The role of membrane lipids in the survival of red cells in hereditary spherocytosis

Hereditary spherocytosis complicated by intrahepatic cholestasis: two case reports

Background

Hereditary spherocytosis (HS) is not a rare disease in the department of hematology; however, in the late stage of the disease, patients often have very severe cholestasis and are referred to the department of hepatology. Hepatologists may have trouble determining the source of cholestasis, causing treatment difficulties.

Case Description

We report two 20-year-old patients complaining of "skin and eyes turned to yellow". Patient 1 had no previous hematologic disorders, and patient 2 had a history of anemia without treatment. Laboratory tests suggested anemia and elevated bilirubin in both patients. The direct bilirubin levels were more significantly elevated than the indirect bilirubin levels in both patients, and the patients both suffered from abdominal pain and pancreatitis. However, the degree of anemia could not fully explain the jaundice. Magnetic resonance imaging findings suggested the presence of hepatosplenomegaly and gallstones. Genetic testing identified new mutations in the relevant genes, ultimately confirming the diagnosis of HS. The liver biopsy results for both patients showed obvious intrahepatic cholestasis. Patient 1 underwent splenectomy at a bilirubin level of 125.4 µmol/L, and the bilirubin level returned to normal after surgery, with a good prognosis. However, Patient 2 suffered from pancreatitis during hospitalization and was unable to undergo splenectomy. Endoscopic retrograde cholangiopancreatography was implemented, but the bilirubin level continued to rise, and Patient 2 ultimately gave up treatment and passed away.

Conclusions

For hepatologists, identifying the source of jaundice (hemolysis, hepatocyte destruction, or biliary obstruction) is important for treatment, supplemented by liver biopsy and genetic testing if necessary. In the 2 cases covered in this article, early-stage HS caused hemolytic jaundice with predominantly elevated indirect bilirubin, and as the disease progressed, patients developed severe cholestasis probably related to transient biliary obstruction caused by gallstones and hepatocellular injury due to abnormal bilirubin metabolism. In addition, in patients with HS combined by intrahepatic cholestasis, early consideration of splenectomy may delay disease progression and achieve a better prognosis. Of course, this conclusion needs to be confirmed by more clinical studies.

Ektacytometry Analysis of Post-splenectomy Red Blood Cell Properties Identifies Cell Membrane Stability Test as a Novel Biomarker of Membrane Health in Hereditary Spherocytosis

Hereditary spherocytosis (HS) is the most common form of hereditary chronic hemolytic anemia. It is caused by mutations in red blood cell (RBC) membrane and cytoskeletal proteins, which compromise membrane integrity, leading to vesiculation. Eventually, this leads to entrapment of poorly deformable spherocytes in the spleen. Splenectomy is a procedure often performed in HS. The clinical benefit results from removing the primary site of destruction, thereby improving RBC survival. But whether changes in RBC properties contribute to the clinical benefit of splenectomy is unknown. In this study we used ektacytometry to investigate the longitudinal effects of splenectomy on RBC properties in five well-characterized HS patients at four different time points and in a case-control cohort of 26 HS patients. Osmotic gradient ektacytometry showed that splenectomy resulted in improved intracellular viscosity (hydration state) whereas total surface area and surface-to-volume ratio remained essentially unchanged. The cell membrane stability test (CMST), which assesses the in vitro response to shear stress, showed that after splenectomy, HS RBCs had partly regained the ability to shed membrane, a property of healthy RBCs, which was confirmed in the case-control cohort. In particular the CMST holds promise as a novel biomarker in HS that reflects RBC membrane health and may be used to asses treatment response in HS.

Spur cell anemia related to alcoholic liver cirrhosis managed without liver transplantation: a case report and literature review

Spur cell anemia is an acquired hemolytic anemia associated with liver cirrhosis and is characterized by the presence of increased large red blood cells, which are covered with spike-like projections that vary in width, length, and distribution. A 26-year-old man was referred to our hospital presenting with jaundice, lower limb edema, and dyspnea. The patient was subsequently diagnosed with spur cell anemia related to alcoholic liver cirrhosis. Spur cell anemia is an independent predictor of mortality in liver cirrhosis and has been associated with extremely poor prognosis. The most effective treatment for spur cell anemia is liver transplantation. As seen in the literature, the treatment of spur cell anemia without liver transplantation is quite challenging. This report highlights the importance of management and treatment strategies, including control of fluid retention, blood transfusion, plasma diafiltration, and administration of diuretics. Our treatment strategies might be useful in patients who are not candidate of liver transplantation or patients waiting for liver transplantation.

Detection of red blood cell antibodies in mitogen-stimulated cultures from patients with hereditary spherocytosis

BACKGROUND

Hereditary spherocytosis (HS) is a congenital hemolytic anemia caused by defects in red blood cell (RBC) membrane proteins leading to premature RBC clearance in the spleen. The presence of RBC autoantibodies has never been extensively investigated in HS.

STUDY DESIGN AND METHODS

RBC antibody-bound immunoglobulin (Ig)G was investigated in 91 consecutive HS patients by mitogen-stimulated direct antiglobulin test (MS-DAT), a sensitive method able to magnify latent RBC antibody autoimmunity and related with hemolytic variables, previous splenectomy, and type of membrane defect.

RESULTS

A total of 61% of HS cases had RBC antibodies by MS-DAT (29 Band 3, 17 spectrin deficiency, and nine no defined defect). The amount of RBC-bound IgG was greater in HS compared with controls (236 ± 192 ng/mL vs. 52 ± 29 ng/mL, p < 0.0001), although lower than that observed in autoimmune hemolytic anemia (AIHA; 634 ± 371 ng/mL vs. 236 ± 192 ng/mL, p < 0.0001). Western blot experiments showed that purified IgG fraction from MS-DAT-positive patients bind to α- and β-spectrin, Band 3, and Band 4.9. Positive cases displayed increased reticulocytosis and slightly reduced hemoglobin (Hb) values compared to negative ones. Patients displaying RBC-bound IgG of more than 250 ng/mL (the positive threshold of AIHA) showed increased number of spherocytes and mainly had spectrin deficiency. RBC-bound IgG and free Hb increased over time after storage at 4°C, a surrogate of ex vivo aging, more evidently in HS than controls, and particularly in Band 3 deficiency.

