Distribution and shedding of the membrane phosphatidylserine during maturation and aging of erythroid cells

Redistribution of the glycocalyx exposes phagocytic determinants on apoptotic cells

Phagocytes remove dead and dying cells by engaging "eat-me" ligands such as phosphatidylserine (PtdSer) on the surface of apoptotic targets. However, PtdSer is obscured by the bulky exofacial glycocalyx, which also exposes ligands that activate "don't-eat-me" receptors such as Siglecs. Clearly, unshielding the juxtamembrane "eat-me" ligands is required for the successful engulfment of apoptotic cells, but the mechanisms underlying this process have not been described. Using human and murine cells, we find that apoptosis-induced retraction and weakening of the cytoskeleton that anchors transmembrane proteins cause an inhomogeneous redistribution of the glycocalyx: actin-depleted blebs emerge, lacking the glycocalyx, while the rest of the apoptotic cell body retains sufficient actin to tether the glycocalyx in place. Thus, apoptotic blebs can be engaged by phagocytes and are targeted for engulfment. Therefore, in cells with an elaborate glycocalyx, such as mucinous cancer cells, this "don't-come-close-to-me" barrier must be removed to enable clearance by phagocytosis.

Pennisetum glaucum Protein Extract Protects RBC, Liver, Kidney, Small Intestine from Oxidative Damage and Exhibits Anticoagulant, Antiplatelet Activity

High level of exogenous ROS in the circulation affects RBC membrane integrity which facilitates the generation of endogenous RBC ROS, implicated in series of physiological changes primarily associated with thrombosis and vital tissue damage. Although, Pennisetum glaucum (pearl millet) stores abundance of proteins, their therapeutic potential is least explored. Thus, the purpose of this study is to examine the role of Pennisetum Glaucum Protein Extract (PGE) on oxidative stress induced cell/tissue damage and thrombosis. In this investigation, protein characterization was done by using SDS-PAGE, Native-PAGE, PAS-staining and HPLC. In-vitro oxidative stress was induced in RBC using sodium nitrite. While, in-vivo oxidative stress was induced in experimental rats using diclofenac. Stress markers and biochemical parameters were evaluated. Role of PGE on thrombosis was assessed by using, in-vitro plasma recalcification time, activated partial thromboplastin time, prothrombin time, mouse tail bleeding time (In-vivo) and platelet aggregation. PGE revealed varied range of molecular weight proteins on SDS-PAGE. PGE normalized the sodium nitrite induced oxidative damage of RBC and diclofenac induced oxidative damage in liver, kidney and small intestine. PGE exhibited anticoagulant effect by increasing the coagulation time of both PRP and PPP and mouse tail bleeding time. Furthermore, PGE prolonged the clotting time of only APTT but did not affect PT. PGE inhibited agonists ADP and epinephrine induced platelet aggregation. Our findings suggest, PGE could be a better contender in the management of oxidative stress and its associated diseases.

ABBREVIATIONS

PGEPennisetum Glaucum protein ExtractAPPTActivated Partial Thromboplastin TimePTProthrombin TimeROSReactive Oxygen SpeciesPRPPlatelet Rich PlasmaPPPPlatelet Poor PlasmaSDS-PAGESodium Dodecyl Sulfate-Polyacrylamide Gel ElectrophoresisPASPeriodic Acid-schiff StainingODOptical DensityINRInternational Normalized RatioPBSPhosphate Buffered SalineSODSuperoxide DismutaseTCATrichloro Acetatic AcidDTNBDi-Thio-bis-NitroBenzoic acidSGOTSerum Glutamate Oxaloacetate TransaminaseSGPTSerum Glutamate Pyruvate TransaminaseALPAlkaline PhosphataseDFCDiclofenacSylSilymarinMEDMinimum Edema DoseMHDMinimum Hemorrhagic Dose.

NonFreezable Preservation of Human Red Blood Cells at -8 °C

Red blood cell (RBC) preservation is very important in human health. The RBCs are usually preserved at 4 ± 2 °C without freezing or at a very low temperature (-80 °C or liquid nitrogen) with deep freezing. Herein, non freezable preservation of RBCs at a subzero temperature is reported to prolong the preservation time compared with that at 4 ± 2 °C. By adding glycerol and poly(ethylene glycol) (PEG) (average number molecular weight 400, PEG-400) into the preservation solution, the freezing point is decreased and the hemolysis is kept low. The cell metabolism of stored RBCs at -8 °C is reduced, and the shelf life of RBCs extends up to at least 70 days. At the end of preservation, the pH decreases a little bit to demonstrate the low metabolic rate of RBCs stored at subzero temperatures. After quick washing, the RBC survival rate is ca. 95%. The adenosine triphosphate, 2,3-diphosphoglycerate, and cell deformation ability of the washed RBCs are maintained at a high level, while the malondialdehyde is relatively low, which verifies the high quality of RBCs stored at this condition.

