Coupling among energy failure, loss of ion homeostasis, and phospholipase A2 and C activation during ischemia

Extracorporeal cardiopulmonary resuscitation: a comparison of two experimental approaches and systematic review of experimental models

BACKGROUND

In patients requiring extracorporeal cardiopulmonary resuscitation (ECPR), there is a need for studies to assess the potential benefits of therapeutic interventions to improve survival and reduce hypoxic-ischemic brain injuries. However, conducting human studies may be challenging. This study aimed to describe two experimental models developed in our laboratory and to conduct a systematic review of existing animal models of ECPR reported in the literature.

RESULTS

In our experiments, pigs were subjected to 12 min (model 1) or 5 min (model 2) of untreated ventricular fibrillation, followed by 18 min (model 1) or 25 min (model 2) of conventional cardiopulmonary resuscitation. Results showed severe distributive shock, decreased brain oxygen pressure and increased intracranial pressure, with model 1 displaying more pronounced brain perfusion impairment. A systematic review of 52 studies, mostly conducted on pigs, revealed heterogeneity in cardiac arrest induction methods, cardiopulmonary resuscitation strategies, and evaluated outcomes.

CONCLUSIONS

This review emphasizes the significant impact of no-flow and low-flow durations on brain injury severity following ECPR. However, the diversity in experimental models hinders direct comparisons, urging the standardization of ECPR models to enhance consistency and comparability across studies.

Effects of Thymoquinone on Small-Molecule Metabolites in a Rat Model of Cerebral Ischemia Reperfusion Injury Assessed using MALDI-MSI

Thymoquinone is one of the main components present in Nigella sativa seeds and is known to have various biological functions in inflammation, oxidative stress, tumors, aging, and in lowering blood glucose levels. Few studies have focused on its neuroprotective effects and its regulation of small-molecule metabolites during cerebral ischemia reperfusion injury. In this study, transient middle cerebral occlusion (tMCAO) was used to establish the rat model of cerebral ischemia reperfusion injury. We investigated the effects of thymoquinone using matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) in a model of ischemia reperfusion injury to explore the changes in small-molecule metabolites in the brain. We found that that thymoquinone significantly improved neurobehavioral scores, reduced the cerebral infarct area, alleviated brain edema, and increased the number of normal neurons following injury. MALDI-MSI revealed that thymoquinone reduced abnormal accumulations of glucose, citric acid, succinate and potassium ions. Thymoquinone also increased the amount of energy-related molecules such as ADP, AMP, GMP, and creatine, antioxidants such as glutathione, ascorbic acid, and taurine, and other metabolism-related molecules such as glutamate, glutamine, aspartate, N-acetyl-L-aspartate, and sodium ions in damaged areas of the brain following cerebral ischemia reperfusion injury. In summary, based on the neuroprotective effect of thymoquinone on cerebral ischemia reperfusion injury, this study revealed the regulation of thymoquinone on energy metabolism and small-molecule substance metabolism.

Neurochemical changes in unilateral cerebral hemisphere during the subacute stage of focal cerebral ischemia-reperfusion in rats: An ex vivo 1H magnetic resonance spectroscopy study

Understanding the subacute may shed light on the mechanism of cerebral ischemia. The present study aimed to explore metabolic features underlying subacute stage of ischemia-reperfusion injury and developing effective treatments. Rats were divided into three groups: the permanent middle cerebral artery occlusion (pMCAO), transient cerebral focal ischemia (tMCAO) and sham group. Evaluation of animal models was performed by the neurological deficit, MR images and pathological morphological abnormality. To elucidate metabolic changes, we conducted a comparative analysis of metabolic composition of unilateral brain tissue using ¹H nuclear magnetic resonance spectroscopy. The successful model was observed low signal on T1WI and high signal on T2WI lesions in the left cerebral. Histopathological results confirmed the formation of apparent lesions in the left striatum, hippocampus CA1 and cortex tissues of subacute cerebral ischemia rats and showed that rats with focal cerebral ischemia-reperfusion could alleviate the extent of pathological damage degree. In pMCAO rats 7 days after surgery, decreased levels of N-acetyl aspartate (NAA), γ-aminobutyric acid (GABA), glutamate (Glu) and succinate (Suc) concomitantly with increased levels of glutamine (Gln), myo-inositol (m-Ins) and lactate (Lac) were observed compared to the control. Whereas, increased level of Lac with decreased levels of NAA, GABA, Glu, Suc, creatine (Cre) were observed in the tMCAO rats. This demonstrated that experimental subacute ischemic stroke in rats caused extensive perturbation in energy metabolism, the tricarboxylic acid cycle and GABA shunt, which provided essential information for understanding the pathogenesis of subacute cerebral ischemia-reperfusion and provided guidance in choosing the suitable therapeutic schedule.

Bystin (BYSL) as a possible marker of severe hypoxic-ischemic changes in neuropathological examination of forensic cases

Bystin (BYSL) is a 306-amino acid protein encoded in humans by the BYSL gene located on the 6p21.1 chromosome. It is conserved across a wide range of eukaryotes. BYSL was reported to be a sensitive marker for the reactive astrocytes induced by ischemia/reperfusion and chemical hypoxia in vitro and is considered to be one of the common characteristics of astrogliosis. In our study we examined whether BYSL could be used as a marker for hypoxic-ischemic changes in forensic cases. Groups suspected of acute hypoxic-ischemic changes presented strong BYSL expression in the cytoplasm of neocortical neurons especially in layers 3–5, that seemed to be short-lasting. In the hypoxic-ischemic-reperfusion group we did not find BYSL expression. BYSL expression in the cytoplasm of cortical neurons was minimal in the control group (cardiac arrest). BYSL seems to be a promising early marker of severe hypoxic-ischemic changes in neuropathological examination of forensic cases and certainly requires further studies.

Guidelines on experimental methods to assess mitochondrial dysfunction in cellular models of neurodegenerative diseases

Neurodegenerative diseases are a spectrum of chronic, debilitating disorders characterised by the progressive degeneration and death of neurons. Mitochondrial dysfunction has been implicated in most neurodegenerative diseases, but in many instances it is unclear whether such dysfunction is a cause or an effect of the underlying pathology, and whether it represents a viable therapeutic target. It is therefore imperative to utilise and optimise cellular models and experimental techniques appropriate to determine the contribution of mitochondrial dysfunction to neurodegenerative disease phenotypes. In this consensus article, we collate details on and discuss pitfalls of existing experimental approaches to assess mitochondrial function in in vitro cellular models of neurodegenerative diseases, including specific protocols for the measurement of oxygen consumption rate in primary neuron cultures, and single-neuron, time-lapse fluorescence imaging of the mitochondrial membrane potential and mitochondrial NAD(P)H. As part of the Cellular Bioenergetics of Neurodegenerative Diseases (CeBioND) consortium (www.cebiond.org), we are performing cross-disease analyses to identify common and distinct molecular mechanisms involved in mitochondrial bioenergetic dysfunction in cellular models of Alzheimer’s, Parkinson’s, and Huntington’s diseases. Here we provide detailed guidelines and protocols as standardised across the five collaborating laboratories of the CeBioND consortium, with additional contributions from other experts in the field.

Metabolic alterations in the rat cerebellum following acute middle cerebral artery occlusion, as determined by 1H NMR spectroscopy

Supratentorial focal ischemia may reduce cerebral blood volume and cerebellar glucose metabolic rate contralateral to the region of ischemia. The present study investigated the effects of middle cerebral artery occlusion (MCAO) on cerebral metabolism in the ischemic cerebral hemisphere and the non‑ischemic cerebellum in rats 1, 3, 9 and 24 h following ischemia using ex vivo proton nuclear magnetic resonance (1H NMR) spectroscopy. The results demonstrated that focal ischemia induced increases in the levels of lactate and alanine, and a decrease in succinate, as early as 1 h following ischemia in the left cerebral hemisphere and the right cerebellum. A continuous increase in lactate levels and decrease in creatine levels were detected in both cerebral areas 3 and 24 h post‑MCAO. The most obvious difference between the two cerebral areas was that there was no statistically significant difference in N‑acetyl aspartate (NAA) levels in the right cerebellum at all time points; however, the amino acid levels of NAA in the left cerebral hemisphere were markedly decreased 3, 9 and 24 h post‑MCAO. In addition, an obvious increase in glutamine was observed in the right and left cerebellum at 3, 9 and 24 h post‑MCAO. Furthermore, the present study demonstrated that γ‑aminobutyric acid levels were decreased at 1 h in the left and right cerebellum and were evidently increased at 24 h in the right cerebellum post‑MCAO. In conclusion, supratentorial ischemia has been indicated to affect the activities of the non‑ischemic contralateral cerebellum. Therefore, these results suggested that an NMR‑based metabonomic approach may be used as a potential means to elucidate cerebral and cerebellar metabolism following MCAO, which may help improve understanding regarding cerebral infarction at a molecular level. Ex vivo 1H NMR analysis may be useful for the assessment of clinical biopsies.

