Biochemical changes associated with selective neuronal death following short-term cerebral ischaemia

Licochalcone A attenuates NMDA-induced neurotoxicity

This study investigates the effect of Licochalcone A (Lico-A), a flavonoid from licorice roots known for its anti-inflammatory, anti-cancer, and antioxidant properties, on NMDA-induced neurotoxicity in primary cultured rat hippocampal neurons. The study measured cell survival following NMDA and Lico-A exposure, revealing that Lico-A at a 2.5 μg/ml significantly improved cell viability, countering the detrimental effects of NMDA. The study also analyzed synaptic changes by examining both postsynaptic density 95 (PSD95) and synaptophysin-targeted imaging, showing that Lico-A treatment resulted in a significant increase in synaptic puncta, contrasting with the reduction observed under NMDA exposure. Furthermore, levels of phosphorylated mixed lineage kinase domain-like pseudokinase (P-MLKL) and phosphorylated receptor-interacting serine/threonine-protein kinase 3 (P-RIP3), key necroptosis regulators, were measured using Western blotting. The results showed an increase in P-MLKL and P-RIP3 in neurons exposed to NMDA, which was reduced following Lico-A treatment. The response of astrocyte and microglia was also evaluated by immunostaining for glial fibrillary acidic protein (GFAP), ionized calcium-binding adaptor molecule 1 (IBA-1) and tumor necrosis factor alpha (TNF-α). These markers exhibited heightened expression in the NMDA group, which was substantially reduced by Lico-A treatment. These findings suggest that Lico-A has neuroprotective effects against NMDA-induced neurotoxicity, potentially contributing to synaptic preservation, inhibition of neuronal necroptosis, and modulation of glial activation. Therefore, Lico-A shows promise as a neuroprotective agent for conditions associated with NMDA-related neurotoxicity.

MST1 mediates the N-methyl-D-aspartate-induced excitotoxicity in mouse cortical neurons

Excessive activation of the ionotropic N-methyl-D-aspartate (NMDA) receptor has been shown to cause abnormally high levels of Ca2+ influx, thereby leading to excitotoxic neuronal death. In this study, exposure of mouse primary cortical neurons to NMDA resulted in the cleavage and activation of mammalian sterile 20-like kinase-1 (MST1), both of which were mediated by calpain 1. In vitro cleavage assay data indicated that calpain 1 cleaves out the autoinhibitory domain of MST1 to generate an active form of the kinase. Furthermore, calpain 1 mediated the cleavage and activation of wild-type MST1, but not of MST1 (G339A). Intriguingly, NMDA/calpain-induced MST1 activation promoted the nuclear translocation of the kinase and the phosphorylation of histone H2B in mouse cortical neurons, leading to excitotoxicity. Thus, we propose a previously unrecognized mechanism of MST1 activation associated with NMDA-induced excitotoxic neuronal death.

Remifentanil Suppresses Oxidative Stress and Inflammation Induced by Glutamate via Activation of PPARγ/HO-1 Signaling Pathway in Hippocampal Neuronal Cells

Excitotoxicity caused by glutamate severely damages the central nervous system, contributing to the progress of neurodegenerative diseases. Remifentanil is an ultra-short acting synthetic α-opioid receptor agonist and it protects the body against oxidative stress. Oxidative stress is a causative factor for neuronal cell death, contributing to the pathogenesis of neurological diseases. More importantly, remifentanil has been confirmed to have neuroprotective effects on cerebral ischemia. Hence, the aim of the present study was to investigate the molecular mechanism underlying the effect of remifentanil on glutamate (Glu)-induced oxidative stress and inflammation in hippocampal cells. In present study, the cell viability was detected via CCk-8 assay. The cell apoptosis was evaluated by tunel assay. Western blot was performed for measurement of protein expression level. Generation of ROS level was detected by the ROS Activity Assay Kit (KA3842, Abnova) and DCF-DA staining method. MDA and SOD levels were detected by corresponding kits. The results from the present study suggested that remifentanil enhanced cell viability, reduced cell apoptosis rate and prevented oxidative stress in glutamate-induced HT22 cells. The PPARγ/HO-1 pathway was activated by remifentanil. After inhibition of PPARγ/HO-1 pathway, the anti-apoptosis and anti-oxidative stress effects of remifentanil were abolished. In conclusion, remifentanil has anti-apoptosis and anti-oxidative stress effects on glutamate-induced HT22 Cells via PPARγ/HO-1 pathway. Hence, remifentanil is a promising agent for attenuation of cytotoxicity induced by glutamate, providing a new strategy for treatment of excitotoxicity caused by glutamate in the central nervous system.

Ischemia-Reperfusion under Hyperthermia Increases Heme Oxygenase-1 in Pyramidal Neurons and Astrocytes with Accelerating Neuronal Loss in Gerbil Hippocampus

It has been studied that the damage or death of neurons in the hippocampus is different according to hippocampal subregions, cornu ammonis 1–3 (CA1–3), after transient ischemia in the forebrain, showing that pyramidal neurons located in the subfield CA1 (CA1) are most vulnerable to this ischemia. Hyperthermia is a proven risk factor for brain ischemia and can develop more severe and extensive brain damage related with mortality rate. It is well known that heme oxygenase-1 (HO-1) activity and expression is increased by various stimuli in the brain, including hyperthermia. HO-1 can be either protective or deleterious in the central nervous system, and its roles depend on the expression levels of enzymes. In this study, we investigated the effects of hyperthermia during ischemia on HO-1 expression and neuronal damage/death in the hippocampus to examine the relationship between HO-1 and neuronal damage/death following 5-min transient ischemia in the forebrain using gerbils. Gerbils were assigned to four groups: (1) sham-operated gerbils with normothermia (Normo + sham group); (2) ischemia-operated gerbils with normothermia (Normo + ischemia group); (3) sham-operated gerbils with hyperthermia (39.5 ± 0.2 °C) during ischemia (Hyper + sham group); and (4) ischemia-operated gerbils with hyperthermia during ischemia (Hyper + ischemia group). HO-1 expression levels in CA1–3 of the Hyper + ischemia group were significantly higher than those in the Normo + ischemia group. HO-1 immunoreactivity in the Hyper + ischemia group was significantly increased in pyramidal neurons and astrocytes with time after ischemia, and the immunoreactivity was significantly higher than that in the Normo + ischemia group. In the Normo + Ischemia group, neuronal death was shown in pyramidal neurons located only in CA1 at 5 days after ischemia. However, in the Hyper + ischemia group, pyramidal neuronal death occurred in CA1–3 at 2 days after ischemia. Taken together, our findings showed that brain ischemic insult during hyperthermic condition brings up earlier and severer neuronal damage/death in the hippocampus, showing that HO-1 expression in neurons and astrocytes is different according to brain subregions and temperature condition. Based on these findings, we suggest that hyperthermia in patients with ischemic stroke must be taken into the consideration in the therapy.

