scholarly journals Is Tmprss6 Required for Hepcidin Inhibition By Erythroferrone?

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 1347-1347 ◽  
Author(s):  
Laura Silvestri ◽  
Grazia Rita Gelsomino ◽  
Antonella Nai ◽  
Marco Rausa ◽  
Alessia Pagani ◽  
...  

Abstract Introduction Hepcidin, the main regulator of iron homeostasis, is inhibited when erythropoiesis is expanded. Several candidates, as GDF15 and TWSG1, have been proposed to mediate this effect but their role remains unproven. Recently, erythroferrone (ERFE), a member of the C1q/tumors necrosis factor-related protein family, has been identified as a new hepcidin inhibitor (Kautz et al., 2014). ERFE is an erythropoietin (EPO) target gene produced by bone marrow and spleen erythroblasts in conditions of stress erythropoiesis, as after bleeding or EPO treatment, and in ineffective erythropoiesis, as in beta thalassemia. Inhibiting hepatocyte hepcidin, ERFE coordinates erythroid differentiation with iron availability. In beta-thalassemia Hbbth3/+ mice, inactivation of Erfe partially reduces liver iron content, suggesting that increased Erfe production contributes to thalassemia iron overload (Kautz et al., 2014). Here we analyzed spleen Erfe expression in models of low (iron loaded Hjv-/- and Tfr2-/- mice) and high (iron deficient, Tmprss6-/- mice) hepcidin, in secondary iron overload (Hbbth3/+ mice), in Hbbth3/+ Tmprss6-/- and Tfr2-/- Tmprss6-/- double mutants and in mice with a diet-induced iron deficiency. Methods Mice were maintained in accordance with the European Union guidelines. The study was approved by the IACUC of San Raffaele Scientific Institute, Milan, Italy. Hjv-/-, Tfr2-/-, Tmprss6-/- and double mutant (Tfr2-/- Tmprss6-/- or Hbbth3/+ Tmprss6-/-) adult male mice were studied. A group of adult wild type mice was maintained an iron-deficient diet (ID, <3 mg/kg iron) for 3 weeks. Appropriate controls were studied. Gene expression levels were measured by quantitative real-time-PCR. Hematological and iron parameters and serum erythropoietin were studied using standard procedures. Results We confirm that Erfe is increased in the spleen of Hbbth3/+ mice, characterized by anemia, ineffective erythropoiesis, high EPO, low hepcidin and iron overload. Erfe is upregulated also in Tmprss6-/- iron deficient animals, consistent with their increased serum Epo. However, their high hepcidin levels suggest that Tmprss6 is indispensable for Erfe-mediated hepcidin inhibition. Consistent with this interpretation, in Hbbth3/+Tmprss6-/- double mutant mice, in which ineffective erythropoiesis and anemia are partially rescued (Nai et al., 2012), hepcidin levels are higher than in Hbbth3/+ and comparable to those of Tmprss6-/- mice, although Erfe remains high and serum Epo levels are similarly increased in all the three genotypes (Tmprss6-/-, Hbbth3/+, Hbbth3/+Tmprss6-/-). To further confirm the need of Tmprss6 for Erfe function, in diet-induced iron deficient animals, in which Tmprss6 is supposed to be active, Erfe expression is increased and hepcidin strongly downregulated. In the spleen of Hjv-/- and Tfr2-/- mice, the expression of the erythroid markers Tfr1 and Glycophorin A (Gypa) is decreased, suggesting that splenic erythropoiesis is reduced in iron overload. In agreement Erfe is downregulated in Tfr2-/- and mildly decreased in Hjv-/- mice. Genetic inactivation of Tmprss6 in Tfr2-/- mice enhances Erfe, Tfr1 and Gypa expression and serum Epo to levels comparable to Tmprss6-/- mice and increases hepcidin although at levels lower than those found in Tmprss6-/-. Conclusions Erfe upregulation in iron deficiency indicates that it is a general mediator of hepcidin inhibition. In Tmprss6-/- mice, notwithstanding Erfe upregulation, hepcidin levels are not suppressed, suggesting that Erfe acts upstream Tmprss6, although results in the double mutant Tfr2-/-Tmprss6-/- require further studies. In disease models of iron overload Erfe expression is downregulated, consistent with decreased splenic erythropoiesis. The mechanisms of hepcidin inhibition by Erfe still remain to be investigated. Disclosures No relevant conflicts of interest to declare.

