Effects of the radical scavenger AVS on behavioral and BBB changes after experimental subarachnoid hemorrhage

Nicaraven mitigates radiation-induced lung injury by downregulating the NF-κB and TGF-β/Smad pathways to suppress the inflammatory response

Radiation-induced lung injury (RILI) is commonly observed in patients receiving radiotherapy, and clinical prevention and treatment remain difficult. We investigated the effect and mechanism of nicaraven for mitigating RILI. C57BL/6 N mice (12-week-old) were treated daily with 6 Gy X-ray thoracic radiation for 5 days in sequences (cumulative dose of 30 Gy), and nicaraven (50 mg/kg) or placebo was injected intraperitoneally in 10 min after each radiation exposure. Mice were sacrificed and lung tissues were collected for experimental assessments at the next day (acute phase) or 100 days (chronic phase) after the last radiation exposure. Of the acute phase, immunohistochemical analysis of lung tissues showed that radiation significantly induced DNA damage of the lung cells, increased the number of Sca-1+ stem cells, and induced the recruitment of CD11c+, F4/80+ and CD206+ inflammatory cells. However, all these changes in the irradiated lungs were effectively mitigated by nicaraven administration. Western blot analysis showed that nicaraven administration effectively attenuated the radiation-induced upregulation of NF-κB, TGF-β, and pSmad2 in lungs. Of the chronic phase, nicaraven administration effectively attenuated the radiation-induced enhancement of α-SMA expression and collagen deposition in lungs. In conclusion we find that nicaraven can effectively mitigate RILI by downregulating NF-κB and TGF-β/pSmad2 pathways to suppress the inflammatory response in the irradiated lungs.

Fluid metabolic pathways after subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a devastating cerebrovascular disease with high mortality and morbidity. In recent years, a large number of studies have focused on the mechanism of early brain injury (EBI) and delayed cerebral ischemia (DCI), including vasospasm, neurotoxicity of hematoma and neuroinflammatory storm, after aSAH. Despite considerable efforts, no novel drugs have significantly improved the prognosis of patients in phase III clinical trials, indicating the need to further re-examine the multifactorial pathophysiological process that occurs after aSAH. The complex pathogenesis is reflected by the destruction of the dynamic balance of the energy metabolism in the nervous system after aSAH, which prevents the maintenance of normal neural function. This review focuses on the fluid metabolic pathways of the central nervous system (CNS), starting with ruptured aneurysms, and discusses the dysfunction of blood circulation, cerebrospinal fluid (CSF) circulation and the glymphatic system during disease progression. It also proposes a hypothesis on the metabolic disorder mechanism and potential therapeutic targets for aSAH patients.

Role of Interleukin-10 in Acute Brain Injuries

Interleukin-10 (IL-10) is an important anti-inflammatory cytokine expressed in response to brain injury, where it facilitates the resolution of inflammatory cascades, which if prolonged causes secondary brain damage. Here, we comprehensively review the current knowledge regarding the role of IL-10 in modulating outcomes following acute brain injury, including traumatic brain injury (TBI) and the various stroke subtypes. The vascular endothelium is closely tied to the pathophysiology of these neurological disorders and research has demonstrated clear vascular endothelial protective properties for IL-10. In vitro and in vivo models of ischemic stroke have convincingly directly and indirectly shown IL-10-mediated neuroprotection; although clinically, the role of IL-10 in predicting risk and outcomes is less clear. Comparatively, conclusive studies investigating the contribution of IL-10 in subarachnoid hemorrhage are lacking. Weak indirect evidence supporting the protective role of IL-10 in preclinical models of intracerebral hemorrhage exists; however, in the limited number of clinical studies, higher IL-10 levels seen post-ictus have been associated with worse outcomes. Similarly, preclinical TBI models have suggested a neuroprotective role for IL-10; although, controversy exists among the several clinical studies. In summary, while IL-10 is consistently elevated following acute brain injury, the effect of IL-10 appears to be pathology dependent, and preclinical and clinical studies often paradoxically yield opposite results. The pronounced and potent effects of IL-10 in the resolution of inflammation and inconsistency in the literature regarding the contribution of IL-10 in the setting of acute brain injury warrant further rigorously controlled and targeted investigation.

Protective effect 3,4-dihydroxyphenylethanol in subarachnoid hemorrhage provoked oxidative neuropathy

Clinical studies have indicated that early brain injury (EBI) following subarachnoid hemorrhage (SAH) is associated with fatal outcomes. Oxidative stress and brain edema are the characteristic pathological events in occurrence EBI following SAH. The present study aimed to examine the effect of 3,4-dihydroxyphenylethanol (DOPET) against SAH-induced EBI, and to demonstrate whether the effect is associated with its potent free radical scavenging property. SAH was induced in rats using an endovascular perforation technique, and 24 h later the rats displayed diminished neurological scores and brain edema. Furthermore, elevated malondialdehyde (an index of lipid peroxidation) and depleted levels of antioxidants were observed in the rat cerebral cortex tissue. Quantitative polymerase chain reaction analysis indicated the upregulated mRNA expression of the apoptotic markers caspase-3 and -9 in the cerebral cortex. Furthermore, the protein expression levels of the proinflammatory cytokines tumor necrosis factor-α, interleukin (IL)-1β and IL-6 were significantly upregulated in SAH-induced rats. By constrast, treatment with DOPET significantly attenuated EBI by reducing brain edema, elevation of antioxidant status, inhibition of apoptosis and inflammation. In this context, DOPET may be a potent agent in the treatment of EBI following SAH, as a result of its free radical scavenging capacity.