Inhaled Gases as Therapies for Post-Cardiac Arrest Syndrome: A Narrative Review of Recent Developments

Despite recent advances in the management of post-cardiac arrest syndrome (PCAS), the survival rate, without neurologic sequelae after resuscitation, remains very low. Whole-body ischemia, followed by reperfusion after cardiac arrest (CA), contributes to PCAS, for which established pharmaceutical interventions are still lacking. It has been shown that a number of different processes can ultimately lead to neuronal injury and cell death in the pathology of PCAS, including vasoconstriction, protein modification, impaired mitochondrial respiration, cell death signaling, inflammation, and excessive oxidative stress. Recently, the pathophysiological effects of inhaled gases including nitric oxide (NO), molecular hydrogen (H₂), and xenon (Xe) have attracted much attention. Herein, we summarize recent literature on the application of NO, H₂, and Xe for treating PCAS. Recent basic and clinical research has shown that these gases have cytoprotective effects against PCAS. Nevertheless, there are likely differences in the mechanisms by which these gases modulate reperfusion injury after CA. Further preclinical and clinical studies examining the combinations of standard post-CA care and inhaled gas treatment to prevent ischemia-reperfusion injury are warranted to improve outcomes in patients who are being failed by our current therapies.

Multicompartment Microreactors Prevent Excitotoxic Dysfunctions In Rat Primary Cortical Neurons

Excitotoxicity is a cellular phenomenon that comprises the consequences of toxic actions of excitatory neurotransmitters, such as glutamate. This process is usually related to overproduction of reactive oxygen species (ROS) and ammonia (NH₄ ⁺ ) toxicity. Platinum nanoparticle (Pt-NP)-based microreactors able to degrade hydrogen peroxide (H₂ O₂ ) and NH₄ ⁺ , are previously described as a novel therapeutical approach against excitotoxicity, conferring protection to neuroblasts. Now, it is demonstrated that these microreactors are compatible with rat primary cortical neurons, show high levels of neuronal membrane interaction, and are able to improve cell survival and neuronal activity when neurons are exposed to H₂ O₂ or NH₄ ⁺ . Additionally, more complex microreactors are assembled, including enzyme-loaded liposomes containing glutamate dehydrogenase and glutathione reductase, in addition to Pt-NP. The in vitro activity of these microreactors is characterized and they are compared to the Pt-NP-based microreactors in terms of biological activity, concluding that they enhance cell viability similarly or more extensively than the latter. Extracellular electrophysiological recordings demonstrate that these microreactors rescue neuronal functionality lost upon incubation with H₂ O₂ or NH₄ ⁺ . This study provides more evidence for the potential application of these microreactors in a biomedical context with more complex cellular environments.

Mitochondrial function and brain Metabolic Score (BMS) in ischemic Stroke: Evaluation of "neuroprotectants" safety and efficacy

The initial and significant event developed in ischemic stroke is the sudden decrease in blood flow and oxygen supply to brain tissue, leading to dysfunction of the mitochondria. Many attempts were and are being made to develop new drugs and treatments that will save the ischemic brain, but the efficacy is not optimal and in many patients, irreversible damage to the brain will persist. We review a unique approach to evaluate mitochondrial function and microcirculatory hemodynamic in real time in vivo. Three out of four monitored physiological parameters are integrated into a new Brain Metabolic Score (BMS) calculated in real time and is correlated to Brain Oxygen Balance. The technology was adapted to various experimental as well as clinical situations for monitoring the brain in real time. The developed protocols could be used in testing the efficacy and safety of new drugs in experimental animals. Few models of brain monitoring during partial or complete ischemia were developed and used in naive animals or under brain activation protocols. It was found that mitochondrial function/dysfunction is the major and dominant parameter affecting the calculated Brain Metabolic Score. Using our monitoring system and protocols will provide direct information regarding the ability of the tested brain to provide enough oxygen consumed by the mitochondria in the "resting" or in the "activated" brain in vivo and in real-time. Preliminary studies, indicated that testing the efficacy and safety of new neuroprotectant drugs provided significant results to the R&D studies of ischemic stroke related to mitochondrial function.

Neuroprotective Agents in the Intensive Care Unit: -Neuroprotective Agents in ICU

Neuroprotection or prevention of neuronal loss is a complicated molecular process that is mediated by various cellular pathways. Use of different pharmacological agents as neuroprotectants has been reported especially in the last decades. These neuroprotective agents act through inhibition of inflammatory processes and apoptosis, attenuation of oxidative stress and reduction of free radicals. Control of this injurious molecular process is essential to the reduction of neuronal injuries and is associated with improved functional outcomes and recovery of the patients admitted to the intensive care unit. This study reviews neuroprotective agents and their mechanisms of action against central nervous system damages.

Neuroprotective effects of leonurine against oxygen-glucose deprivation by targeting Cx36/CaMKII in PC12 cells

Leonurine has been reported to play an important role in ameliorating cognitive dysfunction, inhibiting ischemic stroke, and attenuating perihematomal edema and neuroinflammation in intracerebral hemorrhage. However, the exact mechanism and potential molecular targets of this effect remain unclear. Thus, in this study we investigated the neuroprotective effects of leonurine on hypoxia ischemia injury and explored the underlying mechanisms. An in vitro model of oxygen-glucose deprivation (OGD)-induced PC12 cells was established to mimic ischemic-like conditions. Cell viability, apoptosis, Cx36 and pCaMKII/CaMKII expression levels were evaluated after treatment with leonurine. The Cx36-selective antagonist mefloquine and CaMKII Inhibitor KN-93 were used to investigate the neuroprotective effect of leonurine on and the involvement of Cx36/CaMKII in this process. The results revealed that cell viability decreased and cell apoptosis and the protein expression of Cx36 and pCaMKII/CaMKII increased in the OGD-induced PC12 cells. Leonurine significantly increased cell viability and decreased cell apoptosis and the protein expression of Cx36 and pCaMKII/CaMKII in the OGD-induced PC12 cells. The specific inhibitor of Cx36 and CaMKII displayed similar protective effects. Moreover, the inhibition of Cx36 reduced pCaMKII levels and the ratio of pCaMKII/CaMKII in the OGD-induced PC12 cells, and vice versa. Taken together, these results suggest that leonurine might have a protective effect on OGD-induced PC12 cells through targeting the Cx36/CaMKII pathway. Thus, leonurine appears to have potential as a preventive or therapeutic drug against ischemic-induced neuronal injury.

Neurotransmitters in the mediation of cerebral ischemic injury

Under physiological conditions, neurotransmitters shape neuronal networks and control several cellular and synaptic functions. In the mammalian central nervous system (CNS), excitatory and inhibitory neurotransmission are mediated in large part by glutamate and gamma-aminobutyric acid (GABA), which are excitatory and inhibitory neurotransmitters, respectively. Glutamate and GABA also play crucial roles in neurological disorders such as cerebral ischemia. Glutamate in particular causes excitotoxicity, known as one of the hallmark mechanisms in the pathophysiology of cerebral ischemic injury for more than thirty years. Excitotoxicity occurs due to excessive glutamate release leading to overactivation of postsynaptic glutamate receptors, which evokes a downstream cascade that eventually leads to neuronal dysfunction and degeneration. Also, a reduction in GABA receptor response after ischemia impedes these inhibitory effectors from attenuating excitotoxicity and thereby further enabling the excitotoxic insult. This review focuses on the mechanisms by which glutamate and GABA mediate excitotoxicity and ischemic injury. This article is part of the Special Issue entitled 'Cerebral Ischemia'.

