TLR4 (Toll-Like Receptor 4) Mediates the Development of Intracranial Aneurysm Rupture

Identification of differentially expressed autophagy-related genes in cases of intracranial aneurysm: Bioinformatics analysis

OBJECTIVE

Recent research indicates that autophagy is essential for the rupture of intracranial aneurysm (IA). This study aimed to examine and validate potential autophagy-related genes (ARGs) in cases of IA using bioinformatics analysis.

METHODS

Two expression profiles (GSE54083 and GSE75436) were obtained from the Gene Expression Omnibus database. Differentially expressed ARGs (DEARGs) in cases of IA were screened using GSE75436, and enrichment analysis and Protein-Protein Interaction (PPI) networks were used to identify the hub genes and related pathways. Furthermore, a novel predictive diagnostic signature for IA based on the hub genes was constructed. The area under the Receiver Operating Characteristic curve (AUC) was used to evaluate the signature performance in GSE75436.

RESULTS

In total, 75 co-expressed DEARGs were identified in the GSE75436 and GSE54083 dataset (28 upregulated and 47 downregulated genes). Enrichment analysis of DEARGs revealed several enriched terms associated with proteoglycans in cancer and human immunodeficiency virus 1 infection. PPI analysis revealed interactions between these genes. Hub DEARGs included insulin-like growth factor 1, clusters of differentiation 4, cysteine-aspartic acid protease 8, Bcl-2-like protein 11, mouse double mutant 2 homolog, toll-like receptor 4, growth factor receptor-bound protein 2, Jun proto-oncogene, AP-1 transcription factor subunit, hypoxia inducible factor 1 alpha, and erythroblastic oncogene B-2. Notably, the signature showed good performance in distinguishing IA (AUC = 0.87). The sig calibration curves showed good calibration.

CONCLUSION

Bioinformatic analysis identified 75 potential DEARGs in cases of IA. This study revealed that IA is affected by autophagy, which could explain the pathogenesis of IA and aid in its diagnosis and treatment. However, future research with experimental validation is necessary to identify potential DEARGs in cases of IA.

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.

Pharmacological Inhibition of Epidermal Growth Factor Receptor Prevents Intracranial Aneurysm Rupture by Reducing Endoplasmic Reticulum Stress

BACKGROUND

Multiple pathways and factors are involved in the rupture of intracranial aneurysms. The EGFR (epidermal growth factor receptor) has been shown to mediate inflammatory vascular diseases, including atherosclerosis and aortic aneurysm. However, the role of EGFR in mediating intracranial aneurysm rupture and its underlying mechanisms have yet to be determined. Emerging evidence indicates that endoplasmic reticulum (ER) stress might be the link between EGFR activation and the resultant inflammation. ER stress is strongly implicated in inflammation and apoptosis of vascular smooth muscle cells, both of which are key components of the pathophysiology of aneurysm rupture. Therefore, we hypothesized that EGFR activation promotes aneurysmal rupture by inducing ER stress.

METHODS

Using a preclinical mouse model of intracranial aneurysm, we examined the potential roles of EGFR and ER stress in developing aneurysmal rupture.

RESULTS

Pharmacological inhibition of EGFR markedly decreased the rupture rate of intracranial aneurysms without altering the formation rate. EGFR inhibition also significantly reduced the mRNA (messenger RNA) expression levels of ER-stress markers and inflammatory cytokines in cerebral arteries. Similarly, ER-stress inhibition also significantly decreased the rupture rate. In contrast, ER-stress induction nullified the protective effect of EGFR inhibition on aneurysm rupture.

CONCLUSIONS

Our data suggest that EGFR activation is an upstream event that contributes to aneurysm rupture via the induction of ER stress. Pharmacological inhibition of EGFR or downstream ER stress may be a promising therapeutic strategy for preventing aneurysm rupture and subarachnoid hemorrhage.

Peripheral macrophages in the development and progression of structural cerebrovascular pathologies

The human cerebrovascular system is responsible for maintaining neural function through oxygenation, nutrient supply, filtration of toxins, and additional specialized tasks. While the cerebrovascular system has resilience imparted by elaborate redundant collateral circulation from supportive tertiary structures, it is not infallible, and is susceptible to developing structural vascular abnormalities. The causes of this class of structural cerebrovascular diseases can be broadly categorized as 1) intrinsic developmental diseases resulting from genetic or other underlying aberrations (arteriovenous malformations and cavernous malformations) or 2) extrinsic acquired diseases that cause compensatory mechanisms to drive vascular remodeling (aneurysms and arteriovenous fistulae). Cerebrovascular diseases of both types pose significant risks to patients, in some cases leading to death or disability. The drivers of such diseases are extensive, yet inflammation is intimately tied to all of their progressions. Central to this inflammatory hypothesis is the role of peripheral macrophages; targeting this critical cell type may lead to diagnostic and therapeutic advancement in this area. Here, we comprehensively review the role that peripheral macrophages play in cerebrovascular pathogenesis, provide a schema through which macrophage behavior can be understood in cerebrovascular pathologies, and describe emerging diagnostic and therapeutic avenues in this area.