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.

Nicaraven attenuates radiation-induced injury in hematopoietic stem/progenitor cells in mice

Nicaraven, a chemically synthesized hydroxyl radical-specific scavenger, has been demonstrated to protect against ischemia-reperfusion injury in various organs. We investigated whether nicaraven can attenuate radiation-induced injury in hematopoietic stem/progenitor cells, which is the conmen complication of radiotherapy and one of the major causes of death in sub-acute phase after accidental exposure to high dose radiation. C57BL/6 mice were exposed to 1 Gy γ-ray radiation daily for 5 days in succession (a total of 5 Gy), and given nicaraven or a placebo after each exposure. The mice were sacrificed 2 days after the last radiation treatment, and the protective effects and relevant mechanisms of nicaraven in hematopoietic stem/progenitor cells with radiation-induced damage were investigated by ex vivo examination. We found that post-radiation administration of nicaraven significantly increased the number, improved the colony-forming capacity, and decreased the DNA damage of hematopoietic stem/progenitor cells. The urinary levels of 8-oxo-2′-deoxyguanosine, a marker of DNA oxidation, were significantly lower in mice that were given nicaraven compared with those that received a placebo treatment, although the levels of intracellular and mitochondrial reactive oxygen species in the bone marrow cells did not differ significantly between the two groups. Interestingly, compared with the placebo treatment, the administration of nicaraven significantly decreased the levels of the inflammatory cytokines IL-6 and TNF-α in the plasma of mice. Our data suggest that nicaraven effectively diminished the effects of radiation-induced injury in hematopoietic stem/progenitor cells, which is likely associated with the anti-oxidative and anti-inflammatory properties of this compound.

Acute microvascular changes after subarachnoid hemorrhage and transient global cerebral ischemia

Subarachnoid hemorrhage and transient global cerebral ischemia result in similar pathophysiological changes in the cerebral microcirculation. These changes include microvascular constriction, increased leukocyte-endothelial interactions, blood brain barrier disruption, and microthrombus formation. This paper will look at various animal and preclinical studies that investigate these various microvascular changes, perhaps providing insight in how these microvessels can be a therapeutic target in both subarachnoid hemorrhage and transient global cerebral ischemia.

Early brain injury: a common mechanism in subarachnoid hemorrhage and global cerebral ischemia

Early brain injury (EBI) has become an area of extreme interest in the recent years and seems to be a common denominator in the pathophysiology of global transient ischemia and subarachnoid hemorrhage (SAH). In this paper, we highlight the importance of cerebral hypoperfusion and other mechanisms that occur in tandem in both pathologies and underline their possible roles in triggering brain injury after hemorrhagic or ischemic strokes.

The effect of blood glutamate scavengers oxaloacetate and pyruvate on neurological outcome in a rat model of subarachnoid hemorrhage

Blood glutamate scavengers have been shown to effectively reduce blood glutamate concentrations and improve neurological outcome after traumatic brain injury and stroke in rats. This study investigates the efficacy of blood glutamate scavengers oxaloacetate and pyruvate in the treatment of subarachnoid hemorrhage (SAH) in rats. Isotonic saline, 250 mg/kg oxaloacetate, or 125 mg/kg pyruvate was injected intravenously in 60 rats, 60 minutes after induction of SAH at a rate of 0.1 ml/100 g/min for 30 minutes. There were 20 additional rats that were used as a sham-operated group. Blood samples were collected at baseline and 90 minutes after SAH. Neurological performance was assessed at 24 h after SAH. In half of the rats, glutamate concentrations in the cerebrospinal fluid were measured 24 h after SAH. For the remaining half, the blood brain barrier permeability in the frontal and parieto-occipital lobes was measured 48 h after SAH. Blood glutamate levels were reduced in rats treated with oxaloacetate or pyruvate at 90 minutes after SAH (p < 0.001). Cerebrospinal fluid glutamate was reduced in rats treated with pyruvate (p < 0.05). Neurological performance was significantly improved in rats treated with oxaloacetate (p < 0.05) or pyruvate (p < 0.01). The breakdown of the blood brain barrier was reduced in the frontal lobe in rats treated with pyruvate (p < 0.05) and in the parieto-occipital lobes in rats treated with either pyruvate (p < 0.01) or oxaloacetate (p < 0.01). This study demonstrates the effectiveness of blood glutamate scavengers oxaloacetate and pyruvate as a therapeutic neuroprotective strategy in a rat model of SAH.

