Glycophorin C in atherosclerotic plaque is associated with major adverse cardiovascular events after carotid endarterectomy.

Introduction Histological assessment studies have identified the presence of intraplaque hemorrhage (IPH) as an indicator of plaque instability and resulting ischemic cerebral sequelae. Although the presence of IPH has been studied extensively in relation to neurological symptoms preceding carotid endarterectomy (CEA) or as a predictor for postoperative risk of major adverse cardiovascular events (MACE), the degree of IPH has not been studied before. Glycophorin, an erythrocyte-specific protein, has been suggested as a marker for the degree of previous hemorrhages in atherosclerotic plaque since erythrocytes are prominently present in IPH. We hypothesized that quantified plaque glycophorin C, as a proxy for the degree of IPH, is associated with destabilizing plaque characteristics, preprocedural symptoms, and increased postoperative risk for MACE. Methods We quantified glycophorin C and six other plaque characteristics with the slideToolkit method. We used human atherosclerotic plaque samples from 1971 consecutive asymptomatic and symptomatic (carotid endarterectomy) patients in the Athero-Express Biobank. Results The total area of glycophorin C in plaque was larger in individuals with a plaque with IPH compared to individuals with plaque without IPH (p<0.001). Quantified glycophorin C was significantly associated with ipsilateral pre-procedural neurological symptoms (OR:1.27, 95%CI:1.06-1.41, p=0.005). In addition, quantified glycophorin C was independently associated with an increased postoperative risk for MACE (HR:1.31, 95%CI:1.01-1.68, p=0.04). Stratified by sex, quantified glycophorin C was associated with an increased postoperative risk for MACE in male patients (HR:1.50, 95%CI:1.13-1.97, p=0.004), but not in female patients (HR:0.70, 95%CI:0.39-1.27, p=0.23). Conclusion Quantified glycophorin C, as a proxy for the degree of IPH, was independently associated with the presence of IPH, symptomatic preprocedural symptoms, and with an increased three-year postoperative risk of MACE. These findings indicate that quantified plaque glycophorin C can be considered as a marker for identifying male patients with a high residual risk for secondary MACE after CEA.

The Gardos effect drives erythrocyte senescence and leads to Lu/BCAM and CD44 adhesion molecule activation

Senescence of erythrocytes is characterized by a series of changes that precede their removal from the circulation, including loss of red cell hydration, membrane shedding, loss of deformability, phosphatidyl serine exposure, reduced membrane sialic acid content, and adhesion molecule activation. Little is known about the mechanisms that initiate these changes nor is it known whether they are interrelated. In this study, we show that Ca2+-dependent K+ efflux (the Gardos effect) drives erythrocyte senescence. We found that increased intracellular Ca2+ activates the Gardos channel, leading to shedding of glycophorin-C (GPC)–containing vesicles. This results in a loss of erythrocyte deformability but also in a marked loss of membrane sialic acid content. We found that GPC-derived sialic acid residues suppress activity of both Lutheran/basal cell adhesion molecule (Lu/BCAM) and CD44 by the formation of a complex on the erythrocyte membrane, and Gardos channel–mediated shedding of GPC results in Lu/BCAM and CD44 activation. This phenomenon was observed as erythrocytes aged and on erythrocytes that were otherwise prone to clearance from the circulation, such as sickle erythrocytes, erythrocytes stored for transfusion, or artificially dehydrated erythrocytes. These novel findings provide a unifying concept on erythrocyte senescence in health and disease through initiation of the Gardos effect.

Rosetting revisited: a critical look at the evidence for host erythrocyte receptors in Plasmodium falciparum rosetting

Malaria remains a major cause of mortality in African children, with no adjunctive treatments currently available to ameliorate the severe clinical forms of the disease. Rosetting, the adhesion of infected erythrocytes (IEs) to uninfected erythrocytes, is a parasite phenotype strongly associated with severe malaria, and hence is a potential therapeutic target. However, the molecular mechanisms of rosetting are complex and involve multiple distinct receptor–ligand interactions, with some similarities to the diverse pathways involved in P. falciparum erythrocyte invasion. This review summarizes the current understanding of the molecular interactions that lead to rosette formation, with a particular focus on host uninfected erythrocyte receptors including the A and B blood group trisaccharides, complement receptor one, heparan sulphate, glycophorin A and glycophorin C. There is strong evidence supporting blood group A trisaccharides as rosetting receptors, but evidence for other molecules is incomplete and requires further study. It is likely that additional host erythrocyte rosetting receptors remain to be discovered. A rosette-disrupting low anti-coagulant heparin derivative is being investigated as an adjunctive therapy for severe malaria, and further research into the receptor–ligand interactions underlying rosetting may reveal additional therapeutic approaches to reduce the unacceptably high mortality rate of severe malaria.

