Association of Liver Hemangiosarcoma and Secondary Iron Overload in B6C3F1 Mice?The National Toxicology Program Experience

Disturbances in iron metabolism can be genetic or acquired and accordingly manifest as primary or secondary iron overload state. Organ damage may result from iron overload and manifest clinically as cirrhosis, diabetes mellitus, arthritis, endocrine abnormalities and cardiomyopathy. Hemochromatosis inherited as an autosomal recessive disorder is the most common genetic iron overload disorder. Expert societies recommend screening of asymptomatic and symptomatic individuals with hemochromatosis by obtaining transferrin saturation (calculated as serum iron/total iron binding capacity × 100). Further testing for the hemochromatosis gene is recommended if transferrin saturation is >45% with or without hyperferritinemia. However, management of individuals with low or normal transferrin saturation is not clear. In patients with features of iron overload and high serum ferritin levels, low or normal transferrin saturation should alert the physician to other - primary as well as secondary - causes of iron overload besides hemochromatosis. We present here a possible approach to patients with hyperferritinemia but normal transferrin saturation.

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Pulmonary Invasive Mucormycosis in a Patient with Secondary Iron Overload Following Deferoxamine Therapy

Baylor University Medical Center Proceedings ◽

10.1080/08998280.2008.11928431 ◽

2008 ◽

Vol 21 (4) ◽

pp. 378-381 ◽

Cited By ~ 7

Author(s):

Hector M. Reyes ◽

Eric J. Tingle ◽

Andrew Z. Fenves ◽

Jennifer Spiegel ◽

Elizabeth C. Burton

Keyword(s):

Iron Overload ◽

Secondary Iron Overload

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Iron Does Not Cause Arrhythmias in the Guinea Pig Model of Transfusional Iron Overload.

Blood ◽

10.1182/blood.v108.11.3724.3724 ◽

2006 ◽

Vol 108 (11) ◽

pp. 3724-3724

Author(s):

Lana Kaiser ◽

John Davis ◽

Jon Patterson ◽

N. Bari Olivier ◽

George Bohart ◽

...

Keyword(s):

Guinea Pig ◽

Iron Overload ◽

Cardiac Arrhythmias ◽

Guinea Pigs ◽

Pig Model ◽

Cardiac Events ◽

Liver Iron ◽

Secondary Iron Overload ◽

Life Threatening ◽

Guinea Pig Model

Abstract Cardiac events, including heart failure and arrhythmias, are the major cause of death in patients with b-thalassemia. Although cardiac arrhythmias in humans are believed to result from iron overload, excluding confounding factors in the human population is difficult. The purpose of these studies was to evaluate the development of cardiac arrhythmias using the guinea pig model of secondary iron overload. Electrocardiograms were recorded via surgically implanted telemetry devices in guinea pigs loaded intraperitoneally with iron dextran and controls. Cardiac and liver iron concentrations were significantly elevated in the iron loaded animals when compared to control, and were in the range of those reported for humans with thalassemia. Arrhythmias were noted infrequently in both iron loaded and control guinea pigs. No life threatening arrhythmias were detected in either group. These data suggest that iron alone may be insufficient to cause cardiac arrhythmias, and that arrhythmias detected in individuals with iron overload may be the result of a complex interplay of factors.

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A Prognostic Model for Predicting the Impact of Comorbidities on Survival of Patients with Myelodysplastic Syndromes.

Blood ◽

10.1182/blood.v110.11.2453.2453 ◽

2007 ◽

Vol 110 (11) ◽

pp. 2453-2453 ◽

Cited By ~ 1

Author(s):

Matteo G. Della Porta ◽

Luca Malcovati ◽

Erica Travaglino ◽

Cristiana Pascutto ◽

Margherita Maffioli ◽

...

Keyword(s):

