Comparison of mechanisms of anemia in mice with sickle cell disease and beta-thalassemia: peripheral destruction,ineffective erythropoiesis,and phospholipid scramblase-mediated phosphatidylserine exposure

OBJECTIVES: 1). To study the mechanisms of anemia, erythroid hyperplasia, and red blood cell (RBC) clearance in murine models of sickle cell disease (Sickle) and beta-thalassemia (Th1/Th1); 2) To determine the contribution of the phospholipid scramblase enzyme to phosphatidylserine (PS) exposure and RBC death in Sickle and Th1/Th1 mice. METHODS: We used a combination of flow-cytometric analysis and assays for phospholipid remodeling to determine the extent and sites of erythroid hyperplasia, PS exposure, and cell death. RESULTS: 1) Sickle RBCs have a much shorter half-life than Th1/Th1 RBCs (0.8 days vs. 11 days). A significant proportion of Th1/Th1 peripheral reticulocytes mature into erythrocytes, however, approximately fivefold fewer Sickle reticulocytes mature. While erythroid hyperplasia exists in both Sickle and Th1/Th1 mice, Th1/Th1 produce fourfold more RBCs than necessary to maintain steady state, while Sickle produce no excess RBCs. 2) 61% of Sickle and 34% of Th1/Th1 RBCs are scramblase(+) as measured by internalization assays of the fluorescent phospholipid NBD-PC. The majority of NBD-PC(+) RBCs are also annexin-V(+), supporting a mechanistic link between scramblase activity and PS exposure. A proportion of both reticulocytes and older RBCs in Sickle and Th1/Th1 mice have active scramblase, and the degree of scramblase activation in these strains correlates with the propensity for RBC death. CONCLUSIONS: Sickle and Th1/Th1 mice are both anemic, with significant erythroid hyperplasia. Th1/Th1 mice display ineffective erythropoiesis while Sickle mice show rapid peripheral destruction of RBCs. PS exposure and phospholipid scramblase activity serve as markers of RBCs with altered phospholipid asymmetry and greater propensity for cell death.     

Sulphydryl modifications alter scramblase activity in murine sickle cell disease

Increased oxidant stress has been suggested to play a role in the process of phosphatidylserine (PS) externalization in the red blood cells of sickle cell patients. Inhibition of the ATP-driven translocation from outer to inner monolayer (flippase) by sulphydryl modification has been established. The present study showed that phospholipid scrambling was also sensitive to protein sulphydryl modification. Treatment with N-ethylmaleimide lead to enhanced PS exposure and a lower Ca(++) requirement for scrambling. In contrast, pyridyldithioethylamine treatment inhibited PS exposure. Red blood cells from a murine model for sickle cell disease exhibited a reduced response to both reagents, suggestive of previous sulphydryl modifications to the protein(s) involved in phospholipid scrambling. We conclude that sulphydryl modifications to both scramblase and flippase underlie the enhanced formation of PS-exposing cells in sickle cell disease.     

Cellular properties of human erythrocytes preserved in saline-adenine-glucose-mannitol in the presence of L-carnitine

L-Carnitine (LC) in the preservation medium during storage of red blood cells (RBC) can improve the mean 24-hr percent recovery in vivo and increase RBC life-span after reinfusion. The purpose of the study was to investigate the differences in the biochemical properties of RBCs stored in the presence or absence of LC, and the cell-age related responses to storage conditions and to LC. RBC concentrates in saline-adenine-glucose-mannitol (SAG-M) were stored in the presence or absence of 5 mM LC at 4 degrees C for up to 8 weeks. RBC subpopulations of different densities were prepared by centrifugation on Stractan density gradient. Cells were sampled at 0, 3, 6, and 8 weeks, and hematological and cellular properties analyzed (MCV, MCHC, 4.1a/4.1b ratio as a cell age parameter, intracellular Na(+) and K(+)). After 6 weeks, MCV of RBC stored in the presence of LC was lower than that of controls (6 weeks MCV: controls 95.4 +/- 1.8 fl; LC 91.5 +/- 2.0 fl; n = 6; P < 0.005). This was due to swelling of control cells, and affected mainly older RBCs. LC appeared to reduce or retard cell swelling. Among the osmotically active substances whose changes during storage could contribute to cell swelling, only intracellular Na(+) and K(+) differed between stored control RBCs and LC-treated cells. LC reduces the swelling of older cells during storage at 4 degrees C in SAG-M, possibly by acting on the permeability of cell membrane to monovalent cations.     