CONCLUSION

RBC autoantibodies were detected by MS-DAT in more than a half of HS patients. Positive cases showed a more evident hemolytic pattern suggesting a pathogenic role of these autoantibodies in RBC opsonization and splenic removal.

Quantifying morphological heterogeneity: a study of more than 1 000 000 individual stored red blood cells

BACKGROUND AND OBJECTIVES

The morphology of red blood cells (RBCs) deteriorates progressively during hypothermic storage. The degree of deterioration varies between individual cells, resulting in a highly heterogeneous population of cells contained within each RBC unit. Current techniques capable of categorizing the morphology of individual stored RBCs are manual, laborious and error-prone procedures that limit the number of cells that can be studied. Our objective was to create a simple, automated system for high-throughput RBC morphology classification.

MATERIALS AND METHODS

A simple microfluidic device, designed to enable rapid, consistent acquisition of images of optimally oriented RBCs, was fabricated using soft lithography. A custom image analysis algorithm was developed to categorize the morphology of each individual RBC in the acquired images. The system was used to determine morphology of individual RBCs in several RBC units stored hypothermically for 6-8 weeks.

RESULTS

The system was used to automatically determine the distribution of cell diameter within each morphological class for >1 000 000 individual stored RBCs (speed: >10 000 cells/h; accuracy: 91·9% low resolution, 75·3% high resolution). Diameter mean and standard deviation by morphology class were as follows: discocyte 7·80 ± 0·49 μm, echinocyte 1 7·61 ± 0·63 μm, echinocyte 2 7·02 ± 0·61 μm, echinocyte 3 6·47 ± 0·42 μm, sphero-echinocyte 6·01 ± 0·26 μm, spherocyte 6·02 ± 0·27 μm, stomatocyte 1 6·95 ± 0·61 μm and stomatocyte 2 7·32 ± 0·47 μm.

CONCLUSIONS

The automated morphology classification procedure described in this study is significantly simpler, faster and less subjective than conventional manual procedures. The ability to evaluate the morphology of individual RBCs automatically, rapidly and in statistically significant numbers enabled us to perform the most extensive study of stored RBC morphology to date.

Increases in beta-lipoproteins in hyperlipidemic and dyslipidemic dogs are associated with increased erythrocyte osmotic fragility

BACKGROUND

The capacity of RBCs to traverse endothelium and deliver oxygen to tissues is dependent on a mechanically stable yet flexible plasma membrane. The lipid composition of the RBC membrane is crucial in maintaining its structure and fluidity. Lacking a nucleus and having minimal synthetic capacity, RBCs are exquisitely sensitive to changes in plasma lipids.

OBJECTIVE

The objective of this study was to investigate the effects of plasma lipids on RBC fragility in hyperlipidemic and dyslipidemic dogs.

METHODS

Osmotic fragility of RBCs, plasma lipoprotein fractions, and cholesterol and phospholipid content of RBC membranes were measured in hyperlipidemic, dyslipidemic, and healthy control dogs. Osmotic fragility of normal canine RBCs incubated in phosphate-buffered saline and in both intact and lipid-depleted plasma from diabetic dogs was also measured.

RESULTS

RBCs from hyperlipidemic and dyslipidemic dogs with diabetes mellitus and dogs treated with glucocorticoids were significantly more fragile than RBCs from healthy control dogs. RBCs from hyperlipidemic dogs with cholestatic disease tended to be more stable relative to RBCs from controls. RBC osmotic fragility was positively correlated with beta-lipoprotein levels, but was only weakly correlated with serum cholesterol concentration. Incubation in plasma from hyperlipidemic diabetic dogs rendered RBCs from healthy dogs osmotically fragile, whereas lipid-depleted plasma from the same diabetic dogs had no effect.

CONCLUSIONS

RBCs from hyperlipidemic and dyslipidemic dogs are osmotically fragile, and fragility is highly correlated with increases in beta-lipoproteins. Future studies are planned to address the consequences of lipid-induced fragility and subclinical hemolysis on endothelial cells, platelets, and coagulation.

Hereditary spherocytosis: evaluation of 68 children

To determine the clinical and hematologic features of 68 children with hereditary spherocytosis (HS). In this retrospective study, we analyzed recorded information of 68 HS patients diagnosed between March 1997 and March 2007, including clinical manifestations at admission, gender, median age at diagnosis, family history, hematologic and biochemical data, patient management, complications, median age of splenectomy, and median follow-up time. Sixty-eight patients with HS (36 male and female) were investigated. The median age at diagnosis was 5.6 years (range 3 months to 18 years). Twenty-seven (39.7 %) had parents with consanguineous marriages, and 20 (29.4 %) had parents with first-degree consanguinity. Predominant clinical manifestations at admission were anemia in 59 patients (86.76 %), splenomegaly in 49 (72.05 %), and jaundice in 33 (48.52 %). Patients were classified as mild, moderate, or severe in 29.4, 61.7, and 8.8 % of patients, respectively. Five patients (7.3 %) underwent splenectomy. Major complications of HS were hemolytic, aplastic, and megaloblastic crises and cholelithiasis in 7 (10.2 %), 1 (1.4 %), 7 (10.2 %), and 6 (8.8 %) of patients, respectively. There were no deaths during follow-up. HS should be considered in evaluating possible diagnoses in patients with hemolytic anemia. In this study, the clinical course of patients with HS was relatively benign, with low proportions of patients having splenectomized and aplastic crises.

