Cellular iron regulation in animals: need and use of suitable models

As with virtually all biologically essential transition metals, but probably in a more acute way than most, iron excess and deficiency underlie a range of pathological conditions in animals. Accordingly, regulatory systems maintain the proper iron amount to fulfill the needs of the whole body and of each individual cell, while avoiding deleterious effects. The latter may be due to lack of iron availability, e.g. at the active site of iron enzymes, or to reductive catalysis promoted by uncontrolled ferrous ions leading to the formation of reactive species such as the hydroxyl radical. Two major regulators maintain metazoan iron homeostasis, a systemic one relying on the circulating hormone hepcidin, and a ubiquitous cellular one organized around the Iron Regulatory Proteins. These central nodes of iron homeostasis are themselves regulated by numerous effectors beyond iron availability, and they impact other biological processes not directly