Platelet mitochondrial membrane depolarization reflects disease severity in patients with preeclampsia

BACKGROUND

Thrombocytopenia is a feared complication of preeclampsia (PE) that can additionally complicate the disease course and that carries a poor prognosis. The disease mechanisms of PE on a platelet level are poorly understood and only few platelet-based markers have been investigated. In sepsis, platelet mitochondrial membrane depolarization, a sensitive and early indicator of mitochondrial dysfunction and platelet cell death, correlates with disease severity and outcome as shown in previous studies. The aim of this study was to investigate platelet mitochondrial membrane potential (Mmp-Index) by flow-cytometry in patients with preeclampsia compared to controls and to assess its value in correlation with disease severity of PE and during follow-up after delivery.

METHODS

In this prospective translational case-control study, platelet Mmp-Index was measured in PE (n = 16) by flow cytometry in living platelets in simultaneous comparison to healthy pregnant (n = 32) and non-pregnant controls (n = 16) and was individually reassessed after delivery to investigate recovery of platelet mitochondrial function. Subgroup analysis of patients with severe and non-severe PE was performed. Six patients with isolated gestational hypertension were also included for comparative analysis.

RESULTS

Platelet Mmp-Index in patients with symptomatic preeclampsia (Mmp-Index non-severe PE 0.72 ([0.591; 0.861]; p = 0.002) was significantly reduced compared to healthy pregnant controls (Mmp-Index 0.97 [0.795; 1.117]) and even more pronounced in patients with severe PE (n = 6) (Mmp-Index severe PE 0.542 [0.361; 0.623]; p = 0.03). In the severe PE group, complementary measurements of platelet Annexin V- and CD62 (P-Selectin) surface expression showed apoptosis of platelet populations in the majority of patients. Platelet Mmp normalized after delivery within few days. Patients with isolated gestational hypertension showed normal Mmp-Index values.

CONCLUSIONS

This study shows for the first time that platelet Mmp-Index is a quantifiable, easy-to-measure intracellular marker of platelet mitochondrial function in vital cells that reflects disease severity of preeclampsia. For future investigations, platelet Mmp may serve as a prognostic marker that may aid clinical risk stratification and adds novel information on potential mechanisms for thrombocytopenia in preeclampsia.

Extracellular Matrix-Specific Platelet Activation Leads to a Differential Translational Response and Protein De Novo Synthesis in Human Platelets

Platelets are exposed to extracellular matrix (ECM) proteins like collagen and laminin and to fibrinogen during acute vascular events. However, beyond hemostasis, platelets have the important capacity to migrate on ECM surfaces, but the translational response of platelets to different extracellular matrix stimuli is still not fully characterized. Using 2D-gel electrophoresis, confocal microscopy, polysome analysis and protein sequencing by mass spectrometry, we demonstrate that platelets show a differential expression profile of newly synthesized proteins on laminin, collagen or fibrinogen. In this context, we observed a characteristic, ECM-dependent translocation phenotype of translation initiation factor eIF4E to the ribosomal site. eIF4E accumulated in polysomes with increased binding of mRNA and co-localization with vinculin, leading to de novo synthesis of important cytoskeletal regulator proteins. As the first study, we included a proteome analysis of laminin-adherent platelets and interestingly identified upregulation of essentially important proteins that mediate cytoskeletal regulation and mobility in platelets, such as filamin A, talin, vinculin, gelsolin, coronin or kindlin-3. In summary, we demonstrate that platelet activation with extracellular matrix proteins results in a distinct stimulus-specific translational response of platelets that will help to improve our understanding of the regulation of platelet mobility and migration.

Radiation Dose Reduction Using a Novel Fluoroscopy System in Patients Undergoing Diagnostic Invasive Coronary Angiography

BACKGROUND

Invasive coronary angiography (ICA) still causes a significant amount of radiation exposure for patients and operators. In February 2017, the Azurion system was introduced, a new-generation fluoroscopy image acquisition and processing system. Radiation exposure in patients undergoing ICA was assessed comparing the novel Azurion 7 F12 angiography system to its predecessor Allura Xper in a randomized manner.

