Sites Of Endothelial Injury Research Articles

P2X1 expressed on polymorphonuclear neutrophils and platelets is required for thrombosis in mice

AbstractAdenosine triphosphate (ATP) and its metabolite, adenosine, are key regulators of polymorphonuclear neutrophil (PMN) functions. PMNs have recently been implicated in the initiation of thrombosis. We investigated the role of ATP and adenosine in PMN activation and recruitment at the site of endothelial injury. Following binding to the injured vessel wall, PMNs are activated and release elastase. The recruitment of PMNs and the subsequent fibrin generation and thrombus formation are strongly affected in mice deficient in the P2X1-ATP receptor and in wild-type (WT) mice treated with CGS 21680, an agonist of the A2A adenosine receptor or NF449, a P2X1 antagonist. Infusion of WT PMNs into P2X1-deficient mice increases fibrin generation but not thrombus formation. Restoration of thrombosis requires infusion of both platelets and PMNs from WT mice. In vitro, ATP activates PMNs, whereas CGS 21680 prevents their binding to activated endothelial cells. These data indicate that adenosine triphosphate (ATP) contributes to polymorphonuclear neutrophil (PMN) activation leading to their adhesion at the site of laser-induced endothelial injury, a necessary step leading to the generation of fibrin, and subsequent platelet-dependent thrombus formation. Altogether, our study identifies previously unknown mechanisms by which ATP and adenosine are key molecules involved in thrombosis by regulating the activation state of PMNs.

Glycogen Synthase Kinase-3β and Cathepsin B in Diabetic Endothelial Progenitor Cell Dysfunction: An Old Player Finds a New Partner

Microvascular and macrovascular complications associated with type 2 diabetes are leading causes of morbidity and mortality. In fact, cardiovascular (CV) complications account for a major portion of health care costs in patients with diabetes. Although lifestyle changes and pharmacotherapy aimed at CV disease risk factor modification are the mainstay of medical treatment, revascularization (surgical and endovascular) is often necessary to restore tissue perfusion and function. Indeed, nearly 25% of coronary revascularization procedures performed in the U.S. occur in individuals with diabetes (1). Furthermore, diffuse atherosclerosis, impaired ability to form vascular collaterals, and restenosis contribute to higher rates of repeat revascularization in these patients (1). Consequently, cell-based therapy with bone marrow cells and endothelial progenitor cells (EPCs) aimed at inducing angiogenesis and reendothelialization is a promising strategy that is under active investigation in both preclinical and clinical studies (2,3). EPCs constitute a very small subset of circulating blood cells. They are progenitors of endothelial cells and have the ability to proliferate and differentiate to form perfused blood vessels in vivo and tube-like structures in vitro (4). EPC-induced neovascularization in response to tissue hypoxia and injury is a highly coordinated, temporally regulated, and complex set of events that involves mobilization, migration, and homing of EPCs to the target tissue (5,6). Endothelial injury and hypoxia activate the transcription factor hypoxia-induced factor (HIF) to initiate the expression and release of growth factors and chemokines. These include stromal cell–derived factor 1 (SDF-1), vascular endothelial growth factor (VEGF), c-Kit ligand (or SCF), angiopoietin, and interleukin-8 (IL-8), among others (5,6). Platelet aggregation leads to high levels of platelet-derived SDF-1 at the site of endothelial injury (7). EPCs are retained in the bone marrow in distinct niches by their interaction with stromal cells. …

Distinct CD11b+-monocyte subsets accelerate endothelial cell recovery after acute and chronic endothelial cell damage

