Destruction of injured red cells in vivo

Selective elimination of younger erythrocytes in blood circulation and associated molecular changes in benzo (a) pyrene induced mouse model of lung cancer

Background

Anemia is a common feature in cancer patients. The present research was conducted to explore the mechanisms of induction of anemia in a mouse model of lung cancer.

Methods

The lung cancer was induced by treating orally with BaP (50 mg/kg body weight, twice a week for four weeks). The erythrocyte kinetics were studied using a double in vivo biotinylation (DIB) technique. ROS production and apoptosis analysis were done by staining with the CMH2DCFDA stain and anti-mouse Annexin V antibody, followed by flow cytometry. The expression of antioxidant, apoptotic, anti-apoptotic and inflammatory genes was analyzed by quantitative PCR (RT-qPCR).

Results

BaP-induced tumour reduced body weight and induced persistent haemolytic anaemia. The kinetics data suggest that, though reticulocyte production was enhanced, the proportion of young erythrocytes did not increase in the same proportion. The young aged erythrocytes were selectively eliminated from blood circulation, but intermediate and old aged erythrocytes persisted for a longer duration. The tumour progression leads to a significant increase in ROS production and apoptosis in the erythrocytes. The molecular data suggests that the expression levels of antioxidants (SOD1, catalase, and GPX1) and erythropoietin (Epo) were significantly increased. The anti-inflammatory genes Interleukin-6 (IL-6), Interleukin-10 (IL-10) were significantly decreased.Apoptotic genes Bax, and caspase 3 were significantly decreased while Bcl 2 was significantly increased in the blood of tumour-bearing mice.

Conclusions

The overall data suggest that erythrocyte turnover is severely modulated with the progression of tumor. The apoptosis, ROS levels, antioxidant, anti-apoptotic, and Epo gene expressions were increased, but proapoptotic and anti-inflammatory gene expression were suppressed.

Splenectomy Modulates the Erythrocyte Turnover and Basigin (CD147) Expression in Mice

The present study was designed to study the splenectomy induced modulation of erythrocyte turnover in mice. We have also studied the modulation of reactive oxygen species (ROS) and basigin (CD147) expression level on erythrocytes in splenectomized condition. The erythrocyte turnover was studied by a newly developed double in vivo biotinylation (DIB) technique. This technique enables to discriminate three different age (young, intermediate and old) groups of erythrocytes. The expression level of ROS and CD147 was studied by staining with CM-H₂DCFDA stain and anti-mouse CD147 monocloclonal antibody followed by flow cytometry. We observed that intermediate and old age groups of erythrocytes were randomly eliminated in splenectomized condition. A marked surge in the blood reticulocyte count was observed in splenectomized mice. Splenectomy induced the level of ROS and CD147 expression on erythrocytes. The expression level of ROS was induced up to 35 days, but it reversed to basal level by 42 days indicating the emergence of refractoriness to splenectomy. The CD147 expression was significantly higher on day 7, 21 and 28 but it also normalizes on later time points. We conclude that erythrocyte turnover is significantly modulated in splenectomized mice. The enhanced level of ROS and CD147 expression may be a possible cause to increase erythrocyte removal in splenectomized mice.

Neocytolysis: How to Get Rid of the Extra Erythrocytes Formed by Stress Erythropoiesis Upon Descent From High Altitude

Neocytolysis is the selective destruction of those erythrocytes that had been formed during stress-erythropoiesis in hypoxia in order to increase the oxygen transport capacity of blood. Neocytolysis likely aims at decreasing this excess amount of erythrocytes and hemoglobin (Hb) when it is not required anymore and to decrease blood viscosity. Neocytolysis seems to occur upon descent from high altitude. Similar processes seem to occur in microgravity, and are also discussed to mediate the replacement of erythrocytes containing fetal hemoglobin (HbF) with those having adult hemoglobin (HbA) after birth. This review will focus on hypoxia at high altitude. Hemoglobin concentration and total hemoglobin in blood increase by 20-50% depending on the altitude (i.e., the degree of hypoxia) and the duration of the sojourn. Upon return to normoxia hemoglobin concentration, hematocrit, and reticulocyte counts decrease faster than expected from inhibition of stress-erythropoiesis and normal erythrocyte destruction rates. In parallel, an increase in haptoglobin, bilirubin, and ferritin is observed, which serve as indirect markers of hemolysis and hemoglobin-breakdown. At the same time markers of progressing erythrocyte senescence appear even on reticulocytes. Unexpectedly, reticulocytes from hypoxic mice show decreased levels of the hypoxia-inducible factor HIF-1α and decreased activity of the BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3), which results in elevated mitochondrial activity in these cells. Furthermore, hypoxia increases the expression of miR-21, which inhibits the expression of catalase and thus decreases one of the most important mechanisms protecting against oxygen free radicals in erythrocytes. This unleashes a series of events which likely explain neocytolysis, because upon re-oxygenation systemic and mitochondrial oxygen radical formation increases and causes the selective destruction of those erythrocytes having impaired anti-oxidant capacity.

