Iron Overload, Oxidative Damage and Ineffective Erythropoiesis in Myelodysplastic Syndromes

2010 ◽  
Vol 00 (04) ◽  
pp. 34 ◽  
Author(s):  
Rosangela Invernizzi ◽  
Keyword(s):  
Oxidative Damage ◽  
Iron Overload ◽  
Myelodysplastic Syndromes ◽  
Iron Homeostasis ◽  
Current Knowledge ◽  
Early Stage ◽  
Refractory Anaemia ◽  
Ineffective Erythropoiesis ◽  
Ring Sideroblasts ◽  
High Level

A high level of apoptosis may be responsible for the ineffective haematopoiesis in myelodysplastic syndromes (MDS). Recently, it has been demonstrated that the erythroid apoptosis of low-risk MDS is initiated at a very early stage in stem cells and is associated with mitochondrial dysfunction. However, the underlying pathogenetic mechanisms causing malfunctioning of mitochondria and initiation of the intrinsic apoptotic cascade are not completely clear. Recent studies suggest a close relationship between impaired iron metabolism and pathogenesis of myelodysplasia. In fact, iron overload, which is apparent in refractory anaemia with and without ring sideroblasts, may lead to the generation of intracellular free radicals, thereby causing oxidative damage and inducing apoptosis in haematopoietic progenitors. This review summarises current knowledge supporting the role of iron-related oxidative damage in the pathogenesis of MDS. The relationship between mitochondrial iron homeostasis impairment and ineffective erythropoiesis in refractory anaemia with ring sideroblasts as well as the various functions of the cytosolic and mitochondrial ferritins are also discussed.

scholarly journals Hepcidin Levels and Their Determinants In Different Types of Myelodysplastic Syndromes

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4250-4250
Author(s):  
Valeria Santini ◽  
Domenico Girelli ◽  
Alessandro Sanna ◽  
Nicola Martinelli ◽  
Lorena Duca ◽  
...  
Keyword(s):  
Iron Overload ◽  
Myelodysplastic Syndromes ◽  
Iron Homeostasis ◽  
Conflicts Of Interest ◽  
Iron Status ◽  
Transferrin Saturation ◽  
Ineffective Erythropoiesis ◽  
Transfusion Therapy ◽  
Different Types ◽  
Serum Hepcidin

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.

Does Gene Therapy in Beta Thalassemia Normalize Novel Markers of Ineffective Erythropoiesis and Iron Homeostasis?

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 816-816 ◽  
Author(s):  
Alexis A. Thompson ◽  
Tomas Ganz ◽  
Mary Therese Forsyth ◽  
Elizabeta Nemeth ◽  
Sherif M. Badawy
Keyword(s):  
Gene Therapy ◽  
Stem Cell ◽  
Iron Overload ◽  
Serum Ferritin ◽  
Research Funding ◽  
Iron Homeostasis ◽  
Beta Thalassemia ◽  
Ineffective Erythropoiesis ◽  
Liver Iron ◽  
Equity Ownership

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.

Erythroid Activity, Transfusion Iron Overload, and Hepcidin Levels in Patients with Myelodysplastic Syndrome

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 2676-2676 ◽  
Author(s):  
Luca Malcovati ◽  
Matteo G Della Porta ◽  
Coby M Laarakkers ◽  
Anna Gallì ◽  
Riccardo Albertini ◽  
...  
Keyword(s):  
High Risk ◽  
Iron Overload ◽  
Negative Impact ◽  
Multivariable Analysis ◽  
Organ Damage ◽  
Refractory Anemia ◽  
Ineffective Erythropoiesis ◽  
Ring Sideroblasts ◽  
Serum Hepcidin ◽  
Parenchymal Cells

