A definition of advanced types of atherosclerotic lesions and a histological classification of atherosclerosis. A report from the Committee on Vascular Lesions of the Council on Arteriosclerosis, American Heart Association

Exposure of tropoelastin to peroxynitrous acid gives high yields of nitrated tyrosine residues, di-tyrosine cross-links and altered protein structure and function

Elastin is an abundant extracellular matrix protein in elastic tissues, including the lungs, skin and arteries, and comprises 30-57% of the aorta by dry mass. The monomeric precursor, tropoelastin (TE), undergoes complex processing during elastogenesis to form mature elastic fibres. Peroxynitrous acid (ONOOH), a potent oxidising and nitrating agent, is formed in vivo from superoxide and nitric oxide radicals. Considerable evidence supports ONOOH formation in the inflamed artery wall, and a role for this species in the development of human atherosclerotic lesions, with ONOOH-damaged extracellular matrix implicated in lesion rupture. We demonstrate that TE is highly sensitive to ONOOH, with this resulting in extensive dimerization, fragmentation and nitration of Tyr residues to give 3-nitrotyrosine (3-nitroTyr). This occurs with equimolar or greater levels of oxidant and increases in a dose-dependent manner. Quantification of Tyr loss and 3-nitroTyr formation indicates extensive Tyr modification with up to two modified Tyr per protein molecule, and up to 8% conversion of initial ONOOH to 3-nitroTyr. These effects were modulated by bicarbonate, an alternative target for ONOOH. Inter- and intra-protein di-tyrosine cross-links have been characterized by mass spectrometry. Examination of human atherosclerotic lesions shows colocalization of 3-nitroTyr with elastin epitopes, consistent with TE or elastin modification in vivo, and also an association of 3-nitroTyr containing proteins and elastin with lipid deposits. These data suggest that exposure of TE to ONOOH gives marked chemical and structural changes to TE and altered matrix assembly, and that such damage accumulates in human arterial tissue during the development of atherosclerosis.

Microcalcifications, Their Genesis, Growth, and Biomechanical Stability in Fibrous Cap Rupture

For many decades, cardiovascular calcification has been considered as a passive process, accompanying atheroma progression, correlated with plaque burden, and apparently without a major role on plaque vulnerability. Clinical and pathological analyses have previously focused on the total amount of calcification (calcified area in a whole atheroma cross section) and whether more calcification means higher risk of plaque rupture or not. However, this paradigm has been changing in the last decade or so. Recent research has focused on the presence of microcalcifications (μCalcs) in the atheroma and more importantly on whether clusters of μCalcs are located in the cap of the atheroma. While the vast majority of μCalcs are found in the lipid pool or necrotic core, they are inconsequential to vulnerable plaque. Nevertheless, it has been shown that μCalcs located within the fibrous cap could be numerous and that they behave as an intensifier of the background circumferential stress in the cap. It is now known that such intensifying effect depends on the size and shape of the μCalc as well as the proximity between two or more μCalcs. If μCalcs are located in caps with very low background stress, the increase in stress concentration may not be sufficient to reach the rupture threshold. However, the presence of μCalc(s) in the cap with a background stress of about one fifth to one half the rupture threshold (a stable plaque) will produce a significant increase in local stress, which may exceed the cap rupture threshold and thus transform a non-vulnerable plaque into a vulnerable one. Also, the classic view that treats cardiovascular calcification as a passive process has been challenged, and emerging data suggest that cardiovascular calcification may encompass both passive and active processes. The passive calcification process comprises biochemical factors, specifically circulating nucleating complexes, which would lead to calcification of the atheroma. The active mechanism of atherosclerotic calcification is a cell-mediated process via cell death of macrophages and smooth muscle cells (SMCs) and/or the release of matrix vesicles by SMCs.

Label-free imaging of atherosclerotic plaques using third-harmonic generation microscopy

Multiphoton microscopy using laser sources in the mid-infrared range (MIR, 1,300 nm and 1,700 nm) was used to image atherosclerotic plaques from murine and human samples. Third harmonic generation (THG) from atherosclerotic plaques revealed morphological details of cellular and extracellular lipid deposits. Simultaneous nonlinear optical signals from the same laser source, including second harmonic generation and endogenous fluorescence, resulted in label-free images of various layers within the diseased vessel wall. The THG signal adds an endogenous contrast mechanism with a practical degree of specificity for atherosclerotic plaques that complements current nonlinear optical methods for the investigation of cardiovascular disease. Our use of whole-mount tissue and backward scattered epi-detection suggests THG could potentially be used in the future as a clinical tool.

The proper use of coronary calcium score and coronary computed tomography angiography for screening asymptomatic patients with cardiovascular risk factors

Early detection and treatment of coronary artery disease (CAD) can reduce incidences of acute myocardial infarction. In this study, we determined the proper use of contributing risk factors and coronary artery calcium score (CACS) when screening asymptomatic patients with coronary arterial stenoses using coronary computed tomography angiography (CCTA). We reviewed 934 consecutive patients who received CACS and CCTA between December 2013 and November 2016. At least one cardiovascular disease risk factor was present in each of the 509 asymptomatic participants. Patients were grouped based on CACS into “zero,” “minimal” (0 < CACS ≤ 10), “mild” (10 < CACS ≤ 100), “moderate” (100 < CACS ≤ 400), and “excessive” (CACS > 400). Males over 45 years old with diabetes mellitus and hypertension had a higher risk of significant coronary stenosis. In multivariate analysis, age, sex, hypertension, and diabetes mellitus remained significant predictors of stenosis. A CACS of zero occurred in 227 patients (44.6%). There were no significant differences between the “zero” and “minimal” groups (p = 0.421), but the “mild,” “moderate,” and “excessive” groups showed correlations with significant coronary stenosis. Age, sex, diabetes mellitus, and hypertension were associated with higher risk of significant coronary stenosis. Asymptomatic patients with CACSs of zero do not require CCTA, and thereby avoid unnecessary radiation exposure.

Human induced pluripotent stem cell‑derived mesenchymal stem cells alleviate atherosclerosis by modulating inflammatory responses

The transplantation of mesenchymal stem cells (MSCs) has been a reported method for alleviating atherosclerosis (AS). Because the availability of bone marrow‑derived MSCs (BM‑MSCs) is limited, the authors used this study to explore the use of a new type of MSC, human induced pluripotent stem cell‑derived MSCs (iPSC‑MSCs), to evaluate whether these cells could alleviate AS. iPSC‑MSCs were intravenously administered to ApoE knock out mice fed on a high‑fat diet (HFD) for 12 weeks. It was reported that systematically administering iPSC‑MSCs clearly reduced the size of plaques. In addition, the numbers of macrophages and lipids in plaques were lower in the HFD + iPSC‑MSCs group than in the HFD group. Furthermore, iPSC‑MSCs attenuated AS‑associated inflammation by decreasing the levels of inflammatory cytokines, such as tumor necrosis factor‑α and interleukin‑6, in serum. In addition, the expression of Notch1 was higher in the HFD group, and injecting iPSC‑MSCs reversed this effect. In conclusion, the current study provides the first evidence indicating that iPSC‑MSCs may be a new optional MSC‑based strategy for treating AS.

