Effect of the 21-aminosteroid U-74006F on cerebral vasospasm following subarachnoid hemorrhage

The single and double blood injection rabbit subarachnoid hemorrhage model

Over the past 30 years, the rabbit subarachnoid hemorrhage model (SAH) has been used for investigating the post-hemorrhage pathology, especially with respect to understanding of the mechanisms of cerebral vasospasm. However, the molecular mechanisms of cerebral vasospasm remain to be elucidated. Furthermore, it is not clear whether the rabbit SAH model is suitable for the investigation of pathological conditions other than cerebral vasospasm, such as early brain injury. Therefore, the properties of the rabbit SAH model need to be validated, and the reasons for using the rabbit should be clarified. This review explores the settings and technical issues of establishing a rabbit cisterna magna single and double blood injection SAH model and discusses the characteristics and feasibilities of the models.

A comparison of the effects of tirilazad on subarachnoid hemorrhage-induced blood-brain barrier permeability in male and female rats

Phase III subarachnoid hemorrhage clinical trials have shown a beneficial effect of tirilazad only in men. One explanation for the decreased efficacy in women is that women metabolize the drug up to 60% faster than men. However, it is also possible that other more subtle differences between the sexes alter the pharmacodynamic response of women to tirilazad. The purpose of the present study was to compare the efficacy of tirilazad in attenuating early post-subarachnoid hemorrhage-induced blood-brain barrier damage in the rat, a species in which single-dose metabolism of the drug is comparable between males and females. Male and female rats were treated with 0.1, 0.3, 1.0, or 3.0 mg/kg tirilazad (intravenous) 10 minutes before and 2 hours after subarachnoid hemorrhage. At 3 hours posthemorrhage, the extent of blood-brain barrier damage, as measured by Evan's blue extravasation, did not differ between male and female vehicle-treated rats. In addition, treatment with tirilazad produced a similar effect in both males and females at all doses tested. At 0.3 mg/kg, blood-brain barrier damage was reduced 43.4% in males and 48.0% in females (P</=.01 vs vehicle), at 1.0 mg/kg, 33.1% in males and 29.1% in females (P</=.05), and at 3.0 mg/kg, 28.0% in males and 23.8% in females (P=NS). The lowest dose, 0.1 mg/kg, failed to protect the blood-brain barrier in both genders. These results suggest that gender differences do not significantly effect the blood-brain barrier protective efficacy of tirilazad following subarachnoid hemorrhage in the rat.

Pharmacologic reduction of angiographic vasospasm in experimental subarachnoid hemorrhage: systematic review and meta-analysis

Animal models have been developed to simulate angiographic vasospasm secondary to subarachnoid hemorrhage (SAH) and to test pharmacologic treatments. Our aim was to evaluate the effect of pharmacologic treatments that have been tested in humans and in preclinical studies to determine if animal models inform results reported in humans. A systematic review and meta-analysis of SAH studies was performed. We investigated predictors of translation from animals to humans with multivariate logistic regression. Pharmacologic reduction of vasospasm was effective in mice, rats, rabbits, dogs, nonhuman primates (standard mean difference of -1.74; 95% confidence interval -2.04 to -1.44) and humans. Animal studies were generally of poor methodologic quality and there was evidence of publication bias. Subgroup analysis by drug and species showed that statins, tissue plasminogen activator, erythropoietin, endothelin receptor antagonists, calcium channel antagonists, fasudil, and tirilazad were effective whereas magnesium was not. Only evaluation of vasospasm >3 days after SAH was independently associated with successful translation. We conclude that reduction of vasospasm is effective in animals and humans and that evaluation of vasospasm >3 days after SAH may be preferable for preclinical models.

Antioxidant strategies in neurocritical care

An increase in oxidative stress and overproduction of oxidizing reactive species plays an important role in the pathophysiology of several conditions encountered in the neurocritical care setting including: ischemic and hemorrhagic strokes, traumatic brain injury, acute respiratory distress syndrome, sepsis, and organ failure. The presence of oxidative stress in these conditions is supported by a large body of pre-clinical and clinical studies, and provides a rationale to support a potential therapeutic role for antioxidants. The purpose of this article is to briefly review the basic mechanisms and molecular biology of oxidative stress, summarize its role in critically ill neurological patients, and review available data regarding the potential role of antioxidant strategies in neurocritical care and future directions.

Effect of a free radical scavenger, edaravone, on free radical reactions: related signal transduction and cerebral vasospasm in the rabbit subarachnoid hemorrhage model

OBJECTIVE

it is hypothesized that free radical reactions evoked by oxyhemoglobin (oxyHb) cause cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH), even though the detailed mechanisms have not yet been fully established. The aims of this study were thus to investigate, through the use of the double-hemorrhage rabbit model, the possibility that free radical reactions play a role in cerebral vasospasm and to delineate the mechanism of signal transduction that causes cerebral vasospasm.

METHODS

in the SAH group, SAH was simulated using the double-hemorrhage rabbit model. In the treatment group, edaravone (0.6 mg/kg), a potent free radical scavenger, was injected into the central ear vein twice a day. Four days after SAH, the basilar artery was excised. The degree of cerebral vasospasm was evaluated by measuring the diameter of each basilar artery, and the expression of Rho-kinase in the vascular wall was examined by western blotting.

RESULTS

the diameter of the basilar artery in the edaravone-treated group was 0.64 ± 0.06 mm, which was statistically significantly larger than that in the nontreated SAH group (0.50 ± 0.03 mm; p < 0.01). The expression of Rho-kinase in the edaravone-treated group was statistically significantly reduced in comparison to that of the nontreated SAH group.

CONCLUSION

results from this study have indicated for the first time that free radical reactions mediated by oxyHb may play an important role in the pathogenesis of cerebral vasospasm through the expression of Rho-kinase.

Tirilazad for aneurysmal subarachnoid haemorrhage

BACKGROUND

Delayed cerebral ischaemia is a significant contributor to poor outcome (death or disability) in patients with aneurysmal subarachnoid haemorrhage (SAH). Tirilazad is considered to have neuroprotective properties in animal models of acute cerebral ischaemia.

