Fluorescent histochemical localization of lipid peroxidation during brain reperfusion following cardiac arrest

Post-Cardiac Arrest: Mechanisms, Management, and Future Perspectives

Cardiac arrest is an important public health issue, with a survival rate of approximately 15 to 22%. A great proportion of these deaths occur after resuscitation due to post-cardiac arrest syndrome, which is characterized by the ischemia-reperfusion injury that affects the role body. Understanding physiopathology is mandatory to discover new treatment strategies and obtain better results. Besides improvements in cardiopulmonary resuscitation maneuvers, the great increase in survival rates observed in recent decades is due to new approaches to post-cardiac arrest care. In this review, we will discuss physiopathology, etiologies, and post-resuscitation care, emphasizing targeted temperature management, early coronary angiography, and rehabilitation.

Effects of Lycopene Attenuating Injuries in Ischemia and Reperfusion

Tissue and organ ischemia can lead to cell trauma, tissue necrosis, irreversible damage, and death. While intended to reverse ischemia, reperfusion can further aggravate an ischemic injury (ischemia-reperfusion injury, I/R injury) through a range of pathologic processes. An I/R injury to one organ can also harm other organs, leading to systemic multiorgan failure. A type of carotenoid, lycopene, has been shown to treat and prevent many diseases (e.g., rheumatoid arthritis, cancer, diabetes, osteoporosis, male infertility, neurodegenerative diseases, and cardiovascular disease), making it a hot research topic in health care. Some recent researches have suggested that lycopene can evidently ameliorate ischemic and I/R injuries to many organs, but few clinical studies are available. Therefore, it is essential to review the effects of lycopene on ischemic and I/R injuries to different organs, which may help further research into its potential clinical applications.

Oxidative Stress and C-Reactive Protein in Patients with Cerebrovascular Accident (Ischaemic Stroke): The role of Ginkgo biloba extract

OBJECTIVES

This study aimed to investigate the presence of oxidative stress and inflammation in ischaemic stroke patients by measuring malondialdehyde (MDA), total antioxidant status (TAS), and highly-sensitivity C-reactive protein (hsCRP) in the early post-ischaemic period, and to determine the role of Ginkgo biloba therapy in correcting the markers of oxidative stress and inflammation.

METHODS

This study was conducted at Ibn Seena Hospital, Mosul City, Iraq and included 31 cerebrovascular accident (CVA) patients and 30 healthy controls. Ischaemic stroke patients were divided into two groups: group I (n = 15) received conventional therapy; group II (n = 16) received conventional therapy with G. biloba (1500 mg/day) for 30 days. Blood samples were obtained from patients and controls before treatment and assays done of serum levels of MDA, TAS, and hsCRP. For CVA patients, a post-treatment blood sample was taken and the same parameters reassessed.

RESULTS

Compared with the controls, patients' serum levels of MDA, and hsCRP were significantly higher (P ≤0.001) and TAS significantly lower. Group I and II patients reported a significant reduction in serum levels of MDA and hsCRP and a significant increase in serum levels of TAS, in comparison with pre-treatment levels. There was no significant difference (P = 0.19) in serum MDA levels between groups I and II, whereas, serum TAS levels were significantly higher (P ≤0.01) and hsCRP significantly lower (P ≤0.01) in group II.

CONCLUSION

Acute stroke is associated with oxidative stress and inflammatory response in the early period. G. biloba plays a potential role in reducing oxidative damage and inflammatory response.

Uric acid administration in patients with acute stroke: a novel approach to neuroprotection

Uric acid (UA) is the end product of purine catabolism in humans and is a powerful antioxidant whose generation is increased under ischemic conditions. However, both clinical and experimental studies reveal a gradual exhaustion of the antioxidant capacity after transient cerebral ischemia, and the magnitude of this consumption seems to be correlated with the extent of brain tissue injury, growth of the infarction, severity of neurological impairment in the acute phase, and long-term functional outcome. Growing evidence supports the neuroprotective effect of UA administration after brain ischemia. In experimental conditions, the administration of UA is neuroprotective both in mechanical models of brain ischemia (transient or permanent intraluminal occlusion of the middle cerebral artery) and in thromboembolic models of autologous clot injection. The administration of UA is feasible and safe in healthy volunteers. In acute stroke patients treated with recombinant tissue plasminogen activator (rt-PA), co-administration of UA has proven to reduce lipid peroxidation and to prevent the fall in UA blood levels that occur very early after stroke onset. Currently, a multicentric Phase III clinical trial is testing whether the administration of UA increases the clinical benefits of rt-PA, which represents the only approved therapy in patients with acute ischemic stroke. This review summarizes the available information justifying such a novel therapeutic approach in this devastating clinical condition.

Peroxiredoxins in the central nervous system

Oxidative stress is considered one of the causative pathomechanisms of nervous system diseases such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, stroke and excitotoxicity. The basal expression of six different peroxiredoxin (Prx) isozymes show distinct distribution profiles in different brain regions and different cell types. PrxI and VI are expressed in glial cells but not in neurons; while PrxII, III, IV and V are expressed in neurons. Various diseases or models show altered expression levels of these isozymes, such as by upregulation of PrxI, II and VI and downregulation of PrxIII. Thioredoxin (Trx)I mRNA is distributed widely in the rat brain. This distribution pattern may reflect the specific functions of these isozymes. Recently, the neuroprotective roles of Prx III and V against ibotenate-induced-excitotoxicity were reported by two independent groups. Adenovirus transduction of PrxIII eliminated protein nitration and prevented gliosis caused by direct infusion of ibotenate. Systemic administration of recombinant PrxV diminished brain lesions in animals treated with ibotenate. In this chapter, we review the causative mechanisms of oxidative stress in neurodegenerative diseases, as well as describe the basal and disease-induced changes in Prxs/Trxs/Trx reductases expression levels and neuroprotective roles of Trxs and Prxs as demonstrated in overexpression models.