The Action of Red Cell Calcium Ions on Human Erythrophagocytosis in Vitro

In the present work we have studied in vitro the effect of increasing red cell Ca²⁺ ions on human erythrophagocytosis by peripheral monocyte-derived autologous macrophages. In addition, the relative contribution to phagocytosis of phosphatidylserine exposure, autologous IgG binding, complement deposition and Gárdos channel activity was also investigated. Monocytes were obtained after ficoll-hypaque fractionation and induced to transform by adherence to glass coverslips, for 24 h at 37°C in a RPMI medium, containing 10% fetal calf serum. Red blood cells (RBC) were loaded with Ca²⁺ using 10 μM A23187 and 1 mM Ca-EGTA buffers, in the absence of Mg²⁺. Ca²⁺-loaded cells were transferred to above coverslips and incubated for 2 h at 37°C under various experimental conditions, after which phagocytosis was assessed by light microscopy. Confirming earlier findings, phagocytosis depended on internal Ca²⁺. Accordingly; it was linearly raised from about 2–15% by increasing the free Ca²⁺ content of the loading solution from 0.5 to 20 μM, respectively. Such a linear increase was virtually doubled by the presence of 40% autologous serum. At 7 μM Ca²⁺, the phagocytosis degree attained with serum was practically equal to that obtained with either 2 mg/ml affinity-purified IgG or 40% IgG-depleted serum. However, phagocytosis was reduced to levels found with Ca²⁺ alone when IgG-depleted serum was inactivated by heat, implying an involvement of complement. On the other hand, phagocytosis in the absence of serum was markedly reduced by preincubating macrophages with phosphatidylserine-containing liposomes. In contrast, a similar incubation in the presence of serum affected it partially whereas employing liposomes made only of phosphatidylcholine essentially had no effect. Significantly, the Gárdos channel inhibitors clotrimazole (2 μM) and TRAM-34 (100 nM) fully blocked serum-dependent phagocytosis. These findings show that a raised internal Ca²⁺ promotes erythrophagocytosis by independently triggering phosphatidylserine externalization, complement deposition and IgG binding. Serum appeared to stimulate phagocytosis in a way dependent on Gárdos activity. It seems likely that Ca²⁺ promoted IgG-binding to erythrocytes via Gárdos channel activation. This can be an important signal for clearance of senescent human erythrocytes under physiological conditions.

Effects of primaquine and chloroquine on oxidative stress parameters in rats

Primaquine and chloroquine are used for the treatment of malaria; evidence from the literature suggests that these drugs may induce oxidative stress. In this study we investigated the effects of primaquine and chloroquine on oxidative damage and DNA damage in brain, liver and kidney of rats after 7, 14 and 21 days of administration. Our results demonstrated that primaquine causes DNA damage in brain after 7, 14 and 21 days, and in liver after 7 and 14 days. Moreover, primaquine increases TBARS levels in the kidney and protein carbonyls in the brain after 14 days, and decreases protein carbonyls in the liver after 7 days. Whereas chloroquine causes DNA damage in the kidney after 7 and 14 days, and in the liver after 14 and 21 days, increases TBARS levels in the kidney after 7 days, and decreases TBARS levels in the brain after 21 days. Moreover, decreases protein carbonyls in the liver after 7 and 14 days, and in the brain after 7 and 21 days. However, chloroquine treatment for 14 days increases protein carbonyls in the brain and kidney. In conclusion, these results showed that prolonged treatment with antimalarial may adversely affect the DNA.

Association of chromosome damage detected as micronuclei with hematological diseases and micronutrient status

Epidemiological studies reveal strong association between micronutrient deficiencies and development of cancer. Since chromosome breaks and abnormal chromosome segregation, identified as micronuclei (MN), are central to malignant transformation, the influence of micronutrient status upon MN frequency has been the subject of intense research. Motivating this effort is the idea that marginal micronutrient deficiencies lead to allocation of scarce cellular resources towards immediate survival at the expense of maintaining genomic integrity, placing the individual at greater risk for degenerative diseases and cancer in old age. The challenge in identifying an association between individual micronutrients and MN frequency stems from the complexity of human diet, simultaneous presence of multiple micronutrient deficiencies, variable genetic susceptibility and methodological difficulties. A unique model for studying MN in humans is provided by a group of haematological diseases, the chronic haemolytic anaemias associated with high reticulocyte count and absence of splenic function. These disorders may prove valuable for assessing the influence of micronutrient status once the effect of abnormal erythropoiesis on MN formation is adequately understood. Eventually, large population-based studies that can account for the baseline variability in MN frequency, lifestyle and genetic factors may be needed to uncover the DNA-damaging effect of poor diet. Understanding the link between micronutrient status and MN frequency will contribute towards determining optimal micronutrient intake to preserve long-term health.

Primaquine-Induced Hemolytic Anemia: Role of Membrane Lipid Peroxidation and Cytoskeletal Protein Alterations in the Hemotoxicity of 5-Hydroxyprimaquine

Primaquine-induced hemolytic anemia is a toxic side effect that is due to premature splenic sequestration of intact erythrocytes. Previous studies have suggested that a phenolic metabolite, 5-hydroxyprimaquine (5-HPQ), mediates primaquine hemotoxicity by generating reactive oxygen species (ROS) within erythrocytes that overwhelm antioxidant defenses. However, the nature of the oxidative stress is not understood, and the molecular targets, whether protein and/or lipid, are unknown. To investigate the mechanism underlying the hemolytic activity of 5-HPQ, we have examined the effect of hemolytic concentrations of 5-HPQ on ROS formation within rat erythrocytes using the cellular ROS probe, 2',7'-dichlorodihydrofluoresein diacetate. In addition, we examined the effect of 5-HPQ on membrane lipids and cytoskeletal proteins. The data indicate that 5-HPQ causes a prolonged, concentration-dependent generation of ROS within erythrocytes. Interestingly, 5-HPQ-generated ROS was not associated with the onset of lipid peroxidation or an alteration in phosphatidylserine asymmetry. Instead, 5-HPQ induced oxidative injury to the erythrocyte cytoskeleton, as evidenced by changes in the normal electrophoretic pattern of membrane ghost proteins. Immunoblotting with an anti-hemoglobin antibody revealed that these changes were due primarily to the formation of disulfide-linked hemoglobin-skeletal protein adducts. The data suggest that cytoskeletal protein damage, rather than membrane lipid peroxidation or loss of phosphatidylserine asymmetry, underlies the process of removal of erythrocytes exposed to 5-HPQ.