Glutamine- and phosphate-containing hypotonic storage media better maintain erythrocyte membrane physical properties

We have shown that red blood cell (RBC) adenosine-5'-triphosphate (ATP) is better maintained and that there is less hemolysis and K+ leakage in hypotonic experimental additive solutions (EASs) containing glutamine and glutamine plus phosphate (Pi) than in the conventional additive solution Adsol during blood bank storage. The objective of this study was to determine if the beneficial effect produced in these media correlates with better preservation of RBC membrane properties including lipid content, phospholipid organization, aminophospholipid transport (flippase), and prothrombin converting activity. Aliquots of packed RBCs were stored in EASs containing adenine, glucose, sodium chloride, and mannitol, with 10 mmol/L glutamine (EAS 44) or with 10 mmol/L glutamine and 20 mmol/L Pi(EAS 45), or in Adsol. RBC membranes were studied after 0, 28, 42, and 84 days of storage, and vesicle membranes were studied after 84 days. RBC cholesterol and phospholipid content remained significantly greater (P < .01) in EASs than in Adsol. The degree of membrane vesiculation was more than 50% lower in EASs than in Adsol (P < .01). After 42 days of storage, the accessibility of phosphatidylethanolamine to phospholipases was approximately 1.5 times greater for Adsol and EAS 44 samples than for EAS 45 samples (43.5% v 28%). The rates of phosphatidylserine transport were 43% to 70% lower for stored cells but were not dependent on storage media. The amounts of bands 3 and 4.1 in the microvesicle membranes were not statistically different in any of the preparations. These results suggest that storage of RBCs in glutamine and Pi-medium better maintains ATP, lipid content, and phospholipid asymmetry and results in decreased vesiculation.     

Characterization of the phosphatidylserine-exposing subpopulation of sickle cells

Phosphatidylserine (PS), exclusively present in the inner monolayer of the normal red blood cell (RBC) membrane, is exposed in subpopulations of sickle cells. PS-exposing RBCs were found predominantly among the densest and the very light sickle cells. Within the light RBC fraction, PS exposure was found on reticulocytes, transferrin receptor-expressing reticulocytes, and mature RBCs. The last subset contained low-density valinomycin-resistant RBCs, previously shown to have high Na(+) and low K(+) content. This subpopulation contained the highest percentage of PS-exposing cells. The PS-exposing sickle cells did not show the sustained high cytosolic Ca(++) levels that have been shown to activate scramblase activity. Data from this study indicate that PS exposure can occur at different stages in the life of the sickle RBC and that it correlates with the loss of aminophospholipid translocase activity, the only common denominator of the PS-exposing cells. The additional requirement of scramblase activation may occur during transient increases in cytosolic Ca(++). (Blood. 2001;98:860-867)     

The effects of polyvinyl chloride and polyolefin blood bags on red blood cells stored in a new additive solution.

BACKGROUND AND OBJECTIVES: Red blood cells (RBCs) must be stored in polyvinyl chloride (PVC) bags plasticized with di-2-ethylhexyl phthalate or a similar plasticizer to achieve their full storage life with conventional storage solutions. Improved storage solutions might remove this requirement and allow blood storage in other plastics. Experimental Additive Solution-61 (EAS-61), which maintains RBCs for 9 weeks with reduced haemolysis and satisfactory 51Cr 24-h recovery, is an appropriate candidate improved RBC storage solution. MATERIALS AND METHODS: Twenty-four units of packed RBCs were pooled in groups of four units, each pool was realiquoted into four units and stored, six pooled units per arm, in one of the following: 100 ml of EAS-61 in PVC; 200 ml of EAS-61 in PVC; 100 ml of EAS-61 in polyolefin (PO); and 200 ml of EAS-61 in PO. Haemolysis, RBC morphology indices, RBC ATP concentrations, and other measures of RBC metabolism and function were measured weekly. RESULTS: RBC haemolysis exceeded 1% by 7 weeks in PO bags containing 100 ml or 200 ml of EAS-61. In PVC bags, haemolysis was less than 1% at 11 weeks. RBC ATP concentrations were 1 mol/g of haemoglobin (Hb) higher at 2 weeks in the PVC-stored units. CONCLUSIONS: RBCs stored in PVC had markedly less haemolysis and higher RBC ATP concentrations than those stored in PO. Haemolysis would limit RBC storage in PO bags to a duration of 6 weeks, even with EAS-61.     