Hydrogen-rich saline alleviates early brain injury via reducing oxidative stress and brain edema following experimental subarachnoid hemorrhage in rabbits

Background

Increasing experimental and clinical data indicate that early brain injury (EBI) after subarachnoid hemorrhage (SAH) largely contributes to unfavorable outcomes, and it has been proved that EBI following SAH is closely associated with oxidative stress and brain edema. The present study aimed to examine the effect of hydrogen, a mild and selective cytotoxic oxygen radical scavenger, on oxidative stress injury, brain edema and neurology outcome following experimental SAH in rabbits.

Results

The level of MDA, caspase-12/3 and brain water content increased significantly at 72 hours after experimental SAH. Correspondingly, obvious brain injury was found in the SAH group by terminal deoxynucleotidyl transferase-mediated uridine 5’-triphosphate-biotin nick end-labeling (TUNEL) and Nissl staining. Similar results were found in the SAH + saline group. In contrast, the upregulated level of MDA, caspase-12/3 and brain edema was attenuated and the brain injury was substantially alleviated in the hydrogen treated rabbits, but the improvement of neurology outcome was not obvious.

Conclusion

The results suggest that treatment with hydrogen in experimental SAH rabbits could alleviate brain injury via decreasing the oxidative stress injury and brain edema. Hence, we conclude that hydrogen possesses the potential to be a novel therapeutic agent for EBI 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.

From vasospasm to early brain injury: new frontiers in subarachnoid haemorrhage research

INTRODUCTION

Delayed vasospasm has traditionally been considered the most important determinant of poor outcome after subarachnoid haemorrhage (SAH). Consequently, most of the research and therapies are directed towards reducing the incidence of vasospasm (VSP). To date, however, clinical trials based on this strategy have not delivered a definitive treatment for preventing or reducing brain injury after SAH. This fact has caused a paradigm shift in research, which now focuses on early brain injury (EBI) occurring in the first 72 hours after SAH. It has also changed the idea of VSP's role in brain damage, and suggests the need for re-evaluating the pathophysiological process of SAH.

DEVELOPMENT

This review examines the current state of knowledge on the pathophysiological mechanisms associated with EBI and summarises the diagnostic options currently available.

CONCLUSION

It seems that the research approach needs to be changed so that investigators will focus on prevention of EBI, reduction of secondary brain complications and ultimately, the optimisation neurological outcome.

The anti-inflammatory and neuroprotective effects of ghrelin in subarachnoid hemorrhage-induced oxidative brain damage in rats

To elucidate the putative neuroprotective effects of ghrelin in subarachnoid hemorrhage (SAH)-induced brain injury, Wistar albino rats (n = 54) were divided into sham-operated control, saline-treated SAH, and ghrelin-treated (10 microg/kg/d IP) SAH groups. The rats were injected with blood (0.3 mL) into the cisterna magna to induce SAH, and were sacrificed 48 h after the neurological examination scores were recorded. In plasma samples, neuron-specific enolase (NSE), S-100beta protein, TNF-alpha, and IL-1beta levels were evaluated, while forebrain tissue samples were taken for the measurement of malondialdehyde (MDA), glutathione (GSH), reactive oxygen species levels, myeloperoxidase (MPO), Na(+)-K(+)-ATPase activity, and DNA fragmentation ratio. Brain tissue samples containing the basilar arteries were obtained for histological examination, while cerebrum and cerebellum were removed for the measurement of blood-brain barrier (BBB) permeability and brain water content. The neurological scores were impaired at 48 h after SAH induction, and SAH caused significant decreases in brain GSH content and Na(+)-K(+)-ATPase activity, and increases in chemiluminescence, MDA levels, and MPO activity. Compared with the control group, the protein levels of NSE, S-100beta, TNF-alpha, and IL-1beta in plasma were also increased, while ghrelin treatment prevented all SAH-induced alterations observed both biochemically and histopathologically. The results demonstrate that ghrelin alleviates SAH-induced oxidative brain damage, and exerts neuroprotection by maintaining a balance in oxidant-antioxidant status, by inhibiting proinflammatory mediators, and preventing the depletion of endogenous antioxidants evoked by SAH.

Improvement in neurological outcome and abolition of cerebrovascular endothelin B and 5-hydroxytryptamine 1B receptor upregulation through mitogen-activated protein kinase kinase 1/2 inhibition after subarachnoid hemorrhage in rats

OBJECT

Delayed cerebral ischemia after subarachnoid hemorrhage (SAH) remains a major cause of death and disability. It has been hypothesized that cerebrovascular upregulation of vasoconstrictor receptors is a key step in the development of delayed cerebral ischemia. Upregulation of endothelin-B (ET(B)) and 5-hydroxytryptamine 1B (5-HT(1B)) receptors has been demonstrated in cerebral artery smooth muscles in the delayed ischemic phase after experimental SAH, and intracellular signaling via the mitogen-activated protein kinase kinase (MEK)-extracellular signal-regulated kinase 1/2 pathway has been shown to be involved in this upregulation. The aim in the present study was to determine whether treatment with the MEK1/2 inhibitor U0126 can prevent cerebrovascular receptor upregulation and improve functional outcome after experimental SAH in rats.

