Cell-Derived Microparticles and Acute Coronary Syndromes: Is there a Predictive Role for Microparticles?

Background:

Despite the recent advances in the treatment of Acute Coronary Syndromes (ACS), patients with ACS are still exposed to an increased risk for adverse cardiovascular events, while their prognosis is difficult to determine. Experimental and clinical studies have shown that cell-derived Microparticles (MPs) are associated with the underlying pathophysiological processes that are responsible for atherogenesis and may be causally implicated in the induction of atherothrombosis.

Objective:

In the present article, we aimed to review the available evidence regarding the predictive role of MPs in patients with ACS.

Results:

Evidence suggests that endothelial MPs are associated with future adverse cardiovascular events in patients with ACS. Platelet-derived MPs have been excessively studied, since they have been found to trigger the coagulation cascade; however, their role as predictors of future cardiovascular events remains debatable. The role of red blood cell-derived MPs is more intriguing; they have been proposed as markers of ongoing thrombosis in patients with ACS, while previous studies have shown that they have anti-coagulant properties in healthy individuals. Leukocyte-derived MPs may also have a predictive role, although the studies regarding these are still limited. Last but not least, it was an interesting discovery that circulating MPs can provide information regarding the angiographic lesions in patients with ACS.

Conclusion:

The concept of MPs as potential circulating biomarkers in patients with ACS holds much promise. However, large-scale clinical studies are required to evaluate whether the measurement of plasma MPs could be of clinical significance and, thus, dictate a more aggressive treatment strategy in patients with high levels of circulating MPs.

Plasma signature of apoptotic microvesicles is associated with endothelial dysfunction and plaque rupture in acute coronary syndromes

OBJECTIVE

Circulating microvesicles (MV) are surrogate biomarkers of atherosclerosis. However, their role in acute coronary syndromes (ACS) has not been fully elucidated yet. We sought to examine the association of circulating apoptotic MVs with ACS pathophysiology.

APPROACH AND RESULTS

One hundred and fifty-three patients (n = 153) were included in the study; 49 patients with ST-elevation myocardial infarction (STEMI), 35 with non-STEMI (NSTEMI), 38 with unstable angina, 15 with stable coronary artery disease and 16 control individuals. Flow cytometry analysis was used to quantify circulating apoptotic/non-apoptotic (phospatidyloserine⁺/phospatidyloserine^-) endothelial cell (EMV), red blood cell (RMV) and platelet (PMV) derived MV. Flow-mediated dilatation (FMD) of the brachial artery was assessed by ultrasound to estimate endothelial function. The inflammatory profile was assessed by serum C-reactive protein (hsCRP) levels. Apoptotic only (but not non-apoptotic) MV were increased in patients with ACS (EMV, P = 2.32 × 10^-9; RMV, P = .0019; PMV, P = .01). Hierarchical clustering of the total population of ACS patients (n = 122) by circulating levels of phospatidyloserine⁺ EMV, RMV and PMV identified two discreet clusters of patients without any differences in traditional risk factors, but significant differences in brachial FMD (5.2% (2.5) vs. 4.1% (2.3), P < .05) that remained significant after adjustment for co-variates. The prevalence of STEMI, a surrogate for plaque rupture and vessel thrombotic occlusion, was significantly higher in the patient cluster with impaired endothelial function (60% vs 32%, P = .016, adjusted odds ratio for STEMI, 3.041, 95%CI, 1.160 to 7.968, p = .024).

CONCLUSION

Our findings indicate that the circulating levels of apoptotic MV are increased in ACS patients and their plasma profiles associate with endothelial dysfunction and thrombotic complications in ACS patients.

2229Apoptotic and non-apoptotic circulating microparticles in patients with acute coronary syndromes

Background

Circulating microparticles (MP) are surrogate biomarkers of atherosclerosis but their role in patients with acute coronary syndromes (ACS) remain unknown.

Purpose

To explore the levels of apoptotic and non-apoptotic MP in patients with ACS.