Abdominal aortic calcification on dual-energy X-ray absorptiometry: Methods of assessment and clinical significance

Abdominal aortic calcification (AAC) can be accurately recognized on lateral spine images intended for vertebral fracture assessment, that are obtained with dual-energy X-ray absorptiometry (DXA). Greater amounts of AAC are common in the older population for whom DXA is routinely done, and have been consistently associated with incident atherosclerotic cardiovascular disease (ASCVD) events. AAC has also been associated with incident fractures in some prospective studies, but not in others. However, further research is needed to quantify the extent to which measurement of AAC improves prediction of ASCVD events and its impact on physician and patient ASCVD risk management. Additionally, research to develop better, more precise, automated, quantitative methods of AAC assessment on lateral spine densitometric images will hopefully lead to better prediction of clinical outcomes. In conclusion, although the prime indication for densitometric lateral spine imaging remains vertebral fracture assessment, AAC that is found incidentally on lateral spine images should be reported, so that patients and their health care providers are aware of its presence.

Recommendation on Design, Execution, and Reporting of Animal Atherosclerosis Studies: A Scientific Statement From the American Heart Association

Animal studies are a foundation for defining mechanisms of atherosclerosis and potential targets of drugs to prevent lesion development or reverse the disease. In the current literature, it is common to see contradictions of outcomes in animal studies from different research groups, leading to the paucity of extrapolations of experimental findings into understanding the human disease. The purpose of this statement is to provide guidelines for development and execution of experimental design and interpretation in animal studies. Recommendations include the following: (1) animal model selection, with commentary on the fidelity of mimicking facets of the human disease; (2) experimental design and its impact on the interpretation of data; and (3) standard methods to enhance accuracy of measurements and characterization of atherosclerotic lesions.

Carotid plaque instability is not related to quantity but to elemental composition of calcification

BACKGROUND AND AIMS

Recent studies highlighted the role of calcification processes in the clinical progression of chronic cardiovascular diseases. In this study we investigated the relationship between the chemical composition of calcification and atherosclerotic plaque stability in carotid arteries.

METHODS AND RESULTS

To this end, we characterized the calcification on 229 carotid plaques, by morphology, immunohistochemistry, transmission electron microscopy and energy dispersive X-ray microanalysis. Plaques were classified into two categories: unstable and stable. No significant differences were found in the incidence of the various risk factors between patients with and without carotid calcification, with the exception of diabetes. The energy dispersive X-ray microanalysis allowed us to identify two types of calcium salts in the atheromatous plaques, hydroxyapatite (HA) and calcium oxalate (CO). Our results showed that calcification is a common finding in carotid plaques, being present in 77.3% of cases, and the amount of calcium is not a factor of vulnerability. Noteworthy, we observed an association between HA calcification and unstable plaques. On the contrary, CO calcifications were mainly detected in stable plaques.

CONCLUSIONS

The presence of different types of calcification in atheromatous plaques may open new perspectives in understanding the molecular mechanisms of atheroma formation and plaque instability.

Women with Polycystic Ovary Syndrome and Risk of Cardiovascular Disease

BACKGROUND

Polycystic ovary syndrome (PCOS) is associated with reproductive and metabolic abnormalities. The aim of this study was to analyse risk of cardiovascular disease (CVD) in PCOS, to define individual risk factors and assess their ability to predict risk.

METHODS

Fifty-four young women with PCOS (22 obese and 32 normal weight) were compared to 46 respective controls (17 obese and 29 normal weight). Anthropometric parameters, lipid status parameters, inflammation markers, concentrations of glucose, transaminases, sex and anterior pituitary hormones, sex hormone binding globulin (SHBG) and androgens were measured. Cardiovascular Risk Score (CVRS), indices for identifying Non-Alcoholic Fatty Liver Disease (NAFLD) and the Index of Central Obesity (ICO) were calculated.

RESULTS

Significantly higher CVRS values (p<0.05) were found in obese PCOS women compared to normal weight control and normal weight PCOS groups. Anthropometric parameters, lipid status parameters and fibrinogen (p<0.001, p<0.01) were higher in women with higher CVRS. The most significant CVRS predictors in all PCOS women were SHBG, androstenedione, follicle-stimulating hormone (FSH) and dehydroepiandrosterone sulphate (DHEAS). ICO and all NAFLD indices exhibited significant positive correlation with CVRS and a model consisting of these indices provided good diagnostic accuracy (AUC>0.8) in identifying patients with increased cardiovascular risk (CVR).

CONCLUSIONS

Obesity is a higher risk for developing CVD than PCOS alone. Anthropometric parameters, lipid parameters, fibrinogen, NAFLD indices and ICO increase CVR in PCOS women. For the prediction of CVR in PCOS, we suggest a combination of NAFLD indices and ICO.

Experimental models of hyperlipoproteinemia and atherosclerosis

The first experimental model of atherosclerosis (in rabbits) is more than hundred years old. Several animal species have been used to produce hyperlipoproteinemia and possible atherosclerosis. The gene manipulation produced the most used models recently. This review acknowledges the extensive study of atherosclerotic changes in experimental models of hyperlipoproteinemia and atherosclerosis to come to light thus far and the purpose here is not only to summarize the published data but also to try to add some details of our experience in using these models. In addition to rabbit (the old but also improved model by reno-vascular hypertension) dog, birds, pig, hamster, mice, rat and non-human primate's animal models are described. The gene manipulation produced the most used models two decades ago. Germline genetically engineered (without apoE or LDL receptor genes) animals have become the most used models producing atherosclerotic changes in the aorta. Recent new models also producing atherosclerotic changes but without germline genetic manipulation are also described.

Recommendation on Design, Execution, and Reporting of Animal Atherosclerosis Studies: A Scientific Statement From the American Heart Association

Animal studies are a foundation for defining mechanisms of atherosclerosis and potential targets of drugs to prevent lesion development or reverse the disease. In the current literature, it is common to see contradictions of outcomes in animal studies from different research groups, leading to the paucity of extrapolations of experimental findings into understanding the human disease. The purpose of this statement is to provide guidelines for development and execution of experimental design and interpretation in animal studies. Recommendations include the following: (1) animal model selection, with commentary on the fidelity of mimicking facets of the human disease; (2) experimental design and its impact on the interpretation of data; and (3) standard methods to enhance accuracy of measurements and characterization of atherosclerotic lesions.

