Pathogenesis Of Intracranial Aneurysms Research Articles

Vasa vasorum formation is associated with rupture of intracranial aneurysms.

Subarachnoid hemorrhage (SAH) has a poor outcome despite modern advancements in medical care. The development of a novel therapeutic strategy to prevent rupture of intracranial aneurysms (IAs) or a novel diagnostic marker to predict rupture-prone lesions is thus mandatory. Therefore, in the present study, the authors established a rat model in which IAs spontaneously rupture and examined this model to clarify histopathological features associated with rupture of lesions. Female Sprague Dawley rats were subjected to bilateral ovariectomy; the ligation of the left common carotid, the right external carotid, and the right pterygopalatine arteries; induced systemic hypertension; and the administration of a lysyl oxidase inhibitor. Aneurysmal SAH occurred in one-third of manipulated animals and the locations of ruptured IAs were exclusively at a posterior or anterior communicating artery (PCoA/ACoA). Histopathological examination using ruptured IAs, rupture-prone IAs induced at a PCoA or ACoA, and IAs induced at an anterior cerebral artery-olfactory artery bifurcation that never ruptured revealed the formation of vasa vasorum as an event associated with rupture of IAs. The authors propose the contribution of a structural change in an adventitia, i.e., vasa vasorum formation, to the rupture of IAs. Findings from this study provide important insights about the pathogenesis of IAs.

Upregulation of microRNA-205 is a potential biomarker for intracranial aneurysms.

Inhibition of microRNA-205 is considered to be a therapeutic target for abdominal aortic aneurysm in animal model. Hepatocyte growth factor also plays pivotal roles in the pathogenesis of intracranial aneurysms, and its expression can be regulated by different miRNAs in different processes. We investigated the involvement of microRNA-205 in intracranial aneurysms and explored is potential interaction with hepatocyte growth factor. We found that blood levels of microRNA-205 were significantly higher in patients with intracranial aneurysms than in healthy controls. High blood levels of microRNA-205 showed diagnostic values for intracranial aneurysms. MicroRNA-205 and hepatocyte growth factor were negatively correlated in patients with intracranial aneurysms. MicroRNA-205 overexpression inhibited hepatocyte growth factor expression and reduced cell viability. Therefore, microRNA-205 may participate in intracranial aneurysms and may serve as a diagnostic marker for this disease.

Autophagy regulates the function of vascular smooth muscle cells in the formation and rupture of intracranial aneurysms

Vascular smooth muscle cells (VSMC) are the main cellular component of vessel wall. The changes of VSMC functions including phenotypic transformation and apoptosis play a critical role in the pathogenesis of intracranial aneurysm (IA). Autophagy can participate in the regulation of vascular function by regulating cell function. In the initial stage of IA, the activation of autophagy can accelerate the phenotypic transformation of VSMC and inhibit VSMC apoptosis. With the progress of IA, the relationship between autophagy and apoptosis changes from antagonism to synergy or promotion, and a large number of apoptotic VSMC lead to the rupture of IA. In this review, we describe the role of autophagy regulating the function of VSMC in the occurrence, development and rupture of IA, for further understanding the pathogenesis of IA and finding molecular targets to prevent the formation and rupture of IA.

A functional polymorphism in the promoter region of miR‐155 predicts the risk of intracranial hemorrhage caused by rupture intracranial aneurysm

This study aimed to study the effect and underlying molecular mechanisms of single-nucleotide polymorphism (SNP) rs767649 during the pathogenesis of intracranial aneurysm (IA) rupture. Real-time PCR and Western blot analysis were performed to detect the differentiated expression of miR-155 and matrix metalloproteinase-2 (MMP-2) among different sample groups. Computational analysis and luciferase assay were conducted to study the effect of SNP rs767649 on the expression of miR-155 as well as the regulatory relationship between miR-155 and MMP-2. In unruptured IA samples, the expression of miR-155 was upregulated while the expression of MMP-2 was downregulated compared with the ruptured IA samples. Similarly, the expression of miR-155 was upregulated while the expression of MMP-2 was downregulated in samples genotyped as AA/AT compared with samples genotyped as TT. In addition, compared with the negative controls, the luciferase activities of cells treated with rs767649A and rs767649T were both elevated with rs767649A-transfected cells expressing the highest luciferase activity. Furthermore, a negative relationship was established between miR-155 and MMP-2 by measuring the luciferase activity of cells cotransfected with miR-155 and the wild-type 3'-untranslated region of MMP-2. The results of this study showed that the SNP rs767649 in the promoter of miR-155 could reduce the transcription activity of miR-155, while poorly expressed miR-155 could increase the incidence of IA rupture by increasing the expression of MMP-2, especially in subjects carrying the TT genotype of SNP rs767649.

