith et al. (1984) (2), as first presented in its current form in Sanderson, et al. (2008) (3), which produces reproducible injury to selectively vulnerable brain regions (3-6). The reliability of this model is dictated by precise control of systemic blood pressure during applied hypotension, the duration of ischemia, close temperature control, a specific anesthesia regimen, and diligent post-operative care. An 8-minute ischemic insult produces cell death of CA1 hippocampal neurons that progresses over the course of 6 to 24 hr of reperfusion, while less vulnerable brain regions are spared. This progressive cell death is easily quantified after 7-14 days of reperfusion, as a near complete loss of CA1 neurons is evident at this time. In addition to this brain injury model, we present a method for CA1 damage quantification using a simple, yet thorough, methodology. Importantly, quantification can be accomplished using a simple camera-mounted microscope, and a free ImageJ (NIH) software plugin, obviating the need for cost-prohibitive stereology software programs and a motorized microscopic stage for damage assessment.

Neuroglobin is up-regulated in the cerebellum of pups exposed to maternal epileptic seizures

To evaluate a potential insult in the cerebellum of pups exposed to maternal epileptic seizures during intrauterine life, female rats were subjected to pilocarpine-induced epilepsy. Pups from different litters were sacrificed at 1, 3, 7 and 14 post-natal days (PN) and neuroglobin (Ngb) and gliosis were analyzed in the cerebellum by Western blotting (WB) and RT-PCR. (14)C-l-leucine-[(14)C-Leu] incorporation was used to analyze protein synthesis at PN1. Nitric Oxide (NO) and thiobarbituric acid-reactive substances (TBARS) levels were also measured. Pups from naive mothers were used as controls. The mRNA level of Ngb was increased in experimental animals at PN1 ((**)p ≤ 0.001) and PN3 ((**)p ≤ 0.001), at PN7 ((***)p ≤ 0.0001) and at PN14 ((**)p ≤ 0.001) compared to the respective controls. The protein level of Ngb increased significantly in the experimental pups at PN1 ((*)p ≤ 0.05) and at PN3 ((**)p ≤ 0.001), when compared to the control pups at PN1 and PN3. At PN7 and PN14 no difference was found. The mRNA level of GFAP increased significantly about two times at PN3 ((*)p ≤ 0.05) and PN7 ((*)p ≤ 0.05) in the experimental pups when compared to the respective controls, but was unchanged in the other studied ages. Data showed that experimental pups at PN1 exhibited reduced (about 2 times, (*)p ≤ 0.05) total protein synthesis in the cerebellum when compared to control. No differences were found in the NO and TBARS levels. Our data support the hypothesis that an up-regulation of Ngb could be a compensatory mechanism in response to the hypoxic-ischemic insults caused by seizures in pups during intrauterine life.

Urinary trypsin inhibitor suppresses excessive superoxide anion radical generation in blood, oxidative stress, early inflammation, and endothelial injury in forebrain ischemia/reperfusion rats

OBJECTIVES

To investigate the effects of ulinastatin, a urinary trypsin inhibitor (UTI), on jugular venous superoxide radical (O₂⁻·) generation, oxidative stress, early inflammation, and endothelial activation in forebrain ischemia/reperfusion (FBI/R) rats.

METHODS

Fourteen Wistar rats were allocated to a control group (n = 7) and a UTI group (n = 7). Throughout the experiments, O₂⁻· in the jugular vein was measured by the produced current using a novel electrochemical O₂⁻· sensor. Forebrain ischemia was induced by occlusion of the bilateral common caroti darteries with hemorrhagic hypotension for 20 min, followed by reperfusion. In the UTI group, UTI (5 U/g) was administered intravenously immediately after reperfusion. At 60 min after reperfusion, plasma and brain were harvested, and malondialdehyde, high-mobility group box 1 (HMGB1) protein, and intercellular adhesion molecule-1 (ICAM-1) were measured.

