losartan-potassium and Hemoglobinopathies

This review presents the indications and contraindications (pros and cons) for the potential use of erythropoietin (Epo) as a treatment in β-thalassemia and sickle cell anemia (SCA). Its high cost and route of administration (by injection) are obvious obstacles, especially in underdeveloped countries, where thalassemia is prevalent. We believe that from the data summarized in this review, the time has come to define, by studying in vitro and in vivo models, as well as by controlled clinical trials, the rationale for treating patients with various forms of thalassemia and SCA with Epo alone or in combination with other medications.

Topics: Anemia, Sickle Cell; beta-Thalassemia; Drug Therapy, Combination; Erythropoietin; Hemoglobinopathies; Humans; Treatment Outcome

For the majority of children with beta- hemoglobinopathies and -thalassemias who do not have a transplant donor, survival is shortened and morbidity is high. Hydroxyurea, EPO preparations, sodium phenylbutyrate, arginine butyrate, and 5-azacytidine/decitabine have shown efficacy in approximately 40% to 70% of sickle cell and beta-thalassemia patients. Many responses, although significant, were not completely ameliorating of symptoms or pathology, and trials of new agents with dual actions, or drug combinations, are needed. Ideally, limiting chemotherapeutic exposure is desirable for long-term treatment of children, and an oral therapeutic at tolerable doses is necessary for practical use. A new oral therapeutic candidate that induces fetal hemoglobin production and also stimulates erythropoiesis is entering clinical evaluation. Use of agents that should have additive or synergistic effects in combination, such as EPO and hydroxyurea or a short-chain fatty acid derivative (SCFAD), offer better therapeutic potential than hydroxyurea alone. Childhood is an optimal time to introduce such therapies, particularly the non-mutagenic SCFADs, while the erythroid marrow reserve is preserved and before organ damage has become widespread. A challenge for successful application of these therapies is to define patient subsets that are most likely to respond to a particular agent, or which require combination therapies, and to develop optimal dose regimens in thalassemias with rapid erythroid apoptosis. Development of this therapeutic avenue will require close collaboration among treating and academic physicians, families and patients, funding agencies, and researchers.

Topics: Anemia, Sickle Cell; Antisickling Agents; beta-Thalassemia; Erythropoiesis; Erythropoietin; Fatty Acids; Hemoglobinopathies; Humans; Hydroxyurea; Trans-Activators

Topics: 2,3-Diphosphoglycerate; Bisphosphoglycerate Mutase; Erythropoiesis; Erythropoietin; Gene Expression Regulation; Hemoglobinopathies; Homeostasis; Humans; Hypoxia; Kidney Diseases; Liver Diseases; Neoplasms; Oxygen; Polycythemia; Polycythemia Vera

New drugs, recently available for treatment of different forms of anaemia, have somehow changed the therapeutic scenario in paediatric haematology. The aim of this review is to focus on the newest molecules discussing indications, clinical usefulness and related problems. Erythropoietin, the specific growth factor of red cell precursors, is now an established option for anaemia of chronic renal failure, prematurity, bone marrow transplantation and chemotherapy. Anti-CD20 monoclonal antibody, a novel cytotoxic molecule for mature B lymphocytes, has proven to be effective in the treatment of refractory autoimmune cytopenias. Haemoglobin analogues are currently under investigation, in order to obtain a synthetic oxygen-carrier that can substitute blood transfusions. Finally drugs that are able to increase the production of haemoglobin F have been used in thalassemias and haemoglobinopathies. For patients with sickle cell disease, hydroxyurea is no longer an experimental tool; it has given rise to several trials, where it has proven to be effective in terms of both clinical and haematological improvement.

Topics: Adult; Age Factors; Anemia; Anemia, Hemolytic, Autoimmune; Anemia, Sickle Cell; Antibodies, Monoclonal; Antibodies, Monoclonal, Murine-Derived; Antineoplastic Agents; Antisickling Agents; Blood Substitutes; Bone Marrow Transplantation; Butyrates; Child; Clinical Trials as Topic; Erythropoietin; Fetal Hemoglobin; Forecasting; Hemoglobinopathies; Hemoglobins; Humans; Hydroxyurea; Infant, Newborn; Infant, Premature, Diseases; Kidney Failure, Chronic; Organ Transplantation; Rituximab; Thalassemia; Tissue Donors

