The Role of Epigenetic Modifications in Abdominal Aortic Aneurysm Pathogenesis

LXRα Promotes Abdominal Aortic Aneurysm Formation Through UHRF1 Epigenetic Modification of miR-26b-3p

BACKGROUND

Abdominal aortic aneurysm (AAA) is a severe aortic disease without effective pharmacological approaches. The nuclear hormone receptor LXRα (liver X receptor α), encoded by the NR1H3 gene, serves as a critical transcriptional mediator linked to several vascular pathologies, but its role in AAA remains elusive.

METHODS

Through integrated analyses of human and murine AAA gene expression microarray data sets, we identified NR1H3 as a candidate gene regulating AAA formation. To investigate the role of LXRα in AAA formation, we used global Nr1h3-knockout and vascular smooth muscle cell-specific Nr1h3-knockout mice in 2 AAA mouse models induced with angiotensin II (1000 ng·kg·min; 28 days) or calcium chloride (CaCl2; 0.5 mol/L; 42 days).

RESULTS

Upregulated LXRα was observed in the aortas of patients with AAA and in angiotensin II- or CaCl2-treated mice. Global or vascular smooth muscle cell-specific Nr1h3 knockout inhibited AAA formation in 2 mouse models. Loss of LXRα function prevented extracellular matrix degeneration, inflammation, and vascular smooth muscle cell phenotypic switching. Uhrf1, an epigenetic master regulator, was identified as a direct target gene of LXRα by integrated analysis of transcriptome sequencing and chromatin immunoprecipitation sequencing. Susceptibility to AAA development was consistently enhanced by UHRF1 (ubiquitin-like containing PHD and RING finger domains 1) in both angiotensin II- and CaCl2-induced mouse models. We then determined the CpG methylation status and promoter accessibility of UHRF1-mediated genes using CUT&Tag (cleavage under targets and tagmentation), RRBS (reduced representation bisulfite sequencing), and ATAC-seq (assay for transposase-accessible chromatin with sequencing) in vascular smooth muscle cells, which revealed that the recruitment of UHRF1 to the promoter of miR-26b led to DNA hypermethylation accompanied by relatively closed chromatin states, and caused downregulation of miR-26b expression in AAA. Regarding clinical significance, we found that underexpression of miR-26b-3p correlated with high risk in patients with AAA. Maintaining miR-26b-3p expression prevented AAA progression and alleviated the overall pathological process.

CONCLUSIONS

Our study reveals a pivotal role of the LXRα/UHRF1/miR-26b-3p axis in AAA and provides potential biomarkers and therapeutic targets for AAA.

Construction of the circRNA-miRNA-mRNA axis based on ferroptosis-related gene AKR1C1 to explore the potential pathogenesis of abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a cardiovascular disease that seriously threatens human health and brings huge economic burden. At present, its pathogenesis remains unclear and its treatment is limited to surgical treatment. With the deepening and analysis of studies on the mechanism of ferroptosis, a new idea has been provided for the clinical management of AAA patients, including diagnosis, treatment and prevention. Therefore, this paper aims to construct a competitive endogenous RNA (ceRNA) regulatory axis based on ferroptosis to preliminarily explore the pathogenesis and potential therapeutic targets of AAA. We obtained upregulated and downregulated ferroptosis-related DEGs (FRGs) from GSE144431 dataset and 60 known ferroptosis-related genes. Pearson correlation analysis was used to find aldoketone reductase 1C (AKR1C1) in AAA samples. Enrichment analysis of these genes was performed via Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Correlation test between immune cells and AKR1C1 was investigated through single-sample gene set enrichment analysis (ssGSEA). The AKR1C1-miRNA pairs were predicted by the TargetScan database and miRWalk database. Circular RNA (CircRNA)-miRNA pairs were selected by the CircInteractome database. Overlapping miRNA between circRNA-miRNA and AKR1C1-miRNA pairs was visualized by Venn diagram. Finally, the circRNA-miRNA-mRNA axis was constructed by searching for upstream circRNA and downstream mRNA of overlapping miRNA. Only one downregulated AKR1C1 gene was found in GSE144431 and 60 ferroptosis-related genes. Functional Enrichment and Pathway Analysis of AKR1C1-related genes were further explored, and it was observed that they were mainly enriched in "response to oxidative stress," "glutathione biosynthetic process" and "nonribosomal peptide biosynthetic process," "Ferroptosis," "Glutathione metabolism" and "Chemical carcinogenesis-reactive oxygen species." They were also found to be significantly associated with most immune cells, including Activated Dendritic cells, CD56dim Natural killer cells, Gamma Delta T cells, Immature B cells, Plasmacytoid dendritic cell, Type 2 T helper cell, Activated CD4 T cell and Type 1 T helper cell. Has_circ_0005073-miRNA-543 and AKR1C1-miRNA-543 were identified by Online Database analysis. Therefore, we have established the has_circ_0005073/miRNA-543/AKR1C1 axis in AAA. We found AKR1C1 was differentially expressed between normal and AAA groups. Based on AKR1C1, we constructed the has_circ_0005073/miRNA-543/AKR1C1 axis to analyze AAA.

