Self-digestion of human erythrocyte membranes. Role of adenosine triphosphate and glutathione

Acetaldehyde-induced oxidative modifications and morphological changes in isolated human erythrocytes: an in vitro study

Acetaldehyde is a toxic, mutagenic and carcinogenic metabolite of alcohol which can bind to proteins, DNA and several other cellular macromolecules. Chronic alcohol consumption increases intracellular acetaldehyde levels which enhances the generation of reactive oxygen and nitrogen species (ROS and RNS). In this study, we have examined the effect of acetaldehyde on human erythrocytes under in vitro conditions. Treatment of human erythrocytes with different concentrations of acetaldehyde (0.05-2 mM) for 24 h at 37 °C increased intracellular generation of ROS and RNS. It also increased oxidation of proteins and lipids but decreased glutathione, total sulphhydryl and free amino group content. Methemoglobin level was increased accompanied by a decrease in methemoglobin reductase activity. Acetaldehyde impaired the antioxidant defence system and lowered the total antioxidant capacity of the cell. It decreased the activity of metabolic and membrane-bound enzymes and altered erythrocyte morphology. Our results show that acetaldehyde enhances the generation of ROS and RNS that results in oxidative modification of cellular components. This will lower the oxygen transporting ability of blood and shorten erythrocyte lifespan (red cell senescence).

Erythrocyte senescence and membrane transporters in young and old rats

Alterations at the level of plasma membrane are reported to play an important role in cellular senescence. The present study was undertaken to correlate cellular senescence, membrane transport processes and organismal aging. To achieve this objective activities of membrane linked Na⁺/K ⁺ ATPase (NKA), Na⁺/H⁺ exchanger (NHE) and correlation with membrane hydrxyperoxide level, sialic acid content and membrane protein oxidation was studied in density-gradient fractionated young and old erythrocytes from 4 and 24 month old Wistar rats. The results reveal that cellular aging within the tissue is associated with significant decrease in activities of NKA and NHE of senescent erythrocytes in comparison to younger cell population of same age group. The result shows that impaired ion homeostasis due to altered membrane transporters including functional and compositional changes may be one of the reasons responsible behind rat erythrocyte aging.

Measurement of erythrocyte lipids, lipid peroxidation, antioxidants and osmotic fragility in cervical cancer patients

BACKGROUND

Our aim was to examine the structural integrity of red blood cells in cervical cancer patients by measuring the concentrations of thiobarbituric acid reactive substances (TBARS), antioxidant status, cholesterol/phospholipid (C/P) molar ratio, enzyme activity and osmotic fragility of erythrocytes.

METHODS

This study has been conducted on 32 adult female cervical cancer patients and an equal number of age- and sex-matched normal subjects. Erythrocyte concentrations of lipids, TBARS, vitamin E, reduced glutathione and enzymic activities of catalase and Na(+)K(+)-ATPase were measured as well as plasma concentrations of sodium and potassium. The present study also examined the changes in erythrocyte osmotic fragility in cervical cancer patients and normal subjects. The red cell fluidity and permeability were determined by estimating the C/P ratio and Na(+)K(+)-ATPase activity, respectively.

RESULTS

The release of thiobarbituric acid reactive substances was significantly higher in cervical cancer patients as compared to normal subjects. The increased lipid peroxidation with concomitant decrease in antioxidants was notable in cervical cancer patients. Red blood cells of cervical cancer patients were more fragile than those from normal subjects. Increase in red cell membrane C/P ratio and Na(+)K(+)-ATPase activity was noticed in cervical cancer patients as compared to normal subjects.

CONCLUSIONS

Increased lipid peroxidation, insufficient antioxidant potential and changes in C/P molar ratio as well as activity of Na(+)K(+)-ATPase cause structural and functional abnormalities in the erythrocytes of cervical cancer patients.

