Membrane microfilaments of erythrocytes: alteration in intact cells reproduces the hereditary spherocytosis syndrome (vinblastine-colchicine-strychnine-electron microscopy-cell rigidity)

Spectrin: an alternate target for cytoskeletal drugs

Cytoskeletal drugs having enormous therapeutic potential act on the cytoskeletal components like actin, tubulin either by promoting polymerization or destabilizing the same. Here we present the interaction of the popular cytoskeletal drugs such as taxol, latrunculin and cytochalasin with spectrin, a huge protein with multi domains that forms the cytoskeletal network. Particularly, the actin binding domain of spectrin regulates the dynamics of the actin cytoskeleton. We followed the binding of these drugs to its actin binding domain and intact spectrin as well. These drugs bind with moderate affinity (K_b ∼ 10⁴ M^-1) and the interaction with actin binding domain is entropy driven and hydrophobic in nature as determined by Van't Hoff plot. The docking studies and molecular dynamics simulations further corroborate the experimental findings. Particularly the higher binding constants in the case of latrunculin and cytochalasin to the actin binding domain of spectrin suggest the binding sites are presumably located in its actin binding domain.Communicated by Ramaswamy H. Sarma.

Vincristine-induced anemia in hereditary spherocytosis

Vincristine, a vinca alkaloid, is widely used in many hematologic disorders and pediatric cancers, and acts by binding to the tubulin protein, to inhibit effective cell division. Vincristine-induced anemia has been observed, but its mechanism is not well understood. We describe a case involving serious vincristine-induced anemia in a patient with congenital spherocytosis and provide the explanation to the underlying mechanism. This report demonstrates that vincristine administration to patients with a red cell disorder may require additional clinical interventions to compensate for the vincristine-induced anemia.

Impact statement

Therapy with vincristine (VCR), a vinca alkaloid, is widely used in many hematologic disorders and pediatric cancers, and acts by binding to the tubulin protein, to inhibit effective cell division. Our paper indicates that treatment of patients with a red cell disorder may require additional clinical interventions to compensate for the VCR-induced anemia. Careful evaluation of other hematologic disorders is important in using a well-known oncology treatment. Whereas extreme concentrations of VCR were shown to alter red cell viability, data did not show negative effects in patients treated. Our data show that under conditions of increased hematopoiesis, hemoglobin in the circulation drops rapidly requiring transfusion. VCR administration to patients with a red cell disorder may require additional clinical interventions to compensate for the VCR-induced anemia.

Studies on herediatary spherocytosis in Iceland

Thirty members with typical hereditary spherocytosis (HS) and over 90 apparently unaffected members belonging to 12 families have been studied. Splenectomy has been performed on 22 HS patients. Of nine HS individuals, who had not undergone surgical treatment in 1957, four suffered from temporary severe anaemia, presumably due to aplastic crisis associated with influenza. One of them died, a male 18 years of age. Pedigree studies on one of the families indicate that the HS gene or genes have been transmitted through six generations over the past 200 years. Marked deficiency in the number of affected compared with the apparently unaffected members in the HS families is present. The most striking example of uneven genetic ratio is a sibship of 15 members investigated haematologically, with one suffering from typical HS. Much reduced penetration of the HS gene or the presence of the socalled "mild form" is upheld as the main explanation for the unevenness in the genetic ratio. However, families are also present in which abortions and death at an early age indicated that selection against the affected could also disturb the genetic ratio in HS families.

