losartan-potassium and Reticulocytosis

It has been proposed that the basis of severe malarial anaemia, a major cause of morbidity and mortality in endemic areas, is multifactorial. Inappropriately low reticulocytosis is observed in malaria patients suggesting that insufficient erythropoiesis is a major factor. Clinical studies provide conflicting data concerning the production of adequate levels of erythropoietin (EPO) during malaria. Plasmodium chabaudi AS causes non-lethal infection in resistant C57BL/6 mice, and lethal infection in susceptible A/J mice. In P. chabaudi AS infected C57BL/6 and A/J mice, which experience varying degrees of severity of anaemia, kidney EPO production is appropriate to the severity of anaemia and is regulated by haematocrit level. Neutralisation of endogenous EPO during infection leads to lethal anaemia while timely administration of exogenous EPO rescues mice although reticulocytosis is suppressed in proportion to the parasitemia level. Characterisation of alterations in splenic erythroid compartments in naive and P. chabaudi AS infected A/J mice revealed that infection, with or without EPO treatment, leads to sub-optimal increases in TER119+ erythroblasts compared to EPO-treated naive mice. A lower percentage of TER119+ erythroblasts in infected mice undergo terminal differentiation to become mature haemoglobin-producing cells. Furthermore, there is a shift in transferrin receptor (CD71) expression from TER119+ cells to a non-erythroid population. Deficiencies in the number and maturation of TER119+ erythroblasts during infection coincide with blunted proliferation to EPO stimulation in vitro by splenocytes, although a high frequency express EPO receptor (EPOR). Together, these data suggest that during malaria, EPO-induced proliferation of early EPOR+ erythroid progenitors is suppressed, leading to sub-optimal generation of TER119+ erythroblasts. Moreover, a shift in CD71 expression may result in impaired terminal maturation of erythroblasts. Thus, suppressed proliferation, differentiation, and maturation of erythroid precursors in association with inadequate reticulocytosis may be the basis of insufficient erythropoiesis during malaria.

Topics: Anemia; Animals; Disease Models, Animal; Erythropoiesis; Erythropoietin; Humans; Kidney; Malaria; Mice; Reticulocytosis

An empirical pharmacodynamic model was developed to assess the effect of recombinant human erythropoietin (rHu-EPO) treatment on the reticulocyte production rate and lifespan distribution.. Single doses of rHu-EPO at levels 20, 40, 60, 90, 120, and 160 kIU were administered to healthy volunteers (n = 8 per dose level). Erythropoietin plasma concentrations as well as hematologic responses were measured up to 42 days. The hematological data were used to determine explicit relationships between reticulocyte and red blood cell counts (RBC) and the reticulocytes' production rate and lifespan distribution.. The parameter estimates obtained by simultaneous fitting of the model to the reticulocyte and RBC data revealed that rHu-EPO transiently increased the reticulocyte lifespan from the baseline value of 1.7 days to 3.4 days and the effect lasted for 8.3 days. The dose dependent increase in the reticulocyte production had the maximal value of 77.5 10(9) cells/l/day and was followed by a rebound that was less than 9% of the baseline value. Both reticulocyte and RBC responses were preceded by a dose-independent lag time of 1.7 days.. The effect of rHu-EPO on the reticulocyte production rate and lifespan distribution was characterized. The results of the present study can be further utilized in building more mechanistic pharmacodynamic models of rHu-EPO stimulatory effects.

Topics: Cell Survival; Computer Simulation; Dose-Response Relationship, Drug; Erythrocyte Count; Erythropoietin; Hematinics; Humans; Injections, Subcutaneous; Male; Models, Biological; Predictive Value of Tests; Recombinant Proteins; Reference Values; Reticulocytes; Reticulocytosis; Time Factors

In this study, it is hypothesized that a planned increase in the dose of recombinant human erythropoietin (rh-EPO) can prevent transfusion in very low birth weight infants. Two different regimens of rh-EPO were administrated, one consisting in increasing dosage up to 5000 U/kg/wk, according to the individual reticulocytes response, and the second in a standard therapy of 1250 U/kg/wk. Fifty-one infants participated. Despite a significant higher reticulocytosis, the study was prematurely terminated due to the results of an interim analysis showing that transfusion was not avoided by increasing the rh-EPO. No significant differences were found between the two regimens concerning transfusion rate, volume transfused, gain in weight, and adverse effects. Progressive titration of rh-EPO to improve the biological response does not leave premature infants free of transfusion.

