P. falciparum Invasion and Erythrocyte Aging.

Plasmodium parasites need to find red blood cells (RBCs) that, on the one hand, expose receptors for the pathogen ligands and, on the other hand, maintain the right geometry to facilitate merozoite attachment and entry into the red blood cell. Both characteristics change with the maturation of erythrocytes. Some Plasmodia prefer younger vs. older erythrocytes. How does the life evolution of the RBC affect the invasion of the parasite? What happens when the RBC ages? In this review, we present what is known up until now.

Red blood cell lifespan in long-term hemodialysis patients treated with roxadustat or recombinant human erythropoietin.

INTRODUCTION: A significant decrease in red blood cell (RBC) survival has been observed in patients with renal failure, which is supposed to contribute to renal anemia. The aim of this observational study was to determine RBC survival in hemodialysis (HD) patients treated with roxadustat or recombinant human erythropoietin (rhuEPO) compared with healthy persons. METHODS: RBC lifespan was measured by Levitt's CO breath test with newly developed automatic instrument ELS Tester. RESULTS: A total of 102 patients receiving long-term HD from two independent dialysis centers enrolled in the study, of whom 62 were treated with rhuEPO and 40 were on roxadustat therapy. A total of 25 healthy participants were recruited to match HD participants according to age and sex. Median RBC survival times in rhuEPO, roxadustat, and control groups were 65.0 (25th-75th percentile, 49.5-77.3), 75.5 (25th-75th percentile, 57.3-99.3), and 108.0 (25th-75th percentile, 89.0-141.5) d, respectively. Patients treated with roxadustat had significantly longer RBC survival time than patients treated with rhuEPO (p < .05). In multivariate analysis of factors affecting RBC lifespan in the whole HD patients, anemia treatment drugs (rhuEPO/roxadustat) and levels of hemoglobin were the significantly independent factors. RBC survival was not found to correlate with either weekly rhuEPO dosage (r = -0.087, p = .500) or weekly roxadustat dosage (r = -0.267, p = .110) in our cohort. CONCLUSIONS: HD patients treated with roxadustat had significantly longer RBC survival time than patients treated with rhuEPO, large prospective studies with long-term follow-up are warranted to verify the results in future. Abbreviations RBC: red blood cell; HD: hemodialysis; rhu EPO: recombinant human erythropoietin; ESRD: end-stage renal disease; EPO: erythropoietin; ROS: reactive oxygen species; CKD: chronic kideny disease; ESAs: erythropoiesis-stimulating agents; HIF-PHD: hypoxia-inducible factor prolyl hydroxylase; CO: carbon monoxide; Hb: hemoglobin.

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.

Large conformational dynamics in Band 3 protein: Significance for erythrocyte senescence signalling.

Band 3 (Anion Exchanger 1, AE1), the predominant protein of erythrocyte membranes, facilitates Cl-/HCO3- exchange and anchors the plasma membrane to the cytoskeleton. The Band 3 crystal structure revealed the amino acid 812-830 region as intracellular, conflicting with protein chemical data that suggested extracellular disposition. Further, circulating senescent cell auto-antibody that cannot enter erythrocytes, binds two regions of Band 3: residues 538-554 and 812-830. To reconcile this discrepancy, we assessed localization of residues 812-830 with Band 3 expressed in HEK293 cells and human erythrocytes, using chemical labeling probes and an antibody against residues 812-830. Antibody and chemical probes revealed reorientation of 812-830 region between extracellular and intracellular. This dramatic conformational change is an intrinsic property of the Band 3 molecule, occurring when expressed in HEK293 cells and without the damage that occurs during erythrocyte circulation. Conditions used to crystallize Band 3 for structural determination did not alter conformational dynamics. Collectively, these data reveal large Band 3 conformational dynamics localized to a region previously identified as an erythrocyte senescence epitope. Surface exposure of the senescence epitope (812-830), limited by conformational dynamics, may act as the "molecular clock" in erythrocyte senescence.

Spectroscopic Signature of Red Blood Cells in a D-Galactose-Induced Accelerated Aging Model.

