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

SIRT3 Deacetylates Ceramide Synthases: IMPLICATIONS FOR MITOCHONDRIAL DYSFUNCTION AND BRAIN INJURY

Experimental evidence supports the role of mitochondrial ceramide accumulation as a cause of mitochondrial dysfunction and brain injury after stroke. Herein, we report that SIRT3 regulates mitochondrial ceramide biosynthesis via deacetylation of ceramide synthase (CerS) 1, 2, and 6. Reciprocal immunoprecipitation experiments revealed that CerS1, CerS2, and CerS6, but not CerS4, are associated with SIRT3 in cerebral mitochondria. Furthermore, CerS1, -2, and -6 are hyperacetylated in the mitochondria of SIRT3-null mice, and SIRT3 directly deacetylates the ceramide synthases in a NAD(+)-dependent manner that increases enzyme activity. Investigation of the SIRT3 role in mitochondrial response to brain ischemia/reperfusion (IR) showed that SIRT3-mediated deacetylation of ceramide synthases increased enzyme activity and ceramide accumulation after IR. Functional studies demonstrated that absence of SIRT3 rescued the IR-induced blockade of the electron transport chain at the level of complex III, attenuated mitochondrial outer membrane permeabilization, and decreased reactive oxygen species generation and protein carbonyls in mitochondria. Importantly, Sirt3 gene ablation reduced the brain injury after IR. These data support the hypothesis that IR triggers SIRT3-dependent deacetylation of ceramide synthases and the elevation of ceramide, which could inhibit complex III, leading to increased reactive oxygen species generation and brain injury. The results of these studies highlight a novel mechanism of SIRT3 involvement in modulating mitochondrial ceramide biosynthesis and suggest an important role of SIRT3 in mitochondrial dysfunction and brain injury after experimental stroke.

[THE CONTENT OF LIPIDS AND PRODUCTS OF THEIR PEROXIDATION OF RAT THYMOCYTES IN EXPERIMENTAL ULCEROGENESIS]

The work is dedicated to the research of the content of lipids and products of their peroxidation in rats thymocytes in experimental ulceration. It was found significant increase of the content of lipid peroxidation products diene conjugates (DC), malondialdehyde (MDA), schiff base (SB) in experimental models of gastric ulcers (ethanol and stress). It was established that under ethanol gastric the contents of DC increases by 1.8 times, MDA by 2.1 and SB by 1.3 times relative to control values. Under stress model it was observed an increase in the number of DC by 2 times, MDA by 1.9 and SB by 1.3 times relative to control. When ethanol and stress ulcers cholesterol increased by 1.7 and 1.5 times, triacylglycerol by 2 and 2.3 times and fatty acids by 2.2 and 1.9 times, respectively, relative to controls. Phosphatidylethanolamine content decreases by 1.5 and 1.3 times compared to control. Also, the stress model, it was observed reduction of phosphatidylinositol by 1.3 times and increased lizofosfatydylholinu by 1.7 times compared to control. Therefore, our studies indicate quantitative changes of lipid content (neutral- and phospholipids) in rats' thymocytes under experimental (ethanol and stress) ulceration. The reason of this changes may be activation of lipid peroxidation, as shown by the increase of lipid peroxidation products' (DK, MDA, SB) content.

Ferulic Acid Reduces Cerebral Infarct Through Its Antioxidative and Anti-Inflammatory Effects Following Transient Focal Cerebral Ischemia in Rats

