Role of superoxide dismutase in ischemic brain injury: reduction of edema and infarction in transgenic mice following focal cerebral ischemia

Neuroprotection of antioxidant enzymes against transient global cerebral ischemia in gerbils

Experimentally transient global cerebral ischemia using animal models have been thoroughly studied and numerous reports suggest the involvement of oxidative stress in the pathogenesis of neuronal death in ischemic lesions. In animal models, during the reperfusion period after ischemia, increased oxygen supply results in the overproduction of reactive oxygen species (ROS), which are involved in the process of cell death. ROS, such as superoxide anions, hydroxyl free radicals, hydrogen peroxide and nitric oxide are produced as a consequence of metabolic reactions and central nervous system activity. These reactive species are directly involved in the oxidative damage of cellular macromolecules such as nucleic acids, lipids and proteins in ischemic tissues, which can lead to cell death. Antioxidant enzymes are believed to be among the major mechanisms by which cells counteract the deleterious effect of ROS after cerebral ischemia. Consequently, antioxidant strategies have been long suggested as a therapy for experimental ischemic stroke; however, clinical trials have not yet been able to promote the translation of this concept into patient treatment regimens. This article focuses on the contribution of oxidative stress or antioxidants to the post-ischemic neuronal death following transient global cerebral ischemia by using a gerbil model.

Nanoparticles for targeted delivery of antioxidant enzymes to the brain after cerebral ischemia and reperfusion injury

Stroke is one of the major causes of death and disability in the United States. After cerebral ischemia and reperfusion injury, the generation of reactive oxygen species (ROS) and reactive nitrogen species may contribute to the disease process through alterations in the structure of DNA, RNA, proteins, and lipids. We generated various nanoparticles (liposomes, polybutylcyanoacrylate (PBCA), or poly(lactide-co-glycolide) (PLGA)) that contained active superoxide dismutase (SOD) enzyme (4,000 to 20,000 U/kg) in the mouse model of cerebral ischemia and reperfusion injury to determine the impact of these molecules. In addition, the nanoparticles were untagged or tagged with nonselective antibodies or antibodies directed against the N-methyl-D-aspartate (NMDA) receptor 1. The nanoparticles containing SOD protected primary neurons in vitro from oxygen-glucose deprivation (OGD) and limited the extent of apoptosis. The nanoparticles showed protection against ischemia and reperfusion injury when applied after injury with a 50% to 60% reduction in infarct volume, reduced inflammatory markers, and improved behavior in vivo. The targeted nanoparticles not only showed enhanced protection but also showed localization to the CA regions of the hippocampus. Nanoparticles alone were not effective in reducing infarct volume. These studies show that targeted nanoparticles containing protective factors may be viable candidates for the treatment of 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.

The protective effect of early hypothermia on PTEN phosphorylation correlates with free radical inhibition in rat stroke

We recently showed that intraischemic moderate hypothermia (30 degrees C) reduces ischemic damage through the Akt pathway after permanent distal middle cerebral artery occlusion in rats. The only Akt pathway component preserved by hypothermia is phosphorylated phosphatase and tensin homolog deleted on chromosome 10 (p-PTEN), which suggests that p-PTEN may have a central role in neuroprotection. Reactive oxygen species (ROS) are critically involved in mediating ischemic damage after stroke by interacting with signaling molecules, including Akt, PTEN, and delta-protein kinase C (PKC). We investigated the protective mechanisms of moderate hypothermia on these signaling proteins after transient focal ischemia in rats. Early moderate hypothermia (3 h) was administered 15 mins before reperfusion, and delayed moderate hypothermia (3 h) was applied 15 mins after reperfusion. Our results indicate that early hypothermia reduced infarction, whereas delayed hypothermia did not. However, both early and delayed hypothermia maintained levels of Mn-SOD (superoxide dismutase) and phosphorylated Akt and blocked delta-PKC cleavage, suggesting that these factors may not be critical to the protection of hypothermia. Nevertheless, early hypothermia preserved p-PTEN levels after reperfusion, whereas delayed hypothermia did not. Furthermore, ROS inhibition maintained levels of p-PTEN after stroke. Together, these findings suggest that phosphorylation levels of PTEN are closely associated with the protective effect of early hypothermia against stroke.

Postischemic IGF-1 gene transfer promotes neurovascular regeneration after experimental stroke

Promoting neural regeneration after cerebral infarction has emerged as a potential approach for the treatment of stroke. Insulin-like growth factor 1 (IGF-1) possesses both neurotrophic and angiogenic properties. The aim of this study was to determine whether postischemic gene transfer of IGF-1 enhances neurovascular regeneration in a mouse model of permanent focal cerebral ischemia. Long-term cerebral IGF-1 overexpression was achieved with adeno-associated viral vector (AAV) by stereotaxic injection at 24 h after a stroke. Adeno-associated viral vector-green fluorescent protein (GFP) or saline was injected as a control. The success of postischemic gene transduction was confirmed by a strong GFP signal and by increased IGF-1 protein expression in the peri-infarct region. Postischemic gene transfer of IGF-1 significantly enhanced vascular density at 8 weeks after a stroke in the peri-infarct and injection needle tract area compared with AAV-GFP or saline treatment, as shown by immunohistochemical staining with the vascular marker lectin. Furthermore, increased vascular density was associated with improved local vascular perfusion. Immunohistochemical staining with the neuronal progenitor marker, DCX (doublecortin), and the cell proliferation marker, BrdU (5-bromo-2-deoxyuridine-5-monophosphate), indicated that AAV-IGF-1 treatment potently increased neurogenesis compared with AAV-GFP injection. These data show that postischemic treatment of IGF-1 effectively promoted neural and vascular regeneration in the chronic stage of cerebral infarction.

Faster recovery of cerebral perfusion in SOD1-overexpressed rats after cardiac arrest and resuscitation

BACKGROUND AND PURPOSE

Protracted hypoperfusion is one of the hallmarks of secondary cerebral derangement after cardiac arrest and resuscitation (CAR), and reactive oxygen species have been implicated in reperfusion abnormalities.

METHODS

Using transgenic (Tg) rats overexpressing copper zinc superoxide dismutase (SOD1), we investigated the role of this intrinsic antioxidant in the restoration of cerebral blood flow (CBF) after CAR. Nine Tg and 11 wild-type (WT) rats were subjected to a nominal 15-minute cardiac arrest, and CBF was measured using the noninvasive arterial spin labeling MRI method before and during cardiac arrest, and 0 to 2 hours and 1 to 5 days after resuscitation.

RESULTS

The SOD1-Tg rats showed rapid normalization of CBF 1 day after the insult, whereas CBF in WT animals remained abnormal for at least 5 days, showing a progressive increase in CBF from hypo- to hyperperfusion on postresuscitation days 1 to 5. The long-term outcome, as measured by survival time, change in body weight, and mapping of apparent diffusion coefficient (ADC) for ion/water homeostasis, was significantly better in the SOD1-Tg rats.

CONCLUSIONS

Our results support the notion that reactive oxygen species are at least partially responsible for microvascular reperfusion disorders.