Effects of lead on sialic acid content and survival of rat erythrocytes

The anemia frequently observed in lead poisoning is thought to result from a shortening of erythrocyte survival in combination with inhibition of hemoglobin synthesis. However, the exact mechanism by which lead shortens erythrocyte survival remains unclear. In the present study, the effects of lead, injected intraperitoneally, on sialic acid content and survival of rat erythrocytes were investigated in order to study the relationship between them. As indices of lead exposure, hemoglobin (Hb) levels, hematocrits (Ht) and blood lead (blood Pb) levels in the injected rats were also examined. Exposure to lead significantly decreased the sialic acid content of the erythrocyte membrane. The decreases in sialic acid content were evident to some extent below a blood Pb level of 100 micrograms/100 ml and generally present at a level of 100 micrograms/100 ml and higher. In the rats exposed to lead a significant negative correlation was found between sialic acid content and the logarithm of blood Pb level. A shortening of erythrocyte survival was also observed in the rats exposed to lead.

Red cell membrane (Na+ +K+)-ATPase in diabetes mellitus

The red cell membrane (Na+ +K+)-ATPase activity is significantly elevated in diabetes mellitus. The osmotic fragility of diabetic red cells is also increased. In vivo insulin treatment restores the enzyme activity and the osmotic fragility to the normal level. In vitro insulin treatment of diabetic red cells was found to inhibit the further increase in its activity, but it failed to restore the activity to the normal level as in vivo. In diabetes increased Km of (Na+ +K+) ATPase for ATP was observed but Vmax remained the same. Arrhenius plot of this enzyme was also altered in diabetes.

Re-evaluation of the structural integrity of red-cell glycoproteins during aging in vivo and nutrient deprivation

Results presented in this paper show that removal of white-cell contaminations from human red blood cells by filtration through cellulose [Beutler, West & Blume (1976) J. Lab. Clin. Med. 88, 328-333] is a necessity whenever red cells are incubated at elevated temperatures or haemolysed after density separation. Omission of this precaution results in proteolysis of sialoglycoproteins in membranes from less-dense (young), but not dense (old), subpopulations. This proteolytic damage occurs during haemolysis of the cytoplasmic domain of glycophorin. A different type of proteolysis occurs if white-cell-contaminated red cells are incubated in the absence of glucose at elevated temperatures. Red cells release sialoglycopeptides. This process is stimulated by Ca2+ ions and is accompanied by the release of vesicles that differ from spectrin-free vesicles [Lutz, Liu & Palek (1977) J. Cell Biol. 73, 548-560]. This sialoglycopeptide release is dependent on white-cell contamination and is not required for the release of spectrin-free vesicles.

Erythrocyte membrane abnormalities in patients with amyotrophic chorea with acanthocythosis. Part 2. Abnormal degradation of membrane proteins

Bands 2.1, 3 and 4.2 of the erythrocyte membrane proteins in chorea-acanthocytosis are self-digested faster than those in normal controls. The junction between spectrin and band 3 protein at the cytoplasmic side of the patients' erythrocyte membranes may have some conformational defects. The conformational defects of the proteins may be responsible for the low fluidity in the interior of the patients' erythrocyte membranes. These basic molecular defects may be widespread in other extraneural cell membranes as well as in neuronal cell membranes.

Proteolytic self-digestion of bovine erythrocyte membranes

"Self-digestion" of bovine erythrocyte membrane proteins was studied in isolated membrane preparations during prolonged incubation at 37 C. Protease activities associated with the membrane result in progressive degradation of all main erythrocyte membrane proteins, in particular spectrin and Band 3, and formation of lower molecular weight products which have been tentatively assigned to parent molecules. Membrane protein "self-digestion" occurs in a broad pH range (2-11), is inhibited by increased ionic strength and by inhibitors of metalloproteases, cysteine and serine proteases, and activated by low concentrations of SDS. "Self-digestion" also takes place in NaOH-stripped erythrocyte membranes. The activity of a protease involved in the "self-digestion", of apparent molecular weight of about 35,000, was renatured after SDS-polyacrylamide gel electrophoresis of erythrocyte membrane proteins.