Both Angelica sinensis (Oliv.) Diels (AS) and Ligusticum chuanxiong Hort. (LC) have been used to treat stroke in traditional Chinese medicine for centuries. Ferulic acid (FA), a component in both AS and LC, plays a role in neuroprotection. The purpose of this study was to investigate the effects of FA on cerebral infarct and the involvement of neuroprotective pathway. Rats underwent 2 hours and 24 hours of reperfusion after 90 min middle cerebral artery occlusion (MCAo). The cerebral infarct and neurological deficits were measured after 24 hours of reperfusion. Furthermore, the expression of superoxide radicals, intercellular adhesion molecule-1 (ICAM-1), myeloperoxidase (MPO), nuclear factor-κB (NF-κB) immunoreactive cells were assessed after 2 hours and 24 hours of reperfusion. Administration of 80 and 100 mg/kg of FA at the beginning of MCAo significantly reduced cerebral infarct and neurological deficit-score, similar results were obtained by 100 mg/kg of FA administered 30 min after MCAo. FA treatment (100 mg/kg i.v.) effectively suppressed superoxide radicals in the parenchyma lesion, and ICAM-1 immunoreactive vessels in the ischemic striatum after 2 hours of reperfusion. FA (100 mg/kg i.v.) reduced the expression of ICAM-1 and NF-κB in the ischemic cortex and striatum, also down-regulated MPO immunoreactive cells in the ischemic cortex after 24 hours of reperfusion. These results showed that the effect of FA on reducing cerebral infarct area and neurological deficit-score were at least partially attributed to the inhibition of superoxide radicals, ICAM-1 and NF-κB expression in transient MCAo rats.

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.

Therapeutic strategies for the treatment of stroke

Acute ischaemic stroke is a major health problem with no effective treatments apart from the thrombolytic recombinant tissue plasminogen activator (rt-PA), which must be given within 3h of stroke onset. However, rt-PA increases the risk of symptomatic intracranial haemorrhage and is administered to <5% of stroke patients. New perfusion-enhancing compounds are in development but the risk:benefit ratio remains to be determined. Many neuroprotective drugs have been studied but all those that reached clinical development have failed to demonstrate efficacy. However, adherence to recently published guidelines on preclinical development has resulted in one novel compound (NXY-059) demonstrating efficacy in a Phase III trial, providing encouragement for the validity of the concept of neuroprotection. There are a variety of new neuroprotective compounds in the early stages of investigation and some could prove clinically effective, provided appropriate preclinical development guidelines are observed.

Inflammation and stroke: putative role for cytokines, adhesion molecules and iNOS in brain response to ischemia

Ischemic stroke is a leading cause of death and disability in developed countries. Yet, in spite of substantial research and development efforts, no specific therapy for stroke is available. Several mechanism for neuroprotection have been explored including ion channels, excitatory amino acids and oxygen radicals yet none has culminated in an effective therapeutic effect. The review article on "inflammation and stroke" summarizes key data in support for the possibility that inflammatory cells and mediators are important contributing and confounding factors in ischemic brain injury. In particular, the role of cytokines, endothelial cells and leukocyte adhesion molecules, nitric oxide and cyclooxygenase (COX-2) products are discussed. Furthermore, the potential role for certain cytokines in modulation of brain vulnerability to ischemia is also reviewed. The data suggest that novel therapeutic strategies may evolve from detailed research on some specific inflammatory factors that act in spatial and temporal relationships with traditionally recognized neurotoxic factors. The dual nature of some mediators in reformatting of brain cells for resistance or sensitivity to injury demonstrate the delicate balance needed in interventions based on anti-inflammatory strategies.

Edaravone diminishes free radicals from circulating neutrophils in patients with ischemic brain attack

OBJECTIVE

Treatment with a free radical scavenger could be a new option for ischemic brain attack, however, little is known about the alteration of oxidative stress markers induced by edaravone, a novel free radical scavenger, in human ischemic brain attack.

METHODS

We investigated the effects of edaravone on the oxidative stress markers in patients with ischemic brain attack. Twenty-one patients with ischemic brain attack and 19 controls were enrolled in this study. Blood samples were obtained just before and soon after the first administration of edaravone (30 mg) or ozagrel (40 mg). Intracellular reactive oxygen species of neutrophils were measured using 6-carboxy-2', 7'-dichlorodihydrofluorescin diacetate and a fluorescence-activated cell sorter. Superoxide from neutrophils, induced by phorbol myristate acetate (PMA), was determined by luminol-amplified chemiluminescence assay.

