Molecular basis for intracranial aneurysm formation

Effects of paroxetine, a P2X4 inhibitor, on cerebral aneurysm growth and recanalization after coil embolization: the NHO Drug for Aneurysm Study

OBJECTIVE

Rupture of cerebral aneurysms has a poor prognosis, and growing aneurysms are prone to rupture. Although the number of coil embolization procedures is increasing worldwide, they are more prone to recurrence than clipping surgeries. However, there is still no drug that prevents aneurysm growth or recanalization after coil embolization. The authors have previously focused on the role of hemodynamics in cerebral aneurysm development and reported that inhibition of the P2X4 purinoceptor, by which vascular endothelial cells sense blood flow, reduced the induction and growth of aneurysms in an animal model. In this study, the authors investigated the effects of paroxetine, a P2X4 inhibitor also used as an antidepressant, on aneurysm growth and recanalization after endovascular coiling.

METHODS

Using the J-ASPECT Study registry, the largest comprehensive reimbursement database system for acute stroke inpatient care in Japan, the authors searched for patients incidentally taking paroxetine who were registered in the decade 2010-2019 with an unruptured cerebral aneurysm or who underwent aneurysm coiling. They calculated the growth incidence and growth rate by the person-year method and the odds ratio for recanalization within 1 year after coiling and statistically compared to controls.

RESULTS

Seventy-eight stroke facilities participated, and 275 patients were identified as potentially eligible. Thirty-seven patients with unruptured aneurysms and 38 after coil embolization met all eligibility criteria. They were compared with 396 control cases of unruptured aneurysms and 308 coil-placement controls. Multivariate analysis showed that paroxetine significantly reduced the incidence of aneurysm growth (number of cases with growth/person/year; incidence rate ratio [IRR] 0.24, 95% CI 0.05-0.66; p = 0.003) and the growth rate (total increase in maximum diameter in millimeters/person/year; IRR 0.57, 95% CI 0.28-0.98; p = 0.04). Paroxetine also significantly reduced the odds of recanalization in the year after coiling (OR 0.21, 95% CI 0.05-0.95; p = 0.04). The authors then performed propensity score matching to reduce bias due to imbalances in patient characteristics between the two groups; the outcome confirmed that paroxetine significantly reduced aneurysm growth incidence (IRR 0.02, 95% CI 0.008-0.05; p < 0.0001) and growth rate (IRR 0.03, 95% CI 0.01-0.06; p < 0.0001) and the 1-year recanalization (OR 0.18, 95% CI 0.03-0.99; p = 0.04).

CONCLUSIONS

This observational cohort study suggests that P2X4 inhibitors such as paroxetine may be clinically applicable as prophylaxis against aneurysm rupture and postoperative recanalization.

A dual-targeting therapeutic nanobubble for imaging-guided atherosclerosis treatment

Atherosclerosis is a cardiovascular disease that seriously endangers human health. Low shear stress (LSS) is recognized as a vital factor in causing chronic inflammatory and further inducing the occurrence and development of atherosclerosis. Targeting imaging and treatment are of substantial significance for the diagnosis and therapy of atherosclerosis. On this ground, a kind of ultrasound (US) imaging-guided therapeutic polymer nanobubbles (NBs) with dual targeting of magnetism and antibody was rationally designed and constructed for the efficiently treating LSS-mediated atherosclerosis. Under the combined targeting effect of an external magnetic field and antibodies, the drug-loaded therapeutic NBs can be effectively accumulated in the inflammatory area caused by LSS. Upon US irradiation, the NBs can be selectively disrupted, leading to the rapid release of the loaded drugs at the targeted site. Notably, the US irradiation generates a cavitation effect that induces repairable micro gaps in nearby cells, thereby enhancing the uptake of released drugs and further improving the therapeutic effect. The prominent US imaging, efficient anti-inflammatory effect and treatment outcome of LSS-mediated atherosclerosis had been verified in vivo on a surgically constructed LSS-atherosclerosis animal model. This work showcased the potential of the designed NBs with multifunctionality for in vivo imaging, dual-targeting, and drug delivery in the treatment of atherosclerosis.