Methods

We enrolled a total of 153 patients as follows: 49 patients with STEMI, 35 NSTEMI, 38 with unstable angina (UA), 15 with stable CAD (SCAD) and 16 non-CAD (controls). Flow cytometry analysis was used to quantify circulating apoptotic (annexin+) and non-apoptotic endothelial cell (EMP), red blood cell (RMP) and platelet (PMP) derived microparticles. Circulating C-reactive protein (hsCRP) levels and cardiac troponin I (cTnI) were also assessed. Brachial FMD was also determined as a marker of endothelial function.

Results

There was a stepwise increase in the total number of EMP, RMP and PMP in patients with ACS (STEMI/NSTEMI) compared to UA, SCAD and non-CAD patients. This was mainly explained by the increase in the number of apoptotic EMP, RMP and PMP (a-c), while there were no significant differences in the level of apoptotic EMP, RMP or PMP between patient subgroups (not shown). There was no association between circulating levels of apoptotic or non-apoptotic EMP, RBP or PMP with hsCRP (p=NS for all). Apoptotic EMP only were negatively associated with brachial FMD (rho=−0.185, p=0.04) and positively with cTnI levels (rho= 0.307, p<0.0001).

Conclusions

Circulating apoptotic (but not non-apoptotic) MP are increased in patients with ACS. A negative association is observed between the numbers of circulating apoptotic EMP only and systemic endothelial function. The biological role of circulating apoptotic microparticles' in the pathogenesis of ACS merits further investigation.

P6506Circulating microparticles preceding endothelial dysfunction and inflammatory process in patients with pseudoexfoliative glaucoma

Background

Pseudoexfoliative glaucoma (PEX) is a type of glaucoma characterized by the secretion of a grey-white, fibrogranular material in several tissues. Microparticles are shed membrane vesicles released from a variety of cell types in response to cellular activation or apoptosis and correlate with the pathogenesis of cardiovascular diseases. Endothelial MPs may be used as biomarkers of endothelial function.

Purpose

To evaluated the role of endothelial dysfunction, arterial stiffness and systemic inflammation in patients with PEX compared to patients with Primary open angle glaucoma (POAG) and control subjects as well as the possible pathophysiologic role of a specific microparticle profile associated with endothelial damage.

Methods

We enrolled 29 subjects with PEX, 57 subjects with POAG and 44 control subjects. Endothelial function was evaluated by flow-mediated dilation (FMD). Pulse wave velocity (PWV) was measured as an index of aortic stiffness and augmentation index (AIx) as a measure of arterial wave reflections. Growth differentiation factor-15 (GDF-15) and intercellular adhesion molecule1 (ICAM1) were measured to evaluate systemic inflammatory status. Total circulating MPs and EMPs were isolated and analysed by flow cytometry, utilizing specific labels for EMPs (CD 144+) and Annexin V staining for phospatidylserine bearing-MPs (AnnexinV + MPs).

Results

There was a linear impairment in FMD (p=0.005), PWV (p=0.007) and Aix (p=0.02) and a stepwise increase in GDF-15 (p=0.001) and sICAM-1 levels (p=0.08) between the three study groups (control, POAG, PEX). Interestingly, the PEX subjects expressed greater levels of total circulating MPs (Annexin V+) [1698 (1199–5894) MPs/μL vs. 1641 (1470–2705) MPs/μL. vs 493 (417–1512) MPs/μL, p=0.004] and EMPs (CD144+)[1412 (645–1760) MPs/μL3 vs 1380 (498–2496) MPs/μL vs 34 (184–870) MPs/μL, p<0.001] compared to POAG and control subjects.

Conclusion

Pseudoexfoliative glaucoma is associated with impaired endothelial function, arterial wall properties and vascular inflammation with a parallel increase in EMPs. Our findings indicate the significant role of endothelial damage in the progress of glaucomatous disease especially in subjects with pseudoexfoliative glaucoma.

P5312Sleep duration and carotid atheromatic burden. Insights from the Corinthia study

Background

Sleep is an essential physiological process and disturbance of sleeping pattern may be associated with cardiovascular risk profile and atheromatosis. Short but also long sleep duration (LSD) may be adversely affect cardiovascular parameters.

Purpose

To study how sleep duration is associated with cardiovascular risk profile and carotid atherosclerotic burden.

