Hydroxyurea Therapy Reduces The Hypercoagulability State In a Sickle Cell Mouse Model

Abstract Several lines of evidence show that sickle cell anemia (SCA) is characterized by a hypercoagulable state. SCA patients present an elevated rate of thrombotic complications and increased biological markers of coagulation activation. In a previous study we demonstrated that therapy with hydroxyurea (HU) in SCA patients was associated with reductions in hypercoagulability markers, in addition to reductions in hemolysis, inflammation and endothelial activation markers (Colella et al Journal of Thrombosis and Haemostasis 2012). In the present study, we attempted to further investigate whether the effect of HU on hemostatic activation is dependent on fetal haemoglobin (HbF) expression, hemolysis and/or inflammation. To do so, we used the BERK murine model of SCA, a homozygous model of SCA, incapable of expressing HbF. In this BERK model, treatment with HU results in no improvement in hemolysis, due to the lack of HbF induction (Lebensburger et al Haematologica 2010). The murine SCA model was generated by transplantation of nucleated bone marrow cells from BERK mice into lethally-irradiated C57BL6 mice. Only mice expressing > 97% of human hemoglobin S (HbS) at 10 weeks after transplantation were used in the study. HU therapy at the dose of 50mg/kg (HU group) or saline alone (control mice) was administered through intraperitoneal injections 5 times per week, initiated at 11 weeks after transplantation (approximate time of sickle marrow engraftment). After a treatment period of 16 weeks, blood samples drawn from the inferior cava vein were collected and submitted to evaluation of plasma levels of thrombin-antithrombin III (TAT), a final marker of thrombin generation, in both animal groups. We also evaluated plasma levels of the inflammation marker interleukin 6 (IL6), and the endothelial marker soluble vascular cell adhesion molecule-1 (sVCAM-1). TAT, IL6 and sVCAM-1 were all measured by commercially-available ELISA kits. Statistical analyses were performed using Mann-Whitney’s U test. Treatment with HU resulted in a significant reduction of TAT plasma levels (106.7 μg/L vs 138.5 μg/L; P = 0.05). Plasma levels of IL6 (7.1pg/mL vs 12.4pg/mL; P = 0.18) and sVCAM-1 (765.8 ng/mL vs 848.4 ng/mL; P= 0.43) presented non-significant reductions with HU treatment. Our results show that, in this murine SCA model, long-term HU treatment results in an improvement in the hypercoagulability state, even in the absence of HbF induction, or of a significant improvement of inflammation or endothelial activation. This indicates that HU may have a direct effect on inhibiting the activation of coagulation in SCA. Disclosures: No relevant conflicts of interest to declare.

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Elevated Plasma Levels and Platelet-Associated Expression of the Pro-Thrombotic and Pro-Inflammatory Protein, LIGHT (TNFSF14), In Sickle Cell Anemia (SCA)

Blood ◽

10.1182/blood.v116.21.2651.2651 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2651-2651

Author(s):

Vanessa T. Garrido ◽

Venina M. Dominical ◽

Renata Proença-Ferreira ◽

Marcos André Cavalcanti Bezerra ◽

Mariana R. B. Mello ◽

...

Keyword(s):

