Red blood cell (RBC) membrane proteomics--Part I: Proteomics and RBC physiology

Red blood cells as biomarkers and mediators in complications of diabetes mellitus: A review

Red blood cells (RBCs), traditionally recognized for their oxygen transport role, have garnered increasing attention for their significance as crucial contributors to the pathophysiology of diabetes mellitus. In this comprehensive review, we elucidate the multifaceted roles of RBCs as both biomarkers and mediators in diabetes mellitus. Amidst the intricate interplay of altered metabolic pathways and the diabetic milieu, RBCs manifest distinct alterations in their structure, function, and lifespan. The chronic exposure to hyperglycemia induces oxidative stress, leading to modifications in RBC physiology and membrane integrity. These modifications, including glycation of hemoglobin (HbA1c), establish RBCs as invaluable biomarkers for assessing glycemic control over extended periods. Moreover, RBCs serve as mediators in the progression of diabetic complications. Their involvement in vascular dysfunction, hemorheological changes, and inflammatory pathways contributes significantly to diabetic microangiopathy and associated complications. Exploring the therapeutic implications, this review addresses potential interventions targeting RBC abnormalities to ameliorate diabetic complications. In conclusion, comprehending the nuanced roles of RBCs as biomarkers and mediators in diabetes mellitus offers promising avenues for enhanced diagnostic precision, therapeutic interventions, and improved patient outcomes. This review consolidates the current understanding and emphasizes the imperative need for further research to harness the full potential of RBC-related insights in the realm of diabetes mellitus.

The Changes of Elongation Index of erythrocytes caused by storage of blood at low temperature

Introduction: An important parameter characterizing the ability of erythrocytes to deform depending on the blood flow conditions is the Elongation Index (EI), and it is a parameter defined by the shape of the erythrocyte obtained as a diffraction pattern of erythrocytes at different values of shear stresses.

Material and methods: EI measurements at different shear stress were performed by Laser-assisted Optical Rotational Cell Analyzer (LORRCA) for erythrocytes derived from Tissue Bank in Katowice. Measurements were performed immediately after receiving them from Tissue Bank and after 2, 9, and 28 days of storage of samples at the temperature of 4°C in solution with the anticoagulant.

Results: An increase in the erythrocytes Elongation Index in the first 9 days of storing samples at low temperatures was observed in the entire range of applied shear stresses. This indicates an increase in the elasticity of erythrocytes during short-term storage at 4°C. In turn, on the 28th day of erythrocyte storage, a significant decrease in the Elongation Index for shear stresses greater than 1 Pa was observed, which indicates the stiffening of the erythrocyte membrane structure, reducing their elasticity. The relative decrease in the Elongation Index of erythrocytes stored for 28 days compared to erythrocytes measured at the beginning was similar and slightly greater than 30% for shear stresses greater than 3 Pa. For shear stresses lower than 3 Pa, the relative change in elongation index was smaller than for shear stresses greater than 3 Pa and increased with the increase in shear stress.

Conclusions: The elongation index of erythrocytes stored in the anticoagulant solution at 4°C, initially increases in the entire range of applied shear stresses in the first few days from the moment of blood collection and preparation at the Tissue Bank, and then decreases, but on the ninth day of storage the elongation index is still higher than for blood immediately after collection.

The Effect of Selected Flavonoids and Lipoic Acid on Natural and Model Cell Membranes: Langmuir and Microelectrophoretic Methods

The influence of kaempferol (K), myricetin (M) and lipoic acid (LA) on the properties of natural erythrocytes, isolated from animal blood and biological membrane models (monolayers and liposomes) made of phosphatidylcholine (PC), cholesterol (CHOL), and sphingomyelin (SM), CHOL in a ratio of 10:9, was investigated. The Langmuir method, Brewster angle microscopy (BAM) and microelectrophoresis were used. The presented results showed that modification of liposomes with kaempferol, myricetin and lipoic acid caused changes in the surface charge density and the isoelectric point value. Comparing the tested systems, several conclusions were made. (1) The isoelectric point for the DPPC:Chol:M (~2.2) had lower pH values compared to lipoic acid (pH~2.5) and kaempferol (pH~2.6). (2) The isoelectric point for the SM-Chol with myricetin (~3.0) had lower pH values compared to kaempferol (pH~3.4) and lipoic acid (pH~4.7). (3) The surface charge density values for the DPPC:Chol:M system in the range of pH 2-9 showed values from 0.2 to -2.5 × 10^-2 C m^-2. Meanwhile, for the DPPC:Chol:K and DPPC:Chol:LA systems, these values were higher at pH~2 (0.7 × 10^-2 C m^-2 and 0.8 × 10^-2 C m^-2) and lower at pH~9 (-2.1 × 10^-2 C m^-2 and -1.8 × 10^-2 C m^-2), respectively. (4) The surface charge density values for the SM:Chol:M system in the range of pH 2-9 showed values from 0.5 to -2.3 × 10^-2 C m^-2. Meanwhile, for the DPPC:Chol:K and DPPC:Chol:LA systems, these values were higher at pH~2 (0.8 × 10^-2 C m^-2), and lower at pH~9 (-1.0 × 10^-2 C m^-2 and -1.8 × 10^-2 C m^-2), respectively. (5) The surface charge density values for the erythrocytes with myricetin in the range of pH 2-9 showed values from 1.0 to -1.8 × 10^-2 C m^-2. Meanwhile, for the erythrocytes:K and erythrocytes:LA systems, these values, at pH~2, were 1.3 × 10^-2 C m^-2 and 0.8 × 10^-2 C m^-2 and, at pH~9, -1.7 × 10^-2 C m^-2 and -1.0 × 10^-2 C m^-2, respectively.