Cholesterol-loading of membranes of normal erythrocytes inhibits phospholipid repair and arachidonoyl-CoA:1-palmitoyl-sn-glycero-3- phosphocholine acyl transferase. A model of spur cell anemia

Spur cell anemia may occur in severe liver disease including alcoholic cirrhosis. Spur cell anemia red blood cells (RBCs) have a characteristic morphology, with irregular projections, an increased ratio of membrane cholesterol (Ch) to phospholipid, evidence of oxidative damage, and shortened survival resulting in hemolytic anemia. Normal RBCs may acquire many of the features of spur cells either by transfusion into a spur cell patient or in an in vitro model system that loads the RBC membrane with Ch relative to phospholipid by means of Ch-rich, phospholipid-Ch sonicates. We found evidence of abnormal phospholipid repair metabolism in spur cell anemia RBCs characterized by decreased arachidonate (Ar) uptake into phospholipids and by increased uptake into a fatty acid membrane repair intermediate, acylcarnitine (AcylCn). To study the possible modulation of phospholipid repair metabolism in spur cells by Ch-loading, we compared the Ar metabolism of RBCs loaded with Ch in vitro with that of control cells incubated in autologous serum. Ar, a polyunsaturated fatty acid, is especially sensitive to peroxidation and, thus, is likely to be involved in phospholipid repair. Ch-loading decreased the incorporation of [14C]Ar into total lipids (Ch-loaded, 1,113 +/- 48 pmol/10(10) RBCs; control, 1,525 +/- 48 pmol/10(10) RBCs) including phosphatidylethanolamine, phosphatidylserine, and phosphatidylcholine. Uptake of [14C]Ar into AcylCn increased (control AcylCn, 169 +/- 31 pmol/10(10) RBCs; Ch-loaded AcylCn, 196 +/- 35 pmol/10(10) RBCs; P = .0012). Thimerosal, an inhibitor of arachidonoyl- CoA:l-palmitoyl-sn- glycero-3-phosphocholine acyl transferase or lysophosphocholine acyl transferase (LAT), produced a similar pattern of metabolic abnormality, with decreased incorporation into phospholipid but relative increase into AcylCn. We assayed LAT in RBC membranes from Ch-loaded RBCs, using [14C]arachidonoyl CoA as precursor, and found similar decreased LAT activity at concentrations of 1-palmitoyllysophosphatidylcholine (LPC) from 1 to 30 micromol/L. Similar LAT assay results were obtained using [14C]palmitoyl LPC as the precursor. We conclude that Ch-loading of RBC membranes results in inhibition of LAT in the cell-free system in vitro and may account for the inhibited phospholipid repair in Ch-loaded intact RBCs in vitro and in spur cell anemia RBCs in vivo. Decreased ability to replace peroxidized membrane fatty acid by this metabolic pathway may contribute to the hemolytic process in spur cell anemia.     

Impaired erythrocyte calcium homeostasis in beta-thalassemia

Intracellular calcium (Ca) concentration in erythrocytes (RBCs) is controlled by a low passive influx through a relatively impermeable membrane and by active efflux catalyzed by Ca2+,Mg2+-ATPase. Since precipitation of alpha-globin chains in thalassemic RBCs may interfere with normal membrane function, we studied the RBC intracellular Ca content and the RBC membrane Ca2+,Mg2+-ATPase activity in two groups of patients with nonsplenectomized (n = 9) and splenectomized (n = 9) beta- thalassemia intermedia and in two groups of matched controls. The mean +/- SD Ca concentration in the nonsplenectomized (n = 12) and splenectomized (n = 6) controls were 6.1 +/- 6.0 and 5.8 +/- 3.4 mumol Ca per liter of RBCs, respectively, compared with 26.0 +/- 7.6 (P less than .001) and 85 +/- 24.4 (P less than .001) in the nonsplenectomized and splenectomized thalassemia patients, respectively. The mean +/- SD Ca2+,Mg2+-ATPase activity in the eight nonsplenectomized patients was 0.77 +/- 0.58 mumol inorganic phosphate (Pi) per milligram of protein per hour compared with 0.66 +/- 0.41 in the controls (P = NS). Similar values were obtained for the splenectomized patients and their controls. No correlation was found between either the intracellular Ca content or the Ca2+,Mg2+-ATPase activity with the peripheral nucleated RBC count. These findings suggest that there is a major defect in the membrane of the thalassemic RBC leading to an increased Ca content that is more pronounced in splenectomized patients.     

