Mechanism of oxyhemoglobin-induced release of endothelin-1 from cultured vascular endothelial cells and smooth-muscle cells

Retrospective 6 month-outcomes and prognostic factors following spontaneous angiogram-negative non-perimesencephalic subarachnoid hemorrhage

Our objective was to analyze functional outcomes and prognostic factors in patients suffering from angiogram-negative non-perimesencephalic subarachnoid hemorrhage (non-PMH). In total, 1601 patients presenting with spontaneous SAH between January 2009 to December 2019 admitted to our institution were reviewed. Among them, 51 patients with angiogram negative non-perimesencephalic subarachnoid hemorrhage were analyzed. We divided patients into groups according to hemorrhage pattern and duration. Prognostic factors were assessed according to initial neurologic grade, early hydrocephalus, fisher grade, and duration of hemorrhage. Outcomes were assessed according to the modified Rankin Scale after 6 months. Overall, 41 patients (80.3%) with angiogram-negative non-PMH achieved a favorable outcome. In univariate analysis, good initial neurologic grade, absence of early hydrocephalus, non-Fisher-type 3 bleeding pattern, and short term hemorrhage (blood wash out <7 days after onset) duration were significantly associated with a favorable outcome. In multivariate analysis, a non-Fisher-type 3 hemorrhagic pattern (p < 0.05) and good initial neurologic state (p < 0.01) were independent predictors of favorable outcomes in angiogram-negative non-PMH patients. Patients with angiogram-negative non-PMH generally had favorable outcomes. A non-Fisher-type 3 hemorrhagic pattern and good initial neurologic state were prognostic factors of a favorable outcome in non-PMH. Furthermore, patients with long-term SAH were more likely to develop hydrocephalus. Evaluating the pattern and duration of subarachnoid hemorrhage may allow better prediction of outcomes in patients with angiogram negative and non-PMH.

Cerebral Vasospasm with Delayed Ischemic Neurologic Deficit after Unruptured Aneurysm Surgery : Report of Two Cases and Review of the Literature

Symptomatic cerebral vasospasm (CVS) and delayed ischemic neurologic deficit (DIND) after unruptured aneurysm surgery are extremely rare. Its onset timing is variable, and its mechanisms are unclear. We report two cases of CVS with DIND after unruptured aneurysm surgery and review the literature regarding potential mechanisms. The first case is a 51-year-old woman with non-hemorrhagic vasospasm after unruptured left anterior communicating artery aneurysm surgery. She presented with delayed vasospasm on postoperative day 14. The second case is a 45-year-old woman who suffered from oculomotor nerve palsy caused by an unruptured posterior communicatig artery (PCoA) aneurysm. DIND with non-hemorrhagic vasospasm developed on postoperative day 12. To our knowledge, this is the first report of symptomatic CVS with oculomotor nerve palsy following unruptured PCoA aneurysm surgery. CVS with DIND after unruptured aneurysm surgery is very rare and can be triggered by multiple mechanisms, such as hemorrhage, mechanical stress to the arterial wall, or the trigemino-cerebrovascular system. For unruptured aneurysm surgery, although it is rare, careful observation and treatments can be needed for postoperative CVS with DIND.

Extracellular Mitochondrial Dysfunction in Cerebrospinal Fluid of Patients with Delayed Cerebral Ischemia after Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Mitochondrial dysfunction is related to brain ischemic injury and neural cell death. However, little is known about the association between mitochondrial dysfunction of cerebrospinal fluid (CSF) and delayed cerebral ischemia (DCI) following subarachnoid hemorrhage (SAH). The objective of this study was to investigate whether extracellular CSF mitochondria might serve as a potential biomarker for DCI.

METHODS

CSF samples were serially collected at 1, 3, and 5 days following SAH in 33 patients (DCI, n = 12; and non-DCI, n = 21) who underwent coil embolization. To monitor mitochondrial membrane potentials, JC-1 dye was used. The ratio (red/green) of JC-1 was considered as an indicator of intact mitochondrial membrane potential. Flow cytometry was done to analyze extracellular mitochondria particles and their possible cellular origins.

RESULTS

DCI patients had lower JC-1 red/green ratios than non-DCI patients at 1 day (3.35 [3.20-3.75] vs. 3.70 [3.40-3.95] in non-DCI) and 3 days (4.65 [4.45-5.00] vs. 5.10 [4.65-5.30] in non-DCI) after SAH. At 5 days after SAH, JC-1 red/green ratio was significantly lower in DCI than that in non-DCI (3.05 [2.90-3.35] vs. 4.20 [4.10-4.50]; p < 0.01) patients. DCI patients had a higher percentage of vWF-positive mitochondria (40.10% [38.25%-44.90%] vs. 30.20% [25.70%-36.68%]) and a lower percentage of GLAST-positive mitochondria particles (26.85% [17.10%-30.00%] vs. 31.60% [26.70%-35.00%]) than non-DCI patients. However, there was no significant difference in CD45-positive (p = 0.369) or CD41/61-positive mitochondrial particles (p = 0.155) between the two groups of patients.

CONCLUSIONS

Mitochondrial membrane potential could be a marker of DCI. JC-1 ratios seemed to be able to predict future DCI onset. Further studies are needed to determine detailed mechanisms of extracellular mitochondria-mediated cell-to-cell signals in DCI.

Therapeutically Targeting Platelet-Derived Growth Factor-Mediated Signaling Underlying the Pathogenesis of Subarachnoid Hemorrhage-Related Vasospasm

INTRODUCTION

Vasospasm accounts for a large fraction of the morbidity and mortality burden in patients sustaining subarachnoid hemorrhage (SAH). Platelet-derived growth factor (PDGF)-β levels rise following SAH and correlate with incidence and severity of vasospasm.

METHODS

The literature was reviewed for studies investigating the role of PDGF in the pathogenesis of SAH-related vasospasm and efficacy of pharmacological interventions targeting the PDGF pathway in ameliorating the same and improving clinical outcomes.

RESULTS

Release of blood under high pressure into the subarachnoid space activates the complement cascade, which results in release of PDGF. Abluminal contact of blood with cerebral vessels increases their contractile response to PDGF-β and thrombin, with the latter upregulating PDGF-β receptors and augmenting effects of PDGF-β. PDGF-β figures prominently in the early and late phases of post-SAH vasospasm. PDGF-β binding to the PDGF receptor-β results in receptor tyrosine kinase domain activation and consequent stimulation of intracellular signaling pathways, including p38 mitogen-activated protein kinase, phosphatidylinositol-3-kinase, Rho-associated protein kinase, and extracellular regulated kinase 1 and 2. Consequent increases in intracellular calcium and increased expression of genes mediating cellular growth and proliferation mediate PDGF-induced augmentation of vascular smooth muscle cell contractility, hypertrophy, and proliferation.

CONCLUSION

Treatments with statins, serine protease inhibitors, and small molecular pathway inhibitors have demonstrated varying degrees of efficacy in prevention of cerebral vasospasm, which is improved with earlier institution.

Urotensinergic system genes in experimental subarachnoid hemorrhage

OBJECTIVE

Cerebral vasospasm, one of the main complications of subarachnoid hemorrhage (SAH), is characterized by arterial constriction and mainly occurs from day 4 until the second week after the event. Urotensin-II (U-II) has been described as the most potent vasoconstrictor peptide in mammals. An analysis is made of the serum U-II concentrations and mRNA expression levels of U-II, urotensin related peptide (URP) and urotensin receptor (UT) genes in an experimental murine model of SAH.

DESIGN

An experimental study was carried out.

SETTING

Experimental operating room of the Biomedicine Institute of Seville (IBiS), Virgen del Rocío University Hospital (Seville, Spain).

PARTICIPANTS

96 Wistar rats: 74 SAH and 22 sham intervention animals.

INTERVENTIONS

Day 1: blood sampling, followed by the percutaneous injection of 100μl saline (sham) or blood (SAH) into the subarachnoid space. Day 5: blood sampling, followed by sacrifice of the animals.

