Barrier disruption in the major cerebral arteries following experimental subarachnoid hemorrhage

Blood-brain barrier permeability imaging as a predictor for delayed cerebral ischaemia following subarachnoid haemorrhage. A narrative review

BACKGROUND

Aneurysmal subarachnoid haemorrhage is associated with significant morbidity and mortality due to the myriad of complications contributing to early brain injury and delayed cerebral ischaemia. There is increasing interest in the exploration of the association between blood-brain barrier integrity and risks of delayed cerebral ischaemia and poor outcomes. Despite recent advances in cerebral imaging, radiographic imaging of blood-brain barrier disruption, as a biomarker for outcome prediction, has not been adopted in clinical practice.

METHODS

We performed a narrative review by searching for articles describing molecular changes or radiological identification of changes in BBB permeability following subarachnoid haemorrhage (SAH) on MEDLINE. Preclinical studies were analysed if reported structural changes and clinical studies were included if they investigated for radiological markers of BBB disruption and its correlation with delayed cerebral ischaemia.

RESULTS

There is ample preclinical evidence to suggest that there are structural changes in BBB permeability following SAH. The available clinical literature has demonstrated correlations between permeability imaging and outcomes following aneurysmal subarachnoid haemorrhage (aSAH).

CONCLUSION

Radiological biomarkers offer a potential non-invasive prognostication tool and may also allow early identifications of patients who may be at risk of DCI.

Assessment of tissue permeability by early CT perfusion as a surrogate parameter for early brain injury after subarachnoid hemorrhage

OBJECTIVE

The severity of early brain injury (EBI) after aneurysmal subarachnoid hemorrhage (aSAH) correlates with delayed cerebral ischemia (DCI) and outcome. A disruption of the blood-brain barrier is part of EBI pathophysiology. The aim of this study was to assess tissue permeability (PMB) by CT perfusion (CTP) in the acute phase after aSAH and its impact on DCI and outcome.

METHODS

CTP was performed on day 3 after aSAH. Qualitative and quantitative analyses of all CTP parameters, including PMB, were performed. The areas with increased PMB were documented. The value of an early PMB increase as a predictor of DCI and outcome according to the modified Rankin Scale (mRS) grade 3 to 24 months after aSAH was assessed. Possible associations of increased PMB with the Subarachnoid Hemorrhage Early Brain Edema Score (SEBES) and with early perfusion deficits, as radiographic EBI markers, were evaluated.

RESULTS

A total of 69 patients were enrolled in the study. An increased PMB on early CTP was detected in 10.1% (7/69) of all patients. A favorable outcome (mRS grade ≤ 2) occurred in 40.6% (28/69) of all patients. DCI was detected in 25% (17/69) of all patients. An increased PMB was a predictor of DCI (logistic regression, p = 0.03) but not of outcome (logistic regression, p = 0.40). The detection of increased PMB predicted DCI with a sensitivity of 25%, a specificity of 94%, a positive predictive value of 57%, and a negative predictive value of 79% (chi-square test p = 0.03). Early perfusion deficits were seen in 68.1% (47/69) of the patients, a finding that correlated with DCI (p = 0.005) but not with the outcome. No correlation was found between the SEBES and increased PMB.

CONCLUSIONS

Changes in PMB can be detected by early CTP after aSAH, which correlates with DCI. Future studies are needed to evaluate the time course of PMB changes and their interaction with therapeutic measures.

Upregulation of tissue inhibitor of metalloproteinase-1 contributes to restoration of the extracellular matrix in the rabbit basilar artery during cerebral vasospasm after subarachnoid hemorrhage

Vascular remodeling caused by extracellular matrix (ECM) metabolism contributes to the development of cerebral vasospasm after subarachnoid hemorrhage (SAH). The balance between tissue inhibitor of metalloproteinases (TIMPs) and matrix metalloproteinases (MMPs) plays an important role in ECM remodeling. We investigated the mechanism of vascular remodeling following cerebral vasospasm in a rabbit double hemorrhage model. Rabbit basilar arteries were harvested on days 3, 5, and 7 after initial hemorrhage. TIMP-1, TIMP-2, MMP-2, and MMP-9 mRNA and protein expression were investigated with microarray analysis, quantitative real-time PCR, immunoblot analysis, and enzyme-linked immunosorbent assay (ELISA). The expression and localization of TIMP-1, TIMP-2, MMP-2, MMP-9, elastin, fibronectin, laminin, and collagens I, III, and IV were investigated with immuohistochemical staining. After SAH, TIMP-1 mRNA and protein expression were significantly increased on day 3 and then decreased to the control level on days 5 and 7. MMP-9 protein expression was significantly increased on day 7. TIMP-2 and MMP-2 mRNA and protein expression were significantly increased on day 7. Elastin, fibronectin, laminin, and collagens I, III, and IV protein expression was decreased on day 3 and then restored to control levels on day 7. Upregulation of TIMP-1 during the early phase of cerebral vasospasm may contribute to the recovery of the ECM during the late phase of cerebral vasospasm, resulting in a protective role of TIMP-1 from cerebral vasospasm. Moreover, the increase in arterial compliance by the decrease in ECM during the early phase of cerebral vasospasm may facilitate vasoconstriction of the cerebral artery.

Mechanisms underlying increased vascular smooth muscle contractility in the rabbit basilar artery following subarachnoid hemorrhage

Increased vascular contractility plays an important role in the development of cerebral vasospasm following subarachnoid hemorrhage (SAH). Here, we summarize our current knowledge regarding molecular mechanisms that contribute to increased smooth muscle contractility of rabbit basilar artery following SAH. Our studies demonstrated that upregulation of receptor expression, impairment of feedback regulation of receptor activity, and enhancement of myofilament Ca²⁺ sensitization might lead to increased smooth muscle contractility following SAH.

Role of oxidized LDL and lectin-like oxidized LDL receptor-1 in cerebral vasospasm after subarachnoid hemorrhage

OBJECT

Cerebral vasospasm after subarachnoid hemorrhage (SAH) is a serious complication. Free radicals derived from subarachnoid clotting are recognized to play an important role. Oxidized low-density lipoprotein (ox-LDL) and lectin-like oxidized LDL receptor-1 (LOX-1) have been shown to be related to the pathogenesis of atherosclerosis and may increase in cerebral arteries after SAH, due to the action of free radicals derived from a subarachnoid clot. These molecules may also affect the pathogenesis of vasospasm, generating intracellular reactive oxygen species and downregulating the expression of endothelial NO synthase (eNOS). If so, apple polyphenol might be effective in the prevention of vasospasm due to an abundant content of procyanidins, which exhibit strong radical scavenging effects, and the ability to suppress ox-LDL and LOX-1. The purposes of this study were to investigate changes in levels of ox-LDL and LOX-1 after SAH and whether administering apple polyphenol can modify cerebral vasospasm.

METHODS

Forty Japanese white rabbits were assigned randomly to 4 groups: an SAH group (n = 10); a shamoperation group (n = 10), which underwent intracisternal saline injection; a low-dose polyphenol group (n = 10) with SAH and oral administration of apple polyphenol at 10 mg/kg per day from Day 0 to Day 3; and a high-dose polyphenol group (n = 10) with SAH and oral administration of apple polyphenol at 50 mg/kg per day. At Day 4, the basilar artery and brain was excised from each rabbit. The degree of cerebral vasospasm was evaluated by measuring the cross-sectional area of each basilar artery, and the expression of ox-LDL, LOX-1, and eNOS was examined for each basilar artery by immunohistochemical staining and reverse transcriptase polymerase chain reaction. In addition, neuronal apoptosis in the cerebral cortex was evaluated by TUNEL.

RESULTS

Compared with the sham group, the expression of ox-LDL and LOX-1 in the basilar arterial wall was significantly increased in the SAH group, the expression of eNOS was significantly decreased, and the cross-sectional area of basilar artery was significantly decreased. Compared with the SAH group, the cross-sectional area of basilar artery was increased in the polyphenol groups, together with the decreased expression of ox-LDL and LOX-1 and the increased expression of eNOS. In the high-dose polyphenol group, those changes were statistically significant compared with the SAH group. In the low-dose polyphenol group, those changes were smaller than in the high-dose polyphenol group. No apoptosis and no changes were seen in the cerebral cortex in all groups.