METHODS

Subarachnoid hemorrhage was induced in male Sprague-Dawley rats by the injection of 250 μl of autologous blood into the basal cisterns. Either U0126 or vehicle was intracisternally administered at 6, 12, 24, and 36 hours after SAH. Smooth muscle ET(B) and 5-HT(1B) receptor upregulation was studied in isolated cerebral artery segments through immunohistochemical and myographic studies of contractile responses to receptor-specific agonists. Gross sensorimotor function in the rats after SAH was assessed using a rotating pole test.

RESULTS

Contractile concentration-response curves for middle cerebral artery (MCA) and basilar artery (BA) segments to endothelin-1 (ET-1) and 5-carboxamidotryptamine (5-CT) were shifted leftward for SAH-induced compared with shamoperated rats due to enhanced contractile responses to individual doses of the agonists (for example, contractile responses of the BA to 3 × 10(-10) M of ET-1 and 3 × 10(-7) M of 5-CT were 9.98 ± 5.01% and 16.75 ± 3.62% of the maximal contractile capacity, respectively, in sham-operated rats and 62.78 ± 9.9% and 45.44 ± 10.62%, respectively, in SAH-induced rats). In vivo treatment with 0.19 μg/kg U0126 normalized responses in the SAH-induced rats to levels in the sham-operated rats. Protein expression of ET(B) and 5-HT(1B) receptors in cerebrovascular smooth muscles from SAH-induced rats was increased to 175 ± 33.17% and 167.7 ± 24.74%, respectively, of the levels in sham-operated rats. Endothelin-B and 5-HT(1B) expression levels in U0126-treated SAH-induced rats were at the levels in sham-operated rats (101.9 ± 13.38% and 91.44 ± 16.75%, respectively). In a rotating pole test used to assess gross sensorimotor function on the 2nd day after surgery, sham-operated rats achieved an average score of 5.37 ± 0.23, SAH-induced rats scored 3.35 ± 0.67, and SAH-induced U0126-treated rats scored 5.00 ± 0.4.

CONCLUSIONS

The authors demonstrated that experimental SAH induces upregulation of ET(B) and 5-HT(1B) receptors in cerebrovascular smooth muscles and that treatment with the MEK1/2 inhibitor U0126 abolishes this receptor upregulation. They also demonstrated that experimental SAH results in sensorimotor deficits as assessed by a rotating pole test. These deficits were alleviated by U0126 treatment, suggesting that cerebrovascular receptor upregulation is critical for the functional outcome of delayed cerebral ischemia. The authors suggest that inhibition of MEK1/2 may be a promising new SAH treatment strategy.

Neurological and neurobehavioral assessment of experimental subarachnoid hemorrhage

About 50% of humans with aneurysmal subarachnoid hemorrhage (SAH) die and many survivors have neurological and neurobehavioral dysfunction. Animal studies usually focused on cerebral vasospasm and sometimes neuronal injury. The difference in endpoints may contribute to lack of translation of treatments effective in animals to humans. We reviewed prior animal studies of SAH to determine what neurological and neurobehavioral endpoints had been used, whether they differentiated between appropriate controls and animals with SAH, whether treatment effects were reported and whether they correlated with vasospasm. Only a few studies in rats examined learning and memory. It is concluded that more studies are needed to fully characterize neurobehavioral performance in animals with SAH and assess effects of treatment.

Synergistic induction of heme oxygenase-1 by nicaraven after subarachnoid hemorrhage to prevent delayed cerebral vasospasm

Cerebral vasospasm remains a major cause of morbidity and mortality in patients with subarachnoid hemorrhage. Heme oxygenase-1 (HO-1) is an oxidative stress-inducible enzyme with multiple protective functions against vascular and neurological diseases, including delayed cerebral vasospasm. In the present study, intravenous administration (i.v.) of nicaraven (1 mg/kg/min, for 2 days after subarachnoid hemorrhage) ameliorated delayed cerebral vasospasm in rat subarachnoid hemorrhage models, marked synergistic induction of HO-1 protein (> 2.5-fold than 'subarachnoid hemorrhage with saline i.v.'), and elicited a rapid increase of cGMP accumulation in the basilar arteries. In the sham-operated rats, nicaraven could not induce HO-1 expression. Antisense HO-1 oligodeoxynucleotides abrogated this HO-1 induction and the antivasospastic effect of nicaraven. In vitro study using Hela cells, nicaraven enhanced the human HO-1 promoter (-4.5 kbp) activity, which was pre-activated with the blood component oxyhemoglobin to mimic the ability of subarachnoid hemorrhage. These results suggest that this enhanced HO-1 expression through a combination of pathological state and pharmacological agent could be an effective strategy to improve the prognosis of heme- and oxidative stress-induced diseases, such as delayed cerebral vasospasm.