RESULTS

O₂⁻· current increased gradually during forebrain ischemia in both groups. The current increased markedly in the control group immediately after reperfusion but was significantly attenuated in the UTI group after reperfusion. Brain and plasma malondialdehyde, HMGB1, and ICAM-1 were significantly attenuated in the UTI group compared with those in the control group, except for brain HMGB1, which was associated with the amount of O₂⁻· generated during FBI/R.

DISCUSSION

UTI suppressed jugular venous O₂⁻· generation, oxidative stress, early inflammation, and endothelial activation in FBI/R rats. Therefore, UTI might be a useful agent for the therapy of the cerebral ischemia/reperfusion pathophysiology.

Moderate hypothermia suppresses jugular venous superoxide anion radical, oxidative stress, early inflammation, and endothelial injury in forebrain ischemia/reperfusion rats

The aim of this study was to assess the effect of moderate hypothermia (MH) on generation of jugular venous superoxide radical (O2-.), oxidative stress, early inflammation, and endothelial injury in forebrain ischemia/reperfusion (FBI/R) rats. Twenty-one Wistar rats were allocated to a control group (n=7, 37 degrees C), a pre-MH group (n=7, 32 degrees C before ischemia), and a post-MH group (n=7, 32 degrees C after reperfusion). MH was induced before induction of ischemia in the pre-MH group and just after reperfusion in the post-MH group. Forebrain ischemia was induced by occlusion of bilateral common carotid arteries with hemorrhagic hypotension for 10 min, followed by reperfusion. O(2)(-)(.) in the jugular vein was measured from the produced current using a novel O2-. sensor. The O2-. current showed a gradual increase during forebrain ischemia in the control and post-MH groups but was attenuated in the pre-MH group. Following reperfusion, the current showed a marked increase in the control group but was strongly attenuated in the pre- and post-MH groups. Concentrations of malondialdehyde, high-mobility group box 1 (HMGB1) protein, and intercellular adhesion molecule-1 (ICAM-1) in the brain and plasma 120 min after reperfusion in the pre- and post-MH groups were significantly lower than those in the control group, except for plasma HMGB1 in the post-MH group. In conclusion, MH suppressed O2-. measured in the jugular vein, oxidative stress, early inflammation, and endothelial injury in FBI/R rats.

Xanthine oxidase is one of the major sources of superoxide anion radicals in blood after reperfusion in rats with forebrain ischemia/reperfusion

We recently reported that excessive superoxide anion radical (O(2)(-)) was generated in the jugular vein during reperfusion in rats with forebrain ischemia/reperfusion using a novel electrochemical sensor and excessive O(2)(-) generation was associated with oxidative stress, early inflammation, and endothelial injury. However, the source of O(2)(-) was still unclear. Therefore, we used allopurinol, a potent inhibitor of xanthine oxidase (XO), to clarify the source of O(2)(-) generated in rats with forebrain ischemia/reperfusion. The increased O(2)(-) current and the quantified partial value of electricity (Q), which was calculated by the integration of the current, were significantly attenuated after reperfusion by pretreatment with allopurinol. Malondialdehyde (MDA) in the brain and plasma, high-mobility group box 1 (HMGB1) in plasma, and intercellular adhesion molecule-1 (ICAM-1) in the brain and plasma were significantly attenuated in rats pretreated with allopurinol with dose-dependency in comparison to those in control rats. There were significant correlations between total Q and MDA, HMGB, or ICAM-1 in the brain and plasma. Allopurinol pretreatment suppressed O(2)(-) generation in the brain-perfused blood in the jugular vein, and oxidative stress, early inflammation, and endothelial injury in the acute phase of forebrain ischemia/reperfusion. Thus, XO is one of the major sources of O(2)(-)- in blood after reperfusion in rats with forebrain ischemia/reperfusion.