High Sensitivity Troponins Discriminate Different Morphologies of Coronary Artery Plaques Being Assessed by Coronary Computed Tomography Angiography

BACKGROUND

This study evaluates the association between high sensitivity troponin I (hsTnI) and T (hsTnT) and the morphology of coronary artery plaques detected by coronary computed tomography angiography (CCTA) in patients with suspected coronary artery disease (CAD).

METHODS

Patients undergoing CCTA were prospectively enrolled. CCTA was indicated by a low to intermediate pretest probability for CAD during routine clinical care. Within 24 hours of CCTA examination, peripheral blood samples were taken to measure hsTnI, hsTnT, and N-terminal probrain natriuretic peptide (NT-proBNP).

RESULTS

A total of 99 patients were enrolled with 43% without CAD, 9% with noncalcified plaques, 28% with calcified plaques, and 19% with mixed type plaque lesions. Both hsTnI and hsTnT levels were able to discriminate significantly between the groups, especially in the presence of mixed coronary plaques (AUC range: 0.741-0.752; p = 0.0001). In multivariate logistic regression models, hsTnT, but not hsTnI, was still significantly associated with mixed coronary plaque morphology (odds ratio = 8.968; 95% CI 1.999-40.241; p = 0.004).

CONCLUSIONS

Both hsTnI and hsTnT are able to discriminate between different coronary artery plaques morphologies, whereas hsTnT was significantly associated with mixed coronary plaques in patients with suspected CAD. This trial is registered with NCT03074253.

Identification and Quantitative Assessment of Different Components of Intracranial Atherosclerotic Plaque by Ex Vivo 3T High-Resolution Multicontrast MRI

BACKGROUND AND PURPOSE

High-resolution 3T MR imaging can visualize intracranial atherosclerotic plaque. However, histologic validation is still lacking. This study aimed to evaluate the ability of 3T MR imaging to identify and quantitatively assess intracranial atherosclerotic plaque components ex vivo with histologic validation.

MATERIALS AND METHODS

Fifty-three intracranial arterial specimens with atherosclerotic plaques from 20 cadavers were imaged by 3T MR imaging with T1, T2, and proton-density-weighted FSE and STIR sequences. The signal characteristics and areas of fibrous cap, lipid core, calcification, fibrous tissue, and healthy vessel wall were recorded on MR images and compared with histology. Fibrous cap thickness and maximum wall thickness were also quantified. The percentage of areas of the main plaque components, the ratio of fibrous cap thickness to maximum wall thickness, and plaque burden were calculated and compared.

RESULTS

The signal intensity of the lipid core was significantly lower than that of the fibrous cap on T2-weighted, proton-density, and STIR sequences (P < .01) and was comparable on T1-weighted sequences (P = 1.00). Optimal contrast between the lipid core and fibrous cap was found on T2-weighted images. Plaque component mean percentages were comparable between MR imaging and histology: fibrous component (81.86% ± 10.59% versus 81.87% ± 11.59%, P = .999), lipid core (19.51% ± 10.76% versus 19.86% ± 11.56%, P = .863), and fibrous cap (31.10% ± 11.28% versus 30.83% ± 8.51%, P = .463). However, MR imaging overestimated mean calcification (9.68% ± 5.21% versus 8.83% ± 5.67%, P = .030) and plaque burden (65.18% ± 9.01% versus 52.71% ± 14.58%, P < .001).

CONCLUSIONS

Ex vivo 3T MR imaging can accurately identify and quantitatively assess intracranial atherosclerotic plaque components, providing a direct reference for in vivo intracranial plaque imaging.

Photothermal strain imaging

Vulnerable plaques are the major cause of cardiovascular disease, but they are difficult to detect with conventional intravascular imaging techniques. Techniques are needed to identify plaque vulnerability based on the presence of lipids in plaque. Thermal strain imaging (TSI) is an imaging technique based on ultrasound (US) wave propagation speed, which varies with the medium temperature. In TSI, the strain that occurs during tissue temperature change can be used for lipid detection because it has a different tendency depending on the type of tissue. Here, we demonstrate photothermal strain imaging (pTSI) using an intravascular ultrasound catheter. pTSI is performed by slightly and selectively heating lipid using a relatively inexpensive continuous laser source. We applied a speckle-tracking algorithm to US B-mode images for strain calculations. As a result, the strain produced in porcine fat was different from the strain produced in water-bearing gelatin phantom, which made it possible to distinguish the two. This suggests that pTSI could potentially be a way of differentiating lipids in coronary artery.

Endothelial vascular markers in coronary surgery

Coronary heart disease is associated with high morbidity and mortality. Endothelial dysfunction in affected patients is linked to long-term atherosclerotic disease progression and cardiovascular event rates. The present paper reports on changes in the levels of endothelial progenitor cells (VEGFR2/CD133/CD34), essential for endothelial repair, and of endothelial microvesicles (CD31/annexin V) as indicators of endothelial lesion, in patients undergoing coronary bypass surgery with respect both to baseline levels and to counts in healthy subjects. In an observational descriptive study, 31 patients scheduled for coronary revascularization surgery were compared with those of 25 healthy controls. In a subsequent longitudinal study, patients undergoing surgery were monitored at 5 timepoints up until 48 h after surgery. Endothelial progenitor cell (VEGFR2/CD133/CD34) and endothelial microvesicle (CD31/annexin V) levels were quantified by flow cytometry. Baseline endothelial progenitor cell counts in coronary patients were significantly lower than those of healthy controls (p < 0.001); however, after surgery, levels rose steadily over all 5 timepoints to 48 h  with statistically significant differences (p < 0.001) between intra-operative and 48 h after surgery (T5). Endothelial microvesicle levels were significantly higher in coronary patients prior to surgery than in healthy controls (p < 0.001), and despite declining at 48 h remained significantly higher than those of controls (p < 0.001). Coronary surgery has had a positive impact on the endothelium in the patients, prompting a decrease in signs of endothelial dysfunction and a considerable improvement in the endothelial repair mechanisms involved in angiogenesis, playing an important role in the inflammatory response and the remodelling process of ischemic myocardium in postoperative period.

Diet-induced early-stage atherosclerosis in baboons: Lipoproteins, atherogenesis, and arterial compliance

BACKGROUND

The purpose of this study was to determine whether dietary manipulation can reliably induce early-stage atherosclerosis and clinically relevant changes in vascular function in an established, well-characterized non-human primate model.