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.

Effect of circulating miR‑126 levels on intracranial aneurysms and their predictive value for the rupture of aneurysms: A systematic review and meta‑analysis

Intracranial aneurysm (IA) is a common cerebrovascular disease with a high risk of rupture. At present, the mechanisms underlying the formation and rupture of IAs is not clinically clear. MicroRNAs (miRNAs/miRs) are involved in the development of IAs. The present study aimed to determine the efficacy of circulating miRNA-126 (miR-126) levels as potential biomarkers for predicting aneurysmal ruptures. The present study searched comparative articles involving circulating miR-126 levels and intracranial aneurysms through electronic databases from 1980 to February, 2023. Collected variables included the first author's name, covered study period, publication year, total number of patients and age, and number of males. We collected information about the expression levels of circulating miR-126 in serum. Three articles met the eligibility criteria. The total number of patients was 379 [226 with IA rupture and 153 with non-rupture or/+ controls (healthy)]. The circulating miR-126 can be used as a biomarker for predicting aneurysmal rupture. Interestingly, an aneurysmal size >10 mm was associated with an IA rupture.

Fluid-structure interaction (FSI) simulation for studying the impact of atherosclerosis on hemodynamics, arterial tissue remodeling, and initiation risk of intracranial aneurysms

The biomechanical and hemodynamic effects of atherosclerosis on the initiation of intracranial aneurysms (IA) are not yet clearly discovered. Also, studies for the observation of hemodynamic variation due to atherosclerotic stenosis and its impact on arterial remodeling and aneurysm genesis remain a controversial field of vascular engineering. The majority of studies performed are relevant to computational fluid dynamic (CFD) simulations. CFD studies are limited in consideration of blood and arterial tissue interactions. In this work, the interaction of the blood and vessel tissue because of atherosclerotic occlusions is studied by developing a fluid and structure interaction (FSI) analysis for the first time. The FSI presents a semi-realistic simulation environment to observe how the blood and vessels' structural interactions can increase the accuracy of the biomechanical study results. In the first step, many different intracranial vessels are modeled for an investigation of the biomechanical and hemodynamic effects of atherosclerosis in arterial tissue remodeling. Three physiological conditions of an intact artery, the artery with intracranial atherosclerosis (ICAS), and an atherosclerotic aneurysm (ACA) are employed in the models with required assumptions. Finally, the obtained outputs are studied with comparative and statistical analyses according to the intact model in a normal physiological condition. The results show that existing occlusions in the cross-sectional area of the arteries play a determinative role in changing the hemodynamic behavior of the arterial segments. The undesirable variations in blood velocity and pressure throughout the vessels increase the risk of arterial tissue remodeling and aneurysm formation.

Pharmacological inhibition of STAT3 by BP-1-102 inhibits intracranial aneurysm formation and rupture in mice through modulating inflammatory response

As an inhibitor of STAT3, BP-1-102 can regulate the inflammation response caused by vascular smooth muscle cells (VSMCs) by inhibiting the JAK/STAT3/NF-κB pathway, thereby attenuating the symptoms of intracranial aneurysm (IA). IA mouse model was established by stereotactic injection of elastase to evaluate the effect of BP-1-102. The expression levels of smooth muscle markers and matrix metalloproteinases (MMPs) were detected by qRT-PCR, and the levels of inflammatory factors were detected by ELISA and qRT-PCR. The protein levels of the NF-κB signaling pathway factors were examined by Western blot. BP-1-102 reduced blood pressure in aneurysm mice, up-regulated smooth muscle cell markers MHC, SMA, and SM22, and down-regulated the expression of MMP2 and MMP9 in vascular tissues. At the same time, BP-1-102 also down-regulated the expression levels of inflammatory response factors and the NF-κB pathway proteins. In the IA model, BP-1-102 can reduce the expression of inflammatory factors and MMPs bound to NF-κB by inhibiting the activation of the JAK/STAT3/NF-κB pathway proteins, and then restore the vascular wall elastin to reduce blood pressure, thereby treating aneurysm.