Iron deficiency is the most frequently encountered cause of suboptimal response to recombinant human erythropoietin (rHuEPO). Carefully assessing iron status is of paramount importance in chronic renal failure patients prior to or during rHuEPO therapy. Because there is great need for iron in the EPO-stimulated erythroid progenitors, it is essential that serum ferritin and transferrin saturation levels should be maintained over 300 microg/liter and 30%, respectively. Investigators have shown that oral iron is unlikely to keep pace with the iron demand for an optimal rHuEPO response in uremics. Therefore, patients with iron deficiency will always require intravenous iron therapy. The early and prompt iron supplementation can lead to reductions in rHuEPO dose and hence cost. After the iron deficiency has been corrected or excluded, we must remember all of the possible causes of hyporesponsiveness in every rHuEPO-treated patient. As dose requirements vary, it is not clear which dose of rHuEPO causes this hyporesponsiveness. However, if the patient with iron repletion does not respond well after the induction period, the major causes blunting the response to rHuEPO should be investigated. Most factors are reversible and remediable, except resistant anemia associated with hemoglobinopathy or bone marrow fibrosis, which requires a further increase in the rHuEPO dose. By means of early detection and correction of the possible causes, the goal of increasing therapeutic efficacy can be achieved. Iron overload may lead to an enhanced risk for infection, cardiovascular complication, and cancer. Over-treatment with iron should be avoided in dialysis patients, despite the fact that the safe upper limit of serum ferritin to avoid iron overload is not clearly defined. On the other hand, functional iron deficiency may develop even when serum ferritin levels are increased. Controversy remains as to whether intravenous iron therapy can overcome this form of hyporesponsiveness in iron-overloaded patients. Moreover, a treatment option of iron supplementation is not warranted in these patients, as the potential hazards of iron overload will be worsened. We demonstrated that the mean hematocrit significantly increased from 25.1+/-0.9% to 31+/-1.2% after eight weeks of intravenous ascorbate therapy (300 mg three times a week) in 12 hemodialysis patients with serum ferritin levels of more than 500 microg/liter. The enhanced erythropoiesis paralleled with a rise in transferrin sa

Topics: Aluminum; Anemia; Erythropoietin; Hemoglobinopathies; Hemolysis; Humans; Infections; Inflammation; Iron; Iron Deficiencies; Iron Overload; Kidney Failure, Chronic; Recombinant Proteins; Thalassemia

An erythrocytosis describes an increased peripheral blood packed cell volume (PCV) and is deemed to be absolute or apparent depending on whether or not the measured red cell mass (RCM) is above the reference range. This reference range must be related to the individual's height and weight to avoid erroneous interpretations using ml/kg total body weight expressions in obesity. Absolute erythrocytoses are divided into primary, where the erythropoietic compartment is intrinsically abnormal, secondary, where the erythropoietic compartment is normal but is responding to external pathological events leading to an increased erythropoietin drive, and idiopathic, where neither a primary nor a secondary erythrocytosis can be established. Both primary and secondary erythrocytoses have congenital and acquired forms. The only form of primary acquired erythrocytosis that has been defined is the clonal myeloproliferative disorder, polycythaemia vera (PV). Modified diagnostic markers for PV are proposed. Thrombocytoses can be classified into primary, where megakaryopoiesis is intrinsically abnormal, secondary, where megakaryopoiesis is normal but increased platelet production is a reaction to some other unrelated pathology, and finally idiopathic. This latter new group would be used for patients not satisfying the criteria for primary or secondary thrombocytoses, if these were more precise and rigidly used than currently is the case. While theoretically congenital and acquired forms of primary and secondary thrombocytoses might exist, only one cause of secondary congenital thrombocytosis has been established, and primary congenital thrombocytosis has not yet been precisely defined. Primary (essential) thrombocythaemia (PT) is one of the forms of primary acquired thrombocytoses. The diagnostic criteria of PT traditionally involve the exclusion of secondary thrombocytoses and other myeloproliferative disorders but marrow histology could hold a key positive diagnostic role if objective histological features of PT were agreed.