Phosphatidylserine externalization in sickle red blood cells: associations with cell age,density, and hemoglobin F

Phosphatidylserine (PS) is normally confined to the cytoplasmic leaflet of the red blood cell (RBC) membrane, but some sickle RBCs expose PS in the outer leaflet (PS+ cells). This study examined the relationships among PS externalization, fetal hemoglobin content, hydration state, and cell age. Sickle RBCs exhibit a wide range of PS externalization. Those with low-level exposure (type 1 PS+) include many young transferrin-receptor-positive (TfR+) cells. This is not specific for sickle cell disease because many nonsickle TfR+ cells are also PS+. RBCs with higher PS exposure (type 2 PS+) appear to be more specific for sickle cell disease. Their formation is most likely sickling dependent because type 2 PS+ dense sickle cells have a lower percentage of fetal hemoglobin (HbF) than PS- cells in the same density fraction (1.7 vs 2.9; n = 8; P <.01). In vivo experiments using biotin-labeled sickle cells showed a sharp decrease in the percentage of circulating, labeled PS+ cells in the first 24 hours after reinfusion. This decrease was confined to type 1 PS+ cells and was thus consistent with the reversal of PS exposure in very young cells. As the labeled cells aged in the circulation, the percentages of type 1 and type 2 PS+ cells increased. These studies indicate that PS externalization in sickle cells may be low level, as observed in many immature cells, or high level, which is associated with dehydration and appears to be more specific for sickle RBCs.     

The effects ex vivo and in vitro of insulin and C-peptide on Na/K adenosine triphosphatase activity in red blood cell membranes of type 1 diabetic patients

The decrease in Na/K adenosine triphosphatase (ATPase) activity observed in several tissues of type 1 diabetic patients is thought to play a role in the development of long-term complications. Infusion of insulin may restore this enzyme activity in red blood cells (RBCs), and recent arguments have been developed for a similar role of C-peptide. The aims of this study were to determine whether insulin acts directly on the RBC enzyme and to evaluate the effect of C-peptide on Na/K ATPase activity. Thirty-nine C-peptide-negative type 1 diabetic patients were studied (blood glucose, 11.2 +/- 1.49 mmol/L; hemoglobin A1c [HbA1c], 8.9% +/- 0.1%, mean +/- SEM). Blood samples were obtained in the morning, before breakfast and insulin injection. Intact and living RBCs were resuspended in their own plasma and incubated with or without insulin (50 microU/mL) or C-peptide (6 nmol/L). Ex vivo by microcalorimetry, the heat produced after 1 hour by the enzyme-induced hydrolysis of adenosine triphosphate (ATP), was measured in a thermostated microcalorimeter at 37 degrees C. The results showed that Na/K ATPase activity was significantly increased by insulin (12.4 +/- 0.5 v 15.4 +/- 0.9 mW/L RBCs, P < .05, n = 23) but not by C-peptide (11.9 +/- 0.7 v 12.9 +/- 0.9 mW/L RBCs, NS, P = .26, n = 12). In another experiment, RBC suspensions were incubated at 37 degrees C in a water bath with or without insulin (50 microU/mL) or C-peptide (6 nmol/L) for 10 minutes. RBC membranes were isolated and Na/K ATPase activity was assessed by measuring inorganic phosphate release at saturating concentrations of all substrates. The results showed that insulin and C-peptide significantly increased RBC Na/K ATPase activity (342 +/- 25, P < .005 and 363 +/- 30, P < .005, respectively v255 +/- 22 nmol Pi x mg protein(-1) x h(-1), n = 14). We conclude that insulin and C-peptide act directly on RBC Na/K ATPase, thus restoring this activity in type 1 diabetic patients. The stimulatory effect of C-peptide observed in vitro on RBC Na/K ATPase activity confirms that C-peptide plays a physiological role.     