Mechanoporation induced by diffuse traumatic brain injury: an irreversible or reversible response to injury?

Diffuse traumatic brain injury (DTBI) is associated with neuronal plasmalemmal disruption, leading to either necrosis or reactive change without cell death. This study examined whether enduring membrane perturbation consistently occurs, leading to cell death, or if there is the potential for transient perturbation followed by resealing/recovery. We also examined the relationship of these events to calpain-mediated spectrin proteolysis (CMSP). To assess plasmalemmal disruption, rats (n = 21) received intracerebroventricular infusion 2 h before DTBI of a normally excluded 10 kDa fluorophore-labeled dextran. To reveal plasmalemmal resealing or enduring disruption, rats were infused with another labeled dextran 2 h (n = 10) or 6 h (n = 11) after injury. Immunohistochemistry for the 150 kDa spectrin breakdown product evaluated the concomitant role of CMSP. Neocortical neurons were followed with confocal and electron microscopy. After DTBI at 4 and 8 h, 55% of all tracer-flooded neurons contained both dextrans, demonstrating enduring plasmalemmal leakage, with many demonstrating necrosis. At 4 h, 12.0% and at 8 h, 15.7% of the dual tracer-flooded neurons showed CMSP, yet, these demonstrated less advanced cellular change. At 4 h, 39.0% and at 8 h, 24.4% of all tracer-flooded neurons revealed only preinjury dextran uptake, consistent with membrane resealing, whereas 7.6 and 11.1%, respectively, showed CMSP. At 4 h, 35% and at 8 h, 33% of neurons demonstrated CMSP without dextran flooding. At 4 h, 5.5% and at 8 h, 20.9% of tracer-flooded neurons revealed only postinjury dextran uptake, consistent with delayed membrane perturbation, with 55.0 and 35.4%, respectively, showing CMSP. These studies illustrate that DTBI evokes evolving plasmalemmal changes that highlight mechanical and potential secondary events in membrane poration.

Ca(2+) transport into sarcoplasmic reticulum and immediate-early response proteins in the myocardium of rats resuscitated after systemic circulatory arrest

Activity of antioxidant defense enzymes and content of stress protein HSP70 in the heart increased in passive and, to a lesser extent, in active rats on day 7 of the postresuscitation period after systemic circulatory arrest. The resistance of membrane structures in the heart to endogenous damaging factors in passive rats was lower than in active animals. The degree of compensation in active rats was much higher than in passive animals at these terms of the postresuscitation period.

Ca2+-dependent proteases in ischemic neuronal death: a conserved 'calpain-cathepsin cascade' from nematodes to primates

From rodents to primates, transient global brain ischemia is a well known cause of delayed neuronal death of the vulnerable neurons including cornu Ammonis 1 (CA1) pyramidal cells of the hippocampus. Previous reports using the rodent experimental paradigm indicated that apoptosis is a main contributor to such ischemic neuronal death. In primates, however, the detailed molecular mechanism of ischemic neuronal death still remains obscure. Recent data suggest that necrosis rather than apoptosis appear to be the crucial component of the damage to the nervous system during human ischemic injuries and neurodegenerative diseases. Currently, necrotic neuronal death mediated by Ca2+-dependent cysteine proteases, is becoming accepted to underlie the pathology of neurodegenerative conditions from the nematode Caenorhabditis elegans to primates. This paper reviews the role of cysteine proteases such as caspase, calpain and cathepsin in order to clarify the mechanism of ischemic neuronal death being triggered by the unspecific digestion of lysosomal proteases.

Cerebral ischemia and the unfolded protein response

We review studies of endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) following cerebral ischemia and reperfusion (I/R). The UPR is a cell stress program activated when misfolded proteins accumulate in the ER lumen. UPR activation causes: (i) a PERK-mediated phosphorylation of eIF2alpha, inhibiting protein synthesis to prevent further accumulation of unfolded proteins in the ER and (ii) upregulation of genes coding for ER-resident enzymes and chaperones and others, via eIF2alpha(p), and ATF6 and IRE1 activation. UPR-induced transcription increases capacity of the ER to process misfolded proteins. If ER stress and the UPR are prolonged, apoptosis ensues. Multiple forms of ER stress have been observed following brain I/R. The UPR following brain I/R is not isomorphic between in vivo I/R models and in vitro cell culture systems with pharmacological UPR induction. Although PERK and IRE1 are activated in the initial hours of reperfusion, total PERK decreases, ATF6 is not activated, and there is delayed appearance of UPR-induced mRNAs. Thus, multiple damage mechanisms associated with brain I/R alter UPR expression and contribute to a pro-apoptotic phenotype in neurons. Insights resulting from these studies will be important for the development of therapies to halt neuronal death following brain I/R.

Oxidative damage to the endoplasmic reticulum is implicated in ischemic neuronal cell death

The endoplasmic reticulum (ER), which plays important roles in apoptosis, is susceptible to oxidative stress. Because reactive oxygen species (ROS) are robustly produced in the ischemic brain, ER damage by ROS may be implicated in ischemic neuronal cell death. We induced global brain ischemia on wild-type and copper/zinc superoxide dismutase (SOD1) transgenic rats and compared ER stress and neuronal damage. Phosphorylated forms of eukaryotic initiation factor 2 alpha (eIF2 alpha) and RNA-dependent protein kinase-like ER eIF2 alpha kinase (PERK), both of which play active roles in apoptosis, were increased in hippocampal CA1 neurons after ischemia but to a lesser degree in the transgenic animals. This finding, together with the finding that the transgenic animals showed decreased neuronal degeneration, indicates that oxidative ER damage is involved in ischemic neuronal cell death. To elucidate the mechanisms of ER damage by ROS, we analyzed glucose-regulated protein 78 (GRP78) binding with PERK and oxidative ER protein modification. The proteins were oxidatively modified and stagnated in the ER lumen, and GRP78 was detached from PERK by ischemia, all of which were attenuated by SOD1 overexpression. We propose that ROS attack and modify ER proteins and elicit ER stress response, which results in neuronal cell death.

