Calcium-related damage in ischemia

Mechanism of action and neuroprotective role of nicorandil in ischemic stroke

Nicorandil is a dual mechanism anti-anginal agent that acts as a nitric oxide (NO) donor and a potassium (K+) channel opener. Recent studies have evaluated the effect of nicorandil on ischemic stroke. Neurons have a low tolerance to hypoxia and therefore the brain tissue is significantly vulnerable to ischemia. Current approved treatments for ischemic stroke are tissue plasminogen activators and clot retrieval methods. The narrow therapeutic time window and lack of efficacy in restoring the dying neurons urge researchers to develop an alternative approach. In the terminal stages of anoxia, K+ channels induce hyperpolarization in various types of neuronal cells, leading to decreased neuronal activity and the preservation of the brain's energy. Nicorandil can open these K+ channels and sustain the hyperpolarization phase, which may have a neuroprotective effect during hypoxia. Additionally, we review how nicorandil can improve overall stroke outcomes through its anti-inflammatory, anti-oxidative, and edema-reducing effects. One of the major components evaluated in stroke patients is blood pressure. Studies have demonstrated that the effect of nicorandil on blood pressure is related to both its K+ channel opening and NO donating mechanisms. Since both hypertension and hypotension need correction before stroke intervention, it's crucial to consider the role of nicorandil and its impact on blood pressure. Previously published studies indicate that the right dosage of nicorandil can improve cerebral blood flow without significant changes in hemodynamic profiles. In this review, we discuss how nicorandil may contribute to better stroke outcomes based on previously published literature and laboratory findings.

Effects of In Vivo Intracellular ATP Modulation on Neocortical Extracellular Potassium Concentration

Neuronal and glial activity are dependent on the efflux of potassium ions into the extracellular space. Efflux of K is partly energy-dependent as the activity of pumps and channels which are involved in K transportation is ATP-dependent. In this study, we investigated the effect of decreased intracellular ATP concentration ([ATP]i) on the extracellular potassium ion concentration ([K]o). Using in vivo electrophysiological techniques, we measured neocortical [K]o and the local field potential (LFP) while [ATP]i was reduced through various pharmacological interventions. We observed that reducing [ATP]i led to raised [K]o and DC-shifts resembling spreading depolarization-like events. We proposed that most likely, the increased [K]o is mainly due to the impairment of the Na/K ATPase pump and the ATP-sensitive potassium channel in the absence of sufficient ATP, because Na/K ATPase inhibition led to increased [K]o and ATP-sensitive potassium channel impairment resulted in decreased [K]o. Therefore, an important consequence of decreased [ATP]i is an increased [K]o. The results of this study acknowledge one of the mechanisms involved in [K]o dynamics.

Low Intensity Electromagnetic Fields Act via Voltage-Gated Calcium Channel (VGCC) Activation to Cause Very Early Onset Alzheimer's Disease: 18 Distinct Types of Evidence

Electronically generated electromagnetic fields (EMFs) including those used in wireless communication such as cell phones, Wi-Fi and smart meters, are coherent, producing very high electric and magnetic forces which act on the voltage sensor of voltage-gated calcium channels to produce increases in intracellular calcium [Ca2+]i. The calcium hypothesis of Alzheimer's disease (AD) has shown that each of the important AD-specific and nonspecific causal elements are produced by excessive [Ca2+]i. [Ca2+]i acts in AD via excessive calcium signaling and the peroxynitrite/oxidative stress/inflammation pathway which are each elevated by EMFs. An apparent vicious cycle in AD involves amyloid-beta protein (A) and [Ca2+]i. Three types of epidemiology each suggest EMF causation of AD including early onset AD. Extensive animal model studies show that low intensity EMFs cause neurodegeneration including AD, with AD animals having elevated levels of A, amyloid precursor protein and BACE1. Rats exposed to pulsed EMFs every day are reported to develop universal or near universal very very very early onset neurodegeneration including AD; these findings are superficially similar to humans with digital dementia. EMFs producing modest increases in [Ca2+]i can also produce protective, therapeutic effects. The therapeutic pathway and peroxynitrite pathway inhibit each other. A summary of 18 different findings is provided, which collectively provide powerful evidence for EMF causation of AD. The author is concerned that smarter, more highly pulsed "smart" wireless communication may cause widespread very, very early onset AD in human populations.

Ischemic tolerance - blessing or curse

Application of knowledge about ischemic tolerance to clinic requires the solid understanding of mechanism of creation of this phenomenon. This review summarizes research that has been carried out in many laboratories over a long period of time, but the main focus will be on own experimental research. The main emphasis is devoted to the possibility of preparing full tolerance in the donor's body and its transfer to the patient in the form of activated blood plasma. Such plasma could be administered as soon as the patient is transported to the hospital and would take effect immediately after administration to the patient's bloodstream. One chapter is also devoted to anticonditioning, i.e. the possibility of preventing the activation of tolerance. Anticonditioning could be used to treat oncologic patients. We expect that this method could increase effectiveness of cancer treatment. Cross-tolerance with a wide range of diverse stressors gives us the courage to assume that activated plasma can significantly help with a wide range of pathological events.

Acetylation in Mitochondria Dynamics and Neurodegeneration

Mitochondria are a unique intracellular organelle due to their evolutionary origin and multifunctional role in overall cellular physiology and pathophysiology. To meet the specific spatial metabolic demands within the cell, mitochondria are actively moving, dividing, or fusing. This process of mitochondrial dynamics is fine-tuned by a specific group of proteins and their complex post-translational modifications. In this review, we discuss the mitochondrial dynamics regulatory enzymes, their adaptor proteins, and the effect of acetylation on the activity of fusion and fission machinery as a ubiquitous response to metabolic stresses. Further, we discuss the role of intracellular cytoskeleton structures and their post-translational modifications in the modulation of mitochondrial fusion and fission. Finally, we review the role of mitochondrial dynamics dysregulation in the pathophysiology of acute brain injury and the treatment strategies based on modulation of NAD⁺-dependent deacetylation.

Enhanced expression of P2X4 purinoceptors in pyramidal neurons of the rat hippocampal CA1 region may be involved ischemia-reperfusion injury

Ischemic stroke is the most serious disease that harms human beings. In principle, its treatment is to restore blood flow supply as soon as possible. However, after the blood flow is restored, it will lead to secondary brain injury, that is, ischemia-reperfusion injury. The mechanism of ischemia-reperfusion injury is very complicated. This study showed that P2X4 receptors in the pyramidal neurons of rat hippocampus were significantly upregulated in the early stage of ischemia-reperfusion injury. Neurons with high expression of P2X4 receptors are neurons that are undergoing apoptosis. Intraventricular injection of the P2X4 receptor antagonist 5-(3-bromophenyl)-1,3-dihydro-2H-benzofuro[3,2-e]-1,4-diazepin-2-one (5-BDBD) and PSB-12062 can partially block neuronal apoptosis, to promote the survival of neurons, indicating that ATP through P2X4 receptors is involved in the process of cerebral ischemia-reperfusion injury. Therefore, identifying the mechanism of neuronal degeneration induced by extracellular ATP via P2X4 receptors after ischemia-reperfusion will likely find new targets for the treatment of ischemia-reperfusion injury, and will provide a useful theoretical basis for the treatment of ischemia-reperfusion injury.

