Erythropoietic Response Research Articles

PO19-WE-13 Autosomal dominant limb-girdle muscular dystrophy linked to chromosome 7Q36: description of a phenotype

Background: The haematopoietic effect of recombinant human erythropoietin (rhuEPO) in dialysis patients is well known. Recently rhuEPO has received considerable attention because of the finding that it has also broad neuroprotective and cardioprotective capabilities. Nowadays rhuEPO is tested in clinical trials for various neurological conditions such as stroke, schizophrenia ec. where mostly non-anaemic patients are treated with rhuEPO. In this study we investigated the effects of long-term use of rhuEPO in regard to erythropoesis and iron parameters in a group of non-anaemic patients with Friedreich’s ataxia (FA). Patients and methods: In a clinical study 12 adult patients, suffering from the neurodegenerative diseases Friedreich’s ataxia, received 5.000 units rhuEPO 3 times weekly subcutaneously for 8 weeks. Erythropoietic response and parameters of iron metabolism were recorded during rhuEPO treatment and further followed for 10 weeks post treatment. Haematocrit, haemoglobin, reticulocytes, serum iron, serum ferritin, transferrin, transferrin-saturation were monitored using routine laboratory methods. Results: Treatment with rhuEPO showed a significant change in most iron parameters. Interestingly we found a recovery of all iron parameters within 4 to 10 weeks after treatment. Conclusion: Iron parameters in FRDA-patients were significantly changed during eight weeks treatment with rhuEPO, but recovered to baseline levels after completion of the trial. These results indicate that there possibly appears a mobilisation of body iron through rhuEPO treatment.

PO19-WE-12 Treatment with recombinant human Erythropoietin: focus on iron status and possible mechanism for iron redistribution

Background: The haematopoietic effect of recombinant human erythropoietin (rhuEPO) in dialysis patients is well known. Recently rhuEPO has received considerable attention because of the finding that it has also broad neuroprotective and cardioprotective capabilities. Nowadays rhuEPO is tested in clinical trials for various neurological conditions such as stroke, schizophrenia ec. where mostly non-anaemic patients are treated with rhuEPO. In this study we investigated the effects of long-term use of rhuEPO in regard to erythropoesis and iron parameters in a group of non-anaemic patients with Friedreich’s ataxia (FA). Patients and methods: In a clinical study 12 adult patients, suffering from the neurodegenerative diseases Friedreich’s ataxia, received 5.000 units rhuEPO 3 times weekly subcutaneously for 8 weeks. Erythropoietic response and parameters of iron metabolism were recorded during rhuEPO treatment and further followed for 10 weeks post treatment. Haematocrit, haemoglobin, reticulocytes, serum iron, serum ferritin, transferrin, transferrin-saturation were monitored using routine laboratory methods. Results: Treatment with rhuEPO showed a significant change in most iron parameters. Interestingly we found a recovery of all iron parameters within 4 to 10 weeks after treatment. Conclusion: Iron parameters in FRDA-patients were significantly changed during eight weeks treatment with rhuEPO, but recovered to baseline levels after completion of the trial. These results indicate that there possibly appears a mobilisation of body iron through rhuEPO treatment.

Insights into achieving target hemoglobin levels: Increasing the serum ferritin parameter

AbstractEvidence suggests that higher serum ferritin levels may not be an accurate reflection of iron stores or predict a patient's response to intravenous (IV) iron. Therefore, our dialysis unit revised its IV iron and anemia management protocol, from initially holding IV iron at a lower limit of serum ferritin to now continuing IV iron therapy at higher serum ferritin levels. This article describes our facility's experiences with IV iron administration at higher serum ferritin levels and the resulting improvements in patient outcomes as measured by an improved erythropoietic response.

