Circulating immunoglobulins are not associated with intraplaque mast cell number and other vulnerable plaque characteristics in patients with carotid artery stenosis

Background

Recently, we have shown that intraplaque mast cell numbers are associated with atherosclerotic plaque vulnerability and with future cardiovascular events, which renders inhibition of mast cell activation of interest for future therapeutic interventions. However, the endogenous triggers that activate mast cells during the progression and destabilization of atherosclerotic lesions remain unidentified. Mast cells can be activated by immunoglobulins and in the present study, we aimed to establish whether specific immunoglobulins in plasma of patients scheduled for carotid endarterectomy were related to (activated) intraplaque mast cell numbers and plasma tryptase levels. In addition, the levels were related to other vulnerable plaque characteristics and baseline clinical data.

Methods and Results

OxLDL-IgG, total IgG and total IgE levels were measured in 135 patients who underwent carotid endarterectomy. No associations were observed between the tested plasma immunoglobulin levels and total mast cell numbers in atherosclerotic plaques. Furthermore, no associations were found between IgG levels and the following plaque characteristics: lipid core size, degree of calcification, number of macrophages or smooth muscle cells, amount of collagen and number of microvessels. Interestingly, statin use was negatively associated with plasma IgE and oxLDL-IgG levels.

Conclusions

In patients suffering from carotid artery disease, total IgE, total IgG and oxLDL-IgG levels do not associate with plaque mast cell numbers or other vulnerable plaque histopathological characteristics. This study thus does not provide evidence that the immunoglobulins tested in our cohort play a role in intraplaque mast cell activation or grade of atherosclerosis.

Extracellular vesicle markers in relation to obesity and metabolic complications in patients with manifest cardiovascular disease

Background

Alterations in extracellular vesicles (EVs), including exosomes and microparticles, contribute to cardiovascular disease. We hypothesized that obesity could favour enhanced release of EVs from adipose tissue, and thereby contribute to cardiovascular risk via obesity-induced metabolic complications. The objectives of this study were: 1) to investigate the relation between the quantity, distribution and (dys) function of adipose tissue and plasma concentrations of atherothrombotic EV-markers; 2) to determine the relation between these EV-markers and the prevalence of the metabolic syndrome; and 3) to assess the contribution of EV markers to the risk of incident type 2 diabetes.

Methods

In 1012 patients with clinically manifest vascular disease, subcutaneous and visceral fat thickness was measured ultrasonographically. Plasma EVs were isolated and levels of cystatin C, serpin G1, serpin F2 and CD14 were measured, as well as fasting metabolic parameters, hsCRP and adiponectin. The association between adiposity, EV-markers, and metabolic syndrome was tested by multivariable linear and logistic regression analyses. As sex influences body fat distribution, sex-stratified analyses between adipose tissue distribution and EV-markers were performed. The relation between EV-markers and type 2 diabetes was assessed with Cox regression analyses.

Results

Higher levels of hsCRP (β 5.59; 95% CI 3.00–8.18) and lower HDL-cholesterol levels (β-11.26; 95% CI −18.39 – -4.13) were related to increased EV-cystatin C levels, and EV-cystatin C levels were associated with a 57% higher odds of having the metabolic syndrome (OR 1.57; 95% CI 1.19–2.27). HDL-cholesterol levels were positively related to EV-CD14 levels (β 5.04; 95% CI 0.07–10.0), and EV-CD14 levels were associated with a relative risk reduction of 16% for development of type 2 diabetes (HR 0.84, 95% CI 0.75–0.94), during a median follow up of 6.5 years in which 42 patients developed type 2 diabetes.

Conclusions

In patients with clinically manifest vascular disease, EV-cystatin C levels were positively related, and EV-CD14 levels were negatively related to metabolic complications of obesity.

Spectroscopic intravascular photoacoustic imaging of lipids in atherosclerosis

The natural history of atherosclerosis is marked by changes in the lipid biochemistry in the diseased arterial wall. As lesions become more vulnerable, different cholesterol species accumulate in the plaque. Understanding unstable atherosclerosis as a pharmacological and interventional therapeutic target requires chemically specific imaging of disease foci. In this study, we aim to image atherosclerotic plaque lipids and other vessel wall constituents with spectroscopic intravascular photoacoustics (sIVPA). sIVPA imaging can identify lipids in human coronary atherosclerotic plaque by relying on contrast in the near-infrared absorption spectra of the arterial wall components. Using reference spectra acquired on pure compounds, we analyzed sIVPA data from human coronary plaques ex vivo, to image plaque composition in terms of cholesterol and cholesterol ester content. In addition, we visualized the deeper lying connective tissue layers of the adventitia, as well as the fatty acid containing adipose cells in the peri-adventitial tissue. We performed simultaneous coregistered IVUS imaging to obtain complementary morphological information. Results were corroborated by histopathology. sIVPA imaging can distinguish the most prevalent lipid components of human atherosclerotic plaques and also visualize the connective tissue layers of the adventitia and the fatty acid containing adipose cells in the peri-adventitial tissue.

