Genetics of atherosclerosis and vascular calcification go hand-in-hand

Beyond the Basics: Unraveling the Complexity of Coronary Artery Calcification

Coronary artery calcification (CAC) is mainly associated with coronary atherosclerosis, which is an indicator of coronary artery disease (CAD). CAC refers to the accumulation of calcium phosphate deposits, classified as micro- or macrocalcifications, that lead to the hardening and narrowing of the coronary arteries. CAC is a strong predictor of future cardiovascular events, such as myocardial infarction and sudden death. Our narrative review focuses on the pathophysiology of CAC, exploring its link to plaque vulnerability, genetic factors, and how race and sex can affect the condition. We also examined the connection between the gut microbiome and CAC, and the impact of genetic variants on the cellular processes involved in vascular calcification and atherogenesis. We aimed to thoroughly analyze the existing literature to improve our understanding of CAC and its potential clinical and therapeutic implications.

Association between urinary biomarkers of polycyclic aromatic hydrocarbons and severe abdominal aortic calcification in adults: data from the National Health and Examination Nutrition Survey

OBJECTIVE

Recent studies have found that polycyclic aromatic hydrocarbons (PAHs) exposure may increase the risk of cardiovascular disease. The present study aimed to explore the association between PAHs exposure and severe abdominal aortic calcification (AAC) in adults.

METHODS

Data were collected from the 2013-2014 National Health and Nutrition Examination Survey. PAHs exposure was analyzed from urinary mono hydroxylated metabolites of PAHs. Logistic regression models and subgroup analysis were performed to explore the association of PAHs exposure with severe AAC prevalence.

RESULTS

A total of 1,005 eligible individuals were recruited into the study. After adjusting for confounding factors, those with the highest quartiles of 1-hydroxynaphthalene (1-NAP: OR 2.19, 95% CI 1.03-4.68, P_{for trend} < 0.001), 2-hydroxynaphthalene (2-NAP: OR 2.22, 95% CI 1.04-4.64, P_{for trend} < 0.001) and 1-hydroxypyrene (1-PYR: OR 2.15, 95% CI 1.06-4.33, P_{for trend} < 0.001) were associated with an increased prevalence of severe AAC in the adults compared to those who in the lowest quartile.

CONCLUSION

This study found that urinary 1-NAP, 2-NAP and 1-PYR were positively associated with severe AAC prevalence in adults.

Aortic calcification: A postmortem CT validation study in a middle-aged population

BACKGROUND

Computed tomography (CT)-detected aortic calcification is strongly associated with aortic stiffness and is an accurate predictor of cardiovascular and all-cause mortality and cognitive decline. Some previous pathologic studies have shown calcium accumulation in the medial layer of the vessel wall, while others have suggested localisation in the atherosclerotic intimal layer.

OBJECTIVES

The aim of this study was to histologically validate CT findings of aortic calcification for detectability and location in the aortic wall.

METHODS

We acquired postmortem CT images and collected 170 aortic tissue samples from five different locations in the thoracic and abdominal aorta of 40 individuals who underwent autopsy. Microscopic slides were stained with haematoxylin and eosin and elastic van Gieson stain. Calcified lesions were characterised and calcifications were manually annotated in the intima and media. The presence and morphology of calcifications were scored on CT images.

RESULTS

The mean age of the autopsied individuals was 63 years, and 28 % died of cardiovascular disease. Calcifications were present in 74/170 (44 %) samples. Calcification was more common in the abdominal aorta than in the thoracic aorta. In all samples with calcifications, 99 % were located in the intimal layer. Only 16/170 samples had a small amount of medial arterial calcification. The histological results showed an 85 % concordance for the presence or absence of CT calcifications. There was complete inter-method agreement for annularity of calcifications in 68 % of the samples (linear weighted kappa 0.68 (95 %CI 0.60-0.77).

CONCLUSIONS

Aortic calcifications visible on CT are located in the intimal layer of the abdominal aorta wall, at least in aortas that are not aneurysmatic or dissected. The presence and annularity of these calcifications can be reliably determined by CT.

