Target TMPRSS6 for the Treatment of Hereditary Hemochromatosis

Abstract Abstract 1047 Hereditary hemochromatosis (HH) is a genetic disorder in which hyperabsorption of dietary iron leads to accumulation of iron in multiple tissues including liver and heart. A common clinical manifestation in HH patients is cirrhosis and hepatocellular carcinoma as a result of iron-mediated injury in liver. The most prevalent genetic defect for HH is the failure to up-regulate hepcidin, a peptide hormone that inhibits the absorption of iron in duodenum and the release of iron from intracellular iron storage such as macrophages. Mutations in a number of genes have been identified as the cause for HH, including hepcidin itself. However, the most common mutation is C282Y mutation in HFE, which is a positive regulator for hepcidin expression. C282Y mutation represents about 85% of the HH population. HFE C282Y HH is an autosomal recessive disease with a ∼50% penetrance. Currently, the only treatment available for iron overload is phlebotomy which will continue throughout the patient's life. Hepcidin is mainly expressed and secreted by the liver and its expression is regulated predominantly at the transcription level. TMPRSS6, a transmembrane serine protease mutated in iron-refractory, iron-deficient anemia, is a major suppressor for hepcidin expression. It's been demonstrated that hepcidin expression is significantly elevated in Tmprss6−/− mice and reduction of TMPRSS6 in Hfe−/− mice could ameliorate the iron overload phenotype (Du et al. Science 2008; Folgueras et al. Blood 2008; Finberg KE et al., Blood, 2011). Using second generation antisense technology, we identified antisense oligonucleotides (ASOs) targeting mouse TMPRSS6 for the treatment of HH. These compounds were first identified through in vitro screens in mouse primary hepatocytes. After 4 weeks of treatment in C57BL/6 mice on normal chow, we observed an 80% to 90% reduction of liver TMPRSS6 mRNA with a subsequent 2–3 fold induction of liver hepcidin mRNA. Serum iron and transferrin saturation levels were reduced by ∼50%. These ASOs are currently being evaluated in a diet-induced iron overload model and an Hfe−/− iron overload model. Our preliminary results demonstrate that targeting TMPRSS6 is a viable approach for the treatment of hereditary hemochromatosis and possibly other iron-loading diseases associated with suppressed hepcidin levels. Disclosures: Booten: Isis Pharmaceuticals: Employment. Knox:Isis Pharmaceuticals: Summer Intern. Alvarado:Isis Pharmaceuticals: Employment. Guo:Isis Pharmaceuticals: Employment. Monia:Isis Pharmaceuticals: Employment.

Download Full-text

Iron Overload in C282Y Heterozygotes: Identification of New Rare HFE Gene Mutants and a Step Strategy for Diagnosis.

Blood ◽

10.1182/blood.v112.11.1859.1859 ◽

2008 ◽

Vol 112 (11) ◽

pp. 1859-1859

Author(s):

Patricia Aguilar-Martinez ◽

Severine Cunat ◽

Fabienne Becker ◽

Francois Blanc ◽

Marlene Nourrit ◽

...

Keyword(s):