Leukotriene B4 levels in human atherosclerotic plaques and abdominal aortic aneurysms

BACKGROUND

Leukotriene B4 (LTB4) has been associated with the initiation and progression of atherosclerosis and abdominal aortic aneurysm (AAA) formation. However, associations of LTB4 levels with tissue characteristics and adverse clinical outcome of advanced atherosclerosis and AAA are scarcely studied. We hypothesized that LTB4 levels are associated with a vulnerable plaque phenotype and adverse clinical outcome. Furthermore, that LTB4 levels are associated with inflammatory AAA and adverse clinical outcome.

METHODS

Atherosclerotic plaques and AAA specimens were selected from two independent databases for LTB4 measurements. Plaques were isolated during carotid endarterectomy from asymptomatic (n = 58) or symptomatic (n = 317) patients, classified prior to surgery. LTB4 levels were measured without prior lipid extraction and levels were corrected for protein content. LTB4 levels were related to plaque phenotype, baseline patient characteristics and clinical outcome within three years following surgery. Seven non-diseased mammary artery specimens served as controls. AAA specimens were isolated during open repair, classified as elective (n = 189), symptomatic (n = 29) or ruptured (n = 23). LTB4 levels were measured similar to the plaque measurements and were related to tissue characteristics, baseline patient characteristics and clinical outcome. Twenty-six non-diseased aortic specimens served as controls.

RESULTS

LTB4 levels corrected for protein content were not significantly associated with histological characteristics specific for vulnerable plaques or inflammatory AAA as well as clinical presentation. Moreover, it could not predict secondary manifestations independently investigated in both databases. However, LTB4 levels were significantly lower in controls compared to plaque (p = 0.025) or AAA (p = 0.017).

CONCLUSIONS

LTB4 levels were not associated with a vulnerable plaque phenotype or inflammatory AAA or clinical presentation. This study does not provide supportive evidence for a role of LTB4 in atherosclerotic plaque destabilization or AAA expansion. However, these data should be interpreted with care, since LTB4 measurements were performed without prior lipid extractions.

Extracellular vesicle protein levels are related to brain atrophy and cerebral white matter lesions in patients with manifest vascular disease: the SMART-MR study

OBJECTIVES

Extracellular vesicles (EVs) and their protein levels have been identified as a potential risk marker for the development of vascular disease. In the present study, we assessed whether levels of four previously identified EV proteins (cystatin C, serpin G1, serpin F2 and CD14) are associated with cerebral white matter lesions (WMLs) and brain atrophy.

DESIGN

Cohort study; cross-sectional and prospective.

SETTING

Single centre, secondary and tertiary setting.

PARTICIPANTS

1309 patients with manifest vascular disease from the Second Manifestations of ARTerial disease-MR (SMART-MR) study, of which 994 had successful brain MRI and EV protein level measurements.

OUTCOMES

WML and brain parenchymal fraction (BPF), as parameter for brain atrophy, at baseline and follow-up.

STATISTICAL METHODS

The relationship between EV protein levels and WML volume (expressed as log transformed percentage of intracranial volume) and BPF (expressed percentage of intracranial volume) on 1.5 T brain MRI was assessed with multivariable linear regression modelling. Subsequently, the relationship between baseline EV protein levels and progression of atrophy and WML was analysed in 534 patients, in whom a follow-up MRI was obtained after 4 years.

RESULTS

Higher EV-cystatin C and EV-CD14 were significantly associated with larger WML volume (linear regression coefficient (95% CI) 0.10 log %/SD (0.04 to 0.17) and 0.14 log %/SD (0.07 to 0.20), respectively. Higher EV-CD14 was associated with more brain atrophy (-0.14%/SD; -0.27 to -0.01). Baseline EV-CD14 was significantly associated with increase of WMLs (0.11 log %/SD (0.04 to 0.18)). No relationship with EV-serpins was observed at baseline or at follow-up.

CONCLUSIONS

EV proteins cystatin C and CD14 are related to cerebral WMLs and the progression of brain atrophy in patients with manifest vascular disease, potentially identifying EVs in the aetiology of structural brain changes.

Absence of chemokine (C-x-C motif) ligand 10 diminishes perfusion recovery after local arterial occlusion in mice

OBJECTIVE

In arteriogenesis, pre-existing anastomoses undergo enlargement to restore blood flow in ischemic tissues. Chemokine (C-X-C motif) ligand 10 (CXCL10) is secreted after Toll-like receptor activation. Toll-like receptors are involved in arteriogenesis; however, the role of CXCL10 is still unclear. In this study, we investigated the role for CXCL10 in a murine hindlimb ischemia model.