Topics: Birth Weight; Dose-Response Relationship, Drug; Double-Blind Method; Erythropoietin; Female; Hematologic Tests; Humans; Infant; Male; Recombinant Proteins; Reticulocyte Count; Reticulocytes; Reticulocytosis; Retrospective Studies; Survival Analysis; Transfusion Reaction; Treatment Outcome

Gliflozins provide a breakthrough in the management of type-2 diabetes. In addition to facilitating normoglycemia, these sodium-glucose cotransporter type 2 (SGLT2) inhibitors attenuate obesity, hypertension, dyslipidemia, and fluid retention, reduce cardiovascular morbidity, retard the progression of renal dysfunction, and improve survival. The administration of gliflozins also triggers erythropoietin (EPO) production, with the consequent induction of reticulocytosis and erythrocytosis. The mechanism(s) by which gliflozins induce erythropoiesis is a matter of debate. Whereas the canonical pathway of triggering EPO synthesis is through renal tissue hypoxia, it has been suggested that improved renal oxygenation may facilitate EPO synthesis via noncanonical trails. The latter proposes that recovery of peritubular interstitial fibroblasts producing erythropoietin (EPO) is responsible for enhanced erythropoiesis. According to this hypothesis, enhanced glucose/sodium reuptake by proximal tubules in uncontrolled diabetes generates cortical hypoxia, with injury to these cells. Once transport workload declines with the use of SGLT2i, they recover and regain their capacity to produce EPO. In this short communication, we argue that this hypothesis is incorrect. First, there is no evidence for interstitial cell injury related to hypoxia in the diabetic kidney. Tubular, rather than interstitial cells are prone to hypoxic injury in the diabetic kidney. Moreover, hypoxia, not normoxia, stimulates EPO synthesis by hypoxia-inducible factors (HIFs). Hypoxia regulates EPO synthesis as it blocks HIF prolyl hydroxylases (that initiate HIF alpha degradation), hence stabilizing HIF signals, inducing HIF-dependent genes, including EPO located in the deep cortex, and its production is initiated by the apocrinic formation of HIF-2, colocalized in these same cells.

Topics: Diabetic Nephropathies; Erythropoietin; Glucose; Humans; Hypoxia; Kidney; Polycythemia; Reticulocytosis; Sodium; Sodium-Glucose Transporter 2 Inhibitors

Cell surface proteins Hfe, Tfr2, hemojuvelin and Tmprss6 play key roles in iron homeostasis. Hfe and Tfr2 induce transcription of hepcidin, a small peptide that promotes the degradation of the iron transporter ferroportin. Hemojuvelin, a co-receptor for bone morphogenic proteins, induces hepcidin transcription through a Smad signaling pathway. Tmprss6 (also known as matriptase-2), a membrane serine protease that has been found to bind and degrade hemojuvelin in vitro, is a potent suppressor of hepcidin expression. In order to examine if Hfe and Tfr2 are substrates for Tmprss6, we generated mice lacking functional Hfe or Tfr2 and Tmprss6. We found that double mutant mice lacking functional Hfe or Tfr2 and Tmprss6 exhibited a severe iron deficiency microcytic anemia phenotype mimicking the phenotype of single mutant mice lacking functional Tmprss6 (Tmprss6msk/msk mutant) demonstrating that Hfe and Tfr2 are not substrates for Tmprss6. Nevertheless, the phenotype of the mice lacking Hfe or Tfr2 and Tmprss6 differed from Tmprss6 deficient mice alone, in that the double mutant mice exhibited much greater erythropoiesis. Hfe and Tfr2 have been shown to play important roles in the erythron, independent of their role in regulating liver hepcidin transcription. We demonstrate that lack of functional Tfr2 and Hfe allows for increased erythropoiesis even in the presence of high hepcidin expression, but the high levels of hepcidin levels significantly limit the availability of iron to the erythron, resulting in ineffective erythropoiesis. Furthermore, repression of hepcidin expression by hypoxia was unaffected by the loss of functional Hfe, Tfr2 and Tmprss6.