CONCLUSIONS

This is the first study suggesting that ox-LDL and LOX-1 increase due to SAH and that they may play a role in the pathogenesis of vasospasm. It is assumed that procyanidins in apple polyphenol may inhibit a vicious cycle of ox-LDL, LOX-1, and ROS in a dose-dependent manner. Apple polyphenol is a candidate for preventive treatment of cerebral vasospasm.

Delayed neurological deterioration after subarachnoid haemorrhage

Subarachnoid haemorrhage (SAH) causes early brain injury (EBI) that is mediated by effects of transient cerebral ischaemia during bleeding plus effects of the subarachnoid blood. Secondary effects of SAH include increased intracranial pressure, destruction of brain tissue by intracerebral haemorrhage, brain shift, and herniation, all of which contribute to pathology. Many patients survive these phenomena, but deteriorate days later from delayed cerebral ischaemia (DCI), which causes poor outcome or death in up to 30% of patients with SAH. DCI is thought to be caused by the combined effects of angiographic vasospasm, arteriolar constriction and thrombosis, cortical spreading ischaemia, and processes triggered by EBI. Treatment for DCI includes prophylactic administration of nimodipine, and current neurointensive care. Prompt recognition of DCI and immediate treatment by means of induced hypertension and balloon or pharmacological angioplasty are considered important by many physicians, although the evidence to support such approaches is limited. This Review summarizes the pathophysiology of DCI after SAH and discusses established treatments for this condition. Novel strategies--including drugs such as statins, sodium nitrite, albumin, dantrolene, cilostazol, and intracranial delivery of nimodipine or magnesium--are also discussed.

Phenotypic transformation of smooth muscle in vasospasm after aneurysmal subarachnoid hemorrhage

Differentiated smooth muscle cells (SMC) control vasoconstriction and vasodilation, but they can undergo transformation, proliferate, secret cytokines, and migrate into the subendotherial layer with adverse consequences. In this review, we discuss the phenotypic transformation of SMC in cerebral vasospasm after subarachnoid hemorrhage. Phenotypic transformation starts with an insult as caused by aneurysm rupture: Elevation of intracranial and blood pressure, secretion of norepinephrine, and mechanical force on an artery are factors that can cause aneurysm. The phenotypic transformation of SMC is accelerated by inflammation, thrombin, and growth factors. A wide variety of cytokines (e.g., interleukin (IL)-1β, IL-33, matrix metalloproteinases, nitric oxidase synthases, endothelins, thromboxane A2, mitogen-activated protein kinase, platelet-derived vascular growth factors, and vascular endothelial factor) all play roles in cerebral vasospasm (CVS). We summarize the correlations between various factors and the phenotypic transformation of SMC. A new target of this study is the transient receptor potential channel in CVS. Statin together with fasdil prevents phenotypic transformation of SMC in an animal model. Clazosentan prevents CVS and improves outcome in aneurysmal subarachnoid hemorrhage in a dose-dependent manner. Clinical trials of cilostazol for the prevention of phenotypic transformation of SMC have been reported, along with requisite experimental evidence. To conquer CVS in its complexity, we will ultimately need to elucidate its general, underlying mechanism.

Proposed mechanism of cerebral vasospasm: our hypothesis and current topics

Increased vascular contractility plays an important role in the development of cerebral vasospasm following subarachnoid hemorrhage (SAH). Increased vascular contractility can be attributed to either endothelial dysfunction or increased contractility of vascular smooth muscle. Endothelial damage and dysfunction cause impairment of endothelium-dependent vasodilation of the cerebral artery after SAH. In addition to endothelial damage and dysfunction, receptor upregulation in vascular smooth muscle contributes to the induction and enhancement of contractile responses to agonists. Our recent data revealed that feedback regulation of the activity of the G protein-coupled receptor and myofilament Ca(2+) sensitivity is impaired after SAH. This impaired feedback regulation is suggested to cause a sustained contractile response to various agonists, thereby contributing to increased vascular contractility. In addition, three current topics are reviewed: endothelin type A receptor antagonists, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors for treatment, and cortical spreading depolarization for the mechanism of cerebral vasospasm.

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.

Mechanisms underlying potentiation of endothelin-1-induced myofilament Ca(2+) sensitization after subarachnoid hemorrhage

Increased vascular smooth muscle contractility has an important role in the development of cerebral vasospasm after subarachnoid hemorrhage (SAH). Myofilament Ca(2+) sensitivity is a major determinant of smooth muscle contractility. We investigated changes in the Ca(2+)-sensitizing effect of endothelin-1 (ET-1) and the mechanisms underlying ET-1-induced Ca(2+) sensitization after SAH using a rabbit SAH model. After SAH, the contractile response to ET-1 was enhanced, and the ET(A) receptor expression was upregulated in the basilar artery. In α-toxin-permeabilized preparations, ET-1 induced enhanced and prolonged contraction after SAH, suggesting that ET-1-induced Ca(2+) sensitization is potentiated after SAH. Endothelin-1-induced Ca(2+) sensitization became less sensitive to inhibitors of Rho-associated coiled-coil protein kinase (ROCK) and protein kinase C (PKC) after SAH. The expression of PKCα, ROCK2, PKC-potentiated phosphatase inhibitor of 17 kDa (CPI-17) and myosin phosphatase target subunit 1 (MYPT1) was upregulated, and the level of phosphorylation of CPI-17 and MYPT1 was elevated after SAH. This study demonstrated for the first time that the Ca(2+)-sensitizing effect of ET-1 on myofilaments is potentiated after SAH. The increased expression and activity of PKCα, ROCK2, CPI-17, and MYPT1, as well as the upregulation of ET(A) receptor expression are suggested to underlie the enhanced and prolonged Ca(2+) sensitization induced by ET-1.

Impaired feedback regulation of the receptor activity and the myofilament Ca2+ sensitivity contributes to increased vascular reactiveness after subarachnoid hemorrhage

Cerebral vasospasm determines the prognosis of subarachnoid hemorrhage (SAH). The increased vascular reactiveness has an important role in the development of cerebral vasospasm. This study analyzed the roles of the receptor-mediated signaling and the myofilament Ca(2+) sensitivity in the increased vascular reactiveness in SAH, using the basilar artery of a rabbit SAH model. Endothelin-1, thrombin, and phenylephrine induced transient increases in [Ca(2+)](i), myosin light chain phosphorylation, and contraction in the controls. All these responses were not only enhanced but also became sustained in SAH. In the sequential stimulation of thrombin receptor or alpha(1)-adrenoceptor, the second response was substantially attenuated in the controls, whereas it was maintained in SAH. The thrombin-induced contraction in SAH irreversibly persisted even after terminating the thrombin stimulation. This contraction was completely reversed by trypsin and a Galpha(q) inhibitor YM254890, thus suggesting the sustained receptor activity during the sustained contraction. YM254890 also inhibited the endothelin-1- and phenylephrine-induced sustained contraction. Furthermore, the GTPgammaS-induced transient contraction in the control alpha-toxin-permeabilized strips was converted to a sustained contraction in SAH. The results provide the first evidence that the feedback inactivation of the receptor activity and the myofilament Ca(2+) sensitivity was impaired in SAH, thus contributing to the increased vascular reactiveness.

Magnetic resonance imaging detects and predicts early brain injury after subarachnoid hemorrhage in a canine experimental model

The canine double hemorrhage model is an established model to study cerebral vasospasm, the late sequelae of subarachnoid hemorrhage (SAH). The present study uses magnetic resonance imaging (MRI) to examine the recently reported early brain injury after SAH. Double hemorrhage SAH modeling was obtained by injecting 0.5 mL/kg of autologous arterial blood into the cisterna magna of five adult mongrel dogs on day 0 and day 2, followed by imaging at day 2 and day 7 using a 4.7-Tesla (T) scanner. White matter (WM) showed a remarkable increase in T2 values at day 2 which resolved by day 7, whereas gray matter (GM) T2 values did not resolve. The apparent diffusion coefficient (ADC) values progressively increased in both WM and GM after SAH, suggestive of a transition from vasogenic to cytotoxic edema. Ventricular volume also increased dramatically. Prominent neuronal injury with Nissl's staining was seen in the cortical GM and in the periventricular tissue. Multimodal MRI reveals acute changes in the brain after SAH and can be used to non-invasively study early brain injury and normal pressure hydrocephalus post-SAH. MR can also predict tissue histopathology and may be useful for assessing pharmacological treatments designed to ameliorate SAH.