BackgroundEndothelial cell recovery requires replenishment of primary cells from the endothelial lineage. However, recent evidence suggests that cells of the innate immune system enhance endothelial regeneration. Methods and resultsFocusing on mature CD11b+-monocytes, we analyzed the fate and the effect of transfused CD11b+-monocytes after endothelial injury in vivo. CD11b-diphtheria-toxin-receptor-mice – a mouse model in which administration of diphtheria toxin selectively eliminates endogenous monocytes and macrophages – were treated with WT-derived CD11b+-monocytes from age-matched mice. CD11b+-monocytes improved endothelium-dependent vasoreactivity after 7days while transfusion of WT-derived CD11b−-cells had no beneficial effect on endothelial function. In ApoE−/−-CD11b-DTR-mice with a hypercholesterolemia-induced chronic endothelial injury transfusion of WT-derived CD11b+-monocytes stimulated by interferon-γ (IFNγ) decreased endothelial function, whereas interleukin-4-stimulated (IL4) monocytes had no detectable effect on vascular function. Bioluminescent imaging revealed restriction of transfused CD11b+-monocytes to the endothelial injury site in CD11b-DTR-mice depleted of endogenous monocytes. In vitro co-culture experiments revealed significantly enhanced regeneration properties of human endothelial outgrowth cells (EOCs) when cultured with preconditioned-media (PCM) or monocytes of IL4-stimulated-subsets compared to the effects of IFNγ-stimulated monocytes. ConclusionCD11b+-monocytes play an important role in endothelial cell recovery after endothelial injury by homing to the site of vascular injury, enhancing reendothelialization and improving endothelial function. In vitro experiments suggest that IL4-stimulated monocytes enhance EOC regeneration properties most likely by paracrine induction of proliferation and cellular promotion of differentiation. These results underline novel insights in the biology of endothelial regeneration and provide additional information for the treatment of vascular dysfunction.

Aldosterone Promotes Vascular Remodeling by Direct Effects on Smooth Muscle Cell Mineralocorticoid Receptors

Vascular remodeling occurs after endothelial injury, resulting in smooth muscle cell (SMC) proliferation and vascular fibrosis. We previously demonstrated that the blood pressure-regulating hormone aldosterone enhances vascular remodeling in mice at sites of endothelial injury in a placental growth factor-dependent manner. We now test the hypothesis that SMC mineralocorticoid receptors (MRs) directly mediate the remodeling effects of aldosterone and further explore the mechanism. A wire-induced carotid injury model was performed in wild-type mice and mice with inducible SMC-specific deletion of the MR. Aldosterone did not affect re-endothelialization after injury in wild-type mice. Deletion of SMC-MR prevented the 79% increase in SMC proliferation induced by aldosterone after injury in MR-Intact littermates. Moreover, both injury-induced and aldosterone-enhanced vascular fibrosis were attenuated in SMC-specific MR knockout mice. Further exploration of the mechanism revealed that aldosterone-induced vascular remodeling is prevented by in vivo blockade of the placental growth factor-specific receptor, type 1 vascular endothelial growth factor receptor (VEGFR1), the receptor for placental growth factor. Immunohistochemistry of carotid vessels shows that the induction of VEGFR1 expression in SMC after vascular injury is attenuated by 72% in SMC-specific MR knockout mice. Moreover, aldosterone induction of vascular placental growth factor mRNA expression and protein release are also prevented in vessels lacking SMC-MR. These studies reveal that SMC-MR is necessary for aldosterone-induced vascular remodeling independent of renal effects on blood pressure. SMC-MR contributes to induction of SMC VEGFR1 in the area of vascular injury and to aldosterone-enhanced vascular placental growth factor expression and hence the detrimental effects of aldosterone are prevented by VEGFR1 blockade. This study supports exploring MR antagonists and VEGFR1 blockade to prevent pathological vascular remodeling induced by aldosterone.

