Role of Lu/BCAM in abnormal adhesion of sickle red blood cells to vascular endothelium

AbstractA number of lines of evidence now support the hypothesis that vaso-occlusion and several of the sequelae of sickle cell disease (SCD) arise, at least in part, from adhesive interactions of sickle red blood cells, leukocytes, and the endothelium. Both experimental and genetic evidence provide support for the importance of these interactions. It is likely that future therapies for SCD might target one or more of these interactions.

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Effects of Pan-Selectin Antagonist GMI-1070 on the Treatment of Vaso-Occlusion in Sickle Cell Mice

Blood ◽

10.1182/blood.v112.11.535.535 ◽

2008 ◽

Vol 112 (11) ◽

pp. 535-535 ◽

Cited By ~ 2

Author(s):

Jungshan Chang ◽

John T Patton ◽

Paul S. Frenette ◽

John L. Magnani

Keyword(s):

Blood Flow ◽

Red Blood Cells ◽

Sickle Cell ◽

Small Molecule ◽

Vascular Endothelium ◽

Intravital Microscopy ◽

Blood Cells ◽

Tnf Α ◽

Sickle Red Blood Cells ◽

Adherent Leukocytes

Abstract Acute vaso-occlusion (VOC) in patients with sickle cell disease (SCD) induces intense pain arising from organ damage and is the major cause of morbidity and mortality. Hypoxia and abnormal sickle red blood cells (RBC) induce inflammatory mediators and activation of the vascular endothelium leading to the recruitment of adherent leukocytes and sickle RBC followed by aggregates that eventually occlude blood flow. Previous studies have implicated the critical roles of cell adhesion molecules E- and P-selectins by using intravital microscopy in SCD mice (Berkeley strain) with altered genetic backgrounds (SCD transplanted in recipients lacking E-and P-selectins), or antibodies against endothelial selectins, or small molecules directed against the selectins. Here, we designed a treatment protocol for this SCD mouse model, in which a small molecule pan-selectin antagonist (GMI-1070) is administered to sickle cell mice late in the process of established vaso-occlusion in order to test the effects of GMI-1070 in a more clinically relevant model. GMI-1070 is a small molecule pan-selectin antagonist designed on the bioactive conformation of the carbohydrate ligand and inhibits leukocyte adhesion to activated endothelium in vitro with particularly strong activity against E-selectin (IC50 = 3.4 μM). Berkeley SCD mice were generated by bone marrow transplantation into lethally irradiated C57BL/6 male mice and the fully engrafted (100% donor RBC chimerism) mice were used for intravital microscopy experiments. VOC events were induced by injection with TNF-α at time 0 and the formation of occlusions were allowed to proceed as long as possible just prior to the death of the control mice. GMI-1070 (20 mg/kg) or vehicle (PBS pH 7.4) were administered at t = 110 min. Post-capillary and collecting venules in the cremaster muscle were analyzed for effects on an established VOC event. Under these conditions, GMI-1070 significantly increased the microcirculatory blood flow to levels observed in non-sickle cell mice (vehicle: 237 ± 15 nL/sec; GMI-1070: 533 ± 58 nL/sec; p<0.0001). The recruitment of adherent leukocytes to the vascular endothelium was also significantly reduced (vehicle: 2235 ± 156; GMI-1070: 1270 ± 203 cells/mm2; p=0.0013), and there were significant and dramatic reductions in the capture of sickle red blood cells to adherent leukocytes (vehicle: 0.68 ± 0.27; GMI-1070: 0.03 ± 0.01 interactions/WBC, min, 100ml; p=0.0003). Mice began to succumb to VOC within 2.5 hours after injection of TNF-α and surgical trauma which continued until all of the control SCD mice died. Administration of GMI-1070 prevented the death of half of the treated mice within the timeframe of the experiment and extended the median survival of mice from 5 hours (control, vehicle-treated) to greater than 9 hours for the GMI-1070- treated SCD mice (p = 0.0067). These studies show that GMI-1070 can significantly and dramatically improve the condition and survival of the animals with a severe VOC even when dosed well after the initiating challenge. Thus these data strongly support the use of GMI-1070 for the treatment of patients in acute vaso-occlusive crisis. GMI-1070 is currently in a Phase I clinical trial.

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The Role of Lactadherin in the Phagocytosis of Phosphatidylserine-Expressing Sickle Red Blood Cell by Macrophages.