Quantitative assessment of sensing and sequestration of spherocytic erythrocytes by the human spleen

Splenic sequestration of RBCs with reduced surface area and cellular deformability has long been recognized as contributing to pathogenesis of several RBC disorders, including hereditary spherocytosis. However, the quantitative relationship between the extent of surface area loss and splenic entrapment remains to be defined. To address this issue, in the present study, we perfused ex vivo normal human spleens with RBCs displaying various degrees of surface area loss and monitored the kinetics of their splenic retention. Treatment with increasing concentrations of lysophosphatidylcholine resulted in a dose-dependent reduction of RBC surface area at constant volume, increased osmotic fragility, and decreased deformability. The degree of splenic retention of treated RBCs increased with increasing surface area loss. RBCs with a > 18% average surface area loss (> 27% reduced surface area-to-volume ratio) were rapidly and completely entrapped in the spleen. Surface-deficient RBCs appeared to undergo volume loss after repeated passages through the spleen and escape from splenic retention. The results of the present study for the first time define the critical extent of surface area loss leading to splenic entrapment and identify an adaptive volume regulation mechanism that allows spherocytic RBCs to prolong their life span in circulation. These results have significant implications for understanding the clinical heterogeneity of RBC membrane disorders.

Proteomic identification of erythrocyte membrane protein deficiency in hereditary spherocytosis

Hereditary spherocytosis (HS) is the most common congenital hemolytic anemia in Caucasians, with an estimated prevalence ranging from 1:2000 to 1:5000. The molecular defect in one of the erythrocytes (RBC) membrane proteins underlying HS like; spectrin-α, spectrin-β, ankyrin, band 3 and protein 4.2 that lead to membrane destabilization and vesiculation, may change the RBCs into denser and more rigid cells (spherocytes), which are removed by the spleen, leading to the development of hemolytic anemia. It is classified as mild, moderate and severe, according to the degree of the hemolytic anemia and the associated symptoms. Two-dimensional gel electrophoresis (2-DE) is potentially valuable method for studying heritable disorders as HS that involve membrane proteins. This separation technique of proteins based upon two biophysically unrelated parameters; molecular weight and charge, is a good option in clinical proteomics in terms of ability to separate complex mixtures, display post-translational modifications and changes after phosphorylation. In this study, we have used contemporary methods with some modifications for the solubilisation, separation and identification of erythrocyte membrane proteins in normal and in HS RBCs. Spectrin alpha and beta chain, ankyrin and band 3 proteins expression differences were found with PDQuest software 8.0.1. and peptide mass fingerprinting (PMF) analysis performed for identification of proteins in this study.

Hereditary spherocytosis—defects in proteins that connect the membrane skeleton to the lipid bilayer

The molecular causes of hereditary spherocytosis (HS) have been unraveled in the past decade. No frequent defect is found, and nearly every family has a unique mutation. In dominant HS, nonsense and frameshift mutations of ankyrin, band 3, and beta-spectrin predominate. Recessive HS is most often due to compound heterozygosity of defects in ankyrin, alpha-spectrin, or protein 4.2. Common combinations include a defect in the promoter or 5'-untranslated region of ankyrin paired with a missense mutation, a low expression allele of alpha-spectrin plus a missense mutation, and various mutations in the gene for protein 4.2. In most patients' red cells, no abnormal protein is present. Only rare missense mutations, like ankyrin Walsrode (V463I) or beta-spectrin Kissimmee (W202R), have given any insight into the functional domains of the respective proteins. Although the eminent role of the spleen in the premature hemolysis of red cells in HS is unquestioned, the molecular events that cause splenic conditioning of spherocytes are unclear. Electron micrographs show that small membrane vesicles are shed during the formation of spherocytes. Animal models give further insight into the pathogenetic consequences of membrane protein defects as well as the causes of the variability of disease severity.

Boston City Hospital and the Thorndike Memorial Laboratory: the birth of modern haematology

Established in 1923, the Thorndike Memorial Laboratory at Boston City Hospital was the first clinical research laboratory in a municipal hospital in the United States of America. Minot and Castle, who were the second and third directors of the Laboratory, were pioneer haematologists and clinical investigators of the highest calibre who created an atmosphere at the Laboratory that would foster patient-centred research and attract the best physician-scientists to work and train there. The haematology research division of the Laboratory made important original contributions to the understanding of the pathophysiology of anaemia, the mechanisms of red cell and platelet destruction and the phagocytic role of the spleen, the nature of haemoglobin (normal and sickle cell), the nature of haemophilia and its therapy and the early classification of lymphoma. It contributed to the Thorndike Memorial Laboratory's worldwide reputation as a model research laboratory and established its reputation as the birthplace of modern haematology.

Anemia and hypocholesterolemia

The authors reviewed the available data on the relationship between hypocholesterolemia and anemia with various etiologies. The data were collected from sources identified by a MEDLINE search of English-language literature published between 1966 and 2001 and bibliographies of relevant articles. The study selection included primary research articles, metaanalyses, and abstracts concerning the relation between hypocholesterolemia and anemia. Textbooks, meeting proceedings, and reference lists were also searched. Despite differences in study design, a relation was found between hematocrit and serum cholesterol levels and between hemoglobin and cholesterol levels. Further studies are required to determine the exact etiology and clinical significance of these findings.

Red cell abnormalities in hereditary spherocytosis: relevance to diagnosis and understanding of the variable expression of clinical severity

Marked variations in the clinical manifestations of hereditary spherocytosis (HS) have long been recognized. However, neither the molecular nor the cellular basis for this variable expression has been fully delineated. To better define the cellular basis for variable expression of the disease, we evaluated the pathobiology of red cells in a large series of 55 non-splenectomized and 31 splenectomized patients with HS. Red cell membrane surface area, surface area-to-volume ratio, cell volume, and state of cell hydration were quantitated. We found that decreased membrane surface area was a distinguishing feature of red cells in all patients studied, whereas decreased surface area-to-volume ratio as reflected by increased osmotic fragility was noted in only 66% of the non-splenectomized patients. In terms of red cell indexes, the percentage of microcytes was not a good discriminator of HS phenotype but was the best indicator of the severity of the disease. In contrast, the presence of increased numbers of hyperdense cells was an effective discriminating feature of the HS phenotype but a poor indicator of disease severity. These findings have enabled us to define the dominant cellular changes that account for the variable clinical severity of this common red cell membrane disorder and have allowed development of improved approaches for its diagnosis.