Discovery and Development of Calcium Channel Blockers

In the mid 1960s, experimental work on molecules under screening as coronary dilators allowed the discovery of the mechanism of calcium entry blockade by drugs later named calcium channel blockers. This paper summarizes scientific research on these small molecules interacting directly with L-type voltage-operated calcium channels. It also reports on experimental approaches translated into understanding of their therapeutic actions. The importance of calcium in muscle contraction was discovered by Sidney Ringer who reported this fact in 1883. Interest in the intracellular role of calcium arose 60 years later out of Kamada (Japan) and Heibrunn (USA) experiments in the early 1940s. Studies on pharmacology of calcium function were initiated in the mid 1960s and their therapeutic applications globally occurred in the the 1980s. The first part of this report deals with basic pharmacology in the cardiovascular system particularly in isolated arteries. In the section entitled from calcium antagonists to calcium channel blockers, it is recalled that drugs of a series of diphenylpiperazines screened in vivo on coronary bed precontracted by angiotensin were initially named calcium antagonists on the basis of their effect in depolarized arteries contracted by calcium. Studies on arteries contracted by catecholamines showed that the vasorelaxation resulted from blockade of calcium entry. Radiochemical and electrophysiological studies performed with dihydropyridines allowed their cellular targets to be identified with L-type voltage-operated calcium channels. The modulated receptor theory helped the understanding of their variation in affinity dependent on arterial cell membrane potential and promoted the terminology calcium channel blocker (CCB) of which the various chemical families are introduced in the paper. In the section entitled tissue selectivity of CCBs, it is shown that characteristics of the drug, properties of the tissue, and of the stimuli are important factors of their action. The high sensitivity of hypertensive animals is explained by the partial depolarization of their arteries. It is noted that they are arteriolar dilators and that they cannot be simply considered as vasodilators. The second part of this report provides key information about clinical usefulness of CCBs. A section is devoted to the controversy on their safety closed by the Allhat trial (2002). Sections are dedicated to their effect in cardiac ischemia, in cardiac arrhythmias, in atherosclerosis, in hypertension, and its complications. CCBs appear as the most commonly used for the treatment of cardiovascular diseases. As far as hypertension is concerned, globally the prevalence in adults aged 25 years and over was around 40% in 2008. Usefulness of CCBs is discussed on the basis of large clinical trials. At therapeutic dosage, they reduce the elevated blood pressure of hypertensive patients but don't change blood pressure of normotensive subjects, as was observed in animals. Those active on both L- and T-type channels are efficient in nephropathy. Alteration of cognitive function is a complication of hypertension recognized nowadays as eventually leading to dementia. This question is discussed together with the efficacy of CCBs in cognitive pathology. In the section entitled beyond the cardiovascular system, CCBs actions in migraine, neuropathic pain, and subarachnoid hemorrhage are reported. The final conclusions refer to long-term effects discovered in experimental animals that have not yet been clearly reported as being important in human pharmacotherapy.

Regulation of mRNA following brain ischemia and reperfusion

There is growing appreciation that mRNA regulation plays important roles in disease and injury. mRNA regulation and ribonomics occur in brain ischemia and reperfusion (I/R) following stroke and cardiac arrest and resuscitation. It was recognized over 40 years ago that translation arrest (TA) accompanies brain I/R and is now recognized as part of the intrinsic stress responses triggered in neurons. However, neuron death correlates to a prolonged TA in cells fated to undergo delayed neuronal death (DND). Dysfunction of mRNA regulatory processes in cells fated to DND prevents them from translating stress-induced mRNAs such as heat shock proteins. The morphological and biochemical studies of mRNA regulation in postischemic neurons are discussed in the context of the large variety of molecular damage induced by ischemic injury. Open issues and areas of future investigation are highlighted. A sober look at the molecular complexity of ischemia-induced neuronal injury suggests that a network framework will assist in making sense of this complexity. The ribonomic network sits between the gene network and the various protein and metabolic networks. Thus, targeting the ribonomic network may prove more effective at neuroprotection than targeting specific molecular pathways, for which all efforts have failed to the present time to stop DND in stroke and after cardiac arrest. WIREs RNA 2017, 8:e1415. doi: 10.1002/wrna.1415 For further resources related to this article, please visit the WIREs website.

Pathophysiology and the Monitoring Methods for Cardiac Arrest Associated Brain Injury

Cardiac arrest (CA) is a well-known cause of global brain ischemia. After CA and subsequent loss of consciousness, oxygen tension starts to decline and leads to a series of cellular changes that will lead to cellular death, if not reversed immediately, with brain edema as a result. The electroencephalographic activity starts to change as well. Although increased intracranial pressure (ICP) is not a direct result of cardiac arrest, it can still occur due to hypoxic-ischemic encephalopathy induced changes in brain tissue, and is a measure of brain edema after CA and ischemic brain injury. In this review, we will discuss the pathophysiology of brain edema after CA, some available techniques, and methods to monitor brain oxygen, electroencephalography (EEG), ICP (intracranial pressure), and microdialysis on its measurement of cerebral metabolism and its usefulness both in clinical practice and possible basic science research in development. With this review, we hope to gain knowledge of the more personalized information about patient status and specifics of their brain injury, and thus facilitating the physicians’ decision making in terms of which treatments to pursue.

Hyperglycemia / hypoglycemia-induced mitochondrial dysfunction and cerebral ischemic damage in diabetics

Enhancement of ischemic brain damage is one of the most serious complications of diabetes. Studies from various in vivo and in vitro models of cerebral ischemia have led to an understanding of the role of mitochondria and complex interrelated mitochondrial biochemical pathways leading to the aggravation of ischemic neuronal damage. Advancements in the elucidation of the mechanisms of ischemic brain damage in diabetic subjects have revealed a number of key mitochondrial targets that have been hypothesized to participate in enhancement of brain damage. The present review initially discusses the neurobiology of ischemic neuronal injury, with special emphasis on the central role of mitochondria in mediating its pathogenesis and therapeutic targets. Later it further details the potential role of various biochemical mediators and second messengers causing widespread ischemic brain damage among diabetics via mitochondrial pathways. The present review discusses preclinical data which validates the significance of mitochondrial mechanisms in mediating the aggravation of ischemic cerebral injury in diabetes. Exploitation of these targets may provide effective therapeutic agents for the management of diabetes-related aggravation of ischemic neuronal damage.

mtDNA T8993G mutation-induced F1F0-ATP synthase defect augments mitochondrial dysfunction associated with hypoxia/reoxygenation: the protective role of melatonin

Background

F1F0-ATP synthase (F1F0-ATPase) plays important roles in regulating mitochondrial function during hypoxia, but the effect of F1F0-ATPase defect on hypoxia/reoxygenation (H/RO) is unknown. The aim of this study was to investigate how mtDNA T8993G mutation (NARP)-induced inhibition of F1F0-ATPase modulates the H/RO–induced mitochondrial dysfunction. In addition, the potential for melatonin, a potent antioxidant with multiple mitochondrial protective properties, to protect NARP cells exposed to H/RO was assessed.

Methods And Findings

NARP cybrids harboring 98% of mtDNA T8993G genes were established as an in vitro model for cells with F1F0-ATPase defect; their parental osteosarcoma 143B cells were studied for comparison. Treating the cells with H/RO using a hypoxic chamber resembles ischemia/reperfusion in vivo. NARP significantly enhanced apoptotic death upon H/RO detected by MTT assay and the trypan blue exclusion test of cell viability. Based on fluorescence probe-coupled laser scanning imaging microscopy, NARP significantly enhanced mitochondrial reactive oxygen species (mROS) formation and mitochondrial Ca²⁺ (mCa²⁺) accumulation in response to H/RO, which augmented the depletion of cardiolipin, resulting in the retardation of mitochondrial movement. With stronger H/RO stress (either with longer reoxygenation duration, longer hypoxia duration, or administrating secondary oxidative stress following H/RO), NARP augmented H/RO-induced mROS formation to significantly depolarize mitochondrial membrane potential (ΔΨm), and enhance mCa²⁺ accumulation and nitric oxide formation. Also, NARP augmented H/RO-induced mROS oxidized and depleted cardiolipin, thereby promoting permanent mitochondrial permeability transition, retarded mitochondrial movement, and enhanced apoptosis. Melatonin markedly reduced NARP-augmented H/RO-induced mROS formation and therefore significantly reduced mROS-mediated depolarization of ΔΨm and accumulation of mCa²⁺, stabilized cardiolipin, and then improved mitochondrial movement and cell survival.

Conclusion

NARP-induced inhibition of F1F0-ATPase enhances mROS formation upon H/RO, which augments the depletion of cardiolipin and retardation of mitochondrial movement. Melatonin may have the potential to rescue patients with ischemia/reperfusion insults, even those associated with NARP symptoms.

Choline-containing phospholipids: relevance to brain functional pathways

Choline participates in several relevant neurochemical processes. It is the precursor and metabolite of acetylcholine (ACh), plays a role in single-carbon metabolism and is an essential component of different membrane phospholipids (PLs). PLs are structural components of cell membranes involved in intraneuronal signal transduction. This paper reviews the roles of choline and of choline-containing phospholipids (CCPLs) on brain metabolism in health and disease followed by an analysis of the effects of exogenously administered CCPLs on the brain, a topic extensively investigated by literature. Based on the observation of decreased cholinergic neurotransmission in brain disorders characterized by cognitive impairment, cholinergic precursor loading therapy with CCPLs was the first approach used to attempt for relieving the cognitive symptoms of Alzheimer's disease. This therapeutic strategy was discontinued due to the negative clinical results obtained with choline or lecithin. Negative results obtained with some compounds cannot be generalized for all CCPLs, as CDP-choline (citicoline) and to a greater extent choline alphoscerate (GPC) displayed interesting effects documented in preclinical studies and limited clinical trials. We provide evidence in favor of CDP-choline and GPC activity in cerebrovascular or neurodegenerative disorders characterized by cholinergic neurotransmission impairment. Based on the results of the controlled clinical trials available, we suggest that due to the lack of novel therapeutic strategies, safe compounds developed a long time ago such as effective CCPLs could have still a place in pharmacotherapy. Therefore selected compounds of this class should be further investigated by new appropriate clinical studies.