Sickle Cell ◽

Sickle Cell Anemia ◽

Therapeutic Target ◽

Plasma Levels ◽

Conflicts Of Interest ◽

Fetal Hemoglobin ◽

Endothelial Activation ◽

Potential Therapeutic Target ◽

Activation Markers ◽

Inflammatory Protein

Abstract Abstract 2651 Background: LIGHT (TNFSF14; CD258), a recently-identified member of the TNF superfamily, is found associated with and produced from platelets, amongst other immune cells. Increased circulating levels of this protein have been observed in patients with myocardial infarction and acute atherothrombotic stroke and LIGHT has been proposed as a potential therapeutic target in atherosclerosis, due to its reported pro-thrombotic and pro-inflammatory effects upon human endothelial cells. This study evaluated whether production of LIGHT is altered in patients with sickle cell anemia (SCA), and the participation that the platelets (PLTs) may have in this production, since SCA is characterized by a significant chronic inflammation and endothelial activation that may initiate the vaso-occlusive process. Patients and Methods: Soluble LIGHT (sLIGHT) was determined in PLT-free plasma (obtained by sequential centrifugations and ultrafiltration) from healthy control individuals (CON), SCA patients in steady state (SCA) and SCA patients on hydroxyurea therapy (SCAHU; 20–30 mg/kg/day HU) by ELISA. Expressions of PLT-membrane LIGHT and PLT activation markers were evaluated by flow cytometry using anti-CD258-PE, anti-CD62P-FITC or anti-PAC1-FITC. Subjects had not taken ASA during the previous 14 days. Results: sLIGHT was significantly elevated in the plasma of SCA and SCAHU individuals, compared to CONs (SCA; 35.4 ± 9.4 pg/ml; SCAHU, 37.3 ± 7.5 pg/ml; CON, 9.7 ± 1.5 pg/ml, n=27, 27, 19, resp.; P<0.01 for SCA/SCAHU, compared to CON; Kruskal-Wallis/Dunn's). Plasma sLIGHT in SCA/SCAHU individuals presented no correlation with hematological variables, such as PLT counts (rs=-0.079, P=0.65) and fetal hemoglobin (rs=0.107, P=0.51). In contrast, plasma sLIGHT levels in SCA patients presented an impressive correlation with plasma levels of CD40L, another important PLT-derived inflammatory protein (rs=0.817, P<0.0001 for SCA group and rs=0.651, P<0.0001 for SCA+SCAHU) and correlated with IL-8, an endothelium-derived inflammatory mediator (rs=0.900, P<0.05 for SCA and rs=0.455, P=0.06 for SCA+ SCAHU). Expression of LIGHT protein (CD258) was significantly higher on the membrane of PLTs from SCA and SCAHU individuals, compared to CON PLTs (SCA, 27.1 ± 4.5 %; SCAHU, 33.7 ± 5.8 %; CON, 5.5 ± 1.6 % positive PLTs, n=15, 20, 15, resp.; P<0.001 for SCA/SCAHU comp. CON). Notably, when PLTs were activated by incubation with ADP (20 μM, 30 min), PLTs from SCA/SCAHU individuals still expressed significantly more surface LIGHT than CON PLT (SCA, 41.8 ± 4.5 %; SCAHU, 41.3 ± 5.4 %; CON, 11.1 ± 2.3 % positive PLTs; n=15, 20, 14, resp. P<0.001 for SCA/SCAHU comp. CON); successful activation of PLTs from all groups was confirmed by increased PAC-1 (anti-activated αIIbß3 integrin) binding and increased P-selectin (CD62P, a PLT activation marker) expression (data not shown); furthermore LIGHT expression on ADP-activated cells correlated significantly with both PAC-1 binding (rs=0.483, P=0.03) and P-selectin expression (rs=0.502, P=0.02, n=20) on SCA PLTs. sLIGHT release from SCA PLTs during 90 min (37°C, 5% CO2 in Krebs) was evaluated and demonstrated that PLTs of SCA individuals may be an important source of circulating sLIGHT, releasing 22.2 ± 4.7 pg LIGHT/108 PLTs (n=10); release of sLIGHT from SCA PLT was significantly augmented by incubation with collagen (P<0.01), but not ADP (P>0.05); basal and collagen-stimulated sLIGHT release correlated significantly with CD40L release (rp=0.654; rp=0.764, resp. P<0.05). Conclusion: The pro-inflammatory and atherogenic protein, LIGHT, is found significantly elevated in the plasma of SCA patients. The correlation of plasma LIGHT with IL-8 indicates that LIGHT may participate in, or reflect, endothelial activation, whilst the correlation of circulating LIGHT and PLT release of LIGHT with CD40L indicates that the production of these two proteins may be tightly coupled. LIGHT protein is highly expressed on the PLT surface in SCA and this expression appears to be associated with PLT activation, rather than PLT number. Interestingly, HU therapy was not associated with any significant alteration in circulating LIGHT, nor PLT surface LIGHT. Future investigations will determine the extent of the contribution of LIGHT to endothelial activation, inflammation and vaso-occlusion in SCA and whether this protein holds promise as a potential therapeutic target for the disease. Disclosures: No relevant conflicts of interest to declare.

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Elevation of Hypercoagulability Markers in Hemoglobin SC Disease

Blood ◽

10.1182/blood.v120.21.3227.3227 ◽

2012 ◽

Vol 120 (21) ◽

pp. 3227-3227

Author(s):

Marina P Colella ◽

Erich V De Paula ◽

Nicola Conran ◽

João Machado-Neto ◽

Susan K.P. Quaino ◽

...

Keyword(s):

Pulmonary Embolism ◽

Plasma Levels ◽

Conflicts Of Interest ◽

Statistical Significance ◽

Rank Test ◽

Coagulation Activation ◽

Activation Markers ◽

Clinical Complications ◽

Thrombotic Complications ◽

Hemoglobin Sc Disease

Abstract Abstract 3227 Background: Sickle cell anemia (SCA) patients present an elevated rate of thrombotic complications and increased biological markers of hemostatic activation. Hemoglobin SC disease (HbSC) is the second most prevalent hemoglobinopathy after SCA (homozygous HbSS), has specific clinical and pathological characteristics that may differ from SCA, and viscosity appears to be a hallmark of the disease. Studies have shown an increase in thrombotic events in HbSC patients, especially pulmonary embolism, however, not much is known about the coagulation activation in this population. We herein aimed to evaluate the hypercoagulability markers in HbSC disease and their associations with patients' clinical and laboratory characteristics. Patients and Methods: This was a cross-sectional study performed on a cohort of 41 adult HbSC (mean age of 43 years) and 58 adult HbSS patients (mean age of 36 years), all in steady-state, and 25 healthy age-matched controls. We evaluated the expression of tissue factor (TF), the physiological initiator of coagulation, and thrombin-antithrombin complex (TAT), a final marker of coagulation activation. Leukocyte TFmRNA expression was analyzed by real time quantitative PCR and TAT plasma levels were measured by ELISA. Comparisons between the two patient groups and controls were performed using Kruskal-Wallis test followed by Dunn's Multiple Comparisons test. Fisher's exact test and Mann-Whitney's U test were used to compare patients' clinical complications and laboratory characteristics. Spearman's rank test was used for correlations analysis. Results: Relative TF mRNA expression was significantly up-regulated in HbSC patients when compared to controls (2.6 vs. 1.2), however levels of TF were lower in HbSC than HbSS patients (2.6 vs. 3.3) (P<0.0001). Confirming the biological relevance of TF expression, TAT plasma levels were also higher in HbSC patients in comparison to controls (4.2 vs. 2.4), and lower in HbSC than HbSS patients (4.2 vs. 7.3); (P<0.0001). In the analyses of the HbSC cohort, TAT levels presented significant positive correlations with inflammation markers: leukocyte (r=0.5; P=0.001), monocyte (r=0.4; P=0.01), and platelet counts (r=0.5; P=0.002); and hemolysis markers: reticulocyte counts (r=0.4; P=0.01) and lactate dehydrogenase levels (r=0.6, P=0.0001). We also evaluated associations between TAT levels and clinical complications: stroke, pulmonary arterial hypertension, acute thoracic syndrome, retinopathy, osteonecrosis, leg ulcers, autosplenectomy and microalbuminuria. HbSC patients with retinopathy had significantly higher TAT levels (4.7 vs. 3.9; P=0.03) when compared with patients without this complication. TAT levels were also higher in patients with autosplenectomy (4.8 vs. 3.8; P=0.004), and in patients with osteonecrosis, although this had borderline statistical significance (4.6 vs. 3.9; P=0.06). TF expression significantly correlated with monocyte counts (r=0.6; P=0.01). Conclusions: Our results indicate that HbSC disease patients present elevated coagulation activation markers when compared to controls, although not as intense as seen in SCA. Thrombotic complications in HbSC patients have been mainly linked to the hyperviscosity present in this disease. Our data suggest that inflammation and hemolysis are also important factors contributing to hemostatic activation, which may participate in the pathophysiology of very prevalent chronic complications of HbSC disease: retinopathy and osteonecrosis. Interestingly, in our cohort, patients with autosplenectomy had higher levels of pro-coagulant markers, possibly due to a higher intravascular hemolytic rate and elevated peripheral blood counts. Although HbSC disease is considered a milder form of SCA, autopsy studies have shown that mortality by pulmonary embolism is more frequent in HbSC disease than in SCA, being the second cause of mortality in these patients (Manci et al, 2003). Studies addressing the pathophysiology of coagulation activation in HbSC disease are lacking. Low numbers of cases of HbSC disease are usually included in studies focusing mainly in SCA, and the results are very variable, probably due to the small numbers of patients. In view of the high prevalence and morbimortalilty of thrombotic complications in this population, we believe that future studies should focus on a better understanding of hypercoagulability in HbSC disease. Disclosures: No relevant conflicts of interest to declare.

