111 research outputs found

    Clinical Applications of Automated Reticulocyte Indices.

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    Automated analysis of reticulocytes provides pathologists and clinicians with several new parameters, which need to be evaluated for their role in the diagnosis and management of diseases. We review here the current knowledge on reticulocyte cell volume, hemoglobin concentration and content. Several studies have provided reference values for reticulocyte cell volume (MCVr), cell hemoglobin concentration (CHCMr) and cell hemoglobin content (CHr). Data are available on the changes of these indices in iron deficiency and megaloblastic anemias and their response to therapy. CHr has been shown to be an early indicator of functional irondeficiency in subjects treated with recombinant human erythropoietin (r-HuEPO). Reticulocyte changes have also been described in the early phases of hydroxyurea therapy for sickle cell disease and in bone marrow transplantation. The real-time information provided by reticulocyte indices on the functional state of the erythroid marrow is an important tool in the diagnosis and management of several hematological disorders and in the use of r-HuEPO

    Foxo3 is required for the regulation of oxidative stress in erythropoiesis

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    Erythroid cells accumulate hemoglobin as they mature and as a result are highly prone to oxidative damage. However, mechanisms of transcriptional control of antioxidant defense in erythroid cells have thus far been poorly characterized. We observed that animals deficient in the forkhead box O3 (Foxo3) transcription factor died rapidly when exposed to erythroid oxidative stress-induced conditions, while wild-type mice showed no decreased viability. In view of this striking finding, we investigated the potential role of Foxo3 in the regulation of ROS in erythropoiesis. Foxo3 expression, nuclear localization, and transcriptional activity were all enhanced during normal erythroid cell maturation. Foxo3-deficient erythrocytes exhibited decreased expression of ROS scavenging enzymes and had a ROS-mediated shortened lifespan and evidence of oxidative damage. Furthermore, loss of Foxo3 induced mitotic arrest in erythroid precursor cells, leading to a significant decrease in the rate of in vivo erythroid maturation. We identified ROS-mediated upregulation of P21(CIP1/WAF1/Sdi1) (also known as Cdkn1a) as a major contributor to the interference with cell cycle progression in Foxo3-deficient erythroid precursor cells. These findings establish an essential nonredundant function for Foxo3 in the regulation of oxidative stress, cell cycle, maturation, and lifespan of erythroid cells. These results may have an impact on the understanding of human disorders in which ROS play a role

    Treatment with NS3623, a novel Cl-conductance blocker, ameliorates erythrocyte dehydration in transgenic SAD mice: a possible new therapeutic approach for sickle cell disease

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    The dehydration of sickle red blood cells (RBCs) through the Ca-activated K channel depends on the parallel movement of Cl ions. To study whether Cl-conductance block might prevent dehydration of sickle RBCs, a novel Cl-conductance inhibitor (NS3623) was characterized in vitro using RBCs from healthy donors and sickle cell patients and in vivo using normal mice and a transgenic mouse model of sickle cell disease (SAD mice). In vitro, NS3623 reversibly blocked human RBC Cl-conductance (gCl) with an IC50 value of 210 nmol/L and a maximal block of 95%. In vivo, NS3623 inhibited RBC gCl after oral administration to normal mice (ED50 = 25 mg/kg). Although gCl, at a single dose of 100 mg/kg, was still 70% inhibited 5 hours after dosing, the inhibition disappeared after 24 hours. Repeated administration of 100 mg/kg twice a day for 10 days caused no adverse effects; therefore, this regimen was chosen as the highest dosing for the SAD mice. SAD mice were treated for 3 weeks with 2 daily administrations of 10, 35, and 100 mg/kg NS3623, respectively. The hematocrit increased, and the mean corpuscular hemoglobin concentration decreased in all groups with a concomitant increase in the intracellular cation content. A loss of the densest red cell population was observed in conjunction with a shift from a high proportion of sickled to well-hydrated discoid erythrocytes, with some echinocytes present at the highest dosage. These data indicate feasibility for the potential use of Cl-conductance blockers to treat human sickle cell disease

    Heritability of fetal hemoglobin, white cell count, and other clinical traits from a sickle cell disease family cohort