Role of matrix metalloproteinases in the pathogenesis of intracranial aneurysms.

Intracranial aneurysms (IAs) are a result of complex interactions between biochemical and mechanical forces and can lead to significant morbidity if they rupture and cause subarachnoid hemorrhage. This review explores the role of matrix metalloproteinases (MMPs) in the pathogenesis and progression of IAs. In addition to providing a review of the normal function of MMPs, it is intended to explore the interaction between inflammation and abnormal blood flow and the resultant pathological vascular remodeling processes seen in the development and rupture of IAs. Also reviewed is the potential for the use of MMPs as a diagnostic tool for assessment of aneurysm development and progression.

Genetic Profiles Related to Pathogenesis in Sporadic Intracranial Aneurysm Patients

Intracranial aneurysm (IA) represents a cerebrovascular disorder that featured by dilation or bulging of the weakened blood vessel wall. When it ruptures, an IA leads to subarachnoid hemorrhage with high disability and mortality rates. Despite the numerous studies focusing on IA ruptures, little research on IA pathogenesis has been reported. In this study, we aimed to reveal key genes related to IA formation. Four datasets from Gene Expression Omnibus data were downloaded, normalized, and separated into the IA group and the normal vessel control group for analyses. We screened for differentially expressed genes (DEGs) between groups and conducted functional enrichment, pathway enrichment, and gene set enrichment analysis analyses among significant DEGs. according to our analyses, significant DEGs majorly associate with smooth muscle system and the complement system. Among all DEGs, 5 down-regulated genes (MYH11, CNN1, MYOCD, ACTA1, and LMOD1) and 3 up-regulated genes (C1QB, C3AR1, and VSIG4) are most relevant in IA formation. Key DEGs identified in this study are related to IA pathogenesis. Among identified DEGs, LMOD1 is the most significant and merits more attention.

Roles of macrophages in formation and progression of intracranial aneurysms

Studies have shown that chronic inflammatory response plays a key role in intracranial aneurysms (IA) formation and progression, and macrophages regulate the formation and progression of IA through a variety of pathways. Bone marrow monocyte-derived macrophages and resident-tissue macrophages infiltrate the vessel wall, after infiltration macrophages are polarized into various polarization phenotypes dominated by M1-like and M2-like cells. Polarized phenotypes of macrophages can regulate the formation and progression of intracranial aneurysms by releasing cytokines and regulating the inflammatory response of other immune cells, as well as release different cytokines to regulate the process of extracellular matrix remodeling. Some important progresses have been made in the clinical detection and treatment in targeting macrophages. This review provides a summary on the pathogenesis of IA and potential drug targets to prevent the formation and rupture of intracranial aneurysms.

Increased HDAC9 Expression is Associated with Decreased Estrogen in Female Patients with Intracranial Aneurysm