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 816-816 ◽  
Author(s):  
Alexis A. Thompson ◽  
Tomas Ganz ◽  
Mary Therese Forsyth ◽  
Elizabeta Nemeth ◽  
Sherif M. Badawy

BACKGROUND: Ineffective erythropoiesis in thalassemia alters iron homeostasis, predisposing to systemic iron overload. Successful allogeneic hematopoietic stem cell transplantation (HSCT) in thalassemia major corrects anemia, should eliminate ineffective erythropoiesis (IE) and normalize iron homeostasis (IH). Whether gene therapy (GT) will fully correct IE and IH is not known. This cross-sectional observational study evaluated the iron status of patients with beta thalassemia following HSCT or GT, and compared them with cohorts of patients with thalassemia intermedia (TI) or transfusion-dependent thalassemia (TDT) using recently introduced biomarkers along with imaging studies and other clinical assessments to better understand and characterize IE and IH across groups. METHODS: We evaluated a convenience sample of 29 participants with beta thalassemia (median age 25 years, IQR 21-35; females 55%; Asian 52%). Participants in the HSCT (n=6) and GT (n=10) groups were evaluated on average 116.5 and 46.9 months following cell infusion, respectively. TDT patients (n= 9) were evaluated pre-transfusion and off iron chelation for at least 7 days, and TI (n=4) were un-transfused or not transfused in &gt;3 years. Clinical lab assessments and MRI R2*/ T2* to assess heart and liver iron burden including post-processing, were performed using local clinical protocols. ELISAs for hepcidin, erythroferrone (Erfe) and GDF-15 were performed in a blinded manner. RESULTS: Median values for all IE and IH parameters tested were normal in the HSCT group, and were significantly lower than in all other groups. There were significant differences among all groups for hemoglobin (p=0.003), erythropoietin (Epo) (p=0.03), serum ferritin (SF) (p=0.01), transferrin (p=0.006), soluble transferrin receptor (sTfR) (p=0.02), serum hepcidin: serum ferritin (H:F) ratio (p=0.006), Erfe (p=0.001), GDF15 (p=0.003), and liver iron content (LIC) by MRI R2* (p=0.02). H:F ratio, a surrogate for predisposition to systemic iron loading, inversely correlated with Erfe (rs= -0.85, p&lt;0.0001), GDF15 (rs= -0.69, p=0.0001) and liver R2* (rs= -0.66, p=0.0004). In a multivariate analysis, adjusted for gender and race, H:F ratio and Epo levels predicted Erfe and GDF15 (p=0.05 and p=0.06; p=0.01 and p=0.05), respectively. Even after excluding GT patients that are not transfusion independent (N=2), SF, Epo, sTfR and hepcidin remain abnormal in the GT group, and there were no significant differences in these parameters between GT and TDT. However, novel biomarkers of IH and IE suggested lower ineffective erythropoiesis in GT compared to TDT (median (IQR) Erfe, 12 (11.6-25.2) vs. 39.6 (24.5-54.7), p=0.03; GDF15, 1909.9 (1389-4431) vs. 8906 (4421-12331), p=0.02), respectively. Erfe and GDF15 were also lower in GT compared to TI, however these differences did not reach statistical significance. There were no differences in hepcidin, ferritin, or H:F by race, however Erfe and GDF15 were significantly lower in Asians compared to non-Asians (p=0.006 and p=0.02, respectively). CONCLUSION: Nearly 4 years post infusion, most subjects with TDT treated with GT are transfusion independent with near normal hemoglobin, however, studies in this limited cohort using conventional measures suggest IE and IH improve, particularly when transfusion support is no longer needed, however they remain abnormal compared to HSCT recipients, who using these parameters appear to be cured. STfR did not detect differences, however GDF15 and Erfe were more sensitive assays that could demonstrate significant improvement in IE and IH with GT compared to TDT. Contribution to IE by uncorrected stem cell populations post GT cannot be determined. Transduction enhancement and other recent improvements to GT may yield different results. Longitudinal studies are needed to determine if thalassemia patients treated with GT will have ongoing IE predisposing to systemic iron overload. Disclosures Thompson: bluebird bio, Inc.: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Baxalta: Research Funding. Ganz:Intrinsic LifeSciences: Consultancy, Equity Ownership. Nemeth:Intrinsic LifeSciences: Consultancy, Equity Ownership; Silarus Therapeutics: Consultancy, Equity Ownership; Keryx: Consultancy; Ionis Pharmaceuticals: Consultancy; La Jolla Pharma: Consultancy; Protagonist: Consultancy.


Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 73-73
Author(s):  
Antonella Nai ◽  
Maria Rosa Lidonnici ◽  
Irene Artuso ◽  
Giacomo Mandelli ◽  
Mariateresa Pettinato ◽  
...  

Abstract Transferrin receptor 2 (TFR2), a liver activator of the iron hormone hepcidin mutated in hemochromatosis type 3 (Camaschella C. et al., Nat Genet 2000), is an erythropoietin (EPO) receptor partner in erythroid cells (Forejtnikovà H. et al., Blood 2010). We have recently shown that the loss of bone marrow (BM) Tfr2 increases erythroblast EPO sensitivity and mimics a condition of mild iron-deficiency in mice (Nai A. et al., Blood 2015). β-thalassemias are iron-loading anemias due to recessive mutations in the β-globin gene, characterized by severe ineffective erythropoiesis. Since several studies demonstrated that iron restriction ameliorates the β-thalassemia phenotype, we generated thalassemic mice (Hbbth3/+) with selective BM inactivation of Tfr2 (Tfr2BMKO/Hbbth3/+) through transplantation of BM cells (BMT) from Hbbth3/+ and Tfr2-/-/Hbbth3/+ mice into lethally irradiated wt recipients. Two months after BMT Tfr2BMKO/Hbbth3/+ mice have Hb levels higher than Hbbth3/+ (Hbbth3/+: 9.47±0.59 g/dL; Tfr2BMKO/Hbbth3/+: 11.22±0.47 g/dL; p<0.0001). In contrast, 4 months after BMT Tfr2BMKO/Hbbth3/+ mice have more severe anemia, ineffective and extramedullary erythropoiesis, increased iron in serum (TS) and liver (LIC), reduced spleen iron (SIC), high hepcidin levels, increased Epo-target gene (Epor, Bcl-xL, Erfe) expression in BM and high levels of serum Erfe. These results suggest that deleting Tfr2 in thalassemic erythroblasts increases their Epo sensitivity as occurs in normal ones. This effect is positive during BM repopulation, but transient: on a long-term a severe phenotype develops, similar to the one observed in thalassemia major models (Rivella S. et al., Blood 2003; Huo Y. et al., Blood 2009), likely induced by excessive EPO stimulation of ineffective immature erythropoiesis. We speculate thatin Tfr2BMKO/Hbbth3/+ mice the continuous production of Erfe, the hepcidin inhibitor released by the expanded marrow (Kautz L. et al., Nat Genet 2014), worsens iron-overload, further damaging the thalassemic erythropoiesis. In order to exclude any interference of BMT, we analyzed also Hbbth3/+, Tfr2+/-/Hbbth3/+ and Tfr2-/-/Hbbth3/+ mice, lacking germ-line Tfr2 at the heterozygous and homozygous state respectively. Preliminary data indicate that young Tfr2-/-/Hbbth3/+ mice have less severe anemia than Hbbth3/+, while Tfr2+/-/Hbbth3/+ animals have an intermediate phenotype, suggesting that Tfr2 haploinsufficiency may be sufficient to improve the ineffective erythropoiesis at short time point. Follow up analysis will test whether the phenotype of Tfr2-/-/Hbbth3/+ mice worsens with aging as occurs in transplanted animals. Interestingly we noticed that 2-month-old Tfr2-/-/Hbbth3/+ mice, beside higher Hb levels, have higher LIC than thalassemic littermates, with comparable SIC. This observation lead us to hypothesize that low SIC, rather than high LIC, contributes to the worsening of the phenotype in Tfr2BMKO/Hbbth3/+ mice 4 months after BMT, likely impairing the compensatory spleen erythropoiesis. To dissect causality between high LIC and low SIC we are challenging transplanted mice with iron-deficient diet to decrease LIC or with iron-dextran injection to increase SIC. Moreover, a group of animals sacrificed 2 months after BMT will help to elucidate the mechanism(s) of the early amelioration of anemia. Preliminary results confirm the Hb and red cells count increase in Tfr2BMKO/Hbbth3/+ as compared to Hbbth3/+mice 2 months after BMT without increased spleen size, thus suggesting a real erythropoiesis improvement at this time point. Erythroid cells at the different stages of maturation sorted from these animals will be subjected to RNAseq analysis in comparison to cells isolated from animals at the time of phenotype worsening. The results are expected to define the pathway/s altered by the loss of Tfr2 in thalassemic erythroid cells and those responsible for the amelioration of the phenotype with the aim of identifying potential novel target/s for therapy of β-thalassemia. Disclosures No relevant conflicts of interest to declare.