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    Sickle cell disease (SCD) is the most common monogenic disorder in the world. Notably, there is extensive clinical heterogeneity in SCD that cannot be fully accounted for by known factors, and in particular, the extent to which the phenotypic diversity of SCD can be explained by genetic variation has not been reliably quantified. Here, in a family-based cohort of 449 patients with SCD and 755 relatives, we first show that 5 known modifiers affect 11 adverse outcomes in SCD to varying degrees. We then utilize a restricted maximum likelihood procedure to estimate the heritability of 20 hematologic traits, including fetal hemoglobin (HbF) and white blood cell count (WBC), in the clinically relevant context of inheritance from healthy carriers to SCD patients. We report novel estimations of heritability for HbF at 31.6% (±5.4%) and WBC at 41.2% (±6.8%) in our cohort. Finally, we demonstrate shared genetic bases between HbF, WBC, and other hematologic traits, but surprisingly little overlap between HbF and WBC themselves. In total, our analyses show that HbF and WBC have significant heritable components among individuals with SCD and their relatives, demonstrating the value of using family-based studies to better understand modifiers of SCD

    Aging-like Phenotype and Defective Lineage Specification in SIRT1-Deleted Hematopoietic Stem and Progenitor Cells

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    Summary Aging hematopoietic stem cells (HSCs) exhibit defective lineage specification that is thought to be central to increased incidence of myeloid malignancies and compromised immune competence in the elderly. Mechanisms underlying these age-related defects remain largely unknown. We show that the deacetylase Sirtuin (SIRT)1 is required for homeostatic HSC maintenance. Differentiation of young SIRT1-deleted HSCs is skewed toward myeloid lineage associated with a significant decline in the lymphoid compartment, anemia, and altered expression of associated genes. Combined with HSC accumulation of damaged DNA and expression patterns of age-linked molecules, these have striking overlaps with aged HSCs. We further show that SIRT1 controls HSC homeostasis via the longevity transcription factor FOXO3. These findings suggest that SIRT1 is essential for HSC homeostasis and lineage specification. They also indicate that SIRT1 might contribute to delaying HSC aging

    Early detection of response to hydroxyurea therapy in patients with sickle cell anemia.

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    Red blood cells (RBC) and reticulocyte parameters were determined on peripheral blood from a subset of patients enrolled in the multicenter study of hydroxyuea (HU) in sickle cell anemia. Multiple blood samples were obtained every 2 weeks. Cellular indices were measured by flow cytometry. Generalized linear models were used to determine the relationship between the longitudinal trajectories of RBC and reticulocyte indices and HU usage. There was a significant relationship between HU usage and most of the RBC and reticulocyte indices. Hydroxyurea produced higher value trajectories than those generated by placebo usage for the hemoglobin (Hb) content of both the RBCs and reticulocytes and for the mean corpuscular volume (MCV) of reticulocytes. These changes were first detected 10 weeks after starting HU and before the increase in Hb F levels. The data suggest that subtle and early markers of response to HU reside in the hemogram

    Bitopertin, a selective oral GLYT1 inhibitor, improves anemia in a mouse model of \u3b2-thalassemia

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    Anemia of \u3b2-thalassemia is caused by ineffective erythropoiesis and reduced red cell survival. Several lines of evidence indicate that iron/heme restriction is a potential therapeutic strategy for the disease. Glycine is a key initial substrate for heme and globin synthesis. We provide evidence that bitopertin, a glycine transport inhibitor administered orally, improves anemia, reduces hemolysis, diminishes ineffective erythropoiesis, and increases red cell survival in a mouse model of \u3b2-thalassemia (Hbbth3/+ mice). Bitopertin ameliorates erythroid oxidant damage, as indicated by a reduction in membrane-associated free \u3b1-globin chain aggregates, in reactive oxygen species cellular content, in membrane-bound hemichromes, and in heme-regulated inhibitor activation and eIF2\u3b1 phosphorylation. The improvement of \u3b2-thalassemic ineffective erythropoiesis is associated with diminished mTOR activation and Rab5, Lamp1, and p62 accumulation, indicating an improved autophagy. Bitopertin also upregulates liver hepcidin and diminishes liver iron overload. The hematologic improvements achieved by bitopertin are blunted by the concomitant administration of the iron chelator deferiprone, suggesting that an excessive restriction of iron availability might negate the beneficial effects of bitopertin. These data provide important and clinically relevant insights into glycine restriction and reduced heme synthesis strategies for the treatment of \u3b2-thalassemia
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