Background and purposeSubarachnoid hemorrhage is a devastating consequence of intracranial aneurysm (IA) rupture. Therefore early identification of patients with IA is important. Identification of biomarkers for IA will help improve diagnosis, the understanding of IA pathogenesis, and patient management. A risk allele (rs10230207), located nearby the histone deacetylase 9 (HDAC9) gene on chromosome 7, has been associated with IA incidence. HDAC9 can repress the transcription of estrogen receptors α and β (ESR1 and ESR2). We tested the hypothesis that lymphocytes from patients with IA will have increased HDAC9 and decreased estrogen receptor gene transcription compared to controls.MethodsImmortalized B‐lymphocytes from male and female patients with un‐ruptured IA (N=109) and population controls (N=85) were obtained from the NINDS repository and cultured in RPMI‐1640 medium supplemented with 10% fetal calf serum. Subject genomic DNA was genotyped for presence of the risk allele using TaqMan SNP genotyping assays directed toward rs10230207. HDAC9 and ESR gene expression were analyzed using TaqMan expression assays. In a separate study using subject case (N=23) and control (N=10) blood samples, HDAC9 and ESR2 transcriptional differences were confirmed in peripheral blood mononuclear cells. Plasma estrogen levels were also measured in these subjects.ResultsHDAC9 expression was increased in IA patient lymphoblasts compared to population controls (P= 0.0311) and was associated with the presence of the rs10230207 risk allele (P=0. 0235). Patients harboring the risk allele had an increased risk for IA (OR 9.1, 95% CI 3.6–23.1). While the risk allele puts both males and females at risk for IA, the risk of IA is larger for females (OR 23.9, 95% CI 5.4–105.4) compared to males (OR 5.9, 95% CI 2.7–13.2). Lymphoblasts from female subjects between 19–50 years (premenopausal) were further analyzed (N= 17 cases and 22 population controls). HDAC9 gene expression was increased (P=0.0243) and ESR2 expression was decreased (P= 0.0351) in premenopausal females with IA compared to premenopausal female population controls. Decreased plasma estrogen levels were also detected in the premenopausal female cases (N=7) compared to control (N=5) subjects (P =0.0015).ConclusionsThe presence of the rs10230207 risk allele was associated with increased expression of HDAC9 and decreased expression of ESR2 in case and control immortalized lymphoblasts. Furthermore, we found that female IA patients that had not yet undergone menopause had decreased plasma estrogen levels. Future studies are aimed at defining the positive and negative predictive values of estrogen levels and IA in female patients.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Apc gene suppresses intracranial aneurysm formation and rupture through inhibiting the NF-κB signaling pathway mediated inflammatory response.

Background: Intracranial aneurysm (IA) is a critical acquired cerebrovascular disease that may cause subarachnoid hemorrhage, and nuclear factor-κB (NF-κB)-mediated inflammation is involved in the pathogenesis of IA. Adenomatous polyposis coli (Apc) gene is a tumor suppressor gene associated with both familial and sporadic cancer. Herein, the purpose of our study is to validate effect of Apc gene on IA formation and rupture by regulating the NF-κB signaling pathway mediated inflammatory response. Methods: We collected IA specimens (from incarceration of IA) and normal cerebral arteries (from surgery of traumatic brain injury) to examine expression of Apc and the NF-κB signaling pathway related factors (NF-κB p65 and IκBα). ELISA was used to determine levels of monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), interleukin (IL)-1β (IL-1β), and IL-6. IA model was established in rats, and Apc-siRNA was treated to verify effect of Apc on IA formation and rupture. Next, regulation of Apc on the NF-κB signaling pathway was investigated. Results: Reduced expression of Apc and IκBα, and increased expression of NF-κB p65 were found in IA tissues. MCP-1, TNF-α, IL-1β, and IL-6 exhibited higher levels in unruptured and ruptured IA, which suggested facilitated inflammatory responses. In addition, the IA rats injected with Apc-siRNA showed further enhanced activation of NF-κB signaling pathway, and up-regulated levels of MCP-1, TNF-α, IL-1β, IL-6, MMP-2, and MMP-9 as well as extent of p65 phosphorylation in IA. Conclusion: Above all, Apc has the potential role to attenuate IA formation and rupture by inhibiting inflammatory response through repressing the activation of the NF-κB signaling pathway.

Abstract WP346: A Cost-effective and Reproducible Mouse Model of Intracranial Aneurysm: Renal Hypertension and Local Hemodynamic Change Combined With Elastase Infusion

