How does hormesis impact biology, toxicology, and medicine?

Evolutionary hormesis-based adaptations that enabled organisms to survive and flourish in the presence of toxic metals. The solubilization of iron and copper in rocks results in the formation of ions (Fe2+ and Cu+) that can be highly toxic to cells. During respiration (oxidative phosphorylation), cells generate hydrogen peroxide (H2O2). Interaction of H2O2 with Fe2+ or Cu+ results in the generation of the highly destructive hydroxyl free radical (OH？.), which can kill cells by damaging DNA, proteins, and membrane lipids. Beginning very early in the evolution of life, organisms evolved proteins to protect themselves against Fe2+ or Cu+ toxicity. The proteins include those that sequester the metal ions or expel them from the cell. In addition, various iron- or copper-dependent enzymes evolved that used the redox properties of these elements to their advantage. Examples of proteins involved in iron and copper metabolism are shown. FRO7 ferric chelate reductase oxidase 7; P1C1 permease in chloroplasts; PAM peptidylglycine-alpha-amidating monooxygenase; V1T1 vacuolar iron transporter 1. All images in the figure were obtained from Wikimedia Commons under the Creative Commons copyright 4.0 International, 2.0 Generic, and Share Alike 2.5 Generic (CC-BY) license, and GNU Free Documentation 1.2 licens