Endocrinology ◽  
2011 ◽  
Vol 152 (8) ◽  
pp. 3062-3073 ◽  
Author(s):  
Suzana Kovac ◽  
Gregory J. Anderson ◽  
Warren S. Alexander ◽  
Arthur Shulkes ◽  
Graham S. Baldwin

Gastrins are peptide hormones important for gastric acid secretion and growth of the gastrointestinal mucosa. We have previously demonstrated that ferric ions bind to gastrins, that the gastrin-ferric ion complex interacts with the iron transport protein transferrin in vitro, and that circulating gastrin concentrations positively correlate with transferrin saturation in vivo. Here we report the effect of long-term dietary iron modification on gastrin-deficient (Gas−/−) and hypergastrinemic cholecystokinin receptor 2-deficient (Cck2r−/−) mice, both of which have reduced basal gastric acid secretion. Iron homeostasis in both strains appeared normal unless the animals were challenged by iron deficiency. When fed an iron-deficient diet, Gas−/− mice, but not Cck2r−/−mice, developed severe anemia. In iron-deficient Gas−/−mice, massive splenomegaly was also apparent with an increased number of splenic megakaryocytes accompanied by thrombocytosis. The expression of the mRNA encoding the iron-regulatory peptide hepcidin, Hamp, was down-regulated in both Cck2r−/− and Gas−/−mice on a low-iron diet, but, interestingly, the reduction was greater in Cck2r−/− mice and smaller in Gas−/− mice than in the corresponding wild-type strains. These data suggest that gastrins play an important direct role, unrelated to their ability to stimulate acid secretion, in hematopoiesis under conditions of iron deficiency.


Hematology ◽  
2013 ◽  
Vol 2013 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Clara Camaschella

