allopurinol and Brain-Edema

Cytotoxic brain edema is a major contributor of tissue damage following cerebral ischemia and traumatic brain injury. The pathophysiology of cytotoxic edema formation is still not well understood. Although it is widely believed that oxidative stress causes cytotoxic brain edema, experimental proof is lacking. The aim of the present study was therefore to examine the effect of oxidative stress on cell volume of glial cells. C6 glial cells were exposed to hydrogen peroxide and the superoxide forming complex hypoxanthine/xanthine oxidase (HX/XO). Exposure to hydrogen peroxide (0.5-5 mM) resulted in initial cell shrinkage by 5.7 +/- 1.5% (mean +/- SEM; p < 0.05) and was followed by a dose-dependent recovery to baseline. Exposure to superoxide anions generated by HX/XO provoked a delayed, but sustained decrease of cell volume by 11.8 +/- 0.9% (p < 0.05). Cell volume showed no tendency to recover upon sustained exposure to superoxide. Neither hydrogen peroxide nor HX/XO exposure was associated with a decrease of cell viability. Thereby, the present study demonstrates that oxidative stress by hydrogen peroxide and superoxide anions does not induce cytotoxic cell swelling and suggests that free radicals are not directly involved in the formation of cytotoxic brain edema.

Topics: Animals; Brain Edema; Cell Line; Hydrogen Peroxide; Neuroglia; Oxidants; Oxidative Stress; Rats; Superoxides; Xanthine Oxidase

Time-dependent changes in the activities of antioxidant enzymes and an oxidant enzyme, xanthine oxidase (XO), were detected in primary and peri-ischaemic brain regions during permanent occlusion of the middle cerebral artery (MCAO) in rats. There were no changes in superoxide dismutase (SOD) and catalase (CAT) activities after 3 h of MCAO, whereas antioxidant enzyme activities decreased significantly in ischaemic brain areas following 24 h of ischaemia. After 48 h, the enzyme activities returned to the baseline but then a further increase was observed in ischaemic brain areas by 72 h post-ischaemia. Normally, XO exists as a dehydrogenase (XD), but it is converted to XO which contributes to injury in some ischaemic tissues. The XO activity increased slightly at 3 h after ischaemia, but after 24 h of ischaemia it returned to the baseline and then remained relatively unchanged in ischaemic areas. Pretreatment with allopurinol before ischaemia prevented changes in SOD and CAT activities and attenuated brain oedema during 24 h of ischaemia. Neither XO nor XD activity changed in allopurinol-treated rats at the times of ischaemia. These results indicated that ischaemic brain tissue remained vulnerable to free radical damage for as long as 48 h after ischaemia, and XO was probably not an important source of free radicals in cerebral ischaemia.

Topics: Allopurinol; Animals; Blood Gas Analysis; Blood Pressure; Brain Edema; Brain Ischemia; Catalase; Enzyme Inhibitors; Lipid Peroxidation; Male; Oxidoreductases; Rats; Rats, Sprague-Dawley; Superoxide Dismutase; Time Factors; Xanthine Dehydrogenase; Xanthine Oxidase

To investigate the benefit of the hyperosmolar agent, mannitol, and the xanthine oxidase inhibitor, allopurinol, in experimental pneumococcal meningitis in the rat.. A prospective, randomized, controlled experimental study.. Experimental animal laboratory in a university hospital.. Sixty-five anesthetized and artificially ventilated adult male Wistar rats, weighing 250 to 300 g.. Meningitis was induced by intracisternal injection of live pneumococci. Infected rats were randomized to receive mannitol or allopurinol.. There were marked increases in regional cerebral blood flow (measured by laser-Doppler flowmetry), intracranial pressure, brain water content, and cerebrospinal fluid white blood cell count in infected rats within 6 hrs after infection (p < .05, compared with uninfected controls). Continuous infusion of mannitol (0.6 g/kg/hr iv), started just before infection, attenuated the increases of regional cerebral blood flow, intracranial pressure, and brain water content (p < .05, compared with untreated infected rats 6 hrs after infection). When continuous mannitol treatment was started 4 hrs after infection, intracranial pressure at 6 hrs was significantly lower than in untreated infected rats. When mannitol was given by a bolus injection (1.5 g/ kg iv) at 4 hrs after infection, intracranial pressure measured 0.5 hr thereafter was consistently reduced in all animals (intracranial pressure reduction by 21.3 +/- 5.1 [SEM]%). Pretreatment with allopurinol (150 mg/kg iv) did not significantly influence regional cerebral blood flow, intracranial pressure, and brain water content in pneumococci-injected rats. Both agents, mannitol and allopurinol, did not inhibit cerebrospinal fluid pleocytosis in infected rats. In uninfected rats, mannitol significantly increased regional cerebral blood flow by a nitric oxide-independent mechanism, whereas allopurinol slightly decreased blood flow.. Mannitol attenuated pathophysiologic changes in experimental pneumococcal meningitis. One possible mechanism of the mannitol effect might be scavenging of hydroxyl radicals which have been shown to be involved in the pathophysiology of pneumococcal meningitis. The failure of allopurinol to modulate pathophysiologic parameters may suggest that during early experimental pneumococcal meningitis in the rat, the xanthine oxidase pathway seems not to be a major source of reactive oxygen species.

