Factors that accelerate or retard red blood cell senescence

This article explores information concerning alterations in the time of age-related red blood cell (rbc) death (rbc senescence) in experimental animals and humans. Those factors that accelerate or retard the mean time for senescent death [the mean potential rbc life-span, (T)] are discussed; specifically excluded are conditions in which rbc survival is shortened due to an increase in the rate of age-independent [random hemolysis, (k)]rbc death. The factors prolonging senescence are reduction in metabolic rate through hibernation, reduced environmental temperature, hypophysectomy and thyroidectomy, and splenectomy. In general, these processes prolong rbc senescence by about 10%-15% in the models studied to date. The failure of splenectomy to prolong rbc senescence to any physiologically meaningful extent casts serious doubt on the concept that splenic processes are a major factor in the senescence process. Rbcs made under conditions of increased erythropoiesis and/or increased metabolic rate show acceleration of senescence. Thus, rbcs of animals treated with thyroxine show a 15% acceleration of senescence. "Stress reticulocytes" and normal full-term human newborn rbc may show up to 25% reduction in (T). The maximum acceleration seen to date is 50%-90%, as seen in the rbcs of the fetal and newborn rat. rbc senescence is not accelerated in rats with splenomegaly and increased rates of random hemolysis, again casting strong doubts on the spleen's ability to alter rbc senescence by progressively modifying the rbc during successive passages through that organ. It is postulated that rbc senescence is mainly a function of the red cell's initial endowment, particularly in the dynamic ability of that cell (and its membrane) to adapt to cumulative stresses that exist during its circulation through the body.     

The aging of the red blood cell. A multifactor process

Red blood cell (rbc) senescence is associated with loss of surface sialic acid, which is the principal carrier of surface negative charge and determines the electrokinetic behavior of old rbcs. Loss of sialic acid in an old rbc is demonstrated in its decreased electric mobility and lower negative charge density, determined topographically with cationic particle labeling. Surface sialic acid determines also the mutual attraction--repulsion forces, as demonstrated in enhanced aggluinability with cationic molecules, lectins, and blood group antibodies. Loss of sialic acid accompanies ATP-depletion in vitro; thus, a T-antigen site is unmasked. Macrophages have specific receptors to the site as to newly exposed galactose and N-acetyl galactosamine sugars. Furthermore, the involvement of complement molecules in the recognition of old RBCs by macrophages has been shown. This is possibly due to loss of sialic acid or at least a regrouping--relocation of surface anionic sites due to cell shape changes from discocytes to crenated forms, which accompany both in vivo and in vitro rbc aging. In turn, shape changes are apparently controlled by the cytoskeletal network underlying the rbc membrane, which undergoes structural alteration with physiologic aging in changing the dimensions of oligomeric spectrin and the thickness of the spectrin-actin cytoskeletal assembly.     

Possible involvement of red cell membrane proteins in the hemolytic action of Portuguese Man-of-War toxin.

Glycophorin and the fragments isolated from trypsinizing intact rat, dog, sheep and human red blood cells (rbc's) neutralize the hemolytic action of the Portuguese Man-of-War venom. This action can be blocked by rabbit antisheep hemolysin and phytohemagglutinin, a lectin which preferentially binds to glycophorin. Concanavalin A, which binds to band-3 protein of rbc membranes, does not block the neutralizing action of rbc tryptic fragments or glycophorin. The concentrations of rat, dog, human and sheep glycophorin which half neutralize venom induced hemolysis are inversely and linearly proportional to the hemolytic sensitivities of these rbc's to the venom. These data implicate glycophorin as a possible binding site for the hemolytic component of the Portuguese Man-of-War venom.     