Persistent eIF2alpha(P) is colocalized with cytoplasmic cytochrome c in vulnerable hippocampal neurons after 4 hours of reperfusion following 10-minute complete brain ischemia

Upon brain reperfusion following ischemia, there is widespread inhibition of neuronal protein synthesis that is due to phosphorylation of eukaryotic initiation factor 2alpha (eIF2alpha), which persists in selectively vulnerable neurons (SVNs) destined to die. Other investigators have shown that expression of mutant eIF2alpha (S51D) mimicking phosphorylated eIF2alpha induces apoptosis, and expression of non-phosphorylatable eIF2alpha (S51A) blocks induction of apoptosis. An early event in initiating apoptosis is the release of cytochrome c from mitochondria, and cytochrome c release corresponds to the selective vulnerability of hippocampal CA1 neurons in rats after transient global cerebral ischemia. At present the signaling pathways leading to this are not well defined. We hypothesized that persistent eIF2alpha(P) reflects injury mechanisms that are causally upstream of release of cytochrome c and induction of apoptosis. At 4 h of reperfusion following 10-min cardiac arrest, vulnerable neurons in the striatum, hippocampal hilus and CA1 showed colocalized intense immunostaining for both persistent eIF2alpha(P) and cytoplasmic cytochrome c, while resistant neurons in the dentate gyrus and elsewhere did not immunostain for either. A lower intensity of persistent eIF2alpha(P) immunostaining was present in cortical layer V pyramidal neurons without cytoplasmic cytochrome c, possibly reflecting the lesser vulnerability of this area to ischemia. We did not observe cytoplasmic cytochrome c in any neurons that did not also display persistent eIF2alpha(P) immunostaining. Because phosphorylation of eIF2alpha during early brain reperfusion is carried out by PERK, these findings suggest that there is prolonged activation of the unfolded protein response in the reperfused brain.

Dysfunction of the unfolded protein response during global brain ischemia and reperfusion

A variety of endoplasmic reticulum (ER) stresses trigger the unfolded protein response (UPR), a compensatory response whose most proximal sensors are the ER membrane-bound proteins ATF6, IRE1alpha, and PERK. The authors simultaneously examined the activation of ATF6, IRE1alpha, and PERK, as well as components of downstream UPR pathways, in the rat brain after reperfusion after a 10-minute cardiac arrest. Although ATF6 was not activated, PERK was maximally activated at 10-minute reperfusion, which correlated with maximal eIF2alpha phosphorylation and protein synthesis inhibition. By 4-h reperfusion, there was 80% loss of PERK immunostaining in cortex and 50% loss in brain stem and hippocampus. PERK was degraded in vitro by mu-calpain. Although inactive IRE1alpha was maximally decreased by 90-minute reperfusion, there was no evidence that its substrate xbp-1 messenger RNA had been processed by removal of a 26-nt sequence. Similarly, there was no expression of the UPR effector proteins 55-kd XBP-1, CHOP, or ATF4. These data indicate that there is dysfunction in several key components of the UPR that abrogate the effects of ER stress. In other systems, failure to mount the UPR results in increased cell death. As other studies have shown evidence for ER stress after brain ischemia and reperfusion, the failure of the UPR may play a significant role in reperfusion neuronal death.

Beneficial effects of alpha-lipoic acid plus vitamin E on neurological deficit, reactive gliosis and neuronal remodeling in the penumbra of the ischemic rat brain

During cerebral ischemia-reperfusion, the enhanced production of oxygen-derived free radicals contributes to neuronal death. The antioxidants alpha-lipoic acid and vitamin E have shown synergistic effects against lipid peroxidation by oxidant radicals in several pathological conditions. A thromboembolic stroke model in rats was used to analyze the effects of this mixture under two oral treatments: intensive and prophylactic. Neurological functions, glial reactivity and neuronal remodeling were assessed after experimental infarction. Neurological recovery was only found in the prophylactic group, and both antioxidant schemes produced down-regulation of astrocytic and microglial reactivity, as well as higher neuronal remodeling in the penumbra area, as compared with controls. The beneficial effects of this antioxidant mixture suggest that it may be valuable for the treatment of cerebral ischemia in humans.

The alterations of N-Methyl-D-aspartate receptor expressions and oxidative DNA damage in the CA1 area at the early time after ischemia-reperfusion insult

Delayed neuronal death in the CA1 of the hippocampus following global ischemia has been evoked by both the activation of N-methyl-D-aspartate receptor (NR) and the generate reactive oxygen species in the neurons. In the present study, we investigated whether oxidative DNA damages may be correlated with NR subunits (NR1 and NR2A/B) expression following ischemia insults in vivo. Thirty minutes after ischemia-reperfusion, the intensities of both NR and 8-hydroxy-2'-deoxyguanosine (8-OHdG) immunoreactivities were markedly increased in neurons of CA1. However, NR2A/B and 8-OHdG immunoreactivities were enhanced in CA1 over 24 h after ischemia although NR1 immunoreactivity was decreased. These results suggest that oxidative stress and excitotoxicity in the CA1 may simultaneously trigger neuronal damages at early time after ischemia, and free radical damage including oxidative DNA damage may eventually promote the delayed neuronal death in this region.

Molecular mechanisms of ischemic neuronal injury

Brain ischemia triggers a complex cascade of molecular events that unfolds over hours to days. Identified mechanisms of postischemic neuronal injury include altered Ca(2+) homeostasis, free radical formation, mitochondrial dysfunction, protease activation, altered gene expression, and inflammation. Although many of these events are well characterized, our understanding of how they are integrated into the causal pathways of postischemic neuronal death remains incomplete. The primary goal of this review is to provide an overview of molecular injury mechanisms currently believed to be involved in postischemic neuronal death specifically highlighting their time course and potential interactions.

