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E D Hall

Publications and source records attributed to E D Hall.

At least 55 records · Page 3Linked to original sources
PubMed1996

Neuroprotective efficacy of microvascularly-localized versus brain-penetrating antioxidants.

The 21-aminosteroid (lazaroid) tirilazad mesylate has been demonstrated to be a potent inhibitor of lipid peroxidation and to reduce traumatic and ischemic damage in a number of experimental models. Currently, tirilazad is being actively investigated in phase III clinical trials in head and spinal cord injury, ischemic stroke and subarachnoid hemorrhage. This compound acts in large part to protect the microvascular endothelium and consequently to maintain normal blood-brain barrier (BBB) permeability and cerebral blood flow autoregulatory mechanisms. However, due to its limited penetration into brain parenchyma, tirilazad has generally failed to affect delayed neuronal damage to the selectively vulnerable hippocampal CA1 and striatal regions. Recently, we have discovered a new group of antioxidant compounds, the pyrrolopyrimidines, which possess significantly improved ability to penetrate the BBB and gain direct access to neural tissue. Several compounds in the series, such as U-101033E, have demonstrated greater ability to protect the CA1 region in the gerbil transient forebrain ischemia model with a post-ischemic therapeutic window of at least four hours. In addition, U-101033E has been found to reduce infarct size in the mouse permanent middle cerebral artery occlusion model in contrast to tirilazad which is minimally effective. These results suggest that antioxidant compounds with improved brain parenchymal penetration are better able to limit certain types of ischemic brain damage compared to those which are localized in the cerebral microvasculature. On the other hand, microvascularly-localized agents like tirilazad appear to have better ability to limit BBB damage.

Animals↗
PubMed1996

Induction of apolipoprotein E mRNA in the hippocampus of the gerbil after transient global ischemia.

B/A4 is the major component of brain amyloid plaque, one of the hallmarks of Alzheimer's disease (AD). B/A4 is a product of proteolytic processing of its precursor, the Alzheimer amyloid precursor protein (APP). Recently, apolipoprotein E (APO-E) has also been shown to be associated with Alzheimer's disease pathology because it is localized to plaques and tangles, and the gene encoding one of the isoforms of APO-E (E4) is associated with late-onset familial and sporadic AD. In addition, APO-E exhibits high affinity for binding to the B-peptide (B/A4). In this study, we have investigated changes in the steady state levels of APP, APO-E, and the astrocyte-specific marker, glial fibrillary acidic protein (GFAP) mRNA in the gerbil hippocampal CA1 region after a 10-min period of bilateral carotid occlusion-induced forebrain ischemia. Following this insult, we observed a loss of 90% of the CA1 neurons by 72 h post-ischemia. The mRNA levels on day 1 through day 7 post-ischemia were quantitated using an image analyzer. There was an increase in the transcription of APO-E and GFAP mRNAs, with the levels of APO-E mRNA being the highest (3-fold increase on day 7 post-ischemia) (P < 0.005). However, we did not see an increase in APP mRNA. In a parallel study [Hall, E.D. et al., Exp. Neurol., 135(1995) 17-27], we have also seen an increase in levels of APO-E and GFAP protein measured by immunocytochemistry. However, in contrast to the lack of an increase in APP mRNA, immunocytochemical measurement of APP did show an increase, perhaps due to delayed translation of previously formed mRNA. We suggest that neuronal injury or insult results in the induction of certain genes (and, therefore, protein synthesis) in the surrounding reactive astrocytes, and these proteins may contribute to post-injury amyloidogenesis.

Amyloid beta-Protein Precursor↗
PubMed1996

Tirilazad prevention of reperfusion edema after focal ischemia in cynomolgus monkeys.