TAM receptors and the regulation of erythropoiesis in mice

TAM receptors (Tyro3, Axl and Mer) are expressed in hematopoietic tissues. The roles of the three receptors in hematopoiesis are, however, largely unknown. We investigated the role of TAM receptors in regulating erythropoiesis. Single and double mutant mice for Axl and Mer were used in the study. Cellularity of bone marrow and spleen, hematologic parameters, flow cytometry analysis of erythroid cell maturation, erythropoietic response to acute hemolytic anemia, bone marrow transplantation and the expression of erythropoisis were analyzed to evaluate the function of Axl and Mer in erythropoiesis. Axl and Mer, but not Tyro3, were constitutively expressed in developing erythroid cells. Mice lacking Axl and Mer (Axl(-/-)Me(-/-)) had impaired erythropoiesis in bone marrow and expanded splenic erythropoiesis. We found an inhibition of differentiation at the transition from erythroid progenitors to proerythroblasts in Axl(-/-)Mer(-/-) mice. These mice exhibited a low rate of erythropoietic response to acute anemia induced by phenylhydrazine. Bone marrow transplantation studies showed that the impaired erythropoiesis in Axl(-/-)Mer(-/-) mice is erythroid cell-autonomous. TAM receptors may influence erythropoiesis through the regulation of GATA-1 erythropoietin receptor and EpoR expression in erythroid progenitors. Notably, mice lacking single Axl or Mer exhibited normal erythropoiesis in steady-state conditions. Axl and Mer play an important role in regulating erythropoiesis. This finding provides a novel insight into the mechanism of erythropoiesis.

Assessment of Urinary Concentrations of Hepcidin Provides Novel Insight into Disturbances in Iron Homeostasis during Malarial Infection

Disturbances in iron homeostasis are frequently observed in individuals with malaria. To study the effect of malaria and its treatment on iron homeostasis and to provide a mechanistic explanation for observed alterations in iron distribution, we studied the course of the iron regulatory hormone hepcidin in anemic Tanzanian children with febrile Plasmodium falciparum malaria. Before initiation of antimalarial treatment, urinary concentrations of hepcidin were strongly elevated and were associated with iron maldistribution, as was suggested by the presence of hypoferremia and high serum concentrations of ferritin. Antimalarial treatment resulted in a rapid decrease in urinary concentrations of hepcidin and reversal of the hypoferremia. Exploration of regulatory pathways of hepcidin production by analysis of iron, erythropoietic, and inflammatory indices suggested that reduced erythropoietic activity and inflammation stimulated hepcidin production. We conclude that high concentrations of hepcidin explain the observed disturbances in host iron homeostasis associated with malaria and may contribute to malarial anemia and an impaired erythropoietic response to iron supplementation.

Low red cell production may protect against severe anemia during a malaria infection—Insights from modeling

The malaria parasite causes lysis of red blood cells, resulting in anemia, a major cause of mortality and morbidity. Intuitively, one would expect the production of red blood cells to increase in order to compensate for this loss. However, it has been observed that this response is weaker than would be expected. Furthermore, iron supplementation for iron deficient children in malaria endemic regions can paradoxically adversely affect the clinical outcome of malaria infection. A possible explanation may lie in the preference that some malaria parasites show for infecting immature red blood cells (reticulocytes). In the presence of a parasite preference for immature red cells, a rise in red cell production can ‘fuel the fire’ of infection by increasing the availability of the parasite's preferred target cell. We present a mathematical model of red blood cell production and infection in order to explore this hypothesis. We assess the effect of varying the reticulocyte replacement rate and preference of the parasite for reticulocytes on four key outcome measures assessing anemia and parasitemia. For a given level of parasite preference for reticulocytes we uncover an optimal erythropoietic response which minimizes disease severity. Increasing red blood cell production much above this optimum confers no benefit to the patient, and in fact can increase the degree of anemia and parasitemia. These conclusions are consistent with epidemiological studies demonstrating that both iron deficiency and anemia are protective against severe malaria, whilst iron supplementation in malaria endemic regions is with an increased number of malaria related adverse effects. Thus, suppression of red blood cell production, rather than being an unfortunate side effect of inflammation, may be a host protective effect against severe malarial anemia.