OBJECTIVES

To assess the efficacy and safety of tirilazad in patients with aneurysmal SAH.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched October 2009); the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 2, 2009); MEDLINE (1966 to October 2009); EMBASE (1980 to October 2009); and the Stroke Trials Directory, the National Center for Complementary and Alternative Medicine, and the National Institute of Health Clinical Trials Database (searched October 2009). We handsearched 10 Chinese journals, searched the reference lists of relevant publications, and contacted the manufacturers of tirilazad.

SELECTION CRITERIA

Randomised trials of tirilazad started within four days of SAH onset, compared with placebo or open control in patients with aneurysmal SAH documented by angiography and computerised tomography (CT) scan or cerebrospinal fluid examination, or both.

DATA COLLECTION AND ANALYSIS

We extracted data relating to case fatality, poor outcome (death, vegetative state, or severe disability), delayed cerebral ischaemia (or symptomatic vasospasm), cerebral infarction and adverse events of treatments. We pooled the data using the Peto fixed-effect method for dichotomous data.

MAIN RESULTS

We included five double-blind, placebo-controlled trials involving 3821 patients; there was no significant heterogeneity. Oral or intravenous nimodipine was used routinely as a background treatment in both groups in all trials. There was no significant difference between the two groups at the end of follow up for the primary outcome, death (odds ratio (OR) 0.89, 95% confidence interval (CI) 0.74 to 1.06), or in poor outcome (death, vegetative state or severe disability) (OR 1.04, 95% CI 0.90 to 1.21). During the treatment period, fewer patients developed delayed cerebral ischaemia in the tirilazad group than in the control group (OR 0.80, 95% CI 0.69 to 0.93). Subgroup analyses did not demonstrate any significant difference in effects of tirilazad on clinical outcomes. Leukocytosis and prolongation of Q-T interval occurred significantly more frequently in the treatment group in only one trial evaluating tirilazad at high dose. There was no significant difference in infusion site disorders or other laboratory parameters between the two groups.

AUTHORS' CONCLUSIONS

There is no evidence that tirilazad, in addition to nimodipine, reduces mortality or improves poor outcome in patients with aneurysmal SAH.

PKC and Rho in vascular smooth muscle: activation by BOXes and SAH CSF

Cerebral vasospasm (CV) remains a significant cause of delayed neurological deficit and ischemic damage after subarachnoid hemorrhage (SAH), despite intensive research effort. The current lack of an effective therapeutic approach is somewhat due to our lack of understanding regarding the mechanism by which this pathological constriction develops. Recent evidence implicates bilirubin oxidation products (BOXes) in the etiology of CV after SAH: BOXes are found in cerebrospinal fluid from SAH patients with symptomatic or angiographically visible vasospasm (CSFV) but not in CSF from SAH patients with no vasospasm (CSFC). We have previously published research suggesting that the etiology of CV comprises two components: a physiological stimulation to constrict and a pathological failure to relax. Both these components are elicited by CSFV, but not CSFC, and BOXes synthesized in the laboratory potentiate physiological constriction in arterial smooth muscle in vitro, and elicit contraction in pial arteries in vivo. In this paper, we will present our results concerning the action of BOXes on arterial smooth muscle constriction, compared with CSFV. We will also present evidence implicating temporal changes in PKC isoforms and Rho expression in both BOXes- and CSFV-elicited smooth muscle responses.

Advances in vasospasm treatment and prevention

Outcome after aSAH depends on several factors, including the severity of the initial event, perioperative medical management, surgical variables, and the incidence of complications. Cerebral vasospasm (CV) is ure to consistently respond to treatment, emphasizing the need for further research into the underlying mechanisms of SAH-induced cerebrovascular dysfunction. To this end, our paper reviews the relevant literature on the main therapies employed for CV after aSAH and discusses possible avenues for future investigations. Current management of this condition consists of maximal medical therapy, including triple H regimen and oral administration of calcium antagonists, followed by endovascular balloon angioplasty and/or injection of vasodilatory agents for refractory cases. As the precise pathophysiology of CV is further elucidated, the development of promising investigational therapies will follow.

A review of current and future medical therapies for cerebral vasospasm following aneurysmal subarachnoid hemorrhage

✓In an effort to help clarify the current state of medical therapy for cerebral vasospasm, the authors reviewed the relevant literature on the established medical therapies used for cerebral vasospasm following aneurysmal subarachnoid hemorrhage (SAH), and they discuss burgeoning areas of investigation. Despite advances in the treatment of aneurysmal SAH, cerebral vasospasm remains a common complication and has been correlated with a 1.5- to threefold increase in death during the first 2 weeks after hemorrhage. A number of medical, pharmacological, and surgical therapies are currently in use or being investigated in an attempt to reverse cerebral vasospasm, but only a few have proven to be useful. Although much has been elucidated regarding its pathophysiology, the treatment of cerebral vasospasm remains a dilemma. Although a poor understanding of SAH-induced cerebral vasospasm pathophysiology has, to date, hampered the development of therapeutic interventions, current research efforts promise the eventual production of new medical therapies.

Time course of production of hydroxyl free radical after subarachnoid hemorrhage in dogs

Vasospasm after subarachnoid hemorrhage (SAH) is associated with lipid peroxidation. However, lipid peroxides increase in a delayed fashion after SAH and may be a byproduct of but not a cause of vasospasm. This study correlated vasospasm with hydroxyl free radical and lipid peroxide levels. 24 dogs had baseline cerebral angiography and induction of SAH by 2 injections of blood into the cisterna magna at baseline and 2 days later. Angiography was repeated 4, 7, 10, 14 or 21 days after the first injection (n = 4 per group) and a microdialysis catheter was inserted into the premedullary cistern. Control dogs (n = 4) underwent angiography and microdialysis but not SAH. Salicylic acid, 100 mg/kg, was administered intravenously, and microdialysis fluid was collected and analyzed by high pressure liquid chromatography for 2,3- and 2,5-dihydroxybenzoic acids (DHBA). Malondialdehyde was measured in subarachnoid clot removed from the prepontine cistern and in the basilar artery itself at the time of euthanasia. Significant vasospasm developed 4 to 14 days after SAH. Malondialdehyde levels were significantly elevated in the basilar artery and subarachnoid clot 4 days after SAH (p < 0.0001, ANOVA) but not at other times. 2,5-DHBA levels were significantly greater than control at 4 to 14 days and they peaked at 4 days (p < 0.05, ANOVA). 2,3-DHBA was significantly increased at 4 days after SAH (p < 0.05, ANOVA). There were significant correlations between basilar artery malondialdehyde levels and vasospasm and cerebrospinal fluid 2,5-DHBA levels and vasospasm. These results suggest the presence of hydroxyl free radical after SAH and demonstrate a correlation between such production, as measured by trapping with salicylate, and the early phase of vasospasm. The correlation with vasospasm implicates free radicals and lipid peroxidation in this phase of vasospasm.

