ascorbic-acid and Ischemic-Attack--Transient

Topics: Animals; Antioxidants; Ascorbic Acid; Brain Ischemia; Chromans; Corpus Striatum; Hippocampus; Ischemic Attack, Transient; Male; Neurons; Rats; Rats, Wistar; Reperfusion Injury; Structure-Activity Relationship

Expression and transport activity of Sodium-dependent Vitamin C Transporter 2 (SVCT2) was shown in various tissues and organs. Vitamin C was shown to be cerebroprotective in several animal models of stroke. Data on expression, localization and transport activity of SVCT2 after cerebral ischemia, however, has been scarce so far. Thus, we studied the expression of SVCT2 after middle cerebral artery occlusion (MCAO) in mice by immunohistochemistry. We found an upregulation of SVCT2 after stroke. Co-stainings with Occludin, Von-Willebrand Factor and CD34 demonstrated localization of SVCT2 in brain capillary endothelial cells in the ischemic area after stroke. Time-course analyses of SVCT2 expression by immunohistochemistry and western blots showed upregulation in the subacute phase of 2-5 days. Radioactive uptake assays using (14)C-labelled ascorbic acid showed a significant increase of ascorbic acid uptake into the brain after stroke. Taken together, these results provide evidence for the expression and transport activity of SVCT2 in brain capillary endothelial cells after transient ischemia in mice. These results may lead to the development of novel neuroprotective strategies in stroke therapy.

Topics: Animals; Ascorbic Acid; Blood-Brain Barrier; Brain; Endothelial Cells; Gene Expression Regulation; Infarction, Middle Cerebral Artery; Ischemic Attack, Transient; Male; Mice; Protein Transport; Sodium-Coupled Vitamin C Transporters; Time Factors; Up-Regulation

Topics: Animals; Antioxidants; Ascorbic Acid; Cell Death; Gene Expression Regulation, Enzymologic; Gerbillinae; Ischemic Attack, Transient; Neurons; Neuroprotective Agents; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Vitamin E

Ascorbate is highly concentrated in neuropils, and its extracellular release is closely related to that of the excitatory neurotransmitters. Thus, the extracellular release of ascorbate and glutamate was measured during the early stage of forebrain ischemia-reperfusion in the rat hippocampus using a microdialysis biosensor system. Male Wistar rats were anesthetized with halothane under mechanical ventilation and normothermia. Two probes of the microdialysis biosensor electrode were inserted in the hippocampus bilaterally. One probe was perfused with phosphate-buffered saline (PBS) and the oxidation signal of dialyzed ascorbate was recorded. A second electropolymerized probe was perfused with PBS containing glutamate oxidase for glutamate measurement. Forebrain ischemia-reperfusion was performed by bilateral carotid artery occlusion with hemorrhagic hypotension (MAP=30 mmHg) for 10 min (Group 10, n=10) or 15 min (Group 15, n=10), followed by reperfusion for 60 min. The release of glutamate increased significantly to 294% (Group 10) and 334% (Group 15) during ischemia, and then decreased rapidly. In Group 15, however, it remained significantly higher after reperfusion than in Group 10. The release of ascorbate increased significantly to 504% (Group 10) and 334% (Group 15) after reperfusion. In Group 10, it was significantly higher for 5-15 min after reperfusion than in Group 15. The marked increase of ascorbate during reperfusion was associated with the rapid decrease in glutamate. The extended time of ischemia significantly inhibited glutamate re-uptake and ascorbate release during reperfusion. These findings suggest the extracellular ascorbate release during reperfusion after global ischemia as a marker of glutamate re-uptake.

Topics: Animals; Antioxidants; Ascorbic Acid; Biosensing Techniques; Extracellular Space; Glutamic Acid; Ischemic Attack, Transient; Male; Microdialysis; Prosencephalon; Rats; Rats, Wistar; Reperfusion Injury; Time Factors

Topics: Animals; Ascorbic Acid; Brain; Cell Line; Ferrous Compounds; Free Radical Scavengers; Hippocampus; Imidazoles; Ischemic Attack, Transient; Lactates; Malondialdehyde; Mitochondria; Mitochondria, Liver; Mitochondrial Swelling; Nerve Degeneration; Neurons; Neuroprotective Agents; Rats; Reperfusion Injury