The Bilateral Ovariectomy in a Female Animal Exacerbates the Pathogenesis of an Intracranial Aneurysm

Considering the poor outcome of subarachnoid hemorrhage (SAH) due to the rupture of intracranial aneurysms (IA), mechanisms underlying the pathogenesis of IAs, especially the rupture of lesions, should be clarified. In the present study, a rat model of IAs in which induced lesions spontaneously ruptured resulting in SAH was used. In this model, the combination of the female sex and the bilateral ovariectomy increased the incidence of SAH, similar to epidemiological evidence in human cases. Importantly, unruptured IA lesions induced in female animals with bilateral ovariectomy were histopathologically similar to ruptured ones in the presence of vasa vasorum and the accumulation of abundant inflammatory cells, suggesting the exacerbation of the disease. The post-stenotic dilatation of the carotid artery was disturbed by the bilateral ovariectomy in female rats, which was restored by hormone replacement therapy. The in vivo study thus suggested the protective effect of estrogen from the ovary on endothelial cells loaded by wall shear stress. β-estradiol or dihydrotestosterone also suppressed the lipopolysaccharide-induced expression of pro-inflammatory genes in cultured macrophages and neutrophils. The results of the present study have thus provided new insights about the process regulating the progression of the disease.

Eicosapentaenoic acid prevents the progression of intracranial aneurysms in rats

Background

As subarachnoid hemorrhage due to rupture of an intracranial aneurysm (IA) has quite a poor outcome despite of an intensive medical care, development of a novel treatment targeting unruptured IAs based on the correct understanding of pathogenesis is mandatory for social health.

Methods

Using previously obtained gene expression profile data from surgically resected unruptured human IA lesions, we selected G-protein coupled receptor 120 (GPR120) as a gene whose expression is significantly higher in lesions than that in control arterial walls. To corroborate a contribution of GPR120 signaling to the pathophysiology, we used an animal model of IAs and examine the effect of a GPR120 agonist on the progression of the disease. IA lesion was induced in rats through an increase of hemodynamic stress achieved by a one-sided carotid ligation and induced hypervolemia. Eicosapentaenoic acid (EPA) was used as an agonist for GPR120 in this study and its effect on the size of IAs, the thinning of media, and infiltration of macrophages in lesions were examined.

Result

EPA administered significantly suppressed the size of IAs and the degenerative changes in the media in rats. EPA treatment also inhibited infiltration of macrophages, a hallmark of inflammatory responses in lesions. In in vitro experiments using RAW264.7 cells, pre-treatment of EPA partially suppressed lipopolysaccharide-induced activation of nuclear factor-kappa B and also the transcriptional induction of monocyte chemoattractant protein 1 (MCP-1), a major chemoattractant for macrophages to accumulate in lesions. As a selective agonist of GPR120, TUG-891, could reproduce the effect of EPA in RAW264.7 cells, EPA presumably acted on this receptor to suppress inflammatory responses. Consistently, EPA remarkably suppressed MCP-1 expression in lesions, suggesting the in vivo relevance of in vitro studies.

Conclusions

These results combined together suggest the potential of the medical therapy targeting GPR120 or using EPA to prevent the progression of IAs.

Preclinical Intracranial Aneurysm Models: A Systematic Review

Intracranial aneurysms (IA) are characterized by weakened cerebral vessel walls that may lead to rupture and subarachnoid hemorrhage. The mechanisms behind their formation and progression are yet unclear and warrant preclinical studies. This systematic review aims to provide a comprehensive, systematic overview of available animal models for the study of IA pathobiology. We conducted a systematic literature search using the PubMed database to identify preclinical studies employing IA animal models. Suitable articles were selected based on predefined eligibility criteria following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Included studies were reviewed and categorized according to the experimental animal and aneurysm model. Of 4266 returned results, 3930 articles were excluded based on the title and/or abstract and further articles after screening the full text, leaving 123 studies for detailed analysis. A total of 20 different models were found in rats (nine), mice (five), rabbits (four), and dogs (two). Rat models constituted the most frequently employed intracranial experimental aneurysm model (79 studies), followed by mice (31 studies), rabbits (12 studies), and two studies in dogs. The most common techniques to induce cerebral aneurysms were surgical ligation of the common carotid artery with subsequent induction of hypertension by ligation of the renal arteries, followed by elastase-induced creation of IAs in combination with corticosterone- or angiotensin-induced hypertension. This review provides a comprehensive summary of the multitude of available IA models to study various aspects of aneurysm formation, growth, and rupture. It will serve as a useful reference for researchers by facilitating the selection of the most appropriate model and technique to answer their scientific question.