Olive Oil Phenols Prevent Mercury-Induced Phosphatidylserine Exposure and Morphological Changes in Human Erythrocytes Regardless of Their Different Scavenging Activity

Phosphatidylserine (PS) translocation to the external membrane leaflet represents a key mechanism in the pathophysiology of human erythrocytes (RBC) acting as an "eat me" signal for the removal of aged/stressed cells. Loss of physiological membrane asymmetry, however, can lead to adverse effects on the cardiovascular system, activating a prothrombotic activity. The data presented indicate that structurally related olive oil phenols prevent cell alterations induced in intact human RBC exposed to HgCl₂ (5-40 µM) or Ca²⁺ ionophore (5 µM), as measured by hallmarks including PS exposure, reactive oxygen species generation, glutathione depletion and microvesicles formation. The protective effect is observed in a concentration range of 1-30 µM, hydroxytyrosol being the most effective; its in vivo metabolite homovanillic alcohol still retains the biological activity of its dietary precursor. Significant protection is also exerted by tyrosol, in spite of its weak scavenging activity, indicating that additional mechanisms are involved in the protective effect. When RBC alterations are mediated by an increase in intracellular calcium, the protective effect is observed at higher concentrations, indicating that the selected phenols mainly act on Ca²⁺-independent mechanisms, identified as protection of glutathione depletion. Our findings strengthen the nutritional relevance of olive oil bioactive compounds in the claimed health-promoting effects of the Mediterranean Diet.

The regulation roles of Ca2+ in erythropoiesis: What have we learned?

Calcium (Ca²⁺) is an important second messenger molecule in the body, regulating cell cycle and fate. There is growing evidence that intracellular Ca²⁺ levels play functional roles in the total physiological process of erythroid differentiation, including the proliferation and differentiation of erythroid progenitor cells, terminal enucleation, and mature red blood cell aging and clearance. Moreover, recent research on the pathology of erythroid disorders has made great progress in the past decades, indicating that calcium ion hemostasis is closely related to ineffective erythropoiesis and increased sensitivity to stress factors. In this review, we summarized what is known about the functional roles of intracellular Ca²⁺ in erythropoiesis and erythrocyte-related diseases, with an emphasis on the regulation of the intracellular Ca²⁺ homeostasis during erythroid differentiation. An understanding of the regulation roles of Ca²⁺ homeostasis in erythroid differentiation will facilitate further studies and eventually molecular identification of the pathways involved in the pathological process of erythroid disorders, providing new therapeutic opportunities in erythrocyte-related disease.

Concise review: how do red blood cells born, live, and die?

The average life cycle of a human RBC is approximately 120 days. Generally, by this point, the cell is worn out and damaged. RBCs pass through both the spleen and liver, where specialised immune cells called macrophages are found. Macrophages recognise when an RBC is spent, and undergo a process called phagocytosis where they digest the cell. In this process, the iron in haemoglobin is recycled for use in new blood cells and the hem molecule is degraded, conjugated to bilirubin, and eliminated from the body. All the other cellular proteins are either recycled or eliminated. Historically, this process was thought to occur exclusively in the spleen, but recent studies have shown that it occurs in the bone marrow. The RBC has been analysed from many perspectives: cytological, haematological, and immunological, as well as from the focus of molecular biology, biophysics, and mathematics. Here we analyse how are red blood cells born and how they live and die in a brief overview of the whole process with special mention of the morphological aspects from bone marrow and spleen provided by transmission and scanning electron microscopy.

The Redox Balance and Membrane Shedding in RBC Production, Maturation, and Senescence

Membrane shedding in the form of extracellular vesicles plays a key role in normal physiology and pathology. Partial disturbance of the membrane-cytoskeleton linkage and increased in the intracellular Ca content are considered to be mechanisms underlying the process, but it is questionable whether they constitute the primary initiating steps. Homeostasis of the redox system, which depends on the equilibrium between oxidants and antioxidants, is crucial for many cellular processes. Excess oxidative power results in oxidative stress, which affects many cellular components, including the membrane. Accumulating evidence suggests that oxidative stress indirectly affects membrane shedding most probably by affecting the membrane-cytoskeleton and the Ca content. In red blood cells (RBCs), changes in both the redox system and membrane shedding occur throughout their life-from birth-their production in the bone marrow, to death-aging in the peripheral blood and removal by macrophages in sites of the reticuloendothelial system. Both oxidative stress and membrane shedding are disturbed in diseases affecting the RBC, such as the hereditary and acquired hemolytic anemias (i.e., thalassemia, sickle cell anemia, and autoimmune hemolytic anemia). Herein, I review some data-based and hypothetical possibilities that await experimental confirmation regarding some aspects of the interaction between the redox system and membrane shedding and its role in the normal physiology and pathology of RBCs.