Iron Overload ◽

Iron Status ◽

Hereditary Hemochromatosis ◽

Genetic Defect ◽

Transferrin Saturation ◽

Hfe Gene ◽

Compound Heterozygous ◽

Exon 2 ◽

High Iron ◽

Iron Parameters

Abstract Introduction: Homozygozity for the p.Cys282Tyr (C282Y) mutation of the HFE gene is the main genotype associated with the common form of adult hereditary hemochromatosis. C282Y carriers do not usually develop iron overload, unless they have additional risk factors such as liver diseases, a dysmetabolic syndrome or an associated genetic defect. The commonest is the compound heterozygous state for C282Y and the widespread p.His63Asp (H63D) variant allele. However, a few rare HFE mutations can be found on the 6th chromosome in trans, some of which are of clinical interest to fully understand the disorder. Patients and Methods: We recently investigated four C282Y carrier patients with unusually high iron parameters, including increased levels of serum ferritin (SF), high transferrin saturation (TS) and high iron liver content measured by MRI. They were males, aged 37, 40, 42, 47 at diagnosis. Two brothers (aged 40 and 42) were referred separately. The HFE genotype, including the determination of the C282Y, H63D and S65C mutations was performed using PCR-RFLP. HFE sequencing was undertaken using the previously described SCA method (1). Sequencing of other genes (namely, HAMP, HJV/HFE2, SLC40A1, TFR2) was possibly performed in a last step using the same method. Results: We identified three rare HFE mutant alleles, two of which are undescribed, in the four studied patients. One patient bore a 13 nucleotide-deletion in exon 6 (c.[1022_1034del13], p.His341_Ala345>LeufsX119), which is predicted to lead to an abnormal, elongated protein. The two brothers had a substitution of the last nucleotide of exon 2 (c.[340G>A], p.Glu114Lys) that may modify the splicing of the 2d intron. The third patient, who bore an insertion of a A in exon 4 (c.[794dupA],p.[trp267LeufsX80]), has already been reported (1). Discussion: A vast majority of C282Y carriers will not develop iron overload and can be reassured. However, a careful step by step strategy at the clinical and genetic levels may allow to correctly identify those patients deserving further investigation. First, clinical examination and the assessment of iron parameters (SF and TS) allow identifying C282Y heterozygotes with an abnormal iron status. Once extrinsic factors such as heavy alcohol intake, virus or a dysmetabolic syndrome have been excluded, MRI is very useful to authenticate a high liver iron content. Second, HFE genotype must first exclude the presence of the H63D mutation. Compound heterozygozity for C282Y and H63D, a very widespread condition in our area, is usually associated with mild iron overload. Third, HFE sequencing can be undertaken and may identify new HFE variants as described here. The two novel mutations, a frameshift modifying the composition and the length of the C terminal end of the HFE protein and a substitution located at the last base of an exon, are likely to lead to an impaired function of HFE in association with the C282Y mutant. However, it is noteworthy that three of the four patients were diagnosed relatively late, after the 4th decade, as it is the case for C282Y homozygotes. Three further unrelated patients are currently under investigation in our laboratory for a similar clinical presentation. Finally, it can be noted that in those patients who will not have a HFE gene mutant identified, analysis of other genes implicated in iron overload must be performed to search for digenism or multigenism. None of our investigated patients had an additional gene abnormality.

Download Full-text

Target TMPRSS6 Using Antisense Technology for the Treatment of Hereditary Hemochromatosis and β-Thalassemia

Blood ◽

10.1182/blood.v120.21.481.481 ◽

2012 ◽

Vol 120 (21) ◽

pp. 481-481 ◽

Cited By ~ 1

Author(s):

Shuling Guo ◽

Carla Casu ◽

Sara Gardenghi ◽

Sheri Booten ◽

Andy Watt ◽

...

Keyword(s):