Clinical trials for cytoprotection in stroke

To date, many cytoprotective drugs have reached the stage of pivotal phase 3 efficacy trials in acute stroke patients. (Table 1) Unfortunately, throughout the neuroprotective literature, the phrase "failure to demonstrate efficacy" prevails as a common thread among the many neutral or negative trials, despite the largely encouraging results encountered in preclinical studies. The reasons for this discrepancy are multiple, and have been discussed by Dr. Zivin in his review. Many of the recent trials have addressed deficiencies of the previous ones with more rigorous trial design, including more specific patient selection criteria (ensure homogeneity of stroke location and severity), stratified randomization algorithms (time-to-treat), narrowed therapeutic time-window and pharmacokinetic monitoring. Current trials have also incorporated biologic surrogate markers of toxicity and outcome such as drug levels and neuroimaging. Lastly, multi-modal therapies and coupled cytoprotection/reperfusion strategies are being investigated to optimize tissue salvage. This review will focus on individual therapeutic strategies and we will emphasize what we have learned from these trials both in terms of trial design and the biologic effect (or lack thereof) of these agents.

Effect of edaravone on cerebral vasospasm following experimental subarachnoid hemorrhage

The effect of the free radical scavenger edaravone on experimental cerebral vasospasm following subarachnoid hemorrhage (SAH) was investigated in a canine double hemorrhage model. Changes in the diameter of the basilar artery were assessed by serial angiography. The diameter ratio at day 7 was calculated as the percent of the basilar artery diameter of a given angiogram with respect to that of its control (day 0). The diameter ratios for the basilar artery following SAH in the control and vehicle-treated groups were 49.7% +/- 3.9% (mean +/- SEM) and 50.1% +/- 1.7%, respectively. Edaravone was administered either by continuous intravenous injection for 7 days or by bolus injection for 7 days. Continuous administration of edaravone (1 mg/kg/hr or 10 mg/kg/hr) significantly attenuated the narrowing of the basilar artery following SAH. The diameter ratios in these groups were 71.3% +/- 3.6% (1 mg/kg/hr) and 75.7% +/- 1.7% (10 mg/kg/hr). Bolus administration of edaravone (3 mg/kg, every 12 hours) reduced the arterial narrowing following SAH. The diameter ratio on day 7 was 60.1% +/- 3.3%, but the difference was not significant. These findings suggest that edaravone is effective in preventing cerebral vasospasm following SAH.

Current concepts in neurocritical care

The current concepts in neurocritical care including advancement in therapeutic interventions and monitoring modalities are covered for four entities: stroke, subarachnoid hemorrhage, traumatic brain injury and spinal cord injury. Although therapies were mainly supportive in the past, acute ischemic stroke may now be treated with tissue plasminogen activator if inclusion and exclusion criteria are met. The management of subarachnoid hemorrhage including cerebral vasospasm is discussed in detail. Traumatic brain injury and spinal cord injury with prevention of secondary injury to limit further sequelae are also covered. Medical complications which increase morbidity and mortality are also presented.

Assessment of antioxidant reserves and oxidative stress in cerebrospinal fluid after severe traumatic brain injury in infants and children

Studies in experimental traumatic brain injury (TBI) support a key role for oxidative stress. The degree of oxidative injury in clinical TBI, however, remains to be defined. We assessed antioxidant defenses and oxidative stress in pediatric TBI by applying a comprehensive battery of assays to cerebrospinal fluid samples. Using a protocol approved by our institutional review board, 87 cerebrospinal fluid samples from 11 infants and children with severe TBI (Glasgow Coma Scale score < or = 8) and 8 controls were studied. Cerebrospinal fluid was drained as standard care after TBI. CSF was assessed on d 1, 2, and 5-7 after ventricular drain placement. Biochemical markers of oxidative stress included F(2)-isoprostane and protein sulfhydryl (detected by ELISA and fluorescence assay, respectively). Antioxidant defenses were measured by determination of total antioxidant reserve (via chemiluminescence assay), and ascorbate (via HPLC) and glutathione (via fluorescence assay) concentrations. Free radical production (ascorbate radical) was assessed by electron paramagnetic resonance spectroscopy. F(2)-isoprostane was markedly increased versus control, maximal on d 1 (93.8 +/- 30.8 pg/mL versus 7.6 +/- 5.1 pg/mL, p < 0.05). Total antioxidant reserve was reduced versus control. Reduction was maximal on d 5-7 (81.8 +/- 3.7 microM versus 178.9 +/- 2.2 microM, p < 0.05). Ascorbate was remarkably reduced (53.8 +/- 8 microM versus 163.8 +/- 21 microM on d 1, p < 0.05). Ascorbate depletion was likely associated with its free radical oxidation, as evidenced by electron paramagnetic resonance spectroscopy. Glutathione levels increased on d 1, then decreased versus control (0.19 +/- 0.05 microM versus 1.2 +/- 0.16 microM, p < 0.05). This is the first comprehensive study of antioxidant reserve and oxidative injury in clinical TBI. Progressive compromise of antioxidant defenses and evidence of free radical-mediated lipid peroxidation are noted. These markers could be used to monitor antioxidant strategies in clinical trials.