Introduction: The study of animal models of intracranial aneurysms (IA) can improve our understanding of the IA pathogenesis and identify the potential pharmaceutical targets. Although a variety of mouse models of IA have been described, all the models have their limitations. We here modified the current models and established a cost-effective and reproducible mouse model that recapitulates the key features of human IA. Methods: In adult C57black/6 male mice, the left common carotid arteries and the left renal arteries were ligated with high salt diet. One week later, 35 mU elastase was stereotactically injected into the right basal cistern. The animals were closely monitored each day for any neurological symptoms until the end of the study. All asymptomatic mice were euthanized 4 weeks after stereotactic injection and the circle of Willis (COW) was inspected under microscope for the presence of aneurysm and/or signs of rupture. Histological analyses were then performed to evaluate the pathological features of IA. Quantitative real-time PCR was employed on COW tissue to compare the expression of IA-pathogenesis associated genes between IA-inducing group and sham operative controls group. Results: All of the mice in the IA-inducing group were developed various aneurysmal changes within COW (n=40). A total of 67.5% (27/40) of the mice were successfully induced saccular IA (sIA) and 11% (3/27) had ruptured aneurysms. The average sIA number for each mouse is 1.4 (38/27). Histologically, aneurysms observed in this model closely resembled human IA including fragmentation of internal elastic lamina, thinning or discontinuities of the smooth muscle cell layer, and F4/80 positive macrophage infiltration within the aneurysm wall. Gene expression assay revealed that IA induction significantly increased expression of inflammation ( NF-κBp65, TNF-α, IL-1β, IL-8 ), matrix remodeling ( MMP-2, TIMP-3 ), EC marker ( Vinculin ) and VSMC marker ( KIF5 ) genes. Conclusion: This model can serve as a useful tool for future studies that utilize various inhibitors, knockout mice, or transgenic mice to test how specific molecules and pathways influence IA development.

Intracranial Aneurysm as a Macrophage-mediated Inflammatory Disease.

Subarachnoid hemorrhage (SAH) is mainly attributable to the rupture of intracranial aneurysms (IAs). Although the outcome of SAH is considerably poor in spite of the recent intensive medical care, mechanisms regulating the progression of IAs or triggering rupture remain to be clarified, making the development of effective preemptive medicine to prevent SAH difficult. However, a series of recent studies have been expanding our understanding of the pathogenesis of IAs. These studies have suggested the crucial role of macrophage-mediated chronic inflammation in the pathogenesis of IAs. In histopathological analyses of IA lesions in humans and induced in animal models, the number of macrophages infiltrating in lesions is positively correlated with enlargement or rupture of IAs. In animal models, a genetic deletion or an inhibition of monocyte chemotactic protein-1, a major chemoattractant for macrophages, or a pharmacological depletion of macrophages consistently suppresses the development and progression of IAs. Furthermore, a macrophage-specific deletion of Ptger2 (gene for prostaglandin E receptor subtype 2) or a macrophage-specific expression of a mutated form of IκBα which inhibits nuclear translocation of nuclear factor κB significantly suppress the development of IAs, supporting the role of macrophages and the inflammatory signaling functioning there in the pathogenesis of IAs. The development of drug therapies suppressing macrophage-mediated inflammatory responses in situ can thus be a potential strategy in the pre-emptive medicine targeting SAH. In this manuscript, we summarize the experimental evidences about the pathogenesis of IAs focused on inflammatory responses and propose the definition of IAs as a macrophage-mediated inflammatory disease.

Associations among Genetic Variants and Intracranial Aneurysm in a Chinese Population.

PurposeGenome-wide association studies (GWAS) have revealed that common variants on or near EDNRA, HDAC9, SOX17, RP1, CDKN2B-AS1, and RBBP8 genes are associated with intracranial aneurysm (IA) in European or Japanese populations. However, due to population heterogeneity, whether these loci are associated with IA pathogenesis in Chinese individuals is still unknown. The purpose of this study was to investigate associations among GWAS-identified loci and risk of IA in a Chinese population.Materials and MethodsA total of 765 individuals (including 230 IA patients and 535 controls) were involved in this study. Twelve single nucleotide polymorphisms (SNPs) of candidate loci were genotyped using the Sequenom MassARRAY platform. Associations were analyzed using univariate or multivariate logistic regression analysis.ResultsSNPs in CDKN2B-AS1 (especially rs10757272) showed significant associations with IA in dominant and additive models [odds ratio (OR), 2.99 and 1.43; 95% confidence interval (CI), 1.44–6.24 and 1.10–1.86, respectively]. A SNP near HDAC9 (rs10230207) was associated with IA in the dominant model (OR, 1.42; 95% CI, 1.01–1.99). One SNP near RP1 (rs1072737) showed a protective effect on IA in the dominant model (OR, 0.66; 95% CI, 0.46–0.95), while another SNP in RP1 (rs9298506) showed a risk effect on IA in a recessive model (OR, 3.82; 95% CI, 1.84–7.91). No associations were observed among common variants near EDNRA, SOX17, or RBBP8 and IA.ConclusionThese data partially confirmed earlier results and showed that variants in CDKN2B-AS1, RP1, and HDAC9 could be genetic susceptibility factors for IA in a Chinese population.