Commercial taxane formulations induce stomatocytosis and increase blood viscosity

1. Taxanes are antineoplastic drugs which have cardiovascular side effects of unknown mechanism. We investigated their influence on blood viscosity and erythrocyte morphology. 2. Whole blood was incubated in vitro with increasing concentrations of Taxol, Taxotere, paclitaxel (0-100 microM) and the vehicles Cremophor-EL and Tween 80 (0-5% vol) for 1 h at 37 degrees C. Plasma and whole blood viscosity (Haematocrit 45%) were measured and erythrocyte morphology was assessed on glutaraldehyde-fixed cells. The same investigations were performed in seven patients before and after a Taxol-infusion. 3. Taxol and Taxotere induced a dose- and time-dependent stomatocytic shape transformation of erythrocytes. Paclitaxel alone had no effect, but the vehicles cremophor-EL and Tween 80, used in Taxol and Taxotere, respectively, induced a comparable degree of stomatocytosis. This suggests a preferential intercalation of these substances into the inner hemileaflet of the membrane lipid bilayer. Associated with this shape change a dose-dependent increase in plasma and whole blood viscosity was observed. Neither shape nor viscosity changes were reversible upon removal of the agents. After the infusion of 130-300 mg Taxol in patients a slight shift towards stomatocytosis and an increase in whole blood viscosity at high shear rate from 5.09+/-0.30 to 5.44+/-0.38 mPa.s (P<0.05) were confirmed. 4. Commercial taxane drug formulations induce stomatocytosis and increase blood viscosity, which is due to their formulation vehicles. These findings may contribute to the understanding of the cardiovascular side effects of these drugs.

Ifosfamide-induced stomatocytosis and mesna-induced echinocytosis: influence on biorheological properties of blood

Ifosfamide is an alkylating agent which has poorly understood toxic side effects such as encephalopathy. We hypothesized that ifosfamide and concomitantly applied mesna could have an influence on the flow properties of blood, and thus carried out an in vitro study. Whole blood was incubated in vitro with increasing concentrations of ifosfamide (0-50 mg/ml), mesna (0-20 mg/ml) and combinations thereof. Chloroacetaldehyde, a major metabolite of ifosfamide, was also studied (0-5 mmol/l). Ifosfamide led to a dose-dependent stomatocytic shape transformation and mesna to an echinocytic shape transformation of erythrocytes. These shape changes were reversible upon removal of the causing agent. Both shape changes increased whole blood viscosity. Erythrocyte aggregation was decreased by both drugs at high concentration. Erythrocyte deformability, as measured with the transit time through 5-microm pores, was decreased by mesna and remained unaffected by ifosfamide. These effects were seen at concentrations which may be reached in vivo at the infusion site of the drugs into a vein and in the urinary tract. We conclude that ifosfamide and mesna interact with the lipid bilayer of the cell membrane, which may contribute to the toxicity of the compounds.

Hypertonic cryohemolysis: a diagnostic test for hereditary spherocytosis

Red blood cells of subjects with hereditary spherocytosis are specifically susceptible to temperature changes while suspended in hypertonic solutions. Based on this property, a new diagnostic test for hereditary spherocytosis is presented. The suggested method is 100% sensitive in the diagnosis of all patients, including asymptomatic obligate carriers with hereditary spherocytosis, and is very specific in different control groups. Unlike other methods designed for the diagnosis of hereditary spherocytosis, this test does not depend on the cells' surface- area-to-volume ratio. Normal red blood cells that were induced to become spherocytes by different means (i.e., vinblastine, lysophosphatidyl choline, and heat) and showed increased osmotic fragility did not become susceptible to the hypertonic cryohemolysis conditions.

Forskolin induces supersensitivity of the amylase secretory response of rat parotid tissue

The stimulatory effect of forskolin on amylase secretion was studied by pretreating rat parotid tissue with forskolin for 10 min, incubating it in medium without forskolin for 10 min, and then treating it with forskolin again. Pretreatment with 10 microM forskolin for 10 min resulted in increased amylase secretion and enhanced accumulation of cyclic AMP in the tissue during the second incubation with forskolin. In the presence of colchicine or vinblastine, the enhancement in cyclic AMP accumulation during the second incubation with forskolin was prevented, but the increased amylase secretion remained unchanged. The increased amylase secretion was counteracted only in the presence of concanavalin A. On the other hand, increased amylase secretion induced by isoproterenol (IPR) pretreatment was counteracted by colchicine, vinblastine, concanavalin A or strychnine. These data suggest that the total amount of cyclic AMP in the tissue does not have any essential role in the supersensitivity of the amylase secretory response, and that the supersensitivity induced by forskolin differs from that induced by IPR.