The in vivo uptake and distribution of 6-deoxy-6-[18F]fluoro-L-ascorbic acid (18F-DFA) were investigated in rat brains following postischemic reperfusion. Global cerebral ischemia was induced in male Wistar rats for 20 min by occlusion of four major arteries. Two time points were chosen for 18F-DFA injection to rats subjected to cerebral ischemia, at the start of recirculation and 5 days following recirculation. The rats were then killed at 2 h after tail-vein administration of 18F-DFA and tissue radioactivity concentration was determined. Increased uptake of radioactivity in particular brain regions, including the cerebral cortex, hypothalamus, and amygdala following injection of 18F-DFA, compared to the sham-operated control, was observed 5 days after reperfusion. Similar results were also obtained in in vitro experiments using brain slices. Abnormal in vivo accumulation of 45Ca, a marker of regional postischemic injury, was observed in these brain regions in tissue dissection experiments. Furthermore, metabolite analysis of nonradioactive DFA using 19F-NMR showed that DFA remained intact in the postischemic reperfusion brain. The present results indicate that 18F-DFA increasingly accumulates in damaged regions of postischemic reperfusion brain.

Topics: Animals; Antioxidants; Ascorbic Acid; Brain; Calcium Radioisotopes; Fluorine Radioisotopes; Ischemic Attack, Transient; Magnetic Resonance Spectroscopy; Male; Rats; Rats, Wistar; Reperfusion Injury; Tissue Distribution

In this study the effect of an inhibitor of lipid peroxidation and of phospholipase A2 activity, EPC-K1, on spatial learning deficit and neuronal damage following transient cerebral ischemia was evaluated. Global ischemia was induced by four-vessel occlusion (4VO) for 20 min in rats. EPC-K1 (10 mg/kg IP) was administered either a) 15 min before induction of ischemia, b) immediately after, or c) 30 min after onset of reperfusion. One week after surgery spatial learning was tested in the Morris water maze. EPC-K1 reduced the deficit in spatial learning when given immediately or 30 min after the onset of reperfusion but not when applied 15 min before ischemia. Neuronal damage in the CA1 sector of the hippocampus produced by 4VO was slightly, but not significantly attenuated by posttreatment. The present data demonstrate that posttreatment with EPC-K1 exerts a protective effect on deficits in spatial learning induced by 4VO. These results support the hypothesis that lipid peroxidation and activation of phospholipase A2 contribute to functional alterations of the brain during reperfusion following forebrain ischemia.

Topics: Animals; Ascorbic Acid; Drug Administration Schedule; Ischemic Attack, Transient; Learning; Lipid Peroxidation; Male; Memory; Neurons; Phospholipases A; Phospholipases A2; Prosencephalon; Rats; Rats, Wistar; Spatial Behavior; Vitamin E

Prior work in our laboratory showed that the perivascular application of deferoxamine (an antioxidant and iron-chelating agent) inhibited delayed arterial narrowing after chronic blood exposure in a rat femoral artery model of vasospasm. To determine which of these mechanisms was operant in vasospasm, we compared deferoxamine with two agents (ascorbic acid and U74389F) that have antioxidant but not iron-chelating capacity. For the systemic application of drugs in 23 rats, whole blood encased in a silastic cuff was applied to the right femoral artery of each rat; whole-blood serum (lacking erythrocytes) was similarly applied to the left femoral artery. Deferoxamine (30 mg/kg/d), ascorbic acid (1000 mg/kg/d), U74389F (30 mg/kg/d), or pH-matched control vehicle was administered three times daily by intraperitoneal injection for 7 days. After exposure to whole blood, arteries treated with intraperitoneal vehicle showed an 85% reduction in the lumen, compared with vessels exposed to erythrocyte-free serum (P < 0.001). Intraperitoneal ascorbic acid and U74389F produced moderate amelioration in arterial narrowing (53 and 61% decrease, respectively, in the lumen versus controls; P < 0.05 versus vehicle); deferoxamine had no significant effect when administered intraperitoneally. To test the efficacy of these agents by the perivascular application of drugs, whole blood was applied to both femoral arteries in each of 25 rats. Solutions of deferoxamine (10 mg/ml), ascorbic acid (50 or 100 mg/ml), or U74389F (15 or 30 mg/ml) were directly applied to the perivascular thrombus surrounding the femoral arteries, compared with vehicle applied to contralateral vessels. The perivascular application of 50 mg of ascorbic acid (36% reduction, P < 0.05), 100 mg of ascorbic acid (31% reduction, P < 0.01), or 10 mg of deferoxamine (41% reduction, P < 0.05) significantly inhibited arterial narrowing, compared with vehicle. The application of U74389F at a dose of 15 or 30 mg directly into the perivascular thrombus produced nonsignificant reduction in arterial narrowing. These data suggest that mechanisms other than direct iron toxicity, such as generation of cytotoxic free radicals, may play an important role in cerebral vasospasm. In addition, the route of administration and concentration of drugs in the perivascular region adjacent to the thrombus may be critical to their efficacy.