Tissue Factor Pathway Inhibitor Modulates Fibrin Deposition In The Brain In a Manner That Is Independent Of Thrombomodulin and Activated Protein C

BackgroundFibrin deposition in cerebral vessels contributes to the pathogenesis of stroke and vascular dementia. Under quiescent conditions fibrin deposition is prevented or limited by natural anticoagulants of the endothelium. Tissue factor pathway inhibitor (TFPI) and thrombomodulin (TM) are the two major endothelial anticoagulants and act on different portions of the clotting cascade. TFPI inhibits the initiation of coagulation by inhibiting TF-FVIIa and FXa. TM slows the propagation of coagulation by promoting the activation of protein C (APC), which inactivates FVa and FVIIIa. Both proteins are reported to have low expression in the brain and their function in prevention of cerebral vascular fibrin deposition is unclear. This is emphasized by findings from murine models of decreased TFPI and TM (TMpro/pro) activity. TFPI null embryos have fibrin deposition in the brain and liver, while TMpro/pro mice have fibrin deposition in the lungs, heart, spleen and liver, but the brain is protected from fibrin deposition even following lethal LPS doses. Interestingly, TFPI heterozygosity combined with TMpro/pro results in cerebral vascular fibrin. Here, we report a detailed analysis of TFPI expression in the brain vasculature, the consequences of vascular TFPI deficiency in adult mice, and the capacity of APC to compensate for TFPI deficiency. Methods and ResultsReal time PCR studies demonstrated that TFPI expression in total brain is lower than in other tissues in comparison to the RPL-19 housekeeping gene. However, when the endothelial-specific genes, VE-cadherin or CD31 were used as housekeeping genes, brain TFPI expression was higher than that of lung endothelium (TFPIa: ∼9 fold higher; TFPIb: ∼5-fold higher). In situ hybridization studies revealed that TFPI and TM are expressed on endothelium throughout the brain parenchyma. In addition, TFPI was expressed within the granule layer of the cerebellum. TFPI null embryos succumb to embryonic lethality with necrotic lesions and fibrin deposition in the brain. To determine if increased TM-APC anticoagulant activity would rescue TFPI null embryos, a transgene over expressing human activated protein C (hHPC) was bred into heterozygous TFPI mice, which were then bred to determine if TFPI null mice expressing hHPC survive embryogenesis. However, the hHPC transgene did not rescue TFPI null embryos. Furthermore, TFPI null embryos had similar brain lesions and brain fibrin deposition regardless of the presence of the hHPC transgene. A hematopoietic cell transplant model system was used to examine the consequences of TFPI deficiency in the adult mouse brain. Mice transplanted with hematopoietic cells lacking TFPI had cerebral vascular fibrin deposition that was not observed in mice transplanted with hematopoietic cells producing normal amounts of TFPI. Interestingly, the fibrin was often found at sites of endothelial injury as demonstrated by co-localization with anti-C1qA, which binds to phosphatidylserine on damaged endothelium. ConclusionsTFPI prevents necrotic brain lesions and cerebral fibrin deposition in developing mouse embryos and over expression of hHPC is not sufficient to compensate for the absence of TFPI. Adult mice lacking TFPI in hematopoietic cells have increased amounts of fibrin deposited at sites of cerebral vascular injury despite having normal endothelial TM. These data indicate that the distinct function of TFPI in the cerebral vasculature is not compensated by the anticoagulant activity of TM in regulating cerebral vascular thrombosis. Disclosures:Mast:Novo Nordisk: Honoraria, Research Funding.

The CXCR1/2 ligand NAP-2 promotes directed intravascular leukocyte migration through platelet thrombi

AbstractThrombosis promotes leukocyte infiltration into inflamed tissues, leading to organ injury in a broad range of diseases; however, the mechanisms by which thrombi guide leukocytes to sites of vascular injury remain ill-defined. Using mouse models of endothelial injury (traumatic or ischemia reperfusion), we demonstrate a distinct process of leukocyte recruitment, termed “directed intravascular migration,” specifically mediated by platelet thrombi. Single adherent platelets and platelet aggregates stimulated leukocyte shape change at sites of endothelial injury; however, only thrombi were capable of inducing directed intravascular leukocyte migration. Leukocyte recruitment and migration induced by platelet thrombi occurred most prominently in veins but could also occur in arteries following ischemia-reperfusion injury. In vitro studies demonstrated a major role for platelet-derived NAP-2 (CXCL-7) and its CXCR1/2 receptor in regulating leukocyte polarization and motility. In vivo studies demonstrated the presence of an NAP-2 chemotactic gradient within the thrombus body. Pharmacologic blockade of CXCR1/2 as well as genetic deletion of NAP-2 markedly reduced leukocyte shape change and intrathrombus migration. These studies define a distinct process of leukocyte migration that is initiated by homotypic adhesive interactions between platelets, leading to the development of an NAP-2 chemotactic gradient within the thrombus body that guides leukocytes to sites of vascular injury.