Oxidative stress and neuronal death/survival signaling in cerebral ischemia

It has been demonstrated by numerous studies that apoptotic cell death pathways are implicated in ischemic cerebral injury in ischemia models in vivo. Experimental ischemia and reperfusion models, such as transient focal/global ischemia in rodents, have been thoroughly studied and the numerous reports suggest the involvement of cell survival/death signaling pathways in the pathogenesis of apoptotic cell death in ischemic lesions. In these models, reoxygenation during reperfusion provides oxygen as a substrate for numerous enzymatic oxidation reactions and for mitochondrial oxidative phosphorylation to produce adenosine triphosphate. Oxygen radicals, the products of these biochemical and physiological reactions, are known to damage cellular lipids, proteins, and nucleic acids and to initiate cell signaling pathways after cerebral ischemia. Genetic manipulation of intrinsic antioxidants and factors in the signaling pathways has provided substantial understanding of the mechanisms involved in cell death/survival signaling pathways and the role of oxygen radicals in ischemic cerebral injury. Future studies of these pathways could provide novel therapeutic strategies in clinical stroke.

Glutathione and ascorbic acid enhance recovery of Guinea pig spinal cord white matter following ischemia and acrolein exposure

OBJECTIVE

We have shown that acrolein, a lipid peroxidation byproduct, can inflict significant damage in isolated spinal cord white matter following oxygen glucose deprivation (OGD). The mechanism of such acrolein-induced damage is unclear. The aim of this study was to examine whether glutathione (GSH) and ascorbic acid, two reactive oxygen species (ROS) scavengers, can alleviate functional and anatomical damage due to acrolein.

METHODS

We used an OGD injury model with isolated guinea pig spinal cord white matter. Sucrose gap recording was used to monitor axonal impulse conduction, and a horseradish peroxidase exclusion test was employed to determine membrane integrity. The functional and anatomical parameters were compared in three groups: acrolein, acrolein/GSH and acrolein/ascorbic acid.

RESULTS

We found that while GSH resulted in an 87% recovery of compound action potential conductance, ascorbic acid produced a 97% recovery, compared with a 69% recovery in an injured group without treatment. It is noted that GSH, and to a lesser extent ascorbic acid, preferentially enhanced functional recovery in smaller axons.

CONCLUSION

Acrolein-induced neuronal damage is likely mediated by ROS. Furthermore, GSH and ascorbic acid are effective in suppressing acrolein and free radical-induced injury in spinal cord white matter.

Overexpression of copper/zinc superoxide dismutase decreases ischemia-like astrocyte injury

Overexpression of copper/zinc superoxide dismutase (SOD1) in transgenic mice protects from transient focal cerebral ischemia in adult animals, but increases oxidative injury in perinatal mice. The effect of SOD1 overexpression on astrocytes subjected to ischemia-like insults has not yet been determined. Overexpression of human SOD1 in astrocytes resulted in a 3-fold increase in SOD1 activity without coupled up-regulation of catalase or glutathione peroxidase activities. Cells subjected to oxygen-glucose deprivation (OGD) or glucose deprivation to mimic ischemic injury were protected by SOD1 overexpression. OGD injury was reduced 47.6+/-9.3%, assessed by release of lactate dehydrogenase. OGD also caused a significant increase in catalase activity which was moderated by SOD1 overexpression. The level of glutathione in astrocytes overexpressing SOD1 was maintained at higher levels following 5 h OGD compared to control cultures under the same conditions. Reduction of glutathione prior to OGD significantly increased cell death of SOD1-overexpressing astrocytes as well as controls, but SOD1 still provided significant protection, suggesting that both GSH-dependent scavenging and GSH-independent scavenging are relevant to SOD1 protection in astrocytes.

CD40/CD40 Ligand Signaling in Mouse Cerebral Microvasculature After Focal Ischemia/Reperfusion

BACKGROUND

CD40/CD40 ligand (CD40L) signaling contributes to proinflammatory and prothrombogenic responses in the vasculature. CD40/CD40L expression is elevated in patients after a transient ischemic attack or stroke. The purpose of this study was to investigate the role of CD40/CD40L signaling in cerebral microvascular dysfunction and tissue injury response to middle cerebral artery occlusion (MCAO) and reperfusion.

METHODS AND RESULTS

Intravital fluorescence microscopy was used to visualize the cerebral microcirculation of wild-type (WT), CD40-deficient, and CD40L-deficient mice subjected to 1-hour MCAO and 4-hour reperfusion. The adhesion of platelets and of leukocytes and vascular permeability were measured in postcapillary venules after 4-hour and 1-hour reperfusions, respectively. Cerebral infarct volume was analyzed 24 hours after reperfusion. Platelet and leukocyte adhesion was elevated and blood/brain barrier function was compromised by MCAO in WT mice. Blood cell recruitment and increased permeability were blunted in both CD40-deficient and CD40L-deficient mice. Infarct volume was also reduced in CD40- and CD40L-deficient mice compared with WT mice.

CONCLUSIONS

Our findings indicate that CD40/CD40L signaling contributes to inflammatory and prothrombogenic responses and brain infarction induced by MCAO and reperfusion. The CD40/CD40L dyad may play a significant pathogenic role in the acute phase of ischemic stroke.

Developmental lag in superoxide dismutases relative to other antioxidant enzymes in premyelinated human telencephalic white matter

Periventricular leukomalacia (PVL) involves free radical injury to developing oligodendrocytes (OLs), resulting from ischemia/reperfusion, particularly between 24 and 32 gestational weeks. Using immunocytochemistry and Western blots, we tested the hypothesis that this vulnerability to free radical toxicity results, in part, from developmental lack of superoxide dismutases (SOD)-1 and -2, catalase, and glutathione peroxidase (GPx) in the telencephalic white matter of the human fetus. During the period of greatest PVL risk and through term (> or = 37 weeks), expression of both SODs (for conversion of O2- to H2O2) significantly lagged behind that of catalase and GPx (for breakdown of H2O2), which, in contrast, superseded adult levels by 30 gestational weeks. Our data indicate that a developmental "mismatch" in the sequential antioxidant enzyme cascade likely contributes to the vulnerability to free radical toxicity of the immature cerebral white matter, which is "unprepared" for the transition from a hypoxic intrauterine to an oxygen-rich postnatal environment. All enzymes, localized to astrocytes and OLs, had higher-than-adult expression at 2 to 5 postnatal months (peak of myelin sheath synthesis), suggesting an adaptive mechanism to protect against lipid peroxidation during myelin sheath (lipid) synthesis. The previously unrecognized dissociation between the expression of the SODs and that of catalase and GPx in the fetal period has potential implications for future antioxidant therapy in PVL.