Inhibition of Rho-ROCK signaling induces apoptotic and non-apoptotic PS exposure in cardiomyocytes via inhibition of flippase

Subsequent to myocardial infarction, cardiomyocytes within the infarcted areas and border zones expose phosphatidylserine (PS) in the outer plasma membrane leaflet (flip-flop). We showed earlier that in addition to apoptosis, this flip-flop can be reversible in cardiomyocytes. We now investigated a possible role for Rho and downstream effector Rho-associated kinase (ROCK) in the process of (reversible) PS exposure and apoptosis in cardiomyocytes. In rat cardiomyoblasts (H9c2 cells) and isolated adult ventricular rat cardiomyocytes Clostridium difficile Toxin B (TcdB), a Rho GTPase family inhibitor, C3 transferase (C3), a Rho(A,B,C) inhibitor and the ROCK inhibitors Y27632 and H1152 were used to inhibit Rho-ROCK signaling. PS exposure was assessed via flow cytometry and fluorescent digital imaging microscopy using annexin V. Akt expression and phosphorylation were analyzed via Western blot, and Akt activity was inhibited by wortmannin. The cellular concentration activated caspase 3 was determined as a measure of apoptosis, and flippase activity was assessed via flow cytometry using NBD-labeled PS. TcdB, C3, Y27632 and H1152 all significantly increased PS exposure. TcdB, Y27632 and H1152 all significantly inhibited phosphorylation of the anti-apoptotic protein Akt and Akt inhibition by wortmannin lead to increased PS exposure. However, only TcdB and C3, but not ROCK- or Akt inhibition led to caspase 3 activation and thus apoptosis. Notably, pancaspase inhibitor zVAD only partially inhibited TcdB-induced PS exposure indicating the existence of apoptotic and non-apoptotic PS exposure. The induced PS exposure coincided with decreased flippase activity as measured with NBD-labeled PS flip-flop. In this study, we show a regulatory role for a novel signaling route, Rho-ROCK-flippase signaling, in maintaining asymmetrical membrane phospholipid distribution in cardiomyocytes.     

Erythropoiesis and erythrocyte age distribution in hemodialysis patients undergoing erythropoietin therapy

Renal anemia is caused in part by a reduced life span of red blood cells (RBCs) and by reduced erythropoietin biosynthesis in the damaged kidney. The RBC age can be determined by density gradient centrifugation and estimation of cell-age-dependent enzyme activities, as aspartate aminotransferase. The RBC age distribution influences the median density (D50) of RBCs and the blood rheology in coherence with the hematocrit. In our study, the median density was determined by Percoll density gradient centrifugation in 18 healthy subjects (D50 = 1.0674 +/- 0.0016 g/ml) and in 14 hemodialysis patients (D50 = 1.0674 +/- 0.0016 g/ml in the course of recombinant human erythropoietin (rhEPO) therapy. During the first 4 weeks of therapy, a strong rejuvenation of RBCs was observed whereby the D50 reached a minimum after 2 weeks (D50 = 1.0655 +/- 0.0022 g/ml; p less than 0.05 vs. value before therapy) and a steady state after 4 weeks (D50 = 1.0658 +/- 0.0013 g/ml; p less than 0.1 vs. value before therapy). In 5 of the patients with elevated plasma parathyroid hormone (i-PTH) concentrations greater than 10 pmol/l, a significantly (p less than 0.05) reduced amount of younger RBCs (D50 = 1.0675 +/- 0.0016 g/ml) was observed in the first 2 weeks of rhEPO therapy as compared to patients with i-PTH less than 10 pmol/l (D50 = 1.0677 +/- 0.0019 g/ml). Thus, erythropoiesis in the early phase of rhEPO therapy is strongly influenced by elevated plasma i-PTH concentrations. Therefore, a gradual increase in rhEPO doses is preferable before therapy at elevated doses with an uncontrolled increase in RBC amount.     