Current understanding of macrophages in intracranial aneurysm: relevant etiological manifestations, signaling modulation and therapeutic strategies

Macrophages activation and inflammatory response play crucial roles in intracranial aneurysm (IA) formation and progression. The outcome of ruptured IA is considerably poor, and the mechanisms that trigger IA progression and rupture remain to be clarified, thereby developing effective therapy to prevent subarachnoid hemorrhage (SAH) become difficult. Recently, climbing evidences have been expanding our understanding of the macrophages relevant IA pathogenesis, such as immune cells population, inflammatory activation, intra-/inter-cellular signaling transductions and drug administration responses. Crosstalk between macrophages disorder, inflammation and cellular signaling transduction aggravates the devastating consequences of IA. Illustrating the pros and cons mechanisms of macrophages in IA progression are expected to achieve more efficient treatment interventions. In this review, we summarized the current advanced knowledge of macrophages activation, infiltration, polarization and inflammatory responses in IA occurrence and development, as well as the most relevant NF-κB, signal transducer and activator of transcription 1 (STAT1) and Toll-Like Receptor 4 (TLR4) regulatory signaling modulation. The understanding of macrophages regulatory mechanisms is important for IA patients' clinical outcomes. Gaining insight into the macrophages regulation potentially contributes to more precise IA interventions and will also greatly facilitate the development of novel medical therapy.

Analysis of independent risk factors for aneurysm rupture based on carotid tortuosity index and morphological parameters of single intracranial aneurysms in anterior circulation

PURPOSE

Our study focused on the risk factors associated with anterior circulation intracranial aneurysm (IA) rupture by examining the carotid artery (CA) tortuosity index (TI) and anterior circulation IA morphological parameters.

METHOD

This study conducted a retrospective analysis of clinical and imaging data from 163 patients with anterior circulation IA diagnosed by head and neck computed tomography angiography (CTA). The patients were categorized into two groups: the ruptured group (57 cases) and the unruptured group (106 cases). CA was categorized based on its location into three segments: the extracranial segment of the internal carotid artery (EICA) TI, the angle of the internal carotid artery (ICA) and the common carotid artery (CCA) TI. Measure the morphological parameters of all IA: IA length neck (L), IA height (H), aneurysm diameter width (D), the ratio of L to the mean diameter of the IA-bearing artery (SR), the ratio of H to D (AR), the angle of flow inflow (FA) and IA angle (AA). The study conducted five types of analysis to determine the risk factors for anterior circulation IA rupture. The first was an univariate analysis of the risk factors. The second was an analysis of the correlation between CA TI and IA morphological parameters. The third used multivariate logistic stepwise regression analysis to analyse independent risk factors for IA rupture. The fourth was to plot ROC curves to build a predictive model for IA rupture and calculate diagnostic thresholds. Finally, a data set from another hospital (78 cases) was used as a validation set to validate the multivariate model.

RESULT

Univariate analysis revealed that there were statistically significant differences (P < 0.05) in gender, EICA TI, location of IA and IA morphological parameters (FA, H, AR, L, SR), which acted as risk factors for anterior circulation IA rupture. The results of Spearman correlation analysis indicate that CCA TI is significantly correlated with SR, H and L (P < 0.05), while EICA TI is significantly correlated with FA and L (P < 0.05). The results of multivariate logistic analysis showed that FA (OR = 1.072, 95%CI = 1.04-1.10, P < 0.001), SR (OR = 4.949, 95%CI = 1.96-12.53, P = 0.001), EICA TI (OR = 1.037, 95%CI = 1.01-1.07, P = 0.003) were independent risk factors for IA rupture. The ROC curve plotting results suggest that the area under the curve (AUC) of FA is 0.860 with a diagnostic threshold of 110.1°; the AUC of SR is 0.786 with a diagnostic threshold of 1.67; the AUC of EICA TI is 0.723 with a diagnostic threshold of 28.845; the AUC of the three combined is 0.903 with a threshold of 0.480. The combined factor diagnostic model is validated according to the validation set, and the results show that the AUC (0.866) of the validation set is not much different from the AUC (0.903) of the multivariate model, and the multivariate model has a better diagnostic effect.

CONCLUSION

In clinical practice, it is important to consider the evaluation of aneurysm rupture in combination with imaging, as FA, SR and ECIA TI are independent risk factors for IA rupture in the anterior circulation. Unlike the IA morphological parameters, EICA TI is an often overlooked extracranial parameter, but is equally important in its power to predict IA rupture. When the EICA TI exceeds 28.845, the IA has the possibility of rupture. Finally, multivariate diagnostic model are of interest when considering rupture of the anterior circulation IA.

Molecular Subtypes and Machine Learning-Based Predictive Models for Intracranial Aneurysm Rupture

BACKGROUND

The determination of biological mechanisms and biomarkers related to intracranial aneurysm (IA) rupture is of utmost significance for the development of effective preventive and therapeutic strategies in the clinical field.

METHODS

GSE122897 and GSE13353 datasets were downloaded from Gene Expression Omnibus. Data extracted from GSE122897 were used for analyzing differential gene expression, and consensus clustering was performed to identify stable molecular subtypes. Clinical characteristics were compared between subgroups, and fast gene set enrichment analysis and weighted gene coexpression network analysis were performed. Hub genes were identified via least absolute shrinkage and selection operator analysis. Predictive models were constructed based on hub genes using the Light Gradient Boosting Machine, eXtreme Gradient Boosting, and logistic regression algorithm. Immune cell infiltration in IA samples was analyzed using Microenvironment Cell Population counter, CIBERSORT, and xCell algorithm. The correlation between hub genes and immune cells was analyzed. The predictive model and immune cell infiltration were validated using data from the GSE13353 dataset.