Antioxidant profile and early outcome in stroke patients

BACKGROUND AND PURPOSE

Experimental studies provide evidence of an association between ischemic stroke and increased oxidative stress, but data in humans are still limited and controversial. The purpose of this study was to investigate the time course of plasma antioxidant changes in ischemic stroke patients.

METHODS

Plasma antioxidants, including water-soluble (vitamin C and uric acid) and lipid-soluble (vitamins A and E) compounds as well as antioxidant enzyme activities in plasma (superoxide dismutase [SOD] and glutathione peroxidase) and erythrocytes (SOD), were measured by high-performance liquid chromatography (antioxidant vitamins) and by spectrophotometry (antioxidant enzymes) in 38 subjects (25 men and 13 women aged 77.2+/-7.9 years) with acute ischemic stroke of recent onset (<24 hours) on admission, after 6 and 24 hours, and on days 3, 5, and 7. Antioxidant levels in patients on admission were compared with those of age- and sex-matched controls.

RESULTS

Mean antioxidant levels and activities in patients on admission were lower than those of controls and showed a gradual increase over time. Patients with the worst early outcome (death or functional decline) had higher vitamin A and uric acid plasma levels and lower vitamin C levels and erythrocyte SOD activity than those who remained functionally stable.

CONCLUSIONS

These results suggest that the majority of antioxidants are reduced immediately after an acute ischemic stroke, possibly as a consequence of increased oxidative stress. A specific antioxidant profile is associated with a poor early outcome.

Implication of cysteine proteases calpain, cathepsin and caspase in ischemic neuronal death of primates

Although more than 8000 papers of apoptosis are published annually, there are very few reports concerning necrosis in the past few years. A number of recent studies using lower species animals have suggested that the cornu Ammonis (CA) 1 neuronal death after brief global cerebral ischemia occurs by apoptosis, an active and genetically controlled cell suicide process. However, the studies of monkeys and humans rather support necrosis, the calpain-mediated release of lysosomal enzyme cathepsin after ischemia conceivably contributes to the cell degeneration of CA1 neurons. This paper provides an overview of recent developments in ischemic neuronal death, presents the cascade of the primate neuronal death with particular attentions to the cysteine proteases, and also indicates selective cathepsin inhibitors as a novel neuroprotectant. Furthermore, the possible interaction of calpain, cathepsin, and caspase in the cascade of ischemic neuronal death is discussed.

Brain ischemia and reperfusion: molecular mechanisms of neuronal injury

Brain ischemia and reperfusion engage multiple independently-fatal terminal pathways involving loss of membrane integrity in partitioning ions, progressive proteolysis, and inability to check these processes because of loss of general translation competence and reduced survival signal-transduction. Ischemia results in rapid loss of high-energy phosphate compounds and generalized depolarization, which induces release of glutamate and, in selectively vulnerable neurons (SVNs), opening of both voltage-dependent and glutamate-regulated calcium channels. This allows a large increase in cytosolic Ca(2+) associated with activation of mu-calpain, calcineurin, and phospholipases with consequent proteolysis of calpain substrates (including spectrin and eIF4G), activation of NOS and potentially of Bad, and accumulation of free arachidonic acid, which can induce depletion of Ca(2+) from the ER lumen. A kinase that shuts off translation initiation by phosphorylating the alpha-subunit of eukaryotic initiation factor-2 (eIF2alpha) is activated either by adenosine degradation products or depletion of ER lumenal Ca(2+). Early during reperfusion, oxidative metabolism of arachidonate causes a burst of excess oxygen radicals, iron is released from storage proteins by superoxide-mediated reduction, and NO is generated. These events result in peroxynitrite generation, inappropriate protein nitrosylation, and lipid peroxidation, which ultrastructurally appears to principally damage the plasmalemma of SVNs. The initial recovery of ATP supports very rapid eIF2alpha phosphorylation that in SVNs is prolonged and associated with a major reduction in protein synthesis. High catecholamine levels induced by the ischemic episode itself and/or drug administration down-regulate insulin secretion and induce inhibition of growth-factor receptor tyrosine kinase activity, effects associated with down-regulation of survival signal-transduction through the Ras pathway. Caspase activation occurs during the early hours of reperfusion following mitochondrial release of caspase 9 and cytochrome c. The SVNs find themselves with substantial membrane damage, calpain-mediated proteolytic degradation of eIF4G and cytoskeletal proteins, altered translation initiation mechanisms that substantially reduce total protein synthesis and impose major alterations in message selection, down-regulated survival signal-transduction, and caspase activation. This picture argues powerfully that, for therapy of brain ischemia and reperfusion, the concept of single drug intervention (which has characterized the approaches of basic research, the pharmaceutical industry, and clinical trials) cannot be effective. Although rigorous study of multi-drug protocols is very demanding, effective therapy is likely to require (1) peptide growth factors for early activation of survival-signaling pathways and recovery of translation competence, (2) inhibition of lipid peroxidation, (3) inhibition of calpain, and (4) caspase inhibition. Examination of such protocols will require not only characterization of functional and histopathologic outcome, but also study of biochemical markers of the injury processes to establish the role of each drug.