Topics: Anthropometry; Bone Marrow; Bone Marrow Diseases; Cells, Cultured; Diagnostic Imaging; Diagnostic Tests, Routine; Erythrocyte Volume; Erythroid Precursor Cells; Erythropoietin; Female; Hematocrit; Hemoglobinopathies; Humans; Hypoxia; Kidney Diseases; Liver Diseases; Male; Neoplasms; Polycythemia; Receptors, Erythropoietin; Thrombocytosis

The mechanism of resistance to recombinant human erythropoietin (EPO) in hemodialysis patients with hemoglobinopathy is not yet fully understood. Poor responses to EPO have been reported in anemic dialysis patients with sickle cell disease and thalassemia. We present the first case of a hemodialysis patient with EPO resistance and hemoglobin J-Meinung, which is initially found by hemoglobin electrophoresis and finally proven by molecular genetic analysis. Additionally, the patient was diagnosed as having chronic active hemolysis with hallmarks of splenomegaly, an increased serum bilirubin and reticulocyte index, and a reduced haptoglobin level. We discuss the possible mechanisms and proper treatment options in such patients with a poor response to EPO.

Topics: Adult; Base Sequence; Erythropoietin; Hemoglobin J; Hemoglobinopathies; Heterozygote; Humans; Kidney Failure, Chronic; Male; Molecular Sequence Data; Polymerase Chain Reaction; Recombinant Proteins; Renal Dialysis

Re-activation of the fetal globin genes is the most realistic approach to correct the deranged pathophysiology of the haemoglobinopathies because the presence of gamma-chains can neutralize the toxic effects of the unbound alpha-globin chains in the beta-thalassaemias and inhibit the polymerization of Hb S in the sickle cell syndromes. Re-induction of fetal haemoglobin synthesis can be brought about either by direct activation of the respective promoter genes and possibly other positively acting elements, or by recruitment into proliferation and differentiation of a population of erythroid precursors which retain the gamma-chain synthesis programme but remain dormant in the bone marrow of the adult unless called up in cases of acute erythroid expansion. Examples of the first group include the butyric acid and derivatives and 5' azacytidine. The second group comprises erythropoietin and a series of cytostatics, with hydroxyurea as the main representative. The activity of most of the above agents has already been studied in cell cultures and animals and confirmed in several patients, both at the haematological and biochemical level as well as through their frank clinical improvement. However, application of these drugs at large is not yet justified because a series of questions concerning their long-term efficacy, the correct dosage and timing, their tolerance and toxicity, and the potential long-term dangers, including mutagenicity are still unresolved.

Topics: Anemia, Sickle Cell; Antisickling Agents; Butyrates; Butyric Acid; Drug Therapy, Combination; Erythropoietin; Hemoglobinopathies; Humans; Hydroxyurea; Thalassemia

The term familial and congenital polycythemia encompasses a heterogeneous group of disorders with the common characteristic of an absolute increased red cell mass since birth and/or similar phenotype also present in relatives. In the last 2 decades the differential diagnosis between primary and secondary familial polycythemias became more physiologically relevant as new sensitive techniques, such as accurate measurements of serum erythropoietin (S-EPO) concentration by radioimmunoassay (RIA) or ELISA, and assessment of growth of erythroid progenitor cells in vitro became available. Consequently, correct classification of many older previous reports of familial polycythemias is difficult. While familial secondary polycythemias due to high oxygen affinity hemoglobin mutants are not infrequent and have been well delineated in terms of molecular pathophysiology and phenotype during the last 3 decades, those secondary familial polycythemias due to 2,3 DPG deficiency are very rare. Familial and congenital polycythemias with increased EPO concentration and normal arterial oxygen saturation and oxygen dissociation kinetics represent an intriguing group of disorders wherein the molecular lesions remain obscure; however, in some instances a possibility of abnormal oxygen sensing pathway involving hypoxia inducible factor-1 (HIF-1) open an intriguing yet unexplored area of hematology and biology. In contrast the primary familial and congenital polycythemia (PFCP) has been only recently recognized (the first report published in 1977). Various designations have been used in the past to describe PFCP, a rare clinical syndrome, including: benign familial erythrocytosis, polycythemia vera of childhood, primary polycythemia, pure erythrocytosis, etc. Some of these terms stressed the relatively benign, non-progressive course of the disease with a normal lifespan of affected subjects; however, the apparent benignity of some of these disorders has been questioned. These disorders are familial and/or congenital, and the clinical and laboratory evidence of secondary polycythemias must be excluded. Only about 2 dozen familial and sporadic cases with PFCP have been reported. However, the mutations of erythropoietin receptor (EPOR) found in some of families with PFCP represent the only defined molecular defect of primary polycythemic phenotypes. All reported PFCP associated EPOR mutations result in truncation of its intracytoplasmic C-terminal domain which negatively regulates th