MAIN VARIABLES OF INTEREST

Weight, early mortality, serum U-II levels, mRNA values for U-II, URP and UT.

RESULTS

Serum U-II levels increased in the SAH group from day 1 (0.62pg/mL [IQR 0.36-1.08]) to day 5 (0.74pg/mL [IQR 0.39-1.43]) (p<0.05), though not in the sham group (0.56pg/mL [IQR 0.06-0.83] day 1; 0.37pg/mL [IQR 0.23-0.62] day 5; p=0.959). Between-group differences were found on day 5 (p<0.05). The ROC analysis showed that the day 5 serum U-II levels (AUC=0.691), URP mRNA (AUC=0.706) and UT mRNA (AUC=0.713) could discriminate between sham and SAH rats. The normal serum U-II concentration range in rats was 0.56pg/mL (IQR 0.06-0.83).

CONCLUSION

The urotensinergic system is upregulated on day 5 in an experimental model of SAH.

Cerebral vasospasm and delayed ischaemic deficit following elective aneurysm clipping

Although common after subarachnoid haemorrhage, cerebral vasospasm (CVS) and delayed ischaemic neurological deficit (DIND) rarely occur following elective clipping of unruptured aneurysms. The onset of this complication is variable and its pathophysiology is poorly understood. We report two patients with CVS associated with DIND following unruptured aneurysmal clipping. The literature is reviewed and the potential mechanisms in the context of patient presentations are discussed. A woman aged 53 and a man aged 70 were treated with elective clipping of unruptured middle cerebral artery aneurysms, the older patient also having an anterior communicating artery aneurysm clipped. The operations were uncomplicated with no intra-operative bleeding, no retraction, no contusion, no middle cerebral artery (MCA) temporary clipping, and no intra-operative rupture. Routine post-operative CT scan and CT angiogram showed that in both patients the aneurysms were excluded from the circulation and there was no perioperative subarachnoid blood. Both patients had no neurological deficit post-operatively, but on day 2 developed DIND and vasospasm of the MCA. Both patients had angiographic improvement with intra-arterial verapamil treatment. In one patient, this was done promptly and the patient made a complete recovery, but in the other, the diagnosis was delayed for more than 24hours and the patient had residual hemiparesis and dysphasia due to MCA territory infarction. CVS and DIND following treatment of unruptured aneurysms is a very rare event. However, clinicians should be vigilant as prompt diagnosis and management is required to minimise the risk of cerebral infarction and poor outcome.

Nuclear factor-κB is involved in oxyhemoglobin-induced endothelin-1 expression in cerebrovascular muscle cells of the rabbit basilar artery

The present research was designed to investigate whether endothelin-1 (ET-1) secretion can be induced by oxyhemoglobin and whether nuclear factor κB (NF-κB) is involved in the regulation of ET-1 transcription in cerebrovascular muscle cells. Cerebrovascular muscle cells isolated from a rabbit basilar artery were stimulated by oxyhemoglobin (OxyHb) and ET-1 production was increased significantly in the supernatant. Inhibition of NF-κB with pyrrolidine dithiocarbamate and small interfering RNA decreased the expression of ET-1. Nuclear translocation of NF-κB and the degradation of IkB-α was observed with the stimulation of OxyHb. The supernatant obtained from cerebrovascular muscle cells stimulated by OxyHb produced contractions in arterial rings and was blocked by the ET-1 receptor antagonist (BQ-123). The time course of the OxyHb-induced contractions of the basilar artery rings correlated with the time course of the OxyHb-induced ET-1 secretion. The contraction of the basilar artery rings induced by OxyHb was attenuated when the artery rings were preincubated with pyrrolidine dithiocarbamate and SN50 (20 and 10 µM, respectively). These results indicate that cerebrovascular muscle cells may be an important source of ET-1 production after subarachnoid hemorrhage. NF-κB was involved in the expression of ET-1 and the inhibition of the NF-κB pathway may be beneficial for the treatment of cerebral vasospasm.

Inducible nitric oxide synthase (NOS-2) in subarachnoid hemorrhage: Regulatory mechanisms and therapeutic implications

Aneurysmal subarachnoid hemorrhage (SAH) typically carries a poor prognosis. Growing evidence indicates that overabundant production of nitric oxide (NO) may be responsible for a large part of the secondary injury that follows SAH. Although SAH modulates the activity of all three isoforms of nitric oxide synthase (NOS), the inducible isoform, NOS-2, accounts for a majority of NO-mediated secondary injuries after SAH. Here, we review the indispensable physiological roles of NO that must be preserved, even while attempting to downmodulate the pathophysiologic effects of NO that are induced by SAH. We examine the effects of SAH on the function of the various NOS isoforms, with a particular focus on the pathological effects of NOS-2 and on the mechanisms responsible for its transcriptional upregulation. Finally, we review interventions to block NOS-2 upregulation or to counteract its effects, with an emphasis on the potential therapeutic strategies to improve outcomes in patients afflicted with SAH. There is still much to be learned regarding the apparently maladaptive response of NOS-2 and its harmful product NO in SAH. However, the available evidence points to crucial effects that, on balance, are adverse, making the NOS-2/NO/peroxynitrite axis an attractive therapeutic target in SAH.

A Phase I proof-of-concept and safety trial of sildenafil to treat cerebral vasospasm following subarachnoid hemorrhage

OBJECTIVE

Studies show that phosphodiesterase-V (PDE-V) inhibition reduces cerebral vasospasm (CVS) and improves outcomes after experimental subarachnoid hemorrhage (SAH). This study was performed to investigate the safety and effect of sildenafil (an FDA-approved PDE-V inhibitor) on angiographic CVS in SAH patients.

METHODS

A2-phase, prospective, nonrandomized, human trial was implemented. Subarachnoid hemorrhage patients underwent angiography on Day 7 to assess for CVS. Those with CVS were given 10 mg of intravenous sildenafil in the first phase of the study and 30 mg in the second phase. In both, angiography was repeated 30 minutes after infusion. Safety was assessed by monitoring neurological examination findings and vital signs and for the development of adverse reactions. For angiographic assessment, in a blinded fashion, pre- and post-sildenafil images were graded as "improvement" or "no improvement" in CVS. Unblinded measurements were made between pre- and post-sildenafil angiograms.

RESULTS

Twelve patients received sildenafil; 5 patients received 10 mg and 7 received 30 mg. There were no adverse reactions. There was no adverse effect on heart rate or intracranial pressure. Sildenafil resulted in a transient decline in mean arterial pressure, an average of 17% with a return to baseline in an average of 18 minutes. Eight patients (67%) were found to have a positive angiographic response to sildenafil, 3 (60%) in the low-dose group and 5 (71%) in the high-dose group. The largest degree of vessel dilation was an average of 0.8 mm (range 0-2.1 mm). This corresponded to an average percentage increase in vessel diameter of 62% (range 0%-200%).

CONCLUSIONS

The results from this Phase I safety and proof-of-concept trial assessing the use of intravenous sildenafil in patients with CVS show that sildenafil is safe and well tolerated in the setting of SAH. Furthermore, the angiographic data suggest that sildenafil has a positive impact on human CVS.

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.