RESULTS

A total of 43 IA samples were classified into 2 subgroups based on gene expression profiles. Subgroup I had a higher risk of rupture, while 70% of subgroup II remained unruptured. In subgroup I, specific genes were associated with inflammation and immunity, and weighted gene coexpression network analysis revealed that the black module genes were linked to IA rupture. We identified 4 hub genes (spermine synthase, macrophage receptor with collagenous structure, zymogen granule protein 16B, and LIM and calponin-homology domains 1), which constructed predictive models with good diagnostic performance in differentiating between ruptured and unruptured IA samples. Monocytic lineage was found to be a significant factor in IA rupture, and the 4 hub genes were linked to monocytic lineage (P < 0.05).

CONCLUSIONS

We reveal a new molecular subtype that can reflect the actual pathological state of IA rupture, and our predictive models constructed by machine learning algorithms can efficiently predict IA rupture.

Identifying pyroptosis- and inflammation-related genes in intracranial aneurysms based on bioinformatics analysis

BACKGROUND

Intracranial aneurysm (IA) is the most common cerebrovascular disease, and subarachnoid hemorrhage caused by its rupture can seriously impede nerve function. Pyroptosis is an inflammatory mode of cell death whose underlying mechanisms involving the occurrence and rupture of IAs remain unclear. In this study, using bioinformatics analysis, we identified the potential pyroptosis-related genes (PRGs) and performed their inflammatory response mechanisms in IAs.

METHODS

The mRNA expression matrix of the IA tissue was obtained from the Gene Expression Omnibus database, and 51 PRGs were obtained from previous articles collected from PubMed. The differentially expressed PRGs (DEPRGs) were performed using R software. Subsequently, we performed enrichment analysis, constructed a protein-protein interaction network, performed weighted gene coexpression network analysis (WGCNA) and external validation using another dataset, and identified a correlation between hub genes and immune cell infiltration. Finally, the expression and tissue distribution of these hub genes in IA tissues were detected using Western blotting and immunohistochemical (IHC) staining.

RESULTS

In total, 12 DEPRGs associated with IA were identified in our analysis, which included 11 up-regulated and one down-regulated genes. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses revealed that the DEPRGs were mostly enriched in the NOD-like receptor signaling pathway, interleukin-1 beta production, and the inflammasome complex. Three hub genes, NLRP3, IL1B and IL18, were identified using Cytoscape software and the WGCNA correlation module, and external validation revealed statistically significant differences between the expression of these hub genes in the ruptured and unruptured aneurysm groups (p < 0.05). Furthermore, all AUC values were > 0.75. Immune cell infiltration analysis suggested that the hub genes are related to CD8 T cell, macrophages and mast cells. Finally, IHC staining revealed that the protein levels of these hub genes were higher in ruptured and unruptured IA tissues than in normal tissues (p < 0.05).

CONCLUSION

The results of bioinformatics analysis showed that pyroptosis is closely related to the formation and rupture of IA, and identified three potential hub genes involved in the pyroptosis and infiltration ofcells. Our findings may improve the understanding of the mechanisms underlying pyroptosis in IA.

Integrative analysis of multi-omics data to identify three immune-related genes in the formation and progression of intracranial aneurysms

OBJECTIVE AND DESIGN

The prevalence of intracranial aneurysms (IAs) has increased globally. We performed bioinformatics analysis to identify key biomarkers associated with IA formation.

METHODS AND RESULTS

We conducted a comprehensive analysis combined with multi-omics data and methods to identify immune-related genes (IRGs) and immunocytes involved in IAs. Functional enrichment analyses showed enhanced immune responses and suppressed organizations of extracellular matrix (ECM) during aneurysm progression. xCell analyses showed that the abundance of B cells, macrophages, mast cells, and monocytes significantly increased from levels in control to unruptured aneurysms and to ruptured aneurysms. Of 21 IRGs identified by overlapping, a three-gene (CXCR4, S100B, and OSM) model was constructed through LASSO logistic regression. The diagnostic ability of the three biomarkers in discriminating aneurysms from the control samples demonstrated a favorable diagnostic value. Among the three genes, OSM and CXCR4 were up-regulated and hypomethylated in IAs, while S100B was down-regulated and hypermethylated. The expression of the three IRGs was further validated by qRT-PCR and immunohistochemistry and mouse IA model using scRNA-seq analysis.

CONCLUSION

The present study demonstrated heightened immune response and suppressed ECM organization in aneurysm formation and rupture. The three-gene immune-related signature (CCR4, S100B, and OSM) model may facilitate IA diagnosis and prevention.

Artemisinin exerts a protective effect in the MPTP mouse model of Parkinson's disease by inhibiting microglial activation via the TLR4/Myd88/NF-KB pathway

AIMS

We performed cell and animal experiments to explore the therapeutic effect of artemisinin on Parkinson's disease (PD) and the TLR4/Myd88 signaling pathway.

METHODS

C57 mice were randomly divided into the blank, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced and artemisinin-treated groups. Clinical symptoms, the number of dopaminergic (DAergic) neurons in the substantia nigra, and microglial cell activation were compared among the three groups. Subsequently, BV-2 cell activation and TLR4/Myd88 pathway component expression were compared among the blank, MPP⁺ -treated, artemisinin-treated, and TLR4 activator-treated groups.

RESULTS

Behavioral symptoms were improved, the number of DAergic neurons in the substantia nigra of the midbrain was increased, and microglial cell activation was decreased in artemisinin-treated MPTP-induced PD model mice compared with control-treated MPTP-induced PD model mice (p < 0.05). The cell experiments revealed that artemisinin treatment reduced MPP⁺ -induced BV-2 cell activation and inhibited the TLR4/Myd88 signaling pathway. Moreover, the effect of artemisinin on the BV-2 cell model was inhibited by the TLR4 activator LPS (p < 0.05).