Tat-Endophilin A1 Fusion Protein Protects Neurons from Ischemic Damage in the Gerbil Hippocampus: A Possible Mechanism of Lipid Peroxidation and Neuroinflammation Mitigation as Well as Synaptic Plasticity

The present study explored the effects of endophilin A1 (SH3GL2) against oxidative damage brought about by H₂O₂ in HT22 cells and ischemic damage induced upon transient forebrain ischemia in gerbils. Tat-SH3GL2 and its control protein (Control-SH3GL2) were synthesized to deliver it to the cells by penetrating the cell membrane and blood–brain barrier. Tat-SH3GL2, but not Control-SH3GL2, could be delivered into HT22 cells in a concentration- and time-dependent manner and the hippocampus 8 h after treatment in gerbils. Tat-SH3GL2 was stably present in HT22 cells and degraded with time, by 36 h post treatment. Pre-incubation with Tat-SH3GL2, but not Control-SH3GL2, significantly ameliorated H₂O₂-induced cell death, DNA fragmentation, and reactive oxygen species formation. SH3GL2 immunoreactivity was decreased in the gerbil hippocampal CA1 region with time after ischemia, but it was maintained in the other regions after ischemia. Tat-SH3GL2 treatment in gerbils appreciably improved ischemia-induced hyperactivity 1 day after ischemia and the percentage of NeuN-immunoreactive surviving cells increased 4 days after ischemia. In addition, Tat-SH3GL2 treatment in gerbils alleviated the increase in lipid peroxidation as assessed by the levels of malondialdehyde and 8-iso-prostaglandin F2α and in pro-inflammatory cytokines such as tumor necrosis factor-α, interleukin-1β, and interleukin-6; while the reduction of protein levels in markers for synaptic plasticity, such as postsynaptic density 95, synaptophysin, and synaptosome associated protein 25 after transient forebrain ischemia was also observed. These results suggest that Tat-SH3GL2 protects neurons from oxidative and ischemic damage by reducing lipid peroxidation and inflammation and improving synaptic plasticity after ischemia.

Role of NAD+-Modulated Mitochondrial Free Radical Generation in Mechanisms of Acute Brain Injury

It is commonly accepted that mitochondria represent a major source of free radicals following acute brain injury or during the progression of neurodegenerative diseases. The levels of reactive oxygen species (ROS) in cells are determined by two opposing mechanisms—the one that produces free radicals and the cellular antioxidant system that eliminates ROS. Thus, the balance between the rate of ROS production and the efficiency of the cellular detoxification process determines the levels of harmful reactive oxygen species. Consequently, increase in free radical levels can be a result of higher rates of ROS production or due to the inhibition of the enzymes that participate in the antioxidant mechanisms. The enzymes’ activity can be modulated by post-translational modifications that are commonly altered under pathologic conditions. In this review we will discuss the mechanisms of mitochondrial free radical production following ischemic insult, mechanisms that protect mitochondria against free radical damage, and the impact of post-ischemic nicotinamide adenine mononucleotide (NAD⁺) catabolism on mitochondrial protein acetylation that affects ROS generation and mitochondrial dynamics. We propose a mechanism of mitochondrial free radical generation due to a compromised mitochondrial antioxidant system caused by intra-mitochondrial NAD⁺ depletion. Finally, the interplay between different mechanisms of mitochondrial ROS generation and potential therapeutic approaches are reviewed.

NAD+ precursor modulates post-ischemic mitochondrial fragmentation and reactive oxygen species generation via SIRT3 dependent mechanisms

Global cerebral ischemia depletes brain tissue NAD⁺, an essential cofactor for mitochondrial and cellular metabolism, leading to bioenergetics failure and cell death. The post-ischemic NAD⁺ levels can be replenished by the administration of nicotinamide mononucleotide (NMN), which serves as a precursor for NAD⁺ synthesis. We have shown that NMN administration shows dramatic protection against ischemic brain damage and inhibits post-ischemic hippocampal mitochondrial fragmentation. To understand the mechanism of NMN-induced modulation of mitochondrial dynamics and neuroprotection we used our transgenic mouse models that express mitochondria targeted yellow fluorescent protein in neurons (mito-eYFP) and mice that carry knockout of mitochondrial NAD⁺-dependent deacetylase sirt3 gene (SIRT3KO). Following ischemic insult, the mitochondrial NAD⁺ levels were depleted leading to an increase in mitochondrial protein acetylation, high reactive oxygen species (ROS) production, and excessive mitochondrial fragmentation. Administration of a single dose of NMN normalized hippocampal mitochondria NAD⁺ pools, protein acetylation, and ROS levels. These changes were dependent on SIRT3 activity, which was confirmed using SIRT3KO mice. Ischemia induced increase in acetylation of the key mitochondrial antioxidant enzyme, superoxide dismutase 2 (SOD2) that resulted in inhibition of its activity. This was reversed after NMN treatment followed by reduction of ROS generation and suppression of mitochondrial fragmentation. Specifically, we found that the interaction of mitochondrial fission protein, pDrp1(S616), with neuronal mitochondria was inhibited in NMN treated ischemic mice. Our data thus provide a novel link between mitochondrial NAD⁺ metabolism, ROS production, and mitochondrial fragmentation. Using NMN to target these mechanisms could represent a new therapeutic approach for treatment of acute brain injury and neurodegenerative diseases.

