Endothelin-receptor antagonists for aneurysmal subarachnoid hemorrhage: an updated meta-analysis of randomized controlled trials

Interactions between integrin α9β1 and VCAM-1 promote neutrophil hyperactivation and mediate poststroke DVT

ABSTRACT

Venous thromboembolic events are significant contributors to morbidity and mortality in patients with stroke. Neutrophils are among the first cells in the blood to respond to stroke and are known to promote deep vein thrombosis (DVT). Integrin α9 is a transmembrane glycoprotein highly expressed on neutrophils and stabilizes neutrophil adhesion to activated endothelium via vascular cell adhesion molecule 1 (VCAM-1). Nevertheless, the causative role of neutrophil integrin α9 in poststroke DVT remains unknown. Here, we found higher neutrophil integrin α9 and plasma VCAM-1 levels in humans and mice with stroke. Using mice with embolic stroke, we observed enhanced DVT severity in a novel model of poststroke DVT. Neutrophil-specific integrin α9-deficient mice (α9fl/flMrp8Cre+/-) exhibited a significant reduction in poststroke DVT severity along with decreased neutrophils and citrullinated histone H3 in thrombi. Unbiased transcriptomics indicated that α9/VCAM-1 interactions induced pathways related to neutrophil inflammation, exocytosis, NF-κB signaling, and chemotaxis. Mechanistic studies revealed that integrin α9/VCAM-1 interactions mediate neutrophil adhesion at the venous shear rate, promote neutrophil hyperactivation, increase phosphorylation of extracellular signal-regulated kinase, and induce endothelial cell apoptosis. Using pharmacogenomic profiling, virtual screening, and in vitro assays, we identified macitentan as a potent inhibitor of integrin α9/VCAM-1 interactions and neutrophil adhesion to activated endothelial cells. Macitentan reduced DVT severity in control mice with and without stroke, but not in α9fl/flMrp8Cre+/- mice, suggesting that macitentan improves DVT outcomes by inhibiting neutrophil integrin α9. Collectively, we uncovered a previously unrecognized and critical pathway involving the α9/VCAM-1 axis in neutrophil hyperactivation and DVT.

Efficacy and Safety of Clazosentan After Aneurysmal Subarachnoid Hemorrhage: An Updated Meta-Analysis

BACKGROUND AND OBJECTIVES

Clazosentan has been studied to treat cerebral vasospasm after aneurysmal subarachnoid hemorrhage (aSAH).This meta-analysis of randomized controlled trials updates the current knowledge regarding the efficacy and safety of clazosentan compared with placebo after aSAH.

METHODS

Databases were systematically searched for randomized controlled trials directly comparing the use of clazosentan and placebo for the treatment of cerebral vasospasm after aSAH. Additional eligibility criteria were the report of any of the outcomes of interest (vasospasm, morbidity, functional outcome, or mortality). The primary outcome was vasospasm-related delayed cerebral ischemia (DCI). The analyses were stratified by clazosentan dosage (low or high dose) and aneurysm treatment modality (clipping or coiling). The Cochrane RoB-2 tool was used for studies quality assessment.

RESULTS

Six studies comprising 7 clinical trials were included, involving 2778 patients. Clazosentan decreased the risk of vasospasm-related DCI (risk ratio [RR] 0.56, 95% CI 0.38-0.81) and delayed ischemic neurological deficit (RR 0.63, 95% 0.50-0.80). Angiographic vasospasm (RR 0.54, 95% CI 0.47-0.61) was also decreased. Functional outcomes (favorable Glasgow Outcome Scale, RR 0.99, 95% CI 0.79-1.24) and death (RR 1.03, 95% CI 0.71-1.49) did not change. Meanwhile, adverse events were increased by clazosentan (RR 1.54, 95% CI 1.35-1.76).

CONCLUSION

Clazosentan decreased vasospasm-related DCI and angiographic vasospasm but did not improve functional outcomes or mortality. Adverse events were increased by clazosentan.

