Mechanistic and therapeutic relationships of traumatic brain injury and γ-amino-butyric acid (GABA).

Traumatic brain injury (TBI) is a highly prevalent medical condition for which no medications specific for the prophylaxis or treatment of the condition as a whole exist. The spectrum of symptoms includes coma, headache, seizures, cognitive impairment, depression, and anxiety. Although it has been known for years that the inhibitory neurotransmitter γ-amino-butyric acid (GABA) is involved in TBI, no novel therapeutics based upon this mechanism have been introduced into clinical practice. We review the neuroanatomical, neurophysiological, neurochemical, and neuropharmacological relationships of GABA neurotransmission to TBI with a view toward new potential GABA-based medicines. The long-standing idea that excitatory and inhibitory (GABA and others) balances are disrupted by TBI is supported by the experimental data but has failed to invent novel methods of restoring this balance. The slow progress in advancing new treatments is due to the complexity of the disorder that encompasses multiple dynamically interacting biological processes including hemodynamic and metabolic systems, neurodegeneration and neurogenesis, major disruptions in neural networks and axons, frank brain lesions, and a multitude of symptoms that have differential neuronal and neurohormonal regulatory mechanisms. Although the current and ongoing clinical studies include GABAergic drugs, no novel GABA compounds are being explored. It is suggested that filling the gap in understanding the roles played by specific GABAA receptor configurations within specific neuronal circuits could help define new therapeutic approaches. Further research into the temporal and spatial delivery of GABA modulators should also be useful. Along with GABA modulation, research into the sequencing of GABA and non-GABA treatments will be needed.

Early Neurologic Recovery, Practice Pattern Variation, and the Risk of Endotracheal Intubation Following Established Status Epilepticus.

OBJECTIVE: To quantify the association between early neurologic recovery, practice pattern variation, and endotracheal intubation during established status epilepticus, we performed a secondary analysis within the cohort of patients enrolled in the Established Status Epilepticus Treatment Trial (ESETT). METHODS: We evaluated factors associated with the endpoint of endotracheal intubation occurring within 120 minutes of ESETT study drug initiation. We defined a blocked, stepwise multivariate regression, examining 4 phases during status epilepticus management: (1) baseline characteristics, (2) acute treatment, (3) 20-minute neurologic recovery, and (4) 60-minute recovery, including seizure cessation and improving responsiveness. RESULTS: Of 478 patients, 117 (24.5%) were intubated within 120 minutes. Among high-enrolling sites, intubation rates ranged from 4% to 32% at pediatric sites and 19% to 39% at adult sites. Baseline characteristics, including seizure precipitant, benzodiazepine dosing, and admission vital signs, provided limited discrimination for predicting intubation (area under the curve [AUC] 0.63). However, treatment at sites with an intubation rate in the highest (vs lowest) quartile strongly predicted endotracheal intubation independently of other treatment variables (adjusted odds ratio [aOR] 8.12, 95% confidence interval [CI] 3.08-21.4, model AUC 0.70). Site-specific variation was the factor most strongly associated with endotracheal intubation after adjustment for 20-minute (aOR 23.4, 95% CI 6.99-78.3, model AUC 0.88) and 60-minute (aOR 14.7, 95% CI 3.20-67.5, model AUC 0.98) neurologic recovery. CONCLUSIONS: Endotracheal intubation after established status epilepticus is strongly associated with site-specific practice pattern variation, independently of baseline characteristics, and early neurologic recovery and should not alone serve as a clinical trial endpoint in established status epilepticus. TRIAL REGISTRATION INFORMATION: ClinicalTrials.gov Identifier: NCT01960075.

Effect of CHRFAM7A Δ2bp gene variant on secondary inflammation after spinal cord injury.