Phosphoglycerate mutase 1 reduces neuronal damage in the hippocampus following ischemia/reperfusion through the facilitation of energy utilization

In a previous study, we observed the effect of phosphoglycerate mutase 1 (PGAM1) on proliferating cells and neuroblasts in the subgranular zone of mouse dentate gyrus. In the present study, we examined the roles of PGAM1 in the HT22 hippocampal cell line and in gerbil hippocampus after H₂O₂-induced oxidative stress and after ischemia/reperfusion, respectively. Control-PGAM1 and Tat-PGAM1 proteins were synthesized using Tat-1 expression vector since Tat-1 fusion proteins can easily cross the blood-brain barrier and cell membranes. We found that transduction of Tat-PGAM1 protein into HT22 cells was dose- and time-dependent. Delivery of the protein to the cytoplasm was confirmed by western blotting and immunocytochemistry. Treatment of HT22 cells with Tat-PGAM1 protein showed a concentration-dependent reduction in cell damage and decreased formation of reactive oxygen species after H₂O₂ exposure. Tat-PGAM1 administration significantly ameliorated the ischemia-induced hyperactivity in gerbils at 1 day after ischemia/reperfusion. Additionally, a pronounced decrease in neuronal damage and reactive gliosis were observed in the hippocampal CA1 region of the Tat-PGAM1-treated group at 4 days after ischemia/reperfusion compared to that in the vehicle (Tat peptide) or control-PGAM1-treated groups. Administration of Tat-PGAM1 mitigated the changes in ATP content, succinate dehydrogenase activity, pH, and 4-hydroxynonenal levels in the hippocampus at 4 and 7 days after ischemia/reperfusion compared to that in the vehicle-treated group. In addition, administration of Tat-PGAM1 significantly ameliorated the ischemia-induced increases of lactate levels in the hippocampus at 15 min and 6 h after ischemia/reperfusion than in the vehicle or control-PGAM1-treated groups. These results suggest that Tat-PGAM1 can be used as a therapeutic agent to prevent neuronal damage from oxidative stress or ischemia.

Transcriptome Sequencing Unravels Potential Biomarkers at Different Stages of Cerebral Ischemic Stroke

Ischemic stroke, which accounts for 87% of all strokes, constitutes the leading cause of morbidity and mortality in China. Although the genetics and epigenetics of stroke have been extensively investigated, few studies have examined their relationships at different stages of stroke. This study assessed the characteristics of transcriptome changes at different stages of ischemic stroke using a mouse model of transient middle cerebral artery occlusion (tMCAO) and bioinformatics analyses. Cerebral cortex tissues from tMCAO mice at days 1, 3, 7, 14, and 28 were removed for RNA-Seq and small RNA-Seq library construction, sequencing, and bioinformatics analysis. We identified differentially expressed (DE) genes and miRNAs and revealed an association of the up-regulated or down-regulated DEmiRNAs with the correspondingly altered DEgene targets at each time point. In addition, different biological pathways were activated at different time points; thus, three groups of miRNAs were verified that may represent potential clinical biomarkers corresponding to days 1, 3, and 7 after ischemic stroke. Notably, this represents the first functional association of some of these miRNAs with stroke, e.g., miR-2137, miR-874-5p, and miR-5099. Together, our findings lay the foundation for the transition from a single-point, single-drug stroke treatment approach to multiple-time-point multi-drug combination therapies.

Regional-specific effects of cerebral ischemia/reperfusion and dehydroepiandrosterone on synaptic NMDAR/PSD-95 complex in male Wistar rats

Excessive glutamate efflux and N-methyl-D-aspartate receptor (NMDAR) over-activation represent well-known hallmarks of cerebral ischemia/reperfusion (I/R) injury, still, expression of proteins involved in this aspect of I/R pathophysiology show inconsistent data. Neurosteroid dehydroepiandrosterone (DHEA) has been proposed as potent NMDAR modulator, but its influence on I/R-induced changes up to date remains questionable. Therefore, I/R-governed alteration of vesicular glutamate transporter 1 (vGluT1), synaptic NMDAR subunit composition, postsynaptic density protein 95 (PSD-95) and neuronal morphology alone or following DHEA treatment were examined. For that purpose, adult male Wistar rats were treated with a single dose of vehicle or DHEA (20 mg/kg i.p.) 4 h following sham operation or 15 min bilateral common carotid artery occlusion. Western blot was used for analyses of synaptic protein expressions in hippocampus and prefrontal cortex, while neuronal morphology was assessed using Nissl staining. Regional-specific postischemic changes were detected on protein level i.e. signs of neuronal damage in CA1 area was accompanied with hippocampal vGluT1, NR1, NR2B enhancement and PSD-95 decrement, while histological changes observed in layer III were associated with decreased NR1 subunit in prefrontal cortex. Under physiological conditions DHEA had no effect on protein and histological appearance, while in ischemic milieu it restored hippocampal PSD-95 and NR1 in prefrontal cortex to the control level. Along with intact neurons, ones characterized by morphology observed in I/R group were also present. Future studies involving NMDAR-related intracellular signaling and immunohistochemical analysis will reveal precise effects of I/R and DHEA treatment in selected brain regions.

Mechanisms Underlying Neurotoxicity of Silver Nanoparticles

The potent antimicrobial properties of nanoparticulate silver (AgNPs) have led to broad interest in using them in a wide range of commercial and medical applications. Although numerous in vivo and in vitro studies have provided evidence of toxic effects, rapid commercialization of AgNP-based nanomaterials has advanced without characterization of their potential environmental and health hazards. There is evidence that AgNPs can be translocated from the blood to the brain, regardless the route of exposure, and accumulate in the brain over time. As the brain is responsible for basic physiological functions and controls all human activities, it is important to assess the hazardous influence of AgNPs released from widely used nanoproducts and possible side effects of AgNP-based therapies. A number of studies have suggested that the size, shape and surface coating, as well as rates of silver ion release and interactions with proteins are the key factors determining the neurotoxicity of AgNPs. AgNPs target endothelial cells forming the blood-brain barrier, neurons and glial cells and leads finally to oxidative stress-related cell death. In this chapter, we review in detail current data on the impact of AgNPs on the central nervous system and discuss the possible mechanisms of their neurotoxic effects.

Alzheimer's disease: Is this a brain specific diabetic condition?

Alzheimer's disease (AD) and type 2 diabetes (T2DM) are the two major health issues affecting millions of elderly people worldwide, with major impacts in the patient's daily life. Numerous studies have demonstrated that patients with diabetes have an increased risk of developing AD compared with healthy individuals. The principal biological mechanisms that associate with the progression of diabetes and AD are not completely understood. Impaired insulin signaling, uncontrolled glucose metabolism, oxidative stress, abnormal protein processing, and the stimulation of inflammatory pathways are common features to both AD and T2DM. In recent years brain specific abnormalities in insulin and insulin like growth factor (IGF) signaling considered as a major trigger involved in the etiopathogenesis of AD, showing T2DM like milieu. This review summarizes the pathways that might link diabetes and AD and the effect of diminished insulin.