Differences in the released endothelial microparticle subtypes between human pulmonary microvascular endothelial cells and aortic endothelial cells in vitro

ABSTRACTCirculating endothelial microparticles (EMPs) are membrane vesicles that are shed into the blood stream from activated or apoptotic endothelial cells. We previously reported that circulating EMP numbers significantly increased in stable chronic obstructive pulmonary disease (COPD) patients and during exacerbation compared with healthy control subjects. However, different types of circulating EMPs with distinct time profiles were detectable during exacerbations. We hypothesized that the released EMP subtypes correlated with differences in the inflammatory stimuli and the endothelial cell type. We compared the EMP subtypes from human aortic endothelial cells (Aortic ECs) and human lung microvascular endothelial cells (Pulmonary microvascular ECs) released in response to various stimuli, including proinflammatory cytokines (TNFα), oxidative stress (H2O2), and cigarette smoke extracts (CSE) in vitro. We defined circulating EMPs by the expression of endothelial antigens: CD144+ MPs (VE-cadherin EMPs), CD31+/CD41− MPs (PECAM EMPs), CD62E+ MPs (E-selectin EMPs), and CD146+ MPs (MCAM EMPs). E-selectin EMPs were released from both pulmonary microvascular and aortic ECs in response to TNFα but not to H2O2 or CSE stimulation. The amount of MCAM EMPs released from pulmonary microvascular ECs differed significantly between the cells stimulated with H2O2 and those stimulated with CSE. VE-cadherin EMPs were only released from aortic ECs, whereas PECAM EMPs were released exclusively from pulmonary microvascular ECs. The EMP subtypes released differ in vitro among TNFα, H2O2, and CSE stimulation as well as between pulmonary microvascular and aortic ECs. The differences in circulating EMP subtypes may reflect a condition or site of endothelial injury and may serve as markers for endothelial damage in COPD patients.

Endothelial progenitor cells, cardiovascular risk factors and lifestyle modifications

Endothelial progenitor cells (EPCs) contribute substantially to preservation of a structurally and functionally intact endothelium. EPCs home in to the sites of endothelial injury and ischemia, where they proliferate, differentiate and integrate into the endothelial layer or exert a paracrine function by producing vascular growth factors. This review will focus on successful lifestyle interventions that aim to maintain vascular health through beneficial actions on cell populations with vasculogenic potential. The results of the studies proving the role of healthy lifestyle are particularly emphasized.

Circulation: Clinical Summaries

<i>Circulation:</i> Clinical Summaries

Monocyte Chemotactic Protein-1 Is Associated with Microvascular Abnormalities and Serum Ferritin Concentrations in Sickle Cell Disease Patients

