Pathways for the regulation of body iron homeostasis in response to experimental iron overload

Secondary iron overload is a frequent clinical condition found in association with multiple blood transfusions. To gain insight into adaptive changes in the expression of iron genes in duodenum, liver and spleen upon experimental iron overload we studied C57BL/6 mice receiving repetitive daily injections of iron-dextran for up to 5 days. Iron initially accumulated in spleen macrophages but with subsequent increase in macrophage ferroportin and ferritin expression its content in the spleen decreased while a progressive storage of iron occurred within hepatocytes which was paralleled by a significant increase in hepcidin and hemojuvelin expression. Under these conditions, iron was still absorbed from the duodenal lumen as divalent metal transporter-1 expressions were high, however, most of the absorbed iron was incorporated into duodenal ferritin, while ferroportin expression drastically decreased and iron transfer to the circulation was reduced. Experimental iron overload results in iron accumulation in macrophages and later in hepatocytes. In parallel, the transfer of iron from the gut to the circulation is diminished which may be referred to interference of hepcidin with ferroportin mediated iron export, thus preventing body iron accumulation.