Hereditary spherocytosis associated with deletion of human erythrocyte ankyrin gene on chromosome 8

Hereditary spherocytosis (HS) is one of the most common hereditary haemolytic anaemias. HS red cells from both autosound dominant and recessive variants are spectrin-deficient, which correlates with the severity of the disease. Some patients with recessive HS have a mutation in the spectrin alpha-2 domain (S.L.M. et al., unpublished observations), and a few dominant HS patients have an unstable beta-spectrin that is easily oxidized, which damages the protein 4.1 binding site and weakens spectrin-actin interactions. In most patients, however, the cause of spectrin deficiency is unknown. The alpha- and beta-spectrin loci are on chromosomes 1 and 14 respectively. The only other genetic locus for HS is SPH2, on the short arm of chromosome 8 (8p11). This does not correspond to any of the known loci of genes for red cell membrane proteins including protein 4.1 (1p36.2-p34), the anion exchange protein (AE1, band 3; 17q21-qter), glycophorin C (2q14-q21), and beta-actin (7pter-q22). Human erythrocyte ankyrin, which links beta-spectrin to the anion exchange protein, has recently been cloned. We now show that the ankyrin gene maps to chromosome 8p11.2, and that one copy is missing from DNA of two unrelated children with severe HS and heterozygous deletions of chromosome 8 (del(8)(p11-p21.1)). Affected red cells are also ankyrin-deficient. The data suggest that defects or deficiency or ankyrin are responsible for HS at the SPH2 locus.

Decreased amount of the Rh antigen D in hereditary spherocytosis (HS)

This study was done to determine whether hereditary spherocytosis (HS) red blood cells (RBC) have decreased amounts of Rh antigens. Initially we studied the RBC of five members of one family, two of whom had HS. Using automated quantitative haemagglutination tests, we demonstrated that HS RBC agglutinated less with Rh antisera of four specificities than did normal RBC, indicating that Rh antigens are decreased on HS RBC. In this family, the strength of other blood group antigens on HS RBC was estimated by manual titres and agglutination scores. No appreciable differences in the agglutination of HS and normal RBC were observed with non-Rh antisera. To assess the strength of the D antigen more accurately, the number of D sites was quantitated on the RBC of 19 individuals with HS and 11 of their healthy relatives. HS RBC had 9209 +/- 4084 (mean +/- SD) D sites, whereas the normal RBC had 15 394 +/- 5763 D sites. These two means were significantly different (P less than 0.01). HS RBC were also compared to normal RBC of unrelated individuals who had the same Rh phenotype. These analyses showed that HS RBC had about half of the normal number of D sites. Our data indicate that HS red cells have decreased amount of the Rh antigen D and probably also of other Rh antigens.

Vacuoles in red cells from splenectomized subjects originate during cell life: association with glycosylated haemoglobin?

Whole blood from splenectomized subjects (n = 8) contained a substantial percentage of vacuolated ('pitted') red cells (34.7 +/- 8.3%), while blood from controls revealed none. The percentage of haemoglobin A1 (HbA1) had increased significantly compared with controls (p less than 0.01). Fractionation on cell density revealed that the number of 'pitted' cells and the HbA1 percentage were associated with increased cell density. Fractionation on cell volume showed that 'pitted' cells are equally distributed in fractions with varying mean cell volume (MCV) and that decreasing MCV was associated with a linear rise of HbA1. It appeared that, shortly after splenectomy (n = 4), 'pits' develop early in cell life and that also older cells, after previous splenic contact, are capable of pit formation. A positive correlation found between the number of 'pitted' cells and the percentage of HbA1 might point to an impaired release of HbA1, manifest in the presence of 'pits'. The increased percentage of HbA1 in whole blood from splenectomized subjects may thus be explained.

Ca2+ influx in normal and spherocytic red cells

The influx of 45Ca2+ into normal red cells and various types of spherocytic red cells was studied after blocking active Ca2+ extrusion by vanadate. The measurements were performed with and without verapamil, a calcium antagonist. The influx of Ca2+ into red cells from unsplenectomized persons was 22 +/- 7 mumol/l packed red cells/h (mean +/- SD), and 17 +/- 7 mumol/l per h when incubated with verapamil. The influx of Ca2+ into red cells from four splenectomized normal controls was of the same magnitude as in the unsplenectomized controls but there was no effect of verapamil on the influx rate. The influx of Ca2+ into red cells from nine splenectomized patients with hereditary spherocytosis (HS) was 27 +/- 9 mumol/l per h without and 24 +/- 9 mumol/l per h with verapamil. In 9 normal red cell samples made spherocytic by thermal damage the corresponding values were 32 +/- 16 and 31 +/- 19 mumol/l per h, respectively. The uptake of Ca2+ in chlorpromazine-induced spherocytic red cells was 20 +/- 4 mumol/l per h without and 19 +/- 5 mumol/l per h with verapamil in 9 experiments. These results indicate that although in HS erythrocytes changes in the cell membrane lead to an increased Ca2+ influx, the slow calcium channels are not affected, whereas in spherocytes induced by thermal damage or by incubation with chlorpromazine the channels are blocked, at least partly.