Prostaglandin D2 toxicity in primary neurons is mediated through its bioactive cyclopentenone metabolites

Prostaglandin D2 (PGD2) is the most abundant prostaglandin in brain but its effect on neuronal cell death is complex and not completely understood. PGD2 may modulate neuronal cell death via activation of DP receptors or its metabolism to the cyclopentenone prostaglandins (CyPGs) PGJ2, Δ(12)-PGJ2 and 15-deoxy-Δ(12,14)-PGJ2, inducing cell death independently of prostaglandin receptors. This study aims to elucidate the effect of PGD2 on neuronal cell death and its underlying mechanisms. PGD2 dose-dependently induced cell death in rat primary neuron-enriched cultures in concentrations of ≥10μM, and this effect was not reversed by treatment with either DP1 or DP2 receptor antagonists. Antioxidants N-acetylcysteine (NAC) and glutathione which contain sulfhydryl groups that can bind to CyPGs, but not ascorbate or tocopherol, attenuated PGD2-induced cell death. Conversion of PGD2 to CyPGs was detected in neuronal culture medium; treatment with these CyPG metabolites alone exhibited effects similar to those of PGD2, including apoptotic neuronal cell death and accumulation of ubiquitinated proteins. Disruption of lipocalin-type prostaglandin D synthase (L-PGDS) protected neurons against hypoxia. These results support the hypothesis that PGD2 elicits its cytotoxic effects through its bioactive CyPG metabolites rather than DP receptor activation in primary neuronal culture.

Quantitative in vivo detection of brain cell death after hypoxia ischemia using the lipid peak at 1.3 ppm of proton magnetic resonance spectroscopy in neonatal rats

This study was performed to determine the accuracy of proton magnetic spectroscopy ((1)H-MRS) lipid peak as a noninvasive tool for quantitative in vivo detection of brain cell death. Seven day-old Sprague Dawley rats were subjected to 8% oxygen following a unilateral carotid artery ligation. For treatment, cycloheximide was given immediately after hypoxic ischemia (HI). Lipid peak was measured using (1)H-MRS at 24 hr after HI, and then brains were harvested for fluorocytometric analyses with annexin V/propidium iodide (PI) and fluorescent probe JC-1, and for adenosine-5'-triphosphate (ATP) and lactate. Increased lipid peak at 1.3 ppm measured with (1)H-MRS, apoptotic and necrotic cells, and loss of mitochondrial membrane potential (ΔΨ) at 24 hr after HI were significantly improved with cycloheximide treatment. Significantly reduced brain ATP and increased lactate levels observed at 24 hr after HI showed a tendency to improve without statistical significance with cycloheximide treatment. Lipid peak at 1.3 ppm showed significant positive correlation with both apoptotic and necrotic cells and loss of ΔΨ, and negative correlation with normal live cells. Lipid peak at 1.3 ppm measured by (1)H-MRS might be a sensitive and reliable diagnostic tool for quantitative in vivo detection of brain cell death after HI.

A mechanism of rapidly reversible cerebral ventricular enlargement independent of tissue atrophy

Ventricular enlargement, a common in vivo marker of aging, disease, and insult, is presumed to reflect atrophy of surrounding brain regions. Pathological mechanisms underlying ventricular enlargement, however, are likely specific to the condition under investigation. Here, multimodal imaging, incorporating structural magnetic resonance imaging (MRI), MR spectroscopy (MRS), and diffusion weighted imaging (DWI), was used in rats exposed to binge ethanol (EtOH) to provide insight into a mechanism of reversible ventricular enlargement. During intoxication, MRI revealed expansion of ventricles, but volume changes in dorsal or ventral hippocampi, caudate-putamen, or thalamus were not detectible. MRS of whole-brain parenchyma showed decreases in N-acetylasparate (NAA) and tissue water T2, and increases in choline-containing compounds (Cho). DWI showed decreased diffusivity selective to the thalamus. All MR parameters returned to baseline with 7 days of recovery. Rapid recovery of ventricular volume and the absence of detectable tissue volume reductions in brain regions adjacent to ventricles argue against atrophy as a mechanism of ventricular expansion. Decreased tissue water T2 and decreased thalamic diffusivity suggest lower tissue water content and a role for both NAA and Cho, as osmolytes is proposed. Together, these data support a model of fluid redistribution during acute EtOH intoxication and recovery to account for rapid ventricular volume changes.

Ionotropic receptors and ion channels in ischemic neuronal death and dysfunction

Loss of energy supply to neurons during stroke induces a rapid loss of membrane potential that is called the anoxic depolarization. Anoxic depolarizations result in tremendous physiological stress on the neurons because of the dysregulation of ionic fluxes and the loss of ATP to drive ion pumps that maintain electrochemical gradients. In this review, we present an overview of some of the ionotropic receptors and ion channels that are thought to contribute to the anoxic depolarization of neurons and subsequently, to cell death. The ionotropic receptors for glutamate and ATP that function as ligand-gated cation channels are critical in the death and dysfunction of neurons. Interestingly, two of these receptors (P2X7 and NMDAR) have been shown to couple to the pannexin-1 (Panx1) ion channel. We also discuss the important roles of transient receptor potential (TRP) channels and acid-sensing ion channels (ASICs) in responses to ischemia. The central challenge that emerges from our current understanding of the anoxic depolarization is the need to elucidate the mechanistic and temporal interrelations of these ion channels to fully appreciate their impact on neurons during stroke.

Molecular mechanisms of ischemia-reperfusion injury in brain: pivotal role of the mitochondrial membrane potential in reactive oxygen species generation

Stroke and circulatory arrest cause interferences in blood flow to the brain that result in considerable tissue damage. The primary method to reduce or prevent neurologic damage to patients suffering from brain ischemia is prompt restoration of blood flow to the ischemic tissue. However, paradoxically, restoration of blood flow causes additional damage and exacerbates neurocognitive deficits among patients who suffer a brain ischemic event. Mitochondria play a critical role in reperfusion injury by producing excessive reactive oxygen species (ROS) thereby damaging cellular components, and initiating cell death. In this review, we summarize our current understanding of the mechanisms of mitochondrial ROS generation during reperfusion, and specifically, the role the mitochondrial membrane potential plays in the pathology of cerebral ischemia/reperfusion. Additionally, we propose a temporal model of ROS generation in which posttranslational modifications of key oxidative phosphorylation (OxPhos) proteins caused by ischemia induce a hyperactive state upon reintroduction of oxygen. Hyperactive OxPhos generates high mitochondrial membrane potentials, a condition known to generate excessive ROS. Such a state would lead to a "burst" of ROS upon reperfusion, thereby causing structural and functional damage to the mitochondria and inducing cell death signaling that eventually culminate in tissue damage. Finally, we propose that strategies aimed at modulating this maladaptive hyperpolarization of the mitochondrial membrane potential may be a novel therapeutic intervention and present specific studies demonstrating the cytoprotective effect of this treatment modality.

NMR analysis of the rat neurochemical changes induced by middle cerebral artery occlusion

Stroke is a leading cause of death and disability, affecting millions of people worldwide with almost 80% of them as ischemic stroke and understanding the multiple mechanisms underlying cerebral ischemia is essential for development of effective treatments. To understand metabolic changes induced by focal brain ischemia, we conducted a comparative analysis of metabolic composition of cerebral tissue from rats with sham-operation and middle cerebral artery occlusion (MCAO) using high-resolution nuclear magnetic resonance (NMR) spectroscopy. More than 40 metabolites were assigned including organic acids, amino acids, carbohydrates, choline, pyrimidine and purine metabolites. Our results showed that MCAO led to significant level decreases for glutamate, glutamine, aspartate, γ-aminobutyrate (GABA), taurine, malate, fumarate, acetate, phosphocreatine, and purine and pyrimidine metabolites such as inosine, hypoxanthine, xanthine, uracil and UDP/UTP, together with significant level increases for glucose in focal brain tissue extracts. This demonstrated that experimental ischemic stroke in rats caused extensive perturbation in tricarboxylic acid cycle, GABA shunt, and metabolisms of choline and nucleic acids. These findings provided essential information for our understandings of MCAO-caused biochemical alterations and demonstrated the metabolite composition analysis as a useful tool for understanding the neurochemistry of stroke.

Liposomal-glutathione provides maintenance of intracellular glutathione and neuroprotection in mesencephalic neuronal cells

A liposomal preparation of glutathione (GSH) was investigated for its ability to replenish intracellular GSH and provide neuroprotection in an in vitro model of Parkinson's disease using paraquat plus maneb (PQMB) in rat mesencephalic cultures. In mixed neuronal/glial cultures depleted of intracellular GSH, repletion to control levels occurred over 4 h with liposomal-GSH or non-liposomal-GSH however, liposomal-GSH was 100-fold more potent; EC(50s) 4.75 μM and 533 μM for liposomal and non-liposomal-GSH, respectively. Liposomal-GSH utilization was also observed in neuronal cultures, but with a higher EC(50) (76.5 μM), suggesting that glia facilitate utilization. Blocking γ-glutamylcysteine synthetase with buthionine sulfoxamine prevented replenishment with liposomal-GSH demonstrating the requirement for catabolism and resynthesis. Repletion was significantly attenuated with endosomal inhibition implicating the endosomal system in utilization. Liposomal-GSH provided dose-dependent protection against PQMB with an EC(50) similar to that found for repletion. PQMB depleted intracellular GSH by 50%. Liposomal-GSH spared endogenous GSH during PQMB exposure, but did not require GSH biosynthesis for protection. No toxicity was observed with the liposomal preparation at 200-fold the EC(50) for repletion. These findings indicate that glutathione supplied in a liposomal formulation holds promise as a potential therapeutic for neuronal maintenance.