METHODS

We fed 112 baboons a high-cholesterol, high-fat challenge diet for two years. We assayed circulating biomarkers of cardiovascular disease (CVD) risk, at 0, 7, and 104 weeks into the challenge; assessed arterial compliance noninvasively at 104 weeks; and measured atherosclerotic lesions in three major arteries at necropsy.

RESULTS

We observed evidence of atherosclerosis in all but one baboon fed the two-year challenge diet. CVD risk biomarkers, the prevalence, size, and complexity of arterial lesions, plus consequent arterial stiffness, were increased in comparison with dietary control animals.

CONCLUSIONS

Feeding baboons a high-cholesterol, high-fat diet for two years reliably induces atherosclerosis, with risk factor profiles, arterial lesions, and changes in vascular function also seen in humans.

Depletion of ATP and glucose in advanced human atherosclerotic plaques

Objective

Severe hypoxia develops close to the necrotic core of advanced human atherosclerotic plaques, but the energy metabolic consequences of this hypoxia are not known. In animal models, plaque hypoxia is also associated with depletion of glucose and ATP. ATP depletion may impair healing of plaques and promote necrotic core expansion. To investigate if ATP depletion is present in human plaques, we analyzed the distribution of energy metabolites (ATP, glucose, glycogen and lactate) in intermediate and advanced human plaques.

Approach and results

Snap frozen carotid endarterectomies from 6 symptomatic patients were analyzed. Each endarterectomy included a large plaque ranging from the common carotid artery (CCA) to the internal carotid artery (ICA). ATP, glucose, and glycogen concentrations were lower in advanced (ICA) compared to intermediate plaques (CCA), whereas lactate concentrations were higher. The lowest concentrations of ATP, glucose and glycogen were detected in the perinecrotic zone of advanced plaques.

Conclusions

Our study demonstrates severe ATP depletion and glucose deficiency in the perinecrotic zone of human advanced atherosclerotic plaques. ATP depletion may impair healing of plaques and promote disease progression.

Ziziphus nummularia Inhibits Inflammation-Induced Atherogenic Phenotype of Human Aortic Smooth Muscle Cells

Cardiovascular disease (CVD) continues to be the leading cause of death worldwide. Atherosclerosis is a CVD characterized by plaque formation resulting from inflammation-induced insults to endothelial cells, monocytes, and vascular smooth muscle cells (VSMCs). Despite significant advances, current treatments for atherosclerosis remain insufficient, prompting the search for alternative modalities, including herbal medicine. Ziziphus nummularia is an herb commonly used in the amelioration of symptoms associated with many health conditions such as cold, diarrhea, cancer, and diabetes. However, its effect on the inflammation-induced behavior of VSMCs remains unknown. In this study, we sought to determine the effect of the ethanolic extract of Z. nummularia (ZNE) on TNF-α-induced phenotypic changes of human aortic smooth muscle cells (HASMCs). The treatment of HASMCs with ZNE decreased cell proliferation, adhesion to fibronectin, migration, and invasion. ZNE treatment also caused a concentration- and time-dependent reduction in the TNF-α-induced expression of matrix metalloproteases MMP-2 and MMP-9, NF-κB, and cell adhesion molecules ICAM-1 and VCAM-1. Furthermore, ZNE decreased the adhesion of THP-1 monocytes to HASMCs and endothelial cells in a concentration-dependent manner. These data provide evidence for the anti-inflammatory effect of Ziziphus nummularia, along with potential implications for its use as an agent that could ameliorate inflammation-induced atherogenic phenotype of VSMCs in atherosclerosis.

Nucleolin protects macrophages from oxLDL-induced foam cell formation through up-regulating ABCA1 expression

Our recent studies have indicated that nucleolin, as a multifunctional RNA-binding protein, exerts protective effects in the myocardial cells and endothelial cells under the condition of oxidative stress. However, the function of nucleolin and its potential mechanism in macrophage-derived foam cell formation remain largely unexplored. ApoE-/- mice were fed with a high-fat diet (HFD) for 10-24 weeks. Protein expression was measured by western blotting or immunofluorescence, and gene expression at the mRNA level was detected by qRT-PCR. The level of lipid in macrophages was examined by Oil Red O staining, high-performance liquid chromatography (HPLC) and NBD-cholesterol. Actinomycin D (Act D) was used to determine the stability of ABCA1 mRNA in macrophages. The interaction of nucleolin with ABCA1 mRNA was assessed using co-immunoprecipitation (co-IP). The aortas advanced plaques demonstrated significantly lower levels of nucleolin protein compared with early plaques in ApoE-/- mice, in which the macrophage foam cells occupied main body. Nucleolin expression at the mRNA and protein levels in RAW264.7 macrophages was significantly reduced by oxidized low-density lipoprotein (oxLDL) in a dose- and time-dependent manner. Furthermore, nucleolin overexpression markedly attenuated lipid accumulation in oxLDL-challenged macrophages through increasing cholesterol efflux. In addition, nucleolin overexpression significantly increased the expression of ATP-binding cassette transporter A1 (ABCA1) at the mRNA and protein levels without affecting expressions of scavenger receptors (SR)-A, SR-B1, CD36 and ATP-binding cassette transporter G1 (ABCG1) at the mRNA level. Moreover, nucleolin overexpression increased the stability of ABCA1 mRNA in macrophages, whereas nucleolin ablation abrogated the oxLDL-induced up-regulation of ABCA1. The up-regulation of ABCA1 by nucleolin resulted from its protein-RNA interaction. Our data suggested that nucleolin inhibited foam cell formation through enhancing stability of ABCA1 mRNA and subsequently increasing cholesterol efflux.

Current Understanding of Atherogenesis

Scientific understanding of atherogenesis is constantly developing. From Virchow's observations 160 years ago we now recognize the endothelial response to injury as inflammatory, involved in all stages of atherosclerosis. Endothelial activation may cause reversible injury or dysfunction, or lead to irreparable damage. Indeed, early atherosclerosis is reversible. The introduction of genome-wide association testing has furthered the identification of potentially important genetic variants that help explain the heritability of coronary artery disease as well as spontaneous cases of severe coronary artery disease in patients with otherwise minimal risk factors. However, the mechanisms by which many of the newer variants exert their influence remain unknown.