METHODS

Radiation exposure was prospectively analyzed in 238 patients undergoing diagnostic ICA. Patients were randomly assigned to the novel Azurion system (119 patients) or its predecessor Allura Xper system (119 patients). In each patient, 8 predefined standard projections (5 left coronary artery, 3 right coronary artery) were performed. Image quality was quantified by grading of the images on the basis of a 5-point grading system.

RESULTS

Radiation dose area product was significantly lower in the Azurion group 109 (interquartile range [IQR 75-176] cGy cm) compared with the Allura Xper group 208 [IQR 134-301] cGy cm (P<0.001). Body mass index (26.6 [IQR 23.9-29.7] kg/m vs. 26.2 [IQR 24.2-29.4] kg/m; P=0.607), body surface area (1.96 [IQR 1.81-2.11] m vs. 1.90 [IQR 1.77-20.4] m; P=0.092), and procedure duration (1.5 [IQR 1.2-2.3] min vs. 1.6 [IQR 1.2-2.5] min; P=0.419) were similar in both groups. Images from the Azurion system were at least of equal quality compared with Allura Xper (image quality grade 4.82±0.45 vs. 4.75±0.52, P=0.43).

CONCLUSION

Use of the novel Azurion 7 F12 angiography system resulted in a significant reduction of dose area product in patients undergoing diagnostic ICA by 56%.

Inactivation of the tyrosine phosphatase SHP-2 drives vascular dysfunction in Sepsis

Background

Sepsis, the most severe form of infection, involves endothelial dysfunction which contributes to organ failure. To improve therapeutic prospects, elucidation of molecular mechanisms underlying endothelial vascular failure is of essence.

Methods

Polymicrobial contamination induced sepsis mouse model and primary endothelial cells incubated with sepsis serum were used to study SHP-2 in sepsis-induced endothelial inflammation. SHP-2 activity was assessed by dephosphorylation of pNPP, ROS production was measured by DCF oxidation and protein interactions were assessed by proximity ligation assay. Vascular inflammation was studied in the mouse cremaster model and in an in vitro flow assay.

Findings

We identified ROS-dependent inactivation of the tyrosine phosphatase SHP-2 to be decisive for endothelial activation in sepsis. Using in vivo and in vitro sepsis models, we observed a significant reduction of endothelial SHP-2 activity, accompanied by enhanced adhesion molecule expression. The impaired SHP-2 activity was restored by ROS inhibitors and an IL-1 receptor antagonist. SHP-2 activity inversely correlated with the adhesive phenotype of endothelial cells exposed to IL-1β as well as sepsis serum via p38 MAPK and NF-κB. In vivo, SHP-2 inhibition accelerated IL-1β-induced leukocyte adhesion, extravasation and vascular permeability. Mechanistically, SHP-2 directly interacts with the IL-1R1 adaptor protein MyD88 via its tyrosine 257, resulting in reduced binding of p85/PI3-K to MyD88.

Interpretation

Our data show that SHP-2 inactivation by ROS in sepsis releases a protective break, resulting in endothelial activation.

Fund

German Research Foundation, LMU Mentoring excellence and FöFoLe Programme, Verein zur Förderung von Wissenschaft und Forschung, German Ministry of Education and Research.

The proteasome regulates collagen-induced platelet aggregation via nuclear-factor-kappa-B (NFĸB) activation

INTRODUCTION

Platelets possess critical hemostatic functions in the system of thrombosis and hemostasis, which can be affected by a multitude of external factors. Previous research has shown that platelets have the capacity to synthesize proteins de novo and more recently a multicatalytic protein complex, the proteasome, has been discovered in platelets. Due to its vital function for cellular integrity, the proteasome has become a therapeutic target for anti-proliferative drug therapies in cancer. Clinically thrombocytopenia is a frequent side-effect, but the aggregatory function of platelets also appears to be affected. Little is known however about underlying regulatory mechanisms and functional aspects of proteasome inhibition on platelets. Our study aims to investigate the role of the proteasome in regulating collagen-induced platelet aggregation and its interaction with NFkB in this context.

