Platelet expression of stromal-cell-derived factor-1 (SDF-1): An indicator for ACS?

Atypical Roles of the Chemokine Receptor ACKR3/CXCR7 in Platelet Pathophysiology

The manifold actions of the pro-inflammatory and regenerative chemokine CXCL12/SDF-1α are executed through the canonical GProteinCoupledReceptor CXCR4, and the non-canonical ACKR3/CXCR7. Platelets express CXCR4, ACKR3/CXCR7, and are a vital source of CXCL12/SDF-1α themselves. In recent years, a regulatory impact of the CXCL12-CXCR4-CXCR7 axis on platelet biogenesis, i.e., megakaryopoiesis, thrombotic and thrombo-inflammatory actions have been revealed through experimental and clinical studies. Platelet surface expression of ACKR3/CXCR7 is significantly enhanced following myocardial infarction (MI) in acute coronary syndrome (ACS) patients, and is also associated with improved functional recovery and prognosis. The therapeutic implications of ACKR3/CXCR7 in myocardial regeneration and improved recovery following an ischemic episode, are well documented. Cardiomyocytes, cardiac-fibroblasts, endothelial lining of the blood vessels perfusing the heart, besides infiltrating platelets and monocytes, all express ACKR3/CXCR7. This review recapitulates ligand induced differential trafficking of platelet CXCR4-ACKR3/CXCR7 affecting their surface availability, and in regulating thrombo-inflammatory platelet functions and survival through CXCR4 or ACKR3/CXCR7. It emphasizes the pro-thrombotic influence of CXCL12/SDF-1α exerted through CXCR4, as opposed to the anti-thrombotic impact of ACKR3/CXCR7. Offering an innovative translational perspective, this review also discusses the advantages and challenges of utilizing ACKR3/CXCR7 as a potential anti-thrombotic strategy in platelet-associated cardiovascular disorders, particularly in coronary artery disease (CAD) patients post-MI.

Old and New Biomarkers Associated with Endothelial Dysfunction in Chronic Hyperglycemia

Chronic hyperglycemia and vascular damage are strictly related. Biomarkers of vascular damage have been intensively studied in the recent years in the quest of reliable cardiovascular risk assessment tools able to facilitate risk stratification and early detection of vascular impairment. The present study is a narrative review with the aim of revising the available evidence on current and novel markers of hyperglycemia-induced vascular damage. After a discussion of classic tools used to investigate endothelial dysfunction, we provide an in-depth description of novel circulating biomarkers (chemokines, extracellular vesicles, and epigenetic and metabolomic biomarkers). Appropriate use of a single as well as a cluster of the discussed biomarkers might enable in a near future (a) the prompt identification of targeted and customized treatment strategies and (b) the follow-up of cardiovascular treatment efficacy over time in clinical research and/or in clinical practice.

Platelet ACKR3/CXCR7 Favors Anti-Platelet Lipids over an Atherothrombotic Lipidome and Regulates Thrombo-inflammation