NR1 and GluR2 expression mediates excitotoxicity in chronic hypobaric hypoxia

Hypobaric hypoxia has been reported to cause memory dysfunction. The possible molecular mechanism involved, however, remains to be explored. The role that glutamate and its receptors play in causing excitotoxicity in ischemia and neurodegenerative diseases indicates the possible occurrence of a similar phenomenon in hypobaric hypoxia. The present study aimed to elucidate the molecular events occurring at glutamatergic synapses in hypobaric hypoxia using Sprague-Dawley rats as a model system. The animals were exposed to an altitude of 7,600 m for different durations. Hypobaric hypoxia was found to cause oxidative stress, chromatin condensation, and neurodegeneration. A temporal change in the expression of the ionotropic receptors of glutamate was also observed. Expression of the N-methyl-D-aspartate (NMDA) receptor increased, and expression of glutamate receptor subunit 2 of the alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate receptor decreased. We also observed increased activity of glutamate dehydrogenase, indicating greater synthesis and release of glutamate after 3 and 7 days of exposure. Administration of a selective NMDA antagonist during exposure was found to ameliorate neuronal degeneration, providing evidence for the occurrence of excitotoxicity in hypobaric hypoxia. Our study indicates that excitotoxicity occurs in hypobaric hypoxia. This study also indicates the appropriate period for drug administration during exposure to hypobaric hypoxia and establishes ionotropic receptors of glutamate as potential therapeutic targets for ameliorating high-altitude-induced cognitive dysfunction.

Inhibition of caspases and intracellular free Ca2+ concentrations are involved in resveratrol protection against apoptosis in rat primary neuron cultures

AIM

To investigate the influence of resveratrol (Res), a nutritional antioxidant, on the inhibition of apoptosis in rat primary neuron cultures.

METHODS

The cultured cortical neurons of neonatal Sprague-Dawley rats were pretreated with Res (0.1, 1.0, and 10.0 micromol/L) and oxygen-glucose deprivation/reperfusion (OGD/RP) with oxygen and glucose were initiated at d 10 in vitro. Neuronal apoptosis was determined by flow cytometry, and morphological changes of neurons were observed by an electron microscope. For the mechanism studies, the intracellular free calcium concentration ([Ca2+]i) and the transcription of caspases-3 and -12 in neurons were detected by Fura 2/AM loading and real-time RT-PCR, respectively.

RESULTS

OGD/RP insult could induce an increase in the apoptotic rate of neurons (from 11.1% to 49.0%), and elicit an obvious morphological change in neurons; pretreatments with Res (0.1, 1.0, and 10.0 micromol/L, respectively) significantly reduced the elevated rate of apoptosis to 41.7%, 40.8%, and 37.4%, respectively, and ameliorated the neuronal morphological injury. Similarly, the OGD/RP insult obviously elicited the elevated levels of the [Ca2+]i and the expressions of caspases-3 and -12 mRNA in neurons. Res pretreatments markedly depressed the neuronal abnormal elevation of [Ca2+]i and the overexpression of caspases-3 and -12 mRNA in a concentration-dependent manner.

CONCLUSION

Res can attenuate the rat cortical neuronal apoptosis induced by OGD/RP. The mechanisms are, at least partly, due to the inhibition of the calcium overload and the overexpression of caspases-3 and -12 mRNA.

Profile of glutamate uptake and cellular viability in hippocampal slices exposed to oxygen and glucose deprivation: developmental aspects and protection by guanosine

Stroke syndromes are a major cause of disability in middle and later life resulting in severe neuronal degeneration and loss of brain functions. In situations with energy failure, glutamate transport is impaired and high levels of this amino acid accumulate on the synaptic cleft. Our group has showed that guanosine exerts neuroprotection against neurotoxicity situations. The aim of this work is draw a post-ischemic profile of glutamate uptake and cell damage using an oxygen and glucose deprivation model (OGD) in hippocampal slices from young (P10) and adult (P60) rats, analyzing guanosine effect. OGD decreases glutamate uptake in both ages and recovery times, although decrease in cell viability was only observed 1 and 3 h after OGD in young and adult animals, respectively. Guanosine partially protected cell damage from 1 h in P10 and at 3 h in P60 rats and avoided glutamate uptake decrease from P10 rats at 3 h. The impairment of glutamate transporters since immediately after the insult observed here is probably due to an energetic failure; loss of cell viability was only observed from 1 h after OGD. The mechanism by which guanosine acts in the 'ischemic' model used here is still unknown, but evidence leads to its antiapoptotic effect.