Comparative physiology and molecular analysis of carbonic anhydrase from the red blood cells of teleost fish

This study investigates the early evolution of vertebrate red blood cell (rbc) carbonic anhydrase (CA) by examining the physiological and molecular properties of rbc CA in teleost fish. When representatives of four different families of teleosts were compared, it was found that differences in overall rbc CA activity were due to different concentrations of CA, rather than differences in the enzymes kinetic properties. Additional molecular analysis of CA from the rbcs of rainbow trout provided further evidence that critical elements of the enzyme, such as the active site, have been highly conserved during vertebrate evolution. The active site of the trout CA differed from that of gar rbc CA at only two amino acid positions. The rainbow trout rbc CA sequence also showed high sequence homology with CA sequences from other fish tissues, and fits into an emerging group of fish CAs that are basal to mammalian CA I, II and III. Northern blot analysis of the tissue expression of the sequenced CA indicated that it is primarily found in the rbcs, but high amounts of cytosolic CA activity were also found in the gill, suggesting the presence of other cytosolic CA isozymes in this species.Abbreviations Az acetazolamide - CA carbonic anhydrase - MP maximum parsimony - NJ neighbour joining - RACE rapid amplification of cDNA ends - rbc red blood cellCommunicated by L.C.-H. Wang     

Decreased Ca pump ATPase activity associated with increased density in human red blood cells

Red blood cells (rbcs) from five different normal humans were separated according to density using a simple procedure. The procedure involved centrifugation for 30 minutes in small glass tubes in the absence of any density gradient medium. This produced a column of rbcs arranged according to their density. Samples of the top 8% of the columns and bottom 8% of the columns were removed from the tubes with a micropipet. From each donor, samples of the least and most dense cells, respectively, were pooled from multiple tubes for each donor and designated "top" and "bottom" cells. These top and bottom cells were compared with unselected (total) cells from the same subjects, respectively. Top cells were larger and bottom cells were smaller than total cells. ATPase activities were operationally defined and measured in saponin lysates of these rbcs. The Ca pump ATPase (both in the calmodulin-activated and calmodulin-independent states [achieved by addition of compound 48/80]) of the top cells exhibited greater activity, and the Ca pump ATPase of bottom cells exhibited lower activity than total cells. It was suggested that loss of Ca pump ATPase activity is associated with rbc aging and may be a determinant of rbc life span. A mechanism for the loss of Ca pump ATPase activity was suggested. This speculative mechanism is based upon selective proteolysis of the Ca pump ATPase by the Ca-activated protease, calpain.     

Total sialic acid content of glycophorins during senescence of human red blood cells.

Glycophorins extracted from membranes of young and old human red blood cells have within an error of +/- 1.5% the same sialic acid content when referred to a relative measure of the number of glycophorins. The degree of surface iodination in glycophorins, which was shown to be the same in young and old cells, served as this relative measure. This finding implies that senescent human red blood cells hardly reveal desialylated surface proteins (less than or equal to 3%). However, the sialic acid content per cell was repeatedly reported to be 10 to 15% lower in old than in young cells. Therefore, we conclude 1) that human red blood cells lose intact glycophorin together with membrane during red blood cell senescence, and 2) that removal of desialylated and senescent red blood cells from the circulation proceeds by different routes.     

Control and consequences of adrenergic activation of red blood cell Na+/H+ exchange on blood oxygen and carbon dioxide transport in fish.

The catecholamines, adrenaline and noradrenaline, are released into the circulation of fish during a variety of physical and environmental disturbances that share the common feature of a requirement for enhanced blood oxygen transport. Indeed, the dominant factor controlling the mobilization of catecholamines from chromaffin tissue is a depression of blood oxygen content usually coinciding with a reduction of hemoglobin-O2 (Hb-O2) binding to 50-60% saturation. The elevation of plasma catecholamine levels, under such conditions, activates a beta-adrenergic cyclic AMP-dependent Na+/H+ exchanger on the red blood cell (rbc) membrane. The adrenergic responsiveness AMP-dependent Na+/H+ exchanger on the red blood cell (rbc) membrane. The adrenergic responsiveness of the rbc Na+/H+ exchanger to catecholamines varies both within and between species. Such inter- and intra-specific differences may reflect, in part, the availability of cell surface beta-adrenoceptors that are functionally coupled to adenylate cyclase. The activation of rbc Na+/H+ exchange and the accompanying profound adjustments of intracellular and extracellular acid-base status, nucleoside triphosphate (NTP) levels, and cooperativity of Hb-O2 binding have important consequences on both O2 and CO2 transfer and transport in the blood that vary markedly at the sites of oxygenation (the gill) and deoxygenation (the tissues) thereby enabling simultaneous amelioration of O2 loading and unloading. At the gill, oxygen transfer is enhanced owing to increases in Hb-O2 affinity and capacity while at the tissues, oxygen delivery is facilitated by a reduction of Hb-O2 affinity. This reduction in affinity at the tissues is a consequence of the combined effects of increased cooperativity of Hb-O2 binding and a rise in venous PCO2 (PvCO2) caused by the titration of HCO3- by H+ extruded by the rbc Na+/H+ exchanger. This elevation of PvCO2 may contribute to the rise in arterial PCO2 (PaCO2) observed after adrenergic activation of rbc Na+/H+ exchange that is caused primarily by impairment of rbc CO2 excretion related to modification of the intracellular acid-base status.     