Primaquine-induced hemolytic anemia: effect of 6-methoxy-8-hydroxylaminoquinoline on rat erythrocyte sulfhydryl status, membrane lipids, cytoskeletal proteins, and morphology

Previous studies have shown that 6-methoxy-8-hydroxylaminoquinoline (MAQ-NOH), an N-hydroxy metabolite of the antimalarial drug, primaquine, is a direct-acting hemolytic agent in rats. To investigate the mechanism underlying this hemolytic activity, the effects of hemotoxic concentrations of MAQ-NOH on rat erythrocyte sulfhydryl status, membrane lipids, skeletal proteins, and morphology have been examined. Treatment of rat erythrocytes with a TC(50) concentration of MAQ-NOH (350 microM) caused only a modest and transient depletion of reduced glutathione (GSH) (~30%), which was matched by modest increases in the levels of glutathione disulfide and glutathione-protein mixed disulfides. Lipid peroxidation, as measured by thiobarbituric acid-reactive substances and F(2)-isoprostane formation, was induced in a concentration-dependent manner by MAQ-NOH. However, the formation of disulfide-linked hemoglobin adducts on membrane skeletal proteins and changes in erythrocyte morphology were not observed. These data suggest that hemolytic activity results from peroxidative damage to the lipid of the red cell membrane and is not dependent on skeletal protein thiol oxidation. However, when red cell GSH was depleted (>90%) by titration with diethyl maleate, hemolytic activity of MAQ-NOH was markedly enhanced. Of interest, exacerbation of hemotoxicity was not matched by increases in lipid peroxidation, but by the appearance of hemoglobin-skeletal protein adducts. Collectively, the data are consistent with the concept that MAQ-NOH may operate by more than one mechanism; one that involves lipid peroxidation in the presence of normal amounts of erythrocytic GSH, and one that involves protein oxidation in red cells with low levels of GSH, such as are seen in individuals with glucose-6-phosphate dehydrogenase deficiency.

Immunohematotoxicity studies with combinations of dapsone and zidovudine

We investigated the immunohematoxicities of the antiparasitic drug dapsone (DDS) and the antiretroviral drug zidovudine (ZDV, AZT) given alone or in combination in BALB/c mice. DDS is used for prophylaxis and treatment of Pneumocystis carinii infection in AIDS patients. We examined the impact of concurrent administration of these drugs on the immune and hematopoietic systems because DDS causes hematotoxicity and ZDV therapy results in bone marrow toxicity. Daily oral administration of DDS at 25 and 50 mg/kg for 28 days caused a slight anemia, marked methemoglobinemia, reticulocytosis, and a moderate leukopenia (P < 0.01 for all parameters) but had no discernible effect on platelet count. In DDS-treated mice, the proliferative response of splenic T cells to concanavalin A was > or = 35% higher than that manifested by splenocytes from vehicle-treated control mice. ZDV at 240 and 480 mg/kg was not immunosuppressive but caused low-grade macrocytic anemia, thrombocytosis, and neutropenia; these effects were drug dose-dependent and statistically significant (P < 0.01). Concurrent administration of DDS and ZDV augmented the severity of ZDV-mediated macrocytic anemia, and 7 of 12 (58%) mice did not survive treatment with the high doses of DDS and ZDV (50 and 480 mg/kg, respectively). On the other hand, co-administration of ZDV mitigated DDS-induced methemoglobinemia and the DDS-associated elevation in lymphoproliferative response. These data suggest interaction between DDS and ZDV in mice and indicate a need for caution in using DDS as long-term therapy in AIDS patients receiving ZDV.

Hematological status of beta-thalassemics in Madras

Although rapid technical advances have taken place in the diagnosis of beta-thalassemia, still the hematological factors were found to be suitable screening test in areas like Indian subcontinent where a high prevalence of beta-thalassemia trait was observed. Among various thalassemias reported in Asian Indians, beta-thalassemia account for about 80% and is responsible for very high infantile mortality. Despite this, little is known about the hematological status of beta-thalassemias among this ethnic group which is associated with more than five different predominant beta-globin mutation with high frequency and variable number of rare ones. The present study is the first report of hematological status of beta-thalassemia among this ethnic group particularly from Tamil Nadu, Southern India, who are still practising high degree of consanguinity. In the present study, a total number of 364 beta-thalassemics were investigated. This includes 84 cases of homozygous beta-thalassemias and the remaining 280 were heterozygotes. The hematological factors such as red cell indices, hemoglobin F and hemoglobin A2 were assessed. The results revealed a wide spectrum of hematological variables ranging from severe form as that of Mediterranean thalassemias to very mild form of anemia as that of African Negro population.

Ultrastructural changes in renal tubules associated with glomerular bleeding

Renal biopsies from ten patients presenting with macroscopic or heavy microscopic hematuria, shown to be glomerular in origin, were examined by light and electron microscopy. All biopsies showed erythrocytes within tubules by light microscopy and, in five cases, there were morphologic features of acute tubular necrosis. In four biopsies there was clear evidence by electron microscopy of uptake of erythrocytes by renal tubular epithelial cells, associated with some blunting of epithelial microvilli, vacuolar change and increased lysosomal content. Associated with erythrophagocytosis, the subsequent pathway of erythrocyte destruction within renal tubular epithelial cells closely resembled the hemolytic pathway described in macrophages of the reticuloendothelial system.