Hypothermia for neuroprotection after cardiac arrest: mechanisms, clinical trials and patient care

Therapeutic hypothermia is a proven part of cardio-cerebral resuscitation after cardiac arrest as it improves neurologic outcomes after hypoxic brain injury. This article reviews the mechanisms of hypothermic neuroprotection, the clinical trials that support its use after cardiac arrest, as well as the impact of hypothermia on patient management and prognosis. In caring for patients suffering hypoxic brain injury after cardiac arrest, the role of the neurologist is no longer limited to prognosis but is now to become actively involved in clinical management which includes the use of therapeutic hypothermia.

FeTPPS protects against global cerebral ischemic-reperfusion injury in gerbils

Neuronal damage following cerebral ischemia is mediated by various mechanisms, among which nitrosative stress plays an important role. Peroxynitrite, a powerful oxidant, contributes heavily to the neuronal damage in cerebral ischemic-reperfusion (IR) injury. In the present study, we have investigated the neuroprotective effects of a peroxynitrite decomposition catalyst, 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrinato iron(III) [FeTPPS] in global cerebral IR injury in gerbils. Neurological damage was significantly attenuated by FeTPPS treatment (1 and 3mgkg(-1), i.p.) as evident from reduction in neurological symptoms, hyperlocomotion, memory impairment and CA1 hippocampal neuronal damage in IR challenged gerbils. FeTPPS treatment also attenuated the increased malondialdehyde (MDA) levels and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) positive cells after cerebral IR injury. Results of this study demonstrates the neuroprotective activity of FeTPPS in global cerebral IR injury and its neuroprotective effects may be attributed to reduction in oxidative stress and DNA fragmentation.

Effects of intrathecal bupivacaine in conjunction with hypothermia on neuronal protection against transient spinal cord ischemia in rats

BACKGROUND

Excitotoxic neuronal injury from ischemia may be reduced by local anesthetics. We investigated the neuroprotective effects of intrathecally administered bupivacaine and hypothermia in a rat model of transient spinal cord ischemia.

METHODS

PE-10 intrathecal catheter-implanted male Sprague-Dawley rats were randomly assigned to one of four groups: normothermia (NT) and hypothermia (HT) groups (given 15 microl of normal saline) and bupivacaine (B) and bupivacaine-hypothermia (BHT) groups (given 15 mul of 0.5% bupivacaine). Transient spinal cord ischemia was induced by inflation of a 2F Fogarty catheter placed in the aortic arch for 12 min. The rectal temperature was maintained at 37.0 +/- 0.5 degrees C for the NT and B groups, and at 34.5 +/- 0.5 degrees C for the HT and BHT groups. Motor and sensory deficit scores were assessed 2 and 24 h after reperfusion. Lumbar spinal cords were harvested for histopathology and immunoreactivity of heat shock protein 70 (HSP70).

RESULTS

After reperfusion, the motor and sensory deficit scores of the NT group were significantly higher than those of the HT (P < 0.05) and BHT (P < 0.001) groups. Significant differences were evident in the motor and sensory deficit scores between the HT and BHT groups at 24 h (P < 0.05). Neuronal cell death and immunoreactivity of HSP70 were frequently observed in the NT and BT groups, but not in the HT and BHT groups.

CONCLUSIONS

These results collectively suggest that intrathecal bupivacaine does not provide neuroprotection during normothermic transient spinal cord ischemia in rats, but enhances the neuroprotective effects of hypothermia.