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.

Deciphering disease signatures and molecular targets in vascular Ehlers-Danlos syndrome through transcriptome and miRNome sequencing of dermal fibroblasts

Vascular Ehlers-Danlos syndrome (vEDS) is a severe connective tissue disorder caused by dominant mutations in the COL3A1 gene encoding type III collagen (COLLIII). COLLIII is primarily found in blood vessels and hollow organs, and its deficiency leads to soft connective tissues fragility, resulting in life-threatening arterial and organ ruptures. There are no current targeted therapies available. Although the disease usually results from COLLIII misfolding due to triple helix structure disruption, the underlying pathomechanisms are largely unknown. To address this knowledge gap, we performed a comprehensive transcriptome analysis using RNA- and miRNA-seq on a large cohort of dermal fibroblasts from vEDS patients and healthy donors. Our investigation revealed an intricate interplay between proteostasis abnormalities, inefficient endoplasmic reticulum stress response, and compromised autophagy, which may significantly impact the molecular pathology. We also present the first detailed miRNAs expression profile in patient cells, demonstrating that several aberrantly expressed miRNAs can disrupt critical cellular functions involved in vEDS pathophysiology, such as autophagy, proteostasis, and mTOR signaling. Target prediction and regulatory networks analyses suggested potential interactions among miRNAs, lncRNAs, and candidate target genes linked to extracellular matrix organization and autophagy-lysosome pathway. Our results highlight the importance of understanding the functional role of ncRNAs in vEDS pathogenesis, shedding light on possible miRNAs and lncRNAs signatures and their functional implications for dysregulated pathways related to disease. Deciphering this complex molecular network of RNA interactions may yield additional evidence for potential disease biomolecules and targets, assisting in the design of effective patient treatment strategies.

The Role of Selected Epigenetic Pathways in Cardiovascular Diseases as a Potential Therapeutic Target

Epigenetics is a rapidly developing science that has gained a lot of interest in recent years due to the correlation between characteristic epigenetic marks and cardiovascular diseases (CVDs). Epigenetic modifications contribute to a change in gene expression while maintaining the DNA sequence. The analysis of these modifications provides a thorough insight into the cardiovascular system from its development to its further functioning. Epigenetics is strongly influenced by environmental factors, including known cardiovascular risk factors such as smoking, obesity, and low physical activity. Similarly, conditions affecting the local microenvironment of cells, such as chronic inflammation, worsen the prognosis in cardiovascular diseases and additionally induce further epigenetic modifications leading to the consolidation of unfavorable cardiovascular changes. A deeper understanding of epigenetics may provide an answer to the continuing strong clinical impact of cardiovascular diseases by improving diagnostic capabilities, personalized medical approaches and the development of targeted therapeutic interventions. The aim of the study was to present selected epigenetic pathways, their significance in cardiovascular diseases, and their potential as a therapeutic target in specific medical conditions.