High-dose methylprednisolone prevents vasospasm after subarachnoid hemorrhage through inhibition of protein kinase C activation

We have previously shown that the inflammatory process after subarachnoid hemorrhage causes vasospasm. The efficacy of methylprednisolone by suppression of the inflammatory process has been reported, although pharmacological mechanisms have not been clarified. The purpose of this study was to investigate the pharmacological mechanism of methylprednisolone on vasospasm. Using the 'two-hemorrhage' canine model, progression of angiographic vasospasm was assessed in nontreated and treated groups with methylprednisolone. Methylprednisolone 10 mg kg-1 was injected i.v. after the first injection of blood, and the same dose was injected every 12 h until day 7. Protein kinase C (PKC) activity of canine basilar arteries in both groups was measured during the course of vasospasm. In the isometric tension study, the effect of methylprednisolone on tensions induced by phorbol 12-myristate 13-acetate (PMA), or high-K+ solution, was also evaluated. Methylprednisolone significantly reduced severity of vasospasm. In the treated group, PKC activity was not enhanced compared with the nontreated group at any point. Methylprednisolone inhibited tonic tension induced by PMA, but not that induced by high-K+ solution. We conclude that methylprednisolone prevents severity of vasospasm through inhibition of PKC activation, but does not work as a Ca2+ channel blocker.

Transgenic CuZn-superoxide dismutase inhibits NO synthase induction in experimental subarachnoid hemorrhage

BACKGROUND AND PURPOSE

The expression of inducible NO synthase (iNOS) after experimental subarachnoid hemorrhage (SAH) has been postulated to play a critical role in the pathogenesis of SAH and subsequent cerebral vasospasm. The inhibitory effect of CuZn-superoxide dismutase (CuZn-SOD) on the induction of iNOS after SAH was examined by using transgenic mice overexpressing CuZn-SOD.

METHODS

SOD-transgenic mice and nontransgenic littermates were subjected to SAH by endovascular perforation of the left anterior cerebral artery. The iNOS mRNA expression after SAH was determined by reverse transcription-polymerase chain reaction, and the distribution of iNOS-positive cells was immunohistochemically examined. The nuclear expression of activated nuclear factor-kappaB, a major transcription factor of iNOS gene, was also immunohistochemically examined.

RESULTS

In nontransgenic mice, SAH-induced iNOS protein and mRNA expressions in the arteries of basal cistern as well as in the cerebral cortex were demonstrated by immunohistochemistry and reverse transcription-polymerase chain reaction. SAH-induced iNOS protein and mRNA expressions in those tissues were much reduced in SOD-transgenic mice compared with nontransgenic mice. Moreover, the nuclear expression of the activated form of nuclear factor-kappaB was immunohistochemically detected in the cerebral cortices of nontransgenic mice but not in those of SOD-transgenic mice.

CONCLUSIONS

These results indicate that oxygen-derived free radicals, particularly superoxide, play an important role in the iNOS gene expression after SAH and provide a molecular basis for the protective role of SOD against vasospasm after SAH.

Review of medical prevention of vasospasm after aneurysmal subarachnoid hemorrhage: a problem of neurointensive care

Cerebral vasospasm remains a devastating medical complication of aneurysmal subarachnoid hemorrhage (SAH). It is associated with high morbidity and mortality rates, even after the aneurysm has been secured surgically or radiologically. A great deal of experimental and clinical research has been conducted in an effort to find ways to prevent this complication. The literature includes extensive coverage of in vivo animal model studies of SAH and vasospasm. These experimental studies have contributed to tremendous advances in the understanding of the mechanisms leading to cerebral vasospasm. Most of the experimental settings, however, have demonstrated varying levels of ability to predict accurately what occurs in human SAH. Therefore, although animal models have been developed to test new therapies, most of the treatment effects have been shown to be less compelling when trials have been conducted in clinical settings. The interpretation of current literature is complicated further by the imprecise estimation of the incidence of cerebral vasospasm, which is due to various degrees of clinical expression, ranging from the absence of symptoms in the presence of increased blood flow velocities at transcranial Doppler or vessel diameter reduction at angiography to neurological manifestations of severe ischemic deficits. In addition, a change over time in the incidence pattern of human SAH and vasospasm, possibly related to improved surgical techniques and overall patient management, may have occurred. This topic review collects the relevant literature on clinical trials investigating prophylactic therapies for cerebral vasospasm in patients with aneurysmal SAH and emphasizes the need for large clinical trials to confirm the results derived from clinical experience. In addition, it points out some experimental therapies that may hold promise in future clinical trials to prevent the occurrence of vasospasm.

Tirilazad for acute ischaemic stroke

BACKGROUND

Tirilazad mesylate is neuroprotective in experimental models of ischaemic stroke suggesting it might be of benefit clinically.

OBJECTIVES

To assess whether tirilazad mesylate is safe and effective at improving outcome in patients with acute ischaemic stroke.

SEARCH STRATEGY

Trials of tirilazad were identified from searches of the Cochrane Stroke Group Specialised Trials Register (last searched: May 2001) and the Cochrane Controlled Trials Register (CENTRAL/CCTR). In addition, we contacted the Pharmacia & Upjohn company, the manufacturer of tirilazad, to identify unpublished studies and further information.

SELECTION CRITERIA

Truly and quasi-randomised unconfounded placebo or open controlled trials of tirilazad administered within 24 hours onset of suspected or proven acute ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Data relating to early and end-of-trial case fatality, disability (Barthel Index and Glasgow Outcome Scale), phlebitis, and QTc were extracted by treatment group from published data and company reports.

MAIN RESULTS

Six trials (four published, two unpublished) assessing tirilazad in 1757 patients with presumed acute ischaemic stroke were identified; all were double-blind and placebo-controlled in design. Tirilazad did not alter early case fatality (odds ratio, OR 1.11, 95% confidence intervals, 95% CI 0.79 to 1.56) or end-of-trial case fatality (OR 1.12, 95% CI 0.88 to 1.44). Tirilazad increased the odds of being dead or disabled by about one fifth, though the result was only just statistically significant; the odds ratios were similar whether the expanded Barthel Index or Glasgow Outcome Scale were used to assess outcome (OR 1.23, 95% CI 1.01 to 1.51; OR 1.23, 95% CI 1.01 to 1.50 respectively). Tirilazad significantly increased the rate of infusion site phlebitis (OR 2.81, 95% CI 2.14 to 3.69). Functional outcome (EBI) was significantly worse in prespecified subgroups of patients: females (OR 1.46, 95% CI 1.08 to 1.98) and subjects receiving low dose tirilazad (OR 1.31, 95% CI 1.03 to 1.67); a non-significant worse outcome was also seen in patients with mild-moderate stroke (OR 1.40, 95% CI 0.99 to 1.98).