MATERIAL AND METHODS

Using fluorescence activity assays, platelet aggregometry and immunoblotting, we investigate regulatory interactions of the proteasome and Nuclear-factor-kappa-B (NFkB) in collagen-induced platelet aggregation.

RESULTS

We show that collagen induces proteasome activation in platelets and collagen-induced platelet aggregation can be reduced with proteasome inhibition by the specific inhibitor epoxomicin. This effect does not depend on Rho-kinase/ROCK activation or thromboxane release, but rather depends on NFkB activation. Inhibition of the proteasome prevented cleavage of NFκB-inhibitor protein IκBα and decreased NFκB activity after collagen stimulation. Inhibition of the NFκB-pathway in return reduced collagen-induced platelet proteasome activity and cleavage of proteasome substrates.

CONCLUSIONS

This work offers novel explanations how the proteasome influences collagen-dependent platelet aggregation by involving non-genomic functions of NFkB.

Platelet mitochondrial membrane depolarization reflects disease severity in patients with sepsis and correlates with clinical outcome

Introduction

Sepsis is still a leading cause of morbidity and mortality, even in modern times, and thrombocytopenia has been closely associated with unfavorable disease outcome. Decreases in mitochondrial membrane potential (depolarization) were found in different tissues during sepsis. Previous work suggests that mitochondrial dysfunction of platelets correlates with clinical disease activity in sepsis. However, platelet mitochondrial membrane potential (Mmp) has not been investigated in a clinical follow-up design and not with regard to disease outcome.

Methods

In this study, platelet mitochondrial membrane depolarization was assessed by means of a fluorescent Mmp-Index with flow cytometry in 26 patients with sepsis compared with control patients. Platelet Mmp-Index on admission was correlated with the clinical disease scores Acute Physiology and Chronic Health Evaluation Score II (APACHE II), Sequential Organ Failure Score (SOFA), and Simplified Acute Physiology Score II (SAPS II). Finally, platelet Mmp-Index on admission and follow-up were compared in the group of sepsis survivors and nonsurvivors. Expression of the prosurvival protein Bcl-xL in platelets was quantified by immunoblotting.

Results

Platelet mitochondrial membrane depolarization correlated significantly with the simultaneously assessed clinical disease severity by APACHE II (r = -0.867; P < 0.0001), SOFA (r = -0.857; P <0.0001), and SAPS II score (r = -0.839; P < 0.0001). Patients with severe sepsis showed a significant reduction in platelet Mmp-Index compared with sepsis without organ failure (0.18 (0.12 to 0.25) versus 0.79 (0.49 to 0.85), P < 0.0006) or with the control group (0.18 (0.12 to 0.25) versus 0.89 (0.68 to 1.00), P < 0.0001). Platelet Mmp-Index remained persistently low in sepsis nonsurvivors (0.269 (0.230 to 0.305)), whereas we observed recovery of platelet Mmp-Index in the survivor group (0.9 (0.713 to 1.017)). Furthermore, the level of prosurvival protein Bcl-xL decreased in platelets during severe sepsis.

Conclusion

In this study, we demonstrated that mitochondrial membrane depolarization in platelets correlates with clinical disease severity in patients with sepsis during the disease course and may be a valuable adjunct parameter to aid in the assessment of disease severity, risk stratification, and clinical outcome.

Protein degradation systems in platelets

Protein synthesis and degradation are essential processes that allow cells to survive and adapt to their surrounding milieu. In nucleated cells, the degradation and/or cleavage of proteins is required to eliminate aberrant proteins. Cells also degrade proteins as a mechanism for cell signalling and complex cellular functions. Although the last decade has convincingly shown that platelets synthesise proteins, the roles of protein degradation in these anucleate cytoplasts are less clear. Here we review what is known about protein degradation in platelets placing particular emphasis on the proteasome and the cysteine protease calpain.