Plasticity in the Neonatal Brain following Hypoxic-Ischaemic Injury

Hypoxic-ischaemic damage to the developing brain is a leading cause of child death, with high mortality and morbidity, including cerebral palsy, epilepsy, and cognitive disabilities. The developmental stage of the brain and the severity of the insult influence the selective regional vulnerability and the subsequent clinical manifestations. The increased susceptibility to hypoxia-ischaemia (HI) of periventricular white matter in preterm infants predisposes the immature brain to motor, cognitive, and sensory deficits, with cognitive impairment associated with earlier gestational age. In term infants HI causes selective damage to sensorimotor cortex, basal ganglia, thalamus, and brain stem. Even though the immature brain is more malleable to external stimuli compared to the adult one, a hypoxic-ischaemic event to the neonate interrupts the shaping of central motor pathways and can affect normal developmental plasticity through altering neurotransmission, changes in cellular signalling, neural connectivity and function, wrong targeted innervation, and interruption of developmental apoptosis. Models of neonatal HI demonstrate three morphologically different types of cell death, that is, apoptosis, necrosis, and autophagy, which crosstalk and can exist as a continuum in the same cell. In the present review we discuss the mechanisms of HI injury to the immature brain and the way they affect plasticity.

Inductive and Deductive Approaches to Acute Cell Injury

Many clinically relevant forms of acute injury, such as stroke, traumatic brain injury, and myocardial infarction, have resisted treatments to prevent cell death following injury. The clinical failures can be linked to the currently used inductive models based on biological specifics of the injury system. Here we contrast the application of inductive and deductive models of acute cell injury. Using brain ischemia as a case study, we discuss limitations in inductive inferences, including the inability to unambiguously assign cell death causality and the lack of a systematic quantitative framework. These limitations follow from an overemphasis on qualitative molecular pathways specific to the injured system. Our recently developed nonlinear dynamical theory of cell injury provides a generic, systematic approach to cell injury in which attractor states and system parameters are used to quantitatively characterize acute injury systems. The theoretical, empirical, and therapeutic implications of shifting to a deductive framework are discussed. We illustrate how a deductive mathematical framework offers tangible advantages over qualitative inductive models for the development of therapeutics of acutely injured biological systems.

Cellular alterations in human traumatic brain injury: changes in mitochondrial morphology reflect regional levels of injury severity

Mitochondrial dysfunction may be central to the pathophysiology of traumatic brain injury (TBI) and often can be recognized cytologically by changes in mitochondrial ultrastructure. This study is the first to broadly characterize and quantify mitochondrial morphologic alterations in surgically resected human TBI tissues from three contiguous cortical injury zones. These zones were designated as injury center (Near), periphery (Far), and Penumbra. Tissues from 22 patients with TBI with varying degrees of damage and time intervals from TBI to surgical tissue collection within the first week post-injury were rapidly fixed in the surgical suite and processed for electron microscopy. A large number of mitochondrial structural patterns were identified and divided into four survival categories: normal, normal reactive, reactive degenerating, and end-stage degenerating profiles. A tissue sample acquired at 38 hours post-injury was selected for detailed mitochondrial quantification, because it best exhibited the wide variation in cellular and mitochondrial changes consistently noted in all the other cases. The distribution of mitochondrial morphologic phenotypes varied significantly between the three injury zones and when compared with control cortical tissue obtained from an epilepsy lobectomy. This study is unique in its comparative quantification of the mitochondrial ultrastructural alterations at progressive distances from the center of injury in surviving TBI patients and in relation to control human cortex. These quantitative observations may be useful in guiding the translation of mitochondrial-based neuroprotective interventions to clinical implementation.

The physiological response of the marine platyhelminth Macrostomum lignano to different environmental oxygen concentrations

Respiration rate of meiofauna is difficult to measure, and the response to variations in the environmental oxygen concentrations has so far been mainly addressed through behavioral investigation. We investigated the effect of different oxygen concentrations on the physiology of the marine platyhelminth Macrostomum lignano. Respiration was measured using batches of 20 animals in a glass microtiter plate equipped with optical oxygen sensor spots. At higher oxygen saturations (>12kPa), animals showed a clear oxyconforming behavior. However, below this values, the flatworms kept respiration rates constant at 0.064±0.001 nmol O2 l-1 h-1 ind-1 down to 3 kPa PO2, and this rate was increased in 30% in animals that were reoxygenated after enduring a period of 1.5h in anoxia. Physiological changes related to tissue oxygenation were assessed using live imaging techniques with different fluorophores in animals maintained in normoxic (21 kPa), hyperoxic (40 kPa), near anoxic (≈0 kPa) conditions and subjected to anoxia-reoxygenation. Ageladine-A and BCECF both indicated that pHi under near anoxia increases by about 0.07 to 0.10 units. Mitochondrial membrane potential, Δψm, was higher in anoxic and hyperoxic compared to normoxic conditions (JC1). Staining with ROS sensitive dyes, DHE for detection of superoxide anion (O2•-) formation and C-H2DFFDA for other ROS species aside from O2•- (H2O2, HOO• and ONOO-), both showed increased ROS formation following anoxia reoxygenation treatment. Animals exposed to hyperoxic, normoxic and anoxic treatments displayed no significant differences in O2•- formation, whereas mitochondrial ROS formation as detected by C-H2DFFDA was higher after hyperoxic exposure and lowest under near anoxia compared to the normoxic control group. M. lignano seems to be a species tolerant to a wide range of oxygen concentrations (being able to maintain aerobic metabolism from extremely low PO2 and up to hyperoxic conditions) which is an essential prerequisite for successfully dealing with the drastic environmental oxygen variations that occur within intertidal sediments.

Trimetazidine demonstrated cardioprotective effects through mitochondrial pathway in a model of acute coronary ischemia

Myocardial ischemia affects mitochondrial function leading to ionic imbalance and susceptibility to ventricular fibrillation. Trimetazidine (TMZ), a metabolic agent, is clinically used as an anti-anginal therapy. This study was conducted to compare the effect of TMZ 20 mg immediate release (IR) and TMZ 35 mg modified release (MR), two bioequivalent marketed formulations of TMZ, on cardioprotection during acute ischemia in pigs. A 4-day oral treatment with TMZ 20 mg IR (800 mg, tid) or TMZ 35 mg MR (1,400 mg, bid) had no effect on ventricular fibrillation threshold (VFT) prior to ischemia but significantly prevented the decrease in VFT observed in placebo-treated groups after a 1-min left anterior descending coronary artery occlusion. This effect occurred without modifying cardiac hemodynamic and conduction parameters. In both TMZ-treated groups, a significant reduction of the ischemic area as well as a protection of cardiomyocytes were observed. Cardiac enzymatic activity (phosphorylase, succinate dehydrogenase, ATPase) was increased in TMZ-treated groups. Both formulations preserved mitochondrial structure and improved mitochondrial function as demonstrated by a twofold increase of oxidative phosphorylation, by a reduction of reactive oxygen species (ROS) production (>30 %) and by a trend to increase the mitochondrial calcium retention capacity. In this model of ischemia, both TMZ formulations, leading to equivalent TMZ plasma exposures, demonstrated similar cardioprotective effects. This protection could be attributed to a preservation of mitochondrial structure and function, which plays a central role in ATP and ROS production and consequently could be considered as a target of cardioprotection.