Brain injury and recovery following binge ethanol: evidence from in vivo magnetic resonance spectroscopy

BACKGROUND

The binge-drinking model in rodents using intragastric injections of ethanol (EtOH) for 4 days results in argyrophilic corticolimbic tissue classically interpreted as indicating irreversible neuronal degeneration. However, recent findings suggest that acquired argyrophilia can also identify injured neurons that have the potential to recover. The current in vivo magnetic resonance (MR) imaging and spectroscopy study was conducted to test the hypothesis that binge EtOH exposure would injure but not cause the death of neurons as previously ascertained postmortem.

METHODS

After baseline MR scanning, 11 of 19 rats received a loading dose of 5 g/kg EtOH via oral gavage, then a maximum of 3 g/kg every 8 hours for 4 days, for a total average cumulative EtOH dose of 43 +/- 1.2 g/kg and average blood alcohol levels of 258 +/- 12 mg/dL. All animals were scanned after 4 days of gavage (post-gavage scan) with EtOH (EtOH group) or dextrose (control [Con] group) and again after 7 days of abstinence from EtOH (recovery scan).

RESULTS

Tissue shrinkage at the post-gavage scan was reflected by significantly increased lateral ventricular volume in the EtOH group compared with the Con group. At the post-gavage scan, the EtOH group had lower dorsal hippocampal N-acetylaspartate and total creatine and higher choline-containing compounds than the Con group. At the recovery scan, neither ventricular volume nor metabolite levels differentiated the groups.

CONCLUSIONS

Rapid recovery of ventricular volume and metabolite levels with removal of the causative agent argues for transient rather than permanent effects of a single EtOH binge episode in rats.

Apocynin attenuate spatial learning deficits and oxidative responses to intermittent hypoxia

RATIONALE

The long-term intermittent hypoxia (LTIH) that characterizes sleep-disordered breathing impairs spatial learning and increases oxidative stress in rodents. We hypothesized that LTIH activated brain NADPH oxidase, which served as a critical source of superoxide in the oxidation injury, and that apocynin might attenuate LTIH-induced spatial learning deficits by reducing LTIH-induced NADPH oxidase expression.

OBJECTIVE

To investigate the effects of apocynin on spatial learning and oxidative responses to LTIH in rats.

METHODS

Forty healthy male Sprague-Dawley (SD) rats were randomly divided into four groups of 10 each: a LTIH group, an apocynin-treated LTIH group, a sham LTIH group and an apocynin-treated sham group. Spatial learning in each group was assessed with the Morris water maze test. RT-PCR and Western blot were used to examine mRNA and protein expression of NADPH oxidase subunit p47phox and p22phox in the hippocampus region. The level of MDA and SOD were detected by colorimetric method. The terminal deoxynucleotidyl transferase-mediated dUTP-nick end-labeling (TUNEL) method was used to display the apoptotic cells of the hippocampus tissue.

RESULTS

Apocynin treatment prevented LTIH-induced decreases in spatial learning during the Morris water maze as well as LTIH-induced decrease in SOD levels. In untreated animals, LTIH exposure was related to increase of MDA levels in comparison to sham LTIH animals, and apocynin-treated animal exposure to LTIH showed reduction in MDA levels. Increases in hippocampus NADPH oxidase subunit p47phox mRNA and protein expression were observed in LTIH-exposed animals; there was no statistical difference of p47phox mRNA and protein expression between LTIH group and apocynin treatment group. Treatment with apocynin significantly ameliorated cell apoptosis in LTIH-exposed animals.

CONCLUSION

These results indicate that apocynin attenuates LTIH-induced spatial learning deficits and mitigates LTIH-induced oxidative stress through multiple beneficial effects on oxidant pathways. NADPH oxidase up-expression is closely associated with oxidative processes in LTIH rats, and inhibition of NADPH oxidase activity may hopefully serve as a useful strategy for cognitive function impairment from chronic intermittent hypoxia.

Effects of anoxia, aglycemia, and acidosis on cytosolic Mg2+, ATP, and pH in rat sensory neurons

Sensory neurons can detect ischemia and transmit pain from various organs. Whereas the primary stimulus in ischemia is assumed to be acidosis, little is known about how the inevitable metabolic challenge influences neuron function. In this study we have investigated the effects of anoxia, aglycemia, and acidosis upon intracellular Mg(2+) concentration [Mg(2+)](i) and intracellular pH (pH(i)) in isolated sensory neurons. Anoxia, anoxic aglycemia, and acidosis all caused a rise in [Mg(2+)](i) and a fall in pH(i). The rise in [Mg(2+)](i) in response to acidosis appears to be due to H(+) competing for intracellular Mg(2+) binding sites. The effects of anoxia and aglycemia were mimicked by metabolic inhibition and, in a dorsal root ganglia (DRG)-derived cell line, the rise in [Mg(2+)](i) during metabolic blockade was closely correlated with fall in intracellular ATP concentration ([ATP](i)). Increase in [Mg(2+)](i) during anoxia and aglycemia were therefore assumed to be due to MgATP hydrolysis. Even brief periods of anoxia (<3 min) resulted in rapid internal acidosis and a rise in [Mg(2+)](i) equivalent to a decline in MgATP levels of 15-20%. With more prolonged anoxia (20 min) MgATP depletion is estimated to be around 40%. With anoxic aglycemia, the [Mg(2+)](i) rise occurs in two phases: the first beginning almost immediately and the second after an 8- to 10-min delay. Within 20 min of anoxic aglycemia [Mg(2+)](i) was comparable to that observed following complete metabolic inhibition (dinitrophenol + 2-deoxyglucose, DNP + 2-DOG) indicating a near total loss of MgATP. The consequences of these events therefore need to be considered in the context of sensory neuron function in ischemia.

Neuronal Cyclooxygenase-2 Activity and Prostaglandins PGE2, PGD2, and PGF2α Exacerbate Hypoxic Neuronal Injury in Neuron-enriched Primary Culture

Cyclooxygenase-2 (COX-2) activity has been implicated in the pathogenesis of cerebral ischemia. To determine whether COX-2 activity within the neuron itself exacerbates hypoxic neuronal injury, neuron-enriched cultures were subjected to anoxia. Treatment with COX-2 selective antagonists decreased cell death. Neurons cultured from homozygous COX-2 gene disrupted mice were resistant to hypoxia compared to those of heterozygotes. Infection of primary neurons with AAV expressing COX-2 exacerbated cell death compared to neurons infected with enhanced green fluorescent protein (EGFP) control vector. Addition of PGE2, PGD2 or PGF2 alpha to the medium exacerbated injury, suggesting that the deleterious effects of COX-2 overexpression in hypoxia could be mediated by direct receptor mediated effects of prostaglandins. Overexpression of COX-2 did not increase expression of cyclin D1 or phosphoretinoblastoma protein (pRb), or cleavage of caspase 3 suggesting that this cell cycle mechanism does not mediate COX-2 toxicity in this model.

MEK inhibition exacerbates ischemic calcium imbalance and neuronal cell death in rat cortical cultures

Interruption in the brain's blood supply leads to an ischemic condition, which is characterised by a depletion of energy phosphates and related failure of ionic pumps, increased extracellular potassium, neuronal depolarisation and release of excitatory amino acids, e.g. glutamate. The subsequent activation of N-methyl-d-aspartate glutamate receptors triggers a wide range of intracellular signals, including the mitogen-activated protein kinase (MAPK) pathway. Activation and inhibition of the MAPK/extracellular regulated kinases (ERK) pathway are both reported to be neuroprotective in conditions associated with excitotoxic injury. The present study was designed to explore the involvement of this signalling pathway in cultured rat cortical neurons subjected to chemically-induced ischemia obtained by coupling the mitochondrial toxin 3-nitropropionic acid with glucose deprivation. Loss of neuronal viability, reduced neuronal energy state (ATP level and mitochondrial membrane potential) and increased cytoplasmic mitochondrial calcium were all observed. The NMDA antagonist MK-801 counteracted these effects, suggesting a glutamate-dependent ischemic cell death. Addition of U0126, a selective inhibitor of MAPK kinase, exacerbated this neuronal cell death. However, non-significant changes in activated cAMP response element-binding protein were seen. The rise in cytoplasmic calcium under ischemic conditions was associated with neuronal cell swelling. Both swelling and increase in cytoplasmic calcium were exacerbated and prevented by U0126 and MK-801, respectively. These data suggest that in this ischemic model the MAPK/ERK pathway might exert a regulatory effect on calcium entry independent from gene expression.