Aging-associated changes in CD47 arrangement and interaction with thrombospondin-1 on red blood cells visualized by super-resolution imaging

CD47 serves as a ligand for signaling regulatory protein α (SIRPα) and as a receptor for thrombospondin-1 (TSP-1). Although CD47, TSP-1, and SIRPα are thought to be involved in the clearance of aged red blood cells (RBCs), aging-associated changes in the expression and interaction of these molecules on RBCs have been elusive. Using direct stochastic optical reconstruction microscopy (dSTORM)-based imaging and quantitative analysis, we can report that CD47 molecules on young RBCs reside as nanoclusters with little binding to TSP-1, suggesting a minimal role for TSP-1/CD47 signaling in normal RBCs. On aged RBCs, CD47 molecules decreased in number but formed bigger and denser clusters, with increased ability to bind TSP-1. Exposure of aged RBCs to TSP-1 resulted in a further increase in the size of CD47 clusters via a lipid raft-dependent mechanism. Furthermore, CD47 cluster formation was dramatically inhibited on thbs1-/- mouse RBCs and associated with a significantly prolonged RBC lifespan. These results indicate that the strength of CD47 binding to its ligand TSP-1 is predominantly determined by the distribution pattern and not the amount of CD47 molecules on RBCs, and offer direct evidence for the role of TSP-1 in phagocytosis of aged RBCs. This study provides clear nanoscale pictures of aging-associated changes in CD47 distribution and TSP-1/CD47 interaction on the cell surface, and insights into the molecular basis for how these molecules coordinate to remove aged RBCs.

Erythropoiesis In Vitro-A Research and Therapeutic Tool in Thalassemia

Thalassemia (thal) is a hereditary chronic hemolytic anemia due to a partial or complete deficiency in the production of globin chains, in most cases, α or β, which compose, together with the iron-containing porphyrins (hemes), the hemoglobin molecules in red blood cells (RBC). The major clinical symptom of β-thal is severe chronic anemia—a decrease in RBC number and their hemoglobin content. In spite of the improvement in therapy, thal still severely affects the quality of life of the patients and their families and imposes a substantial financial burden on the community. These considerations position β-thal, among other hemoglobinopathies, as a major health and social problem that deserves increased efforts in research and its clinical application. These efforts are based on clinical studies, experiments in animal models and the use of erythroid cells grown in culture. The latter include immortal cell lines and cultures initiated by erythroid progenitor and stem cells derived from the blood and RBC producing (erythropoietic) sites of normal and thal donors, embryonic stem cells, and recently, "induced pluripotent stem cells" generated by manipulation of differentiated somatic cells. The present review summarizes the use of erythroid cultures, their technological aspects and their contribution to the research and its clinical application in thal. The former includes deciphering of the normal and pathological biology of the erythroid cell development, and the latter—their role in developing innovative therapeutics—drugs and methods of gene therapy, as well as providing an alternative source of RBC that may complement or substitute blood transfusions.

Red blood cells: the forgotten player in hemostasis and thrombosis

New evidence has stirred up a long-standing but undeservedly forgotten interest in the role of erythrocytes, or red blood cells (RBCs), in blood clotting and its disorders. This review summarizes the most recent research that describes the involvement of RBCs in hemostasis and thrombosis. There are both quantitative and qualitative changes in RBCs that affect bleeding and thrombosis, as well as interactions of RBCs with cellular and molecular components of the hemostatic system. The changes in RBCs that affect hemostasis and thrombosis include RBC counts or hematocrit (modulating blood rheology through viscosity) and qualitative changes, such as deformability, aggregation, expression of adhesive proteins and phosphatidylserine, release of extracellular microvesicles, and hemolysis. The pathogenic mechanisms implicated in thrombotic and hemorrhagic risk include variable adherence of RBCs to the vessel wall, which depends on the functional state of RBCs and/or endothelium, modulation of platelet reactivity and platelet margination, alterations of fibrin structure and reduced susceptibility to fibrinolysis, modulation of nitric oxide availability, and the levels of von Willebrand factor and factor VIII in blood related to the ABO blood group system. RBCs are involved in platelet-driven contraction of clots and thrombi that results in formation of a tightly packed array of polyhedral erythrocytes, or polyhedrocytes, which comprises a nearly impermeable barrier that is important for hemostasis and wound healing. The revisited notion of the importance of RBCs is largely based on clinical and experimental associations between RBCs and thrombosis or bleeding, implying that RBCs are a prospective therapeutic target in hemostatic and thrombotic disorders.

