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3 metabolismo del hierro
- 1. Metabolismo del Hierro Felipe González Velázquez
- 2. BODY IRON SUPPLY AND STORAGE.
- 3. ACQUISITION AND UTILIZATION OF IRON BY ERYTHROID PRECURSORS.
- 4. RECYCLING OF ERYTHROCYTE IRON BY MACROPHAGES.
- 5. ACQUISITION, UTILIZATION, STORAGE, AND EXPORT OF IRON BY HEPATOCYTES.
- 6. REGULATION OF CELLULAR IRON HOMEOSTASIS BY THE IRON REGULATORY PROTEINS (IRP1 AND IRP2).
- 7. CONTROL OF IRON ENTRY INTO PLASMA BY FERROPORTIN AND HEPCIDIN IN THE REGULATION OF SYSTEMIC IRON HOMEOSTASIS.
- 8. TRANSCRIPTIONAL REGULATION OF HEPCIDIN EXPRESSION IN HEPATOCYTES.
- 9. ABSORPTION OF DIETARY IRON BY THE INTESTINAL ENTEROCYTE
Editor's Notes
- Iron Imports. II. Iron uptake at the apical membrane in the ...ajpgi.physiology.org1280 × 744Buscar por imágenesIntestinal iron uptake. Nonheme dietary iron includes Fe(II) and Fe(III) salts and organic complexes. Fe3+ is reduced to Fe2+ by ascorbic acid and apical ...
- Figure 6. Systemic iron homeostasis and regulation of hepcidin expression. (A) Iron is absorbed by duodenal enterocytes using the divalent metal transporter-1 (DMT-1), where it is oxidized by hephaestin to ferric iron and exported into the plasma by ferroportin. In the plasma, iron binds to transferrin (Tf). Binding of holotransferrin to the transferrin receptor (TfR1) leads to iron uptake in multiple tissues including the bone marrow, where it is used for erythropoiesis. Senescent red blood cells are phagocytosed by spleen macrophages leading to recycling of iron back into the plasma. If iron is released into the plasma at a level that exceeds the binding capacity of transferrin, the excess iron is deposited in the liver. Hepcidin, a peptide hormone secreted by the liver, regulates iron absorption, recycling, and mobilization by binding to ferroportin and triggering its internalization and lysosomal degradation in both enterocytes and macrophages. (B) The Hamp gene, which encodes hepcidin, is activated in response to elevated iron levels as well as inflammatory cytokines such as IL-6. Increased plasma iron and holotransferrin levels leads to the stabilization of the transferrin receptor 2 (TfR2) resulting in the dissociation of the hemachromatosis protein (HFE) from TfR1 to TfR2. This complex has been shown to associate with hemojuvelin (HJV), a coreceptor for bone morphogenetic proteins (BMP). Binding of BMPs to the BMP receptor complex activates the BMP signaling pathway resulting in Hamp upregulation. Certain BMPs can regulate hepcidin expression independently of HJV, TfR2 and HFE. Low plasma iron leads to HJV cleavage and the production of soluble hemojuvelin (sHJV), which can bind to BMP and block the activation of BMP receptors. Two proteases, furin and TMPRSS6, have been shown to be capable of HJV cleavage. Inflammatory cytokines, such as IL-6, activate signal transducer and activator of transcription-3 (STAT3). STAT3 then binds to the Hamp gene promoter and induces hepcidin expression.