The role of autophagy in abdominal aortic aneurysm: protective but dysfunctional

N6-methyladenosine-associated genetic variants in NECTIN2 and HPCAL1 are risk factors for abdominal aortic aneurysm

Although N6-methyladenosine (m6A) modification has been implicated in the pathogenesis of abdominal aortic aneurysm (AAA), the relationship between m6A-associated single nucleotide polymorphisms (m6A-SNPs) and AAA remains unknown. This study used integrative multi-omics analysis and clinical validation approaches to systematically identify potential m6A-SNPs connected with AAA risk. We found that rs6859 and rs10198139 could modulate the expression of local genes, NECTIN2 and HPCAL1, respectively, which exhibited upregulation in AAA tissues, and their risk variants were significantly correlated with an increased susceptibility to AAA. Incorporating rs6859 and rs10198139 improved the efficiency of AAA risk prediction compared to the model considering only conventional risk factors. Additionally, these two SNPs were predicted to be located within the regulatory sequences, and rs6859 showed a substantial impact on m6A modification levels. Our findings suggest that m6A-SNPs rs6859 and rs10198139 confer an elevated risk of AAA, possibly by promoting local gene expression through an m6A-mediated manner.

The occurrence and development of abdominal aortic aneurysm may be related to the energy metabolism disorder and local inflammation

Background

The cellular mechanism of the formation of abdominal aortic aneurysm (AAA) is very complicated. A series of sophisticated events eventually led to significant pathological changes in the anatomical structure and function of the arterial wall and they are still not clear nowadays.

Methods

We pooled publicly available GEO datasets (GSE57691 and GSE47472) to get a comprehensive comparisons between normal tissues and AAA tissues to try to reveal molecular mechanism underlying the disease. Total 63 AAA samples and 18 normal tissue samples were compared and we fond that there were 784 significantly different gene (DEGs, threshold set as adjusted P < 0.05 and Log FC < 1) were identified. At the same time, we validate the possible signaling factor expression of AAA by comparing the normal tissue of the human body with the AAA tissue.

Results

In the pathway enrichment, we found that FOXP3 related signaling pathways, inflammation-related cytokine signaling pathways, interleukin-8-CXCR1 related signaling pathways and VEGFA and FGFR1 related signal pathway were significantly enrichmented. In Weighted gene co-expression network analysis (WGCNA), we found that the key hub genes were significantly related to lipid catabolic metabolism, which further verified the possibility that AAA might relate to energy metabolism disorders.

Conclusion

Based on the comprehensive analysis of previous high-throughput data and the validation of basic experiments, we found that the occurrence of AAA may be related to energy metabolism disorders and local inflammation.

Comprehensive view of macrophage autophagy and its application in cardiovascular diseases

Cardiovascular diseases (CVDs) are the primary drivers of the growing public health epidemic and the leading cause of premature mortality and economic burden worldwide. With decades of research, CVDs have been proven to be associated with the dysregulation of the inflammatory response, with macrophages playing imperative roles in influencing the prognosis of CVDs. Autophagy is a conserved pathway that maintains cellular functions. Emerging evidence has revealed an intrinsic connection between autophagy and macrophage functions. This review focuses on the role and underlying mechanisms of autophagy-mediated regulation of macrophage plasticity in polarization, inflammasome activation, cytokine secretion, metabolism, phagocytosis, and the number of macrophages. In addition, autophagy has been shown to connect macrophages and heart cells. It is attributed to specific substrate degradation or signalling pathway activation by autophagy-related proteins. Referring to the latest reports, applications targeting macrophage autophagy have been discussed in CVDs, such as atherosclerosis, myocardial infarction, heart failure, and myocarditis. This review describes a novel approach for future CVD therapies.