Increased plasma endothelin-1 levels in patients with intracerebral hemorrhage

Endothelins (ETs) are discovered peptides that are widely distributed in neurons and nonneuronal cells of the human nervous system. Previous studies showed that ischemic stroke may be associated with increased plasma ET-1 levels. There are no studies to show plasma ET-1 levels in intracerebral hemorrhage. Plasma ET-1 levels in 30 patients with cerebral hemorrhage within 72 hours after the onset of focal neurological deficit were measured by a microplate enzyme immunoassay. Thirty sex- and age-matched healthy subjects were accepted as a control group. The clinical neurological status in the patients was evaluated according to the modified Matthew Scale. The mean plasma ET-1 level in hemorrhagic stroke patients was significantly higher than in control subjects (2.39±2.08 v 0.65±0.32 fmol/mL, (P < .05). There was a significant difference in ET levels between patients who died in the hospital and patients who survived (P < .05). The mean ET-1 concentration in patients with severe neurologic deficit was significantly higher than in patients with mild neurologic deficit (P < .05). There was a correlation between hematoma volumes and plasma ET-1 levels in the patients (r = 0.66, Pt < .001). The mean plasma ET-1 concentration was found to be significantly higher in patients with intraventricular hemorrhage than in patients without intraventricular hemorrhage (P < 0.05). There were no significant differences in ET-1 levels between supratentorial and infratentorial subgroups or among supratentorial subgroups (P > .05). It was concluded that plasma ET-1 levels were increased in the acute period of hemorrhagic stroke. Plasma ET-1 levels may be associated with hematoma volume, which is related to a poor prognosis of the cerebral hematoma. We suggest that increased plasma ET-1 levels may be a consequence of local cerebral hemorrhage or the acute stress condition of the disease.

Targeted over-expression of endothelin-1 in astrocytes leads to more severe brain damage and vasospasm after subarachnoid hemorrhage

Background

Endothelin-1 (ET-1) is a potent vasoconstrictor, and astrocytic ET-1 is reported to play a role in the pathogenesis of cerebral ischemic injury and cytotoxic edema. However, it is still unknown whether astrocytic ET-1 also contributes to vasogenic edema and vasospasm during subarachnoid hemorrhage (SAH). In the present study, transgenic mice with astrocytic endothelin-1 over-expression (GET-1 mice) were used to investigate the pathophysiological role of ET-1 in SAH pathogenesis.

Results

The GET-1 mice experienced a higher mortality rate and significantly more severe neurological deficits, blood–brain barrier breakdown and vasogenic edema compared to the non-transgenic (Ntg) mice following SAH. Oral administration of vasopressin V_1a receptor antagonist, SR 49059, significantly reduced the cerebral water content in the GET-1 mice. Furthermore, the GET-1 mice showed significantly more pronounced middle cerebral arterial (MCA) constriction after SAH. Immunocytochemical analysis showed that the calcium-activated potassium channels and the phospho-eNOS were significantly downregulated, whereas PKC-α expression was significantly upregulated in the MCA of the GET-1 mice when compared to Ntg mice after SAH. Administration of ABT-627 (ET_A receptor antagonist) significantly down-regulated PKC-α expression in the MCA of the GET-1 mice following SAH.

Conclusions

The present study suggests that astrocytic ET-1 involves in SAH-induced cerebral injury, edema and vasospasm, through ET_A receptor and PKC-mediated potassium channel dysfunction. Administration of ABT-627 (ET_A receptor antagonist) and SR 49059 (vasopressin V_1a receptor antagonist) resulted in amelioration of edema and vasospasm in mice following SAH. These data provide a strong rationale to investigate SR 49059 and ABT-627 as therapeutic drugs for the treatment of SAH patients.

The role of endothelin and endothelin antagonists in traumatic brain injury: a review of the literature

OBJECTIVES

To date, there is increasing evidence for the role of endothelins in the pathophysiological development of cerebral vasospasms associated with a variety of neurological diseases, e.g., stroke and subarachnoid hemorrhage. In contrast, only little is known regarding the role of endothelins in impaired cerebral hemodynamics after traumatic brain injury. Therapeutic work in blocking the endothelin system has led to the discovery of a number of antagonists potentially useful in restoring cerebral blood flow after traumatic brain injury, potentially reducing the detrimental effects of secondary brain injury. Therefore, the present work provides an overview of background topics such as structures and biosynthesis of endothelins, different types as well as potential mechanisms and sites of action. In addition, the role of age for the effects of endothelins on cerebral hemodynamics after traumatic brain injury is discussed.

RESULTS

Description of data supporting the role of the endothelins play in a host of neurological deficits.

CONCLUSIONS

Endothelin antagonists may be effective as novel treatments for various neuropathologies.

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.

Regulation of blood pressure and salt homeostasis by endothelin

Endothelin (ET) peptides and their receptors are intimately involved in the physiological control of systemic blood pressure and body Na homeostasis, exerting these effects through alterations in a host of circulating and local factors. Hormonal systems affected by ET include natriuretic peptides, aldosterone, catecholamines, and angiotensin. ET also directly regulates cardiac output, central and peripheral nervous system activity, renal Na and water excretion, systemic vascular resistance, and venous capacitance. ET regulation of these systems is often complex, sometimes involving opposing actions depending on which receptor isoform is activated, which cells are affected, and what other prevailing factors exist. A detailed understanding of this system is important; disordered regulation of the ET system is strongly associated with hypertension and dysregulated extracellular fluid volume homeostasis. In addition, ET receptor antagonists are being increasingly used for the treatment of a variety of diseases; while demonstrating benefit, these agents also have adverse effects on fluid retention that may substantially limit their clinical utility. This review provides a detailed analysis of how the ET system is involved in the control of blood pressure and Na homeostasis, focusing primarily on physiological regulation with some discussion of the role of the ET system in hypertension.

Endothelin-1(1-31) induces spreading depolarization in rats

BACKGROUND

The vasoconstrictor endothelin-1(1-21) (ET-1) seems to induce cerebral vasospasm after aneurismal subarachnoid hemorrhage (aSAH). Moreover, ET-1 causes spreading depolarization (SD) via vasoconstriction/ischemia. ET-1(1-31) is an alternate metabolic intermediate in the generation of ET-1. Our aim was to investigate whether endothelin-1(1-31) causes SD in a similar fashion to ET-1.

METHOD

Increasing concentrations of either ET-1, ET-1(1-31) or vehicle were brain topically applied in 29 rats. Each concentration was superfused for one hour while regional cerebral blood flow (rCBF) and direct current electrocorticogram (DC-ECoG) were recorded.

FINDINGS

In response to the highest concentration of 10(-6) M, all animals of both ET groups developed typical SD. At concentrations below 10(-6) M only ET-1 induced SD (n=14 of 19 rats). Thus, the efficacy of ET-1(1-31) to induce SD was significantly lower (P<0.001, two-tailed Fisher's Exact Test).

CONCLUSIONS

Our findings suggest that ET-1(1-31) less potently induces SD compared to ET-1 which implicates that it is a less potent vasoconstrictor. Speculatively, it could be interesting to shift the metabolic pathway towards the alternate intermediate ET-1(1-31) after aSAH as an alternative strategy to ETA receptor inhibition. This could decrease ET-induced vasoconstriction and SD generation while a potentially beneficial basal ETA receptor activation is maintained.

Metamorphosis of subarachnoid hemorrhage research: from delayed vasospasm to early brain injury

Delayed vasospasm that develops 3–7 days after aneurysmal subarachnoid hemorrhage (SAH) has traditionally been considered the most important determinant of delayed ischemic injury and poor outcome. Consequently, most therapies against delayed ischemic injury are directed towards reducing the incidence of vasospasm. The clinical trials based on this strategy, however, have so far claimed limited success; the incidence of vasospasm is reduced without reduction in delayed ischemic injury or improvement in the long-term outcome. This fact has shifted research interest to the early brain injury (first 72 h) evoked by SAH. In recent years, several pathological mechanisms that activate within minutes after the initial bleed and lead to early brain injury are identified. In addition, it is found that many of these mechanisms evolve with time and participate in the pathogenesis of delayed ischemic injury and poor outcome. Therefore, a therapy or therapies focused on these early mechanisms may not only prevent the early brain injury but may also help reduce the intensity of later developing neurological complications. This manuscript reviews the pathological mechanisms of early brain injury after SAH and summarizes the status of current therapies.