Topics: Animals; Antioxidants; Ascorbic Acid; Deferoxamine; Dose-Response Relationship, Drug; Femoral Artery; Free Radicals; Iron; Iron Chelating Agents; Ischemic Attack, Transient; Male; Pregnatrienes; Rats; Rats, Sprague-Dawley; Thrombosis; Vascular Resistance

Oxidative damage by free radicals has been proposed as a mechanism of cerebral injury due to ischemia and reperfusion. Hypothermia protects against ischemic necrosis; however, its effect on oxidative stress has not been investigated. In this study, the effects of hypothermia on oxidative stress were studied by determining consumption of endogenous antioxidants after temporary focal ischemia in rats. Thirty-two Sprague-Dawley rats anesthetized with 1.5% isoflurane underwent 3 h of middle cerebral artery occlusion under hypothermic (33 degrees C) or normothermic (37 degrees C) conditions followed by 3 h of normothermic reperfusion. In the first study (n = 8 per group), intraischemic hypothermia suppressed the reduction of tissue concentrations of endogenous antioxidants, ascorbate (P < or = 0.05), and glutathione (P < or = 0.05) in ischemic cortex but not in caudoputamen. In a parallel study (n = 8 per group), hypothermia reduced tissue damage in ischemic frontoparietal cortex (P < or = 0.05), but not in caudoputamen. Laser-Doppler estimates of cortical blood flow showed that intraischemic hypothermia significantly attenuated early postischemic hyperperfusion (P < or = 0.01) and delayed postischemic hypoperfusion (P < or = 0.01). These results demonstrate that intraischemic mild hypothermia reduces oxidative stress and cell injury after prolonged focal ischemia followed by reperfusion. The reduction of oxidative stress by hypothermia may be related indirectly to attenuation of postischemic blood flow changes.

Topics: Animals; Antioxidants; Ascorbic Acid; Blood Pressure; Body Temperature; Brain; Cerebral Arteries; Cerebrovascular Circulation; Glutathione; Hypothermia, Induced; Ischemic Attack, Transient; Male; Oxidative Stress; Rats; Rats, Sprague-Dawley; Reperfusion

Free radical reactions are supposed to cause ischaemic brain damage, and active oxygens can initiate these chains reaction. If active oxygens play important roles in ischaemic brain damage, the activity of superoxide dismutase, scavenger of superoxide anion, is supposed to decrease in ischaemic brain. The reduced form of ascorbic acid also scavenges superoxide anion. In rat middle cerebral artery focal ischaemia, we investigated the changes in superoxide dismutase activity and the concentration of reduced ascorbate up to 48 hours. Middle cerebral artery territory of each cerebral hemisphere was homogenized. The supernatant was divided into two aliquots; one was dialysed to remove ascorbate and the other was not. The enzyme activity of the dialysed specimen from the ischaemic hemisphere did not decrease within 4 h after the arterial occlusion. The activity of the dialysed specimen from the nonischaemic side remained unchanged during the examination. Reduced ascorbate levels in nondialysed samples showed similar changes to the superoxide dismutase activities in the dialysed samples. Our data suggest that ascorbic acid may exert the enzyme activity and that the enzyme activity remains at the normal level in the early phase of ischaemia despite the irreversible ischaemic changes that take place within 4 h after the onset of ischaemia.

Topics: Animals; Ascorbic Acid; Free Radicals; Ischemic Attack, Transient; Male; Rats; Rats, Inbred Strains; Superoxide Dismutase; Superoxides

Oxyhemoglobin (Oxy-Hb) produced a concentration-dependent contraction of monkey, dog, and bovine cerebral artery strips. Treatment of Oxy-Hb with ascorbic acid suppressed the ability of Oxy-Hb to contract the arteries, especially in the monkey arteries. The ability of intracisternally applied Oxy-Hb to constrict the basilar artery in anesthetized dogs was diminished when Oxy-Hb was treated previously with ascorbic acid (AsA-Hb). The contraction caused by Oxy-Hb was suppressed by treatment with indomethacin and aspirin in isolated bovine cerebral arteries. Endothelium-dependent relaxations elicited by substance P and relaxations induced by stimulation of the vasodilator nerves with nicotine were suppressed by treatment with Oxy-Hb and AsA-Hb; however, the inhibitory effect of AsA-Hb was markedly less. Oxy-Hb attenuated nitroglycerin-induced relaxations in a dose-dependent fashion, whereas AsA-Hb in concentrations up to 1.6 x 10(-5) M did not significantly influence the relaxations. It is concluded that incubation of Oxy-Hb with ascorbic acid alters markedly the biological activity of Oxy-Hb; the vasoconstrictor activity is suppressed, and the ability to diminish vasodilator actions is minimized. These findings provide a rationale for the use of ascorbic acid in cisternal irrigation to prevent the development of cerebral vasospasm after a subarachnoid hemorrhage.

