FIGURE 1.

Main generation and modulation of ROS. Mitochondrial and membrane NADPH oxidases (NOXs) are the main sources of endogenous ROS production. The superoxide dismutase (SOD) enzymes transform superoxide radical anion (O₂ ^·−) into hydrogen peroxide (H₂O₂). H₂O₂ can undergo Fenton chemistry with Fe²⁺ to form a hydroxyl radical (OH^·−), causing damage to DNA, proteins, and lipids. H₂O₂ can be reduced and converted to H₂O by peroxiredoxins (PRXs), glutathione peroxidases (GPXs), and catalase (CAT). ROS, as a signaling molecule, impacts the development and progression of normal body and disease cells depending on its concentration.