Drug-induced stomatocytosis and anemia during consolidation chemotherapy of childhood acute leukemia

In a group of 23 children with acute leukemia, all but one of whom had entered complete remission, retrospective analysis of hematological profiles demonstrated that administration of consolidation chemotherapy, with a combination of cytosine arabinoside (Ara-C) and 6-thioguanine (TG), was associated with a fall in the erythrocyte concentration in peripheral blood, the rate of which was at least as fast as would have occurred with total marrow ablation and consequent red cell aplasia. In the absence of profound myelosuppression or detectable hemorrhage, drug-induced erythrocytotoxicity was suspected, prompting in vitro studies of erythrocytes from children with acute leukemia and normal adults. At therapeutic concentration, Ara-C and TG, individually and in combination, produced significant stomatocytosis in samples from both groups. Since phenothiazines are stomatocytogenic and are administered as anti-emetics in conjunction with cancer chemotherapy, chlorpromazine was investigated in parallel studies that demonstrated stomatocytosis at therapeutic concentration, but no consistent interaction with the effects of Ara-C and TG in this regard. These observations suggest a possible pathogenetic mechanism for the development of anemia resulting from drug-induced erythrocytotoxicity.

The normal range of osmotic fragility of red blood cells

With the technique of Parpart et al (1947), the normal range for osmotic fragility of red blood cells had been estimated to include 5%--45% haemolysis at a salt concentration corresponding to 4.5 g NaCl/l (Dacie 1954). This estimate may be questioned, however. Thus, nearly 20% of the data obtained from 50 presumably healthy subjects fell outside these limits. Furthermore, the distribution pattern was very asymmetric with erroneously small standard deviation. On the other had, if the technical conditions (salt concentration, buffer) were properly adjusted, nearly all the observations were located with the straight part of the s-shaped haemolysis curve and scattered symmetrically around the mean. Under these conditions, the normal range (mean +/- 2 SD) included 22%--88% haemolysis. Moreover, this wider range included about 95% of the observations, even adapted to the original experimental situation. The present estimates should therefore replace earlier statements in the literature.

Desacetyl vinblastine amide sulfate induced ineffective erythropoiesis

Ineffective erythropoiesis occurred during desacetyl vinblastine amide sulfate (VDS) therapy of a patient with metastatic Ewing's sarcoma. The peripheral blood was characterized by anisocytosis, poikilocytosis and reticulocytopenia. Bone marrow showed megaloblastic red cell hyperplasia with nuclear fragmentation, binuclearity and abnormal metaphases. Radioiron incorporation into red cells was markedly decreased. Electron microscopy showed red cell surface changes previously called ropalocytosis. Normal erythropoiesis promptly resumed when VDS treatment was withheld. Although less common than leukopenia, red cell abnormalities are part of the spectrum of vinca alkaloid toxicity.

Lazy leucocyte syndrome--disorder of the granulocyte membrane?

An adult with long-standing neutropenia had the functional granulocyte abnormalities typical of the lazy leucocyte syndrome. Scanning electron microscopy of the patient's neutrophils showed alteration in the surface configuration of the cell with coarsening of the normal fine ruffles and the appearance of knob-like projections. Similar functional and anatomical changes were induced in normal neutrophils by treatment with vinblastine. The lazy leucocyte syndrome may be a consequence of altered membrane microfilamentous protein structure or function, and undue rigidity of the affected neutrophils may explain the clinicopathological features of the disease.

Hereditary spherocytosis revisited. Eighth annual Paul M. Aggeler Memorial Lecture. Delivered October 25, 1977, San Francisco General Hospital Medical Center

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The effect of vincristine on haemoglobin synthesis

Vincristine in a concentration of 0.5 and 4 X 10--(5) M causes a decrease of 16% and 73% respectively, in the synthesis of globin by peripheral blood reticulocytes. At the higher drug concentration alpha/beta ratio is significantly lower than the normal ratio of unity and is 0.83 +/- 0.09. These effects of vincristine are probably related to the ability of the vinca alkaloids to bind to ribosomes and their subunits.