APPROACH AND RESULTS

Unilateral femoral artery ligation was performed in wild-type (WT) and CXCL10(-/-) knockout (KO) mice and perfusion recovery was measured using laser-Doppler perfusion analysis. Perfusion recovery was significantly lower in KO mice compared with WT at days 4 and 7 after surgery (KO versus WT: 28±5% versus 81±13% at day 4; P=0.003 and 57±12% versus 107±8% at day 7; P=0.003). Vessel measurements of α-smooth muscle actin-positive vessels revealed increasing numbers in time after surgery, which was significantly higher in WT when compared with that in KO. Furthermore, α-smooth muscle actin-positive vessels were significantly larger in WT when compared with those in KO at day 7 (wall thickness, P<0.001; lumen area, P=0.003). Local inflammation was assessed in hindlimb muscles, but this did not differ between WT and KO. Chimerization experiments analyzing perfusion recovery and histology revealed an equal contribution for bone marrow-derived and circulating CXCL10. Migration assays showed a stimulating role for both intrinsic and extrinsic CXCL10 in vascular smooth muscle cell migration.

CONCLUSIONS

CXCL10 plays a causal role in arteriogenesis. Bone marrow-derived CXCL10 and tissue-derived CXCL10 play a critical role in accelerating perfusion recovery after arterial occlusion in mice probably by promoting vascular smooth muscle cell recruitment and maturation of pre-existing anastomoses.

Extracellular vesicle-derived CD14 is independently associated with the extent of cardiovascular disease burden in patients with manifest vascular disease

BACKGROUND

In patients with established cardiovascular disease, high levels of the extracellular vesicle (EV)-derived proteins cystatin C, CD14, and α2-antiplasmin predict recurrent cardiovascular events. We examined whether these proteins are associated with the extent of vascular disease.

METHODS

In 1062 patients from the SMART (Secondary Manifestations in ARTerial disease) study, EVs were isolated from plasma at baseline. Cystatin C, CD14, and α2-antiplasmin were measured in these vesicles using a multiplex assay. The extent of vascular disease burden was determined by a sum score that incorporates history and current presence of clinically manifest coronary, cerebrovascular, peripheral arterial, and abdominal aneurysm disease, and parameters of atherosclerosis that were assessed during the SMART screening protocol (ankle-brachial index, common carotid intima-media thickness, carotid stenosis, and aorta diameter). The relation between EV protein levels and extent of vascular disease was evaluated using ordinal multivariable regression models.

RESULTS

EV-derived CD14 was significantly associated with the number of affected vascular territories (OR 2.4, 95% CI 1.4-4.1) as represented by the sum score, independently of cardiovascular risk factors. Cystatin C and α2-antiplasmin EV levels did not show an independent association with vascular disease extent. When investigating parameters of the sum score separately, we did not observe a strong association between any of the EV-derived proteins and the markers of atherosclerosis.

CONCLUSIONS

EV-derived CD14 levels are strongly correlated to the extent of vascular disease, but not specifically to markers that reflect atherosclerosis burden, in patients with manifest cardiovascular disease.

10-years experience with the Athero-Express study

From cross-sectional studies we have learned that composition of atherosclerotic plaques differs, and that thrombosis on top of an inflammatory lipid rich plaque is a frequently observed pathological substrate of a cerebral or coronary event. Atherosclerosis develops over decades which hampers human studies on the natural history of the diseases. Therefore, the predictive value of atherosclerotic plaque composition for development of an adverse cardiovascular event is not clear. The elucidation of markers for atherosclerotic disease progression is essential to identify patients at high risk for vascular events, to refine treatment allocation and to serve as surrogate endpoints in pharmaceutical studies. The Athero-Express study is a large scale vascular biobank that collects vascular specimens including a clinical follow-up. This study design allows the prospective study of the local atherosclerotic plaque in relation to future local and systemic vascular outcome. The readout of the study can be assessed in terms of histology as well as RNA or protein level. This paper aims to give an overview of the results of the Athero-Express biobank since its initiation in 2002. We will also discuss the clinical implications and future directions in biobanking research.

Sex is associated with the presence of atherosclerotic plaque hemorrhage and modifies the relation between plaque hemorrhage and cardiovascular outcome

BACKGROUND AND PURPOSE

Plaque hemorrhage (PH) may lead to accelerated progression of atherosclerotic disease. The presence of local PH in the carotid plaque predicts future cardiovascular events in any vascular territory. We investigated the prevalence of local PH and the predictive value of PH for the occurrence of cardiovascular events in men and women separately.

METHODS

Atherosclerotic plaques from 1422 patients (969 men, 453 women) who underwent carotid endarterectomy were analyzed histologically for the presence of PH. Patients were monitored for 3 years for cardiovascular events (nonfatal stroke, nonfatal myocardial infarction, vascular death, and vascular intervention).

RESULTS

Plaques from men showed a significantly higher prevalence of PH compared with women (67% versus 54%; P<0.001). In 1353 patients with available follow-up data, with a median duration of 2.9 years, 270 events had occurred in men (29%) and 94 in women (22%). Stratified by presence of PH, the event rate was 32% in men with PH versus 23% in men without PH, and 23% in women with PH versus 21% in women without PH. A multivariable Cox proportional hazards model found a significant interaction between sex and PH. PH was significantly associated with events in men (adjusted hazard ratio, 1.9; 95% CI, 1.2-2.8) but not in women (adjusted hazard ratio, 1.0; 95% CI, 0.6-1.7).

