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Query: UMLS:C0002895 (sickle cell disease)
 11,747 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The phospholipids of the human red cell are distributed asymmetrically in the bilayer of the red cell membrane. In certain pathologic states, such as sickle cell anemia, phospholipid asymmetry is altered. Although several methods can be used to measure phospholipid organization, small organizational changes have been very difficult to assess. Moreover, these methods fail to identify subpopulations of cells that have lost their normal phospholipid asymmetry. Using fluorescently labeled annexin V in flow cytometry and fluorescent microscopy, we were able to identify and quantify red cells that had lost their phospholipid asymmetry in populations as small as 1 million cells. Moreover, loss of phospholipid organization in subpopulations as small as 0.1% of the total population could be identified, and individual cells could be studied by fluorescent microscopy. An excellent correlation was found between fluorescence-activated cell sorter (FACS) analysis results using annexin V to detect red cells with phosphatidylserine (PS) on their surface and a PS-requiring prothrombinase assay using similar red cells. Cells that bound fluorescein isothiocyanate (FITC)-labeled annexin V could be isolated from the population using magnetic beads covered with an anti-FITC antibody. Evaluation of blood samples from patients with sickle cell anemia under oxygenated conditions demonstrated the presence of subpopulations of cells that had lost phospholipid asymmetry. While only a few red cells were labeled in normal control samples (0.21% +/- 0.12%, n = 8), significantly increased (P < .001) annexin V labeling was observed in samples from patients with sickle cell anemia (2.18% +/- 1.21%, n = 13). We conclude that loss of phospholipid asymmetry may occur in small subpopulations of red cells and that fluorescently labeled annexin V can be used to quantify and isolate these cells.
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PMID:Detection of altered membrane phospholipid asymmetry in subpopulations of human red blood cells using fluorescently labeled annexin V. 856 45

It has recently been proved that, in vitro, red blood cells (RBCs) from patients with homozygous beta-thalassemia behave as procoagulant cells. The procoagulant activity of beta-thalassemia RBCs might be the result of an increased exposure of procoagulant phospholipids (i.e. phosphatidylserine) in the outer leaflet of the membrane. In order to test this hypothesis, we compared the catalytic properties of RBCs of patients with beta-thalassemia and homozygous sickle cell disease (SS-RBCs) with that of controls. The catalytic parameters (Km, kcat) of prothrombin activation by factor Xa were determined both in the absence and in the presence of RBCs. The turn-over number (kcat) of the reaction was not modified by normal, SS- or beta-thalassemia RBCs. The Km was lower in the presence of normal RBCs (mean value: 9.1 microM) than in the absence of cells (26 microM). The Km measured in the presence of either SS-RBCs (mean value: 1.6 microM) or beta-thalassemia RBCs (mean value: 1.5 microM) was significantly lower compared to normal RBCs (p < 0.001). No significant difference was observed between SS-RBCs and beta-thalassemia RBCs. Annexin V, a protein with high affinity and specificity for anionic phospholipids, inhibited the procoagulant activity of both SS-RBCs and beta-thalassemia RBCs, in a dose-dependent manner. More than 95% inhibition was achieved at nanomolar concentrations of annexin V. These results indicate that the procoagulant activity of both beta-thalassemia RBCs and SS-RBCs may be fully ascribed to an abnormal exposure of phosphatidylserine at the outer surface of the red cells.
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PMID:Increased procoagulant activity of red blood cells from patients with homozygous sickle cell disease and beta-thalassemia. 888 64