Treatment Group ◽

Iron Overload ◽

Hereditary Hemochromatosis ◽

Iron Concentration ◽

Transferrin Saturation ◽

Control Group ◽

Mrna Levels ◽

Liver Iron ◽

Hepcidin Expression ◽

Antisense Technology

Abstract Abstract 481 Hepcidin, the master regulator of iron homeostasis, is a peptide that is mainly expressed and secreted by the liver. Low levels of hepcidin are associated with increased iron absorption. In conditions in which hepcidin is chronically repressed, such as hereditary hemochromatosis and b-thalassemia, patients suffer from iron overload and very severe pathophysiological sequelae associated with this condition. Hepcidin expression is regulated predominantly at the transcriptional level by multiple factors. TMPRSS6, a transmembrane serine protease mutated in iron-refractory, iron-deficient anemia, is a major suppressor of hepcidin expression. It has been demonstrated that hepcidin expression is significantly elevated in Tmprss6−/− mice and reduction of Tmprss6 expression in hereditary hemochromatosis (Hfe−/−) mice ameliorates the iron overload phenotype (Finberg et al. Nature Genetics, 2008; Du et al. Science 2008; Folgueras et al. Blood 2008; Finberg et al., Blood, 2011). It has also been demonstrated that hepcidin up-regulation using either a hepcidin transgene or Tmprss6−/− significantly improves iron overload and anemia in a mouse model of β-thalassemia intermedia (th3/+ mice) (Gardenghi et al. JCI, 120:4466, 2010; Nai et al. Blood, 119: 5021, 2012). In this report, we have examined whether reduction of Tmprss6 expression using antisense technology is an effective approach for the treatment of hereditary hemochromatosis and β-thalassemia. Second generation antisense oligonucleotides (ASOs) targeting mouse Tmprss6 were identified. When normal male C57BL/6 mice were treated with 25, 50 and 100mg/kg/week ASO for four weeks, we achieved up to >90% reduction of liver Tmprss6 mRNA levels and up to 5-fold induction of hepcidin mRNA levels in a dose-dependent manner. Dose-dependent reductions of serum iron and transferrin saturation were also observed. ASOs were well tolerated in these animals. In Hfe−/− mice (both males and females), ASOs were administrated at 100 mg/kg for six weeks. This treatment normalized transferrin saturation (from 92% in control animals to 26% in treatment group) and significantly reduced serum iron (from >300ug/dl in control group to <150ug/dl in treatment group), as well as liver iron accumulation. Histopathological evaluation and Prussian's Perl Blue staining indicated that iron was sequestered by macrophages, which led to an increase in spleen iron concentration. The mouse model of thalassemia intermedia that we utilized mimics a condition defined as non-transfusion dependent thalassemia (NTDT) in humans. These patients exhibit increased iron absorption and iron overload due to ineffective erythropoiesis and suppression of hepcidin; iron overload is the most frequent cause of morbidity and mortality. Th3/+ animals exhibit ineffective erythropoiesis, characterized by increased proliferation and decreased differentiation of the erythroid progenitors, apoptosis of erythroblasts due to the presence of toxic hemichromes, reticulocytosis and shorter lifespan of red cells in circulation, leading to splenomegaly, extramedullary hematopoiesis and anemia (∼ 8 g/dL; Libani et al, Blood 112(3):875–85, 2008). Five month old th3/+ mice (both males and females) were treated with Tmprss6 ASO for six weeks. In th3/+ mice, ∼85% Tmprss6 reduction led to dramatic reductions of serum transferrin saturation (from 55–63% in control group down to 20–26% in treatment group). Liver iron concentration (LIC) was also greatly reduced (40–50%). Moreover, anemia endpoints were significantly improved with ASO treatment, including increases in red blood cells (∼30–40%), hemoglobin (∼2 g/dl), and hematocrit (∼20%); reduction of splenomegaly (∼50%); decrease of serum erythropoietin levels (∼50%); improved erythroid maturation as indicated by a strong reduction in reticulocyte number (50–70%) and in a normalized proportion between the pool of erythroblasts and enucleated erythroid cells. Hemichrome analysis showed a significant decrease in the formation of toxic alpha-globin/heme aggregates associated with the red cell membrane. This was consistent with a remarkable improvement of the red cell distribution width (RDW) as well as morphology of the erythrocytes. In conclusion, these data demonstrate that targeting TMPRSS6 using antisense technology is a promising novel therapy for the treatment of hereditary hemochromatosis and β-thalassemia. Disclosures: Guo: Isis Pharmaceuticals: Employment. Booten:Isis Pharmaceuticals: Employment. Watt:Isis Pharmaceuticals: Employment. Freier:Isis Pharmaceuticals: Employment. Rivella:Novartis Pharmaceuticals: Consultancy; Biomarin: Consultancy; Merganser Biotech: Consultancy, Equity Ownership, Research Funding; Isis Pharma: Consultancy, Research Funding. Monia:Isis Pharmaceuticals: Employment.

Download Full-text

Expression of hepcidin in hereditary hemochromatosis: evidence for a regulation in response to the serum transferrin saturation and to non-transferrin-bound iron

Blood ◽

10.1182/blood-2002-11-3610 ◽

2003 ◽

Vol 102 (1) ◽

pp. 371-376 ◽

Cited By ~ 167

Author(s):

Sven G. Gehrke ◽

Hasan Kulaksiz ◽

Thomas Herrmann ◽

Hans-Dieter Riedel ◽

Karin Bents ◽

...

Keyword(s):