Heart Failure ◽

Iron Overload ◽

Myelodysplastic Syndromes ◽

Cardiac Death ◽

Multivariable Analysis ◽

Risk Groups ◽

Increased Risk ◽

Secondary Iron Overload ◽

Transfusion Dependency ◽

The Impact

Abstract Myelodysplastic syndromes (MDS) occur mainly in older persons, and these patients are likely to have comorbidities. We studied the impact of comorbidities on non-leukemic death (NLD) and overall survival (OS) in MDS patients with the aim of developing a specific prognostic index. Eight hundred forty consecutive patients receiving a diagnosis of MDS at Policlinico San Matteo, Pavia, Italy, between 1992 and 2006 were retrospectively evaluated. One or more comorbidities were present in 455/840 (54%) patients: the older the age, the higher their prevalence (P<0.001). Cardiac disease was observed in 25% of patients, liver disease in 16%, diabetes in 11%, prior solid tumor in 10%, nephropathy and pulmonary disease in 4%. Non-leukemic causes of death included cardiac failure (63%), infection (24%) and hemorrhage (7%). In a Cox analysis with age, sex, WHO category, cytogenetics and transfusion-dependency as time-dependent covariates, the presence of one or more comorbidities significantly affected both the risk of NLD (HR=1.91, P=0.001) and OS (HR=1.51, P=0.01), while it did not influence the risk of leukemic progression. The negative effect of comorbidities on OS was more evident in patients without excess of blasts (HR=1.8 P=0.007), while it retained a borderline significance in patients with more advanced disease (P=0.05). By including comorbidities as distinct entities in multivariable analysis, cardiac failure, liver or pulmonary disease, and solid tumors were found to independently affect the risk of NLD (HR=3.7, HR=2.08, HR=2.07 HR=2.23, respectively; P values from <0.001 to 0.033). Based on results of uni- and multivariable analysis, we developed a prognostic model for predicting the effect of comorbidities on NLD and OS. For each comorbidity, risk scores were estimated from the coefficients of the Cox regression. This MDS-specific comorbidity index (MDS-CI) allowed us to identify 3 groups of patients with different probability of NLD and OS (HR 2.78, P<0.001; HR 1.67 P=0.001), and provided a better stratification than the available non MDS-specific indices. Focusing on WPSS categories [J Clin Oncol2007; 25:3503–10], MDS-CI significantly stratified survival of patients with very-low, low and intermediate risk groups (P<0.001), while it had no effect in high and very-high risk groups. We then investigated the relationship between transfusion-dependency, secondary iron overload and comorbidities. Heart failure (28% vs. 18% P=0.001) and cardiac death (69% vs 55% P=0.03) were significantly more frequent in transfusion-dependent patients. In a Cox analysis with time-dependent covariates, transfusion-dependent patients showed an increased risk of NLD (HR=2.12 P=<0.001), heart failure (HR 1.34 P=0.03), and cardiac death (HR 2.99 P=0.01). The development of secondary iron overload significantly affected the risk of NLD and OS (HR=1.25 and 1.16 respectively, P<0.001), and this effect was maintained after adjusting for transfusion burden. Iron overload specifically increased the risk of developing heart failure (HR=1.17, P<0.001). In summary, the presence of non-hematological comorbidities significantly worsens the survival of MDS patients. Transfusion-dependency and secondary iron overload are associated with an increased risk of cardiac complications and cardiac death. The MDS-CI might be a useful tool for clinical decision making in patients with myelodysplastic syndromes.

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Iron Chelation by Deferoxamine Induces Autophagy

Blood ◽

10.1182/blood.v112.11.117.117 ◽

2008 ◽

Vol 112 (11) ◽

pp. 117-117 ◽

Cited By ~ 1

Author(s):

Ivana De Domenico ◽

Diane McVey Ward ◽

James P. Kushner ◽

Jerry Kaplan

Keyword(s):

Molecular Weight ◽

Iron Overload ◽

Iron Chelation ◽

Iron Chelators ◽

Immunochemical Analysis ◽

Alternate Route ◽

High Affinity ◽

Secondary Iron Overload ◽

Proteosomal Degradation ◽

Permeable Iron

Abstract Deferoxamine (DFO) is a high affinity Fe (III) chelator produced by Streptomyces pilosus that is used clinically to remove systemic iron in secondary iron overload disorders. DFO cannot be absorbed through the intestine and must be injected. As shown previously, De Domenico et al. EMBO J (2006), expression of Ferroportin (Fpn), the only mammalian iron exporter, can deplete cells of ferritin by lowering cytosolic iron and by exporting iron from cells. Fpn-mediated iron loss induces ferritin degradation by the proteosome. In this study we show that permeable iron chelators, desferirax or deferriprone also induce the proteosomal degradation of ferritin. In contrast, DFO-mediated iron chelation at clinically useful concentrations, leads to ferritin degradation in lysosomes. Immunochemical analysis revealed that DFO-treated cells show increased levels of LC3B, a protein required for autophagy, suggesting that DFO induces autophagy. Treatment of cells with desferasirox or deferriprone did not lead to accumulation of LC3B. Studies using high molecular weight conjugates of DFO or inhibitors of endocytosis showed that the presence of DFO in lysosomes was responsible for the induction of autophagy. Incubation of DFO-treated cells with 3-methyladenine, an autophagy inhibitor, does not, however, prevent ferritin loss suggesting there may be an alternate route for ferritin degradation. This hypothesis was confirmed by examining the effect of the proteosome inhibitor, MG132, on DFOinduced autophagy in cells treated with DFO and 3-methyladenine. Addition of MG132 to 3-methyladenine treated cells prevents ferritin degradation. These results indicate that ferritin degradation occurs by two routes: a DFO-induced entry of ferritin into lysosomes and a cytosolic route in which iron is extracted from ferritin prior to degradation by the proteosome.