Melatonin reduces experimental subarachnoid hemorrhage-induced oxidative brain damage and neurological symptoms

Oxidative stress has detrimental effects in several models of neurodegenerative diseases, including subarachnoid hemorrhage (SAH). This study investigated the putative neuroprotective effect of melatonin, a powerful antioxidant, in a rat model of SAH. Male Wistar albino rats were divided as control, vehicle-treated SAH, and melatonin-treated (10 mg/kg, i.p.) SAH groups. To induce SAH, 0.3 mL blood was injected into cisterna magna of rats. Forty-eight hours after SAH induction, neurological examination scores were measured and the rats were decapitated. Brain tissue samples were taken for blood-brain barrier (BBB) permeability, brain water content, histological examination, or determination of malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO), and Na+-K+-ATPase activities. Formation of reactive oxygen species in brain tissue samples was monitored by using a chemiluminescence (CL) technique. The neurological examination scores were increased in SAH groups on the second day of SAH induction and SAH caused a significant decrease in brain GSH content and Na+-K+-ATPase activity, which was accompanied with significant increases in CL, MDA levels, and MPO activity. On the other hand, melatonin treatment reversed all these biochemical indices as well as SAH-induced histopathological alterations, while increased brain water content and impaired BBB were also reversed by melatonin treatment. This study suggests that melatonin, which can easily cross BBB, alleviates SAH-induced oxidative stress and exerts neuroprotection by preserving BBB permeability and by reducing brain edema.

Correlation of free radical level and apoptosis after intracerebral hemorrhage in rats

OBJECTIVE

To investigate the correlation of perihematomal free radical level and neuronal apoptosis following the intracerebral hemorrhage (ICH).

METHODS

Animals were randomly divided into 4 groups: sham operation group, model group, 1 mg/kg edaravone group, and 3 mg/kg edaravone group. Each group was then divided into seven subgroups, in which the rats were correspondingly killed at 6 h, 12 h, 24 h, 48 h, 72 h, 7 d or 14 d (n = 1 in each subgroup of the sham group, and n = 6 in each subgroup of the other 3 groups). By Horseley-Clarke technique, autoblood (80 microL) were administered into the left caudate putamen of SD rats in a double administration-withdrawal way. Rats in the sham group were needled in but not administered with autoblood. The ICH model was then evaluated by Bederson's scale. Around the hematoma, the levels of malonaldehyde (MDA) and hydroxyl radical were tested by spectrophotometer, and the process of apoptosis was tested by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) method.

RESULTS

(1) ICH significantly increased the levels of MDA and hydroxyl radicals. Significant differences in MDA and hydroxyl radical contents were observed among the four groups. (2) In the sham group, a small number of TUNEL-positive cells were found. In the other three groups, the TUNEL-positive cells were observed at 6 h, increased significantly at 24 h, and reached peak level at 3 d, then fell profoundly at 7 d, but remained detectable at 14 d. (3) The positive correlation existed between apoptosis and free radical level (r = 0.2003), and existed between apoptosis and MDA content (r = 0.6563) in the brain.

CONCLUSION

Post-hemorrhagic apoptosis was related to the production of free radicals, indicating that the elevated free radicals following the ICH could induce neuron and glial cell apoptosis.

Long-term assessment of motor and cognitive behaviours in the intraluminal perforation model of subarachnoid hemorrhage in rats

The endovascular perforation model of subarachnoid hemorrhage (SAH) is a commonly used model in rats as it is performed without a craniotomy and accurately mimics the physiological effects of SAH in humans. The long-term behavioural profile of the model, however, has not been characterized. Given that humans often have cognitive deficits following SAH, we set out to characterize the behavioural profile as well as the spontaneous temperature changes of rats following intraluminal perforation. Rats were pre-trained on three motor tasks (tapered beam, limb-use asymmetry and the horizontal ladder tasks) prior to receiving a SAH. The animals were then assessed on post-surgical days 3, 7, 14 and 21 on these tasks. At the completion of motor testing, the rats were assessed on a moving platform version of the Morris water task. Despite significant mortality (33%), SAH did not result in lasting motor deficits on any of the tasks examined. However, the SAH group did show a minor cognitive impairment in the Morris water task. In addition, SAH produced a slight, but significant elevation in body temperature (vs. sham operated rats) despite an acute decrease in general home cage activity. The majority of the animals did not have any observable infarcts and the SAH did not significantly affect cortical thickness. In summary, the endovascular perforation model of SAH results in no lasting motor deficits and only minor cognitive impairment in survivors, which alone would be difficult to evaluate in neuroprotection or rehabilitation studies.

