Flow cytometric analysis of band 3 protein of human erythrocytes

Contemporary blood doping-Performance, mechanism, and detection

Blood doping is prohibited for athletes but has been a well-described practice within endurance sports throughout the years. With improved direct and indirect detection methods, the practice has allegedly moved towards micro-dosing, that is, reducing the blood doping regime amplitude. This narrative review evaluates whether blood doping, specifically recombinant human erythropoietin (rhEpo) treatment and blood transfusions are performance-enhancing, the responsible mechanism as well as detection possibilities with a special emphasis on micro-dosing. In general, studies evaluating micro-doses of blood doping are limited. However, in randomized, double-blinded, placebo-controlled trials, three studies find that infusing as little as 130 ml red blood cells or injecting 9 IU × kg bw-1 rhEpo three times per week for 4 weeks improve endurance performance ~4%-6%. The responsible mechanism for a performance-enhancing effect following rhEpo or blood transfusions appear to be increased O2 -carrying capacity, which is accompanied by an increased muscular O2 extraction and likely increased blood flow to the working muscles, enabling the ability to sustain a higher exercise intensity for a given period. Blood doping in micro-doses challenges indirect detection by the Athlete Biological Passport, albeit it can identify ~20%-60% of the individuals depending on the sample timing. However, novel biomarkers are emerging, and some may provide additive value for detection of micro blood doping such as the immature reticulocytes or the iron regulatory hormones hepcidin and erythroferrone. Future studies should attempt to validate these biomarkers for implementation in real-world anti-doping efforts and continue the biomarker discovery.

Anemia in the Neonate: The Differential Diagnosis and Treatment

Anemia is a common problem in the neonatal period. Presenting symptoms may suggest numerous possible diagnoses ranging from anemia seen as a normal part of development to anemia due to critical pathology. An illustrative case is presented to highlight the appropriate evaluation of the neonate with significant anemia. Several important features of the evaluation of neonatal anemia are highlighted. The constellation of signs and symptoms that occur in conjunction with the anemia are critical for the evaluation. The evaluation should be performed in a step-wise process that starts by eliminating common causes of anemia. Manual review of the peripheral blood smear with a hematologist can be helpful.

Red blood cell vesiculation in hereditary hemolytic anemia

Hereditary hemolytic anemia encompasses a heterogeneous group of anemias characterized by decreased red blood cell survival because of inherited membrane, enzyme, or hemoglobin disorders. Affected red blood cells are more fragile, less deformable, and more susceptible to shear stress and oxidative damage, and show increased vesiculation. Red blood cells, as essentially all cells, constitutively release phospholipid extracellular vesicles in vivo and in vitro in a process known as vesiculation. These extracellular vesicles comprise a heterogeneous group of vesicles of different sizes and intracellular origins. They are described in literature as exosomes if they originate from multi-vesicular bodies, or as microvesicles when formed by a one-step budding process directly from the plasma membrane. Extracellular vesicles contain a multitude of bioactive molecules that are implicated in intercellular communication and in different biological and pathophysiological processes. Mature red blood cells release in principle only microvesicles. In hereditary hemolytic anemias, the underlying molecular defect affects and determines red blood cell vesiculation, resulting in shedding microvesicles of different compositions and concentrations. Despite extensive research into red blood cell biochemistry and physiology, little is known about red cell deformability and vesiculation in hereditary hemolytic anemias, and the associated pathophysiological role is incompletely assessed. In this review, we discuss recent progress in understanding extracellular vesicles biology, with focus on red blood cell vesiculation. Also, we review recent scientific findings on the molecular defects of hereditary hemolytic anemias, and their correlation with red blood cell deformability and vesiculation. Integrating bio-analytical findings on abnormalities of red blood cells and their microvesicles will be critical for a better understanding of the pathophysiology of hereditary hemolytic anemias.