Methods

Corinthia study is a cross sectional epidemiological study based on 2043 inhabitants (age 40–99 years) of Corinthia region in Greece. Ultrasonography was used to measure intima media thickness (IMT) in the left and right common carotid artery, carotid bulb and internal carotid artery. The mean IMT (meanIMT) were determined as representative values of carotid atherosclerosis burden. Thickness of IMT>1.5 mm or protrusion >50% compared to adjacent segments was considered as atherosclerotic plaque. Based on questionnaires of Corinthia study, total sleeping time per day was recorded. A sleep duration of 7 to 8 h was consider normal (NSD), sleep duration <6 h was consider very short (VSSD), 6–7 h sleep duration was considered short (SSD) and participants with >8 h sleep duration was categorized as LSD.

Results

Concerning gender more men than women were categorized in the NSD (26% vs. 21%, p<0.001). Subjects in the NSD were also younger compared to subjects categorized in other sleeping patterns (VSSD: 66±12 y vs. SSD: 63±12 y vs. NSD: 62±12 y vs. LSD: 66±12 y, p<0.001), have less prevalence of diabetes mellitus (p<0.05). There was no difference according to sleeping pattern in body mass index, prevalence of hypertension, cardiovascular disease, hyperlipidemia and on current smoking habits according to sleeping patterns. Interestingly, meanIMT (VSSD: 1.08±0.51 mm vs. SSD: 0.97±0.42 mm vs. NSD: 0.97±0.41 mm vs. LSD: 1.14±1.64 mm, p=0.04) and carotid atherosclerotic plaque (VSSD: 35% vs. SSD: 25% vs. NSD: 20% vs. LSD: 30%, p=0.006) was decreased in NSD subjects. Importantly, even after adjustment for the confounders logistic regression analysis revealed that subjects in the NSD group have 50% less odds of carotid atheromatic plaque than subjects in the VSSD (Odds ratio: 0.5, 95% CI 0.28–0.90, p=0.02) (Figure).

Conclusion

A balanced sleeping pattern with 8h of sleep daily can act as an additive cardioprotective factor in the modern western type societies. Short especially less than 6 hours and long (>8 hours) sleeping duration may act as a cardiovascular risk factor.

P6602Plasma signature of apoptotic microparticles in acute coronary syndromes is associated with endothelial dysfunction and plaque rupture

Background

Circulating microparticles (MP) are surrogate biomarkers of atherosclerosis and are elevated in acute coronary syndromes (ACS) but its exact biological role remains unknown.

Purpose

To explore the diagnostic and biological significance of circulating apoptotic MP signature in patients with ACS.

Methods

We enrolled 122 ACS patients: n=38 with unstable angina (UA), n=49 with STEMI, 35 with NSTEMI. Flow cytometry analysis was used to quantify circulating apoptotic (annexin+) endothelial cell (EMP), red blood cell (RMP) and platelet (PMP) derived microparticles. Endothelial function was estimated with flow mediated dilation (FMD), and inflammatory status with C-reactive protein (hsCRP).

Results

The association between EMP, RMP and PMP is shown on a cloud plot (A). Using an unbiased approach, we performed hierarchical clustering (A) of the total population of patients with ACS by using the circulating levels of EMP, RMP and PMP (B). Hierachical clustering identified two discreet clusters of patients (Cluster A and B) without any differences in the presence of traditional risk factors (not shown), but significant differences in the distribution of ACS type (C). STEMI subtype (a surrogate for definite plaque rupture) was significantly increased in Cluster B, which also had significantly decreased FMD (D), but not hsCRP (p=NS).

Conclusions

Apoptotic MP are involved in the pathogenesis of acute coronary syndromes via promotion of endothelial dysfunction and plaque rupture. The diagnostic and/or predictive value of microparticles' profiling for plaque vulnerability should be explored in future studies.