Cellular and molecular pathways of ischemic neuronal death

Three routes have been identified triggering neuronal death under physiological and pathological conditions. Excess activation of ionotropic glutamate receptors cause influx and accumulation of Ca2+ and Na+ that result in rapid swelling and subsequent neuronal death within a few hours. The second route is caused by oxidative stress due to accumulation of reactive oxygen and nitrogen species. Apoptosis or programmed cell death that often occurs during developmental process has been coined as additional route to pathological neuronal death in the mature nervous system. Evidence is being accumulated that excitotoxicity, oxidative stress, and apoptosis propagate through distinctive and mutually exclusive signal transduction pathway and contribute to neuronal loss following hypoxic-ischemic brain injury. Thus, the therapeutic intervention of hypoxic-ischemic neuronal injury should be aimed to prevent excitotoxicity, oxidative stress, and apoptosis in a concerted way.

Near-infrared spectroscopy: a tool to monitor cerebral hemodynamic and metabolic changes after cardiac arrest in rats

INTRODUCTION

Cardiac arrest (CA) is associated with poor neurological outcome and is associated with a poor understanding of the cerebral hemodynamic and metabolic changes. The objective of this study was to determine the applicability of near-infrared spectroscopy (NIRS), to observe the changes in cerebral total hemoglobin (T-Hb) reflecting cerebral blood volume, oxygenation state of Hb, oxidized cytochrome oxidase (Cyto-C), and brain water content following CA.

METHODS

Fourteen rats were subjected to normothermic (37.5 degrees C) or hypothermic (34 degrees C) CA induced by 8 min of asphyxiation. Animals were resuscitated with ventilation, cardiopulmonary resuscitation (CPR), and epinephrine (adrenaline). Hypothermia was induced before CA. NIRS was applied to the animal head to measure T-Hb with a wavelength of 808 nm (n = 10) and oxygenated/deoxygenated Hb, Cyto-C, and brain water content with wavelengths of 620-1120 nm (n = 4).

RESULTS

There were no technical difficulties in applying NIRS to the animal, and the signals were strong and consistent. Normothermic CA caused post-resuscitation hyperemia followed by hypoperfusion determined by the level of T-Hb. Hypothermic CA blunted post-resuscitation hyperemia and resulted in more prominent post-resuscitation hypoperfusion. Both, normothermic and hypothermic CA resulted in a sharp decrease in oxygenated Hb and Cyto-C, and the level of oxygenated Hb was higher in hypothermic CA after resuscitation. There was a rapid increase in brain water signals following CA. Hypothermic CA attenuated increased water signals in normothermic CA following resuscitation.

CONCLUSION

NIRS can be applied to monitor cerebral blood volume, oxygenation state of Hb, Cyto-C, and water content following CA in rats.

Temporal changes in cerebral antioxidant enzyme activities after ischemia and reperfusion in a rat focal brain ischemia model: effect of dietary fish oil

This study investigated the neuroprotective effects of dietary supplementation of fish oil on both brain infarction and the activities of antioxidant enzymes. Male Sprague-Dawley rats (4-weeks old) were divided into two groups and received either a regular diet (RD) or a fish-oil-supplemented diet (FOD) for 6 weeks prior to middle cerebral artery (MCA) occlusion. The infarction volume of the brain was calculated using image analysis after staining. Antioxidant enzymes were measured before ischemia (BI), after 2 h of ischemia (AI) and after 24 h (24hR), 48 h (48hR) and after 7 days (7dR) of reperfusion. The infarction volume of the brain was significantly smaller in the FOD group than in the RD group after 24 h of reperfusion (p<0.05). Before ischemia, the levels of lipid peroxide and the glutathione peroxidase (GPx) activity were higher in the FOD group than in the RD group. During reperfusion, the catalase (CAT) activity in the FOD group remained at the preischemia level until after 48 h of reperfusion, while those in the RD group did not. The Mn-superoxide dismutase (SOD) activity and GPx activity were higher in the FOD group than in the RD group only after 2 h of ischemia. In the fatty acid analysis, the ratio of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) were higher in the FOD group than in the RD group (p<0.05). Our results demonstrate that supplementing the diet with fish oil could decrease the cerebral infarction volume following ischemia and reperfusion (I/R) partly by working directly as an antioxidant and partly by modulating antioxidant enzyme activities.

