The effects of chronic two-fold dietary vitamin E supplementation on subarachnoid hemorrhage-induced brain hypoperfusion

Mechanisms of acute brain injury after subarachnoid hemorrhage

Brain injury after subarachnoid hemorrhage (SAH) is a biphasic event with an acute ischemic insult at the time of the initial bleed and secondary events such as cerebral vasospasm 3 to 7 days later. Although much has been learned about the delayed effects of SAH, less is known about the mechanisms of acute SAH-induced injury. Distribution of blood in the subarachnoid space, elevation of intracranial pressure, reduced cerebral perfusion and cerebral blood flow (CBF) initiates the acute injury cascade. Together they lead to direct microvascular injury, plugging of vessels and release of vasoactive substances by platelet aggregates, alterations in the nitric oxide (NO)/nitric oxide synthase (NOS) pathways and lipid peroxidation. This review will summarize some of these mechanisms that contribute to acute cerebral injury after SAH.

The importance of early brain injury after subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a medical emergency that accounts for 5% of all stroke cases. Individuals affected are typically in the prime of their lives (mean age 50 years). Approximately 12% of patients die before receiving medical attention, 33% within 48 h and 50% within 30 days of aSAH. Of the survivors 50% suffer from permanent disability with an estimated lifetime cost more than double that of an ischemic stroke. Traditionally, spasm that develops in large cerebral arteries 3-7 days after aneurysm rupture is considered the most important determinant of brain injury and outcome after aSAH. However, recent studies show that prevention of delayed vasospasm does not improve outcome in aSAH patients. This finding has finally brought in focus the influence of early brain injury on outcome of aSAH. A substantial amount of evidence indicates that brain injury begins at the aneurysm rupture, evolves with time and plays an important role in patients' outcome. In this manuscript we review early brain injury after aSAH. Due to the early nature, most of the information on this injury comes from animals and few only from autopsy of patients who died within days after aSAH. Consequently, we began with a review of animal models of early brain injury, next we review the mechanisms of brain injury according to the sequence of their temporal appearance and finally we discuss the failure of clinical translation of therapies successful in animal models of aSAH.

Stuck at the bench: Potential natural neuroprotective compounds for concussion

Background:

While numerous laboratory studies have searched for neuroprotective treatment approaches to traumatic brain injury, no therapies have successfully translated from the bench to the bedside. Concussion is a unique form of brain injury, in that the current mainstay of treatment focuses on both physical and cognitive rest. Treatments for concussion are lacking. The concept of neuro-prophylactic compounds or supplements is also an intriguing one, especially as we are learning more about the relationship of numerous sub-concussive blows and/or repetitive concussive impacts and the development of chronic neurodegenerative disease. The use of dietary supplements and herbal remedies has become more common place.

Methods:

A literature search was conducted with the objective of identifying and reviewing the pre-clinical and clinical studies investigating the neuroprotective properties of a few of the more widely known compounds and supplements.

Results:

There are an abundance of pre-clinical studies demonstrating the neuroprotective properties of a variety of these compounds and we review some of those here. While there are an increasing number of well-designed studies investigating the therapeutic potential of these nutraceutical preparations, the clinical evidence is still fairly thin.

Conclusion:

There are encouraging results from laboratory studies demonstrating the multi-mechanistic neuroprotective properties of many naturally occurring compounds. Similarly, there are some intriguing clinical observational studies that potentially suggest both acute and chronic neuroprotective effects. Thus, there is a need for future trials exploring the potential therapeutic benefits of these compounds in the treatment of traumatic brain injury, particularly concussion.

Nitric oxide in early brain injury after subarachnoid hemorrhage

Nitric Oxide (NO) is the major regulator of cerebral blood flow. In addition, it inhibits platelet adherence and aggregation, reduces adherence of leukocytes to the endothelium, and suppresses vessel injury. NO is produced on demand by nitric oxide synthase and has a very short half life. Hence maintenance of its cerebral level is crucial for normal vascular physiology. Time dependent alterations in cerebral NO level and the enzymes responsible for its synthesis are found after subarachnoid hemorrhage (SAH). Cerebral NO level decreases, recovers and increases within the first 24 h after SAH. Each change in cerebral NO level elicits a different pathological response form already compromised brain. These response range from constriction, platelet aggregation and vascular injury that occurs during the early hours and delayed occurring vasospasm, neuronal and axonal damage. This review summarizes the underlying mechanism and the consequence of alteration in cerebral NO level on brain during the first 72 h after SAH.