Methicillin-resistant Staphylococcus aureus-induced thrombo-inflammatory response is reduced with timely antibiotic administration

Methicillin-resistant Staphylococcus aureus (MRSA) induces a pro-thrombotic and pro-inflammatory milieu. Although timely antibiotic administration in MRSAsepsis may improve outcomes by arresting bacterial growth, the effects of antibiotics on mitigating injurious thrombo-inflammatory cellular responses remains unexplored. Using a newly developed human whole blood model and an in vivo mouse model of MRSAinfection, we examined how antibiotics inhibit MRSAinduced thrombo-inflammatory pathways. Human whole blood was inoculated with MRSA. Thrombin generation and inflammatory cytokine synthesis was measured in the presence or absence of linezolid and vancomycin. C57BL/6 mice were injected with MRSA and the effect of vancomycin administration was examined. MRSAaccelerated thrombin generation in a time- and concentration-dependent manner andinduced the release of cytokines, including interleukin (IL)-6, IL-8, and monocyte chemotactic protein (MCP)-1. The increase in thrombin generation and inflammatory responses was mediated through the synthesis of tissue factor and cytokines, respectively, and the release of microparticles. The early administration of antibiotics restored normal thrombin generation patterns and significantly reduced the synthesis of cytokines. In contrast, when antibiotic administration was delayed, thrombin generation and cytokine synthesis were not significantly reduced. In mice infected with MRSA, early antibiotic administration reduced thrombin anti-thrombin complexes and cytokine synthesis, whereas delayed antibiotic administration did not. These data provide novel mechanistic evidence of the importance of prompt antibiotic administration in infectious syndromes.

Hydrogen sulfide-releasing aspirin derivative ACS14 exerts strong antithrombotic effects in vitro and in vivo

OBJECTIVE

Hydrogen sulfide (H(2)S)-releasing NSAIDs exert potent anti-inflammatory effects beyond classical cyclooxygenase inhibition. Here, we compared the platelet inhibitory effects of the H(2)S-releasing aspirin derivative ACS14 with its mother compound aspirin to analyze additional effects on platelets.

METHODS AND RESULTS

In platelets of mice fed with ACS14 for 6 days (50 mg/kg per day), not only arachidonic acid-induced platelet aggregation but also ADP-dependent aggregation was decreased, an effect that was not observed with an equimolar dose of aspirin (23 mg/kg per day). ACS14 led to a significantly longer arterial occlusion time after light-dye-induced endothelial injury as well as decreased thrombus formation after ferric chloride-induced injury in the carotid artery. Bleeding time was not prolonged compared with animals treated with equimolar doses of aspirin. In vitro, in human whole blood, ACS14 (25-500 µmol/L) inhibited arachidonic acid-induced platelet aggregation, but compared with aspirin additionally reduced thrombin receptor-activating peptide-, ADP-, and collagen-dependent aggregation. In washed human platelets, ACS14 (500 µmol/L) attenuated αIIbβ3 integrin activation and fibrinogen binding and increased intracellular cAMP levels and cAMP-dependent vasodilator-stimulated phosphoprotein (VASP) phosphorylation.

CONCLUSIONS

The H(2)S-releasing aspirin derivative ACS14 exerts strong antiaggregatory effects by impairing the activation of the fibrinogen receptor by mechanisms involving increased intracellular cyclic nucleotides. These additional antithrombotic properties result in a more efficient inhibition of thrombus formation in vivo as achieved with aspirin alone.

SGK1 sensitivity of platelet migration

Recent observations pointed to the ability of platelets to migrate and thus to invade the inflamed vascular wall. Platelet migration could be stimulated by stromal cell-derived factor-1 (SDF-1), an effect dependent on phosphatidylinositide-3-kinase (PI3K) and paralleled by activation and phosphorylation of Wiskott-Aldrich syndrome protein (WASP). Migration is inhibited by vinculin, which is similarly regulated by phosphorylation. PI3K-sensitive kinases include the serum- and glucocorticoid-inducible kinase 1 (SGK1). The present study explored whether SGK1 modifies WASP and vinculin phosphorylation in murine platelets and participates in the regulation of platelet migration. Platelets were isolated from gene-targeted mice lacking SGK1 (sgk1(-/-)) and from their wild type littermates (sgk1(+/+)). Platelet migration stimulated with SDF-1 was significantly less pronounced in sgk1(-/-)platelets than in sgk1(+/+) platelets. Moreover, SDF-1 significantly induced WASP phosphorylation, an effect again reduced in platelets lacking SGK1. Phosphorylation of vinculin was significantly enhanced in sgk1(-/-)platelets and was significantly reduced following treatment of platelets with Ca(2+) chelator BAPTA. Immunohistochemical analysis of in vivo experiments in intestinal vessels after vascular inflammation revealed that transmigration of platelets into inflamed vessel walls was significantly less pronounced in sgk1(-/-)than in sgk1(+/+) mice. In conclusion, SGK1 is a powerful regulator of platelet migration.