Topics: Anemia, Hypochromic; Animals; Erythropoiesis; Erythropoietin; Female; Hemochromatosis Protein; Histocompatibility Antigens Class I; Hypoxia; Male; Membrane Proteins; Mice; Mice, 129 Strain; Mice, Inbred AKR; Mice, Inbred C57BL; Mice, Knockout; Phenotype; Receptors, Transferrin; Reticulocytosis; Serine Endopeptidases

Erythropoiesis-stimulating agents are widely used to treat anemia for chronic kidney disease (CKD) and cancer, however, several clinical limitations impede their effectiveness. Nonviral gene therapy systems are a novel solution to these problems as they provide stable and low immunogenic protein expression levels. Here, we show the application of an arginine-grafted bioreducible poly(disulfide amine) (ABP) polymer gene delivery system as a platform for in vivo transfer of human erythropoietin plasmid DNA (phEPO) to produce long-term, therapeutic erythropoiesis. A single systemic injection of phEPO/ABP polyplex led to higher hematocrit levels over a 60-day period accompanied with reticulocytosis and high hEPO protein expression. In addition, we found that the distinct temporal and spatial distribution of phEPO/ABP polyplexes contributed to increased erythropoietic effects compared to those of traditional EPO therapies. Overall, our study suggests that ABP polymer-based gene therapy provides a promising clinical strategy to reach effective therapeutic levels of hEPO gene.

Topics: Anemia; Animals; Arginine; DNA; Erythrocytes; Erythropoiesis; Erythropoietin; Gene Transfer Techniques; Genetic Therapy; Genetic Vectors; Hematocrit; Humans; Kidney; Male; Nanoparticles; Polyamines; Random Allocation; Rats; Reticulocytosis; RNA, Messenger; Transfection

The postgenomic era has revolutionized approaches to defining host-pathogen interactions and the investigation of the influence of genetic variation in either protagonist upon infection outcome. We analyzed pathology induced by infection with two genetically distinct Trypanosoma brucei strains and found that pathogenesis is partly strain specific, involving distinct host mechanisms. Infections of BALB/c mice with one strain (927) resulted in more severe anemia and greater erythropoietin production compared to infections with the second strain (247), which, contrastingly, produced greater splenomegaly and reticulocytosis. Plasma interleukin-10 (IL-10) and gamma interferon levels were significantly higher in strain 927-infected mice, whereas IL-12 was higher in strain 247-infected mice. To define mechanisms underlying these differences, expression microarray analysis of host genes in the spleen at day 10 postinfection was undertaken. Rank product analysis (RPA) showed that 40% of the significantly differentially expressed genes were specific to infection with one or the other trypanosome strain. RPA and pathway analysis identified LXR/RXR signaling, IL-10 signaling, and alternative macrophage activation as the most significantly differentially activated host processes. These data suggest that innate immune response modulation is a key determinant in trypanosome infections, the pattern of which can vary, dependent upon the trypanosome strain. This strongly suggests that a parasite genetic component is responsible for causing disease in the host. Our understanding of trypanosome infections is largely based on studies involving single parasite strains, and our results suggest that an integrated host-parasite approach is required for future studies on trypanosome pathogenesis. Furthermore, it is necessary to incorporate parasite variation into both experimental systems and models of pathogenesis.

Topics: Anemia; Animals; Erythropoietin; Gene Expression Profiling; Genetic Variation; Interferon-gamma; Interleukin-10; Interleukin-12; Macrophage Activation; Mice; Mice, Inbred BALB C; Reticulocytosis; Splenomegaly; Trypanosoma brucei brucei; Trypanosomiasis, African

