Molecular Medicine Branch

Bethesda, MD, United States

Molecular Medicine Branch

Bethesda, MD, United States
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Tanno T.,Molecular Medicine Branch | Noel P.,U.S. National Institutes of Health | Miller J.L.,Molecular Medicine Branch
Current Opinion in Hematology | Year: 2010

PURPOSE OF REVIEW: Growth differentiation factor 15 (GDF15) was identified as a hepcidin-suppression factor that is expressed at high levels in patients with ineffective erythropoiesis. This review addresses the regulation, expression and potential functions of GDF15 in the context of erythroid biology. RECENT FINDINGS: GDF15 expression during late erythroid differentiation was discovered as part of an erythroblast transcriptome project. As GDF15 expression is associated with cellular stress or apoptosis, further investigation of the cytokine was focused upon its involvement in ineffective erythropoiesis. Remarkably high serum levels were detected in patients with thalassemia syndromes, congenital dyserythropoiesis and some acquired sideroblastic anemias. High-level GDF15 expression is not a feature of normal erythropoiesis, or erythroid recovery after bone-marrow transplantation. As GDF15 is a transforming growth factor-β superfamily member, it was investigated as an effector of ineffective erythropoiesis that suppresses hepcidin expression despite iron overloading. SUMMARY: In contrast to the low levels of GDF15 expressed during normal erythropoiesis, ineffective erythropoiesis causes high-level expression of GDF15. In patients with thalassemia and related anemias, GDF15 expression may contribute to iron overloading or other features of the disease phenotype. © 2010 Lippincott Williams & Wilkins, Inc.

Tanno T.,Molecular Medicine Branch | Rabel A.,Molecular Medicine Branch | Lee Y.T.,Molecular Medicine Branch | Yau Y.Y.,Molecular Medicine Branch | And 2 more authors.
Transfusion | Year: 2010

Background: Low serum hepcidin levels provide a physiologic response to iron demand in patients with iron deficiency (ID). Based on a discovery of suppressed hepcidin expression by a cytokine named growth differentiation factor 15 (GDF15), it was hypothesized that GDF15 may suppress hepcidin expression in humans with ID due to blood loss. Study Design and Methods: To test this hypothesis, GDF15 and hepcidin levels were measured in peripheral blood from subjects with iron-deficient erythropoiesis before and after iron supplementation. Results: Iron variables and hepcidin levels were significantly suppressed in iron-deficient blood donors compared to healthy volunteers. However, ID was not associated with elevated serum levels of GDF15. Instead, iron-deficient subjects' GDF15 levels were slightly lower than those measured in the control group of subjects (307 ± 90 and 386 ± 104 pg/mL, respectively). Additionally, GDF15 levels were not significantly altered by iron repletion. Conclusions: ID due to blood loss is not associated with a significant change in serum levels of GDF15. © 2010 American Association of Blood Banks.

Rogers H.,Molecular Medicine Branch | Wang L.,Molecular Medicine Branch | Yu X.,Molecular Medicine Branch | Yu X.,University of California at San Francisco | And 8 more authors.
Journal of Biological Chemistry | Year: 2012

Background: Erythropoietin is required for erythrocyte production and stimulates erythroid gene expression including EPO-R. Results: TAL1 induction promotes accessibility of EPO-R promoter to the GATA-1-TAL1-LMO2-LDB1 transcription activation complex to increase EPO-R expression. Conclusion: Forced TAL1 expression increases EPO-R and erythropoietin hypersensitivity in erythroid progenitors. Significance: Providing insight into the molecular link between TAL1 and erythropoietin activity.

PubMed | Molecular Medicine Branch
Type: | Journal: Journal of visualized experiments : JoVE | Year: 2017

Nitric oxide (NO) is one of the main regulator molecules in vascular homeostasis and also a neurotransmitter. Enzymatically produced NO is oxidized into nitrite and nitrate by interactions with various oxy-heme proteins and other still not well known pathways. The reverse process, reduction of nitrite and nitrate into NO had been discovered in mammals in the last decade and it is gaining attention as one of the possible pathways to either prevent or ease a whole range of cardiovascular, metabolic and muscular disorders that are thought to be associated with decreased levels of NO. It is therefore important to estimate the amount of NO and its metabolites in different body compartments - blood, body fluids and the various tissues. Blood, due to its easy accessibility, is the preferred compartment used for estimation of NO metabolites. Due to its short lifetime (few milliseconds) and low sub-nanomolar concentration, direct reliable measurements of blood NO in vivo present great technical difficulties. Thus NO availability is usually estimated based on the amount of its oxidation products, nitrite and nitrate. These two metabolites are always measured separately. There are several well established methods to determine their concentrations in biological fluids and tissues. Here we present a protocol for chemiluminescence method (CL), based on spectrophotometrical detection of NO after nitrite or nitrate reduction by tri-iodide or vanadium(III) chloride solutions, respectively. The sensitivity for nitrite and nitrate detection is in low nanomolar range, which sets CL as the most sensitive method currently available to determine changes in NO metabolic pathways. We explain in detail how to prepare samples from biological fluids and tissues in order to preserve original amounts of nitrite and nitrate present at the time of collection and how to determine their respective amounts in samples. Limitations of the CL technique are also explained.

PubMed | Urologic, Molecular Medicine Branch, Biostatistics Program and. and Molecular Medicine Branch.
Type: Comparative Study | Journal: Clinical journal of the American Society of Nephrology : CJASN | Year: 2015

Recombinant human erythropoietin (epoetin) is used routinely to increase blood hemoglobin levels in patients with ESRD and anemia. Although lower doses of epoetin are required to achieve equivalent hemoglobin responses when administered subcutaneously rather than intravenously, standard practice has been to administer epoetin to patients on hemodialysis intravenously. Randomized trials of alternative epoetin treatment regimens in patients with kidney failure have shown that risks of cardiovascular complications and death are related to the dose levels of epoetin used. Therefore, given the dose-sparing advantages of subcutaneous epoetin administration, the possibility that treatment of patients on hemodialysis with subcutaneous epoetin might be associated with more favorable outcomes compared with intravenous treatment was investigated.A retrospective cohort study of 62,710 adult patients on hemodialysis treated with either intravenous or subcutaneous epoetin- and enrolled in the Centers for Medicare and Medicaid Services ESRD Clinical Performance Measures Project from 1997 to 2005 was carried out. Risks of death and/or hospitalization for cardiovascular complications (adverse composite event outcomes) during 2 years of follow-up were determined in relationship to epoetin dose and route of administration (intravenous versus subcutaneous) by multivariate Cox proportional hazard modeling adjusted for demographics and clinical parameters.Epoetin doses used to achieve equivalent hemoglobin responses in study patients were, on average, 25% higher when epoetin was administered intravenously rather than subcutaneously (as expected). Moreover, adverse composite event outcomes were found to be significantly more likely to occur during follow-up for patients on hemodialysis managed with intravenous rather than subcutaneous epoetin (adjusted hazard ratio for adverse events within 1 year [intravenous versus subcutaneous] was 1.11 [95% confidence interval, 1.04 to 1.18]).This study finds that treatment of patients on hemodialysis with subcutaneous epoetin is associated with more favorable clinical outcomes than those associated with intravenous epoetin treatment.

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