Novel anti-bacterial activities of β-defensin 1 in human platelets: suppression of pathogen growth and signaling of neutrophil extracellular trap formation

Human β-defensins (hBD) are antimicrobial peptides that curb microbial activity. Although hBD's are primarily expressed by epithelial cells, we show that human platelets express hBD-1 that has both predicted and novel antibacterial activities. We observed that activated platelets surround Staphylococcus aureus (S. aureus), forcing the pathogens into clusters that have a reduced growth rate compared to S. aureus alone. Given the microbicidal activity of β-defensins, we determined whether hBD family members were present in platelets and found mRNA and protein for hBD-1. We also established that hBD-1 protein resided in extragranular cytoplasmic compartments of platelets. Consistent with this localization pattern, agonists that elicit granular secretion by platelets did not readily induce hBD-1 release. Nevertheless, platelets released hBD-1 when they were stimulated by α-toxin, a S. aureus product that permeabilizes target cells. Platelet-derived hBD-1 significantly impaired the growth of clinical strains of S. aureus. hBD-1 also induced robust neutrophil extracellular trap (NET) formation by target polymorphonuclear leukocytes (PMNs), which is a novel antimicrobial function of β-defensins that was not previously identified. Taken together, these data demonstrate that hBD-1 is a previously-unrecognized component of platelets that displays classic antimicrobial activity and, in addition, signals PMNs to extrude DNA lattices that capture and kill bacteria.

Platelets are small cells in the bloodstream whose primary function is to stop bleeding. In addition to their clotting functions, we show that human platelets stall bacterial growth. This inhibitory property of platelets is due to β-defensin 1, a small antimicrobial protein that kills bacteria. β-defensin 1 also induces white blood cells to discharge spider-like webs that trap and kill bacteria. Together, these findings indicate that human platelets use β-defensin 1 to fight off bacterial infection.

Ion channels in the regulation of platelet migration

Platelets have been shown to migrate and thus to invade the vascular wall. Platelet migration is stimulated by SDF-1. In other cell types, migration is dependent on Ca(2+) entry via Ca(2+) channels. Ca(2+) influx is sensitive to cell membrane potential which is maintained by K(+) channel activity and/or Cl(-) channel activity. The present study explored the role of ion channels in the regulation of SDF-1 induced migration. Platelets were isolated from human volunteers as well as from gene targeted mice lacking the Ca(2+) activated K(+) channel SK4 (sk4(-/-)) and their wild type littermates (sk4(+/+)). According to confocal microscopy human platelets expressed the Ca(2+) channel Orai1 and the Ca(2+)-activated K(+) channel K(Ca)3.1 (SK4). SDF-1 (100 ng/ml) stimulated migration in human platelets, an effect blunted by Orai1 inhibitors 2-aminoethoxydiphenyl borate 2-APB (10 μM) and SKF-96365 (10 μM), by unspecific K(+) channel inhibitor TEA (30 mM), by SK4 specific K(+) channel blocker clotrimazole (10 μM), but not by Cl(-) channel inhibitor 5-nitro-2-(3-phenylpropylamino) benzoic acid NPPB (100 μM). Significant stimulation of migration by SDF-1 was further observed in sk4(+/+) platelets but was virtually absent in sk4(-/-) platelets. In conclusion, platelet migration requires activity of the Ca(2+) channel Orai1 and of the Ca(2+) activated K(+) channel SK4, but not of NPPB-sensitive Cl(-) channels.

The septic milieu triggers expression of spliced tissue factor mRNA in human platelets

BACKGROUND

Activated platelets have previously-unrecognized mechanisms of post-transcriptional gene expression that may influence hemostasis and inflammation. A novel pathway involves splicing of pre-mRNAs in resting platelets to mature, translatable mRNAs in response to cellular activation.