Abstract To avoid iron deficiency and overload, iron availability is tightly regulated at both the cellular and systemic levels. The liver peptide hepcidin controls iron flux to plasma from enterocytes and macrophages through degradation of the cellular iron exporter ferroportin. The hepcidin-ferroportin axis is essential to maintaining iron homeostasis. Genetic inactivation of proteins of the hepcidin-activating pathway causes iron overload of varying severity in human and mice. Hepcidin insufficiency and increased iron absorption are also characteristic of anemia due to ineffective erythropoiesis in which, despite high total body iron, hepcidin is suppressed by the high erythropoietic activity, worsening both iron overload and anemia in a vicious cycle. Hepcidin excess resulting from genetic inactivation of a hepcidin inhibitor, the transmembrane protease serine 6 (TMPRSS6) leads to a form of iron deficiency refractory to oral iron. Increased hepcidin explains the iron sequestration and iron-restricted erythropoiesis of anemia associated with chronic inflammatory diseases. In mice, deletion of TMPRSS6 in vivo has profound effects on the iron phenotype of hemochromatosis and beta-thalassemia. Hepcidin manipulation to restrict iron is a successful strategy to improve erythropoiesis in thalassemia, as shown clearly in preclinical studies targeting TMPRSS6; attempts to control anemia of chronic diseases by antagonizing the hepcidin effect are ongoing. Finally, the metabolic pathways identified from iron disorders are now being explored in other human pathologic conditions, including cancer.


Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3581-3581
Author(s):  
Seth Rivera ◽  
Miguel Lopez ◽  
Dina Farshidi ◽  
Victoria Gabayan ◽  
Tomas Ganz

Abstract In extracellular fluid, iron is in the ferric (oxidized form) but the intracellular form is ferrous iron (reduced). The outflow of iron from cells is dependent on oxidase activity that converts ferrous to ferric iron. Iron-absorbing enterocytes possess a unique iron oxidase, hephaestin. It is presumed that the circulating hephaestin paralog ceruloplasmin fulfils this role in hepatocytes and macrophages. The DiSnA mouse lacks ceruloplasmin. We hypothesized that iron homeostasis in this mouse would be unusually dependent on dietary iron because the mouse would not be able to mobilize iron from tissue stores in hepatocytes and macrophages. We fed 4-week-old DiSnA and wildtype (WT) mice a high iron (1%) diet for 4 weeks to load tissue stores. We then switched them to an iron-deficient diet and analyzed them weekly to measure iron and hemoglobin concentrations. Even on the high iron diet, DiSnA mice had lower serum iron concentrations than WT control (32.9±17.9 vs. 53.5±17.6 μM, p=0.05) but after two weeks on the iron deficient diet, the DiSnA mice had almost undetectable serum iron (4.2±1.8 μM) whereas the WT controls had only declined slightly (43.2±9.6 μM, p&lt;0.001). Iron saturation followed a similar trend. Neither WT nor DiSnA mice were anemic at baseline (Hgb = 13.9±0.3 and 13.9±1.1 g/dL, respectively; p=0.994) but by the end of two weeks, the DiSnA mice had developed anemia whereas the WT mice had not (Hgb = 10.4±0.5 vs. 12.6±0.5 g/dL; p&lt;0.001). The difference in hemoglobin concentrations persisted to the 6-week timepoint (Hgb = 8.4±0.5 vs. 12.6±1.4; p&lt;0.001). After 6-weeks on a low iron diet, iron was still present in livers and spleens of both groups. Ceruloplasmin is essential for the mobilization of iron stores to protect against iron deficiency anemia in response to periods of dietary iron deficiency.


Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4250-4250
Author(s):  
Valeria Santini ◽  
Domenico Girelli ◽  
Alessandro Sanna ◽  
Nicola Martinelli ◽  
Lorena Duca ◽  
...  