Exclusion of erythrocyte-specific membrane proteins from clathrin- coated pits during differentiation of human erythroleukemic cells

When human erythroleukemic cells are induced to differentiate, they produce globin and redistribute glycophorin and spectrin to one pole of the cell. This process was accompanied by an alteration in the clathrin-coated pits at the cell surface. In nondifferentiating cells, receptors for Concanavalin A have been shown, using electron microscopy, to be concentrated into coated pits and rapidly internalized. Glycophorin was also internalized via coated pits, but was not greatly concentrated into these portions of the surface membrane. Ligands attached to glycophorin were, therefore, cleared from the cell surface more slowly than Concanavalin A. In nondifferentiating cells, immunoelectron microscopy showed that spectrin is largely excluded from coated pits. After erythroid differentiation proceeded for several days, glycophorin was totally excluded from the coated pits along with spectrin. This did not reflect a general cessation of endocytosis, however, because Concanavalin A receptors continued to be internalized. It is possible that the specific exclusion of glycophorin from coated pits is part of the remodeling process that occurs when the precursor cell membrane differentiates into that of the mature erythrocyte.     

RBCS1A and RBCS3B, two major members within the Arabidopsis RBCS multigene family, function to yield sufficient Rubisco content for leaf photosynthetic capacity

Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) small subunit (RBCS) is encoded by a nuclear RBCS multigene family in many plant species. The contribution of the RBCS multigenes to accumulation of Rubisco holoenzyme and photosynthetic characteristics remains unclear. T-DNA insertion mutants of RBCS1A (rbcs1a-1) and RBCS3B (rbcs3b-1) were isolated among the four Arabidopsis RBCS genes, and a double mutant (rbcs1a3b-1) was generated. RBCS1A mRNA was not detected in rbcs1a-1 and rbcs1a3b-1, while the RBCS3B mRNA level was suppressed to ～20% of the wild-type level in rbcs3b-1 and rbcs1a3b-1 leaves. As a result, total RBCS mRNA levels declined to 52, 79, and 23% of the wild-type level in rbcs1a-1, rbcs3b-1, and rbcs1a3b-1, respectively. Rubisco contents showed declines similar to total RBCS mRNA levels, and the ratio of Rubisco-nitrogen to total nitrogen was 62, 78, and 40% of the wild-type level in rbcs1a-1, rbcs3b-1, and rbcs1a3b-1, respectively. The effects of RBCS1A and RBCS3B mutations in rbcs1a3b-1 were clearly additive. The rates of CO(2) assimilation at ambient CO(2) of 40 Pa were reduced with decreased Rubisco contents in the respective mutant leaves. Although the RBCS composition in the Rubisco holoenzyme changed, the CO(2) assimilation rates per unit of Rubisco content were the same irrespective of the genotype. These results clearly indicate that RBCS1A and RBCS3B contribute to accumulation of Rubisco in Arabidopsis leaves and that these genes work additively to yield sufficient Rubisco for photosynthetic capacity. It is also suggested that the RBCS composition in the Rubisco holoenzyme does not affect photosynthesis under the present ambient [CO(2)] conditions.     

