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In the brain, vascular endothelial cells conserve blood viscosity, control blood flow, and form the interface between central nervous system and circulating blood. Clinical outcome after aneurysmal subarachnoid hemorrhage is linked to early brain injury, cerebral vasospasm, and other causes of delayed cerebral ischemia. The cerebral vasculature remains a unique target for therapies since it becomes rapidly disrupted after subarachnoid hemorrhage, and damage to the blood vessels continues into the delayed injury phase. The current failure of therapies to improve clinical outcome warrants a re-evaluation of current therapeutic approaches. The mechanisms of endothelial cell injury and blood–brain barrier breakdown are critical to the pathway of cerebral injury, and an improved understanding of these mechanisms may lead to novel therapeutic targets. This review provides an update on the current understanding of endothelial cell injury following aneurysmal subarachnoid hemorrhage, including blood–brain barrier dysfunction.

Background Inflammatory mechanism has been implicated in delayed cerebral ischemia (DCI) and poor functional outcomes after subarachnoid hemorrhage (SAH). Identification of cytokine patterns associated with inflammation in acute SAH will provide insights into underlying biological processes of DCI and poor outcomes that may be amenable to interventions. Methods Serum samples were collected from a prospective cohort of 60 patients with acute non-traumatic SAH at four time periods (< 24 h, 24–48 h, 3–5 days, and 6–8 days after SAH) and concentration levels of 41 cytokines were measured by multiplex immunoassay. Logistic regression analysis was used to identify cytokines associated with DCI and poor functional outcomes. Correlation networks were constructed to identify cytokine clusters. Results Of the 60 patients enrolled in the study, 14 (23.3%) developed DCI and 16 (26.7%) had poor functional outcomes at 3 months. DCI was associated with increased levels of PDGF-ABBB and CCL5 and decreased levels of IP-10 and MIP-1α. Poor functional outcome was associated with increased levels of IL-6 and MCP-1α. Network analysis identified distinct cytokine clusters associated with DCI and functional outcomes. Conclusions Serum cytokine patterns in early SAH are associated with poor functional outcomes and DCI. The significant cytokines primarily modulate the inflammatory response. This supports earlier SAH studies linking inflammation and poor outcomes. In particular, this study identifies novel cytokine patterns over time that may indicate impending DCI.

PurposePituitary apoplexy can be a life threatening and vision compromising event. Antiplatelet and anticoagulation use has been reported as a contributing factor in pituitary apoplexy (PA). Utilizing one of the largest cohorts in the literature, this study aims to determine the risk of PA in patients on antiplatelet/anticoagulation (AP/AC) therapy.MethodsA single center, retrospective study was conducted on 342 pituitary adenoma patients, of which 77 patients presented with PA (23%). Several potential risk factors for PA were assessed, including: patient demographics, tumor characteristics, pre-operative hormone replacement, neurologic deficits, coagulation studies, platelet count, and AP/AC therapy.ResultsComparing patients with and without apoplexy, there was no significant difference in the proportion of patients taking aspirin (45 no apoplexy vs. 10 apoplexy; p = 0.5), clopidogrel (10 no apoplexy vs. 4 apoplexy; p = 0.5), and anticoagulation (7 no apoplexy vs. 3 apoplexy; p = 0.7). However, male sex (p-value < 0.001) was a predictor for apoplexy while pre-operative hormone treatment was a protective factor from apoplexy (p-value < 0.001). A non-clinical difference in INR was also noted as a predictor for apoplexy (no apoplexy: 1.01 ± 0.09, apoplexy: 1.07 ± 0.15; p < 0.001).ConclusionsAlthough pituitary tumors have a high risk for spontaneous hemorrhage, the use of aspirin is not a risk for hemorrhage. Our study did not find an increased risk of apoplexy with clopidogrel or anticoagulation, but further investigation is needed with a larger cohort. Confirming other reports, male sex is associated with an increased risk for PA.

The vessels of the central nervous system (CNS) have unique barrier properties. The endothelial cells (ECs) which comprise the CNS vessels contribute to the barrier via strong tight junctions, specific transporters, and limited endocytosis which combine to protect the brain from toxins and maintains brain homeostasis. Blood–brain barrier (BBB) leakage is a serious secondary injury in various CNS disorders like stroke, brain tumors, and neurodegenerative disorders. Currently, there are no drugs or therapeutics available to treat specifically BBB damage after a brain injury. Growing knowledge in the field of epigenetics can enhance the understanding of gene level of the BBB and has great potential for the development of novel therapeutic strategies or targets to repair a disrupted BBB. In this brief review, we summarize the epigenetic mechanisms or regulators that have a protective or disruptive role for components of BBB, along with the promising approaches to regain the integrity of BBB.