Microfluidic-Based Novel Optical Quantification of Red Blood Cell Concentration in Blood Flow

The optical quantification of hematocrit (volumetric percentage of red blood cells) in blood flow in microfluidic systems provides enormous help in designing microfluidic biosensing platforms with enhanced sensitivity. Although several existing methods, such as centrifugation, complete blood cell count, etc., have been developed to measure the hematocrit of the blood at the sample preparation stage, these methods are impractical to measure the hematocrit in dynamic microfluidic blood flow cases. An easy-to-access optical method has emerged as a hematocrit quantification technique to address this limitation, especially for the microfluidic-based biosensing platform. A novel optical quantification method is demonstrated in this study, which can measure the hematocrit of the blood flow at a targeted location in a microchannel at any given instant. The images of the blood flow were shot using a high-speed camera through an inverted transmission microscope at various light source intensities, and the grayscale of the images was measured using an image processing code. By measuring the average grayscale of the images of blood flow at different luminous exposures, a relationship between hematocrit and grayscale has been developed. The quantification of the hematocrit in the microfluidic system can be instant and easy with this method. The innovative proposed technique has been evaluated with porcine blood samples with hematocrit ranging from 5% to 70%, flowing through 1000 µm wide and 100 µm deep microchannels. The experimental results obtained strongly supported the proposed optical technique of hematocrit measurement in microfluidic systems.

An Insight into the Stages of Ion Leakage during Red Blood Cell Storage

Packed red blood cells (pRBCs), the most commonly transfused blood product, are exposed to environmental disruptions during storage in blood banks. In this study, temporal sequence of changes in the ion exchange in pRBCs was analyzed. Standard techniques commonly used in electrolyte measurements were implemented. The relationship between ion exchange and red blood cells (RBCs) morphology was assessed with use of atomic force microscopy with reference to morphological parameters. Variations observed in the Na⁺, K⁺, Cl⁻, H⁺, HCO₃⁻, and lactate ions concentration show a complete picture of singly-charged ion changes in pRBCs during storage. Correlation between the rate of ion changes and blood group type, regarding the limitations of our research, suggested, that group 0 is the most sensitive to the time-dependent ionic changes. Additionally, the impact of irreversible changes in ion exchange on the RBCs membrane was observed in nanoscale. Results demonstrate that the level of ion leakage that leads to destructive alterations in biochemical and morphological properties of pRBCs depend on the storage timepoint.

Analysis of Red Blood Cell Parameters in Dogs with Various Stages of Degenerative Mitral Valve Disease

Introduction

Although peripheral blood analysis has become increasingly automated, microscopy is the only available method for the diagnosis of anisocytosis and poikilocytosis. The aims of the study were to compare RBC volume data obtained with two different analysers and by manual assessment of smears and to compare this data between dogs in various stages of heart failure secondary to degenerative mitral valvular (DMV) disease. The impact of diuretic administration on RBC morphology was also assessed.

Material and Methods

Sixty-eight dogs, 56 in different stages of DMV disease and 12 as healthy controls, were studied. Impedance and flow cytometry haematological analyses were performed for each animal. Additionally, two smears were prepared for manual analysis. RBC structure, staining, and size differences were recorded.

Results

There were no significant differences between the blood morphological parameters assessed using haematological analysers nor between dogs receiving diuretic treatment and those not treated. Based on the manual smear, significantly higher erythrocyte anisocytosis was observed in the dogs with symptomatic DMV disease than in the control group.

Conclusion

Haematological analysers based on impedance and flow cytometry provide reliable and comparable morphological results in dogs with heart failure. However, microscopic assessment of blood smears is a more reliable tool to detect erythrocyte anisocytosis.

Multimodal detection and analysis of a new type of advanced Heinz body-like aggregate (AHBA) and cytoskeleton deformation in human RBCs

A new type of aggregate, formed in human red blood cells (RBCs) in response to glutaraldehyde treatment, was discovered and analyzed with the classical and advanced biomolecular imaging techniques. Advanced Heinz body-like aggregates (AHBA) formed in a single human RBC are characterized by a higher level of hemoglobin (Hb) degradation compared to typical Heinz bodies, which consist of hemichromes. The complete destruction of the porphyrin structure of Hb and the aggregation of the degraded proteins in the presence of Fe³⁺ ions are observed. The presence of such aggregated, highly degraded proteins inside RBCs, without cell membrane destruction, has been never reported before. For the first time the spatial differentiation of two kinds of protein mixtures inside a single RBC, with different phenylalanine (Phe) conformations, is visualized. The non-resonant Raman spectra of altered RBCs with AHBA are characterized by the presence of a strong band located at 1037 cm^-1, which confirms that glutaraldehyde interacts strongly with Phe. The shape-shifting of RBCs from a biconcave disk to a spherical structure and sinking of AHBA to the bottom of the cell are observed. Results reveal that the presence of AHBA should be considered when fixing RBCs and indicate the analytical potential of Raman spectroscopy, atomic force microscopy and scanning near-field optical microscopy in AHBA detection and analysis.

An Analysis of Isolated and Intact RBC Membranes-A Comparison of a Semiquantitative Approach by Means of FTIR, Nano-FTIR, and Raman Spectroscopies

This work presents the potential of vibrational spectroscopy, Vis and NIR Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) in reflection and transmission modes, and nano-FTIR microscopy to study the biochemical alterations in membranes of isolated and intact red blood cells (RBCs). The main goal was to propose the best spectroscopic method which enabled following biochemical alterations in the RBC membranes and then to translate this spectroscopic signature of degradation to in situ analysis of RBCs. Two models corresponding to two distinct cases of RBC membrane conditions were employed, and they were derived from healthy and young mice and mature mice with advanced atherosclerosis. It was shown that each technique provided essential information about biochemical alterations of the isolated membranes as well as membranes in the intact RBCs, which can be used in the development of a rapid and in situ analytical technology. Finally, we proposed that the combination of macro- and nanoprobing implemented in IR spectroscopy provided a wide chemical characterization of the RBC membranes, including alterations in lipid and protein fractions. This study also examined the effect of the sample preparation to determine destructive factors influencing a spectroscopic analysis of isolated membranes and intact RBCs derived from healthy and disease-affected mice.