Changes in cerebral membrane lipid composition and fluidity during thioacetamide-induced hepatic encephalopathy

Lipids are an essential structural and functional component of cellular membranes. Changes in membrane lipid composition are known to affect the activities of many membrane-associated enzymes, endocytosis, exocytosis, membrane fusion and neurotransmitter uptake, and have been implicated in the pathophysiology of many neurodegenerative disorders. In the present study, we investigated changes in the lipid composition of membranes isolated from the cerebral cortex of rats treated with thioacetamide (TAA), a hepatotoxin that induces fulminant hepatic failure (FHF) and thereon hepatic encephalopathy (HE). HE refers to acute neuropsychiatric changes accompanying FHF. The estimation of membrane phospholipids, cholesterol and fatty acid content in cerebral cortex membranes from TAA-treated rats revealed a decrease in cholesterol, phosphatidylserine, sphingomyelin, a monounsaturated fatty acid, namely oleic acid, and the polyunsaturated fatty acids gamma-linolenic acid, decosa hexanoic acid and arachidonic acid compared with controls. Assessment of membrane fluidity with pyrene, 1,6-diphenyl-1,3,5-hexatriene and 1-[4-(trimethylammonio)phenyl]-6-phenyl-1,3,5-hexatriene revealed a decrease in the annular membrane fluidity, whereas the global fluidity was unaffected. The level of the thiobarbituric acid reactive species marker for lipid peroxidation also increased in membranes from TAA-treated rats, thereby indicating the prevalence of oxidative stress. Results from the present study demonstrate gross alterations in cerebral cortical membrane lipid composition and fluidity during TAA-induced HE, and their possible implications in the pathogenesis of this condition are also discussed.

Interaction between tissue oxygen tension and NADH imaging during synaptic stimulation and hypoxia in rat hippocampal slices

Oxygen and NADH are essential components in the production of ATP in the CNS. This study examined the dynamic interaction between tissue oxygen tension (pO(2)) and NADH imaging changes within hippocampal tissue slices, during metabolic stresses including hypoxia and synaptic activation. The initiation of abrupt hypoxia (from 95% O(2) to 95% N(2)) caused a rapid decrease in pO(2), onset of hypoxic spreading depression (hsd; at 6.7+/-1.3 mm Hg; n=15), and a monophasic increase in NADH. Provided that reoxygenation was prompt, synaptic responses, pO(2) and NADH levels returned to baseline following hsd. Longer hypoxia caused irreversible neuronal dysfunction, an increase in pO(2) beyond baseline (due to decreased tissue demand), and hyperoxidation of NADH (10+/-2% decrease below baseline; n=7). Synaptic activation in ambient 95% O(2) caused a decrease or 'initial dip' in pO(2) and a biphasic NADH response (oxidation followed by reduction). The oxidizing phase of the NADH response was mitochondrial as it was synchronous with the 'initial' dip in pO(2). Following slow graded reductions in ambient oxygen levels to 8%, four of seven slices developed hsd following synaptic stimulation. The hypoxic threshold for graded oxygen reductions occurred at 7.9+/-5.8 mm Hg O(2) (n=7). Our hypoxic threshold range (6.7-7.9 mm Hg O(2) from abrupt and graded oxygen reduction, respectively) correlates well with reported in vivo values of <12 mm Hg O(2). The major findings of this study include: 1) determination of the critical physiological threshold of pO(2) (based upon hsd), which is a marker of imminent neuronal death if oxygen is not rapidly restored; 2) NADH hyperoxidation and an increase in pO(2) beyond baseline levels following longer periods of hypoxia; and 3) the occurrence of a pO(2) 'dip' during synaptic stimulation, which correlates with the early oxidizing phase of the biphasic NADH response.

Association between elevated brain tissue glycerol levels and poor outcome following severe traumatic brain injury

Object. Glycerol is considered to be a marker of cell membrane degradation and thus cellular lysis. Recently, it has become feasible to measure via microdialysis cerebral extracellular fluid (ECF) glycerol concentrations at the patient's bedside. Therefore the aim of this study was to investigate the ECF concentration and time course of glycerol after severe traumatic brain injury (TBI) and its relationship to patient outcome and other monitoring parameters.

Methods. As soon as possible after injury for up to 4 days, 76 severely head-injured patients were monitored using a microdialysis probe (cerebral glycerol) and a Neurotrend sensor (brain tissue PO2) in uninjured brain tissue confirmed by computerized tomography scanning. The mean brain tissue glycerol concentration in all monitored patients decreased significantly from 206 ± 31 µmol/L on Day 1 to 9 ± 3 µmol/L on Day 4 after injury (p < 0.0001). Note, however, that there was no significant difference in the time course between patients with a favorable outcome (Glasgow Outcome Scale [GOS] Scores 4 and 5) and those with an unfavorable outcome (GOS Scores 1–3). Significantly increased glycerol concentrations were observed when brain tissue PO2 was less than 10 mm Hg or when cerebral perfusion pressure was less than 70 mm Hg.

Conclusions. Based on results in the present study one can infer that microdialysate glycerol is a marker of severe tissue damage, as seen immediately after brain injury or during profound tissue hypoxia. Given that brain tissue glycerol levels do not yet add new clinically significant information, however, routine monitoring of this parameter following traumatic brain injury needs further validation.

Na(+) and Ca(2+) homeostasis pathways, cell death and protection after oxygen-glucose-deprivation in organotypic hippocampal slice cultures

Intracellular ATP supply and ion homeostasis determine neuronal survival and degeneration after ischemic stroke. The present study provides a systematic investigation in organotypic hippocampal slice cultures of the influence of experimental ischemia, induced by oxygen-glucose-deprivation (OGD). The pathways controlling intracellular Na(+) and Ca(2+) concentration ([Na(+)](i) and [Ca(2+)](i)) and their inhibition were correlated with delayed cell death or protection. OGD induced a marked decrease in the ATP level and a transient elevation of [Ca(2+)](i) and [Na(+)](i) in cell soma of pyramidal neurons. ATP level, [Na(+)](i) and [Ca(2+)](i) rapidly recovered after reintroduction of oxygen and glucose. Pharmacological analysis showed that the OGD-induced [Ca(2+)](i) elevation in neuronal cell soma resulted from activation of both N-methyl-d-aspartate (NMDA)-glutamate receptors and Na(+)/Ca(2+) exchangers, while the abnormal [Na(+)](i) elevation during OGD was due to Na(+) influx through voltage-dependent Na(+) channels. In hippocampal slices, cellular degeneration occurring 24 h after OGD, selectively affected the pyramidal cell population through apoptotic and non-apoptotic cell death. OGD-induced cell loss was mediated by activation of ionotropic glutamate receptors, voltage-dependent Na(+) channels, and both plasma membrane and mitochondrial Na(+)/Ca(2+) exchangers. Thus, we show that neuroprotection induced by blockade of NMDA receptors and plasma membrane Na(+)/Ca(2+) exchangers is mediated by reduction of Ca(2+) entry into neuronal soma, whereas neuroprotection induced by blockade of AMPA/kainate receptors and mitochondrial Na(+)/Ca(2+) exchangers might result from reduced Na(+) entry at dendrites level.

Effects of hyperglycemia and hypercapnia on lipid metabolism during complete brain ischemia

Ischemic damage is greatly enhanced by preischemic hyperglycemia or hypercapnia, which affects many intracellular responses including protein kinase C (PKC) translocation. We explored whether hyperglycemic or hypercapnic ischemia affects lipid metabolism, especially ischemia-induced release of free fatty acids (FFAs) and diacylglycerols (DAGs). A change in intraischemic level of acidosis was induced either by injecting glucose (hyperglycemic, HG) or by adding CO(2) (hypercapnic, HC). Complete cerebral ischemia was induced, and the brain was frozen in situ after 3, 5, and 10 min at 37 degrees C. Frontoparietal neocortex was dissected for FFA and DAG lipid analysis by thin-layer chromatography and gas-liquid chromatography. Significant differences were shown between normoglycemic and either hypercapnic or hyperglycemic values for individual and total FFAs. A significant delay in the release of FFA in ischemia with hyperglycemia or hypercapnia was observed. Significant differences were also shown in individual DAG-acyl groups and total DAGs. Hyperglycemic or hypercapnic ischemia resulted in a significant decrease of DAG at 10 min of ischemia. This was unexpected because a previous study showed that PKC translocation was significantly enhanced under similar condition at this time point. Upon cellular depolarization, massive influx of calcium and FFA accumulation may decrease the PKC dependence of DAG for translocation. In addition, PKC activation may lead to a negative feedback inhibition of phospholipase C.

Oxidative stress: a theoretical model or a biological reality?

Although oxidative stress has been extensively studied the last fifteen years, many physicians and biologists are still sceptical concerning its interest in biology and medicine. This is probably due, in part, to the fact that this subject is a matter of biophysics, and the first studies reported were written using a physical language that inspired these people used to a more concrete problematic very little. Another problem is the difficulty to detect the species mediating oxidative stress, and to determine their role in biological processes. This review is aimed at presenting oxidative stress, as well as reactive oxygen species and free radicals--the molecules that mediate it--in a clear form able to convince all researchers involved in life sciences that these short-lived intermediates are indissociable from any aerobic organism. Moreover, if reactive oxygen species and free radicals are undoubtedly involved in many pathologies, they have physiological functions too.

A potentially critical role of phospholipases in central nervous system ischemic, traumatic, and neurodegenerative disorders

Phospholipases are a diverse group of enzymes whose activation may be responsible for the development of injury following insult to the brain. Amongst the numerous isoforms of phospholipase proteins expressed in mammals are 19 different phospholipase A2's (PLA2s), classified functionally as either secretory, calcium dependent, or calcium independent, 11 isozymes belonging to three structural groups of PLC, and 3 PLD gene products. Many of these phospholipases have been identified in selected brain regions. Under normal conditions, these enzymes regulate the turnover of free fatty acids (FFAs) in membrane phospholipids affecting membrane stability, fluidity, and transport processes. The measurement of free fatty acids thus provides a convenient method to follow phospholipase activity and their regulation. Phospholipase activity is also responsible for the generation of an extensive list of intracellular messengers including arachidonic acid metabolites. Phospholipases are regulated by many factors including selective phosphorylation, intracellular calcium and pH. However, under abnormal conditions, excessive phospholipase activation, along with a decreased ability to resynthesize membrane phospholipids, can lead to the generation of free radicals, excitotoxicity, mitochondrial dysfunction, and apoptosis/necrosis. This review evaluates the critical contribution of the various phospholipases to brain injury following ischemia and trauma and in neurodegenerative diseases.

