High Prevalence of Acquired Platelet Secretion Defects in Multiple Myeloma.

Thrombocytopenia at admission predicts mortality in multiple myeloma (MM) and might link to disease progression. Although thrombocytopenia is known to be associated with MM, a possible thrombopathy is clinically less known. We conducted a case-control study comparing platelet responses of MM patients to controls via flow cytometry, integrin αIIbβ3 activation and P-selectin exposure, and a bioluminescent assay, ATP release.

Functional characterization of a nanobody-based glycoprotein VI-specific platelet agonist.

Background: Glycoprotein (GP)VI is a platelet-specific collagen receptor required for platelet activation during hemostasis. Platelet reactivity toward collagen is routinely assessed during diagnostic workup of platelet disorders. GPVI can be activated by inducing receptor clustering with suspensions of fibrillar collagen or synthetic cross-linked collagen-related peptide (CRP-XL).

Flow Cytometry Based Platelet Reactivity Testing to Predict the Occurrence of Per-operative Solid Microemboli During Carotid Endarterectomy.

Objective: Peri-operative antiplatelet therapy (APT) aims to prevent thrombotic events such as stroke. High platelet reactivity ,despite the use use of APT, increases the risk of thrombotic events. Transcranial Doppler imaging (TCD) is used to detect peri-operative microembolic signals (MES) during carotid endarterectomy (CEA).

Bone Marrow Ts65Dn Trisomy-Induced Changes in Platelet Functionality and Lymphocytopenia Do Not Impact Atherosclerosis Susceptibility in Mice.

The genetic disorder Down syndrome is associated with a decreased susceptibility for atherosclerotic cardiovascular disease. Hematological and immune abnormalities occur frequently in Down syndrome patients. We evaluated, in a preclinical setting, the impact of a Down syndrome-like hematological/immune phenotype on atherosclerosis susceptibility.

Sex differences in flow cytometry-based platelet reactivity in stable outpatients suspected of myocardial ischemia.

Background: Antiplatelet therapy is the mainstay of secondary prevention of cardiovascular events. Studies suggest that women do not obtain equal therapeutic benefit from antiplatelet therapy compared with men. The link between sex differences in platelet biology and response to antiplatelet therapies is unclear.

Flow cytometric mepacrine fluorescence can be used for the exclusion of platelet dense granule deficiency.

Background: δ-storage pool disease (δ-SPD) is a bleeding disorder characterized by a reduced number of platelet-dense granules. The diagnosis of δ-SPD depends on the measurement of platelet ADP content, but this test is time consuming and requires a relatively large blood volume. Flow cytometric analysis of platelet mepacrine uptake is a potential alternative, but this approach lacks validation, which precludes its use in a diagnostic setting.

Peptide Antagonists for P-selectin Discriminate between Sulfatide-Dependent Platelet Aggregation and PSGL-1-Mediated Cell Adhesion.

Background: Membrane-exposed sulfatides are proposed to contribute to P-selectin-dependent platelet aggregation. Here, we demonstrated that P-selectin-mediated platelet aggregation on a collagen-coated surface under flow indeed depended on sulfatides and that this interaction differed considerably from the interaction of P-selectin with P-selectin Glycoprotein Ligand-1 (PSGL-1), which underlies leukocyte-endothelium adhesion.

Methods And Results: Upon platelet activation, sulfatides were translocated to the platelet surface to form focal hot-spots.

Estrogen Contributions to Microvascular Dysfunction Evolving to Heart Failure With Preserved Ejection Fraction.

Heart failure with preserved ejection fraction (HFpEF) is a syndrome involving microvascular dysfunction. No treatment is available yet and as the HFpEF patient group is expanding due to the aging population, more knowledge on dysfunction of the cardiac microvasculature is required. Endothelial dysfunction, impaired angiogenesis, (perivascular) fibrosis and the pruning of capillaries (rarefaction) may all contribute to microvascular dysfunction in the heart and other organs, e.

Hypercholesterolemia impairs megakaryopoiesis and platelet production in scavenger receptor BI knockout mice.

Background And Aims: Thrombocytopenia in scavenger receptor BI (SR-BI) knockout mice is suggested to result from augmented platelet clearance induced by elevated intracellular unesterified cholesterol (UC) levels. We hypothesize that SR-BI deficiency may also influence platelet production at the level of its precursor cell in the bone marrow, the megakaryocyte.

Methods: In this study, we compared megakaryopoiesis and platelet production in SR-BI knockout and wild-type mice.

Platelet function is disturbed by the angiogenesis inhibitors sunitinib and sorafenib, but unaffected by bevacizumab.