The glutathione content of retinal Müller (glial) cells: effect of pathological conditions

Maintenance of isolated retinal Müller (glial) cells in glutamate-free solutions over 7 h causes a significant loss of their initial glutathione content; this loss is largely prevented by the blockade of glutamine synthesis using methionine sulfoximine (5 mM). Anoxia does not reduce the glutathione content of Müller cells when glucose (11 mM), glutamate and cystine (0.1 mM each) are present. In contrast, simulation of total ischemia (i.e., anoxia plus removal of glucose) decreases the glutathione levels dramatically, even in the presence of glutamate and cystine. Less severe effects are caused by high extracellular K+ (40 mM). Reactive oxygen species are generated in the retina under various conditions, such as anoxia, ischemia, and reperfusion. One of the crucial substances protecting the retina against reactive oxygen species is glutathione, a tripeptide constituted of glutamate, cysteine and glycine. It was recently shown that glutathione can be synthesized in retinal Müller glial cells and that glutamate is the rate-limiting substance. In this study, glutathione levels were determined in acutely isolated guinea-pig Müller cells using the glutathione-sensitive fluorescent dye monochlorobimane. The purpose was to find out how the glial glutathione content is affected by anoxia/ischemia and accompanying pathophysiological events such as depolarization of the cell membrane. Our results further strengthen the view that glutamate is rate-limiting for the glutathione synthesis in glial cells. During glutamate deficiency, as caused by e.g., impaired glutamate uptake, this amino acid is preferentially delivered to the glutamate-glutamine pathway, at the expense of glutathione. This mechanism may contribute to the finding that total ischemia (but not anoxia) causes a depletion of glial glutathione. In situ depletion may be accelerated by the ischemia-induced increase of extracellular K+, decreasing the driving force for glutamate uptake. The ischemia-induced lack of glutathione is particularly fatal considering the increased production of reactive oxygen species under this condition. Therefore the therapeutic application of exogenous free radical scavengers is greatly recommended.

Free radicals are involved in the damage to protein synthesis after anoxia/aglycemia and NMDA exposure

Neuronal protein synthesis is inhibited in CA1 pyramidal neurons for many hours after ischemia, hypoxia or hypoglycemia. This inhibition precedes cell death, is a hallmark characteristic of necrotic damage and may play a key role in the death of vulnerable neurons after these insults. The sequence of events leading to this inhibition remains to be fully elucidated. The protein synthesis failure after 7.5 min anoxia/aglycemia in the rat hippocampal slice can be prevented by blocking N-methyl-D-aspartate receptors in a reduced calcium environment during the insult. In this study, we demonstrate that N-methyl-D-aspartate exposure directly causes a dose-dependent, receptor-mediated and prolonged protein synthesis inhibition in CA1 pyramidal neurons. The free radical scavenger Vitamin E significantly attenuates this damage due to low concentrations of N-methyl-D-aspartate (10 microM). Free radical generation by xanthine/xanthine oxidase (XOD) can directly damage protein synthesis in neurons of the slice. Vitamin E, ascorbic acid and N-acetylcysteine can each prevent the damage due to anoxia/aglycemia and to higher concentrations of N-methyl-D-aspartate (50 microM), provided calcium levels are reduced concomitantly. These findings indicate that both free radicals and calcium play a role in the sequence of events leading to protein synthesis failure after energetic stress like anoxia/aglycemia. They further suggest that the mechanism by which N-methyl-D-aspartate receptor activation damages protein synthesis involves free radical generation.

Cell death, calcium mobilization, and immunostaining for phosphorylated eukaryotic initiation factor 2-alpha (eIF2alpha) in neuronally differentiated NB-104 cells: arachidonate and radical-mediated injury mechanisms

These experiments examine the effects of arachidonate with respect to cell death, radical-mediated injury, Ca2+ mobilization, and formation of ser-51-phosphorylated eukaryotic initiation factor 2alpha [eIF2alpha(P)]. It is known that during brain ischemia the concentration of free arachidonate can reach 180 microM, and during reperfusion oxidative metabolism of arachidonate leads to generation of superoxide that can reduce stored ferric iron and promote lipid peroxidation. During early brain reperfusion, we have shown an approximately 20-fold increase in eIF2alpha(P) which maps to vulnerable neurons that display inhibition of protein synthesis. Here in neuronally differentiated NB-104 cells, equivalent cell death (assessed by LDH release) was induced by 40 microM arachidonate and 20 microM cumene hydroperoxide (CumOOH, a known alkoxyl radical generator). In these injury models (1) radical inhibitors (BHA, BHT, and the lipophilic iron chelator EMHP) block CumOOH-induced cell death but do not block arachidonate-induced death; (2) 40 microM arachidonate (but not up to 40 microM CumOOH) rapidly induces Ca2+ release from intracellular stores; (3) both 40 microM arachidonate and 20 microM CumOOH induce intense immunostaining for eIF2alpha(P); and (4) the elF2alpha(P) immunostaining induced by CumOOH but not that induced by arachidonate is completely blocked by anti-radical intervention with EMHP. Arachidonate-induced formation of eIF2alpha(P) and cell death do not require iron-mediated radical mechanisms and are associated with Ca2+ release from intracellular stores; however, radical-mediated injury also induces both eIF2alpha(P) and cell death without release of intracellular Ca2+. Our data link eIF2alpha(P) formation during brain reperfusion to two established injury mechanisms that may operate concurrently.

Usual and unusual methods for detection of lipid peroxides as indicators of tissue injury in cerebral ischemia: what is appropriate and useful?

1. Free radical-dependent lipid peroxidation processes have long been thought to contribute to brain damage following stroke or cerebral ischemia/reperfusion. 2. The preponderance of evidence for this belief has been derived indirectly, through diminution of tissue injury indices (e.g., brain infarct volume) facilitated by application of free radical scavenger substances. 3. Direct, unequivocal evidence for lipid peroxidation in terms of classical assays (detection of conjugated diene absorbance or thiobarbituric acid-reactive substances) is considerably less common, and its validity can be questioned. 4. Correlations of treatment-induced diminishment of brain injury indices with reductions in lipid peroxidation level are rarer still. 5. Reasons underlying the disparity between the belief that lipid peroxidation contributes to ischemic brain injury and direct evidence for this contribution (at least acutely) are proposed, along with evidence that new methods are being developed which should provide the basis for obtaining a definitive answer.