Environmental, pharmacological, and genetic modulation of the HD phenotype in transgenic mice

The HD-N171-82Q (line 81) mouse model of Huntington's disease (HD), expresses an N-terminal fragment of mutant huntingtin (htt), loses motor function, displays HD-related pathological features, and dies prematurely. In the present study, we compare the efficacy with which environmental, pharmacological, and genetic interventions ameliorate these abnormalities. As previously reported for the R6/2 mouse model of HD, housing mice in enriched environments improved the motor skills of N171-82Q mice. However, life expectancy was not prolonged. Significant improvements in motor function, without prolonging survival, were also observed in N171-82Q mice treated with Coenzyme Q10 (CoQ10, an energy metabolism enhancer). Several compounds were not effective in either improving motor skills or prolonging life, including Remacemide (a glutamate antagonist), Celecoxib (a COX-2 inhibitor), and Chlorpromazine (a prion inhibitor); Celecoxib dramatically shortened life expectancy. We also tested whether raising cellular antioxidant capacity by co-expressing high levels of wild-type human Cu/Zn superoxide dismutase 1 (SOD1) was beneficial. However, no improvement in motor performance or life expectancy was observed. Although we would argue that positive outcomes in mice carry far greater weight than negative outcomes, we suggest that caution may be warranted in testing Celecoxib in HD patients. The positive outcomes achieved by CoQ10 therapy and environmental stimuli point toward two potentially therapeutic approaches that should be readily accessible to HD patients and at-risk family members.

Gene-environment interplay in neurogenesis and neurodegeneration

Factors associated with predisposition and vulnerability to neurodegenerative disorders may be described usefully within the context of gene-environment interplay. There are many identified genetic determinants for so-called genetic disorders, and it is possible to duplicate many elements of recognized human neurodegenerative disorders in either knock-in or knock-out mice. However, there are similarly, many identifiable environmental influences on outcomes of the genetic defects; and the course of a progressive neurodegenerative disorder can be greatly modified by environmental elements. Constituent cellular defense mechanisms responsive to the challenge of increased reactive oxygen species represent only one crossroad whereby environment can influence genetic predisposition. In this paper we highlight some of the major neurodegenerative disorders and discuss possible links of gene-environment interplay. The process of adult neurogenesis in brain is also presented as an additional element that influences gene-environment interplay. And the so-called priming processes (i.e., production of receptor supersensitization by repeated drug dosing), is introduced as yet another process that influences how genes and environment ultimately and co-dependently govern behavioral ontogeny and outcome. In studies attributing the influence of genetic alteration on behavioral phenotypy, it is essential to carefully control environmental influences.

Neuronal death/survival signaling pathways in cerebral ischemia

Cumulative evidence suggests that apoptosis plays a pivotal role in cell death in vitro after hypoxia. Apoptotic cell death pathways have also been implicated in ischemic cerebral injury in in vivo ischemia models. Experimental ischemia and reperfusion models, such as transient focal/global ischemia in rodents, have been thoroughly studied and the numerous reports suggest the involvement of cell survival/death signaling pathways in the pathogenesis of apoptotic cell death in ischemic lesions. In these models, reoxygenation during reperfusion provides a substrate for numerous enzymatic oxidation reactions. Oxygen radicals damage cellular lipids, proteins and nucleic acids, and initiate cell signaling pathways after cerebral ischemia. Genetic manipulation of intrinsic antioxidants and factors in the signaling pathways has provided substantial understanding of the mechanisms involved in cell death/survival signaling pathways and the role of oxygen radicals in ischemic cerebral injury. Future studies of these pathways may provide novel therapeutic strategies in clinical stroke.

Reactive oxygen radicals and pathogenesis of neuronal death after cerebral ischemia

Reactive oxygen species have been implicated in brain injury after cerebral ischemia. These oxidants can damage proteins, lipids, and DNA, and lead to cell injury and necrosis. Oxidants are also initiators in intracellular cell death signaling pathways that may lead to apoptosis. The possible targets of this redox signaling include mitochondria, death membrane receptors, and DNA repair enzymes. Genetic manipulation of intrinsic antioxidants and the factors in the signaling pathways has provided substantial progress in understanding the mechanisms in cell death signaling pathways and involvement of oxygen radicals in ischemic brain injury. Future studies of these pathways may provide novel therapeutic strategies in clinical stroke.

Attenuated induction of heme oxygenase after intrathecal exposure to lysed blood in mice overexpressing superoxide dismutase

Induction of heme oxygenase-1 (HO-1) in the spinal cord was studied in adult wildtype and transgenic mice overexpressing the antioxidant copper, zinc superoxide dismutase (CuZn SOD) 24 h after intrathecal infusion of heterologous lysed blood. Double immunolabeling techniques were used to determine the extent to which HO-1 was induced in astrocytes and microglia/macrophages. HO-1 was induced in both astrocytes and microglia/macrophages in the dorsal horns near the site of infusion of lysed blood in all mice. However, the number of HO-1 labeled cells was significantly less in the transgenic as compared to the wildtype animals. Together, these findings suggest that lysed blood preferentially induces HO-1 in glia and macrophages through the generation of oxidative stress.

Mice lacking glutathione peroxidase-1 activity show increased TUNEL staining and an accelerated inflammatory response in brain following a cold-induced injury

The mechanisms leading to neurodegeneration are complex and multifactorial. Oxidative stress has been identified as an important constituent in this process and the use of transgenic and knockout mice has allowed the role of key components of the antioxidant pathway to be evaluated. In this study, we have used mice lacking the glutathione peroxidase-1 gene in order to determine the consequences of a reduced capacity to neutralize hydrogen peroxide toward the pathological outcomes following cold-induced brain injury. Analysis of brain cryosections using TUNEL staining revealed a significant increase in brain cell death in knockout mice compared to that seen in wild-type mice. Interestingly, cell death appeared to be uncoupled to a neuro-inflammatory response which was observed in both knockout and wild-type mice but which proceeded in an accelerated manner in glutathione peroxidase-1 knockout mice at 24 h, rapidly diminishing by 96 h postinjury. Our data suggest an important role for glutathione peroxidase-1 in modulating molecular pathways involved in both the level of cell death and inflammatory cascades in brain through its antioxidant capacity in regulating levels of oxygen species such as hydrogen peroxide.

Transgenic mice expressing human copper-zinc superoxide dismutase exhibit attenuated apparent diffusion coefficient reduction during reperfusion following focal cerebral ischemia

Since ADC reduction reflects intracellular edema which is an early indicator of ischemic cellular metabolic stress, we hypothesized that a decrease in ADC as determined by diffusion weighted MR imaging could be attenuated by SOD expression in transgenic mice during reperfusion following focal cerebral ischemia. Diffusion weighted imaging (DWI) was performed to evaluate apparent diffusion coefficient (ADC) reduction by constructing ADC maps with a color scale to localize ADC change in transgenic (Tg) mice expressing human CuZn superoxide dismutase (SOD) and wild type (Wt) mice during 1 h middle cerebral artery occlusion (MCAO) and 1 h reperfusion. Heat shock protein (hsp) 70-kDa mRNA analysis was evaluated as a marker of sublethal cell stress by in situ hybridization after 4 h reperfusion for comparison with Nissl staining of adjacent sections to assess infarction. Sequential ADC maps were prepared in Tg mice with sufficient temporal and spatial resolution to permit comparison with Wt mice. Tg mice showed substantial recovery of the ADC lesion after reperfusion, while Wt mice showed no recovery. There was no difference between Tg and Wt mice in the size or distribution of the ADC lesion during ischemia. The area with strong expression of hsp70 mRNA in the ischemic hemisphere was substantially larger in the Tg mice. Nissl staining showed less damage of brain tissue in Tg mice than Wt mice especially in the cortex after 4 h reperfusion following 1 h MCAO. Results demonstrate that antioxidant effects of human CuZn-SOD reduce cellular edema due to oxidative stress during reperfusion but not during ischemia after 1 h MCAO. Hsp70 could be one of the proteins that mediates protection by SOD against oxidative stress.