Iron Overload ◽

Serum Ferritin ◽

Iron Homeostasis ◽

Iron Status ◽

Hereditary Hemochromatosis ◽

Transferrin Saturation ◽

Serum Transferrin ◽

Transcript Levels ◽

Hepcidin Expression

Abstract Experimental data suggest the antimicrobial peptide hepcidin as a central regulator in iron homeostasis. In this study, we characterized the expression of human hepcidin in experimental and clinical iron overload conditions, including hereditary hemochromatosis. Using quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), we determined expression of hepcidin and the most relevant iron-related genes in liver biopsies from patients with hemochromatosis and iron-stain-negative control subjects. Regulation of hepcidin mRNA expression in response to transferrin-bound iron, non-transferrin-bound iron, and deferoxamine was analyzed in HepG2 cells. Hepcidin expression correlated significantly with serum ferritin levels in controls, whereas no significant up-regulation was observed in patients with hemochromatosis despite iron-overload conditions and high serum ferritin levels. However, patients with hemochromatosis showed an inverse correlation between hepcidin transcript levels and the serum transferrin saturation. Moreover, we found a significant correlation between hepatic transcript levels of hepcidin and transferrin receptor-2 irrespective of the iron status. In vitro data indicated that hepcidin expression is down-regulated in response to non-transferrin-bound iron. In conclusion, the presented data suggest a close relationship between the transferrin saturation and hepatic hepcidin expression in hereditary hemochromatosis. Although the causality is not yet clear, this interaction might result from a down-regulation of hepcidin expression in response to significant levels of non-transferrin-bound iron. (Blood. 2003;102:371-376)

Download Full-text

Design of an Ongoing Phase I/II Open-Label, Dose-Escalation Trial Using the Oral Chelator Deferasirox To Treat Iron Overload in HFE-Related Hereditary Hemochromatosis (HH).

Blood ◽

10.1182/blood.v110.11.2680.2680 ◽

2007 ◽

Vol 110 (11) ◽

pp. 2680-2680 ◽

Cited By ~ 2

Author(s):

A. Pietrangelo ◽

P. Brissot ◽

H. Bonkovsky ◽

C. Niederau ◽

L. Rojkjaer ◽

...

Keyword(s):

Iron Overload ◽

Dose Escalation ◽

Genetic Disorder ◽

Hereditary Hemochromatosis ◽

Transferrin Saturation ◽

Analysis Of Covariance ◽

Dose Escalation Study ◽

True Incidence ◽

Medical Disorders ◽

Alternative Treatment Option

Abstract HH is a genetic disorder commonly associated with homozygosity for the C282Y HFE mutation and characterized by progressive iron overload through increased intestinal absorption. Organ failure due to iron toxicity may develop. Iron removal by phlebotomy is the preferred treatment and has been demonstrated to prevent or reverse some of the complications of iron overload. However, compliance with a weekly phlebotomy schedule is variable, and some patients are ineligible for phlebotomy due to underlying medical disorders. Thus, if an oral iron chelator such as deferasirox proves to be safe and effective, HH patients will have an alternative treatment option. This is an inter-patient dose-escalation study of deferasirox (5, 10, 15, 20 mg/kg) given daily for 24 weeks to C282Y homozygous HH patients with a pre-treatment serum ferritin (SF) value ≥300 μg/L and ≤2000 μg/L, and transferrin saturation ≥45%. Major exclusion criteria are men with hemoglobin <13 g/dL, women with hemoglobin <12 g/dL, a history of blood transfusion during 6 months prior to study entry, serum creatinine above the upper limit of normal (ULN), and serum ALT ≥2xULN at screening. The primary endpoint is the incidence and severity of adverse events (AEs). Secondary endpoints include the change in SF from baseline at 24 weeks, the time to normalization of SF (defined as the first occurrence of reduction of SF to <100 μg/L), the longitudinal course of SF, and the pharmacokinetics of deferasirox. It is estimated that at least 40 patients are needed to evaluate safety at all dose levels. Cohorts of 8 patients per dose level will be used in order to detect AEs with a 25% true incidence rate at that dose with 90% power. Safety monitoring will be based on medical review and a 2-parameter Bayesian logistic regression model for dose-dependent probabilities of a severe AE. To assess efficacy, the change from baseline in SF after 24 weeks of treatment will be analyzed by performing an analysis of covariance (ANCOVA). To date, 11 patients (9 men, 2 women; all Caucasian; mean age 56 years) with a mean of 7 years since HH diagnosis have been treated at 5 mg/kg/day for at least 4 weeks. There was a mean of 7 years since HH diagnosis, with 2 patients not having been previously treated. The remaining 9 had been treated with phlebotomy, one of whom had also been treated with deferoxamine. Baseline iron studies and ALT values for the 11 patients treated at 5 mg/kg/day are summarized in the table. The dose of deferasirox has been escalated to 10 mg/kg/day after no patients were seen to experience severe AEs at 5 mg/kg/day. In conclusion, this ongoing study will generate preliminary safety and efficacy data for deferasirox use in iron-overloaded HH patients, indicating whether deferasirox could be an alternative to phlebotomy in selected patients. Parameter n Mean±SD Median Range Normal range SF, ng/mL 11 633.0±428.9 567.0 350–1880 30–400 (men); 15–150 (women) Transferrin saturation, % 11 75.5±19.6 82.0 39–95 20–55 ALT, U/L 11 43.4±33.4 34.0 8–122 0–45