The α7 neuronal nicotinic acetylcholine receptors (α7nAChRs) are essential for anti-inflammatory responses. The human-specific CHRFAM7A gene and its 2bp deletion polymorphism (Δ2bp variant) encodes a structurally-deficient α7nAChRs that may impact the anti-inflammatory function. We studied 45 spinal cord injury (SCI) patients for up to six weeks post SCI to investigate the role of the Δ2bp variant on multiple circulating inflammatory mediators and two outcome measures (neuropathic pain and risk of pressure ulcers). The patient's SCI were classified as either severe or mild. Missing values were imputed. Overall genetic effect was conducted with independent sample t-test and corrected with false discovery rate (FDR). Univariate analysis and regression analysis were applied to evaluate the Δ2bp effects on temporal variation of inflammatory mediators post SCI and their interaction with outcome measures. In severe SCI, the Δ2bp carriers showed higher levels of circulating inflammatory mediators than the Δ2bp non-carriers in TNF-α (FDR = 9.6x10-4), IFN-γ (FDR = 1.3x10-3), IL-13 (FDR = 1.6x10-3), CCL11 (FDR = 2.1x10-3), IL-12p70 (FDR = 2.2x10-3), IL-8 (FDR = 2.2x10-3), CXCL10 (FDR = 3.1x10-3), CCL4 (FDR = 5.7x10-3), IL-12p40 (FDR = 7.1x10-3), IL-1b (FDR = 0.014), IL-15 (FDR = 0.024), and IL-2 (FDR = 0.037). IL-8 and CCL2 were negatively associated with days post injury (DPI) for the Δ2bp carriers (P = 2x10-7 and P = 2x10-8, respectively) and IL-5 was positively associated with DPI for the Δ2bp non-carriers (P = 0.015). Neuropathic pain was marginally positively associated with IL-13 for the Δ2bp carriers (P = 0.056). In mild SCI, the Δ2bp carriers had lower circulating levels of IL-15 (FDR = 0.04) than the Δ2bp non-carriers. Temporal variation of inflammatory mediators post SCI was not associated with the Δ2bp variant. For the mild SCI Δ2bp carriers, risk of pressure ulcers was positively associated with circulating levels of IFN-γ, CXCL10, and CCL4 and negatively associated with circulating levels of IL-12p70. These findings support an important role for the human-specific CHRFAM7A Δ2bp gene variant in modifying anti-inflammatory function of α7nAChRs following SCI.

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.

Haplotype analysis of SERPINE1 gene: Risk for aneurysmal subarachnoid hemorrhage and clinical outcomes.

BACKGROUND: Aneurysmal subarachnoid hemorrhage (aSAH) has high fatality and permanent disability rates due to the severe damage to brain cells and inflammation. The SERPINE1 gene that encodes PAI-1 for the regulation of tissue plasminogen activator is considered an important therapeutic target for aSAH. METHODS: Six SNPs in the SERPINE1 gene (in order of rs2227631, rs1799889, rs6092, rs6090, rs2227684, rs7242) were investigated. Blood samples were genotyped with Taqman genotyping assays and pyrosequencing. The experiment-wide statistically significant threshold for single marker analysis was set at p < 0.01 after evaluation of independent markers. Haplotype analysis was performed in Haplo.stats package with permutation tests. Bonferroni correction for multiple comparison in dominant, additive, and recessive model was applied. RESULTS: A total of 146 aSAH patients and 49 control subjects were involved in this study. The rs2227631 G allele is significant (p = 0.01) for aSAH compared to control. In aSAH group, haplotype analysis showed that G5GGGT homozygotes in recessive model were associated with delayed cerebral ischemia (p < 0.01, Odds Ratio = 5.14, 95% CI = 1.45-18.18), clinical vasospasm (p = 0.01, Odds Ratio = 4.58, 95% CI = 1.30-16.13), and longer intensive care unit stay (p = 0.01). By contrast, the G5GGAG carriers were associated with less incidence of cerebral edema (p < 0.01) and higher Glasgow Coma Scale (p < 0.01). The A4GGGT carriers were associated with less incidence of severe hypertension (>140/90) (p < 0.01). CONCLUSION: The results suggested an important regulatory role of the SERPINE1 gene polymorphism in clinical outcomes of aSAH.

Association of a Functional Polymorphism in the CHRFAM7A Gene with Inflammatory Response Mediators and Neuropathic Pain after Spinal Cord Injury.