Valsartan impedes epinephrine-induced ICAM-4 activation on normal, sickle cell trait and sickle cell disease red blood cells

Abnormal red blood cell (RBC) adhesion to endothelial αvβ3 plays a crucial role in triggering vaso-occlusive episodes in sickle cell disease (SCD). It is known that epinephrine, a β-adrenergic receptor (β-AR) stimulator, increases the RBC surface density of active intercellular adhesion molecule-4 (ICAM-4) which binds to the endothelial αvβ3. It has also been demonstrated that in human embryonic kidney 293 cells, mouse cardiomyocytes, and COS-7 cell lines, the β-adrenergic and renin-angiotensin systems are interrelated and that there is a direct interaction and cross-regulation between β-AR and angiotensin II type 1 receptor (AT1R). Selective blockade of AT1R reciprocally inhibits the downstream signaling of β-ARs, similar to the inhibition observed in the presence of a β-AR-blocker. However, it is not known if this mechanism is active in human RBCs. Here, we studied the effect of valsartan, an AT1R blocker, on the surface density of active ICAM-4 receptors in normal, sickle cell trait, and homozygous sickle RBCs. We applied single molecule force spectroscopy to detect active ICAM-4 receptors on the RBC plasma membrane with and without the presence of valsartan and epinephrine. We found that epinephrine significantly increased whereas valsartan decreased their surface density. Importantly, we found that pretreatment of RBCs with valsartan significantly impeded the activation of ICAM-4 receptors induced by epinephrine. The observed reduced expression of active ICAM-4 receptors on the RBC plasma membrane leads us to conjecture that valsartan may be used as a supporting remedy for the prevention and treatment of vaso-occlusive crisis in SCD.

Repository of Enriched Structures of Proteins Involved in the Red Blood Cell Environment (RESPIRE)

The Red Blood Cell (RBC) is a metabolically-driven cell vital for processes such a gas transport and homeostasis. RBC possesses at its surface exposing antigens proteins that are critical in blood transfusion. Due to their importance, numerous studies address the cell function as a whole but more and more details of RBC structure and protein content are now studied using massive state-of-the art characterisation techniques. Yet, the resulting information is frequently scattered in many scientific articles, in many databases and specialized web servers. To provide a more compendious view of erythrocytes and of their protein content, we developed a dedicated database called RESPIRE that aims at gathering a comprehensive and coherent ensemble of information and data about proteins in RBC. This cell-driven database lists proteins found in erythrocytes. For a given protein entry, initial data are processed from external portals and enriched by using state-of-the-art bioinformatics methods. As structural information is extremely useful to understand protein function and predict the impact of mutations, a strong effort has been put on the prediction of protein structures with a special treatment for membrane proteins. Browsing the database is available through text search for reference gene names or protein identifiers, through pre-defined queries or via hyperlinks. The RESPIRE database provides valuable information and unique annotations that should be useful to a wide audience of biologists, clinicians and structural biologists.

Database URL:http://www.dsimb.inserm.fr/respire

Assessment of the red blood cell proteome in a dog with unexplained hemolytic anemia

A 7-year-old female neutered Jack Russell Terrier was presented to Langford Vets, the University of Bristol, with a history of chronic intermittent lethargy. Investigations and clinical course were compatible with hereditary hemolysis due to a red blood cell membrane defect. Proteomics was used to explore protein alterations in the presence of a hypothesized red blood cell membrane protein deficiency. Proteomic analysis revealed downregulation of the band 3, and alpha- and beta-adducin proteins, and alterations in the red blood cell proteome consistent with previous reports of changes due to the presence of reticulocytosis and ongoing hemolysis. The spectrum of protein alterations identified in the affected dog may be homologous to a band 3 protein deficiency secondary to hereditary spherocytosis, as described in people.

Evaluation of lipid peroxidation and the level of some elements in rat erythrocytes during separate and combined vanadium and magnesium administration

The impact of vanadium (V) and magnesium (Mg) as sodium metavanadate (SMV, 0.125 mg V/ml) and magnesium sulfate (MS, 0.06 mg Mg/ml) on lipid peroxidation (LPO) and selected elements in the rat erythrocytes (RBCs) was investigated. Relationships between some indices determined in RBC were also studied. SMV alone (Group II) elevated the malondialdehyde level (MDA_RBC) (by 95% and 60%), compared with the control (Group I) and MS-supplemented rats (Group III), respectively, reduced the concentration of Cu_RBC (by 23.5%), in comparison with Group I, but did not change the levels of Na_RBC, K_RBC, and Ca_RBC, whereas MS alone (Group III) only reduced the Cu_RBC concentration (by 22%), compared with Group I. The SMV + MS combination (Group IV) reduced and elevated the Cu_RBC (by 24%) and Ca_RBC (by 111%) concentrations, respectively, in comparison with Groups I and III, and these changes were induced by the V-Mg antagonistic and synergistic interaction, respectively. The combined SMV + MS effect also enhanced the MDA_RBC level, compared with Groups I (by 79%) and III (by 47%) and slightly limited its concentration, compared with Group II, which, in turn, resulted from the distinct trend toward the V-Mg antagonistic interaction. We can conclude that V (as SMV) is able to stimulate LPO in rat RBCs and that V-Mg interactive effects are involved in changes in Cu_RBC, Ca_RBC, and MDA_RBC. Further studies are needed to elucidate the exact mechanisms of the V-Mg antagonistic/synergistic interactions and to provide insight into the biochemical mechanisms of changes in rats suffering from anemia [1], characterized by a disrupted antioxidant barrier in RBCs [2] and an intensified free radical process in these cells.

Proteomics of Stored Red Blood Cell Membrane and Storage-Induced Microvesicles Reveals the Association of Flotillin-2 With Band 3 Complexes

The storage of erythrocyte concentrates (ECs) induces lesions that notably affect metabolism, protein activity, deformability of red blood cells (RBCs), as well as the release of oxygen. Band 3 is one of the proteins affected during the ex vivo aging of RBCs. This membrane protein is an anion transporter, an anchor site for the cytoskeleton and other membrane proteins as well as a binding site for glycolytic enzymes and bears blood group antigens. In the present study, band 3 complexes were isolated from RBCs stored for 7 and 42 days in average (n = 3), as well as from microvesicles (n = 3). After extraction of membrane proteins with a deoxycholate containing buffer, band 3 complexes were co-immunoprecipitated on magnetic beads coated with two anti-band 3 antibodies. Both total membrane protein extracts and eluates (containing band 3 complexes) were separated on SDS-PAGE and analyzed by bottom-up proteomics. It revealed that three proteins were present or absent in band 3 complexes stemming from long-stored or short-stored ECs, respectively, whereas the membrane protein contents remained equivalent. These potential markers for storage-induced RBC aging are adenylosuccinate lyase (ADSL), α-adducin and flotillin-2, and were further analyzed using western blots. ADSL abundance tended to increase during storage in both total membrane protein and band 3 complexes, whereas α-adducin mainly tended to stay onto the membrane extract. Interestingly, flotillin-2 was equivalently present in total membrane proteins whereas it clearly co-immunoprecipitated with band 3 complexes during storage (1.6-fold-change, p = 0.0024). Moreover, flotillin-2 was enriched (almost threefold) in RBCs compared to microvesicles (MVs) (p < 0.001) and the amount found in MVs was associated to band 3 complexes. Different types of band 3 complexes are known to exist in RBCs and further studies will be required to better understand involvement of this protein in microvesiculation during the storage of RBCs.