Increased plasma levels of lipid hydroperoxides in patients with ischemic stroke

A large body of experimental research indicates that the generation of free radicals leading to oxidative stress plays a role in the pathogenesis of ischemic brain injury, but evidence in humans is limited. We examined plasma levels of lipid hydroperoxides (measured as cholesteryl ester hydroperoxides, CEOOH) and ascorbic acid in 32 patients with cortical stroke, as compared with 13 patients with lacunar infarct. Patients with cortical stroke had significantly increased levels of CEOOH, which peaked on Day 5 after the ictus. Small decreases in ascorbic acid concentrations were not significant. There was a significant positive correlation of CEOOH with the NIH stroke scale, and a significant negative correlation with the Glasgow coma scale. Concentrations of CEOOH were significantly higher in patients with total anterior cerebral syndrome as compared with patients with partial anterior cerebral syndrome or posterior cerebral syndrome. Stroke volumes computed from CT or MRI scans were significantly correlated with plasma CEOOH levels. These findings implicate oxidative stress in ischemic brain injury in humans and suggest that measurements of CEOOH in plasma may be useful both prognostically as well as in monitoring therapeutic interventions.

Arachidonate transport through the blood-retina and blood-brain barrier of the rat after reperfusion of varying duration following complete cerebral ischemia

The permeability-surface area product (PS) of [1-14C]arachidonate at the blood-retina and blood-brain barrier was determined by short carotid perfusion in young Wistar rats 1 or 6 h after recovery period following complete cerebral ischemia induced by temporary cardiac arrest. For the retina and structures of visual system, hypothalamus and olfactory bulb there was no significant difference over sham-operated rats among mean PSs. For cortex, hippocampus and striatum, significant increases were found at both time intervals of recovery after cardiac arrest. The ischemia-reperfusion model was characterized by a significant increase in tissue conjugated diene in the hippocampus and microsomal lysophosphatidylcholine acyltransferase activity in the cortex. Consistent with these findings, we also show ultrastructural evidence mainly represented by partial opening of interendothelial junctions and mild signs of tissue edema in surrounding neuropil, suggesting barrier leakiness predominantly in the cortex, hippocampus and striatum but almost absent in the retina microvessels. Our results indicate that ischemia-reperfusion does affect influex through blood-brain barrier into regional structures of rat central nervous system of arachidonate, a metabolic substrate and lipid mediator rapidly incorporated into microcapillary and brain lipids. The data also suggested that: (i) reactive oxyradicals were moderately generated during the early phase of ischemic-reperfusion process in the rat; (ii) after reperfusion, in vitro susceptibility of different brain regions to iron-induced peroxidation was highest in the hippocampus and lowest in the cortex and striatum; (iii) membrane phospholipid repair mechanisms were activated at the same time.

Expression of nuclear redox factor ref-1 in the rat hippocampus following global ischemia induced by cardiac arrest

The Ref-1 protein is a bifunctional nuclear enzyme involved in repair of DNA lesions and in redox regulation of DNA-binding activity of AP-1 family members, such as Fos and Jun transcription factors. In the present study, we demonstrate by in situ hybridization that transient global ischemia induced by cardiac arrest activates ref-1 mRNA expression in the granular cells of the rat dentate gyrus after 6 h and in CA1 pyramidal neurons of the hippocampus proper after 24 h, respectively. Immunohistochemical analysis revealed nuclear accumulation of Ref-1 protein in granular cells of the ischemia-resistant dentate gyrus, whereas Ref-1 protein expression progressively decreased in vulnerable CA1 neurons of the post-ischemic hippocampus from 24 h onwards. At the same time point, intense nuclear c-Jun immunoreactivity was observed in both neuronal cell populations. Our data suggest that oxidative stress induced by ischemia-reperfusion may increase neuronal ref-1 expression. However, inability of ref-1 mRNA translation and nuclear translocation of encoded protein in CA1 pyramidal neurons may inhibit repair of oxidative DNA damage or cellular adaptive responses leading to delayed neuronal cell death.

Diabetics do not have increased Alzheimer-type pathology compared with age-matched control subjects. A retrospective postmortem immunocytochemical and histofluorescent study

Diabetics have impaired cognitive performance relative to age-matched control subjects, but the pathologic basis for this impairment is unknown. Because Alzheimer-type lesions, including both senile plaques and neurofibrillary tangles, contain glycated proteins and glycation is known to be increased in diabetes, we hypothesized that cognitive impairment in diabetes may be due in part to increased Alzheimer-type pathology. We measured the amount of Alzheimer-type pathology in postmortem brains of diabetic and age-matched control subjects with sensitive and specific histofluorescent and immunocytochemical methods. As expected, there were strong correlations between severity of senile plaques and neurofibrillary degeneration and age and also a strong correlation between severity of senile plaques and neurofibrillary degeneration and age and also a strong correlation between the pathologic measures. On the other hand, there was no significant difference between diabetics and control subjects with respect to severity of Alzheimer-type pathology, on average, or with respect to age. This finding was true for diabetics with and without insulin dependence. The results confirm reports showing that diabetes is not a risk factor for Alzheimer-type pathology and suggest that factors other than Alzheimer's disease are responsible for cognitive impairment in diabetics.