Neuronal and astrocytic apoptosis after subarachnoid hemorrhage: a possible cause for poor prognosis

Clinical evidence suggests that factors other than cerebral vasospasm, such as delayed neuronal and astrocytic cell death, may play a role in the poor prognosis of patients with subarachnoid hemorrhage (SAH). Here we examined this using immunohistochemistry and confocal microscopy in 3 different brain areas in a dog model of SAH. Using antibodies against neuronal marker neuronal nuclear protein (NeuN) and astrocyte marker glial fibrillary acidic protein (GFAP) in conjunction with apoptosis marker (cleaved caspase-3), we quantified neurons and astrocytes to monitor the degree of apoptosis in both groups. Experimental SAH group showed 44 +/- 1% caspase-3 positive neurons in comparison to the 2.0 +/- 0.1% in the control group (P < 0.001, 6 animals each group). For astrocytes, a total 25 +/- 1% were caspase-3 positive in day 7 SAH group, as compared to 0.40 +/- 0.01% for controls (P < 0.001). Regional analysis revealed that neuronal caspase-3 immunoreactivity in all 3 regions were significantly higher (P < 0.001) in SAH animals than that in the control animals. However, the analysis of total area, size and signal co-localization of GFAP with caspase-3 indicated that astrocytic reactivity and proliferation are seen primarily in the hippocampal area, with the least changes detectable in the brainstem. We conclude that in the dog model, there was a significant increase of neuronal and astrocytic cleaved caspase-3, possibly reflecting apoptosis, following SAH induction. These changes coupled with neurological deterioration seen in patients may present a possible reason for the poor outcome in SAH patients.

Leflunomide prevents vasospasm secondary to subarachnoid haemorrhage

BACKGROUND

Though cerebral vasospasm is one of the most serious complications of subarachnoid haemorrhage (SAH), its complex pathogenesis is poorly understood and available clinical treatment options are unsatisfactory. This study was designed to examine the efficacy of leflunomide, an immunomodulatory agent with inhibitory properties, on vascular smooth muscle cell proliferation and inflammation in a rabbit cerebral vasospasm model.

METHODS

Twenty-two adult New-Zealand rabbits were assigned to 4 groups: control, SAH, SAH plus vehicle, SAH plus leflunomide. Subarachnoid haemorrhage was induced by administration of 1 ml of fresh unheparinised autologous arterial blood into the cisterna magna. Oral leflunomide (2 mg/kg) or vehicle treatment was started 12 h after the induction of subarachnoid haemorrhage and administered once a day. Three days later, the animals were sacrificed and the basilar artery was examined histologically for the lumen area and the thickness of the vessel wall. Inflammatory reaction was also examined by counting white blood cells within the vessel wall by means of light microscopic examination using haematoxylin and eosin staining.

FINDINGS

Severe and moderate vasospasms were detected in the basilar artery of the SAH and SAH plus vehicle treated groups, respectively. Leflunomide effectively reduced the vasospasm of the basilar artery. Compared to the vehicle treated group, leflunomide significantly reduced the lumen area (p < 0.01) and hyperplasia of the vessel wall (p < 0.01). Although inflammatory response within the vessel wall was reduced in the leflunomide treated group, no statistical significance was found between groups (p = 0.07).

CONCLUSION

This study demonstrates for the first time that leflunomide treatment attenuates cerebral vasospasm in a rabbit SAH model while inflammatory reaction in the vessel wall is not affected. Although further studies are needed to reveal its molecular mechanisms in relieving vasospasm, leflunomide may provide a therapeutic potential for human cerebral vasospasm induced by 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.

Persistent intracranial hypertension treated by hypothermic therapy after severe head injury might induce late-phase cerebral vasospasm

BACKGROUND

Vasospasm caused by intracranial hypertension in head injury remains controversial.

METHODS

Between 1996 and 2004, we prospectively and consecutively performed conventional cerebral angiography for six patients with head injuries who showed persistent intracranial hypertension (over 20 mm Hg for longer than 5 days) despite performing various treatments for intracranial hypertension.

RESULTS

All subjects had a minor hemorrhage at admission, classified as Fisher group 2. Five of the six patients had angiographically confirmed vasospasm, and one of them later developed a cerebral infarction. Four of the five subjects who exhibited cerebral vasospasm had undergone hypothermic therapy to control the intracranial hypertension.

CONCLUSION

Our results suggest that persistent intracranial hypertension that is treated by hypothermic therapy may be related to late phase cerebral vasospasm.

Mechanisms of early brain injury after subarachnoid hemorrhage

Apoptosis is the term given to programmed cell death, which has been widely connected to a number of intracranial pathologies including stroke, Alzheimer's disease, and more recently subarachnoid hemorrhage (SAH). Subarachnoid hemorrhage is a disease, without any form of effective treatment, that affects mainly the young and middle aged and as a result is responsible for severe disability in otherwise healthy and productive individuals. Despite intense research efforts in the field, we currently possess a very limited understanding of the underlying mechanisms that result in injury after SAH. However, a number of studies have recently indicated that apoptosis may be a major player in the pathogenesis of secondary brain injury after SAH. As a result, the apoptotic cascades present a number of potential therapeutic opportunities that may ameliorate secondary brain injury after SAH. Experimental data suggest that these cascades occur very early after the initial insult and may be related directly to physiologic sequela commonly associated with SAH. It is imperative, therefore, to obtain a thorough understanding of the early events that occur after SAH, which will enable future therapies to be developed.

Cytotoxicity of cytokines in cerebral microvascular endothelial cell

OBJECTIVE

Several studies reported that the levels of proinflammatory cytokines such as TNF-alpha, IL-1beta, IL-6, and IL-8 are elevated in the cerebrospinal fluid (CSF) of patients after subarachnoid hemorrhage (SAH). Cytokines in CSF may contribute to the development of vasospasm and cerebral ischemia. In the present study, we investigated the possible cytotoxic effects of these cytokines on cultured cerebral microvascular endothelial cells.

METHOD

The effects of TNF-alpha, IL-1beta, IL-6, and IL-8 were tested using cell viability assay, DNA fragmentation analysis (DNA laddering), Western blot analysis (Anti-poly-(ADP-ribose) polymerase [PARP] antibody), and caspase-3 activity.

RESULTS

TNF-alpha and IL-1beta, but not IL-6 or IL-8, caused cell detachment in a dose-dependent manner (p<0.05). TNF-alpha (200 pg/ml) and IL-1beta (150 pg/ml) produced DNA ladders at 24-72 h. TNF-alpha but not IL-1beta cleaved the PARP from 116- to 85-kDa fragments and enhanced caspase-3 activity at 24-72 h after incubation with endothelial cells. Caspase-3 inhibitor at 10 micromol/l significantly prevented TNF-alpha-induced cell detachment (p<0.05).

DISCUSSION

TNF-alpha induces apoptosis in cultured cerebral endothelial cells through the cleavage of caspase-3. IL-1beta decreases the adherent cells, produces DNA ladders, but fails to cleave PARP or increase caspase-3 activity. IL-1beta may induce apoptosis in cerebral endothelial cells through different pathway from that of TNF-alpha.

Bilirubin produces apoptosis in cultured bovine brain endothelial cells

Blood components such as oxyhemoglobin are believed to cause cerebral vasospasm by inducing contraction and cell death in cerebral arteries. We have observed previously that oxyhemoglobin produces apoptotic changes in cultured endothelial cells. This study was undertaken to explore if bilirubin, a bi-product of hemoglobin degradation, will produce similar cytotoxicity in endothelial cells. Cultured bovine brain microvascular endothelial cells were incubated in four concentrations of bilirubin (10, 25, 50, and 100 microM) for varying times (6, 12, and 24 h). Control cells were incubated in saline or vehicle (NaOH solution, <0.01% of 0.01 N) for similar time periods. The cultured cells were then observed microscopically for evidence of cellular alterations. Bilirubin (10-100 microM) produced apoptosis that appeared time-dependent but not clearly concentration-dependent. Biochemical markers for apoptosis such as DNA fragmentation and PARP cleavage were induced by bilirubin. We conclude that endothelial cells may undergo apoptosis after exposure to bilirubin.