Evaluation of in vivo and in vitro Quality of Apheresis-Collected RBC Stored for 42 Days

Background and Objectives : New technological developments make it possible to collect red blood cells (RBCs) by apheresis, which allows for better product consistency and has the potential for improved RBC quality. The purpose of these studies was to evaluate the quality and consistency of units of RBCs collected by apheresis using the MCS+® machine (Haemonetics Corp., Braintree, Mass., USA). Materials and Methods : Two studies were performed. In study 1 (n = 10), using containers and CP2D/AS-3 solutions from Medsep Corp. (Covina, Calif. USA), one-unit apheresis RBCs were compared to manually collected RBCs in a random crossover design. In study 2 (n = 12), 6 subjects had one unit collected, while the remaining 6 subjects had two units of RBCs collected with comparison to previously manually collected RBCs from the same donors. Haemonetics containers and solutions were used in study 2. Results : Low RBC volume variability was found for the apheresis collections with a standard deviation of only 6 ml difference between actual and target volumes. Combining the data from the two studies (n = 21 pairs), at 42 days of storage, the apheresis units showed slightly lower hemolysis (0.44±0.26 vs. 0.61±0.50%), lower supernatant potassium levels (50±3 vs. 53±3 mEq/l), and improved tolerance to osmotic shock (47±3 vs. 49±3%) as compared to manual units (p < 0.05). There was no statistically significant difference in RBC ATP (3.0±0.6 vs. 2.9±0.5 μmol/g Hb) or in 24-hour percent recoveries (81±6 for apheresis vs. 81±4% for apheresis red cells). Apheresis RBC quality was not affected by the manufacturer (Haemonetics vs. Medsep) of solutions and containers. Conclusions : RBC units collected by apheresis demonstrated low variability in volume of RBC mass collected, and showed similar RBC properties as compared to manually collected RBCs after processing and after 42 days of storage.     

Factors affecting volume reduction and red blood cell depletion of bone marrow on the COBE Spectra cell separator before haematopoietic stem cell transplantation

The COBE Spectra is used to volume/red blood cell (RBC) deplete BM before transplantation or cryopreservation. We have audited our results to identify the effect of transit time, refrigerated storage, age and cellular composition on mononuclear cells (MNC) and CD34+ cell recoveries, volume/RBC depletion and neutrophil engraftment. In total, 88 consecutive collections from autologous (n = 25) and allogeneic (n = 63) donors were included. The mean collection volume was 1250 +/- 398 ml with RBC content of 341 +/- 113 ml. The MNC and CD34+ cell recoveries were 83.3 +/- 18.5 and 88.1 +/- 18.9%, respectively, volume depletion was 88.2+/-4.4% and RBC depletion 98.3 +/- 1.8%. Neutrophil engraftment was achieved in 20.1 +/- 6.4 days. Factors affecting MNC and CD34+ cell recoveries were transit time (P = 0.0060), overall age (P < 0.0210) and MNC/CD34+ cell concentrations (P < 0.0313). The presence of crenated RBC also reduced CD34+ cell recovery (P = 0.0028). Refrigerated storage did not adversely affect cell recovery (P > 0.8161) or neutrophil engraftment (P = 0.8959). This study demonstrates that time in transit, overall age, MNC and CD34+ cell concentrations and RBC condition were important factors affecting processing. RBCs show artefacts soon after collection at ambient temperatures and these may interfere with the separation and collection of MNC/CD34+ cells. Refrigeration at 4-6 degrees C during transit and storage may reduce formation of RBC artefacts and maximize MNC and CD34+ cell recoveries.     

Adherence of phosphatidylserine-exposing erythrocytes to endothelial matrix thrombospondin

Phospholipid asymmetry is well maintained in erythrocyte (RBC) membranes with phosphatidylserine (PS) exclusively present in the inner leaflet. The appearance of PS on the surface of the cell can have major physiologic consequences, including increased cell-cell interactions. Because increased adherence of PS-exposing RBCs to endothelial cells (ECs) may be pathologically important in hemoglobinopathies such as sickle cell disease and thalassemia, we studied the role of PS exposure in calcium ionophore-treated normal RBC adherence to human umbilical vein endothelial cell (HUVEC) monolayers. When HUVEC monolayers were incubated with these PS-exposing RBCs, the ECs retracted and the RBCs adhered primarily in the gaps opened between the ECs. A linear correlation was found between the number of PS-exposing RBCs in the population and the number of adhering RBCs to the monolayer. Pretreatment of RBCs with annexin V significantly decreased adherence by shielding PS on the RBCs. Similarly, PS-containing lipid vesicles decreased RBC binding by competing for the PS binding sites in the monolayer. PS-exposing RBCs and PS-containing lipid vesicles adhered to immobilized thrombospondin (TSP) and matrix TSP, respectively, and adherence of PS-exposing RBCs to EC monolayers was reduced by antibodies to TSP and to its EC receptor, alpha(v)beta(3). Together, these results indicate a role for PS and matrix TSP in the adherence of PS-exposing RBCs to EC monolayers, and suggest an important contribution of PS-exposing RBCs in pathologies with reported vascular damage, such as sickle cell anemia. (Blood. 2000;95:1293-1300)     