BACKGROUND: The purpose of the present investigation was to determine if post-ischemic treatment with the 21-aminosteroid lipid peroxidation inhibitor tirilazad mesylate (U-74006F) could affect reperfusion brain edema during the first 3h following a 3h period of middle cerebral artery occlusion-induced focal ischemia in cynomolgus monkeys. METHODS: Adult female cynomolgus monkeys (N = 14) were subjected under halothane anesthesia to a 3h period of middle cerebral artery occlusion, followed by 3h of reperfusion. U-74006F, 3.0 mg/kg i.v. or citrate vehicle, was administered 10 min before beginning reperfusion. Multiple spin-echo (8 echoes: TE = 26.3 msec; TR = 3.0 secs; 2.35 Tesla) magnetic resonance imaging was performed every 30 min, beginning at 1h after reperfusion. Transverse relaxation rates (T2) for the caudate, putamen, cortex, insular cortex, parietal cortex and central white matter were calculated as an index of focal brain edema. After the final images, corresponding regions were removed for determination of water content by the wet weight/dry weight method. RESULTS: The T2 measurements strongly suggested the presence of post-reperfusion edema in all gray matter, but not white matter, regions at 1h after reperfusion in vehicle-treated animals. Significant attenuation of edema development was seen in the putamen and insular cortex in U-74006F-treated animals. An effect was also observed in the parietal cortex, but none in the caudate. The measurement of water content at 3h after reperfusion yielded similar results. CONCLUSIONS: These results showing the ability of U-74006F to attenuate post-reperfusion brain edema support the concept that lipid peroxidation is a significant mediator of reperfusion brain edema after focal ischemia. The therapeutic window for U-74006F's anti-edema effect appears to be at least 3h after the onset of focal ischemia since delaying treatment until just before reperfusion largely prevented subsequent edema in cortical regions and the putamen. The effects of U-74006F on edema may play a mechanistic role in the compound's reported neuroprotective efficacy in a variety of focal ischemia models.

Animals↗
PubMed1996

Efficacy and mechanisms of action of the cytoprotective lipid peroxidation inhibitor tirilazad mesylate in subarachnoid haemorrhage.

Subarachnoid haemorrhage (SAH) following cerebral aneurysm rupture or trauma can result in the induction of secondary ischaemic brain damage via a decrease in microvascular perfusion, a disruption of the blood-brain barrier and consequent vasogenic oedema, and the delayed spasm of the major cerebral arteries (i.e. vasospasm). It is increasingly apparent that oxygen radical-induced, iron-catalyzed lipid peroxidation (LP) within the subarachnoid blood and vascular wall plays a key role in the occurrence of these secondary events. Tirilazad mesylate is a potent cytoprotective inhibitor of LP that works by a combination of radical scavenging and membrane stabilizing properties. It has been demonstrated to attenuate the acute and delayed vascular consequences of SAH and to protect the brain against ischaemic insults. Much of its action is mediated by an effect on the vascular endothelium, although it also appears to exert some direct neuroprotection and to inhibit LP in the subarachnoid blood. These actions of tirilazad in experimental SAH are reviewed.

Animals↗
PubMed1996

Direct measurement of lipid hydroperoxides in iron-dependent spinal neuronal injury.

The relationship between iron-dependent fetal mouse spinal cord neuron injury and the generation of endogenous lipid hydroperoxides (LOOHs) has been investigated. Cultured spinal cord neurons were incubated with ferrous iron (3-200 microM). Cell viability was measured in terms of the uptake of alpha-[methyl-3H]aminoisobutyric acid ([3H]AIB). Both endogenously and iron-generated LOOH, i.e., free fatty acid hydroperoxide (FFAOOH), phosphatidylethanolamine hydroperoxide (PEOOH), and phosphatidylcholine hydroperoxide (PCOOH), were measured directly by an HPLC-chemiluminescence (HPLC-CL) assay. The FFAOOH, PEOOH, and PCOOH levels in neurons incubated with 200 microM Fe2+ for 40 min were, respectively, 22-, 158-, and sevenfold higher than those in non-iron-exposed cultures, demonstrating that phosphatidylethanolamine (PE) was most sensitive to peroxidation. The dose-response and time course of Fe(2+)-induced generation of these LOOHs were also established. In both experiments, the LOOH levels were correlated directly with loss of neuronal viability, suggesting strongly a direct relationship between lipid peroxidation and cell injury. On examination of the time course of the LOOH generation, an immediate increase in PEOOH and PCOOH levels with only 30 s of Fe2+ incubation was observed. In contrast, a lag phase in the increase in FFAOOH level (2 min after Fe2+ addition) suggested a delay in the activation of phospholipase A2 (PLA2) required for the hydrolysis and generation of FFAOOH. This culture system provides an excellent model for screening antioxidant neuroprotective compounds with regard to their ability to protect against iron-dependent peroxidative injury and the relationship of the neuroprotection to inhibition of lipid peroxidation and/or PLA2.

Animals↗
PubMed1996

Mild pre- and posttraumatic hypothermia attenuates blood-brain barrier damage following controlled cortical impact injury in the rat.