Immunocytochemical method for investigating in vivo neuronal oxygen radical-induced lipid peroxidation

The investigation of oxygen radical-induced lipid peroxidative neuronal damage in the context of acute and chronic neurodegenerative disorders has been largely limited to the use of ex vivo analytical methodologies. These are often fraught with sensitivity or specificity problems, or they are indirect. Furthermore, none of the analytical methods allow precise anatomical identification of the cells that are undergoing peroxidative injury. This paper describes an immunocytochemical method for localization of central nervous system (CNS) lipid peroxidation (LP) that employs a rabbit-derived antibody raised against malondialdehyde (MDA)-modified rabbit serum albumin (RSA). MDA is a breakdown product of peroxidized membrane polyunsaturated fatty acids that avidly binds to cellular proteins. Using the anti-MDA-RSA, we herein illustrate increased MDA-derived immunostaining: (1) in the spinal cord of transgenic familial amyotrophic lateral sclerosis (ALS) mice; and (2) in the selectively vulnerable gerbil hippocampal CA1 region after a 5 min episode of forebrain ischemia and its relationship to the time course of neuronal degeneration.

Postischemic accumulation of lipid peroxidation products in the rat brain: immunohistochemical detection of 4-hydroxy-2-nonenal modified proteins

We report an immunohistochemical study on the distribution and alterations of 4-hydroxy-2-nonenal (HNE)-modified proteins, an indicator of lipid peroxidation, in the rat brain after 3 h of middle cerebral artery (MCA) occlusion followed by reperfusion. HNE immunoreactivity was not observed in intact neurons, but it appeared in some shrunken neurons within the infarcted zone at 3 h after reperfusion. The number of HNE-positive neurons increased with the spread of the infarcted area. The pyramidal neurons in the third layer of the frontoparietal cortex were HNE-positive and the intensity of their HNE immunoreactivity was highest at 24 h after reperfusion. At 48 h, HNE-positive neurons were observed in the medial part of the striatum, the lateral side of the frontoparietal cortex, and at the boundary between the infarcted and noninfarcted zones. In addition, strong HNE immunoreactivity was seen in microglia (identified by OX-42 immunostaining). This method seems to be useful to follow the progress of lipid peroxidation at the cellular level after ischemic injury.

Postresuscitation changes in brain free radical-mediated processes and nitric oxide synthase activity in rats: effects of individual behavior in "emotional resonance" test

Effects of 7-min cardiac arrest and individual behavior on free radical-mediated processes and nitric oxide synthase (NOS) activity was evaluated in brains of male Wistar rats one hour and one week after resuscitation. "Emotional resonance" test was used for the behavioral selection of rats. The test includes factors of significance for rats: the choice between large and lighted or small and dark space as well as signals of pain of another rat. Free radical generation (using chemiluminescence method), superoxide scavenging/generating activity, substances reacting with 2-thiobarbituric acid and NOS activity (by measuring mononitrosyl iron complex of NO with diethyl dithiocarbamate and endogenous brain Fe2+ by electron spin resonance spectroscopy) were determined in cerebral cortex, cerebellum and hippocampus. Cardiac arrest induced oxidative stress accompanied by the loss of NOS activity, as well as compensatory changes of free radical-mediated processes in cerebral cortex. Oxidative stress was also evident in cerebellum and, to a lesser extent, in hippocampus. Most of neurochemical differences between behavioral groups were induced by cardiac arrest. These differences were global, related to a specific brain region or became apparent in cerebral lateralization of biochemical indices.

Cardiac arrest induces decrease of nitric oxide synthase activity and increase of free radical generation in rat brain regions

Rats were subjected to 15 min cardiac arrest and sacrificed 1 h or 15-20 days after resuscitation. Homogenates of brain regions were assayed for nitric oxide synthase (NOS) activity (by measuring the mononitrosyl iron complex of NO with diethyl dithiocarbamate and endogenous brain Fe2+ using electron spin resonance spectroscopy) and generation of free radicals (FRG; by measuring H2O2-induced, luminol-dependent chemiluminescence). Cardiac arrest induced marked decrease of NOS activity and the increase of FRG, most prominent in cerebellum and less marked in cerebral cortex. Two groups of rats were revealed 15-20 days after cardiac arrest: with NOS activity significantly lower than control and not different from control. Positive linear inter-regional cross-correlations of both NOS activity and FRG (except of the group 1 h after resuscitation) as well as negative correlations between NOS and FRG were demonstrated.

Macroscopic indices of lipid peroxidation in cerebral ischemia/reperfusion: validity and sensitivity enhancement in terms of conjugated diene detection

Recent evidence for the occurrence of in vivo lipid peroxidation in the context of cerebral ischemia/reperfusion, as detected by classical tests such thiobarbituric acid reactivity and conjugated diene absorbance, is critically reviewed. Despite the widespread perception that lipid peroxidation is well-established and to be expected under such circumstances, in general these detection methods have not been applied with rigor sufficient to prove the quantitative existence of lipid peroxides unequivocally. The development of sensitive methods which can be utilized in small tissue samples at early times after brain injury is needed. In particular, the conditions necessary for the establishment of a more rigorous and sensitive method of conjugated diene detection in terms of difference spectral analysis are detailed and illustrated. In addition, a new autofluorescence in the far-ultraviolet region is shown to be associated with oxygenated conjugated diene-containing compounds.

Altered neuronal and microglial responses to excitotoxic and ischemic brain injury in mice lacking TNF receptors

Brain injury, as occurs in stroke or head trauma, induces a dramatic increase in levels of tumor necrosis factor-alpha (TNF), but its role in brain injury response is unknown. We generated mice genetically deficient in TNF receptors (TNFR-KO) to determine the role of TNF in brain cell injury responses. Damage to neurons caused by focal cerebral ischemia and epileptic seizures was exacerbated in TNFR-KO mice, indicating that TNF serves a neuroprotective function. Oxidative stress was increased and levels of an antioxidant enzyme reduced in brain cells of TNFR-KO mice, indicating that TNF protects neurons by stimulating antioxidant pathways. Injury-induced microglial activation was suppressed in TNFR-KO mice, demonstrating a key role for TNF in injury-induced immune response. Drugs that target TNF signaling pathways may prove beneficial in treating stroke and traumatic brain injury.