Abnormal phospholipid metabolism in spur cell anemia: decreased fatty acid incorporation into phosphatidylethanolamine and increased incorporation into acylcarnitine in spur cell anemia erythrocytes

Spur cell anemia is a hemolytic anemia seen in severe alcoholic cirrhosis that is characterized by unusual morphology and a decreased ratio of phospholipids to cholesterol in the erythrocyte membrane. We hypothesized that defective phospholipid repair may contribute to the red blood cell (RBC) phospholipid abnormalities of spur cell anemia. Therefore, we compared RBCs from normal control subjects with RBCs from spur cell anemia patients. The incorporation of [14C] arachidonic acid into the phospholipids and acylcarnitine (acyl-Cn) of spur cells and normal RBCs was analyzed by a direct-phase high performance liquid chromatography column to separate both the phospholipids and acyl-Cn. There was less uptake of the [14C] arachidonate into phosphatidylethanolamine of spur cell RBCs (12.9% +/- 1.0%) compared with normal RBCs (20.5% +/- 2.8%; P = .0245). However, more arachidonate was incorporated into the acyl-Cn of spur cells (spur cell acyl-Cn [24.5% +/- 2.9%] v normal control acyl-Cn [10.1% +/- 1.9%]; P = .0018). We conclude that phospholipid biosynthesis is inhibited and that acyl-Cn formation is spared in spur cell anemia RBCs. These metabolic changes may help account for the lipid abnormalities seen in spur cell anemia RBCs and contribute to the hemolytic process.     

Concurrent collection of in-line filtered platelets and red blood cells by apheresis

Multicomponent apheresis procedures offer the possibility to collect standardized blood components as compared to whole blood donations. A new program for the concurrent collection of platelets (PLTs) and red blood cells (RBCs) was evaluated in a prospective study. Apheresis donors ( n=18) underwent concurrent collection of PLTs and RBCs using the Haemonetics MCS+ blood cell separator. Aliquots of PLTs and RBCs were collected during five to six passes of the discontinuous flow procedure. The platelet product was in-line filtered during the last pass of the separation procedure. After collection, saline-adenine-glucose-mannitol (SAGM) preservative solution was automatically added to the RBCs. Thereafter, the RBCs were in-line leukodepleted by gravity filtration at room temperature. The PLTs and RBCs were subsequently stored at 22+/-2 degrees C for 5 days and 4+/-2 degrees C for 35 days, respectively. The following in vitro parameters were evaluated over the storage periods: blood cell counts, glucose, lactate, lactate dehydrogenase, pH, plasma hemoglobin, and potassium. Two ready-to-use blood components from one donor were collected in an average procedure time of 86+/-10 min; 2.47+/-0.74 x 10(11) PLTs were collected in a product volume of 232+/-43 ml. The RBC volume averaged 280+/-20 ml and the hemoglobin content was 56.8+/-2.4 g per unit. The leukocyte contamination of the platelet product was 0.44+/-0.56 x 10(5) and the residual leukocyte content of the RBC product was 0.28+/-0.02 x 10(5). Storage data showed no relevant drop in pH. Day 35 results of the RBC products showed that all of the units had less than 0.8% hemolysis. Standardized PLT and RBC products of good quality can be concurrently collected with the MCS+ blood cell separator. In vitro testing of the products collected and stored for 5 and 35 days, respectively, met the Council of Europe criteria for leukodepleted blood products.     