REVIEWER'S CONCLUSIONS

Tirilazad mesylate increased the combined end-point of 'death or disability' by about one-fifth, but did not alter case fatality, when given to patients with acute ischaemic stroke. Although further trials of tirilazad are now not warranted, analysis of individual patient data from the trials may help elucidate why tirilazad appears to worsen outcome in acute ischaemic stroke.

Tirilazad mesylate in acute ischemic stroke: A systematic review. Tirilazad International Steering Committee

BACKGROUND AND PURPOSE

Tirilazad is a nonglucocorticoid, 21-aminosteroid that inhibits lipid peroxidation. Studies in experimental models of ischemic stroke had suggested that tirilazad had neuroprotective properties. As a result, clinical studies were undertaken to assess the safety and efficacy of tirilazad in the treatment of acute ischemic stroke. We performed a systematic review of randomized, controlled trials that assessed the safety and efficacy of tirilazad in patients with acute ischemic stroke.

METHODS

Trials of tirilazad were identified from searches of the Cochrane Library and communication with the Pharmacia & Upjohn company, the manufacturer of tirilazad. Data relating to early and end-of-trial case fatality, disability (Barthel Index and Glasgow Outcome Scale), phlebitis, and corrected QT interval were extracted by treatment group from published data and company reports and analyzed by using the Cochrane Collaboration meta-analysis software REVMAN.

RESULTS

Six trials (4 published, 2 unpublished) assessing tirilazad in 1757 patients with presumed acute ischemic stroke were identified; all were double-blind and placebo controlled in design. Tirilazad did not alter early case fatality (odds ratio [OR] 1.11, 95% confidence interval [CI] 0.79 to 1.56) or end-of-trial case fatality (OR 1.12, 95% CI 0.88 to 1.44). A just-significant increase in death and disability, assessed as either the expanded Barthel Index (OR 1.23, 95% CI 1.01 to 1.51) or Glasgow Outcome Scale (OR 1. 23, 95% CI 1.01 to 1.50) was observed. Tirilazad significantly increased the rate of infusion site phlebitis (OR 2.81, 95% CI 2.14 to 3.69). Functional outcome (expanded Barthel Index) was significantly worse in prespecified subgroups of patients: females (OR 1.46, 95% CI 1.08 to 1.98) and subjects receiving low-dose tirilazad (OR 1.31, 95% CI 1.03 to 1.67); a nonsignificant worse outcome was also seen in patients with mild to moderate stroke (OR 1. 40, 95% CI 0.99 to 1.98).

CONCLUSIONS

Tirilazad mesylate increases death and disability by about one fifth when given to patients with acute ischemic stroke. Although further trials of tirilazad are now unwarranted, analysis of individual patient data from the trials may help elucidate why tirilazad appears to worsen outcome in acute ischemic stroke.

Effect of an antioxidant, ebselen, on development of chronic cerebral vasospasm after subarachnoid hemorrhage in primates

BACKGROUND

Oxidation and/or free radical reactions after subarachnoid hemorrhage (SAH) may be involved in the development of chronic cerebral vasospasm. The inhibition of these reactions is thought to be one of the therapeutic strategies for prevention of cerebral vasospasm. We investigated the effect of Ebselen, a synthetic seleno-organic compound, which exhibits anti-oxidation by glutathione peroxidaselike activity to inhibit free radical reactions by lipid peroxidation on the development of chronic cerebral vasospasm in a primate model.

METHODS

Seventeen monkeys were used. SAH was produced by introduction of a blood clot around the right middle cerebral artery and the right side of the circle of Willis in all animals. The monkeys were randomly divided into three groups according to Ebselen dosage: 1) no dosage or non-treated group; 2) high-dose Ebselen group; and 3) low-dose Ebselen group. The drug was administered at 10 mg/Kg in the high-dose group and 5 mg/Kg in the low-dose group twice a day in each group for 7 days after SAH. The vessel diameter was evaluated on angiograms before the induction of SAH and at Day 7 following SAH.

RESULTS

In the untreated group, the angiograms showed significant (p < 0.05) reductions of the mean vessel caliber of the right internal carotid (ICA) (38 +/- 10% reduction) and the middle cerebral artery (MCA) (56 +/- 9.7%) compared with the baseline value before SAH. In the high-dose Ebselen-treated group, the mean percent reduction in vessel caliber of the right ICA (16 +/- 11%) and MCA (28 +/- 9.5%) on Day 7 angiograms were significantly (p < 0.05) lower than those in the nontreated group, whereas the mean percent reduction of these vessels in the low-dose Ebselen-treated group showed no significant difference compared with the untreated group.

CONCLUSIONS

Chronic cerebral vasospasm was inhibited in the animals in which a relatively large amount of Ebselen was administered for 7 days after SAH. The results suggest that the oxidation or free radical reaction by lipid peroxidation after SAH might be involved in the pathogenesis of vasospasm, and that inhibition of these reactions by drugs, such as Ebselen, may have a promising effect for prevention of vasospasm.

Double-blind, randomized, vehicle-controlled study of high-dose tirilazad mesylate in women with aneurysmal subarachnoid hemorrhage. Part I. A cooperative study in Europe, Australia, New Zealand, and South Africa

OBJECT

Findings from previous multicenter clinical trials have suggested that tirilazad mesylate, a synthetic nonhormonal 21-aminosteroid, might be effective in preventing delayed cerebral ischemia following subarachnoid hemorrhage (SAH). This beneficial effect, however, was greater in males than females, possibly because of gender-related pharmacokinetic differences. The authors sought to assess the effects of administering a larger dose of tirilazad in women with SAH.