Oxyhemoglobin induces caspase-mediated cell death in cerebral endothelial cells

Damaged endothelium is one of the pathological changes of the cerebral vasospastic vessels following subarachnoid hemorrhage. Our recent study shows that oxyhemoglobin (OxyHb) induces apoptosis in vascular endothelial cells. Apoptosis generally requires the action of various classes of proteases, including a family of cysteine proteases, known collectively as the caspases. This study was undertaken to investigate the activation of caspases and the efficacy of caspase inhibitors, z-IETD-fmk and z-LEHD-fmk, for oxyhemoglobin-induced apoptosis in vascular endothelial cells. Cultured bovine brain microvascular endothelial cells (passages 5-9) were used for this study. OxyHb (10 micromol/L) was added during the 24-72 h incubation with and without caspase-8 or - 9 inhibitors (z-IETD-fmk and z-LEHD-fmk). Counting surviving cells, DNA laddering, western blotting of poly(ADP-ribose) polymerase, and measurement of caspase activities were employed to confirm the cytotoxic effects of OxyHb and the protective effects of the caspase inhibitors. OxyHb produced cell detachment in a time-dependent manner and increased caspase-8 and -9 activities in the cells. z-IETD-fmk and z-LEHD-fmk (100 micromol/L) attenuated OxyHb-induced cell loss, DNA laddering, and proteolytic cleavage of PARP, although a lower concentration (10 micromol/L) of caspase inhibitors showed partial effects. OxyHb activates caspase-8 and -9 in cultured vascular endothelial cells, and blocking the action of the caspases with the inhibitors efficiently prevents loss of vascular endothelial cells from OxyHb-induced apoptosis in vitro. These results suggest that the caspase cascade participates in OxyHb-induced apoptosis.

Caspase inhibitors attenuate oxyhemoglobin-induced apoptosis in endothelial cells

BACKGROUND AND PURPOSE

Our recent study showed that oxyhemoglobin (OxyHb) induces apoptosis in cultured endothelial cells. Apoptosis requires the action of various classes of proteases, including a family of cysteine proteases known collectively as the caspases. This study was undertaken to investigate the effect of 2 caspase inhibitors, Z-VDVAD-FMK and Z-DEVD-FMK, in the protection of endothelial cells from OxyHb-induced apoptosis.

METHODS

Cultured bovine brain microvascular endothelial cells (passages 5 to 9) were exposed to OxyHb (10 micromol/L) for 24 to 72 hours with and without caspase inhibitors. Cell attachment, DNA ladder, Western blotting of poly(ADP-ribose) polymerase (PARP), and caspase activities were measured to confirm the cytotoxic effect of OxyHb and the protective effect of the caspase inhibitors.

RESULTS

(1) OxyHb produced cell detachment in a time-dependent manner. (2) OxyHb increased caspase-2 and -3 activities, produced DNA ladders, and cleaved PARP in endothelial cells. (3) Z-VDVAD-FMK and Z-DEVD-FMK (100 micromol/L) attenuated OxyHb-induced cell detachment, reduced caspase-2 and -3 activities, abolished OxyHb-induced DNA ladders, and prevented OxyHb-induced cleavage of PARP.

CONCLUSIONS

OxyHb activates caspase-2 and -3 in cultured brain microvessel endothelial cells. Caspase inhibitors attenuated the cytotoxic effect of OxyHb.

Role of calcium channels in oxyhemoglobin-induced apoptosis in endothelial cells

OBJECT

Oxyhemoglobin (OxyHb) released from hemolysed erythrocytes has been considered to be responsible for cerebral vasospasm after subarachnoid hemorrhage. The authors previously reported that OxyHb produced apoptosis in cultured vascular endothelial cells. The change in intracellular Ca++ homeostasis was expected to be one of the possible mechanisms of the cytotoxic effects of OxyHb. This study was undertaken to investigate the protective effects of Ca++ channel blockers on OxyHb-induced apoptosis.

METHODS

Cultured bovine coronary artery and brain microvascular endothelial cells (passages 5-9) were used. A cell density study, immunohistochemical staining, and DNA fragmentation analysis were performed to confirm apoptosis. Various concentrations (1-50 microM) of OxyHb were used for 24- to 72-hour incubations with and without Ca++-channel blockers. Oxyhemoglobin produced cytotoxicity leading to cell detachment from the culture dish in time- and concentration-dependent manners. The highest dose (50 microM) of OxyHb produced cell detachment after a 24-hour incubation, and the lower doses (1-10 microM) produced cell detachment after 48 to 72 hours. Immunohistochemical analysis showed that apoptosis occurred in cells that were still attached to the side of the culture dish after 48 to 72 hours of OxyHb treatment (5 microM). The OxyHb (10 microM) produced DNA ladders at 48 to 72 hours. Three Ca++-channel blockers were used to prevent the toxic effect of OxyHb. The voltage-dependent Ca++-channel blocker nicardipine (1 microM), the voltage-independent Ca++-channel blocker econazole (10 microM), and the inorganic Ca++-channel blocker lanthanum (100 microM) all failed to prevent cell detachment or DNA ladders produced by OxyHb. These results were similar in both cell lines.

CONCLUSIONS

Oxyhemoglobin produced apoptotic changes in cultured vascular endothelial cells, and Ca++-channel blockers did not prevent OxyHb-induced apoptosis.

Ventricular cerebrospinal fluid and serum concentrations of sTNFR-I, IL-1ra, and IL-6 after aneurysmal subarachnoid hemorrhage

Postsubarachnoid hemorrhage, systemic inflammatory response syndrome and associated organ system failure are more frequently found in patients in poor neurologic condition. Since subarachnoid hemorrhage causes a profound intrathecal inflammatory response with production of proinflammatory cytokines TNFalpha, IL-1beta, and IL-6, a possible explanation for this association is that brain-derived cytokines may enter the systemic circulation in the presence of postsubarachnoid hemorrhage blood brain barrier disruption to systemically activate inflammatory cascades and thereby contribute to the development of postsubarachnoid hemorrhage systemic inflammatory response syndrome and extracerebral organ system failures. In 44 patients with aneurysmal subarachnoid hemorrhage admitted within 3 days of the initial bleed, extracerebral organ system functions were assessed individually and in aggregate using the modified Multiple Organ Dysfunction Score. Serum and cerebrospinal fluid concentrations of soluble tumor necrosis factor-alpha receptor-I, interleukin-1beta receptor antagonist, and IL-6 were determined during the first 2 weeks after subarachnoid hemorrhage and tested for correlation with (1) admission Hunt-Hess grade, (2) development of systemic inflammatory response syndrome and extracerebral organ system failures, and (3) neurologic outcome. The development of postsubarachnoid hemorrhage systemic inflammatory response syndrome and extracerebral organ system failures was paralleled by a significant increase in serum but not in cerebrospinal fluid levels of soluble tumor necrosis factor-alpha receptor-I and IL-1ra, that is, patients with and without extracerebral organ system failures did not differ in pattern and time course of cerebrospinal fluid cytokine concentrations. In contrast, increasing soluble tumor necrosis factor-alpha receptor-I and interleukin-1beta receptor antagonist serum levels correlated with a higher Multiple Organ Dysfunction score and with individual organ system dysfunctions. Postsubarachnoid hemorrhage, systemic inflammatory response syndrome and extracerebral organ system failures could therefore not be linked to changes in cerebrospinal fluid cytokine concentration profiles.

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

Free radicals are important contributors to the global brain dysfunction that follows subarachnoid hemorrhage (SAH). We evaluated the effects of hydroxyl radical scavenger AVS [(+/-)-N,N'-propylenedinicotinamide; Nicaraven] after experimental SAH on rodent behavioral deficits (employing a battery of well-characterized assessment tasks over a 2-day observation period) and blood-brain barrier (BBB) permeability changes two days after SAH (quantifying the microvascular alterations according to the extravasation of protein-bound Evans Blue using a spectrophotofluorimetric technique) in dose-response and time-window experiments. Groups of 10 rats were injected with 400 microl of autologous blood into the cisterna magna, and followed by intravenous continuous infusion of saline or 0.1, 03 or 1 mg/kg/min of AVS beginning within 5 minutes or 6 or 12 hours after SAH. The results were compared with sham-operated saline-treated and with SAH saline-treated animals. AVS significantly ameliorated performances on Beam Balance (p < 0.01) and decreased BBB permeability changes in frontal, temporal, parietal, occipital and cerebellar cortices and subcortical and cerebellar nuclei and brainstem (p < 0.01), but did not significantly affect changes in Beam Walking. This study demonstrates the neuroprotective effects of AVS when administered after experimental SAH in rats. These effects were dose-dependent and, moreover, were evident within the therapeutic window of 6-12 hours after SAH. These results reinforce the concept of a participation of reactive oxygen intermediates in the cerebral dysfunction following SAH.