RNA sequencing analysis revealed the induction of CCL3 expression in human intracranial aneurysms

Intracranial aneurysm (IA) is a socially important disease as a major cause of subarachnoid hemorrhage. Recent experimental studies mainly using animal models have revealed a crucial role of macrophage-mediated chronic inflammatory responses in its pathogenesis. However, as findings from comprehensive analysis of unruptured human IAs are limited, factors regulating progression and rupture of IAs in humans remain unclear. Using surgically dissected human unruptured IA lesions and control arterial walls, gene expression profiles were obtained by RNA sequence analysis. RNA sequencing analysis was done with read count about 60~100 million which yielded 6~10 billion bases per sample. 79 over-expressed and 329 under-expressed genes in IA lesions were identified. Through Gene Ontology analysis, ‘chemokine activity’, ‘defense response’ and ‘extracellular region’ were picked up as over-represented terms which included CCL3 and CCL4 in common. Among these genes, quantitative RT-PCR analysis using another set of samples reproduced the above result. Finally, increase of CCL3 protein compared with that in control arterial walls was clarified in IA lesions. Findings of the present study again highlight importance of macrophage recruitment via CCL3 in the pathogenesis of IA progression.

Molecular mechanisms of the intracranial aneurysms and their association with the long noncoding ribonucleic acid ANRIL - A review of literature

Long noncoding ribonucleic acids (RNAs) are important regulators of gene expression. Antisense noncoding RNA in the INK4 locus (ANRIL), which was coded on the Chr9p21.3 loci, participates in the pathogenesis of tumor, coronary artery disease, type 2 diabetes mellitus, and other diseases. A genome-wide association study indicated ANRIL to be a candidate gene that may lead to the development of an intracranial aneurysm (IA) formation. However, the detailed molecular mechanisms are unknown and have not been studied. Through reviewing the molecular mechanisms responsible for the development of IA and the regulation pathway of ANRIL, this paper presents four possible molecular mechanisms that may be responsible for the influence of ANRIL on the development of IAs, that is, cell cycling, Krüppel-like factor 2 (KLF2), caspase recruitment domain family member 8, and retinoid metabolism. ANRIL may become a molecular marker or therapeutic target of IA in the future. To the best of our knowledge, this is the first paper elucidating the molecular linkage between ANRIL and IAs.

Real-time Imaging of an Experimental Intracranial Aneurysm in Rats

Subarachnoid hemorrhage due to rupture of a pre-existing intracranial aneurysm has quite a poor outcome in spite of intensive medical care. Hemodynamic stress loaded on intracranial arterial walls is considered as a trigger and a regulator of formation and progression of the disease, but how intracranial arterial walls or intracranial aneurysm walls behave under hemodynamic stress loading remains unclear. The purpose of this study was to visualize and analyze the wall motion of intracranial aneurysms to detect a pathological flow condition. We subjected a transgenic rat line, in which endothelial cells are specifically visualized by expression of a green fluorescent protein, to an intracranial aneurysm model and observed a real-time motion of intracranial arterial walls or intracranial aneurysm walls by a multiphoton laser confocal microscopy. The anterior cerebral artery–olfactory artery bifurcation was surgically exposed for the monitoring. First, we observed the proper flow-dependent physiological dilatation of a contralateral intracranial artery in response to increase of blood flow by one side of carotid ligation. Next, we observed intracranial aneurysm lesions induced in a rat model and confirmed that a wall motion of the dome was static, whereas that of the neck was more dynamic in response to pulsation of blood flow. We successfully monitored a real-time motion of intracranial aneurysm walls. Findings obtained from such a real-time imaging will provide us many insights especially about the correlation of mechanical force and the pathogenesis of the disease and greatly promote our understanding of the disease.