Abstract The vast majority of patients with myelodysplastic syndrome (MDS) present with anemia, and many of them become transfusion dependent in the long term. Although transfusion iron is primarily taken up by the reticuloendothelial cells, the metal is later redistributed to parenchymal cells, and a portion of MDS patients develop parenchymal iron overload, which may have a negative impact on survival (N Engl J Med2005;352:536–8). The redistribution of transfusion iron from macrophages to parenchymal cells is likely to be modulated by hepcidin levels and erythroid activity. In fact, hepcidin prevents the release of iron from macrophages, and its synthesis is partly down-regulated by erythroid activity, which varies considerably within MDS patients. Expanded but ineffective erythropoiesis is the major mechanism responsible for anemia in low-risk MDS patients, particularly in those with refractory anemia with ringed sideroblasts, while erythroid marrow hypoproliferation is generally found in high-risk patients, typically in those with excess of blasts. We studied 76 patients with MDS followed at the Department of Hematology Oncology, University of Pavia & Fondazione IRCCS Policlinico San Matteo, Pavia, Italy. The WHO classification criteria were employed for diagnosis of MDS. Median time since diagnosis was 12 months (range 0–241). Twenty-five patients were RBC transfusion-dependent (median number of RBC units received was 15, range 4–160). Erythroid activity was evaluated through measurement of soluble transferrin receptor (sTfR) and serum Epo, while body iron status was assessed through serum iron, TIBC and serum ferritin (sFtn). Serum hepcidin was quantified by laser desorption ionization time-of-flight mass spectrometry preceded by weak cation-exchange chromatography exploiting des-Asp hepcidin (hepcidin-24) as an internal standard (www.hepcidinanalysis.com or PLoS ONE2008;16;3:e2706). sTfR levels were found to be independently associated with hemoglobin (Hb) (the higher Hb, the lower sTfR; P&lt;.001), serum Epo (the higher Epo, the lower sTfR; P&lt;.001), and WHO category (patients with purely erythroid disorders having higher values than those with multilineage dysplasia and excess blasts; P&lt;.001), as well as with sFtn (the higher sFtn, the lower sTfR; P=.02). A wide variability in hepcidin level was found in MDS patients (median 6.98 nM, range 0.18–92.05 nM). Patients with pure erythroid disorders had significantly lower hepcidin levels compared with those with multilineage dysplasia or excess of blasts (median values 4.41, 7.62, and 15.31 nM, respectively; P&lt;.001). Transfusion-dependent patients had significantly higher hepcidin levels compared with transfusion-independent subjects (15.31 vs 4.73 nM, P&lt;.001). Significant linear correlations were found between serum hepcidin and Hb (r=−.28, P=0.02), serum Epo (r=.44, P&lt;.001), sFtn (r=.68, P&lt;.001) and sTfR (r=−.64, P&lt;.001). Considering all MDS patients, multivariable analysis showed that serum hepcidin levels were independently determined by sTfR levels (the higher sTfR, the lower serum hepcidin; P&lt;.001) and sFtn (the higher sFtn, the higher serum hepcidin; P&lt;.001). Restricting multivariable analysis to MDS patients receiving regular blood transfusion, the presence of ring sideroblasts and their number were also found to have an independent, negative impact of serum hepcidin levels (P=.005). These findings suggest that in MDS patients the redistribution of transfusion iron from reticuloendothelial cells to parenchymal cells is influenced by erythroid activity through its effect on serum hepcidin levels. MDS patients with expanded but ineffective erythropoiesis have low levels of hepcidin and enhanced iron release from macrophages, and therefore a higher likelihood of parenchymal iron loading. In particular, patients with refractory anemia with ring sideroblasts show low hepcidin levels in spite of iron overload, and therefore appear to be at high risk of parenchymal organ damage. Since these this condition has a benign clinical course, preventing organ damage through iron chelation therapy appears clinically important.

The Relationship Between Erythropoetic Activity and Iron Burden In Patients With Myelodysplastic Syndrome

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 5225-5225
Author(s):  
Rui Cui ◽  
Guoqing Zhu ◽  
Zefeng Xu ◽  
Yue Zhang ◽  
Gang Huang ◽  
...  
Keyword(s):  
Iron Overload ◽  
Mrna Expression ◽  
Negative Correlation ◽  
Conflicts Of Interest ◽  
Early Stage ◽  
Iron Status ◽  
Multivariable Analysis ◽  
Refractory Anemia ◽  
Transfusion Therapy ◽  
High Level