Biomimetic Virulomics for Capture and Identification of Cell-Type Specific Effector Proteins

An unmet challenge in the study of disease is to accurately streamline the identification of important virulence factors. Traditional, genetically driven approaches miss biologically relevant markers due to discordance between the genome and proteome. Here, we developed a nanotechnology-enabled affinity enrichment strategy coupled with multiplexed quantitative proteomics, namely Biomimetic Virulomics, for successful identification of cell-type specific effector proteins of both prokaryotic and eukaryotic pathogens. We highlight the power of Biomimetic Virulomics by capturing known virulence factors in a high-throughput, cell-type guided fashion. Additionally, a comprehensive characterization of the membrane protein component of biomimetics utilized in this strategy is provided. Interfacing cell-derived nanomaterials with multiplexed quantitative proteomics allow for a specific targeting strategy of virulence factors that can be utilized for drug discovery against prominent human diseases.

Determination of dolutegravir's unbound fraction in human plasma using validated equilibrium dialysis and LC-MS/MS methods

Assessment of the unbound pharmacologically active fraction (fu; as the ratio of unbound to total concentration) of dolutegravir could improve therapeutic drug monitoring (TDM) in patients that experience virological failure or toxicity, despite receiving adequate total concentrations. This study evaluated (i) dolutegravir's fu through equilibrium dialysis (ED), (ii) the pre-analytical parameters that influence fu, and (iii) fu's inter-individual variability in HIV patients. Validation of the LC-MS/MS method followed FDA guidelines. The results, based on coefficients of variation (results from nominal concentrations <15%), allowed accurate measurement of unbound and total dolutegravir concentrations. Equilibrium during ED was obtained in 4h. Sparse non-specific binding (9%) was observed, allowing results interpretation without interference. Steps before analysis (e.g., conservation at +4°C, freeze/thaw cycles) did not influence fu, allowing easy integration of fu analysis within laboratory routines. Anticoagulants from samples (citrated versus heparinized; p<0.001) and hemolysis (p=0.007) influenced fu and could lead to misinterpretation. Developed was then performed to the HIV-patients' plasma (n=54). Results, expressed as median InterQuartile Range [25%;75%] were 0.45% IQR [0.38; 0.55] for fu, 9.26μg/L IQR [4.62; 15.14] for unbound, and 2035μg/L IQR [878.5; 2640] for total concentration. The high inter-individual variability observed in the unbound form from HIV patients was a first step towards integrating dolutegravir TDM.

Proteomic analysis of red blood cells and the potential for the clinic: what have we learned so far?

INTRODUCTION

Red blood cells (RBC) are the most abundant host cells in the human body. Mature erythrocytes are devoid of nuclei and organelles and have always been regarded as circulating 'bags of hemoglobin'. The advent of proteomics has challenged this assumption, revealing unanticipated complexity and novel roles for RBCs not just in gas transport, but also in systemic metabolic homeostasis in health and disease. Areas covered: In this review we will summarize the main advancements in the field of discovery mode and redox/quantitative proteomics with respect to RBC biology. We thus focus on translational/clinical applications, such as transfusion medicine, hematology (e.g. hemoglobinopathies) and personalized medicine. Synergy of omics technologies - especially proteomics and metabolomics - are highlighted as a hallmark of clinical metabolomics applications for the foreseeable future. Expert commentary: The introduction of advanced proteomics technologies, especially quantitative and redox proteomics, and the integration of proteomics data with omics information gathered through orthogonal technologies (especially metabolomics) promise to revolutionize many biomedical areas, from hematology and transfusion medicine to personalized medicine and clinical biochemistry.

The mechanism of formation, structure and physiological relevance of covalent hemoglobin attachment to the erythrocyte membrane

Covalent hemoglobin binding to membranes leads to band 3 (AE1) clustering and the removal of erythrocytes from the circulation; it is also implicated in blood storage lesions. Damaged hemoglobin, with the heme being in a redox and oxygen-binding inactive hemichrome form, has been implicated as the binding species. However, previous studies used strong non-physiological oxidants. In vivo hemoglobin is constantly being oxidised to methemoglobin (ferric), with around 1% of hemoglobin being in this form at any one time. In this study we tested the ability of the natural oxidised form of hemoglobin (methemoglobin) in the presence or absence of the physiological oxidant hydrogen peroxide to initiate membrane binding. The higher the oxidation state of hemoglobin (from Fe(III) to Fe(V)) the more binding was observed, with approximately 50% of this binding requiring reactive sulphydryl groups. The hemoglobin bound was in a high molecular weight complex containing spectrin, ankyrin and band 4.2, which are common to one of the cytoskeletal nodes. Unusually, we showed that hemoglobin bound in this way was redox active and capable of ligand binding. It can initiate lipid peroxidation showing the potential to cause cell damage. In vivo oxidative stress studies using extreme endurance exercise challenges showed an increase in hemoglobin membrane binding, especially in older cells with lower levels of antioxidant enzymes. These are then targeted for destruction. We propose a model where mild oxidative stress initiates the binding of redox active hemoglobin to the membrane. The maximum lifetime of the erythrocyte is thus governed by the redox activity of the cell; from the moment of its release into the circulation the timer is set.

Insights into red blood cell storage lesion: Toward a new appreciation

Red blood cell storage lesion (RSL) is a multifaceted biological phenomenon. It refers to deterioration in RBC quality that is characterized by lethal and sub-lethal, reversible and irreversible defects. RSL is influenced by prestorage variables and it might be associated with variable clinical outcomes. Optimal biopreservation conditions are expected to offer maximum levels of RBC survival and acceptable functionality and bioreactivity in-bag and in vivo; consequently, full appraisal of RSL requires understanding of how RSL changes interact with each other and with the recipient. Recent technological innovation in MS-based omics, imaging, cytometry, small particle and systems biology has offered better understanding of RSL contributing factors and effects. A number of elegant in vivo and in vitro studies have paved the way for the identification of quality control biomarkers useful to predict RSL profile and posttransfusion performance. Moreover, screening tools for the early detection of good or poor "storers" and donors have been developed. In the light of new perspectives, storage time is not the touchstone to rule on the quality of a packed RBC unit. At least by a biochemical standpoint, the metabolic aging pattern during storage may not correspond to the currently fresh/old distinction of stored RBCs. Finally, although each unit of RBCs is probably unique, a metabolic signature of RSL across storage variables might exist. Moving forward from traditional hematologic measures to integrated information on structure, composition, biochemistry and interactions collected in bag and in vivo will allow identification of points for intervention in a transfusion meaningful context.