CONCLUSION

Artemisinin may reduce damage to DAergic neurons in a PD mouse model by decreasing microglial activation through the TLR4-mediated MyD88-dependent signaling pathway. However, this finding cannot explain the relationship between microglia and DAergic neurons.

A machine learning-derived gene signature for assessing rupture risk and circulatory immunopathologic landscape in patients with intracranial aneurysms

Background

Intracranial aneurysm (IA) is an uncommon but severe subtype of cerebrovascular disease, with high mortality after aneurysm rupture. Current risk assessments are mainly based on clinical and imaging data. This study aimed to develop a molecular assay tool for optimizing the IA risk monitoring system.

Methods

Peripheral blood gene expression datasets obtained from the Gene Expression Omnibus were integrated into a discovery cohort. Weighted gene co-expression network analysis (WGCNA) and machine learning integrative approaches were utilized to construct a risk signature. QRT-PCR assay was performed to validate the model in an in-house cohort. Immunopathological features were estimated using bioinformatics methods.

Results

A four-gene machine learning-derived gene signature (MLDGS) was constructed for identifying patients with IA rupture. The AUC of MLDGS was 1.00 and 0.88 in discovery and validation cohorts, respectively. Calibration curve and decision curve analysis also confirmed the good performance of the MLDGS model. MLDGS was remarkably correlated with the circulating immunopathologic landscape. Higher MLDGS scores may represent higher abundance of innate immune cells, lower abundance of adaptive immune cells, and worse vascular stability.

Conclusions

The MLDGS provides a promising molecular assay panel for identifying patients with adverse immunopathological features and high risk of aneurysm rupture, contributing to advances in IA precision medicine.

Animal model contributes to the development of intracranial aneurysm: A bibliometric analysis

Introduction

Studies on intracranial aneurysms (IAs) using animal models have evolved for decades. This study aimed to analyze major contributors and trends in IA-related animal research using bibliometric analysis.

Methods

IA-related animal studies were retrieved from the Web of Science database. Microsoft Excel 2010, GraphPad Prism 6, VOSviewer, and CiteSpace were used to collect and analyze the characteristics of this field.

Results

A total of 273 publications were retrieved. All publications were published between 1976 and 2021, and the peak publication year is 2019. Rat model were used in most of the publications, followed by mice and rabbits. Japan (35.5%), the United States (30.0%), and China (20.1%) were the top three most prolific countries. Although China ranks third in the number of publications, it still lacks high-quality articles and influential institutions. Stroke was the most prolific journal that accepted publications related to IA research using animal models. Circulation has the highest impact factor with IA-related animal studies. Hashimoto N contributed the largest number of articles. Meng hui journal published the first and second highest cited publications. The keywords “subarachnoid hemorrhage,” “macrophage,” “rupture,” “mice,” “elastase,” “gene,” “protein,” “proliferation,” and “risk factors” might be a new trend for studying IA-related animal research.

Conclusions

Japan and the Unites States contributed the most to IA–related animal studies, in terms of both researchers and institutions. Although China ranks third in terms of the number of publications, it should strengthen the quality of its publications. Researchers should pay attention to the latest progress of Stroke, Journal of Neurosurgery, Neurosurgery, and Circulation for their high-quality IA-related animal studies. Using animal IA models, especially mice, to investigate the molecular mechanisms of IA may be the frontier topic now and in future.

TLR4-Pathway-Associated Biomarkers in Subarachnoid Hemorrhage (SAH): Potential Targets for Future Anti-Inflammatory Therapies

Subarachnoid hemorrhage is associated with severe neurological deficits for survivors. Among survivors of the initial bleeding, secondary brain injury leads to additional brain damage. Apart from cerebral vasospasm, secondary brain injury mainly results from cerebral inflammation taking place in the brain parenchyma after bleeding. The brain’s innate immune system is activated, which leads to disturbances in brain homeostasis, cleavage of inflammatory cytokines and, subsequently, neuronal cell death. The toll-like receptor (TLR)4 signaling pathway has been found to play an essential role in the pathophysiology of acute brain injuries such as subarachnoid hemorrhage (SAH). TLR4 is expressed on the cell surface of microglia, which are key players in the cellular immune responses of the brain. The participants in the signaling pathway, such as TLR4-pathway-like ligands, the receptor itself, and inflammatory cytokines, can act as biomarkers, serving as clues regarding the inflammatory status after SAH. Moreover, protein complexes such as the NLRP3 inflammasome or receptors such as TREM1 frame the TLR4 pathway and are indicative of inflammation. In this review, we focus on the activity of the TLR4 pathway and its contributors, which can act as biomarkers of neuroinflammation or even offer potential new treatment targets for secondary neuronal cell death after SAH.

Cellular loci involved in the development of brain arteriovenous malformations

Brain arteriovenous malformations (bAVMs) are abnormal vessels that are prone to rupture, causing life-threatening intracranial bleeding. The mechanism of bAVM formation is poorly understood. Nevertheless, animal studies revealed that gene mutation in endothelial cells (ECs) and angiogenic stimulation are necessary for bAVM initiation. Evidence collected through analyzing bAVM specimens of human and mouse models indicate that cells other than ECs also are involved in bAVM pathogenesis. Both human and mouse bAVMs vessels showed lower mural cell-coverage, suggesting a role of pericytes and vascular smooth muscle cells (vSMCs) in bAVM pathogenesis. Perivascular astrocytes also are important in maintaining cerebral vascular function and take part in bAVM development. Furthermore, higher inflammatory cytokines in bAVM tissue and blood demonstrate the contribution of inflammatory cells in bAVM progression, and rupture. The goal of this paper is to provide our current understanding of the roles of different cellular loci in bAVM pathogenesis.