CONCLUSIONS

Atherosclerotic carotid plaques obtained from men reveal a higher prevalence of PH compared with women. Local PH is strongly related to secondary manifestations of cardiovascular disease in men but not in women.

Soluble ST2 levels are not associated with secondary cardiovascular events and vulnerable plaque phenotype in patients with carotid artery stenosis

OBJECTIVE

Soluble ST2 (sST2), a novel biomarker predictive for heart disease, has recently been shown associated with the progression of atherosclerotic disease in a mouse model. The present study was designed to assess sST2 plasma levels in patients scheduled for carotid endarterectomy and relate it with the occurrence of adverse cardiovascular events during follow-up. In addition, sST2 levels were associated to patient clinical data and atherosclerotic plaque characteristics.

METHODS AND RESULTS

Plasma sST2 levels were measured in 391 patients who underwent carotid endarterectomy and were subsequently followed for 3 years. Primary composite endpoint was the occurrence of an adverse cardiovascular event. At baseline, no differences were observed in sST2 levels between asymptomatic (n = 75) and symptomatic (n = 316) patients (85 [49-122] versus 90 [58-137] pg/ml, p = 0.263). Soluble ST2 plasma levels did not differ between patients who experienced a secondary manifestation of cardiovascular disease and patients who remained free of symptoms (90 [60-129] versus 88 [46-140] pg/ml, p = 0.519). There was no association between sST2 levels and any of the following plaque characteristics: size of a lipid core, degree of calcification, number of macrophages or smooth muscle cells, amount of collagen and number of microvessels.

CONCLUSIONS

Soluble ST2 plasma levels have no predictive value for future cardiovascular events in patients with significant carotid artery stenosis. In addition, we did not observe an association between plasma sST2 levels and the histopathological features of a rupture prone plaque. This study does not provide supportive evidence that sST2 reflects a progressive state of advanced atherosclerotic disease.

Mast cells in human carotid atherosclerotic plaques are associated with intraplaque microvessel density and the occurrence of future cardiovascular events

AIMS

Human autopsy, animal, and cell culture studies together have merged in a concept suggesting participation of mast cells (MCs) in the generation of atherosclerotic plaques. More specifically, these studies have suggested MC-induced intraplaque neovascularization as one mechanism by which MCs may render the plaques vulnerable. The present study was designed to assess the association between MC numbers and neovascularization in human atherosclerotic plaques, and to relate the abundance of plaque MCs to the occurrence of adverse cardiovascular events during the follow-up.

METHODS AND RESULTS

Atherosclerotic plaques of 270 patients suffering from carotid artery stenosis were stained for the presence of MCs (MC tryptase). Furthermore, during a follow-up of 3 years, cardiovascular-related endpoints were assessed in 253 patients. On average a high number of MCs were observed per plaque cross-section [median 108 (55-233) cells per section]. Plaques with high MC numbers revealed an unstable lipid-rich inflammatory phenotype and were associated with symptomatic patients. In addition, MC numbers were positively associated with microvessel density (r = 0.416, P < 0.001). Patients with high intraplaque MC numbers showed significantly more cardiovascular events during the follow-up (58/142 vs. 31/111 events, P = 0.029). In a multivariate analysis with correction for the main risk factors of cardiovascular diseases, MCs remained independently associated with adverse cardiovascular events (P = 0.025).

CONCLUSION

Mast cells are highly prevalent in human carotid atherosclerotic lesions and associated with plaque microvessel density. Furthermore, intraplaque MC numbers associate with future cardiovascular events.

Microvesicle protein levels are associated with increased risk for future vascular events and mortality in patients with clinically manifest vascular disease

BACKGROUND AND OBJECTIVES

Microvesicles (MVs) are small membrane vesicles that are involved in atherotrombotic processes. In the present study, we evaluated the risk of MV protein levels on the occurrence of new vascular events in patients with clinically manifest vascular disease.

METHODS

In this cohort study 1060 patients were prospectively followed for the occurrence of a new vascular event or death (median follow up 6.4 years, interquartile range 5.2-7.3 years). MVs were isolated from plasma and MV protein levels of Cystatin C, Serpin G1, Serpin F2 and CD14 were measured. Multivariable Cox proportional hazards models were used to estimate the risk for new vascular events, vascular mortality and all-cause mortality. During follow up 136 vascular events occurred, 65 vascular mortality and 114 all-cause mortality.

RESULTS

An increase in 1 standard deviation (SD) of Cystatin C MV level was related to an increased risk for myocardial infarction (HR 1.49; 95%CI 1.20-1.86), vascular mortality (HR 1.48; 95%CI 1.17-1.86), vascular events (HR 1.27; 1.07-1.52) and all-cause mortality (HR 1.41; 95%CI 1.18-1.69). Serpin F2 MV levels were related to an increased risk for myocardial infarction (HR 1.22; 95%CI 1.00-1.51), vascular mortality (HR 1.25; 95%CI 1.00-1.56), and all-cause mortality (HR 1.22; 95% CI 1.03-1.45). CD14 MV levels were related to an increased risk for myocardial infarction (HR 1.55; 95%CI 1.27-1.91), vascular mortality (HR 1.37; 95%CI 1.10-1.70), vascular events (HR 1.32; 95%CI 1.12-1.55), all-cause mortality (HR 1.36; 95%CI 1.15-1.62) and occurrence of ischemic stroke (HR 1.32; 95%CI 1.00-1.74).