Introduction: At the clinical introduction of antiangiogenic agents as anticancer agents, no major toxicities were expected as merely just endothelial cells (ECs) in tumors would be affected. However, several (serious) toxicities became apparent, of which underlying mechanisms are largely unknown. We investigated to what extent sunitinib (multitargeted antiangiogenic tyrosine kinase inhibitor (TKI)), sorafenib (TKI) and bevacizumab [specific antibody against vascular endothelial growth factor (VEGF)] may impair platelet function, which might explain treatment-related bleedings.

The use of platelet reactivity testing in patients on antiplatelet therapy for prediction of bleeding events after cardiac surgery.

Many patients are treated with platelet inhibitors such as aspirin and clopidogrel for prevention of thrombotic cardiovascular events. However, the inhibitory effect of antiplatelet therapy is variable between patients; in some, the platelets are hardly inhibited, while in others, the platelets are excessively inhibited. The newer and more potent platelet inhibitors, prasugrel and ticagrelor, often lead to low platelet reactivity, which potentially leads to bleeding events.

LR11/SorLA links triglyceride-rich lipoproteins to risk of developing cardiovascular disease in FH patients.

Objective: Familial Hypercholesterolemia (FH) is associated with an increased risk of cardiovascular disease (CVD). However, whether an individual heterozygous FH patient will develop CVD depends on other genetic- and environmental risk factors as well. LDL receptor-related protein with 11 ligand binding repeat (LR11) and its soluble form (sLR11) play a role in the progression of atherosclerosis.

High-density lipoprotein as a modulator of platelet and coagulation responses.

Platelets and coagulation factors are involved in the process of haemostasis, which ensures undisturbed blood flow upon vessel wall damage. However, excessive platelet aggregation and/or coagulation may lead to arterial or venous thrombosis. Pro-atherogenic lipoproteins, including native and oxidized low-density lipoprotein (LDL), are associated with an increased susceptibility to thrombosis.

Supporting roles of platelet thrombospondin-1 and CD36 in thrombus formation on collagen.

Objective: Platelets abundantly express the membrane receptor CD36 and store its ligand thrombospondin-1 (TSP1) in the α-granules. We investigated whether released TSP1 can support platelet adhesion and thrombus formation via interaction with CD36.

Approach And Results: Mouse platelets deficient in CD36 showed reduced adhesion to TSP1 and subsequent phosphatidylserine expression.

Elimination of macrophages drives LXR-induced regression both in initial and advanced stages of atherosclerotic lesion development.

While numerous studies have aimed to develop strategies to inhibit the development and progression of atherosclerosis, recent attention has focussed on the regression of pre-existing atherosclerotic plaques. As important regulator of total body cholesterol homeostasis, the liver X receptor (LXR) could possibly be an important target to induce regression. Here, we describe the effect of LXR activation by the synthetic agonist T0901317 on lesion regression in different mouse models with early fatty streak lesions or advanced collagen-rich lesions.

Leukocyte-specific CCL3 deficiency inhibits atherosclerotic lesion development by affecting neutrophil accumulation.

Objective: Despite common disbelief that neutrophils are involved in atherosclerosis, evidence is accumulating for a causal role of neutrophils in atherosclerosis. CC chemokine ligand (CCL)3 is an inflammatory chemokine and its expression is significantly increased during atherosclerotic lesion formation in mice. It has recently been shown that under conditions of inflammation neutrophils can migrate along a CCL3 gradient.

LCAT deficiency in mice is associated with a diminished adrenal glucocorticoid function.

In vitro studies have suggested that HDL and apoB-containing lipoproteins can provide cholesterol for synthesis of glucocorticoids. Here we assessed adrenal glucocorticoid function in LCAT knockout (KO) mice to determine the specific contribution of HDL-cholesteryl esters to adrenal glucocorticoid output in vivo. LCAT KO mice exhibit an 8-fold higher plasma free cholesterol-to-cholesteryl ester ratio (P < 0.

Adenosine A₂B receptor agonism inhibits neointimal lesion development after arterial injury in apolipoprotein E-deficient mice.

Objective: The A(2B) adenosine receptor (A(2B)R) is highly expressed in macrophages and vascular smooth muscle cells and has been established as an important regulator of inflammation and vascular adhesion. Recently, it has been demonstrated that A(2B)R deficiency enhances neointimal lesion formation after vascular injury. Therefore, we hypothesize that A(2B)R agonism protects against injury-induced intimal hyperplasia.

Effects of deletion of macrophage ABCA7 on lipid metabolism and the development of atherosclerosis in the presence and absence of ABCA1.

ABCA7, a close relative of ABCA1 which facilitates cholesterol efflux to lipid-poor apoproteins, has been implicated in macrophage lipid efflux and clearance of apoptotic cells in in vitro studies. In the current study, we investigated the in vivo effects of macrophage ABCA7 deficiency on lipid metabolism and atherosclerosis. Chimeras with dysfunctional ABCA7 in macrophages and other blood cells were generated by transplantation of bone marrow from ABCA7 knockout (KO) mice into irradiated low-density lipoprotein receptor (LDLr) KO mice.