Distribution of glycophorin on the surface of human erythrocyte membranes and its association with intramembrane particles: An immunochemical and freeze-fracture study of normal and En(a−) erythrocytes

Human erythrocyte membranes of the En(a–) blood group lack the major sialoglycoprotein (glycophorin). By absorption of a crude antiglycophorin antiserum with En(a–) membranes a specific antiglycophorin antiserum was obtained. By immune electron microscopy we showed that glycophorin is randomly distributed on the surface of normal erythrocytes. When polycationized ferritin, which mainly binds to glycophorin, was used as a marker a similar even labeling of normal erythrocyte membranes was seen. En(a–) membranes bound much less of this marker. In freeze-fracturing the intramembrane particles of both membrane types had a similar distribution and appeared in equal amounts. However, partial removal of spectrin from these membranes, followed by incubation at pH 6 resulted in more extensive aggregation of the particles in En(a–) membranes than in normal membranes. The results may be interpreted as glycophorin contributing by electrostatic repulsion to the random distribution of the intramembrane particles in normal cells. This repulsion is weakened in En(a–) cells by the lack of glycophorin.     

Dexamethasone treatment improves sarcoplasmic reticulum function and contractile performance in aged myocardium

Corticosteroids are thought to be involved in the maintenance of normal myocardial function by mechanisms incompletely understood. This study investigated the potential therapeutic benefit of the synthetic glucocorticoid, dexamethasone, in reversing age-associated deterioration in cardiac contractile performance and Ca2+ sequestration function of the sarcoplasmic reticulum. Dexamethasone was administered to senescent (26-28-month old), male Fischer 344 rats at a rate of 4 microg/h for 5 days via subcutaneously implanted osmotic mini pumps. Control rats received vehicle solution in similar manner. Contractile performance was assessed in Langendorff-perfused, electrically paced hearts from control and dexamethasone-treated rats. The results obtained showed that dexamethasone-treatment of aged rats resulted in significant improvement in myocardial contractile performance as evidenced by (i) increase (approximately 30-60%) in developed peak tension at a wide range of beating frequencies (2-6 Hz), (ii) unaltered time to peak tension, and (iii) decrease (approximately 8-15%) in time to half-relaxation. Also, SR isolated from dexamethasone-treated rats displayed approximately 2-fold higher rates of ATP-energized Ca2+ uptake compared to SR from control rats. The deficits in contractile performance of the senescent heart (prolonged contraction duration and diminished contractile force) are reversible through a glucocorticoid-mediated improvement in SR Ca2+ pump function.     

Ultrastructural localization of erythrocyte cytoskeletal and integral membrane proteins in Plasmodium falciparum-infected erythrocytes

The distributions of ankyrin, spectrin, band 3, and glycophorin A were examined in Plasmodium falciparum-infected erythrocytes by immunoelectron microscopy to determine whether movement of parasite proteins and membrane vesicles between the parasitophorous vacuole membrane and erythrocyte surface membrane involves internalization of host membrane skeleton proteins. Monospecific rabbit antisera to spectrin, band 3 and ankyrin and a mouse monoclonal antibody to glycophorin A reacted with these erythrocyte proteins in infected and uninfected human erythrocytes by immunoblotting. Cross-reacting malarial proteins were not detected. The rabbit sera also failed to immunoprecipitate [3H]isoleucine labeled malarial proteins from Triton X-100 and sodium dodecyl sulfate (SDS) extracts of infected erythrocytes. These three antibodies as well as the monoclonal antibody to glycophorin A bound to the membrane skeleton of infected and uninfected erythrocytes. The parasitophorous vacuole membrane was devoid of bound antibody, a result indicating that this membrane contains little, if any, of these host membrane proteins. With ring-, trophozoite- and schizont-infected erythrocytes, spectrin, band 3 and glycophorin A were absent from intracellular membranes including Maurer's clefts and other vesicles in the erythrocyte cytoplasm. In contrast, Maurer's clefts were specifically labeled by anti-ankyrin antibody. There was a slight, corresponding decrease in labeling of the membrane skeleton of infected erythrocytes. A second, morphologically distinct population of circular, vesicle-like membranes in the erythrocyte cytoplasm was not labeled with anti-ankyrin antibody. We conclude that membrane movement between the host erythrocyte surface membrane and parasitophorous vacuole membrane involves preferential sorting of ankyrin into a subpopulation of cytoplasmic membranes.     