Aneurysmal subarachnoid hemorrhage (aSAH) causes a robust inflammatory response which leads worse brain injury and poor outcomes. We investigated if stimulation of nicotinic acetylcholine α7 receptors (α7-AChR) (receptors shown to have anti-inflammatory effects) would reduce inflammation and improve outcomes. To investigate the level of peripheral inflammation after aSAH, inflammatory markers were measured in plasma samples collected in a cohort of aSAH patients. To study the effect of α7-AChR stimulation, SAH was induced in adult mice which were then treated with a α7-AChR agonist, galantamine, or vehicle. A battery of motor and cognitive tests were performed 24 h after subarachnoid hemorrhage. Mice were euthanized and tissue collected for analysis of markers of inflammation or activation of α7-AChR-mediated transduction cascades. A separate cohort of mice was allowed to survive for 28 days to assess long-term neurological deficits and histological outcome. Microglia cell culture subjected to hemoglobin toxicity was used to assess the effects of α7-AChR agonism. Analysis of eighty-two patient plasma samples confirmed enhanced systemic inflammation after aSAH. α7-AChR agonism reduced neuroinflammation at 24 h after SAH in male and female mice, which was associated with improved outcomes. This coincided with JAK2/STAT3 and IRAK-M activity modulations and a robust improvement in neurological/cognitive status that was effectively reversed by interfering with various components of these signaling pathways. Pharmacologic inhibition partially reversed the α7-AChR agonist's benefits, supporting α7-AChR as a target of the agonist's therapeutic effect. The cell culture experiment showed that α7-AChR agonism is directly beneficial to microglia. Our results demonstrate that activation of α7-AChR represents an attractive target for treatment of SAH. Our findings suggest that α7-AChR agonists, and specifically galantamine, might provide therapeutic benefit to aSAH patients.

The blood-brain barrier (BBB) controls the movement of molecules into and out of the central nervous system (CNS). Since a functional BBB forms by mouse embryonic day E15.5, we reasoned that gene cohorts expressed in CNS endothelial cells (EC) at E13.5 contribute to BBB formation. In contrast, adult gene signatures reflect BBB maintenance mechanisms. Supporting this hypothesis, transcriptomic analysis revealed distinct cohorts of EC genes involved in BBB formation and maintenance. Here, we demonstrate that epigenetic regulator’s histone deacetylase 2 (HDAC2) and polycomb repressive complex 2 (PRC2) control EC gene expression for BBB development and prevent Wnt/β-catenin (Wnt) target genes from being expressed in adult CNS ECs. Low Wnt activity during development modifies BBB genes epigenetically for the formation of functional BBB. As a Class-I HDAC inhibitor induces adult CNS ECs to regain Wnt activity and BBB genetic signatures that support BBB formation, our results inform strategies to promote BBB repair.

Background: Aneurysmal subarachnoid hemorrhage (aSAH) is notoriously known for its high mortality and morbidity. Approximately one-third of the patients who survive aneurysm rupture are reported to develop delayed cerebral ischemia (DCI), which contributes to a poor clinical outcome. Currently, there are no biomarkers for identifying which aSAH patients are at risk of developing DCI. We aimed to determine the feasibility of cerebrospinal fluid (CSF) exosomal microRNAs (miRNAs) for predicting DCI post-aSAH. Methods: aSAH patients were prospectively enrolled, and CSF samples were collected at two time points (<24 h and 72 h post-aSAH) from individuals undergoing external ventricular drainage. Exosomal miRNAs were isolated from the CSF for analysis. In the initial group of patients (discovery cohort), an exploratory analysis was conducted using a CSF panel containing 84 miRNAs, assessed by quantitative real-time PCR (RT-qPCR). Based on this analysis, 27 miRNAs were selected for further evaluation in a second group of patients (validation cohort). Among these, 10 miRNAs had previously been reported in SAH-related CSF studies, supporting their relevance for continued investigation. Results: In this study, RT-qPCR analysis of 84 miRNAs in CSF samples from aSAH patients (n = 10 DCI, n = 16 no DCI) and non-aSAH controls (n = 5) identified 9 upregulated and 13 downregulated miRNAs in the DCI group, and 7 upregulated and 18 downregulated miRNAs in the no-DCI group, compared to the controls. When comparing DCI to no-DCI patients, 13 miRNAs were found to be upregulated in the DCI group. Additionally, seven miRNAs showed temporal upregulation in DCI patients between early (<24 h/T1) and later (72 h/T3) time points across both discovery and validation cohorts. However, no miRNAs were uniquely expressed in either DCI or no-DCI groups, limiting their potential as specific biomarkers for DCI. Conclusions: Despite analyses in both the discovery and validation phases, no miRNAs emerged as consistent and reliable biomarkers for distinguishing DCI from no-DCI patients. However, the identified miRNAs are involved in the key KEGG pathways that regulate vascular integrity, neuronal survival, and inflammatory processes central to DCI pathophysiology. These findings highlight the complexity of miRNA regulation following aSAH, as reflected by the variability in differentially expressed miRNAs between cohorts. This variability may be influenced by factors such as limited sample size, patient heterogeneity, individual biological differences, and experimental variability. Comprehensive profiling using larger, well-characterized cohorts, along with rigorous validation, is essential to determine the predictive value and mechanistic significance of candidate miRNAs in DCI.