Download Full-text

Neutrophils from hereditary hemochromatosis patients are protected from iron excess and are primed

Blood Advances ◽

10.1182/bloodadvances.2020002198 ◽

2020 ◽

Vol 4 (16) ◽

pp. 3853-3863

Author(s):

Cyril Renassia ◽

Sabine Louis ◽

Sylvain Cuvellier ◽

Nadia Boussetta ◽

Jean-Christophe Deschemin ◽

...

Keyword(s):

Iron Overload ◽

Mouse Models ◽

Oxidative Burst ◽

Iron Homeostasis ◽

Genetic Disorder ◽

Hereditary Hemochromatosis ◽

Neutrophil Function ◽

Intracellular Iron ◽

Hepcidin Expression ◽

Neutrophil Priming

Abstract Iron is required for the oxidative response of neutrophils to allow the production of reactive oxygen species (ROS). However, neutrophil function may be severely altered in conditions of iron overload, as observed in chronically transfused patients. Therefore, a tight regulation of neutrophil iron homeostasis seems to be critical for avoiding iron toxicity. Hepcidin is the key iron regulator in organisms; however, no studies have investigated its role in maintaining neutrophil iron homeostasis or characterized neutrophil function in patients with hereditary hemochromatosis (HH), a common iron overload genetic disorder that results from a defect in hepcidin production. To explore these issues, we studied 2 mouse models of iron overload: an experimentally induced iron overload model (EIO), in which hepcidin is increased, and a genetic HH model of iron overload with a deletion of hepatic hepcidin. We found that iron-dependent increase of hepatic hepcidin results in neutrophil intracellular iron trapping and consecutive defects in oxidative burst activity. In contrast, in both HH mouse models and HH patients, the lack of hepcidin expression protects neutrophils from toxic iron accumulation. Moreover, systemic iron overload correlated with a surprising neutrophil priming and resulted in a more powerful oxidative burst. Indeed, important factors in neutrophil priming and activation, such as tumor necrosis factor α (TNF-α), VCAM-1, and ICAM-1 are increased in the plasma of HH patients and are associated with an increase in HH neutrophil phagocytosis capacity and a decrease in L-selectin surface expression. This is the first study to characterize neutrophil iron homeostasis and associated functions in patients with HH.

Download Full-text

Molecular basis for the recently described hereditary hyperferritinemia- cataract syndrome: a mutation in the iron-responsive element of ferritin L-subunit gene (the "Verona mutation") [see comments]

Blood ◽

10.1182/blood.v86.11.4050.bloodjournal86114050 ◽

1995 ◽

Vol 86 (11) ◽

pp. 4050-4053 ◽

Cited By ~ 127

Author(s):

D Girelli ◽

R Corrocher ◽

L Bisceglia ◽

O Olivieri ◽

L De Franceschi ◽

...

Keyword(s):

Iron Overload ◽

Serum Ferritin ◽

Molecular Basis ◽

Genetic Disorder ◽

Transferrin Saturation ◽

Elevated Serum ◽

Iron Responsive Element ◽

Ferritin Synthesis ◽

Iron Deficient ◽

Responsive Element

Recently,we described a new genetic disorder (the “hereditary hyperferritinemia-cataract syndrome”) clinically characterized by the combination of elevated serum ferritin and congenital bilateral nuclear cataract, both cotransmitted as an autosomal dominant trait. In affected subjects, hyperferritinemia (ranging from 950 to 2,259 micrograms/L) is typically not related to iron overload. Differently from subjects with hereditary hemochromatosis, they have normal to low levels of serum iron and percent of transferrin saturation and absence of iron overload in parenchymal organs. When unnecessary phlebotomies are performed, they rapidly develop iron-deficient anemia, with persistently elevated levels of serum ferritin. By RNA-single-strand conformation polymorphism screening of the L-subunit ferritin gene on chromosome 19, we were able to identify in affected subjects a mutation in the 5′ untranslated region. This mutation involves the five nucleotides sequence [CAGUG] of the iron-responsive element (IRE), which is critical for the posttranscriptional regulation of ferritin synthesis by means of IRE-binding protein (IRE-BP). Thus, it is very likely to provide the molecular basis for the iron-insensitive upregulation of ferritin synthesis in affected subjects.