Solubilization, reconstitution, and attempted affinity chromatography of the sugar transporter of the erythrocyte membrane

Reconstitution of the sugar transport system of human erythrocytes into artificial liposomes was achieved by freezing, thawing, and sonicating preformed phospholipid vesicles in the presence of intact ghosts, protein-depleted ghosts, or detergent-treated ghosts. D-glucose equilibrium exchange activities and affinity constants in the range of the reported erythrocyte values were reached in the best experiments. Whereas the extraction of peripheral membrane proteins did not depress the transport function crucially after reconstituting these protein-depleted ghosts, the selective solubilization of integral membrane proteins by a variety of nonionic detergents resulted in an uncontrollable, continuously increasing inactivation of the carrier. However, Emulphogene BC-720 extracts could be prepared in which the glucose transporter retained activity for days at 4 degrees C. These extracts were applied to affinity chromatography matrices of phloretin-Agarose, prepared by coupling phloretinyl-3'-benzylamine (PBA) to CH-Sepharose 4B and to Affigel 202. Although the solubilized sugar transporter appeared to be selectively adsorbed to both PBA matrices, it could not be eluted by specific counter ligands or gentle eluants in a biologically active form. However, chaotropic agents could be used to elute intrinsic proteins, including bands 3 and 4.5, from the Affigel affinity medium.

Changes of reduced glutathion, glutathion reductase, and glutathione peroxidase after radiation in guinea pigs

In this series of experiments the protective action of reduced glutathion due to ionizing radiation has been studied. In the experimental group 18 guinea pigs were exposed to successive radiations of 150 rad 3 or 4 days apart. Total dose given amounted to 750 rad which is the LD50 for guinea pigs. Blood samples were taken 30 min after each exposure. The control series were sham radiated but otherwise treated identically. The cells of the removed blood samples were separated by centrifugation and were subjected to the reduced glutathion stability test. GSSGR, GPer, and LDH enzyme activities were also measured of which the latter served as a marked enzyme. It was found that LDH did not show any alteration after radiation. The reduced glutathion stability test showed a consistent but minor reduction (P greater than 0.05), in the experimental group. GSSGR enzyme activity on the other hand was reduced significantly (from 176.48 +/- 11.32 to 41.34 +/- 1.17 IU/ml of packed erythrocytes, P less than 0.001) in the same group. GPer activity showed a consistent but minor elevation during the early phase of the experimental group. It was later increased significantly beginning after 600 rad total radiation on the fourth session (P less than 0.050).

Modification of membrane protein organization during in vitro aging of human erythrocytes

In in vitro aged human erythrocytes, the presence of protein clusters can be found on the membrane; these clusters are made up of peptides held together by disulfide bridges, since they can be nearly completely dissociated by dithiothreitol treatment. SDS-polyacrylamide gel electrophoresis after dithiothreitol dissociation indicates that the aggregates are made of peptide fragments with a molecular weight ranging from 20 to approximately 110 kdalton; none of these fragments correspond to an intact protein component of the membrane. Their formation results from oxidation and proteolysis of membrane, and perhaps cytoplasmic proteins.

Surface affinity chromatographic separation of blood cells. III. Effect of molecular weight of polyethylene glycol bonded stationary phases on elution behaviour of human blood cells

The chromatographic behaviour of human peripheral blood cells on four kinds of oxirane-coupled polyethylene glycol (PEG)--Sepharose 6B columns was investigated by using an eluent containing 2% of dextran T40. The retention volumes of lymphocytes, granulocytes and platelets at pH 7.5 have a strong dependence on the average molecular weight of the bonded PEG in the range 400-20,000, increasing with increasing molecular weight. Further, the same tendency for the retention behaviour was also observed at the isoelectric points determined for the four kinds of blood cells by using the cross-partition method. For lymphocytes and granulocytes hydrophobic interactions with the bonded PEG phase were found to be predominant, whereas for erythrocytes and platelets electrostatic interactions were also taken into account.

Time-dependence of, and effects of inhibition and cellular aging on, chloride efflux across erythrocyte membranes in Huntington's disease

Previous studies have demonstrated an increased rate of chloride transport across erythrocyte membranes in Huntington's disease, a process regulated at the external side of the major transmembrane protein Band 3. A marked effect of time was noted in 3 Huntington's disease samples that were studied more than 4 h after obtaining the blood. In order to study anion transport more closely in Huntington's disease and the apparent time-dependence of chloride efflux in this disorder, we have performed several sets of experiments. Chloride transport in Huntington's disease erythrocytes was found to be extremely sensitive to time with the efflux rate constant decreasing by approximately 30% over a 24 h period. Chloride transport in control cells was unaffected by time. Inhibition studies with the specific anion transport blocker 4,4'-diisothiocyanto-2,2'-disulfonic acid stilbene (DIDS) demonstrated that the same degree of inhibition of chloride transport could be achieved at a much lower concentration of DIDS in Huntington's disease than in controls. Comparison of chloride efflux in fractions enriched in young and old erythrocytes, respectively, obtained by density centrifugation of fresh blood, demonstrated that only in the young fraction of cells was chloride efflux diminished with time in Huntington's disease. Chloride transport in in vivo aged Huntington's cells or both young and old control cells was essentially not dependent on time. These results are discussed in terms of proposed molecular mechanisms for neuronal loss in this disorder. The alterations in chloride efflux in extraneural erythrocytes are consistent with a proposed cell-surface membrane defect involving a protein in Huntington's disease.