The alpha 7 nicotinic acetylcholine receptor, α7 nAChR, plays a central role in regulating inflammatory responses. Previous studies showed that pharmacological inhibitors of α7nAChR have a pro-inflammatory effect, increasing the circulating levels of cytokines such as tumor necrosis factor alpha (TNFα). This study focused on how genetic polymorphisms of the partially duplicated α7nAChR gene (CHRFAM7A), which is highly expressed in peripheral blood cells, contribute to functional outcome after spinal cord injury (SCI). In a cohort of 27 SCI patients and 25 emergency room consented controls (% F/M: 15/85, 24/76; mean ± SE age: 35 ± 1.38 and 35 ± 2.0 respectively), a panel of circulating cytokines, noradrenergic metabolite (normetanephrine [NMN]) levels, and clinical data were available within the first 7 days post-injury (DPI) up to 90 DPI, and were investigated in the acute/subacute (DPI 1-21) and intermediate (DPI 22-90) temporal periods. Cytokine and NMN plasma levels on different DPI were analyzed as a function of CHRFAM7A genotype. TNFα levels, as a representative of some elevated inflammatory mediators, were nearly threefold higher in individuals carrying the del-2bp variant of the CHRFAM7A gene compared with that in the no-deletion genotype (p = 0.001 analysis of variance [ANOVA]) 3 weeks DPI, and twofold higher than genotype-matched acute/subacute non-SCI injury controls within 7 days DPI. In contrast, NMN levels were initially unchanged, although after 3 weeks, NMN levels were significantly decreased in SCI individuals carrying the del-2bp variant compared with non-carriers (p = 0.011 ANOVA). Numerical pain scores over this same period post-injury were significantly elevated in SCI patients carrying the del-2bp variant relative to non-carriers (p = 0.001 ANOVA). Taken together, these data reveal that pro-inflammatory responses associated with CHRFAM7A gene variation may also be associated with differences in pain experience in patients following SCI, at least during the intermediate phase.

Mice lacking the transcriptional regulator Bhlhe40 have enhanced neuronal excitability and impaired synaptic plasticity in the hippocampus.

Bhlhe40 is a transcription factor that is highly expressed in the hippocampus; however, its role in neuronal function is not well understood. Here, we used Bhlhe40 null mice on a congenic C57Bl6/J background (Bhlhe40 KO) to investigate the impact of Bhlhe40 on neuronal excitability and synaptic plasticity in the hippocampus. Bhlhe40 KO CA1 neurons had increased miniature excitatory post-synaptic current amplitude and decreased inhibitory post-synaptic current amplitude, indicating CA1 neuronal hyperexcitability. Increased CA1 neuronal excitability was not associated with increased seizure severity as Bhlhe40 KO relative to +/+ (WT) control mice injected with the convulsant kainic acid. However, significant reductions in long term potentiation and long term depression at CA1 synapses were observed in Bhlhe40 KO mice, indicating impaired hippocampal synaptic plasticity. Behavioral testing for spatial learning and memory on the Morris Water Maze (MWM) revealed that while Bhlhe40 KO mice performed similarly to WT controls initially, when the hidden platform was moved to the opposite quadrant Bhlhe40 KO mice showed impairments in relearning, consistent with decreased hippocampal synaptic plasticity. To investigate possible mechanisms for increased neuronal excitability and decreased synaptic plasticity, a whole genome mRNA expression profile of Bhlhe40 KO hippocampus was performed followed by a chromatin immunoprecipitation sequencing (ChIP-Seq) screen of the validated candidate genes for Bhlhe40 protein-DNA interactions consistent with transcriptional regulation. Of the validated genes identified from mRNA expression analysis, insulin degrading enzyme (Ide) had the most significantly altered expression in hippocampus and was significantly downregulated on the RNA and protein levels; although Bhlhe40 did not occupy the Ide gene by ChIP-Seq. Together, these findings support a role for Bhlhe40 in regulating neuronal excitability and synaptic plasticity in the hippocampus and that indirect regulation of Ide transcription may be involved in these phenotypes.

PHASES score applied to a prospective cohort of aneurysmal subarachnoid hemorrhage patients.