Thick and Diffuse Subarachnoid Blood as a Treatment Effect Modifier of Clazosentan After Subarachnoid Hemorrhage

Background and Purpose- Clazosentan, an endothelin receptor antagonist, has been shown to reduce angiographic vasospasm and vasospasm-related morbidity after aneurysmal subarachnoid hemorrhage (SAH), although no effect on long-term functional outcome has been demonstrated. Thick clot on initial computed tomography is associated with an increased risk of vasospasm and delayed cerebral ischemia. In this post hoc analysis, we hypothesized that use of clazosentan in this subpopulation would provide stronger benefit. Methods- We analyzed SAH patients enrolled in the CONSCIOUS-2 and CONSCIOUS-3 studies (Clazosentan to Overcome Neurological Ischemia and Infarction Occurring After Subarachnoid Hemorrhage) and compared the effects of clazosentan 5 mg/h, 15 mg/h, and placebo starting the day after aneurysm repair. The analysis was performed separately based on the presence or absence of thick (≥4 mm) and diffuse (≥3 cisterns) SAH on admission computed tomography. The primary composite end point was all-cause mortality and vasospasm-related morbidity at 6 weeks, and the main secondary end point was the extended Glasgow Outcome Scale at 3 months, adjusted for admission clinical grade. Results- Of 1718 randomized patients, 919 (53%) had thick and diffuse SAH. The primary composite end point in this group occurred in 36% of placebo-treated patients (n=294), 30% patients treated with clazosentan 5 mg/h (n=514; relative risk, 0.82; 95% CI, 0.67-0.99), and 19% patients treated with clazosentan 15 mg/h (n=111; relative risk, 0.54; 95% CI, 0.36-0.80). Despite this, death or poor functional outcome (Glasgow Outcome Scale ≤4) occurred in 33% of placebo-treated patients, 34% of patients treated with clazosentan 5 mg/h (relative risk 1.02; 95% CI, 0.84-1.23), and 35% of patients treated with clazosentan 15 mg/h (relative risk 1.14; 95% CI, 0.88-1.48). Conclusions- In an enriched population with thick and diffuse SAH, clazosentan at a dose of 5 and 15 mg/h was able to significantly reduce vasospasm-related morbidity in a dose-dependent manner. The absence of an effect on long-term functional status likely reflects the complexity and multiplicity of factors that contribute to poor outcome after SAH. Clinical Trial Registration- URL: https://www.clinicaltrials.gov. Unique identifier: NCT00558311; NCT00940095.

Clazosentan for Aneurysmal Subarachnoid Hemorrhage: An Updated Meta-Analysis with Trial Sequential Analysis

OBJECTIVE

Clazosentan, an endothelin receptor antagonist, reduced vasospasm and delayed ischemic neurologic deficit (DIND) but did not improve outcome after subarachnoid hemorrhage (SAH) in clinical trials. However, a lack of dose-dependent analysis and potential overestimation of clazosentan's effect are concerning. We used stratified analysis and trial sequential analysis (TSA) of existing data to investigate the effects of clazosentan on SAH outcome.

METHODS

Studies from PubMed, Embase, and Cochrane were reviewed for eligibility. Primary outcomes were DIND requiring rescue therapy, all-cause mortality, and vasospasm-related morbidity at 6 weeks. Secondary outcomes were moderate-to-severe angiographic vasospasm, new cerebral infarction, and poor clinical outcome at 3 months. TSA was performed to assess the required information size and the α-spending monitoring boundary effect of relative risk (RR) reduction. A stratified analysis of clazosentan dosage was performed.

RESULTS

Five studies (N = 2317) were included. Clazosentan significantly reduced the risk of DIND requiring rescue therapy (RR, 0.625; 95% confidence interval [CI], 0.462-0.846) and vasospasm (RR, 0.543; 95% CI, 0.464-0.635), but did not significantly affect mortality or vasospasm-related morbidity (RR, 0.775; 95% CI, 0.578-1.039), new cerebral infarction (RR, 0.604; 95% CI, 0.383-0.952), or outcome (RR, 1.131; 95% CI, 0.959-1.334). TSA revealed that the studies were underpowered to evaluate the effects of clazosentan on mortality and vasospasm-associated morbidity. We found 10-15 mg/h of clazosentan administration was associated with lower rates of vasospasm and new cerebral infarctions compared with 5 mg/h.