Cardiac myocyte KLF5 regulates body weight via alteration of cardiac FGF21

Cardiac metabolism affects systemic energetic balance. Previously, we showed that Krüppel-like factor (KLF)-5 regulates cardiomyocyte PPARα and fatty acid oxidation-related gene expression in diabetes. We surprisingly found that cardiomyocyte-specific KLF5 knockout mice (αMHC-KLF5-/-) have accelerated diet-induced obesity, associated with increased white adipose tissue (WAT). Alterations in cardiac expression of the mediator complex subunit 13 (Med13) modulates obesity. αMHC-KLF5-/- mice had reduced cardiac Med13 expression likely because KLF5 upregulates Med13 expression in cardiomyocytes. We then investigated potential mechanisms that mediate cross-talk between cardiomyocytes and WAT. High fat diet-fed αMHC-KLF5-/- mice had increased levels of cardiac and plasma FGF21, while food intake, activity, plasma leptin, and natriuretic peptides expression were unchanged. Consistent with studies reporting that FGF21 signaling in WAT decreases sumoylation-driven PPARγ inactivation, αMHC-KLF5-/- mice had less SUMO-PPARγ in WAT. Increased diet-induced obesity found in αMHC-KLF5-/- mice was absent in αMHC-[KLF5-/-;FGF21-/-] double knockout mice, as well as in αMHC-FGF21-/- mice that we generated. Thus, cardiomyocyte-derived FGF21 is a component of pro-adipogenic crosstalk between heart and WAT.

Biomarkers Associated with Stroke Risk in Atrial Fibrillation

Background:

Atrial fibrillation (AF) is associated with an increased risk of cardioembolic stroke. The risk of cardioembolism is not adequately reduced with the administration of oral anticoagulants, since a number of patients continue to experience thromboembolic events despite receiving treatment. Therefore, identification of a circulating biomarker to identify these high-risk patients would be clinically beneficial.

Objective:

In the present article, we aim to review the available data regarding use of biomarkers to predict cardioembolic stroke in patients with AF.

Methods:

We performed a thorough search of the literature in order to analyze the biomarkers identified thus far and critically evaluate their clinical significance.

Results:

A number of biomarkers have been proposed to predict cardioembolic stroke in patients with AF. Some of them are already used in the clinical practice, such as d-dimers, troponins and brain natriuretic peptide. Novel biomarkers, such as the inflammatory growth differentiation factor-15, appear to be promising, while the role of micro-RNAs and genetics appear to be useful as well. Even though these biomarkers are associated with an increased risk for thromboembolism, they cannot accurately predict future events. In light of this, the use of a scoring system, that would incorporate both circulating biomarkers and clinical factors, might be more useful.

Conclusions:

Recent research has disclosed several biomarkers as potential predictors of cardioembolic stroke in patients with AF. However, further research is required to establish a multifactorial scoring system that will identify patients at high-risk of thromboembolism, who would benefit from more intensive treatment and monitoring.

High-density Lipoprotein and Low-density Lipoprotein Therapeutic Approaches in Acute Coronary Syndromes

BACKGROUND

Low-density lipoprotein cholesterol (LDL), and especially its oxidized form, renders the atherosclerotic plaque vulnerable to rupture in acute coronary syndromes (ACS). On the other hand, high-density lipoprotein (HDL) is considered an anti-atherogenic molecule. The more recent HDL-targeted drugs may prove to be superior to those used before. Indeed, delipidated HDL and HDL mimetics are efficient in increasing HDL levels, while the apoA-I upregulation with RVX-208 appears to offer a clinical benefit which is beyond the HDL related effects. HDL treatment however has not shown a significant improvement in the outcomes of patients with ACS so far, studies have therefore focused again on LDL. In addition to statins and ezetimibe, novel drugs such as PSCK9 inhibitors and apolipoprotein B inhibitors appear to be both effective and safe for patients with hyperlipidemia.

CONCLUSION

Data suggest these could potentially improve the cardiovascular outcomes of patient with ACS. Yet, there is still research to be done, in order to confirm whether ACS patients would benefit from LDL- or HDL-targeted therapies or a combination of both.

Coronary Artery Atherosclerosis in Hypertensive Patients: The Role of Fibrinogen Genetic Variability

INTRODUCTION AND OBJECTIVES

We examined whether the rs180070 and rs2070011 polymorphisms of the fibrinogen gene could affect the risk of coronary artery disease in hypertensive patients by modifying the inflammatory process and coagulation.