Topics: Animals; Ascorbic Acid; Aspirin; Basilar Artery; Cattle; Cerebral Arteries; Dogs; Female; Ischemic Attack, Transient; Macaca; Male; Nicotine; Nitroglycerin; Oxyhemoglobins; Potassium Chloride; Substance P; Time Factors; Vasoconstriction

Oxygen-derived free radicals have been implicated in the pathogenesis of vasogenic edema and infarction caused by ischemia and reperfusion injury. In earlier studies, exogenously supplied liposome-entrapped CuZn superoxide dismutase (CuZn-SOD) ameliorated ischemic brain edema and infarction in rats following focal cerebral ischemia. To ascertain directly the role of SOD in the protection against superoxide radical-induced injury, we measured infarct size and water content 24 hr following focal cerebral ischemia in nontransgenic mice and in transgenic mice bearing the human SOD1 gene. These transgenic mice have 3.1-fold higher cellular CuZn-SOD activity in the brain than do their nontransgenic littermates. We also measured antioxidant levels (reduced glutathione and reduced ascorbate) of contralateral cortex, infarct cortex, surrounding cortex, and striatum. Infarct size and brain edema were significantly decreased in transgenic mice compared with nontransgenic mice. Reduced glutathione and reduced ascorbate levels decreased in the ischemic hemisphere, but levels in surrounding cortex and striatum were significantly higher in transgenic mice than in nontransgenic mice. These results indicate that increased endogenous SOD activity in brain reduces the level of ischemic damage and support the concept that superoxide radicals play an important role in the pathogenesis of infarction and edema following focal cerebral ischemia.

Topics: Animals; Ascorbic Acid; Body Water; Brain; Brain Chemistry; Cerebral Cortex; Cerebral Infarction; Glutathione; Humans; Ischemic Attack, Transient; Male; Mice; Mice, Transgenic; Superoxide Dismutase

It has been proposed that free radical reactions are involved in ischemic brain damage. Since irreversible pathological changes occurs very early phase of the focal ischemia and the ischemic brain edema reaches its peak at about 2 days of ischemia, the free radical reactions must take place before these changes. Superoxide dismutase is a famous enzyme that dismutase superoxide anion, which is believed to be one of the initiator of the free radical reactions. If superoxide anion plays a pivotal role in the genesis of pathological ischemic brain damage and edema, the activity of the enzyme may decrease in the early phase of ischemia. Ascorbic acid is also known to be a scavenger of superoxide anion, and brain tissue contains it in a high concentration. We investigated the changes in superoxide dismutase activity and concentration of reduced ascorbate in focal ischemia. Focal ischemia was produced in rats by permanent occlusion of the left middle cerebral artery. The animals were decapitated 30 minutes, 4, 24, and 48 hours after the operation. Middle cerebral artery territory of each cerebral hemisphere was homogenized and centrifuged with phosphate buffer. The supernatant was divided into two aliquots; one was dialyzed to remove ascorbate and the other was not. The SOD activity was measured by electron-spin-resonance (ESR) spin trapping method, and the ascorbic acid concentration was measured by high performance liquid chromatography with electrochemical detection (HPLC-ECD). Protein concentration was measured by Lowry's method. The enzyme activity was expressed as unit/mg protein, and the ascorbic acid concentration was expressed as microgram/g tissue. The SOD activity decreased markedly by dialysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Ascorbic Acid; Dialysis; Disease Models, Animal; Free Radicals; Ischemic Attack, Transient; Male; Rats; Rats, Inbred Strains; Superoxide Dismutase; Time Factors