Forebrain and brain stem neural circuits contribute to altered sympathetic responses to heating in senescent rats.

Acute heating in young rats increases visceral sympathetic nerve discharge (SND); however, renal and splanchnic SND responses to hyperthermia are attenuated in senescent compared with young Fischer 344 (F344) rats (Kenney MJ and Fels RJ. Am J Physiol Regul Integr Comp Physiol 283: R513-R520, 2002). Central mechanisms by which aging alters visceral SND responses to heating are unknown. We tested the hypothesis that forebrain neural circuits are involved in suppressing sympathoexcitatory responses to heating in chloralose-anesthetized, senescent F344 rats. Renal and splanchnic SND responses to increased (38 degrees C-41 degrees C) internal temperature were determined in midbrain-transected (MT) and sham-MT young (3-mo-old), mature (12-mo-old), and senescent (24-mo-old) F344 rats and in cervical-transected (CT) and sham-CT senescent rats. Renal SND remained unchanged during heating in MT and sham-MT senescent rats but was increased in CT senescent rats. Splanchnic SND responses to heating were higher in MT vs. sham-MT senescent rats and in CT vs. MT senescent rats. SND responses to heating were similar in MT and sham-MT young and mature rats. Mean arterial pressure (MAP) was increased during heating in MT but not in sham-MT senescent rats, whereas heating-induced increases in MAP were higher in sham-MT vs. MT young rats. These data suggest that in senescent rats suppression of splanchnic SND to heating involves forebrain and brain stem neural circuits, whereas renal suppression is mediated solely by brain stem neural circuits. These results support the concept that aging alters the functional organization of pathways regulating SND and arterial blood pressure responses to acute heating.     

A novel ligand from Plasmodium falciparum that binds to a sialic acid-containing receptor on the surface of human erythrocytes

Invasion of the merozoite form of Plasmodium falciparum into human erythrocytes involves multiple receptor-ligand interactions. The EBA175 protein of P. falciparum has been shown to be the ligand that binds to a sialic acid-dependent site on glycophorin A. We have identified a novel P. falciparum ligand, termed erythrocyte-binding antigen 140 (EBA140), that shares structural features and homology with EBA175. Subcellular localization of EBA140 suggests that it is located in the micronemes, the same localization as EBA175. EBA140 binds to a sialic acid-dependent receptor on the surface of human erythrocytes. Binding of EBA140 to this erythrocyte receptor is sensitive to neuraminidase and resistant to trypsin, proteinase K and pronase. The protease-resistant properties of the erythrocyte receptor suggests that it is not glycophorin A or C. Additionally, analysis of mutant erythrocytes from humans has shown that EBA140 does not bind glycophorin B. Interestingly, we have identified a parasite line that lacks the eba140 gene, suggesting that this protein is not essential for in vitro invasion. These results suggest that EBA140 may be involved in merozoite invasion using a sialic acid-dependent receptor on human erythrocytes.     

Different red blood cell characteristics in a primitive agnathan (M. glutinosa) and a more recent teleost (O. mykiss) influence their strategies for blood CO2 transport

This study examines how the different red blood cell (rbc) characteristics in two lower vertebrates, the phylogenetically primitive hagfish and a more recent teleost, the rainbow trout, influence their strategies for blood CO2 transport. Deoxygenation of the blood resulted in a significant increase in rbc CO2 content in hagfish, but there were no significant changes in the CO2 content of plasma or whole blood under these conditions. In contrast, deoxygenation increased the CO2 content of the rbc, plasma and whole blood in the trout. These results demonstrate that the Haldane effect is much less important for CO2 transport in the hagfish as compared to the trout. The relative importance of the rbc and plasma in blood CO2 transport were roughly similar in hagfish and trout and were very different from that previously documented in another primitive vertebrate, the lamprey. In trout, however, the role of the rbc in CO2 carriage was increased upon the addition of the beta-adrenergic agonist isoproterenol (10(-5) M) to the blood. Taken together, these results and those recently collected for lampreys demonstrate that changes in rbc characteristics during vertebrate evolution have probably resulted in several important transitions in the strategy for blood CO2 transport.     

