Ferritin as a source of iron and protection from iron-induced toxicities

Abstract

The iron storage protein ferritin can contribute to or protect against toxicities which involve iron. Iron can catalyze the oxidation of lipid, protein, DNA and various biomolecules that can reduce iron. Iron can be reduced and released from ferritin by the free radical form of various toxins or superoxide resulting from oxygen reduction by chemicals which redox cycle. Iron can also increase ferritin synthesis by an iron-binding protein which releases from an iron-responsive element in mRNA for ferritin. This increase in ferritin synthesis provides a non-reactive storage site for iron. The mechanism by which iron is placed into ferritin is unknown. We propose that it is catalyzed by ceruloplasmin, the copper-containing ferroxidase that loads iron into transferrin. We believe that the ferroxidase activity, thought to reside in the heavy chain of ferritin, is an artifact resulting from ferrous iron autoxidation. We load iron into ferritin with ceruloplasmin so ferritin plus ceruloplasmin is an effective 'antioxidant'.