Associations of renin-angiotensin system genetic polymorphisms and clinical course after aneurysmal subarachnoid hemorrhage

Aspirin treatment for unruptured intracranial aneurysms: Focusing on its anti-inflammatory role

Intracranial aneurysms (IAs), as a common cerebrovascular disease, claims a worldwide morbidity rate of 3.2%. Inflammation, pivotal in the pathogenesis of IAs, influences their formation, growth, and rupture. This review investigates aspirin's modulation of inflammatory pathways within this context. With IAs carrying significant morbidity and mortality upon IAs rupture and current interventions limited to surgical clipping and endovascular coiling, the quest for pharmacological options is imperative. Aspirin's role in cardiovascular prevention, due to its anti-inflammatory effects, presents a potential therapeutic avenue for IAs. In this review, we examine aspirin's efficacy in experimental models and clinical settings, highlighting its impact on the progression and rupture risks of unruptured IAs. The underlying mechanisms of aspirin's impact on IAs are explored, with its ability examined to attenuate endothelial dysfunction and vascular injury. This review may provide a theoretical basis for the use of aspirin, suggesting a promising strategy for IAs management. However, the optimal dosing, safety, and long-term efficacy remain to be established. The implications of aspirin therapy are significant in light of current surgical and endovascular treatments. Further research is encouraged to refine aspirin's clinical application in the management of unruptured IAs, with the ultimate aim of reducing the incidence of aneurysms rupture.

Candidate neuroinflammatory markers of cerebral autoregulation dysfunction in human acute brain injury

The loss of cerebral autoregulation (CA) is a common and detrimental secondary injury mechanism following acute brain injury and has been associated with worse morbidity and mortality. However patient outcomes have not as yet been conclusively proven to have improved as a result of CA-directed therapy. While CA monitoring has been used to modify CPP targets, this approach cannot work if the impairment of CA is not simply related to CPP but involves other underlying mechanisms and triggers, which at present are largely unknown. Neuroinflammation, particularly inflammation affecting the cerebral vasculature, is an important cascade that occurs following acute injury. We hypothesise that disturbances to the cerebral vasculature can affect the regulation of CBF, and hence the vascular inflammatory pathways could be a putative mechanism that causes CA dysfunction. This review provides a brief overview of CA, and its impairment following brain injury. We discuss candidate vascular and endothelial markers and what is known about their link to disturbance of the CBF and autoregulation. We focus on human traumatic brain injury (TBI) and subarachnoid haemorrhage (SAH), with supporting evidence from animal work and applicability to wider neurologic diseases.

Immunological Profile of Vasospasm after Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) carries high mortality and disability rates, which are substantially driven by complications. Early brain injury and vasospasm can happen after SAH and are crucial events to prevent and treat to improve prognosis. In recent decades, immunological mechanisms have been implicated in SAH complications, with both innate and adaptive immunity involved in mechanisms of damage after SAH. The purpose of this review is to summarize the immunological profile of vasospasm, highlighting the potential implementation of biomarkers for its prediction and management. Overall, the kinetics of central nervous system (CNS) immune invasion and soluble factors' production critically differs between patients developing vasospasm compared to those not experiencing this complication. In particular, in people developing vasospasm, a neutrophil increase develops in the first minutes to days and pairs with a mild depletion of CD45+ lymphocytes. Cytokine production is boosted early on after SAH, and a steep increase in interleukin-6, metalloproteinase-9 and vascular endothelial growth factor (VEGF) anticipates the development of vasospasm after SAH. We also highlight the role of microglia and the potential influence of genetic polymorphism in the development of vasospasm and SAH-related complications.

A Review of Genetic Polymorphisms and Susceptibilities to Complications after Aneurysmal Subarachnoid Hemorrhage

Delayed cerebral ischemia (DCI) and vasospasm are two complications of subarachnoid hemorrhages (SAHs) which entail high risks of morbidity and mortality. However, it is unknown why only some patients who suffer SAHs will experience DCI and vasospasm. The purpose of this review is to describe the main genetic single nucleotide polymorphisms (SNPs) that have demonstrated a relationship with these complications. The SNP of the nitric oxide endothelial synthase (eNOS) has been related to the size and rupture of an aneurysm, as well as to DCI, vasospasm, and poor neurological outcome. The SNPs responsible for the asymmetric dimetilarginine and the high-mobility group box 1 have also been associated with DCI. An association between vasospasm and the SNPs of the eNOS, the haptoglobin, and the endothelin-1 receptor has been found. The SNPs of the angiotensin-converting enzyme have been related to DCI and poor neurological outcome. Studies on the SNPs of the Ryanodine Receptor yielded varying results regarding their association with vasospasm.