REEXAMINATION OF PHYLOGENETIC RELATIONSHIPS WITHIN THE COLONIAL VOLVOCALES (CHLOROPHYTA): AN ANALYSIS OF atpB AND rbcL GENE SEQUENCES

The chloroplast-encoded atp B gene was sequenced from 33 strains representing 28 species of the colonial Volvocales (the Volvocaceae and its relatives) to reexamine phylogenetic relationships as previously deduced by morphological data and rbc L gene sequence data.1128 base pairs in the coding regions of the atp B gene were analyzed by MP, NJ, and ML analyses. Although supported with relatively low bootstrap values (75% and 65% in the NJ and ML analyses, respectively), three anisogamous/oogamous volvocacean genera— Eudorina, Pleodorina, and Volvox, excluding the section Volvox (= Euvolvox, illegitimate name), constituted a large monophyletic group (Eudorina group). Outside the Eudorina group, a robust lineage composed of three species of Volvox sect. Volvox was resolved as in the rbc L gene trees, rejecting the hypothesis of the previous cladistic analysis based on morphological data that the genus Volvox is monophyletic. In addition, the NJ and ML trees suggested that Eudorina is a nonmonophyletic genus as inferred from the morphological data and rbc L gene sequences. Although phylogenetic status of the genus Gonium is ambiguous in the rbc L gene trees and the paraphyly of this genus is resolved in the cladistic analysis based on morphological data, the atp B gene sequence data suggest monophyly of Gonium with relatively low bootstrap values (56–61%) in the NJ and ML trees. On the basis of the combined sequence data (2256 base pairs) from atp B and rbc L genes, Gonium was resolved as a robust monophyletic genus in the NJ and ML trees (with 68–86% bootstrap values), and Eudorina elegans Ehrenberg represented a paraphyletic species positioned most basally within the Eudorina group. However, phylogenetic status and relationships of the families of the colonial Volvocales were still almost ambiguous even in the combined analysis.     

Characterization of erythrocyte carbonic anhydrase in an ancient fish,the longnose gar ( Lepisosteus osseus)

This study investigates the evolutionary history of vertebrate red blood cell carbonic anhydrase (CA) by characterizing the isozyme properties and nucleotide sequence of an ancient fish, the longnose gar ( Lepisosteus osseus). The inhibitor sensitivities of gar rbc CA closely resembled those for mammalian CA II, as well as those for CAs from more recently evolved fishes. The kinetic properties of gar rbc CA were not closely aligned with either mammalian CA I and CA II, but fit well into an emerging phylogenetic pattern for early vertebrates. Gar rbc CA cDNA was also amplified from mRNA using 5' and 3'-RACE and the open reading frame consisted of 786 bp. This sequence shares approximately 65% identity with the nucleotide and amino acid sequences of both mammalian CA I and CA II. When the amino acid sequences within the active site are compared, gar rbc CA differs from mammalian CA I, CA II and CA VII by 9, 4 and 3 of the 36 amino acids, respectively. Phylogenetic analyses suggest that gar rbc CA diverged before the amniotic CAs (CA I, CA II and CA III), but after CA V and CA VII.     

Site of attachment of encephalomyocarditis virus on human erythrocytes.

Previous studies of the attachment of encephalomyocarditis (EMC) virus to human erythrocytes concluded that the glycophorins, a family of human erythrocyte sialoglycoproteins, act as EMC virus receptors. Evidence is presented that the major glycophorin species, glycophorin A, is the receptor for EMC virus attachment to human erythrocytes. Comparison of the structures of glycophorins A and B and sialoglycopeptides released by chymotrypsin and trypsin treatment of erythrocytes confirmed our previous suggestion (A. T. H. Burness and I. U. Pardoe, J. Gen. Virol. 64:1137-1148, 1983) that attachment of EMC virus to glycophorin A involves the region containing amino acids 35 to approximately 70 (numbered from the NH2 terminus), four of which (amino acids 37, 44, 47, and 50) are glycosylated. In addition, we provide evidence that the segment containing amino acids 35 to 39 with an oligosaccharide side chain on threonine-37 is particularly important for EMC virus attachment.