The role of Ca2+-calmodulin stimulated protein kinase II in ischaemic stroke - A potential target for neuroprotective therapies

Studies in multiple experimental systems show that Ca²⁺-calmodulin stimulated protein kinase II (CaMKII) is a major mediator of ischaemia-induced cell death and suggest that CaMKII would be a good target for neuroprotective therapies in acute treatment of stroke. However, as CaMKII regulates many cellular processes in many tissues any clinical treatment involving the inhibition of CaMKII would need to be able to specifically target the functions of ischaemia-activated CaMKII. In this review we summarise new developments in our understanding of the molecular mechanisms involved in ischaemia-induced CaMKII-mediated cell death that have identified ways in which such specificity of CaMKII inhibition after stroke could be achieved. We also review the mechanisms and phases of tissue damage in ischaemic stroke to identify where and when CaMKII-mediated mechanisms may be involved.

Glutamate carboxypeptidase II gene knockout attenuates oxidative stress and cortical apoptosis after traumatic brain injury

Background

Glutamate carboxypeptidase II (GCPII) inactivates the peptide co-transmitter N-acetylaspartylglutamate following synaptic release. Inhibition of GCPII elevates extracellular levels of the peptide, inhibits glutamate release and is neuroprotective in an animal model of traumatic brain injury. GCPII gene knockout mice were used to examine the cellular mechanisms underlying the neuroprotective efficacy of this transmitter system.

Results

Following controlled cortical impact injury, GCPII knockout (KO) mice exhibited reduced TUNEL-positive nuclei in the contusion margin of the cerebral cortex relative to wild type mice. Impact injury reduced glutathione levels and superoxide dismutase and glutathione peroxidase activities and increased malondialdehyde. Each of these effects was moderated in KO mice relative to wild type. Similarly, the injury-induced increases in cleaved caspase-3, cytosolic cytochrome c levels and Bcl-2/Bax ratio observed in wild type mice were attenuated in the knockout mice.

Conclusions

These data support the hypothesis that the neuroprotective efficacy of GCPII KO in traumatic brain injury is mediated via a reduction in oxidative stress.

Developing drug strategies for the neuroprotective treatment of acute ischemic stroke

Developing new treatment strategies for acute ischemic stroke in the last twenty years has offered some important successes, but also several failures. Most trials of neuroprotective therapies have been uniformly negative to date. Recent research has reported how excitatory amino acids act as the major excitatory neurotransmitters in the cerebral cortex and hippocampus. Furthermore, other therapeutic targets such as free radical scavenger strategies and the anti-inflammatory neuroprotective strategy have been evaluated with conflicting data in animal models and human subjects with acute ischemic stroke. Whereas promising combinations of neuroprotection and neurorecovery, such as citicoline, albumin and cerebrolysin have been tested with findings worthy of further evaluation in larger randomized clinical trials. Understanding the complexities of the ischemic cascade is essential to developing pharmacological targets for acute ischemic stroke in neuroprotective or flow restoration therapeutic strategies.

Motor and cognitive deficits due to permanent cerebral hypoperfusion/ischemia improve by pomegranate seed extract in rats

This study aimed to evaluate the effect of two weeks oral administration of Pomegranate Seed Extract (PGSE) on active avoidance memory and motor coordination activities after permanent bilateral common carotid arteries occlusion (2CCAO) in male adult rats. Adult male albino rats of Wistar strain (250 ± 20 g, 3-4 months) were used. Animals were divided into eight groups with 10 in each: (1) Sham operated (Sh); (2) Ischemic (I); (3) Ischemic received 100 mg kg(-1) PGSE, orally (I+E100); (4) Ischemic received 200 mg kg(-1) PGSE, orally (I+E200); (5) Ischemic received 400 mg kg(-1) PGSE, orally (I+E400); (6) Ischemic received 800 mg kg(-1) PGSE, orally (I+ E800); (7) Ischemic received 2 mL kg(-1) normal saline, orally (I+Veh); (8) Sham operated received 400 mg kg(-1) PGSE, orally (Sh+E400). In order to make 2CCAO an animal Cerebral Hypoperfusion Ischemia (CHI) model, carotid arteries were ligatured and then bilaterally cut. To evaluate active avoidance task, Correct Response Percentages (CRP) was measured by Y-maze apparatus and motor coordination activity was evaluated using standard behavioral tests by rotarod apparatus in all the rats. It was found that memory. Memory and motor coordination activities were significantly impaired in the rats after CHI (p < 0.01). PGSE treatment significantly improved impairment of memory and motor coordination in the rats with 2CCAO (p < 0.001). PGSE exhibited therapeutic potential for memory and muscular coordination, which was most likely related at least in some part to its antioxidative and free radical scavenging actions.

H₂S attenuates cognitive deficits through Akt1/JNK3 signaling pathway in ischemic stroke

Neuronal damage in the hippocampal formation which is more sensitive to ischemic stimulation and easily injured will cause severe learning and memory impairment. Therefore, inhibiting hippocampal neuron injuries is the main contributor for learning and memory impairment during cerebral ischemia. Hydrogen sulfide (H2S) is a new type of neurotransmitter that regulates the nervous, circulatory and immune systems as well as various adverse factors that can reduce cerebral vascular or brain parenchyma injury. During an ischemic stroke, H2S inhibits hippocampal neuronal damage, reducing learning and memory impairment. However, this molecular mechanism has not been elucidated clearly. In this study, we established four-vessel occlusion model in rats with cerebral ischemia. We found that NaHS (28 mmol/kg, intraperitoneally, for 7 days before ischemia), donor of H2S, significantly shortened the distance and time of loading onto the hidden platform in the positioning navigation process, decreased the latency in the space exploration process when cognitive testing with Morris water maze was performed during ischemic stroke in rats. NaHS also significantly shortened latency and reduced the number of errors in the platform diving experiment. The survival rate of neurons in the CA1 area of the hippocampus and the phosphorylation of Akt in the neurons were increased, the phosphorylation ASK1 and JNK3 were inhibited by NaHS. After an intracerebroventricular injection of LY294002 (inhibitor of PI3K/Akt, 10 μL, 100 nmol in 25% DMSO in PBS), the above effects of NaHS were attenuated. These findings suggest that H2S may improve the survival rate of hippocampal neurons and reduce the impairment of learning and memory by increasing the phosphorylation of Akt, inhibiting the phosphorylation of ASK1 and JNK3 in rats with induced ischemic stroke.

Do sodium channel blockers have neuroprotective effect after onset of ischemic insult?

OBJECTIVE

Cerebral ischemia causes a series of pathophysiologic events that may result in cerebral infarct. Some neurons are more vulnerable to ischemia, particularly pyramidal neurons in the hippocampal CA1 region. Pharmacologic intervention for treatment of cerebral ischemia aims to counteract secondary neurotoxic events or to interrupt the progression of this process. In the present study, we compare the neuroprotective effects of sodium channel blockers (mexiletine, riluzole and phenytoin) and investigate whether they have neuroprotective effect when given after ischemic insult.

METHODS

A transient global cerebral ischemia model was performed in this study by clipping bilateral common carotid arteries during 45 minutes. Riluzole (8 mg/kg), mexiletine (80 mg/kg) and phenytoin (200 mg/kg) were injected into the rats intraperitoneally 30 minutes before or after reperfusion. Lipid peroxidation levels and cerebral water contents were evaluated 24 hours after ischemia. Histopathologic assessment of hippocampal region was determined 7 days after ischemia.