To verify the lipid peroxidation in the focal cerebral ischemia, the levels of alpha-tocopherol, ubiquinone and ascorbate were measured in the ischemic center in rats. The former two were endogeneous lipid soluble antioxidants and the last was a water soluble antioxidant. alpha-Tocopherol, reduced ubiquinone-9 and -10, and reduced ascorbate decreased to 79%, 73%, 66%, and 76% 0.5 hour after ischemia, respectively. alpha-Tocopherol decreased to 63% 6 hours after ischemia, and then reached a plateau, while reduced ubiquinones and reduced ascorbate declined further to 16% and 10% 12 hours after ischemia, respectively, and then reached plateau levels. These results suggest their functional and durational differences as antioxidants against lipid peroxidation in this ischemic model. Although the reciprocal increase in oxidized ubiquinones during ischemia was not observed, that in oxidized ascorbate was noted. The complementary antioxidant system between cytoplasmic and membranous components, the combination alpha-tocopherol/ascorbate, was estimated from the calculated consumption ratio of these antioxidants, assuming that the loss of these reduced antioxidants is due to neutralization of free radicals. This system was suggested to play an important role in an early ischemic period. Urate also markedly increased during ischemia. Therefore, xanthine oxidase activity was measured in rats both in normal brain and in ischemic brain induced by four-vessel occlusion method. In the control rat, the enzyme activity was 0.87 +/- 0.13 nmol/g wet brain/min at 25 degrees C (mean +/- S.D.): 92.4% was associated with the NAD-dependent dehydrogenase form and only 7.6% with the oxygen-dependent superoxide-producing oxidase form. However, the ratio of the latter form increased to 43.7% after 0.5 hour of global ischemia despite the same level in total xanthine oxidase activity. This result suggests the involvement of the oxygen free radicals generated from the xanthine oxidase pathway in the pathogenesis of the ischemic injury of the rat brain.

Topics: Animals; Ascorbic Acid; Brain; Brain Ischemia; Ischemic Attack, Transient; Lipid Peroxidation; Male; Oxidation-Reduction; Rats; Rats, Inbred Strains; Ubiquinone; Vitamin E; Xanthine Oxidase

Extracellular (EC) ascorbate concentrations were measured in microdialysates from the striatum bilaterally in rats subjected to unilateral middle cerebral artery occlusion (MCAO). The focal cerebral ischemia induced a dramatic increase in ascorbate on the ipsilateral (operated) side while the levels remained at the preocclusion level in the striatum of the contralateral (control) hemisphere. The possibility that ascorbate may aggravate ischemic neuronal damage by its proposed neuromodulatory properties and/or by its ability to induce lipid peroxidation is discussed.

Topics: Animals; Ascorbic Acid; Corpus Striatum; Extracellular Space; Functional Laterality; Ischemic Attack, Transient; Male; Rats; Rats, Inbred Strains; Time Factors

Topics: Animals; Ascorbic Acid; Basilar Artery; Cats; Free Radicals; Humans; Ischemic Attack, Transient; Lipid Peroxidation; Oxyhemoglobins; Vasoconstriction

Topics: Aged; Animals; Ascorbic Acid; Cats; Female; Humans; Ischemic Attack, Transient; Male; Middle Aged; Subarachnoid Hemorrhage

Delayed cerebral vasospams is caused by excessive accumulation of dopamine-beta-hydroxylase (DBH) and noradrenaline in cerebral vessel walls. This study demonstrates the mechanisms of delayed spasm, particularly the role of red blood cell components, and the successful relief of delayed cerebral vasospasm. Spasmogenic substances which contained a heme component, such as methemoglobin, methemalbumin and catalase enhanced DBH activity in human serum as measured by a one step chemical spectrophotometric assay. The concentration which gave the highest DBH activity caused the maximum constriction of the basilar artery, when the substances were applied topically. Among components of red cells, methemoglobin, methemalbumin, catalase and nicotinamid adenin dinucleotide (NADH) caused constriction of basilar artery in cats, when applied topically, whereas hematin, hemin and bilirubin caused no significant spasm. An oxyhemoglobin solution obtained by mixture with methemoglobin and ascorbic acid produced no significant vascular spasm either. Relief of delayed cerebral vasospasm was obtained with topical application of specific alpha adrenergic blocking drug such as phenoxybenzamine, specific inhibitors of DBH such as fusaric acid, o-phenanthroline and alphaalpha' dipyridyl beta2 adrenergic stimulants such as salbutamol, and a phosphodiesterase inhibitor, ascorbic acid.

Topics: Albuterol; Animals; Ascorbic Acid; Basilar Artery; Catalase; Cats; Dopamine; Dopamine beta-Hydroxylase; Fusaric Acid; Ischemic Attack, Transient; Methemalbumin; Methemoglobin; NAD; Phenanthrolines; Phenoxybenzamine; Vasoconstriction