Whole Blood Reveals More Metabolic Detail of the Human Metabolome than Serum as Measured by 1H-NMR Spectroscopy: Implications for Sepsis Metabolomics

Serum is a common sample of convenience for metabolomics studies. Its processing time can be lengthy and may result in the loss of metabolites including those of red blood cells (RBCs). Unlike serum, whole blood (WB) is quickly processed, minimizing the influence of variable hemolysis while including RBC metabolites. To determine differences between serum and WB metabolomes, both sample types, collected from healthy volunteers, were assayed by H-NMR (proton nuclear magnetic resonance) spectroscopy. A total of 34 and 50 aqueous metabolites were quantified from serum and WB, respectively. Free hemoglobin (Hgb) levels in serum were measured, and the correlation between Hgb and metabolite concentrations was determined. Most metabolites detected in serum were at higher concentrations in WB with the exception of acetoacetate and propylene glycol. The 18 unique metabolites of WB included adenosine, AMP, ADP, and ATP, which are associated with RBC metabolism. The use of serum results in the underrepresentation of a number of metabolic pathways including branched-chain amino acid degradation and glycolysis and gluconeogenesis. The range of free Hgb in serum was 0.03 to 0.01 g/dL, and eight metabolites were associated (P ≤ 0.05) with free Hgb. The range of free Hgb in serum samples from 18 sepsis patients was 0.02 to 0.46 g/dL. Whole blood and serum have unique aqueous metabolite profiles, but the use of serum may introduce potential pathway bias. Use of WB for metabolomics may be particularly important for studies in diseases such as sepsis in which RBC metabolism is altered, and mechanical and sepsis-induced hemolysis contributes to variance in the metabolome.

Hemolysis by surfactants--A review

An overview of the use of surfactants for erythrocyte lysis and their cell membrane action mechanisms is given. Erythrocyte membrane characteristics and its association with the cell cytoskeleton are presented in order to complete understanding of the erythrocyte membrane distortion. Cell homeostasis disturbances caused by surfactants might induce changes starting from shape modification to cell lysis. Two main mechanisms are hypothesized in literature which are osmotic lysis and lysis by solubilization even if the boundary between them is not clearly defined. Another specific mechanism based on the formation of membrane pores is suggested in the particular case of saponins. The lytic potency of a surfactant is related to its affinity for the membrane and the modification of the lipid membrane curvature. This is to be related to the surfactant shape defined by its hydrophobic and hydrophilic moieties but also by experimental conditions. As a consequence, prediction of the hemolytic potency of a given surfactant is challenging. Several studies are focused on the relation between surfactant erythrolytic potency and their physico-chemical parameters such as the critical micellar concentration (CMC), the hydrophile-lipophile balance (HLB), the surfactant membrane/water partition coefficient (K) or the packing parameter (P). The CMC is one of the most important factors considered even if a lytic activity cut-off effect points out that the only consideration of CMC not enough predictive. The relation K.CMC must be considered in addition to the CMC to predict the surfactant lytic capacity within the same family of non ionic surfactant. Those surfactant structure/lytic activity studies demonstrate the requirement to take into account a combination of physico-chemical parameters to understand and foresee surfactant lytic potency.

Physicochemical characterization of artificial nanoerythrosomes derived from erythrocyte ghost membranes

Colloidal stabile nanoerythrosomes with 200 nm average diameter were formed from hemoglobin-free erythrocyte ghost membrane via sonication and membrane extrusion. The incorporation of extra lipid (1,2-dipalmitoyl-sn-glycero-3-phosphocholine, DPPC), added to the sonicated ghosts, caused significant changes in the thermotropic character of the original membranes. As a result of the increased DPPC ratio the chain melting of the hydrated DPPC system and the characteristic small angle X-ray scattering (SAXS) of the lipid bilayers appeared. Significant morphological changes were followed by transmission electron microscopy combined with freeze fracture method (FF-TEM). After the ultrasonic treatment the large entities of erythrocyte ghosts transformed into nearly spherical nanoerythrosomes with diameters between 100 and 300 nm and at the same time a great number of 10-30 nm large membrane proteins or protein clusters were dispersed in the aqueous medium. The infrared spectroscopy (FT-IR) pointed out, that the sonication did not cause changes in the secondary structures of the membrane proteins under our preparation conditions. About fivefold of extra lipid--compared to the lipid content of the original membrane--caused homogeneous dispersion of nanoerythrosomes however the shape of the vesicles was not uniform. After the addition of about tenfold of DPPC, monoform and monodisperse nanoerythrosomes became typical. The outer surfaces of these roughly spherical objects were frequently polygonal, consisting of a net of pentagons and hexagons.

Alterations of membrane protein expression in red blood cells of Alzheimer's disease patients

Preventive measures, prognosis, or selected therapy in multifactorial maladies, including Alzheimer's disease (AD), require the application of a wide range of diagnostic assays. There is a large unmet need for relatively simple, blood-based biomarkers in this regard. We have recently developed a rapid and reliable flow cytometry and antibody-based method for the quantitative measurement of various red blood cell (RBC) membrane proteins from a drop of blood. Here, we document that the RBC expression of certain membrane proteins, especially that of the GLUT1 transporter and the insulin receptor (INSR), is significantly higher in AD patients than in age-matched healthy subjects. The observed differences may reflect long-term metabolic alterations relevant in the development of AD. These findings may pave the way for a diagnostic application of RBC membrane proteins as relatively stable and easily accessible personalized biomarkers in AD.