MRI evaluation and functional assessment of brain injury after hypoxic ischemia in neonatal mice

BACKGROUND AND PURPOSE

Severe perinatal asphyxia is an important cause of brain injury in the newborn infant. We examined early events after hypoxic ischemia (HI) in the 7-day-old mouse brain by MRI and related them to long-term functional effects and histopathology in the same animals at 4 to 5 weeks of age.

METHODS

HI was induced in 7-day-old CD1 mice by exposure to 8% oxygen for 30 minutes after occlusion of the left common carotid artery. The resulting unilateral focal lesion was evaluated in vivo by MRI (T2 maps and apparent diffusion coefficient maps) at 3, 6, and 24 hours and 5 days after hypoxia. Locomotion and sensorimotor function were analyzed after 3 weeks. Four weeks after HI, the mice were killed, and cresyl violet-stained brain sections were examined morphologically.

RESULTS

A decrease in apparent diffusion coefficient values in cortex on the affected side was found at 3 hours after HI. T2 values were significantly increased after 6 hours and remained so for 5 days. Maximal size of the lesion was attained at 3 to 6 hours after HI and declined thereafter. Animals with MRI-detected lesions had decreased forward locomotion, performed worse than controls in the beam-walking test, and showed a unilateral hypotrophy in the cresyl violet-stained brain sections 4 weeks later.

CONCLUSIONS

The temporal progression of the damage after HI in 7-day-old mice differs from that of the adult brain as judged by MRI. The early lesions detected by MRI were related to functional impairments for these mice in near-adult life.

Ischaemic brain oedema

Ischaemic brain oedema appears to involve two distinct processes, the relative contribution and time course of which depend on the duration and severity of ischaemia, and the presence of reperfusion. The first process involves an increase in tissue Na+ and water content accompanying increased pinocytosis and Na+, K+ ATPase activity across the endothelium. This is apparent during the early phase of infarction and before any structural damage is evident. This phenomenon is augmented by reperfusion. A second process results from a more indiscriminate and delayed BBB breakdown that is associated with infarction of both the parenchyma and the vasculature itself. Although, tissue Na+ level still seems to be the major osmotic force for oedema formation at this second stage, the extravasation of serum proteases is an additional potentially deleterious factor. The relative importance of protease action is not yet clear, however, degradation of the extracellular matrix conceivably leads to further BBB disruption and softening of the tissue, setting the stage for the most pronounced forms of brain swelling. A number of factors mediate or modulate ischaemic oedema formation, however, most current information comes from experimental models, and clinical data on this microcosmic level is lacking. Clinically significant brain oedema develops in a delayed fashion after large hemispheric strokes and is a cause of substantial mortality. Neurological signs appear to be at least as good as direct ICP measurement and neuroimaging in detecting and gauging the secondary damage produced by stroke oedema. The neuroimaging characteristics of the stroke, specifically the early involvement of greater than half of the MCA territory, are, however, highly predictive of the development of severe oedema over the subsequent hours and days. None of the available medical therapies provide substantial relief from the oedema and raised ICP, or at best, they are temporizing in most cases. Hemicraniectomy appears most promising as a method of avoiding death from brain compression, but the optimum timing and manner of patient selection are currently being investigated. All approaches to massive ischaemic brain swelling are clouded by the potential for survival with poor functional outcome. It is possible to manage blood pressure, serum osmolarity by way of selective fluid administration, and a number of other systemic factors that exaggerate brain oedema. Broad guidelines for treatment of stroke oedema can therefore be given at this time.

Protective effect of green tea extract on ischemia/reperfusion-induced brain injury in Mongolian gerbils

Free radical-induced oxidative damages of macromolecules and cell death are important factors in the pathogenesis of ischemia/reperfusion brain injury. In the present study, an investigation as to whether green tea extract reduces ischemia/reperfusion-induced brain injury in Mongolian gerbils was conducted. The effect of green tea on the ischemia/reperfusion-induced production of hydrogen peroxide, lipid peroxidation and oxidative DNA damage (formation of 8-hydroxydeoxyguanosine), and cell death in addition to locomotor activity was studied. Two doses (0.5 or 2%) of green tea extract were added into the drinking water and to be accessed by animals ad libitum for 3 weeks prior to the induction of ischemia. A global ischemia was induced by the bilateral occlusion of the common carotid arteries for 5 min. Reperfusion was achieved by releasing the occlusion and restoring blood circulation for 48 h. The infarction volumes were 112+/-31 mm(3) and 76+/-11 mm(3) in the 0.5 and 2% green tea pretreated animals compared to 189+/-12 mm(3) in the ischemia/reperfusion animals. Green tea extract also reduced the levels of ischemia/reperfusion-induced hydrogen peroxide (from 1470+/-170 to 1034+/-46 and 555+/-30 nmole/mg protein), lipid peroxidation products (from 1410+/-210 to 930+/-40 and 330+/-20 nmole/mg protein) and 8-oxodG (from 3.9+/-0.1 to 2.8+/-0.3 and1.9+/-0.3 ng/microg DNA, x10(-2)) by pretreatment of 0.5 or 2% green tea for 3 weeks, respectively. Moreover, green tea also reduced the number of ischemia/reperfusion-induced apoptotic cells (from 59+/-12 to 37+/-8, 15+/-11 apoptotic cells/high power field in the striatum region) and locomotor activity (from 15140+/-2940 to 3900+/-600 and 4100+/-1200). This study therefore suggests that green tea may be a useful agent for the prevention of cerebral ischemia damage.

Reactive oxygen radicals in signaling and damage in the ischemic brain

Reactive oxygen species have been implicated in brain injury after ischemic stroke. These oxidants can react and damage the cellular macromolecules by virtue of the reactivity that leads to cell injury and necrosis. Oxidants are also mediators in signaling involving mitochondria, DNA repair enzymes, and transcription factors that may lead to apoptosis after cerebral ischemia. Transgenic or knockout mice with cell- or site-specific prooxidant and antioxidant enzymes provide useful tools in dissecting the events involving oxidative stress in signaling and damage in ischemic brain injury.