Download Full-text

Examination of ALAS2, ABC7, Rag1, and IL6 Genes as Candidate Modifiers of Iron Overload in HFE C282Y Homozygotes with Severe Iron Overload.

Blood ◽

10.1182/blood.v106.11.3724.3724 ◽

2005 ◽

Vol 106 (11) ◽

pp. 3724-3724

Author(s):

Pauline L. Lee ◽

James C. Barton ◽

Carol West ◽

Karen Crain ◽

Sreenivas V. Rao ◽

...

Keyword(s):

Iron Overload ◽

Transferrin Saturation ◽

Allele Frequencies ◽

Iron Loading ◽

Promoter Polymorphisms ◽

Sideroblastic Anemia ◽

Iron Storage ◽

Exon 2 ◽

Hepcidin Expression ◽

Control Subjects

Abstract The variable penetrance of HFE hemochromatosis led us to examine candidate modifier genes in 24 adult probands homozygous for the HFE C282Y mutation with severe iron overload. Mutations of the X-linked genes ALAS2 and ABC7 are associated with sideroblastic anemia and are such candidate genes. One C282Y homozygote had a P520L mutation in ALAS2 and another had an an ABC7 ivs2+1 G->A mutation that would result in the loss of a splice site and predict skipping of exon 2 with an in-frame deletion of 27 amino acids from the mature protein. Examination of respective family members demonstrated that inheritance of the ALAS2 P520L mutation or the ABC7 ivs2+1 mutation alone was not associated with excessive iron storage or sideroblastic anemia. Only subjects homozygous for HFE C282Y and hemizygous or heterozygous for these ALAS2 or ABC7 mutations had iron overload. Because the families were small, it was not possible to establish conclusively that these mutations affected the severity of iron overload. Nevertheless, these data suggest that if ALAS2 and ABC7 mutations are modifers of HFE hemochromatosis, they occur at a low frequency and do not account for the majority of cases of severe iron overload in C282Y homozygotes. Mice expressing double knockouts of rag1 and hfe or beta 2 microglobulin exhibit more severe iron overload than mice with knockouts of either gene alone. Thus, we sought to determine if mutations in RAG1 were associated with severe iron overload in 20 HFE C282Y homozygotes with severe iron overload. Four non-synonymous SNPs were identified in the HFE C282Y homozygotes: R249H, R449K, K820R, and M1006V. These mutations occurred at allele frequencies of 0.3500, 0.0238, 0.1190, and 0.0227, respectively. In 364 control subjects, the allele frequencies of R249H (0.3750) and K820R (0.1133) did not differ significantly from those in HFE C282Y homozygotes. A promoter polymorphism in IL6 at nt −174 has been shown to be associated with IL-6 expression: the G allele with high expression and the C allele with low expression. Lower levels of IL-6 expression might result in lower levels of hepcidin expression, further decreasing the already lower levels of hepcidin resulting from HFE C282Y homozygosity. Analysis of 340 control whites disclosed 62 IL6 -174C/C subjects had a mean transferrin saturation of 28% and 107 IL6 -174G/G subjects had a mean transferrin saturation of 25% (p <0.05). We found that the C allele frequency was 0.4800 in C282Y homozygotes with severe iron overload; this did not differ significantly from the frequency of 0.4338 in white control subjects. These data suggest that the IL6 -174 C allele is not significantly associated with severe iron overload in HFE C282Y homozygotes. We conclude that mutations of ALAS2 and ABC7 may be rare causes of severe iron loading in HFE C282Y homozygotes, but it is unlikely that RAG1 and the IL6 promoter polymorphisms contribute significantly to the iron loading of such subjects.