Neuronal ageing from an intraneuronal perspective: roles of endoplasmic reticulum and mitochondria

The nature of brain ageing and the age-dependent decline in cognitive functions remains poorly understood. Physiological brain ageing is characterised by mild mental dysfunctions, whereas age-dependent neurodegeneration, as illustrated by Alzheimer disease (AD), results rapidly in severe dementia. These two states of the aged brain, the physiological and the pathological, are fundamentally different as the latter stems from significant neuronal loss, whereas the former develops without significant neuronal demise. In this paper, we review the changes in neuronal Ca(2+) homeostasis that occur during brain ageing, and conclude that normal, physiological ageing is characterised mainly by a decrease of neuronal homeostatic reserve, defined as the capacity to respond effectively to functional and metabolic stressors, but does not reach the trigger required to induce neuronal death. In contrast, during neurodegenerative states, Ca(2+) homeostasis is affected early during the pathological process and result in significant neuronal demise. We also review recent evidence suggesting that the endoplasmic reticulum (ER) might play an important role in controlling the balance between healthy and pathological neuronal ageing.

Intermittent hypoxia is associated with oxidative stress and spatial learning deficits in the rat

In the adult rat, exposure to intermittent hypoxia (IH), such as occurs in sleep-disordered breathing, is associated with neurobehavioral impairments and increased apoptosis in the hippocampal CA1 region and cortex. We hypothesized that the episodic hypoxic-reoxygenation cycles of IH would induce oxidant stress, and the latter may underlie the IH-associated spatial learning and retention deficits. Adult male rats were therefore exposed to IH (90-second alternations of 10% oxygen and 21% oxygen) or room air (RA) for 7 days, and received twice-daily injections of either 3 mg/kg of the antioxidant PNU-101033E (PNU) or vehicle (V). Rats were then trained in a standard place-training task in the water maze. V-IH displayed significant impairments of spatial learning in the water maze, which were attenuated by PNU-101033E. Post hoc analyses further revealed that V-IH had significantly longer latencies and pathlengths to locate the hidden platform than PNU-IH, V-RA, or PNU-RA, indicating that PNU-101033E treatment reduced the behavioral impairments associated with IH. In addition, treatment with PNU-101033E markedly attenuated the increase in lipid peroxidation, and isoprostane concentrations associated with exposure to IH. Collectively, these findings indicate that the IH exposure is associated with increased oxidative stress, which is likely to play an important role in the behavioral impairments observed in a rodent model of sleep-disordered breathing.

The influence of MK-801 on the hippocampal free arachidonic acid level and Na+,K+-ATPase activity in global cerebral ischemia-exposed rats

The influence of 20 min global cerebral ischemia on the free arachidonic acid (FAA) level and Na+,K+-ATPase activity in the rat hippocampus at different time points after ischemia was examined. In addition, the effect of MK-801 on mentioned parameters was studied. Animals were exposed to 20 min global cerebral ischemia and were sacrificed immediately, 0.5, 1, 2, 6, 24, 48, 72, and 168 h after ischemic procedure. The level of the FAA and the Na+,K+-ATPase activity was measured during all reperfusion periods examined. Various doses of MK-801 (0.3, 1.0, 3.0, and 5.0 mg/kg) had been injected 30 min before ischemic procedure started. It was found that 20 min global cerebral ischemia induces a statistically significant increase of the FAA level immediately after ischemia and during the first 0.5 h of reperfusion. After a transient decrease, the level of FAA level increased again after 24 and 168 h of recirculation. Treatment with 3.0 mg/kg of MK-801 significantly prevented the FAA accumulation immediately and 0.5 h after ischemic insult while application of 5.0 mg/kg of MK-801 exerted a protective effect during the first 24 h. Global cerebral ischemia induces the significant decline in the Na+,K+-ATPase activity in the hippocampus starting from 1 to 168 h of reperfusion. Maximal inhibition was obtained 24 h after the ischemic damage. Application of 3.0 mg/kg of MK-801 exerted statistically significant protection during the first 24 h while the treatment with 5.0 mg/kg of MK-801 prevented fall in enzymatic activity during all reperfusion periods examined. Our results suggest that, in spite of different and complex pathophysiological mechanisms involved in the increase of FAA level and the decrease of the Na+,K+-ATPase activity, blockade of NMDA receptor subtype provides a very important strategy for the treatment of the postischemic excitotoxicity.

Systemic fatty acid responses to transient focal cerebral ischemia: influence of neuroprotectant therapy with human albumin

Human albumin therapy is highly neuroprotective in focal cerebral ischemia. Because albumin is the main carrier of free fatty acids (FFA) in plasma, we investigated the content and composition of plasma FFA in jugular vein (JV), femoral artery (FA) and femoral vein (FV) of rats given intravenous human albumin (1.25 g/kg) or saline vehicle (5 mL/kg) 1 h after a 2 h middle cerebral artery occlusion (MCAo) or sham surgery. Arachidonic acid was the only FFA significantly increased by MCAo in all plasma samples prior to albumin administration, remaining at the same level regardless of subsequent treatments. Albumin treatment induced in both MCAo- and sham-groups a 1.7-fold increase in total plasma FFA (mainly 16:0, 18:1, 18:2n-6) during 90-min reperfusion. MCAo selectively stimulated the albumin-mediated mobilization of n-3 polyunsaturated fatty acids (PUFA), with an early increase in 22:5n-3 and 22:6n-3 in the FA prior to detectable changes in the JV. In the MCAo-albumin group, the lower level of FFA in JV as compared with FA and FV suggests an albumin-mediated systemic mobilization and supply of FFA to the brain, which may favor the replenishment of PUFA lost from cellular membranes during ischemia and/or to serve as an alternative source of energy, thus contributing to albumin neuroprotection.

Neuronal mechanisms of the anoxia-induced network oscillations in the rat hippocampus in vitro

1. A spindle of fast network oscillations precedes the ischaemia-induced rapid depolarisation in the rat hippocampus in vivo. However, this oscillatory pattern could not be reproduced in slices and the underlying mechanisms remain poorly understood. We have found that anoxia-induced network oscillations (ANOs, 20-40 Hz, lasting for 1-2 min) can be reproduced in the intact hippocampi of postnatal day P7-10 rats in vitro, and we have examined the underlying mechanisms using whole-cell and extracellular field potential recordings in a CA3 pyramidal layer. 2. ANOs were generated at the beginning of the anoxic depolarisation, when pyramidal cells depolarised to subthreshold values. Maximal power of the ANOs was attained when pyramidal cells depolarised to -56 mV; depolarisation above -47 mV resulted in a depolarisation block of pyramidal cells and a waning of ANOs. 3. A multiple unit activity in extracellular field recordings was phase locked to the negative and ascending phases of ANOs. Pyramidal cells recorded in current-clamp mode generated action potentials with an average probability of about 0.05 per cycle. The AMPA receptor-mediated EPSCs and the GABA receptor-mediated IPSCs in CA3 pyramidal cells were also phase locked with ANOs. 4. ANOs were prevented by tetrodotoxin and glutamate receptor antagonists CNQX and APV, and were slowed down by the allosteric GABA(A) receptor modulator diazepam. In the presence of the GABA(A) receptor antagonist bicuculline, ANOs were transformed to epileptiform discharges. 5. In the presence of the A1 adenosine receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), the anoxia induced an epileptiform activity and no ANOs were observed. 6. In normoxic conditions, a rise of extracellular potassium to 10 mM induced an epileptiform activity. Increasing extracellular potassium in conjunction with a bath application of the adenosine A1 receptor agonist cyclopentyladenosine induced oscillations similar to ANOs. 7. Multisite recordings along the septo-temporal hippocampal axis revealed that ANOs and anoxic depolarisation originate in the temporal part, and propagate towards the septal pole at a speed of 1.9 mm x min(-1). 8. ANOs were observed starting from P7, i.e. at a developmental stage when the effects of GABA change from depolarisation to hyperpolarisation. 9. These results suggest that the synchronisation of anoxia-induced oscillations relies on synaptic mechanisms; that the inhibition by GABA and adenosine sets the tune for a generation of oscillations and prevents an epileptiform activity; and that a synchronous GABAergic inhibition is instrumental in a phase locking neuronal activity similarly to other types of oscillatory activities in the gamma frequency range.