Recent studies have demonstrated a neuroprotective effect of mild/moderate hypothermia in models of cerebral trauma and ischemia. In contrast, hypotension is known to exacerbate CNS injury. To better understand the mechanisms whereby hypothermia and hypotension influence secondary neural injury, the present study assessed the effects of these two variables upon blood-brain barrier (BBB) permeability following controlled cortical impact injury. Rats were subjected to either 0, 15, or 30 min of hypotension under normothermic or slightly hypothermic brain temperature conditions. Brain temperature was maintained within 0.5 degrees C of baseline (normothermic) or allowed to float freely (e.g., become hypothermic) throughout the study. Hypotension was induced immediately after head injury by rapid hemorrhage down to a mean arterial pressure of 50 mm Hg and held there for 15 or 30 min. Blood-brain barrier permeability was measured by the extravasation of plasma protein-bound Evan's blue dye into the injured cortex at 60 min postinjury. The results revealed that mild hypothermia (< 1.6 +/- 0.2 degrees C), right before and 15-30 min following head injury, significantly reduced BBB permeability 28.0, 21.8, and 26.2% in rats subjected to 0, 15, or 30 min hypotension, respectively (all p values < or = 0.05). Hypotension did not increase BBB permeability nor did it significantly interact with the brain temperature effect. Previous results, using this same model, have shown that the progressive posttraumatic increase in BBB permeability is preceded by an increase in cortical .OH and lipid hydroperoxides at the site of injury and is attenuated by the lipid peroxidation inhibitor tirilazad mesylate. Thus, the present results are discussed in terms of the role of free radical-induced lipid peroxidation in the genesis of posttraumatic BBB damage and the possible effects of hypothermia upon this injury process.

Animals↗
PubMed1996

Cyclophosphamide is neuroprotective in a gerbil model of transient severe focal cerebral ischemia: correlation with effects of tirilazad mesylate (U-74006F).

Using a gerbil model of severe, temporary focal ischemia (3 h unilateral carotid occlusion), preliminary experiments identified an involvement of neutrophils in the reperfusion injury to the ischemic hemisphere. The present experiments were designed to (1) quantitate the temporal accumulation of neutrophils in the gerbil model, (2) determine if cyclophosphamide-induced neutropenia provided cytoprotection to the ischemic hemisphere, and (3) attempt to correlate the cytoprotective efficacy of tirilazad mesylate with possible effects on postischemic neutrophil accumulation. Following 3 h of unilateral carotid occlusion, animals were collected at increasing times of reperfusion and the CA1 region of the hippocampus and the lateral cortex were assessed for postischemic neuronal damage using a semiquantitative index (N.D.I.) of 0 (no damage) to 4 (>75% neuronal loss). The extent of neutrophil accumulation was determined by counting intensely cytochrome oxidase-positive cells. Minimal neuronal death was evident after 2 h of reperfusion, mean N.D.I. = 0.36. However, between 2 and 4 h of reperfusion, neuronal death did not increase. By 6 h of reperfusion, the neuronal death began to proceed at an accelerated rate, N.D.I. = 0.78. By 12 h, the N.D.I. reached 3.20. The accelerated neuronal death coincided with parenchymal invasion of neutrophils. Cyclophosphamide administration delayed neuronal death in the hippocampus, but exhibited a more sustained protective effect in the lateral cortex. Administration of tirilazad mesylate also resulted in a significant reduction in neutrophil accumulation and significant neuronal protection in both brain areas. Thus, in this gerbil model of transient, but prolonged focal cerebral ischemia, neutrophils appear to play an active role in the reperfusion injury to brain tissue. Our experiments confirm the previously demonstrated neuroprotective efficacy of tirilazad mesylate in this model and provide evidence for a similar protective effect of cyclophosphamide. Although other effects of this antioxidant are also thought to contribute to the overall efficacy, the data are consistent with the hypothesis that one mechanism by which tirilazad acts involves limiting the ability of neutrophils to participate in the reperfusion phase of ischemic cerebral injury.

Animals↗
PubMed1996

Amelioration of impaired cerebral metabolism after severe acidotic ischemia by tirilazad posttreatment in dogs.