Angiotensin-(1-7) as a Potential Therapeutic Strategy for Delayed Cerebral Ischemia in Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is a substantial cause of mortality and morbidity worldwide. Moreover, survivors after the initial bleeding are often subject to secondary brain injuries and delayed cerebral ischemia, further increasing the risk of a poor outcome. In recent years, the renin-angiotensin system (RAS) has been proposed as a target pathway for therapeutic interventions after brain injury. The RAS is a complex system of biochemical reactions critical for several systemic functions, namely, inflammation, vascular tone, endothelial activation, water balance, fibrosis, and apoptosis. The RAS system is classically divided into a pro-inflammatory axis, mediated by angiotensin (Ang)-II and its specific receptor AT₁R, and a counterbalancing system, presented in humans as Ang-(1-7) and its receptor, MasR. Experimental data suggest that upregulation of the Ang-(1-7)/MasR axis might be neuroprotective in numerous pathological conditions, namely, ischemic stroke, cognitive disorders, Parkinson's disease, and depression. In the presence of SAH, Ang-(1-7)/MasR neuroprotective and modulating properties could help reduce brain damage by acting on neuroinflammation, and through direct vascular and anti-thrombotic effects. Here we review the role of RAS in brain ischemia, with specific focus on SAH and the therapeutic potential of Ang-(1-7).

Nomogram for predicting delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage in the Chinese population

BACKGROUND

Delayed cerebral ischemia is a serious complication of aneurysmal subarachnoid hemorrhage with debilitating and fatal consequences. Lack of well-established risk factors impedes early identification of high-risk patients with delayed cerebral ischemia. A nomogram provides personalized, evidence-based, and accurate risk estimation. To offset the lack of a predictive tool, we developed a nomogram to predict delayed cerebral ischemia before performing surgical interventions for aneurysmal subarachnoid hemorrhage to aid surgical decision-making.

METHODS

We retrospectively collected data from 887 consecutive eligible Chinese patients who underwent surgical clipping or endovascular coiling for aneurysmal subarachnoid hemorrhage. Patients who previously underwent surgery formed the training cohort (n = 621) for nomogram development; those who underwent surgery later formed the validation cohort (n = 266) to confirm the performance of the model. A multivariate logistic regression analysis identified the independent risk factors associated with delayed cerebral ischemia, which were then incorporated into the nomogram.

RESULTS

Delayed cerebral ischemia was identified in 158/621 patients (25.4%) in the training cohort and in 66/266 patients (24.8%) in the validation cohort. Preoperative factors associated with delayed cerebral ischemia were age > 65 years, modified Fisher grade of 3-4, ruptured aneurysm in the anterior circulation, Hunt-Hess grade of 4-5, high blood pressure on admission, and plasma homocysteine level ≥ 10 μmol/L. Incorporating these six factors in the nomogram achieved efficient concordance indices of 0.73 (95% confidence interval, 0.68-0.77) and 0.65 (95% confidence interval, 0.57-0.72) in predicting delayed cerebral ischemia in the training and validation cohorts, respectively.

CONCLUSIONS

Our model can help determine an individual's risk of developing delayed cerebral ischemia in the Chinese population, and thereby, facilitate reasonable treatment-related decision-making.

Genetic drivers of cerebral blood flow dysfunction in TBI: a speculative synthesis

Cerebral autoregulatory dysfunction after traumatic brain injury (TBI) is strongly linked to poor global outcome in patients at 6 months after injury. However, our understanding of the drivers of this dysfunction is limited. Genetic variation among individuals within a population gives rise to single-nucleotide polymorphisms (SNPs) that have the potential to influence a given patient's cerebrovascular response to an injury. Associations have been reported between a variety of genetic polymorphisms and global outcome in patients with TBI, but few studies have explored the association between genetic variants and cerebrovascular function after injury. In this Review, we explore polymorphisms that might play an important part in cerebral autoregulatory capacity after TBI. We outline a variety of SNPs, their biological substrates and their potential role in mediating cerebrovascular reactivity. A number of candidate polymorphisms exist in genes that are involved in myogenic, endothelial, metabolic and neurogenic vascular responses to injury. Furthermore, polymorphisms in genes involved in inflammation, the central autonomic response and cortical spreading depression might drive cerebrovascular reactivity. Identification of candidate genes involved in cerebral autoregulation after TBI provides a platform and rationale for further prospective investigation of the link between genetic polymorphisms and autoregulatory function.