Novel insight into ferroptosis-related genes, molecular subtypes, and immune characteristics in intracranial aneurysms

OBJECTIVES

This study aimed to identify the role of ferroptosis in intracranial aneurysm (IA).

METHODS

GSE122897, GSE75436, GSE15629, and GSE75434 datasets were downloaded from the Gene Expression Omnibus database. The differentially expressed ferroptosis-related genes (DEFRGs) were selected to construct a diagnostic model integrating with machine learning. Then, a consensus clustering algorithm was performed to classify IA patients into distinct ferroptosis-related clusters. Functional analyses, including GO, KEGG, GSVA, and GSEA analyses, were conducted to elucidate the underlying mechanisms. ssGSEA and xCell algorithms were performed to uncover the immune characteristics.

RESULTS

We identified 28 DEFRGs between IAs and controls from the GSE122897 dataset. GO and KEGG results showed that these genes were enriched in cytokine activity, ferroptosis, and the IL-17 signaling pathway. Immune analysis showed that the IAs had higher levels of immune infiltration. A four FRGs model (MT3, CDKN1A, ZEP69B, and ABCC1) was established and validated with great IA diagnostic ability. We divided the IA samples into two clusters and found that cluster 2 had a higher proportion of rupture and immune infiltration. We identified 10 ferroptosis phenotypes-related markers in IAs.

CONCLUSION

Ferroptosis and the immune microenvironment are closely associated with IAs, providing a basis for understanding the IA development.

High-Dimensional Immune Profiling by Mass Cytometry Revealed the Circulating Immune Cell Landscape in Patients With Intracranial Aneurysm

Background

Increasing evidence supports a critical role of chronic inflammation in intracranial aneurysm (IA). Understanding how the immunological alterations in IA provides opportunities for targeted treatment. However, there is a lack of comprehensive and detailed characterization of the changes in circulating immune cells in IA.

Objective

To perform a comprehensive and detailed characterization of the changes in circulating immune cells in patients with IA.

Methods

Peripheral blood mononuclear cell samples from IA patients (n = 26) and age-and sex-matched healthy controls (HCs, n = 20) were analyzed using high dimensional mass cytometry, and the frequency and phenotype of immune cell subtypes were assessed.

Results

We identified 28 cell clusters and found that the immune signature of IA consists of cluster changes. IA patients exhibited dysfunction of immunity, with dysregulation of CD4⁺ T-cell clusters, increased B cells and monocytes, and decreased CD8⁺ T cells, DNT cells, and DPT cells. Moreover, compared with findings in HC, IA was associated with enhanced lymphocyte and monocyte immune activation, with a higher expression of HLA-DR, CXCR3, and CX3CR1. In addition, the expression of TLR4, p-STAT3, and the exhaustion marker PD1 was increased in T cells, B cells, and NK cells in IA patients.

Conclusions

Our data provide an overview of the circulating immune cell landscape of IA patients, and reveal that the dysfunction of circulating immunity may play a potential role in the development of IA.

RNA sequencing analysis between ruptured and un-ruptured brain AVM

BACKGROUND

A brain arteriovenous malformation (BAVM) is a tangle of abnormal blood vessels connecting the arteries and veins in the brain and is associated with a higher risk for intracerebral hemorrhage (ICH). RNA sequencing technology has been recently used to investigate the mechanism of diseases owing to its ability to identify the gene changes on a transcriptome-wide level. This study aims to gain insights into the potential mechanism involved in BAVM rupture.

METHODS

Sixty-five BAVM nidus samples were collected, among which 28 were ruptured and 37 were un-ruptured. Then, next-generation RNA sequencing was performed on all of them to obtain differential expressed genes (DEGs) between the two groups. In addition, bioinformatics analysis was performed to evaluate the involved biological processes and pathways by GO and KEGG analysis. Finally, we performed a univariate Cox regression analysis to obtain the early rupture-prone DEGs.

RESULTS

A total of 951 genes were differentially expressed between the ruptured and un-ruptured BAVM groups, of which 740 genes were upregulated and 211 genes were downregulated in ruptured BAVMs. Then, bioinformatics analysis showed the biological processes and pathways related to the inflammatory processes and extracellular matrix organization were significantly enriched. Meanwhile, some downregulated genes are involved in cell adhesion and genes participating in response to muscle activity and the terms of nervous system development. Finally, one hundred twenty-five genes, many were involved in inflammation, were correlated with the early rupture of BAVMs.

CONCLUSIONS

The upregulated genes in the ruptured BAVM group were involved in inflammatory processes and extracellular matrix organization. Some of the downregulated genes participated in cell adhesion and myofibril assembly, indicating the role of enhanced inflammation and reduced inflammation vessel strength in BAVMs rupture.

Identification of Potential Core Genes for the Rupture of Intracranial Aneurysms by a Bioinformatics Analysis

Background: Previous studies, using autopsy and angiography, have shown that 3.6–6% of the population have intracranial aneurysms, and the rupture of aneurysm can lead to brain dysfunction or even death in patients.