FGF21 promotes angiotensin II-induced abdominal aortic aneurysm via PI3K/AKT/mTOR pathway

BACKGROUND

Abdominal aortic aneurysm (AAA) is a potentially fatal vascular disorder with a high mortality rate. It was previously reported that fibroblast growth factor 21 (FGF21) was highly expressed in AAA patients. Nonetheless, its underlying mechanism in AAA progression is unclarified.

METHODS

Angiotensin II (Ang-II) was used to induce AAA in human aortic vascular smooth muscle cells (HASMCs) and mouse models. Western blotting and RT-qPCR were utilized for measuring protein and RNA levels. Immunofluorescence staining was utilized for detecting LC3B expression in HASMCs. Elastica van Gieson staining was conducted for histological analysis of the abdominal aortas of mice.

RESULTS

FGF21 displayed a high level in Ang-II-stimulated HASMCs and AAA mice. FGF21 depletion ameliorated abdominal aorta dilation and Ang-II-triggered pathological changes in mice. FGF21 silencing hindered autophagy and PI3K/AKT/mTOR pathway.

CONCLUSIONS

FGF21 contributes to AAA progression by enhancing autophagy and activating PI3K/AKT/mTOR pathway.

Dexmedetomidine Alleviates Abdominal Aortic Aneurysm by Activating Autophagy Via AMPK/mTOR Pathway

BACKGROUND

Abdominal aortic aneurysms (AAA) are a critical global health issue with increasing prevalence. Dexmedetomidine (DEX) is a highly selective α2-adrenoceptor agonist that has previously been shown to play a protective role in AAA. Nevertheless, the mechanisms underlying its protection effect remain not fully understood.

METHODS

A rat AAA model was established via intra-aortic porcine pancreatic elastase perfusion with or without DEX administration. The abdominal aortic diameters of rats were measured. Hematoxylin-eosin and Elastica van Gieson staining were conducted for histopathological observation. TUNEL and immunofluorescence staining were utilized to detect cell apoptosis and α-SMA/LC3 expression in the abdominal aortas. Protein levels were determined using western blotting.

RESULTS

DEX administration repressed the dilation of aortas, alleviated pathological damage and cell apoptosis, and suppressed phenotype switching of vascular smooth muscle cells (VSMCs). Moreover, DEX activated autophagy and regulated the AMP-activated protein kinase/mammalian target of the rapamycin (AMPK/mTOR) signaling pathway in AAA rats. Administration of the AMPK inhibitor attenuated the DEX-mediated ameliorative effects on AAA in rats.

CONCLUSION

DEX ameliorates AAA in rat models by activating autophagy via the AMPK/mTOR pathway.

Protective Role for Smooth Muscle Cell Hepcidin in Abdominal Aortic Aneurysm

BACKGROUND

Hepcidin is a liver-derived hormone that controls systemic iron homeostasis, by inhibiting the iron exporter ferroportin in the gut and spleen, respective sites of iron absorption and recycling. Hepcidin is also expressed ectopically in the context of cardiovascular disease. However, the precise role of ectopic hepcidin in underlying pathophysiology is unknown. In patients with abdominal aortic aneurysm (AAA), hepcidin is markedly induced in smooth muscle cells (SMCs) of the aneurysm wall and inversely correlated with the expression of LCN2 (lipocalin-2), a protein implicated in AAA pathology. In addition, plasma hepcidin levels were inversely correlated with aneurysm growth, suggesting hepcidin has a potential disease-modifying role.

METHODS

To probe the role of SMC-derived hepcidin in the setting of AAA, we applied AngII (Angiotensin-II)-induced AAA model to mice harbouring an inducible, SMC-specific deletion of hepcidin. To determine whether SMC-derived hepcidin acted cell-autonomously, we also used mice harboring an inducible SMC-specific knock-in of hepcidin-resistant ferroportinC326Y. The involvement of LCN2 was established using a LCN2-neutralizing antibody.