Abdominal aortic calcification: from ancient friend to modern foe

Background

Abdominal aortic calcifications were already ubiquitous in ancient populations from all continents. Although nowadays generally considered as an innocent end stage of stabilised atherosclerotic plaques, increasing evidence suggests that arterial calcifications contribute to cardiovascular risk. In this review we address abdominal aortic calcification from an evolutionary perspective and review the literature on histology, prevalence, risk factors, clinical outcomes and pharmacological interventions of abdominal aortic calcification.

Design

The design of this study was based on a literature review.

Methods

Pubmed and Embase were systematically searched for articles on abdominal aortic calcification and its synonyms without language restrictions. Articles with data on histology, prevalence, risk factors clinical outcomes and/or pharmacological interventions were selected.

Results

Abdominal aortic calcification is highly prevalent in the general population and prevalence and extent increase with age. Prevalence and risk factors differ between males and females and different ethnicities. Risk factors include traditional cardiovascular risk factors and decreased bone mineral density. Abdominal aortic calcification is shown to contribute to arterial stiffness and is a strong predictor of cardiovascular events and mortality. Several therapies to inhibit arterial calcification have been developed and investigated in small clinical trials.

Conclusions

Abdominal aortic calcification is from all eras and increasingly acknowledged as an independent contributor to cardiovascular disease. Large studies with long follow-up must be carried out to show whether inhibition of abdominal aortic calcification will further reduce cardiovascular risk.

U. diffracta extract mitigates high fat diet and VD3-induced atherosclerosis and biochemical changes in the serum liver and aorta of rats

BACKGROUND AND AIMS

Usnea diff ;racta Vain. (U. diffracta) belonging to the Usnea genus, is widely used as a folk medicine for the treatment of ulcer, abdominal pain, diarrhea, malaria and so on. However, the antiatherogenic effect of U. diffracta has not yet been reported. This study aims to investigate the antiatherogenic effects of the ethanol extract of U. diffracta and its mechanism.

METHOD

A high fat diet and VD3 were used to establish the atherosclerotic rat model, with 0.004 g/kg/d of simvastatin as a positive control, fed with 0.7, 1.4, and 2.8 g/kg/d of Usnea ethanol extract for 21 days. The blood, liver, and aorta samples from each rat were collected after the last administration. Pharmacodynamic effects were evaluated. The inflammation related factors, the gene expressions of Toll-like receptor 5 (TLR5), myeloid differentiating factor 88 (MyD88), and nuclear factor-κB (NF-κB) were detected.

RESULTS AND CONCLUSIONS

Compared with the model group, simvastatin and ethanol extract of U. diffracta can significantly reduce the serum levels of triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), Ca²⁺, AST, ALT, the liver contents of total cholesterol (TC), TG, AI and liver index, as well as significantly increase the contents of high-density lipoprotein cholesterol (HDL-C) both in serum and liver (p < 0.01 or p < 0.05). The serum level of ox-LDL can be significantly reduced by simvastatin, low and medium U. diffracta ethanol extract doses (p < 0.01). In addition, simvastatin and low dosage of U. diffracta ethanol extract can significantly reduce the liver content of LDL-C (p < 0.01). U. diffracta ethanol extract shows a positive antiatherogenic effect. Furthermore, the mechanism may be related to promoting the expression of serum IL-10 and inhibition of TLR5/NF-κB signaling pathway.

Differentiation of human iPSCs into VSMCs and generation of VSMC-derived calcifying vascular cells

Vascular calcification displays a major cause of death worldwide, which involve mainly vascular smooth muscle cells (VSMCs). Since 2007, there are increasing numbers of protocols to obtain different cell types from human induced-pluripotent stem cells (iPSCs), however a protocol for calcification is missing. Few protocols exist today for the differentiation of iPSCs towards VSMCs and none are known for their calcification. Here we present a protocol for the calcification of iPSC-derived VSMCs. We successfully differentiated iPSCs into VSMCs based on a modified protocol. Calcification in VSMCs is induced by a commercial StemXVivo™ osteogenic medium. Calcification was verified using Calcein and Alizarin Red S staining or Calcium assays, and molecular analyses showed enhanced expression of calcification-associated genes. The presented method could help to study genetic risk variants, using the CRISPR/Cas technology through the introduction of Knockouts or Knockins of risk variants. Finally, this method can be applied for drug screening.