Docosahexaenoic acid-deficient phosphatidyl serine and high alpha-tocopherol in a fetal mouse brain over-expressing Cu/Zn-superoxide dismutase

The over-expressed Cu/Zn-superoxide dismutase (Cu/Zn-SOD) gene has been found in some circumstances phenotypically deleterious and associated with oxidative injury-mediated aberrations while in other studies it was considered neuroprotective. In this work we examine a number of biochemical markers in fetal and adult brain from transgenic (tg) mice expressing the human Cu/Zn-SOD gene, which may determine this dual characteristic. These markers include the polyunsaturated fatty acid (PUFA) profile in discrete phospholipid species, the alpha-tocopherol levels, a marker for lipid anti-oxidant status, and thiobarbituric acid reactive substance (TBARS), a marker for the tissue oxidative status. The PUFA profile in choline- and ethanolamine-phosphoglycerides was similar in tg and nontransgenic (ntg) animals of either fetal or adult brain. Serine-phosphoglycerides, however, showed a marked decrease from 20. 07+/-0.53 to 14.92+/-0.87 wt% and 14.52+/-1.15 wt% in docosahexaenoic acid (DHA; 22:6 n3), in the tg 51 and tg 69 fetal brains, respectively, but not in the comparable adult tissues. The alpha-tocopherol levels were significantly higher in the fetal compared to the adult brain. There were no differences in the anti-oxidant levels between the ntg and tg fetal brains, but there were differences in the adult animals; the tg mice were higher by at least two-fold than the control animals. The basal TBARS in the tg 51 fetal brain was 35% lower than that of ntg mouse and in the presence of Fe(2+), brain slices from the former released less TBARS (57% reduction) into the medium than the latter. These results suggest that higher dosages of Cu/Zn-SOD gene are compatible with increased alpha-tocopherol levels, reduced basal TBARS levels and a DHA deficiency in the fetal, but not the adult, tg brain.

Intraluminal increase of superoxide anion following transient focal cerebral ischemia in rats

Using a modification of Karnovsky's Mn2+/diaminobenzizine (DAB) technique, we examined the production of superoxide anion (.O-2) in the vascular lumen following transient occlusion and reperfusion of the left middle cerebral artery (MCA) in Sprague-Dawley rats. The MCA was occluded for 2 h using an intraluminal suture method. Zero, 15, 30, and 60 min after reperfusion, animals were perfused transcardially with buffer containing Mn2+ and DAB, and brain samples were prepared for light and electron microscopic examination. The amber reaction deposits of.O-2 were observable to the naked eye along the major cerebral vessels of the ischemic hemisphere after each reperfusion period. Upon microscopic examination the deposits were revealed to be within arterial, capillary, and venular lumen. The amount of reaction deposits in the ischemic hemisphere corresponded to the duration of reperfusion. The formation of.O-2 was suppressed when the perfusate contained superoxide dismutase and when either Mn2+ or DAB was omitted, confirming that the reaction products produced are due to the enhanced production of.O-2. These results show that there is a progressive increase in intraluminal. O-2 during reperfusion following an ischemic insult which may participate in the aggravation of cerebral damage.

Role of superoxide dismutase in ischemic brain injury: a study using SOD-1 transgenic mice

1. Nitric oxide radicals (NO) play an important role in the pathophysiology of focal cerebral ischemia. 2. Vascular NO can reduce ischemic brain injury by increasing CBF, whereas neuronal NO may mediate neurotoxicity following brain ischemia, mainly by its reaction with superoxide to generate peroxynitrite. 3. These findings could contribute to a strategy for the treatment of cerebral ischemia.

Overexpression of SOD1 in transgenic rats protects vulnerable neurons against ischemic damage after global cerebral ischemia and reperfusion

Transient global cerebral ischemia resulting from cardiac arrest is known to cause selective death in vulnerable neurons, including hippocampal CA1 pyramidal neurons. It is postulated that oxygen radicals, superoxide in particular, are involved in cell death processes. To test this hypothesis, we first used in situ imaging of superoxide radical distribution by hydroethidine oxidation in vulnerable neurons. We then generated SOD1 transgenic (Tg) rats with a five-fold increase in copper zinc superoxide dismutase activity. The Tg rats and their non-Tg wild-type littermates were subjected to 10 min of global ischemia followed by 1 and 3 d of reperfusion. Neuronal damage, as assessed by cresyl violet staining and DNA fragmentation analysis, was significantly reduced in the hippocampal CA1 region, cortex, striatum, and thalamus in SOD1 Tg rats at 3 d, as compared with the non-Tg littermates. There were no changes in the hippocampal CA3 subregion and dentate gyrus, resistant areas in both SOD1 Tg and non-Tg rats. Quantitative analysis of the damaged CA1 subregion showed marked neuroprotection against transient global cerebral ischemia in SOD1 Tg rats. These results suggest that superoxide radicals play a role in the delayed ischemic death of hippocampal CA1 neurons. Our data also indicate that SOD1 Tg rats are useful tools for studying the role of oxygen radicals in the pathogenesis of neuronal death after transient global cerebral ischemia.

Effect of aluminum on superoxide dismutase activity in the adult rat brain

Male rats were treated daily with an intraperitoneal injection of 15 mg aluminum (Al chloride)/kg body weight for 17 d, in order to study the effects on superoxide dismutase (SOD) activities in the brain (cortex). No significant difference between control and treated animals was registered in the Cu/Zn and Mn SOD activities in the gray matter of the cortex. High Al levels were found in the plasma, the spleen, and the liver of the treated animals in comparison to the controls, but not in the cortex homogenates (gray matter). In addition, Al induced a significant decrease in food ingestion and weight gain.

Transient global ischemia triggers expression of the DNA damage-inducible gene GADD45 in the rat brain

Using in situ hybridization, Northern blot analysis, Western blot analysis, and immunocytochemistry, mRNA and protein expression of the novel DNA damage-inducible gene GADD45 was examined in the rat brain at 0.5, 2, 4, 8, 16, 24, 48, and 72 hours after 15 minutes of transient global ischemia. Transient ischemia produced by the four-vessel occlusion method resulted in DNA double-strand breaks and delayed neuronal cell death in vulnerable neurons of the hippocampal CA1 sector, the hilus, dorsal caudate-putamen, and thalamus, as shown by in situ DNA nick end-labeling and histologic staining. GADD45 mRNA was transiently increased in less-vulnerable regions such as the parietal cortex (up to 8 hours after ischemia) and dentate granule cells (up to 24 hours after ischemia) but was persistently increased in vulnerable neurons such as CA1 pyramidal neurons (up to 48 hours). GADD45 immunoreactivity was increased in both vulnerable and less-vulnerable regions at earlier reperfusion periods (4 to 16 hours), but thereafter immunoreactivity was decreased below control levels in most vulnerable regions before delayed cell death and DNA double-strand breaks. At 72 hours after transient ischemia, a moderate increase in GADD45 immunoreactivity was still detectable in some CA3 neurons and in a few surviving neurons in the CA1 region. Double staining performed at 16 to 72 hours after ischemia revealed that GADD45 immunoreactivity was persistently increased in neurons that did not develop DNA damage. Because GADD45 protein may participate in the DNA excision repair process and because it has been shown that this protein is also overexpressed in neurons that survive focal ischemia and kainate-induced epileptic seizures, the results reported here support the hypothesis that GADD45 could have a protective role in neuronal injury.