RESULTS

Riluzole, mexiletine and phenytoin treatment after global ischemia significantly decreased water content of the ischemic brain (p<0.05 for each). No significant difference was observed in cerebral edema among the drug treatment groups (p>0.05). When pre-treatment and post-treatment groups were compared with each other, only riluzole pre-treatment group revealed better result for cerebral edema (p<0.05). Pre-treatment with these drugs revealed significantly better results for the malonyldialdehyde (MDA) level and the number of survival neuron on the hippocampal region than the post-treatment groups.

CONCLUSION

It is demonstrated that riluzole, mexiletine and phenytoin are potent neuroprotective agents in the rat model of transient global cerebral ischemia, but they are more effective when given before onset of the ischemia.

Diethylmaleate and iodoacetate in combination caused profound cell death in astrocytes

Energy failure and oxidative stress have been implicated in the pathogenesis of ischemia. Here, we report a potential link between cytosolic phospholipase A₂ (cPLA₂) activation and energy failure/oxidative stress-induced astrocyte damage involving reactive oxygen species (ROS), protein kinase C-α (PKC-α), Src, Raf, and extracellular signal-regulated kinase (ERK) signaling and concurrent elevation of endogenous chelatable zinc. Energy failure and oxidative stress were produced by treating astrocytes with glycolytic inhibitor iodoacetate and glutathione chelator diethylmaleate, respectively. Diethylmaleate and iodoacetate in combination caused augmented damage to astrocytes in a time- and concentration-dependent manner. The cell death caused by diethylmaleate/iodoacetate was accompanied by increased ROS generation, PKC-α membrane translocation, Src, Raf, ERK, and cPLA₂ phosphorylation. Pharmacological studies revealed that these activations all contributed to diethylmaleate/iodoacetate-induced astrocyte death. Intriguingly, the mobilization of endogenous chelatable zinc was observed in diethylmaleate/iodoacetate-treated astrocytes. Zinc appears to act as a downstream mediator in response to diethylmaleate/iodoacetate treatment because of the attenuating effects of its chelator N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine. These observations indicate that ROS/PKC-α, Src/Raf/ERK signaling and cPLA₂ are active participants in diethylmaleate/iodoacetate-induced astrocyte death and contribute to a vicious cycle between the depletion of ATP/glutathione and the mobilization of chelatable zinc as critical upstream effectors in initiating cytotoxic cascades.

Neuronal damage and gliosis in the somatosensory cortex induced by various durations of transient cerebral ischemia in gerbils

Although many studies regarding ischemic brain damage in the gerbil have been reported, studies on neuronal damage according to various durations of ischemia-reperfusion (I-R) have been limited. In this study, we examined neuronal damage/death and glial changes in the somatosensory cortex 4 days after 5, 10 and 15 min of transient cerebral ischemia using the gerbil. To examine neuronal damage, we used Fluoro-Jade B (F-J B, a marker for neuronal degeneration) histofluorescence staining as well as cresyl violet (CV) staining and neuronal nuclei (NeuN, neuronal marker) immunohistochemistry. In the somatosensory cortex, some CV and NeuN positive (+) neurons were slightly decreased only in layers III and VI in the 5 min ischemia-group, and the number of CV+ and NeuN+ neurons were decreased with longer ischemic time. The F-J B histofluorescence staining showed a clear neuronal damage in layers III and VI, and the number of F-J B+ neurons was increased with time of ischemia-reperfusion: in the 15 min ischemia-group, the number of F-J B+ neurons was much higher in layer III than in layer VI. In addition, we immunohistochemically examined gliosis of astrocytes and microglia using anti-glial fibrillary acidic protein (GFAP) and anti-ionized calcium-binding adapter molecule 1 (Iba-1) antibody, respectively. In the 5 min ischemia-group, GFAP+ astrocytes and Iba-1+ microglia were distinctively increased in number, and their immunoreactivity was stronger than that in the sham-group. In the 10 and 15 min ischemia-groups, numbers of GFAP+ and Iba-1+ glial cells were much more increased with time of ischemia-reperfusion; in the 15 min ischemia-group, their distribution patterns of GFAP+ and Iba-1+ glial cells were similar to those in the 10 min ischemia-group. Our fining indicates that neuronal death/damage and gliosis of astrocytes and microglia were apparently increased with longer time of ischemia-reperfusion.

Reperfusion promotes mitochondrial dysfunction following focal cerebral ischemia in rats

BACKGROUND AND PURPOSE

Mitochondrial dysfunction has been implicated in the cell death observed after cerebral ischemia, and several mechanisms for this dysfunction have been proposed. Reperfusion after transient cerebral ischemia may cause continued and even more severe damage to the brain. Many lines of evidence have shown that mitochondria suffer severe damage in response to ischemic injury. The purpose of this study was to observe the features of mitochondrial dysfunction in isolated mitochondria during the reperfusion period following focal cerebral ischemia.

METHODS

Male Wistar rats were subjected to focal cerebral ischemia. Mitochondria were isolated using Percoll density gradient centrifugation. The isolated mitochondria were fixed for electron microscopic examination; calcium-induced mitochondrial swelling was quantified using spectrophotometry. Cyclophilin D was detected by Western blotting. Fluorescent probes were used to selectively stain mitochondria to measure their membrane potential and to measure reactive oxidative species production using flow cytometric analysis.

RESULTS

Signs of damage were observed in the mitochondrial morphology after exposure to reperfusion. The mitochondrial swelling induced by Ca(2+) increased gradually with the increasing calcium concentration, and this tendency was exacerbated as the reperfusion time was extended. Cyclophilin D protein expression peaked after 24 hours of reperfusion. The mitochondrial membrane potential was decreased significantly during the reperfusion period, with the greatest decrease observed after 24 hours of reperfusion. The surge in mitochondrial reactive oxidative species occurred after 2 hours of reperfusion and was maintained at a high level during the reperfusion period.

CONCLUSIONS

Reperfusion following focal cerebral ischemia induced significant mitochondrial morphological damage and Ca(2+)-induced mitochondrial swelling. The mechanism of this swelling may be mediated by the upregulation of the Cyclophilin D protein, the destruction of the mitochondrial membrane potential and the generation of excessive reactive oxidative species.

Probucol attenuates oxidative stress, energy starvation, and nitric acid production following transient forebrain ischemia in the rat hippocampus

Oxidative stress and energy depletion are believed to participate in hippocampal neuronal damage after forebrain ischemia. This study has been initiated to investigate the potential neuroprotective effects of probucol, a lipid-lowering drug with strong antioxidant properties, against transient forebrain ischemia-induced neuronal damage and biochemical abnormalities in rat hippocampal CA1 region. Adult male Wistar albino rats were subjected to forebrain ischemia and injected with probucol for the next 7 successive days, and compared to controls. Forebrain ischemia resulted in a significant decrease in the number of intact neurons (77%), glutathione (GSH), and adenosine triphosphate (ATP), and a significant increase in thiobarbituric acid reactive substances (TBARS) and total nitrate/nitrite, (NO_x) production in hippocampal tissues. The administration of probucol attenuated forebrain ischemia-induced neuronal damage, manifested as a complete reversal of the decrease in the number of intact neurons, ATP and GSH and the increase in TBARS and NO_x in hippocampal tissues. This study demonstrates that probucol treatment abates forebrain ischemia-induced hippocampal neuronal loss, energy depletion, and oxidative stress in hippocampal CA1 region. Thus, probucol could be a promising neuroprotective agent in the treatment of forebrain ischemia.