CONCLUSIONS

Cystatin C, Serpin F2 and CD14 MV levels are related to an elevated risk for future vascular events and mortality in patients with clinically manifest vascular disease.

Temporal changes of soluble ST2 after cardiovascular interventions

BACKGROUND

Soluble ST2 (sST2), a member of the IL-1 receptor family, has been proposed as a novel biomarker with predictive value for heart failure and mortality in patients suffering from cardiovascular diseases. The influence of clinical characteristics on variability of sST2 levels is relatively unexplored. Here, we studied the effect of cardiovascular interventions and clinical characteristics on plasma sST2 expression levels.

MATERIAL AND METHODS

In the current study, sST2 levels were assessed in the plasma of patients scheduled for coronary artery bypass grafting (CABG) (n = 76), percutaneous coronary intervention (PCI) (n = 68) or peripheral vascular surgery (n = 27).

RESULTS

Age was the only classical risk factor significantly correlating with sST2 levels. Soluble ST2 levels were significantly increased 1 h after CABG (48 [33-70] vs. 61 [42-89] pg/mL, P = 0·001) and increased even further after 24 h (1116 [578-13 666] pg/mL, P < 0·001). An average threefold increase in sST2 levels was also observed in patients 24 h after peripheral interventions (30 [21-41] vs. 98 [48-211] pg/mL, P < 0·001). Two months after PCI, we found that sST2 levels were significantly higher compared with baseline levels (41 [29-61] vs. 48 [31-80] pg/mL, P = 0·007, n = 52). In addition, we did not observe an association between sST2 and any inflammatory or cardiac-specific markers that were measured in this study.

CONCLUSIONS

Soluble ST2 increases significantly following cardiovascular interventions. The notion of a recent cardiovascular intervention is a strong determinant of sST2 levels and therefore needs to be taken into account when exploring sST2 as predictor of future cardiovascular events.

Distinct CD44 splice variants differentially affect collateral artery growth

OBJECTIVE

Lack of the adhesion molecule CD44 reduces collateral artery growth (arteriogenesis) in a murine hindlimb model. CD44 function is influenced by expression of 10 alternatively spliced exons (v1-v10), with unknown effects on arteriogenesis. As the variant exon CD44v3 binds heparan sulphate and facilitates preservation of growth factors, we hypothesized that the variably spliced exon region of CD44, especially exon CD44v3, is involved in arteriogenesis.

MATERIALS AND METHODS

The right femoral artery of C57BL/6J-mice was ligated and tissue was processed for histological and qPCR analysis of CD44-isoform expression. Microsphere perfusion measurements were performed in mice lacking the variably spliced exon region (CD44s knock-in mice), and in knock-in strains with specific isoform expression (CD44v3-10 and CD44v4-10), as well as in double knock-in mice, expressing CD44v3-10 and CD44s.

RESULTS

Expression of total CD44 and CD44v3 mRNA following femoral artery ligation was increased, accompanied by increased mRNA levels of the CD44-relevant splicing factors Tra2-beta1 and SRm160. CD44v3-expression was limited to the vessel wall of growing collateral arteries. Perfusion restoration was significantly reduced in mice lacking the variably spliced exon region (CD44s):20.1 ± 1.3%, compared to the background strain: 57.3 ± 2.2%. Mice expressing exon v3 (CD44v3-10) showed perfusion percentages of 25.9 ± 1.1%, compared to mice lacking this exon (CD44v4-10):19.1 ± 0.7%. Combined expression of CD44v3 and CD44s further improved perfusion restoration: 33.1 ± 2.6%.

CONCLUSION

Total CD44 and CD44v3 mRNA are upregulated during arteriogenesis. The absence of the variably spliced exon region impairs arteriogenesis. Presence of exon v3 of CD44 results in improved arteriogenesis. Expression of CD44s and CD44v3 provides a synergistic effect on arteriogenesis. As this combined expression still resulted in hampered arteriogenesis, a specific role of exon v2 in arteriogenesis appears likely.

CD26 inhibition enhances perfusion recovery in ApoE-/-mice

OBJECTIVE

The adaptive growth of blood vessels is important to prevent tissue loss following arterial occlusion. Extravasation of monocytes is essential for this process. The peptidase CD26 targets SDF-1 alpha, a chemokine regulating monocyte trafficking. We hypothesized that blocking SDF-1 alpha inactivation, using a commercially available CD26 inhibitor, accelerates perfusion recovery without detrimental side effects on plaque stability.