Download Full-text

Iron age: novel targets for iron overload

Hematology ◽

10.1182/asheducation-2014.1.216 ◽

2014 ◽

Vol 2014 (1) ◽

pp. 216-221 ◽

Cited By ~ 9

Author(s):

Carla Casu ◽

Stefano Rivella

Keyword(s):

Iron Overload ◽

Iron Age ◽

Iron Metabolism ◽

Iron Absorption ◽

Hereditary Hemochromatosis ◽

Therapeutic Approaches ◽

Hepcidin Expression ◽

Beneficial Effects ◽

Excess Iron ◽

Major Factors

Abstract Excess iron deposition in vital organs is the main cause of morbidity and mortality in patients affected by β-thalassemia and hereditary hemochromatosis. In both disorders, inappropriately low levels of the liver hormone hepcidin are responsible for the increased iron absorption, leading to toxic iron accumulation in many organs. Several studies have shown that targeting iron absorption could be beneficial in reducing or preventing iron overload in these 2 disorders, with promising preclinical data. New approaches target Tmprss6, the main suppressor of hepcidin expression, or use minihepcidins, small peptide hepcidin agonists. Additional strategies in β-thalassemia are showing beneficial effects in ameliorating ineffective erythropoiesis and anemia. Due to the suppressive nature of the erythropoiesis on hepcidin expression, these approaches are also showing beneficial effects on iron metabolism. The goal of this review is to discuss the major factors controlling iron metabolism and erythropoiesis and to discuss potential novel therapeutic approaches to reduce or prevent iron overload in these 2 disorders and ameliorate anemia in β-thalassemia.

Download Full-text

RNAi-Mediated Inhibition of Tmprss6 Elevates Hamp1 Expression and Reduces Serum Iron Levels in Mice

Blood ◽

10.1182/blood.v118.21.1045.1045 ◽

2011 ◽

Vol 118 (21) ◽

pp. 1045-1045 ◽

Cited By ~ 1

Author(s):

Ivanka Toudjarska ◽

Zuhua Cai ◽

Tim Racie ◽

Stuart Milstein ◽

Brian R Bettencourt ◽

...

Keyword(s):

Iron Overload ◽

Serum Iron ◽

Iron Concentration ◽

Transferrin Saturation ◽

Elevated Serum ◽

High Serum ◽

Therapeutic Modality ◽

Deficiency Anemia ◽

Loss Of Function ◽

Hepcidin Expression

Abstract Abstract 1045 The liver hormone Hepcidin (encoded by Hamp1) regulates serum iron levels by controlling the efflux of iron from intestinal enterocytes and macrophages. Maintaining sufficient iron levels to support erythropoiesis while preventing iron overload requires tight control of Hepcidin expression. Transcription of Hamp1 in hepatocytes is stimulated by high serum iron levels, via Transferrin Receptor signaling, as well as by activation of the BMP/SMAD pathway. The membrane serine protease Matriptase-2 (encoded by Tmprss6) inhibits BMP induced Hamp1 induction through the regulation of the BMP co-receptor, Hemojuvelin. In humans, loss of function mutations in TMPRSS6 lead to elevated Hepcidin levels resulting in iron-resistant iron-deficiency anemia (IRIDA). In diseases associated with iron overload, such as Thalassemia intermedia (TI) and Familial Hemochromatosis (FH), Hepcidin levels are low despite elevated serum iron concentrations. Studies in murine models of TI and FH have shown that elevating Hepcidin levels by genetic inactivation of Tmprss6 can prevent iron overload and correct aspects of the disease phenotype. Therefore, therapeutic strategies aimed at specifically inhibiting Tmprss6 expression could prove efficacious in these, and other, iron overloading diseases. Here we show that systemic administration of a potent lipid nanoparticle (LNP) formulated siRNA directed against Tmprss6 leads to durable inhibition of Tmprss6 mRNA in the mouse liver, with concomitant elevation of Hamp1 expression. This leads to significant decreases in serum iron concentration and Transferrin saturation, along with changes in hematologic parameters consistent with iron restriction. Further testing in mouse genetic models of TI and FH will support the rationale for developing LNP formulated Tmprss6 siRNA as a novel therapeutic modality. Disclosures: Toudjarska: Alnylam Pharmaceuticals, Inc.: Employment. Cai:Alnylam Pharmaceuticals, Inc.: Employment. Racie:Alnylam Pharmaceuticals, Inc.: Employment. Milstein:Alnylam Pharmaceuticals, Inc.: Employment. Bettencourt:Alnylam Pharmaceuticals, Inc.: Employment. Hettinger:Alnylam Pharmaceuticals, Inc.: Employment. Sah:Alnylam Pharmaceuticals, Inc.: Employment. Vaishnaw:Alnylam Pharmaceuticals, Inc.: Employment. Bumcrot:Alnylam Pharmaceuticals, Inc.: Employment.