Role of phospholipid synthesis in the development and differentiation of malaria parasites in the blood

The life cycle of malaria parasites in both their mammalian host and mosquito vector consists of multiple developmental stages that ensure proper replication and progeny survival. The transition between these stages is fueled by nutrients scavenged from the host and fed into specialized metabolic pathways of the parasite. One such pathway is used by Plasmodium falciparum, which causes the most severe form of human malaria, to synthesize its major phospholipids, phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine. Much is known about the enzymes involved in the synthesis of these phospholipids, and recent advances in genetic engineering, single-cell RNA-Seq analyses, and drug screening have provided new perspectives on the importance of some of these enzymes in parasite development and sexual differentiation and have identified targets for the development of new antimalarial drugs. This Minireview focuses on two phospholipid biosynthesis enzymes of P. falciparum that catalyze phosphoethanolamine transmethylation (PfPMT) and phosphatidylserine decarboxylation (PfPSD) during the blood stages of the parasite. We also discuss our current understanding of the biochemical, structural, and biological functions of these enzymes and highlight efforts to use them as antimalarial drug targets.

Plasma Membrane Lipid Domains as Platforms for Vesicle Biogenesis and Shedding?

Extracellular vesicles (EVs) contribute to several pathophysiological processes and appear as emerging targets for disease diagnosis and therapy. However, successful translation from bench to bedside requires deeper understanding of EVs, in particular their diversity, composition, biogenesis and shedding mechanisms. In this review, we focus on plasma membrane-derived microvesicles (MVs), far less appreciated than exosomes. We integrate documented mechanisms involved in MV biogenesis and shedding, focusing on the red blood cell as a model. We then provide a perspective for the relevance of plasma membrane lipid composition and biophysical properties in microvesiculation on red blood cells but also platelets, immune and nervous cells as well as tumor cells. Although only a few data are available in this respect, most of them appear to converge to the idea that modulation of plasma membrane lipid content, transversal asymmetry and lateral heterogeneity in lipid domains may play a significant role in the vesiculation process. We suggest that lipid domains may represent platforms for inclusion/exclusion of membrane lipids and proteins into MVs and that MVs could originate from distinct domains during physiological processes and disease evolution.

Optimization of lipid extraction and analytical protocols for UHPLC-ESI-HRMS-based lipidomic analysis of adherent mammalian cancer cells

Lipidomics, which reveals comprehensive characterization of molecular lipids, is a rapidly growing technology used in biomedical research. Lipid extraction is a critical step in lipidomic analysis. However, the effectiveness of different lipid extract solvent systems from cellular samples still remains unclear. In the current study, the protocol of reverse-phase liquid chromatography mass spectrometry (LC/MS)-based lipidomics was optimized for extraction and detection of lipids from human pancreatic cancer cell line PANC-1. Four different extraction methods were compared, including methanol/methyl-tert-butyl ether (MTBE)/H₂O, methanol/chloroform, methanol/MTBE/chloroform, and hexane/isopropanol. Data were acquired using high-resolution mass spectrometry in positive and negative ion modes respectively. The number of total detected and identified lipids was assessed with the aid of automated lipid identification software LipidSearch. Results demonstrated that methanol/MTBE/H₂O provided a better extraction efficiency for different lipid classes, which was chosen as the optimized extraction solvent system. This validated method enables highly sensitive and reproducible analysis for a variety of cellular lipids, which was further applied to an untargeted lipidomic study on human pancreatic cancer PANC-1 cell lines. Moreover, this optimized extraction solvent system can be further applied to other cancer cell lines with similar chemical and physical properties. Graphical abstract Optimized UHPLC-ESI-HRMS-based lipidomic analysis of cancer cells.