Cytokines released during inflammatory processes have been proposed to play a central role in mediating mechanism(s) leading to anemia. Here, we used CpG-ODN to investigate the effects of a pro-inflammatory response on the pathophysiological processes leading to anemia.. Naïve and erythropoietin (EPO)-treated mice were injected for 2 days with 100 microg CpG-ODN or control ODN and the effects on the course of red blood cell (RBC) and reticulocyte counts, RBC turnover, and EPO-stimulated maturation of erythroid cells were analyzed. To study the effect of CpG-ODN on erythroid cell maturation in vitro, we obtained primary EPO-responsive cells by treating mice with thiamphenicol (15 mg/g body weight).. CpG-ODN-treated mice developed anemia, which persisted for 5 days and was associated with a 50% reduction in EPO-stimulated differentiation of EPOR+ cells to TER119+ erythroblasts. CpG-ODN-induced suppression required accessory cells, including antigen presenting cells, which activated other cells to produce pro-inflammatory cytokines. In vitro neutralization of IFN-gamma, but not IL-12, TNF-alpha, IFN-alpha, IL-1alpha, or IL-1beta, abrogated the erythropoietic suppression induced by CpG-ODN. The anemia observed in CpG-ODN-treated mice was also associated with reduced RBC survival in vivo, as demonstrated by a sevenfold to eightfold higher turnover of biotinylated RBC compared to control ODN-treated mice. In vivo IFN-gamma neutralization confirmed that IFN-gamma contributed to erythropoietic suppression but not reduced RBC survival.. Together, these results demonstrate that CpG-ODN anemia is associated with suppressed erythropoiesis and decreased RBC survival. Importantly, CpG-ODN-induced IFN-gamma was found to be the major factor mediating erythropoietic suppression but not decreased RBC survival.

Topics: Anemia; Animals; Cell Survival; Erythrocytes; Erythropoiesis; Erythropoietin; Female; Injections, Intraperitoneal; Injections, Intravenous; Injections, Subcutaneous; Interferon-gamma; Mice; Mice, Inbred C57BL; Oligodeoxyribonucleotides; Recombinant Proteins; Reticulocytosis; Spleen; Thiamphenicol

Inappropriately low reticulocytosis may exacerbate malarial anemia, but the under-lying mechanism is not clear. In this study, naive and infected mice were treated with recombinant murine erythropoietin (EPO), and the upstream events of erythropoiesis affected by blood-stage Plasmodium chabaudi AS were investigated. Malaria infection, with or without EPO treatment, led to a suboptimal increase in TER119(+) erythroblasts compared with EPO-treated naive mice. Furthermore, a lower percentage of TER119(+) erythroblasts in infected mice were undergoing terminal differentiation to become mature hemoglobin-producing erythroblasts. The impaired maturation of erythroblasts during infection was associated with a shift in the transferrin receptor (CD71) expression from the TER119(+) population to B220(+) population. Moreover, the suboptimal increase in TER119(+) erythroblasts during infection coincided with a blunted proliferative response by splenocytes to EPO stimulation in vitro, although a high frequency of these splenocytes expressed EPO receptor (EPOR). Taken together, these data suggest that during malaria, EPO-induced proliferation of early EPOR-positive erythroid progenitors is suppressed, which may lead to a suboptimal generation of TER119(+) erythroblasts. The shift in CD71 expression may result in impaired terminal maturation of these erythroblasts. Thus, inadequate reticulocytosis during malaria is associated with suppressed proliferation, differentiation, and maturation of erythroid precursors.

Topics: Anemia; Animals; Cell Differentiation; Cell Division; Erythroid Precursor Cells; Erythropoiesis; Erythropoietin; Leukocyte Common Antigens; Malaria; Male; Mice; Mice, Inbred Strains; Plasmodium chabaudi; Receptors, Transferrin; Recombinant Proteins; Reticulocytosis; Spleen

Severe anemia is a major life-threatening complication of malaria. The roles of erythropoietin (Epo) and erythropoiesis during blood-stage malaria were investigated. By treating Plasmodium chabaudi AS-infected C57BL/6 (B6) mice, which are resistant to malaria, with polyclonal anti-human Epo neutralizing antibody, we demonstrated that Epo-induced reticulocytosis was important for alleviating malarial anemia and for host survival. By inducing erythropoiesis in A/J mice, which are susceptible to malaria, and in B6 mice at various periods during infection, by use of exogenous recombinant murine Epo, untimely onset of reticulocytosis was shown to augment multiplication of parasites and result in lethal infection. However, timely inducement of reticulocytosis with Epo treatment alleviated malarial anemia and increased survival. Our data reveal the important role of Epo-induced reticulocytosis in modulating the course and outcome of blood-stage malaria. However, the mechanisms underlying the increased mortality associated with untimely treatment with Epo and the increased protection associated with timely treatment with Epo remain to be investigated.

Topics: Animals; Disease Models, Animal; Disease Susceptibility; Epoetin Alfa; Erythropoietin; Malaria; Male; Mice; Mice, Inbred A; Mice, Inbred C57BL; Plasmodium chabaudi; Recombinant Proteins; Reticulocytosis; Treatment Outcome