[Carotid dissection during angioplasty for vasospasm induced by subarachnoid haemorrhage. The use of multimodal cerebral monitoring]

We report the case of a 54-year-old woman presenting subarachnoid haemorrhage. She experienced multiple vasospasms and treatment included triple-H (hypervolaemia, hypertension, and haemodilution) and endovascular therapies. Right internal carotid dissection complicated angioplasty of the right middle cerebral artery. Combined brain tissue partial pressure of oxygen monitoring and transcranial echo-Doppler could have facilitated early diagnosis. Despite successful revascularization of right internal carotid by stenting, this complication caused acute stroke with refractory intracranial hypertension.

Cerebral vasospasm following subarachnoid hemorrhage: time for a new world of thought

OBJECTIVE

Delayed cerebral vasospasm has long been recognized as an important cause of poor outcome after an otherwise successful treatment of a ruptured intracranial aneurysm, but it remains a pathophysiological enigma despite intensive research for more than half a century.

METHOD

Summarized in this review are highlights of research from North America, Europe and Asia reflecting recent advances in the understanding of delayed ischemic deficit.

RESULT

It will focus on current accepted mechanisms and on new frontiers in vasospasm research.

CONCLUSION

A key issue is the recognition of events other than arterial narrowing such as early brain injury and cortical spreading depression and of their contribution to overall mortality and morbidity.

Clazosentan, an endothelin receptor antagonist, prevents early hypoperfusion during the acute phase of massive experimental subarachnoid hemorrhage: a laser Doppler flowmetry study in rats

Object

Acute cerebral hypoperfusion and early disturbances in cerebral autoregulation after subarachnoid hemorrhage (SAH) have been demonstrated repeatedly and have been shown to contribute significantly to acute and secondary brain injury. Acute vasoconstriction has been identified as a major contributing factor. Although increasing evidence implicates endothelin (ET)–1 in the development of cerebral vasospasm, its role in the acute phase after SAH has not yet been investigated. The purpose of this study was to further determine the role of ET in the first minutes to hours after massive experimental SAH induced by prophylactic treatment with the ET receptor antagonist clazosentan.

Methods

Subarachnoid hemorrhage was induced in 22 anesthetized rats by injection of 0.5-ml arterial, nonheparinized blood into the cisterna magna over the course of 60 seconds. In addition to monitoring intracranial pressure (ICP) and mean arterial blood pressure, laser Doppler flowmetry (LDF) probes were placed stereotactically over the cranial windows to allow online recording of cerebral blood flow (CBF) starting 30 minutes prior to SAH and continuing for 3 hours after SAH. The control group (Group A, 11 rats) received vehicle saline solution via a femoral catheter before SAH, and a second group (Group B, 11 rats) was treated prophylactically with clazosentan, an ETA receptor antagonist. Treatment was started 30 minutes prior to bolus injection (1 mg/kg body weight), immediately followed by a continuous infusion of 1 mg/kg body weight/hr until the end of the experiment.

Results

Induction of SAH in the rats caused an immediate increase in ICP, which led to an acute decrease in cerebral perfusion pressure (CPP). Perfusion, as measured with LDF, was found to have decreased relative to baseline by 30 ±20% in the control group and 20 ±9% in the clazosentan-treated group. Intracranial pressure and CPP recovered comparably in both groups thereafter within minutes. Control animals demonstrated prolonged hypoperfusion with a loss of autoregulation independent of CPP changes, finally approaching 80% of baseline values toward the end of the experiment. The authors observed that clazosentan did not influence peracute CPP-dependent hypoperfusion, but prevented continuous CBF reduction. Laser Doppler flowmetry perfusion readings remained depressed in control animals at 73 ±19% of baseline in comparison with 106 ±25% of baseline in clazosentan-treated animals (p = 0.001).

Conclusions

The first hours after a massive experimental SAH can be characterized by a CPP-independent compromise in cerebral perfusion. Prophylactic treatment with the ET receptor antagonist clazosentan prevented hypoperfusion. It is known that in the first days after SAH, a reduction in CBF correlates clinically to high-grade SAH. Although research currently focuses on delayed vasospasm, administration of vasoactive drugs in the acute phase of SAH may reverse perfusion deficits and improve patient recovery.

Sickle cell disease vasculopathy: a state of nitric oxide resistance

Sickle cell disease (SCD) is a hereditary hemoglobinopathy characterized by microvascular vaso-occlusion with erythrocytes containing polymerized sickle (S) hemoglobin, erythrocyte hemolysis, vasculopathy, and both acute and chronic multiorgan injury. It is associated with steady state increases in plasma cell-free hemoglobin and overproduction of reactive oxygen species (ROS). Hereditary and acquired hemolytic conditions release into plasma hemoglobin and other erythrocyte components that scavenge endothelium-derived NO and metabolize its precursor arginine, impairing NO homeostasis. Overproduction of ROS, such as superoxide, by enzymatic (xanthine oxidase, NADPH oxidase, uncoupled eNOS) and nonenzymatic pathways (Fenton chemistry), promotes intravascular oxidant stress that can likewise disrupt NO homeostasis. The synergistic bioinactivation of NO by dioxygenation and oxidation reactions with cell-free plasma hemoglobin and ROS, respectively, is discussed as a mechanism for NO resistance in SCD vasculopathy. Human physiological and transgenic animal studies provide experimental evidence of cardiovascular and pulmonary resistance to NO donors and reduced NO bioavailability that is associated with vasoconstriction, decreased blood flow, platelet activation, increased endothelin-1 expression, and end-organ injury. Emerging epidemiological data now suggest that chronic intravascular hemolysis is associated with certain clinical complications: pulmonary hypertension, cutaneous leg ulcerations, priapism, and possibly stroke. New therapeutic strategies to limit intravascular hemolysis and ROS generation and increase NO bioavailability are discussed.

Inhibitory effect of deuterium oxide on cerebral vasospasm after experimental subarachnoid hemorrhage in a rabbit model

OBJECT

We wished to determine the inhibitory effect of deuterium oxide (D(2)O) on cerebral vasospasm (CVS) after subarachnoid hemorrhage (SAH).

METHODS AND RESULTS

An established rabbit single-hemorrhage was used. Thirty-five rabbits were randomly divided into four groups: non-treatment, sham control, lower-D(2)O, and higher-D(2)O treatment groups. Angiography was performed before (day 0) and after (day 2) SAH and the CVS ratio was calculated by comparing the diameter of the basilar artery (BA) on day 2 with that on day 0. After death, blood clot volume was assessed and the BA was dissected from the brain for histological examination. The CVS ratio in D(2)O-treatment groups was significantly higher in comparison with that in non-treatment and sham control groups (p < 0.0001). Furthermore, the volume of blood clot around the BA was reduced significantly in D(2)O-treatment groups, compared with those in both the non-treatment and the sham control groups (p < 0.05). Histological examination showed that the BA represented less folding of the internal elastic lumina in D(2)O-treatment groups, while a corrugation of the intima with the thickened vessel wall was seen in both the non-treatment and sham control groups.

CONCLUSION

Therapeutic administration of D(2)O into the cisterna magna exhibited an inhibitory effect on CVS after SAH in rabbits.

Clazosentan (AXV-034343), a selective endothelin A receptor antagonist, in the prevention of cerebral vasospasm following severe aneurysmal subarachnoid hemorrhage: results of a randomized, double-blind, placebo-controlled, multicenter Phase IIa study

OBJECTIVE

The goal of this study was to investigate the safety and tolerability of the novel endothelin A (ETA) receptor antagonist clazosentan in patients with subarachnoid hemorrhage (SAH) and its potential to reduce the incidence and severity of cerebral vasospasm following surgical clipping of the aneurysm.