N-Acylphosphatidylethanolamine accumulation in potato cells upon energy shortage caused by anoxia or respiratory inhibitors

A minor phospholipid was isolated from potato (Solanum tuberosum L. cv Bintje) cells, chromatographically purified, and identified by electrospray ionization mass spectrometry as N-acylphosphatidylethanolamine (NAPE). The NAPE level was low in unstressed cells (13 +/- 4 nmol g fresh weight(-1)). According to acyl chain length, only 16/18/18 species (group II) and 18/18/18 species (group III) were present. NAPE increased up to 13-fold in anoxia-stressed cells, but only when free fatty acids (FFAs) started being released, after about 10 h of treatment. The level of groups II and III was increased by unspecific N-acylation of phosphatidylethanolamine, and new 16/16/18 species (group I) appeared via N-palmitoylation. NAPE also accumulated in aerated cells treated with NaN(3) plus salicylhydroxamate. N-acyl patterns of NAPE were dominated by 18:1, 18:2, and 16:0, but never reflected the FFA composition. Moreover, they did not change greatly after the treatments, in contrast with O-acyl patterns. Anoxia-induced NAPE accumulation is rooted in the metabolic homeostasis failure due to energy deprivation, but not in the absence of O(2), and is part of an oncotic death process. The acyl composition of basal and stress-induced NAPE suggests the existence of spatially distinct FFA and phosphatidylethanolamine pools. It reflects the specificity of NAPE synthase, the acyl composition, localization and availability of substrates, which are intrinsic cell properties, but has no predictive value as to the type of stress imposed. Whether NAPE has a physiological role depends on the cell being still alive and its compartmentation maintained during the stress period.

Magnetic resonance lipid signals in rat brain after experimental stroke correlate with neutral lipid accumulation

Proton magnetic resonance spectroscopy (MRS) signals from lipids in brain have been observed to increase after ischemic brain injury. However, neither the chemical identity nor the cellular location of these lipids has been established. The aim of the present study was to identify the origin of MRS lipid signals in rat brain after temporary (90 min) middle cerebral artery occlusion (MCAO). Fatty acyl proton signals were detected by short-echo one and two dimensional (1)H MRS in superfused brain slices from the infarcted hemisphere 1-5 days after MCAO. The intensities of these signals were strongly correlated with the amount of triacylglyceride and cholesterol ester in lipid extracts from the samples (r(2)=0.96, P<0.05) and were not correlated with the amount of free fatty acids in the tissue. Histological staining of tissue revealed the presence of neutral lipid droplets in infarcted regions. Dual labeling by immunohistochemistry demonstrated that these droplets were localized to microglia/macrophage (OX-42-labeled cells). These results strongly suggest that (1)H MRS lipid signals from brain after stroke arise from microglia/macrophage phagocytosis of cellular membranes.

Mobile lipid production after confluence and pH stress in perfused C6 cells

NMR-visible mobile lipid (ML) has been observed in aggressive tumors and also in in vitro tumor cell models subjected to growth-inhibiting conditions, such as confluence or low-pH stress. The aim of the present study was to determine if ML production after confluence or low pH stress in a cultured cell model of brain tumor is due to growth arrest alone. ML was observed in situ by one- and two-dimensional (1)H NMR in viable but growth-arrested C6 glioma cells superfused for a period of 48 h after harvesting. The rate of ML production in cells harvested at subconfluence was compared to the rate in cells confluent for one cell cycle and to the rate in subconfluent-harvested cells superfused at low pH (pH 6.1). Confluent-harvested cells produced ML at a markedly greater rate than that of cells harvested at subconfluence, suggesting the involvement of prior cell-cell contact rather than simple growth arrest. A high rate was also observed in subconfluent-harvested cells subjected to low pH, indicating that ML in pH-stressed cells also does not arise from growth arrest alone. Furthermore, two-dimensional data on the degree of unsaturation of the ML fatty acyl chains and one-dimensional (31)P and two-dimensional (1)H NMR data on the GPC content of the cells suggest distinct metabolic pathways for the production of ML following confluence and low-pH stress.

The regulation of CoA-independent transacylation reactions in neuronal nuclei by lysophospholipid, free fatty acid, and lysophospholipase: the control of nuclear lyso platelet-activating factor metabolism

CoA-independent transacylase activities generating alkylacylglycerophosphocholine (AAGPC) from alkylglycerophosphocholine (1-alkyl GPC) were considerably enriched in neuronal nuclei isolated from rabbit cerebral cortex. Specific nuclear transacylation activities were 13 times the corresponding microsomal values. Several lysophospholipids, notably 1-acyl glycerophosphocholine (1-acyl GPC), 1-alkenyl GPC and 1-alkenyl GPE (1-alkenyl glycerophosphoethanolamine) inhibited the transacylation of 1-alkyl GPC. The inhibitory effects of 1-acyl GPC were seen in the presence of MAFP (methyl arachidonoylfluorophosphonate) or free oleate, compounds that inhibit neuronal nuclear lysophospholipase. When neuronal nuclei were preincubated with 1-alkyl GPC, the radioactive AAGPC product served as donor in transacylation reactions, to generate 1-alkyl GPC. In these nuclear reactions, 1-palmitoyl GPE and 1-palmitoyl GPC appeared to be poor acceptor substrates, when compared with corresponding 1-alkyl and 1-alkenyl analogues. The presence of free oleate or MAFP in the reactions containing 1-acyl GPC boosted the release of 1-alkyl GPC from AAGPC. These observations are of particular relevance to brain ischemia in which lysophospholipid, free fatty acid, and platelet-activating factor (PAF) levels rise dramatically. PAF can be made by the nuclear acetylation of 1-alkyl GPC, which is formed by nuclear transacylation mechanisms. Yet transacylase also removes 1-alkyl GPC, and thus this enzyme activity can regulate 1-alkyl GPC availability. Our observations indicate that lysophospholipids promote the formation of 1-alkyl GPC from nuclear AAGPC via transacylation, while free fatty acid likely prolongs the lifetime of 1-acyl lysophospholipids substrates by lysophospholipase inhibition. Similarly, once 1-alkyl GPC is formed, other lysophospholipids effectively compete with this 1-alkyl analogue and reduce its conversion back to AAGPC by transacylation. Free oleate, in this case, sustains 1-acyl lysophospholipid inhibitors of 1-alkyl GPC transacylation. Thus the cycle of transacylation may favour 1-alkyl GPC formation during ischemia, increasing levels of 1-alkyl GPC for nuclear acetylation reactions and PAF formation. The nuclear generation of PAF is of considerable importance as PAF can play regulatory roles in transcription events associated with inflammation.

On the regulation of ischaemia-induced glutamate efflux from rat cortex by GABA; in vitro studies with GABA, clomethiazole and pentobarbitone

Prisms of adult rat cortex were maintained in vitro in either aerobic conditions (control) or conditions simulating an acute ischaemic challenge (hypoxia with no added glucose). Endogenous glutamate efflux increased with time in ischaemic conditions, being 2.7 fold higher than control efflux at 45 min. Returning prisms to control solution after 20 min of simulated ischaemia resulted in glutamate efflux returning to near-control values. Endogenous GABA efflux in ischaemic conditions also increased, being 4.5 fold higher than control efflux at 45 min. Ischaemia-induced glutamate efflux was not accompanied by increased lactate dehydrogenase efflux and was unaltered by omitting calcium from the extra-cellular solution and adding EGTA (0.1 mM). Both GABA and the GABA-mimetic clomethiazole inhibited ischaemia-induced glutamate efflux, with IC(50) values of 26 and 24 microM respectively. The maximum inhibition by either drug was 60 - 70%. Bicuculline (10 microM) abolished the inhibitory effect of GABA (100 microM) but not clomethiazole (100 microM). Picrotoxin (100 microM) abolished the action of both GABA and clomethiazole. Pentobarbitone inhibited glutamate efflux at 100 - 300 microM (maximal inhibition: 39%). Bicuculline (10 microM) abolished this effect. These data suggest that ischaemia-induced glutamate efflux from rat cerebral cortex is calcium-independent and not due to cell damage up to 45 min. The inhibitory effect of GABA, clomethiazole and pentobarbitone on ischaemia-induced glutamate efflux appears to be mediated by GABA(A) receptors. The results suggest that clomethiazole, unlike pentobarbitone, is able to activate the GABAA receptor-linked chloride channel directly and not merely potentiate the effect of endogenous GABA.

Glycerophospholipids in brain: their metabolism, incorporation into membranes, functions, and involvement in neurological disorders

Neural membranes contain several classes of glycerophospholipids which turnover at different rates with respect to their structure and localization in different cells and membranes. The glycerophospholipid composition of neural membranes greatly alters their functional efficacy. The length of glycerophospholipid acyl chain and the degree of saturation are important determinants of many membrane characteristics including the formation of lateral domains that are rich in polyunsaturated fatty acids. Receptor-mediated degradation of glycerophospholipids by phospholipases A(l), A(2), C, and D results in generation of second messengers such as arachidonic acid, eicosanoids, platelet activating factor and diacylglycerol. Thus, neural membrane phospholipids are a reservoir for second messengers. They are also involved in apoptosis, modulation of activities of transporters, and membrane-bound enzymes. Marked alterations in neural membrane glycerophospholipid composition have been reported to occur in neurological disorders. These alterations result in changes in membrane fluidity and permeability. These processes along with the accumulation of lipid peroxides and compromised energy metabolism may be responsible for the neurodegeneration observed in neurological disorders.