Abstract Background Although prolonged red blood cells (RBC) transfusion therapy appears to be the main contributor to iron overload, many patients have developed it at an early stage of the disease, before the onset of transfusions in MDS. Growth differentiation factor 15 (GDF-15), a protein produced by erythroid precursors, has been proposed to be a major hepcidin suppressor in ß-thalassemia, but data in the expression of hepcidin and GDF15 levels in MDS are less conclusive. To determine whether the erythropoetic activity affect the iron burden though GDF15 in patients with MDS, we determined the GDF15 levels as well as other markers of erythropoiesis and iron overload (soluble transferrin receptor [sTfR], erythropoietin [EPO], ferritin and hepcidin) in MDS without transfution. Patients and Methods One hundred and seven consecutive patients (mean age 50 years; 62% males) with MDS diagnosed between April, 2011 and March, 2013 at the Institute of Hematology and Blood Disease Hospital, Chinese Academy of Medical Sciences (CAMS) were included. To be enrolled in this study, patients had to be previously treated without transfusion. To do a comparison with respect to serum hepcidin levels, the hepcidin/ferritin ratio and GDF15 levels, a group of forty healthy individuals (45% males) with rigorous definition of normal iron status were used as controls. Results MDS patients had significantly higher levels of serum SF, GDF-15, and EPO as compared to the controls. GDF15 concentrations significant positively correlated with percent of bone marrow erythroblasts (P <0.001), sTfR (P = 0.018), ISAT (P =0.038) and negatively correlated with TRF (P=0.008). The hepcidin to ferritin ratio was strongly decreased in MDS patients as compared to the controls (P<0.001). The hepcidin to ferritin ratio also showed a significant variability across different MDS subtypes (P = 0.011), with the lowest values in patients with refractory anemia with ringed sideroblasts (RARS). GDF15 levels consistently heterogeneous across different MDS subtypes (P=0.005), with the highest levels in patients with RARS and the lowest levels in the RAEB and RCMD cohorts. A negative correlation between the hepcidin/SF ratio and GDF15 was found(r=-0.279, P=0.014). Both hepcidin and hepcidin/SF ratio were negatively correlated with EPO in MDS patients (r=-0.250, P=0.022 and r=-0.449, P<0.001 respectively). Furthermore, a negative correlation between hepcidin levels and HIF-1α mRNA expression was found in 28 MDS patients(r=-0.377, P=0.048), but there was no relationship in terms of hepcidin and HIF-2α mRNA expression. The hepcidin to ferritin ratio was independently associated with GDF15 concentration and WHO subtype in multivariable analysis (β=-0.292，P =0.029 and β=-0.390，P =0.006). Conclusions Iron overload occurs in MDS patients even without transfusion. Hepcidin concentrations are inappropriately low considering the severe iron overload. High level of GDF15 is a feature of ineffective erythropiesis in MDS. GDF15 is among the erythroid factors down-regulating hepcidin and contributes to iron overload in conditions of dyserythropoiesis in MDS. Disclosures: No relevant conflicts of interest to declare.

Ineffective erythropoiesis and its treatment

Blood ◽  
2021 ◽  
Author(s):  
Mario Cazzola
Keyword(s):  
Molecular Mechanisms ◽  
Early Stage ◽  
Iron Loading ◽  
Murine Models ◽  
Ineffective Erythropoiesis ◽  
Inherited Disorders ◽  
Iron Restriction ◽  
Novel Treatments ◽  
Ring Sideroblasts

The erythroid marrow and circulating red blood cells (RBCs) are the key components of the human erythron. Abnormalities of the erythron that are responsible for anemia can be distinguished into 3 major categories, that is, erythroid hypoproliferation, ineffective erythropoiesis, and peripheral hemolysis. Ineffective erythropoiesis is characterized by erythropoietin-driven expansion of early-stage erythroid precursors, associated with apoptosis of late-stage precursors. This mechanism is primarily responsible for anemia in inherited disorders like β-thalassemia, inherited sideroblastic anemias, and congenital dyserythropoietic anemias, as well as in acquired conditions like some subtypes of myelodysplastic syndromes (MDS). The inherited anemias due to ineffective erythropoiesis are also defined as iron loading anemias because of the associated parenchymal iron loading caused by the release of erythroid factors that suppress hepcidin production. Novel treatments specifically targeting ineffective erythropoiesis are being developed. Iron restriction through enhancement of hepcidin activity or inhibition of ferroportin function has been shown to reduce ineffective erythropoiesis in murine models of β-thalassemia. Luspatercept is a TGF-β ligand trap that inhibits SMAD2/3 signaling. Based on pre-clinical and clinical studies, this compound is now approved for the treatment of anemia in adult patients with β-thalassemia who require regular RBC transfusions. Luspatercept is also approved for the treatment of transfusion-dependent anemia in patients with MDS with ring sideroblasts, most of whom carry a somatic SF3B1mutation. While long-term efficacy and safety of luspatercept need to be evaluated both in β-thalassemia and MDS, defining the molecular mechanisms of ineffective erythropoiesis in different disorders might allow the discovery of new effective compounds.

Dysmetabolic Hyperferritinemia and Dysmetabolic Iron Overload Syndrome (DIOS): Two Related Conditions or Different Entities?