Application of fuzzy logic to predicting erythropoietic response in hemodialysis patients

The purpose of this study was to demonstrate how fuzzy sets can be used in a pharmacodynamic model to represent the uncertainty about the classification of an end-stage renal disease patient's response to erythropoietin. A pharmacodynamic model was developed to predict future hemoglobin response to administered erythropoietin for a population of 186 patients with end-stage renal failure and anemia. The prediction was performed by a weighted linear combination of past hemoglobin, transferrin saturation, and erythropoietin dose. Patients were classified based on their response to administered erythropoietin into (i) all patients into 1 group (population approach), (ii) all patients into either a poor or normal responder group (subpopulation approach--traditional classification), and (iii) all patients by partial membership into the poor and normal responder groups (subpopulation approach--fuzzy classification). One half of the data set was randomly selected to estimate the model parameters, and the second half was used to test the estimated model. This randomization was repeated 100 times for both males and females. Mean square error decreased significantly through the incorporation of hemoglobin response categorization from the control group (1.32 +/- 0.07), to crisp coding (1.23 +/- 0.07), to fuzzy coding (1.20 +/- 0.07) with an overall p value < 0.001. Uncertainty in the categorization of subjects into 2 erythropoietin response groups of poor or normal response has been shown to benefit from the use of fuzzy categories, with a significant improvement in model performance.

Erythropoietic Stimuli and Response in Hereditary Spherocytosis

Hereditary Spherocytosis (HS) is the most common non-immune hemolytic anemia in Europe. HS ranges from assymptomatic to transfusion-dependent hemolytic anemia and is clinically classified as mild, moderate or severe. Clinical, biochemical and molecular heterogeneous patterns are HS trademarks. In a previous work, we reported that in HS patients the erythropoietic response appears to be impaired in the more severe cases of the disease, since erythropoietin (EPO) levels did not correlate with reticulocyte count or with reticulocyte production index (RPI) [Rocha S. et al. (2005) Br J Haematol. 131(4):534]. It is known that spherocytes are removed by splenic macrophages. The activation of these cells is associated with cytokine release, namely, tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ), both known as EPO inhibitors. The aim of our work was to evaluate the erythropoietic stimuli and response according to HS severity and to clarify the role of these cytokines in HS. We studied 31 HS patients and 25 healthy individuals as the control group. The HS group included only unsplenectomised patients classified as presenting mild (n=19), moderate (n=9) or severe HS (n=3) according to the Guidelines for the diagnosis and management of hereditary spherocytosis [Bolton-Maggs et al. (2004) Br J Haematol. 126(4):455]. The basic hematological study was performed in all samples, as well as the reticulocyte count and RPI calculation; the plasma levels of EPO and soluble transferrin receptor (sTfR) (as markers of erythropoietic stimuli), of bilirubin (as a marker of hemolysis) and of TNF-α and IFN-γ (known as EPO inhibitors) were also determined. Data was analysed according to the severity of HS and versus the control group. Erythrocyte count, hemoglobin concentration, hematocrit and mean cell volume were found to be significantly lower in patients than in controls and their values decreased with HS severity; for MCHC, RDW, reticulocytes, RPI, bilirubin, EPO and sTfR patients presented significantly higher values than controls, and their values increased with HS severity. However, the increment in EPO and sTfR levels was more marked than for reticulocytes and RPI. As for TNF-α and IFN-γ no differences were found between patients and controls or between HS severities; no correlations with the other studied variables were observed. In mild HS patients, sTfR was found to be statistically and positively correlated with reticulocytes (r=0.783; p<0.001), RPI (r=0.748; p<0.001) and bilirubin (r=0.870; p<0.001); in patients with more severe forms (moderate and severe HS) these correlations were lower and only a statistically and positively correlation between sTfR and reticulocytes (r=0.657; p<0.05) was found. Our results confirm the inadequate erythropoietic response in the more severe cases of HS, given that, the erythropoietic stimuli (shown by higher EPO, sTfR and indirectly, by bilirubin levels) was not able to trigger an adequate erythropoietic response as shown by the reticulocyte number and RPI, as occured in mild HS patients. Our hypothesis, that this disturbance could be due to an increase in TNF-α and IFN-γ, was not confirmed, as we did not found any significant increase in these cytokines that could explain the non adequate erythropoietic response in moderate/severe HS patients. In conclusion, the erythropoietic stimuli seem to increase with HS severity; however, the response to that stimulus appears to be impaired in the more severe cases of HS. Further studies are needed to clarify this erythropoietic disturbance in HS patients, which may contribute to the severity of the clinical presentation of the disease.