METHODS

This Phase IIa multicenter study had two parts: a double-blind, randomized Part A (some patients given clazosentan [0.2 mg/kg/hr] and others given placebo), in which statistical inference was performed, and an open-label Part B (patients with established vasospasm given clazosentan [0.4 mg/kg/hr for 12 hours followed by 0.2 mg/kg/hr]) for exploratory purposes only. Primary end points were the incidence and severity of angiographic vasospasm on Day 8 after SAH and the safety and tolerability of the drug. Thirty-four patients (Hunt and Hess Grades III and IV and Fisher Grade > or = 3) were recruited and 32 (15 in the clazosentan group and 17 in the placebo group) were retained in the intent-to-treat population; 19 patients entered Part B. In Part A, treatment with clazosentan resulted in a reduced incidence of angiographically evident cerebral vasospasm (40% compared with 88% of patients, p = 0.008). In addition, the severity of vasospasm was reduced in the clazosentan group (p = 0.012). In Part B of the study, in 50% of assessable patients who were initially treated with placebo reversal of vasospasm was observed following the initiation of clazosentan therapy. The incidence of new infarctions was 15% in the clazosentan group and 44% in the placebo group (p = 0.130). There was no adverse event pattern indicating a specific organ toxicity of clazosentan.

CONCLUSIONS

This study indicates that clazosentan reduces the frequency and severity of cerebral vasospasm following severe aneurysmal SAH with the incidence and severity of adverse events comparable to that of placebo.

Outcome of carpal tunnel release surgery in patients with diabetes

The surgical outcomes in 149 patients with diabetes and carpal tunnel syndrome who underwent transverse carpal ligament release surgery are reported. Associated factors such as insulin dependence, length of time with diabetes, electrodiagnostic studies, severity of neurological deficit, presence of polyneuropathy, and cervical disc disease were considered. Analysis of preoperative and postoperative symptoms, clinical findings, diagnostic studies, and patient self-assessment indicated that the majority of patients with diabetes experienced a favorable surgical outcome, regardless of any associated factors. Eighty-four percent of the patients reported good to excellent postoperative results in their hands. Further analysis of the subpopulation of insulin-dependent diabetics showed that 81% experienced good to excellent postoperative results. These results compare favorably with those of the control group: 200 nondiabetic patients, of whom 90% rated their results from carpal tunnel release surgery as good to excellent. There were no major complications in any group.

Molecular biological considerations in cerebral vasospasm following aneurysmal subarachnoid hemorrhage

Chronic delayed cerebral vasospasm (CDCV) remains a serious and often fatal complication of aneurysmal subarachnoid hemorrhage (SAH). The current understanding of its fundamental mechanisms and molecular biological characterization is rudimentary. Two important vasoactive substances have been implicated in CDCV: endothelin-1 (ET-1) and nitric oxide (NO). A 21--amino acid vasoconstrictor peptide, ET-1 has generated interest as a possible important contributor to cerebral vasospasm on the basis of both clinical and experimental evidence suggesting abnormally enhanced production. Nitric oxide is a cell membrane--permeable free radical gas that accounts for the vasodilatory effect of endothelium-derived relaxation factor and is a physiological antagonist of ET-1. As with ET-1, abnormalities of NO production have been implicated in several pathological conditions including cerebral vasospasm. This brief report reviews some of the physiological and regulatory features of these two molecules and explores the possibility of their relationship to cerebral vasospasm.

Endothelin-1 modulates hemoglobin-mediated signaling in cerebrovascular smooth muscle via RhoA/Rho kinase and protein kinase C

Endothelin-1 (ET-1) and oxyhemoglobin (OxyHb) have been implicated in the pathogenesis of cerebral vasospasm after subarachnoid hemorrhage. However, the contribution of ET-1 to this condition has not been definitely established. In this study, we investigated whether threshold concentration of ET-1 enhances cerebrovascular smooth muscle (CVSM) contraction to OxyHb by activating the RhoA/Rho kinase and protein kinase C (PKC) pathways. CVSM contraction was measured in endothelium-denuded rabbit basilar arteries. Cytosolic and particulate fractions of CVSM cells were examined for RhoA and PKC reactivity with specific antibodies using immunoblotting procedures. ET-1 (0.1 nM) alone did not produce any significant contraction, but it markedly potentiated the magnitude (223% of control) and rate (149% of control) of contraction in response to OxyHb, which was attenuated by the inhibitors of Rho kinase Y-27632 and HA-1077. ET-1-mediated potentiation of the contraction was also inhibited by inhibitors of PKC, Ro-32-0432, and GF-109203X. BQ-123 prevented potentiation of vasoconstriction mediated by ET-1, indicating that the action of ET-1 was mediated by the endothelin type A receptor. Pretreatment with ET-1 significantly enhanced OxyHb-mediated RhoA translocation in CVSM cells and intact basilar arteries. ET-1 also caused potentiation of PKC-ϵ expression in membranes of CVSM cells exposed to OxyHb for 10 and 60 min but did not markedly change the distribution of PKC-α. Thus, in CVSM, threshold concentration of ET-1 potentiates contraction induced by OxyHb via RhoA/Rho kinase- and PKC-ϵ-dependent mechanisms. This process may contribute to the pathological contraction of cerebral arteries observed after subarachnoid hemorrhage.

Type V phosphodiesterase expression in cerebral arteries with vasospasm after subarachnoid hemorrhage in a canine model

Cyclic GMP (cGMP) mediates smooth muscle relaxation in the central nervous system. In subarachnoid hemorrhage (SAH), decreases in intrinsic nitric oxide (NO) cause cerebral vasospasms due to the regulation of cGMP formation by NO-mediated pathways. As phosphodiesterase type V (PDE V) selectively hydrolyzes cGMP, we hypothesized that PDE V may function in the initiation of vasospasm. This study sought to identify the altered PDE V expression and activity in the vasospastic artery in a canine SAH model. We also used this system to examine possible therapeutic strategies to prevent vasospasm. Using a canine model of SAH, we induced cerebral vasospasm in the basilar artery (BA). Following angiographic confirmation of vasospasm on day 7, PDE V expression was immunohistochemically identified in smooth muscle cells of the vasospastic BA but not in cells of a control artery. The isolation of PDE enzymes using a sepharose column confirmed increased PDE V activity in the vasospastic artery only through both inhibition studies, using the highly selective PDE V inhibitor, sildenafil citrate, and Western blotting. Preliminary in vivo experiment using an oral PDE V inhibitor at 0.83 mg kg(-1) demonstrated partial relaxation of the spastic BA. PDE V activity was increased from control levels within the BA seven days after SAH. PDE V expression was most prominent in smooth muscle cells following SAH. These results suggest that clinical administration of a PDE V inhibitor may be a useful therapeutic tool in the prevention of vasospasm following SAH.

Protein kinase C and cerebral vasospasm

Twenty-five years after the discovery of protein kinase C (PKC), the physiologic function of PKC, and especially its role in pathologic conditions, remains a subject of great interest with 30,000 studies published on these aspects. In the cerebral circulation, PKC plays a role in the regulation of myogenic tone by sensitization of myofilaments to calcium. Protein kinase C phosphorylates various ion channels including augmenting voltage-dependent Ca2+ channels and inhibiting K+ channels, which both lead to vessel contraction. These actions of PKC amplify vascular reactivity to different agonists and may be critical in the regulation of cerebral artery tone during vasospasm. Evidence accumulated during at least the last decade suggest that activation of PKC in cerebral vasospasm results in a delayed but prolonged contraction of major arteries after subarachnoid hemorrhage. Most of the experimental results in vitro or in animal models support the view that PKC is involved in cerebral vasospasm. Implication of PKC in cerebral vasospasm helps explain increased arterial narrowing at the signal transduction level and alters current perceptions that the pathophysiology is caused by a combination of multiple receptor activation, hemoglobin toxicity, and damaged neurogenic control. Activation of protein kinase C also interacts with other signaling pathways such as myosin light chain kinase, nitric oxide, intracellular Ca2+, protein tyrosine kinase, and its substrates such as mitogen-activated protein kinase. Even though identifying PKC revolutionized the understanding of cerebral vasospasm, clinical advances are hampered by the lack of clinical trials using selective PKC inhibitors.