METHODS

A total of 744 participants underwent coronary angiography due to symptoms of stable angina, while hypertension was present in 332 patients.

RESULTS

The presence of the A allele (rs180070) was associated with significantly high levels of fibrinogen in hypertensive patients (P=.05). On multivariate analysis, A homozygosity (rs180070) (β = 0.257 ± 18.6; P<.001), but not hypertension status (β = 0.05 ± 11.9; P=.29) was an independent predictor of fibrinogen levels. In hypertensive patients, higher fibrinogen levels>443mg/dL (odds ratio = 3.50; 95% confidence interval, 1.14-10.90; P=.029), but not A homozygosity (odds ratio = 3.00; 95% confidence interval, 0.78-11.90; P = .110) were independent predictors of the presence of coronary artery disease. Moreover, interleukin-6 levels were higher in A homozygotes for the rs180070 polymorphism compared with all other genotypes (P=.046). Indeed, this genotype was the only adjusted independent predictor of interleukin-6 levels (β = 0.151 ± 0.642; P=.032). It was also associated with higher D-dimer levels in hypertension compared with G allele carriers (P=.048).

CONCLUSIONS

The presence of A homozygosity (rs180070) is associated with increased levels of inflammatory mediators and a higher incidence of angiographic coronary artery disease. Importantly, fibrinogen is an independent predictor of the angiographic presence of coronary artery disease in hypertensive patients.

Association between microRNAs and coronary collateral circulation: is there a new role for the small non-coding RNAs?

We read with interest the article entitled "Circulating microRNAs characterizing patients with insufficient coronary collateral artery function" which was recently published in the PLOS ONE journal. It was demonstrated for the first time that specific circulating microRNAs (miRNAs) can distinguish patients with sufficient from those with insufficient coronary collateral circulation. Circulating miRNAs in the plasma of patients with stable CAD and chronic CTO could provide information with regard to the coronary collateral artery capacity. However, several aspects need to be taken into consideration before the use of miRNAs in the clinical practice. A risk model that would incorporate risk factors for cardiovascular disease and miRNAs could prove to be very useful. Although an association between the levels of miRNAs and the collateral artery capacity appears promising, it still does not confirm any causal role for miRNAs. Therefore, large clinical studies in populations with CTO are warranted to evaluate this finding.

HDL as a prognostic biomarker for coronary atherosclerosis: the role of inflammation

INTRODUCTION

Emerging evidence suggests that the role of high density lipoprotein (HDL) in the atherosclerotic process is not as clear as previously thought, since atheroprotective HDL becomes atherogenic in states of increased inflammatory processes.

AREAS COVERED

In this review we aim to elucidate the role of HDL as a prognostic biomarker and we discuss therapeutic approaches that aim to increase HDL and their possible clinical benefit.

EXPERT OPINION

Given the structural variability and biological complexity of the HDL particle, its role in the atherosclerotic process is far from clear. According to current evidence, the atheroprotective role of HDL turns atherogenic in states of increased inflammatory processes, while even minor alterations in systemic inflammation are likely to hinder the endothelial protective effects of HDL. In accordance, significant data have revealed that HDL-related drugs may be effective in reducing cardiovascular mortality; however they are not as encouraging or unanimous as expected. Possible future goals could be to quantify either HDL subclasses or functions in an attempt to reach safer conclusions as to the prognostic importance of HDL in coronary atherosclerosis. Having achieved that, a more targeted therapy that would aim to raise either HDL functionality or to remodel HDL structure would be more easily designed.

Statins and myocardial infarction: Type, dose, and administration time: Does it matter?

Patients with ST-elevation myocardial infarction (STEMI) constitute a vulnerable group that demands the careful assessment and application of all the up-to-date clinical and experimental knowledge, with final aim, the improvement of their prognosis. Statins are an indispensable part of the primary and secondary prevention of coronary artery disease (CAD), not only due to their strong hypolipidemic effect, but also due to their numerous pleiotropic properties that play an important role in the treatment of CAD, especially when the more vulnerable group of STEMI patients is addressed. Nevertheless, there are still issues that require further discussion and clarification, such as the type of statin, the dose of the regimen, the administration time, and the treatment duration.