Amelioration of vasospasm after subarachnoid hemorrhage in transgenic mice overexpressing CuZn-superoxide dismutase

BACKGROUND AND PURPOSE

To clarify the effect of superoxide dismutase (SOD) on vasospasm after subarachnoid hemorrhage (SAH), we investigated sequential changes in arterial diameter after SAH in transgenic mice overexpressing CuZn-SOD (SOD-1).

METHODS

SOD-transgenic mice and nontransgenic littermates (35 to 40 g) were subjected to SAH produced by endovascular perforation of left anterior cerebral artery. At 4 hours and 1, 3, 7, and 14 days after SAH, the mice were perfused with 10% formalin and consequently with a mixture of carbon black and 10% gelatin to cast all vessels. Vasospasm was evaluated by measuring the diameter of the left middle cerebral artery (MCA) with a microscope.

RESULTS

In nontransgenic mice, the diameter of the MCA on day 3 after SAH (110.5+/-20.5 microm [mean+/-SD]; n=16) was significantly reduced compared with that without SAH (138.5+/-14.5 microm; n=12) (P<0.01). Moreover, on day 3 after SAH, the diameter of the MCA in SOD-transgenic mice (127. 9+/-20.2 microm; n=20) was significantly larger than that in nontransgenic mice (110.5+/-20.5 microm; n=16) (P<0.05).

CONCLUSIONS

These results suggest that SOD is effective on the amelioration of vasospasm after SAH and that oxygen free radicals, particularly superoxide, play an important role in the pathogenesis of vasospasm after SAH.

Extrinsic pathway of blood coagulation and thrombin in the cerebrospinal fluid after subarachnoid hemorrhage

OBJECTIVE

The involvement of thrombin in the pathophysiology of subarachnoid hemorrhage (SAH) was investigated by comparing thrombin expression and extrinsic pathway activation in the cerebrospinal fluid (CSF) and blood of patients with SAH with the neurological grades, outcome, and presence of delayed cerebral vasospasm.

METHODS

Blood and CSF samples were obtained from 38 patients with SAH on Days 3 through 5, 7 through 9, and 12 through 14 after the onset of SAH. CSF samples were also obtained from control patients. Thrombin-antithrombin III complex, prothrombin fragment F1 +2, tissue factor, and tissue factor pathway inhibitor were analyzed using enzyme-linked immunosorbent assay.

RESULTS

No markers in the blood or CSF were correlated with neurological grades and outcome. Thrombin-antithrombin III complex and prothrombin fragment F1 +2 levels were significantly higher in the CSF of patients with SAH than in the blood or the CSF of control patients and were significantly higher in patients with vasospasm than in patients without vasospasm on Days 7 through 9. Tissue factor levels were significantly higher in the CSF of patients with SAH than in the blood, but the levels were close to those in the CSF of control patients. Tissue factor pathway inhibitor levels in the CSF of patients with SAH and control patients were under the detection limit.

CONCLUSION

Thrombin in the blood may not reflect the pathophysiology of SAH. Imbalance between tissue factor and tissue factor pathway inhibitor in the CSF may tend to thrombin generation under normal physiological conditions and also after SAH. Thrombin in the CSF may be involved in the pathophysiology of vasospasm.

Tirilazad widens the therapeutic window for riluzole-induced attenuation of progressive cortical degeneration in an infant rat model of the shaken baby syndrome

Our infant rat model of traumatic subarchnoid hemorrhage combines violent shaking and hypoxia to produce subdural hemorrhaging and progressive cortical degeneration similar to that seen in victims of the shaken baby syndrome. Anesthetized, 6-day-old male rats were subjected to one episode of shaking under hypoxic conditions. Brain histologies revealed moderate-to-severe cortical hemorrhaging at 48 h postinjury and progressive cortical degeneration, as indicated by a 15.3% and 20.2% reduction in cortical wet weight, at 7 and 14 days postinjury, respectively. The purpose of the present study was to assess the effects of two antioxidant lipid peroxidation inhibitors (tirilazad mesylate and PNU-101033E), and the glutamate release inhibitor (riluzole), upon the brain pathology seen in this model. A significant, 54.3-75.3%, reduction in cortical hemorrhaging was observed in rats that were treated with a total of three doses of tirilazad (10 mg/kg, i.p.): 10 min before or 5-30 min after injury, and again at 2 and 24 h postinjury (p < 0.01 vs. vehicle). However, treatment with tirilazad or the more potent, brain-penetrating pyrrolopyrimidine, PNU-101033E (10 min before plus 2, 24, 48, and 72 h after), did not attenuate the progressive cortical degeneration typically seen at 14 days postinjury. These results suggest that free radicals play an important role in the pathophysiology of secondary brain hemorrhaging due to shaking + hypoxia, but may not be critical in the mediation of the subsequent neurodegeneration. Rather, glutamate neurotoxicity may be a key factor here. This is suggested by our observation that the glutamate release inhibitor, riluzole, significantly reduced cortical degeneration when it was administered up to 1 h postinjury in the present model. Specifically, the cortical wet weights of rats treated with 8 mg/kg riluzole (i.p.) 10 min before or 1 h after shaking + hypoxia (and again at 24 h postinjury) were 95.3% and 97.4% of noninjured controls, respectively, at 14 days postinjury (p < 0.02 vs. vehicle). Riluzole treatment beyond 1 h (e.g., 2 or 4 h postinjury) did not reduce the neurodegeneration. Lastly, we attempted to demonstrate that the therapeutic window for riluzole-induced attenuation of cortical degeneration could be extended beyond 1 h through the use of combination therapy. In this experiment, rat pups were treated with 10 mg/kg tirilazad (i.p.) at 30 min postinjury followed by 8 mg/kg riluzole (i.p.) at 4 and 24 h postinjury. At 14 days postinjury, the cortical wet weights of these rats were 94.5% of noninjured controls, thus demonstrating significant neuroprotection (p < 0.05 vs. vehicle) and a widening of the therapeutic window from 1 to 4 h in length. These results suggest that early attenuation of free radical-induced lipid peroxidation may slow down the biochemical cascade of events related to glutamate-induced excitotoxicity and, in doing so, prolong the time during which a glutamate release inhibitor, such as riluzole, is effective.

Infant rat model of the shaken baby syndrome: preliminary characterization and evidence for the role of free radicals in cortical hemorrhaging and progressive neuronal degeneration

Infants subjected to repeated episodes of violent shaking develop brain damage characterized by intracranial hemorrhage and progressive cortical atrophy. We have developed an animal model that mimics this pathological state and investigated its etiology and treatment. Anesthetized male rats, 6 days of age, were subjected to one episode of shaking per day for 3 consecutive days. Separate groups of rats were sacrificed 1 h postinjury on the third day of shaking for HPLC quantification of cortical .OH and vitamin E levels, and histological assessment of cortical hemorrhaging. Additional groups were sacrificed 7 or 14 days postinjury to demonstrate progressive neuronal degeneration via cortical wet weight comparisons. In comparison to noninjured shams, the results indicated that cortical vitamin E and .OH levels rose 53.7% (p < 0.005) and 457.1% (p < 0.001), respectively, in shaken infant rats. Brain histologies revealed a moderate-to-severe degree of cortical hemorrhaging in these animals 1 h postinjury. By 7 and 14 days postinjury, there was a 13.3% and 28.7% (p < 0.0001 vs. sham) loss of cortical tissue in shaken infants, respectively, indicating progressive neuronal degeneration. Treatment with 10 mg/kg (ip) of the 21-aminosteroid antioxidant, tirilazad mesylate, 10 min before and 2 h after each episode of shaking, resulted in a 53.1% attenuation of cortical .OH levels and a 34.9% decrease in brain hemorrhaging (p < 0.05 vs. vehicle). Tirilazad treatment did not, however, significantly effect cortical vitamin E concentrations at 1 h postinjury or the extent of progressive neuronal degeneration at either 7 or 14 days postinjury. The present animal model mimics the brain pathology seen in abused children. Our observation that tirilazad mesylate, an antioxidant-lipid peroxidation inhibitor, significantly reduces cortical .OH levels and brain hemorrhaging in shaken infant rats supports a role for oxygen radicals in the pathophysiology of this type of CNS injury. The failure of tirilazad to block progressive cortical degeneration suggests that mechanisms other than free radicals may be of prime importance in the mediation of this aspect of the pathology.

