FIGURE 2.

Stepwise demonstration of the Fenton reactions and subsequent pathological effects. Reactions depicted with dotted arrows represent reverse reactions mediated by cellular antioxidants. Production of superoxide radical anion (SORA) in the first reaction is exploited and secreted by immune cells for pathogenic control, indicated by the solid curved arrow. Pathological consequences include oxidation of susceptible iron atoms in [4Fe–4S]²⁺ clusters. Production of hydrogen peroxide in the second reaction is damaging to lipid bilayers, DNA, mitochondrial membrane potential, causes apoptotic cascades, damages ICS, and disrupts the actin cytoskeleton. Production of hydroxyl radical in the final reaction is similarly known to damage lipid bilayers, cause DNA strand breaks, and be reactive with all known biomolecules.