OBJECTIVES

We asked if bacterial products and host agonists present in the septic milieu induce tissue factor pre-mRNA splicing in platelets from healthy subjects. In parallel, we asked if spliced tissue factor (TF) mRNA is present in platelets from septic patients in a proof-of-principle analysis.

PATIENTS/METHODS

TF pre-mRNA and mRNA expression patterns were characterized in platelets from septic patients and in platelets isolated from healthy subjects activated with bacteria, toxins and inflammatory agonists. Procoagulant activity was also measured.

RESULTS AND CONCLUSIONS

Live bacteria, staphylococcal α-toxin and lipopolysaccharide (LPS) induced TF pre-mRNA splicing in platelets isolated from healthy subjects. Toxin-stimulated platelets accelerated plasma clotting, a response that was blocked by a previously-characterized splicing inhibitor and by an anti-tissue factor antibody. Platelets from septic patients expressed spliced TF mRNA, whereas it was absent from unselected and age-matched control subjects. Tissue factor-dependent procoagulant activity was elevated in platelets from a subset of septic patients. Thus, bacterial and host factors induce splicing of TF pre-mRNA, expression of TF mRNA and tissue factor-dependent clotting activity in human platelets. TF mRNA is present in platelets from some septic patients, indicating that it may be a marker of altered platelet phenotype and function in sepsis and that splicing pathways are induced in this syndrome.

High shear flow induces migration of adherent human platelets

Shear forces are generated in all parts of the vascular system and contribute directly and indirectly to vascular disease progression. Endothelial cells are able to adapt to flow conditions, and are known to polarize and migrate in response to shear forces. Platelets exposed to shear stress are activated and release bioactive molecules from their alpha granules. So far, platelets have been considered to be static cells that do not leave the site of tight adhesion. However, we have recently been able to demonstrate the capacity of platelets to migrate in response to stromal derived factor-1 (SDF-1). In this project, we have demonstrated that platelets accumulate in areas with a high concentration of SDF-1 under flow conditions and respond to high shear stress by cellular polarization, cytoskeletal reorganisation, and flow-directed migration. In this context, we have shown increased Wiskott-Aldrich Syndrome protein (WASP) phosphorylation and intracellular redistribution of focal adhesion kinase (FAK) under high-shear stress conditions. The effect of flow-induced platelet migration has not previously been recognized and offers a new role for platelets as mobile cells. Their migratory potential may enable platelets to cover intimal lesions and contribute to vascular repair.

PI3 kinase-dependent stimulation of platelet migration by stromal cell-derived factor 1 (SDF-1)

Platelets have been regarded as static cells that do not move once they adhere to a matrix. The present study explored, whether platelets are able to migrate. In contrast to the current opinion, we found that platelets were mobile, able to migrate over a surface, and transmigrate through a transwell membrane and endothelium toward a source of stromal cell-derived factor 1 (SDF-1). Platelet migration was stimulated by SDF-1, which led to the downstream activation and phosphorylation of Wiskott-Aldrich syndrome protein. SDF-1 signaling and subsequent platelet migration could be inhibited by CXCR4-receptor blocker AMD3100, pertussis toxin, inhibition of phosphoinositol 3-kinase (PI3 kinase) with LY294002 or wortmannin, and disruption of actin polymerization with cytochalasin B. The potential of platelets to migrate in an SDF-1-mediated fashion may redefine the role of platelets in the pathophysiology of vascular inflammation, subsequent atherosclerotic degeneration, and vascular regeneration.

Persistent troponin elevation in a patient with cardiac amyloidosis

A 79-year-old patient repeatedly presented with chest discomfort and dyspnea on exertion. With echocardiography a prominent left ventricular and septal hypertrophy was detected with reduced left ventricular function. Despite successful revascularization and excellent results after stenting, the patient showed persistently elevated troponin levels. To investigate the abnormal findings of persistent troponin elevation, septal hypertrophy, and heart failure we performed endomyocardial biopsies which showed widespread myocardial amyloidosis. Amyloid subtyping revealed transthyretin amyloidosis. This is the first case showing persistent troponin elevation in a patient with tranthyretin amyloidosis. Very few other cases have been published on the topic of cardiac amyloidosis and troponin elevation so far. Our case serves as an illustrating example in the differential diagnosis of nonischemic causes of persistent troponin elevation. It is important to consider cardiac amyloidosis in patients with troponin elevation and heart failure since the clinical management differs significantly from other causes of heart failure.