Topics: 2,3-Diphosphoglycerate; Diphosphoglyceric Acids; Erythropoiesis; Erythropoietin; Hemoglobinopathies; Humans; Polycythemia; Receptors, Angiotensin; Receptors, Erythropoietin

Topics: Erythropoietin; Fatty Acids, Volatile; Genetic Therapy; Globins; Hemoglobinopathies; Humans; Hydroxyurea

Transfusion is associated with improvement of life expectancy in beta thalassemia and sickle cell disease (SCD). Bone marrow transplantation concerns only a few patients. Among potentially useful therapeutic agents which can induce fetal hemoglobin (HbF) production, hydroxyurea (HU) stands out in particular for SCD. In our sickle cell center, 10 patients with SCD received HU for chronic leg ulcer with good results in terms of healing (7 among 10, who required no additional transfusion). A few patients, most of them over 30 years, received HU for chronic organ failure at the onset. HU on long term therapy over one year improved general status, Hb level, in 7 patients with beta thalassemia intermedia. A major challenge in the coming years will be the effective evaluation of clinical efficiency and the comparison of risks and benefits of such compounds versus transfusion.

Topics: Adolescent; Adult; Anemia, Sickle Cell; Blood Substitutes; Butyrates; Child; Erythrocyte Transfusion; Erythropoietin; Hemoglobinopathies; Humans; Hydroxyurea; Middle Aged

The past decade has witnessed profound increases in knowledge of the structure, function, and developmental regulation of the human globin genes. This information has deepened our understanding of the molecular and cellular mechanisms underlying inherited disorders affecting hemoglobin, and it has provided a new perspective for attaining meaningful increases in fetal hemoglobin synthesis in the management of sickle cell anemia and beta thalassemia. Efforts to provide therapy for these disorders are based on three factors: an understanding of their pathophysiology; the potential for fetal hemoglobin to alter its manifestation; and the concept that developmental changes in globin gene expression might be reversed by manipulating cellular and molecular regulatory mechanisms. In this review we discuss these topics and examine critically recent efforts to apply various pharmacological agents to in vitro, animal, and human models with the goal of increasing HbF synthesis. Several agents have demonstrated activity in patients with hemoglobin disorders. One such agent, hydroxyurea, has been shown to be potentially efficacious in phase II clinical trials in patients with sickle cell anemia and awaits testing in a placebo-controlled phase III study.

Topics: Anemia, Sickle Cell; Animals; Azacitidine; Erythropoietin; Fetal Hemoglobin; Gene Expression Regulation; Hemoglobinopathies; Humans; Hydroxyurea; Thalassemia

I have reviewed areas of development in the use of blood and blood products, placing emphasis on the complications of transfusion, particularly transmission of infection. Alloimmunization in relation to transfusion of red cells and platelets has been covered and suggestions for reducing this problem assessed. The potential methods of avoiding the infective complications have been discussed including the screening of blood for infective agents, the virucidal treatment of blood products during the manufacturing process and white cell depletion. The use of recombinant DNA technology to produce coagulation factors offers the possibility of further reducing infective risks. An area of clinical promise is the use of haematopoietic growth factors to treat bone marrow failure, either congenital or acquired, such as the myelosuppressive effects of cancer chemotherapy, and reduce reliance on blood products. The aim of the chapter is to encourage the rational use of a limited resource by considering the risks inherent in transfusion and alternative strategies. In doing this it is important to audit current and future practice, and it is suggested that reference is made to the suggestions of Hume (1989) for quality assessment and assurance in paediatric transfusion medicine.

Topics: Acquired Immunodeficiency Syndrome; Blood Coagulation Factors; Blood Group Antigens; Blood Platelets; Blood Specimen Collection; Blood Transfusion; Blood Transfusion, Intrauterine; Child; Child, Preschool; Colony-Stimulating Factors; Erythrocyte Transfusion; Erythropoietin; Female; Fetal Blood; Fetal Diseases; Hemoglobinopathies; Humans; Immunization; Immunization, Passive; Incidence; Infant; Neoplasm Recurrence, Local; Platelet Transfusion; Pregnancy; Pregnancy Complications, Hematologic; Prenatal Diagnosis; Thrombocytopenia; Transfusion Reaction; Virus Diseases

Topics: Adolescent; Adult; Anemia; Erythrocyte Volume; Erythrocytes; Erythropoiesis; Erythropoietin; Female; Fetal Blood; Fetus; Glucosephosphate Dehydrogenase Deficiency; Hemoglobinopathies; Hemoglobins; Humans; Hyperbilirubinemia; Infant, Newborn; Iron; Maternal-Fetal Exchange; Pregnancy; Pregnancy Complications; Pyruvate Kinase; Smoking

There have been numerous new contributions to the knowledge of foetal haemoglobin over the last few years. It is, therefore, timely to review them together. They throw light on the arrangement on the chromosome of non-alpha chain genes, and on the condition generally known as Hereditary Persistence of Foetal Haemoglobin (HPFH) and have contributed to other aspects of human ontogeny and physiology.