Platelet ACKR3/CXCR7 surface expression is enhanced and influences prognosis in coronary artery disease-(CAD) patients, who exhibit a distinct atherothrombotic platelet lipidome. Current investigation validates the potential of ACKR3/CXCR7 in regulating thrombo-inflammatory response, through its impact on the platelet lipidome. CAD patients-(n=230) with enhanced platelet-ACKR3/CXCR7 expression exhibited reduced aggregation. Pharmacological CXCR7-agonist-(VUF11207) significantly reduced pro-thrombotic platelet response in blood from ACS patients-(n=11) ex vivo. CXCR7-agonist administration reduced thrombotic functions and thrombo-inflammatory platelet-leukocyte interactions post myocardial infarction-(MI) and arterial injury in vivo. ACKR3/CXCR7-ligation did not affect surface availability of GPIbα, GPV, GPVI, GPIX, αv-integrin, β3-integrin, coagulation profile-(APTT, PT), bleeding time, plasma-dependent thrombin generation-(thrombinoscopy) or clot formation-(thromboelastography), but counteracted activation-induced phosphatidylserine exposure and procoagulant platelet-assisted thrombin generation. Targeted-(micro-UHPLC-ESI-QTrap-MS/MS) and untargeted-(UHPLC-ESI-QTOF-MS/MS) lipidomics analysis revealed that ACKR3/CXCR7-ligation favored generation of anti-thrombotic lipids-(dihomo-γ-linolenic acid-DGLA, 12-hydroxyeicosatrienoic acid-12-HETrE) over cyclooxygenase-COX-1-(thromboxane-TxA2), or 12-lipoxygenase-LOX-(12-HETE) metabolized pro-thrombotic, and phospholipase derived atherogenic-(lysophosphatidylcholine-LPC) lipids, in healthy subjects and CAD patients, contrary to anti-platelet therapy. Through 12-HETrE, ACKR3/CXCR7-ligation coordinated with Gαs-coupled prostacyclin receptor-(IP) to trigger cAMP-PKA mediated platelet inhibition. ACKR3/CXCR7-ligation reduced generation of lipid agonists-(arachidonic acid-AA,TxA2), lipid signaling intermediates-(lyophosphatidylinositol-LPI, diacylglycerol-DG), which affected calcium mobilization, intracellular signaling, consequently platelet interaction with physiological matrices and thrombo-inflammatory secretion-(IL1β,IFN-γ,TGF-β,IL-8), emphasizing its functional dichotomy from pro-thrombotic CXCR4. Moreover, CXCR7-agonist regulated heparin-induced thrombocytopenia-(HIT)-sera/IgG-induced platelet and neutrophil activation, heparin induced platelet aggregation-(HIPA), generation of COX-1-(TxA2), 12-LOX-(12-HETE) derived thrombo-inflammatory lipids, platelet-neutrophil aggregate formation, and thrombo-inflammatory secretion (sCD40L, IL-1β, IFN-γ, TNF-α, sP-selectin, IL-8, tissue factor-TF) ex vivo. Therefore, ACKR3/CXCR7 may offer a novel therapeutic strategy in acute/chronic thrombo-inflammation exaggerated cardiovascular pathologies, and CAD.

Role and implications of the CXCL12/CXCR4/CXCR7 axis in atherosclerosis: still a debate

Atherosclerosis is one of the leading causes of mortality and morbidity worldwide. Chemokines and their receptors are implicated in the pathogenesis of atherosclerosis. CXCL12 is a member of the chemokine family exerting a myriad role in atherosclerosis through its classical CXCR4 and atypical ACKR3 (CXCR7) receptors. The modulatory and regulatory functional spectrum of CXCL12/CXCR4/ACKR3 axis in atherosclerosis spans from proatherogenic, prothrombotic and proinflammatory to atheroprotective, plaque stabilizer and dyslipidemia rectifier. This diverse continuum is executed in a wide range of biological units including endothelial cells (ECs), progenitor cells, macrophages, monocytes, platelets, lymphocytes, neutrophils and vascular smooth muscle cells (VSMCs) through complex heterogeneous and homogenous coupling of CXCR4 and ACKR3 receptors, employing different downstream signalling pathways, which often cross-talk among themselves and with other signalling interactomes. Hence, a better understanding of this structural and functional heterogeneity and complex phenomenon involving CXCL12/CXCR4/ACKR3 axis in atherosclerosis would not only help in formulation of novel therapeutics, but also in elucidation of the CXCL12 ligand and its receptors, as possible diagnostic and prognostic biomarkers.Key messagesThe role of CXCL12 per se is proatherogenic in atherosclerosis development and progression.The CXCL12 receptors, CXCR4 and ACKR3 perform both proatherogenic and athero-protective functions in various cell typesDue to functional heterogeneity and cross talk of CXCR4 and ACKR3 at receptor level and downstream pathways, regional boosting with specific temporal and spatial modulators of CXCL12, CXCR4 and ACKR3 need to be explored.