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Tissue factor promotes activation of coagulation and inflammation in a mouse model of sickle cell disease

Blood ◽

10.1182/blood-2012-04-424143 ◽

2012 ◽

Vol 120 (3) ◽

pp. 636-646 ◽

Cited By ~ 63

Author(s):

Pichika Chantrathammachart ◽

Nigel Mackman ◽

Erica Sparkenbaugh ◽

Jian-Guo Wang ◽

Leslie V. Parise ◽

...

Keyword(s):

Endothelial Cell ◽

Sickle Cell Disease ◽

Tissue Factor ◽

Sickle Cell ◽

Plasma Levels ◽

Cell Injury ◽

Vascular Inflammation ◽

Cell Disease ◽

Endothelial Cell Injury ◽

Cell Adhesion Molecule 1

Abstract Sickle cell disease (SCD) is associated with a complex vascular pathophysiology that includes activation of coagulation and inflammation. However, the crosstalk between these 2 systems in SCD has not been investigated. Here, we examined the role of tissue factor (TF) in the activation of coagulation and inflammation in 2 different mouse models of SCD (BERK and Townes). Leukocytes isolated from BERK mice expressed TF protein and had increased TF activity compared with control mice. We found that an inhibitory anti-TF antibody abrogated the activation of coagulation but had no effect on hemolysis or anemia. Importantly, inhibition of TF also attenuated inflammation and endothelial cell injury as demonstrated by reduced plasma levels of IL-6, serum amyloid P, and soluble vascular cell adhesion molecule-1. In addition, we found decreased levels of the chemokines MCP-1 and KC, as well as myeloperoxidase in the lungs of sickle cell mice treated with the anti-TF antibody. Finally, we found that endothelial cell-specific deletion of TF had no effect on coagulation but selectively attenuated plasma levels of IL-6. Our data indicate that different cellular sources of TF contribute to activation of coagulation, vascular inflammation, and endothelial cell injury. Furthermore, it appears that TF contributes to these processes without affecting intravascular hemolysis.

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Protective Effect of Fetal Hemoglobin On Inflammation-Induced Expression of Hypoxia-Inducible Factor-1α (HIF-1α) in Sickle Mice: Microvascular Implications

Blood ◽

10.1182/blood.v120.21.3250.3250 ◽

2012 ◽

Vol 120 (21) ◽

pp. 3250-3250

Author(s):

Dhananjay K. Kaul ◽

Mary E. Fabry ◽

Sandra M Suzuka ◽

Janki Shah

Keyword(s):