Disruption of GAS6-MER Pathway Leads to Defects in Physiological Clearance of Expelled Nuclei from Erythroblasts by Bone Marrow Macrophages

Late in erythropoiesis, nuclei are expelled from erythroblasts and 2×1011 anucleated new red blood cells are daily delivered in the peripheral blood. Expelled nuclei expose phosphatidylserine (PS) on their surface, which is used as an “eat me” signal for their engulfment by macrophages located in the blood island. The two PS opsonins, milk-fatglobule EGF8 (MFG-E8) and Growth arrest-specific gene 6 product (GAS6) together with their respective receptors αvβ5/αvβ3 and TAM (TYRO3, AXL and MER), are involved in the phagocytosis of apoptotic cells, but their role in the phagocytosis of expelled nuclei from erythroblasts is not determined. Because fetal liver and bone marrow macrophages do not express MFG-E8, the GAS6-MER pathway might constitute a crucial pathway for the engulfment of nuclei expelled from erythroblasts. To test this hypothesis, we isolated nuclei from late-stage erythroblasts from spleens of phlebotomized mice, and studied nuclei internalization capacity of bone marrow derived macrophages (BMDM) from mice deficient either in GAS6 (GAS6−/−), AXL (AXL−/−) or TYRO3 (TYRO3−/−), or lacking MER kinase domain (MERkd). Released nuclei were identified by flow cytometry according to their size and their double positive staining for the erythroid lineage marker Ter119 and Annexin V for PS. Purity of the preparation was checked by morphological examination of cytospin preparations. In vitro phagocytosis assays show that GAS6−/− BMDM cleared 30% less nuclei than wild-type (WT) BMDM. We observed a slight decrease of internalization capacity for AXL−/− BMDM, whereas TYRO3−/− BMDM engulfed the nuclei as efficiently as WT BMDM. In contrast, MER deficiency nearly abolished nuclei phagocytosis. AXL−/−/TYRO3−/− and AXL−/−/MERkd BMDM were tested and did not show any cumulative effects when compared to WT and single knockouts. We also investigated the signalling pathway downstream of MER in BMDM. In particular, we assessed the expression of the activated form of Rac1, which is crucial for the cytoskeletal reorganization in phagocytosis. Activation of Rac1 after the initiation of the phagocytosis was delayed for 45 minutes in MERkd as compared to WT BMDM. In vivo, we found an accumulation of nuclei in MERkd mice 4 days post phlebotomy, when erythropoiesis is increased in response to anemia. Nuclei circulated in the blood of MERkd mice at a level of 0.08 ± 0.042 G/L and were identified on peripheral blood smears of these mice whereas they were undetectable in the blood of WT mice. We demonstrated an increase of a double labelled Ter119/AnnexinV population corresponding to nuclei in BM (2-fold) and spleen (1.5-fold) of MERkd mice as compared to WT mice. The augmentation of this double labelled population in the MERkd mice translated the phenotype of splenomegaly of these mice. Hematocrit and reticulocyte levels were comparable between WT and MERkd as previously reported (JCI 118:583–596, 2008). Thus, MER was critical for in vitro phagocytosis of nuclei from erythroblasts whereas the role of AXL and TYRO3 appeared to be negligible. GAS6 binding to nuclei exposing PS on their surface might form a bridge between PS and MER receptor on BMDM, allowing nuclei clearance. In vivo, the absence of MER caused an accumulation of nuclei in BM and spleen and their appearance in circulating blood due to their inefficient elimination during erythropoietic response to anemia. In conclusion, we postulate that GAS6 and its receptor MER were involved in late erythropoiesis when nuclei are expelled from the erythroblasts and engulfed by BMDM in the blood island, through Rac1 activation.

REP Regimen (Rituximab, Erythropoietin and Prednisone) in the Treatment of Refractory Autoimmune Hemolytic Anemia (R-AIHA).