Screening of potential gene markers for predicting carotid atheroma plaque formation using bioinformatics approaches

The present study aimed to investigate potential gene markers for predicting the formation of carotid atheroma plaques using high-throughput bioinformatics methods. The GSE43292 gene expression profile was downloaded from the Gene Expression Omnibus database. Following data processing, differentially expressed genes (DEGs) were screened using a paired t-test in the Linear Models for Microarray Data package with the criteria of a false discovery rate of P<0.05 and |log2 fold-change| ≥0.58, followed by functional enrichment, protein-protein interaction (PPI) network construction, key node and module analysis, and prediction of transcription factors (TFs) targeting genes in the significant modules. The results revealed that the gene expression profiles from 32 paired samples of carotid atheroma plaque tissue and macroscopically intact tissue were obtained, based on which 886 DEGs, including 513 upregulated genes and 373 downregulated genes, were identified. The upregulated and downregulated gene sets were enriched in 24 and 13 pathways, respectively. The PPI network constructed with these DEGs comprised 35 key nodes with degrees ≥20, among which spleen tyrosine kinase (SYK), LYN and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit γ (PIK3CG) were the three highest. A significant module was mined in the PPI network, which consisted of 29 DEGs targeted by 11 TFs. The DEGs between the carotid atheroma plaque and macroscopically intact tissue samples may be involved in carotid atherogenesis. Key nodes in the PPI network constructed from these DEGs and the genes involved in the significant module, including SYK, LYN and PIK3CG, are promising for the prediction of carotid plaque formation.

Features and risk factors of carotid atherosclerosis in a population with high stroke incidence in China

Epidemiological studies have reported associations between traditional cardiovascular risk factors and carotid intima-media thickness (CIMT) or carotid plaque. However, definite risk factors at different phases of carotid atherosclerosis remain controversial. We aimed to explore risk factors and characteristics of carotid atherosclerosis at different stages in a low-income population with a high incidence of stroke in China. Between April 2014 and January 2015, we recruited 3789 stroke-free and cardiovascular disease-free residents aged ≥ 45 years. B-mode ultrasonography was performed to measure CIMT and the presence of carotid plaque. Traditional risk factors were compared between the increased CIMT group and normal CIMT group, and between those with and without carotid plaque. A total of 3789 participants were assessed in this study, with a mean age (standard deviation) of 59.92 (9.70) years. The prevalence of increased CIMT and carotid plaque increased with older age and higher education levels. Age, hypertension, diabetes, and high low-density lipoprotein cholesterol levels were risk factors for increased CIMT and carotid plaque. Furthermore, compared to never smoking, passive smoking was positively associated with increased CIMT, with an odds ratio (95% confidence interval) of 1.26 (1.05, 1.53; P = 0.016); high body mass index was an obvious protective factor against carotid plaque, with an odds ratio (95% confidence interval) of 0.97 (0.95, 0.99; P = 0.004). It is important to identify factors associated with atherosclerosis to prevent cardiovascular disease and stroke and reduce the burden of stroke in this high-risk population.

An active electrolocation catheter system for imaging and analysis of coronary plaques

Coronary artery disease-currently one of the most frequent causes of death-is characterized by atherosclerotic plaques grown in the wall of blood vessels and inhibiting blood flow. Preventive assessment focusses on critical sizes of structural plaque parameters like relative lipid core area and cap thickness to identify high-risk plaques called thin cap fibroatheromas. Although state-of-the-art catheter systems were successfully applied in invasive plaque diagnostics, the high costs induced by these devices inhibit usage in daily clinical practice. To overcome this shortcoming, we follow a biomimetic approach to construct a prospective low-cost catheter system that adapts the active electrolocation principles of weakly electric fish Gnathonemus petersii. Only a few and simple parameters relevant for plaque detection and characterization are estimated from plaque-evoked electric images which are projected on the surface of the catheter. Two prototypical electrolocation catheter systems were tested. The first catheter system featured a ring electrode catheter and was used to obtain dynamic 1D electric images of synthetic plaques in an agarose atherosclerosis model. Our proof of concept showed that synthetic plaques could be reliably detected from 1D electric images. Based on a cluster analysis of selected key image features, synthetic plaques could be categorized into four plaque conditions, predefined from thresholds for critical structural parameters, representing high to low risk plaques. In the second recording approach, plaque-evoked dynamic and static spatial electric images were obtained by a multi-electrode catheter system. Based on these recordings, a synthetic plaque with a critical cap thickness could be detected and localized in a pig coronary artery.

Histopathologic Validation of Grayscale Carotid Plaque Characteristics Related to Plaque Vulnerability

Inflammation and angiogenesis play major roles in carotid plaque vulnerability. The purpose of this study was to determine whether gray-scale features of carotid plaques are associated with histologic markers for inflammation. Thirty-eight individuals completed a dedicated research carotid ultrasound exam before carotid endarterectomy. Gray-scale analysis was performed on plaque images to measure plaque echogenicity (gray-scale median [GSM] pixel brightness), plaque area, presence of discrete white areas (DWAs) and the percent of black area near the lumen on any one component of the plaque. Plaques with higher ultrasound GSM had greater percent calcification (p = 0.013) on histopathology. Presence of an ultrasound DWA was associated with more plaque hemosiderin (p = 0.0005) and inflammation (p = 0.019) on histopathology examination. The percent of plaque black area in any one component was associated with a higher score for macroscopic ulceration (p = 0.028). Ultrasound plaque characteristics (GSM, DWAs and black areas) represent histopathologic markers associated with plaque vulnerability. ClinicalTrials.gov identifier: NCT02476396.

Macrophage Apoptosis and Necrotic Core Development in Atherosclerosis: A Rapidly Advancing Field with Clinical Relevance to Imaging and Therapy

Cardiovascular diseases represent 1 of the main causes of death worldwide, and atherosclerosis is 1 of the major contributors leading to ischemic heart disease. Macrophages actively participate in all stages of atherosclerosis development, from plaque initiation to the transition to vulnerable plaques. Macrophage apoptosis, in particular, has been recognized as a critical step in the formation of the necrotic core, a key characteristic of unstable lesions. In this review, we discuss the role of macrophage apoptosis and clearance of apoptotic cells by efferocytosis in the development of atherosclerosis, with particular emphasis on their contribution to the development of the necrotic core and the clinical implications of this process for plaque stabilization. We consider the molecular triggers of macrophage apoptosis during atherogenesis, the role of endoplasmic reticulum (ER) stress, the roles of key cellular mediators of apoptosis and efferocytosis, and mechanisms of defective efferocytosis in the progression of atherosclerotic plaques. Finally, we discuss the important clinical implications of rapidly evolving macrophage science, such as novel approaches to imaging vulnerable atherosclerotic plaques with macrophage-sensitive positron emission tomography and magnetic resonance imaging, the role of macrophages in mediating beneficial pleiotropic actions of lipid-lowering therapies, and novel therapeutic modalities targeting ER stress, autophagy, and deficient efferocytosis. Advances in understanding the critical role of macrophages in the progression and destabilization of atherosclerosis have the potential to greatly improve the prevention and management of atherosclerotic diseases over the next decade.