Early micro vascular changes after subarachnoid hemorrhage

During the last decade much effort has been invested in understanding the events that occur early after SAH. It is now widely accepted that these early events not only participate in the early ischemic injury but also set the stage for the pathogenesis of delayed vasospasm. That early cerebral ischemia occurs after SAH is documented in both experimental SAH and in human autopsy studies; however, angiographic evidence for vasoconstriction early after SAH is lacking and the source of early ischemic injury is therefore unclear. Recently, the cerebral microvasculature has been identified as an early target of SAH. Changes in the anatomical structure of cerebral microvessels, sufficient to cause functional deficits, are found early after experimental SAH. These changes may explain cerebral ischemia in human in the absence of angiographic evidence of large vessel vasoconstriction. This paper summarizes known alterations in cerebral microvasculature during the first 48 h after SAH.

Escape of intraluminal platelets into brain parenchyma after subarachnoid hemorrhage

Platelet aggregates are present in parenchymal vessels as early as 10 min after experimental subarachnoid hemorrhage (SAH). Structural injury to parenchymal vessel walls and depletion of collagen-IV (the major protein of basal lamina) occur in a similar time frame. Since platelets upon activation release enzymes which can digest collagen-IV, we investigated the topographic relationship between platelet aggregates, endothelium, and basal lamina after SAH produced by endovascular perforation, using triple immunofluorescence and confocal microscopy with deconvolution. The location of platelet aggregates in relation to zymography-detected active collagenase was also examined. As reported previously, most cerebral vessels profiles contained platelets aggregates at 10 min after SAH. High-resolution three-dimensional image analysis placed many platelets at the ab-luminal (basal) side of endothelium at 10 min, and others either within the vascular basal lamina or in nearby parenchyma. By 24 h post hemorrhage, large numbers of platelets had entered the brain parenchyma. The vascular sites of platelet movement were devoid of endothelium and collagen-IV. Collagenase activity colocalized with vascular platelet aggregates. Our data demonstrate that parenchymal entry of platelets into brain parenchyma begins within minutes after hemorrhage. Three-dimensional analysis suggests that platelet aggregates initiate or stimulate local disruption of endothelium and destruction of adjacent basal lamina after SAH.

Neuroprotective properties of the natural vitamin E alpha-tocotrienol

BACKGROUND AND PURPOSE

The current work is based on our previous finding that in neuronal cells, nmol/L concentrations of alpha-tocotrienol (TCT), but not alpha-tocopherol (TCP), blocked glutamate-induced death by suppressing early activation of c-Src kinase and 12-lipoxygenase.

METHODS

The single neuron microinjection technique was used to compare the neuroprotective effects of TCT with that of the more widely known TCP. Stroke-dependent brain tissue damage was studied in 12-Lox-deficient mice and spontaneously hypertensive rats orally supplemented with TCT.

RESULTS

Subattomole quantity of TCT, but not TCP, protected neurons from glutamate challenge. Pharmacological as well as genetic approaches revealed that 12-Lox is rapidly tyrosine phosphorylated in the glutamate-challenged neuron and that this phosphorylation is catalyzed by c-Src. 12-Lox-deficient mice were more resistant to stroke-induced brain injury than their wild-type controls. Oral supplementation of TCT to spontaneously hypertensive rats led to increased TCT levels in the brain. TCT-supplemented rats showed more protection against stroke-induced injury compared with matched controls. Such protection was associated with lower c-Src activation and 12-Lox phosphorylation at the stroke site.

CONCLUSIONS

The natural vitamin E, TCT, acts on key molecular checkpoints to protect against glutamate- and stroke-induced neurodegeneration.

