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ABSTRACT: In HFE-related hereditary hemochromatosis an inappropriately low hepatic expression of the iron-regulatory peptide hepcidin (encoded by HAMP) has been suggested to cause iron overload. The aim of the present study was to evaluate whether the hepatic expression of HAMP in relation to iron stores requires HFE or might involve other important iron-related genes including HJV (encoding hemojuvelin) and TFR2 (encoding transferrin receptor-2).
Using quantitative RT-PCR, the iron-dependent hepatic expression patterns of HAMP, HJV, and TFR2 were evaluated in human and murine HFE-related hemochromatosis.
The overall level of hepatic HAMP expression in human and murine HFE-related hemochromatosis is impaired but can still be modulated by iron stores. Moreover, we demonstrate an HFE-independent correlation between the expression of HAMP and TFR2 in mouse and human livers. On the other hand, a strong correlation between the hepatic expression of HAMP and HJV was only found in hemochromatosis patients and Hfe-deficient mice.
The central pathogenetic step in HFE-related hemochromatosis is an impaired basal expression of HAMP rather than a lack of HAMP upregulation in response to iron stores. An HFE-independent pathway that seems to involve TFR2 and HJV can regulate HAMP expression under conditions of iron overload.
Digestion 02/2005; 72(1):25-32. · 2.05 Impact Factor
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ABSTRACT: Mild iron overload in chronic hepatitis C is associated with liver fibrosis, hepatitis C virus (HCV) genotype 1b infection, and an impaired response to interferon therapy. In this study we evaluated whether polymorphisms in the hemochromatosis gene HFE and the transferrin receptor gene TFR1 are associated with these typical findings. The study considered 246 HCV-infected patients and 200 blood donors as controls, in which C282Y, H63D, and S65C mutations ( HFE) and the S142G polymorphism ( TFR1) were detected. HCV genotype, serum ferritin levels, stainable intrahepatic iron, and grade of fibrosis according to the METAVIR score (F0-F4) were determined. In HCV-infected patients, heterozygosity for the C282Y mutation in HFE was significantly associated with elevated serum ferritin levels, stainable liver iron, and advanced fibrosis or cirrhosis (F2-F4). By multivariate logistic regression analysis the odds ratio for the development of advanced fibrosis or cirrhosis (F2-F4) was 2.5 for HCV-infected patients carrying a heterozygous C282Y mutation and 4.8 for HCV-infected patients with C282Y/H63D and C282Y/S65C compound heterozygosity. Heterozygosity for the C282Y mutation in HFE contributes to iron accumulation and fibrosis progression in chronic hepatitis C.
Journal of Molecular Medicine 01/2004; 81(12):780-7. · 4.67 Impact Factor
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ABSTRACT: Mild iron overload in chronic hepatitis C is associated with liver fibrosis, hepatitis C virus (HCV) genotype 1b infection, and an impaired response to interferon therapy. In this study we evaluated whether polymorphisms in the hemochromatosis gene HFE and the transferrin receptor gene TFR1 are associated with these typical findings. The study considered 246 HCV-infected patients and 200 blood donors as controls, in which C282Y, H63D, and S65C mutations (HFE) and the S142G polymorphism (TFR1) were detected. HCV genotype, serum ferritin levels, stainable intrahepatic iron, and grade of fibrosis according to the METAVIR score (F0–F4) were determined. In HCV-infected patients, heterozygosity for the C282Y mutation in HFE was significantly associated with elevated serum ferritin levels, stainable liver iron, and advanced fibrosis or cirrhosis (F2–F4). By multivariate logistic regression analysis the odds ratio for the development of advanced fibrosis or cirrhosis (F2–F4) was 2.5 for HCV-infected patients carrying a heterozygous C282Y mutation and 4.8 for HCV-infected patients with C282Y/H63D and C282Y/S65C compound heterozygosity. Heterozygosity for the C282Y mutation in HFE contributes to iron accumulation and fibrosis progression in chronic hepatitis C.
Journal of Molecular Medicine 11/2003; 81(12):780-787. · 4.67 Impact Factor
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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 08/2003; 102(1):371-6. · 9.90 Impact Factor
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ABSTRACT: SFT, a stimulator of iron (Fe) transport, has been described as a transmembrane protein that facilitates the uptake of ferrous and ferric iron in mammalian cells. This study was initiated to investigate the 5' regulatory region of SFT and its role in the etiology of hereditary hemochromatosis. Sequence analyses of the putative 5' regulatory region revealed that the SFT cDNA sequence corresponds to intron 6/exon 7 of UbcH5A, a member of E2 ubiquitin-conjugating enzymes, which is involved in the iron-dependent ubiquitination of the hypoxia-inducible factor (HIF) by the von Hippel-Lindau tumor suppressor (pVHL) E3 ligase complex. Further mRNA expression studies using a sequence-specific reverse transcriptase-polymerase chain reaction (RT-PCR) assay showed that UbcH5A is significantly up-regulated in the liver of iron-overloaded patients with hereditary hemochromatosis, as previously published for SFT. However, in vitro studies on HepG2 cells failed to demonstrate any significant UbcH5A regulation in response to iron loading or iron chelation. In conclusion, in vivo mRNA expression data previously obtained for SFT might be attributed to UbcH5A. The role of UbcH5A and the ubiquitination pathway in the etiology of hereditary hemochromatosis remains to be elucidated further.
Blood 05/2003; 101(8):3288-93. · 9.90 Impact Factor