The treatment of unruptured intracranial aneurysms remains controversial. The PHASES score was developed to predict the 5-year risk of aneurysm rupture. We have assigned PHASES scores to a cohort of aneurysmal subarachnoid hemorrhage (aSAH) patients to assess the distribution of scores and its ability to predict outcome. In this study, the PHASES score was applied to a prospective cohort of aSAH patients that were enrolled in the Cerebral Aneurysm Renin Angiotensin System (CARAS) study. The CARAS study enrolled patients from two academic institutions in the United States from 2012 to 2015. Univariable and multivariable analyses were performed to identify factors predictive of outcome at last follow up. One hundred and forty-nine aSAH patients were included with a mean age of 54.9 ±â€¯12.5 years. Most ruptured aneurysms were <7 mm (62.4%) and located in the anterior circulation (80.5%). Favorable functional outcome (mRS 0-2) at last follow up was achieved in 61.7% of patients. PHASES scores ranged from 0 to 16 with a median of 5; the majority of patients had a score of 4 (20.1%) or 5 (32.2%). Multivariable modeling identified higher PHASES scores (OR 1.235, CI 1.016-1.501, p = 0.034) and higher Hunt and Hess grades (OR 2.224, CI 1.353-3.655, p = 0.002) as independent predictors of poor functional outcome (mRS 3-6) at last follow up. The majority of aSAH patients present with low (≤5) PHASES scores. Elevated PHASES scores are independently associated with poor functional outcome in patients with aSAH.

Association of renin-angiotensin system genetic polymorphisms and aneurysmal subarachnoid hemorrhage.

OBJECTIVE Renin-angiotensin system (RAS) genetic polymorphisms are thought to play a role in cerebral aneurysm formation and rupture. The Cerebral Aneurysm Renin-Angiotensin System (CARAS) study prospectively evaluated common RAS polymorphisms and their relation to aneurysmal subarachnoid hemorrhage (aSAH). METHODS The CARAS study prospectively enrolled aSAH patients and controls at 2 academic centers in the United States. A blood sample was obtained from all patients for genetic evaluation and measurement of plasma angiotensin-converting enzyme (ACE) concentration. Common RAS polymorphisms were detected using 5' exonuclease (TaqMan) genotyping assays and restriction fragment length polymorphism analysis. RESULTS Two hundred forty-eight patients were screened, and 149 aSAH patients and 50 controls were available for analysis. There was a recessive effect of the C allele of the angiotensinogen ( AGT) C/T single-nucleotide polymorphism (SNP) (OR 1.94, 95% CI 0.912-4.12, p = 0.0853) and a dominant effect of the G allele of the angiotensin II receptor Type 2 ( AT2) G/A SNP (OR 2.11, 95% CI 0.972-4.57, p = 0.0590) on aSAH that did not reach statistical significance after adjustment for potential confounders. The ACE level was significantly lower in aSAH patients with the II genotype (17.6 ± 8.0 U/L) as compared with the ID (22.5 ± 12.1 U/L) and DD genotypes (26.6 ± 14.2 U/L) (p = 0.0195). CONCLUSIONS The AGT C/T and AT2 G/A polymorphisms were not significantly associated with aSAH after controlling for potential confounders. However, a strong trend was identified for a dominant effect of the G allele of the AT2 G/A SNP. Downregulation of the local RAS may contribute to the formation of cerebral aneurysms and subsequent presentation with aSAH. Further studies are required to elucidate the relevant pathophysiology and its potential implication in treatment of patients with aSAH.

Association of cystathionine beta-synthase polymorphisms and aneurysmal subarachnoid hemorrhage.