Membrane processes in myotonic dystrophy during in vitro aging of erythrocytes

The present communication is devoted to investigating the possibility that in myotonic dystrophy (MyD) a decreased ATP utilization by the membrane may produce modifications in glycoprotein structure and/or in the supramolecular arrangement of some membrane proteins. The study was carried out a) by determining the membrane sialic acid content and the cellular ATP concentration in 10 cases of MyD, b) by evaluating the structural modifications of membrane glycoproteins occurring during in vitro incubation, c) by testing the presence on the membrane of high molecular weight aggregates of proteins, and d) by evaluating the distribution of hydrophobic and hydrophilic domains of the membrane by using 1-anilino-8-naphthalene sulfonate (1,8 ANS) as a fluorescent probe. Our evidence suggests that the ATP concentration and membrane sialic acid content are within normal values. Only in two cases did structural modifications of membrane glycoproteins occur while the supramolecular assembly of membrane proteins could be considered normal. The fluorescent probe behaviour after in vitro aging was indicative of a decreased polarity of its environment.

Degradation of band-3 glycoprotein in vitro by a protease isolated from human erythrocyte membrane

The use of soybean-trypsin-inhibitor-Sepharose-4B to purify a protease present in human erythrocyte membranes is described. The fraction bound in the presence of calcium to the affinity absorbent is active on band-3 glycoprotein in a non-ionic detergent solution at neutral pH. Band-3 glycoprotein is degraded into components having the mobilities of the proteins of bands 4.5, 7 and of lower molecular weights. When calcium is omitted from the membrane extract, an inactive form of this enzyme can be purified. By DEAE-cellulose chromatography this inactive form can be converted into the active form, presumably by dissociation of an enzyme-inhibitor complex.

Myotonic muscular dystrophy. Time-dependent alterations in erythrocyte membrane fluidity

The muscle cell membrane may be the site of the basic molecular defect in myotonic muscular dystrophy. Many laboratories, including our own, have suggested that this defect may also be manifested in membrane of extraneural tissue. In previous studies, we found that electron spin resonance results suggested an increased membrane fluidity in erythrocyte membranes that had aged two days in buffer, but we and others could find no such changes in fresh erythrocyte membranes. To investigate these findings further, the results of an initial study of the time course of the membrane fluidity changes in erythrocytes in myotonic muscular dystrophy are given in the present report. They suggested that increased membrane fluidity changes in erythrocytes in myotonic muscular dystrophy are given in the present report. They suggested that increased membrane fluidity in myotonic dystrophy is manifested after two days of in vivo ageing and confirm our original findings. These results are discussed in relation to possible effects of metabolic deprivation or of protein-lipid alterations in erythrocytes.

Inhibition of human polymorphonuclear leukocyte function by 2-cyclohexene-1-one. A role for glutathione in cell activation