RESULTS

Treatment with 30 mg of edaravone significantly decreased the intracellular reactive oxygen species (ROS) of neutrophils (Wilcoxon test, p=0.0001) and PMA-induced superoxide produced by neutrophils (Wilcoxon test, p=0.001). Ozagrel did not alter the intracellular ROS or superoxide production of neutrophils.

CONCLUSION

Reduction of intracellular ROS and suppression of superoxide production in neutrophils provide a potential explanation for the clinical efficacy of edaravone in patients with ischemic brain attack.

Single-dose ebselen does not afford sustained neuroprotection to rats subjected to severe focal cerebral ischemia

Oxygen free radicals have been involved in the pathophysiology of cerebral ischemia, especially after spontaneous or thrombolytic reperfusion. In this study with rats, we have combined a severe focal ischemic insult (2 h) and a prolonged reperfusion time (7 days) to assess the possible sustained neuroprotective effect of ebselen (10 or 100 mg/kg), a small, lipophilic organoselenium compound which mimics glutathione peroxidase. Parietal cortical perfusion was measured by laser-Doppler flowmetry, and focal cerebral ischemia was carried out by the intraluminal thread method. We have measured plasma selenium levels, brain reduced glutathione levels, as a marker of oxidative stress, and infarct volume associated with cerebral ischemia. Focal ischemia did not alter reduced glutathione levels, while 60 min reperfusion following ischemia induced a significant (P < 0.05) decrease in reduced glutathione levels of the ipsilateral hemisphere. Pretreatment with ebselen, which induced significant (P < 0.05) increase in plasma selenium levels, did not significantly alter the decrease in reduced glutathione levels. The ischemic insult induced 30% mortality on average, with deaths always occurring within 12-48 h. Surviving rats suffered up to 25% body weight loss 1 week after the ischemic insult. Infarct volumes were 26.8 +/- 4.7% of the hemisphere in placebo-treated rats, 26.6 +/- 3.6% in 10 mg/kg ebselen-treated rats, and 25.6 +/- 6.4% in 100 mg/kg ebselen-treated rats (not significantly different). Single-dose administration of ebselen does not reduce the size of brain infarct resulting from severe focal cerebral ischemia in rats. In contrast to previous studies with relatively earlier endpoints, we have delayed the measurement of infarct volume to 1 week after the ischemic insult.

Attenuation of a delayed increase in the extracellular glutamate level in the peri-infarct area following focal cerebral ischemia by a novel agent ONO-2506

A novel agent, ONO-2506 [(R)-(-)-2-propyloctanoic acid, ONO Pharmaceutical Co. Ltd.] was previously shown to mitigate delayed infarct expansion through inhibition of the enhanced production of S-100beta, while inducing a prompt symptomatic improvement that attained a significant level as early as 24h after drug administration. To elucidate the mechanism underlying the prompt symptomatic improvement, the present study aimed to examine whether ONO-2506 modulates the level of extracellular glutamate ([Glu]e) in the rat subjected to transient middle cerebral artery occlusion (tMCAO). In this model, it had been shown that ONO-2506 reduces the infarct volume, improves the neurological deficits, and enhances the mRNA expression of glial glutamate transporters (GLT-1 and GLAST). The [Glu]e levels in the ischemic cortices were continuously measured using intracerebral microdialysis. The alterations in the [Glu]e levels in the sham-operated and tMCAO-operated groups with or without drug administration were compared. In the tMCAO groups, the [Glu]e level increased during tMCAO to a similar extent, returned to normal on reperfusion, and increased again around 5h. In the saline-treated group, however, the [Glu]e level further increased from 15 h on to reach about 280% of the normal level at 24h. This secondary increase in the [Glu]e level in the late phase of reperfusion was prevented by ONO-2506. The intracerebral infusion of glutamate transporter inhibitor, l-trans-pyrrolidine-2,4-dicarboxylic acid, at 24h after tMCAO induced an increase in the [Glu]e level, which was marked in both the sham-operated and ONO-2506-treated groups, but much less pronounced in the saline-treated group. The above results suggest that functional modulation of activated astrocytes by pharmacological agents like ONO-2506 may inhibit the secondary rise of [Glu]e level in the late phase of reperfusion, leading to amelioration of delayed infarct expansion and neurological deficits.