Oxidative stress and NAD+ in ischemic brain injury: current advances and future perspectives

Numerous studies have indicated oxidative stress as a key pathological factor in ischemic brain injury. One of the key links between oxidative stress and cell death is excessive activation of poly(ADP-ribose) polymerase-1 (PARP-1), which plays an important role in the ischemic brain damage in male animals. Multiple studies have also suggested that NAD+ depletion mediates PARP-1 cytotoxicity, and NAD+ administration can decrease ischemic brain injury. A number of recent studies have provided novel information regarding the mechanisms underlying the roles of oxidative stress and NAD+-dependent enzymes in ischemic brain injury. Of particular interest, there have been exciting progresses regarding the mechanisms underlying the roles of NADPH oxidase and PARP-1 in cerebral ischemia. For examples, it has been suggested that androgen signaling and binding of PARP-1 onto estrogen receptors could account for the intriguing findings that PARP-1 plays remarkably differential roles in the ischemic brain damage of male and female animals; and some studies have suggested casein kinase 2, copper-zinc superoxide dismutase, and estrogen signaling can modulate the expression and activity of NADPH oxidase. This review summarizes these important current advances, and proposes future perspectives for the studies on the roles of oxidative stress and NAD+ in cerebral ischemia. It is increasingly likely that future studies on NAD- and NADP-dependent enzymes, such as NADPH oxidase, PARP-1, and sirtuins, would expose novel mechanisms underlying the roles of oxidative stress in cerebral ischemia, and suggest new therapeutic strategies for treating the debilitating disease.

Behavioral, biochemical and cellular correlates in the protective effect of sertraline against transient global ischemia induced behavioral despair: possible involvement of nitric oxide-cyclic guanosine monophosphate study pathway

Post-stroke depression (PSD) is one of the psychiatric complications after stroke. Present study was conducted to elucidate the protective effect of sertraline and possible involvement of nitric oxide mechanism against transient global ischemia induced behavioral despair. Bilateral common carotid artery occlusion was given twice for 5 min at 10 min interval followed by 96 h reperfusion. Ischemia reperfusion significantly increased immobility period and decreased resistance to lateral push as compared to sham-operated group. Ischemia reperfusion caused significant oxidative damage and mitochondrial enzyme complex (I-III) dysfunction as compared to sham group. Sertraline (5 and 10mg/kg) treatment significantly reduced immobility period, increased resistance to lateral push, attenuated oxidative damage and restored mitochondrial enzyme complex activities as compared to ischemia group. L-Arginine (100mg/kg) or sildenafil (5mg/kg) pretreatment with sertraline (5mg/kg) significantly reversed the protective effect of sertraline. However, L-NAME (10mg/kg) or 7NI (10mg/kg) pretreatment with sertraline (5mg/kg) significantly potentiated their protective effect which were significant as compared to their effect alone. The present study shows that nitric oxide modulation is involved in the protective effect of sertraline.

Lawrence K. Cerebral metabolic rate of oxygen and amplitude-integrated electroencephalography during early reperfusion after hypoxia-ischemia in piglets

The therapeutic window following perinatal hypoxia-ischemia is brief, and early clinical signs of injury can be subtle. Electroencephalography (EEG) represents the most promising early diagnostic of hypoxia-ischemia; however, some studies have questioned the sensitivity and specificity of EEG. The present study investigated the use of both near-infrared spectroscopy (NIRS) measurements of the cerebral metabolic rate of oxygen (CMRO2) and amplitude-integrated EEG (aEEG) to detect the severity of hypoxia-ischemia after 1 h of reperfusion in newborn piglets (10 insult, 3 control). The CMRO2 was measured before and after 1 h of reperfusion from hypoxia-ischemia, the duration of which was varied from piglet to piglet with a range of 3–24 min, under fentanyl/nitrous oxide anesthesia to mimic awake-like levels of cerebral metabolism. EEG data were collected throughout the study. On average, the CMRO2 and mean aEEG background signals were significantly depressed following the insult ( P < 0.05). Mean CMRO2 and mean aEEG background were 2.61 ± 0.11 ml O2·min−1·100 g−1 and 20.4 ± 2.7 μV before the insult and 1.58 ± 0.09 ml O2·min−1·100 g−1 and 11.8 ± 2.9 μV after 1 h of reperfusion, respectively. Both CMRO2 and aEEG displayed statistically significant correlations with duration of ischemia ( P < 0.05; r = 0.71 and r = 0.89, respectively); however, only CMRO2 was sensitive to milder injuries (<5 min). This study highlights the potential for combining NIRS measures of CMRO2 with EEG in the neonatal intensive care unit to improve early detection of perinatal hypoxia-ischemia.

Molecular mechanisms of excitotoxicity and their relevance to pathogenesis of neurodegenerative diseases

A pivotal role for excitotoxicity in neurodegenerative diseases is gaining increasingly more acceptance, but the underlying mechanisms through which it participates in neurodegeneration still need further investigation. Excessive activation of glutamate receptors by excitatory amino acids leads to a number of deleterious consequences, including impairment of calcium buffering, generation of free radicals, activation of the mitochondrial permeability transition and secondary excitotoxicity. Recent studies implicate excitotoxicity in a variety of neuropathological conditions, suggesting that neurodegenerative diseases with distinct genetic etiologies may share excitotoxicity as a common pathogenic pathway. Thus, understanding the pathways involved in excitotoxicity is of critical importance for the future clinical treatment of many neurodegenerative diseases. This review discusses the current understanding of excitotoxic mechanisms and how they are involved in the pathogenesis of neurodegenerative diseases.

Assessing the severity of perinatal hypoxia-ischemia in piglets using near-infrared spectroscopy to measure the cerebral metabolic rate of oxygen

Reduced cerebral function after neonatal hypoxia-ischemia is an early indicator of hypoxic-ischemic encephalopathy. Near-infrared spectroscopy offers a clinically relevant means of detecting impaired cerebral metabolism from the measurement of the cerebral metabolic rate of oxygen (CMRO2). The purpose of this study was to determine the relationship between postinsult CMRO2 and duration of hypoxia-ischemia in piglets. Twelve piglets were subjected to randomly selected durations of hypoxia-ischemia (5-28 min) and five animals served as controls. Measurements of CMRO2 were taken before and for 24 h after hypoxia-ischemia. Histology was carried out in nine piglets (six insults, three controls) to estimate brain injury. In the first 4 h after the insult, average CMRO2 of the insult group was significantly depressed (33 +/- 3% reduction compared with controls) and by 8 h, a significant correlation developed, which persisted for the remainder of the study, between CMRO2 and the duration of ischemia. Histologic staining suggested little brain damage resulted from shorter insult durations and considerable damage from more prolonged insults. This study demonstrated that near-infrared spectroscopy could detect early changes in CMRO2 after hypoxia-ischemia for a range of insult severities and CMRO2 could be used to distinguish insult severity by 8 h after the insult.