Influence of aflibercept on platelet activation profile

Aflibercept appears to accumulate in systemic circulation following intravitreal injections in therapy of neovascular age-related macular degeneration. This gives raise to the question of whether aflibercept affects platelets and their function such as activation and aggregation, which are substantial in the pathogenesis of an arterial thromboembolic event (ATE). In order to determine the effect of aflibercept in platelet activation, platelets from healthy volunteers were treated with aflibercept and its solvents at equal concentrations (0.04 μg/mL - 4 μg/mL - 40 μg/mL - 400 μg/mL - 4 mg/mL) for 10 and 30 min before addition of agonists. IgG1 antibody was used as a control. The surface expression of GPIIb/IIIa, P-selectin, and platelet-bound stromal-cell-derived factor-1, which are potential blood biomarkers for ATEs, was determined on resting and activated platelets by the multispectral imaging flow cytometry, combining the features of flow cytometry with fluorescence microscopy. Platelet aggregation was assessed with light transmission aggregometry. To determine whether aflibercept directly interacts with platelets, aflibercept was labeled with the fluorescence FITC. Co-treatment of platelets with thrombin or PAR-4-AP and aflibercept resulted in increased activation of the fibrinogen receptor GPIIb/IIIa in comparison to controls (P < 0.05). Interestingly, the expression of platelet-derived P-selectin and SDF-1 was not affected by aflibercept, except thrombin-activated CD62P with 0.04 μg/mL aflibercept (aflibercept vs. its solvent: MSI = 1.54, IC = 1.201-1.879 vs. MSI = 1.37, IC = 1.136-1.604 [P = 0.031]) and SDF-1 with 4 mg/mL aflibercept (aflibercept vs. its solvent: MSI = 1.971, IC = 1.206-2.737 vs. MSI = 1.200, IC = 0.738-1.662 [P = 0.041]). Although the levels of platelet-bound aflibercept-FITC were significantly increased in all activated platelets, no effect was observed in platelet aggregation. Albeit no impact of aflibercept was found on platelet aggregation under the studied experimental conditions, the increased activation of the fibrinogen receptor GPIIb/IIIa and the presence of a direct interaction between aflibercept and platelets may partially explain the risk of ATE in patients under aflibercept treatment due to FcγRIIa mediated αIIbβ3 outside-in integrin signaling and transport of aflibercept into platelets. Therefore, the Fc domain seems to be involved in interactions between aflibercept and platelets. Further research is needed to explain the role of Fc containing aflibercept in the pathogenesis of drug-associated vascular events involving platelets, coagulation cascade, extracellular matrix proteins and other cells.

The influence of low-grade inflammation on platelets in patients with stable coronary artery disease

Inflammation is likely to be involved in all stages of atherosclerosis. Numerous inflammatory biomarkers are currently being studied, and even subtle increases in inflammatory biomarkers have been associated with increased risk of cardiovascular events in patients with coronary artery disease (CAD). Low-grade inflammation may influence both platelet production and platelet activation potentially leading to enhanced platelet aggregation. Thrombopoietin is considered the primary regulator of platelet production, but it likely acts in conjunction with numerous cytokines, of which many have altered levels in CAD. Previous studies have shown that high-sensitive C-reactive protein (CRP) independently predicts increased platelet aggregation in stable CAD patients. Increased levels of CRP, fibrinogen, interleukin-6, stromal cell-derived factor-1, CXC motif ligand 16, macrophage migration inhibitory factor, RANTES, calprotectin, and copeptin have been associated with increased risk of cardiovascular events in CAD patients. Additionally, some of these inflammatory markers have been associated with enhanced platelet activation and aggregation. However, CRP and other inflammatory markers provide only limited additional predictive value to classical risk factors such as smoking, blood pressure, and cholesterol levels. Existing data do not clarify whether inflammation simply accompanies CAD and increased production and aggregation of platelets, or whether a causal relationship exists. In this review, we provide a comprehensive overview of inflammatory markers in stable CAD with particular emphasis on platelet production, activation, and aggregation in CAD patients.