Melatonin decreases mortality following severe subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is a devastating disease that is associated with significant morbidity and mortality. There is substantial evidence to suggest that oxidative stress is significant in the development of acute brain injury following SAH. Melatonin is a strong antioxidant that has low toxicity and easily passes through the blood-brain barrier. Previous studies have shown that melatonin provides neuroprotection in animal models of ischemic stroke. This study hypothesizes that melatonin will provide neuroprotection when administered 2 hr after SAH. The filament perforation model of SAH was performed in male Sprague-Dawley rats weighing between 300 and 380 g. Melatonin (15 or 150 mg/kg), or vehicle was given via intraperitoneal injection 2 hr after SAH. Mortality and neurologic deficits were assessed 24 hr after SAH. A significant reduction in 24-hr mortality was seen following treatment with high dose melatonin. There was no improvement in neurologic scores with treatment. Brain water content and lipid peroxidation were measured following the administration of high dose melatonin to identify a mechanism for the increased survival. High dose melatonin tended to reduce brain water content following SAH, but had no effect on the lipid peroxidation of brain samples. Large doses of melatonin significantly reduces mortality and brain water content in rats following SAH through a mechanism unrelated to oxidative stress.

Neurological impairment in rats after subarachnoid hemorrhage--a comparison of functional tests

Functional outcome has become a key parameter for the determination of the efficacy of therapeutic interventions. Unfortunately, functional tests are not established for filament perforation induced subarachnoid hemorrhage (SAH). Therefore, we evaluated generally applied functional tasks for their potential to discriminate between various degrees of neuronal damage. Rats were subjected to SAH by an endovascular filament and were randomly assigned to controls treated with 0.9% NaCl, moderately neuroprotective therapy with 7.5% NaCl, and highly effective neuroprotection by 7.5% NaCl+6% dextran 70 (HSD). Functional deficit was quantified daily using beam balance task, prehensile traction task, rotarod, a 6-point motor function score and a general neurological 100-point score. Only the HSD group exhibited significantly more surviving neurons at postoperative day 7. Despite significant variations in histomorphometry, beam balance, prehensile traction and rotarod failed to distinguish between groups. On the other hand, the 100-point neuroscore showed improved neurological recovery on postoperative day 1 for HSD. The 100-point neuroscore failed to discriminate between treatment arms at later time points and therefore seems to reflect predominantly early neurological dysfunction. In conclusion, the results of pure motor tasks after experimental SAH in rats should be carefully interpreted. The integration of a test regimen to examine long term cognitive deficits after rat SAH might be valuable to gain additional information about the functional consequences of morphological damage.

The clinical significance of acute brain injury in subarachnoid hemorrhage and opportunity for intervention

Aneurysmal subarachnoid hemorrhage (SAH) is a devastating neurological event that accounts for 3-7% of all strokes and carries a mortality rate as high as 40%. Delayed cerebral vasospasm has traditionally been recognized as the most treatable cause of morbidity and mortality from SAH. However, evidence is mounting that the physiological and cellular events of acute brain injury, which occur during the 24-72 h following aneurysm rupture, make significant contributions to patient outcomes, and may even be a more significant factor than delayed cerebral vasospasm. Acute brain injury in aneurysmal SAH is the result of physiological derangements such as increased intracranial pressure and decreased cerebral blood flow that result in global cerebral ischemia, and lead to the acute development of edema, oxidative stress, inflammation, apoptosis, and infarction. The consequence of these events is often death or significant neurological disability. In this study of acute brain injury, we elucidate some of the complex molecular signaling pathways responsible for these poor outcomes. Continued research in this area and the development of therapies to interrupt these cascades should be a major focus in the future as we continue to seek effective therapies for aneurysmal SAH.

NMDA receptor antagonist felbamate reduces behavioral deficits and blood-brain barrier permeability changes after experimental subarachnoid hemorrhage in the rat

Increased levels of glutamate and aspartate have been detected after subarachnoid hemorrhage (SAH) that correlate with neurological status. The NMDA receptor antagonist felbamate (FBM; 2-phenyl-1,3-propanediol dicarbamate) is an anti-epileptic drug that elicits neuroprotective effects in different experimental models of hypoxia-ischemia. The aim of this dose-response study was to evaluate the effect of FBM after experimental SAH in rats on (1) behavioral deficits (employing a battery of assessment tasks days 1-5 post-injury) and (2) blood-brain barrier (BBB) permeability changes (quantifying microvascular alterations according to the extravasation of protein-bound Evans Blue by a spectrophotofluorimetric technique 2 days post-injury). Animals were injected with 400 muL of autologous blood into the cisterna magna. Within 5 min, rats received daily oral administration of FBM (15, 30, or 45 mg/kg) for 2 or 5 days. Results were compared with sham-injured controls treated with oral saline or FBM (15, 30, or 45 mg/kg). FBM administration significantly ameliorated SAH-related changes in Beam Balance scores on days 1 and 2 and Beam Balance time on days 1-3, Beam Walking performance on days 1 and 2, and Body Weight on days 3-5. FBM also decreased BBB permeability changes in frontal, temporal, parietal, occipital, and cerebellar cortices; subcortical and cerebellar gray matter; and brainstem. This study demonstrates that, in terms of behavioral and microvascular effects, FBM is beneficial in a dose-dependent manner after experimental SAH in rats. These results reinforce the concept that NMDA excitotoxicity is involved in the cerebral dysfunction that follows SAH.