Oxidative Stress ◽

Sickle Cell Disease ◽

Sickle Cell ◽

Conflicts Of Interest ◽

Hypoxia Inducible Factor ◽

Heme Oxygenase 1 ◽

No Production ◽

Cell Disease ◽

Activation Markers ◽

No Bioavailability

Abstract Abstract 3250 Chronic inflammation is a salient feature of human sickle cell disease (SCD) and transgenic-knockout sickle (BERK) mouse model. Although tissue ischemia is the primary instigator of hypoxia-inducible factor (HIF) activation, a number of inflammatory factors/pathways and oxidative stress can potentially induce expression of HIF-1α. Increased oxidative stress and inflammation are implicated in the activation of HIF-1α under normoxic conditions. HIF can trigger transcription of genes for vasoactive molecules such as vascular endothelial growth factor (VEGF), heme oxygenase-1 (HO-1) and endothelin, which are implicated in the pathophysiology of SCD. We hypothesize that, in SCD, inflammation coupled with nitric oxide (NO) depletion will induce expression of HIF-1α. To this end, we have examined the expression of HIF-1α in normoxic BERK mice expressing exclusively human α- and βS- globins, and evaluated the effect of HbF in BERK mice (i.e., <1.0%, 20% and 40% HbF). We have previously shown that HbF exerts anti-sickling and anti-inflammatory effects (Kaul et al. J Clin Invest, 2004; Dasgupta et al. Am J Physiol, 2010). Here, we show that HIF-1α is expressed in BERK mice under normoxic conditions (i.e., normal hemoglobin oxygen saturation levels). In BERK mice expressing HbF, HIF-1α expression decreased concomitantly with increasing HbF, commensurately with increased NO bioavailability, and showed a strong inverse correlation with plasma NO metabolites (NOx) levels. Reduced HIF-1α expression in BERK mice expressing HbF was associated with decreased HO-1 and VEGF expression, and reduced serum endothelin-1 (ET-1) levels, which are among the target vasoactive molecules of HIF-1α. Furthermore, the commensurate decrease in HIF-1α expression with increase in HbF levels in BERK mice was accompanied by a distinct decrease in soluble (s) forms of endothelial activation markers such as sP-selectin and vascular cell adhesion molecule-1 (sVCAM-1). Notably, arteriolar dilation, enhanced volumetric blood flow and low blood pressure in normoxic BERK mice all showed a trend toward normalization with the introduction of HbF. Also, arginine treatment reduced HIF-1α expression as well as ET-1 levels in normoxic BERK mice, supporting a role of decreased NO bioavailability in HIF-1α activation. The present in vivo studies show that reduced inflammation and increased NO production in normoxic BERK mice (expressing HbF or treated with arginine) are distinctly associated with suppression of HIF-1α activation and inhibition of vasodilators, resulting in improved microvascular and hemodynamic parameters in the BERK model of sickle cell disease. The unique feature of inflammation in SCD is that it can be ameliorated by increased HbF, thereby coupling HbS polymerization/sickling to NO depletion, HIF-1α expression and inflammation in this disease. Disclosures: No relevant conflicts of interest to declare.

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Increased Platelet-Derived CD40L May Modulate Endothelial Cell ICAM-1 Expression and Interact With Leukocytes In Sickle Cell Anemia

Blood ◽

10.1182/blood.v122.21.974.974 ◽

2013 ◽

Vol 122 (21) ◽

pp. 974-974

Author(s):

Vanessa Tonin Garrido ◽

Renata Proença-Ferreira ◽

Venina M. Dominical ◽

Marcos André Cavalcanti Bezerra ◽

Aderson S. Araujo ◽

...

Keyword(s):

Flow Cytometry ◽

Endothelial Cells ◽

Steady State ◽

Sickle Cell ◽

Sickle Cell Anemia ◽

Repeated Measures ◽

Conflicts Of Interest ◽

Endothelial Activation ◽

Surface Expression ◽

Platelet Surface

Abstract Background Vaso-occlusive events are a major cause of morbidity in sickle cell anemia (SCA) and attributable to the abnormal adhesion of red cells and leukocytes to the endothelium. Platelets may contribute to the chronic inflammation and endothelial activation that initiates the vaso-occlusive process. We hypothesized that platelet-associated CD40 ligand (CD40L) may contribute to platelet-mediated inflammatory responses in SCA. Aims This study evaluated the platelet (PLT) release of CD40L, the expression of its receptor (CD40) on platelets, neutrophils, lymphocytes and monocytes of control individuals (CON) and SCA patients, and also the ability of platelet-derived CD40L to activate endothelial cells. Methods IL-8, soluble ICAM-1, VCAM-1 and CD40L were determined in PLT-free plasma or the supernatant of stimulated (ADP or Collagen) and unstimulated PLTs (2•10⁸/mL in Kreb’s buffer), from CON individuals and steady-state SCA patients, by ELISA. Flow cytometry was used to analyze CD40 expression on platelets, neutrophils, lymphocytes and monocytes from the peripheral blood of the study’s subjects. Human umbilical vein endothelial cells (HUVECs) were cultured (1x106cells/well; 37°C, 5% CO2) together with PLTs (3x108PLTs/well) from CON individuals or steady-state SCA patients for 24h, 37°C, 5%CO2, in the presence, or not, of blocking antibodies against CD40L. After incubation, PLTs were removed and HUVECs analyzed by flow cytometry for CD54 (ICAM-1) surface expression. Results SCA individuals presented elevated levels of plasma CD40L (724.4± 55.7 pg/ml; n=90) compared to CON (241.5±34.6 pg/ml; n=41; P<0.0001) and these levels correlated with PLT counts (rs=0.255; P=0.015). No correlation was found between plasma CD40L and plasma IL-8, ICAM-1 or VCAM-1. PLT release of CD40L (90 min, 37°C, 5%CO2) was evaluated; PLTs of SCA patients released higher quantities of CD40L (8347±1464 pg/108 PLTs; n=10) than PLTs of CON individuals (3652±568 pg/108 PLTs; n=5; P=0.019). CD40L release from SCA PLTs was augmented by incubation with collagen (P<0.001), but not ADP. Expression of the CD40 receptor on the platelet surface was elevated in the SCA group (52.4±2.7% positive cells; n=23), compared to the CON group (36.8±3.7% positive cells; n=9; P=0.005). The surface expression of CD40 was also elevated on neutrophils (SCA, 10.4±1.5% positive cells, n=14; CON, 5.5±1.1% positive cells, n=13; P=0.03), lymphocytes (SCA, 8.3±0.8% positive cells, n=16; CON, 3.6±0.4% positive cells, n=14; P<0.001) and monocytes (SCA 69.6±5.9% positive cells, n=16; CON, 49.9±5.8% positive cells, n=14; P=0.03) of SCA patients, compared to controls. ICAM-1 expression on the surface of HUVECs (Basal expression 32.8±1.8%, n=11) was significantly increased following incubation with SCA PLTs (54.0±4.8%, n=11, p<0.0001) and slightly augmented after incubation with CON PLTs (40.8±3.1%, n=11, p<0.05; Repeated measures ANOVA). Interestingly, when HUVECs and SCA PLTs were incubated with a blocking antibody against CD40L, the increase in ICAM-1 expression was significantly reversed on HUVECs (HUVECs, 28.1±0.2%, n=6; HUVECs+SCA PLTs, 42.0±3.3%, n=6; HUVECs+SCA PLTs+anti-CD40L 28.9±1.5%, n=6; P<0.01). Conclusions Plasma levels and platelet release of CD40L were found to be significantly elevated in SCA, in association with increased expressions of the CD40 receptor on SCA PLTs, neutrophils, lymphocytes and monocytes, possibly indicating a CD40L-mediated crosstalk between platelets and leukocytes in SCA. Platelets from SCA patients can induce adhesion molecule expression on the surface of endothelial cells in vitro, and this up-regulation may be modulated by platelet-derived CD40L. Results suggest that the CD40/CD40L pathway may be altered in SCA and that platelets may participate in this up-regulation. Given the potent inflammatory effect of this cytokine, a role for platelets and this cytokine in endothelial activation, inflammation and consequent vaso-occlusion, is likely. Disclosures: No relevant conflicts of interest to declare.