Abstract 3255 Introduction:Microvascular abnormalities underlie much of the morbidity observed in sickle cell disease (SCD). Adherence of sickle erythrocytes and leukocytes to the microvascular endothelium leads to vaso-occlusion and end organ ischemia/reperfusion injury. Monocyte chemotactic protein-1 (MCP-1) is a chemokine involved in the recruitment of monocytes to sites of endothelial activation or injury and thus contributes to the pathophysiology of vascular disease. In SCD patients, circulating MCP-1 concentrations are elevated during both steady state and vaso-occlusive crisis. However, the relationship between MCP-1 and microvascular abnormalities in SCD patients has not been assessed. In the present study, we measured a panel of circulating cytokines including serum MCP-1 and hematological biomarkers including serum ferritin in SCD patients who were being monitored by computer-assisted intravital microscopy (CAIM) to assess severity of microvasculopathy. Methods:The study included 31 steady state SCD patients (22 females, 9 males) ranging in age from 4–61 years. MCP-1 concentrations were measured by Luminex multiple analyte profiling. Ferritin concentrations were measured by chemiluminometric immunossay. The conjunctival microvasculature was assessed using CAIM. A severity index on a scale of 0–15 was calculated as described previously (Cheung et al, Am J Hematol 85:899, 2010) to quantify the degree of microvasculopathy observed among the patients. Results:The mean ± SD MCP-1 concentration was 445 ± 253 pg/ml (range: 122–1180 pg/ml), mean ± SD ferritin concentration was 1675 ± 1883 ng/ml (range 18–5825 ng/ml), and mean ± SD severity index was 5.0 ± 2.5 (range: 0–9). By multiple regression analysis, with controlling for age and gender, MCP-1 was directly correlated with severity index (p = 0.046), and serum ferritin was directly correlated with MCP-1 (p = 0.019). Conclusions:Monocyte recruitment to the site of endothelial injury involves chemotactic signaling mediated in part by MCP-1, levels of which rise in SCD. Our results indicate that MCP-1 is associated with and may directly contribute to the microvasculopathy observed in SCD patients. Furthermore, we find that MCP-1 levels are correlated with ferritin concentrations. Ferritin reflects body iron stores, and an increase of iron stores in SCD resulting from chronic blood transfusion as well as increased iron absorption associated with hemolysis may thus lead to monocyte/macrophage recruitment to the vascular endothelium and contribute to vasculopathy. Measurements of MCP-1 and ferritin may also serve as surrogate biomarkers of microvasculopathy severity and inflammation. Disclosures:Green:Emisphere - Consultancy : Consultancy; Teva Pharmaceuticals - expert testimony: Consultancy.

Maturing EPCs into endothelial cells: may the force be with the EPCs. Focus on “Fluid shear stress induces differentiation of circulating phenotype endothelial progenitor cells”

endothelial progenitor cells (EPCs) are a unique cell type found circulating in the peripheral blood with the capacity to become mature endothelial cells. EPCs can be released from many sources including the bone marrow, adipose tissue, the vessel wall, as well as potentially the spleen, liver, and

Biologic nanoparticles promote mineralization of vascular smooth muscle cells in vitro

Biologic nanoparticles (NPs) ‐ protein/mineral complexes isolatable from human calcified, but not uncalcified arteries and from plasma ‐ propagate and accumulate calcium phosphate when in cell culture conditions. IV injection of NPs into animals results in vascular calcification at sites of endothelial injury. Our aim was to determine if NPs promote mineralization by localizing to vascular smooth muscle cells (VSMCs), then sequestering calcium from their environment. Porcine VSMCs were cultured in 24‐well plates to sub‐confluency (day 0). 45Ca (1 μCi/well) to label deposited mineral was added to media containing vehicle (control), NPs (10 or 100 nephelometric turbidity units; NTU; average diameter 210 nm), or 2 mM Pi (positive‐control). After 15 days, VSMCs formed multicellular nodules. VSMCs in control media were negative for calcification by von Kossa staining; whereas micron‐sized to smaller particles stained positive for calcium in nodules from NP‐treated and Pi‐treated cells. Cells treated identically were demineralized with 0.6N HCl and the liberated 45Ca was quantified by scintillation counting. CPM/well (x103) were 1.5 in controls and 4.6, 28.2 and 64.7 in cells treated with 10 NTU NPs, Pi, and 100 NTU NPs, respectively. NPs localize to VSMCs in vitro and promote mineralization through sequestration of Ca from the environment. (Supported by NIH grant HL88988, and Mayo Clinic).