METHODS

To test the efficacy of a higher tirilazad mesylate dose in female patients, a prospective randomized, double-blind, vehicle-controlled trial was conducted at 56 neurosurgical centers in Europe, Australia, New Zealand, and South Africa. Eight hundred nineteen patients were randomly assigned to receive either 15 mg/kg/day of tirilazad mesylate or a placebo containing the citrate vehicle. The two groups were similar in prognostic factors for delayed cerebral ischemia and overall outcome. High-dose tirilazad appeared to be well tolerated because no differences in the incidence of untoward medical events were noted between the two groups. Medical and surgical interventions were no different in the two treatment groups except for hyperdynamic therapy (intentional hypervolemia, induced hypertension, and/or hemodilution), which was more often used in the placebo-treated group to counteract symptomatic vasospasm (24% of patients given placebo compared with 18% of patients given tirilazad, p = 0.02). Mortality rates and overall outcome, assessed using the Glasgow Outcome Scale at 3 months post-SAH, were not different between the two groups, despite a significantly lower incidence of delayed cerebral ischemia in patients given tirilazad. Post hoc subgroup analysis by neurological grade also did not reveal significant differences in outcome, although a trend toward a lower mortality rate favoring the study drug was present in patients with neurological Grade IV and V at admission (32% compared with 37%). Symptomatic vasospasm occurred in 33.7% of the placebo-treated patients as opposed to 24.8% of the patients who were given tirilazad (p = 0.005). The severity of symptomatic vasospasm was also attenuated by administration of the study drug (severe symptomatic vasospasm was reported in 11% of the placebo-treated patients compared with 6% of patients in the tirilazad-treated group (p = 0.008). Clinical cerebral infarction from vasospasm was also reduced from 13% in the vehicle-treated group to 8% in the tirilazad-treated group (p < 0.04).

CONCLUSIONS

The authors conclude that high-dose tirilazad mesylate is well tolerated in women with aneurysmal SAH. Although a significant reduction in the incidence of symptomatic vasospasm was observed in the treatment group, the primary end point (mortality rate at 3 months post-SAH) was not affected by the study drug. The use of other potentially effective rescue therapies (that is, hypervolemia, hemodilution, and induced hypertension) to counteract vasospasm may have been responsible for these contrasting observations between the two groups.

Effects of tirilazad mesylate on vasospasm and phospholipid hydroperoxides in a primate model of subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Tirilazad mesylate has been used in the attempt to prevent cerebral vasospasm after subarachnoid hemorrhage (SAH), although the actual targets of this agent in vivo have thus far been controversial. Chemiluminescence/high-performance liquid chromatography provided a new method for direct measurements of phosphatidylcholine hydroperoxide (PCOOH) and phosphatidylethanolamine hydroperoxide (PEOOH) in vivo and showed that phosphatidylcholine is the lipid class most susceptible to lipid peroxidation. In the present study we measured those levels in a primate model of SAH for determination of the effects of tirilazad on vasospasm.

METHODS

Fourteen Macaca monkeys of both sexes were randomly assigned into 2 groups: a tirilazad group receiving a dosage of 0.3 mg/kg and a placebo group receiving only the vehicle in which tirilazad was delivered. After the induction of experimental SAH around the right middle cerebral artery on day 0, tirilazad or vehicle was administered intravenously every 8 hours for 6 days. On day 7, the animals were killed after angiography and regional cerebral blood flow measurements were performed. The levels of PCOOH and PEOOH were measured in the clots, bilateral parietal cortices, right frontal cortex contact with clots, cerebellar hemispheres, bilateral middle cerebral arteries, and basilar arteries.

RESULTS

In the placebo group, a significant vasospasm occurred in the cerebral arteries on both sides, but most prominently on the right side. The degree of vasospasm in the cerebral arteries was significantly attenuated in the tirilazad group (P<0.005). There were no significant differences in regional cerebral blood flow, PCOOH, and PEOOH levels in the clots, cerebral cortices, and cerebellar hemispheres between the 2 groups. In contrast, the levels of PCOOH in the cerebral arteries were significantly higher in the placebo group than in the tirilazad group (P<0.025). It was remarkable that the tirilazad treatments eliminated PCOOH in any vascular territory after SAH.

CONCLUSIONS

PCOOH in the artery wall may be an important indicator for vasospasm, and the inhibition of PCOOH may explain the efficacy of tirilazad on vasospasm.

Novel pharmacologic strategies in the treatment of experimental traumatic brain injury: 1998

The mechanisms underlying secondary or delayed cell death following traumatic brain injury are poorly understood. Recent evidence from experimental models suggests that widespread neuronal loss is progressive and continues in selectively vulnerable brain regions for months to years after the initial insult. The mechanisms underlying delayed cell death are believed to result, in part, from the release or activation of endogenous "autodestructive" pathways induced by the traumatic injury. The development of sophisticated neurochemical, histopathological and molecular techniques to study animal models of TBI have enabled researchers to begin to explore the cellular and genomic pathways that mediate cell damage and death. This new knowledge has stimulated the development of novel therapeutic agents designed to modify gene expression, synthesis, release, receptor or functional activity of these pathological factors with subsequent attenuation of cellular damage and improvement in behavioral function. This article represents a compendium of recent studies suggesting that modification of post-traumatic neurochemical and cellular events with targeted pharmacotherapy can promote functional recovery following traumatic injury to the central nervous system.

Protection from renal ischemia-reperfusion injury by the 2-methylaminochroman U83836E

BACKGROUND

In a prior study the 21-aminosteroid (lazaroid) U74389F provided in vivo protection from oxidative stress when used as a preventive therapy in ischemia-reperfusion injury in the kidney. As the cell membrane is the principal site for lipoperoxidation, in the current study the very lipophilic 2-methylaminochroman U83836E, a recently developed lazaroid, was administered to rats at 3 mg/kg before renal ischemia-reperfusion. In addition to the biochemical parameters, the renal function and the histological appearance were carefully evaluated.

METHODS

Glutathione, adenine nucleotides and lipid peroxidation products were determined in kidneys reperfused for 2 and 24 hours after 90 minutes of ischemia. Renal function was assessed by plasma creatinine, and renal injury by histological examination.

RESULTS

Reperfusion-induced glutathione oxidation, expressed as an oxidized-to-total glutathione ratio, was significantly attenuated both after 2 and 24 hours of reperfusion by treatment with U83836E. Adenosine triphosphate (ATP) was still significantly depleted after 24 hours in the control group, while at the same time treated animals had already recovered to baseline values. Lipid peroxidation products were significantly lower in lazaroid-groups both after 2 and 24 hours of reperfusion. Renal function after 24 hours of reperfusion was notably better in the treated rats. Histological examination confirmed the protective action of the drug. After 24 hours the control group showed large areas of parenchymal hemorrhage and necrosis with dilated tubules and blood vessel thrombosis, while treated animals showed small necrotic areas with a background of mild interstitial inflammatory cells.

CONCLUSIONS

Our results suggest that there is a protective effect of U83836E in ischemia-reperfusion injury, in that tissue damage due to oxidative stress is reduced, thus ameliorating renal function impairment.