RESULTS

Mice with SMC-specific deletion of hepcidin or knock-in of hepcidin-resistant ferroportinC326Y had a heightened AAA phenotype compared with controls. In both models, SMCs exhibited raised ferroportin expression and reduced iron retention, accompanied by failure to suppress LCN2, impaired autophagy in SMCs, and greater aortic neutrophil infiltration. Pretreatment with LCN2-neutralizing antibody restored autophagy, reduced neutrophil infiltration, and prevented the heightened AAA phenotype. Finally, plasma hepcidin levels were consistently lower in mice with SMC-specific deletion of hepcidin than in controls, indicating that SMC-derived hepcidin contributes to the circulating pool in AAA.

CONCLUSIONS

Hepcidin elevation in SMCs plays a protective role in the setting of AAA. These findings are the first demonstration of a protective rather than deleterious role for hepcidin in cardiovascular disease. They highlight the need to further explore the prognostic and therapeutic value of hepcidin outside disorders of iron homeostasis.

Trehalose attenuates abdominal aortic aneurysm formation by inducing autophagy in smooth muscle cells

BACKGROUND

Trehalose is a naturally occurring disaccharide, which has been identified as an autophagy inducer and exhibits protective effect in cardiovascular diseases such as myocardial infraction and atherosclerosis. However, the functional role of trehalose in abdominal aortic aneurysm (AAA) remains undefined.

METHODS

To study the effect of trehalose in AAA, trehalose (1 g/kg per day) were given for 14 continuous days in a mouse model of elastase-induced abdominal aortic aneurysm. On day 14, ultrasound was performed to measure aortic diameter before the abdominal aortas were harvested and processed for further analysis. Verhoeff-Van Gieson staining and TUNEL staining were performed on paraffin sections to evaluate vascular histology and apoptosis, immunofluorescence staining and Western-blot were performed to evaluate expression of autophagy markers.

RESULTS

Echocardiography and in situ pictures demonstrated that trehalose attenuated infrarenal aorta dilation. Verhoeff-Van Gieson staining showed elastin degradation was improved in trehalose-treated group. Compared with vehicle-treated mice, trehalose treatment restored smooth muscle cell contractile phenotype with increased α-SMA, Calponin and Myh11 expression. Furthermore, trehalose also attenuated cell apoptosis and leukocytes infiltration. Importantly, trehalose induced autophagy with decrease SQSTM1/p62 accumulation, increased lamp2 expression and LC3B conversion.

CONCLUSION

Trehalose attenuated AAA progression with decreased inflammation and restored SMC contractile phenotype by inducing autophagy. These results demonstrated the therapeutic potential of trehalose in AAA.

Identification of differentially expressed ferroptosis-related genes in abdominal aortic aneurysm: Bioinformatics analysis

Purpose

Ferroptosis plays a crucial role in the development and progression of abdominal aortic aneurysm (AAA). The aim of this study was to identify differentially expressed genes associated with ferroptosis in AAA through bioinformatics analysis combined with experimental validation.

Materials and methods

Firstly, the mRNA expression profile datasets GSE57691 and GSE47472 from Gene Expression Omnibus database were screened, and principal component analysis was carried out. Next, the R software (version 4.0.0) was used to analyze potentially differentially expressed genes associated with AAA and ferroptosis. Subsequently, protein–protein interaction analysis, gene ontology enrichment analysis, and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis were performed on the selected candidate genes. Finally, quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression levels of the first five selected abnormal ferroptosis-related genes in clinical samples obtained from patients with AAA and healthy controls.

Results

Based on the information contained in the two datasets, a total of 20 differentially expressed ferroptosis-related genes (three upregulated genes and 17 downregulated genes) were selected. Protein–protein interaction analysis demonstrated interaction between these genes, while gene ontology enrichment analysis of ferroptosis genes with differential expression indicated that some enrichment items were associated with oxidative stress. The qRT-PCR results showed that the expression levels of interleukin-6 (IL-6), peroxiredoxin 1 (PRDX1), and stearoyl-CoA desaturase (SCD) were consistent with the bioinformatics prediction results obtained from the mRNA chip.