Neuroprotective effect of antioxidants on ischaemia and reperfusion-induced cerebral injury

The present study is designed to investigate the effect of dietary flavanoid rutin, micronutrient selenium and garlic oil on ischaemia and reperfusion-induced cerebral injury. Global cerebral ischaemia was induced by occluding right and left common carotid arteries for 10min followed by reperfusion for 24h. Cerebral infarct size was estimated using triphenyltetrazolium chloride staining. Elevated plus maze was employed to estimate short-term memory. Degree of motor incoordination was evaluated using inclined beam-walking test and lateral push test. Mitochondrial thiobarbituric acid reactive substances (TBARS) assay was employed as an index of oxidative stress. Global cerebral ischaemia followed by reperfusion produced a significant impairment in short-term memory and motor coordination and produced a notable increase in mitochondrial TBARS. Administration of rutin and garlic oil before global cerebral ischaemia markedly reduced cerebral infarct size and attenuated impairment in short-term memory and motor coordination. Administration of sodium selenite either before or after global cerebral ischaemia markedly reduced cerebral infarct size and attenuated impairment in short-term memory and motor coordination. The protective effect of rutin, sodium selenite and garlic oil was accompanied by a marked decrease in mitochondrial TBARS. On the basis of these results, it may be suggested that rutin and garlic oil administrated before cerebral ischaemia may scavenge reactive oxygen species and consequently attenuate global cerebral ischaemia and reperfusion-induced cerebral injury. Sodium selenite administrated before and after cerebral ischaemia may be neuroprotective due to its antioxidant effect.

Molecular mechanisms of cerebral ischemia-induced neuronal death

The mode of neuronal death caused by cerebral ischemia and reperfusion appears on the continuum between the poles of catastrophic necrosis and apoptosis: ischemic neurons exhibit many biochemical hallmarks of apoptosis but remain cytologically necrotic. The position on this continuum may be modulated by the severity of the ischemic insult. The ischemia-induced neuronal death is an active process (energy dependent) and is the result of activation of cascades of detrimental biochemical events that include perturbion of calcium homeostasis leading to increased excitotoxicity, malfunction of endoplasmic reticulum and mitochondria, elevation of oxidative stress causing DNA damage, alteration in proapoptotic gene expression, and activation of the effector cysteine proteases (caspases) and endonucleases leading to the final degradation of the genome. In spite of strong evidence showing that brain infarction can be reduced by inhibiting any one of the above biochemical events, such as targeting excitotoxicity, up-regulation of an antiapoptotic gene, or inhibition of a down-stream effector caspase, it is becoming clear that targeting a single gene or factor is not sufficient for stroke therapeutics. An effective neuroprotective therapy is likely to be a cocktail aimed at all of the above detrimental events evoked by cerebral ischemia and the success of such therapeutic intervention relies upon the complete elucidation of pathways and mechanisms of the cerebral ischemia-induced active neuronal death.