OBJECTIVE Cystathionine ß-synthase (CBS) is involved in homocysteine and hydrogen sulfide (H2S) metabolism. Both products have been implicated in the pathophysiology of cerebrovascular diseases. The impact of CBS polymorphisms on aneurysmal subarachnoid hemorrhage (aSAH) and its clinical sequelae is poorly understood. METHODS Blood samples from all patients enrolled in the CARAS (Cerebral Aneurysm Renin Angiotensin System) study were used for genetic evaluation. The CARAS study prospectively enrolled aSAH patients at 2 academic institutions in the United States from 2012 to 2015. Common CBS polymorphisms were detected using 5'exonuclease genotyping assays. Analysis of associations between CBS polymorphisms and aSAH was performed. RESULTS Samples from 149 aSAH patients and 50 controls were available for analysis. In multivariate logistic regression analysis, the insertion allele of the 844ins68 CBS insertion polymorphism showed a dominant effect on aSAH. The GG genotype of the CBS G/A single nucleotide polymorphism (rs234706) was independently associated with unfavorable functional outcome (modified Rankin Scale Score 3-6) at discharge and last follow-up, but not clinical vasospasm or delayed cerebral ischemia (DCI). CONCLUSIONS The insertion allele of the 844ins68 CBS insertion polymorphism was independently associated with aSAH while the GG genotype of rs234706 was associated with an unfavorable outcome both at discharge and last follow-up. Increased CBS activity may exert its neuroprotective effects through alteration of H2S levels, and independent of clinical vasospasm and DCI.

Associations between endothelin polymorphisms and aneurysmal subarachnoid hemorrhage, clinical vasospasm, delayed cerebral ischemia, and functional outcome.

OBJECTIVE Endothelin-1, a potent vasoconstrictor, and its receptors may be involved in the pathogenesis of aneurysmal subarachnoid hemorrhage (aSAH), clinical vasospasm, delayed cerebral ischemia (DCI), and functional outcome following aSAH. In the present study, common endothelin single nucleotide polymorphisms (SNPs) and their relation to aSAH were evaluated. METHODS Blood samples from all patients enrolled in the Cerebral Aneurysm Renin Angiotensin System (CARAS) study were used for genetic evaluation. The CARAS study prospectively enrolled patients with aSAH at 2 academic institutions in the US from 2012 to 2015. Common endothelin SNPs were detected using 5' exonnuclease (TaqMan) genotyping assays. Analysis of associations between endothelin SNPs and aSAH and its clinical sequelae was performed. RESULTS Samples from 149 patients with aSAH and 50 controls were available for analysis. In multivariate logistic regression analysis, the TG (odds ratio [OR] 2.102, 95% confidence interval [CI] 1.048-4.218, p = 0.036) and TT genotypes (OR 7.884, 95% CI 1.003-61.995, p = 0.05) of the endothelin-1 T/G SNP (rs1800541) were significantly associated with aSAH. There was a dominant effect of the G allele (CG/GG genotypes; OR 4.617, 95% CI 1.311-16.262, p = 0.017) of the endothelin receptor A G/C SNP (rs5335) on clinical vasospasm. Endothelin SNPs were not associated with DCI or functional outcome. CONCLUSIONS Common endothelin SNPs were found to be associated with presentation with aSAH and clinical vasospasm. Further studies are required to elucidate the relevant pathophysiology and its potential implications in the treatment of patients with aSAH.

The role of endothelial nitric oxide synthase -786 T/C polymorphism in cardiac instability following aneurysmal subarachnoid hemorrhage.

INTRODUCTION: Cardiac abnormalities are observed frequently after aneurysmal subarachnoid hemorrhage (aSAH). A subset of aSAH patients develops neurogenic cardiomyopathy, likely induced by catecholamine excess. Genetic polymorphisms of the endothelial nitric oxide synthase (eNOS) gene have been linked to decreased nitric oxide (NO) levels, coronary artery spasm, and myocardial infarction. The role of the eNOS single nucleotide polymorphism (SNP) -786 T/C in cardiac instability following aSAH has not been previously investigated. METHODS: From 2012 to 2015, aSAH patients were prospectively enrolled in the Cerebral Aneurysm Renin Angiotensin System (CARAS) study at two academic institutions. Blood samples were used to assess the eNOS SNP -786 T/C rs2070744 through 5'exonuclease (Taqman) genotyping assays. Associations between this polymorphism and cardiac instability following aSAH were analyzed. RESULTS: Multivariable analysis demonstrated a dominant effect of the C allele of eNOS SNP -786 T/C on cardiac instability in patients with aSAH. A lower Glasgow Coma Scale score and a history of ischemic vascular disease were also associated with cardiac instability. Furthermore, cardiac instability independently predicted poor functional outcome upon discharge from the hospital. CONCLUSIONS: The C allele of the eNOS SNP -786 T/C was independently associated with an increased risk for cardiac instability following aSAH. Cardiac instability itself was a risk factor for an unfavorable functional outcome upon discharge from the hospital.