This work presents a semi-quantitative spectroscopic approach, including FTIR-ATR and Raman spectroscopies, for the biochemical analysis of red blood cells (RBCs) supported by the biochemical, morphological and rheological reference techniques. This multi-modal approach provided the description of the RBC alterations at the molecular level in a model of accelerated aging induced by administration of D-galactose (D-gal), in comparison to natural aging. Such an approach allowed to conclude that most age-related biochemical RBC membrane changes (a decrease in lipid unsaturation and the level of phospholipids, or an increase in acyl chain shortening) as well as alterations in the morphological parameters and RBC deformability are well reflected in the D-gal model of accelerated aging. Similarly, as in natural aging, a decrease in LDL level in blood plasma and no changes in the fraction of glucose, creatinine, total cholesterol, HDL, iron, or triglycerides were observed during the course of accelerated aging. Contrary to natural aging, the D-gal model led to an increase in cholesterol esters and the fraction of total esterified lipids in RBC membranes, and evoked significant changes in the secondary structure of the membrane proteins. Moreover, a significant decrease in the phosphorous level of blood plasma was specific for the D-gal model. On the other hand, natural aging induced stronger changes in the secondary structures of the proteins of the RBCs' interior. This work proves that research on the aging mechanism, especially in circulation-related diseases, should employ the D-gal model with caution. Nonetheless, the D-gal model enables to imitate age-related rheological alterations in RBCs, although they are partially derived from different changes observed in the RBC membrane at the molecular level.

Marginally reduced maternal hepatic and splenic ferroportin under severe nutritional iron deficiency in pregnancy maintains systemic iron supply.

The demand for iron is high in pregnancy to meet the increased requirements for erythropoiesis. Even pregnant females with initially iron-replete stores develop iron-deficiency anemia, due to inadequate iron absorption. In anemic females, the maternal iron supply is dedicated to maintaining iron metabolism in the fetus and placenta. Here, using a mouse model of iron deficiency in pregnancy, we show that iron recycled from senescent erythrocytes becomes a predominant source of this microelement that can be transferred to the placenta in females with depleted iron stores. Ferroportin is a key protein in the molecular machinery of cellular iron egress. We demonstrate that under iron deficiency in pregnancy, levels of ferroportin are greatly reduced in the duodenum, placenta and fetal liver, but not in maternal liver macrophages and in the spleen. Although low expression of both maternal and fetal hepcidin predicted ferroportin up-regulation in examined locations, its final expression level was very likely correlated with tissue iron status. Our results argue that iron released into the circulation of anemic females is taken up by the placenta, as evidenced by high expression of iron importers on syncytiotrophoblasts. Then, a substantial decrease in levels of ferroportin on the basolateral side of syncytiotrophoblasts, may be responsible for the reduced transfer of iron to the fetus. As attested by the lowest decrease in iron content among analyzed tissues, some part is retained in the placenta. These findings confirm the key role played by ferroportin in tuning iron turnover in iron-deficient pregnant mouse females and their fetuses.

Does endurance training improve red blood cell aging and hemorheology in moderate-trained healthy individuals?

OBJECTIVE: To examine the impact of a 6-week endurance training on red blood cell (RBC) aging and deformability of healthy participants to detect possible improved hemorheological and performance-related adaptations. METHODS: A total of 31 participants (17 females and 14 males) performed a 6-week moderate training protocol (three 1-h running sessions per week at 70% of maximal heart rate). Blood was sampled before and after the training. RBCs from each participant were fractioned according to density and age into 4 RBC subfractions. Subfractions were examined for changes of RBC properties, including aging distribution, RBC deformability, RBC microparticles, and phosphatidylserine concentrations. RBC and plasma nitrite levels were measured as indicators of nitric oxide metabolism. RESULTS: Aerobic performance, peak oxygen consumption, ventilatory thresholds, velocity at the aerobic-anaerobic threshold, and lactate at exhaustion improved after training. The relative amount of both young RBCs and old RBCs increased, and the amount of the main RBC fraction decreased. Phosphatidylserine externalization and RBC-derived microparticles decreased. Overall deformability expressed as shear stress required to achieve half-maximum deformation to theoretical maximal elongation index at infinite shear stress improved in unfractioned RBCs (p < 0.001). Nitrite decreased in total (p = 0.001), young (p < 0.001), main (p < 0.001), and old (p = 0.020) aged RBCs and in plasma (p = 0.002), but not in very old RBCs. CONCLUSION: These results indicate that non-endurance-trained healthy participants benefit from a regular moderate running training program because performance-related parameters improve and a younger RBC population with improved RBC properties is induced, which might support oxygen supply in the microcirculation.