Changes in cerebral oxygen consumption and high-energy phosphates during early recovery in hypoxic-ischemic piglets: a combined near-infrared and magnetic resonance spectroscopy study

Near-infrared spectroscopy (NIRS) offers the ability to assess brain function at the bedside of critically ill neonates. Our group previously demonstrated a persistent reduction in the cerebral metabolic rate of oxygen (CMRO(2)) after hypoxia-ischemia (HI) in newborn piglets. The purpose of this current study was to determine the causes of this reduction by combining NIRS with magnetic resonance spectroscopy (MRS) to measure high-energy metabolites and diffusion-weighted imaging to measure cellular edema. Nine piglets were exposed to 30 min of HI and nine piglets served as controls. Proton and phosphorous MRS spectra, apparent diffusion coefficient (ADC) maps, and CMRO(2) measurements were collected periodically before and for 5.5 h after HI. A significant decrease in CMRO(2) (26 +/- 7%) was observed after HI. Incomplete recovery of nucleotide triphosphate concentration (8 +/- 3% <controls) and reduced ADC (16 +/- 5%) suggested mitochondrial dysfunction. However, CMRO(2) did not correlate with any metabolite concentration during the last 3 h of the recovery period, and no significant changes were found in phosphocreatine and lactate levels. Therefore, the CMRO(2) decrease is likely a combination of impaired mitochondrial function and reduced energy demands during the acute phase, which has been previously observed in the mature brain.

Na+/Ca2+ exchanger subtype (NCX1, NCX2, NCX3) protein expression in the rat hippocampus following 3 min and 8 min durations of global cerebral ischemia

There is increasing evidence that the sodium-calcium exchanger (NCX) subtypes, NCX1, NCX2 and NCX3 play an important role in intracellular calcium homeostasis/dysregulation following cerebral ischemia. In the present study we examined NCX1, NCX2 and NCX3 protein levels in the rat hippocampus at 3, 6, 12, 18, 24 and 48 h following a 3 min and 8 min duration of global cerebral ischemia. We observed that NCX1 protein levels were significantly increased by 22.3% and 20.6% at the 6 and 12 h respective time points following a 3 min duration of global ischemia, while NCX2 and NCX3 protein levels remained relatively constant. Following a 8 min duration of global ischemia, NCX1 protein levels remained relatively constant, while NCX2 protein levels were down-regulated by 6.9%, 10.8%, 14.4% and 10.3% at the 6, 18, 24 and 48 h respective time points, and NCX3 protein levels were up-regulated by 22.1% at the 18 h time point. Taken together, our results show that NCX subtype protein expression is sensitive to cerebral ischemia, and indicates that changes in NCX activity may be playing an important role in calcium maintenance and neuronal outcome following ischemia.

Carnitine esters prevent oxidative stress damage and energy depletion following transient forebrain ischaemia in the rat hippocampus

1. The present study investigated whether propionyl-L-carnitine (PLC) has neuroprotective effects, similar to those reported for acetyl-L-carnitine (AC), against transient forebrain ischaemia-induced neuronal damage and biochemical derangement in the rat hippocampal CA1 region. 2. In total, 105 adult male Wistar albino rats were divided into seven groups of 15 animals each. The first three groups were injected i.p. with normal saline, AC (300 mg/kg) or PLC (300 mg/kg) for 7 successive days. The next three groups were injected i.p. with the same doses of normal saline, AC or PLC immediately after the induction of 10 min forebrain ischaemia and i.p. injections were continued for 7 successive days. Rats in the seventh group were subjected to sham-operated ischaemia and injected with normal saline for 7 successive days. 3. Seven days after treatment, animals were killed and their brains isolated for histopathological examination and biochemical studies. 4. Forebrain ischaemia resulted in a significant decrease in the number of intact neurons (77%), ATP concentration (51%) and glutathione content (32%), whereas there was a significant increase in the production of thiobarbituric acid-reactive substances (TBARS; 71%) and total nitrate/nitrite (NOx; 260%) in hippocampal tissues. 5. Administration of either AC or PLC attenuated forebrain ischaemia-induced neuronal damage, manifested by a greater number of intact neurons, ATP and glutathione, as well as a decrease in TBARS and NOx in hippocampal tissues. 6. Results from the present study suggest, for the first time, that PLC attenuates forebrain ischaemia-induced neuronal injury, oxidative stress and energy depletion in the hippocampal CA1 region. Propionyl-L-carnitine has neuroprotective effects similar to AC and could have a potential use in the treatment of neurodegenerative diseases. 7. The results of the present study will open up new perspectives for the use of PLC in the treatment of neurodegenerative diseases associated with, or secondary to, myocardial ischaemia-reperfusion injury and chronic circulatory failure.

JNK3 signaling pathway activates ceramide synthase leading to mitochondrial dysfunction

A cardinal feature of brain tissue injury in stroke is mitochondrial dysfunction leading to cell death, yet remarkably little is known about the mechanisms underlying mitochondrial injury in cerebral ischemia/reperfusion (IR). Ceramide, a naturally occurring membrane sphingolipid, functions as an important second messenger in apoptosis signaling and is generated by de novo synthesis, sphingomyelin hydrolysis, or recycling of sphingolipids. In this study, cerebral IR-induced ceramide elevation resulted from ceramide biosynthesis rather than from hydrolysis of sphingomyelin. Investigation of intracellular sites of ceramide accumulation revealed the elevation of ceramide in mitochondria because of activation of mitochondrial ceramide synthase via post-translational mechanisms. Furthermore, ceramide accumulation appears to cause mitochondrial respiratory chain damage that could be mimicked by exogenously added natural ceramide to mitochondria. The effect of ceramide on mitochondria was somewhat specific; dihydroceramide, a structure closely related to ceramide, did not inflict damage. Stimulation of ceramide biosynthesis seems to be under control of JNK3 signaling: IR-induced ceramide generation and respiratory chain damage was abolished in mitochondria of JNK3-deficient mice, which exhibited reduced infarct volume after IR. These studies suggest that the hallmark of mitochondrial injury in cerebral IR, respiratory chain dysfunction, is caused by the accumulation of ceramide via stimulation of ceramide synthase activity in mitochondria, and that JNK3 has a pivotal role in regulation of ceramide biosynthesis in cerebral IR.

Exacerbation of excitotoxic neuronal death induced during mitochondrial inhibition in vivo: relation to energy imbalance or ATP depletion?

During the past two decades a close relationship between the energy state of the cell and glutamate neurotoxicity has been suggested. We have previously shown that increasing the extracellular concentration of glutamate does not cause neuronal death unless a deficit in energy metabolism occurs. The mechanisms of glutamate-induced neuronal death have been extensively studied in vitro and it has been associated with a rapid and severe decrease in ATP levels, accompanied with mitochondrial dysfunction. In this study we aimed to investigate the time course of the changes in energy metabolites during glutamate-induced neuronal death, in the presence of a moderate inhibition of mitochondrial metabolism in the rat striatum in vivo. We also aimed to study whether or not, as reported in vitro, changes in ATP levels are related to the extension of neuronal death. Results show that glutamate-induced lesions are exacerbated when rats are previously treated with a subtoxic dose of the mitochondrial toxin 3-nitropropionic acid (3-NP). However, changes in nucleotide levels were similar in rats injected with glutamate alone and in rats injected with glutamate and previously treated with 3-NP. In spite of the presence of an extensive striatal lesion, nucleotide levels were recovered in 3-NP-treated rats 24 h after glutamate injection. Results show that 3-NP pre-treatment induced an imbalance in nucleotide levels that predisposed cells to glutamate toxicity; however it did not influence the bioenergetic changes induced by glutamate alone. Enhancement of glutamate neurotoxicity in 3-NP pre-treated rats is more related to a sustained nucleotide imbalance than just to a rapid decrease in ATP levels.