Background: The management of AIHA, based mainly on empirical data and uncontrolled studies, relies principally on corticosteroids as a first-line therapy. Patients who are refractory or intolerant to these therapies (approximately 5–10% of the cases) constitute an important therapeutic challenge. The most frequent second-line options are splenectomy or immunosuppressive agents. Rituximab (R), an anti-CD20 chimeric monoclonal antibody being increasingly used in autoimmune disorders. Transfusion in patients with autoimmune hemolytic anemia generally is unwise, because the autoantibody in the serum usually reacts with the RBCs of all potential donors, making a satisfactory cross match impossible. Moreover, the erythroid response, can be inappropriately low, and several reports or senies' have highlighted cases that have been associated with reticulocytopenia. Aim of this study is to test if the introduction of Rh-Epo in the refractory AIHA treatment may reduce the blood transfusion need and related risksMethods: 14 pts (M 7, F 7) median age 59.2 yr (range, 18–82) and AIHA resistant to standard treatment were treated with a schedule containing Rituximab, rh-EPO and prednisone (R-EP) 6 pts were idiopathic and the remaining 8 were associated with chronic lymphoproliferative syndromes (3), connective tissue diseases (2), primary antiphospholipid syndrome (APS)(1) and ulcerative colitis (2). mean Hb value and Ht at presentation were 6.3 g/dL ± 1.2, and 24 mL/dL, Median reticulocyte percentage was 9%, and median reticulocyte production index was 2.8 times basal. 24 % of cases had an initial reticulocyte count less than 4%, and 40% had an initial reticulocyte production index less than 2.0 times basal. These reticulocytopenic patients were prevalent in secondary cases. Serum erythropoietin level at baseline was (14 +/− 11 mU/mL)) Pts had altered hemolysis markers and direct antiglobulin test (DAT) was positive for both complement and IgG (IgA 1 pts). All cases had a bone marrow examination during hospitalization Erythroid hypoplasia was seen only in CLL pts.14/14 pts had serial reticulocyte measurements, Rituximab was administered intravenously at a dose of 375mg/m2 weekly for 4 weeks; prednisone 1 mg/Kg/day /for 30 days ; rh-EPO 30.000U/weekly for 4 weeks.Results: All pts completed treatment. No major infusion related side effects to R-EP were observed. Response criteria to R-EP were defined as follows: Complete Response (CR): Hb >10 g/dl or Hb increase >1.5 g/dl, resolution of symptoms of anemia, transfusion independent; Partial Response (PR): Hb > 9 g/dl or Hb increase of 1–1.5 g/dl. improvement in symptoms of anemia, transfusion independent; NR (failure to meet CR/PR). 100% were eligible for response. Responses were seen in 14/14 pts. CR in 13/14 and PR in 1/14, median follow up of 25.8 months (range 5–66 months). At the end of treatment DAT became negative in 12/14 pts, concentration of lactic dehydrogenase, total bilirubin and indirect bilirubin began to decrease at 12 days after the first dose of rituximab, and decreased to normal range after 22 days.. Three patients required packed red cell transfusions before starting R-EP and all became transfusion-free. A moderate hemolysis still persisted only in one patient. In the cases that were initially reticulocytopenic, reticulocyte production index rapidly increased, indicating a marrow erythropoietic response to REPConclusion: Our experience demonstrates that R-EP is an effective and safe alternative for the treatment of refractory autoimmune hemolytic anemia. Awareness of the frequency of an initial reticulocytopenia in cases of autoimmune hemolysis may be important in initial diagnosis and treatment, because low reticulocyte production index may represent a lag in marrow responsiveness to hemolytic stress. Striking, the introduction of rh-Epo clearly avoids blood transfusions and overcame inappropriately low erythroid response in reticulocytopenic patients