Human ether-a-gogo related gene (HERG) K+ channels as pharmacological targets: present and future implications

Electrophysiological and molecular biology techniques have widely expanded our knowledge of the diverse functions where K+ channels are implicated as potential and proven pharmacological targets. The aim of the present commentary is to review the recent progress in the understanding of the functional role of the K+ channels encoded by the human ether-a-gogo related gene (HERG), with particular emphasis on their direct pharmacological modulation by drugs, or on their regulation by pharmacologically relevant phenomena. About 3 years have passed since the cloning, expression, and description of the pathophysiological role of HERG K+ channels in human cardiac repolarization. Despite this short lapse of time, these K+ channels have already gained considerable attention as pharmacological targets. In fact, interference with HERG K+ channels seems to be the main mechanism explaining both the therapeutic actions of the class III antiarrhythmics and the potential cardiotoxicity of second-generation H1 receptor antagonists such as terfenadine and astemizole, as well as of psychotropic drugs such as some antidepressants and neuroleptics. It seems possible to anticipate that the main tasks for future investigation will be, on the one side, the better understanding of the intimate mechanism of action of HERG K+ channel-blocking drugs in order to elucidate the conditions regulating the delicate balance between antiarrhythmic and proarrhythmic potential and, on the other, to unravel the pathophysiological role of this K+ channel in the function of the brain and of other excitable tissues.

The effect of nitric oxide inhibition on ischemic brain edema

The involvement of nitric oxide (NO) in the development of ischemic cytotoxic edema was investigated by inhibiting nitric oxide synthase (NOS) activity with N omega-nitro-L-arginine (NLA). Bilateral carotid artery occlusion (15 min) alone or with release (15 and 60 min) served as a model for edema induction. NLA, N omega-nitro-D-arginine methyl ester (D-NAME) or Ringer's solution were administered 4 hr prior to ischemia or sham operation. Treatment with a stable nitroxide radical, 4-hydroxy-2,2, 6,6-tetramethylpiperidine-L-oxyl (TPL), was used to assess free radical involvement in edema. Accumulation of tissue water was evaluated by measuring specific gravity (SG) of brain cortex and histological examination. There was a greater reduction of cortical SG in early reperfusion (15 min) and a lesser decrease in SG (60 min later) in NLA-than in D-NAME- or Ringer's-treated gerbils. The NLA effect was confirmed by histological examination of the brain tissue. TPL treatment (pre- and postischemic) ameliorated the formation of edema to the same degree as NLA. The findings indicate a biphasic NLA modulation of cytotoxic edema most likely mediated through absence or presence of NO-derived free radicals.

(-)-Deprenyl attenuates spinal motor neuron degeneration and associated locomotor deficits in rats subjected to spinal cord ischemia

We have evaluated potential neuroprotection offered by (-)-deprenyl on degenerating motor neurons of the spinal cord when subjected to transient ischemia. Thirty-six healthy adult male Wistar rats were trained for a motor function test in a staircase maze and randomly but equally (n = 6) grouped into normal control, sham control, ischemia (IS), IS rats treated with vehicle (IV), and rats treated with low (0.1 mg/kg) and high (1.0 mg/kg) doses of (-)-deprenyl. (-)-Deprenyl was given intraperitoneally 30 min after the induction of ischemia and thereafter everyday for 14 days. Spinal cord ischemia was produced at the lumbar level in conscious rats by occluding the abdominal aorta just below the branching point of the left renal artery for 30 min. Analysis of the motor performance in all groups of rats revealed a significant (P < 0.001) increase in the time taken to cross the run way of the maze, in i.s. and i.v. rats compared to all other groups of rats. In addition, qualitative and quantitative examination of spinal motor neurons at the lumbar level showed a significant (P < 0.001) decrease in the number of healthy motor neurons in i.s. and i.v. rats compared to controls. Postischemic administration of (-)-deprenyl, at both doses, significantly prevented motor neuron degeneration and the associated locomotor deficits in IS rats.

Superoxide dismutase activity in serum of patients with acute cerebral ischemic injury. Correlation with clinical course and infarct size

BACKGROUND AND PURPOSE

Superoxide dismutase (SOD) is one of the major free radical scavenging systems that might play a role in both degenerative and acute diseases of the central nervous system.

METHODS

We measured SOD activity in the serum of 41 patients with acute ischemic stroke with a chemiluminometric assay based on the generation of oxygen free radicals by xanthine and xanthine oxidase.

RESULTS

SOD activity was significantly lower in patients with ischemic stroke than in age-matched control patients with nonvascular, neurological illnesses (n = 24; P < .034, Wilcoxon rank test). The activity was inversely correlated with the size of infarction on CT (P = .01, Spearman correlation) and the severity of neurological deficits (P < .001, Spearman correlation). The decreased SOD activity recovered within 5 days after stroke to values found in serum of control patients.

CONCLUSIONS

Our data suggest that the SOD activity in serum is reduced in stroke patients, and replacement of antioxidative activity could be beneficial in the acute treatment of cerebral ischemia.

Regulation of the human ether-a-gogo related gene (HERG) K+ channels by reactive oxygen species

Human ether-a-gogo related gene (HERG) K+ channels are key elements in the control of cell excitability in both the cardiovascular and the central nervous systems. For this reason, the possible modulation by reactive oxygen species (ROS) of HERG and other cloned K+ channels expressed in Xenopus oocytes has been explored in the present study. Exposure of Xenopus oocytes to an extracellular solution containing FeSO4 (25-100 microM) and ascorbic acid (50-200 microM) (Fe/Asc) increased both malondialdehyde content and 2',7'-dichlorofluorescin fluorescence, two indexes of ROS production. Oocyte perfusion with Fe/Asc caused a 50% increase of the outward K+ currents carried by HERG channels, whereas inward currents were not modified. This ROS-induced increase in HERG outward K+ currents was due to a depolarizing shift of the voltage-dependence of channel inactivation, with no change in channel activation. No effect of Fe/Asc was observed on the expressed K+ currents carried by other K+ channels such as bEAG, rDRK1, and mIRK1. Fe/Asc-induced stimulation of HERG outward currents was completely prevented by perfusion of the oocytes with a ROS scavenger mixture (containing 1,000 units/ml catalase, 200 ng/ml superoxide dismutase, and 2 mM mannitol). Furthermore, the scavenger mixture also was able to reduce HERG outward currents in resting conditions by 30%, an effect mimicked by catalase alone. In conclusion, the present results seem to suggest that changes in ROS production can specifically influence K+ currents carried by the HERG channels.

ARL 17477, a potent and selective neuronal NOS inhibitor decreases infarct volume after transient middle cerebral artery occlusion in rats

We tested the effects of administration of a selective neuronal nitric oxide synthase (nNOS) inhibitor, ARL 17477, on ischemic cell damage and regional cerebral blood flow (rCBF), in rats subjected to transient (2 h) middle cerebral artery (MCA) occlusion and 166 h of reperfusion (n = 48) and in rats without MCA occlusion (n = 25), respectively. Animals were administered ARL 17477 (i.v.): 10 mg/kg; 1 mg/kg; 3mg/kg; N-nitro-L-arginine (L-NA) 10 mg/kg L-NA 1 mg/kg; and Vehicle. Administration of ARL 17477 1 mg/kg, 3 mg/kg and 10 mg/kg reduced ischemic infarct volume by 53 (p < 0.05), 23, and 6.5%, respectively. L-NA 1 mg/kg and 10 mg/kg increased infarct volume by 2 and 15%, respectively (p > 0.05). Administration of ARL 17477 (10 mg/kg) significantly (p < 0.05) decreased rCBF by 27 +/- 5.3 and 24 +/- 14.08% and cortical NOS activity by 86 +/- 14.9 and 91 +/- 8.9% at 10 min or 3 h, respectively, and did not alter mean arterial blood pressure (MABP). L-NA (10 mg/kg) significantly reduced rCBF by 23 +/- 9.8% and NOS activity by 81 +/- 7% and significantly (p < 0.05) increased MABP. Treatment with 3 mg/kg and 1 mg/kg ARL 17477 reduced rCBF by only 2.4 +/- 4.5 and 0%, respectively, even when NOS activity was reduced by 63 +/- 13.4 and 45 +/- 15.7% at 3 h, respectively, (p < 0.05). The data demonstrate that ARL 17477 inhibits nNOS in the rat brain and causes a dose-dependent reduction in infarct volume after transient MCA occlusion.