Unraveling the role of Calcium ions in the mechanical properties of individual collagen fibrils

Collagen, the dominating material in the extracellular matrix, provides the strength, elasticity and mechanical stability to the organisms. The mechanical property of collagen is mainly dominated by its surrounding environments. However, the variation and origin of the mechanics of collagen fibril under different concentrations of calcium ions (χ_Ca) remains unknown. By using the atomic force microscopy based nanoindentation, the mechanics and structure of individual type II collagen fibril were first investigated under different χ_Ca in this study. The results demonstrate that both of the mechanical and structural properties of the collagen fibril show a prominent dependence on χ_Ca. The mechanism of χ_Ca-dependence of the collagen fibril was attributed to the chelation between collagen molecules and the calcium ions. Given the role of calcium in the pathology of osteoarthritis, the current study may cast new light on the understanding of osteoarthritis and other soft tissue hardening related diseases in the future.

Shift of Macrophage Phenotype Due to Cartilage Oligomeric Matrix Protein Deficiency Drives Atherosclerotic Calcification

Rationale:

Intimal calcification is highly correlated with atherosclerotic plaque burden, but the underlying mechanism is poorly understood. We recently reported that cartilage oligomeric matrix protein (COMP), a component of vascular extracellular matrix, is an endogenous inhibitor of vascular smooth muscle cell calcification.

Objective:

To investigate whether COMP affects atherosclerotic calcification.

Methods and Results:

ApoE −/− COMP −/− mice fed with chow diet for 12 months manifested more extensive atherosclerotic calcification in the innominate arteries than did ApoE −/− mice. To investigate which origins of COMP contributed to atherosclerotic calcification, bone marrow transplantation was performed between ApoE −/− and ApoE −/− COMP −/− mice. Enhanced calcification was observed in mice transplanted with ApoE −/− COMP −/− bone marrow compared with mice transplanted with ApoE −/− bone marrow, indicating that bone marrow–derived COMP may play a critical role in atherosclerotic calcification. Furthermore, microarray profiling of wild-type and COMP −/− macrophages revealed that COMP-deficient macrophages exerted atherogenic and osteogenic characters. Integrin β3 protein was attenuated in COMP −/− macrophages, and overexpression of integrin β3 inhibited the shift of macrophage phenotypes by COMP deficiency. Furthermore, adeno-associated virus 2–integrin β3 infection attenuated atherosclerotic calcification in ApoE −/− COMP −/− mice. Mechanistically, COMP bound directly to β-tail domain of integrin β3 via its C-terminus, and blocking of the COMP–integrin β3 association by β-tail domain mimicked the COMP deficiency–induced shift in macrophage phenotypes. Similar to COMP deficiency in mice, transduction of adeno-associated virus 2–β-tail domain enhanced atherosclerotic calcification in ApoE −/− mice.

Conclusions:

These results reveal that COMP deficiency acted via integrin β3 to drive macrophages toward the atherogenic and osteogenic phenotype and thereby aggravate atherosclerotic calcification.

Disruption of phactr-1 pathway triggers pro-inflammatory and pro-atherogenic factors: New insights in atherosclerosis development

Significant interest has recently emerged for phosphatase and actin regulatory protein (PHACTR1) gene in heart diseases prognosis. However, the functional role of phactr-1 protein remains elusive in heart related-diseases such as atherosclerosis, coronary artery calcification, ischaemic stroke, coronary artery stenosis and early-onset myocardial infarction. Phactr-1 is directly regulated by vascular endothelial growth factor A165 (VEGF-A165) through VEGF receptor 1 (VEGR-1) and Neuropilin-1 (NRP-1). Using an antagonist peptide approach to inhibit the interaction of VEGF-A165 to NRP-1 and VEGF-R1, we highlighted the importance of both cysteine residues located at the end of VEGF-A165 exon-7 and at the exon-8 to generate functional peptides, which decreased Phactr-1 expression. Here, we report original data showing Phactr-1 down-expression induces the expression of Matrix Metalloproteinase (MMP) regulators such as Tissue inhibitor of metalloproteinase (TIMP-1/-2) and Reversion-inducing-cysteine-rich protein with kazal motifs (RECK). Furthermore, focal adhesion kinases (FAK/PYK2/PAXILLIN) and metabolic stress (AMPK/CREB/eNOS) pathways were inhibited in endothelial cells. Moreover, the decrease of phactr-1 expression induced several factors implicated in atherosclerotic events such as oxidized low-density lipoprotein receptors (CD36, Clusterin, Cadherin-13), pro-inflammatory proteins including Thrombin, Thrombin receptor 1 (PAR-1), A Disintegrin And Metalloprotease domain-9/-17 (ADAM-9/-17), Trombospondin-2 and Galectin-3. Besides, Phactr-1 down-expression also induces emerging atherosclerosis biomarkers such as semicarbazide-sensitive amine oxidase (SSAO) and TGF-beta-inducible gene h3 (βIG-H3). In this report, we show for the first time the direct evidence of the phactr-1 biological function in the regulation of pro-atherosclerotic molecules. This intriguing result strengthened heart diseases PHACTR-1 single-nucleotide polymorphisms (SNP) correlation. Taken together, our result highlighted the pivotal role of phactr-1 protein in the pathogenesis of atherosclerosis.