The effects of chronic alpha-tocopherol administration on lipid peroxidation in an experimental model of acute spinal cord injury

Most of the numerous experimental studies to research pathophysiological changes following acute spinal cord injury suggest a two-step mechanism of damage to the spinal cord in which the primary (direct) or mechanical injury caused by the trauma initiates secondary (indirect) or progressive autodestructive injury of the cord. During recent years, free oxygen radical generation and lipid peroxidation have been considered to be responsible for secondary autodestructive injury. Alpha tocopherol occupies an important and unique position in the overall antioxidant defense. Alpha tocopherol-depleted animals are generally more susceptible to the adverse effects of environmental agents than are supplemented animals. This study was planned to study the effectiveness in counteracting this autodestructive process by supplementing alpha-tocopherol in rats maintained on a nutritionally adequate diet, and also to evaluate whether it will provide additional protection or not. Eighty healthy Wistar rats (treatment and controls) were included. The treatment group received 100 mg/kg alpha tocopherol each day, intraperitoneally for seven days. Using a standard acute spinal cord trauma model in Wistar rats trauma was applied, an malondialdehyde (MDA) which is a lipid peroxidation product was measured in the traumatized spinal cord at various times following the trauma in order to indirectly evaluate the lipid peroxidation and generation of free oxygen radicals in a time sequence. Statistical analysis of the values demonstrated that malondialdehyde formation in the alpha-tocopherol administered group was significantly lower than in the control group. These findings indicate that longterm administration of alpha-tocopherol may be useful to decrease lipid peroxidation following acute spinal cord trauma.

Bimoclomol protects against vascular consequences of experimental subarachnoid hemorrhage in rats

Bimoclomol (BRLP-42) is a novel antiischemic compound acting against peripheral vascular complications of diabetes mellitus (neuropathy, retinopathy, and nephropathy). In the present study the activity of bimoclomol was tested in experimental subarachnoid hemorrhage (SAH) and arachidonic acid (AA)-induced brain edema in rats to elucidate whether the compound may also have beneficial effect in cerebrovascular disturbances. For comparison, a neuroprotective AMPA antagonist, GYKI-52466, was examined. Injury caused by autologous intracranial blood injection or sodium-arachidonate was evaluated by the damage of blood-brain barrier (BBB) reflected in the extravasation of Evans blue dye into the cerebral tissue. Bimoclomol (2 x 2 mg/kg IV) markedly reduced, while GYKI-52466 (2 x 2 mg/kg IV) moderately diminished the extravasation produced by SAH (39.9%, p < 0.01 and 26.7%, p > 0.05, respectively). In the case of AA-induced brain edema, bimoclomol showed less pronounced (19.6%, p < 0.05) inhibitory action, and GYKI-52466 seemed to be more effective (34.2%, p < 0.05). These results suggest that bimoclomol may be active not only in peripheral micro- and macroangiopathy, but also in some types of cerebrovascular disorders.

Increased levels of plasma cholesteryl ester hydroperoxides in patients with subarachnoid hemorrhage

The pathophysiology of subarachnoid hemorrhage (SAH) may involve free radical production and lipid peroxidation. We examined plasma levels of cholesteryl ester hydroperoxides (CEOOH) and antioxidants in 25 patients with SAH, and 10 neurologic controls with lacunar stroke. Patients with SAH had significantly increased plasma levels of CEOOH, which peaked on day 5 after the ictus. Concentrations of CEOOH were significantly increased, and ascorbic acid concentrations were significantly decreased in patients who developed vasospasm compared with patients without vasospasm. Increased levels of CEOOH were associated with increased mortality and correlated with clinical outcome scales. These results implicate oxidative stress in the pathogenesis of SAH and suggest that measurements of CEOOH in plasma may be useful both prognostically as well as in monitoring therapeutic interventions.

Brain energy metabolism in the acute stage of experimental subarachnoid haemorrhage: local changes in cerebral glucose utilization

An experimental model was used to investigate acute alterations of cerebral metabolic activity in rats subjected to subarachnoid haemorrhage (SAH). Haemorrhages were produced in anaesthetized animals by injecting 0.3 ml of autologous, arterial nonheparinized blood into the cisterna magna. Control rats received subarachnoid injections of mock-cerebrospinal fluid to study the effect of sudden raised intracranial pressure, or underwent sham operation. Three hours after SAH rats were given an intravenous injection of [14C]-2-deoxyglucose. Experiments were terminated by decapitation, and the brains were removed and frozen. Regional brain metabolic activity was studied by quantitative autoradiography. In comparison with sham-operated controls, cerebral metabolic activity was diffusely decreased after SAH. Statistically significant decreases in metabolic rate were observed in 23 of 27 brain regions studied. Subarachnoid injections of mock-cerebrospinal fluid also produced depression of cerebral metabolic activity, but quantitatively these changes were not as pronounced and diffuse as in SAH rats. The present study shows that a widespread depression of brain metabolism occurs in the acute stage after experimental SAH and is probably secondary to the subarachnoid presence of blood itself and/or blood products.