METHODS AND RESULTS

Atherosclerosis prone ApoE-/- mice underwent femoral artery ligation and received a CD26 inhibitor or placebo. CD26 inhibition increased short term (7 days) perfusion recovery after both single and daily doses compared to placebo, 36% ± 2 (p=0.017) and 39% ± 2 (p=0.008) vs. 29% ± 3 respectively. Long term (56 days) perfusion recovery increased after daily treatment compared to placebo 83% ± 3 vs. 60% ± 2, (p<0.001). CD26 inhibition did not result in increased atherosclerotic plaque instability or inflammatory cell infiltration. CD26 inhibition increased macrophage number around growing collaterals, SDF-1 alpha plasma levels and monocyte expression of the activation marker CD11b and the SDF-1 alpha receptor CXCR-4.

CONCLUSIONS

CD26 inhibition enhanced perfusion recovery following arterial occlusion via attenuated SDF-1 alpha inactivation and increased monocyte activation. There was no observable aggravation of atherosclerosis and CD26 inhibition could therefore offer a novel approach for therapeutic arteriogenesis in patients.

Lack of haptoglobin results in unbalanced VEGFα/angiopoietin-1 expression, intramural hemorrhage and impaired wound healing after myocardial infarction

Decreased haptoglobin (Hp) functionality due to allelic variations is associated with worsened outcome in patients after myocardial infarction (MI). However, mechanisms through which haptoglobin deficiency impairs cardiac repair remain to be elucidated. In the present study, we identified novel molecular alterations mediated by Hp involved in early and late cardiac repair responses after left coronary artery ligation in Hp(-/-) and wild-type (WT) mice. We observed a higher mortality rate in Hp(-/-) mice despite similar infarct size between groups. Deaths were commonly caused by cardiac rupture in Hp(-/-) animals. Histological analysis of 3 and 7days old non-ruptured infarcted hearts revealed more frequent and more severe intramural hemorrhage and increased leukocyte infiltration in Hp(-/-) mice. Analyses of non-ruptured hearts revealed increased oxidative stress, reduced PAI-1 activity and enhanced VEGFα transcription in Hp(-/-) mice. In line with these observations, we found increased microvascular permeability in Hp(-/-) hearts 3days after infarction. In vitro, haptoglobin prevented hemoglobin-induced oxidative stress and restored VEGF/Ang-1 balance in endothelial cell cultures. During long-term follow-up of the surviving animals, we observed altered matrix turnover, impaired scar formation and worsened cardiac function and geometry in Hp(-/-)mice. In conclusion, haptoglobin deficiency severely deteriorates tissue repair and cardiac performance after experimental MI. Haptoglobin plays a crucial role in both short- and long-term cardiac repair responses by reducing oxidative stress, maintaining microvascular integrity, myocardial architecture and proper scar formation.

Carotid atherosclerotic plaque matrix metalloproteinase-12-positive macrophage subpopulation predicts adverse outcome after endarterectomy

Background

Matrix metalloproteinase-12 (MMP-12) promotes atherosclerosis in animal models. MMP-12 is expressed in only a subset of foam-cell macrophages (FCMs) in human plaques. We investigated whether the prevalence of this MMP-12–expressing subpopulation is a prognostic indicator of adverse outcome in patients after carotid endarterectomy (CEA).

Methods and Results

Serial sections of culprit lesions from 236 patients who underwent CEA and had undergone 3 years of clinical follow-up were stained immunocytochemically for MMP-12 and for CD68, and the MMP-12/CD68 ratio was used to quantify the MMP-12–expressing subpopulation. A high MMP-12/CD68 ratio correlated with a high content of lipid and total macrophages and a low content of vascular smooth muscle cells, as well as with MMP-8 (R=0.211, P=0.001), MMP-9 (R=0.251, P<0.001), and cleaved caspase-3 (R=0.142, P=0.036) activity measured in a neighboring segment. Dual immunohistochemical examination confirmed the location of MMP-12 in a subpopulation of MMP-8– and MMP-9–positive FCMs, whereas all apoptotic FCMs were MMP-12 positive. Patients who yielded plaques within the highest quartile compared with the lowest quartile of MMP-12/CD68 ratio had a 2.4-fold (hazard ratio, 2.4; 95% CI, 1.1- to 5.1-fold; adjusted P=0.027) increased risk of major adverse cardiovascular event and a 3.4-fold (3.4; 1.2- to 9.6-fold, P=0.024) increased risk for stroke.

Conclusions

The prevalence of an MMP-12–positive subset of FCMs is a prognostic marker for adverse clinical outcome after CEA.