Increased vulnerability to focal ischemic brain injury in human apolipoprotein E4 knock-in mice

Accumulating evidence suggests that among the 3 human apolipoprotein E (apoE) isoforms encoded by the human APOE gene, the e4 allele may act to exacerbate brain damage in humans and animals. This study aimed to compare the isoform-specific vulnerability conferred by human apoE to ischemic brain damage, using mice expressing human apoE isoforms (apoE2, apoE3, or apoE4) in place of mouse apoE, produced by the gene-targeting technique in embryonic stem cells (knock-in, KI). Homozygous human apoE2 (2/2), apoE3 (3/3), or apoE4 (4/4) KI mice were subjected to permanent focal cerebral ischemia by a modified intraluminal suture method. Twenty-four h thereafter, brain damage, (as estimated by infarct volume and neurologic deficit) was significantly worse in 4/4 KI mice versus 2/2 or 3/3 KI mice (p < 0.001 for each comparison), with no significant differences between 2/2 and 3/3 KI mice. Immunohistochemistry for human apoE expression revealed similar apoE distribution with no significant difference in the immunostaining intensity among the 3 lines of KI mice. Notably. increased expression of human apoE was detected in neurons and astrocytes in the peri-infarct area, and a punctate expression pattern was evident in the border between the infarct and peri-infarct areas in all KI mice subjected to ischemia. Taken together, our results show that apoE affects the outcome of acute brain damage in an isoform-specific fashion (apoE4 > apoE3 = apoE2) in genetically engineered mice.

Attenuation of ischemia-induced mouse brain injury by SAG, a redox-inducible antioxidant protein

Cerebral ischemia resulting from a disruption of blood flow to the brain initiates a cascade of events that causes neuron death and leads to neurologic dysfunction. Reactive oxygen species are thought, at least in part, to mediate this disease process. The authors recently cloned and characterized an antioxidant protein, SAG (sensitive to apoptosis gene), that is redox inducible and protects cells from apoptosis induced by redox agents in a number of in vitro cell model systems. This study reports a neuroprotective role of SAG in ischemia/reperfusion-induced brain injury in an in vivo mouse model. SAG was expressed at a low level in brain tissue and was inducible after middle cerebral artery occlusion with peak expression at 6 to 12 hours. At the cellular level, SAG was mainly expressed in the cytoplasm of neurons and astrocytes, revealed by double immunofluorescence. An injection of recombinant adenoviral vector carrying human SAG into mouse brain produced an overexpression of SAG protein in the injected areas. Transduction of AdCMVSAG (wild-type), but not AdCMVmSAG (mutant), nor the AdCMVlacZ control, protected brain cells from ischemic brain injury, as evidenced by significant reduction of the infarct areas where SAG was highly expressed. The result suggests a rather specific protective role of SAG in the current in vivo model. Mechanistically, SAG overexpression decreased reactive oxygen species production and reduced the number of apoptotic cells in the ischemic areas. Thus, antioxidant SAG appears to protect against reactive oxygen species-induced brain damage in mice. Identification of SAG as a neuroprotective molecule could lead to potential stroke therapies.

Intracisternal increase of superoxide anion production in a canine subarachnoid hemorrhage model

BACKGROUND AND PURPOSE

Reactive oxygen species (ROS) are thought to be primary in the pathogenesis of cerebral vasospasm after subarachnoid hemorrhage (SAH). However, as direct evidence of ROS has not yet been demonstrated in cerebral vasospasm, we sought to substantiate superoxide anion (.O(2)(-)) generation in the subarachnoid space after SAH using a modification of Karnovsky's manganese/diaminobenzidine (Mn(2+)/DAB) technique.

METHODS

SAH or sham operation was induced according to a 2-hemorrhage model in a total of 24 beagle dogs. On day 2 or 7 after SAH or sham operation, dogs were intrathecally infused with buffer containing Mn(2+) and DAB, and the brain stem was prepared for light and electron microscopy. Possible colocalization of ferrous (Fe(2+)) or ferric (Fe(3+)) iron ions with.O(2)(-) was also examined with the use of Turnbull blue or Berlin blue staining, respectively.

RESULTS

Light microscopy revealed amorphous, amber deposits within the subarachnoid hematoma, the periarterial space, and the tunica adventitia of the basilar artery on days 2 and 7 after SAH.O(2)(-) deposits were eliminated by addition of superoxide dismutase or exclusion of either Mn(2+) or DAB from the perfusate, confirming the specificity of the reaction. These deposits were colocalized with blue reaction deposits indicating Fe(2+) and Fe(3+). Within the subarachnoid space,.O(2)(-) indicating electron-dense fine granules were preferentially located around degenerated erythrocytes and, secondarily, infiltrating macrophages and neutrophils.