Methods: To explore potential preventional target genes for the ruptured of aneurysm, we analyze three gene expression datasets (GSE13353, GSE15629 and GSE54083) derived from the GEO database. We confirm DEGs associated with the unrupture of aneurysms by R package. DAVID version provides functional classification and annotation analyses of associated genes, including GO and KEGG pathway. PPI of these DEGs is analyzed based on the string database and visualized by Cytoscape software. DEGs are verified by qRT-PCR using samples isolated from the patients.

Results: 249 overlapping DEGs, including 96 up-regulated genes and 153 down-regulated genes are screened using the Venn diagram webtool. The GO term and KEGG pathways analysis results indicate that these DEGs are mainly enriched in protein phosphorylation, apoptotic process and inflammatory response in the BP term and focal adhesion, thyroid hormone signaling pathway, ErbB signaling pathway, cytokine-cytokine receptor interaction and some disease processes in the KEGG pathways. 6 candidates are confirmed by Cytoscape software and qRT-PCR, including APP, JUN, GSK3B, ErbB2, PPBP and THBS1.

Conclusions: Our data and previous studies show that ErbB2 and THBS1 are crucial to prevent aneurysm rupture, while APP, JUN, GSK3B and PPBP performs the opposite role, and further experiments are needed to verify these findings.

A Systematic Review of Inflammatory Cytokine Changes Following Aneurysmal Subarachnoid Hemorrhage in Animal Models and Humans

Aneurysmal subarachnoid hemorrhage (aSAH) is a severe form of stroke that occurs following rupture of a cerebral aneurysm. Acute inflammation and secondary delayed inflammatory responses, both largely controlled by cytokines, work together to create high mortality and morbidity for this group. The trajectory and time course of cytokine change must be better understood in order to effectively manage unregulated inflammation and improve patient outcomes following aSAH. A systematic review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Three different search phrases ("cytokines and subarachnoid hemorrhage," "cytokine levels and subarachnoid hemorrhage," and "cytokine measurement and subarachnoid hemorrhage") were applied across three databases (PubMed, SCOPUS, and the Cochrane Library). Our procedures returned 856 papers. After application of inclusion/exclusion criteria, 95 preclinical animal studies and 41 clinical studies remained. Across studies, 22 different cytokines had been investigated, 5 different tissue types were analyzed, and 3 animal models were utilized. Three main pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) demonstrated reliable increases following aSAH across the included studies. While this is a promising area of research for potential therapeutics, there are gaps in the knowledge base that bar progress for clinical translation of this information. In particular, there is a need for investigations that explore the systemic inflammatory response following injury in a more diverse number of cytokines, the balance of specific pro-/anti- inflammatory cytokines, and how these biomarkers relate to patient outcomes and recovery over time.

Polymorphisms in genes related to oxidative stress and inflammation: Emerging links with the pathogenesis and severity of Cerebral Cavernous Malformation disease

Cerebral Cavernous Malformation (CCM) is a cerebrovascular disease of genetic origin affecting 0.5% of the population and characterized by abnormally enlarged and leaky capillaries that predispose to seizures, neurological deficits, and intracerebral hemorrhage (ICH). CCM occurs sporadically or is inherited as dominant condition with incomplete penetrance and highly variable expressivity. Three disease genes have been identified: KRIT1 (CCM1), CCM2 and CCM3. Previous results demonstrated that loss-of-function mutations of CCM genes cause pleiotropic effects, including defective autophagy, altered reactive oxygen species (ROS) homeostasis, and enhanced sensitivity to oxidative stress and inflammatory events, suggesting a novel unifying pathogenetic mechanism, and raising the possibility that CCM disease onset and severity are influenced by the presence of susceptibility and modifier genes. Consistently, genome-wide association studies (GWAS) in large and homogeneous cohorts of patients sharing the familial form of CCM disease and identical mutations in CCM genes have led to the discovery of distinct genetic modifiers of major disease severity phenotypes, such as development of numerous and large CCM lesions, and susceptibility to ICH. This review deals with the identification of genetic modifiers with a significant impact on inter-individual variability in CCM disease onset and severity, including highly polymorphic genes involved in oxidative stress, inflammatory and immune responses, such as cytochrome P450 monooxygenases (CYP), matrix metalloproteinases (MMP), and Toll-like receptors (TLR), pointing to their emerging prognostic value, and opening up new perspectives for risk stratification and personalized medicine strategies.

Shedding the Light on the Natural History of Intracranial Aneurysms: An Updated Overview

The exact molecular pathways underlying the multifactorial natural history of intracranial aneurysms (IAs) are still largely unknown, to the point that their understanding represents an imperative challenge in neurovascular research. Wall shear stress (WSS) promotes the genesis of IAs through an endothelial dysfunction causing an inflammatory cascade, vessel remodeling, phenotypic switching of the smooth muscle cells, and myointimal hyperplasia. Aneurysm growth is supported by endothelial oxidative stress and inflammatory mediators, whereas low and high WSS determine the rupture in sidewall and endwall IAs, respectively. Angioarchitecture, age older than 60 years, female gender, hypertension, cigarette smoking, alcohol abuse, and hypercholesterolemia also contribute to growth and rupture. The improvements of aneurysm wall imaging techniques and the implementation of target therapies targeted against inflammatory cascade may contribute to significantly modify the natural history of IAs. This narrative review strives to summarize the recent advances in the comprehension of the mechanisms underlying the genesis, growth, and rupture of IAs.