Alterations in size, shape and osmotic behaviour of red cells after splenectomy: a study of their age dependence

In whole blood from splenectomized subjects (n = 20), red cells showed a significant increase of mean surface area (MSA), mean cell volume (MCV), MSA/MCV-ratio and osmotic resistance, with the mean cell haemoglobin concentration (MCHC) being decreased. Studies on red cell populations of different cell age revealed that the increase of MSA affects younger and older cells, whereas the increase of MCV can mainly be ascribed to young cells with low density. The increased osmotic resistance is mainly determined by older cells due to a more favourable MSA/MCV-ratio. Shortly after splenectomy (n = 5) the MSA of younger and older cells increased, whereas the increase of MCV affected only young cells with a lowered density; moreover, the MSA/MCV-ratio increased in older cells in particular, resulting in a relatively greater increase of osmotic resistance. An impaired maturation of the reticulocyte may underlie the initial increase of MSA and MCV of young cells, but the present results contradict the current view that delayed maturation explains the changes in morphology and osmotic resistance of asplenic red cells.

Clinical disorders of the red cell membrane skeleton

The lipid bilayer of the adult red cell is supported on its inner surface by a complex arrangement of proteins known as the membrane skeleton. This filamentous network, a major component of which is a multifunctional protein called spectrin, has an essential role in determining the shape, structural integrity, and deformability of the red cell. A significant achievement of modern biochemistry and hematology has been the elucidation of the organization of the components of the membrane skeleton and their relationship to other membrane proteins and lipids. This article reviews current concepts of membrane skeleton structure and function and emphasizes recent advances which have been made in characterizing and classifying molecular defects of the skeleton which manifest clinically with changes in the shape and stability of the red cell. The pathobiology of hereditary skeletal defects associated with hereditary spherocytosis (HS), hereditary elliptocytosis (HE), and hereditary pyropoikilocytosis (HPP) are comprehensively discussed. Secondary defects of the membrane skeleton occurring in glucose-6-phosphate dehydrogenase deficiency and sickle cell anemia are also briefly considered.

Abnormal transbilayer mobility of phosphatidylcholine in hereditary pyropoikilocytosis reflects the increased heat sensitivity of the membrane skeleton

We determined whether the membrane defect in hereditary pyropoikilocytosis (HPP) is associated with thermally induced changes in the lipid bilayer, the stability of which was probed by the rate of translocation of phosphatidylcholine (PC) over the two leaflets. [14C]PC was incorporated into the outer leaflet of the lipid bilayer of the intact erythrocytes using a PC-specific phospholipid exchange protein. The transbilayer equilibration of this PC was determined by measuring the time-dependent changes in its accessibility to exogenous phospholipase A2. The rate of transbilayer equilibration of PC was increased in HPP cells at 37 degrees C when compared to normal erythrocytes (rate constants, 0.07 +/- 0.02 and 0.03 +/- 0.01 h-1, respectively). A further dramatic increase in PC transbilayer equilibration was noted in HPP cells incubated at 44 degrees C (rate constant, 0.15 +/- 0.02 h-1). A similar marked acceleration in transbilayer movement of PC was also seen in normal erythrocytes when incubated at 46 degrees C (rate constant, 0.13 +/- 0.03 h-1). Despite the enhanced transbilayer mobility of PC in HPP cells when compared to normal erythrocytes, no major alteration in the asymmetric distribution could be observed when probed with phospholipase A2. Since changes in transbilayer mobility of PC and cell morphology occur in HPP cells at lower temperature than in normal red cells, it may be concluded that the enhanced thermal sensitivity of spectrin is the major factor responsible for these changes. Our results therefore support the view that the structural integrity of the skeletal network is essential for stabilization of the lipid bilayer of the red cell membrane.

Partial deficiency of erythrocyte spectrin in hereditary spherocytosis

Hereditary spherocytosis (HS) is a common, clinically heterogeneous haemolytic anaemia in which the primary erythrocyte defect is believed to be some abnormality in the spectrin-actin membrane skeleton, leading to loss of surface membrane. Recessively inherited spectrin deficiency with extreme erythrocyte fragility and spherocytosis has been identified in certain mutant mice and two severely anaemic humans. Although suspected, deficiency of spectrin has not been demonstrated in less severe forms of human HS. We not report the quantitation of erythrocytes spectrin by radioimmunoassay. We found that normal erythrocytes contained 240,000 copies of spectrin heterodimer, whereas erythrocytes from 14 patients with a variety of types of HS were all partially deficient in spectrin (range 74,000-200,000 copies), the magnitude of the deficiency correlating with the severity of the disease. Spectrin deficiency of varying degrees is common in HS and probably represents the principal structural defect leading to loss of surface membrane.

Mammalian reticulocytes lose adhesion to fibronectin during maturation to erythrocytes

We describe three situations in which a large fraction of circulating red blood cells attach tightly and specifically to fibronectin: (i) rabbits made anemic by repeated bleeding, (ii) patients with hemolytic anemia and functional asplenia and splenectomized normal humans, and (iii) splenectomized mice. Upon induction of anemia in rabbits, the proportion of circulating red blood cells capable of specifically attaching to fibronectin-coated plastic increased in parallel with the number of reticulocytes. Fibronectin-adherent red cells were barely detectable when the rabbit had recovered from the anemia. Attachment of reticulocytes to fibronectin was specific; cells did not attach to dishes coated with albumin, laminin, or collagen. None of these proteins promoted the attachment of normal erythrocytes. About 75% of the erythrocytes from splenectomized mice (but not control mice) also attached specifically to fibronectin 40 days after surgery. The effect of splenectomy was incomplete and transient; adherent cells were not detectable 8 weeks after splenectomy. As judged by labeling studies with [35S]methionine, newly emergent reticulocytes preferentially attached to fibronectin. We suggest that about half of the reticulocytes in erythropoietically unstressed mice lose their ability to attach to fibronectin, possibly due to loss of fibronectin-adhesive components, during passage through the spleen. The others lose their ability to interact with fibronectin before release, in the bone marrow, or in some extrasplenic site.