Topics: Allopurinol; Animals; Brain Edema; Cerebrovascular Circulation; Hemodynamics; Infusions, Intravenous; Intracranial Pressure; Male; Mannitol; Meningitis, Pneumococcal; Rats; Rats, Wistar

Toxic oxidants (oxygen free radicals) have been implicated in the formation of brain edema from ischemia-reperfusion injury or tumor growth. We investigated the ability of an iron chelator, a calcium channel blocker, and a xanthine oxidase inhibitor to reduce formation of brain edema following a cold lesion in cats. The agents were given independently of each other in an attempt to inhibit the Haber-Weiss reaction, prevent Ca++ modulated uncoupling of oxidative phosphorylation, and inhibit the generation of toxic oxidants via xanthine oxidase, respectively. Pentastarch-deferoxamine conjugate at a dose of 50 mg/kg was given 15 minutes before and 60 minutes after the cold lesion. Nimodipine was given at a dose of 1 mg/kg 1 hour before and 2 hours after the cold lesion. Allopurinol was given at a dose of 50 mg/kg 24 hours before, at the time of the lesion and, 24 and 48 hours after the lesion. Gravimetric measurements of multiple brain areas were performed at 24 hours post-lesion in the pentastarch-deferoxamine and nimodipine groups and at 72 hours post-lesion in the allopurinol group. None of these agents led to significant reduction in brain edema formation as measured with a gravimetric column of kerosene and bromobenzene. Pentastarch-deferoxamine conjugate was utilized to avoid the confounding effects of arterial hypotension which is seen with intravenous deferoxamine. There was even a suggestion of increased edema in the periventricular white matter in animals treated with nimodipine. Taken together, independent inhibition of the Haber-Weiss reaction, of calcium channels, or of xanthine oxidase does not reduce formation of brain edema in the cold lesion model.

Topics: Allopurinol; Animals; Brain Edema; Brain Injuries; Calcium; Cats; Cerebral Cortex; Cerebral Infarction; Deferoxamine; Dose-Response Relationship, Drug; Freezing; Nimodipine; Reactive Oxygen Species; Water-Electrolyte Balance

Xanthine oxidase (XO) has been proposed as an important source of free radicals during ischemia. This enzyme normally exists as a dehydrogenase (XD), but it is converted to XO in some ischemic tissues. Recently, treatment of animals with the XD and XO inhibitor allopurinol or with free radical scavengers before cerebral ischemia has been shown to reduce brain injury. Therefore, we studied conversion of XD to XO in three ischemic and nonischemic brain regions during focal cerebral ischemia resulting from permanent occlusion of the middle cerebral artery (MCAO) in anesthetized rats. In nonischemic brain, 16-22% of the enzyme was in the XO form. After 24 h of ischemia this value was not significantly different (10-15%). Neither the total activity of XO nor that of XD changed, indicating that there was no irreversible conversion of XD to XO. To further explore the possible role of XO, we examined the effect of various doses of allopurinol (5, 20, or 100 mg/kg given 1 h before MCAO or 100 mg/kg given 48, 24, and 1 h before MCAO) on uric acid accumulation, brain edema formation, and cerebral blood flow (CBF) 24 h after MCAO. All but the lowest dose of allopurinol greatly reduced the appearance of uric acid in the ischemic brain; however, only the highest dose of allopurinol had any beneficial effect on brain edema. This reduction in brain edema occurred without a significant improvement in CBF. Thus XO is probably not an important source of free radicals in this model of focal cerebral ischemia.