Effect of treadmill exercise on cell damage in rat hippocampal slices submitted to oxygen and glucose deprivation

We have recently demonstrated that high intensity training exercise exacerbates brain damage, while a moderate intensity (2 weeks of 20 min/day of treadmill training) reduces the injury caused by in vitro ischemia, oxygen and glucose deprivation (OGD), to hippocampal slices from Wistar rats. In the present paper, the effect of different running programs on severity of ischemic OGD lesion was examined, by the evaluation of three protocols designed to simulate exercise conditions common to humans: one or three 20-min sessions per week, during 12 weeks (moderate intensity), and two 20-min daily sessions for 3 weeks. OGD caused an increase of lactate dehydrogenase (LDH) release into the incubation media, a marker of tissue necrosis, and a decline of cell viability, as assessed by the decrease of mitochondrial dehydrogenase activity (MTT method). Moderate exercise, three times a week during 12-week treadmill training, decreased LDH release after OGD, while one weekly session and 3 weeks of two daily sessions did not affect OGD-induced LDH released. No exercise protocol evaluated altered MTT reduction. Our data support the hypothesis that moderate intensity exercise reduces hippocampal susceptibility to in vitro ischemia.

Acidotoxicity in brain ischaemia

Intracellular calcium toxicity remains the central feature in the pathophysiology of ischaemic cell death in brain. Glutamate-gated channels have been thought to be the major sites of ischaemia-induced toxic calcium entry, but the failure of glutamate antagonists in clinical trials has suggested that glutamate-independent mechanisms of calcium entry during ischaemia must exist and may prove central to ischaemic injury. We have shown that ASICs (acid-sensing ion channels) in brain are glutamate-independent vehicles of calcium flux and transport calcium in greater measure in the setting of the two major neurochemical components of ischaemia: acidosis and substrate depletion. Pharmacological blockade of ASICs markedly attenuates stroke injury with a robust therapeutic time window of 5 h following stroke onset. Here, we describe this new mechanism of calcium toxicity in brain ischaemia and offer a potential new therapy for stroke.

Neuronal Nitric Oxide Synthase Immunopositivity in Motoneurons of the Rabbit's Spinal Cord After Transient Ischemia/Reperfusion Injury

1. Motoneurons in the spinal cord are especially vulnerable to ischemic injury and selectively destroyed after transient ischemia. To evaluate the role of nitric oxide (NO) in the pathophysiology of the spinal cord ischemia, the expression of neuronal nitric oxide synthase (nNOS) in the motoneurons of the lumbosacral spinal cord was examined in the rabbit model of transient abdominal aorta occlusion. 2. The aim of the present study was to find if there is any consensus between the duration of transient abdominal aorta occlusion, nNOS positivity of the motoneurons and neurological hind limb impairment. 3. According to the degree of neurological damage (i.e., from the group with almost no sign of damage to a group with fully developed paraplegia), the experimental animals were divided into three groups. The respective spinal cord segments of each experimental group were compared to the control group. 4. Spinal cord ischemia (15 min) was induced by Fogarty arterial embolectomy catheter occlusion of abdominal aorta with a reperfusion period of 7 days. On seventh day, the sections of lumbosacral segments were immunohistochemically treated and L1-L7, and S1-S2 segment sections were monitored using light microscopy.

Effect of D-003, a mixture of very-long-chain aliphatic acids purified from sugarcane wax, on cerebral ischemia in Mongolian gerbils

D-003 is a mixture of very-high-molecular-weight aliphatic acids purified from sugar cane wax (Saccharum officinarum), which inhibits platelet aggregation and lipid peroxidation. The objective of the present study was to evaluate the effect of D-003 on cerebral ischemia induced by ischemia-reperfusion (I-R) in Mongolian gerbils. Two experimental series were conducted. The first series investigated the effects of D-003 on cerebral edema, neurological symptoms, and mortality in Mongolian gerbils with cerebral ischemia induced by I-R, while the second series investigated the effects on histological markers of cerebral injury, such as edema intensity (vacuolization) and cerebral necrosis. Animals were randomly distributed in five experimental groups: a sham-operated group experiencing surgical handling except the clamping and orally treated with Tween/water vehicle and four groups subjected to the I-R surgical procedure. One of these groups was treated with the same vehicle, and the other three groups received D-003 at 25, 100, and 200 mg/kg, respectively. All treatments were administered for 14 days. D-003 (200 mg/kg) significantly reduced the cerebral edema and clinical symptoms provoked by I-R compared with the positive control group, whereas lower doses (25 and 100 mg/kg) were not effective. Positive control animals showed an injury profile characterized by swelling (tissue vacuolization) and necrosis of neurons in all areas of the brain studied (frontal cortex, hippocampus, and striatum). The results of the histological study were consistent with those observed by determining cerebral edema and symptoms observation. Thus, D-003 at 200 mg/kg significantly reduced histological markers of brain injury (swelling and necrosis) compared with the control group. It is concluded that D-003 administered orally at 200 mg/kg for 14 days protected against cerebral damage caused by bilateral cerebral ischemia in Mongolian gerbils.

Tenoxicam Exerts a Neuroprotective Action after Cerebral Ischemia in Rats

In this study we investigated the effects of Tenoxicam, a type 2 cyclooxygenase (COX-2) inhibitor, on brain damage induced by ischemia-reperfusion. Male Wistar rats (18-month old average) were anesthetized and submitted to ischemia occlusion of both common carotid arteries (BCAO) for 45 min. After 24 h of reperfusion, rats were decapitated and hippocampi removed for further assays. Animals were divided into sham-operated, ischemia, ischemia + Tenoxicam 2.5 mg/kg, and ischemia + Tenoxicam 10 mg/kg groups. Tenoxicam was administered intraperitoneally immediately after BCAO. Histological analyses show that ischemia produced significant striatal as well as hippocampal lesions which were reversed by the Tenoxicam treatment. Tenoxicam also significantly reduced, to control levels, the increased myeloperoxidase activity in hippocampus homogenates observed after ischemia. However, nitrite concentrations showed only a tendency to decrease in the ischemia + Tenoxicam groups, as compared to that of ischemia alone. On the other hand, hippocampal glutamate and aspartate levels were not altered by Tenoxicam. In conclusion, we showed that ischemia is certainly related to inflammation and to increased free radical production, and selective COX-2 inhibitors might be neuroprotective agents of potential benefit in the treatment of cerebral brain ischemia.