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FXIIa Differentially Regulates Thrombin Generation during Steady State and Vaso-Occlusive Crisis in Sickle Cell Mice

Blood ◽

10.1182/blood.v128.22.162.162 ◽

2016 ◽

Vol 128 (22) ◽

pp. 162-162 ◽

Cited By ~ 4

Author(s):

Erica M Sparkenbaugh ◽

Camille Faes ◽

Denis Noubouossie ◽

Daniel K. Kirchhofer ◽

András Gruber ◽

...

Keyword(s):

Steady State ◽

Mouse Model ◽

Vascular Permeability ◽

Sickle Cell ◽

Plasma Levels ◽

Thrombin Generation ◽

Conflicts Of Interest ◽

Control Group ◽

Liver And Kidney

Abstract Sickle cell disease (SCD) is associated with chronic activation of coagulation. Previously, we demonstrated that inhibition of tissue factor (TF) attenuates thrombin generation (measured by plasma levels of thrombin-antithrombin complexes [TAT]) in a mouse model of SCD during steady state. Furthermore, we showed that neither inhibition of FXIIa-dependent activation of FXI (using 14E11 antibody) nor FXI deficiency reduces thrombin generation (TG) in sickle mice. In contrast, genetic deficiency of FXII or kininogen (HK) reduced plasma TAT levels. These data suggest that during steady state, FXIIa contributes to TG in sickle mice via activation of the kallikrein/HK pathway, but not FXI. In the present study, we further investigated the mechanisms of HK-induced TG at steady state, and increased TG observed during vaso-occlusive crisis (VOC). All experiments were performed using 4-5 month old Townes SS (sickle) and AA (control) mice. Kallikrein cleaves HK into HK fragments (HKFs) and bradykinin (BK). First, we investigated whether a BK-mediated increase in vascular permeability contributes to TG by exposing perivascular TF. This hypothesis was disproved by data demonstrating no difference in vascular permeability (measured by the extravasation of Evans blue in the heart, lung, liver and kidney) between AA (n=8) and SS (n=10) mice. HKFs were shown to induce leukocyte TF expression in vitro via binding to CD11b/CD18 (Mac-1). Therefore, we investigated whether Mac-1 inhibition affects TG in SS mice. AA and SS mice were treated with an inhibitory anti Mac-1 (M1/70) or IgG control antibody on days 0, 3 and 6 (i.p. 1 mg/kg) and TG was analyzed 1 day after the last injection. In the control group, SS mice demonstrated higher plasma TAT levels compared to AA mice (8.1±1.6 vs 4.2±0.6 ng/mL, n=10-11, p<0.05), but inhibition of Mac-1 significantly reduced plasma TAT levels in SS mice (4.6±0.7 ng/mL, n=11, p<0.05). These data suggest that HK might contribute to TG during steady state via Mac-1-dependent induction of monocyte TF. The steady state of SCD is interspersed with acute periods of VOC. Clinical data demonstrate that compared to the steady state, plasma levels of cell free DNA (cfDNA), activation of the contact system, and TG are further enhanced during VOC. To determine the mechanism of increased TG during VOC, we used the previously characterized mouse model of TNFα -induced VOC. Townes AA and SS mice were injected with recombinant TNFα (2 µg/g body weight) or the same volume of PBS, and plasma was collected 5 hours later. TNFα not only dramatically increased plasma levels of cfDNA in SS mice (14.78 ± 1.64 vs 679 ± 300 ng/mL; p<0.01), but also further increased plasma TAT levels compared to those observed in PBS-treated SS mice (2.9 fold, p<0.001, n=8). Importantly, there was a significant positive correlation between cfDNA and TAT in SS mice (r2 =0.65, p<0.001). Since cfDNA can activate FXII, we determined whether FXIIa-dependent activation of FXI contributes to TG during VOC. AA and SS mice received 14E11 or IgG control (4 mg/kg) 30 minutes before TNFα (2 μg/g) or PBS injection, and plasma TAT was assessed 5 hours later. Strikingly, 14E11 attenuated the increased TAT level in TNFα-treated SS mice, to the level observed in SS mice injected with PBS and IgG (IgG/SS/PBS: 9 ng/mL ± 1.8 vs. IgG/SS/TNF: 18.9 ± 3.6, p<0.001; 14E11/SS/TNF: 9.86 ± 0.72, p<0.05 vs. IgG/SS/TNF). We also determined if TF activity is required for the increased TG observed during VOC. Interestingly, inhibition of TF with an inhibitory 1H1 antibody (25 or 75 mg/kg injected i.p. 1 or 18 hours prior to TNFα, respectively) had no effect on the increased TG observed in TNFα treated SS mice. In aggregate, our data suggest that during the steady state of SCD, FXII-dependent TG is not FXI-dependent, but instead is mediated by a pathway involving HK, Mac-1 integrin and leukocyte TF. Furthermore, we propose that during VOC the massive release of cfDNA results in FXIIa-dependent FXI activation and enhances TG independently of TF. This study provides mechanistic insight into the initiators of TG in SCD. Moreover, it implicates FXIIa as a potential therapeutic target to reduce the prothrombotic state in SCD, during both steady state and VOC. Disclosures No relevant conflicts of interest to declare.