Hypoxia associated NMDA receptor 2 subunit composition: developmental comparison between the hypoxia-tolerant subterranean mole-rat, Spalax, and the hypoxia-sensitive rat

Vertebrate brains are sensitive to oxygen depletion, which may lead to cell death. Hypoxia sensitivity originates from the high intrinsic rate of ATP consumption of brain tissue, accompanied by the release of glutamate, leading to the opening of ionotropic glutamate receptors, such as N-methyl-D-aspartate (NMDA) receptors (NMDARs). The relative expression levels of the four NMDAR-2 (NR2) subunits change during mammalian development with higher levels of units NR2B and NR2D observed during early development and correlated with hypoxic tolerance during embryonic and neonatal stages of development. Higher levels of NR2D are also abundant in brains of hypoxia tolerant species such as the crucian carp. The subterranean mole-rat, Spalax spends its life underground in sealed burrows and has developed a wide range of adaptations to this special niche including hypoxia-tolerance. In this study, we compared the in vivo mRNA expression of NR2 subunits in the brains of embryonic, neonatal and adult Spalax and rat. Our results demonstrate that under normoxic conditions, mRNA levels of NR2D are higher in Spalax than in rat at all developmental stages studied and are similar to levels in neonatal rat and in other hypoxia/anoxia tolerant species. Furthermore, under hypoxia Spalax NR2D mRNA levels increase while no response was observed in rat. Similarly, hypoxia induces an increase in mRNA levels of Spalax NR2A, claimed to promote neuronal survival. We suggest that indeed the proportional combinations of NMDAR-2 subunits contribute to the ability of the Spalax brain to cope with hypoxic environments.

Crystal and molecular structures of 4-substituted 3,4-dihydropyrimidin-2(1H)-ones studied by X-ray and AM1 and B3LYP calculations

(1) C13H13N3O5, Mr = 291.26, P-1, a = 7.4629(9), b = 7.9203(9), c = 12.126(2) Å, α = 86.804(5), β = 78.471(7), γ = 69.401(8)°, V = 657.3(2) Å3, Z = 2, R 1 = 0.0454; (2) C11H12N2O4, Mr = 236.23, Pbca, a = 7.2713(9), b = 14.234(1), c = 20.848(3) Å, V = 2157.8(4) Å3, Z = 8, R 1 = 0.0504; (3) C13H13N2O3Cl, Mr = 280.70, P2/n, a = 17.344(2), b = 9.237(1), c = 18.398(2) Å; β = 92.61(2)°, V = 2944.4(6) Å3, Z = 8, R 1 = 0.0714. The conformational features of three 4-substituted-3-4-dihydropyrimidin-2(1H)-ones were investigated by computational and single crystal X-ray crystallographic studies. The geometries were optimized using semiempirical (AM1) and first principle calculations (B3LYP/6-31G**) methods, the rotational barriers for important functional groups were studied. In all structures the pyrimidinone rings are in a more or less distorted boat conformation. The phenyl and the furane rings are almost perpendicular to the best least-squares plane through the dihydropyrimidinone ring.

Mitochondrial calcium function and dysfunction in the central nervous system

The ability of isolated brain mitochondria to accumulate, store and release calcium has been extensively characterized. Extrapolation to the intact neuron led to predictions that the in situ mitochondria would reversibly accumulate Ca(2+) when the concentration of the cation in the vicinity of the mitochondria rose above the 'set-point' at which uptake and efflux were in balance, storing Ca(2+) as a complex with phosphate, and slowly releasing the cation when plasma membrane ion pumps lowered the cytoplasmic free Ca(2+). Excessive accumulation of the cation was predicted to lead to activation of the permeability transition, with catastrophic consequences for the neuron. Each of these predictions has been confirmed with intact neurons, and there is convincing evidence for the permeability transition in cellular Ca(2+) overload associated with glutamate excitotoxicity and stroke, while the neurodegenerative disease in which possible defects in mitochondrial Ca(2+) handling have been most intensively investigated is Huntington's Disease. In this brief review evidence that mitochondrial Ca(2+) transport is relevant to neuronal survival in these conditions will be discussed.

Neuroprotective effects of berberine on stroke models in vitro and in vivo

Berberine is an alkaloid derived from herb medicine Coptidis Rhizom. Although there are increasing evidences that berberine exhibits neuroprotective effects against ischemic brain damage, little is known about the mechanism. In this study, we investigated the effect of berberine on ischemic injury in a middle cerebral artery occlusion (MCAO) model. We found that berberine improved neurological outcome and reduced ischemia/reperfusion (I/R)-induced cerebral infarction 48h after MCAO. The protective effect of berberine was confirmed in in vitro study. Berberine protected PC12 cells against oxygen-glucose deprivation (OGD)-induced injury. The results showed that berberine inhibited reactive oxygen species (ROS) generation, and subsequent release of pro-apoptotic factor cytochrome c and apoptosis-inducing factors (AIFs) evoked by OGD. Findings of this study suggest that berberine protects against ischemic brain injury by decreasing the intracellular ROS level and subsequently inhibiting mitochondrial apoptotic pathway.

Ameliorative effect of PN-277 on laser-induced retinal damage

BACKGROUND

The retinal damage induced by laser photocoagulation increases considerably by the secondary degeneration process whereby tissues adjacent to the primary lesion are destroyed. As the neuroprotective effect of immunization by PN-277 was previously demonstrated in models of retina, optic nerve, brain, and spinal cord lesions, it may be used also for reducing retinal damage induced by laser. The aim of this study was to evaluate the neuroprotective effect of immunization with PN-277 in reducing the spread of laser-induced retinal damage.

METHODS

Standard argon laser lesions were created in 36 DA pigmented rats. Seven days before exposure to laser, the rats were divided into a test group (n = 18) that was pre-immunized with intraperitoneal injection of PN-277 and control group (n = 18) treated with saline. Histological and morphometrical evaluations of the retinal lesions were preformed 3, 20, and 60 days after the injury.

RESULTS

Significant ameliorative effect was demonstrated in the retinas of the pre-immunized animals 60 days after exposure to laser. The diameter of the lesion was 356 microm as compared with 406 microm (P < 0.01), the cell density of the photoreceptor cell bodies measured in the whole lesion was 72.4% of normal as compared with 64.5% (P = 0.01), and at the center of the lesion it was 57.3% of normal as compared with 38.2% (P < 0.01) (treated and control groups, respectively).