Regulation of hematopoiesis by the BMP signaling pathway in adult zebrafish

The zebrafish is an established model system for studying the embryonic emergence of tissues and organs, including the hematopoietic system. We hypothesized that key signaling pathways controlling embryonic hematopoiesis continue to be important in the adult, and we sought to develop approaches to test this in zebrafish, focused on the bone morphogenetic protein (BMP) signaling pathway. Functions for this pathway in adult hematopoiesis have been challenging to probe in other models. Several approaches tested the function of BMP signaling during adult zebrafish hematopoiesis. First, we evaluated steady-state hematopoiesis in adult fish that are heterozygous for mutant alleles of Smad5, or are homozygous for mutant alleles, and rescued to adulthood by injection of RNA encoding Smad5. Second, we tested the relative ability of smad5 mutant fish to recover from hemolytic anemia. Third, we generated a transgenic line that targets the expression of a dominant-negative BMP receptor to adult-stage Gata1+ progenitor cells. Adult fish with a strong mutant smad5 allele are anemic at steady state and, in addition, respond to hemolytic anemia with kinetics that are altered compared to wild-type fish. Fish expressing a mutant BMP receptor in early Gata1+ definitive progenitors generate excessive eosinophils. Our study provides proof of principle that regulation of adult hematopoiesis can be studied in zebrafish by altering specific pathways. We show that the BMP signaling pathway is relevant for adult hematopoiesis to maintain steady state erythropoiesis, control the erythropoietic response following stress anemia, and to generate normal numbers of eosinophils.

Anemia of Critical Illness

Anemia of critical illness, a commonly encountered clinical situation, is hematologically similar to that of chronic anemia, except that the onset is generally sudden. The etiology is usually multifactorial, occurring as a consequence of direct inhibitory effects of inflammatory cytokines, erythropoietin deficiency, blunted erythropoietic response, blood loss, nutritional deficiencies, and renal insufficiency. Although anemia is not well tolerated by critically ill patients, aggressive treatment of anemia can be just as detrimental as no treatment. Different types of anemia may coexist in a patient in the intensive care unit, making diagnosis and differentiation among these anemias complex, therefore requiring good diagnostic skills. Although several therapeutic options are available to treat anemia, critically ill patients often receive a transfusion, and yet, most recent studies indicate that blood transfusions in critically ill patients are associated with worse outcomes, including higher morbidity and mortality. These studies have generated interest in the administration of exogenous erythropoietin and iron therapy. Unfortunately, the accurate determination of iron status can be a rather difficult task, an undertaking that is made even more difficult by the presence of comorbid conditions that can affect the commonly used parameters for guiding iron therapy. The use of erythropoiesis-stimulating agents is rapidly gaining acceptance, although they also present potential problems of their own.

Anemia in the Critically Ill Patient

Anemia in critically ill patients has been described as an acute form of anemia of inflammatory disease and is characterized by a blunted erythropoietic response due in part to proinflammatory mediators. Management of anemia in critically ill patients is a complex issue and is best approached via a multiprofessional team regarding the use of allogenic blood, iron, nutritional therapy, and erythropoietic agents. Indiscriminant, ``routine'' red blood cell transfusions may not only be unnecessary, but may pose unnecessary risk to the intensive care unit patient. Most intensive care unit patients can tolerate lower hemoglobin/hematocrit concentrations than the typically accepted ``10/30 rule.'' Lower transfusion triggers with an overall transfusion strategy is warranted in the intensive care unit patient. The use of recombinant human erythropoietic agents may not be necessary with appropriate transfusion practices.

Acellular haemoglobin attenuates hypoxia-inducible factor-1α (HIF-1α) and its target genes in haemodiluted rats

Hb (haemoglobin)-based blood substitutes represent a class of therapeutics designed to correct oxygen deficit under conditions of anaemia and traumatic blood loss. The influences of these agents on HIF-1alpha (hypoxia-inducible factor-1alpha) target genes involved in adaptation to hypoxia have so far not been studied. In the study presented here, rats underwent 80% ET (exchange transfusion) with either HS (hetastarch) or a polymerized Hb OG (Oxyglobin). HS induced dramatic EPO (erythropoietin) gene transcription, reaching a maximum at 4 h post-ET. In contrast, OG suppressed EPO transcription until approx. 24 h post-ET. Large plasma EPO levels that were observed post-ET with HS were significantly blunted in animals transfused with OG. OG, unlike HS, induced a sharp increase in HO-1 (haem oxygenase-1) transcription at 4 h, which declined rapidly within 24 h, whereas modest increases in iNOS [inducible (nitric oxide synthase)] and constitutive NOS [eNOS (endothelial NOS)] were detected over the control. Our results demonstrate for the first time that severe haemodilution-induced erythropoietic responses in kidneys were attenuated by a low-oxygen-affinity cell-free Hb and suggest that tissue-specific oxygen-sensing pathways can be influenced by allosterically modified Hbs.