METTL3-METTL14 complex induces necroptosis and inflammation of vascular smooth muscle cells via promoting N6 methyladenosine mRNA methylation of receptor-interacting protein 3 in abdominal aortic aneurysms

Abdominal aortic aneurysms (AAA) have the highest incidence and rupture rate of all aortic aneurysms. The N6 methyladenosine (m6A) modification is closely associated with angiotensin (Ang II)-induced aortic diseases. This study aimed to identify whether the m6A writer METTL3/METTL4 regulates rip3 mRNA expression in AAA. To induce the mouse AAA model, apolipoprotein E-deficient (ApoE-/-) mice were subcutaneously infused with Ang II, and C57BL/6 mice were infused with type I elastase. Vascular smooth muscle cells (VSMCs) were induced with Ang II. Necroptosis was detected using an Annexin V-FITC/PI apoptosis detection kit, and ELISA assays measured inflammatory cytokines. The RNA immunoprecipitation-qPCR determined the methylated rip3 mRNA level. The increased expressions of inflammatory factors, aortic adventitia injury, degradation of elastin, and CD68-positive cells suggested the successful establishment of mouse AAA models. In AAA aorta wall tissues, the m6A modification level and the expression of METTL3/METTL14 were elevated. In Ang II-induced VSMCs, necroptosis and inflammatory cytokines in the supernatants were increased. RNA immunoprecipitation and co-immunoprecipitation assays confirmed the binding between the METTL3-METTL14 complex and rip3 mRNA, the interaction between YTHDF3 and rip3 mRNA, and between the METTL3-METTL14 complex and SMAD2/3. Interference with METTL3/METTL14 attenuated VSMC necroptosis, inflammatory response, and the AAA pathological process in vivo. The METTL3-METTL14 complex, which was increased by the activation of the SMAD2/3, elevated the m6A modification of rip3 mRNA by promoting the binding between YTHDF3 and rip3 mRNA, thus contributing to the progression of AAA. The activation of SMAD2/3 in VSMCs of abdominal aortic wall tissues is stimulated by Ang II. Subsequently, it promotes METTL3 METTL14 complex mediated m6A modification of rip3 mRNA. Meanwhile, the level of rip3 mRNA becomes more stable under the m6A reader of YTHDF3, which increases the protein level of RIP3 and further induces VSMC necroptosis. In addition, cell debris induces inflammatory factors in neighboring VSMCs and recruit monocytes/macrophages to the lesion.

Identification of Potential Abnormal Methylation-Modified Genes in Coronary Artery Ectasia

Background

Coronary artery ectasia (CAE) is an easily recognized abnormality of coronary artery anatomy and morphology. However, its pathogenesis remains unclear.

Objectives

This study aimed to identify abnormal methylation-modified genes in patients with CAE, which could provide a research basis for CAE.

Methods

Peripheral venous blood samples from patients with CAE were collected for RNA sequencing to identify differentially expressed genes (DEGs), followed by functional enrichment. Then, the DNA methylation profile of CAE was downloaded from GSE87016 (HumanMethylation450 BeadChip data, involving 11 cases and 12 normal controls) to identify differentially methylated genes (DMGs). Finally, after taking interaction genes between DEGs and DMGs, abnormal methylation-modified genes were identified, followed by protein-protein interaction analysis and expression validation using reverse transcriptase polymerase chain reaction.