Monoclonal antibodies against ICAM-1 and CD18 attenuate cerebral vasospasm after experimental subarachnoid hemorrhage in rabbits

BACKGROUND AND PURPOSE

Inflammatory responses have been implicated in the elaboration of several forms of central nervous system injury, including cerebral vasospasm after subarachnoid hemorrhage (SAH). A critical event participating in such responses is the recruitment of circulating leukocytes into the inflammatory site. Two of the key adhesion molecules responsible for the attachment of leukocytes to endothelial cells are intercellular adhesion molecule-1 (ICAM-1) and the common beta chain of the integrin superfamily (CD18). This study examined the effects of monoclonal antibodies on ICAM-1 and the effects of CD18 on cerebral vasospasm after SAH.

METHODS

A rabbit model of SAH was utilized to test the influence of intracisternally administered antibodies to ICAM-1 and CD18 on cerebral vasospasm. Antibodies were administered alone or in combination, and the cross-sectional area of basilar arteries was assessed histologically on day 2 post-SAH.

RESULTS

Treatment with antibodies to ICAM-1 or CD18 inhibited vasospasm by 22% and 27%, respectively. When administered together, the attenuation of vasospasm increased to 56%. All of these effects achieved statistical significance.

CONCLUSIONS

These findings provide the first evidence that the severity of cerebral vasospasm can be attenuated using monoclonal antibodies against ICAM-1 and CD18. The results reinforce the concept that cell-mediated inflammation plays an important role in cerebral vasospasm after SAH and suggest that therapeutic targeting of cellular adhesion molecules can be of benefit in treating cerebral vasospasm.

Antivasospastic and brain-protective effects of a hydroxyl radical scavenger (AVS) after experimental subarachnoid hemorrhage

OBJECT

The radical scavenger (+/-)-N,N'-propylenedinicotinamide (AVS) was shown recently to ameliorate delayed neurological deficits resulting from ischemia in patients who have had an aneurysmal subarachnoid hemorrhage (SAH). The aim of this study was to evaluate the effect of AVS administration after experimental SAH on 1) behavioral deficits; 2) angiographically confirmed basilar artery (BA) spasm; and 3) blood-brain barrier (BBB) permeability changes.

METHODS

These parameters were measured by 1) using a battery of well-characterized chronic assessment tasks over a 5-day observation period; 2) assessing in vivo the mean vessel diameter 2 days after SAH; and 3) evaluating the extravasation of protein-bound Evans Blue dye by using a spectrophotofluorimetric technique 2 days after SAH. Groups of eight to 10 rats received injections of 400 microl of autologous blood into the cisterna magna. Within 5 minutes after the surgical procedures were completed the rats were treated with an intravenously administered continuous infusion of saline (Group III) or AVS (1 mg/kg/minutes, Group IV). Results were compared with those in sham-operated animals treated with intravenously administered saline (Group I) or AVS (Group II). The AVS-treated rats had significantly improved balance beam scores on Days 1 to 2 (p < 0.05), shorter beam traverse times on Day 1 (p < 0.05), and better beam walking performance on Days 1 to 4 (p < 0.01), but no significant effect was seen in terms of SAH-related changes in body weight. Treatment with AVS also attenuated the SAH-induced BA spasm (p < 0.05) and decreased BBB permeability changes in frontal, temporal, parietal, occipital, and cerebellar cortices, and in the subcortical and cerebellar gray matter and brainstem (p < 0.01).

CONCLUSIONS

These results demonstrate useful antivasospastic and brain-protective actions of AVS after induction of experimental SAH and provide support for observations of beneficial effects of AVS made in the clinical setting.

Fibrinolytic activity in the CSF and blood following subarachnoid haemorrhage

Fibrinolytic agents are administered to resolve subarachnoid clot, a major reservoir for spasmogen, to prevent delayed cerebral vasospasm (VS) in patients with subarachnoid haemorrhage (SAH). However, intracranial bleeding often occurs, which may be caused by over-activation of fibrinolysis in the cerebrospinal fluid (CSF) milieu. We measured the levels of D dimer in the CSF and blood of patients with SAH to analyse the correlation between fibrinolytic activity and VS. CSF and blood samples were obtained three times, and VS was identified by angiography. The levels of D dimer in the CSF were significantly higher than in the blood, but changes with time were inverse. Patients with VS showed significantly lower levels of D dimer in both CSF and blood in the initial stage compared to those without VS. These observations suggest that monitoring of fibrinolytic activity in the CSF to identify patients eligible for additional fibrinolytic treatment could reduce the risk of VS and iatrogenic intracranial bleeding.

Coagulative and fibrinolytic activation in cerebrospinal fluid and plasma after subarachnoid hemorrhage

OBJECTIVE

Intrathecal fibrinolytic therapy has been used as one of the anticerebral vasospasm (VS) preventative therapies in patients with subarachnoid hemorrhage (SAH). However, the changes in coagulation and fibrinolysis in the blood and cerebrospinal fluid (CSF) after SAH remain unknown.

METHODS

Fifty patients with SAH caused by ruptured cerebral aneurysms were studied postoperatively to detect the serial changes of the thrombin-antithrombin III complex, active plasminogen activator inhibitor (PAI)-1, and tissue plasminogen activator (tPA)-PAI complex (tPA-PAI) activities in the plasma and CSF collected from cisternal drainage catheters.

RESULTS

The CSF levels of all parameters and plasma PAI-1 levels were significantly higher in patients with severe SAH than in those with mild SAH. There was no relationship between the CSF and plasma levels of these parameters (except the CSF levels of tPA-PAI) and the initial neurological statuses. The CSF PAI-1 levels increased to greater than 20 ng/ml near the time of the occurrence of cerebral VS, whereas they remained below 20 ng/ml in patients without VS. The CSF tPA-PAI levels showed the highest peak near the time of VS remission. The CSF PAI-1 and tPA-PAI levels were significantly lower in patients with good outcomes than in those with poor outcomes.

CONCLUSION

Both the coagulative and fibrinolytic systems were activated in the CSF and plasma after SAH in correlating to the amount of SAH clot. The intrathecal administration of fibrinolytic agents should be started early after surgery, before CSF PAI-1 levels increase, for patients with severe SAH. Patients with CSF PAI-1 levels greater than 20 ng/ml experienced high incidence of VS and poor outcomes.

Effects of intraluminal or extraluminal endothelin on perfused rabbit basilar arteries

The authors investigated selective intra- and extraluminal effects of endothelin (ET) on perfused basilar and extracranial arteries and also studied the interaction between ET and extraluminal oxyhemoglobin (oxyHb). The basilar, mesenteric, and femoral arteries were isolated from 23 Japanese White rabbits. After isolation of the intra- and extraluminal sides of the preparation, 3 x 10(-10) to 3 x 10(-8) mol/L of ET was administered intra- or extraluminally. After extraluminal pretreatment with 10(-5) mol/L oxyHb, 10(-5) mol/L N(G)-monomethyl-L-arginine (L-NMMA), or 10(-6) mol/L indomethacin, 10(-10) to 10(-8) mol/L of ET was administered intra- or extraluminally. Arterial contraction was evaluated by measuring the increase in the perfusion pressure gradient with a differential pressure gauge. Both intra- and extraluminal ET (10(-9) to 3 x 10(-8) mol/L) showed potent and dose-dependent vasoconstricting effects on basilar arteries (p < 0.01). The effect of ET on the basilar arteries was significantly greater than on the femoral or mesenteric arteries (both p < 0.01). The effect of intraluminal ET was enhanced by extraluminal oxyHb (p < 0.05) and L-NMMA (p < 0.01), but not by extraluminal indomethacin. Extraluminal oxyHb did not potentiate the contraction induced by extraluminal ET. These results indicate that the sensitivity of the basilar artery to intraluminal ET is greater than that of the femoral or mesenteric artery. Endothelin may act as a potent vasoconstrictor intra- as well as extraluminally under conditions such as subarachnoid hemorrhage in which oxyHb is present in the extraluminal space and endothelium-derived relaxing factors are inhibited.