CONCLUSIONS

Immunization with PN-277 has an ameliorative effect in neural tissue such as the retina. This type of immunization may be of clinical significance in reducing laser-induced retinal injuries in humans.

Mebudipine and dibudipine protect PC12 cells against oxygen-glucose deprivation and glutamate-induced cell death

The protective effect of two new L-type calcium-channel blockers, mebudipine and dibudipine on neurotoxic effects induced by glutamate and oxygen-glucose deprivation (OGD) in PC12 cells was investigated. PC12 cells were intoxicated with two different methods. First, the cells were incubated with glutamate (10muM/L), glutamate and mebudipine (10muM/L), dibudipine (10muM/L) or nimodipine (10muM/L), on three different treatment schedules (concurrently, pre-3h and pre-24h). In the second method PC12 cells were exposed to in vitro oxygen-glucose deprivation for 30min and 60min alone or with the drugs in the same time schedules described above. Cellular viability was assessed by MTT assay. Glutamate-induced cell death and OGD-induced cell injury were attenuated significantly by mebudipine, dibudipine in comparison with nimodipine in all three different treatment schedules. Application of MK801 (10muM/L), an antagonist of NMDA glutamate receptors inhibited PC12 cell death in both methods. Our study suggests that mebudipine and dibudipine, like nimodipine, may have protective effects against glutamate and oxygen-glucose deprivation-induced neurotoxicity.

Astrocyte Responses after Neonatal Ischemia: The Yin and the Yang

Neonatal encephalopathy is a major predictor of neurodevelopmental disability in term infants and occurs in 1 to 6 of every 1000 live term births. Despite improvements in perinatal practice during the past several decades, the incidence of cerebral palsy attributed to neonatal asphyxia remained essentially unchanged, primarily because management strategies were supportive and not targeted toward the processes of ongoing injury. Traditionally, experimental research in vivo focused on neurons, and more recently, oligodendrocytes whereas astrocytes have been more or less neglected. This review aims at dissecting possible protective as well as destructive roles of astrocytes in the immature ischemic brain to stimulate further research into this unexplored aspect of brain pathophysiology. NEUROSCIENTIST 14(4):339ndash;344, 2008. DOI: 10.1177/1073858408316003

Salidroside attenuates glutamate-induced apoptotic cell death in primary cultured hippocampal neurons of rats

Salidroside, a compound of natural origin, has displayed a broad spectrum of pharmacological properties. This study aimed to evaluate the inhibitory effects of salidroside on glutamate-induced cell death in a primary culture of rat hippocampal neurons as compared to brain-derived neurotrophic factor (BDNF), a usual positive control. MTT and LDH assays, together with Hoechst 33342 staining, terminal deoxynucleotidyl transferase dUTP-mediated nicked end labeling (TUNEL) assay and flow cytometric analysis using annexin-V and propidium (PI) label, indicated that salidroside pretreatment attenuated glutamate-induced apoptotic cell death in primary cultured hippocampal neurons, showing a dose-dependent pattern. Furthermore, caspase-3 activity assay and calcium measurements with Fluo 4-AM, respectively, revealed that salidroside pretreatment antagonized activation of caspase-3 and elevation of intracellular calcium level, both of which were induced by glutamate stimulation, thus adding to the understanding of how salidroside offered neuroprotection against glutamate excitotoxicity.

Expression of genes involved in excitatory neurotransmission in anoxic crucian carp (Carassius carassius) brain

The crucian carp, Carassius carassius, survives months without oxygen. During anoxia it needs to keep energy expenditure low, particularly in the brain, with its high rate of ATP use related to neuronal activity. This could be accomplished by reducing neuronal excitability through altered expression of genes involved in excitatory neurotransmission. Through cloning and the use of a recently developed real-time RT-PCR approach, with an external RNA control for normalization, we investigated the effect of 1 and 7 days of anoxia (12 degrees C) on the expression of 29 genes, including 8 3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor subunits, 6 N-methyl-d-aspartate (NMDA) receptor subunits, 7 voltage-gated sodium and calcium channels, 4 glutamate transporters, and 4 genes involved in NMDA receptor-mediated neuroplasticity. The subunits of the majority of the gene families had expression profiles similar to those observed in the mammalian brain and showed remarkably stable expression during anoxia. This suggests that the genes may have similar functions in crucian carp and mammals, and that the excitatory abilities of the crucian carp brain are retained during anoxia. Although the data generally argue against profound neural depression ("channel arrest"), NMDA receptor subunit (NR) expression showed features that could mediate reduced neural excitability. Primarily, the NR2 subunit expression, which was dominated by NR2B and NR2D, resembled that seen in hypoxia-tolerant neonatal rats, and decreased anoxic expression of NR1, NR2C, and NR3A indicated reduced numbers of functional NMDA receptors. We also report the full-length sequence of crucian carp NR1 mRNA and a novel NR1 splice cassette introducing an N-glycosylation site into the extracellular S1S2 domain.

Protective effect of ultra low molecular weight heparin on glutamate-induced apoptosis in cortical cells

PURPOSE

To investigate the effect of ultra low molecular weight heparin (ULMWH) on glutamate induced apoptosis in rat cortical cells and to explore the possible mechanisms.

MATERIALS AND METHODS

Cell viability was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Apoptosis was first analyzed with Hoechst 33258 and then confirmed by DNA fragmentation. The concentration of free intracellular calcium ([Ca(2+)](i)) was determined with fura-2/AM fluorometry. The expression of Bcl-2 family protein and caspase-3 were evaluated with Western blot.

RESULTS

Typical apoptotic morphological change in rat cortical cells treated with 100 micromol/L glutamate for 24h was detected by Hoechst 33258 staining, which was then confirmed by the DNA ladder of agarose gel electrophoresis. The apoptotic rate of the glutamate treated cells was up to 33.21%, and 24 h of treatment with glutamate increased [Ca(2+)](i), down-regulated Bcl-2 expression, up-regulated Bax expression, and increased caspase-3 activation in rat cortical cells. Our research demonstrated that ULMWH pretreatment can prevent the glutamate-induced apoptosis, attenuate the increase of [Ca(2+)](i) not only in medium containing Ca(2+) but also in Ca(2+)-free medium, up-regulate the expression of Bcl-2, down-regulate the expression of Bax, and decrease caspase-3 activation.

CONCLUSION

ULMWH has neuroprotective capacity to antagonize glutamate-induced apoptosis in cortical cells, through decrease of Ca(2+) release and modulation of apoptotic processes.