Topics: Adult; Amino Acid Sequence; Anemia, Aplastic; Anemia, Sickle Cell; Child; Erythrocytes; Erythropoietin; Female; Fetal Blood; Fetal Hemoglobin; Genes; Genetic Linkage; Genetic Variation; Genetics, Population; Hemoglobinopathies; Humans; Infant; Infant, Newborn; Leukemia; Oxygen; Pregnancy; Protein Denaturation; Suppression, Genetic; Thalassemia

Topics: Alkylating Agents; Blood Cell Count; Blood Volume; Erythrocyte Count; Erythropoiesis; Erythropoietin; Hematocrit; Hemoglobinopathies; Hemoglobins; Humans; Hypoxia; Oxygen Consumption; Polycythemia; Polycythemia Vera; Protein Binding

The aim of this study was to determine the response to recombinant human erythropoietin (rhEPO) in anemic pregnant women with heterozygous hemoglobinopathies.. A prospective study including 19 consecutive pregnant women with anemia and heterozygous hemoglobinopathy was performed. Treatment was divided into two phases: the initial low-dose phase and the subsequent high-rhEPO phase. In the initial phase, 3 x 10,000 U of rhEPO was administered with intravenous iron sucrose. In patients showing a poor response (Hb increase <1 g/dl) to low-dose rhEPO, the rhEPO dose was increased to 20,000 U per treatment in the subsequent phase.. All patients showed stimulation of erythropoiesis as evidenced by an increase in hemoglobin. In 13 patients, a good response to therapy was observed (mean Hb increase 1.6 +/- 0.5 g/dl). In 6 patients, resistance to rhEPO was noted (mean Hb increase 0.5 +/- 0.5 g/dl). The mean gestational age at the start of therapy was 28 weeks of gestation and at the end 32 weeks. The mean duration of a complete therapy was 3.5 weeks (range 2-4.5 weeks). If calculated for body weight, the initial low- rhEPO dose of 160.4 +/- 30.6 U/kg body weight/treatment was increased to 320.9 +/- 61.2 U/kg body weight/treatment in the subsequent phase.. Response to rhEPO treatment differs widely in anemic pregnant patients with heterozygous hemoglobinopathy. Resistance was observed in anemic pregnant patients with the beta-thalassemia trait originally from the Mediterranean region.

Topics: Adult; Anemia; Dose-Response Relationship, Drug; Erythropoietin; Female; Hemoglobinopathies; Heterozygote; Humans; Pregnancy; Pregnancy Complications, Hematologic; Recombinant Proteins; Treatment Outcome

Algorithms that combine scores from multiple blood parameters are demonstrably effective in highlighting recombinant human erythropoietin (rHuEPO) administration, and have been used to deter rHuEPO use by athletes. These models are sensitive to atypical levels of blood parameters encountered during altered states of red cell production. Because hematologic abnormalities can also result in unusual blood profiles, the aim of this study was to document the incidence and magnitude of such abnormalities in an elite athlete population.. We screened blood samples obtained from 413 female and 739 male elite athletes from 12 countries for known hematologic abnormalities, and compared the algorithm scores for these athletes with those of their healthy counterparts. We also established the magnitude of blood parameters required for model scores to exceed cut-offs associated with rHuEPO use.. We found that 0.7% of male and 2.4% of female athletes were iron deficient either with our without anemia. An additional 1.4% of males and 1.0% of females had hemoglobinopathies. On average these athletes' model scores were at or below the score of their healthy counterparts. The greatest influence on our models was hemoglobin concentration. Values of other parameters must exceed normal ranges by a substantial margin in order for model scores to approach levels associated with rHuEPO use.. The hematologic disorders we encountered in elite athletes were not associated with model scores that exceeded the nominal cut-offs that we have previously recommended to delineate rHuEPO use. We did not find any abnormalities among elite endurance athletes that were associated with high model scores.