Abnormality of erythrocyte membrane protein in a case of congenital stomatocytosis

A new method of membrane protein analysis was used to demonstrate an erythrocyte membrane protein anomaly. Our approach employed electrofocusing linked to sodiumdodecylsulfate polyacrylamide gel electrophoresis. We observed an aberrant protein, isoelectric at approximately pH 4.5 with an apparent molecular weight of approximately 25,000 in membrane preparations from a patient with congenital stomatocytosis. This protein has not been observed in any healthy donor examined to date.

Microtubular proteins in pigeon erythrocyte membranes

[3H]Colchicine binds in a concentration and temperature dependent, saturatable and noncooperative manner to cytoplasmic proteins from pigeon erythrocytes: Kd = 3.5 x 10(-7) M at 37 degrees C. Binding of [3H] colchicine at 0 degrees C and of [3H]lumicolchicine at 37 degrees C was significantly reduced. Hence microtubular proteins are present in the cytoplasm of pigeon erythrocytes. Antibody against bovine brain tubulin was raised in rabbits and confirmed by immunodiffusion, passive immunohaemolysis and in radioimmunoassay. Pigeon erythrocyte membrane proteins solubilized with 2% sodium cholate competed with 125I-labelled tubulin in the radioimmununoassay although much higher concentrations of membrane proteins than of purified bovine brain tubulin were required for effective competition. No binding to antibody occurred with boiled solubilized membrane preparations. Similar results were obtained with antitubulin-dependent passive immunohaemolysis of tubulin-coated sheep erythrocytes in the presence of complement. The presence of tubulin in membranes was verified by binding intact pigeon erythrocytes to colchicine-Sepharose beads at 37 degrees C. Free colchicine (5mM) or incubation at 0 degrees C prevented binding. Lumicolchicine-Sepharose beads did not attach to erythrocytes at 37 degrees S. Thus pigeon erythrocyte membranes contain microtubular protein.

Effect of vinblastine on the brush border of proximal tubule cells of rat kidney

A vinblastine-induced lesion of the brush border of proximal tubule cells of rat kidney was studied by scanning and transmission electron microscopy. Adult rats were given two tail-vein injections of vinblastine sulfate and then sacrificed either three or sixteen hours after administration of the first injection. The proximal tubules of animals treated with the drug for three hours differed from those of saline-treated controls in possessing (1) well defined areas of apical cell surface devoid of microvilli and (2) fewer microcraters in the brush border. In tubules of animals treated with vinblastine for sixteen hours, the areas devoid of microvilli were much more extensive, and microcraters were less frequently seen. Cilia did not appear to be affected by exposure to the drug and were observed both in regions devoid of microvilli and in areas with a well developed brush border. The mechanism of action of vinblastine in eliciting focal loss of microvilli of proximal tubule cells is not known. Several hypotheses to account for this lesion of the brush border are discussed.

Inverse localization of Ca2+ and La3+ high affinity binding sites of the red cell membrane

Glutaraldehyde fixation in the presence of both 90 mM La3+ resulted in opaque deposits were also seen in specimens fixed in a glutaraldehyde-CaCl2 medium devoid of La3+. In that case only small amounts of a moderately opaque substance had accumulated or remained at the external surface of the erythrocyte membrane. Specimens previously fixed with Ca2+, La3+ supplemented glutaraldehyde lost their internal deposits completely during postifixation with OsO4. The findings provide evidence of Ca2+ high affinity binding sites at the internal surface of the erythrocyte membrane presumably identical with the filamentous matrix. Glycocalyx constituents are considered external Ca2+ low affinity binding sites, however, capable of accumulating high amounts of La3+ during glutaraldehyde fixation.