CONCLUSIONS

Clazosentan reduced the risk of DIND requiring rescue therapy and moderate-to-severe vasospasm. Further meta-analyses based on individual patient data with different clazosentan doses and more refined outcome measures are necessary to clarify clazosentan's efficacy in improving post-SAH outcome.

Dose-related effect of statins in patients with endovascular coiling or microsurgical clipping for aneurysmal subarachnoid hemorrhage: updated study-level meta-analysis

PURPOSE

We aimed to quantitatively assess the effects of short-term statin use on delayed ischemic neurologic deficits (DINDs) and clinical outcomes in patients with aneurysmal subarachnoid hemorrhage (SAH) through a meta-analysis of the available evidence.

METHODS

We searched the electronic databases up to April 8, 2016 to retrieve relevant studies comparing the outcomes between immediate statin-treated in statin-naïve patients and untreated patients following aneurysmal SAH. Meta-analysis was performed using Review Manager 5.3.

RESULTS

Eight randomized controlled clinical trials (RCTs) and 5 observational studies involving 2148 patients met the eligibility criteria. In the RCTs, statins were found to significantly reduce the occurrence of DINDs (relative risk (RR), 0.76; 95% confidence interval (CI), 0.61-0.94; P = 0.01), but did not significantly reduce poor functional outcomes (RR, 1.01; 95% CI, 0.87-1.16; P = 0.93) or mortality (RR, 0.80; 95% CI, 0.58-1.11; P = 0.18). In observational studies, statin use was not associated with any reduction in DINDs, poor outcome, or mortality. Meta-analysis of RCTs indicated a significant reduction in DINDs and mortality in patients with high-dose statin use (RR, 0.63; 95% CI, 0.42-0.95; P = 0.03; I ² = 0%; and RR, 0.36; 95% CI, 0.15-0.86; P = 0.02; I ² = 0%, respectively).

CONCLUSION

The present meta-analysis suggests that statin use may prevent DINDs in patients with aneurysmal SAH. Based on our findings, the role of statins in improving neurological outcome was limited. However, the risk of DINDs and mortality decreased with higher statin doses in a dose-dependent manner. Hence, further well-designed RCTs with modified protocols in specific patients are required.

Precision medicine of aneurysmal subarachnoid hemorrhage, vasospasm and delayed cerebral ischemia

INTRODUCTION

Precision medicine provides individualized treatment of diseases through leveraging patient-to-patient variation. Aneurysmal subarachnoid hemorrhage carries tremendous morbidity and mortality with cerebral vasospasm and delayed cerebral ischemia proving devastating and unpredictable. Lack of treatment measures for these conditions could be improved through precision medicine. Areas covered: Discussed are the pathophysiology of CV and DCI, treatment guidelines, and evidence for precision medicine used for prediction and prevention of poor outcomes following aSAH. A PubMed search was performed using keywords cerebral vasospasm or delayed cerebral ischemia and either biomarkers, precision medicine, metabolomics, proteomics, or genomics. Over 200 peer-reviewed articles were evaluated. The studies presented cover biomarkers identified as predictive markers or therapeutic targets following aSAH. Expert commentary: The biomarkers reviewed here correlate with CV, DCI, and neurologic outcomes after aSAH. Though practical use in clinical management of aSAH is not well established, using these biomarkers as predictive tools or therapeutic targets demonstrates the potential of precision medicine.