Saturation transfer EPR studies of membrane alteration in hereditary spherocytosis

Our earlier spin label electron paramagnetic resonance (EPR) studies of hereditary spherocytosis (HS) erythrocyte revealed the existence of structural alteration(s) when the membrane is subjected to heat stress. We have now used saturation transfer EPR to show restricted motion in membrane proteins even without subjecting membrane to stress. The abnormal motional behavior is amplified when membranes are incubated at 47 degrees C and is readily detectable by conventional EPR. Gel electrophoresis and lipid assays show that proteins but not lipids are released upon heating. Thus, the more restricted motions in HS membranes may be due to a different membrane protein organization, ultimately resulting in the abnormal morphology of HS cells.

Disappearance of microspherocytes in peripheral circulation and normalization of decreased lipids in plasma and in red cells of patients with hereditary spherocytosis after splenectomy

A possible mechanism of the formation of microspherocytosis in unsplenectomized patients with hereditary spherocytosis (HS) was investigated in relation to lipid metabolism in plasma and in red cells of these patients. Plasma lipids (total cholesterol, free cholesterol, high density lipoprotein cholesterol, free fatty acids, and phospholipids) were markedly reduced in unsplenectomized HS patients with microspherocytosis. Red cell membrane lipids (free cholesterol and phospholipids such as phosphatidyl ethanolamine, sphingomyelin, phosphatidyl choline, and lysophosphatidyl choline) were also decreased in these unsplenectomized HS patients. After splenectomy, microspherocytosis disappeared concomitant to substantial normalization of plasma and red cell membrane lipids. These observations suggest that plasma lipid decrement in the unsplenectomized HS patients is at least one of the causative factors in pathogenesis of the formation of microspherocytosis. So-called "splenic conditioning" may not imply a physical "loss" of membrane by fragmentation or pitting of the once-formed HS red cells in the peripheral circulation. Instead, the decreased plasma lipids in the presence of the spleen may affect the de novo synthesis of red cell membrane lipids, resulting in the formation of microspherocytosis.

Observations on plasma and red cell lipids in hereditary spherocytosis

Plasma lipids and red cell lipids were determined in hereditary spherocytosis (HS), 15 unsplenectomized and eight splenectomized patients. Plasma lipids (cholesterol: total, free and high density lipoproteins, free fatty acids, and phospholipids) were markedly decreased in HS, especially in the unsplenectomized patients. Concomitantly, red cell membrane lipids (free cholesterol and phospholipids: total, phosphatidyl ethanolamine, sphingomyelin, phosphatidyl choline, and lysophosphatidyl choline) were also diminished. The plasma lipids stay low even after splenectomy although partially restored. Thus, decreased membrane surface, a hallmark of HS, could be partly attributed to the diminished membrane lipids induced by plasma lipid abnormalities in the patients.

Increased adsorption of cytoplasmic proteins to the erythrocyte membrane in ATP-depleted normal and pyruvate kinase-deficient mature cells and reticulocytes

How the metabolic defect of pyruvate kinase deficiency (PK(-)) accelerates red blood cell (RBC) destruction is not established, but may be related to RBC membrane abnormalities associated with altered cellular metabolism. Furthermore, it has been shown that PK(-) reticulocytes are especially sensitive to metabolic depletion. Therefore, we compared the membranes of reticulocyte-rich PK(-) RBC, both fresh and ATP depleted, with membranes of fresh and ATP depleted normal mature RBC and reticulocytes. There was no difference between the specific gravity (SG) of the membranes of normal mature RBC (SG 1.152 +/- 0.004) and membranes of reticulocyte-rich RBC from several anemias (SG 1.150 +/- 0.002). However, membranes from fresh, reticulocyte-rich PK(-) RBC were dense with SG of 1.165 +/- 0.004 which correlated with a corresponding increase of protein to lipid phosphorus ratio of 66 +/- 8 micrograms protein/micrograms lipid phosphorus (normal 52 +/- 6 micrograms/micrograms). The membrane density of PK(-) RBC was further increased when the PK(-) RBC ATP was depleted by anaerobic incubation (SG 1.188 +/- 0.004) or cyanide inhibition (SG 1.182 +/- 0.001). When ATP was depleted in normal RBC and in non-PK(-) reticulocytes, corresponding increases in membrane SG occurred. A distinctive 50,000 MW peptide is adsorbed from the cytoplasm to the membranes of reticulocytes (both normal and PK(-) when these cells were depleted of ATP. The increased membrane adsorption of cytoplasmic proteins by PK(-) RBC was not associated with increased RBC calcium uptake, sulfhydryl oxidation, or altered membrane protein phosphorylation. All the observed abnormalities of PK(-) RBC membranes could by reproduced by ATP depletion of reticulocyte-enriched non-PK(-) RBC.

Thrombocyte aggregation in hereditary spherocytosis

Thrombocyte function was studied in seven splenectomized patients and one unsplenectomized patient with hereditary or congenital spherocytosis (HS). Adenosine diphosphate (ADP) concentrations, which trigger the aggregation of control thrombocytes, induced only a release reaction in thrombocytes from six of the HS patients. Collagen-induced thrombocyte aggregation was also diminished in two patients, and epinephrine-induced thrombocyte aggregation in one patient. Two patients whose thrombocytes responded normally to ADP, collagen and epinephrine, were identical twins with spherocytosis of equivocal hereditary. Ristocetin-induced aggregation was normal in all the patients studied. Xanthines (pentoxifylline, theophylline) had no effect on the aggregation of thrombocytes from HS patients or controls. Half-life of thrombocytes was normal in the two splenectomized patients studied. The results demonstrate that not only red cells but also thrombocytes are defective in HS.