BACKGROUND AND PURPOSE: Acidosis may contribute to ischemic injury by mobilizing iron because the iron chelator deferoxamine improves early metabolic recovery from hyperglycermic ischemia. Mobilized iron may then promote oxygen radical-induced lipid peroxidative injury during reperfusion. We tested the hypothesis that administration of the antioxidant tirilazad at the start of reperfusion improves early metabolic recovery after severe acidotic ischemia and ameliorates depletion of the endogenous antioxidant glutathione. METHODS: In anesthetized dogs, arterial glucose concentration was increased to 500 to 600 mg/dL and global incomplete cerebral ischemia was produced for 30 minutes by ventricular fluid infusion to reduce perfusion pressure to 10 to 12 mm Hg. Metabolic recovery and intracellular pH were measured by phosphorus MR spectroscopy. In the first experiment, four groups of eight dogs each received either vehicle or 0.25, 1, or 2.5 mg/kg of tirilizad mesylate at reperfusion. Cerebral blood flow was measured with microspheres. In the second experiment, two groups of eight dogs each each received either vehicle or 2.5 mg/kg of tirilazad at reperfusion, and cortical glutathione was measured at 3 hours of reperfusion. RESULTS: Cerebral blood flow decreased to approximately 6 mL/min per 100 g and intracellular pH decreased to approximately 5.6 during ischemia in all groups. In the vehicle group, ATP recovery was transient and pH remained less than 6.0. Cerebral blood flow, O2 consumption, and ATP eventually declined to near-zero levels by 3 hours. Recovery was improved by tirilazad posttreatment in a dose-dependent fashion. At the highest dose, cerebral blood flow and O2 consumption were sustained near preischemic levels, and five of eight dogs had recovery of ATP greater than 50% and of pH greater than 6.7. Recovery of ATP and phosphocreatine became significantly greater than that in the vehicle group by 17 minutes of reperfusion despite similar levels of early hyperemia, indicating that the drug was acting before the onset of hypoperfusion. Cortical glutathione concentration in the vehicle group was 27% less than that in the tirilazad group and 34% less than that in nonischemic controls. CONCLUSIONS: Decreased depletion of the endogenous antioxidant glutathione is consistent with tirilazad acting as an antioxidant in vivo. Improvement in high-energy phosphate recovery 17 minutes after starting tirilazad infusion during reperfusion is consistent with an early onset of a functionally significant oxygen radical injury. Thus, severe acidosis appears to contribute to early ischemic injury through an oxygen radical mechanism sufficient to impede metabolic recovery.

Acidosis↗
PubMed1996

Protective effects of tirilazad mesylate and metabolite U-89678 against blood-brain barrier damage after subarachnoid hemorrhage and lipid peroxidative neuronal injury.

The 21-aminosteroid lipid-peroxidation inhibitor, tirilazad mesylate (U-74006F), recently was shown in a large multinational Phase III clinical trial to decrease mortality and improve neurological recovery in patients 3 months after onset of aneurysmal subarachnoid hemorrhage (SAH). A major tirilazad metabolite in animals and man, U-89678 is formed when the 4-5 double bond in the A-ring is reduced and has been postulated to contribute significantly to tirilazad's neuroprotective effects. In the first experiment of the present study, the authors compared the effects of tirilazad and U-89678 on acute blood-brain barrier (BBB) damage in rats subjected to SAH via injection of 300 microliters of autologous nonheparinized blood under the dura of the left cortex. The rats were treated by intravenous administration of either 0.3 or 1.0 mg/kg of tirilazad or U-89678 10 minutes before and 2 hours after SAH, and BBB damage was quantified according to the extravasation of the protein-bound Evans' blue dye into the injured cortex 3 hours post-SAH. The results revealed that 0.3 and 1.0 mg/kg tirilazad significantly reduced SAH-induced BBB damage 35.2% (p < 0.05) and 60.6% (p < 0.0001), respectively, in comparison to treatment with vehicle. The 0.3- and 1.0-mg/kg doses of U-89678 also decreased injury by 39.1% (p < 0.05) and 21.3% (not significant), respectively. In the second experiment, the investigators assessed the relative abilities of tirilazad and U-89678 to protect cultured neurons from iron-induced lipid peroxidative injury. Fetal mouse spinal cord cells were pretreated with 3, 10, or 30 microM tirilazad or U-89678 for 1 hour and then exposed to 200 microM ferrous ammonium sulfate (FAS) for 40 minutes. Cell viability was measured in terms of the uptake of [3H]alpha-(methyl)-aminoisobutyric acid 45 minutes after the FAS treatment. Both compounds enhanced neuronal survival in a concentration-dependent fashion. Although the two were equally efficacious, U-89678 was slightly more potent than its parent. On the basis of these findings, the authors conclude that the tirilazad metabolite, U-89678, possesses vaso- and neuroprotective properties that are essentially equivalent to the parent 21-aminosteroid. Hence, U-89678 probably contributes to the protective effects of tirilazad in SAH and other insults to the central nervous system.