Topics: Allopurinol; Animals; Brain; Brain Edema; Brain Ischemia; Cerebrovascular Circulation; Dose-Response Relationship, Drug; Free Radicals; Male; Oxygen; Rats; Rats, Inbred Strains; Uric Acid; Xanthine Dehydrogenase; Xanthine Oxidase

The formation of oxygen-derived free radicals in cerebral ischaemia has been implicated in altering the BBB permeability, cause oedema and tissue damage. However little attention has been paid regarding the involvement of xanthine oxidase in the cerebral ischaemic events. Recently we demonstrated that cerebral ischaemia promotes the conversion of xanthine oxidase type D (nicotinamide adenine dinucleotide-dependent dehydrogenase) to type 0 (oxygen-dependent superoxide-producing oxidase). This investigation was concerned with elucidating the relationship between the conversion of xanthide oxidase and the duration of brain ischaemia. Four vessel-occlusion served as a model for the induction of cerebral ischaemia in rats. Xanthine oxidase was assayed by high pressure liquid chromatography using ultraviolet and electrochemical detection. The enzymatic conversion of xanthine oxidase from type D to type O increased with time from 7.6-15% during 5 min ischaemia to 27% and 36% at 15 min and 30 min after ischaemia, respectively. These results support the contention that xanthine oxidase may participate in free radical-induced ischaemic brain oedema.

Topics: Animals; Brain Edema; Brain Ischemia; Chromatography, High Pressure Liquid; Male; Rats; Rats, Inbred Strains; Time Factors; Xanthine; Xanthine Oxidase; Xanthines

Since hydrogen peroxide (H2O2) can react with ferrous iron (FE++) to form the more toxic hydroxyl radical (OH) in vitro, and since H2O2 is generated brain xanthine oxidase (XO) during ischemia/reperfusion (I/R), we hypothesized that gerbils depleted of iron by dietary restriction or treated with iron chelators would be less susceptible to I/R injury. We found that gerbils fed a low iron diet for 8 weeks had decreased brain and serum iron levels, less neurologic deficits, and decreased brain edema after temporary unilateral carotid ligation (ischemia) and then reperfusion than gerbils fed a control standard iron diet. In addition, brains from gerbils treated with iron-free deferoxamine (an iron chelator), but not iron-loaded deferoxamine, had decreased (P less than .05) brain edema following ischemia and reperfusion. The results indicate that iron may contribute to cerebral ischemia/reperfusion damage.

Topics: Animals; Brain; Brain Chemistry; Brain Edema; Brain Ischemia; Deferoxamine; Female; Gerbillinae; Hematocrit; Iron; Iron Deficiencies; Male; Reperfusion Injury; Xanthine Dehydrogenase; Xanthine Oxidase

Cytotoxic free radicals are generated during cerebral hypoxia-ischemia and reperfusion. We studied the efficacy of allopurinol, a xanthine oxidase inhibitor and free radical scavenger, in reducing posthypoxic-ischemic damage in the developing brain of 7-d-old rat pups. Hypoxic-ischemic injury to the right cerebral hemisphere was produced by ligation of the right common carotid artery followed by 3 h of hypoxia with 8% oxygen. Thirty to 45 min before the hypoxia, the rats received either allopurinol (dose = 130-138 mg/kg) or an equal vol of saline (0.2 mL). Some pups were killed at 42 h of recovery for measurement of cerebral hemispheric water content, whereas others were killed at 30 or more d for neuropathologic examination. A total of 18 allopurinol treated rats had significantly less water content in the right hemisphere (89.07 +/- 0.32%) than 23 saline-treated animals (91.64 +/- 0.25%, mean +/- SEM, p less than 0.0001). Rank scoring of neuropathologic alterations revealed that the allopurinol treated rats were less damaged (p = 0.001). Only two of 13 brains from the allopurinol group suffered infarction compared to 10 of the 14 saline-treated animals. The results indicate that allopurinol reduces both cerebral edema and the extent of perinatal hypoxic-ischemic brain damage.