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Interleukin 8 Level, Reticulocyte Counting and aPTT Ratio in Brazilian Sickle Cell Anemia Patients with Leg Ulcers

Blood ◽

10.1182/blood.v118.21.4835.4835 ◽

2011 ◽

Vol 118 (21) ◽

pp. 4835-4835

Author(s):

Magnun N N Santos ◽

Eliel Wagner Faber ◽

Dulcinéia Martins Albuquerque ◽

Romulo Tadeu Dias Oliveira ◽

Marcos André Cavalcanti Bezerra ◽

...

Keyword(s):

Gene Expression ◽

Sickle Cell ◽

Sickle Cell Anemia ◽

Plasma Levels ◽

Conflicts Of Interest ◽

Organ Damage ◽

Northeastern Brazil ◽

Leg Ulcers ◽

Increased Risk ◽

History Of

Abstract Abstract 4835 Background: Sickle cell anemia (SCA) is characterized by a chronic inflammatory state in which oxidative stress, particularly in the endothelium, exerts a strong influence on the pathogenesis of vaso-occlusion and may be implicated in patients' clinical heterogeneity and survival. It has been suggested that the cytokine production profile of cells involved in the immune response may vary among patients with SCA. Leg ulcers (LU) represent a severe complication in these patients, and this condition has been associated with specific end-organ damage and an increase in morbidity and mortality. Recent studies have shown that venous obstruction, endothelial dysfunction, coagulopathy and infections are implicated in the complex pathogenesis of LU. Aims: To determine IL-1β, IL-6 and IL-8 plasma levels and gene expression rates as well as hematological and coagulation parameters and correlate these with the history of LU in adult SCA patients followed up at HEMOPE, in the state of Pernambuco, northeastern Brazil. Methods: Peripheral blood samples from 92 patients (median age 27 years; 42 female; 52 male; all Afro-descendants) in the steady state who had been diagnosed with SCA (HbSS), had not received a transfusion and were not using hydroxyurea were analyzed. Plasma levels of cytokines were determined by ELISA, and the gene expression rates by qRT-PCR. The patients' clinical and laboratorial characteristics were obtained from their medical charts. Statistical analysis was performed using the SAS System for Windows version 9.2. Results: Median age was higher in patients with a history of LU than in those without a history (33.1 vs. 28.4; p = 0.04). Although no statistically significant (p = 0.5) differences in IL-8 gene expression rates were observed, IL-8 plasma levels were significantly higher in patients with a history of LU than in patients without a history (23.8 vs. 7.7; p = 0.01) (Figure 1). Thus, patients with high levels of IL-8 had an increased risk for the occurrence of leg ulcers (OR = 1.01; 95% CI = 1.00–1.02). The ROC curve showed that IL-8 levels higher than 8.55 pg/mL could indicate the presence of LU (accuracy = 71.6%; sensitivity = 73.7%; specificity = 68.5%). The laboratory tests revealed reticulocyte counts and activated partial thromboplastin time (aPTT) ratios (R) that were significantly higher in patients with a history of LU than in those without a history (11.8 vs. 8.4, p = 0.01; 1.1 vs. 0.9, p = 0.04, respectively). Both the higher reticulocyte counts and R values were associated with increased risk for the occurrence of leg ulcers in these patients (OR = 1.12, 95% CI = 1.02 – 1.20; OR = 24.28, 95% CI = 1.20 – 486.09, respectively). Conclusion: In this study, patients who had had LU at some time in their lives showed significantly higher IL-8 levels, reticulocyte counts and R values than patients who had never had LU. Our results therefore suggest a relationship between the parameters described above and LU in patients with SCA. These parameters could perhaps be used, in association with different genetic modulators that may contribute to different clinical phenotypes observed in this disease, as markers of this clinical manifestation of SCA or of a propensity to develop it. Financial Support: CAPES (Brazil)/FAPESP/CNPq/INCTS Disclosures: No relevant conflicts of interest to declare.

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Four Cases of Aaplha Dysfibrinogenemia in Childhood

Blood ◽

10.1182/blood.v126.23.4697.4697 ◽

2015 ◽

Vol 126 (23) ◽

pp. 4697-4697

Author(s):

Roman Kotlín ◽

Eliška Ceznerova ◽

Stikarová Jana ◽

Alzbeta Hlavackova ◽

Ondrej Pastva ◽

...