Abstract Abstract 4250 Background and Aims. Iron overload is frequently occurring in patients with myelodysplastic syndromes (MDS), with recent data suggesting an impact on both overall and leukemia-free survival1,2. Though prolonged RBC transfusion therapy appears the main contributor, many patients develop iron overload at an early stage of the disease, before the onset of transfusion dependency. It has been postulated that an altered production of hepcidin, the key hormone regulating iron homeostasis, may play a role at this regard. Until recently, studies have been hampered by problems in the development of reliable hepcidin assays, so that only scanty and conflicting data based on semi-quantitative measurement of urinary hepcidin have been reported3,4. This study mainly focused on analyzing serum hepcidin levels in MDS patients by means of a recently validated and improved Mass-Spectrometry based method5. Patients and Methods. One hundred and thirteen consecutive patients (mean age 72.8 ± 9.2 years; 68.1% males) with different types of MDS according to the WHO classification were included in this study. To be enrolled, patients had to be previously untreated or treated only with transfusions. Besides hepcidin, in all subjects we determined serum ferritin, transferrin saturation (TS), non-transferrin-bound-iron (NTBI), along with some putative determinants of hepcidin, like GDF-156 known to be associated with ineffective erythropoiesis, and C-Reactive Protein (CRP) as a surrogate of systemic IL-6 production. Fifty-four healthy individuals (61.1% males) with rigorous definition of normal iron status were used as controls. Main Results. Biochemical markers of iron overload (ferritin and TS), but also CRP and GDF-15 were significantly higher in MDS patients than in controls, even when considering only non-transfused patients. Patients with RARS and the 5q- syndrome appeared as the most iron overloaded, having the highest levels of ferritin, TS, and NTBI. In the whole MDS population, serum hepcidin levels showed a considerable variability, with overall mean values not significantly different from controls [geometric means (gm) with 95% CIs: 5.31 (3.98-7.08) versus 4.2 (3.53-5.0) nM, P=0.28], while the hepcidin/ferritin ratio was significantly lower than in controls [10.1 (7.53-13.53) versus 52.9 (43.6-64.3), P<0.001]. After stratification according to WHO subtypes, hepcidin levels showed significant differences, with the lowest levels in patients with RARS (gm 1.43 nM) and the highest levels in patients with RAEB 1–2 (gm 11.3 nM) and with CMML (gm 10.04 nM) (P=0.003 by ANOVA). The latter groups had substantial elevation of CRP as compared to other MDS subtypes (P=0.008 by ANOVA), while GDF-15 was consistently but uniformly elevated in all MDS subtypes (P=0.97 by ANOVA). Multivariate linear regression models adjusted also for age, sex, and history of RBC transfusions, showed ferritin (β-coefficient 0.45, P=0.002), CRP (β-coefficient 0.21, P=0.02), and different MDS subtypes as the main independent predictors of hepcidin levels. The different degree of correlation between hepcidin and ferritin among the MDS subtypes were analyzed in a general linear model using the F test for slopes. Hepcidin regulation by iron appeared conserved, though relatively blunted in RA, RARS, and 5q- patients, while it was lost in RAEB 1–2 and CMML. Conclusions. Hepcidin levels are consistently heterogeneous in MDS according to different subtypes, likely as the result of the relative strength of competing stimuli. Relative inhibition by ineffective erythropoiesis (but not mediated by GDF-15) seems to prevail particularly in RARS and 5q- syndrome, and is likely to increase the risk of iron overload in these subgroups. On the other hand, patients with RAEB 1–2 and CMML appears to have hepcidin induction that could be driven by cytokines. If confirmed, these results may be relevant not only for a better understanding of iron pathophysiology in MDS, but also for possible future approach with hepcidin modulators7. References: 1) Sanz G, et al. Blood 2008;112: abs 640. 2) Alessandrino EP, et al. Haematologica 2010;95:476-84. 3) Winder A, et al. Br J Haematol 2008;142:669-71. 4) Murphy PT, et al. Br J Haematol 2009;144:451-2. 5) Campostrini N, et al. J Biomed Biotechnol 2010;2010:329646. 6) Tanno T, et al. Nat Med 2007;13:1096-101. 7) Sasu BJ, et al. Blood 2010;115:3616-24. Disclosures: No relevant conflicts of interest to declare.


Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 2340-2340 ◽  
Author(s):  
Sandro Altamura ◽  
Sandro Altamura ◽  
Martina U. Muckenthaler ◽  
Sibylle Dames ◽  
Christian Frauendorf ◽  
...  