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.

Functional human GRIN2B promoter polymorphism and variation of mental processing speed in older adults.

We investigated the role of a single nucleotide polymorphism rs3764030 (G>A) within the human GRIN2B promoter in mental processing speed in healthy, cognitively intact, older adults. In vitro DNA-binding and reporter gene assays of different allele combinations in transfected cells showed that the A allele was a gain-of-function variant associated with increasing GRIN2B mRNA levels. We tested the hypothesis that individuals with A allele will have better memory performance (i.e. faster reaction times) in older age. Twenty-eight older adults (ages 65-86) from a well-characterized longitudinal cohort were recruited and performed a modified delayed match-to-sample task. The rs3764030 polymorphism was genotyped and participants were grouped based on the presence of the A allele into GG and AA/AG. Carriers of the A allele maintained their speed of memory retrieval over age compared to GG carriers (p = 0.026 slope of the regression line between AA and AG versus GG groups). To validate the results, 12 older adults from the same cohort participated in a different version of the short-term memory task. Reaction times were significantly slower with age in older adults with G allele (p < 0.001). These findings support a role for rs3764030 in maintaining faster mental processing speed over aging.

Endothelin polymorphisms as a risk factor for cerebral aneurysm rebleeding following aneurysmal subarachnoid hemorrhage.

BACKGROUND: Aneurysm rebleeding following presentation with aneurysmal subarachnoid hemorrhage (aSAH) is associated with high mortality and poor functional outcome. While a substantial genetic contribution to aneurysm formation and rupture is known, the genetic influence on the risk of rebleeding is poorly understood. OBJECTIVE: To evaluate the role of common endothelin polymorphisms in aneurysm rebleeding. PATIENTS AND METHODS: Blood sample from all patients enrolled in the CARAS (Cerebral Aneurysm Renin Angiotensin System) study were used for genetic evaluation. The CARAS study prospectively enrolled aSAH patients at two academic institutions in the United States from 2012 to 2015. Common endothelin SNPs were detected using 5'exonnuclease (Taqman) genotyping assays. Analysis of associations between endothelin single nucleotide polymorphisms (SNP) and aneurysm rebleeding was performed. RESULTS: One hundred and forty-nine aSAH patients were included. Acute spontaneous aneurysm rebleeding occurred in 5 (3.4%) patients. Multivariable analysis identified the TT genotype for EDN1 G/T SNP (rs2070699; OR 97.4, 95% CI 3.825-2479.984, p=0.006) as an independent risk factor for aneurysm rebleeding. Aneurysm rebleeding was associated with an unfavorable functional outcome (mRS 3-6) at last follow up in all 5 patients. CONCLUSION: Aneurysm rebleeding following presentation with aSAH was independently associated with the TT genotype of the EDN1 G/T SNP. All patients with acute spontaneous aneurysm rebleeding suffered a poor functional outcome at last follow up.

Endothelial Nitric Oxide Synthase Polymorphism Is Associated with Delayed Cerebral Ischemia Following Aneurysmal Subarachnoid Hemorrhage.

