Profiling of Histone Modifications Reveals Epigenomic Dynamics During Abdominal Aortic Aneurysm Formation in Mouse Models

Abstract

Introduction: Abdominal aortic aneurysms (AAA) are characterized by localized inflammation, extracellular matrix degradation, and apoptosis of smooth muscle cells, which together lead to progressive and irreversible aortic dilation. Major risk factors for AAA include smoking and aging, both of which prominently alter gene expression via epigenetic mechanisms, including histone methylation (me) and acetylation (ac).However, little is known about epigenomic dynamics during AAA formation. Here, we profiled histone modification patterns in aortic tissues during AAA formation in two distinct mouse models; (1) angiotensin II (AngII) infusion in low density lipoprotein receptor (LDLR) knockout (KO) mice, and (2) calcium chloride (CaCl 2 ) application in wild type mice. Methods and Results:AAA formed in both models, in conjunction with enhanced macrophage infiltration, elastin degradation and matrix metalloproteinases expression as evaluated by immunohistochemistry. To investigate the histone modification patterns during AAA formation, total histone proteins were extracted from AAA tissues, and histone H3 modifications were quantified using profiling kits. Intriguingly, we observed dynamic changes in histone H3 modifications of lysine (K) residues at different time points during AAA formation. In mature aneurysmal tissues at 3 weeks after AngII infusion, we detected reduced K4/K27/K36 monomethylation, K9 trimethylation K9, and K9/K56 acetylation (<70%), and increased K4 trimethylation (>130%). Conversely, in CaCl 2 -induced AAA, K4/K9/K27/K36/K79 monomethylation and K9/K18/K56 acetylation were reduced in AAA tissues, whereas K27 di-/tri-methylation and K14 acetylation were upregulated. Interestingly, K4/K27/K36 monomethylation, K9 trimethylation, and K9/K56 acetylation were commonly downregulated in both animal models, while no H3 modifications were uniformly upregulated. Western blot of AAA tissues confirmed Greenway et al.Profiling of Histone H3 Modifications in AAA markedly reduced levels of key H3 modifications, including H3K4me1, H3K9me3, and H3K56ac. Furthermore, pathway enrichment analysis using an integrative bioinformatics approach identified specific molecular pathways, including endocytosis, exon guidance and focal adhesion signaling, that may potentially be linked to these histone H3 modifications during AAA formation.Conclusions: Dynamic modifications of histone H3 occur during AAA formation in both animal models. We identified 6 discreet H3 modifications that are consistently downregulated in both models, suggesting a possible role in AAA pathobiology. Identifying the functional mechanisms may facilitate development of novel strategies for AAA prevention or treatment.

EZH2 Regulates ANXA6 Expression via H3K27me3 and Is Involved in Angiotensin II-Induced Vascular Smooth Muscle Cell Senescence

“…Histone methylation is a posttranslational process in which methyl groups are linked to H3 and H4 proteins by the enzyme histone methyltransferase (HMT), thereby altering the interaction of histones with DNA and nuclear proteins. Depending on the methylation site and its effect on chromatin structure, either transcriptional repression or activation can occur [ 37 ]. H3K27me3 is associated with transcriptional silencing during mammalian embryogenesis [ 38 ].…”

“…Some epigenetic factors are involved in the pathogenesis of AAA by regulating gene expression [ 40 ]. It is known that H3K27me3 is downregulated in Ang II-induced AAA tissues [ 37 ].…”

“…Some epigenetic factors are involved in the pathogenesis of AAA by regulating gene expression [40]. It is known that H3K27me3 is downregulated in Ang II-induced AAA tissues [37]. EZH2 suppressed gene expression by adding a methyl group to histone H3 lysine 27, which promotes heterochromatin formation [41,42].…”

Integrative multiomics analysis of neointima proliferation in human saphenous vein: implications for bypass graft disease

“…Real time quantification of mRNA levels of the genes of interest was performed using Brilliant II SYBR Green QPCR Master Mix (Agilent Technologies) per manufacturer’s instructions. Normalized Ct values were subjected to statistical analysis and fold change was calculated by ΔΔ Ct method as described previously, normalized against 18S 26,27 . Primer sequences are listed in Table S1.…”

Smoking and the Pathophysiology of Peripheral Artery Disease

“…At present, the three most commonly used animal models of AAA are calcium chloride-induced AAA, subrenal abdominal aortic perfusion with elastase, and subcutaneous injection of angiotensin II (AngII) (186,187). Smoking not only affects the mechanical properties of the aorta and substantially changes the structure of the arterial wall but also changes gene expression through epigenetic mechanisms, thereby promoting the formation of AAA (188,189). In a model of AAA induced by AngII, smoking further increased the expression of a matrix metalloproteinase (MMP) gene in the abdominal aorta, thereby enhancing the proteolytic activity of MMP (190).…”