Coronary artery calcium score and coronary computed tomography angiography for patients with asymptomatic polyvascular (non-coronary) atherosclerosis

INTRODUCTION

The primary endpoint of this study was to determine the prevalence of coronary artery disease (CAD) and coronary artery calcium score (CACS) using coronary computed tomography angiography (CCTA) among patients with polyvascular atherosclerosis (PVA). Secondary endpoints were to evaluate the prevalence of cardiovascular risk factors and determine the predictors of PVA.

METHODS

The presence of atherosclerotic disease was assessed using ultrasonographic vascular examination in 515 asymptomatic patients. All patients with presence of stenosis over 50% and moderate-to-severe cardiovascular risk profile underwent CCTA to identify atherosclerotic coronary disease.

RESULTS

Among 515 participants, 143 patients had no evidence of atherosclerotic plaque. Of the 372 patients with atherosclerotic plaque, 184 patients had single-vessel disease, 111 patients had double-vessel disease and 77 patients had triple-vessel disease; among these patients, those who also presented with stenosis > 50% underwent CCTA. Coronary stenosis categories included: normal (6.4%); haemodynamically insignificant (34.6%); intermediate (28.7%); significant (26.6%); and total artery occlusion (3.7%). Based on the coronary vessel involved, the patients were categorised as having single- (41.0%), double- (42.0%) or triple- (17.0%) coronary disease. CACS was significantly higher in patients with double- or triple-vessel disease when compared to those with single-vessel disease.

CONCLUSION

Our study confirmed not only the high sensitivity of CCTA for highlighting CAD, but also its negative predictive value for excluding the presence of coronary stenosis or ischaemia. We found good correlation between PVA and CACS, and were able to confirm the risk factors for PVA.

PET/CT Imaging of Unstable Carotid Plaque with 68Ga-Labeled Somatostatin Receptor Ligand

⁶⁸Ga-labeled somatostatin receptor ligand PET imaging has recently been shown in preclinical and early human studies to have a potential role in the evaluation of vulnerable arterial plaques. We prospectively evaluated carotid plaque ⁶⁸Ga-DOTATATE uptake in patients with recent carotid events, assessed inter- and intraobserver variability of such measurements, and explored the mechanism of any plaque DOTATATE activity with immunohistochemistry in resected specimens. Methods: Twenty consecutively consenting patients with recent symptomatic carotid events (transient ischemic attack, stroke, or amaurosis fugax), due for carotid endarterectomy, were prospectively recruited. ⁶⁸Ga-DOTATATE PET/CT of the neck was performed before surgery. ⁶⁸Ga-DOTATATE uptake was measured by drawing regions of interest along the carotid plaques and contralateral plaques/carotid arteries by an experienced radionuclide radiologist and radiographer. Two PET quantification methods with inter- and intraobserver variability were assessed. Resected carotid plaques were retrieved for somatostatin receptor subtype-2 (sst2) immunohistochemical staining. Results: The median time delay between research PET and surgery was 2 d. SUVs and target-to-background ratios for the symptomatic plaques and the asymptomatic contralateral carotid arteries/plaques showed no significant difference (n = 19, P > 0.10), regardless of quantification method. The intraclass correlation coefficient was greater than 0.8 in all measures of carotid artery/plaque uptake (SUV) and greater than 0.6 in almost all measures of target-to-background ratio. None of the excised plaques was shown to contain cells (macrophages, lymphocytes, vessel-associated cells) expressing sst2 on their cell membrane. Conclusion:⁶⁸Ga-DOTATATE activity on PET in recently symptomatic carotid plaques is not significantly different from contralateral carotids/plaques. Any activity seen on PET is not shown to be from specific sst2 receptor-mediated uptake in vitro. It is therefore unlikely that sst2 PET/CT imaging will have a role in the detection and characterization of symptomatic carotid plaques.

Quantitative evaluation of atherosclerotic plaques using cross-polarization optical coherence tomography, nonlinear, and atomic force microscopy

A combination of approaches to the image analysis in cross-polarization optical coherence tomography (CP OCT) and high-resolution imaging by nonlinear microscopy and atomic force microscopy (AFM) at the different stages of atherosclerotic plaque development is studied. This combination allowed us to qualitatively and quantitatively assess the disorganization of collagen in the atherosclerotic arterial tissue (reduction and increase of CP backscatter), at the fiber (change of the geometric distribution of fibers in the second-harmonic generation microscopy images) and fibrillar (violation of packing and different nature of a basket-weave network of fibrils in the AFM images) organization levels. The calculated CP channel-related parameters are shown to have a statistically significant difference between stable and unstable (also called vulnerable) plaques, and hence, CP OCT could be a potentially powerful, minimally invasive method for vulnerable plaques detection.

Human cells involved in atherosclerosis have a sex

The influence of sex has been largely described in cardiovascular diseases. Atherosclerosis is a complex process that involves many cell types such as vessel cells, immune cells and endothelial progenitor cells; however, many, if not all, studies do not report the sex of the cells. This review focuses on sex differences in human cells involved in the atherosclerotic process, emphasizing the role of sex hormones. Furthermore, we report sex differences and issues related to the processes that determine the fate of the cells such as apoptotic and autophagic mechanisms. The analysis of the data reveals that there are still many gaps in our knowledge regarding sex influences in atherosclerosis, largely for the cell types that have not been well studied, stressing the urgent need for a clear definition of experimental conditions and the inclusion of both sexes in preclinical studies.

Age and Cardiovascular Risk Attributable to Apolipoprotein B, Low-Density Lipoprotein Cholesterol or Non-High-Density Lipoprotein Cholesterol

BACKGROUND

Higher concentrations of the apolipoprotein B (apoB) lipoproteins increase the risk of cardiovascular disease. However, whether the risk associated with apoB lipoproteins varies with age has not been well examined.

METHODS AND RESULTS

We determined the associations for total cholesterol, low-density lipoprotein (LDL)-cholesterol (LDL-C), non-high-density lipoprotein-cholesterol (non-HDL-C), apoB, apolipoprotein A-I (apoA-I), and HDL-cholesterol (HDL-C) with myocardial infarction at different ages in 11 760 controls and 8998 myocardial infarction cases of the INTERHEART Study. Logistic regression was used to compute the odds ratio of myocardial infarction for 1 SD change in each lipid marker by decade from <40 to >70 years of age. Except for those >70, plasma levels of total cholesterol, LDL-C, and non-HDL-C and apoB were greater in cases than controls. However, the average levels of these markers decreased significantly as age increased. By contrast, levels of apoA-I and HDL-C were significantly greater in controls than cases but increased significantly as age increased. The cardiovascular risk associated with the atherogenic lipid markers differed at different ages. Most notably, there was a significant decline in the odds ratio for total cholesterol, LDL-C, and non-HDL-C, and apoB with increases in age whereas the odds ratios associated with apoA-I and HDL-C were consistent across the age groups.