Cerebral ischemia and reperfusion: the pathophysiologic concept as a basis for clinical therapy

The ischemic penumbra has been documented in the laboratory animal as severely hypoperfused, nonfunctional, but still viable brain tissue surrounding the irreversibly damaged ischemic core. Saving the penumbra is the main target of acute stroke therapy, and is the theoretical basis behind the reperfusion concept. In experimental focal ischemia, early reperfusion has been reported to both prevent infarct growth and aggravate edema formation and hemorrhage, depending on the severity and duration of prior ischemia and the efficiency of reperfusion, whereas neuronal damage with or without enlarged infarction also may result from reperfusion (so-called reperfusion injury). Activated neutrophils contribute to vascular reperfusion damage, yet posthypoxic cellular injury occurs in the absence of inflammatory species. Protein synthesis inhibition occurs in neurons during reperfusion after ischemia, underlying the role that these pathways play in prosurvival and proapoptotic processes that may be differentially expressed in vulnerable and resistant regions of the reperfused brain tissue. Ischemia-induced decreases in the mitochondrial capacity for respiratory activity probably contribute to the ongoing impairment of energy metabolism during reperfusion and possibly also the magnitude of changes seen during ischemia. From these experimental data, the concept of single-drug intervention cannot be effective. Further experimental research is needed, especially of the study of biochemical markers of the injury process to establish the role of several drugs.

Different susceptibility of facilitatory and inhibitory spinal pathways to ischemia in the cat

The sensitivity of different excitatory and inhibitory segmental reflex pathways to ischemia was investigated by monosynaptic reflex testing in the spinal cat. Spinal cord ischemia was established by aortal snare occlusion of 1-10 min duration. Excitatory and inhibitory spinal pathways showed statistically significant different susceptibility to ischemic impact. In the period of decreasing responses after the onset of ischemia the transmission through oligo- or polysynaptic, facilitatory or inhibitory pathways was found to be depressed earlier than that of monosynaptic pathways. The period from the end of ischemia until the beginning of recovery of reflex effects was significantly longer for inhibitory effects, compared to the monosynaptic reflexes alone.The results indicated that interneurones of excitatory segmental pathways may be less sensitive to ischemia than motoneurones, and motoneurones seem to be less sensitive to ischemia than interneurones of inhibitory pathways. In high spinal animals, with a relatively high level of extensor inhibition, the enhanced excitability of inhibitory interneurones to GS motoneurones may be responsible for their sensitivity to ischemia, due to an increased rate of O(2) consumption and exhaustion of high-energy phosphate resources.

The role of pharmacology in spinal cord protection during thoracic aortic reconstruction

Surgery of the thoracic aorta continues to have a significant risk of neurologic complication. Several strategies to minimize this risk are emerging. Pharmacologic protection from these complications continues to be researched, but at this point few medications are being used clinically. This article reviews the pathophysiology of ischemic spinal cord injury and summarizes the investigational pharmacology that may prevent these serious complications.

Centrifugal pump support for distal aortic perfusion during repair of traumatic thoracic aortic injury

Paraplegia from ischemic injury of the spinal cord and renal failure from inadequate perfusion of the kidneys may occur from aortic cross-clamping during repair of traumatic thoracic aortic injuries. After Institutional Review Board approval, we retrospectively reviewed the charts of 26 patients surgically treated for traumatic transection of the descending thoracic aorta during a 14 year period (1987-2001), using centrifugal pump (Sarns) support for distal aortic perfusion. The study group comprised 19 males and 7 females, whose ages ranged from 15 to 69 years. For all but 1 patient, who fell from a flagpole, the injuries were incurred in motor vehicle accidents. Aortic cross-clamp time lasted between 5 to 78 min (median = 40 min). Mean arterial pressure ranged from 50 to 80 mm Hg (median = 70 mm Hg). All patients survived operation without developing paraplegia or renal failure. Distal centrifugal pump perfusion during repair of traumatic injury of the descending thoracic aorta is a valuable adjunct during surgical treatment and aids in preservation of spinal cord and renal function.