Cell surface membrane proteins as personalized biomarkers: where we stand and where we are headed

Personalized medicine requires the development of a wide array of biomarker diagnostic assays, reflecting individual variations and thus allowing tailored therapeutic interventions. Membrane proteins comprise approximately 30% of total human proteins; they play a key role in various physiological functions and pathological conditions, although, currently, only a limited number of membrane proteins are applied as biomarkers. In many normal tissues, cell surface membrane proteins are not easily accessible for diagnostic sampling, and tumor-derived membrane preparations - while serving as potential tumor biomarkers - may not reflect physiological protein expression. In addition to post-translational modifications, which may include glycosylation, phosphorylation and lipid modifications, the trafficking of membrane proteins is also regulated. Moreover, a tight cellular quality control monitors membrane protein maturation, and continuous removal and reinsertion, involving special signaling systems, occurs in many cases. However, cell surface membrane proteins already serve as valuable prognostic and predicative biomarkers, for example, in hematological and immunological diseases, by the determination of the cluster of differentiation markers. In this review, we demonstrate the relevance of cell surface membrane biomarkers in various diseases and call attention to the potential application of red blood cell (erythrocyte) membrane proteins in this regard. Surprisingly, red blood cells express hundreds of membrane proteins, which seem to reflect a general genetic and regulatory background, and may serve as relatively stable and easily accessible personalized membrane biomarkers. Quantitative membrane protein detection in red blood cells by flow cytometry may bring a breakthrough in this regard.

Profound morphological changes in the erythrocytes and fibrin networks of patients with hemochromatosis or with hyperferritinemia, and their normalization by iron chelators and other agents

It is well-known that individuals with increased iron levels are more prone to thrombotic diseases, mainly due to the presence of unliganded iron, and thereby the increased production of hydroxyl radicals. It is also known that erythrocytes (RBCs) may play an important role during thrombotic events. Therefore the purpose of the current study was to assess whether RBCs had an altered morphology in individuals with hereditary hemochromatosis (HH), as well as some who displayed hyperferritinemia (HF). Using scanning electron microscopy, we also assessed means by which the RBC and fibrin morphology might be normalized. An important objective was to test the hypothesis that the altered RBC morphology was due to the presence of excess unliganded iron by removing it through chelation. Very striking differences were observed, in that the erythrocytes from HH and HF individuals were distorted and had a much greater axial ratio compared to that accompanying the discoid appearance seen in the normal samples. The response to thrombin, and the appearance of a platelet-rich plasma smear, were also markedly different. These differences could largely be reversed by the iron chelator desferal and to some degree by the iron chelator clioquinol, or by the free radical trapping agents salicylate or selenite (that may themselves also be iron chelators). These findings are consistent with the view that the aberrant morphology of the HH and HF erythrocytes is caused, at least in part, by unliganded (‘free’) iron, whether derived directly via raised ferritin levels or otherwise, and that lowering it or affecting the consequences of its action may be of therapeutic benefit. The findings also bear on the question of the extent to which accepting blood donations from HH individuals may be desirable or otherwise.

The proteomics and interactomics of human erythrocytes

In this minireview, we focus on advances in our knowledge of the human erythrocyte proteome and interactome that have occurred since our seminal review on the topic published in 2007. As will be explained, the number of unique proteins has grown from 751 in 2007 to 2289 as of today. We describe how proteomics and interactomics tools have been used to probe critical protein changes in disorders impacting the blood. The primary example used is the work done on sickle cell disease where biomarkers of severity have been identified, protein changes in the erythrocyte membranes identified, pharmacoproteomic impact of hydroxyurea studied and interactomics used to identify erythrocyte protein changes that are predicted to have the greatest impact on protein interaction networks.

Expression levels of the ABCG2 multidrug transporter in human erythrocytes correspond to pharmacologically relevant genetic variations

We have developed a rapid, simple and reliable, antibody-based flow cytometry assay for the quantitative determination of membrane proteins in human erythrocytes. Our method reveals significant differences between the expression levels of the wild-type ABCG2 protein and the heterozygous Q141K polymorphic variant. Moreover, we find that nonsense mutations on one allele result in a 50% reduction in the erythrocyte expression of this protein. Since ABCG2 polymorphisms are known to modify essential pharmacokinetic parameters, uric acid metabolism and cancer drug resistance, a direct determination of the erythrocyte membrane ABCG2 protein expression may provide valuable information for assessing these conditions or for devising drug treatments. Our findings suggest that erythrocyte membrane protein levels may reflect genotype-dependent tissue expression patterns. Extension of this methodology to other disease-related or pharmacologically important membrane proteins may yield new protein biomarkers for personalized diagnostics.

Phospholipidomics reveals differences in glycerophosphoserine profiles of hypothermically stored red blood cells and microvesicles

During their normal in vivo life cycle erythrocytes (red blood cells, RBCs) undergo biochemical changes leading to membrane microvesiculation and shedding. RBC microvesiculation also occurs in vitro under conditions of blood bank storage, so microvesicles (MVs) accumulate in the storage (preservation) medium over storage time. Considerable effort has been put into gaining a mechanistic understanding of the RBC microvesiculation process, as this is crucial to better understand RBC biology in disease and in health. Additionally, MVs accumulated in stored RBCs have been implicated in transfusion adverse inflammatory reactions, with chloroform extractable compounds, thus lipophilic, known to trigger the effect. However, because thin layer chromatography resolution of RBC and MV lipids has always enabled one to conclude high compositional similarities, in depth analysis of MV lipids has not been extensively pursued. Here we present an orbitrap mass spectrometry (MS) approach to compare the phospholipid composition of RBCs and MVs from leukoreduced, hypothermically (2-6°C) stored RBC units. We used shotgun MS analysis and electrospray ionization (ESI) intra-source separation, and demonstrated high similarity of compositional profiles, except for glycerophosphoserines (PS). Contrasting abundances of PS 38:4 and PS 38:1 characterized MV and RBC profiles and suggested that storage-associated microvesiculation possibly involves shedding of specific membrane rafts. This finding indicates that phospholipidomics could likely contribute to a better understanding of the RBC microvesiculation process.