Understanding quasi-apoptosis of the most numerous enucleated components of blood needs detailed molecular autopsy

Erythrocytes are the most numerous cells in human body and their function of oxygen transport is pivotal to human physiology. However, being enucleated, they are often referred to as a sac of molecules and their cellularity is challenged. Interestingly, their programmed death stands a testimony to their cell-hood. They are capable of self-execution after a defined life span by both cell-specific mechanism and that resembling the cytoplasmic events in apoptosis of nucleated cells. Since the execution process lacks the nuclear and mitochondrial events in apoptosis, it has been referred to as quasi-apoptosis or eryptosis. Several studies on molecular mechanisms underlying death of erythrocytes have been reported. The data has generated a non-cohesive sketch of the process. The lacunae in the present knowledge need to be filled to gain deeper insight into the mechanism of physiological ageing and death of erythrocytes, as well as the effect of age of organism on RBCs survival. This would entail how the most numerous cells in the human body die and enable a better understanding of signaling mechanisms of their senescence and premature eryptosis observed in individuals of advanced age.

How do red blood cells know when to die?

Human red blood cells (RBCs) are normally phagocytized by macrophages of splenic and hepatic sinusoids at 120 days of age. The destruction of RBCs is ultimately controlled by antagonist effects of phosphatidylserine (PS) and CD47 on the phagocytic activity of macrophages. In this work, we introduce a conceptual model that explains RBC lifespan as a consequence of the dynamics of these molecules. Specifically, we suggest that PS and CD47 define a molecular algorithm that sets the timing of RBC phagocytosis. We show that significant changes in RBC lifespan described in the literature can be explained as alternative outcomes of this algorithm when it is executed in different conditions of oxygen availability. The theoretical model introduced here provides a unified framework to understand a variety of empirical observations regarding RBC biology. It also highlights the role of RBC lifespan as a key element of RBC homeostasis.

Role of red blood cells in haemostasis and thrombosis

In contrast to an obsolete notion that erythrocytes, or red blood cells (RBCs), play a passive and minor role in hemostasis and thrombosis, over the past decades there has been increasing evidence that RBCs have biologically and clinically important functions in blood clotting and its disorders. This review summarizes the main mechanisms that underlie the involvement of RBCs in hemostasis and thrombosis in vivo, such as rheological effects on blood viscosity and platelet margination, aggregation and deformability of RBCs; direct adhesion and indirect biochemical interactions with endothelial cells and platelets, etc. The ability of stored and pathologically altered RBCs to generate thrombin through exposure of phosphatidylserine has been emphasized. The procoagulant and prothrombotic potential of RBC-derived microparticles transfused with stored RBCs or formed in various pathological conditions associated with hemolysis has been described along with prothrombotic effects of free hemoglobin and heme. Binding of fibrinogen or fibrin to RBCs may influence their effects on fibrin network structure, clot mechanical properties, and fibrinolytic resistance. Recent data on platelet-driven clot contraction show that RBCs compressed by platelets pulling on fibrin form a tightly packed array of polyhedral erythrocytes, or polyhedrocytes, which comprises a nearly impermeable barrier important for hemostasis and wound healing. RBCs may perform dual roles, both helping to stem bleeding but at the same time contributing to thrombosis in a variety of ways.

Shedding of phosphatidylserine from developing erythroid cells involves microtubule depolymerization and affects membrane lipid composition

Phosphatidylserine (PS), which is normally localized in the cytoplasmic leaflet of the membrane, flip-flops to the external leaflet during aging of, or trauma to, cells. A fraction of this PS undergoes shedding into the extracellular milieu. PS externalization and shedding change during maturation of erythroid cells and affect the functioning, senescence and elimination of mature RBCs. Several lines of evidence suggest dependence of PS shedding on intracellular Ca concentration as well as on interaction between plasma membrane phospholipids and microtubules (MTs), the key components of the cytoskeleton. We investigated the effect of Ca flux and MT assembly on the distribution of PS across, and shedding from, the membranes of erythroid precursors. Cultured human and murine erythroid precursors were treated with the Ca ionophore A23187, the MT assembly enhancer paclitaxel (Taxol) or the inhibitor colchicine. PS externalization and shedding were measured by flow cytometry and the cholesterol/phospholipids in RBC membranes and supernatants, by ¹H-NMR. We found that treatment with Taxol or colchicine resulted in a marked increase in PS externalization, while shedding was increased by colchicine but inhibited by Taxol. These results indicate that PS externalization is mediated by Ca flux, and PS shedding by both Ca flux and MT assembly. The cholesterol/phospholipid ratio in the membrane is modified by PS shedding; we now show that it was increased by colchicine and A23187, while taxol had no effect. In summary, the results indicate that the Ca flux and MT depolymerization of erythroid precursors mediate their PS externalization and shedding, which in turn changes their membrane composition.