U74389G prevents vasospasm after subarachnoid hemorrhage in dogs

OBJECTIVE

Oxygen-derived free radicals may contribute to vasospasm after the rupture of an intracranial aneurysm through direct vasoconstricting effects occurring within the arterial wall or, secondarily, by causing lipid peroxidation in the subarachnoid erythrocytes with secondary induction of vasoconstriction. U74389G is a potent inhibitor of lipid peroxidation and a scavenger of oxygen-derived free radicals. This study determined the relative contributions of oxygen-derived free radicals and lipid peroxidation to vasospasm in the double-hemorrhage dog model.

METHODS

Sixteen dogs underwent baseline (Day 0) cerebral angiography and induction of subarachnoid hemorrhage by two injections of blood into the cisterna magna 2 days apart. They were randomized to receive drug vehicle (n=8) or U74389G (n=8, 3 mg/kg of body weight/d) intravenously. Drug administration and end point analysis were blinded. The end points were angiographic vasospasm, as assessed by comparison of angiograms obtained before and 7 days after subarachnoid hemorrhage, and the levels of malondialdehyde and salicylate hydroxylation products (dihydroxybenzoic acids) in cerebrospinal fluid and of malondialdehyde in subarachnoid blood clots and basilar arteries 7 days after hemorrhage.

RESULTS

Comparisons within groups of Day 0 and Day 7 angiograms and between groups of angiograms obtained at Day 7, showed significant vasospasm in animals in the vehicle group (mean+/-standard error, 51%+/-4) but not in the U74389G group (25%+/-11, P < 0.05, unpaired t test). High-pressure liquid chromatographic assays of malondialdehyde and dihydroxybenzoic acids in cerebrospinal fluid, subarachnoid blood clots, and basilar arteries showed no significant differences between groups.

CONCLUSION

The significant prevention of vasospasm by U74389G without change in levels of indicators of free radical reactions suggests that the effect of the drug is related to other processes occurring in the arterial wall and that cerebrospinal fluid levels of oxygen radicals and lipid peroxides are not useful markers of vasospasm.

Central nervous system resuscitation

Traumatic injury to the central nervous system induces delayed neuronal death, which may be mediated by acute and chronic neurochemical changes. Experimental identification of these injury mechanisms and elucidation of the neurochemical cascade following trauma may provide enhanced opportunities for treatment with novel neuroprotective strategies.

A randomized, double-blind, vehicle-controlled trial of tirilazad mesylate in patients with aneurysmal subarachnoid hemorrhage: a cooperative study in North America

To test the safety and efficacy of tirilazad mesylate, a nonglucocorticoid 21-aminosteroid, in improving the outcome of patients with aneurysmal subarachnoid hemorrhage (SAH), 902 patients were enrolled in a prospective randomized, double-blind, vehicle-controlled trial at 54 North American neurosurgical centers. Five patients were excluded prior to receiving any study drug. Of 897 patients who received at least one dose of study medication, 300 received a placebo containing a citrate vehicle, 298 received 2 mg/kg per day tirilazad, and 299 received 6 mg/kg per day tirilazad, all administered intravenously beginning within 48 hours of the SAH and continuing through 10 days posthemorrhage. All patients were also treated with orally administered nimodipine. At 3 months post-SAH, there were no significant differences (p < 0.025) among the groups with regard to mortality rate, favorable outcome on the Glasgow Outcome Scale, or employment status. During the first 14 days after the SAH, there were no significant differences among the groups in the incidence or severity of clinically symptomatic or angiographically identifiable cerebral vasospasm. Mortality data stratified by gender and neurological grade on admission (assessed according to a modified World Federation of Neurological Surgeons scale) demonstrated that the men with Grades IV to V had a 33% mortality rate in the vehicle group, 52% in the 2 mg/kg per day tirilazad group (p = 0.29), and 5% in the 6 mg/kg per day tirilazad group (p = 0.03). Tirilazad was well tolerated at both dose levels. Tirilazad mesylate at dosage levels of up to 6 mg/kg per day for 8 to 10 days following SAH did not improve the overall outcome in patients with aneurysmal SAH in this trial. The differences in the efficacy of tirilazad in this trial and a previously reported trial in Europe, Australia, and New Zealand, in which dosage levels of tirilazad of 6 mg/kg per day reduced mortality rates and increased good recovery, may be a result of differences in admission characteristics of the patients and/or differences in management protocols, including the use of anticonvulsant medications.

Synaptosomal iron-dependent lipid peroxidation inhibition after subarachnoid hemorrhage by lazaroid in vivo treatment

The production of oxygen-free radicals and their subsequent peroxidative action on membrane unsaturated fatty acids could be enhanced after subarachnoid hemorrhage (SAH). We have studied the effects of the in vivo pharmacological treatment with a lazaroid (U78517F) after experimental SAH, on lipid peroxidative patterns in cortical synaptosomal preparations. U78517F is a lipid-soluble antioxidant with a potent action to inhibit iron-dependent lipid peroxidation. Experimental SAH was induced in anesthetized rats by slow injection of 0.3 mL of autologous arterial blood into cisterna magna. The hemorrhagic animals were treated with 5 mg/kg iv of U78517F immediately after surgical operation. The animals were sacrificed 1 d after the hemorrhage and the thiobarbituric acid reactive material (TBAR) was assayed in basal conditions and after 1, 3, 5, 10, and 20 min of incubation at 37 degrees C with a pro-oxidant mixture on three different rat groups: sham-operated (0.3 mL of mock cerebrospinal fluid (CSF) into cisterna magna), hemorrhagic (0.3 mL of autologous arterial blood into cisterna magna), and hemorrhagic-treated. The hemorrhagic event did not influence the membrane lipoperoxidation levels in basal conditions, whereas peroxidative stimulation in vitro caused significant increases in hemorrhagic animals compared to the sham-operated, and in hemorrhagic-treated animals, the synaptosomal TBARs were similar to controls. The pharmacological treatment showed its effectiveness only following incubations with pro-oxidants; therefore, U78517F seems to be protective for membranes in case of severe lipid peroxidative stress.