Topics: Adolescent; Anemia; Anemia, Iron-Deficiency; Doping in Sports; Erythrocyte Indices; Erythropoiesis; Erythropoietin; Female; Hematologic Diseases; Hematologic Tests; Hemoglobinopathies; Hemoglobins; Humans; Male; Models, Biological; Recombinant Proteins; Reticulocyte Count; Sensitivity and Specificity; Sex Characteristics; Sex Distribution; Sports

Topics: Diagnosis, Differential; Erythropoietin; France; Hemoglobinopathies; Hemoglobins, Abnormal; Humans; Male; Middle Aged; Myeloproliferative Disorders; Oxyhemoglobins; Polycythemia

Hb Sitia [beta128(H6)Ala-->Val] was found in a Greek female with slightly reduced red blood cell indices. The abnormal hemoglobin was indistinguishable from Hb A by electrophoresis but eluted after Hb A on cation exchange high performance liquid chromatography. DNA sequence analysis revealed a GCT-->GTT mutation at codon 128, which is predicted to encode an Ala-->Val substitution. This was confirmed by mass spectrometry analyses of the beta-globin chain. Since alanine at beta128(H6) interacts with several amino acids of the alpha1beta1 contact, its replacement by a larger residue results in a mild instability of the molecule and slight modifications of the oxygen binding properties.

Topics: Adult; Amino Acid Substitution; Chromatography, Ion Exchange; Codon; DNA Mutational Analysis; Erythropoietin; Female; Globins; Greece; Heinz Bodies; Hemoglobinopathies; Hemoglobins, Abnormal; Humans; Kinetics; Mass Spectrometry; Mutation, Missense; Oxygen; Protein Binding; Protein Conformation; Receptors, Transferrin; RNA, Messenger; Transcription, Genetic

Serum erythropoietin (EPO) levels were determined by enzyme linked immunosorbent assay (ELISA) in 61 thalassemic patients, consisting of 23 thalassemia major (TM) patients with multiple transfusion, 38 patients with thalassemia intermedia (TI). Thirty-two normal controls were also studied. The mean serum EPO levels were significantly higher in both groups with TM (165.96 +/- 17.31 mlU/ml) and TI (126.43 +/- 50.56 mlU/ml) compared with the control group (8.33 +/- 3.91 mlU/ml). The mean value of hematocrit (Hct) in the patients with TM (18.70 +/- 3.51%) was lower than those with TI (25.24 +/- 4.19 %) whereas the mean serum EPO level were significantly higher in TM than TI patients. An inverse correlation between the serum values of EPO and Hct was observed in both TI and TM patients, however this correlation was significant only in TI (r = -0.61, p<0.001). These data showed that serum EPO levels increased in all thalassemia patients despite repeated transfusion. Multiple transfusion may modulate the response of serum EPO to the degree of anemia, resulting in increased EPO levels and independent anemia in the TM patients.

Topics: Adolescent; Adult; beta-Thalassemia; Biomarkers; Case-Control Studies; Child; Child, Preschool; Erythropoietin; Female; Hematocrit; Hemoglobin E; Hemoglobinopathies; Humans; Linear Models; Male; Thailand

Butyrate, a four-carbon fatty acid, and its two-carbon metabolic product, acetate, are inducers of gamma-globin synthesis. To test whether other short-chain fatty acids share this property, we first examined whether propionic acid, a three-carbon fatty acid that is not catabolized to acetate, induces gamma-globin expression. Sodium propionate increased the frequency of fetal hemoglobin containing erythroblasts and the gamma/gamma + beta mRNA ratios in adult erythroid cell cultures and F reticulocyte production in a nonanemic juvenile baboon. Short-chain fatty acids containing five (pentanoic), six (hexanoic), seven (heptanoic), eight (octanoic), and nine (nonanoic) carbons induced gamma-globin expression (as measured by increase in gamma-positive erythroblasts and gamma/gamma + beta mRNA ratios) in adult erythroid burst-forming unit cultures. There was a clear-cut relationship between the concentration of fatty acids in culture and the degree of induction of gamma-globin expression. Three-, four-, and five-carbon fatty acids were better inducers of gamma globin in culture as compared with six- to nine-carbon fatty acids. These results suggest that all short-chain fatty acids share the property of gamma-globin gene inducibility. The fact that valproic acid, a derivative of pentanoic acid, also induces gamma-globin expression suggests that short-chain fatty acid derivatives that are already approved for human use may possess the property of gamma-globin inducibility and may be of therapeutic relevance to the beta-chain hemoglobinopathies.