Expression profile analysis of differentially expressed genes in ruptured intracranial aneurysms: In search of biomarkers

Intracranial aneurysms (IAs) result from the bulging of arterial walls secondary to several factors such as flow, vessel morphology, and genetics. Subarachnoid hemorrhage occurs when such walls rupture, leading to high disability and mortality. Despite numerous investigations pertaining to the relationship between geometric characteristics and IA rupture, only a few have obtained consistent results. This study aimed to further identify the potential genes associated with the pathogenesis of IAs, which may provide novel molecular biomarkers. We downloaded and reanalyzed six datasets, which were divided into four groups. IA walls and blood samples were screened for differentially expressed genes (DEGs); then, functional and pathway enrichment analyses were conducted. In total, 158 common DEGs were identified from Groups 1–3 and 396 genes (187 upregulated and 209 downregulated genes) were differentially expressed in Group 4. The functional analysis revealed that the DEGs were mainly associated with the major histocompatibility complex class II protein complex and antigen processing and presentation. Finally, we identified nine key genes, both in aneurysm tissue samples and blood samples, of which three were mostly associated with the progression and rupture of IAs. Bioinformatics was used to analyze the datasets of the ruptured IAs and identify potential biomarkers, which may provide information for the early detection and treatment of IAs.

Gender-specific effects of MMP-2 and MMP-9 gene variants and the risk of aneurysmal subarachnoid haemorrhage

Matrix metalloproteinases (MMPs), a family of zinc-dependent proteases, have been linked with the pathogenesis of intracranial aneurysm (IA) formation and rupture. Patients with IA have elevated serum levels of MMP-2 and MMP-9 gene expression has been shown to be increased in aneurysm tissue. In this study, we have evaluated the association between MMP gene variants and aneurysmal subarachnoid hemorrhage (aSAH). The rs243865 in MMP-2 and rs17576 in MMP-9 genes were genotyped using Taqman allelic discrimination assay. Upon gender stratification, the presence of G allele of MMP-9 gene exon variant was found to increase the risk of aSAH by 1.4 fold (p = 0.032), in men. The GG genotype also showed a trend towards association with the risk of aSAH (OR: 1.785, CI: 0.971–3.283, p = 0.062) in men, after adjusting for the vascular risk factors. In women, no association was observed. The MMP-2 gene variants were not associated with aSAH in both genders. Further functional studies are required to describe the exact basis of the association between MMP-9 polymorphism and intracranial aneurysm in men.

The active participation of p22phox-214T/C in the formation of intracranial aneurysm and the suppressive potential of edaravone.

Oxidative stress reactions play an important role in the pathogenesis of intracranial aneurysm (IA). p22phox is involved in the oxidative stress reaction, and it is a critical subunit of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. The present study investigated the association of genetic variants within the gene encoding p22phox‑214T/C with IA. The p22phox‑214T/C gene polymorphisms in 192cases of IA and 112 controls were analyzed by polymerase chain reaction‑restriction fragment length polymorphism (PCR‑RFLP). The mRNA expression of NADPH oxidase was also analyzed by RT‑PCR. The results of RT‑PCR were validated by ELISA. In a rabbit model of elastase‑induced aneurysm, we used edaravone for anti‑oxidative stress treatment to observe the curative effects. In the clinical cases, a significant difference in p22phox‑214T/C allele frequencies in the IA group was observed compared with the control group (P<0.001). The expression level of NADPH oxidase was differed significantly between the IA group and the control group. In the rabbit model of elastase‑induced aneurysm, the success rate of the aneurysmal model in the edaravone group and the wound ulcer rate were lower than those in the control group. In addition, the diameter of the aneurysm was smaller than in the edaravone group than in the control group (3.26±0.13mm vs. 3.85±0.07mm), and the expression of matrix metalloproteinase‑9 (MMP‑9) was significantly lower than that in the control group (P<0.0001). Thus, these data suggest the active participation of p22phox‑214T/C in the formation of IA and the suppressive potential of edaravone against IA formation.