Atherosclerotic plaque biomarkers: beyond the horizon of the vulnerable plaque

Cardiovascular disease (CVD) is the number one cause of death globally, and the majority of CVD is caused by atherosclerosis. Atherosclerosis is a systemic inflammatory disease that leads to myocardial infarction, stroke and lower limb ischemia. Pathological studies have given insight to development of atherosclerosis and the importance of local plaque vulnerability, leading to thrombus formation and cardiovascular events. Due to the burden of cardiovascular disease, identification of patients at risk for cardiovascular events and treatment stratification is needed. The predictive power of classical risk factors is limited, especially in patients with manifest atherosclerosis. Imaging modalities have focused on the characteristics of the vulnerable plaque. However, it has become evident that not all so-called vulnerable plaques lead to rupture and subsequent thrombosis. The latter obviously limits the positive predictive value for imaging assessment of plaques and patients at risk. Serum biomarkers have also been studied extensively, but have very limited application in a clinical setting for risk stratification. In line with the important relation between vulnerable plaques and cardiovascular events, plaque biomarker studies have been initiated. These longitudinal studies are based on the concept, that a vulnerable plaque contains predictive information for future cardiovascular events, also in other territories of the vascular tree. Results look promising and plaque markers can be used to develop imaging modalities to identify patients at risk, or to monitor treatment effect. Plaque biomarker studies do not challenge the definition of the vulnerable plaque, but use its concept in favor of prediction improvement for vascular patients.

Clinical prediction rule to estimate the absolute 3-year risk of major cardiovascular events after carotid endarterectomy

BACKGROUND AND PURPOSE

Prognosis after carotid endarterectomy is mainly determined by the occurrence of major adverse cardiovascular events (MACEs). Optimal medical treatment to reduce risk is the mainstay of MACE prevention. The level of risk of MACE may determine the initiation and aggressiveness of medical treatment, yet a prediction rule to assess that absolute MACE risk after carotid endarterectomy is currently unavailable.

METHODS

The prediction model was developed in a consecutive cohort of 1138 patients who underwent carotid endarterectomy between 2002 and 2009. Primary end point was MACE and encompassed myocardial infarction, stroke, and cardiovascular death. Fourteen potential clinical predictors were entered into a Cox proportional hazard model. After backward stepwise regression, internal validation was conducted with bootstrapping techniques to correct for overfitting. To provide an easily applicable clinical tool, a score chart was constructed, dividing patients into 4 risk groups. Model performance was assessed in terms of discrimination, calibration, and risk stratification.

RESULTS

During a mean follow-up of 2.28 (± 0.95) years, 148 events occurred, corresponding to a cumulative incidence of 13%. Clinical predictors in the final model were age, history of coronary or peripheral artery disease, smoking, systolic blood pressure, use of antihypertensive drugs, clinical presentation, presence of contralateral carotid stenosis, and serum creatinine levels. Discrimination of the final model, in terms of a C statistic, was 0.69 (0.64-0.73) and calibration showed a good overall fit (Gronnesby and Borgan, P=0.39). The observed incidence of MACE in the 4 risk groups was 6%, 9%, 19%, and 35%, respectively, indicating good overall risk stratification.

CONCLUSIONS

The clinical prediction model for MACE in the first 3 years after carotid endarterectomy may be used to identify high-risk patients to help optimize medical treatment and risk factor management as part of secondary prevention to increase life expectancy free from MACE. Despite our success in stratifying risk among these patients, even the lowest stratum remains at high risk and all of these patients should receive maximal secondary preventive measures.

TGF-β1 content in atherosclerotic plaques, TGF-β1 serum concentrations and incident coronary events

BACKGROUND

We tested the hypothesis that high TGF-β1 content in atherosclerotic plaques and high TGF-β1 serum levels are associated with lower risk of coronary events in two independent prospective studies.

MATERIALS AND METHODS

In the prospective Athero-Express biobank study, total TGF-β1 plaque levels were measured in 632 atherosclerotic lesions from patients who underwent carotid endarterectomy. In a population-based case-cohort study within the Monitoring of trends and determinants in cardiovascular disease (MONICA)/Cooperative Health Research in the Region of Augsburg (KORA) Augsburg studies, baseline total TGF-β1 serum levels were measured in 333 individuals with and 1728 without incident coronary events.

RESULTS

Patients with TGF-β1 content in their plaques above the study median did not have a lower risk of coronary events than patients with lower TGF-β1 levels [adjusted HR (95% CI) 1·46 (0·83-2·53); P = 0·16; mean follow-up 2·6 ± 0·7 years] in the Athero-Express biobank study. Cox proportional hazard models adjusting for age, sex, body mass index, metabolic factors, lifestyle factors and survey did not reveal a significant association between TGF-β1 serum levels and incident coronary events [HR (95% CI) for increasing TGF-β1 tertiles 1·0, 1·22 (0·88-1·68), 1·13 (0·82-1·57); P = 0·47; mean follow-up: 10·8 ± 4·6 years] in the MONICA/KORA Augsburg studies.

CONCLUSION

Our results indicate that high TGF-β1 content in human atherosclerotic plaques and high serum levels of TGF-β1 are not associated with reduced risk of coronary events.

Treatment with OPN-305, a humanized anti-Toll-Like receptor-2 antibody, reduces myocardial ischemia/reperfusion injury in pigs

BACKGROUND

Toll-like receptor (TLR)-2 is an important mediator of innate immunity and ischemia/reperfusion-induced cardiac injury. We have previously shown that TLR2 inhibition reduces infarct size and improves cardiac function in mice. However, the therapeutic efficacy of a clinical grade humanized anti-TLR2 antibody, OPN-305, in a large-animal model remained to be addressed.