SDF-1α/CXCR4 Signaling in Lipid Rafts Induces Platelet Aggregation via PI3 Kinase-Dependent Akt Phosphorylation

Stromal cell-derived factor-1α (SDF-1α)-induced platelet aggregation is mediated through its G protein-coupled receptor CXCR4 and phosphatidylinositol 3 kinase (PI3K). Here, we demonstrate that SDF-1α induces phosphorylation of Akt at Thr308 and Ser473 in human platelets. SDF-1α-induced platelet aggregation and Akt phosphorylation are inhibited by pretreatment with the CXCR4 antagonist AMD3100 or the PI3K inhibitor LY294002. SDF-1α also induces the phosphorylation of PDK1 at Ser241 (an upstream activator of Akt), GSK3β at Ser9 (a downstream substrate of Akt), and myosin light chain at Ser19 (a downstream element of the Akt signaling pathway). SDF-1α-induced platelet aggregation is inhibited by pretreatment with the Akt inhibitor MK-2206 in a dose-dependent manner. Furthermore, SDF-1α-induced platelet aggregation and Akt phosphorylation are inhibited by pretreatment with the raft-disrupting agent methyl-β-cyclodextrin. Sucrose density gradient analysis shows that 35% of CXCR4, 93% of the heterotrimeric G proteins Gαi-1, 91% of Gαi-2, 50% of Gβ and 4.0% of PI3Kβ, and 4.5% of Akt2 are localized in the detergent-resistant membrane raft fraction. These findings suggest that SDF-1α/CXCR4 signaling in lipid rafts induces platelet aggregation via PI3K-dependent Akt phosphorylation.

Platelet surface expression of SDF-1 is associated with clinical outcomes in the patients with cardiovascular disease

Platelet surface expression levels of stromal cell derived factor 1 (SDF-1) are elevated in acute coronary syndrome and associated with LVEF% improvement after myocardial infarction (MI). Platelet SDF-1 might facilitate thrombus formation and endomyocardial expression of SDF-1 is enhanced in inflammatory cardiomyopathy and positively correlates with myocardial fibrosis. The influence of platelet SDF-1 on outcome in the patients with symptomatic coronary artery disease (CAD) is to the best of our knowledge unknown. Blood samples of 608 consecutive CAD patients were collected during the percutaneous coronary intervention and analyzed for surface expression of SDF-1 by flow cytometry. The primary combined endpoint was defined as the composite of either MI, or ischemic stroke, or all-cause death. Secondary endpoints were defined as the aforementioned single events. The patients with baseline platelet SDF-1 levels above the third quartile showed a significantly worse cumulative event-free survival when compared to the patients with lower baseline SDF-1 levels (first to third quartile) (log rank 0.009 for primary combined endpoint and log rank 0.016 for secondary endpoint all-cause death). Multivariate Cox regression analysis showed that SDF-1 levels above the third quartile were independently associated with the primary combined endpoint and the secondary endpoint all-cause death. We provide first clinical evidence that high platelet expression levels of SDF-1 influence clinical outcomes in CAD patients in a negative way.

Chemokines and their receptors in Atherosclerosis

Atherosclerosis, a chronic inflammatory disease of the medium- and large-sized arteries, is the main underlying cause of cardiovascular diseases (CVDs) most often leading to a myocardial infarction or stroke. However, atherosclerosis can also develop without this clinical manifestation. The pathophysiology of atherosclerosis is very complex and consists of many cells and molecules interacting with each other. Over the last years, chemokines (small 8-12 kDa cytokines with chemotactic properties) have been identified as key players in atherogenesis. However, this remains a very active and dynamic field of research. Here, we will give an overview of the current knowledge about the involvement of chemokines in all phases of atherosclerotic lesion development. Furthermore, we will focus on two chemokines that recently have been associated with atherogenesis, CXCL12, and macrophage migration inhibitory factor (MIF). Both chemokines play a crucial role in leukocyte recruitment and arrest, a critical step in atherosclerosis development. MIF has shown to be a more pro-inflammatory and thus pro-atherogenic chemokine, instead CXCL12 seems to have a more protective function. However, results about this protective role are still quite debatable. Future research will further elucidate the precise role of these chemokines in atherosclerosis and determine the potential of chemokine-based therapies.

Different Effects of Ranibizumab and Bevacizumab on Platelet Activation Profile

PURPOSE

The aim of the study was to evaluate the potential influence of ranibizumab and bevacizumab on platelet activation and aggregation, which are critical processes in the pathogenesis of arterial thromboembolic events (ATEs).