Statins do not adversely affect post-interventional residual platelet aggregation and outcomes in patients undergoing coronary stenting treated by dual antiplatelet therapy

AIMS

There are growing data suggesting a clinical relevance of residual platelet aggregation (RPA) in patients undergoing PCI. Drug-drug interaction of statins and clopidogrel has been controversially discussed in ex vivo studies and clinical trials. The aim of the present study was to investigate the effects of peri-procedural statin medication on the metabolization of aspirin and clopidogrel with regard to platelet aggregation and clinical outcome in patients undergoing coronary intervention.

METHODS AND RESULTS

Patients with coronary stenting for symptomatic coronary artery disease are routinely evaluated by platelet function analysis in a monocentre registry, and for the present study, a consecutive cohort of 1155 patients were analysed. About 87.7% of the patients were treated with statins at the time of platelet function analysis. Residual platelet activity assessed by adenosine diphosphate (20 micromol/L)-induced platelet aggregation was not significantly influenced by statin treatment. Nor the significant effects of CYP3A4-metabolization pathway on post-treatment aggregation were recorded, although there was even a trend to lower RPA values in patients treated with CYP3A4-metabolized statins. Further, in an inter-individual analysis comparing patients treated with CYP3A4- and non-CYP3A4-metabolized statins, no time-dependent difference of clopidogreĺs anti-aggregatory effects was observed. Clinical follow-up of major adverse events (myocardial infarction, ischaemic stroke, death) in 991 patients within 3 months revealed no significant adverse effects of statin treatment on clinical outcome. Instead, statin treatment was independently associated with lower incidence of composite events (HR 0.44, 95% confidence interval 0.23-0.83, P = 0.01).

CONCLUSION

Peri-procedural co-administration of statins does not increase the post-interventional RPA in cardiovascular patients treated with dual antiplatelet therapy and does not worsen the clinical prognosis of these patients.

Platelet-Derived Stromal Cell–Derived Factor-1 Regulates Adhesion and Promotes Differentiation of Human CD34 + Cells to Endothelial Progenitor Cells

Background— Peripheral homing of progenitor cells in areas of diseased organs is critical for tissue regeneration. The chemokine stromal cell–derived factor-1 (SDF-1) regulates homing of CD34 + stem cells. We evaluated the role of platelet-derived SDF-1 in adhesion and differentiation of human CD34 + cells into endothelial progenitor cells.

Methods and Results— Adherent platelets express substantial amounts of SDF-1 and recruit CD34 + cells in vitro and in vivo. A monoclonal antibody to SDF-1 or to its counterreceptor, CXCR4, inhibits stem cell adhesion on adherent platelets under high arterial shear in vitro and after carotid ligation in mice, as determined by intravital fluorescence microscopy. Platelets that adhere to human arterial endothelial cells enhance the adhesion of CD34 + cells on endothelium under flow conditions, a process that is inhibited by anti-SDF-1. During intestinal ischemia/reperfusion in mice, anti-SDF-1 and anti-CXCR4, but not isotype control antibodies, abolish the recruitment of CD34 + cells in microcirculation. Moreover, platelet-derived SDF-1 binding to CXCR4 receptor promotes platelet-induced differentiation of CD34 + cells into endothelial progenitor cells, as verified by colony-forming assays in vitro.

Conclusions— These findings imply that platelet-derived SDF-1 regulates adhesion of stem cells in vitro and in vivo and promotes differentiation of CD34 + cells to endothelial progenitor cells. Because tissue regeneration depends on recruitment of progenitor cells to peripheral vasculature and their subsequent differentiation, platelet-derived SDF-1 may contribute to vascular and myocardial regeneration.