Role of oxidants in ischemic brain damage

BACKGROUND AND PURPOSE

Oxygen free radicals or oxidants have been proposed to be involved in acute central nervous system injury that is produced by cerebral ischemia and reperfusion. Because of the transient nature of oxygen radicals and the technical difficulties inherent in accurately measuring their levels in the brain, experimental strategies have been focused on the use of pharmacological agents and antioxidants to seek a correlation between the exogenously supplied specific radical scavengers (ie, superoxide dismutase and catalase) and the subsequent protection of cerebral tissues from ischemic injury. However, this strategy entails problems (hemodynamic, pharmacokinetic, toxicity, blood-brain barrier permeability, etc) that may cloud the data interpretation. This mini-review will focus on the oxidant mechanisms in cerebral ischemic brain injury by using transgenic and knockout mice as an alternative approach.

METHODS

Transgenic and knockout mutants that either overexpress or are deficient in antioxidant enzyme/protein levels have been successfully produced. The availability of these genetically modified animals has made it possible to investigate the role of certain oxidants in ischemic brain cell damage in molecular fashion.

RESULTS

It has been shown that an increased level of CuZn-superoxide dismutase and antiapoptotic protein Bcl-2 in the brains of transgenic mice protects neurons from ischemic/reperfusion injury, whereas a deficiency in CuZn-superoxide dismutase or mitochondrial Mn-superoxide dismutase exacerbates ischemic brain damage. Target disruption of neuronal nitric oxide synthase in mice also provides neuronal protection against permanent and transient focal cerebral ischemia.

CONCLUSIONS

I conclude that molecular genetic approaches in modifying antioxidant levels in the brain offer a unique tool for understanding the role of oxidants in ischemic brain damage.

Differential abundance of superoxide dismutase in interneurons versus projection neurons and in matrix versus striosome neurons in monkey striatum

To investigate whether differences in vulnerability to free radicals might underlie differences among striatal neurons in their vulnerability to neurodegenerative processes such as occur in ischemia and Huntington's disease, we have analyzed the localization of superoxide free radical scavengers in different striatal neuron types in normal rhesus monkey. Single- and double-label immunohistochemical experiments were carried out using antibodies against the enzymes copper, zinc superoxide dismutase (SOD1), or manganese superoxide dismutase (SOD2), and against markers of various striatal cell types. Our results indicate that the striatal cholinergic and parvalbumin interneurons are enriched in SOD1 and/or SOD2, whereas striatal projection neurons and neuropeptide Y/somatostatin (NPY+/SS+) interneurons express only low levels of both SOD1 and SOD2. We also found that projection neurons of the matrix compartment express significantly higher levels of SOD than those in the striosome compartment. Since projection neurons have been reported to be more vulnerable than interneurons and striosome neurons more vulnerable than matrix neurons to neurodegenerative processes, our results are consistent with the notion that superoxide free radicals are at least partly involved in producing the differential neuron loss observed in the striatum following global brain ischemia or in Huntington's disease.

Brain injury after perinatal hypoxia-ischemia is exacerbated in copper/zinc superoxide dismutase transgenic mice

The role of superoxide radical formation in the pathogenesis of perinatal hypoxic-ischemic injury was examined using transgenic (Tg) mice expressing three times normal amounts of copper/zinc-superoxide dismutase (CuZn/SOD). Fourteen litters of postnatal d 7 strain 218/3 mice were subjected to right common carotid artery ligation followed by 90 min of hypoxia in an 8% oxygen/humidified chamber maintained at 37 degrees C. Both Tg mice (n = 32) and their nontransgenic (nTg) littermates (n = 30) survived the injury equally. Evaluation of infarcted brain areas measured by video image analysis of three coronal brain sections through the anterior hippocampus from each animal revealed that the Tg animals suffered brain infarction more frequently than did nTg mice. Blinded histologic scoring of cerebral cortex and striatum 5 d after injury revealed that Tg mice were more likely to have higher histologic severity scores than their nTg littermates (p = 0.0463, Mann-Whitney U test). These findings suggest that brain injury in perinatal hypoxia-ischemia may be mediated in part by free radical formation from excessive hydrogen peroxide or nitric oxide production.

Transgenic mice and knockout mutants in the study of oxidative stress in brain injury

A rapid increase in the need to explore the molecular basis of cellular function and injury in the central nervous system has led neuroscientists to employ transgenic mouse technology. The successful making of transgenic mice (Tg) overexpressing human CuZn-superoxide dismutase (SOD-1) activity has made it possible to investigate the role of oxygen free radicals in ischemic and traumatic brain injury in a molecular fashion. It has been demonstrated that the 3-fold increase in SOD-1 transgene activity in SOD-1 Tg mice offers protection against cerebral ischemia and reperfusion in two different models of focal cerebral ischemia, as compared to nontransgenic wild-type littermates. Studies involving traumatic brain injury have also demonstrated that acute injuries, including brain edema and blood-brain barrier permeability, are significantly reduced in SOD-1 Tg mice. Furthermore, chronic neurological deficits, such as beam walking, beam balance, and body weight, are significantly improved in these transgenic animals following traumatic brain injury. In addition to the SOD-1 Tg mice being a useful tool for the study of CNS injury, targeted disruption of the mouse gene for mitochondrial manganese SOD (SOD-2) has been successful. These SOD-2 knockout mutant mice, in addition to the recently developed knockout mutants of neuronal nitric oxide synthase (NOS), are believed to offer a unique opportunity to elucidate the oxidative mechanisms in brain injury following stroke and trauma.

Survival of neurons containing the enzyme nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase in static slice cultures of adult rat striatum

The present study concerns the survival potential of mature neurons containing the enzyme nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase in the static slice culture of adult rat striatum. In the striatal tissues immediately after slicing, there was a scattered distribution of NADPH-diaphorase neurons stained in a Golgi-like manner, and the cell density of those neurons was 53 +/- 5 (mean +/- SEM; n = 10) cells per mm2. The time-sequential cell density analysis disclosed that the number of striatal NADPH-diaphorase neurons surviving after 1, 2, 4 and 6 day in culture were 26 +/- 5, 8 +/- 2, 5 +/- 2, and 3 +/- 2 (means +/- SEM; n = 10) cells per mm2, respectively. Thus, approximately 50% of striatal NADPH-diaphorase neurons survived for 1 day and a significant proportion of these neurons, although their number gradually decreased, were maintained in culture for at least several days. The conspicuous survival of the striatal NADPH-diaphorase neurons in slice culture is thought to reflect the damage-resistant natures of these cells.