Abstract Accumulation of excess iron in tissues causes organ damage and dysfunction and may lead to serious clinical consequences including liver cirrhosis, diabetes, growth retardation and heart failure. Iron overload is a major health threat in iron loading anemias, like beta-thalassemia, myelodysplastic syndrome and in hereditary hemochromatosis. In patients with beta-thalassemia major, iron overload develops due to frequent blood transfusions to control the severe anemia. In addition, iron overload also occurs in patients with beta thalassemia intermedia (non-transfusion dependent beta-thalassemia). In the later cases, iron overload develops through gastrointestinal iron hyperabsorption due to stressed and ineffective erythropoiesis. Importantly, expression of the peptide hormone hepcidin, which is the key modulator in iron homeostasis, is abnormally low and unable to block ferroportin-mediated intestinal iron absorption. In hereditary hemochromatosis, gene defects in the hepcidin-ferroportin axis controlling iron homeostasis, lead to hepatic iron overload. Therefore, in these indications, iron overload is caused by dysregulation or dysfunction of the hepcidin-ferroportin axis. Hepcidin is predominantly produced by the liver and is induced by activation of the BMP/SMAD signaling pathway. Furthermore, hepcidin is under the negative control of the transmembrane protease matriptase-2, encoded by the TMPRSS6 gene. RNA interference is a natural mechanism and a powerful approach for inhibiting the expression of disease-associated genes. Silence Therapeutics has developed short interfering RNA (siRNA) conjugate technology for the selective inhibition of target gene expression in the liver. GalNAc-conjugated siRNAs bind efficiently to the asialoglycoprotein (ASGP) receptor expressed predominantly by hepatocytes thereby providing a highly specific, safe and efficient delivery technology to enable a new class of therapeutic use. Here we present the pharmacological characterization of SLN124, our GalNAc-siRNA conjugate targeting TMPRSS6 expression, in preclinical models. A single subcutaneous administration is sufficient to achieve significant modulation of target gene expression in mice and in non-human primates over several weeks. SLN124 treatment reduces systemic iron levels, transferrin saturation and tissue iron levels in a rodent model for hereditary hemochromatosis type 1. In addition, we report for the first time the therapeutic efficacy of iron restriction by SLN124 in mice with established iron overload both as monotherapy and in combination with an oral iron chelator - current standard of care- over an extended treatment period. The effects of these treatments on red blood cell parameters and tissue iron levels will be presented. In addition, we assessed the therapeutic effects of SLN124 in an animal model for beta-thalassemia intermedia, showing dose-dependent and long-lasting effects on target gene expression as well as on modulation of iron stores and normalization of erythropoiesis and anemia. Safety and tolerability studies in relevant preclinical models confirmed that SLN124 is well tolerated and shows promise as an effective and safe treatment for unmet medical need in iron loading anemias, such as beta-thalassemia. SLN124 is currently in preclinical development. The first in human study is planned to commence in 2019 in patients with beta-thalassemia and in patients with myelodysplastic syndrome. Disclosures Muckenthaler: Novartis: Research Funding. Dames:Silence Therapeutics GmbH: Employment. Frauendorf:Silence Therapeutics GmbH: Employment. Schubert:Silence Therapeutics GmbH: Employment. Aleku:Silence Therapeutics GmbH: Employment. Zügel:Silence Therapeutics GmbH: Employment.


2022 ◽  
Author(s):  
Amanda K. Barks ◽  
Montana M. Beeson ◽  
Timothy C. Hallstrom ◽  
Michael K. Georgieff ◽  
Phu V. Tran