Neuroprotective effects of alpha-lipoic acid and its enantiomers demonstrated in rodent models of focal cerebral ischemia

The purpose of this study was to investigate whether alpha-lipoic acid (LA), the oxidized form of the radical scavenger dihydrolipoic acid (DLA), protected brain tissue against ischemic damage and whether there were differences in the neuroprotective potencies between its enantiomers. We used the models of focal cerebral ischemia in mice and rats. The infarct area on the mouse brain surface and the infarct volume of the rat brain were determined by means of an image analyzing system. The LA was capable of reducing the infarct area only when it was administered subcutaneously, but not when it was administered intraperitoneally or into the cisterna magna. Both the R- and the S-enantiomer of LA protected brain tissue against ischemic damage, but their protective activities seemed to be related to the time period of pretreatment. In mice, both enantiomers revealed a similar neuroprotective potency when they were administered subcutaneously 1 or 2 hr before occlusion of the middle cerebral artery (MCA), whereas a longer time period of pretreatment (4 or 6 hr) failed to exert neuroprotection. In rats, subcutaneous pretreatment with R- or S-LA for 2 hr before ischemia significantly diminished the infarct volume. We assume that LA has to be reduced to DLA which finally causes neuroprotection.

Oligodendroglial precursor cell susceptibility to hypoxia is related to poor ability to cope with reactive oxygen species

Oligodendrocyte precursors and astrocytes in 2-week-old rat primary glial cultures survived 24 h of anoxia, suggesting both cell types could survive using glycolysis for ATP synthesis; however, when the hypoxia developed gradually, the majority of oligodendrocyte precursor cells died within 24 h of the beginning of the experiment but astrocytes survived. Similarly when cultures were exposed to an atmosphere of 1% oxygen, but not 2% or greater, oligodendrocyte precursors died within 24 h. Much more lipid peroxidation was seen under conditions of hypoxia than under conditions of anoxia suggesting that oligodendrocyte precursors died under the former condition because of free radical-induced damage. Using 5-(and -6)-carboxy-2',7'-dichlorodihydrofluorescein (DCFH) as an intracellular probe of oxidative stress, we have demonstrated directly on living cells that oligodendrocyte precursors have a poorer ability to scavenge free radicals than astrocytes. Furthermore, when free radicals were induced to form in the cells either by cysteine auto-oxidation or menadione redox cycling, oligodendrocyte precursors were more readily damaged than astrocytes. We conclude that oligodendroglial precursor cells are exquisitively sensitive to reactive oxygen species.

Global brain ischemia and reperfusion: Golgi apparatus ultrastructure in neurons selectively vulnerable to death

The neocortex and the hippocampus were examined for lipid peroxidation products and ultrastructural alterations by fluorescence and electron microscopy, respectively, in rats subjected to 10 min of cardiac arrest or 10 min cardiac arrest and either 90 or 360 min reperfusion. Lipid peroxidation products were observed after 90 min reperfusion in the perikarya and proximal dendrites of neocortical pyramidal neurons and in the hippocampal hilar cells and CA1, region; the fluorescence was most intense at the base of the apical dendrite, the region of the Golgi apparatus. After 90 min of reperfusion, the CA1, showed considerable stretches of rough endoplasmic reticulum devoid of ribosomes and the Golgi cisternae were shorter and widely dilated. The neocortex showed similar endoplasmic reticulum changes, but no significant alterations to the Golgi were noted. In addition there were areas where strings of ribosomes appear to be detaching from the endoplasmic reticulum. After 360 min reperfusion in both the neocortex and the hippocampus, the damage appeared more severe. The Golgi was fragmented into vacuoles, membranous whorls had appeared, and dense aggregates of smooth vesicles were seen coalescing with each other and the vacuoles. These observations suggest that early Golgi involvement is a more important marker of lethal injury than ribosome release from the endoplasmic reticulum. The areas of disturbed Golgi ultrastructure correspond to those areas that show evidence of lipid peroxidation and imply that lipid peroxidation may be causally related to the disturbance in Golgi ultrastructure.

Nuclear-envelope nucleoside triphosphatase kinetics and mRNA transport following brain ischemia and reperfusion

STUDY HYPOTHESIS

We attempted to determine whether the reduced egress of mRNA from brain nuclei following in vivo ischemia and reperfusion is caused by direct damage to the nuclear pore-associated NTPase that impairs the system for nuclear export of polyadenylated, or poly(A)+, mRNA.

DESIGN

Prospective animal study.

INTERVENTIONS

NTPase activity and poly(A)+ mRNA transport were studied in nuclear envelope vesicles (NEVs) prepared from canine parietal cortex isolated after 20 minutes of ischemia or 20 minutes of ischemia and 2 or 6 hours of reperfusion.

RESULTS

Brain NEV NTPase Michaelis-Menten constant (Km) and maximum uptake velocity (Vmax) and the ATP-stimulated poly(A)+ mRNA egress rates were not significantly affected by ischemia and reperfusion. In vitro exposure of the NEVs to the OH. radical-generating system completely abolished NTPase activity.

CONCLUSION

We conclude that brain ischemia and reperfusion do not induce direct inhibition of nucleocytoplasmic transport of poly(A)+ mRNA. This suggests that the nuclear membrane is not exposed to significant concentrations of OH. radical during reperfusion.

Hyperthermic injury of oligodendrocyte precursor cells: implications for dysmyelination disorders

Although 6 h of exposure to 41 degrees C did not affect the viability of oligodendrocyte precursors in culture, a 2-h exposure to 42 degrees C caused them to die. In contrast, astrocytes could tolerate 42 degrees C for at least 6 h. There was an increase in lipid peroxidation following the 42 degrees C insult, particularly in the oligodendrocyte precursors. These findings may be of relevance in understanding certain dysmyelination disorders in humans.