METHODS

For the assessment of platelet function, flow cytometry and aggregometry were employed. Platelets were isolated from healthy volunteers and exposed to ranibizumab (1 mg/ml and 150 ng/ml) and bevacizumab (2.5 mg/ml and 3 μg/ml) or their solvents for 10 and 30 min prior to the addition of TRAP (25 μM), PAR-4-AP (25 μM) or thrombin (0.02 U/ml). The surface expression of activated GP IIb/IIIa, P-selectin (CD62P) and platelet-bound stromal cell-derived factor-1 (SDF-1) was measured on resting (nonactivated) and activated platelets by flow cytometry. The platelet aggregation capacity was examined using light transmission aggregometry.

RESULTS

The expression of surface activation markers did not differ significantly between nonstimulated and TRAP-, PAR-4-AP- or thrombin-activated platelets after incubating with ranibizumab. However, GP IIb/IIIa, CD62P and SDF-1 were significantly downregulated in PAR-4-AP- and thrombin-activated platelets after exposure to bevacizumab 2.5 mg/ml. In addition, ranibizumab- and bevacizumab-FITC were significantly increased in all activated platelets. No significant differences were observed in the aggregation of activated platelets after incubation with ranibizumab or bevacizumab.

CONCLUSION

All ranibizumab concentrations as well as the bevacizumab concentration of 3 μg/ml had no influence on platelet activation and aggregation. Therefore, this in vitro study did not show any relationship between the exposition of activated platelets to ranibizumab or bevacizumab and the development of ATEs. However, the highest level of bevacizumab interfered with platelet activation, leading to downregulation of platelet activation markers. This observation might explain why the systemic treatment with high-dose bevacizumab could be associated with an increased risk of bleeding. Regarding the use of lower intravitreal dosages, further research should focus on the complex interactions between platelets and other cells, such as endothelial cells, which might stronger relate to a potentially increased risk of ATEs and depend on systemic vascular endothelial growth factor levels. Facing the different activation profiles, the diverse effects of the drugs on the cellular level have to be critically scrutinized for their clinical relevance.

MIF and CXCL12 in Cardiovascular Diseases: Functional Differences and Similarities

Coronary artery disease (CAD) as part of the cardiovascular diseases is a pathology caused by atherosclerosis, a chronic inflammatory disease of the vessel wall characterized by a massive invasion of lipids and inflammatory cells into the inner vessel layer (intima) leading to the formation of atherosclerotic lesions; their constant growth may cause complications such as flow-limiting stenosis and plaque rupture, the latter triggering vessel occlusion through thrombus formation. Pathophysiology of CAD is complex and over the last years many players have entered the picture. One of the latter being chemokines (small 8-12 kDa cytokines) and their receptors, known to orchestrate cell chemotaxis and arrest. Here, we will focus on the chemokine CXCL12, also known as stromal cell-derived factor 1 (SDF-1) and the chemokine-like function chemokine, macrophage migration-inhibitory factor (MIF). Both are ubiquitously expressed and highly conserved proteins and play an important role in cell homeostasis, recruitment, and arrest through binding to their corresponding chemokine receptors CXCR4 (CXCL12 and MIF), ACKR3 (CXCL12), and CXCR2 (MIF). In addition, MIF also binds to the receptor CD44 and the co-receptor CD74. CXCL12 has mostly been studied for its crucial role in the homing of (hematopoietic) progenitor cells in the bone marrow and their mobilization into the periphery. In contrast to CXCL12, MIF is secreted in response to diverse inflammatory stimuli, and has been associated with a clear pro-inflammatory and pro-atherogenic role in multiple studies of patients and animal models. Ongoing research on CXCL12 points at a protective function of this chemokine in atherosclerotic lesion development. This review will focus on the role of CXCL12 and MIF and their differences and similarities in CAD of high risk patients.

Platelet surface expression of stromal cell-derived factor-1 receptors CXCR4 and CXCR7 is associated with clinical outcomes in patients with coronary artery disease

BACKGROUND

Surface expression of stromal cell-derived factor-1 (SDF-1, CXCL12) on platelets is enhanced during ischemic events and plays an important role in peripheral homing of stem cells and myocardial repair mechanisms. SDF-1 effects are mediated through CXCR4 and CXCR7. Both CXCR4 and CXCR7 are surface expressed on human platelets and to a higher degree in patients with coronary artery disease (CAD) compared with healthy controls. In this study, we investigated the prognostic role of platelet CXCR4- and CXCR7 surface expression in patients with symptomatic CAD.