MicroRNA‑29a contributes to intracranial aneurysm by regulating the mitochondrial apoptotic pathway.

Intracranial aneurysm (IA) is an abnormal expansion in the intracranial arteries that weakens the arterial wall by consistently pushing the vascular wall outwards, which leads to a higher risk of aneurysm rupture. A number of reports have demonstrated that apoptosis is associated with the growth and rupture of IA. MicroRNAs (miRNAs/miRs) perform vital roles in the regulation of the mitochondrial apoptotic pathway and signaling proteins. Increasing evidence has already revealed the role of miR‑29a in injury, including liver injury, cardiovascular injury and ischaemia‑reperfusion injury. However, the role of miR‑29a in IA remains unclear at present. The present study investigated the role of miR‑29a in IA pathogenesis and the underlying mechanisms. By using reverse transcription‑quantitative polymerase chain reaction and western blot analysis, the present study demonstrated that genes, including caspase‑3, ‑8 and ‑9, and proteins, including cytochrome c and myeloid cell leukemia1 (Mcl‑1), involved in mitochondrial apoptosis pathways were upregulated in IA groups compared with controls. In addition, microarray analysis demonstrated that miR‑29a, one of the most altered miRs in IA mice, was overexpressed in IA mice compared with controls. Invitro experiments revealed that miR‑29a downregulation attenuated human brain vascular smooth muscle cell (HBVSMC) apoptosis, while miR‑29a overexpression increased the apoptosis of HBVSMCs. Furthermore, luciferase reporter analysis revealed that Mcl‑1 is a direct target gene of miR‑29a. An invivo IA model confirmed that miR‑29a overexpression may promote apoptosis through mitochondrial pathways. It was therefore concluded that miR‑29a may contribute to the progression of IA by regulating mitochondrial apoptotic pathways. Thus, miR‑29a is a potential therapeutic target for IA.

High Serum Level of Matrix Metalloproteinase-7 Is Associated With Increased Risk of Spontaneous Subarachnoid Hemorrhage.

Increased degradation of the extracellular matrix in the arterial wall by matrix metalloproteinases (MMPs) may be an important mechanism in the pathogenesis of intracranial aneurysms and subarachnoid hemorrhage (SAH). MMP-2 and MMP-9 have been suggested to be involved in matrix degradation preceding SAH. We studied serum levels of MMP-1, -2, -3, -7, -9, -10, and -12 and the risk of incident SAH. A nested case-control study within the population-based cohort, Malmö Diet and Cancer study, was performed including incident cases of spontaneous SAH (n=79) and controls matched by age, sex, and follow-up time (n=232). MMPs were measured in serum from the baseline examination in 1991 to 1996. MMPs were compared between cases and controls, using conditional logistic regression adjusting for risk factors. Baseline levels of MMP-7, MMP-10, and MMP-12 were significantly higher in incident SAH cases compared with controls. Odds ratios (95% confidence interval) for SAH per 1 SD increase of MMP-7, MMP-10, and MMP-12 were 1.78 (1.31-2.41), 1.45 (1.11-1.91), and 1.53 (1.17-2.01), respectively. After adjustment for SAH risk factors, MMP-7 was still significantly associated with SAH (odds ratio: 1.64; 95% confidence interval: 1.19-2.27; P=0.0026), whereas associations for MMP-10 and MMP-12 were attenuated and nonsignificant. We did not find any association between high serum levels of MMP-2 or MMP-9 and SAH risk. High serum level of MMP-7 was associated with increased risk of incident spontaneous SAH, independently of the main risk factors for SAH. High serum levels of MMP-2 and MMP-9 did not predict SAH risk.

Berberine Attenuates Macrophages Infiltration in Intracranial Aneurysms Potentially Through FAK/Grp78/UPR Axis.