Oxidant-induced damage has been proposed to be the underlying mechanism for loss of membrane phospholipid asymmetry in the erythrocyte membrane. In sickle cell disease, thalassemia, and diabetes as well as in senescent erythrocytes, an apparent correlation between oxidative damage and loss of phosphatidylserine asymmetry has been reported. In the present study, erythrocytes were subjected to various levels of oxidative stress and/or sulfhydryl modifying agents. The transmembrane location of phosphatidylserine (PS) was assessed by FITC-conjugated annexin V labeling and the PS-dependent prothrombinase assay. Transbilayer movement of spin-labeled PS was used to determine aminophospholipid translocase activity. Our data show that cells did not expose PS as the result of oxidative stress induced by phenylhydrazine, hydrogen peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, or sulfhydryl modification by N-ethylmaleimide (NEM) and diamide, even under conditions that led to severe cellular damage and impairment of aminophospholipid translocase activity. In contrast, the increase of intracellular calcium induced by treatment with calcium and ionophore A23187 leads to a rapid scrambling of the lipid bilayer and the exposure of PS, which can be exacerbated by the inhibition of aminophospholipid translocase activity. Oxidation of the cells with hydrogen peroxide or phenylhydrazine did not affect A23187-induced uptake of calcium, but partly inhibited calcium-induced membrane scrambling. In conclusion, oxidative damage of erythrocytes does not induce exposure of phosphatidylserine on the membrane surface, but can interfere with both aminophospholipid translocase activity and calcium-induced randomization of membrane phospholipids.
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PMID:Oxidative damage does not alter membrane phospholipid asymmetry in human erythrocytes. 918 59

In the present study we examined if, among other mechanisms, the abnormal exposure of phosphatidylserine at the surface of sickle red blood cells (RBCs) contributes to the hypercoagulability which characterizes homozygous sickle cell disease (SCD). The question was addressed by comparison of the procoagulant properties of RBCs from subjects with various phenotypes (SS, SC and AS) that differ in clinical presentation. As previously reported, SS-RBCs accelerated the prothrombin activation by factor Xa, by decreasing the Km of the reaction compared to normal RBCs. SC-RBCs and AS-RBCs also promoted prothrombin activation although their procoagulant properties were milder compared to SS-RBCs. A significant increase of the thrombin-antithrombin complexes was observed in SS subjects. Prothrombin fragment 1+2 (F1+2) was elevated in half of the SS subjects, but the difference with controls did not reach significance. Elevated levels of thrombin-antithrombin complexes were observed in a number of SC (4/11) and AS (3/12) subjects, but the difference with controls was not significant. A significant correlation was observed between the plasma levels of thrombin-antithrombin complexes in the subjects with SS, AS and AA phenotypes, and the procoagulant properties of RBCs. Our results strongly suggest that the procoagulant properties which characterize SS-RBCs also affect SC-RBCs and AS-RBCs, and that exposure of phosphatidylserine by RBCs contributes to the hypercoagulable state observed in SCD.
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PMID:Sickle cell disease: relation between procoagulant activity of red blood cells from different phenotypes and in vivo blood coagulation activation. 937 37

The structure of red blood cell (RBC) membranes in homozygous sickle cell disease (SCD) is significantly disturbed, with an increased exposure of aminophospholipids (phosphatidylserine and phosphatidylethanolamine) at the outer surface, responsible for a procoagulant activity of SS RBCs. Aminophospholipids are known not only to promote procoagulant reactions, but also to support inhibition of blood coagulation by the protein C system. The aim of the present study was to examine whether SS RBCs could serve as a catalytic surface for the inactivation of factor Va by activated protein C (APC). Venous blood was obtained from 19 consecutive SS patients and 13 controls (AA). In all SS patients, the amount of phosphatidylserine exposed at the outer surface of RBCs was increased compared with controls, as demonstrated by a prothrombinase assay. In addition, SS RBCs significantly (P < 0.0001) increased the rate of FVa inactivation by APC: the mean values (and ranges) of the factor Va inactivation rates were 30 (0-57) vs 9.5 (0-32) mmol Vai/min/mol APC for SS RBCs and normal RBCs respectively. Our results indicate that SS RBCs provide a catalytic surface for the negative control of blood coagulation, which may partially control the procoagulant activity of these cells.
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PMID:Red blood cells from patients with homozygous sickle cell disease provide a catalytic surface for factor Va inactivation by activated protein C. 1197 26