METHODS AND RESULTS

In a cohort study, platelet surface expression of CXCR4 and CXCR7 was measured by using flow cytometry in 284 patients with symptomatic CAD at the time of percutaneous coronary intervention (PCI). The primary combined end point was defined as all-cause death and/or myocardial infarction (MI) during 12-month follow-up. Secondary end points were defined as the single events of all-cause death and MI. We found significant differences of CXCR4 values in patients who developed a combined end point compared with event-free patients (mean MFIAUTHOR: Please define MFI at first use. 3.17 vs. 3.44, 95% confidence interval [CI] 0.09-0.45) and in patients who subsequently died (mean MFI 3.10 vs. 3.42, 95% CI 0.09-0.56). In multivariate Cox regression analysis, lower platelet CXCR4 levels were independently and significantly associated with all-cause mortality (hazard ratio 0.24, 95% CI 0.07-0.87) and the primary combined end point of all-cause death and/or MI (hazard ratio 0.30, 95% CI 0.13-0.72).

CONCLUSION

These findings highlight a potential prognostic value of platelet expression CXCR4 on clinical outcomes in patients with CAD.

Plasma stromal cell-derived factor 1α/CXCL12 level predicts long-term adverse cardiovascular outcomes in patients with coronary artery disease

OBJECTIVE

Stromal derived factor-1α/CXCL12 is a chemoattractant responsible for homing of progenitor cells to ischemic tissues. We aimed to investigate the association of plasma CXCL12 with long-term cardiovascular outcomes in patients with coronary artery disease (CAD).

METHODS

785 patients aged: 63 ± 12 undergoing coronary angiography were independently enrolled into discovery (N = 186) and replication (N = 599) cohorts. Baseline levels of plasma CXCL12 were measured using Quantikine CXCL12 ELISA assay (R&D systems). Patients were followed for cardiovascular death and/or myocardial infarction (MI) for a mean of 2.6 yrs. Cox proportional hazard was used to determine independent predictors of cardiovascular death/MI.

RESULTS

The incidence of cardiovascular death/MI was 13% (N = 99). High CXCL12 level based on best discriminatory threshold derived from the ROC analysis predicted risk of cardiovascular death/MI (HR = 4.81, p = 1 × 10(-6)) independent of traditional risk factors in the pooled cohort. Addition of CXCL12 to a baseline model was associated with a significant improvement in c-statistic (AUC: 0.67-0.73, p = 0.03). Addition of CXCL12 was associated with correct risk reclassification of 40% of events and 10.5% of non-events. Similarly for the outcome of cardiovascular death, the addition of the CXCL12 to the baseline model was associated with correct reclassification of 20.7% of events and 9% of non-events. These results were replicated in two independent cohorts.

CONCLUSION

Plasma CXCL12 level is a strong independent predictor of adverse cardiovascular outcomes in patients with CAD and improves risk reclassification.

Impact of platelet phenotype on myocardial infarction

In acute myocardial infarction patients the injured vascular wall triggers thrombus formation in the damage site. Fibrin fibers and blood cellular elements are the major components of thrombus formed in acute occlusion of coronary arteries. It has been established that the initial thrombus is primarily composed of activated platelets rapidly stabilized by fibrin fibers. This review highlights the role of platelet membrane phenotype in pathophysiology of myocardial infarction. Here, we regard platelet phenotype as quantitative and qualitative parameters of the plasma membrane outer surface, which are crucial for platelet participation in blood coagulation, development of local inflammation and tissue repair.

Platelet expression of stromal cell-derived factor-1 is associated with the degree of valvular aortic stenosis

Background and Purpose

Platelet surface expression of stromal-cell-derived factor-1 (SDF-1) is increased during platelet activation and constitutes an important factor in hematopoetic progenitor cell trafficking at sites of vascular injury and ischemia. Enhanced platelet SDF-1 expression has been reported previously in patients suffering from acute coronary syndrome (ACS). We hypothesized that expression of platelet associated SDF-1 may also be influenced by calcified valvular aortic stenosis (AS).