Blood ◽

10.1182/blood.v106.11.3773.3773 ◽

2005 ◽

Vol 106 (11) ◽

pp. 3773-3773

Author(s):

Swapan K. Dasgupta ◽

Perumal Thiagarajan

Keyword(s):

Flow Cytometry ◽

Red Blood Cells ◽

Sickle Cell ◽

Blood Cells ◽

Milk Fat ◽

Integrin Αvβ3 ◽

Fold Increase ◽

Anionic Phospholipid ◽

Sickle Red Blood Cells

Abstract Sickle cell anemia, the most common serious hemoglobinopathy, is associated with a markedly reduced life span of red blood cells due to their preferential clearance by macrophages. During polymerization of sickle hemoglobin, phosphatidylserine, an anionic phospholipid normally present exclusively on the inner leaflet of the membrane bilayer is exteriorized to outer leaflet. This exposure of phosphatidylserine is thought to be a tag for macrophage recognition. Lactadherin, also known as milk fat globule-EGF factor 8, is a phosphatidylserine-binding glycoprotein secreted by macrophages that promotes the engulfment of apoptotic cells. Here, we investigated the role of lactadherin in the phagocytosis of sickle red blood cells. The binding of fluorescein-lactadherin to normal and sickle red blood cells was studied by flow cytometry. We quantified the effect of lactadherin on phagocytosis of red blood cells by monocyte-derived macrophage. In normal individuals, less than 0.5% of red blood cells showed any binding to lactadherin when analyzed by flow cytometry. However, in sickle cell patients, circulating red blood cells showed 2 to 10- fold increase in lactadherin binding (P<0.0002). Lactadherin stimulated the phagocytosis of resting sickle red blood cells by macrophages but had no significant effect on the phagocytosis of normal red blood cells. Deoxygenation of sickle red blood cells further increased the lactadherin binding and phagocytosis. Antibodies to integrin αVβ3 also inhibited macrophage binding and phagocytosis. These results show lactadherin may play a major role in sickle red cell clearance by anchoring the phosphatidylserine-expressing sickle red blood cells to integrins on tissue macrophages.

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t-BOOH-induced oxidative damage in sickle red blood cells and the role of flavonoids

Biomedicine & Pharmacotherapy ◽

10.1016/s0753-3322(03)00018-0 ◽

2003 ◽

Vol 57 (3-4) ◽

pp. 124-129 ◽

Cited By ~ 50

Author(s):

M. Cesquini ◽

M.A. Torsoni ◽

G.R. Stoppa ◽

S.H. Ogo

Keyword(s):

Oxidative Damage ◽

Red Blood Cells ◽

Blood Cells ◽

Sickle Red Blood Cells

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Role of Calcium in Phosphatidylserine Externalisation in Red Blood Cells from Sickle Cell Patients

Anemia ◽

10.1155/2011/379894 ◽

2011 ◽

Vol 2011 ◽

pp. 1-8 ◽

Cited By ~ 11

Author(s):

Erwin Weiss ◽

David Charles Rees ◽

John Stanley Gibson

Keyword(s):

Red Blood Cells ◽

Sickle Cell ◽

Blood Cells ◽

Phosphatidylserine Exposure ◽

Channel Inhibition ◽

Cation Conductance ◽

Gardos Channel ◽

Cation Permeability

Phosphatidylserine exposure occurs in red blood cells (RBCs) from sickle cell disease (SCD) patients and is increased by deoxygenation. The mechanisms responsible remain unclear. RBCs from SCD patients also have elevated cation permeability, and, in particular, a deoxygenation-induced cation conductance which mediates entry, providing an obvious link with phosphatidylserine exposure. The role of was investigated using FITC-labelled annexin. Results confirmed high phosphatidylserine exposure in RBCs from SCD patients increasing upon deoxygenation. When deoxygenated, phosphatidylserine exposure was further elevated as extracellular [] was increased. This effect was inhibited by dipyridamole, intracellular chelation, and Gardos channel inhibition. Phosphatidylserine exposure was reduced in high saline. levels required to elicit phosphatidylserine exposure were in the low micromolar range. Findings are consistent with entry through the deoxygenation-induced pathway (), activating the Gardos channel. [] required for phosphatidylserine scrambling are in the range achievablein vivo.

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