Download Full-text

Role of Magnetic Ressonance Imaging – T2* in Hereditary Hemochromatosis.

Blood ◽

10.1182/blood.v120.21.2096.2096 ◽

2012 ◽

Vol 120 (21) ◽

pp. 2096-2096

Author(s):

Reijane Alves de Assis ◽

Fernando Uliana Kay ◽

Paulo Vidal Campregher ◽

Gilberto Szarf ◽

Fabiana Mendes Conti ◽

...

Keyword(s):

Iron Overload ◽

Serum Ferritin ◽

Conflicts Of Interest ◽

Hereditary Hemochromatosis ◽

Transferrin Saturation ◽

Laboratory Data ◽

Surrogate Marker ◽

Control Group ◽

Double Mutation ◽

H63d Mutation

Abstract Abstract 2096 Introduction: Hereditary hemochromatosis (HH) is an autossomic recessive disorder characterized by increased iron absorption. Magnetic resonance imaging – T2* (MRI-T2*) has become a reliable and robust methodology to directly assess the iron burden, with better results in transfusional hemosiderosis compared to indirect methods, such as serum ferritin and transferrin saturation (TS). However, little is known about its role in HH. Objectives: Describe the demographic profile of HH type 1 patients as to the type of the HFE mutation and correlate laboratory parameters to MRI-T2*results. Methods: We collected data from patients with a positive HFE gene mutation who performed abdominal and/or cardiac MRI-T2* in our institution from 2004 to 2011. Images retrieved from the digital archive were analyzed by two blinded independent radiologists using the Thalassemia-Tools software (Cardiovascular Imaging Solutions, London, UK). Laboratory data available within 6 months before or after the MRI study were analyzed using the t-Student test, Exact Fisher's test analysis and multivariate analyses. Results: We analyzed 81 patients, 76 (93%) males and 5 (6.2%) females, with a median age of 48 years (21–80). Liver, pancreatic and splenic MRI-T2*values and LIC calculation were performed in 80 patients, and cardiac T2* assessment in 57 patients. The inter-observer T2* variation coefficient was 5%. Serum ferritin was abnormal in 70 patients (90.9%), while TS was abnormal in 34% of the tests. In our study sample, the H63D mutation was present in 70 patients (86.4%): 11 (13.6%) were homozygous, 59 (72.8%) heterozygous and 7 (8.6%) double heterozygous for C282Y/H63D. Only three patients (3.7%) were homozygous and 6 (7.4%) were heterozygous only for the C282Y mutation. The S65C mutation was detected in heterozygous state in 2 (2.5%) of cases. Two out 57 cases had a positive T2* result and were classified as light cardiac overload (T2*:18.98 e 19.14 ms). Both had the H63D mutation (1 homozygous and 1 heterozygous). Thirty seven out of 80 patients (46.3%) had liver overload in abdominal MRI (T2*: 3.8–11.4ms), being 33 (41.3%) light overload and four (5%) moderate overload (T2*:1.8–3.8ms). We found that 77.8% of patients with liver overload were C282Y carriers, of which 57.2% had double mutation and 40.3% had H63D mutation in hetero or homozigosity. Pancreatic overload was found in 20 patients (25.1%), while 30 patients (37.5%) had splenic overload. There was a slight correlation (r: 0.365) between liver T2* and splenic T2* (p=0.001). The presence of C282Y and H63D mutations was statistically associated with a higher frequency of abnormal liver T2* (p=0.017 and p=0.042, respectively). The H63D mutation was associated with iron accumulation in the liver (p=0,037) and homozygous carriers showed higher levels of liver overload (p=0,038). Conclusion: In our study, serum ferritin was a better surrogate marker for iron overload than ST. In addition, up to 40.3% of patients with H63D mutation had evidence of hepatic iron overload by MRI. These findings differ from the currente literature. The higher RMI positivity might be due to a higher sensitivity to detect lower levels of organic iron. Despite the lack of a control group and laboratory tests or MRI in all the cases studied, our results suggest that RMI-T2* is a promising methodology to guide the therapeutic management of HH patients. The clinical impact of this finding must be investigated in further studies. Disclosures: No relevant conflicts of interest to declare.

Download Full-text