Topics: Allopurinol; Animals; Animals, Newborn; Body Water; Brain Edema; Brain Injuries; Brain Ischemia; Female; Free Radicals; Hypoxia, Brain; Male; Rats; Rats, Inbred Strains

The contribution of toxic O2 metabolites to cerebral ischemia reperfusion injury has not been determined. We found that gerbils subjected to temporary unilateral carotid artery occlusion (ischemia) consistently developed neurologic deficits during ischemia with severities that correlated with increasing degrees of brain edema and brain H2O2 levels after reperfusion. In contrast, gerbils treated just before reperfusion (after ischemia) with dimethylthiourea (DMTU), but not urea, had decreased brain edema and brain H2O2 levels. In addition, gerbils fed a tungsten-rich diet for 4, 5, or 6 wk developed progressive decreases in brain xanthine oxidase (XO) and brain XO + xanthine dehydrogenase (XD) activities, brain edema, and brain H2O2 levels after temporary unilateral carotid artery occlusion and reperfusion. In contrast to tungsten-treated gerbils, allopurinol-treated gerbils did not have statistically significant decreases in brain XO or XO + XD levels, and reduced brain edema and brain H2O2 levels occurred only in gerbils developing mild but not severe neurologic deficits during ischemia. Finally, gerbils treated with DMTU or tungsten all survived, while greater than 60% of gerbils treated with urea, allopurinol, or saline died by 48 h after temporary unilateral carotid artery occlusion and reperfusion. Our findings indicate that H2O2 from XO contributes to reperfusion-induced edema in brains subjected to temporary ischemia.

Topics: Allopurinol; Animals; Brain; Brain Chemistry; Brain Edema; Brain Ischemia; Female; Gerbillinae; Hydrogen Peroxide; Male; Nervous System Diseases; Thiourea; Tungsten; Urea; Xanthine Oxidase

We studied the cerebral effects of oxygen-derived free radicals generated from the xanthine oxidase/hypoxanthine/ADP-Fe3+ system. Xanthine oxidase/hypoxanthine/ADP-Fe3+ solution (0.1 ml) was infused into caudate putamen, and brain was frozen rapidly in situ. Brain water and sodium content increased concomitant with decreased potassium content at 24 hours and 48 hours after the infusion. The degree of brain edema and injury depended on the dose of xanthine oxidase. Spongy neuropil and neuronal cytoplasmic vacuoles were seen at 2 hours, with an infiltration by polymorphonuclear leukocytes at 24 hours, followed by lipid-laden macrophages and reactive astrocytes. Leakage of fluorescent dye into neuropil was seen at 2 hours, but not later. These data suggest that oxygen-derived free radicals damage endothelial cells of the blood-brain barrier; the brain injury is characterized by edema and by structural damage of neurons and glia.

Topics: Adenosine Diphosphate; Animals; Blood-Brain Barrier; Brain; Brain Diseases; Brain Edema; Capillary Permeability; Free Radicals; Hypoxanthine; Hypoxanthines; Iron; Male; Oxygen; Rats; Rats, Inbred Strains; Xanthine Oxidase

Cellular edema and increased lactate production were induced in rat brain cortical slices by xanthine oxidase and xanthine, in the presence of ferric dialdehyde, was increased 174%. Among the various subcellular fractions of brain cortex, xanthine oxidase-stimulated lipid peroxidation was highest in myelin, mitochondria, and synaptosomes, followed by microsomes and nuclei. Antioxidants, catalase, chlorpromazine, and butylated hydroxytoluene inhibited lipid peroxidation in both homogenates and synaptosomes, indicating H2O2 and radicals were involved. Further, several free fatty acids, especially oleic acid (18:1), arachidonic acid (20:4), and docosahexaenoic acid (22:6) were released from the phospholipid pool concomitant with the degradation of membrane phospholipids in xanthine oxidase-treated synaptosomes. These data suggest that lipases are activated by free radicals and lipid peroxides in the pathogenesis of cellular swelling.

Topics: Animals; Brain Edema; Cerebral Cortex; Dimethyl Sulfoxide; Free Radicals; Lactates; Lactic Acid; Lipid Peroxides; Male; Membrane Lipids; Phospholipids; Rats; Time Factors; Xanthine; Xanthine Oxidase; Xanthines