Protein 4.1R-dependent multiprotein complex: new insights into the structural organization of the red blood cell membrane

Protein 4.1R (4.1R) is a multifunctional component of the red cell membrane. It forms a ternary complex with actin and spectrin, which defines the nodal junctions of the membrane-skeletal network, and its attachment to the transmembrane protein glycophorin C creates a bridge between the protein network and the membrane bilayer. We now show that deletion of 4.1R in mouse red cells leads to a large diminution of actin accompanied by extensive loss of cytoskeletal lattice structure, with formation of bare areas of membrane. Whereas band 3, the preponderant transmembrane constituent, and proteins known to be associated with it are present in normal or increased amounts, glycophorin C is missing and XK, Duffy, and Rh are much reduced in the 4.1R-deficient cells. The inference that these are associated with 4.1R was borne out by the results of in vitro pull-down assays. Furthermore, whereas Western blot analysis showed normal levels of band 3 and Kell, flow cytometric analysis using an antibody against the extracellular region of band 3 or Kell revealed reduction of these two proteins, suggesting a conformational change of band 3 and Kell epitopes. Taken together, we suggest that 4.1R organizes a macromolecular complex of skeletal and transmembrane proteins at the junctional node and that perturbation of this macromolecular complex not only is responsible for the well characterized membrane instability but may also remodel the red cell surface.

Flow cytometry as a diagnostic tool for hereditary spherocytosis

Flow cytometric analysis of eosin-5'-maleimide-labeled red blood cells has been proposed as a new method of identifying hereditary spherocytosis (HS). The aim of the present study was to analyze sensitivity and specificity of this method. Red blood cells from patients with HS (n = 58) revealed significantly lower mean channel fluorescence values than red blood cells from normal subjects (n = 110), unaffected HS family members (n = 8), and patients with other anemias (n = 44). Taking a mean channel fluorescence of 400.0 units as the threshold value identified by logistic regression, sensitivity and specificity of the test for HS were 96.6 and 99.1%, respectively. Flow cytometric analysis is a valuable screening test for the diagnosis of HS.

Experience with eosin-5'-maleimide as a diagnostic tool for red cell membrane cytoskeleton disorders

The diagnosis of hereditary spherocytosis (HS) is based on red cell morphology and other conventional tests such as osmotic fragility, autohemolysis and acidified glycerol lysis. However, milder cases are at times difficult to diagnose. Confirmation by red blood cell (RBC) membrane protein analysis is not possible in most laboratories. Recently, a flow cytometric method has been described for quantitating the fluorescence intensity of intact red cells after incubation with the dye eosin-5'-maleimide (EMA), which binds specifically to the anion transport protein (band-3) at lysine-430. This has been shown to be an effective screening test for red cell membrane disorders. We evaluated the usefulness of this approach for screening membrane protein disorders such as HS and hereditary elliptocytosis (HE) and its value in discriminating this group from other hemolytic anemias, such as glucose-6-phosphate dehydrogenase (G6PD) deficiency, beta-thalassemia trait, sickle cell anemia and autoimmune hemolytic anemia. Fluorescence intensity, expressed in mean channel fluorescence (MCF) units, was determined using a Becton Dickinson FACS Caliber flow cytometer. Membrane protein analysis was carried out by sodium dodecyl sulfate-polyacrylamide gel eletrophoresis (SDS-PAGE). RBCs from patients with HS and HE gave significantly lower MCF values (P < 0.001) than the normal control group and other patient groups. The diagnosis of HS in four cases was confirmed by RBC membrane protein electrophoresis and all showed a deficiency of spectrin. The advantage of the EMA dye method are its specificity for membrane disorders, as well as being a simple, user-friendly and rapid method which is inexpensive, provided a flow cytometer is available.

Ultrastructural alterations in red blood cell membranes exposed to shear stress

In the mechanism of damage to red blood cells (RBCs) caused by a centrifugal pump, the prolonged effects to the RBC membrane caused by exposure to shear stress remain unclear. We focused on the band 3 protein (B3), one of the major proteins in the membrane skeleton, and investigated the ultrastructural alterations of the RBC membrane with loaded shear stress. Using flow cytometry, the relative amount of B3 was examined in relation to RBC deformability. The results, with continuous exposure to low shear stress, showed cell downsizing, an increase in B3 density, and a decrease in the deformability of the RBC membrane. Exposure to high shear stress does not appear to exert any influence on the membrane skeleton of the RBC. Therefore, in addition to conventional processes including the instantaneous destruction of a cell due to intense shear stresses, the results of the present study indicate the presence of another process based on changes in membrane proteins leading to cell fragmentation. Under low shear stress, the RBC membrane skeleton shows delayed destruction, which is exhibited as a disorder of B3 distribution, and the related membrane dysfunction includes decreases in RBC deformability and stability.