Protective effects of BP-1-102 against intracranial aneurysms-induced impairments in mice

The development of non-invasive pharmacological therapies to prevent the progression and rupture of intracranial aneurysms (IAs) is an important field of research. This study attempts to reveal the role of BP-1-102, an oral bioavailable signal transducer and activator of transcription 3 (STAT3) inhibitor, in IA. We first constructed an IA mouse model by injecting elastase into the cerebrospinal fluid with simultaneous induction of hypertension by deoxycorticosterone acetate (DOCA) implantation. The results showed that the proportion of IA rupture in mice after BP-1-102 administration was significantly reduced, and the survival time was significantly extended. Further research showed that compared with the vehicle group, the proportion of macrophages infiltrated at the aneurysm and the expression of pro-inflammatory cytokines in the BP-1-102 administration group were significantly reduced. The contractile phenotype vascular smooth muscle cell (VSMC) specific markers, SM22α and αSMA, were significantly upregulated in the BP-1-102 group. Furthermore, we found that BP-1-102 inhibited the expression of critical proteins in the nuclear factor kappa-B and Janus kinase 2/STAT3 signalling pathways. Our study shows that BP-1-102 significantly decreases the rupture of IA, reduces the inflammatory responses and modulates the phenotype of VSMCs, suggesting that BP-1-102 could be utilised as a potential intervention drug for IA.

Roles of Phytoestrogen in the Pathophysiology of Intracranial Aneurysm

[Figure: see text].

Involvement of Microglia in the Pathophysiology of Intracranial Aneurysms and Vascular Malformations-A Short Overview

Aneurysms and vascular malformations of the brain represent an important source of intracranial hemorrhage and subsequent mortality and morbidity. We are only beginning to discern the involvement of microglia, the resident immune cell of the central nervous system, in these pathologies and their outcomes. Recent evidence suggests that activated proinflammatory microglia are implicated in the expansion of brain injury following subarachnoid hemorrhage (SAH) in both the acute and chronic phases, being also a main actor in vasospasm, considerably the most severe complication of SAH. On the other hand, anti-inflammatory microglia may be involved in the resolution of cerebral injury and hemorrhage. These immune cells have also been observed in high numbers in brain arteriovenous malformations (bAVM) and cerebral cavernomas (CCM), although their roles in these lesions are currently incompletely ascertained. The following review aims to shed a light on the most significant findings related to microglia and their roles in intracranial aneurysms and vascular malformations, as well as possibly establish the course for future research.

Association between longitudinal blood pressure and prognosis after treatment of cerebral aneurysm: A nationwide population-based cohort study

BACKGROUND

High blood pressure is a major risk factor for the development and rupture of cerebral aneurysm. Endovascular coil embolization and surgical clipping are established procedures to treat cerebral aneurysm. However, longitudinal data of blood pressure after the treatment of cerebral aneurysm and its impact on long-term prognosis are not well known.

METHODS

This retrospective cohort study included 1275 patients who underwent endovascular coil embolization (n = 558) or surgical clipping (n = 717) of cerebral aneurysm in 2002-2015 using the nationwide health screening database of Korea. Systolic and diastolic blood pressure of patients were repeatedly obtained from the nationwide health screening program. We performed a multivariate time-dependent Cox regression analysis of the primary composite outcome of stroke, myocardial infarction, and all-cause death.

RESULTS

During the mean follow-up period of 6.13 ± 3.41 years, 89 patients suffered the primary outcome. Among the total 3546 times of blood pressure measurement, uncontrolled high blood pressure (systolic ≥140 mmHg or diastolic ≥90 mmHg) was 22.9%. There was a significantly increased risk of primary outcome with high systolic (adjusted HR [95% CI] per 10 mmHg, 1.16 [1.01-1.35]) and diastolic (adjusted HR [95% CI] per 10 mmHg, 1.32 [1.06-1.64]) blood pressure.

CONCLUSIONS

High blood pressure is prevalent even in patients who received treatment for cerebral aneurysm, which is significantly associated with poor outcome. Strict control of high blood pressure may further improve the prognosis of patients with cerebral aneurysm.

Neutrophil Extracellular Traps Promote the Development of Intracranial Aneurysm Rupture

[Figure: see text].

Integrated Transcriptional Profiling Analysis and Immune-Related Risk Model Construction for Intracranial Aneurysm Rupture

Intracranial aneurysms (IAs) may cause lethal subarachnoid hemorrhage upon rupture, but the molecular mechanisms are poorly understood. The aims of this study were to analyze the transcriptional profiles to explore the functions and regulatory networks of differentially expressed genes (DEGs) in IA rupture by bioinformatics methods and to identify the underlying mechanisms. In this study, 1,471 DEGs were obtained, of which 619 were upregulated and 852 were downregulated. Gene enrichment analysis showed that the DEGs were mainly enriched in the inflammatory response, immune response, neutrophil chemotaxis, and macrophage differentiation. Related pathways include the regulation of actin cytoskeleton, leukocyte transendothelial migration, nuclear factor κB signaling pathway, Toll-like receptor signaling pathway, tumor necrosis factor signaling pathway, and chemokine signaling pathway. The enrichment analysis of 20 hub genes, subnetworks, and significant enrichment modules of weighted gene coexpression network analysis showed that the inflammatory response and immune response had a causal relationship with the rupture of unruptured IAs (UIAs). Next, the CIBERSORT method was used to analyze immune cell infiltration into ruptured IAs (RIAs) and UIAs. Macrophage infiltration into RIAs increased significantly compared with that into UIAs. The result of principal component analysis revealed that there was a difference between RIAs and UIAs in immune cell infiltration. A 4-gene immune-related risk model for IA rupture (IRMIR), containing CXCR4, CXCL3, CX3CL1, and CXCL16, was established using the glmnet package in R software. The receiver operating characteristic value revealed that the model represented an excellent clinical situation for potential application. Enzyme-linked immunosorbent assay was performed and showed that the concentrations of CXCR4 and CXCL3 in serum from RIA patients were significantly higher than those in serum from UIA patients. Finally, a competing endogenous RNA network was constructed to provide a potential explanation for the mechanism of immune cell infiltration into IAs. Our findings highlighted the importance of immune cell infiltration into RIAs, providing a direction for further research.