Host Control of Malaria Infections: Constraints on Immune and Erythropoeitic Response Kinetics

The two main agents of human malaria, Plasmodium vivax and Plasmodium falciparum, can induce severe anemia and provoke strong, complex immune reactions. Which dynamical behaviors of host immune and erythropoietic responses would foster control of infection, and which would lead to runaway parasitemia and/or severe anemia? To answer these questions, we developed differential equation models of interacting parasite and red blood cell (RBC) populations modulated by host immune and erythropoietic responses. The model immune responses incorporate both a rapidly responding innate component and a slower-responding, long-term antibody component, with several parasite developmental stages considered as targets for each type of immune response. We found that simulated infections with the highest parasitemia tended to be those with ineffective innate immunity even if antibodies were present. We also compared infections with dyserythropoiesis (reduced RBC production during infection) to those with compensatory erythropoiesis (boosted RBC production) or a fixed basal RBC production rate. Dyserythropoiesis tended to reduce parasitemia slightly but at a cost to the host of aggravating anemia. On the other hand, compensatory erythropoiesis tended to reduce the severity of anemia but with enhanced parasitemia if the innate response was ineffective. For both parasite species, sharp transitions between the schizont and the merozoite stages of development (i.e., with standard deviation in intra-RBC development time ≤2.4 h) were associated with lower parasitemia and less severe anemia. Thus tight synchronization in asexual parasite development might help control parasitemia. Finally, our simulations suggest that P. vivax can induce severe anemia as readily as P. falciparum for the same type of immune response, though P. vivax attacks a much smaller subset of RBCs. Since most P. vivax infections are nonlethal (if debilitating) clinically, this suggests that P. falciparum adaptations for countering or evading immune responses are more effective than those of P. vivax.

Classical altitude training

For more than 40 years, the effects of classical altitude training on sea-level performance have been the subject of many scientific investigations in individual endurance sports. To our knowledge, no studies have been performed in team sports like football. Two well-controlled studies showed that living and training at an altitude of >or=1800-2700 m for 3-4 weeks is superior to equivalent training at sea level in well-trained athletes. Most of the controlled studies with elite athletes did not reveal such an effect. However, the results of some uncontrolled studies indicate that sea-level performance might be enhanced after altitude training also in elite athletes. Whether hypoxia provides an additional stimulus for muscular adaptation, when training is performed with equal intensity compared with sea-level training is not known. There is some evidence for an augmentation of total hemoglobin mass after classical altitude training with duration >or=3 weeks at an altitude >or=2000 m due to altitude acclimatization. Considerable individual variation is observed in the erythropoietic response to hypoxia and in the hypoxia-induced reduction of aerobic performance capacity during training at altitude, both of which are thought to contribute to inter-individual variation in the improvement of sea-level performance after altitude training.

The effect of severe hepatic impairment on the pharmacokinetics and haematological response of C.E.R.A.

ABSTRACTAim: To examine the effect of severe hepatic impairment (HI) on the pharmacokinetics (PK) and pharmacodynamics (PD) of the continuous erythropoietin receptor activator, C.E.R.A.Methods: A non-randomised, multicentre, single-dose, open-label study in patients with HI (n = 12) and healthy subjects (n = 12). After 2 weeks of screening, participants received a single intravenous dose of C.E.R.A. (200 µg), and were then followed for ≈8 weeks. The area under the concentration–time curve (AUC) from drug administration to last measurable concentration (AUClast), and maximum C.E.R.A. concentration (Cmax) were calculated to assess PK. The baseline-corrected area under the effect curve over 22 days (AUEcorr) for reticulocyte count was the primary PD parameter.Results: The PK profile was similar in patients and healthy subjects (AUClast: 6678 vs 6985 ng*h/mL; Cmax: 63 vs 75 ng/mL) C.E.R.A. produced a sustained erythropoietic response in bothgroups, with increases in reticulocyte counts peaking 7–9 days post-dose and returning to baseline by Day 22. Although mean AUEcorr was 64% lower in patients, this may have been an artefact of higher baseline reticulocyte counts. Lower reticulocyte responses in patients did not translate into lower responses for haemoglobin, haematocrit or erythrocytes, suggesting that HI had no clinically relevant effect on the PD of C.E.R.A. C.E.R.A. was well tolerated. Four AEs (none considered drug related) were reported in three patients (mild myocardial ischaemia; mild pyrexia and liver transplant; severe bacterial peritonitis [serious AE]); no AEs were reported in healthy subjects.Conclusions: Severe HI has no clinically relevant effect on PK parameters or haematological response after single-dose C.E.R.A.