Iron deficiency (ID) during neurodevelopment is associated with lasting cognitive and socioemotional deficits, and increased risk for neuropsychiatric disease throughout the lifespan. These neurophenotypical changes are underlain by gene dysregulation in the brain that outlasts the period of ID; however, the mechanisms by which ID establishes and maintains gene expression changes are incompletely understood. The epigenetic modification 5-hydroxymethylcytosine (5hmC), or DNA hydroxymethylation, is one candidate mechanism because of its dependence on iron-containing TET enzymes. The aim of the present study was to determine the effect of fetal-neonatal ID on regional brain TET activity, Tet expression, and 5hmC in the developing rat hippocampus and cerebellum, and to determine whether changes are reversible with dietary iron treatment. Timed pregnant Sprague-Dawley rats were fed iron deficient diet (ID; 4 mg/kg Fe) from gestational day (G)2 to generate iron deficient anemic (IDA) offspring. Control dams were fed iron sufficient diet (IS; 200 mg/kg Fe). At postnatal day (P)7, a subset of ID-fed litters was randomized to IS diet, generating treated IDA (TIDA) offspring. At P15, hippocampus and cerebellum were isolated for subsequent analysis. TET activity was quantified by ELISA from nuclear proteins. Expression of Tet1, Tet2, and Tet3 was quantified by qPCR from total RNA. Global %5hmC was quantified by ELISA from genomic DNA. ID increased DNA hydroxymethylation (p=0.0105), with a corresponding increase in TET activity (p<0.0001) and Tet3 expression (p<0.0001) in the P15 hippocampus. In contrast, ID reduced TET activity (p=0.0016) in the P15 cerebellum, with minimal effect on DNA hydroxymethylation. Neonatal dietary iron treatment resulted in partial normalization of these changes in both brain regions. These results demonstrate that the TET/DNA hydroxymethylation system is disrupted by developmental ID in a brain region-specific manner. Differential regional disruption of this epigenetic system may contribute to the lasting neural circuit dysfunction and neurobehavioral dysfunction associated with developmental ID.


2011 ◽  
Vol 47 (3) ◽  
pp. 151-160 ◽  
Author(s):  
Jennifer L. McCown ◽  
Andrew J. Specht

Iron is an essential element for nearly all living organisms and disruption of iron homeostasis can lead to a number of clinical manifestations. Iron is used in the formation of both hemoglobin and myoglobin, as well as numerous enzyme systems of the body. Disorders of iron in the body include iron deficiency anemia, anemia of inflammatory disease, and iron overload. This article reviews normal iron metabolism, disease syndromes of iron imbalance, diagnostic testing, and treatment of either iron deficiency or excess. Recent advances in diagnosing iron deficiency using reticulocyte indices are reviewed.


Endocrinology ◽  
2021 ◽  
Author(s):  
Hannah Roberts ◽  
Andrew G Woodman ◽  
Kelly J Baines ◽  
Mariyan J Jeyarajah ◽  
Stephane L Bourque ◽  
...  

Abstract Iron deficiency occurs when iron demands chronically exceed intake, and is prevalent in pregnant women. Iron deficiency during pregnancy poses major risks for the baby, including fetal growth restriction and long-term health complications. The placenta serves as the interface between a pregnant mother and her baby, and ensures adequate nutrient provisions for the fetus. Thus, maternal iron deficiency may impact fetal growth and development by altering placental function. We used a rat model of diet-induced iron deficiency to investigate changes in placental growth and development. Pregnant Sprague-Dawley rats were fed either a low-iron or iron-replete diet starting two weeks before mating. Compared to controls, both maternal and fetal hemoglobin were reduced in dams fed low-iron diets. Iron deficiency decreased fetal liver and body weight, but not brain, heart or kidney weight. Placental weight was increased in iron deficiency, due primarily to expansion of the placental junctional zone. The stimulatory effect of iron deficiency on junctional zone development was recapitulated in vitro, as exposure of rat trophoblast stem cells to the iron chelator deferoxamine increased differentiation toward junctional zone trophoblast subtypes. Gene expression analysis revealed 464 transcripts changed at least 1.5-fold (P&lt;0.05) in placentas from iron-deficient dams, including altered expression of genes associated with oxygen transport and lipoprotein metabolism. Expression of genes associated with iron homeostasis was unchanged despite differences in levels of their encoded proteins. Our findings reveal robust changes in placentation during maternal iron deficiency, which could contribute to the increased risk of fetal distress in these pregnancies.


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