Aneurysmal Subarachnoid Hemorrhage and Neuroinflammation: A Comprehensive Review

Aneurysmal subarachnoid hemorrhage (SAH) can lead to devastating outcomes including vasospasm, cognitive decline, and even death. Currently, treatment options are limited for this potentially life threatening injury. Recent evidence suggests that neuroinflammation plays a critical role in injury expansion and brain damage. Red blood cell breakdown products can lead to the release of inflammatory cytokines that trigger vasospasm and tissue injury. Preclinical models have been used successfully to improve understanding about neuroinflammation following aneurysmal rupture. The focus of this review is to provide an overview of how neuroinflammation relates to secondary outcomes such as vasospasm after aneurysmal rupture and to critically discuss pharmaceutical agents that warrant further investigation for the treatment of subarachnoid hemorrhage. We provide a concise overview of the neuroinflammatory pathways that are upregulated following aneurysmal rupture and how these pathways correlate to long-term outcomes. Treatment of aneurysm rupture is limited and few pharmaceutical drugs are available. Through improved understanding of biochemical mechanisms of injury, novel treatment solutions are being developed that target neuroinflammation. In the final sections of this review, we highlight a few of these novel treatment approaches and emphasize why targeting neuroinflammation following aneurysmal subarachnoid hemorrhage may improve patient care. We encourage ongoing research into the pathophysiology of aneurysmal subarachnoid hemorrhage, especially in regards to neuroinflammatory cascades and the translation to randomized clinical trials.

MEK1/2 inhibitor U0126 but not endothelin receptor antagonist clazosentan reduces upregulation of cerebrovascular contractile receptors and delayed cerebral ischemia, and improves outcome after subarachnoid hemorrhage in rats

Cerebral vasospasm and late cerebral ischemia (LCI) remain leading causes of mortality in patients experiencing a subarachnoid hemorrhage (SAH). This occurs typically 3 to 4 days after the initial bleeding and peaks at 5 to 7 days. The underlying pathophysiology is still poorly understood. Because SAH is associated with elevated levels of endothelin-1 (ET-1), focus has been on counteracting endothelin receptor activation with receptor antagonists like clazosentan, however, with poor outcome in clinical trials. We hypothesize that inhibition of intracellular transcription signaling will be an effective approach to prevent LCI. Here, we compare the effects of clazosentan versus the MEK1/2 blocker U0126 in a rat model of SAH. Although clazosentan directly inhibits the contractile responses in vivo to ET-1, it did not prevent SAH-induced upregulation of ET receptors in cerebral arteries and did not show a beneficial effect on neurologic outcome. U0126 had no vasomotor effect by itself but counteracts SAH-induced receptor upregulation in cerebral arteries and improved outcome after SAH. We suggest that because SAH induces elevated expression of several contractile receptor subtypes, it is not sufficient to block only one of these (ET receptors) but inhibition of transcriptional MEK1/2-mediated upregulation of several contractile receptors may be a viable way towards alleviating LCI.

Value of transcranial Doppler, perfusion-CT and neurological evaluation to forecast secondary ischemia after aneurysmal SAH

INTRODUCTION

This study was conducted to prospectively evaluate the diagnostic value of detailed neurological evaluation, transcranial Doppler sonography (TCD) and Perfusion-CT (PCT) to predict delayed vasospasm (DV) and delayed cerebral infarction (DCI) within the following 3 days in patients with aneurysmal subarachnoid hemorrhage (SAH).

METHODS

A total of 61 patients with aneurysmal SAH were included in the study. All patients were amenable for neurological evaluation throughout the critical phase to develop secondary ischemia after SAH. The neurological status was assessed three times a day according to a detailed examination protocol. Mean flow velocities (MFV) in intracranial vessel trunks were measured daily by TCD. Native CT and PCT were routinely acquired at 3-day intervals and, in addition, whenever it was thought to be of diagnostic relevance. The predictive values of abnormal PCT and accelerations in TCD (MFV > 140 cm/s) to detect angiographic DV and DCI within the following 2 days were calculated and compared to the predictive value of delayed ischemic neurological deficits (DIND).

RESULTS

The accuracy of TCD and PCT to predict DV or DCI was 0.65 and 0.63, respectively. In comparison, DIND predicted DV or DCI with an accuracy of 0.96. Pathological PCT findings had a higher sensitivity (0.93) and negative predictive value (0.98) than TCD (0.81 and 0.96).

CONCLUSION

Neurological assessment at close intervals is the most accurate parameter to detect DV and DCI in the following 3 days. However, DIND may not be reversible. The routine acquisition of PCT in addition to daily TCD examinations seems reasonable, particularly in patients who are not amenable to a detailed neurological examination since it has a higher sensitivity and negative predictive value than TCD and leaves a lower number of undetected cases of vasospasm and infarction.