2-cyclohexene-1-one and diethyl maleate specifically decrease reduced glutathione (GSH) levels in human polymorphonuclear leukocytes (PMN) by direct conjugation, and by interaction with the glutathione-s-transferase system. Using these two nontoxic reagents we have examined the effect of decreased GSH levels on five parameters of PMN activation: superoxide generation, release of the lysosomal enzymes lysozyme and beta-glucuronidase, and increases in the influx of Na+ and Ca2+. When PMN pretreated with 2-cyclohexene-1-one or diethyl maleate were incubated with formyl-methionyl-leucyl-phenylalanine (FMLP) or the proteolytic fragment of the fifth component membrane of complement, C5a, agents that interact with surface membrane receptors, increases in all five parameters were inhibited in a dose-dependent manner. For O-2 generation and lysosomal enzyme release the ID50 for 2-CHX-1 was 40--90 micrometers corresponding with a 30--50% decrease in intracellular GHS. In contrast stimulation of treated PMN by the divalent cation ionophore A23187 or 5-hydroxyeicosatetraenoic acid was much less sensitive to depressed GSH; the ID50 for 2-cyclohexene-1-one was 1 mM or greater, corresponding with an 80--90% decrease in GSH. The effect of lowered GSH was not the result of decreased binding of FMLP to surface receptors because [3H]-FMLP binding studies demonstrated a two- to three-fold increase in the number of available binding sites. These data indicate that normal GSH levels are necessary for the transduction of the activation signal from the exterior to the interior of the PMN, but once initiated the activation sequence proceeds normally despite markedly lowered intracellular GSH.

The stereospecific D-glucose transport activity of cholate extracts from human erythrocyte membranes

The glucose transport protein of human erythrocyte membranes was solubilized with cholate to facilitate rapid reconstitution and direct glucose transport measurements. This may simplify the isolation of the native glucose transporter. In most experiments the membranes were prepared from fresh blood within 8 h, frozen in liquid nitrogen and stored at -70 degrees C to minimize proteolytic degradation. Solubilization with 25 mM cholate in the presence of 200 mM NaCl at pH 8.4 for 12 min at room temperature gave a high D-glucose transport activity. The solubilized mixture contained 20% of the total membrane protein, only 6% of the polypeptides of molecular weight around 90000, 23% of the polypeptides of molecular weight around 55000, 30% of the phospholipids and at least 6% of the stereospecific D-glucose transport activity. At cholate concentrations up to 22 mM the ratio of solubilized phospholipids to cholate increased steeply, concomitant with an increase in solubilized activity. Above 30 mM cholate the activity diminished. At 4 degrees C the activity of the extract decreased rapidly within the first day and slowly during the next few days. The initial changes seem to have produced a fairly stable, but not native form or fragment of the transporter. When 20 mM EDTA and 5 mM dithioerythritol were included in the solubilization mixture a high activity was preserved for about one day.

Membrane abnormalities of pyruvate kinase deficient red cells

Two experimental systems have been applied to the study of PK-deficient red cells in an attempt to reveal possible membrane abnormalities of these erythrocytes: (1) the glycoprotein self-digestion of intact erythrocytes during in vitro incubation at 37 degrees C; (2) the red cell sensitivity to the lytic action of mouse macrophages. PK-deficient erythrocytes display a more precocious than normal membrane glycoprotein self-digestion and are much more susceptible than normal to the cytotoxic activity of mouse macrophages. This latter effect is more pronounced in young than in old PK-deficient red cells. These observations indicate the existence of membrane abnormality in PK-deficient red cells other than those so far suspected.

Structural modifications in membrane glycoproteins during the erythrocyte life-span

Erythrocyte membrane glycoproteins undergo various types of modification during the life of the cell in the circulation; when only sialic acid is removed, the younger red cells can be repaired in the liver and return to the circulation. Otherwise, when an autolytic mechanism removing a sialopeptide becomes active as a consequence of the metabolic impairment of the cell, the erythrocyte is probably trapped by the hemocatheretic organs and destroyed.

Vesicles isolated from ATP-depleted erythrocytes and out of thrombocyte-rich plasma

When human erythrocytes are depleted of endogenous ATP they release spectrin-free vesicles as a light vesicle fraction [Lutz et al: J Cell Biol 73: 548, 1977] and chains of rounded vesicles as well as flattened myelin forms in a heavy vesicle fraction. The heavy fraction retains some spectrin, and glycophorin is partially degraded. The release of both types of fragments is not dependent upon added Ca+2, and 50 micrometer EGTA does not prevent the vesicle release. Concomitant with vesicle release, a large fraction of the major protein components of the cell is found in disulfide-bonded aggregates. A protocol is outlined to recover erythrocyte-specific fragments from thrombocyte-rich plasma. It allows detection of spectrin-free vesicles in whole blood stored under blood bank conditions for 12 days. In freshly drawn blood no such vesicles are observed, but particles are obtained that are different from thrombocyte fragments and that show a prominent glycoprotein running slightly faster than glycophorin.