Acute cerebral vascular injury after subarachnoid hemorrhage and its prevention by administration of a nitric oxide donor

Object

Structural changes in brain parenchymal vessels occur within minutes after subarachnoid hemorrhage (SAH). These changes include platelet aggregation, activation of vascular collagenases, and destruction of perivascular collagen IV. Because collagen IV is an important component of the basal lamina, the authors attempted to further define changes in vascular structure (length and luminal diameter) and their relationship to vascular permeability immediately after SAH. In addition, the authors explored whether such alterations were attenuated by administration of a nitric oxide (NO) donor.

Methods

Endovascular perforation was used to induce SAH in rats. Two sets of experiments were performed. The first established changes in vascular structure and permeability (collagen IV and endothelial barrier antigen [EBA] dual immunofluorescence) during the first 24 hours after SAH. In the second, the investigators examined the effects of an NO donor on vascular structure, permeability, and collagenase activity (in situ zymography). In this second study, animals received intravenous infusion of the NO donor S-nitrosoglutathione (GSNO, 1 μM/8 μl/min) 15 minutes after induction of SAH and were killed 3 hours after SAH onset. Controls were naive unoperated animals for the first study and saline-infused SAH animals for the second.

The authors found a time-dependent decrease in area fraction, length, and luminal diameter of collagen IV– and EBA-immunofluorescent vessels after SAH. The greatest change occurred at 3 hours after onset of SAH. Administration of GSNO was associated with striking preservation of collagen IV and EBA immunofluorescence compared with saline treatment. Zymography indicated decreased collagenase activity in GSNO-treated SAH animals compared with saline-treated SAH animals.

Conclusions

These results demonstrate changes in the structure and permeability of brain parenchymal microvessels after SAH and their reversal by treatment with an NO donor.

Molecular mechanisms of early brain injury after subarachnoid hemorrhage

OBJECTIVES

Increasing body of experimental and clinical data indicates that early brain injury after initial bleeding largely contributes to unfavorable outcome after subarachnoid hemorrhage (SAH). This review presents molecular mechanisms underlying brain injury at its early stages after SAH.

METHODS

PubMed was searched using term 'subarachnoid hemorrhage' and key words referring to molecular and cellular pathomechanisms of SAH-induced early brain injury.

RESULTS

The authors reviewed intracranial phenomena and molecular agents that contribute to the early development of pathological sequelae of SAH in cerebral and vascular tissues, including cerebral ischemia and its interactions with injurious blood components, blood-brain barrier disruption, brain edema and apoptosis.

DISCUSSION

It is believed that detailed knowledge of molecular signaling pathways after SAH will serve to improve therapeutic interventions. The most promising approach is the protection of neurovascular unit including anti-apoptosis therapy.

Hypersensitivity to hydroxyl radicals in rat basilar artery after subarachnoid hemorrhage

Vasospasm after subarachnoid hemorrhage (SAH) is a serious complication and we have been investigating the relationship between vasoconstrictors and vasospasm after SAH. The present study was designed to investigate the vasocontractile responses to reactive oxygen species in isolated rat basilar arteries from the control and experimental SAH rats. Contractile responses to hydroxyl radicals in basilar arteries from SAH rats were 3-6-fold higher than those in control rats. The present results clearly indicate that hypersensitivity to hydroxyl radicals may contribute to the vasospasm after SAH.

Acute alterations in microvascular basal lamina after subarachnoid hemorrhage

Object. Aneurysmal subarachnoid hemorrhage (SAH) causes acute and delayed ischemic brain injuries. The mechanisms of acute ischemic injury following SAH are poorly understood, although an acute increase in microvascular permeability has been noted. The integrity of cerebral microvessels is maintained in part by components of basal lamina: collagen IV, elastin, lamina, and so forth. Destruction of basal lamina components by collagenases and matrix metalloproteinases (MMPs), especially MMP-9, has been known to occur in other ischemic models. The authors assessed the integrity of cerebral microvasculature after acute SAH by examining collagen IV and MMP-9 levels and collagenase activity in the microvessels.

Methods. Subarachnoid hemorrhage was induced in rats through endovascular perforation of the intracranial bifurcation of the internal carotid artery. Animals were killed 10 minutes to 48 hours after SAH or sham operation (time-matched controls). Levels of collagen IV and MMP-9 were studied in the microvasculature by performing immunoperoxidase and immunofluorescence staining, and collagenase activity was assessed by in situ zymography.