Plasma Estrogen Levels Are Associated With Severity of Injury and Outcomes After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Biochemical mediators alter cerebral perfusion and have been implicated in delayed cerebral ischemia (DCI) and poor outcomes after aneurysmal subarachnoid hemorrhage (aSAH). Estrogens (estrone [E1] and estradiol [E2]) are mediators with neuroprotective properties that could play a role in DCI. This study explored associations between plasma estrogen levels and outcomes following aSAH.

METHODS

Plasma samples from 1-4, 4-6, and 7-10 days after hemorrhage from 99 adult aSAH patients were analyzed for estrogen levels using liquid chromatography tandem mass spectrometry. DCI was operationalized as radiographic/ultrasonic evidence of impaired cerebral blood flow accompanied by neurological deterioration. Outcomes were assessed using the Modified Rankin Scale at 3 and 12 months after hemorrhage. Statistical analysis included correlation, regression, and group-based trajectory.

RESULTS

Higher E1 and E2 levels were associated with higher Hunt and Hess grade (E1, p = .01; E2, p = .03), the presence of DCI (E1, p = .02; E2, p = .02), and poor 3-month outcomes (E1, p = .002; E2, p = .002). Trajectory analysis identified distinct populations over time for E1 (61% E1 high) and E2 (68% E2 high). Patients in higher trajectory groups had higher Fisher grades (E1, p = .008; E2, p = .01), more frequent DCI (E1, p = .04; E2, p = .08), and worse 3-month outcomes (E1, p = .01; E2, p = .004) than low groups.

CONCLUSIONS

These results provide the first clinical evidence that plasma E1 and E2 concentrations are associated with severity of injury and outcomes after aSAH.

Neuroprotective effect of hydrogen-rich saline against neurologic damage and apoptosis in early brain injury following subarachnoid hemorrhage: possible role of the Akt/GSK3β signaling pathway

Backgrounds

Early brain injury (EBI) plays a key role in the pathogenesis of subarachnoid hemorrhage (SAH). Neuronal apoptosis is involved in the pathological process of EBI. Hydrogen can inhibit neuronal apoptosis and attenuate EBI following SAH. However, the molecular mechanism underlying hydrogen-mediated anti-apoptotic effects in SAH has not been elucidated. In the present study, we aimed to evaluate whether hydrogen alleviates EBI after SAH, specifically neuronal apoptosis, partially via the Akt/GSK3β signaling pathway.

Methods

Sprague-Dawley rats (n = 85) were randomly divided into the following groups: sham group (n = 17), SAH group (n = 17), SAH + saline group (n = 17), SAH + hydrogen-rich saline (HS) group (n = 17) and SAH + HS + Ly294002 (n = 17) group. HS or an equal volume of physiological saline was administered immediately after surgery and repeated 8 hours later. The PI3K inhibitor, Ly294002, was applied to manipulate the proposed pathway. Neurological score and SAH grade were assessed at 24 hours after SAH. Western blot was used for the quantification of Akt, pAkt, GSK3β, pGSK3β, Bcl-2, Bax and cleaved caspase-3 proteins. Neuronal apoptosis was identified by double staining of terminal deoxynucleotidyl transferase mediated nick end labeling (TUNEL) staining and NeuN, and quantified by apoptosis index. Immunohistochemistry and immunofluorescent double-labeling staining was performed to clarify the relationships between neuronal apoptosis and pAkt or pGSK3β.

Results

HS significantly reduced neuronal apoptosis and improved neurological function at 24 hours after SAH. The levels of pAkt and pGSK3β, mainly expressed in neurons, were markedly up-regulated. Additionally, Bcl-2 was significantly increased while Bax and cleaved caspase-3 was decreased by HS treatment. Double staining of pAkt and TUNEL showed few colocalization of pAkt-positive cells and TUNEL-positive cells. The inhibitor of PI3K, Ly294002, suppressed the beneficial effects of HS.