Membrane proteins of human fetal primitive nucleated red blood cells

In humans, primitive fetal nucleated red blood cells (FNRBCs) are thought to be as vital for embryonic life as their counterpart, adult red blood cells (adult RBCs) are in later-gestation fetuses and adults. Unlike adult RBCs, the identity and functions of FNRBC proteins are poorly understood owing to a scarcity of FNRBCs for proteomic investigations. The study aimed to investigate membrane proteins of this unique cell type. We present here, the first report on the membrane proteome of human primitive FNRBCs investigated by two-dimensional liquid chromatography coupled with mass-spectrometry (2D-LCMS/MS) and bioinformatics analysis. A total of 273 proteins were identified, of which 133 (48.7%) were membrane proteins. We compared our data with membrane proteins of adult RBCs to identify common, and unique, surface membrane proteins. Twelve plasma membrane proteins with transmembrane domains and eight proteins with transmembrane domains but without known sub-cellular location were identified as unique-to-FNRBCs. Except for the transferrin receptor, all other 19 unique-to-FNRBC membrane proteins have never been described in RBCs. Reverse-transcriptase PCR (RT-PCR) and immunocytochemistry validated the 2D-LCMS/MS data. Our findings provide potential surface antigens for separation of primitive FNRBCs from maternal blood for noninvasive prenatal diagnosis, and to understand the biology of these rare cells.

Computational identification of phospho-tyrosine sub-networks related to acanthocyte generation in neuroacanthocytosis

Acanthocytes, abnormal thorny red blood cells (RBC), are one of the biological hallmarks of neuroacanthocytosis syndromes (NA), a group of rare hereditary neurodegenerative disorders. Since RBCs are easily accessible, the study of acanthocytes in NA may provide insights into potential mechanisms of neurodegeneration. Previous studies have shown that changes in RBC membrane protein phosphorylation state affect RBC membrane mechanical stability and morphology. Here, we coupled tyrosine-phosphoproteomic analysis to topological network analysis. We aimed to predict signaling sub-networks possibly involved in the generation of acanthocytes in patients affected by the two core NA disorders, namely McLeod syndrome (MLS, XK-related, Xk protein) and chorea-acanthocytosis (ChAc, VPS13A-related, chorein protein). The experimentally determined phosphoproteomic data-sets allowed us to relate the subsequent network analysis to the pathogenetic background. To reduce the network complexity, we combined several algorithms of topological network analysis including cluster determination by shortest path analysis, protein categorization based on centrality indexes, along with annotation-based node filtering. We first identified XK- and VPS13A-related protein-protein interaction networks by identifying all the interactomic shortest paths linking Xk and chorein to the corresponding set of proteins whose tyrosine phosphorylation was altered in patients. These networks include the most likely paths of functional influence of Xk and chorein on phosphorylated proteins. We further refined the analysis by extracting restricted sets of highly interacting signaling proteins representing a common molecular background bridging the generation of acanthocytes in MLS and ChAc. The final analysis pointed to a novel, very restricted, signaling module of 14 highly interconnected kinases, whose alteration is possibly involved in generation of acanthocytes in MLS and ChAc.

Depletion of hemoglobin and carbonic anhydrase from erythrocyte cytosolic samples by preparative clear native electrophoresis

Proteomic analysis of red cells is compromised by the presence of high-abundance proteins (hemoglobin and carbonic anhydrase-1), which completely obscure low-abundance species. The depletion method presented here involves performing native gel electrophoresis in a polyacrylamide gel tube using a modified electroelution cell. The electrophoretic run is interrupted intermittently to allow the recovery of at least three different liquid fractions, which can be analyzed by both native PAGE and 2D isoelectric focusing SDS-PAGE, or by shotgun mass spectrometry analysis after trypsin in-solution protein digestion. This low-cost, reproducible technique can be used to process large amounts of sample, and it increases the likelihood of detecting low-abundance proteins, thereby resulting in greater proteome coverage. The separation procedure takes approximately 6-7 h.

Erythrocyte membrane changes of chorea-acanthocytosis are the result of altered Lyn kinase activity

Acanthocytic RBCs are a peculiar diagnostic feature of chorea-acanthocytosis (ChAc), a rare autosomal recessive neurodegenerative disorder. Although recent years have witnessed some progress in the molecular characterization of ChAc, the mechanism(s) responsible for generation of acanthocytes in ChAc is largely unknown. As the membrane protein composition of ChAc RBCs is similar to that of normal RBCs, we evaluated the tyrosine (Tyr)-phosphorylation profile of RBCs using comparative proteomics. Increased Tyr phosphorylation state of several membrane proteins, including band 3, β-spectrin, and adducin, was noted in ChAc RBCs. In particular, band 3 was highly phosphorylated on the Tyr-904 residue, a functional target of Lyn, but not on Tyr-8, a functional target of Syk. In ChAc RBCs, band 3 Tyr phosphorylation by Lyn was independent of the canonical Syk-mediated pathway. The ChAc-associated alterations in RBC membrane protein organization appear to be the result of increased Tyr phosphorylation leading to altered linkage of band 3 to the junctional complexes involved in anchoring the membrane to the cytoskeleton as supported by coimmunoprecipitation of β-adducin with band 3 only in ChAc RBC-membrane treated with the Lyn-inhibitor PP2. We propose this altered association between membrane skeleton and membrane proteins as novel mechanism in the generation of acanthocytes in ChAc.

Erythrocyte peripheral type benzodiazepine receptor/voltage-dependent anion channels are upregulated by Plasmodium falciparum

Plasmodium falciparum relies on anion channels activated in the erythrocyte membrane to ensure the transport of nutrients and waste products necessary for its replication and survival after invasion. The molecular identity of these anion channels, termed "new permeability pathways" is unknown, but their currents correspond to up-regulation of endogenous channels displaying complex gating and kinetics similar to those of ligand-gated channels. This report demonstrates that a peripheral-type benzodiazepine receptor, including the voltage dependent anion channel, is present in the human erythrocyte membrane. This receptor mediates the maxi-anion currents previously described in the erythrocyte membrane. Ligands that block this peripheral-type benzodiazepine receptor reduce membrane transport and conductance in P falciparum-infected erythrocytes. These ligands also inhibit in vitro intraerythrocytic growth of P falciparum. These data support the hypothesis that dormant peripheral-type benzodiazepine receptors become the "new permeability pathways" in infected erythrocytes after up-regulation by P falciparum. These channels are obvious targets for selective inhibition in anti-malarial therapies, as well as potential routes for drug delivery in pharmacologic applications.