Methods

We consecutively evaluated 941 patients, who were admitted to the emergency department with dyspnea and chest pain. Platelet surface expression of SDF-1 was determined by flow cytometry, AS was assessed using echocardiography and hemodynamic assessment by heart catheterization. A 1∶1 propensity score matching was implemented to match 218 cases with 109 pairs adjusting for age, sex, cardiovascular risk factors, and medication including ACE inhibitors, angiotensin receptor blockers, beta blockers, statins, aspirin, clopidogrel, GPIIb/IIIa antagonists, and vitamin K antagonists.

Results

Patients with valvular AS showed enhanced platelet SDF-1 expression compared to patients without AS (non-valvular disease, NV) independent of ACS and stable coronary artery disease (SAP) [mean fluorescence intensity (MFI) for ACS (AS vs. NV): 75±40.4 vs. 39.5±23.3; P = 0.002; for SAP (AS vs. NV): 54.9±44.6 vs. 24.3±11.2; P = 0.008]. Moreover, the degree of AS significantly correlated with SDF-1 platelet surface expression (r = 0.462; P = 0.002).

Conclusions

Valvular AS is associated with enhanced platelet-SDF-1 expression; moreover the degree of valvular AS correlates with SDF-1 platelet surface expression. These findings may have clinical implications in the future.

Platelet-derived CXCL12 (SDF-1α): basic mechanisms and clinical implications

Platelets are a major source of CXCL12 (stromal cell-derived factor -1α, SDF-1α) and store CXCL12 as part of their α-granule secretome. Platelet activation enhances surface expression and release of CXCL12. Platelets and megakaryocytes express CXCR4, the major receptor for CXCL12, and interaction of CXCL12 with CXCR4 regulates megakaryopoiesis and the function of circulating platelets. Platelet-derived CXCL12 also modulates paracrine mechanisms such as chemotaxis, adhesion, proliferation and differentiation of nucleated cells, including progenitor cells. Platelet-derived CXCL12 enhances peripheral recruitment of progenitor cells to the sites of vascular and tissue injury both in vitro and in vivo and thereby promotes repair mechanisms. CXCL12 expression on platelets is elevated in patients with acute myocardial infarction, correlates with the number of circulating progenitor cells, is associated with preservation of myocardial function and is an independent predictor of clinical outcome. Administration of recombinant CXCL12 reduces infarct size following transient ischemia in mice. The present review summarizes the role of platelet-derived CXCL12 in cardiovascular biology and its diagnostic and therapeutic implications.

Copeptin as a prognostic factor for major adverse cardiovascular events in patients with coronary artery disease

BACKGROUND

C-terminal portion of provasopressin (copeptin) has recently been discussed as a novel biomarker for the early rule-out of acute myocardial infarction (AMI). The aim is to investigate the prognostic value of copeptin with regard to mortality and morbidity in patients with symptomatic coronary artery disease (CAD).

METHODS

We consecutively recruited a cath lab cohort of 2,700 patients (74.1% male; AMI, n=1316; stable angina pectoris, n=1384) presenting to the emergency department of a large primary care hospital. All patients received coronary angiography. Copeptin and other laboratory markers were sampled at the time of presentation or in the cath lab. Clinical outcomes were assessed by hospital chart analysis and telephone interviews. 2621 patients (97.1%) have been successfully followed-up at three months. The primary endpoint was a combined endpoint of rehospitalization for cardiovascular events, stroke, and all-cause death.

RESULTS

Using receiver operating characteristic curves, we calculated areas under the curve of 0.703 (95%confidence interval(CI):0.681-0.725) for the composite endpoint after three months (myocardial reinfarction, stroke, all-cause death;n=183), and 0.770 (95%CI:0.736-0.803) for all-cause death (n=76) for copeptin. A cutoff value of 21.6 pmol/L for the composite endpoint yielded a sensitivity of 56.3% and a specificity of 78.6%. The predictive performance of copeptin was independent of other clinical variables or cardiovascular risk factors, and superior to that of troponin I or other cardiac biomarkers (all:P<0.0001).

CONCLUSIONS

Copeptin may help in the prediction of major adverse cardiovascular events in patients with symptomatic CAD. Further studies should substantiate the findings and support the suggested cutoff value of the present study.