Results

A total of 152 DEGs and 4318 DMGs were obtained from RNA sequencing and the GSE87016 dataset, respectively. After taking interaction genes, 9 down-regulated DEGs due to hypermethylation and 11 up-regulated DEGs due to hypomethylation were identified in CAE. A total of 10 core abnormal methylation-modified genes were identified, including six down-regulated DEGs due to hypermethylation (netrin G1, ADAM metallopeptidase domain 12, immunoglobulin superfamily member 10, sarcoglycan dela, Dickkopf WNT signaling pathway inhibitor 3, and GATA binding protein 6), and four up-regulated DEGs due to hypomethylation (adrenomedullin, ubiquitin specific peptidase 18, lymphocyte antigen 6 family member E, and MX dynamin-like GTPase 1). Some signaling pathways were identified in patients with CAE, including cell adhesion molecule, O-glycan biosynthesis, and the renin-angiotensin system.

Conclusions

Abnormal methylation-modified DEGs involved in signaling pathways may be involved in CAE development.

Tributyrin Intake Attenuates Angiotensin II-Induced Abdominal Aortic Aneurysm in LDLR-/- Mice

Abdominal aortic aneurysm (AAA) is a multifactorial cardiovascular disease with a high risk of death, and it occurs in the infrarenal aorta with vascular dilatation. High blood pressure acts on the aortic wall, resulting in rupture and causing life-threatening intra-abdominal hemorrhage. Vascular smooth muscle cell (VSMC) dysregulation and extracellular matrix (ECM) degradation, especially elastin breaks, contribute to structural changes in the aortic wall. The pathogenesis of AAA includes the occurrence of oxidative stress, inflammatory cell infiltration, elastic fiber fragmentation, VSMC apoptosis, and phenotypic transformation. Tributyrin (TB) is decomposed by intestinal lipase and has a function similar to that of butyrate. Whether TB has a protective effect against AAA remains uncertain. In the present study, we established an AAA murine model by angiotensin II (AngII) induction in low-density lipoprotein receptor knockout (LDLR^-/-) mice and investigated the effects of orally administered TB on the AAA size, ratio of macrophage infiltration, levels of matrix metalloproteinase (MMP) expression, and epigenetic regulation. TB attenuates AngII-induced AAA size and decreases elastin fragmentation, macrophage infiltration, and MMP expression in the medial layer of the aorta and reduces the levels of SBP (systolic blood pressure, p < 0.001) and MMP-2 (p < 0.02) in the serum. TB reduces the AngII-stimulated expression levels of MMP2 (p < 0.05), MMP9 (p < 0.05), MMP12, and MMP14 in human aortic smooth muscle cells (HASMCs). Moreover, TB and valproic acid (VPA), a histone deacetylase (HDAC) inhibitor, suppress AngII receptor type 1 (AT1R, p < 0.05) activation and increase the expression of acetyl histone H3 by HDAC activity inhibition (p < 0.05). Our findings suggest that TB exerts its protective effect by suppressing the activation of HDAC to attenuate the AngII-induced AT1R signaling cascade.

Aortic Aneurysm and Dissection: Heterogeneity and Molecular Mechanisms

Aortic aneurysms and dissections (AAD) are devastating aortic diseases with high risks for aortic rupture, leading to uncontrolled bleeding and death [...].

Large Vessel Cell Heterogeneity and Plasticity: Focus in Aortic Aneurysms

Smooth muscle cells and endothelial cells have a remarkable level of plasticity in vascular pathologies. In thoracic and abdominal aortic aneurysms, smooth muscle cells have been suggested to undergo phenotypic switching and to contribute to degradation of the aortic wall structure in response to, for example, inflammatory mediators, dysregulation of growth factor signaling or oxidative stress. Recently, endothelial-to-mesenchymal transition, and a clonal expansion of degradative smooth muscle cells and immune cells, as well as mesenchymal stem-like cells have been suggested to contribute to the progression of aortic aneurysms. What are the factors driving the aortic cell phenotype changes and how vascular flow, known to affect aortic wall structure and to be altered in aortic aneurysms, could affect aortic cell remodeling? In this review, we summarize the current literature on aortic cell heterogeneity and phenotypic switching in relation to changes in vascular flow and aortic wall structure in aortic aneurysms in clinical samples with special focus on smooth muscle and endothelial cells. The differences between thoracic and abdominal aortic aneurysms are discussed.