The polycationic aminoglycosides modulate the vasoconstrictive effects of endothelin: relevance to cerebral vasospasm

1. The vasoactive peptide endothelin (ET) has been implicated in the pathogenesis of cerebral vasospasm following subarachnoid haemorrhage. In these studies we investigated the involvement of protein kinase C (PKC) in sustained vasoconstriction induced by ET-1 in canine cerebral arteries. We also examined the ability of the aminoglycoside antibiotics to reverse the effects mediated by ET-1 in canine cerebrovascular smooth muscle cells (CVSMC). 2. The ET(A) receptor antagonist, BQ-123, showed a competitive inhibition of the ET-1 responses. 3. The vasoconstrictor action of both ET-1 (0.5 nM) and phorbol myristate acetate (PMA) (160 nM) was reversed by a selective PKC inhibitor, Ro-32-0432. 4. In cerebral arteries precontracted with ET-1 the aminoglycosides caused a concentration-dependent relaxation. The EC(50s) for the relaxation were as follows: 0.54+/-0.05, 0.63+/-0.01, 1.88+/-0.46 and 2.3+/-0.92 mM for gentamicin, neomycin, streptomycin and kanamycin, respectively. 5. Gentamicin caused a concentration-dependent decrease of the PMA-induced responses in calcium free medium. 6. PKC activity was elevated in CVSMC exposed to ET-1 (170%) and PMA (167%) for a period of time (60 min) corresponding to maximum tonic contraction induced by these agents in arterial rings. 7. The administration of the aminoglycosides to CVSMC, in concentrations corresponding to the EC(50s) from contractility studies, reduced the effects of both ET-1 and PMA on PKC activity to the levels not different from controls. 8. These results show that the aminoglycosides are able to inhibit sustained vasoconstriction induced by ET-1, an effect which is due, at least in part, to the inhibition of PKC.

Inhibition of endothelin-converting enzyme activity in the rabbit basilar artery

OBJECTIVE

Endothelin (ET)-1 may be involved in the regulation of cerebrovascular resistance under pathological conditions, most notably during the development of vasospasm after subarachnoid hemorrhage. Blocking ET-converting enzyme activity may be a promising approach to the prevention of cerebral vasospasm after subarachnoid hemorrhage.

METHODS

In this study, the effects of several putative ET-converting enzyme inhibitors were investigated after intracisternal application in rabbits, to inhibit basilar artery contractions induced by big ET-1 (2 x 10(-6) mol/L).

RESULTS

In the group pretreated with [D-Val22]big ET-1[16-38] (2 x 10(-5) mol/L) (n = 8), the angiographically measured diameter of the basilar artery changed from 0.63 +/- 0.12 mm to 0.66 +/- 0.12 mm. In the control group (n = 8), the diameter of the basilar artery decreased from 0.71 +/- 0.13 mm to 0.57 +/- 0.15 mm. These results corresponded to an increase in vessel diameter of 5 +/- 10% in the treatment group and a decrease in vessel diameter of 20 +/- 16% in the control group (P = 0.014). In the group pretreated with captopril (2 x 10(-4) mol/L) (n = 8), the angiographically measured diameter of the basilar artery changed from 0.64 +/- 0.11 mm to 0.71 +/- 0.10 mm. These results corresponded to an increase in vessel diameter of 14 +/- 19% in the treatment group, compared with a decrease in vessel diameter of 20 +/- 16% in the control group (P = 0.014).

CONCLUSION

These results demonstrate that [D-Val22]big ET-1[16-38] and captopril act as highly potent ET-converting enzyme inhibitors, affecting big ET-1-induced contraction of the rabbit basilar artery.

Hemoglobin increases endothelin-1 in endothelial cells by decreasing nitric oxide

We determined whether ferrous hemoglobin increases endothelin-1 (ET-1) secretion from bovine cerebral artery endothelial cells and the mechanisms involved. Exposure of endothelial cells to hemoglobin caused dose-dependent increases in pre-proET-1 mRNA and peptide. The increase in ET-1 peptide was inhibited by cycloheximide or actinomycin D whereas only cycloheximide decreased basal ET-1 release. N(G)-nitro-l-arginine significantly increased ET-1 concentration and reduced hemoglobin stimulation of ET-1 release. 8-Bromo-cGMP did not alter basal ET-1 concentration but suppressed hemoglobin-induced ET-1 production. Methemoglobin and S-nitrosylated methemoglobin were less potent inducers of ET-1 release. In summary, hemoglobin increases ET-1 in cerebral endothelial cells by mechanisms that involve transcription and translation. Nitric oxide production inhibits ET-1 production. Ferrous hemoglobin increases ET-1 by binding nitric oxide and abolishing this inhibitory pathway although other mechanisms are involved since N(G)-nitro-l-arginine reduces hemoglobin-induced ET-1 release.

Hypoxic modulation of striatal lesions induced by administration of endothelin-1

Levels of endothelin-1 (ET-1), a potent endogenous vasoconstrictor, are elevated in plasma and cerebrospinal fluid (CSF) following cerebral ischemia and reperfusion injury. The present study sought insight into the potential differential vasoactive effects on the cerebral vasculature and resultant neural damage of ET-1 during normoxic vs. ischemic conditions and upon reperfusion. Under normoxic conditions, intrastriatal stereotaxic injection of exogenous ET-1 (40 pmol) induced a significant (P<0.05) reduction (</=29+/-12%) in the regional (striatal) cerebral blood flow measured by Laser Doppler flowmetry (CBF(LDF)) for up to 40 min in halothane-anesthetized male Long-Evans rats. Intrastriatal injection of ET-1 10 min after the onset of hypoxia (12% O(2), balance N(2)) tended to blunt, but not significantly, the striatal CBF(LDF) responses to the 35 min period of hypoxia. ET-1 given during reoxygenation significantly (P<0.05) reduced striatal CBF(LDF), which was similar to the effect of ET-1 during normoxia. ET-1-induced infarction when administered prior to hypoxia, but not during or post-hypoxia, was significantly (P<0.05) exacerbated compared to infarction of ET-1 without hypoxia. These results suggest that exogenous ET-1 administered into the brain parenchyma can induce an infarction associated with modulation of CBF(LDF) during the normoxic or reoxygenation period, but not during the hypoxic period and that the increased release of ET-1 in any pathological phase of cerebral ischemia contributes to irreversible neural damage with associated hemodynamic disturbances.

Hypocapnic constriction in rabbit basilar artery in vitro: triggering by N(G)-monomethyl-L-arginine monoacetate and dependence on endothelin-1 and alkalosis

This study tested whether hypocapnic constriction of the rabbit basilar artery in vitro can be triggered by a nitric oxide (NO) synthase inhibitor, and whether the resulting constriction is (1) due to the alkaline pH associated with hypocapnia, and (2) endothelin-1 mediated. Hypocapnic (25 mM NaHCO(3); pH 7.76; pCO(2) 14.2) or isocapnic alkaline solution (50 mM NaHCO(3); pH 7.73; pCO(2) 35.0) rarely altered basal tension. N(G)-monomethyl-L-arginine monoacetate (L-NMMA; 0.1 mM) challenge in hypocapnic or isocapnic alkaline solution resulted in near maximal tension that was maintained for 2-2.5 h even following L-NMMA washout. L-NMMA challenge in normal solution (25 mM NaHCO(3); pH 7. 42; pCO(2) 36.9) also induced near maximal tension, although the tension was maintained for only 25 min (mean). Ac-D-Bhg-L-Leu-Asp-L-Ile-L-Ile-L-Trp (PD145065), homopiperidinyl-CO-Leu-D-Trp(CHO)-D-Trp (BQ610), and N-cis-2, 6-dimethyl-piperidinocarbonyl L-gamma-MeLeu-D-Trp (COOCH(3))-Nle (BQ788; 1-3 microM), endothelin ET(A)/ET(B), endothelin ET(A), and endothelin ET(B) receptor antagonists, respectively, completely relaxed the tension that resulted from L-NMMA challenge in hypocapnic or isocapnic alkaline solution. These results demonstrate that constriction due to hypocapnia in vitro can be triggered by an NO synthase inhibitor and is endothelin-1 mediated. Additionally, alkaline pH in the absence of decreased pCO(2) is sufficient to elicit the constriction.