Effects of additional treatment of sarpogrelate to aspirin therapy on platelet aggregation and plasma plasminogen activator inhibitor activity in patients with stable effort angina

Introduction Serotonin is secreted from platelets at sites of endothelial injury, where it promotes thrombogenic reactions. Serotonin is reported to be associated with not only coronary artery disease but also cardiac events. Materials and Methods We studied 33 patients with stable effort angina (SEA) (11 patients with multivessel disease (MVD) and 22 patients with singlevessel disease (SVD)) and 25 patients with chest pain syndrome (CPS). Sarpogrelate was administered to 22 of 33 patients with SEA in addition to aspirin therapy, and platelet aggregation, plasma serotonin concentration, and plasma plasminogen activator inhibitor (PAI) activity were measured before and 1 week after administration. Results and Conclusions Serotonin level was higher in patients with MVD than in those with SVD (p < 0.05) and in those with CPS (p < 0.001). The formation of small-sized platelet aggregates was significantly higher in the high serotonin group than in the low serotonin group of SEA patients. The formation of large-sized platelet aggregates was significantly decreased by administration of sarpogrelate (P < 0.05). The formation of small- or medium-sized aggregates was not significantly decreased. Plasma PAI activity decreased significantly (P < 0.05) although the plasma serotonin concentration did not show significant change by administration of sarpogrelate. Plasma serotonin level is increased in relation to severity of coronary artery disease and plasma serotonin level is associated with increased platelet aggregation. Administration of sarpogrelate in addition to aspirin therapy reduces the increased platelet aggregation and PAI activity, and it may indicate that additional administration of sarpogrelate is useful for patients with SEA.

Could hydroxyethyl starch be a therapeutic option in management of acute aluminum phosphide toxicity?

Acute aluminum phosphide poisoning is a serious toxicity and results in high mortality rate despite the progress of critical care. After ingestion, phosphine gas is released and absorbed quickly, causing systemic poisoning and cell hypoxia. Excessive thirst, severe hypotension, arrhythmias, tachypnea, and severe metabolic acidosis are the common clinical manifestations. We think acute metabolic response which characteristically occurs in severe injury also happens in aluminum phosphide poisoning. Necropsy examinations indicate congestion in almost all vital organs because of leakage of fluids from intravascular to extravascular space. The most favorable type of fluid for intravascular volume resuscitation persists and is disputed. Colloids remain in the intravascular space rather than crystalloids, and provide more rapid hemodynamic stabilization. Furthermore, hydroxyethyl starch solution may have other benefits e.g. it can reduce the extra vascular leak of albumin and fluids from an endothelial injury site. As refractory hypotension and cardiovascular collapse, because leakage of fluids from intravascular to extravascular space are common cause of death in this toxicity, we propose that hydroxyethyl starch can dominate this refractory hypotension and consequently acute metabolic response.

Platelet–Leukocyte Interactions in Cardiovascular Disease and Beyond

Platelet-leukocyte interactions define a basic cell process that is characterized by the exchange of signals between platelets and different types of leukocytes and that bridges 2 fundamental pathophysiological events: atherothrombosis and inflammatory immune reactions. When this process takes place at the site of atherosclerotic plaque development or at the site of endothelial injury, platelet-dependent leukocyte recruitment and activation contributes to the inflammatory reaction of the vessel wall, which accounts for the exacerbation of atherosclerosis and for intimal hyperplasia and plaque instability. Moreover, platelet-leukocyte interactions may have a key role in modulating a wide array of responses of both the innate and adaptive immune systems, thus contributing to the pathogenesis of inflammatory diseases and tissue damage, as well as to host defense.