CONCLUSIONS

We show direct evidence for enhanced production of.O(2)(-) and Fe(2+)/Fe(3+) iron ions in the subarachnoid space after SAH, lending further support to the pathogenic role of ROS in cerebral vasospasm after SAH.

Overexpression of Cu,Zn superoxide dismutase attenuates oxidative inhibition of astrocyte glutamate uptake

Glutamate neurotoxicity in brain is normally prevented by rapid uptake of glutamate by astrocytes. Increased expression of Cu,Zn superoxide dismutase (SOD1) can increase resistance to cerebral ischemia and other oxidative insults, but the cellular mechanisms by which this occurs are not well established. Here we examine whether increased SOD1 expression can attenuate inhibition of astrocyte glutamate uptake by reactive oxygen species. Primary cortical astrocyte cultures were prepared from transgenic mice that overexpress human SOD1 and from nontransgenic littermate controls. Glutamate uptake was assessed after exposure of these cultures to xanthine oxidase plus hypoxanthine, an extracellular superoxide generating system, or to menadione, which generates superoxide in the cytosol. These treatments produced dose-dependent reductions in astrocyte glutamate uptake, and the reductions were significantly attenuated in the SOD1 transgenic astrocytes. A specific effect of reactive oxygen species on glutamate transporters was suggested by the much smaller inhibitory effects of xanthine oxidase/hypoxanthine and menadione on GABA uptake than on glutamate uptake. These findings suggest that the cerebroprotective effects of increased SOD1 expression during cerebral ischemia-reperfusion could be mediated in part by astrocyte glutamate transport.

Possible role of the superoxide anion in the development of neuronal tolerance following ischaemic preconditioning in rats

There is a large body of evidence that reactive oxygen species play a major role in the pathogenesis of ischaemic brain damage. On the other hand, it has recently been suggested that superoxide anions participate in the development of neuronal tolerance against lethal ischaemia following ischaemic preconditioning (PC). The present study aimed to examine whether or not the intravenous administration of human recombinant Cu/Zn superoxide dismutase (hr SOD) prior to PC would affect the subsequent development of neuronal tolerance. Animals were randomly assigned to the following three groups: group 1, sham PC treated with vehicle; group 2, PC treated with hr SOD and group 3, PC treated with vehicle. For PC, 10 min occlusion of the middle cerebral artery (MCA) by a modified intraluminal suture method was followed by 60 min recirculation and this procedure was successively repeated three times. The procedures were similar for sham PC except that the MCA was kept unoccluded. Just prior to PC or sham PC, a bolus of hr SOD (6 x 103 IU/2 ml/kg) was administered intravenously. Seventy-two hours thereafter, rats were subjected to lethal ischaemia, i.e. MCA occlusion for 100 min followed by recirculation for 48 h. The infarct area and volume were assessed with the 2,3,5-triphenyltetrazolium stain. A significant difference in the infarct volume was revealed between the sham PC/vehicle and the PC/vehicle groups (total and cortex P < 0.01; striatum P < 0.05), showing that PC induced a marked neuronal tolerance against lethal ischaemia. The infarct volume in the PC/SOD group was close to that in the sham PC/vehicle group, being significantly greater than that in the PC/vehicle group (total and cortex P < 0.01) and showing that the administration of hr SOD suppressed the development of neuronal tolerance induced by PC. In a parallel experiment, expression of 72-kDa heat-shock protein (hsp 72) at 72 h after PC was considerably reduced in rats treated with hr SOD compared with those treated with vehicle. These results suggest that superoxide anions intraluminally generated within cerebral microvessels participate in the development of neuronal tolerance as well as the induction of hsp 72 following PC.