5-Hydroxytryptamine-induced vasoconstriction after cerebral hematoma in piglets

Subarachnoid hematoma produces cerebral vasoconstriction that may lead to death or permanent disability. After hematoma, enhanced pial arteriolar responses to vasoconstrictor agents have been reported in newborn pigs. The present study was designed to address the hypothesis that 5-hydroxytryptamine (5-HT) constricts piglet pial arterioles, and hematoma augments this constriction. Piglets (1-3 d old) anesthetized with ketamine and acepromazine received either 3 mL of artificial cerebrospinal fluid (control) or autologous nonheparinized blood (hematoma) injected onto the cortical surface. Four days after injection, closed cranial windows were implanted over the injected area under alpha-chloralose anesthesia. Vascular reactivity to 5-HT was examined. In control piglets, topical application of 5-HT (10(-9), 10(-7), and 10(-5) M) induced very mild, dose-dependent constriction of pial arterioles (-6 +/- 1, -10 +/- 2, and -12 +/- 4%, respectively). These constrictions were substantially augmented in piglets with hematoma (-12 +/- 2, -19 +/- 1, and -30 +/- 2%, respectively). After topical application of 5-HT, cerebrospinal fluid samples were collected from under the window to determine the effects of 5-HT on the levels of 6-keto-prostaglandin F1 alpha and thromboxane B2. The baseline levels of 6-keto-prostaglandin F1 alpha and thromboxane B2 before 5-HT were 1791 +/- 387 and 434 +/- 74 pg/mL, respectively, in the control. 5-HT application had no significant effects on these prostanoid levels (levels at the highest concentration of 5-HT had a corresponding value of 1175 +/- 301 and 288 +/- 74 pg/mL for 6-keto-prostaglandin F1 alpha and thromboxane B2, respectively). However, indomethacin (5 mg/kg, i.v.) treatment of the control piglets potentiated the constriction in response to 5-HT (-11 +/- 1, -15 +/- 2, and -24 +/- 3%, respectively) sufficiently to produce constriction similar to that in the hematoma group. 5-HT has little effect on normal pial arterioles of newborn piglets but is a more potent cerebral vasoconstrictor in conjunction with cerebral hematoma.

Reduced expression of calponin in canine basilar artery after subarachnoid haemorrhage

Calponin, an actin- and tropomyosin-binding protein, has been characterized as an inhibitory factor in the smooth-muscle actomyosin activity. The level of calponin was determined in canine basilar arteries in a double-haemorrhage model. Thirty dogs were assigned to three groups: day 0 group, control; day 2 group, dogs sacrificed 2 days after cisternal injection of blood; and day 7 group, dogs given double cisternal injections of blood and sacrificed 7 days after the first injection. Constriction of the basilar artery was confirmed by arterial angiography. Portions of the affected arteries or the corresponding region in control animals were solubilized for sodium dodecylsulphate-polyacrylamide gel electrophoresis and Western blotting. A major band corresponding to calponin was seen at 34 kD in the basilar artery extracts using chicken gizzard polyclonal antibodies. The densitometer values of the band on Coomassie blue-stained gels were expressed as percentages of day 0 control values. The signals of day 2 and day 7 samples were 47% +/- 20% and 23% +/- 12%, respectively (mean +/- standard deviation). The proportions of calponin to actin/tropomyosin in the day 0, day 2, and day 7 groups were 13% +/- 6%, 6% +/- 2%, and 4% +/- 2%, respectively. The reduced expression of calponin may be related to sustained contraction during cerebral vasospasm.

Plasma levels of protein C, protein S, and antithrombin III in patients with subarachnoid haemorrhage

This study was designed to evaluate the clinical value of consecutive measurements of the levels of the anticoagulation factors protein C. protein S and antithrombin III in the plasma of patients with subarachnoid haemorrhage (SAH). Sequential samples of plasma were obtained from 34 patients at days 0 to 3, 5, 8, 14, and 20 days after SAH. Their levels of protein C, protein S and antithrombin III were measured by specific immuno-assays, and the symptomatic vasospasm and clinical states of the patients were monitored. Based on the retrospective comparisons between the measured levels of the three factors and the levels in pooled plasma from normal volunteers, the time course of changes in the levels allowed the classification of the patients into five groups as follows: A, the levels of the three factors decreased suddenly at 5 days after SAH, then increased again (n = 6); B, the three factors increased continuously (n = 13); C, the three factors remained below the normal range (n = 3); D, the three factors remained within the normal range (n = 6); and E, the three factors decreased continuously (n = 6). In group A patients, temporary deficiencies in the three factors occurred that coincided with the occurrence of delayed neurological deficit (DND). Twelve patients (92%) in group B had a favourable outcome (good and moderate disability) without DND. The patients in group C had low levels of anticoagulation factors and mild DND followed by a favourable outcome. Five patients (83%) in group D had a favourable outcome. In group E, five patients (83%) had a poor outcome (severe disability and death) due to DND. When clinical outcomes were compared by patient group, the patients in group E had significantly more unfavourable outcomes than did the other groups (P < 0.01). Although the mechanism responsible for the decrease in anticoagulation factor levels remained unclear, the results suggested that the decrease in anticoagulation factors may indicate hypercoagulability and cerebral ischaemia after SAH.

Systemic complement depletion inhibits experimental cerebral vasospasm

OBJECTIVE

Cerebral vasospasm is the leading cause of morbidity and mortality in patients who are hospitalized because of aneurysmal subarachnoid hemorrhage (SAH). Recent work has suggested that activation of the complement cascade contributes to the development of cerebral vasospasm. To further examine this hypothesis, a rabbit model of SAH was employed.

METHODS

Two milliliters of autologous arterial blood was injected into the region of the perimesencephalic cistern. Forty-eight hours after SAH was induced, intravital perfusion-fixation was performed. Morphometric analysis of the basilar artery was used to assess the extent of cerebral vasospasm after pretreatment with the complement depleting agent, cobra venom factor (CVF), or vehicle. Rabbits were randomized to one of four groups: 1) sham (n = 5); 2) sham + CVF (n = 4); 3) SAH (n = 10); or 4) SAH + CVF (n = 7). Twenty-four hours before induction of SAH, the animals received either 100 units/kg CVF or vehicle. The total hemolytic potential of the serum confirmed a significant (P < 0.05) reduction in serum complement activity 24 hours after the administration of CVF.

RESULTS

Pretreatment with CVF significantly (P < 0.0083) reduced the extent of vasospasm, as assessed by lumen diameter from 393.9 +/- 100.1 microns (mean +/- standard deviation) in the SAH group to 510.7 +/- 72.8 microns in the SAH + CVF group, when compared with the sham (594.5 +/- 27.9 microns) and sham + CVF (587.7 +/- 47.3 microns) groups.

CONCLUSION

The results suggest a role for complement activation in SAH.

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.

Cisternal talc injection in dog can induce delayed and prolonged arterial constriction resembling cerebral vasospasm morphologically and pharmacologically

BACKGROUND

The possible role of inflammation in the pathogenesis of cerebral vasospasm has been noted in recent studies. In order to examine the role of inflammation, we examined the vasocontractile activity of talc, which is known to cause severe inflammation, using a canine cisternal talc injection model.

METHODS

Under general anesthesia, a sterile talc powder suspended in saline was injected into the cisterna magna of the dog. Serial vertebral angiography and postmortem histologic changes of the harvested basilar artery were examined. The morphologic and pharmacologic features of talc-induced vessel spasm were compared with the usual autologous blood-induced artery spasm.

RESULTS

Cisternal injection of sterile talc powder caused no early spasm, but induced definite basilar arterial constriction 2 days after injection. This vascular constriction was observed to continue up to 7 days after injection. Ultrastructural study of the constricted vessel revealed several morphologic changes, such as corrugation of the elastic lamina, subintimal proliferation, migration of smooth muscle cells, detachment of endothelial cells, etc.; findings that are compatible with the changes observed in vasospasm. Pharmacologic study showed a moderate decrease in the maximal contraction to KCl and UTP. Endothelium-dependent relaxation was markedly disturbed, while endothelium-independent relaxation was preserved. These pharmacologic properties were also similar to those reported in vasospasm.

CONCLUSIONS

Our present study indicates that the several changes of vascular properties, which had been considered to be specific to cerebral vasospasm, can be regarded as a nonspecific biologic defense reaction against the foreign body. The analysis of the common pathway from talc and autologous blood to vasospasm may lead to the pathogenesis of cerebral vasospasm.