Pathogenesis and red blood cell destruction in haemoglobinaemic leptospirosis

Sequential morphological changes were seen in RBCs, spleen and liver from hamsters during the development of haemoglobinaemia following infection with Leptospira interrogans serovar ballum. Spleens from pre-haemoglobinaemic hamsters showed sequestration of RBCs and erythrophagocytosis but to a lesser degree than was seen in the haemoglobinaemic hamsters. Erythrophagocytosis and RBC sequestration were also seen in the liver, particularly in the haemoglobinaemic animals. None of these changes was seen in the RBCs, spleens and livers from moribund and dead hamsters suffering from non-haemoglobinaemic disease resulting from infection with Leptospira interrogans serovar pomona. Intracellular leptospires were readily identifiable within the spleens and livers of hamster infected with both ballum and pomona. It is suggested that leptospiral toxins affect RBC metabolism and eventually RBC morphology. The affected cells are detected and removed by the reticulo-macrophage system, usually before intravascular haemolysis can take place. If the toxins affect a certain enzyme or biochemical pathway, there are sufficient normal metabolic differences in RBCs between animals of different species and, in the same species of animal, between the same and different aged animals, to explain the differing susceptibilities of the RBCs to leptospiral toxins.

Liver phagocytosis in late stages of lethal canine endotoxin shock. A patho-morphological study

Liver phagocytosis was studied by means of electron microscopy in late stages of lethal canine endotoxin shock. A massive phagocytic activity was found within hepatic macrophages. The phagocytosed material found within Kupffer cells consisted of red cells, red-cell fragments, platelets, a fibrin-like material and damaged polymorphonuclear leukocytes. Red cells and red-cell fragments seemed to constitute the major part of the material involved.

Phagocytic activity in mouse embryonic liver and spleen following hemolysis

Phenylhydrazine (PHZ) was injected into pregnant mice and the number of phagocytizing cells was counted in the embryonic livers and spleens at 11th to 14th gestational days. A marked increase in the number of phagocytizing cells was observed in the embryonic spleen, whereas in the embryonic liver it was only slightly enhanced. This observation indicates that the response to hemolytic events is similar in embryonic and adult mammals.

Mechanism of action of divicine in a cell-free system and in glucose-6-phosphate dehydrogenase-deficient red cells

Favism is an acute hemolysis occurring in glucose-6-phosphate dehydrogenase (G6PD)-deficient (Mediterranean variant) individuals after intake of fava beans. Divicine (D), 2,6-diamino-4,5-dihydroxypyrimidine, is present in high amounts in the beans, and is suspected to play a role in hemolysis. Its mechanism of action was studied in a cell-free system and in G6PD (Mediterranean variant)-deficient red cells (RBC). Upon hydrolysis of the inactive beta-glucoside vicine, reduced divicine is formed. Oxygen acts as a one- or two-electron acceptor; superoxide anion and hydrogen peroxide are formed, respectively, together with the semiquinoid free-radical form of D. This free radical gives an electron spin resonance (ESR) signal, which is similar to that of the alloxan free radical. Added reduced glutathione (GSH) is rapidly oxidized with a stoichiometry of one to one, and the ESR signal is abolished. Additional GSH is oxidized by hydrogen peroxide and by a slow redox cycle which continuously regenerates oxidized D. The fast-direct and the slow-indirect oxidation result in nonstoichiometric oxidation of GSH. D added to G6PD-deficient RBC rapidly oxidizes GSH with an end point kinetics and a stoichiometry of one to one. Hydrogen peroxide and superoxide anion are scavenged in the RBC and no redox cycling is taking place. No GSH is regenerated even after long incubation periods. After the primary event, i.e., oxidation of GSH and--SH groups, a number of metabolic, rheologic, and membrane modifications, together with increased erythrophagocytosis take place in G6PD-deficient, D-treated RBC only.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of inorganic lead and/or a polychlorinated biphenyl on the developing immune system of mice

Approximately 200 female Swiss-Webster mice, six to eight weeks of age, were divided into eight groups. Three of these groups were fed 10, 100, or 250 ppm Aroclor 1254. One group was treated with 1000 ppm lead. Three groups were exposed simultaneously to lead and Aroclor 1254 at concentrations of 10 ppm PCB + 1000 ppm Pb, 100 ppm PCB + 1000 ppm Pb, and 250 ppm PCB + 1000 ppm Pb. Control mice received deionized water and rat food only. All groups were exposed for a period of 12 wk, then bred, with exposure continued throughout gestation and lactation. Offspring were weaned onto the control diet at 3 wk of age. Results from this study indicate a varied effect of lead and/or PCBs on body and organ weights of both dams and their pups, no noticeable detrimental effect on reproduction, and very little effect on the pups' ability to mount an immune response upon challenge with foreign antigens.