Hereditary spherocytosis of man. Altered binding of cytoskeletal components to the erythrocyte membrane

Human erythrocytes possess a lattice work of extrinsic proteins on the inner face of the membrane (;cytoskeleton') that maintains the shape and deformability of the cell. The major proteins of the cytoskeleton are spectrin and actin, which are attached to the membrane by protein bands 2.1 (;ankyrin') and 4.1. The interactions of spectrin/actin with erythrocyte membranes from normal subjects and from patients with hereditary spherocytosis (HS) have been studied by using an air-driven ultracentrifuge, which can rapidly separate membranes from soluble proteins (150000g for 30s). The total amount of spectrin/actin in HS and normal ghosts is similar. However, the rate of dissociation of spectrin and actin from HS erythrocyte membranes at low ionic strength is significantly lower than that observed for normal membranes. Spectrin and actin isolated from either HS or normal membranes re-associated in a similar manner to spectrin/actin-depleted vesicles prepared from normal cells. Scatchard analysis showed an average binding capacity of 278mug/mg of membrane protein. However, spectrin/actin-depleted vesicles prepared from HS cells bound significantly less spectrin/actin prepared from either the normal or abnormal cells (average binding capacity 158mug/mg of membrane protein). The defect was defined further by studying the cytoskeleton obtained by Triton X-100 extraction of membranes. Under conditions of low ionic strength cytoskeletons prepared from HS membranes dissociated more slowly than those prepared from normal membranes, and only 80% of the protein from HS cytoskeletons could be solubilized after 180min compared with 100% for normal cytoskeletons. The difference between HS and normal membranes, which persists in isolated cytoskeletons, suggests that alterations in either the primary structure or the degree of phosphorylation of protein bands 2.1 or 4.1 may be central to the molecular basis of hereditary spherocytosis.

Plasma and erythrocyte lipids in hereditary spherocytosis

Determinations were made of the concentrations of cholesterol, triglycerides and phospholipids in plasma from 18 patients with hereditary or congenital spherocytosis (HS). The plasma cholesterol and phospholipid levels of these patients were significantly depressed, whereas the triglyceride levels were normal. Phospholipids from plasma and red cell ghosts were analysed by thin-layer chromatography. The relative amount of phosphatidylethanolamine was decreased in both plasma and red cell membranes from HS patients, whereas significant alterations were not observed in the relative amounts of the other major phospholipid classes. These data show that in HS the abnormal lipid metabolism is not confined only to the red cell; it also affects the plasma lipids and therefore probably other cells as well.

Role of the spleen in congenital stomatocytosis associated with high sodium-low potassium erythrocytes

A girl of German origin with severe congenital hemolytic anemia was found to have overhydrated erythrocytes with markedly increased sodium and reduced potassium concentrations. The cells were stomatocytic with increased osmotic fragility and autohemolysis. Their excessively increased energy production was mainly used for active cation transport. The cells were highly vulnerable to metabolic depletion. Their normal deformability was reduced rapidly during deprivation of glucose. In acidic, hypoglycemic environment of the splenic pulp the cells become swollen and lysed. After splenectomy anemia improved though increased hemolysis persisted.

Erythrocyte phospholipid fatty acid fluctuations in patients with beta-thalassemia minor

The result of an analysis of red cell individual phospho-lipid fatty acids are presented in patients suffering from beta-thalassemia minor. A significant decrease of each of the following sphingomyelin fatty acids was found: 16:0, 18:1, 18:2, 22:0, 24:0. Phosphatidylcholine fatty acids showed an increase of 16:0, 18:2, 22:0, and 22:1 and a decrease of 18:0 and 20:4. Changes of phosphatidylserine fatty acids, an increase of 14:0, 16:0, 18:0, 18:2, and 22:1, and a decrease of 20:4, 24:0, and 24:1, were observed. An increase of 14:0, 16:0 and a decrease of 18:1, 20:4, and 24:1 phosphatidylethanolamine fatty acids were found. The considerable changes observed in individual phospholipid fatty acids, especially long chain unsaturated ones and primarily arachidonic acid (20:4), indicate a tendency for red cell peroxidation and thus an increased predisposition to hemolysis.

Effect of ouabain on osmotic resistance and monovalent cation transport of red cells in hereditary spherocytosis

The effect of ouabain on the osmotic resistance of red cells from 17 splenectomized patients with congenital or hereditary spherocytosis (HS), from 5 of their relatives suspected of having a subclinical form of the disease and from unsplenectomized and splenectomized normal controls was studied. In red cells from the HS patients and the splenectomized controls a small ouabain-induced decrease in osmotic resistance was seen, whereas in the unsplenectomized controls no such change was observed. The osmotic resistance of red cells from the 5 relatives, on the other hand, was significantly decreased by ouabain. The usefulness of ouabain in unmasking HS in its subclinical form was further tested by studying monovalent cation influx into red cells. The active influx of 86Rb+ into red cells from HS suffers was significantly increased. A similar degree of ouabain-induced inhibition of 86Rb+ transport was seen in all groups studied. The passive influx of 22Na+, which was also increased in HS red cells, was not affected by ouabain in any of the four groups.

Analysis of factors regulating erythrocyte deformability

Using a laser diffraction technique, we have studied factors that influence the deformability of erythrocytes. Variations in suspending medium osmolality and applied shear stress were employed to isolate the individual contributions to whole cell deformability of internal viscosity, surface area-to-volume ratio, and viscoelastic properties of the membrane. An experimental system was devised in which normal cells were modified in vitro to induce specific alterations in each factor. Measurements of deformability as a function of medium osmolality showed characteristic behavior of the modified cells. Reduced surface area-to-volume ratio was detected by an exaggeration of the normal decrease in deformability as medium osmolality was decreased. In contrast, increased internal viscosity was detected by an increase in deformability as osmolality was decreased. Finally, decreased membrane flexibility was detected by reduced deformation at low shear stress. These methods of analysis were applied to cells from patients with hereditary spherocytosis, hereditary pyropoikilocytosis, and hemoglobin CC disease to define the basis of reduced deformability. Hereditary spherocytes showed the combined effects of reduced surface area and increased internal viscosity. Hereditary pyropoikilocytes revealed the effects of severely reduced surface area-to-volume ratio. Hemoglobin CC cells showed only the effects of high internal viscosity. An increase in the membrane shear modulus (decreased membrane deformability) was not evident in these disorders.