Keyword(s):

Czech Republic ◽

Genetic Analysis ◽

Plasma Levels ◽

Fibrinogen Level ◽

Conflicts Of Interest ◽

Clinical Manifestations ◽

Bleeding Complications ◽

Thrombin Time ◽

Fibrin Polymerization ◽

Thrombotic Complications

Abstract Introduction Hemostasis in childhood differs from that of adults; and the hemostatic system is still developing during childhood. These differences offer a protective advantage to children with hemorrhagic and thrombotic complications. Plasma levels of coagulation factors (except for fibrinogen, factor V and factor VIII), as well as plasma levels of protein C, protein S and antithrombin are reduced. Hereditary dysfibrinogenemia is a rare disorder wherein an inherited abnormality in fibrinogen structure may result in defective fibrin function and/or structure. Clinical symptoms may vary from asymptomatic to life-threatening bleeding complications. Venous or arterial thrombotic complications occur extremely rarely during childhood. Fibrinogen, a key component in hemostasis, is a 340-kDa glycoprotein. The molecule consists of three different pairs of polypeptide chains (Aa, Bb, and g) each encoded by a distinct gene (FGA, FGB, and FGG). N-terminal parts of the Aa chain - fibrinopeptides A and the Bb chain - fibrinopeptides B are situated in the central part of the molecule and block polymerization of the molecules. Conversion of fibrinogen to fibrin occurs after the cleavage of N-terminal fibrinopeptides by the serine protease thrombin. Correct conformation of fibrinopeptides is important for the cleavage by thrombin. Methods Routine coagulation tests were performed with citrated plasma samples on a STA-R coagulation analyzer. The functional fibrinogen level was measured by the Clauss method. Total fibrinogen level was determined by an immunoturbidimetric assay performed on a UV-2401PC spectrophotometer. Fibrin polymerization induced by either thrombin or reptilase and fibrinolysis experiments were obtained by the turbidimetrical method. Fibrinopeptide release was measured as a function of time; and the fibrinopeptides were determined by the reversed-phase, high-performance liquid chromatography (RP-HPLC) method. The purified genomic DNA was amplified by polymerase chain reaction, using specific primers; and dideoxysequencing was performed with Dye Terminator Cycle Sequencing with a Quick Start kit and a CEQ 8000 genetic analysis system). Results We have examined four unrelated children suspected dysfibrinogenemia. The first patient was a 5-yr old boy with prolonged thrombin time and low functional fibrinogen level. He presented with easy bruising and epistaxis. Genetic analysis revealed a heterozygous substitution Aalpha R16H. The second patient was a 13-yr old girl with prolonged thrombin and reptilase times and low functional fibrinogen level. She presented with menorrhagia. Genetic analysis revealed a heterozygous substitution Aalpha G17V. The third patient was a 12-yr old asymptomatic boy. Genetic analysis revealed a heterozygous substitution Aalpha R16H. Kinetics of fibrinopeptide release was impaired in all these cases. The fourth patient was a 3-yr old girl with low functional fibrinogen level. She presented with easy bruising. Genetic analysis revealed a heterozygous substitution Aalpha K448N. All patients presented with impaired fibrin polymerization. Conclusion All patients were found to be heterozygous for point mutations in FGA gene. Three mutations were found in the site of fibrinopeptide cleavage and one in the alphaC-domain. Mutations had different clinical manifestations from asymptomatic to bleeding. Mutations Aalpha Arg16His and Aalpha Gly17Val are among the most common fibrinogen mutations and both decelerate fibrinopeptide A cleavage from mutant fibrinogens. We describe here a novel previously unreported mutation Aalpha Lys448Asn affecting fibrin formation. Acknowledgment This work was supported by the project of the Ministry of Health of the Czech Republic for conceptual development of the research organization 00023736, by Grant from the Academy of Sciences, Czech Republic (P205/12/G118), and by ERDF OPPK CZ.2.16/3.1.00/28007. Disclosures No relevant conflicts of interest to declare.

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Regulating Transcriptional Co-Activator PGC-1α for the Treatment of Sickle Cell Disease

Blood ◽

10.1182/blood-2018-99-111022 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 2358-2358

Author(s):

Alawi Habara ◽

Cuong LE ◽

George J Murphy ◽

David H.K. Chui ◽

Martin H. Steinberg ◽

...

Keyword(s):

Sickle Cell Disease ◽

Sickle Cell ◽

Bone Marrow Cells ◽

Conflicts Of Interest ◽

Globin Gene ◽

Human Umbilical Cord Blood ◽

Human Umbilical Cord ◽

Globin Genes ◽

Cell Disease ◽

Erythroid Progenitor

Abstract Sickle cell disease (SCD) is the most common inherited human hematologic disease, which causes hemolytic anemia, pain, disability, progressive multi-organ damage and early mortality. Clinical studies have shown that increased synthesis of fetal hemoglobin (HbF) in sickled erythroid cells leads to diminished severity of many clinical features of SCD. Therefore, therapeutic agents that can increase HbF production will be of benefit to SCD patients. Hydroxyurea (HU) is the FDA-approved therapeutic for treatment of SCD, but not all patients respond favorably or adequately. Therefore, other methods of targeting HbF are highly desired, particularly those that act by different mechanisms that might be used in combination with HU or alone (for those who do not tolerate HU). We recently identified PPARγ co-activator (PGC-1α) as a new protein involved in the regulation of the fetal globin genes. Forced overexpression of PGC-1α in vitro by adenovirus infection in bone marrow cells from SCD mice resulted in significantly increased human γ- and murine εy- and βh1-globin genes. Furthermore, up-regulation of PGC-1α by a small molecular agonist (Compound Z) in human umbilical cord blood-derived erythroid progenitor (HUDEP-1) cells markedly increases γ-globin gene expression and HbF synthesis. The highest response was achieved when HUDEP-1 cells were treated with 5µM Compound Z for 2 days, which results in 66.6% HbF+ cells compared to vehicle control (29.5% HbF+ cells). The effect of Compound Z in inducing HbF was further validated in erythroblasts derived from cultures of normal adults' CD34+ cells as well as in iPSC-derived sickle erythroblasts (SS24 cells). These data suggest that modulating PGC-1α activity may be effectively applied to the treatment of SCD since enhanced HbF synthesis would alleviate pathophysiological effects of SCD. Disclosures No relevant conflicts of interest to declare.