Gamma-ray-irradiated red blood cells stored in mannitol-adenine-phosphate medium: rheological evaluation and susceptibility to oxidative stress

BACKGROUND AND OBJECTIVES: To evaluate the rheological properties and the oxidative susceptibility of gamma-ray-irradiated red blood cells (RBCs). MATERIALS AND METHODS: RBCs in mannitol-adenine-phosphate (MAP) medium were irradiated with 35 Gy and stored at 4 degrees C for 4 weeks. The deformability of the RBCs was examined under shear flow in relation to the morphological and biochemical changes. The RBCs were further exposed to 1 mM FeSO(4) and 5 mM ascorbate to examine the oxidative susceptibility. RESULTS: The RBC deformability was decreased during storage, and the impairment was further enhanced by the irradiation, which promoted cell shrinkage and intracellular hemoglobin condensation accompanying potassium loss. Lipid peroxidation and protein aggregation of the RBC membrane as well as echinocytosis were not enhanced by the irradiation. The exposure to free iron did not stimulate the oxidation of the irradiated RBC membrane. CONCLUSION: The decreased deformability of gamma-ray-irradiated RBCs in MAP medium was mainly induced by dehydration due to potassium loss, and the membrane lipids and proteins were stably preserved against oxidative stress.     

Effects of storage time and leucocyte burden of packed and buffy-coat depleted red blood cell units on red cell storage lesion

Background

The red cell storage lesion (RCSL) comprises the biochemical and biomechanical changes that take place during red blood cell (RBC) storage, reducing the survival and function of these cells. Contaminating white blood cells have been major contributors to the RCSL. Markers of RCSL, such as CD47 and phosphatidylserine (PS), on RBC are attracting more attention. The aim of this study was to elucidate the effects of storage time and buffy-coat removal on CD47 and PS expression on RBC. Potassium and free haemoglobin levels in the supernatant plasma were also assessed.

Materials and methods

Forty-three red cell concentrates were divided into two groups [Group 1: packed red cells (n=22); Group 2: red cell units from which the buffy-coat had been removed (n=21)] and samples were collected on days 1, 14 and 28. Flow cytometry was used to monitor changes of CD47 and PS expression on RBC over times. Supernatant potassium was measured and percent of haemolysis calculated.

Results

A significant, progressive decrease in RBC CD47 expression during storage was observed in both groups. The decrease in RBC CD47 expression was significantly less in the buffy-coat-removed group of units than in the other group. The percentage of annexin V-positive cells increased significantly in both groups. Buffy-coat depleted components showed less expression of PS only in the early samples. There were significant, progressive increases in percentage of haemolysis and supernatant potassium during storage in both groups.

Conclusion

RBC stored for more than 14 days exhibited reduced CD47 and increased PS. Buffy coat removal reduced the loss of CD47, but had no impact on plasma haemoglobin, potassium or RBC PS exposure.     

抗咯萘啶的伯氏疟原虫感染红细胞多胺量的测定

目的：了解疟原虫的多胺代谢与咯萘啶（ＰＮＤ）抗药性的关系。方法：感染伯氏疟原虫ＡＮＫＡ株（ＰＳ）和由该株培育的中抗ＰＮＤ品系（ＰＲＡ）及高抗ＰＮＤ品系（ＰＲＢ）的昆明株小鼠于腹腔接种（ｉｐ）后ｄ７取血，经薄层层析后用荧光分光光度法测定正常ＲＢＣ、ＰＳ、ＰＲＡ和ＰＲＢ感染ＲＢＣ的丁二胺（ＰＴＣ）、精脒（ＳＰＤ）和精胺（ＳＰＭ）量。另有感染ＰＳ和ＰＲＢ的小鼠于ｉｐ后ｄ６分别１次灌胃（ｉｇ）ＰＮＤ５ｍｇ／ｋｇ和１０ｍｇ／ｋｇ，ｄ７取血，按上述方法测定给药后感染ＲＢＣ的多胺量，并与不给药组比较。结果：ＰＳ感染ＲＢＣ的多胺量均明显高于未感染疟原虫的正常ＲＢＣ，而感染ＰＲＡ和ＰＲＢ的ＲＢＣ多胺量又显著高于ＰＳ感染ＲＢＣ，且多胺量的增高与抗性程度有关。经ＰＮＤ治疗后ＰＳ感染ＲＢＣ的ＳＰＤ和ＳＰＭ较未治疗组显著下降，而ＰＲＢ感染ＲＢＣ则未见明显变化。结论：伯氏疟原虫对ＰＮＤ的抗药性与其多胺代谢有关。