Induction of DNA fragmentation after 10 to 120 minutes of focal cerebral ischemia in rats

BACKGROUND AND PURPOSE

The induction of neuronal necrosis has been studied after various durations of transient middle cerebral artery (MCA) occlusion in the rat. The objective of the present study was to measure the numbers and anatomic distribution of cells exhibiting apoptotic bodies as an indication of DNA fragmentation and apoptotic cell death as a function of duration of transient MCA occlusion in the rat.

METHODS

The MCA of male Wistar rats (n = 24) was occluded for 10, 20, 30, 60, 90, and 120 minutes (n = 4 per group) with the use of an intraluminal monofilament, and reperfusion was instituted for 48 hours. DNA fragmentation was measured in paraffin sections with the use of a terminal deoxynucleotidyl-transferase (TdT)-mediated dUTP-biotin nick end-labeling (TUNEL) method. Adjacent sections were stained with hematoxylin and eosin for analysis of ischemic cell damage, and immunohistochemical double staining methods were used for cell identification. Sham-operated rats (n = 4) and normal rats not subjected to any surgical procedure (n = 4) were used as controls for apoptosis detection.

RESULTS

Within 5-microns-thick coronal sections, DNA fragmentation was present in 0 to 3 apoptotic cells in each hemisphere of normal, sham-operated rats as well as in the contralateral hemisphere of ischemic rats. After 10 to 20 minutes of MCA occlusion, apoptotic cells exhibiting DNA fragmentation (10 to 20) increased in the regions of selective neuronal necrosis in the preoptic area and in the striatum. After 30 to 60 minutes of ischemia, scattered apoptotic cells (30 to 60) exhibited DNA fragmentation and expanded into areas of selective neuronal necrosis in the cortex. After 90 to 120 minutes of occlusion, groups of apoptotic cells (70 to 200, > 95% neurons) were primarily localized to the inner boundary zone of the infarct.

CONCLUSIONS

A range of mild to severe ischemia-reperfusion stimuli induce internucleosomal DNA cleavage. The presence and anatomic location of apoptotic cells exhibiting DNA fragmentation after transient cerebral occlusion indicate that apoptosis accompanies neuronal necrosis.

Immunohistochemical localization of superoxide dismutase in the hippocampus following ischemia in a gerbil model of ischemic tolerance

Pretreatment of the gerbil brain with a 2-min period of sublethal ischemia protects against neuronal damage following a subsequent 3-min period of ischemia, which normally destroys pyramidal neurons in the CA1 region of the hippocampus. To clarify the role of superoxide dismutase (SOD) in this ischemic tolerance, we immunohistochemically investigated the alterations in copper-zinc SOD (CuZnSOD) and manganese SOD (Mn-SOD) in the gerbil hippocampus following 3-min ischemia with or without the first mild ischemia. Normal hippocampus showed an intense CuZnSOD immunostaining in pyramidal neurons but relatively less MnSOD immunostaining. MnSOD, but not CuZnSOD, immunoreactivity increased after the first ischemia. Both CuZnSOD and MnSOD immunoreactivities decreased throughout the hippocampus 4 h after 3 min of ischemia both with and without the first ischemia. The immunostaining recovered in resistant regions (CA3 and dentate gyrus) after 1 day in both groups and in the pretreated CA1 after 2 days. Without pretreatment, however, the immunostaining never recovered in the vulnerable CA1 region. The results suggest that ischemic tolerance is induced in part by enhanced synthesis of MnSOD in the tolerance-acquired hippocampus. Both CuZnSOD and MnSOD immunoreactivities decreased after the second ischemia even in the pretreated hippocampus in the early reperfusion periods, but ischemic tolerance facilitated the recovery from the postischemic reductions in SOD immunoreactivity.

Induction of CL100 protein tyrosine phosphatase following transient forebrain ischemia in the rat brain

Protein tyrosine phosphorylation is thought to play an important role in the regulation of neural function. To elucidate the role that protein tyrosine phosphatases (PTPs) may play in the postischemic brain, PTPs expressed in regions of the rat brain vulnerable to transient forebrain ischemia were examined. With the reverse-transcriptase polymerase chain reaction using degenerate primers, three PTPs, STEP, PTP delta, and SH-PTP2, were identified. They were expressed in the hippocampus 12 h after transient ischemia for 20 min. During the reperfusion period, the mRNA levels of these PTPs were not different from those in sham-operated rats. In contrast, a fourfold increase in the mRNA level of CL100 (3CH134), a PTP that is inducible by oxidative stress, was detected by Northern blotting in the hippocampus and cerebral cortex 1 h after the onset of reperfusion. In situ hybridization histochemistry showed a slight increase in the level of CL100 mRNA in neuronal cells in the hippocampus and cortex of postischemic rats compared to control rats. These findings suggest that PTPs play a role in the normal function of the hippocampus and cerebral cortex and demonstrate that ischemia induced CL100 expression.

Liposome-entrapped superoxide dismutase reduces ischemia/reperfusion 'oxidative stress' in gerbil brain

Bilateral common carotid artery occlusion (15 min.) followed by two hours of recirculation reduced mitochondrial superoxide dismutase (SOD) and glutathione reductase (GR) activities, and increased susceptibility of mitochondrial membranes to in vitro lipid peroxidation in brain regions (i.e., cortex, striatum and hippocampus) of Mongolian gerbil. Intraperitoneal bolus injection (2 mg/kg b.w.) of liposome-entrapped CuZn superoxide dismutase (1-SOD) increased the endogenous SOD activity in normal brain tissue and, when given at the end of ischemia, counteracted both the ischemic reduction of endogenous SOD and the increased peroxidation of mitochondrial membranes. 1-SOD treatment was ineffective in reducing brain swelling, suggesting that superoxide radicals are not a main participant in the process of (post)ischemic brain edema formation.

Carvedilol, a new antihypertensive drug with unique antioxidant activity: potential role in cerebroprotection

The antioxidant activities of carvedilol have been demonstrated in a wide variety of test systems, including (i) physicochemical (EPR studies), (ii) biochemical (measurement of lipid peroxidation and endogenous antioxidant depletion), (iii) cellular, and (iv) in vivo. The antioxidant activity of carvedilol clearly emanates from the carbazole moiety which is unique to carvedilol. The antioxidant activity resides equally in both of the enantiomers of carvedilol, as well as in some of its metabolites which are devoid of either the alpha 1-adrenoceptor blocking activity or beta-adrenoceptor blocking activity. This novel antioxidant property of carvedilol may account, at least in part, for its cerebroprotection. The data discussed in this article suggest that carvedilol may not only provide effective and safe antihypertensive therapy and therefore reduce a major risk factor for stroke, but will also be better able to provide additional benefits to patients by protecting against oxygen free radicals generated during cerebral ischemia and stroke.