Neurogenesis response to hypoxia-induced cell death: map kinase signal transduction mechanisms

Hypoxic stress induces apoptosis of hippocampal CA1 neurons while selectively sparing those in CA2-3. Proliferation and differentiation of local stem cells may potentially replace lost neurons. We examined MAP kinase signaling regulation of these dual responses. Rat organotypic hippocampal cultures were exposed to hypoxia for up to 6 h followed by reoxygenation. JNKs and ERKs were maximally activated by 4 h, returning approximately to basal levels by 6 h. Apoptosis of CA1 neurons was maximal by 6-h hypoxia, although JNK activation had returned to basal levels. A neuroprotective protein, JNK-interacting protein 1 (JIP1), an inhibitor of JNK-mediated apoptosis, was reduced by 6-h hypoxia and markedly decreased by 24-h reoxygenation in CA1 neurons as was DENN/MADD, which also modulates JNK-mediated cell death. A second peak of ERK1 activation occurred at 24-h reoxygenation and declined to control levels by 48 h. Stem cells were detected by antinestin and cell proliferation confirmed with anti-PCNA immunohistochemistry and BrdU incorporation. With U0126, an inhibitor of ERK activation, BrdU labeling was strikingly reduced implicating ERKs in the proliferation response. Antidoublecortin (DCX), which detects neural progenitor cells, colabeled a subset of BrdU-positive cells that extended from the dentate granule neurons into CA1. Astrocytes were colabeled with BrdU. Thus, hypoxia concurrently triggered both JNK and ERK signaling, and with reoxygenation, ERK1 activation and stem cell proliferation followed by neuronal progenitor cell differentiation and targeted migration to the site of pyramidal neuronal loss.

Neuroprotective effects of Ptychopetalum olacoides Bentham (Olacaceae) on oxygen and glucose deprivation induced damage in rat hippocampal slices

Alcoholic infusions of Ptychopetalum olacoides Bentham (PO, Olacaceae) are used in traditional medicine by patients presenting age associated symptoms and those recovering from stroke. The aim of this study is to evaluate the neuroprotective properties of PO ethanol extract (POEE) using hippocampal slices from Wistar rats exposed to oxygen and glucose deprivation (OGD, followed by reoxygenation). Mitochondrial activity, an index of cell viability, was assessed by the MTT assay; in addition, the free radicals content was estimated by the use of dichlorofluorescein diacetate as probe. The OGD ischemic condition significantly impaired cellular viability, and increased free radicals generation. In non-OGD slices, incubation with POEE (0.6 microg/ml) increased (approximately 40%) mitochondrial activity, without affecting free radicals levels. In comparison to OGD controls, slices incubated with POEE (0.6 microg/ml) during and after OGD exposure had significantly increased cellular viability. In addition, at this same concentration, POEE prevented the increase of free radicals content induced by OGD. In view of the fact that respiratory chain inhibition and increased generation of free radicals are major consequences of the ischemic injury, this study suggests that Ptychopetalum olacoides contains useful neuroprotective compounds and, therefore, deserves further scrutiny.

Glucose-Deprivation-Induced [3H]D-Aspartate Release from Isolated Bovine and Human Retinae

The glucose deprivation-induced release of [3H]D-aspartate was studied in bovine and human retinas in a superfusion apparatus. [3H]D-aspartate release was significantly increased upon omitting glucose in the superfusion buffer. This effect was dependent on external Ca2+ because L- and N-type Ca2+-channel blockers, such as diltiazem (1 microM), nitrendipine (1 microM), and omega-conotoxin (100 nM), significantly reduced the effect of glucose-deprivation induced release of [3H]D-aspartate. Furthermore, while glutamate receptor agonists (L-glutamate, N-methyl-D-aspartate, but not kainate) potentiated the effects of glucose deprivation, antagonists (MK-801, MCPG, ifenprodil, and L-AP3) at these receptors blocked the glucose deprivation-induced release process. Taken together, these studies have demonstrated that under conditions of glucose deprivation, as may happen during ischemic events in vivo, the retinal glutamatergic nerve endings and/or glial cells promote the efflux of [3H]D-aspartate into the extracellular environment. This process appears to be receptor-mediated and dependent on extracellular Ca2+ and is similar to previous reports pertaining to brain tissues.

Primary cortical neuronal cultures reduce cellular energy utilization during anoxic energy deprivation

It has been widely hypothesized that neurons reduce cellular energy use in response to periods of energy deprivation. To test this hypothesis, we measured rates of energy use under normoxia and anoxia in immature (6 days in vitro) and mature (13 days in vitro) neuronal cultures. During anoxic incubation immature and mature cultures reduced cellular energy use by 80% and 45%, respectively. Reduced cellular energy use dramatically affected ATP depletion in neuronal cultures under anoxia. Intracellular ATP stores were expected to deplete within 3 min of anoxia. However, ATP was maintained at decreased but stabilized concentrations for at least 3 h. The capacity of neuronal cultures to reduce cellular energy use during anoxia correlated with their sensitivity towards simulated ischemia. Immature cultures, with the largest capacity to reduce cellular energy use, survived simulated ischemia 2.5 times longer than mature cultures. The addition of glutamate receptor antagonists to mature cultures further decreased cellular energy use during anoxia and significantly extended their survival time under simulated ischemia. This study verifies that primary cortical neuronal cultures reduce cellular energy use during energy deprivation. Additionally, we show that maturation of glutamate receptor activity increases non-depressible energy demand in neuronal cultures.

L-type voltage-gated calcium channel attends regulation of tyrosine phosphorylation of NMDA receptor subunit 2A induced by transient brain ischemia

To study the mechanism of the L-type voltage-gated calcium channel (L-VGCC) involved in neuronal injury induced by brain ischemia and reperfusion (I/R), transient (15 min) brain ischemia was induced by four-vessel occlusion of Sprague-Dawley (SD) rats. Tyrosine phosphorylation of NR2A and interaction of NR2A with Src and Pyk2 in hippocampus induced by brain ischemia and reperfusion (I/R) were determined by immunoprecipitation and immunoblot(ting). Tyrosine phosphorylation of NR2A in hippocampus was enhanced after I/R. Interaction of NR2A with Src and Pyk2, tyrosine phosphorylation and kinase activity of Src and Pyk2 also increased after I/R. All the increases were partly inhibited by L-VGCC antagonist nifedipine administered to rats 20 min prior to brain ischemia. The results suggested that increase of tyrosine phosphorylation of NR2A induced by I/R had a relation to activation of L-VGCC. Src and Pyk2 interacting with NR2A might also be involved in this regulation of the tyrosine phosphorylation of NR2A induced by I/R.

Astrocytes and stroke: networking for survival?

Astrocytes are now known to be involved in the most integrated functions of the central nervous system. These functions are not only necessary for the normally working brain but are also critically involved in many pathological conditions, including stroke. Astrocytes may contribute to damage by propagating spreading depression or by sending proapoptotic signals to otherwise healthy tissue via gap junction channels. Astrocytes may also inhibit regeneration by participating in formation of the glial scar. On the other hand, astrocytes are important in neuronal antioxidant defense and secrete growth factors, which probably provide neuroprotection in the acute phase, as well as promoting neurogenesis and regeneration in the chronic phase after injury. A detailed understanding of the astrocytic response, as well as the timing and location of the changes, is necessary to develop effective treatment strategies for stroke patients.