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Amsterdam-Zuidoost, Netherlands

Van Zwieten R.,Laboratory of Red Blood Cell Diagnostics | Verhoeven A.J.,University of Amsterdam | Roos D.,Laboratory of Red Blood Cell Diagnostics
Free Radical Biology and Medicine | Year: 2014

Red blood cells (RBCs) contain large amounts of iron and operate in highly oxygenated tissues. As a result, these cells encounter a continuous oxidative stress. Protective mechanisms against oxidation include prevention of formation of reactive oxygen species (ROS), scavenging of various forms of ROS, and repair of oxidized cellular contents. In general, a partial defect in any of these systems can harm RBCs and promote senescence, but is without chronic hemolytic complaints. In this review we summarize the often rare inborn defects that interfere with the various protective mechanisms present in RBCs. NADPH is the main source of reduction equivalents in RBCs, used by most of the protective systems. When NADPH becomes limiting, red cells are prone to being damaged. In many of the severe RBC enzyme deficiencies, a lack of protective enzyme activity is frustrating erythropoiesis or is not restricted to RBCs. Common hereditary RBC disorders, such as thalassemia, sickle-cell trait, and unstable hemoglobins, give rise to increased oxidative stress caused by free heme and iron generated from hemoglobin. The beneficial effect of thalassemia minor, sickle-cell trait, and glucose-6-phosphate dehydrogenase deficiency on survival of malaria infection may well be due to the shared feature of enhanced oxidative stress. This may inhibit parasite growth, enhance uptake of infected RBCs by spleen macrophages, and/or cause less cytoadherence of the infected cells to capillary endothelium. © 2013 Elsevier Inc. All rights reserved. Source

Van Zwieten R.,Laboratory of Red Blood Cell Diagnostics | Veldthuis M.,Laboratory of Red Blood Cell Diagnostics | Delzenne B.,University of Amsterdam | Berghuis J.,Laboratory of Red Blood Cell Diagnostics | And 5 more authors.
Hemoglobin | Year: 2014

More than 20,000 blood samples of individuals living in The Netherlands and suspected of hemolytic anemia or diabetes were analyzed by high resolution cation exchange high performance liquid chromatography (HPLC). Besides common disease-related hemoglobins (Hbs), rare variants were also detected. The variant Hbs were retrospectively analyzed by capillary zone electrophoresis (CZE) and by isoelectric focusing (IEF). For unambiguous identification, the globin genes were sequenced. Most of the 80 Hb variants detected by initial screening on HPLC were also separated by capillary electrophoresis (CE), but a few variants were only detectable with one of these methods. Some variants were unstable, had thalassemic properties or increased oxygen affinity, and some interfered with Hb A2 measurement, detection of sickle cell Hb or Hb A1c quantification. Two of the six novel variants, Hb Enschede (HBA2: c.308G, p.Ser103Asn) and Hb Weesp (HBA1: c.301CT, p.Leu101Phe), had no clinical consequences. In contrast, two others appeared clinically significant: Hb Ede (HBB: c.53AT, p.Lys18Met) caused thalassemia and Hb Waterland (HBB: c.428CT, pAla143Val) was related to mild polycytemia. Hb A2-Venlo (HBD: c.193 p.Gly65Ser) and Hb A2-Rotterdam (HBD: c.38AC, p.Asn13Thr) interfered with Hb A2 quantification. This survey shows that HPLC analysis followed by globin gene sequencing of rare variants is an effective method to reveal Hb variants. © 2014 Informa Healthcare USA, Inc. Source

Bots M.,University of Amsterdam | Stroobants A.K.,University of Amsterdam | Delzenne B.,University of Amsterdam | Soeters M.R.,University of Amsterdam | And 6 more authors.
Clinical Chemistry and Laboratory Medicine | Year: 2015