CONCLUSIONS

These data indicate that the risk of cardiovascular events associated with apoB particles is greater in younger compared to older individuals. This finding is consistent with greater relative benefit from LDL-lowering therapy in younger compared to older individuals and so argues for therapy in younger individuals with elevated lipids.

Early Transcriptomic Response to LDL and oxLDL in Human Vascular Smooth Muscle Cells

Background

Although nowadays it is well known that the human transcriptome can importantly vary according to external or environmental condition, the reflection of this concept when studying oxidative stress and its direct relationship with gene expression profiling during the process of atherogenesis has not been thoroughly achieved.

Objective

The ability to analyze genome-wide gene expression through transcriptomics has shown that the genome responds dynamically to diverse stimuli. Here, we describe the transcriptome of human vascular smooth muscle cells (hVSMC) stimulated by native and oxidized low-density lipoprotein (nLDL and oxLDL respectively), with the aim of assessing the early molecular changes that induce a response in this cell type resulting in a transcriptomic transformation. This expression has been demonstrated in atherosclerotic plaques in vivo and in vitro, particularly in the light of the oxidative modification hypothesis of atherosclerosis.

Approach and Results

Total RNA was isolated with TRIzol reagent (Life Technologies) and quality estimated using an Agilent 2100 bioanalyzer. The transcriptome of hVSMC under different experimental conditions (1,5 and 24 hours for nLDL and oxLDL) was obtained using the GeneChip Human Gene 1.0 ST (Affymetrix) designed to measure gene expression of 28,869 well-annotated genes. A fixed fold-change cut-off corresponding to ± 2 was used to identify genes exhibiting the most significant variation and statistical significance (P< 0.05), and 8 genes validated by qPCR using Taqman probes.

Conclusions

10 molecular processes were significantly affected in hVSMC: Apoptosis and cell cycle, extracellular matrix remodeling, DNA repair, cholesterol efflux, cGMP biosynthesis, endocytic mechanisms, calcium homeostasis, redox balance, membrane trafficking and finally, the immune response to inflammation. The evidence we present supporting the hypothesis for the involvement of oxidative modification of several processes and metabolic pathways in atherosclerosis is strengthen by the fact that gene expression patterns obtained when hVSMC are incubated for a long period of time in the presence of nLDL, correspond very much the same as when cells are incubated for a short period of time in the presence of chemically modified oxLDL. Our results indicate that under physiological conditions and directly related to specific environmental conditions, LDL particles most probably suffer chemical modifications that initially serve as an alert signal to overcome a harmful stimulus that with time might get transformed to a pathological pattern and therefore consolidate a pathological condition.

Live Observation of Atherosclerotic Plaque Disruption in Apolipoprotein E-Deficient Mouse

AIM

The actual occurrence of spontaneous plaque rupture in mice has been a matter of debate. We report on an in vivo observation of the actual event of possible plaque disruption in a living ApoE(-/-) mouse.

METHODS AND RESULTS

During live contrast-enhanced ultrasonography of a 50-week-old ApoE(-/-) male mouse, symptoms suggesting plaque disruption in the brachiocephalic artery were observed. Histological analysis confirmed the presence of advanced atherosclerotic lesions with dissections and intraplaque hemorrhage in the affected brachiocephalic trunk, pointing towards plaque rupture as the cause of the observed event. However, we did not detect a luminal thrombus or cap rupture, which is a key criterion for plaque rupture in human atherosclerosis.

CONCLUSION

This study reports the real-time occurrence of a possible plaque rupture in a living ApoE(-/-) mouse.

Multi-modal optical imaging characterization of atherosclerotic plaques

We combined cross-polarization optical coherence tomography (CP OCT) and non-linear microscopy based on second harmonic generation (SHG) and two-photon-excited fluorescence (2PEF) to assess collagen and elastin fibers and other vascular structures in the development of atherosclerosis, including identification of vulnerable plaques, which remains an important clinical problem and imaging application. CP OCT's ability to visualize tissue birefringence and cross-scattering adds new information about the microstructure and composition of the plaque. However its interpretation can be ambiguous, because backscattering contrast may have a similar appearance to the birefringence related fringes. Our results represent a step towards minimally invasive characterization and monitoring of different stages of atherosclerosis, including vulnerable plaques. CP OCT image of intimal thickening in the human coronary artery. The dark stripe in the cross-polarization channel (arrow) is a polarization fringe related to the phase retardation between two eigen polarization states. It is histologically located in the area of the lipid pool, however this stripe is a polarization artifact, rather than direct visualization of the lipid pool.

Development of Advanced Atherosclerotic Plaque by Injection of Inflammatory Proteins in a Rabbit Iliac Artery Model

PURPOSE

Appropriate animal models of atherosclerotic plaque are crucial to investigating the pathophysiology of atherosclerosis, as well as for the evaluation of the efficacy and safety of vascular devices. We aimed to develop a novel animal model that would be suitable for the study of advanced atherosclerotic lesions in vivo.

MATERIALS AND METHODS

Atherosclerotic plaque was induced in 24 iliac arteries from 12 rabbits by combining a high cholesterol diet, endothelial denudation, and injection into the vessel wall with either saline (n=5), olive oil (n=6), or inflammatory proteins [n=13, high-mobility group protein B1 (HMGB1) n=8 and tumor necrosis factor (TNF)-α n=5] using a Cricket™ Micro-infusion catheter. Optical coherence tomography (OCT) was performed to detect plaque characteristics after 4 weeks, and all tissues were harvested for histological evaluation.

RESULTS

Advanced plaque was more frequently observed in the group injected with inflammatory proteins. Macrophage infiltration was present to a higher degree in the HMGB1 and TNF-α groups, compared to the oil or saline group (82.1±5.1% and 94.6±2.2% compared to 49.6±14.0% and 46.5±9.6%, p-value<0.001), using RAM11 antibody staining. On OCT, lipid rich plaques were more frequently detected in the inflammatory protein group [saline group: 2/5 (40%), oil group: 3/5 (50%), HMGB1 group: 6/8 (75%), and TNF-α group: 5/5 (100%)].

CONCLUSION

These data indicate that this rabbit model of atherosclerotic lesion formation via direct injection of pro-inflammatory proteins into the vessel wall is useful for in vivo studies investigating atherosclerosis.