Conclusions

HS could attenuate neuronal apoptosis in EBI and improve the neurofunctional outcome after SAH, partially via the Akt/GSK3β pathway.

Astragaloside IV alleviates early brain injury following experimental subarachnoid hemorrhage in rats

Astragaloside IV, one of the main effective components isolated from Astragalus membranaceus, has multiple neuroprotective properties, while the effects of astragaloside IV on the attenuation of subarachnoid hemorrhage (SAH)-induced early brain injury (EBI) and its possible mechanisms are unknown. In the present study, we aimed to determine whether astragaloside IV could inhibit oxidative stress, reduce neuronal apoptosis, and improve neurological deficits after experimental SAH in rats. Rats (n=68) were randomly divided into the following groups: Sham group, SAH group, SAH+vehicle group, and SAH+astragaloside IV group. Astragaloside IV or an equal volume of vehicle was administered at 1 h and 6 h after SAH, all the rats were subsequently sacrificed at 24 h after SAH. Mortality, neurological scores, and brain edema were assessed, biochemical tests and histological studies were also performed at that point. SAH induced an increase in the malondialdehyde (MDA) level, neuronal apoptosis, cleaved caspase 3, brain edema and decreased activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Astragaloside IV treatment reversed these changes and improved neurobehavioral outcomes of SAH rats. Our findings suggested that astragaloside IV may alleviate EBI after SAH through antioxidative and anti-apoptotic effects.

Inhibition of the Sur1-Trpm4 channel reduces neuroinflammation and cognitive impairment in subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Subarachnoid hemorrhage (SAH) can leave patients with memory impairments that may not recover fully. Molecular mechanisms are poorly understood, and no treatment is available. The sulfonylurea receptor 1-transient receptor potential melastatin 4 (Sur1-Trpm4) channel plays an important role in acute central nervous system injury. We evaluated upregulation of Sur1-Trpm4 in humans with SAH and, in rat models of SAH, we examined Sur1-Trpm4 upregulation, its role in barrier dysfunction and neuroinflammation, and its consequences on spatial learning.

METHODS

We used Förster resonance energy transfer to detect coassociated Sur1 and Trpm4 in human autopsy brains with SAH. We studied rat models of SAH involving filament puncture of the internal carotid artery or injection of blood into the subarachnoid space of the entorhinal cortex. In rats, we used Förster resonance energy transfer and coimmunoprecipitation to detect coassociated Sur1 and Trpm4, we measured immunoglobulin G extravasation and tumor necrosis α overexpression as measures of barrier dysfunction and neuroinflammation, and we assessed spatial learning and memory on days 7 to 19.

RESULTS

Sur1-Trpm4 channels were upregulated in humans and rats with SAH. In rats, inhibiting Sur1 using antisense or the selective Sur1 inhibitor glibenclamide reduced SAH-induced immunoglobulin G extravasation and tumor necrosis α overexpression. In models with entorhinal SAH, rats treated with glibenclamide for 7 days after SAH exhibited better platform search strategies and better performance on incremental and rapid spatial learning than vehicle-treated controls.

CONCLUSIONS

Sur1-Trpm4 channels are upregulated in humans and rats with SAH. Channel inhibition with glibenclamide may reduce neuroinflammation and the severity of cognitive deficits after SAH.

Endothelin antagonists in subarachnoid hemorrhage: what next?

In the previous issue of Critical Care, Ma and colleagues perform a meta-analysis of five randomized, clinical trials of endothelin antagonists in patients with aneurysmal subarachnoid hemorrhage. There are four trials using clazosentan and one trial with TAK-044. These studies show that endothelin plays an important role in the genesis of angiographic vasospasm. The benefit of these drugs is less on delayed cerebral ischemia and nonexistent on overall clinical outcome. Why the drugs reduce vasospasm but do not improve outcome could be because of side effects such as hypotension and pulmonary complications that are more common in patients treated with endothelin antagonists or because rescue therapy, which is used more in the placebo groups, improves outcome in these patients to the same extent as the endothelin antagonists. As the authors conclude, future studies of these drugs will need to consider these and other factors in their design.