Recombinant Activated Factor VII for Postoperative Hemorrhage Following Repair of Acute Type A Aortic Dissection

Perioperative hemorrhage in the repair of acute type A aortic dissection increases morbidity, mortality, and costs of treatment. Recombinant activated factor VII (rFVIIa) mitigates intractable blood loss in surgery. By enhancing thrombin generation on activated platelet surfaces and activating thrombin-activatable fibrinolysis inhibitor and factor XIII, rFVIIa promotes platelet aggregation and fibrin plug formation at the site of endothelial injury. We report outcomes for type A aortic dissection patients treated postoperatively with rFVIIa for life-threatening hemorrhage. Patients' charts were reviewed to gather demographic, procedural, and laboratory data as well as information regarding clinical outcomes and blood product use. Nine patients with acute type A aortic dissection received rFVIIa in the perioperative period. In the 6 hour period after rFVIIa treatment, transfusion of blood products was reduced. The international normalized ratio decreased after treatment (1.6 versus 0.9, P < .01). One patient experienced perioperative stroke. In patients with acute type A aortic dissections who have life-threatening bleeding, early administration of rFVIIa may safely normalize coagulation variables, decrease transfusion requirements, and enhance hemostasis.

Current perspective of pathophysiological and interventional effects on endothelial progenitor cell biology: Focus on Pi3K/AKT/eNOS pathway

For more than a decade, endothelial progenitor cells (EPCs) have been implicated in cardiovascular homeostasis. EPCs are believed to reside within the bone marrow in close contact with surrounding stromal cells, and, under stimulation of pro-inflammatory cytokines, EPCs are mobilized out of the bone marrow. Hereafter circulating EPCs home to peripheral tissues, undergoing further proliferation and differentiation. Under certain pathophysiologic conditions this process seems to be blunted, resulting in a reduced capacity of EPCs to engage in vasculogenesis at sites of endothelial injury or tissue ischemia. In this review, we focus on the effects of traditional cardiovascular risk factors on EPC biology and we explore whether pharmacological, dietary and lifestyle interventions can favorably restore EPC mobilization, differentiation, homing and angiogenic properties. Because the PI3K/Akt/eNOS pathway plays a pivotal role in the process of EPC mobilization, migration and homing, we specifically emphasize the involvement of PI3K, Akt and eNOS in EPC biology under these different (patho)physiologic conditions. (Pre)clinically used drugs or lifestyle interventions that have been shown to ameliorate EPC biology are reviewed. These treatment strategies remain attractive targets to restore the regenerative capacity of EPCs in cardiovascular diseases.

Is it naive to load only clopidogrel-naive patients prior to PCI?

This editorial refers to ‘Clopidogrel reloading in patients undergoing percutaneous coronary intervention on chronic clopidogrel therapy. Results of the ARMYDA-4 RELOAD (Antiplatelet therapy for Reduction of MYocardial Damage during Angioplasty) randomized trial’, by S. Di Sciascio et al. doi:10.1093/eurheartj/ehq081 Percutaneous coronary intervention (PCI) has become the predominant form of coronary revascularization in Europe and the USA. Although overall a safe procedure, PCI may be complicated by adverse events, with myocardial infarction (MI) and bleeding being the most frequent and important contributors to mortality and morbidity after the procedure. It is estimated that ∼25% of patients undergoing PCI may have significant post-procedural myonecrosis, as identified by creatinine kinase (CK) and CK-MB isoenzyme elevations, and that up to 50% of PCI patients develop post-procedural troponin elevations.1 The development of strategies that help prevent post-procedural MI has therefore been a major research interest in the field of interventional cardiology. Ever since the late 1990s, it is generally accepted that platelets, adhering and aggregating at sites of endothelial injury and mechanical plaque disruption, are the key determinants of PCI-related myocardial necrosis. Accordingly, several trials, including the Intracoronary Stenting and Antithrombotic Regimen (ISAR) trial,2 demonstrated that dual antiplatelet therapy with aspirin plus thienopyridines is efficient in reducing post-PCI ischaemic complications. Since then, dual antiplatelet therapy with the thienopyridine clopidogrel and aspirin has become an integral part of PCI treatment of patients presenting with various forms of coronary artery disease—ST elevation myocardial infarction (STEMI), non-ST elevation acute coronary syndrome (NSTE ACS), and stable angina. An important limitation of clopidogrel, however, lies in its pharmacokinetic and pharmacodynamic properties.3 Clopidogrel is a prodrug that has to undergo two sequential cytochrome P-450 (CYP)-dependent oxidation steps after intestinal absorption in order to be converted into its active metabolite. This leads to delayed onset of action and interindividual … *Corresponding author. Tel: + 49 89 12184578, Fax: +49 89 12184053, Email: kastrati{at}dhm.mhn.de

