Labile iron pool (cellular free iron) (LIP)

Cellular "free iron" refers to the labile iron pool (LIP), a small fraction of weakly bound, redox-active iron within the cytosol not incorporated into proteins or stored in ferritin. This pool serves as a rapidly accessible source for biosynthetic and metabolic needs, but its redox activity also enables participation in Fenton chemistry, producing reactive oxygen species and contributing to potential cytotoxicity and tissue damage if not tightly regulated. Most cellular iron is either protein-bound (e.g., hemoglobin, cytochromes, ferritin) or incorporated into iron-sulfur clusters and heme, with the "free" or labile pool representing a tiny but metabolically crucial fraction[1][3][5][7]. Iron homeostasis in cells is tightly controlled through the iron-regulatory protein (IRP)/iron-responsive element (IRE) system, which balances import (via transferrin receptor, DMT1), storage (ferritin), and export (ferroportin) depending on intracellular iron levels[2][3][7]. Disruption of LIP can lead to iron overload or deficiency, implicated in multiple diseases, including cancer, infection, and neurodegeneration[3][4][8]. Therapeutically, most drugs act not on the free iron directly but on its chelation or by modulating proteins that control iron homeostasis. "Free iron in cells" is not a canonical therapeutic target (such as a protein or receptor), but rather a pool or chemical state within the cell. Drugs target this pool indirectly via chelation or by modulating iron-handling proteins. For this reason, "free iron in cells" is not an ideal entry as a drug target and may be considered incorrect for a strict "target" field[3][5][7].

Other names

labile ironchelatable iron poolcytosolic ironcellular free iron

Chelation of free iron to reduce oxidative damage; Limiting iron availability to pathogens or tumor cells.