Differential fall in ATP accounts for effects of temperature on hypoxic damage in rat hippocampal slices

Intracellular recordings, ATP and cytosolic calcium measurements from CA1 pyramidal cells in rat hippocampal slices were used to examine the mechanisms by which temperature alters hypoxic damage. Hypothermia (34 degrees C) preserved ATP (1.7 vs. 0.8 nM/mg) and improved electrophysiologic recovery of the CA1 neurons after hypoxia; 58% of the neurons subjected to 10 min of hypoxia (34 degrees C) recovered their resting and action potentials, while none of the neurons at 37 degrees C recovered. Increasing the glucose concentration from 4 to 6 mM during normothermic hypoxia improved ATP (1.3 vs. 0.8 nM/mg) and mimicked the effects of hypothermia; 67% of the neurons recovered their resting and action potentials. Hypothermia attenuated the membrane potential changes and the increase in intracellular Ca(2+) (212 vs. 384 nM) induced by hypoxia. Changing the glucose concentration in the artificial cerebrospinal fluid primarily affects ATP levels during hypoxia. Decreasing the glucose concentration from 4 to 2 mM during hypothermic hypoxia worsened ATP, cytosolic Ca(2+), and electrophysiologic recovery. Ten percent of the neurons subjected to 4 min of hypoxia at 40 degrees C recovered their resting and action potentials; this compared with 60% of the neurons subjected to 4 min of normothermic hypoxia. None of the neurons subjected to 10 min of hypoxia at 40 degrees C recovered their resting and action potentials. Hyperthermia (40 degrees C) worsens the electrophysiologic changes and induced a greater increase in intracellular Ca(2+) (538 vs. 384 nM) during hypoxia. Increasing the glucose concentration from 4 to 8 mM during 10 min of hyperthermic hypoxia improved ATP (1.4 vs. 0.6 nM/mg), Ca(2+) (267 vs. 538 nM), and electrophysiologic recovery (90 vs. 0%). Our results indicate that the changes in electrophysiologic recovery with temperature are primarily due to changes in ATP and that the changes in depolarization and Ca(2+) are secondary to these ATP changes. Both primary and secondary changes are important for explaining the improved electrophysiologic recovery with hypothermia.

Early microglial reaction following mild forebrain ischemia induced by common carotid artery occlusion in rats

Early microglial reaction following mild ischemic injury caused by bilateral common carotid artery occlusion has been investigated in rats. The ischemic insults lasted for 10, 15 and 20 min without recirculation, and with several reperfusion intervals from 1 h to 3 days. The resting and activated microglial cells were visualized with immunohistochemistry using monoclonal antibodies raised against the CR3 complement receptor, the MHC class I and class II antigens, the macrophage common antigen and with Bandeiiraea simplicifolia lectin-histochemistry. The neuroprotective effect of hypothermia on the early microglial activation was also studied. Ten minutes bilateral common carotid artery occlusion in hypothermic rats without reperfusion caused a mild microglial reaction in the hippocampus. Strong reaction was seen following 20 min insult without reperfusion. Ischemia followed by recirculation caused milder reaction than without reperfusion. Our results suggest that the microglial cells are very sensitive indicators of a mild, transient ischemic insult that does not result in neuronal cell death.

Cortical impact injury in rats promotes a rapid and sustained increase in polyunsaturated free fatty acids and diacylglycerols

Neurotrauma activates the release of membrane phospholipid-derived second messengers, such as free arachidonic acid (20:4n-6, AA) and diacylglycerols (DAGs). In the present study, we analyze the effect of cortical impact injury of low-grade severity applied to the rat frontal right sensory-motor cortex (FRC) on the accumulation of free fatty acids (FFAs) and DAGs in eight brain areas 30 min and 24 hours after the insult. At these times, accumulation of FFAs and DAGs occurred mainly in the damaged FRC. The cerebellum was the only other brain area that displayed a significant accumulation of DAGs by day one post-injury. By 30 min, accumulation of free AA in the FRC displayed the greatest relative increase (300% over sham value), followed by free docosahexaenoic acid (22:6n-3, DHA, 150%), while both 20:4-DAGs and 22:6-DAGs were increased 100% over sham values. At day one, free 22:6 and 22:6-DAGs showed the greatest increase (590% and 230%, respectively). These results suggest that TBI elicits the hydrolysis of phospholipids enriched in excitable membranes, targeting early on 20:4-phospholipids (by 30 min post- trauma) and followed 24 hours later by preferential hydrolysis of DHA-phospholipids. These lipid metabolic changes may contribute to the initiation and maturation of neuronal and fiber track degeneration observed following cortical impact injury.

Mitochondria and neuronal survival

Mitochondria play a central role in the survival and death of neurons. The detailed bioenergetic mechanisms by which isolated mitochondria generate ATP, sequester Ca(2+), generate reactive oxygen species, and undergo Ca(2+)-dependent permeabilization of their inner membrane are currently being applied to the function of mitochondria in situ within neurons under physiological and pathophysiological conditions. Here we review the functional bioenergetics of isolated mitochondria, with emphasis on the chemiosmotic proton circuit and the application (and occasional misapplication) of these principles to intact neurons. Mitochondria play an integral role in both necrotic and apoptotic neuronal cell death, and the bioenergetic principles underlying current studies are reviewed.

Brain water diffusion in normal and creatine-supplemented rats during transient global ischemia

Brain water diffusion in response to transient global ischemia (12 min), reperfusion (60 min), and cardiac arrest was monitored by localized proton magnetic resonance spectroscopy. The trace of the apparent diffusion coefficient tensor (ADC(Av)) was determined at high temporal resolution (10 sec) to assess the putative neuroprotective potential of oral creatine (Cr) in rats that received 2.2 g Cr-monohydrate per kg body weight per day for 10 days (n = 8) relative to controls (n = 9). Cr-fed rats revealed a statistically significant increase of the cerebral concentration ratio of Cr to choline-containing compounds (20%). The decrease of the ADC(Av) value during acute ischemia showed a three-phasic behavior in line with energy depletion, cytotoxic edema, and brain cooling. In Cr-fed rats, slightly less severe and mildly delayed diffusion changes during ischemia and similar beneficial trends during early reperfusion did not reach statistical significance. Magn Reson Med 42:798-802, 1999.

Ischemic cell death in brain neurons

This review is directed at understanding how neuronal death occurs in two distinct insults, global ischemia and focal ischemia. These are the two principal rodent models for human disease. Cell death occurs by a necrotic pathway characterized by either ischemic/homogenizing cell change or edematous cell change. Death also occurs via an apoptotic-like pathway that is characterized, minimally, by DNA laddering and a dependence on caspase activity and, optimally, by those properties, additional characteristic protein and phospholipid changes, and morphological attributes of apoptosis. Death may also occur by autophagocytosis. The cell death process has four major stages. The first, the induction stage, includes several changes initiated by ischemia and reperfusion that are very likely to play major roles in cell death. These include inhibition (and subsequent reactivation) of electron transport, decreased ATP, decreased pH, increased cell Ca(2+), release of glutamate, increased arachidonic acid, and also gene activation leading to cytokine synthesis, synthesis of enzymes involved in free radical production, and accumulation of leukocytes. These changes lead to the activation of five damaging events, termed perpetrators. These are the damaging actions of free radicals and their product peroxynitrite, the actions of the Ca(2+)-dependent protease calpain, the activity of phospholipases, the activity of poly-ADPribose polymerase (PARP), and the activation of the apoptotic pathway. The second stage of cell death involves the long-term changes in macromolecules or key metabolites that are caused by the perpetrators. The third stage of cell death involves long-term damaging effects of these macromolecular and metabolite changes, and of some of the induction processes, on critical cell functions and structures that lead to the defined end stages of cell damage. These targeted functions and structures include the plasmalemma, the mitochondria, the cytoskeleton, protein synthesis, and kinase activities. The fourth stage is the progression to the morphological and biochemical end stages of cell death. Of these four stages, the last two are the least well understood. Quite little is known of how the perpetrators affect the structures and functions and whether and how each of these changes contribute to cell death. According to this description, the key step in ischemic cell death is adequate activation of the perpetrators, and thus a major unifying thread of the review is a consideration of how the changes occurring during and after ischemia, including gene activation and synthesis of new proteins, conspire to produce damaging levels of free radicals and peroxynitrite, to activate calpain and other Ca(2+)-driven processes that are damaging, and to initiate the apoptotic process. Although it is not fully established for all cases, the major driving force for the necrotic cell death process, and very possibly the other processes, appears to be the generation of free radicals and peroxynitrite. Effects of a large number of damaging changes can be explained on the basis of their ability to generate free radicals in early or late stages of damage. Several important issues are defined for future study. These include determining the triggers for apoptosis and autophagocytosis and establishing greater confidence in most of the cellular changes that are hypothesized to be involved in cell death. A very important outstanding issue is identifying the critical functional and structural changes caused by the perpetrators of cell death. These changes are responsible for cell death, and their identity and mechanisms of action are almost completely unknown.

Lactate and free fatty acids after subarachnoid hemorrhage

The hypothesis that lactate and free fatty acids (FFA) are elevated in the first minutes after subarachnoid hemorrhage (SAH) is tested. Adult rats were subjected to an endovascular SAH through the right internal carotid artery while under anesthesia. The brains were frozen in-situ at 15, 30, 60 min, and 24 h post-hemorrhage. Regional measures of tissue lactic acid and FFA were made in the hippocampi, ipsilateral cortex, contralateral cortex, and cerebellum. Lactic acid levels were significantly elevated from sham animals in each region within the first hour (p<0.0001 cerebellum, right, and contralateral cortex, p<0.01 hippocampus), but did not change significantly over the first hour. At 24 h post-hemorrhage, there was no significant difference in the lactic acid levels from controls. Similarly, total FFA were significantly higher in each region as compared to sham operated controls within the first hour (p<0.001 cerebellum, p<0.05 hippocampus, p<0.05 contralateral cortex, p<0.0001 ipsilateral cortex). By 24 h, there was no significant difference in FFA levels from shams. The data indicate that aerobic metabolism fails and cellular damage with degradation of cell membranes occurs in the first minutes after SAH, and lasts for at least 1 h. However, this process is stabilized within 24 h in our model. Although the largest effect was seen in the ipsilateral cortex, all areas of the brain were effected.