Immunological aspects of acute stroke: therapeutic implications

Recent studies strongly suggest that cerebral ischaemia initiates a focal inflammatory response that results in significant secondary injury to brain tissue,thereby extending the ultimate size of a stroke. Factors involved in this cascade include the release of cytokines that cause a pro-inflammatory and prothrombotic state on cerebral vessel endothelium, the expression of leucocyte adhesion molecules, and the release of chemotactic factors allowing the migration of leucocytes into the area of injured brain tissue causing further damage. Animal studies have clearly demonstrated the detrimental effects of these inflammatory mediators in stroke models and additionally have shown dramatic reduction in infarct size using leucocyte adhesion modification and cytokine receptor blockade. The approach of modifying the effects of inflammatory cytokines and/or limiting leucocyte adhesion and migration into the region of injury holds great promise for identifying agents that will give significant neuronal protection following a stroke.

Protective effects of ginsenoside Rg2 against glutamate-induced neurotoxicity in PC12 cells

We investigated the effect of ginsenoside Rg2 on neurotoxic activities induced by glutamate in PC12 cells. The cells were incubated with glutamate (1 mmol/L), glutamate and ginsenoside Rg2 (0.05, 0.1, 0.2 mmol/L) or nimodipine (5 micromol/L) for 24 h. The cellular viability was assessed by MTT assay. The lipid peroxidation products malondialdehyde (MDA) and nitrogen oxide (NO) were measured by a spectrophotometric method. Fura-2/AM, as a cell permeable fluorescent probe for Ca2+, was used to detect intracellular Ca2+ concentration ([Ca2+]i) using a monespectrofluorometer. Immunocytochemical techniques were employed to check the protein expression levels of calpain II, caspase-3 and beta-amyloid (Abeta)1-40 in PC12 cells. The results showed that glutamate decreased the cell viability, increased [Ca2+]i, lipid peroxidation (the excessive production of MDA, NO) and the protein expression levels of calpain II, caspase-3 and Abeta1-40 in PC12 cells. Ginsenoside Rg2 significantly attenuated glutamate-induced neurotoxic effects upon these parameters at all doses tested. Our study suggests that ginsenoside Rg2 has a neuroprotective effect against glutamate-induced neurotoxicity through mechanisms related to anti-oxidation and anti-apoptosis. In addition, the inhibitory effect of ginsenoside Rg2 against the formation of Abeta1-40 suggests that ginsenoside Rg2 may also represent a potential treatment strategy for Alzheimer's disease.

Hypothyroidism provides resistance to kidney mitochondria against the injury induced by renal ischemia-reperfusion

Massive Ca(2+) accumulation in mitochondria, plus the stimulating effect of an inducing agent, i.e., oxidative stress, induces the so-called permeability transition, which is characterized by the opening of a nonspecific pore. This work was aimed at studying the influence of thyroid hormone on the opening of such a nonspecific pore in kidney mitochondria, as induced by an oxidative stress. To meet this objective, membrane permeability transition was examined in mitochondria isolated from kidney of euthyroid and hypothyroid rats, after a period of ischemia/reperfusion. It was found that mitochondria from hypothyroid rats were able to retain accumulated Ca(2+) to sustain a transmembrane potential after Ca(2+) addition, as well as to maintain matrix NAD(+) and membrane cytochrome c content. The protective effect of hypothyroidism was clearly opposed to that occurring in ischemic reperfused mitochondria from euthyroid rats. Our findings demonstrate that these mitochondria were unable to preserve selective membrane permeability, except when cyclosporin A was added. It is proposed that the protection is conferred by the low content of cardiolipin found in the inner membrane. This phospholipid is required to switch adenine nucleotide translocase from specific carrier to a non-specific pore.

The effect of nimodipine on calcium homeostasis and pain sensitivity in diabetic rats

1. The pathogenesis of diabetic neuropathy is a complex phenomenon, the mechanisms of which are not fully understood. Our previous studies have shown that the intracellular calcium signaling is impaired in primary and secondary nociceptive neurons in rats with streptozotocin (STZ)-induced diabetes. Here, we investigated the effect of prolonged treatment with the L-type calcium channel blocker nimodipine on diabetes-induced changes in neuronal calcium signaling and pain sensitivity. 2. Diabetes was induced in young rats (21 p.d.) by a streptozotocin injection. After 3 weeks of diabetes development, the rats were treated with nimodipine for another 3 weeks. The effect of nimodipine treatment on calcium homeostasis in nociceptive dorsal root ganglion neurons (DRG) and substantia gelatinosa (SG) neurons of the spinal cord slices was examined with fluorescent imaging technique. 3. Nimodipine treatment was not able to normalize elevated resting intracellular calcium ([Ca(2+)]( i )) levels in small DRG neurons. However, it was able to restore impaired Ca(2+) release from the ER, induced by either activation of ryanodine receptors or by receptor-independent mechanism in both DRG and SG neurons. 4. The beneficiary effects of nimodipine treatment on [Ca(2+)]( i ) signaling were paralleled with the reversal of diabetes-induced thermal hypoalgesia and normalization of the acute phase of the response to formalin injection. Nimodipine treatment was also able to shorten the duration of the tonic phase of formalin response to the control values. 5. To separate vasodilating effect of nimodipine Biessels et al., (Brain Res. 1035:86-93) from its effect on neuronal Ca(2+) channels, a group of STZ-diabetic rats was treated with vasodilator - enalapril. Enalapril treatment also have some beneficial effect on normalizing Ca(2+) release from the ER, however, it was far less explicit than the normalizing effect of nimodipine. Effect of enalapril treatment on nociceptive behavioral responses was also much less pronounced. It partially reversed diabetes-induced thermal hypoalgesia, but did not change the characteristics of the response to formalin injection. 6. The results of this study suggest that chronic nimodipine treatment may be effective in restoring diabetes-impaired neuronal calcium homeostasis as well as reduction of diabetes-induced thermal hypoalgesia and noxious stimuli responses. The nimodipine effect is mediated through a direct neuronal action combined with some vascular mechanism.

The mitochondrial K-ATP channel opener, diazoxide, prevents ischemia-reperfusion injury in the rabbit spinal cord

Paraplegia resulting from ischemia is a catastrophic complication of thoracoabdominal aortic surgery. The current study was designed to investigate the effects of diazoxide (DZ) on mitochondrial structure, neurological function, DNA damage-repair, and apoptosis in spinal cord ischemia-reperfusion injury. Rabbits were subjected to 30 minutes of spinal cord ischemia and reperfusion (1 hour) with or without diazoxide (n = 6 in each group) by clamping and releasing the infrarenal aorta. The neurological functional score was significantly improved in the DZ-treated ischemia-reperfusion injury group. Electron microscopic studies demonstrated that mitochondrial damage in the spinal cord after injury was significantly reduced by DZ. Mitochondrial superoxide and hydrogen peroxide levels were also markedly decreased in the DZ-treated injury group compared with the untreated group. DZ decreased levels of the oxidative DNA damage product 8-oxoG and increased levels of the DNA repair enzyme OGG-1. Furthermore, DZ inhibited apoptosis via caspase-dependent and -independent pathways. These studies indicate for the first time that the mitochondrial K-ATP channel opener diazoxide improves neurological function after spinal cord ischemia and reperfusion by diminishing levels of reactive oxygen species, decreasing DNA oxidative damage, and inhibiting caspase-dependent and -independent apoptotic pathways while preserving mitochondrial structure.