Haemoglobin is released into the CNS during the breakdown of red blood cells after intracranial bleeding. Extracellular free haemoglobin is directly neurotoxic. Haemoglobin scavenging mechanisms clear haemoglobin and reduce toxicity; these mechanisms include erythrophagocytosis, haptoglobin binding of haemoglobin, haemopexin binding of haem and haem oxygenase breakdown of haem. However, the capacity of these mechanisms is limited in the CNS, and they easily become overwhelmed. Targeting of haemoglobin toxicity and scavenging is, therefore, a rational therapeutic strategy. In this Review, we summarize the neurotoxic mechanisms of extracellular haemoglobin and the peculiarities of haemoglobin scavenging pathways in the brain. Evidence for a role of haemoglobin toxicity in neurological disorders is discussed, with a focus on subarachnoid haemorrhage and intracerebral haemorrhage, and emerging treatment strategies based on the molecular pathways involved are considered. By focusing on a fundamental biological commonality between diverse neurological conditions, we aim to encourage the application of knowledge of haemoglobin toxicity and scavenging across various conditions. We also hope that the principles highlighted will stimulate research to explore the potential of the pathways discussed. Finally, we present a consensus opinion on the research priorities that will help to bring about clinical benefits.

Introduction. The best treatment for unruptured middle cerebral artery (MCA) aneurysms is unclear. We perform a meta-analysis of recent publications to evaluate the results of unruptured MCA aneurysms treated with surgical clipping and endovascular coiling. Methods. A PubMed search for articles published between January 2004 and November 2013 was performed. The R statistical software package was used to create a random effects model for each desired incidence rate. Cochran’s Q test was used to evaluate possible heterogeneity among the rates observed in each study. Results. A total of 1891 unruptured MCA aneurysms, 1052 clipped and 839 coiled, were included for analysis. The complete occlusion rate at 6–9 months mean follow-up was 95.5% in the clipped group and 67.8% in the coiled group ( P < 0.05 ). The periprocedural thromboembolism rate in the clipping group was 1.8% compared with 10.7% in the aneurysms treated by coiling ( P < 0.05 ). The recanalization rate was 0% for clipping and 14.3% for coiling ( P = 0.05 ). Modified Rankin scores of 0–2 were obtained in 98.9% of clipped patients compared to 95.5% of coiled (NS). Conclusions. This review weakly supports clipping as the preferred treatment of unruptured MCA aneurysms. Clinical outcomes did not differ significantly between the two groups.

Dysembryoplastic neuroepithelial tumors (DNETs) have traditionally been viewed as benign “quasihamartomatous” tumors widely considered curable with surgery alone. More recently, case reports have described malignant gliomas arising after irradiation and recurrences following subtotal or even gross total resection. Herein, we describe five cases of DNET with recurrences 2–7 years after resection. Although the radiology was often alarming (e.g., new ring enhancing mass), the pathology remained benign in most cases. Nonetheless, a probably radiation induced anaplastic astrocytoma was encountered in one case 7 years after therapy. These findings suggest that these patients may need closer follow-up than initially suggested, lending further support to the notion that this tumor behaves more like a benign neoplasm, rather than a dysplastic or hamartomatous lesion.