Sumatriptan scavenges superoxide, hydroxyl, and nitric oxide radicals: in vitro electron spin resonance study

BACKGROUND

The molecular mechanisms of migraine have not yet been clarified. Oxygen free radicals have been implicated in the genesis of many pathological processes, including migraine. Sumatriptan succinate is known to be a very effective drug for acute relief of migraine attack.

OBJECTIVE

To investigate the direct scavenging activities of sumatriptan for superoxide, hydroxyl, and nitric oxide (NO) radicals using electron spin resonance (ESR) spectroscopy.

METHODS

Measurement of superoxide and hydroxyl radical scavenging activities was performed by ESR using 5,5-dimethyl-1-pyrroline-N-oxide as a spin trap. NO was generated from 1-hydroxy-2-oxo-3-(N-3-methyl-3-aminopropyl)-3-methyl-1-triazene and analyzed by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl produced from the reaction between 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and NO.

RESULTS

The ESR study demonstrated that sumatriptan scavenged superoxide, hydroxyl, and NO in a dose-dependent manner.

CONCLUSIONS

Sumatriptan has direct scavenging activity on free radicals and NO. Acute migraine drugs with antioxidant properties may provide heretofore unheralded benefits via this mechanism.

Angiotensin protects cortical neurons from hypoxic-induced apoptosis via the angiotensin type 2 receptor

The effects of angiotensin on mouse cortical neuronal cultures exposed to chemical-induced hypoxia was investigated. Cultures exposed to 10 mM sodium azide for 5 min showed a 17% increase in apoptosis when assayed 24 h postinsult. The N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 blocked sodium azide-induced cell death suggesting that the NMDA receptor contributes to the mediated cell death. Pretreatment of cultured neurons with angiotensin decreased sodium azide-induced apoptosis by 94%. When the AT(1) receptor was blocked by its receptor antagonist, losartan, angiotensin activation of the AT(2) receptor completely inhibited sodium azide-induced apoptosis. Pretreatment of neurons with the AT(2) receptor antagonist PD123319 resulted in angiotensin reducing sodium azide-induced apoptosis by 48%. These results demonstrate that angiotensin can significantly attenuate sodium azide-induced apoptosis primarily through activation of the AT(2) receptor and suggests that angiotensin may have a protective role in neurons undergoing ischemic injury.

GCPII (NAALADase) inhibition prevents long-term diabetic neuropathy in type 1 diabetic BB/Wor rats

AIMS/HYPOTHESIS

Hyperglutamatergic activity induced by ischemia is believed to underlie neuronal damage in a variety of neurological disorders, including neuropathic pain. Since ischemia is believed to be a prominent mechanism involved in diabetic polyneuropathy (DPN), we investigated the effect of the glutamate carboxypeptidase II (GCPII, EC #3.4-17.21; previously termed NAALADase), an enzyme responsible for the hydrolysis of the neuropeptide NAAG to NAA and glutamate, on the development of DPN in type 1 diabetic BB/Wor rats.

METHODS

Diabetic animals were treated with 10 mg/kg/day i.p. of the selective GCPII inhibitor GPI-5232 from onset of diabetes for 6 months. Hyperalgesia to thermal stimulation and nerve conduction velocity (NCV) were measured monthly. The effect on structural DPN was assessed by scoring of single, teased myelinated fibers, myelinated fiber morphometry and ultrastructural examination of C-fibers at 6 months.

RESULTS

GCPII inhibition showed significant but partial effects on hyperalgesia (p<0.001), nerve conduction slowing (p<0.01) axonal and nodal structural changes (p<0.001), small myelinated fiber atrophy, and degenerative changes of C-fibers.

CONCLUSIONS

GCPII inhibition has beneficial effects on hyperalgesia, nerve function, and structural degenerative changes in DPN, which are likely mediated by inhibition of ischemia-induced glutamate release.