Differential red blood cell age fractionation and Band 3 phosphorylation distinguish two different subtypes of warm autoimmune hemolytic anemia.

Warm autoimmune hemolytic anemia (wAIHA) is a blood disorder characterized by the increased destruction of autologous red blood cells (RBCs) due to the presence of opsonizing pathogenic autoantibodies. Preliminary reports published more than three decades ago proposed the presence of two wAIHA subtypes: Type I, in which autoantibodies preferentially recognize the oldest, most dense RBCs; and Type II, characterized by autoantibodies that show no preference. STUDY DESIGN AND METHODS: We evaluated patients having wAIHA for Type I and II subtype using discontinuous Percoll gradient age fractionation and direct antiglobulin test (DAT). We performed Western immunoblotting and mass spectrometry to show autoantibody specificity for Band 3. We investigated Band 3 tyrosine phosphorylation in different Percoll fractions to determine aging associated with oxidative stress. RESULTS: We confirm the existence of two subtypes of wAIHA, Type I and Type II, and that autoantibodies recognize Band 3. Type I patients were characterized by five Percoll fractions, with a DAT showing IgG opsonization F1 < F5 and elevated Band 3 phosphorylation compared to healthy controls (HCs). In contrast, Type II wAIHA patients were characterized by three to four Percoll fractions, where the DAT IgG opsonization shows F1 ≥ F3/4 and Band 3 phosphorylation was absent or significantly decreased compared to HC. CONCLUSIONS: Type I patients have increased Band 3 tyrosine phosphorylation that may represent accelerated aging of their RBCs resulting in exacerbation of a pathologic form of RBC senescence. Type II patients show decreased Band 3 tyrosine phosphorylation and lack the oldest, most dense RBCs suggesting premature RBC clearance and a more severe wAIHA.

Hemolysis in the spleen drives erythrocyte turnover.

Red pulp macrophages (RPMs) of the spleen mediate turnover of billions of senescent erythrocytes per day. However, the molecular mechanisms involved in sequestration of senescent erythrocytes, their recognition, and their subsequent degradation by RPMs remain unclear. In this study, we provide evidence that the splenic environment is of substantial importance in facilitating erythrocyte turnover through induction of hemolysis. Upon isolating human spleen RPMs, we noted a substantial lack of macrophages that were in the process of phagocytosing intact erythrocytes. Detailed characterization of erythrocyte and macrophage subpopulations from human spleen tissue led to the identification of erythrocytes that are devoid of hemoglobin, so-called erythrocyte ghosts. By using in vivo imaging and transfusion experiments, we further confirmed that senescent erythrocytes that are retained in the spleen are subject to hemolysis. In addition, we showed that erythrocyte adhesion molecules, which are specifically activated on aged erythrocytes, cause senescent erythrocytes to interact with extracellular matrix proteins that are exposed within the splenic architecture. Such adhesion molecule-driven retention of senescent erythrocytes under low shear conditions was found to result in steady shrinkage of the cell and ultimately resulted in hemolysis. In contrast to intact senescent erythrocytes, the remnant erythrocyte ghost shells were prone to recognition and breakdown by RPMs. These data identify hemolysis as a key event in the turnover of senescent erythrocytes, which alters our current understanding of how erythrocyte degradation is regulated.

A novel method for calculating mean erythrocyte age using erythrocyte creatine.

Estimating the lifespan of erythrocytes is useful for the differential diagnosis of anemia. However, measuring the lifespan of erythrocytes was very difficult; therefore, it was seldom measured. Erythrocyte creatine (EC) decreases reflecting erythrocyte age. We developed a method to obtain mean erythrocyte age (MRBC) from EC.We reanalyzed the previously published data from 21 patients with hemolytic anemia, which included EC and the half-life of 51Cr.MRBC and loge EC showed excellent significant linearity (r = -0.9475, p < 0.001), proving that it could be treated as a mono-exponential relationship within the studied range (EC: 1.45 - 11.76 µmol/g Hb). We established an equation to obtain MRBC (days) from EC (µmol/g Hb): MRBC = -22.84loge EC + 65.83.This equation allowed calculation of MRBC based on EC which has practical applications such as the diagnosis of anemia.

Elastic hysteresis loop acts as cell deformability in erythrocyte aging.

