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Abstract: The field of hereditary iron overload has known, in the recent period, deep changes mainly related to major advances in molecular biology. It encompasses now a series of genetic entities. The mechanistic understanding of iron overload development and iron toxicity has greatly improved. The diagnostic approach has become essentially noninvasive with a major role for biological tests. From the therapeutic viewpoint, the phlebotomy treatment is now enriched by the possibility of resorting to oral chelation and by innovative perspectives directly linked to our improvement in the molecular understanding of these diseases. [ABSTRACT FROM AUTHOR]

Inductively coupled plasma mass spectrometry (ICP-MS) is an analytical technique for inorganic, quantitative, and multi-elemental compounds commonly used in clinical biology. In recent years, it has gradually replaced atomic absorption techniques. It is based on the combination of an ion source formed of an inductively coupled plasma torch by a high-frequency electromagnetic generator, and a mass spectrometer, which allows the separation of ions generated according to their mass and energy. It allows the simultaneous detection of most metal and metalloid elements (about 80, 40 generally). It is extremely sensitive for determining analyte concentrations up to nanograms per liter. ICP-MS is fast and suitable for continued use on different types of biological samples. Its use requires, however, good knowledge of the different types of interferences, whether spectral or non-spectral. This method may require specific adaptations depending on the samples used due to the matrix effect. In this review, we will present the main principles of the realization of dosages, as well as the various devices currently commercialized. It is currently used for the determination of the most critical metals in clinical biochemistry, copper, zinc, and selenium, but also in clinical toxicology and pharmacology.

The field of hereditary iron overload has known, in the recent period, deep changes mainly related to major advances in molecular biology. It encompasses now a series of genetic entities. The mechanistic understanding of iron overload development and iron toxicity has greatly improved. The diagnostic approach has become essentially noninvasive with a major role for biological tests. From the therapeutic viewpoint, the phlebotomy treatment is now enriched by the possibility of resorting to oral chelation and by innovative perspectives directly linked to our improvement in the molecular understanding of these diseases., (Copyright © 2009 Elsevier Masson SAS. All rights reserved.)

Hereditary type 1 HFE hemochromatosis is associated with homozygosity for the p.Cys282Tyr mutation of the HFE gene (C282Y mutation). The p.Cys282Tyr mutation of the HFE gene leads to an abnormal reduction in hepatic expression of hepcidin, a protein that appears to control the release of iron from enterocytes and macrophages towards plasma. Abnormally low hepcidin levels promote an increase in the bioavailability of plasma iron, characterized by elevated transferrin saturation and the appearance of non transferrin bound iron. This nontransferrin-bound iron is avidly taken up by the liver, heart, and pancreas, the principal target organs for systemic iron overload. The variable penetrance of this disease is related to environmental and genetic factors. Among the genetic factors, mutations of some newly identified genes may aggravate the phenotype of iron overload associated with homozygosity for the p.Cys282Tyr mutation of the HFE gene; these new genes include those of hemojuvelin (HJV), transferrin receptor 2 (TfR2), and hepcidin (HAMP).

Iron is required for proper cell life functioning. Iron metabolism dysfunction leads in humans to deleterious situations. Maintenance of correct iron plasmatic bioavailability is crucial to permit adequate iron addressing to the different cell types. This implicates especially macrophages and enterocytes, ensuring the import of iron into plasma, as well as systemic signals, including hepcidin a peptide mainly produced by hepatocytes and secreted in plasma, which modulates iron leakage from these cells into plasma. The control of intracellular iron content is under the dependence of the IRE/IRP system which modulates cellular iron ingress and storage. The description of new iron metabolism genes, including hepcidin, paves the road for novel diagnostic tools and therapeutic strategies in the field of diseases associated with iron metabolism abnormalities.

Normal iron metabolism is highly regulated and takes a crucial role in the maintenance of cell functions. The plasmatic iron bioavailability control is a key step of this metabolism which involves numerous proteins implicated at various levels, including the digestive iron absorption by enterocytes, and iron release from macrophages. These two phenomenons are modulated in a coordonated fashion by the plasmatic level of hepcidin, a peptide mainly synthetized by the liver, secreted in plasma and modulating the expression of ferroportin, the cellular exporter of iron, and thus the iron egress. Numerous factors are able to modulate the hepcidin expression, including iron status, erythropoietic activity, inflammation and hepatic status which are already identified. Abnormalities occurring in the regulation of hepcidin expression may favour the development of iron metabolism disturbance, including systemic iron overload or relative iron deficiency. The use of hepcidin for diagnostic purpose or as a therapeutic target remains to be determined.

Iron overload diseases are a quickly and deeply changing world, due to major advances in genetics and molecular biology. Five main entities are concerned: a frequent one, namely HFE-related or type1 haemochromatosis, and four rare or exceptional diseases which are types 2, 3 and 4 haemochromatosis and aceruloplasminemia. Increased duodenal iron absorption and enhanced macrophagic iron recycling, both due to hypo-hepcidinemia, account for the development of cellular excess in types 1, 2, 3 haemochromatosis whereas decreased cellular iron egress is the main explanation for type 4 haemochromatosis and aceruloplasminemia. Non-transferrin bound iron plays an important role in cellular iron excess and damage. Phlebotomies remain an essential therapeutic tool but the improved understanding of the intimate mechanisms underlying these diseases open the road for innovative therapeutic approaches.

Iron is required for cellular life. However, abnormalities of its metabolism may lead to iron deficiency or iron overload, both conditions which are deleterious. Therefore, stock and distribution of iron in the body must be very stable. Classically, four major proteins are involved in iron metabolism: (a) transferrin which is implicated in its plasmatic transport, (b) transferrin receptor which regulates iron-transferrin uptake, (c) ferritin, the major iron storage protein, and (d) IRP (Iron Regulatory Protein) which regulates both the entry and storage of iron by linking to the IRE (Iron Responsive Element), a nucleotidic sequence found on transferrin receptor and ferritin mRNA. Thus, IRP adapts gene expression to the iron cellular status. Recent data give informations about new proteins involved in iron metabolism: HFE whose gene is mutated in genetic hemochromatosis, ceruloplasmin which permits cellular iron egress and frataxin which is implicated in the exit of iron from mitochondria.