Elevated microviscosity in membranes of erythrocytes affected by hereditary spherocytosis

Erythrocytes affected by hereditary spherocytosis (HS), obtained from several splenectomized patients, showed a varying degree of elevated osmotic fragility. In order to evaluate a possible role of the erythrocyte membrane lipids in HS, microviscosity of the membrane lipid core was measured by a fluorescence-polarization technique. Intact HS-affected red cells, as well as their ghost membranes and liposomes prepared from their lipid extract, all showed a distinctly higher micro-viscosity than the respective normal control. The increased microviscosity correlated with the severity of HS. The data support the proposition that the defect in HS-affected red cells is associated, at least in part, with alterations in the membrane lipids.

The kinetics of resealing of washed erythrocyte ghosts

The kinetics of resealing, defined as the recovery of impermeability to macromolecules, of well-washed human erythrocyte ghosts has been determined. The resealing process is first-order at temperatures above 20-25 degrees C in isotonic salt, with rate constants ranging from 0.01-0.15 min-1. Below 20 degrees C, resealing occurs, but a long lag period is observed. Other erythrocyte membrane properties suggest a transition at about 20 degrees C, and it is possible that resealing rates are a measure of membrane fluidity. A temperature-induced reduction of resealed ghost volume was also observed. The effect of ionic strength on resealing parameters was determined. Low ionic strength buffers prevent resealing, which is also consistent with resealing as a lipid-related event. The effect of microtubule disrupting drugs and changes in the method of preparing ghosts are also described.

Effect of drugs on red cell membranes: insights into normal red cell shape

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Cellular action of antidiuretic hormone in mice with inherited vasopressin-resistant urinary concentrating defects

Previous work has suggested that resistance to vasopressin in two strains of mice with nephrogenic deficiency of urinary concentration may entail a defect in the action of vasopressin at the cellular level. Several components involved in this action were therefore examined in vitro in renal medullary tissues from control mice (genotype VII +/+) and two genotypes with mild diabetes insipidus (DI +/+ nonsevere) and marked (DI +/+ severe) vasopressin-resistant concentrating defects. No significant differences were found in the affinity of adenylate cyclase for [8-arginine]-vasopressin (AVP), tested over a range of hormone concentration from 10(-10) to 10(-5) M. However, maximal stimulation of adenylate cyclase by saturating concentrations of AVP (intrinsic activity) was markedly decreased from control values in DI +/+ severe mice, and decreased to a lesser extent in DI +/+ nonsevere animals. A significant correlation was found between the activity of adenylate cyclase maximally stimulated by AVP in a given genotype, and the urine osmolality in the same animals. There were no significant differences in maximal stimulation of renal medullary adenylate cyclase in control experiments: not when stimulated nonspecifically by sodium fluoride, nor when stimulated by AVP in tissues from rats with induced water diuresis as compared to antidiuretic rats. Nor were there significant differences between VII +/+ and DI +/+ severe mice in the activity of renal cortical adenylate cyclase, either basal or when stimulated by parathyroid hormone. Furthermore, the abnormal genotypes did not differ significantly from control mice in the renal medullary activities of cyclic AMP phosphodiesterase or cyclic AMP-dependent protein kinase, nor in the content of microtubular subunits (assessed as colchicinebinding protein). The results are compatible with the view that impaired stimulation of renal medullary adenylate cyclase by vasopressin might be the sole or contributing cause of the vasopressin-resistant concentrating defect in the diseased mice; however, a causal relationship has not yet been proved.

Effect of vinblastine on the chemotactic responsiveness of normal human neutrophils

The effect of vinblastine on the mobility of human neutrophils was studied. Chemotactic responsiveness was decreased by approximately 80 to 95%, as measured in Boyden chambers, whereas random mobility, as measured in glass capillary tubes, was approximately doubled. Chemotactic responsiveness could be partially restored after dialysis of the treated cells, which is not compatible with an action of vinblastine on microtubules. The possibility is considered that this observation is an additional example of the effect of several microtubular binding agents on phenomena mediated at the phagocytic surface.

Effect of colchicine and vinblastine on the topographical separation of membrane functions

The topographical separation of membrane functions into phagocytic and transport areas, inferred from physiological studies, is not demonstrable in cells treated with colchicine and vinblastine, alkaloids which bind to microtubular proteins.