The decrease in cellular deformability shows strong correlation with erythrocyte aging. Cell deformation can be divided into passive deformation and active deformation; however, the active deformation has been ignored in previous studies. In this work, Young's moduli of age-related erythrocytes were tested by atomic force microscopy. Furthermore, the deformation and passive and active deformation values were calculated by respective areas. Our results showed that erythrocytes in the densest fraction had the highest values of the Young's modulus, deformation, and active deformation, but the lowest values of passive deformation. Moreover, values of the deformation and active deformation both increased gradually with erythrocyte aging. The present data indicate that the elastic hysteresis loop between the approach and the retract curve could be regarded as erythrocyte deformability, and cellular deformability could be characterized by energy states. In addition, active deformation might be a crucial mechanical factor for clearing aged erythrocytes. This could provide an important information on erythrocyte biomechanics in the removal of aged cell.

Circulating bilirubin level is determined by both erythrocyte amounts and the proportion of aged erythrocytes in ageing and cardiovascular diseases.

BACKGROUND: Bilirubin has been involved in the process of ageing and the pathology of ageing-related diseases. Circulating bilirubin is mainly derived from the clearance of disintegrated erythrocytes in the blood. However, the change of serum bilirubin level and its regulation during ageing and in ageing-related diseases remain to be elucidated. METHODS: A retrospective study was conducted by analyzing the blood cell test results and liver function results of 14,049 healthy research subjects at the Physical Examination Center and 2052 patients with various types of cardiovascular diseases (CVD) at the Department of Cardiology in Renmin Hospital of Wuhan University. Spearman correlation analysis and linear-regression analysis were used for correlation studies. Differences between male and female were investigated. RESULTS: Whereas the erythrocyte counts continuously decreased along with age, the proportion of aged erythrocytes was significantly increased in both male and female. The level of total circulating bilirubin was positively correlated with age and erythrocyte counts. The increase of bilirubin was associated with the increased morphological deviation of erythrocytes during ageing. Compared with health controls, the level of circulating bilirubin in CVD patients was significantly decreased consistent with the decline of erythrocyte counts and hemoglobin. CONCLUSIONS: Ageing may be accompanied by an increased ageing rate of erythrocytes, which contributes to the ageing-related decline of erythrocyte counts. Both erythrocyte counts and the proportion of aged erythrocytes coordinately might determine the circulating level of bilirubin during ageing. In CVD, the decline of circulating bilirubin may be largely attributed to concurrent anemia.

A Flow Induced Autoimmune Response and Accelerated Senescence of Red Blood Cells in Cardiovascular Devices.

Red blood cells (RBCs) passing through heart pumps, prosthetic heart valves and other cardiovascular devices undergo early senescence attributed to non-physiologic forces. We hypothesized that mechanical trauma accelerates aging by deformation of membrane proteins to cause binding of naturally occurring IgG. RBCs isolated from blood of healthy volunteers were exposed to high shear stress in a viscometer or microfluidics channel to mimic mechanical trauma and then incubated with autologous plasma. Increased binding of IgG was observed indicating forces caused conformational changes in a membrane protein exposing an epitope(s), probably the senescent cell antigen of band 3. The binding of immunoglobulin suggests it plays a role in the premature sequestration and phagocytosis of RBCs in the spleen. Measurement of IgG holds promise as a marker foreshadowing complications in cardiovascular patients and as a means to improve the design of medical devices in which RBCs are susceptible to sublethal trauma.

The emerging roles of eryptosis in liver diseases.

Erythrocytes undergo programmed cell death, similar to apoptosis, known as eryptosis. This process is a result of several factors including hyperosmolarity, oxidative stress, and exposure to xenobiotics, and is characterized by the breakdown of membrane phospholipid asymmetry, the clustering of band 3, and the generation of red blood cell-derived microparticles. Under pathological conditions, the liver is the primary site of erythrocyte clearance and plays an important role in iron recycling. Phosphatidylserine exposure and band-3 clustering on eryptotic erythrocytes represent mainly pro-phagocytic signals. Further, the percentage of eryptotic erythrocytes is enhanced in the circulating blood of patients with hepatic failure, hyperbilirubinemia, and nonalcoholic steatohepatitis. In this review, we concentrate on recent progress regarding the pathophysiological roles of eryptosis in liver diseases.