Circulating platelets play a pivotal role in hemostasis. The platelet hemostatic function involves the direct interaction with damaged vessel walls, and circulating coagulation factors, primarily thrombin resulting in platelet activation, aggregation and formation of hemostatic plug. Flow cytometry is a useful technique for the study of platelet activation in circulating blood. Platelet activation markers for ex vivo analysis may include a) activation-dependent epitopes of the membrane glycoprotein (GP) IIb/IIIa (CD41a) receptor, as demonstrated by the binding of activation-specific monoclonal antibodies (MoAbs) PAC1, anti-LIBS1 and anti-RIBS); b) the expression of P-selectin (CD62p), the alpha-granule GP translocated to the platelet surface following release reaction; and c) platelet procoagulant activity, as demonstrated by the binding of i) annexin V protein to the prothrombinase-complex (prothrombin, activated factor X (Xa) and V (Va)) binding sites on the surface of activated platelets, and of ii) MoAbs against activated coagulation factors V and X bound to the surface of activated platelets. Using this method, platelet activation as a marker for in vivo prothrombotic activity can be demonstrated in various clinical conditions including coronary angioplasty, orthostatic challenge in primary depression, sickle cell disease in clinical remission and during pain episode, and in pregnancy-related hypertension with marked increase during preeclampsia. The finding of platelet procoagulant activity is corroborated by increased levels of plasma markers for thrombin generation and fibrinolytic activity.
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PMID:Platelet activation as a marker for in vivo prothrombotic activity: detection by flow cytometry. 1547 Dec 23

The objective of this study was to validate a simple factor Xa-based clotting test developed to monitor procoagulant phospholipids (PPLs) and platelet-derived microparticles (PMPs). This assay is easily automated, giving it a major advantage over the more laborious and expensive flow cytometry, electron microscopy and ELISA techniques in general usage at present. The intra-assay and inter-assay variation coefficients were less than 5% at both low and high levels of PPLs. The test is not affected by other clotting factors is assured by the use of a phospholipid-free animal plasma, which provides excess factor V, fibrinogen and prothrombin. This test was evaluated in apparently healthy volunteers and in selected patient groups associated with increased levels of PMPs in the circulation (diabetes mellitus, sickle cell disease, thyroid cancer and patients with multiple trauma). The study showed that XaCT has a high discriminating power for PPLs and that the patient groups have significantly highly increased PPLs activities when compared with healthy volunteers. Although of a preliminary nature, the test has shown that it has the sensitivity for discriminating severity of disease, as it could detect patients in sickle cell crisis and differentiate between type 1 and 2 diabetes. In conclusion, the combination of reliability, reproducibility and easy performance makes the XaCT assay a simple test to screen for PPLs in plasma samples.
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PMID:Clinical evaluation of a new functional test for detection of plasma procoagulant phospholipids. 1959 17

Vaso-occlusive crisis (VOC) is the primary cause of morbidity and hospitalization in sickle cell disease (SCD); however, only 4 therapies (hydroxyurea, l-glutamine, crizanlizumab, and voxeletor) are currently approved in SCD. These agents limit the duration, severity, and frequency of crises. Activation of coagulation is a hallmark of SCD. Studies in animal models of SCD have shown that coagulation contributes to the chronic inflammation and end-organ damage associated with the disease; however, it is unknown whether coagulation directly contributes to the microvascular stasis that causes VOC. Herein, we demonstrate that inhibition of tissue factor (TF) and the downstream coagulation proteases factor Xa and thrombin significantly attenuates heme-induced microvascular stasis in mouse models of VOC. Pharmacologic inhibition of the principal thrombin receptor, protease activated receptor-1 (PAR-1), as well as deficiency of PAR-1 in all nonhematopoietic cells, also reduces stasis in sickle mice. PAR-1 deficiency was associated with reduced endothelial von Willebrand factor expression, which has been shown to mediate microvascular stasis. In addition, TF inhibition reduces lung vaso-occlusion in sickle mice mediated by arteriolar neutrophil-platelet microemboli. In sum, these results suggest that prophylactic anticoagulation might attenuate the incidence of VOC.
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PMID:Thrombin activation of PAR-1 contributes to microvascular stasis in mouse models of sickle cell disease. 3240 25