Conclusion

Bioinformatics analysis identified 20 potential ferroptosis-related differentially expressed genes in AAA. Further verification by qRT-PCR showed that IL-6, PRXD1, and SCD might affect the process of AAA by regulating ferroptosis. Our results might assist in further understanding the pathogenesis of AAA and guiding treatment.

Expression Pattern and Clinical Value of Key m6A RNA Modification Regulators in Abdominal Aortic Aneurysm

Background

Aberrant expression of N6-methyladenosine (m6A) RNA modification regulators plays a critical role in a variety of human diseases. However, their implication in abdominal aortic aneurysm (AAA) remains largely unknown. Herein, we sought to explore the general expression pattern and potential functions of m6A regulators in AAA.

Methods

We analyzed gene expression data of m6A regulators in human AAA and normal tissues from public GEO database. The R package and other tools such as m6A2Target database, Gene ontology (GO) functional and Kyoto encyclopedia of genes and genomes (KEGG) pathway analyses, gene set variation analysis (GSVA), Search Tool for the Retrieval of Interacting Genes (STRING), starBase, miRDB and Cytoscape software were applied for bioinformatics analysis to investigate the downstream molecular mechanisms and upstream regulatory mechanisms for distinctly expressed regulators. Quantitative real-time PCR (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA) were performed to validate the expression of key m6A regulators in our collected human AAA specimens.

Results

We found that METTL14 and HNRNPC were the downregulated m6A regulators, and RBM15B was the upregulated methylation transferase in human AAA. The modified genes were primarily enriched in RNA catabolic process, regulation of translation, focal adhesion, transcription coregulator activity, ribosome, RNA transport, cell cycle, et al. METTL14, HNRNPC and RBM15B levels were correlated with the immune infiltration degree of Tcm, macrophages, mast cells, Tgd and NK CD56bright cells. A total of 154 and 76 target genes of three regulators were separately involved in body metabolism and autophagy in AAA disease, and their interactive relationships and hub genes were identified. The lncRNA-miRNA-mRNA interaction regulatory networks were also constructed for METTL14, HNRNPC and RBM15B. Based on our clinical tissue and serum samples, METTL14 exhibited lower expression levels in AAA and its rupture type, and low METTL14 expression was associated with high levels of WBC and CRP (all P < 0.05).

Conclusion

Our study presents an overview of the expression pattern and functional significance of m6A regulators in human AAA. Our findings will provide a valuable resource that may guide both mechanistic and therapeutic analyses about the role of key m6A regulators in AAA.

Different types of cell death in vascular diseases

In a mature organism, tissue homeostasis is regulated by cell division and cell demise as the two major physiological procedures. There is increasing evidence that deregulation of these processes is important in the pathogenicity of main diseases, including myocardial infarction, stroke, atherosclerosis, and inflammatory diseases. Therefore, there are ongoing efforts to discover modulating factors of the cell cycle and cell demise planners aiming at shaping innovative therapeutically modalities to the therapy of such diseases. Although the life of a cell is terminated by several modes of action, a few cell deaths exist-some of which resemble apoptosis and/or necrosis, and most of them are different from one another-that contribute to a wide range of functions to either support or disrupt the homoeostasis. Even in normal physiological conditions, cell life is severe within the cardiovascular system. Cells are persistently undergoing stretch, contraction, injurious metabolic byproducts, and hemodynamic forces, and a few of cells sustain decade-long lifetimes. The duration of vascular disease causes further exposure of vascular cells to a novel range of offences, most of which induce cell death. There is growing evidence on consequences of direct damage to a cell, as well as on responses of adjacent and infiltrating cells, which also have an effect on the pathology. In this study, by focusing on different pathways of cell death in different vascular diseases, an attempt is made to open a new perspective on the therapeutic goals associated with cell death in these diseases.