Effect of splenic sequestration of erythrocytes on splenic clearance function and susceptibility to septic peritonitis

The effect of splenic sequestration of erythrocytes (RBC) on splenic clearance function and susceptibility to septic peritonitis was studied. Homologous RBC were treated with 20 mM phenylhydrazine hydrochloride in vitro and injected into rats at doses of 5, 15, 75, and 150 mg of hemoglobin per 100 g. Splenic 93, 23, and 13% of the injected dose, respectively, whereas less than 2.1% of the same doses of washed RBC were localized in the spleen. The total quantity of phenylhydrazine-treated RBC sequestered by the spleen was similar for the three larger doses (40 to 45 mg of hemoglobin per g of tissue), indicating that this is the capacity of the spleen to take up this type of RBC in 234 h. The phenylhydrazine-treated RBC in doses of 15, 75, and 150 mg of hemoglobin per 100 g depressed the clearance rate and splenic localization of a test dose of phenylhydrazine-treated RBC, whereas splenic clearance function was unchanged after a dose of 5 mg of hemoglobin per 100 g. Splenectomy or injection of doses of phenylhydrazine-treated RBC which depressed splenic clearance function increased the susceptibility to septic peritonitis induced by cecal ligation and puncture. After thermal injury, splenic clearance function was found to be depressed. Also, splenic localization of RBC 24 h after thermal injury was found to be approximately equal to that after injection of the doses of phenylhydrazine-treated RBC which depressed splenic clearance function. It is concluded that splenic sequestration of RBC can depress splenic clearance function and increase susceptibility to peritonitis, and that this may be one mechanism for the increased susceptibility to infection seen after thermal injury.

Development of the embryonic chick phagocytic system: intraembryonic erythrophagocytosis induced by phenylhydrazine

The intraembryonic reticuloendothelial response to phenylhydrazine-induced hemolytic anemia was studied embryonic chicks (days 13-16) by light and electron microscopy and histochemical and biochemical assays for acid phosphatase. Phenylhydrazine was given on day 13 and tissue taken at 2, 5, and 10 h and at 1, 2, and 3 days after injections. The response varied in the three major reticuloendothelial organs. The spleen first demonstrated an increase in erythrophagocytosis that was accompanied by increased acid phosphatase levels. Erythrophagocytosis occurred primarily in the red pulp resulting in increased numbers of macrophages, increased to enlarge the spleens. By 2 days after phenylhydrazine injection, greatly enlarged macrophages began to migrate into the venous system, where some erythrophagocytosis continued to occur. The liver was also a major erythroclastic organ in which Kupffer cells became increasingly erythrophagocytic. However, erythrophagocytosis began later than in the spleen, and as measured by acid phosphatase levels, the liver was not as effective in removing damaged erythroid cells. Marrow erythrophagocytosis was only slightly enhanced; however, the marrow responded by increasing its production of red blood cells. Thus, the intraembryonic reticuloendothelial organs of the embryonic chick responded to phenylhydrazine-induced hemolytic anemia in much the same manner as might be expected of the adult bird.

Erythrocytes as carriers of chemotherapeutic agents for targeting the reticuloendothelial system

The object of this work was to define a model using hypotonically loaded erythrocytes as a vehicle to target drugs to the reticuloendothelial system (RES). The optimum hemolytic event was found to occur at 100 mOsm/kg using a 0.5-min exposure at 0 degrees C. Approximately one third of the total volume of the cells could be replaced with hypotonic drug solutions under these conditions. Although cytosine-beta-D-arabinofuranoside, ara C, is membrane permeable and could not be entrapped in the erythrocytes, phosphorylation of this nucleoside antimetabolite enabled it to be loaded efficiently. Actinomycin D could be loaded and retained within the cells at 0 degrees C, but 90% of this loaded drug leaked out of the erythrocytes in 1 min at 37 degrees C. Actinomycin D-DNA complexes, however, could be loaded and retained for longer periods. In this case, 50% of the DNA-bound drug was retained in the cells for one hour at 37 degrees C. It was found that the glycopeptide antitumor antibiotic, bleomycin, could be entrapped and retained in the cells without appreciable leakage. It was possible to load a human therapeutic dose of this drug in 1-2 ml of packed cells. Furthermore, it was demonstrated that bleomycin entrapped in erythrocytes was significantly more effective than the same dose of free drug in suppressing the phagocytic function of the RES in Balb/C and C3H mice. The rationale is discussed for the possible use of these drugs, entrapped in erythrocytes, for the production of RES blockade in the treatment of disorders in man.

The possible role of hypertension in aggravating hemolytic episodes in G-6PD deficient persons

Approximately 13 percent of American Negro males carry a mutant [A-variant] glucose-6-phosphate dehydrogenase enzyme in their red blood cells that predisposes them to hemolytic episodes following exposure to oxidant drugs such as primaquine. Most hemolytic episodes to standard prophylactic treatment are mild and self-limited, but as many as 2 percent of Negro males develop severe hemolysis when similarly treated. The exaggerated response may be due in part to the combination of G-6-PD deficiency and hypertension since hypertension can cause red cell fragmentation, and the stressed cells of G-6-PD deficient person would be more sensitive to such fragmentation.

The annular hematoma of the shrew yolk-sac placenta

The annular hematoma of the shrew, Blarina brevicauda, is a specialized portion of the yolk-sac wall. In this study, we have examined the fine structure of the different cellular components of the anular hematoma. Small pieces of the gestation sacs from seven pregnant shrews were fixed in glutaraldehyde and osmium tetroxide and processed for transmission electron microscopy. In the area of the trophoblastic curtain, the maternal capillary endothelial cells were hypertrophied and syncytial trophoblast surrounded the capillaries. Cellular trophoblast covered part of the luminal surface of the curtain region, whereas masses of apparently degenerating syncytium were present on other areas of the surface. Maternal erythrocytes, released into the uterine lumen from the curtain region, were phagocytized and degraded by the columnar cells of the trophoblastic annulus. No evidence of iron or pigment accumulation was evident in the parietal endodermal cells underlying the annular trophoblast. Parietal endodermal cells were characterized by cuboidal shape, widely dilated intercellular spaces, and cytoplasm containing granular endoplasmic reticulum. Endodermal cells of the visceral yolk-sac accumulated large numbers of electron-dense granules as well as glycogen in their cytoplasm. Hemopoietic areas and vitelline capillaries were found subjacent to the visceral endoderm. The various portions of the yolk-sac wall of Blarina appear to perform complementary functions which are probably important in maternal-fetal iron transfer.