Little change occurred in collagen IV and MMP-9 immunostaining or collagenase activity at 10 minutes or 1 hour after SAH. Starting 3 hours after SAH, collagen IV immunostaining was reduced or eliminated along segments of microvessels whereas MMP-9 staining was segmentally increased. These effects reached a maximum at 6 hours and returned toward those values in sham-operated controls at 48 hours.

Conclusions. Results of this study demonstrated an acute loss of collagen IV from the cerebral microvasculature after SAH and indicated that MMP-9 contributes to this event. The loss of collagen IV might contribute to the known failure of the blood—brain barrier after SAH.

Signaling pathways for early brain injury after subarachnoid hemorrhage

Few studies have examined the signaling pathways that contribute to early brain injury after subarachnoid hemorrhage (SAH). Using a rat SAH model, the authors explored the role of vascular endothelial growth factor (VEGF) and mitogen-activation protein kinase (MAPK) in early brain injury. Male Sprague-Dawley rats (n = 172) weighing 300 to 350 g were used for the experimental SAH model, which was induced by puncturing the bifurcation of the left anterior cerebral and middle cerebral arteries. The blood-brain barrier (BBB), brain edema, intracranial pressure, and mortality were evaluated at 24 hours after SAH. The phosphorylation of VEGF and different MAPK subgroups (ERK1/2, p38, and JNK) were examined in both the cortex and the major cerebral arteries. Experimental SAH increased intracranial pressure, BBB permeability, and brain edema and produced high mortality. SAH induced phosphorylation of VEGF and MAPKs in the cerebral arteries and, to a lesser degree, in the cortex. PP1, an Src-family kinase inhibitor, reduced BBB permeability, brain edema, and mortality and decreased the phosphorylation of VEGF and MAPKs. The authors conclude that VEGF contributes to early brain injury after SAH by enhancing the activation of the MAPK pathways, and that the inhibition of these pathways might offer new treatment strategies for SAH.

Possible role of nicaraven in neuroprotective effect on hippocampal slice culture

Nicaraven is an agent that is especially beneficial in vasospasm or brain damage caused by subarachnoid hemorrhage. It ameliorates neurological deficits of patients and protects the central nervous system from ischemia. We investigated the neuroprotective effect of nicaraven against oxygen-glucose deprivation (OGD) induced or N-methyl-D-aspartic acid (NMDA) induced hippocampal neuronal cell death in organotypic brain slice cultures. The effect of nicaraven on hippocampal neuronal injury was evaluated by inhibition of uptake of propidium iodide (PI) into dead cells. The results demonstrated that nicaraven protected neuronal cells from both OGD- and NMDA-induced cell death. While nicaraven has a strong hydroxyl radical scavenging effect, another radical scavenger, N-acetyl-L-cysteine (NAC), inhibited cell death only caused by OGD. In contrast, the poly(ADP-ribose) synthetase (PARS) inhibitors 3-aminobenzamide (3-AB) and theophylline protected cells from both OGD- and NMDA-induced cell death. Since nicaraven has an inhibitory effect in PARS, as well as a radical scavenging effect, these results suggest that inhibition of hippocampal cell death caused by NMDA may be attributable to PARS inhibition by nicaraven.

Systemic administration of a calpain inhibitor reduces behavioral deficits and blood-brain barrier permeability changes after experimental subarachnoid hemorrhage in the rat

Increases in intracellular calcium and subsequent activation of calcium-activated proteases (e.g., calpains) may play a critical role in central nervous system injury. Several studies have implicated calpain activation following subarachnoid hemorrhage (SAH). This study evaluated the effect of a calpain inhibitor administration following SAH in the rat on behavioral deficits (postinjury days 1-5, employing a battery of well-characterized assessment tasks), and blood-brain barrier permeability changes (48 h post-SAH, quantifying the microvascular alterations according to the extravasation of protein-bound Evans Blue using a spectrophotofluorimetric technique). Rats were injected with 400 microl of autologous blood into the cisterna magna to induce SAH. Within 5 min after the surgical procedure, Calpain Inhibitor II or vehicle was continuously administered intravenously for 2 days. Results indicated that Calpain Inhibitor II treatment after SAH significantly improved (a) beam balance time (day 1, p < 0.05), but not beam balance score, (b) latency to traverse the beam on days 1-4 (day 1-3, p < 0.001; day 4, p < 0.01), and (c) loss in body weight on days 4-5 (p < 0.05). Evans Blue dye extravasation was significantly less in SAH Calpain Inhibitor II-treated rats compared to SAH vehicle-treated rats in seven out of the eight brain regions studied (p < 0.001, 0.01, and 0.05). These results suggest that pharmacological inhibition of a relatively selective, membrane-permeant calpain inhibitor can significantly reduce some pathophysiological SAH consequences, and indicate that the inhibition of calpain may be a beneficial therapeutic approach to reduce post-SAH global brain dysfunction.