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RNAi-Mediated Inhibition of Tmprss6 Ameliorates Anemia and Secondary Iron Overload in a Mouse Model of β-Thalassemia Intermedia and Decreases Iron Overload in Hfe−/− Mice

Blood ◽

10.1182/blood.v120.21.1018.1018 ◽

2012 ◽

Vol 120 (21) ◽

pp. 1018-1018

Author(s):

Paul J Schmidt ◽

Anoop K Sendamarai ◽

Ivanka Toudjarska ◽

Tim Racie ◽

Jim S Butler ◽

...

Keyword(s):

Mouse Model ◽

Iron Overload ◽

Iron Absorption ◽

Disease Phenotype ◽

Ineffective Erythropoiesis ◽

Employment Equity ◽

Liver Iron ◽

Secondary Iron Overload ◽

Equity Ownership ◽

Low Levels

Abstract Abstract 1018 β-Thalassemia intermedia (TI), an inherited hemoglobinopathy caused by partial loss of β-globin synthesis, is characterized by anemia, extramedullary hematopoiesis and ineffective erythropoiesis as well as secondary iron overload. Hereditary hemochromatosis (HH) is most frequently caused by mutations in HFE and is marked by excess uptake of dietary iron with concomitant tissue iron overload. In both diseases, increased iron absorption is due to inappropriately low levels of the liver hormone, hepcidin (encoded by Hamp1). The membrane serine protease Matriptase-2 (encoded by Tmprss6) attenuates BMP-mediated Hamp1 induction by cleaving the BMP co-receptor, hemojuvelin. Previously, it has been shown that elevating Hamp1 expression by genetic inactivation of Tmprss6 reduces disease severity in the Hbbth3/+ mouse model of TI and prevents iron overload in Hfe−/− mice. Therefore, a therapeutic approach comprising specific inhibition of Tmprss6 could prove efficacious in TI and HH. Here we show that systemic administration of a potent lipid nanoparticle (LNP) formulated siRNA directed against Tmprss6 leads to >80% inhibition of Tmprss6 mRNA in the livers of Hbbth3/+ and Hfe−/− mice with concomitant >2-fold elevation in Hamp1 expression. In the TI model, Tmprss6 silencing leads to ∼30% reductions in serum iron and non-heme liver iron. In Hfe−/− mice, serum iron and non-heme liver iron are similarly reduced, and Perls staining of peri-portal iron is diminished. Remarkably, the partial iron restriction induced by Tmprss6 inhibition in Hbbth3/+ mice leads to dramatic improvements in the hematological aspects of the disease phenotype: the severity of the anemia is decreased as evidenced by an approximately 1 g/dL increase in total hemoglobin and a 50% decrease in circulating erythropoietin levels. As in the human disease, Hbbth3/+ mice exhibit the hallmarks of ineffective erythropoiesis including splenomegaly, decreased erythrocyte survival and marked reticulocytosis. Treatment with LNP formulated Tmprss6 siRNA leads to a dramatic 2–3 fold decrease in spleen size, a 3–4 fold decrease in reticulocyte counts and a >7-day increase in RBC half-life. Histological analysis of spleens from Tmprss6 siRNA treated animals demonstrates restoration of normal splenic architecture, as well as a reduction in the number of Tfr1-positive erythrocyte precursors in the spleen. Furthermore, as evidenced by the near normalization of blood smears, the overall quality of erythropoiesis in treated animals is vastly improved. Taken together, these data demonstrate that RNAi-mediated silencing of liver Tmprss6 elevates Hamp1 expression and reduces iron overload in both TI and HH model mice. More significantly, Tmprss6 siRNA treatment ameliorates all aspects of the disease phenotype in the TI mouse model. These results support the development of an RNAi therapeutic targeting TMPRSS6 for the treatment of TI, HH and potentially other disorders characterized by excess iron absorption due to physiologically inappropriately low levels of hepcidin. Disclosures: Racie: Alnylam Pharmaceuticals: Employment. Butler:Alnylam Pharmaceuticals, Inc.: Employment, Equity Ownership. Bumcrot:Alnylam Pharmaceuticals, Inc.: Employment, Equity Ownership.

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