Background: Haemoglobin (Hb) variants are well-known factors interfering with accurate HbA1c testing. This report describes two novel Hb variants leading to inappropriate quantification of HbA1c by ion-exchange chromatography. Methods: Glycated forms of novel Hb variants were recognised in the blood of two patients with diabetes mellitus screened by HbA1c ion-exchange chromatography. Dedicated high-resolution cation-exchange chromatography and subsequent DNA sequencing revealed the exact nature of the variants. Other common techniques for quantifying HbA1c were applied on both samples and haematological parameters were determined to judge possible pathology associated with the novel Hb variants. Results: A fraction of 15% of abnormal Hb was observed in a 37-year-old female. DNA sequencing revealed a heterozygous mutation in the α1-globin gene, resulting in a leucine-to-phenylalanine amino-acid substitution (HBA1: c.301C>T, p.Leu101Phe). We named this variant Hb Weesp. The other novel variant, Hb Haelen, presented as a 40% fraction in a 63-year-old male and resulted from a heterozygous amino acid substitution in the β-globin gene (HBB: c.335T>C, p.Val112Gly). The presence of both Hb variants resulted in aberrant separation of the Hb components, leading to an inadequate quantification of HbA1c. Conclusions: Close examination of HbA1c chromatograms revealed two novel, clinically silent Hb variants that interfere with HbA1c quantification. Healthcare providers need to be aware of the potential of such Hb variants when interpreting HbA1c results. © 2015 by De Gruyter. Source

van Zwieten R.,Laboratory of Red Blood Cell Diagnostics | van Oirschot B.A.,University Utrecht | Veldthuis M.,Laboratory of Red Blood Cell Diagnostics | Dobbe J.G.,University of Amsterdam | And 4 more authors.
American Journal of Hematology | Year: 2015

In a family with mild dominant spherocytosis, affected members showed partial band 3 deficiency. The index patient showed more severe clinical symptoms than his relatives, and his red blood cells displayed concomitant low pyruvate kinase activity. We investigated the contribution of partial PK deficiency to the phenotypic expression of mutant band 3 in this family. Pyruvate kinase deficiency and band 3 deficiency were characterized by DNA analysis. Results of red cell osmotic fragility testing, the results of cell deformability obtained by the Automated Rheoscope and Cell Analyzer and the results obtained by Osmotic Gradient Ektacytometry, which is a combination of these tests, were related to the red cell ATP content. Spherocytosis in this family was due to a novel heterozygous mutation in SLC4A1, the gene for band 3. Reduced PK activity of the index patient was attributed to a novel mutation in PKLR inherited from his mother, who was without clinical symptoms. Partial PK deficiency was associated with decreased red cell ATP content and markedly increased osmotic fragility. This suggests an aggravating effect of low ATP levels on the phenotypic expression of band 3 deficiency. © 2014 Wiley Periodicals, Inc. Source

Van Zwieten R.,Laboratory of Red Blood Cell Diagnostics | Bochem A.E.,University of Amsterdam | Hilarius P.M.,Laboratory of Red Blood Cell Diagnostics | Van Bruggen R.,Laboratory of Red Blood Cell Diagnostics | And 3 more authors.
Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids | Year: 2012

Maintenance of the asymmetric distribution of phospholipids across the plasma membrane is a prerequisite for the survival of erythrocytes. Various stimuli have been shown to induce scrambling of phospholipids and thereby exposure of phosphatidylserine (PS). In two types of patients, both with aberrant plasma cholesterol levels, we observed an aberrant PS exposure in erythrocytes upon stimulation. We investigated the effect of high and low levels of cholesterol on the ATP-dependent flippase, which maintains phospholipid asymmetry, and the ATP-independent scrambling activity, which breaks down phospholipid asymmetry. We analyzed erythrocytes of a patient with spur cell anemia, characterized by elevated plasma cholesterol, and the erythrocytes of Tangier disease patients with very low levels of plasma cholesterol. In normal erythrocytes, loaded with cholesterol or depleted of cholesterol in vitro, the same analyses were performed. Changes in the cholesterol/phospholipid ratio of erythrocytes had marked effects on PS exposure upon cell activation. Excess cholesterol profoundly inhibited PS exposure, whereas cholesterol depletion led to increased PS exposure. The activity of the ATP-dependent flippase was not changed, suggesting a major influence of cholesterol on the outward translocation of PS. The effects of cholesterol were not accompanied by eminent changes in cytoskeletal and membrane proteins. These findings emphasize the importance of cholesterol exchange between circulating plasma and the erythrocyte membrane as determinant for phosphatidylserine exposure in erythrocytes. © 2012 Elsevier B.V. All rights reserved. Source

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