New Pathophysiological Considerations on Cerebral Aneurysms

Cerebral aneurysm is a common cerebrovascular disease that is sometimes complicated by rupture or an enlarged mass. We are now aggressively evaluating and managing unruptured cerebral aneurysms based on a significant concern for the high morbidity and mortality related to its associated complications. However, the actual rupture rate is very low and the diagnostic and treatment modalities are expensive and invasive, which may lead to unnecessary costs and potential medical complications. This disproportionate situation is related to a poor understanding of the natural course and pathophysiology of cerebral aneurysms. In consideration of the concept that not all cerebral aneurysms must be removed, we need to examine their course and progression more accurately. Cerebral aneurysms may follow a variety of pathophysiological scenarios over their lifetime, from formation to growth and rupture. The disease course and the final outcome can differ depending on the timing and intensity of the pathological signals acting on the cerebral vessel wall. We should delineate a method of predicting the stability and risk of rupture of the lesion based on a comprehensive knowledge of the vessel wall integrity. This review deals with the basic knowledge and advanced concepts underlying the pathophysiology of cerebral aneurysms.

A sphingosine-1-phosphate receptor type 1 agonist, ASP4058, suppresses intracranial aneurysm through promoting endothelial integrity and blocking macrophage transmigration

Background and Purpose

Intracranial aneurysm (IA), common in the general public, causes lethal subarachnoid haemorrhage on rupture. It is, therefore, of utmost importance to prevent the IA from rupturing. However, there is currently no medical treatment. Recent studies suggest that IA is the result of chronic inflammation in the arterial wall caused by endothelial dysfunction and infiltrating macrophages. The sphingosine‐1‐phosphate receptor type 1 (S1P₁ receptor) is present on the endothelium and promotes its barrier function. Here we have tested the potential of an S1P₁ agonist, ASP4058, to prevent IA in an animal model.

Experimental Approach

The effects of a selective S1P₁ agonist, ASP4058, on endothelial permeability and migration of macrophages across an endothelial cell monolayer were tested in vitro using a Transwell system, and its effects on the size of IAs were evaluated in a rat model of IA.

Key Results

S1P₁ receptor was expressed in endothelial cells of human IA lesions and control arterial walls. ASP4058 significantly reduced FITC‐dextran leakage through an endothelial monolayer and suppressed the migration of macrophages across the monolayer in vitro. Oral administration of ASP4058 reduced the vascular permeability, macrophage infiltration and size of the IAs by acting as an S1P₁ agonist in the rat model. This effect was mimicked by another two structurally‐unrelated S1P₁ agonists.

Conclusion and Implications

A selective S1P₁ agonist is a strong drug candidate for IA treatment as it promotes the endothelial cell barrier and suppresses the trans‐endothelial migration of macrophages in IA lesions.

T cell function is dispensable for intracranial aneurysm formation and progression

Given the social importance of intracranial aneurysm as a major cause of a lethal subarachnoid hemorrhage, clarification of mechanisms underlying the pathogenesis of this disease is essential for improving poor prognosis once after rupture. Previous histopathological analyses of human aneurysm walls have revealed the presence of T cells in lesions suggesting involvement of this type of cell in the pathogenesis. However, it remains unclear whether T cell actively participates in intracranial aneurysm progression. To examine whether T cell is involved in aneurysm progression, intracranial aneurysm model of rat was used. In this model, aneurysm is induced by increase in hemodynamic force loaded on bifurcation site of intracranial arteries where aneurysms are developed. Deficiency in T cells and pharmacological inhibition of T cell function were applied to this model. CD3-positive T cells were present in human aneurysm walls, whose number was significantly larger compared with that in control arterial walls. Deficiency in T cells in rats and pharmacological inhibition of T cell function by oral administration of Cyclosporine A both failed to affect intracranial aneurysm progression, degenerative changes of arterial walls and macrophage infiltration in lesions. Although T cells are detectable in intracranial aneurysm walls, their function is dispensable for macrophage-mediated inflammation and degenerative changes in arterial walls, which presumably leads to intracranial aneurysm progression.