Animals↗
PubMed1996

Pathogenic mechanisms in familial amyotrophic lateral sclerosis due to mutation of Cu, Zn superoxide dismutase.

Oxidative mechanisms of damage have been implicated indirectly in the damage to brain tissue caused acutely by ischemia or chronically by neurodegenerative diseases. A direct link between pathogenesis and antioxidant enzyme systems has come from studies of a genetic form of amyotrophic lateral sclerosis (ALS). ALS causes the degeneration of motor neurons in cortex, brainstem and spinal cord with consequent progressive paralysis and death. The disease occurs in both sporadic and familial forms. Some 20% of kindreds in which ALS is inherited in an autosomal dominant fashion have mutations in the gene (SOD1) encoding Cu, Zn superoxide dismutase (SOD). Several SOD1 mutations have been shown by ourselves and others to cause motor neuron disease when expressed at high levels in transgenic mice, whereas transgenic mice expressing comparable amounts of wild-type human SOD do not show clinical disease. Thus, we have argued that motor neuron disease is caused by gain-of-function mutations in the human SOD1 gene. Our current experiments investigate the link between mutation of SOD1 and oxidative pathways of damage.

Amyotrophic Lateral Sclerosis↗
PubMed1996

Protective effects of tirilazad mesylate in a cellular model of peroxynitrite toxicity.

Following CNS trauma or ischemia, peroxynitrite may be a toxic intermediate which forms in vivo when nitric oxide condenses with superoxide. Alone, peroxynitrite appears to directly react with aromatic and sulfhydryl nucleophiles. However, at physiological pH, peroxynitrite is protonated and, in that form, will rapidly (within seconds) decompose to species with hydroxyl radical and nitrogen dioxide characteristics. These reactive species are shown to initiate lipid peroxidation, hydroxylate aromatic residues, and nitrate aromatic residues. This reactivity may contribute to differential toxicity in vivo and in vitro. Tirilazad mesylate (TZ) is a lipid-soluble antioxidant shown to inhibit iron-dependent lipid peroxidation. It is an effective therapy in a variety of CNS injury and ischemia models and is currently undergoing human clinical evaluation in stroke, head injury, and spinal injury. This study was designed to investigate the cytoprotective properties of TZ in a cerebellar granule cell model of peroxynitrite toxicity. Cytoprotective efficacy of TZ was based on viability measurements, blockade of lipid hydroperoxide generation, and blockade of nitrotyrosine formation. Cell viability was determined by [3H]-aminoisobutyric acid (3H-AIB) uptake, and lipid hydroperoxide and nitrotyrosine content were determined by HPLC assays. Tirilazad mesylate was found to have similar cytoprotective effects (approximately 50% protection at 100 microM) when applied before or after exposure of cells to peroxynitrite. In contrast, post-treatment with superoxide dismutase (50 units/ml) or allopurinol (100 microM) failed to produce any cytoprotection. Furthermore, we discovered that TZ inhibited the peroxynitrite-induced increase of phosphatidylethanolamine hydroperoxide (PEOOH), but did not affect the peroxynitrite-induced formation of nitrotyrosine formation. This suggests that the ability of TZ to afford cytoprotection in this peroxynitrite toxicity model is due to the inhibition of membrane-localized lipid peroxidation, and not to the inhibition of nitration of tyrosine residues.

Aminoisobutyric Acids↗
PubMed1996

Comparison of tirilazad mesylate (U-74006F) and methylprednisolone sodium succinate treatments in experimental allergic encephalomyelitis in the guinea pig.