Background: Inflammatory cells, such as macrophages, play key roles in the pathogenesis of intracranial aneurysms (IAs). Berberine (BBR), an active component of a Chinese herb Coptis chinensis French, has been shown to have anti-inflammatory properties through suppressing macrophage migration in various inflammation animal model. The goal of this study was to examine BBR’s effect on inflammation and IAs formation in a rodent aneurysm model.Methods and Results: Human aneurysm tissues were collected by microsurgical clipping and immunostained for phospho-Focal adhesion kinase (FAK) and CD68+ macrophages. A rodent aneurysm model was induced in 5-week-old male Sprague Dawley (SD) rats by intracranial surgery, then these rats were orally administrated 200 mg/kg/day BBR for 35 days. Immunostaining data showed that BBR inhibited CD68+ macrophages accumulation in IAs tissues and suppressed FAK phosphorylation. In lipopolysaccharide (LPS)-stimulated RAW264.7 cells, BBR treatment remarkably attenuated macrophages infiltration, suppressed the expression of matrix metalloproteinases (MMPs), and reduced proinflammatory cytokine secretion, including MCP-1, interleukin 1β (IL-1β), interleukin 6 (IL-6) and tumor necrosis factor-a (TNF-α). Mechanistically, BBR downregulated FAK/Grp78/Unfolded Protein Response (UPR) signaling pathway in RAW264.7 cells.Conclusion: BBR prevents IAs formation potentially through inhibiting FAK phosphorylation and inactivating UPR pathway in macrophages, which causes less macrophage infiltration and reduced proinflammatory cytokine release.

TLR4 gene polymorphisms rs11536889 is associated with intracranial aneurysm susceptibility

Intracranial aneurysm (IA) is a common lesion which often present asymptomatic until the time of rupture and result in subarachnoid hemorrhage (SAH). The pathogenesis of IA formation is complex and is influenced by both genetic and environmental risk factors. For exploring the detailed molecular and cellular mechanisms involved in the pathogenesis of IA, recent studies indicated inflammatory pathways and their genetic variants may as potential biomarkers. In this study, functionally relevant polymorphisms in the toll-like receptor 4 (TLR4) were screened in 330 IA patients and 313 controls from a Han Chinese population. Eight single nucleotide gene polymorphisms (SNPs) genotyped by the Improved Multiple Ligase Detection Reaction (iMLDR) method. Our results indicated that the presence of the minor allele (C) of the TLR4 SNP rs11536889 was associated with a decreased risk of IA (C vs. G, OR = 0.731; 95% CI 0.567–0.943; P = 0.017). This association was also present at the genotype level in a codominant model (GC vs. GG, OR = 0.447; 95% CI 0.226–0.884; P = 0.020) and a recessive model (CC vs. GG + GC, OR = 0.489; 95% CI 0.250–0.955; P = 0.035). In summary, we firstly found that the TLR4 SNP rs11536889 was significantly associated with the susceptibility of IA. Our results indicated TLR4 SNP rs11536889 may be a marker for IA risk, though the exact functional roles of TLR4 SNP rs11536889 in IA formation are still not very clear.

Correlating Clinical Risk Factors and Histological Features in Ruptured and Unruptured Human Intracranial Aneurysms: The Swiss AneuX Study

Pathogenesis of intracranial aneurysm is complex and the precise biomechanical processes leading to their rupture are uncertain. The goal of our study was to characterize the aneurysmal wall histologically and to correlate histological characteristics with clinical and radiological factors used to estimate the risk of rupture. A new biobank of aneurysm domes resected at the Geneva University Hospitals (Switzerland) was used. Histological analysis revealed that unruptured aneurysms have a higher smooth muscle cell (SMC) content and a lower macrophage content than ruptured domes. These differences were associated with more collagen in unruptured samples, whereas the elastin content was not affected. Collagen content and type distribution were different between thick and thin walls of unruptured aneurysms. Classification of aneurysm domes based on histological characteristics showed that unruptured samples present organized wall rich in endothelial and SMCs compared with ruptured samples. Finally, aneurysm wall composition was altered in unruptured domes of patients presenting specific clinical factors used to predict rupture such as large dome diameter, dome irregularities, and smoking. Our study shows that the wall of aneurysm suspected to be at risk for rupture undergoes structural alterations relatively well associated with clinical and radiological factors currently used to predict this risk.