Correlation of single nucleotide polymorphisms in the pregnancy-associated plasma protein-A gene with carotid plaques

Background

Pregnancy-associated plasma protein A (PAPP-A) is abundantly expressed in carotid plaques. This study investigated the association between single nucleotide polymorphisms (SNPs) of PAPP-A and the presence of carotid plaques.

Methods

A total of 408 patients with carotid plaques and 493 controls were included in the study. All subjects were Southern Chinese Han. Carotid plaques were analyzed by computer tomography angiography. PAPP-A SNPs were identified by ligase detection reaction-polymerase chain reaction analysis. The PAPP-A genotypes rs3747823, rs7020782, and rs13290387 were analyzed.

Results

The rs7020782 C allele genotype correlated with an increased risk of developing carotid plaques under the dominant, recessive, and additive models (adjusted odds ratios: 2.60, 2.36, and 3.48, respectively; P ≤ 0.001). Only C allele-carrying genotypes correlated with a significantly increased risk of carotid plaque based on studies stratified by age and sex under the dominant model. rs7020782 remained significantly associated with the risk of carotid plaque calcification after adjusting for age and potential confounders (adjusted odds ratio, 1.89; 95 % confidence interval, 1.17–3.08; P = 0.010).

Conclusions

This study found, for the first time, that the A˃C variation of rs7020782 might be an independent risk factor for carotid plaque development and calcification. The determination of such genotypes could provide a new tool for identifying individuals at high risk for carotid atherosclerosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-015-0041-1) contains supplementary material, which is available to authorized users.

Serum lipid levels, body mass index, and their role in coronary artery calcification: a polygenic analysis

BACKGROUND

Coronary artery calcification (CAC) is widely regarded as a cumulative lifetime measure of atherosclerosis, but it remains unclear what is the relationship between calcification and traditional risk factors for coronary artery disease (CAD) and myocardial infarction (MI). This study characterizes the genetic architecture of CAC by evaluating the overall impact of common alleles associated with CAD/MI and its traditional risk factors.

METHODS AND RESULTS

On the basis of summary-association results from the CARDIoGRAMplusC4D study of CAD/MI, we calculated polygenic risk scores in 2599 participants of the Dutch and Belgian Lung Cancer Screening (NELSON) trial, in whom quantitative CAC levels (Agatston scores) were determined from chest computerized tomographic imaging data. The most significant polygenic model explained ≈14% of the observed CAC variance (P=1.6×10(-11)), which points to a residual effect because of many as yet unknown loci that overlap between CAD/MI and CAC. In addition, we constructed risk scores based on published single-nucleotide polymorphism associations for traditional cardiovascular risk factors and tested these scores for association with CAC. We found nominally significant associations for genetic risk scores of low-density lipoprotein-cholesterol, total cholesterol, and body mass index, which were successfully replicated in 2182 individuals of the Heinz Nixdorf Recall Study.

CONCLUSIONS

Pervasive polygenic sharing between CAC and CAD/MI suggests that a substantial fraction of the heritable risk for CAD/MI is mediated through arterial calcification. We also provide evidence that genetic variants associated with serum lipid levels and body mass index influence CAC levels.