The effects of the non-glucocorticoid 21-aminosteroid, tirilazad mesylate (U-74006F), on MRI and clinical findings in guinea pigs with experimental allergic encephalomyelitis were compared to treatment with methylprednisolone sodium succinate (MPSS). A dose response experiment for U-74006F was performed 1, 3 and 10 mg/kg/day i.p. on day 0-12 after immunization. Additionally, the 3 mg/kg/day i.p. dose was extended to 24 and 35 days. MPSS was given in three different protocols at doses ranging from 0.8 to 3.2 mg/kg/day. Abnormalities in T2-weighted images were assessed as measures of edema and inflammation and gadolinium-DTPA enhanced T1-weighted images were used to determine blood-brain barrier integrity. U-74006F improved the clinical status at doses of 3 and 10 mg/kg. For example, maximum clinical score was halved at 10 mg/ kg/day (P < 0.01). The presence of gadolinium-DTPA in the parenchyma was also decreased at 3 and 10 mg/kg/day U-74006F although maximum MRI scores were decreased only in the 10 mg/kg U-74006F group. Clinical disease suppression seen with 3 mg/kg treatment on days 0-12 reverted to control at > 24 days of dosing. MPSS treatment considerably worsened the clinical outcome of EAE. Mean clinical scores for vehicle and the highest MPSS dose were 0.94 +/- 0.66 versus 2.64 +/- 1.49 (P < 0.05). The combination of decreased T2-weighted abnormalities, clinical signs and gadolinium-DTPA permeation in the U-74006F treated animals suggested protection of the blood-brain barrier without the severe glucocorticoid effects associated with steroid therapy.

Acute Disease↗
PubMed1995

Increased amyloid protein precursor and apolipoprotein E immunoreactivity in the selectively vulnerable hippocampus following transient forebrain ischemia in gerbils.

The postischemic time course of amyloid protein precursor (APP), beta-amyloid protein (beta-AP), and apolipoprotein E (APO-E) immunoreactivity were examined in comparison to neuronal necrosis in the selectively vulnerable hippocampal CA1 region of gerbils subjected to 10 min of bilateral carotid occlusion-induced forebrain ischemia. Loss of 90% of the CA neurons occurred between 24 and 72 h after ischemia, after which no further neuronal necrosis was observed. At 24 h postischemia, there was a decrease in APP and beta-AP immunostaining in the CA1 region. However, beginning at 2 days, there was a dramatic increase in the staining for both proteins. This coincided with a progressive increase in the expression of APO-E and glial fibrillary acidic protein (GFAP) staining between Days 2 and 6, indicative of an activation of astrocytic protein synthesis. Each of the immunocytochemical markers also increased in the less vulnerable CA3 region. However, the peak increase in that region was much less than that in CA1 and, by 7 days, only the GFAP staining remained significantly above the sham level. It has been shown that the E4 isoform of APO-E, when oxidized, avidly binds to beta-AP and thus increases the likelihood of co-beta-AP/APO-E deposition. Therefore, it is postulated that the increased levels of amyloid proteins coincident with an increased production of APO-E in response to ischemic neuronal necrosis may provide conditions that are favorable for the postischemic formation of amyloid deposits.

Amyloid beta-Protein Precursor↗
PubMed1995

Inhibition of lipid peroxidation in central nervous system trauma and ischemia.

A novel group of compounds, the 21-aminosteroids ("lazaroids"), have been designed that are potent inhibitors of oxygen free radical-induced, iron-catalyzed lipid peroxidation (LP) in microvascular and nervous tissue. One of these, tirilazad mesylate (U-74006F), has been selected for clinical evaluation as a cerebroprotective agent. In vitro studies suggest that tirilazad exerts its antioxidant activity by multiple mechanisms including: increasing membrane stability, scavenging of lipid peroxyl radicals, reducing LP-induced arachidonic acid release, decreased formation or scavenging of hydroxyl radicals, and maintenance of the levels of endogenous vitamin E. The major site of action appears to be the blood-brain barrier based upon its known localization in cerebrovascular endothelium and numerous studies showing an attenuation of subarachnoid hemorrhage (SAH), injury, and ischemia-induced blood-brain barrier permeability. Tirilazad has demonstrated neuroprotective efficacy in multiple preclinical models of spinal cord and head injury, SAH, and focal cerebral ischemia, as measured by a decrease in cerebral vasospasm, blood-brain barrier compromise, post-traumatic ischemia, edema, ischemic neuronal necrosis and infarction, and improved neurological recovery. This efficacy is correlated with a reduction in markers of oxygen radical-induced LP. Phase III clinical trials are currently ongoing in spinal cord and head injury, SAH, and ischemic stroke. Initial results from a European/Australian/New Zealand trial in SAH have shown a significant decrease in mortality and an increase in the incidence of good recovery.

Animals↗
PubMed1995

HPLC-chemiluminescence and thermospray LC/MS study of hydroperoxides generated from phosphatidylcholine.