BACKGROUND AND PURPOSE: Nitric oxide is critical in the regulation of cerebral blood flow and smooth muscle proliferation. It is synthesized by 3 nitric oxide synthase (NOS) isoforms: neuronal, inducible, and endothelial NOS (eNOS). Aneurysmal subarachnoid hemorrhage (aSAH) causes endothelial dysfunction that, in turn, contributes to pathophysiologic processes surrounding aSAH. Previous studies reported an association of an eNOS single nucleotide polymorphism (SNP) with the clinical sequelae of aSAH. Here, we further elucidate the impact of this eNOS SNP on the clinical course after aSAH. METHODS: The Cerebral Aneurysm Renin Angiotensin System study prospectively enrolled aSAH patients at 2 academic institutions in the United States from 2012-2015. Blood samples from all patients enrolled in the study were used for genetic evaluation using 5'exonuclease (Taqman) genotyping assays. Associations between the eNOS SNP rs2070744 (786 T->C) and clinical course after aSAH were analyzed. RESULTS: Samples from 149 aSAH patients were available for analysis. The C allele of the eNOS SNP independently predicted an increased risk for delayed cerebral ischemia (OR = 2.936, 95% CI 1.048-8.226, P = 0.040). The eNOS SNP rs2070744 was not associated with functional outcome or size of aneurysm at the time of rupture. CONCLUSIONS: The present study is the first to demonstrate that the C allele of the eNOS SNP 786 T->C rs2070744 is independently associated with an increased risk for delayed cerebral ischemia following aSAH.

Associations of Endothelin Polymorphisms and Aneurysm Size at Time of Rupture.

BACKGROUND AND PURPOSE: Aneurysm size is an important risk factor for aneurysm rupture. The pathophysiologic mechanisms underlying aneurysm growth remain poorly understood. Endothelin signaling is critical for cerebrovascular blood flow regulation. The influence of endothelin single nucleotide polymorphisms (SNPs) on aneurysm size at the time of rupture has not been previously investigated. METHODS: Eight common endothelin SNPs were assessed using blood samples from aneurysmal subarachnoid hemorrhage (aSAH) patients enrolled in the Cerebral Aneurysm Renin Angiotensin System study, a prospective, 2-center study that enrolled aSAH patients and controls in the United States from 2012-2015. Genetic evaluation was performed using 5'exonnuclease (Taqman) genotyping assays. Associations of endothelin SNPs and aneurysm size were analyzed. RESULTS: One-hundred and forty-nine blood samples from aSAH patients were available for analysis. There was a dominant effect of the G allele of the endothelin receptor type A (EDNRA) SNP rs5335 on aneurysm size ≥7 mm (odds ratio = 2.740, 95% confidence interval 1.039-7.228, P = 0.042) along with associations with race and presence of additional aneurysms. The other endothelin SNPs were not associated with aneurysm size. CONCLUSIONS: The EDNRA SNP rs5335 was independently associated with aneurysms ≥7 mm in size at the time of rupture. Patients with cerebral aneurysms also carrying the G allele of EDNRA SNP rs5335 may develop larger aneurysms before rupture.

Impact of High-Mobility Group Box 1 Polymorphism on Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage.

BACKGROUND AND OBJECTIVE: The high-mobility group box 1 (HMGB1) protein is a eukaryotic, ubiquitously expressed protein that serves as a biomarker for various diseases and is involved in the promotion of a proinflammatory response to cell injury. In aneurysmal subarachnoid hemorrhage (aSAH), increased HMGB1 levels have been linked to poor outcome and an increased risk for cerebral vasospasm. The role of HMGB1 polymorphisms in aSAH has not been previously investigated. METHODS: Patients with aSAH and controls enrolled in the prospective, 2-center CARAS (Cerebral Aneurysm Renin Angiotensin System) study were evaluated. The 3814 C/G HMGB1 single nucleotide polymorphism (SNP) rs2249825 was detected using 5'exonuclease (Taqman) genotyping assays from blood samples from patients with aSAH and controls. Associations between aSAH and its clinical sequelae with the HMGB1 SNP were assessed. RESULTS: Samples from 149 patients with aSAH and 50 controls were available for analysis. No increased risk for aSAH associated with the SNP was found compared with the control group. Delayed cerebral ischemia (DCI) was defined as a cerebral infarction at the time of discharge from the intensive care unit and identified in 21.2% of patients with aSAH. In multivariable logistic regression analysis, the G allele of rs2249825 was independently associated with DCI (odds ratio, 5.695; 95% confidence interval, 1.804-17.975; P = 0.003). CONCLUSIONS: The minor allele G of rs2249825 was associated with an increased risk for DCI, or cerebral infarction, after aSAH. This finding may be attributable to an increased HMGB1 protein expression in these patients.

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.