Topics: Adult; Anemia, Sickle Cell; Animals; Anticonvulsants; Butyrates; Butyric Acid; Cells, Cultured; Epilepsy; Erythroid Precursor Cells; Erythropoietin; Fatty Acids, Volatile; Fetal Hemoglobin; Gene Expression Regulation; Globins; Hemoglobinopathies; Humans; Papio; Pentanoic Acids; Propionates; Reticulocytes; RNA, Messenger; Structure-Activity Relationship; Valproic Acid

In order to clarify the mechanism of the effect of erythropoietin (Epo) on the fetal haemoglobin (HbF) phenotype of peripheral erythrocytes, we studied the dose-response effect of Epo on HbF production by erythroid precursors derived from the peripheral blood of normal adult individuals and grown in a two-phase liquid culture system. The proportion of HbF out of the total haemoglobin (Hb) content (%HbF) was dependent on the duration of exposure to Epo; on day 6 it comprised up to 15%, but dropped to < 2% on day 14. Both cell yield and cellular Hb content were markedly increased by high (1 U/ml) Epo, compared to normal physiological (20-50 mU/ml) levels, but neither the initial nor final %HbF were dependent on the increased Epo dose. However, when cells grown with high Epo were transferred on day 7 to low Epo, their progeny contained by day 14 a higher %HbF as compared to cells that were continuously exposed to high Epo. This was accompanied by acceleration and synchronization of their maturation process, as evidenced by their morphology, density and size, and restriction on cell multiplication, as indicated by the lower cell yield. These results are consistent with the following model. As early erythroid precursors, with relatively high HbF, mature under steady-state levels of Epo, HbA production predominates and HbF is diluted. However, when such precursors are switched from high to low levels of Epo they undergo a synchronized, accelerated maturation which shortens the period of HbA production, leading to a decreased Hb content and a relatively high proportion of HbF. This mechanism may contribute to the elevated HbF observed following Epo administration (due to short half-life of Epo in vivo), and might also explain the HbF-augmenting effect of Epo administered together with hydroxyurea observed in patients with sickle cell anaemia.

Topics: Cell Division; Cells, Cultured; Chromatography, High Pressure Liquid; Dose-Response Relationship, Drug; Erythroid Precursor Cells; Erythropoietin; Fetal Hemoglobin; Hemoglobin A; Hemoglobinopathies; Humans; Time Factors

The absolute adult and fetal hemoglobin (HbF) contents of the erythroid cells derived from the differentiation of normal human and simian erythroid progenitors and of the peripheral blood erythroid burst-forming units (BFU-E) of patients with nondeletion hemoglobinopathies have been measured with a sensitive radioligand immunoassay. The HbF content varied between 0.13 and 2.96 pg/cell, representing between 0.7% and 19.6% of the total hemoglobin with a mean value of 7.0%. The absolute content of HbF was indistinguishable in the well-hemoglobinized progeny of marrow erythroid colony-forming units, marrow or blood BFU-E, or of mixed colony-forming units. The term HbF program refers to this inherent capacity to produce fetal hemoglobin (HbF) in the erythroid cells derived from these progenitors in vitro. The HbF content of marrow erythroblasts as determined by the same radioligand immunoassay was similar to that found in the peripheral blood, suggesting that the switch off of gamma-chain production occurs after the erythroid colony-forming unit stage of maturation. Increasing concentrations of a crude erythropoietin-containing preparation induced higher numbers of erythroid colonies, which were larger in size, but the HbF program was unaffected. In contrast to the hemoglobin accumulation in human progenitor-derived colonies, simian progenitor-derived colonies produced considerably more HbF, and the amount of HbF was strongly influenced by progenitor maturity. Assays of the HbF content of erythroblasts derived from culture of the peripheral blood BFU-E of patients with nondeletion hemoglobinopathies and their parents showed that the HbF program in the progenitors of such patients is highly variable. Some produce only a slight excess of HbF in progenitor-derived erythroblasts, whereas others have extraordinarily high HbF programs. The molecular basis of this variability is presently unknown.