Lipid hydroperoxides generated from phosphatidylcholine (PC) by two commonly employed phosphatidylcholine hydroperoxide (PCOOH) generation methods were examined by HPLC-chemiluminescence (CL) and thermospray LC/MS assay. This HPLC-CL assay is specific for hydroperoxides. In the HPLC-CL chromatograms, a major peak eluted at 4.7 min for the samples generated by the photooxidation of PC in the presence of methylene blue. The direct LC/MS analysis of the hydroperoxides contained in this peak determined that the hydroperoxides are mono- and di-PCOOH. Quantitation showed that over 90% of the hydroperoxides generated by photooxidation are PCOOH. In contrast, a different major peak appeared at 3.7 min for the hydroperoxides generated by the incubation of PC with the azo compound AMVN. We determined by LC/MS analysis that the hydroperoxides contained in this peak were not equivalent to either mono- or di-PCOOH. Indeed, 70%-95% of the hydroperoxides generated by AMVN incubation were not PCOOH, but rather a large portion were AMVN-derived hydroperoxides. The hydroperoxides contained in the 4.7-min peak (i.e., PCOOH) were preferentially responsive to cytochrome c-luminol CL cocktail (about 100-fold more responsive than the hydroperoxides in the 3.7-min peak), whereas the hydroperoxides in the 3.7-min peak (including AMVN-derived hydroperoxide) were preferentially responsive to microperoxidase-isoluminol CL cocktail (about 20-fold more responsive than the PCOOH), suggesting a substrate specificity for the CL cocktail.

Chromatography, High Pressure Liquid↗
PubMed1995

Lack of effect of postinjury treatment with methylprednisolone or tirilazad mesylate on the increase in eicosanoid levels in the acutely injured cat spinal cord.

Methylprednisolone (MP) improves motor recovery in spinal cord-injured patients when administered in a 24 h intensive high dose regimen beginning within 8 h after spinal cord injury (SCI). The rationale for this regimen has been based upon the need for high doses (i.e., 30 mg/kg initial IV dose) to inhibit posttraumatic lipid peroxidation (LP) in the injured spinal segment. However, injury also triggers the immediate calcium-mediated activation of phospholipase A2 (PLA2), the release of arachidonic acid, and the enzymatic formation of potentially deleterious prostaglandins (PGE2 alpha, PGE2), thromboxane A2 (TXA2), and leukotrienes (LTs). Thus, in view of the glucocorticoid receptor-mediated inhibition of PLA2 that underlies much of MP's antiinflammatory actions, an additional neuroprotective mechanism may relate to an inhibition of eicosanoid formation. Using the cat spinal cord compression model (180g x 5 min at L3; Na pentobarbitol anesthesia), we examined whether 30 min postinjury dosing with MP (30 mg/kg IV) could attenuate spinal tissue eicosanoid levels measured by enzyme immunoassay at 1 h (Experiment 1). Pial blood flow was measured over the dorsal columns at the injury site using laser doppler flowmetry to monitor posttraumatic hyperperfusion as an index of the microvascular pathophysiology of acute SCI. In vehicle treated animals at 1 h postinjury, there was a significant increase in the tissue levels of PGF2 alpha (+290%), PGE2 (+260%), TXB2 (stable analog of TXA2, +126%), and LTB4 (+73%) in comparison to sham, uninjured animals. However, 6-keto-PGF1 alpha (stable analog of prostacyclin or PGI2) and LTC4 did not increase. Methylprednisolone did not reduce the increase in eicosanoid production. In the case of LTB4 and LTC4, MP actually increased the levels further. In addition, we examined the effects of a double dose MP regimen (30 mg/kg IV at 30 min plus 15 mg/kg IV at 2.5 h postinjury) on spinal cord eicosanoid levels at 4 h postinjury (Experiment 2). At 4 h postinjury, significant increases in PGF2 alpha, PGE2, TXB2, and 6-keto-PGF1 alpha were observed, and with the exception of PGE2, no MP attenuation of the increased eicosanoids was seen. These results fail to provide evidence that postinjury administration of high dose MP exerts a significant anti-PLA2 action. On the other hand, MP effectively inhibited secondary spinal cord pial hyperperfusion, which is believed to be largely mediated by free radical-lipid peroxidative mechanisms. Thus, it seems likely that the protective action of MP on the acute microvascular pathophysiology of SCI is mediated by its well-documented effects on posttraumatic LP.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