Novel imaging approaches to cerebrovascular disease

Imaging techniques available to the physician treating neurovascular disease have substantially grown over the past several decades. New techniques as well as advances in imaging modalities continuously develop and provide an extensive array of modalities to diagnose, characterize, and understand neurovascular pathology. Modern noninvasive neurovascular imaging is generally based on computed tomography (CT), magnetic resonance (MR) imaging, or nuclear imaging and includes CT angiography, CT perfusion, xenon-enhanced CT, single-photon emission CT, positron emission tomography, magnetic resonance angiography, MR perfusion, functional magnetic resonance imaging with global and regional blood oxygen level dependent imaging, and magnetic resonance angiography with the use of the noninvasive optional vessel analysis software (River Forest, Ill). In addition to a brief overview of the technique, this review article discusses the clinical indications, advantages, and disadvantages of each of those modalities.

The relationship between preoperative serum cortisol level and the stability of plaque in carotid artery stenosis patients undergoing carotid endarterectomy

BACKGROUND

Stability of plaque has been implicated as risk factor for stroke. Serum cortisol regulates lipoprotein metabolism and immune response, contributing to plaque stability in atherosclerosis. However, the relationship between serum cortisol and stability of carotid plaque has not been well characterized. We conducted a serology analysis to identify the relationship between serum cortisol and carotid plaque stability.

METHODS

Between May 2013 to October 2015, 73 patients with carotid stenosis patients undergoing carotid endarterectomy (CEA) were enrolled in our study. Serum cortisol was analyzed at 8:00 AM in the morning before surgery via liquid chromatography tandem mass spectrometry. According to the classification made by the American Heart Association, hematoxylin-and-eosin staining was performed to divide these patients into either a stable or unstable group, according to the morphology of fibrous cap, lipid core and intima layer. A curve fitting method was used to identify the relationship between preoperative serum cortisol and stability of carotid plaque. Univariate and multivariate logistic regression analysis were used to identify carotid plaque stability-associated serum cortisol.

RESULTS

Curve fitting's result represents a U-shape characteristic. A total of 314.92 and 395.23 nmol/L were considered as the cut point for preoperative serum cortisol when trisected the patients. When adjusted for degree of stenosis, hyperlipemia, smoking and low-density lipoprotein (LDL), univariate and multivariate logistic regression analysis' results demonstrated that preoperative serum cortisol can significantly affect carotid plaque stability. The odds ratio values in multivariate logistic regression analysis for C reactive protein (CRP), white blood cell (WBC), interleukin-6 (IL-6) and preoperative serum cortisol level were 7.67 and 20.86 respectively.

CONCLUSIONS

Preoperative serum cortisol was associated with stability of carotid plaque in patients undergoing CEA. Low or high levels of preoperative serum cortisol might be an adverse factor for carotid plaque stability.

Peroxynitrite-mediated oxidation of plasma fibronectin

Fibronectin is a large dimeric glycoprotein present in both human plasma and in basement membranes. The latter are specialized extracellular matrices underlying endothelial cells in the artery wall. Peroxynitrous acid (ONOOH) a potent oxidizing and nitrating agent, is formed in vivo from superoxide and nitric oxide radicals by stimulated macrophages and other cells. Considerable evidence supports ONOOH involvement in human atherosclerotic lesion development and rupture, possibly via extracellular matrix damage. Here we demonstrate that Tyr and Trp residues on human plasma fibronectin are highly sensitive to ONOOH with this resulting in the formation of 3-nitrotyrosine, 6-nitrotryptophan and dityrosine as well as protein aggregation and fragmentation. This occurs with equimolar or greater levels of oxidant, and in a dose-dependent manner. Modification of Tyr was quantitatively more significant than Trp (9.1% versus 1.5% conversion with 500μM ONOOH) after accounting for parent amino acid abundance, but only accounts for a small percentage of the total oxidant added. LC-MS studies identified 28 nitration sites (24 Tyr, 4 Trp) with many of these present within domains critical to protein function, including the cell-binding and anastellin domains. Human coronary artery endothelial cells showed decreased adherence and cell-spreading on ONOOH-modified fibronectin compared to control, consistent with cellular dysfunction induced by the modified matrix. Studies on human atherosclerotic lesions have provided evidence for co-localization of 3-nitrotyrosine and fibronectin. ONOOH-mediated fibronectin modification and compromised cell-matrix interactions, may contribute to endothelial cell dysfunction, a weakening of the fibrous cap of atherosclerotic lesions, and an increased propensity to rupture.

Intracranial Vessel Wall MRI: Principles and Expert Consensus Recommendations of the American Society of Neuroradiology

Intracranial vessel wall MR imaging is an adjunct to conventional angiographic imaging with CTA, MRA, or DSA. The technique has multiple potential uses in the context of ischemic stroke and intracranial hemorrhage. There remain gaps in our understanding of intracranial vessel wall MR imaging findings and research is ongoing, but the technique is already used on a clinical basis at many centers. This article, on behalf of the Vessel Wall Imaging Study Group of the American Society of Neuroradiology, provides expert consensus recommendations for current clinical practice.

p38δ MAPK: A Novel Regulator of NLRP3 Inflammasome Activation With Increased Expression in Coronary Atherogenesis

OBJECTIVE

Activation of the inflammasome pathway in macrophages results in the secretion of 2 potent proinflammatory and proatherogenic cytokines, interleukin (IL)-1β, and IL-18. Atherosclerotic lesions are characterized by the presence of various endogenous activators of the NLR family pyrin domain containing 3 (NLRP3) inflammasome, including cholesterol crystals and extracellular ATP. The aim of this study was to comprehensively characterize the expression of inflammasome pathway components and regulators in human atherosclerotic lesions.

APPROACH AND RESULTS

Twenty human coronary artery RNA samples from 10 explanted hearts were analyzed using an inflammasome pathway-focused quantitative polymerase chain reaction array. Advanced atherosclerotic plaques, when compared with early-to-intermediate lesions from the same coronary trees, displayed significant upregulation of 12 target genes, including the key inflammasome components apoptosis-associated speck-like protein containing a CARD domain, caspase-1, and IL-18. Immunohistochemical stainings of the advanced plaques revealed macrophage foam cells positive for NLRP3 inflammasome components around the necrotic lipid cores. The polymerase chain reaction array target p38δ mitogen-activated protein kinase was upregulated in advanced plaques and strongly expressed by lesional macrophage foam cells. In cultured human monocyte-derived macrophages, the p38δ mitogen-activated protein kinase was activated by intracellular stress signals triggered during ATP- and cholesterol crystal-induced NLRP3 inflammasome activation and was required for NLRP3-mediated IL-1β secretion.

CONCLUSIONS

Increased expression of the key inflammasome components in advanced coronary lesions implies enhanced activity of the inflammasome pathway in progression of coronary atherosclerosis. The p38δ mitogen-activated protein kinase was identified as a novel regulator of NLRP3 inflammasome activation in primary human macrophages, and thus, represents a potential target for modulation of atherosclerotic inflammation.