Glycophorin-C sialylation regulates Lu/BCAM adhesive capacity during erythrocyte aging

Key Points The Lu/BCAM adhesion molecule is gradually activated during erythrocyte aging due to loss of sialic acid on glycophorin-C. Upon activation, Lu/BCAM engages a sialic acid–dependent interaction with the extracellular matrix protein laminin-α5.

Congenital Undifferentiated Pure Erythroid Leukemia

INTRODUCTION: Congenital pure erythroid leukemia (M6b) is exceedingly rare with only a few reported cases to date. Because of the extreme rarity, almost nothing is known about the pathogenesis, appropriate therapy and prognosis. Diagnosis of erythroid leukemia is usually based on the positivity for Glycophorin A, Glycophorin C or PAS staining. We report a first case of congenital pure erythroid leukemia expressing E-cadherin in the absence of Glycophorin A, Glycophorin C and PAS staining. We analyzed the cytogenetic abnormalities of this extremely rare disease. RESULTS: The patient was the first daughter of healthy and non-consanguineous Japanese parents, born at 40 weeks of gestation by emergency cesarean section in non-reassuring fetal state after uncomplicated pregnancy. Apgar score was 8/9. Characteristic facial appearance was not recognized. At birth, she presented with marked hepatomegaly, purpura and disseminated intravascular coagulation. White blood cell (WBC) count was 63.5x109/L with blastic cells with vacuoles. Although congenital leukemia was suspected, flow cytometric analyses using CD45 blast gating failed to demonstrate leukemic cells. Karyotype was 46, XX. Fluorescence in situ hybridization (FISH) for trisomy 21 and MLL split signal were negative. GATA1 mutation was not detected. WBC count has gradually decreased within 3-4 weeks with supportive care.However, liver failure, hemophagocytic lymphohistiocytosis and schistocytosis developed. Although treatment with dexamethasone and etoposide has started, multiple nodules appeared in the liver 11 weeks after birth. Liver biopsy demonstrated small round cell tumor with high N/C ratio and vacuoles infiltrating the liver. The tumor cells were immunohistochemically positive for CD43, CD71, E-cadherin, beta-catenin, Ki-67 and c-Myc and negative for CD45, CD20, CD10, PAX5, CD3, CD4, CD8, TdT, CD1a, CD34, CD56, cyMPO, c-kit, CD42b, CD61, Glycophorin A, Glycophorin C, tyrosine hydroxylase, PGP9.5, myogenin, glypican3, NKX2.2, CAM5.2 and Periodic Acid Schiff (PAS) staining etc. Flow cytometric analysis revealed CD43+ CD71+ CD36+ CD58+ cells within large CD45 negative cell population. These cells expressed almost no other hematopoietic cell markers used to screen for leukemia. These cells were indistinguishable from normal erythroblast based on surface markers only. However, flow cytometric cell sorting revealed these cells are blasts with vacuoles. Karyotype of tumor cells has changed to 50, XX, +7, +8, add(15)(q22), +19, add(19)(q13.1-13.3)×2, +21. Based on these results, she was diagnosed with pure erythroid leukemia. Low dose Cytosine Arabinoside improved her clinical symptoms. She is alive at 5 months of age. DISCUSSION: E-cadherin is a selective marker of immature erythroblast. In our case, E-cadherin was key in erythroid lineage assignment. To our knowledge, this is the first reported case of infantile pure erythroid leukemia expressing E-cadherin in the absence of Glycophorin A, Glycophorin C and PAS staining. These results suggest that the tumor cells originated from undifferentiated erythroblast. This disease entity should be recognized. Immunohistochemical staining of c-Myc showed strong positivity. The c-Myc gene is located on chromosome 8. FISH for c-Myc split signal was negative. G-banding and FISH revealed trisomy 8. Overexpression of c-Myc may be involved in the pathogenesis of this undifferentiated pure erythroid leukemia. At birth, karyotype was 46, XX and blasts in peripheral blood decreased with supportive care only. However, we observed changes in karyotype of blasts. We assume that second hit was added during clinical course. Whole exome sequencing analysis is in progress to reveal somatic and germline mutations underlying this unrecognized disease. Disclosures No relevant conflicts of interest to declare.