Prevention of subarachnoid hemorrhage-induced cerebral vasospasm by oral administration of endothelin receptor antagonists

The purpose of this study was to investigate the effectiveness of oral treatment with the endothelin (ET) A/B receptor antagonist Ro 47-0203, 4-tert-butyl-N-[6-(hydroxy- ethoxy)-5-(2-methoxy-phenoxy)-2'-bipyrimidin-4-yl]-benzenesulfonam ide (bosentan), and the ET A receptor antagonist 2-benzo[1,3]dioxol-5-yl-3-benzyl-4-(4-methoxy- phenyl)-4-oxo-but-2-enoic acid monosodium salt (PD155080), in the prevention of subarachnoid hemorrhage (SAH)-induced delayed cerebral vasospasm. Double hemorrhage in the rabbit constricted the basilar artery to 34% if control as determined by angiography. Oral bosentan and PD155080 administration after the initial SAH decreased the magnitude of constriction to 9% and 16% of control, respectively. Plasma and cerebrospinal fluid bosentan levels and plasma PD155808 levels were consistent with concentrations reported to inhibit ET-1 constriction of blood vessels in vitro. These results support the use of oral administration of ET A/B and ET A receptor antagonists as potential specific treatment for vasospasm resulting from SAH in humans.

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

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

Percutaneous transluminal angioplasty in a canine model of cerebral vasospasm: angiographic, histologic, and pharmacologic evaluation

BACKGROUND

Cerebral vasospasm following subarachnoid hemorrhage (SAH) is one of the leading factors that deteriorate the clinical outcome after aneurysmal surgery. Percutaneous transluminal angioplasty (PTA) is a method to directly dilate the constricted vessel using the intravascular neurosurgical technique.

METHODS

Angiographic, histologic, and pharmacologic evaluations related to PTA are presented, using a canine double-injection model of SAH. In angiographic evaluation, we studied the effect of PTA performed on day 1, 4, or 7 of SAH. We performed sequential histologic study by light microscopy using the same for the angiographic evaluation. In pharmacologic evaluation, we measured in vitro isotonic constrictive force using two vasoconstrictors immediately after PTA on normal basilar arteries (control group) and basilar arteries on day 7 of SAH.

RESULTS

In angiographic evaluation, we observed the effective dilation of spastic artery immediately after PTA and saw no recurrence of vessel constriction when PTA was performed on day 7 of SAH. However, the preventive effect of PTA was inconsistent when it was performed earlier after SAH (days 1, 4). In histologic evaluation, PTA segments immediately after PTA showed denuding of endothelial cells and stretching of the internal elastic lamina without disruption of the muscle layer. In pharmacologic evaluation, there was no difference in isotonic constrictive force created by vasoconstrictors between the PTA and non-PTA segments without SAH. However, there was a statistically significant reduction of isotonic constrictive force on the PTA segment with SAH.

CONCLUSIONS

We suggest that the mechanism of PTA vasodilation in vasospasm after SAH may result from mild functional changes in the vascular wall when PTA was applied on day 7 of SAH. The functional changes would not be adequately induced to prevent recurrence of vasoconstriction when PTA was applied soon after SAH.

Expression of intercellular adhesion molecule 1 (ICAM-1) on the cerebral artery following subarachnoid haemorrhage in rats

In order to study how immune-inflammatory responses are involved in the pathogenesis of cerebral vasospasm after subarachnoid haemorrhage (SAH), the kinetics of expression of the intercellular adhesion molecule 1 (ICAM-1), a ligand for the leucocyte adhesion receptor, were studied on the cerebral arteries following SAH in rats. The SAH was induced by intracisternal injection of arterial blood. The rats were sacrificed at specified times: immediately after induction of SAH to seven days after SAH. Cryostat sections of the basilar artery (BA) were prepared and incubated with anti-rat ICAM-1 antibody. Morphometric analysis of the BA revealed a significant narrowing of the luminal diameter on Day 2 following SAH. While in the non-treated normal animals, no nor only weak expression of ICAM-1 was observed on the endothelial layer of the BA, there was greater expression of ICAM-1 on the endothelial layer of the BA in SAH rats, and the expression was observed also in the medial layer of the artery from Day 2 to Day 5 following SAH. The present results indicate that SAH really causes responses in the cellular immunity not only in the endothelial layer, but also in the medial layer of the artery as a target of immune damage, which is presumed to be one of the important steps in the development of cerebral vasospasm.

[CSF total proteins in the prognosis of patients with subarachnoid hemorrhage]

The main purpose of this study was to verify the value of CSF total proteins level on the prognosis of subarachnoid hemorrhage. In order of this, samples of 254 patients with diagnosis of intracranial bleeding were analyzed, with special attention to the rate of CSF total proteins. Statistical tests for evaluation of the results have been accomplished, revealing a close relationship between the total proteins rates increase and death in patients with subarachnoid hemorrhage, independent of sex and age. The limit score of total proteins level for survive was 3000 mg/100 ml (nephelometric method).

Nitric oxide synthase and guanylate cyclase levels in canine basilar artery after subarachnoid hemorrhage

Endothelium-dependent vasodilation may be impaired during cerebral vasospasm following subarachnoid hemorrhage. Under normal circumstances nitric oxide (NO) released by endothelial cells induces relaxation of smooth muscle by activating the soluble form of guanylate cyclase within muscle cells. In this study the levels of both endothelial NO synthase, the enzyme that produces NO, and soluble guanylate cyclase were determined in canine basilar arteries in a double-hemorrhage model using Western blot immunoassays. Thirty dogs were assigned to three groups: Group D0, control; Group D2, dogs sacrificed 2 days after cisternal injection of blood; and Group D7, dogs given double cisternal injections of blood and sacrificed 7 days after the first injection. Constriction of the basilar artery was confirmed by arterial angiography. Portions of the affected arteries or the corresponding region in control animals were solubilized for sodium dodecylsulfate-polyacrylamide gel electrophoresis and Western blotting. A specific monoclonal antibody against endothelial NO synthase was used. The extract from basilar arteries showed two bands on the blots: 135 kD, characteristic of endothelial NO synthase, and 120 kD, which may be a degradation product of the enzyme. The densitometer values of the bands were presented as percentages of D0 control values. Although the total signal in the D7 group was less than that of the D0 control group (D2, 97% +/- 22%; D7, 78% +/- 40%), it was not statistically significant. The proportion of the 135-kD form decreased between Groups D0 and D7, but the difference was not significant. A single major band corresponding to the alpha-subunit of soluble guanylate cyclase was seen at 70 kD in the basilar artery extracts. The signals of D2 and D7 samples were 69% +/- 40% and 25% +/- 18%, respectively. There was a significant difference between D7 and D0 (p < 0.001). The reduced expression of soluble guanylate cyclase may be related to the impairment of endothelium-dependent vasodilation in vasospasm.

Effects of protease inhibitor and immunosuppressant on cerebral vasospasm after subarachnoid hemorrhage in rabbits

The possible role of the immune-defense system in the development of cerebral vasospasm after subarachnoid hemorrhage (SAH) was investigated in rabbits. We used a synthetic serine protease inhibitor, gabexate mesilate (GM), a glucocorticoid, betamethasone sodium phosphate (B-P), and an immunosuppressant, ciclosporin (Cyclosporin A, CYA), to prevent cerebral vasospasm. These agents were administered intra-venously every 12 hours for three injections, starting 20 minutes after SAH. In the group treated with GM, B-P, or CYA, there were no statistically significant differences in arterial calibers between treated and untreated controls on day 2. The synthetic serine protease inhibitor, FUT-175 has been reported to prevent cerebral vasospasm when the treatment is started 20 minutes after SAH in rabbits [38]. In rabbits treated with FUT-175 at different starting times from 3 to 6 hours, reductions in arterial caliber on day 2 were significantly prevented in each group. The contrasting effects of the two serine protease inhibitors, GM and FUT-175, are discussed.

Prevention of delayed vasospasm by an endothelin ETA receptor antagonist, BQ-123: change of ETA receptor mRNA expression in a canine subarachnoid hemorrhage model

The authors investigated the roles of endothelin (ET)-1 and the ETA receptor in the pathogenesis of delayed cerebral vasospasm following subarachnoid hemorrhage (SAH). A study was made of the preventive effect of a novel ETA receptor antagonist, BQ-123, on vasospasm and the expression of the ETA receptor messenger ribonucleic acid (mRNA) using a canine two-hemorrhage SAH model. Continuous intrathecal administration of BQ-123 (5 x 10(-6) mol/day) prevented narrowing of the basilar artery on Day 7 after SAH in 97.6% of cases in the study group versus 70.7% of cases in the control group (p < 0.05). While expression of the mRNA-coding ETA receptor was not detected in the control animals, it markedly increased on Day 3 after SAH and was also detected on Day 7. The results suggest that endothelin-1 and the ETA receptor participate in the pathogenesis of delayed cerebral vasospasm following SAH.