The fluidity gradient in erythrocyte membranes in hereditary spherocytosis: a spin label study

The fluidity gradient and sulphydryl groups in erythrocyte ghost membranes from healthy subjects and from seven patients with hereditary spherocytosis (HS) were studied by spin label techniques. The mobility of the stearic acid spin labels was lower in the spherocyte membranes, indicating greater stability of the phospholipid layer in these membranes than in those of matched controls. This stabilization was most distinct in the intermediate and deep membrane layers. No clear differences were observed in the protein sulphydryl groups. It is suggested that the decreased cellular deformability characterizing spherocytes reflects altered lipid organization or lipid-protein interaction in the interior of the cell membrane.

Inherited disorders of the red cell membrane skeleton

Current knowledge of red cell membrane structure and function are briefly presented, and the pathophysiology, diagnosis, and treatment of hereditary spherocytosis, hereditary elliptocytosis, and hereditary pyropoikilocytosis are discussed.

Hereditary spherocytosis revisited. Eighth annual Paul M. Aggeler Memorial Lecture. Delivered October 25, 1977, San Francisco General Hospital Medical Center

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Effects of abnormal cation transport on deformability of desiccytes

We have studied the deformability of subpopulations of red cells from a patient with "desiccytosis," a disorder characterized by increased membrane permeability to potassium and associated with a probable increase in sodium-sodium exchange. Cells become increasingly dehydrated after maturation because of continued potassium loss without compensatory sodium gain, and they exhibit a progressive increase in mean cell hemoglobin concentration (MCHC). This increase in MCHC causes the cells to become underformable at shear stress values which result in extensive deformation of normal cells. Reduction of MCHC to approximately normal levels by suspending the cells in hypotonic medium restores normal deformability to all but 0.1--0.2% of the cells. These results suggest that the major factor leading to premature destruction in this disorder is whole cell rigidity conferred by increased intracellular hemoglobin concentrations, rather than any associated membrane rigidity.

[Changes of erythrocyte membrane lipids in ethanol induced hyperlipidemia (Zieve's syndrome) (author's transl)]

In 11 patients with alcohol-induced hyperlipemia, of whom 6 showed a Zieve Syndrome increased phospholipids, triglycerides and total cholesterol were found in the red cells stromal. The gasliquid chromatographic analysis of the phospholipid fatty acids showed increased contents of saturated and monounsaturated fatty acids C 16-C 18 smaller contents of longchain highly unsaturated fatty acids. The changes in the fatty acid pattern mainly occurred in patients with Zieve Syndrome and could be important for the mechanism of the hemolytic anemia. Theses findings could be in connexion with vitamin E deficiency.

Hemolytic anemias. Failure of the red cell membrane

The normal erythrocyte membrane is composed of nearly equivalent amounts of lipid and protein. The lipid portion of the membrane has been well studied. Even though de novo synthesis of lipid does not occur in human red cells, many biochemical pathways exist which facilitate detoxification of lipid breakdown products and lipid renewal. Rare defects in these processes are associated with hemolytic disorders. Recent studies have revealed that the membrane proteins are diverse and suggest that protein dysfunction may also account for clinical disease. Protein and lipid are entwined in a physicochemical relationship which is probably best depicted by the classic lipid bilayer with interspersed proteins in both the inner and outer surfaces and also spanning the bilayer. Membrane failure results in hemolytic anemia. This failure can be intrinsic, caused by abnormal lipid or protein constituents; or extrinsic, with a normal membrane being unable to counteract physical, chemical or immunologic stress. Clinical examples of membrane failure and hemolytic anemia can be separated into three groups according to the predominant mechanism of the hemolysis: fragmentation, whole-cell lysis, and filtration and entrapment. Although these mechanisms can act separately or in concert, the final hemolytic destruction of the cell can usually be traced to a failure of membrane function.

Relationship between Intralipid-induced hyperlipemia and pulmonary function

One unit (500 ml) of 10% Intralipid (an intravenous soy bean oil-egg yolk lecithin preparation) was infused into 20 normal subjects over 4 hr. Serum triglyceride concentration and plasma optic density (at 700 nm) increased to maximal levels of 339 +/- 102 mg/100 ml and 1.14 +/- 0.41, respectively, at the completion of the infusion, and returned to basal levels in most subjects within 4 hr. Pulmonary membrane diffusion was decreased in six subjects at rest and with exercise at 25 and 50% maximum oxygen uptake. Only one subject showed a minor change in PO2 and none showed clinical signs of ischemia. The changes in pulmonary diffusion reverted to basal levels when serum lipids were cleared. Heparin (60 IU/kg) prevented the marked increase in serum lipids and, as a consequence, the changes in pulmonary function. Changes in pulmonary function from Intralipid-induced lipemia are similar to those known to result from diet-induced lipemia. The findings suggest that in the presence of normal vasculature and pulmonary function, Intralipid-induced lipemia should cause no clinical consequences. However, patients with preexisting pulmonary or vascular disease may be at greater risk after Intralipid-induced lipemia.

Elevated microviscosity in membranes of erythrocytes affected by hereditary spherocytosis

Erythrocytes affected by hereditary spherocytosis (HS), obtained from several splenectomized patients, showed a varying degree of elevated osmotic fragility. In order to evaluate a possible role of the erythrocyte membrane lipids in HS, microviscosity of the membrane lipid core was measured by a fluorescence-polarization technique. Intact HS-affected red cells, as well as their ghost membranes and liposomes prepared from their lipid extract, all showed a distinctly higher micro-viscosity than the respective normal control. The increased microviscosity correlated with the severity of HS. The data support the proposition that the defect in HS-affected red cells is associated, at least in part, with alterations in the membrane lipids.