Evaluation of big endothelin-1 concentrations in serum and ventricular cerebrospinal fluid after early surgical compared with nonsurgical management of ruptured intracranial aneurysms

OBJECT

Whereas the removal of subarachnoid blood is possible during early-stage aneurysm surgery, this cannot be achieved in aneurysms treated by endovascular means. The levels of potential spasmogens in the cerebrospinal fluid (CSF) in patients receiving endovascular treatment might therefore be higher, with the potential for more severe post-subarachnoid hemorrhage (SAH) vasospasm.

METHODS

Serum and CSF concentrations of big endothelin (ET)-1 were serially measured in patients with SAH receiving one of the following treatments: 1) early (within 72 hours of SAH) aneurysm surgical treatment (15 patients), 2) early endovascular treatment (17 patients), or 3) no intervention in the acute phase (12 patients). In patients suffering delayed infarctions higher levels of big ET-1 CSF were demonstrated than in those without infarctions (p = 0.01). In patients in whom surgery was performed in the acute phase lower big ET-1 CSF concentrations were demonstrated than in those who received embolization treatment or no treatment (p = 0.02). Subgroup analysis demonstrated that in patients receiving early endovascular treatment, higher big ET-1 CSF concentrations were revealed than in those undergoing early aneurysm surgery; this was true for patients with (microsurgerytreated, 1.84 +/- 0.83 pg/ml; and embolization-treated 2.19 +/- 0.54 pg/ml) and without (microsurgery-treated 1.76 +/- 0.61 pg/ml; and embolization-treated 2.01 +/- 0.48 pg/ml) delayed infarctions.

CONCLUSIONS

Among patients with SAH who received treatment during the acute phase, those undergoing early aneurysm surgery were shown to have lower big ET-1 CSF levels than those receiving embolization and no treatment (that is, the nonsurgical treatment groups). The clinical significance of this finding remains to be established in future clinical trials, because in the present study the trend toward lower levels of big ET-1 CSF in the microsurgically treated group was not paralleled by a lower delayed stroke rate or an improvement in neurological outcome.

Plasma endothelin concentrations after aneurysmal subarachnoid hemorrhage

OBJECT

The pathogenesis of cerebral vasospasm and delayed ischemia after subarachnoid hemorrhage (SAH) seems to be complex. An important mediator of chronic vasospasm may be endothelin (ET), with its powerful and long-lasting vasoconstricting activity. In this study the author investigated the correlation between serial plasma concentrations of ET and ischemic symptoms, angiographically demonstrated evidence of vasospasm, and computerized tomography (CT) findings after aneurysmal SAH.

METHODS

Endothelin-1 immunoreactivity in plasma was studied in 70 patients with aneurysmal SAH and in 25 healthy volunteers by using a double-antibody sandwich-enzyme immunoassay (immunometric) technique. On the whole, mean plasma ET concentrations in patients with SAH (mean +/- standard error of mean, 2.1 +/- 0.1 pg/ml) did not differ from those of healthy volunteers (1.9 +/- 0.2 pg/ml). Endothelin concentrations were significantly higher (p < 0.05) in patients who experienced delayed cerebral ischemia with fixed neurological deficits compared with those in other patients (post-SAH Days 0-5, 3.1 +/- 0.8 pg/ml compared with 2.1 +/- 0.2 pg/ml; post-SAH Days 6-14, 2.5 +/- 0.4 pg/ml compared with 1.9 +/- 0.2 pg/ml). Patients with angiographic evidence of severe vasospasm also had significantly (p < 0.05) elevated ET concentrations (post-SAH Days 0-5, 3.2 +/- 0.8 pg/ml; post-SAH Days 6-14, 2.7 +/- 0.5 pg/ml) as did those with a cerebral infarction larger than a lacuna on the follow-up CT scan (post-SAH Days 0-5, 3.1 +/- 0.8 pg/ml; post-SAH Days 6-14, 2.5 +/- 0.4 pg/ml) compared with other patients. Patients in whom angiography revealed diffuse moderate-to-severe vasospasm had significantly (p < 0.05) higher ET levels than other patients within 24 hours before or after angiography (2.6 +/- 0.3 compared with 1.9 +/- 0.2 pg/ml). In addition, patients with a history of hypertension or cigarette smoking experienced cerebral infarctions significantly more often than other patients, although angiography did not demonstrate severe or diffuse vasospasm more often in these patients than in others.

CONCLUSIONS

Endothelin concentrations seem to correlate with delayed cerebral ischemia and vasospasm after SAH. The highest levels of ET are predictive of the symptoms of cerebral ischemia and vasospasm, and ET may also worsen ischemia in patients with a history of hypertension. Thus, ET may be an important causal or contributing factor to vasospasm, but its significance in the pathogenesis of vasospasm remains unknown.

Prevention of cerebral vasospasm by a novel endothelin receptor antagonist, TA-0201

This study was designed to examine the preventive effect of a novel endothelin (ET)-receptor antagonist TA-0201 on the cerebral vasospasm in a canine double-hemorrhage model. TA-0201 (10(-9)-10(-7) M) inhibited ET-1-induced vasoconstriction in the isolated canine basilar artery without endothelium in a concentration-dependent manner. Its pA2 value was 9.2 (ET(A) antagonism). In a canine double-hemorrhage model, intravenous treatment with TA-0201 (3 mg/kg, twice a day for 7 days) ameliorated the basilar artery narrowing significantly on day 7 compared with that in nontreated dogs. The reductions of the basilar artery diameter were 26.1+/-3.9% and 40.5+/-4.1% with and without TA-0201 treatment, respectively (p<0.05). Histologic study on day 7 indicated that treatment with TA-0201 inhibited vessel-wall damage such as disintegration of endothelium architecture and degeneration of medial smooth-muscle cells. We conclude that intravenous treatment with TA-0201 prevents the development of cerebral vasospasm and accompanying pathologic changes of the vessel wall, probably through blockade of ET(A) receptors.

Oxyhemoglobin-induced apoptosis in cultured endothelial cells

OBJECT

Oxyhemoglobin (OxyHb) is one of the most important spasmogens for cerebral vasospasm that follows aneurysmal subarachnoid hemorrhage. The cytotoxic effect of OxyHb has been documented in endothelial and smooth-muscle cells; however, the pattern of cell death--necrosis or apoptosis--as the final stage of cell damage has not been demonstrated. This study was undertaken to determine if OxyHb induces apoptotic changes in cultured bovine aortic endothelial cells.

METHODS

Confluent bovine aortic endothelial cells were treated with OxyHb in a concentration- and time-dependent manner. Cell density was assayed by counting the number of cells that attached to culture dishes after exposure to OxyHb. To identify apoptotic changes, the investigators used three specific methods: DNA fragmentation (electrophoreses), the apoptotic body (transmission electron microscopy), and cleavage of poly (adenosine diphosphate ribose) polymerase (PARP [Western blotting]).

CONCLUSIONS

Oxyhemoglobin decreased cell density in a concentration- and time-dependent manner. Analysis of DNA showed a pattern of internucleosomal cleavage characteristic of apoptosis (DNA ladder). Transmission electron microscopy demonstrated condensation of nuclei and apoptotic bodies in OxyHb-treated endothelial cells. Western blotting with the PARP antibody revealed that the 116-kD PARP was cleaved to the 85-kD apoptosis-related fragment. These results for the first time demonstrated that the OxyHb induces apoptosis in cultured endothelial cells.

Safety of intrathecal sodium nitroprusside for the treatment and prevention of refractory cerebral vasospasm and ischemia in humans

BACKGROUND AND PURPOSE

The delayed type of cerebral vasoconstriction known as cerebral vasospasm (DCV) remains an important cause of permanent neurological injury and death following aneurysmal subarachnoid hemorrhage despite best current medical therapy. The mechanism of DCV remains unknown. A new treatment for refractory DCV using intrathecally delivered sodium nitroprusside and results in 21 patients is reported.