Effects of oxidative challenge and calcium on ATP-levels in neuronal cells

BACKGROUND

Neurocellular overload with hydrogen peroxide (H2O2) induces oxidative stress and may initiate a cascade of intracellular toxic events leading to energy failure, increased lipid peroxidation and subsequently cell death. Studies suggest that hippocampal neurons may be more vulnerable to oxidative stress than cortical cells pointing to a differential vulnerability of neuronal cells. Since disturbed ATP- and calcium (Ca2+)-metabolism may be involved in this process, we here evaluated the effects of H2O2-induced oxidative stress and the involvement of Ca2+-regulation on neuronal energy metabolism.

METHODS

Using primary cortical and hippocampal neurons as well as immortalized hippocampal HT22 cells, we determined ATP-levels and accompanying cell death after oxidative challenge with H2O2. Additionally, the combined effects of H2O2 and alterations in Ca2+-concentrations were pharmacologically characterized in more detail.

RESULTS

H2O2-incubation decreased ATP-levels in a dose- and time-dependent manner in all neuronal cell systems tested. Such effects were most pronounced in primary hippocampal neurons. In cortical cells, increased ATP-levels were notable under low H2O2-concentrations. A dose-dependent decrease in ATP-concentrations was observed after treatment with Ca2+, which was further enhanced by additional H2O2-challenge.

CONCLUSIONS

Our data underline that both, H2O2- and Ca2+-treatment, are able to disturb intracellular energy metabolism. Out of the different systems studied, the ATP-decrease is most pronounced in hippocampal primary neurons, suggesting that this mechanism contributes to the selective neuronal vulnerability to oxidative stress in these neurons.

Modulation of calcium entry and glutamate release in cultured cerebellar granule cells by palytoxin

A channel open on the membrane can be formed by palytoxin (PTX). Ten nanomolar PTX caused an irreversible increase in the cytosolic calcium concentration ([Ca(2+)](c)), which was abolished in the absence of external calcium. The increase was eliminated by saxitoxin (STX) and nifedipine (NIF). Calcium rise is secondary to the membrane depolarization. PTX effect on calcium was dependent on extracellular Na(+). Li(+) decreased the PTX-evoked rise in [Ca(2+)](c); replacement of Na(+) by N-methyl-D-glucamine (NMDG) abolished PTX-induced calcium increase. [Ca(2+)](c) increase by PTX was strongly reduced after inhibition of the reverse operation of the Na(+)/Ca(2+) exchanger, in the presence of antagonists of excitatory amino acid (EAA) receptors, and by inhibition of neurotransmitter release. PTX did not modify calcium extrusion by the plasma membrane Ca(2+)-ATPase (PMCA), because blockade of the calcium pump increased rather than decreased the PTX-induced calcium influx. Extracellular levels of glutamate and aspartate were measured by HPLC and exocytotic neurotransmitter release by determination of synaptic vesicle exocytosis using total internal reflection fluorescence microscopy (TIRFM). PTX caused a concentration-dependent increase in EAA release to the culture medium. Ten nanomolar PTX decreased cell viability by 30% within 5 min. PTX-induced calcium influx involves three pathways: Na(+)-dependent activation of voltage-dependent sodium channels (VDSC) and voltage-dependent calcium channels (VDCC), reverse operation of the Na(+)/Ca(2+) exchanger, and indirect activation of EAA receptors through glutamate release. The neuronal injury produced by the toxin could be partially mediated by the PTX-induced overactivation of EAA receptors, VDSC, VDCC and the glutamate efflux into the extracellular space.

Implementation of X-ray fluorescence microscopy for investigation of elemental abnormalities in amyotrophic lateral sclerosis

The abnormalities of metallochemical reactions may contribute to the pathogenesis of Amyotrophic Lateral Sclerosis (ALS). In the present work, an investigation of the elemental composition of the gray matter, nerve cells and white matter from spinal cord tissues representing three ALS cases and five non-ALS controls was performed. This was done with the use of the synchrotron microbeam X-ray fluorescence technique (micro-SRXRF). The following elements were detected in the tissue sections: P, S, Cl, K, Ca, Fe, Cu, Zn and Br. A higher accumulation of Cl, K, Ca, Zn and Br was observed in the nerve cell bodies than in the surrounding tissue. Contrary to all other elements, Zn accumulation was lower in the white matter areas than in the gray matter ones. The results of quantitative analysis showed that there were no general abnormalities in the elemental accumulation between the ALS and the control group. However, for individual ALS cases such abnormalities were observed for the nerve cells. We also demonstrated differences in the elemental accumulation between the analyzed ALS cases.

Reduction in oxidative stress and cell death explains hypothyroidism induced neuroprotection subsequent to ischemia/reperfusion insult

Hypometabolic state following hypothermia is known to protect tissues from ischemic injury. Hypothyroidism produces a hypometabolic state. The present study was undertaken to investigate the protective effects of hypothyroidism following cerebral ischemia and to ascertain the underlying mechanism. Euthyroid (E) and hypothyroid (H) animals were exposed to a 2 h of middle cerebral artery occlusion followed by 24 h of reperfusion (I/R). Specific enzymatic methods and flowcytometry were used to assess the quantitative changes of molecules involved in neuronal damage as well as in protection. As compared to euthyroid ischemic reperfused (E + I/R) rats, H + I/R rats had insignificant neurological deficit, and smaller area of infarct. H + I/R rats had significantly lower markers of oxidative stress, and lactate dehydrogenase (LDH) activity (a marker for necrosis). Natural antioxidant activity (particularly superoxide dismutase) and integrity of mitochondria (membrane potential) were maintained in H + I/R group but not in E + I/R group. The number of neurons undergoing apoptosis significantly lower in hypothyroid ischemic rats as compared to euthyroid ones. These results suggest that hypothyroid animals face ischemia and reperfusion much better compared to euthyroid animals. A possible explanation could be the decreased oxidative stress and maintained antioxidant activity that finally leads to a decrease in necrosis and apoptosis. These observations may suggest strategies to induce brain-specific downregulation of metabolism that may have implications in the management of strokes in human beings.