Pathological study on experimental Heinz body anemia: intracellular changes of phagocytized red cells in macrophages of the spleen and liver

Heinz body anemia was experimentally produced in mice by phenylhydrazine injection and the mechanism of hemolysis was investigated. Both in acute and chronic experiments, the "culling" function of the spleen was more important in removing the red cells containing Heinz bodies than the "pitting" function. In addition to extravascular hemolysis, intravascular hemolysis in the spleen, liver and in the peripheral circulation was evident as manifested by the presence of ghost cells and hemosiderin deposition in the kidney. In the absence of the spleen, the liver can replace the function of the spleen to a certain extent and selective removal of Heinz bodies by the Kupffer cell was occasionally demonstrated. Deposition of yellowish-brown pigments was noted in the cordal macrophages and the Kupffer cells, but the precise nature of these pigments is unknown.

Alpha-beta thalassaemia

In a Greek Cypriot family in which genes for both alpha and beta thalassaemias were expressed, haematological and biosynthetic investigations indicated that one family member was homozygous for beta thalassaemia and had alpha-thalassaemia1 trait. The concurrent inheritance of an alpha-thalassaemia gene in the beta-thalassaemia homozygote seemed to have modified his degree of chain imbalance and to have reduced the clinical severity of the disease.

Effect of glutaraldehyde treatment on enzyme-loaded erythrocytes

In principle, enzyme-loaded erythrocytes can be used as a vehicle for enzyme replacement therapy in lysosomal storage diseases. Glutaraldehyde treatment renders these erythrocytes more resistant to lysis without inactivating the enzymes that have been entrapped inside them. Glutaraldehyde treatment does not prevent ingestion of enzyme-loaded erythrocytes by macrophages in vitro so that these cells can be used to deliver enzymes to lysosomes. In vivo, the glutaraldehyde-treated cells are quickly removed from the circulation by the spleen or liver. The degree of glutaraldehyde treatment allows the erythrocytes to be targeted either to the spleen (low glutaraldehyde concentrations) or to the liver (higher glutaraldehyde concentrations).

The effects of splenectomy and glucocorticoids on survival and hepatic uptake of damaged red cells in the mouse

We have studied the effects of splenectomy and glucocorticoids on the survival and sequestration of Heinz body-containing red blood cells (RBC-HZB). Mice were injected with phenylhydrazine damaged 51Cr labeled isologous red blood cells (RBCs). The spleen removed 36% and the liver 19% of the injected dose after 120 hrs. Red cell survival (T 1/2) fell from 180 hrs for undamaged red cells to 16 hrs for RBC-HZB. Splenectomy resulted in an increase in hepatic uptake of damaged RBCs (36% of the injected dose) and a modest improvement in red cell survival (T 1/2 54 hrs). Treatment of non-splenectomized mice with glucocorticoids reduced the splenic uptake to 16% and the hepatic uptake to 14% of the injected dose. The reduction of splenic upatke was associated with a decrease in splenic mass rather than a decrease in uptake per unit weight of splenic tissue, while reduction in hepatic uptake was associated with both a decrease in hepatic mass and uptake per unit weight. A marked decrease was observed in hepatic uptake and in phagocytosis by Kupffer cells in glucocorticoid-treated splenectomized mice. These data suggest that increased hepatic uptake may decrease the effectiveness of splenectomy in RBC-HZB hemolytic anemia and that glucocorticoids may decrease the hepatic uptake by reducing phagocytosis by Kupffer cells.

The role of complement in the clearance of cold agglutinin-sensitized erythrocytes in man

To define the pathophysiologic mechanisms of cold agglutinin disease, we investigated a human model of this syndrome in normal volunteers and in patients with diminished levels of serum complement. Subjects received intravenous injections of autologous, chromated (51Cr) erythrocytes which had been exposed in vitro to purified cold agglutinin preparations and to fresh autologous serum (as a source of complement). In vitro tests confirmed that such cells were coated with activated complement components (C3b), but not with immunoglobulin. Studies of erythrocyte clearance and simultaneous organ scanning showed that erythrocytes sensitized with low levels of cold agglutinin primarily undergo reticuloendothelial sequestration by the liver rather than intravascular hemolysis. After the initial sequestration of C3b-coated erythrocytes, a fraction of the cells are released back into the circulation and survive normally thereafter. Both phenomena are dose dependent and closely follow the sequestration and release pattern observed with IgM isoagglutinin sensitization. Experiments that used heated autologous serum as a source of B3 inactivator demonstrated that functionally intact C3b is required for hepatic sequestration. Erythrocytes coated with C3d were not cleared from the circulation. In vitro assays that sued human macrophage monolayers suggested that the intrahepatic conversion of C3b to C3d is responsible for the release of sensitized erythrocytes back into the circulation. The clearance of cold agglutinin-sensititzed erythrocytes was compared to the clearance mediated by IgM isoagglutinin. We found that the rate of complement fixation by an IgM antibody proceeds rapidly in vivo that the time for complement activation is not a factor in limiting the rate of hepatic sequestration. The major limiting factor appears to be the rate of liver blood flow. Maximal in vitro coating of erythrocytes with C3d conferred protection from further cold agglutinin sensitization but not from IgM isoagglutinin-mediated clearance. This suggests a mechanism for the resistance to lysis observed in cells obtained from patients with the cold agglutinin syndrome and confirms the marked dependence of the site of C3 attachment on the site of membrane localization of the sensitizing antibody.