The Time course of the Erythropoietic Response to Natural Altitude Training in Elite Endurance Cyclists

The Time course of the Erythropoietic Response to Natural Altitude Training in Elite Endurance Cyclists

Ablation of Gata1 in adult mice results in aplastic crisis, revealing its essential role in steady-state and stress erythropoiesis

AbstractThe transcription factor Gata1 is expressed in several hematopoietic lineages and plays essential roles in normal hematopoietic development during embryonic stages. The lethality of Gata1-null embryos has precluded determination of its role in adult erythropoiesis. Here we have examined the effects of Gata1 loss in adult erythropoiesis using conditional Gata1 knockout mice expressing either interferon- or tamoxifen-inducible Cre recombinase (Mx-Cre and Tx-Cre, respectively). Mx-Cre–mediated Gata1 recombination, although incomplete, resulted in maturation arrest of Gata1-null erythroid cells at the proerythroblast stage, thrombocytopenia, and excessive proliferation of megakaryocytes in the spleen. Tx-Cre–mediated Gata1 recombination resulted in depletion of the erythroid compartment in bone marrow and spleen. Formation of the early and late erythroid progenitors in bone marrow was significantly reduced in the absence of Gata1. Furthermore, on treatment with a hemolytic agent, these mice failed to activate a stress erythropoietic response, despite the rising erythropoietin levels. These results indicate that, in addition to the requirement of Gata1 in adult megakaryopoiesis, Gata1 is necessary for steady-state erythropoiesis and for erythroid expansion in response to anemia. Thus, ablation of Gata1 in adult mice results in a condition resembling aplastic crisis in human.

Hubungan antara Indeks Produksi Retikulosit (IPR) dengan Red Blood Cell Distribution Width (RDW) pada Klasifikasi Anemia berdasarkan Defek Fungsional

Reticulocyte Production Index (RPI) is a shift correction for the presence of reticulocyte that can assesses the real erythropoietic response of the bone marrow. RPI can be used to classify anemia as result from functional defect, i.e. RPI 3 for hemolytic anemia. Measurement of Red Blood Cell Distribution Width (RDW) is the mathematical representation of variance within the size distribution of the red cell population. The objective of this study was to identify the variation of the red cell size within the population measured (anisocytosis) enable to determine the cell population as homogeneous (normal RDW) or heterogenous (increased or high RDW). The role of RDW to differentiate functional defect anemia with RPI 3 classified as hemolytic anemia. Means for reticulocyte count, corrected reticulocyte count, RPI, and RDW for hypoproliferative and maturation defect anemia were 2,8% and 2,3%; 1,1% and 1,1%; 0,4 and 0,5; 21,8% and 17,8% respectively, with p value by the Wilcoxon Signed Ranks Test are = 0,322; 0,52; 0,273; and 0,27 (CI = 95%). The proportion of anisocytosis and normocytosis for hypoproliferative anemia were 76,08% and 23,9% and for maturation defect anemia were 76,19% and 23,8% with Chi-Square test 0,000 and p = 0,993. No correlation between was observed RDW and RPI<2 with Spearman correlation (r = 0,0297 and p = 0,993). It is concluded that the use of RDW and RPI is not always useful to differentiate hypoproliferative and maturation defect anemia on the group of anemia categorized as RPI<2 without support from another laboratory test especially in combined anemia.