METHODS AND RESULTS

Pigs (n=38) underwent 75 minutes ischemia followed by 24 hours of reperfusion. Saline or OPN-305 (12.5, 6.25, or 1.56 mg/kg) was infused intravenously 15 minutes before reperfusion. Cardiac function and geometry were assessed by echocardiography. Infarct size was calculated as the percentage of the area at risk and by serum Troponin-I levels. Flow cytometry analysis revealed specific binding of OPN-305 to porcine TLR2. In vivo, OPN-305 exhibited a secondary half-life of 8±2 days. Intravenous administration of OPN-305 before reperfusion significantly reduced infarct size (45% reduction, P=0.041) in a dose-dependent manner. In addition, pigs treated with OPN-305 exhibited a significant preservation of systolic performance in a dose-dependent fashion, whereas saline treatment completely diminished the contractile performance of the ischemic/reperfused myocardium.

CONCLUSIONS

OPN-305 significantly reduces infarct size and preserves cardiac function in pigs after ischemia/reperfusion injury. Hence, OPN-305 is a promising adjunctive therapeutic for patients with acute myocardial infarction.

RANTES/CCL5 and risk for coronary events: results from the MONICA/KORA Augsburg case-cohort, Athero-Express and CARDIoGRAM studies

BACKGROUND

The chemokine RANTES (regulated on activation, normal T-cell expressed and secreted)/CCL5 is involved in the pathogenesis of cardiovascular disease in mice, whereas less is known in humans. We hypothesised that its relevance for atherosclerosis should be reflected by associations between CCL5 gene variants, RANTES serum concentrations and protein levels in atherosclerotic plaques and risk for coronary events.

METHODS AND FINDINGS

We conducted a case-cohort study within the population-based MONICA/KORA Augsburg studies. Baseline RANTES serum levels were measured in 363 individuals with incident coronary events and 1,908 non-cases (mean follow-up: 10.2±4.8 years). Cox proportional hazard models adjusting for age, sex, body mass index, metabolic factors and lifestyle factors revealed no significant association between RANTES and incident coronary events (HR [95% CI] for increasing RANTES tertiles 1.0, 1.03 [0.75-1.42] and 1.11 [0.81-1.54]). None of six CCL5 single nucleotide polymorphisms and no common haplotype showed significant associations with coronary events. Also in the CARDIoGRAM study (>22,000 cases, >60,000 controls), none of these CCL5 SNPs was significantly associated with coronary artery disease. In the prospective Athero-Express biobank study, RANTES plaque levels were measured in 606 atherosclerotic lesions from patients who underwent carotid endarterectomy. RANTES content in atherosclerotic plaques was positively associated with macrophage infiltration and inversely associated with plaque calcification. However, there was no significant association between RANTES content in plaques and risk for coronary events (mean follow-up 2.8±0.8 years).

CONCLUSIONS

High RANTES plaque levels were associated with an unstable plaque phenotype. However, the absence of associations between (i) RANTES serum levels, (ii) CCL5 genotypes and (iii) RANTES content in carotid plaques and either coronary artery disease or incident coronary events in our cohorts suggests that RANTES may not be a novel coronary risk biomarker. However, the potential relevance of RANTES levels in platelet-poor plasma needs to be investigated in further studies.

Atherosclerotic plaque vulnerability as an explanation for the increased risk of stroke in elderly undergoing carotid artery stenting

BACKGROUND AND PURPOSE

Recent randomized trials showed an increased periprocedural risk for stroke with increasing age in patients undergoing carotid artery stenting. Manipulation of atherosclerotic plaques during carotid artery stenting can result in plaque rupture with subsequent superimposed thrombus formation, embolization, and cerebrovascular events. We hypothesized that atherosclerotic plaques become more unstable with increasing age and thereby might provide insight into the age-related increased risk of cerebrovascular events during carotid artery stenting.

METHODS

Carotid atherosclerotic plaques were harvested from 1385 consecutive patients undergoing carotid endarterectomy between 2002 and 2010. Carotid plaques were quantitatively analyzed for macrophages, smooth muscle cells, and microvessels; and semiquantitatively analyzed for collagen, calcifications lipid cores, and intraplaque hemorrhages. Patients were divided in 4 groups by age: <60, 60 to 69, 70 to 79, and ≥80 years. Measures of association between age as a continuous variable and histological characteristics were also calculated.

RESULTS

Increasing age was associated with a decrease in the amount of smooth muscle cells in the carotid plaque. More plaques with large atheroma and heavy plaque calcifications were observed among elderly patients. After correction for baseline differences, risk factors, and medication use, age was independently associated with a more vulnerable carotid plaque composition.

CONCLUSIONS

Plaque stability decreases gradually with age. Older patients with carotid stenosis have relatively unstable plaques with low smooth muscle cell content, a high amount of large lipid cores, and more calcified plaques as compared with younger patients. The underlying vulnerable plaque composition in the elderly might be an important contributing factor to the increased risk of stroke for older patients undergoing carotid artery stenting.