METHODS

Candidates for treatment were patients with secured cerebral aneurysms presenting with clinical or radiographic SAH of grade 3 or higher. Patients with and without established DCV were treated. In 57% (12/21 patients) the diagnosis of severe DCV refractory to conventional treatment (HHH therapy and nimodipine) was established before treatment. Ten patients received ITSNP prophylactically. All patients with established DCV were in grave neurological condition before treatment. Procedures for vasospasm reversal were performed under simultaneous angiographic control with extensive hemodynamic and neurophysiologic monitoring. ITSNP was delivered by intraventricular or subdural catheter or by direct intraoperative suffusion. End points of intervention for established DCV were (1) durable angiographic reversal of vasoconstriction, (2) failure to effect reversal within 30 minutes, and (3) adverse effect. End points for DCV prevention were (1) post-SAH day 10 without evidence of vasoconstriction and (2) adverse effect. Cerebral angioplasty was used concomitantly in 9 treatments. The total number of treatments recorded was 171.

RESULTS

The overall neurological outcome was good or excellent in 76% of patients (16/21) overall and in 88.9% of patients (16/18) having at least a 1-month follow-up. Of the 5 patients with less-than-good outcome, 4 had presented initially with severe neurological injury (clinical SAH grade 4). Angiography demonstrated reversal or amelioration of vasoconstriction in 83% (5/6 cases) of established DCV treated by ITSNP alone. Among patients treated prophylactically, none developed clinical DCV.

CONCLUSIONS

These results suggest that ITSNP is a safe and potentially effective treatment for established DCV and cerebral ischemia refractory to conventional treatment. The preliminary results of prophylactic treatment are also favorable with regard to safety.

Antisense preproendothelin-oligoDNA therapy for vasospasm in a canine model of subarachnoid hemorrhage

OBJECT

The purpose of this study is twofold: 1) to test antisense genetic techniques used in the prevention of cerebral vasospasm in a canine model of subarachnoid hemorrhage (SAH), targeting the endothelin-1 (ET-1) gene; and 2) to determine if fibrinolysis of subarachnoid clot with recombinant tissue plasminogen activator (rtPA) could enhance the effect of antisense treatment.

METHODS

A total of 39 dogs were studied in this experiment. Placebo (six animals), rtPA (six animals), antisense preproET-1 oligodeoxynucleotide (ASOD; five animals), or rtPA plus ASOD (combined treatment; six animals) was injected into the cisterna magna 30 minutes after a second SAH was induced on the 2nd day of the experiment. The animals were observed until Day 7, when they underwent follow-up angiography and then were killed; their basilar arteries were removed for analysis. Control animals included in this study (two animals in each group) received placebo, rtPA, ASOD, or rtPA plus ASOD without induction of SAH, or rtPA with mismatched (nonsense) preproET-1 oligodeoxynucleotide following SAH. Six additional dogs were analyzed earlier following SAH. Dogs that received placebo developed severe vasospasm (51+/-8% of baseline caliber). Administration of ASOD alone resulted in a mild reduction in vasospasm (64+/-13% of baseline caliber) and rtPA alone resulted in a moderate reduction in vasospasm (81+/-5% of baseline caliber); however, the combined therapy of rtPA plus ASOD almost completely prevented vasospasm (95+/-6%, of baseline caliber), which was significantly different from all other groups (p < 0.05). Morphological analysis of the basilar arteries yielded results similar to angiography with respect to vasospasm severity. The ASOD treatment combined with rtPA resulted in reduced ET-1 expression, as demonstrated by immunohistochemical staining of the arteries, and reduced preproET-1 levels on Day 4, as measured by reverse transcription-polymerase chain reaction. Nonsense DNA sequences had no effect on the vessels.

CONCLUSIONS

Antisense preproET-1 oligodeoxynucleotide treatment, when combined with clot lysis caused by rtPA, reduced vasospasm in the canine model of SAH, and this effect appeared to be related to reduced ET-1 synthesis. The results of this experiment support a causative role for ET-1 early in the course of vasospasm development in dogs. The apparent additive therapeutic effects of antisense and fibrinolytic treatments could be due to clot lysis, which allows better delivery of oligodeoxynucleotides to arteries within the subarachnoid space.

Blockade and reversal of endothelin-induced constriction in pial arteries from human brain

BACKGROUND AND PURPOSE

Substantial evidence now implicates endothelin (ET) in the pathophysiology of cerebrovascular disorders such as the delayed vasospasm associated with subarachnoid hemorrhage and ischemic stroke. We investigated the ET receptor subtypes mediating vasoconstriction in human pial arteries.

METHODS

ET receptors on human pial and intracerebral arteries were visualized with the use of autoradiography, and the subtypes mediating vasoconstriction were identified by means of wire myography.

RESULTS

ET-1 was more potent than ET-3 as a vasoconstrictor, indicating an ETA-mediated effect. Similarly, the selective ETB agonist sarafotoxin S6c had no effect on contractile action at concentrations up to 30 nmol/L. The nonpeptide ETA receptor antagonist PD156707 (3 to 30 nmol/L) caused a parallel rightward shift of the ET-1-induced response, yielding a pA2 of 9.2. Consistent with these results, PD156707 (30 nmol/L) fully reversed an established constriction in pial arteries induced by 1 nmol/L ET-1, while the selective ETB receptor antagonist BQ788 (1 micromol/L) had little effect. The calcium channel blocker nimodipine (0.3 to 3 micromol/L) significantly attenuated the maximum response to ET-1 in a concentration-dependent manner without changing potency. In agreement with the functional data, specific binding of [125I]PD151242 to ETA receptors was localized to the smooth muscle layer of pial and intracerebral blood vessels. In contrast, little or no [125I]BQ3020 binding to ETB receptors was detected.

CONCLUSIONS

These data indicate an important role for ETA receptors in ET-1-induced constriction of human pial arteries and suggest that ETA receptor antagonists may provide additional dilatory benefit in cerebrovascular disorders associated with raised ET levels.

Effect of ebselen on contractile responses in perfused rabbit basilar artery

OBJECTIVE

To evaluate the possible role of the antioxidant ebselen in the treatment of cerebral vasospasm, we examined the effects of ebselen on the vasoactive mechanisms induced by endothelin (ET)-1, oxyhemoglobin, and oxygen-derived radicals.

METHODS

Isolated rabbit basilar arteries with intact endothelium were fixed in a perfusion system and perfused intraluminally. Contraction of the artery was detected as an increase in perfusion pressure.

RESULTS

Ebselen, in a certain concentration range (3 x 10(-6) and 10(-5) mol/L), significantly reduced the contractile response to ET-1 (10(-10) to 10(-8) mol/L) but not the contraction induced by 40 mmol/L potassium. It reduced the contraction induced by 10(-4) mol/L 1,2-dioctanoyl-sn-glycerol, a protein kinase C activator. Addition of 10(-5) mol/L dithiothreitol, a sulfhydryl-reducing agent, partially reversed the inhibitory effects of ebselen on ET-1- and 1,2-dioctanoyl-sn-glycerol-induced contractions. Ebselen (10(-5) mol/L) as well as a combination of catalase (1000 units/mL) and superoxide dismutase (150 units/mL) inhibited the potentiating effects of oxyhemoglobin (10(-5) mol/L) on ET-1-induced contraction. Both ebselen and catalase inhibited the contractile response to hydroxyl radical generated by ferrous ion (10(-3) mol/L) plus hydrogen peroxide (10(-2) mol/L). Ebselen reduced the response to potassium when a high dose (3 x 10(-5) mol/L) was applied and failed to preserve contractility of the preparation after exposure to hydroxyl radical.

CONCLUSION

Ebselen suppressed ET-1-induced contraction and synergetic interaction between oxyhemoglobin and ET-1, where free radical formation was involved. These effects may result from modification of the intracellular regulatory system including protein kinase C, as well as from protection against free radicals.