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Association of Endothelial Biomarkers with Cerebral MRI Perfusion Analysis in Patients with Sickle Cell Disease

Blood ◽

10.1182/blood-2019-124688 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 1000-1000

Author(s):

Liza Afzali-Hashemi ◽

Lena Vaclavu ◽

Erfan Nur ◽

Aart J Nederveen ◽

Bart J. Biemond

Keyword(s):

Sickle Cell Disease ◽

Sickle Cell ◽

Adhesion Molecule ◽

Plasma Levels ◽

Cerebral Perfusion ◽

Endothelial Activation ◽

Healthy Controls ◽

Standard Laboratory ◽

Cell Disease ◽

Laboratory Parameters

Introduction Sickle cell disease (SCD) is associated with silent cerebral infarcts (SCI) which are related to neurocognitive damage. One of the major causes of SCI is the impaired cerebral oxygenation, which makes cerebral blood flow (CBF) an essential parameter to measure. Previous hemodynamic studies have shown elevated CBF and reduced cerebrovascular reserve (CVR) in patients with SCD (Helton 2015; Václavů 2018). CVR is known as the increase of CBF in response to vasoactive stimulus, relative to the baseline. The reduced CVR renders SCD patients susceptible to cerebral ischemia, especially under hypotensive or hypoxic conditions. Possible factors contributing to microvascular damage and thus reduced CVR include hemoglobin S polymerization, neutrophil activation and endothelial activation and adhesion. Previous studies examined the role of these factors in patients with SCD (Sins 2017; Al Najjar 2017). However, the association between the endothelial biomarkers and hemodynamic parameters is unknown in adult patients with SCD. In this study, we investigated the correlation between CBF and CVR and the adhesion molecules including sVCAM-1, sP-selectin, VWF-Ag and ADAMTS13. Additionally, we studied the association of these endothelial biomarkers with standard laboratory parameters. Methods This study was performed in accordance with the Declaration of Helsinki and was approved by the Review Board of Amsterdam UMC. For this study, 33 steady state patients with SCD (mean age 32.1 ± 10.7, 64% male, 29 HbSS, 4 HbSß) and 10 healthy volunteers (mean age 36,4 ± 15.9, 60% male, 2 HbAS, 8 HbAA) were included. Hematologic laboratory parameters were assessed using standard laboratory procedures. Plasma levels of sVCAM-1 and sP-selectin were determined using ELISA (R&D Systems, USA) and ADAMTS13 and VWF-Ag were measured with the INNOVANCE assay (Siemens Healthcare Diagnostics). For the CBF measurements, pseudo-continuous arterial spin labelling (pCASL) was acquired at 3T MRI (Philips Healthcare, The Netherlands). CBF was measured before and after acetazolamide (vasoactive stimulus) administration and subsequently CVR was calculated using the following equation: CVR = (CBFafter - CBFbefore) / CBFbefore x 100% Plasma levels of endothelial biomarkers were compared between groups using ANOVA test. Correlation between the parameters were measured using single regression model where p<0.05 was considered as statistically significant. Results sVCAM-1 levels and VWF-Ag were significantly higher in SCD patients compared to healthy controls (p < 0.01 and p = 0.01). ADAMTS13 and sP-selectin were not significantly different between the two groups (p = 0.06 and p = 0.33). sVCAM-1 was significantly associated with CBF, and parameters of hemolysis LDH and bilirubin in SCD patients (Fig. 1A and 2C). Negative correlation was observed between sVCAM-1 and hemoglobin (Fig. 1B). The relationship between sVCAM-1 and hemodynamic and laboratory parameters are shown in Table 1. No significant correlation was found between sVCAM-1, hemodynamic and standard laboratory parameters in healthy controls. VWF-Ag, ADAMTS13 and sP-selectin were not significantly associated with hemodynamic MRI parameters. Discussion Our results show elevated sVCAM-1 levels in sickle cell patients, strongly related to CBF. sVCAM-1 is an adhesion molecule and elevated plasma levels are found in patients with endothelial activation due to inflammation or atherosclerosis (Cook-Mills 2013; Cybulsky 2001). Previous studies showed elevated levels in sickle cell disease but no correlation with parameters of cerebral perfusion have been demonstrated yet (Antwi-Boasiako 2018; Kato 2005). The strong correlation with CBF is mostly related to the chronic hemolysis given the association found with hemoglobin levels and markers of hemolysis like LDH and bilirubin. In contrast to sVCAM-1, no such relation was found with other markers of endothelial activation such as VWF activity and sP-selectin levels. No correlation between endothelial markers and the CVR was demonstrated, suggesting that endothelial damage itself may not related to the impaired cerebral vasodilatation in response to a vasoactive stimulus. Conclusion Endothelial adhesion molecule sVCAM-1 showed a strong correlation with CBF and parameters of hemolysis, suggesting a relation between the hemolytic damage of endothelial cells and impaired cerebral perfusion. Disclosures Nur: Novartis Pharmaceuticals: Consultancy.

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