Construction and Validation of a New Model for the Prediction of Rupture in Patients with Intracranial Aneurysms

BACKGROUND

Despite progress in the detection of biological molecules that contribute to intracranial aneurysm (IA) development, many pathophysiological mechanisms remain unclear, particularly with regard to predicting IA rupture. In this study, we aimed to identify hub genes and construct a new model to predict IA rupture.

METHODS

Four datasets (62 ruptured IAs, 16 unruptured IAs, and 31 normal controls) were downloaded from the Gene Expression Omnibus. Differentially expressed genes (DEGs) were identified between the IAs and normal controls. All overlapping genes were analyzed using weighted gene co-expression network analysis. Functional enrichment analyses were performed using key modules. We then intersected the key module genes with DEGs. Protein-protein interaction networks were assessed to identify key hub genes. Least absolute shrinkage and selection operator logistic regression analysis was performed to construct a prediction model. A receiver operating characteristic curve was constructed to evaluate the reliability of the scoring system.

RESULTS

After intersection and normalization, 433 DEGs were identified and 15,388 genes were selected for weighted gene co-expression network analysis. The black module with 1145 genes exhibited the highest correlation with IA rupture. Many potential mechanisms are involved, such as the inflammatory response, innate immune response, extracellular exosome, and extracellular space. Thirty hub genes were selected from the protein-protein interaction, and 4 independent risk genes, TNFAIP6, NCF2, OSM, and IRAK3, were identified in the least absolute shrinkage and selection operator logistic regression model.

CONCLUSIONS

Our prediction model not only serves as a useful tool for assessing the risk of IA rupture, but the key genes identified herein could also serve as biomarkers and therapeutic targets.

Roles of inflammation in the natural history of intracranial saccular aneurysms

Aneurysmal subarachnoid hemorrhage is caused by intracranial aneurysm (IA) rupture and results in high rates of mortality and morbidity. Factors contributing to IA generation, growth and rupture can involve genetics, injury, hemodynamics, environmental factors, and inflammation, in which inflammatory factors are believed to play central roles in the whole natural history. Inflammatory reactions that contribute to IA development may involve synthesis of many functional proteins and expression of genes induced by changes of blood flow, external stimuli such as smoking, internal balance such as hormonal status changes, and blood pressure. Meanwhile, inflammatory reactions itself can evoke inflammatory cytokines release and aggregation such as MMPs, MCP-1, TNF-α and ZO-1, directly or indirectly promoting aneurysm growth and rupture. However, the details of these inflammatory reactions and their action on inflammatory chemokines are still unknown. Moreover, some agents with the function of anti-inflammation, lipid-lowering, antihypertension or inflammatory factor inhibition may have the potential benefit to reduce the risk of aneurysm development or rupture in a group of population despite the underlying mechanism remains unclear. Consequently, we reviewed the potential inflammatory responses and their mechanisms contributing to aneurysm development and rupture and sought intervention targets that may prevent IA rupture or generation.

Identification and validation of key genes mediating intracranial aneurysm rupture by weighted correlation network analysis

Background

Rupture of intracranial aneurysm (IA) is the leading cause of subarachnoid hemorrhage. However, there are few pharmacological therapies available for the prevention of IA rupture. Therefore, exploring the molecular mechanisms which underlie IA rupture and identifying the potential molecular targets for preventing the rupture of IA is of vital importance.

Methods

We used the Gene Expression Omnibus (GEO) datasets GSE13353, GSE15629, and GSE54083 in our study. The 3 datasets were merged and normalized. Differentially expressed gene (DEG) screening and weighted correlation network analysis (WGCNA) were conducted. The co-expression patterns between ruptured IA samples and unruptured IA samples were compared. Then, the DEGs were mapped into the whole co-expression network of ruptured IA samples, and a DEG co-expression network was generated. Molecular Complex Detection (MCODE) (http://baderlab.org/Software/MCODE) was used to identify key genes based on the DEG co-expression network. Finally, key genes were validated using another GEO dataset (GSE122897), and their potential diagnostic values were shown using receiver operating characteristic (ROC) analysis.

Results

In our study, 49 DEGs were screened while 8 and 6 gene modules were detected based on ruptured IA samples and unruptured IA samples, respectively. Pathways associated with inflammation and immune response were clustered in the salmon module of ruptured IA samples. The DEG co-expression network with 35 nodes and 168 edges was generated, and 14 key genes were identified based on this DEG co-expression network. The gene with the highest degree in the key gene cluster was CXCR4. All key genes were validated using GSE122897, and they all showed the potential diagnostic value in predicting IA rupture.

Conclusions

Using a weighted gene co-expression network approach, we identified 8 and 6 modules for ruptured IA and unruptured IA, respectively. After that, we identified the hub genes for each module and key genes based on the DEG co-expression network. All these key genes were validated by another GEO dataset and might serve as potential targets for pharmacological therapies and diagnostic markers in predicting IA rupture. Further studies are needed to elucidate the detailed molecular mechanisms and biological functions of these key genes which underlie the rupture of IA.