Effect of [dl]-alpha-tocopherol on FeCl2-induced lipid peroxidation in rat amygdala

Peroxidative injury of neural membrane lipids can be initiated by iron-containing blood products, chelated ferrous or ferric ions, and low valence iron in aqueous solution. Lipid peroxidation was measured following focal injection of 3 microliters of 100 mM FeCl2 into rat amygdala. Acute parenteral administration of [dl]-alpha-tocopherol as the alcohol limited the quantity of peroxidation products generated. These data suggest a potential role for alpha-tocopherol administration in limiting brain injury responses.

Altered cerebrovascular CO2 reactivity following subarachnoid hemorrhage in cats

The authors tested the hypothesis that cerebral blood flow (CBF) reactivity to CO2 was blunted following subarachnoid hemorrhage (SAH). Subarachnoid hemorrhage was produced in five cats by performing four cisterna magna injections of blood in each (SAH Group). A second group of six cats was treated with an antifibrinolytic agent (AF) in addition to four cisterna magna blood injections (SAH+AF Group). Four cats received AF and four cisterna magna injections of saline (Control Group). The presence or absence of basilar artery vasospasm was determined by comparing baseline and follow-up selective angiograms. Cerebral blood flow reactivity was determined by randomly varying the concentration of inspired CO2 to alter PaCO2 from 20 to 75 mm Hg. Regional CBF was measured with radiolabeled microspheres. Basilar artery vasospasm was seen following subarachnoid injection of blood but not of saline. Normocapnic CBF was similar in all three groups in the brain stem (mean +/- standard error of the mean: SAH Group 46 +/- 6, SAH+AF Group 46 +/- 6, and Control Group 44 +/- 9 ml/min/100 gm) and in the supratentorial compartment (SAH Group 53 +/- 8, SAH+AF Group 61 +/- 9, and Control Group 51 +/- 13 ml/min/100 gm). At intermediate levels of hypercarbia (PaCO2 50 +/- 3 mm Hg), CBF increased similarly in all three groups (SAH Group 161% +/- 32%, SAH+AF Group 118% +/- 33%, and Control Group 174% +/- 19% compared to baseline); at higher levels of PaCO2 (60 +/- 3 mm Hg), CBF values were SAH Group 265% +/- 50%, SAH+AF Group 205% +/- 47%, and Control Group 159% +/- 30% of baseline. At the highest level of PaCO2 (75 +/- 6 mm Hg), supratentorial CBF did not increase as much in the SAH+AF Group as in the Control Group (179% +/- 59% vs. 463% +/- 58% of baseline, respectively). The authors conclude that, in this model of SAH, there is no change in normocapnic CBF; however, blood flow reactivity to hypercarbia is blunted. It is possible that this may result from a combination of narrowing of proximal large vessels and globally impaired reactivity of small vessels.