Unclassified haemolytic anaemia with splenomegaly and erythrocyte cation abnormalities--a disease of the spleen?

An unclassified case of haemolytic anaemia with voluminous splenomegaly is reported. This anaemia was normocytic without any specific morphologic aspect of red blood cells (RBC); Coombs test was negative; the osmotic fragility was normal; the increased autohaemolysis was not affected by the presence of glucose; Hb studies were normal; no RBC enzyme deficiency was found; RBC lipids and membrane proteins were normal; there was a marked reduction in RBC survival with exclusive splenic uptake of erythrocytes. Before splenectomy, RBC cations and water content were abnormal: 1) the RBC water was decreased moderately; 2) the RBC sodium was about twice the normal mean with an increased 22Na turn-over; 3) the RBC potassium was markedly reduced and 42K influx was twice the normal mean; 4) the RBC calcium content was increased. Splenectomy was followed by rapid disappearance of haemolysis and RBC water and cation disturbances. Because of this extremely rapid disappearance after splenectomy the authors suggest this case of haemolytic anaemia could be a primary disease of the spleen.

Enzymatic degradation of uric acid by uricase-loaded human erythrocytes

Erythrocytes containing pig liver uricase have been prepared by hypotonic hemolysis in the presence of the enzyme. Uricase is shown to be active within the erythrocytes and to degrade uric acid as rapidly as it enters the cells when high intracellular enzyme concentrations are employed. The kinetics and characteristics of uric acid entry are shown to be the same for hemolysed and normal erythrocytes. At physiological concentrations of uric acid, loaded erythrocytes can degrade a maximum of about 21 mumol uric acid/liter erythrocytes per min. The possible application of enzyme-loaded erythrocytes to medicine is discussed.

Studies on the in vivo effects of antibody. Interaction of IgM antibody and complement in the immune clearance and destruction of erythrocytes in man

Purified human IgM isoagglutinins were utilized to sensitize (51)Cr-labeled erythrocytes so as to produce a known number of complement-fixing sites. These cells were then reinfused into the erythrocyte donor. A minimum of 20 C1-fixing sites/erythrocyte were required for decreased survival. As the amount of antibody coating the erythrocytes was increased, a larger percentage was sequestered. With 80 C1-fixing sites, more than 75% of the injected erythrocytes were removed from the circulation within 10 min. In each case, the clearance pattern consisted of rapid hepatic sequestration followed by a gradual return of a portion of the erythrocytes into the circulation where they survived normally. Clearance was shown to be dependent upon activation of the classical complement pathway, since sensitized cells survived normally in hereditary angioedema patients with low levels of C4 and no detectable C2. Exposure of sensitized cells to fresh serum for 15 min led to the deposition of 550-800 C3 molecules/C1-fixing site. Such cells were immune adherence positive, were agglutinated by anti-C3b, formed rosettes with human alveolar macrophages, and were sequestered in vivo, presumably because of the interaction of cell-bound C3b with the C3b receptor on hepatic macrophages. After exposure to heated serum as a source of the C3b inactivator, the cells were immune adherence negative, were agglutinated only by anti-C3d, did not form rosettes with macrophages, and survived normally in vivo despite, being Coombs positive. Cleavage of cell-bound C3b to C3d may explain the release phase of the IgM clearance pattern. Whereas erythrocytes coated with IgM antibody and complement were previously thought to be sequestered in the liver because of extensive membrane damage, these experiments suggest that clearance is determined by the interaction of erythrocyte-bound complement fragments with specific receptors on hepatic macrophages.

The effect of Bacillus Calmette-Guerin-induced macrophage activation on the in vivo clearance of sensitized erythrocytes

The clearance of (51)Cr-labeled guinea pig erythrocytes, sensitized with a known amount of IgM or IgG antibody, was examined in normal and BCG-infected guinea pigs. In normal animals, IgM-coated cells were rapidly sequestered in the liver. Most of these cells were then slowly released into the circulation where they survived normally as Coombs-positive erythrocytes. Neither the site nor extent of initial clearance showed major alterations in BCG-infected animals; however, there was no return of the sequestered erythrocytes into the circulation. This pattern of clearance was only seen in normals at very high levels of sensitization. In contrast to the IgM studies, the pattern of clearance of IgG-sensitized erythrocytes was not altered, but the rate and magnitude was markedly increased at all levels of sensitization. In addition, complement-independent clearance of IgG-sensitized erythrocytes was augmented in BCG-infected guinea pigs lacking classical complement pathway function. The spleen remained the organ primarily responsible for this increased clearance of IgG-sensitized erythrocytes. Sensitized cells in BCG-infected animals were removed from the circulation as if they were coated with several times the amount of antibody. Serum factors were shown not to be responsible for the increased clearance. These data suggest that increased macrophage activation in BCG-infected animals plays a critical role in determining the consequences of cell sensitization in vivo. These studies may help to explain exacerbations of hemolytic anemias and related states after intercurrent infections.