Endothelial progenitor cells in vascular health: Focus on lifestyle

Endothelial dysfunction, which is considered the functional equivalent of a disrupted balance between endothelial injury and repair, precedes overt atherosclerosis by many years. Although this phenomenon is part of the normal aging process, prevention of early and progressive endothelial dysfunction has become an important therapeutic target. Evidence has accumulated to show that endothelial progenitor cells (EPC), contribute substantially to preservation of a structurally and functionally intact endothelium. There has been considerable progress in our understanding of the various cell types that were in the past all covered by the term “EPC.” EPC home to sites of endothelial injury and ischemia, where they proliferate, differentiate and integrate into the endothelial layer or exert a paracrine function by producing vascular growth factors. Although more emphasis has been put on the pharmacological approach of endothelial dysfunction, the effect of a healthy lifestyle, via mobilization and functional improvement of EPC, is increasingly recognized. This review will focus on successful lifestyle interventions that aim to maintain vascular health through beneficial actions on cell populations with vasculogenic potential (“EPC”). The role of physical activity and dietary recommendations, which are considered essential elements of a healthy lifestyle, will be particularly emphasized. A thorough understanding of the physiology of endothelial benefits, derived from such interventions, may help to implement these measures on top of classical drug therapy, but also provides a solid basis for primary prevention. The effects of additional elements of a comprehensive lifestyle advice, such as smoking cessation, weight and stress reduction, also comprise a modulation of EPC function and circulating numbers and are therefore included in this review as well.

Mechanisms of leukocyte distribution during sepsis: an experimental study on the interdependence of cell activation, shear stress and endothelial injury

IntroductionThis study was carried out to determine whether interactions of cell activation, shear stress and platelets at sites of endothelial injury explain the paradoxical maldistribution of activated leukocytes during sepsis away from local sites of infection towards disseminated leukocyte accumulation at remote sites.MethodsHuman umbilical venous endothelial cells (HUVEC) and polymorphonuclear neutrophils (PMN) were activated with lipopolysaccharide at 100 and 10 ng/ml to achieve adhesion molecule patterns as have been reported from the hyper- and hypo-inflammatory stage of sepsis. To examine effects of leukocyte activation on leukocyte-endothelial interactions, activated HUVEC were perfused with activated and non-activated neutrophils in a parallel plate flow chamber. Adhesion molecule expression and function were assessed by flow cytometry and blocking antibodies. In a subset of experiments the sub-endothelial matrix was exposed and covered with platelets to account for the effects of endothelial injury. To investigate interactions of these effects with flow, all experiments were done at various shear stress levels (3 to 0.25 dyne/cm2). Leukocyte-endothelial interactions were analyzed by videomicroscopy and analysis of covariance.ResultsActivation of neutrophils rendered adhesion increasingly dependent on shear stress reduction. At normal shear stress, shedding of L-selectin decreased adhesion by 56%. Increased rolling fractions of activated PMN at low shear stress revealed impaired integrin affinity despite numerical up-regulation of CD11b. On sub-maximally activated, intact HUVEC shear stress became the prevailing determinant of adhesion. Presence of a platelet-covered injury with high surface density of P-selectin was the strongest variable for adhesion. When compared to maximally activated HUVEC, platelets increased neutrophil adhesion by 2.7-fold. At sub-maximal activation a 10-fold increase was observed (P < 0.05 for all).ConclusionsL-selectin shedding and integrin dysfunction render leukocyte adhesion increasingly susceptible to shear stress and alternative adhesion receptors. In combination, these effects inhibit recruitment to normally perfused sites with intact endothelium and favor maldistribution towards sites with compromised perfusion or endothelial injury.