Effect of U88999E on experimental cerebral vasospasm in rabbits

U88999E, 7-[4,(4, 4'-difluorobenzhydryl)piperazino-1-methyl]-4- isopropyl-2-methoxy-2,4,6-cycloheptatrien-1-one hydrochloride, is a recently developed tropolone derivative that inhibits lipid peroxidation and also acts as a calcium antagonist. The effects of U88999E on basilar artery tone were examined in two model systems: 1) an in vitro preparation of arterial rings that measures isometric tension, and 2) an in vivo model of cerebral vasospasm measuring arterial diameter. U88999E elicited dose-dependent relaxation of preconstricted arterial rings maintained in vitro. Ring preparations were preconstricted using elevated potassium (40 mmol/L), uridine triphosphate (10(-3) mol/L), or endothelin-1 (10(-8) mol/L); U88999E reversed these constrictions across a concentration range of 10(-8) to 10(-5) mol/L. The potency of U88999E for relaxing preconstricted vessels was slightly less than that observed for flunarizine or diltiazem. A dose-dependent, relaxing effect of U88999E on potassium-induced contractions was observed in the presence of calcium concentrations ranging from 0.03 to 20 mmol/L. Vasospasm of basilar arteries after subarachnoid hemorrhage was inhibited in a dose-dependent and significant manner by intravenous injections of U88999E. Animals receiving intraperitoneal injections of U88999E also exhibited a tendency for reduced vasospasm; however, this effect did not achieve statistical significance. These findings suggest that U88999E may be useful in the prevention of cerebral vasospasm after subarachnoid hemorrhage.

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

The purpose of this study was to use a new 21-aminosteroid (U-74006F) with in vitro antioxidant and antilipolytic properties as a pharmacological probe to assess the role of lipid hydrolysis and peroxidation in a rabbit model of subarachnoid hemorrhage (SAH)-induced vasospasm. Cerebral angiograms were performed on 15 rabbits. Eighteen hours later, 1 cc/kg of autologous blood was infused into the cisterna magna of all 15 animals. Six rabbits received no treatment, six received U-74006F starting 30 minutes after SAH, and three rabbits received the vehicle for U-74006F starting 30 minutes after SAH. At 72 hours post-SAH, a second angiogram was obtained. Digital subtraction angiographic techniques were used to measure the diameter of and contrast material flow through the basilar artery. At 72 hours post-SAH, vasospasm was evident in all untreated and vehicle-treated rabbits. The diameter of and the flow through the basilar artery were significantly reduced 42.3% +/- 6.6% and 46.8% +/- 5.8%, respectively, below pre-SAH levels (means +/- standard error of the means). Treatment with U-74006F eliminated the SAH-induced vasospasm; in treated animals, both the flow through and the diameter of the basilar arteries were at pre-SAH levels. These findings indicate that: 1) membrane lipid changes (that is, hydrolysis with eicosanoid production and/or peroxidation) contribute to the chronic vasospasm resulting from SAH, and 2) U-74006F prevents the SAH-induced chronic vasospasm in this model by limiting these pathological membrane events.

Effect of the nonglucocorticoid 21-aminosteroid U74006F experimental cerebral vasospasm

The present work was performed to establish whether the nonglucocorticoid, 21-aminosteroid, U74006F, could prevent the development of delayed cerebral vasospasm after experimental subarachnoid hemorrhage. The subarachnoid hemorrhage was produced by percutaneous injection of 4.5 mL of nonheparinized autologous blood into the cisterna magna of rabbits. U74006F (1 mg/kg) or placebo was injected intraperitoneally every 12 hours starting 12 hours prior to induction of hemorrhage for a total of six doses. The animals were sacrificed by perfusion fixation. The basilar artery was removed on day 2 and processed for morphometric analysis. Control/placebo and subarachnoid hemorrhage/placebo basilar artery diameters were 651.2 +/- 25.4 and 366.3 +/- 34.2 mu, respectively. Control/U74006F basilar artery diameters (669.8 +/- 21.8 mu) were not significantly different from that of the control/placebo group. U74006F treatment greatly minimized subarachnoid hemorrhage-induced reduction in mean luminal diameter (563.7 +/- 48.2 mu) (p less than 0.001). These results demonstrate considerable therapeutic promise for U74006F in the prevention of cerebral vasospasm.

Protective effect of a 21-aminosteroid on the blood-brain barrier following subarachnoid hemorrhage in rats

The effects of subarachnoid injection of blood on blood-brain barrier permeability to albumin was assessed in a rat model. Subarachnoid injection of blood caused a significant sixfold increase in Evans blue extravasation, whereas sham operation or NaCl injection had no effect. In addition, subarachnoid injections of arachidonic acid or FeCl2 increased blood-brain barrier permeability to Evans blue 16- and 10-fold, respectively. The capillary permeability after subarachnoid injection of blood was normalized by pretreatment with a novel 21-aminosteroid, U-74006F, that has antioxidant and antilipolytic activity. Pretreatment with U-74006F also reduced the vascular leakage induced by subarachnoid injection of arachidonic acid or FeCl2 by 50% and 45%, respectively. We conclude that damage to membrane lipids by peroxidative and/or lipolytic processes is involved in the subarachnoid hemorrhage-induced blood-brain barrier opening and that U-74006F protects the blood-brain barrier against the effects of subarachnoid hemorrhage by preventing or limiting these pathologic membrane lipid changes.