Enzyme loading of erythrocytes

We demonstrated that beta-glucosidase and beta-galactosidase can be trapped inside erythrocytes by rapid hemolysis of the cell in the presence of these enzymes. Enzyme enters only during hemolysis, and optimum uptake occurs within 60 sec. There is no loss in cell number after hemolysis-induced enzyme uptake, and the ghosts have only a slightly increased mean cell volume. Smaller proteins enter more readily than larger proteins, although enzymes with a molecular weight of at least 180,000 can be readily entrapped by erythrocytes. This finding may provide a useful approach to the problem of enzyme replacement in certain diseases, including Gaucher's disease.

Effects of corticosteroids and splenectomy on the immune clearance and destruction of erythrocytes

Corticosteroids and splenectomy constitute two important therapeutic modalities in the treatment of autoimmune hemolytic anemia. Each of these may affect both the rate of synthesis of autoantibody and the clearance of antibody sensitized cells. The latter possibility has been examined in an experimental model which allows evaluation of the role of antibody and complement in the immune clearance of erythrocytes in molecular terms. The in vivo clearance of (51)Cr-labeled guinea pig erythrocytes sensitized with purified rabbit IgG or IgM antibody to produce a known number of complement-fixing sites per cell was studied. Corticosteroid therapy increased the survival of both IgG and IgM sensitized erythrocytes by decreasing sequestration in the reticuloendothelial system (RES). 5 days of therapy prior to injection of antibody coated cells were required for a maximal effect. It appeared that the RES of cortisone-treated animals had a lowered sensitivity to erythrocytes coated with antibody and complement and the cells were removed as though they were coated with fewer complement sites/cell. The general pattern and kinetics of clearance and the localization of sequestered cells were not modified by corticosteroids. As the number of IgG C1-fixing sites was increased, the difference betwen cortisone treated and control animals was less marked. Splenectomy led to an increased survival of IgG-coated cells and a sixfold increase in IgG C1-fixing sites was necessary in order to obtain similar rates of clearance in splenectomized and control animals. The liver was responsible for this much less efficient clearance of cells in splenectomized animals: the clearance pattern was typical of that noted for IgG. No effect at all was noted on the clearance of IgM sensitized cells in splenectomized animals. These experiments clearly demonstrate that both corticosteroid therapy and splenectomy act to decrease the in vivo clearance of IgG-sensitized cells: only corticosteroids alter the clearance of IgM-sensitized erythrocytes. This effect may be of major importance in explaining the efficacy of these therapeutic modalities in autoimune hemolytic anemia.

Erythrocyte catabolism by macrophages in vitro. The effect of hydrocortisone on erythrophagocytosis and on the induction of heme oxygenase

Phagocytosis of erythrocytes was studied in vitro in an incubation system consisting of rat peritoneal macrophages and antibody-coated (59)Fe-labeled erythrocytes. The system was characterized in terms of the rate and magnitude of erythrophagocytosis, determined by the interiorization of the (59)Fe label. On incubation of 150 x 10(6) macrophages with 75 x 10(6) antibodycoated erythrocytes, erythrophagocytosis began within a few minutes and was essentially completed after 2 h when 50% of the offered red cells had been ingested by the macrophages. Heme oxygenase (HO) activity, which is very low in native macrophages, increased 4- to 10- fold in response to the ingested erythrocytes; this enzyme stimulation occurred with a delay of 3 h in relation to erythrophagocytosis. Actinomycin D or puromycin prevented the increase of HO activity without affecting erythrophagocytosis, which suggests that the enzyme stimulation was due to substrate-mediated enzyme induction. Hydrocortisone (HC) (0.1 mg/ml medium) dissociated erythrophagocytosis from HO induction, leaving the former unimpaired but completely suppressing the latter. The suppressive effect of HC on the enzyme induction was completely prevented by 5 mg glucose and 0.02 U insulin/ml of the medium. In macrophages engaged in erythrophagocytosis. HC also lowered glucose removal from the medium and reduced formation of (14)CO(2) from [1-(14)C]glucose. These results suggest that induction of HO in macrophages by the hemoglobin of ingested erythrocytes requires intact transport or metabolism of glucose. Glucose utilization appears to be impaired by HC, but is restored by additional glucose and insulin. The findings suggest that plasma steroid concentrations in the pharmacological range could reduce bilirubin formation in phagocytic cells in vivo without affecting the sequestration and degradation of erythrocytes. This provides a possible explanation for the observation that in patients with hepatogenous jaundice, steroids often lower the serum bilirubin level.

Drug-induced erythrocyte membrane internalization

In vitro erythrocyte membrane internalization, resulting in the formation of membrane-lined vacuoles, can be quantified by a radioisotopic method. A complex of (37)Co-labeled vitamin B(12) and its plasma protein binders is first adsorbed to the cell surface, and after vacuoles are formed, the noninternalized label is removed by washing and trypsin treatment. The residual radioactivity represents trapped label and can be used to measure the extent of membrane internalization. Using this method, it was found that in addition to primaquine, a group of membrane-active drugs, specifically hydrocortisone, vinblastine, and chlorpromazine can induce membrane internalization in erythrocytes. This is a metabolic process dependent on drug concentration, temperature, and pH. Vacuole formation by all agents tested can be blocked by prior depletion of endogenous substrates or by poisoning the erythrocytes with sodium fluoride and sulfhydryl blocking agents. This phenomenon resembles in some respects the previously reported membrane internalization of energized erythrocyte ghosts. It is suggested that membrane internalization is dependent on an ATP-energized state and is influenced by the balance between the concentrations of magnesium and calcium in the membrane. This study provides a basis for proposing a unifying concept of the action of some membrane-active drugs, and for considering the role of erythrocyte membrane internalization in pathophysiologic events.