Topics: Animals; Cells, Cultured; Erythropoiesis; Erythropoietin; Fetal Hemoglobin; Hematopoietic Stem Cells; Hemoglobin A; Hemoglobinopathies; Humans; Macaca fascicularis; Species Specificity

Topics: Adaptation, Physiological; Adolescent; Adult; Cardiac Output; Erythropoietin; Female; Germany, West; Hematocrit; Hemoglobinopathies; Hemoglobins; Hemoglobins, Abnormal; Hemolysis; Humans; Kidney; Male; Oxygen; Oxygen Consumption; Polycythemia; Regional Blood Flow

Topics: Alkaline Phosphatase; Blood Viscosity; Bone Marrow Examination; Carrier Proteins; Erythropoietin; Female; Hematocrit; Hemoglobinopathies; Histamine; Humans; Hypoxia; Leukocytosis; Male; Plasma Volume; Polycythemia; Splenomegaly; Thrombocytosis; Uric Acid; Vitamin B 12

Hemoglobin Bethesda (beta145 histidine) is one of the two mutants known to affect the penultimate hemoglobin tyrosines. The result of this substitution is extreme disorganization of the oxygenation function of the molecule. Red cells containing 45% Hb Bethesda and 55% Hb A have increased oxygen affinity but, paradoxically, a normal Bohr effect. As is usually seen with other hemoglobins with increased oxygen affinity, Hb Bethesda clinically is manifest in heterozygotes by erythrocytosis. Red cell production in affected individuals is erythropoietin dependent. The reciprocal interdependence of oxygen delivery and effective erythropoiesis was documented by alterations in erythropoietin excretion, quantitative iron kinetics, and reticulocyte production in response to phlebotomy-induced reduction in the oxygen-carrying capacity.

Topics: Adult; Blood Protein Electrophoresis; Bone Marrow; Chromatography; Erythrocytes; Erythropoiesis; Erythropoietin; Hematocrit; Hemoglobinopathies; Hemoglobins, Abnormal; Humans; Iron; Oxygen Consumption; Pedigree; Polycythemia; Reticulocytes

Topics: Adult; Erythrocyte Count; Erythropoietin; Female; Hematocrit; Hemoglobinopathies; Hemoglobins; Hemoglobins, Abnormal; Humans; Infant, Newborn; Male; Oxygen; Polycythemia; Pregnancy

Topics: Adult; Anemia; Child; Erythropoietin; Female; Hematocrit; Hemoglobinopathies; Hemoglobins, Abnormal; Heterozygote; Humans; Hydrogen-Ion Concentration; Iron; Male; Oxygen; Oxygen Consumption; Partial Pressure

This investigation is concerned with the kinetics of the reciprocal relationship between sheep hemoglobin (Hb) A and Hb C formation in response to anemia. The relative synthesis of the hemoglobin types was assessed at various times in bone marrow erythroid cells incubated in vitro with (59)Fe. The changeover from Hb A to Hb C formation lagged by about 3 days behind the development of anemia and was complete within about 11 days. After recovery from anemia the reciprocal change back to preanemic conditions proceeded at a much slower rate, Hb C formation gradually declining to unmeasurable levels over about 25 days. Infusions of plasma with high erythropoietin titre induced the formation of relatively large quantities of Hb C in erythroid cells of nonanemic sheep, demonstrating the central importance of a humoral mechanism in the change of expression of the hemoglobin genes. THE FOLLOWING CONCLUSIONS WERE DRAWN: hemoglobin phenotype is determined at a stem cell level. Erythroid stem cells appear to undergo gradual renewal. The identity of the plasma factor which induces Hb C formation is not yet known; it is not present in plasma from nonanemic sheep, and its production is not dependent upon hemoglobin genotype. If the plasma factor turns out to be erythropoietin, then this hormone must have an important influence on the pool of erythroid stem cells.

Topics: Anemia, Hemolytic; Animals; Bone Marrow; Bone Marrow Cells; Cytogenetics; Erythropoiesis; Erythropoietin; Female; Genes, Regulator; Hemoglobin C; Hemoglobinopathies; Hemoglobins; Hormones; Iron Isotopes; Kinetics; Models, Theoretical; Phenotype; Sheep

Topics: Adult; Aged; Animals; Blood Cell Count; Blood Platelets; Blood Volume; Bone Marrow Cells; Dehydration; Duodenal Ulcer; Erythrocyte Count; Erythropoietin; Hematocrit; Hemodynamics; Hemoglobinopathies; Humans; Hypoxia; Iron Isotopes; Kidney Neoplasms; Leukocyte Count; Lung Diseases; Male; Mice; Middle Aged; Obesity Hypoventilation Syndrome; Oxygen; Oxygen Consumption; Phosphorus Isotopes; Plasma Volume; Polycythemia; Polycythemia Vera; Pulmonary Emphysema