Vitamin E attenuates the toxic effects of intrastriatal injection of 6-hydroxydopamine (6-OHDA) in rats: behavioral and biochemical evidence

Unilateral 6-hydroxydopamine (6-OHDA) injections into the striatum lead to the development of apomorphine-induced rotation in rats. The circling behavior was associated with significant decreases in dopamine, dihydroxyphenylacetic acid and homovanillic acid in the ipsilateral striatum. Pretreatments with either D-alpha-tocopherol or all-racemic-alpha-tocopherol caused significant attenuation of both the behavioral and biochemical abnormalities. These results are discussed in terms of their support for the free radical hypothesis of Parkinson's disease and for the role of antioxidants in the treatment of this neurodegenerative disorder.

Vitamin E and neurologic function in man

Despite the well-known detrimental effect of vitamin E deficiency on the nervous system of many experimental animal models for decades, only over the past decade has vitamin E become recognized as essential for the maintenance of the structure and function of the human nervous system. This discovery of the neurologic role of vitamin E in man is due primarily to the identification of a degenerative neurologic syndrome in children and adults with chronic vitamin E deficiency caused by gastrointestinal diseases impairing fat and vitamin E absorption. A compelling body of clinical, neuropathologic, and therapeutic response evidence conclusively demonstrates that vitamin E deficiency is responsible for the neurologic disorder seen in such patients. In addition, an inborn error in vitamin E metabolism, the Isolated Vitamin E Deficiency Syndrome, causes vitamin E deficiency and similar neurologic degeneration in the absence of fat malabsorption. Guidelines for the evaluation and treatment of vitamin E deficiency in relevant clinical circumstances are provided. The possible role of vitamin E in treating other neurologic diseases is discussed.

Attenuation of progressive brain hypoperfusion following experimental subarachnoid hemorrhage by large intravenous doses of methylprednisolone

Experimental subarachnoid hemorrhage was produced in chloralose-anesthetized cats by slow injection of 0.5 ml/kg autologous arterial blood into the cisterna magna. As a result, there was an initial (within 5 min) 25.1% decrease in caudate nuclear blood flow as measured by hydrogen clearance. Between 5 min and 3 h postinjection, there was a further and progressive 25.9% decline in caudate blood flow. The hemorrhage also caused a slow increase in intracranial pressure, a decrease in cerebral perfusion pressure, and an increase in caudate vascular resistance. In contrast, the administration of a single 30 mg/kg i.v. dose of methylprednisolone sodium succinate 30 min after the acute hemorrhage resulted in stabilization of caudate blood flow and vascular resistance and some restoration of those parameters toward prehemorrhage values. This effect was not correlated with a decrease in intracranial pressure or an increase in cerebral perfusion pressure. A 15 mg/kg i.v. dose of the drug had only a slight effect on caudate blood flow. A 60 mg/kg i.v. dose, while initially supportive, lost its effect during the later stages of the experiment, indicating a sharp biphasic dose-response relationship for the effect of methylprednisolone on caudate blood flow after subarachnoid hemorrhage. However, of the three doses, only 60 mg/kg significantly decreased the slow posthemorrhage rise in intracranial pressure. The beneficial effect of the 30 mg/kg i.v. dose of the drug on caudate blood flow, separate from an effect on the slow rise in intracranial pressure, suggests that the steroid support of caudate perfusion is due to a direct protective effect of the drug on the microvasculature. Based on previous studies showing an identical dose-response pattern for the ability of methylprednisolone to prevent posttraumatic lipid peroxidation of central nervous system tissue and progressive ischemia development, the possibility of the drug's inhibition of hemorrhage-initiated vasoconstrictor prostanoid action and microvascular lipid peroxidation is proposed.