Loss of consciousness at onset of aneurysmal subarachnoid hemorrhage in good-grade patients

Loss of consciousness (LOC) at presentation with aneurysmal subarachnoid hemorrhage (aSAH) has been associated with early brain injury and poor functional outcome. The impact of LOC on the clinical course after aSAH deserves further exploration. A retrospective analysis of 149 aSAH patients who were prospectively enrolled in the Cerebral Aneurysm Renin Angiotensin Study (CARAS) between 2012 and 2015 was performed. The impact of LOC was analyzed with emphasis on patients presenting in excellent or good neurological condition (Hunt and Hess 1 and 2). A total of 50/149 aSAH patients (33.6%) experienced LOC at presentation. Loss of consciousness was associated with severity of neurological condition upon admission (Hunt and Hess, World Federation of Neurosurgical Societies (WFNS), Glasgow Coma Scale (GCS) grade), hemorrhage burden on initial head CT (Fisher CT grade), acute hydrocephalus, cardiac instability, and nosocomial infection. Of Hunt and Hess grade 1 and 2 patients, 21/84 (25.0%) suffered LOC at presentation. Cardiac instability and nosocomial infection were significantly more frequent in these patients. In multivariable analysis, LOC was the predominant predictor of cardiac instability and nosocomial infection. Loss of consciousness at presentation with aSAH is associated with an increased rate of complications, even in good-grade patients. The presence of LOC may identify good-grade patients at risk for complications such as cardiac instability and nosocomial infection.

Association of Plasminogen Activator Inhibitor 1 (SERPINE1) Polymorphisms and Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Genetic variations of the serine proteinase inhibitor family E member 1 (SERPINE1) gene, which encodes plasminogen activator inhibitor 1, correlate with serum levels of its product and are associated with thrombophilia and coronary atherosclerosis. Various SERPINE1 ;gene polymorphisms have been identified. However, only the functional 5G/4G polymorphism has been assessed in the context of aneurysmal subarachnoid hemorrhage (aSAH). We assessed associations of 6 SERPINE1 polymorphisms with the clinical sequelae of aSAH.

METHODS

From 2012 to 2015, patients with aSAH were prospectively enrolled into the CARAS (Cerebral Aneurysm Renin Angiotensin System) study at 2 major academic institutions. Blood samples were used to evaluate 6 common SERPINE1 single nucleotide polymorphisms via 5' exonuclease (Taqman) genotyping assays.

RESULTS

There was an association of the AA genotype of rs2227631 with the 4G/4G genotype and of the GG genotype of rs7242 with the AA genotype of rs2227684. In multivariable analysis, patients with the AA genotype of rs2227631 and 4G/4G genotype had an increased risk for developing delayed cerebral ischemia. Patients with the GG genotype of rs7242 and AA genotype of rs2227684 had a decreased risk for a poor functional outcome.

CONCLUSIONS

SERPINE1 gene polymorphisms were associated with delayed cerebral ischemia and functional outcome after aSAH. These associations may arise from alterations of plasminogen activator inhibitor 1 levels.

Ryanodine Receptor 1 Polymorphism Is Not Associated with Aneurysmal Subarachnoid Hemorrhage or its Clinical Sequelae

OBJECTIVE

The pathophysiologic mechanisms underlying cerebral vasospasm after aneurysmal subarachnoid hemorrhage (aSAH) remain poorly understand. Ryanodine receptors (RYR) are intracellular calcium channels involved in the regulation of vascular smooth muscle cells and cerebrovascular tone and diameter. Previous work reported an association between an RYR polymorphism and cerebral vasospasm. Here, we sought to assess the impact of that RYR polymorphism on aSAH and its clinical sequelae.

METHODS

Blood samples from all patients enrolled in the CARAS (Cerebral Aneurysm Renin Angiotensin System) study were used for genetic evaluation. The RYR1 single nucleotide polymorphism (SNP) rs35364374 was detected using 5'exonuclease (Taqman) genotyping assays. Associations between the RYR1 polymorphism and aSAH and its clinical sequelae were analyzed.

RESULTS

Samples from 149 patients with aSAH and 50 controls were available for analysis. Multivariable regression analysis did not show an association of RYR1 SNP rs35364374 with aSAH. Moreover, there was no association of RYR1 SNP rs35364374 with clinical vasospasm, delayed cerebral ischemia, functional outcome at discharge, or functional outcome at last follow-up.

CONCLUSIONS

Contrary to a previous report, the RYR1 SNP rs35364374 was not associated with aSAH or its clinical sequelae.