2020 ◽  
Vol 26 (10) ◽  
pp. 1025-1035 ◽  
Author(s):  
Raffaela Rametta ◽  
Anna L. Fracanzani ◽  
Silvia Fargion ◽  
Paola Dongiovanni
Keyword(s):  
Iron Overload ◽  
Iron Homeostasis ◽  
Genetic Factors ◽  
Current Knowledge ◽  
Elevated Serum ◽  
Iron Accumulation ◽  
Hormone Production ◽  
Alcoholic Fatty Liver ◽  
Serum Hepcidin ◽  
Alcoholic Fatty Liver Disease

: Hyperferritinemia is observed in one-third of patients with non-alcoholic fatty liver disease (NAFLD) and Metabolic Syndrome (MetS). The condition characterized by increased body iron stores associated with components of MetS has been defined as Dysmetabolic Iron Overload Syndrome (DIOS). DIOS represents the most frequent iron overload condition, since it is observed in 15% of patients with MetS and in half of those with NAFLD and its clinical presentation overlaps almost completely with that of dysmetabolic hyperferritinemia (DH). : The pathogenetic mechanisms linking insulin resistance (IR), NAFLD and DIOS to iron overload are still debated. Hepcidin seems to play a role in iron accumulation in DIOS and NAFLD patients who show elevated serum hepcidin levels. The iron challenge does not restrain iron absorption despite adequate hepcidin production, suggesting that an impaired hepcidin activity rather than a deficit of hormone production underlies DIOS pathogenesis. : Acquired and genetic factors are recognized to contribute to iron accumulation in NAFLD whereas additional studies are required to clearly demonstrate whether the same or different genetic factors lead to iron overload in DIOS. : Finally, iron depletion by phlebotomy, together with the modification of diet and life-style habits, represents the therapeutic approach to decrease metabolic alterations and liver enzymes in NAFLD and DIOS patients. : n this review, we summarized the current knowledge on the dysregulation of iron homeostasis in NAFLD and DIOS in the attempt to clarify whether they are different or more likely strictly related conditions, sharing the same pathogenic cause i.e. the MetS.

scholarly journals Erythroferrone contributes to hepcidin suppression and iron overload in a mouse model of β-thalassemia

Blood ◽  
2015 ◽  
Vol 126 (17) ◽  
pp. 2031-2037 ◽  
Author(s):  
Léon Kautz ◽  
Grace Jung ◽  
Xin Du ◽  
Victoria Gabayan ◽  
Justin Chapman ◽  
...  
Keyword(s):  
Mouse Model ◽  
Iron Overload ◽  
Mean Corpuscular Volume ◽  
Iron Homeostasis ◽  
Dietary Iron ◽  
Red Cell ◽  
Cell Distribution ◽  
Ineffective Erythropoiesis ◽  
Distribution Width ◽  
Hepcidin Mrna

Abstract Inherited anemias with ineffective erythropoiesis, such as β-thalassemia, manifest inappropriately low hepcidin production and consequent excessive absorption of dietary iron, leading to iron overload. Erythroferrone (ERFE) is an erythroid regulator of hepcidin synthesis and iron homeostasis. Erfe expression was highly increased in the marrow and spleen of HbbTh3/+ mice (Th3/+), a mouse model of thalassemia intermedia. Ablation of Erfe in Th3/+ mice restored normal levels of circulating hepcidin at 6 weeks of age, suggesting ERFE could be a factor suppressing hepcidin production in β-thalassemia. We examined the expression of Erfe and the consequences of its ablation in thalassemic mice from 3 to 12 weeks of age. The loss of ERFE in thalassemic mice led to full restoration of hepcidin mRNA expression at 3 and 6 weeks of age, and significant reduction in liver and spleen iron content at 6 and 12 weeks of age. Ablation of Erfe slightly ameliorated ineffective erythropoiesis, as indicated by reduced spleen index, red cell distribution width, and mean corpuscular volume, but did not improve the anemia. Thus, ERFE mediates hepcidin suppression and contributes to iron overload in a mouse model of β-thalassemia.

scholarly journals SLN124, a Galnac-siRNA Conjugate Targeting TMPRSS6, for the Treatment of Iron Overload and Ineffective Erythropoiesis Such As in Beta-Thalassemia

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 2340-2340 ◽  
Author(s):  
Sandro Altamura ◽  
Sandro Altamura ◽  
Martina U. Muckenthaler ◽  
Sibylle Dames ◽  
Christian Frauendorf ◽  
...  
Keyword(s):  
Gene Expression ◽  
Iron Overload ◽  
Target Gene ◽  
Iron Homeostasis ◽  
Hereditary Hemochromatosis ◽  
Beta Thalassemia ◽  
Iron Loading ◽  
Ineffective Erythropoiesis ◽  
Target Gene Expression ◽  
Tissue Iron

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.

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 ◽  
...  
Keyword(s):  
Iron Deficiency ◽  
Iron Overload ◽  
Double Mutant ◽  
Iron Homeostasis ◽  
Conflicts Of Interest ◽  
Beta Thalassemia ◽  
The European Union ◽  
Ineffective Erythropoiesis ◽  
Deficient Diet ◽  
Iron Deficient

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.

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