Lazaroids: Mechanisms of Action and Implications for Disorders of the CNS

Oxygen radical-induced lipid peroxidation to cerebrovascular or brain parenchymal cell membranes has been implicated as a pathophysiological mechanism in both acute and chronic neurodegenerative disorders, including brain and spinal cord trauma, ischemic and hemorrhagic stroke, Alzheimer's and Parkinson's diseases, and amyotrophic lateral sclerosis. As a result, pharmacological strategies have been aimed at antagonizing lipid peroxidative damage in a safe and effective manner. Perhaps the first successful antioxidant neuroprotective approach is high dose treatment with the glucocorticoid steroid methylprednisolone, which has been reported to be effective in improving neurological recovery after blunt spinal cord injury in animals and humans. After a determination that these effects were based upon inhibition of posttraumatic lipid peroxidative reactions rather than steroid receptor interactions, a new class of 21-aminosteroids (“lazaroids”) was discovered. The lazaroids are more effective inhibitors of lipid peroxidation and, at the same time, devoid of glucocorticoid side effect potential. One of them, tirilazad (U-74006F), was found protective in a variety of preclinical neuroprotection models and is currently the subject of Phase III clinical trials. Thus far, the compound has been demonstrated to significantly improve 3-month survival and neurological recovery after subarachnoid hemorrhage in humans. Although tirilazad does penetrate the injured CNS, much of its protective activity is mediated by an action on vascular endothelium. Recently, the 21-aminosteroids have been followed up with a newer series of non-steroidal compounds, the pyrrolopyrimidines, which possess even greater antioxidant efficacy and brain penetration that may be useful for the treatment of chronic neurodegenerative disorders.

Protective effect of 21-aminosteroid pretreatment in peripheral nerve low-load crush injury in mature and immature rats

The effects of U-74006F (tirilazad mesylate), a 21-aminosteroid antioxidant, on injured peripheral nerve were studied. Twenty-two immature and 44 mature rats were divided equally into two groups. The experimental group received two injections of 3 mg/kg of U-74006F at a 2 hour interval. The control group received the same volumes of a citrate buffer. A 5 mm segment of the sciatic nerve was subjected to a crush load of 100 g for 2 hours. Motor function (sciatic functional index) was assessed to day 48 postoperatively. There was total paralysis of the crushed limb in all rats the first week after crushing. The experimental group had a statistically significant improvement in motor function compared with the controls on days 14, 21, 25, and 28 for the mature rats and on days 11 and 14 for the immature rats. The mature controls attained complete recovery on day 42 and had a significantly slower recovery rate than the immature controls, which had recovered fully by day 25. The recovery rates were almost similar among mature and immature groups pretreated with U-74006F, both of which had fully recovered motor function by day 28. The results indicate that pretreatment with U-74006F can significantly promote peripheral nerve function after low-load crush injury and that the age of the animal influences the rate of peripheral nerve recovery.

Tirilazad does not protect rat brain from brachytherapy-induced injury

BACKGROUND

Acute and chronic brain injury are common sequelae of high-dose focused radiation, as in radiosurgery and brachytherapy. Development of protectors of radiation injury, which would work in brain but not in tumor, would help enhance the therapeutic ratio of focused-radiation therapy.

METHODS

Radiation protection by a clinically available 21-aminosteroid, Tirilazad, was studied in a rat brain brachytherapy model, both in tumor and non-tumor bearing animals. For the tumor model, 9L Glioma/SF line cells were implanted stereotactically into the right frontal lobe of F-344 rats and grew to a sphere of 5.0-mm diameter after 12 days. Animals received a standard brachytherapy dose of 80 Gy to a 5.5-mm radius volume administered by a high-activity removable iodine-125 seed. Radiation damage was evaluated 24 hours after removal of the seeds in all animals and again at 3 months in non-tumor-bearing animals, by T1-weighted gadolinium-enhanced and T2-weighted magnetic resonance imaging (MRI) on a 1.5-T unit. Treated animals received Tirilazad 5 mg/kg intravenously 15 minutes prior to implant, 1 hour after implant, every 6 hours for the duration of the implant, and for 24 hours after removal of the seed. Control animals were administered vehicle only.

RESULTS

In both non-tumor-bearing and tumor-bearing rats, no difference in the volume of lesions on enhanced T1 or T2 MRI was seen between the Tirilazad-treated and control groups. In the non-tumor-bearing rats, volume of both T1 enhanced and T2 MRI lesions was significantly reduced at 3 months compared to the values at 24 hours.

CONCLUSIONS

In the present model, Tirilazad failed to reduce the volume of radiation brain injury from brachytherapy as seen on MRI, studied acutely in tumor-bearing and non-tumor-bearing animals and also at 3 months in non-tumor-bearing rats.

Randomized, double-blind, vehicle-controlled trial of tirilazad mesylate in patients with aneurysmal subarachnoid hemorrhage: a cooperative study in Europe, Australia, and New Zealand

Tirilazad mesylate, a nonglucocorticoid 21-aminosteroid, has been shown in experimental models to reduce vasospasm following subarachnoid hemorrhage (SAH) and to reduce infarct size from focal cerebral ischemia. To test whether treatment with tirilazad would reduce ischemic symptoms from vasospasm and improve overall outcome in patients with ruptured aneurysms, a prospective randomized, double-blind, vehicle-controlled trial was conducted at 41 neurosurgical centers in Europe, Australia, and New Zealand. One thousand twenty-three patients were randomly assigned to receive 0.6, 2, or 6 mg/kg per day of intravenously administered tirilazad or a placebo containing the citrate vehicle. All patients were also treated with intravenously administered nimodipine. Patients receiving 6 mg/kg per day of tirilazad had reduced mortality (p = 0.01) and a greater frequency of good recovery on the Glasgow Outcome Scale 3 months after SAH (p = 0.01) than similar patients treated with vehicle. There was a reduction in symptomatic vasospasm in the group that received 6 mg/kg per day tirilazad; however, the difference was not statistically significant (p = 0.048). The benefits of treatment with tirilazad were predominantly shown in men rather than in women. There were no material differences between the outcomes in the groups treated with 0.6 and 2 mg/kg tirilazad per day and the group treated with vehicle. Tirilazad was well tolerated at all three dose levels. These observations suggest that tirilazad mesylate, at a dosage of 6 mg/kg per day, is safe and improves overall outcome in patients (especially in men) who have experienced an aneurysmal SAH.