Elevated levels of redox regulators, membrane-bound globin chains, and cytoskeletal protein fragments in hereditary spherocytosis erythrocyte proteome

OBJECTIVE

Hereditary spherocytosis (HS), a common inherited hemolytic anemia characterized by decreased deformability, reduced surface to volume ratio, and increased osmotic fragility of the spheroidal erythrocytes, is associated with several mutations of α- and β-spectrin, ankyrin, band 3, band 4.2. HS manifests itself with high degrees of clinical heterogeneity and the molecular events leading to premature hemolysis of the spherocytes are unclear. We have employed proteomic techniques to identify differentially regulated proteins in the membrane and hemoglobin-depleted cytosol of HS erythrocytes.

METHODS

We have employed 2-D gel electrophoresis and tandem matrix assisted laser desorption ionization-time of flight/time of flight mass spectrometry to investigate the differential proteome profiling of membrane and hemoglobin-depleted cytosol of erythrocytes isolated from the peripheral blood samples of HS patients and normal volunteers.

RESULTS

Our study showed that redox regulators are up-regulated; while a co-chaperone and a nucleotide kinase are down-regulated in HS erythrocyte cytosol. We observed elevated levels of membrane-associated globin chains and low-molecular weight fragments of several major cytoskeletal proteins.

CONCLUSION

The observed changes in the erythrocyte proteomes indicate altered redox regulation, nucleotide metabolism, protein aggregation and/or degradation, cytoskeletal disorganization, and severe oxidative stress in HS. Taken together, this study could enlighten upon disease progression and pathophysiology of HS.

Molecular origin of Na(+)/Li(+) exchanger: Evidence against the involvement of major cloned erythrocyte transporters

Numerous studies have demonstrated heightened Na(+)/Li(+) countertransport (NLCT) activity in erythrocytes of patients with essential hypertension or diabetic nephropathy. The same carrier also contributes to the therapeutic action of lithium salt, widely used in the treatment of psychiatric disorders. However, the molecular origin of NLCT remains unknown. This study examined the role of major ion transporters in NLCT by comparative analysis of its activity and that of ion transporters providing inwardly directed (86)Rb, (22)Na and (32)P fluxes. NLCT was below the detection limit in rat erythrocytes and ∼50-fold higher in rabbits compared to humans. Unlike NLCT, the activities of Na(+),K(+)-ATPase, Na(+),K(+),2Cl(-) cotransporter and anion exchanger were somewhat similar in the erythrocytes of these species, whereas Na(+),P(i) cotransport was in 1:2:6 proportion in rats, humans and rabbits, respectively. Loading of erythrocytes with Li(+) for NLCT measurement did not affect the activity of Na(+),P(i) cotransporter. Keeping in mind that NLCT is much higher in rabbits vs humans and rats, we compared the set of membrane proteins in these species using 2-dimensional gel electrophoresis. This approach revealed 174 common spots, whereas 132 proteins were detected only in human and rabbit erythrocyte membranes. Among these proteins, we found 17 spots whose expression was higher by more than 5-fold in rabbit compared to human erythrocytes. Thus, our results argue against the involvement of major ion transporters in NLCT. They also show that comparative proteomics is a potent tool to identify the molecular origin of this carrier.

The proteome of sickle cell disease: insights from exploratory proteomic profiling

The expanding realm of exploratory proteomics has added a unique dimension to the study of the complex pathophysiology involved in sickle cell disease. A review of proteomic studies published on sickle cell erythrocytes and plasma shows trends of upregulation of antioxidant proteins, an increase in cytoskeletal defects, an increase in protein repair and turnover components, a decrease in lipid raft proteins and apolipoprotein dysregulation. Many of these findings are consistent with the pathophysiology of sickle cell disease, including high oxidant burden, resulting in damage to cytoskeletal and other proteins, and erythrocyte rigidity. More unexpected findings, such as a decrease in lipid raft components and apolipoprotein dysregulation, offer previously unexplored targets for future investigation and potential therapeutic intervention. Exploratory proteomic profiling is a valuable source of hypothesis generation for the cellular and molecular pathophysiology of sickle cell disease.

Red blood cell proteomics

Since its discovery in the 17th century, the red blood cell, recognized in time as the critical cell component for survival, has been the focus of much attention. Its unique role in gas exchange (oxygen/CO(2) transport) and its distinct characteristics (absence of nucleus; biconcave cell shape) together with an - in essence - unlimited supply lead to extensive targeted biochemical, molecular and structural studies. A quick PubMed query with the word "erythrocyte" results in 198 013 scientific articles of which 162 are red blood cell proteomics studies, indicating that this new technique has been only recently applied to the red blood cell and related fields. Standard and comparative proteomics have been widely used to study different blood components. A growing body of proteomics literature has since developed, which deals with the characterization of red blood cells in health and disease. The possibility offered by proteomics to obtain a global snapshot of the whole red blood cell protein make-up, has provided unique insights to many fields including transfusion medicine, anaemia studies, intra-red blood cell parasite biology and translational research. While the contribution of proteomics is beyond doubt, a full red blood cell understanding will ultimately require, in addition to proteomics, lipidomics, glycomics, interactomics and study of post-translational modifications. In this review we will briefly discuss the methodology and limitations of proteomics, the contribution it made to the understanding of the erythrocyte and the advances in red blood cell-related fields brought about by comparative proteomics.

Extraction methods of red blood cell membrane proteins for Multidimensional Protein Identification Technology (MudPIT) analysis

Since red blood cells (RBCs) lack nuclei and organelles, cell membrane is their main load-bearing component and, according to a dynamic interaction with the cytoskeleton compartment, plays a pivotal role in their functioning. Even if erythrocyte membranes are available in large quantities, the low abundance and the hydrophobic nature of cell membrane proteins complicate their purification and detection by conventional 2D gel-based proteomic approaches. So, in order to increase the efficiency of RBC membrane proteome identification, here we took advantage of a simple and reproducible membrane sub-fractionation method coupled to Multidimensional Protein Identification Technology (MudPIT). In addition, the adoption of a stringent RBC filtration strategy from the whole blood, permitted to remove exhaustively contaminants, such as platelets and white blood cells, and to identify a total of 275 proteins in the three RBC membrane fractions collected and analysed. Finally, by means of software for the elaboration of the great quantity of data obtained and programs for statistical analysis and protein classification, it was possible to determine the validity of the entire system workflow and to assign the proper sub-cellular localization and function for the greatest number of the identified proteins.