Figure 3.

Major pathways of reactive oxygen (nitrogen) species generation and metabolism. Several proinflammatory factors can stimulate O₂ ^∙− generation through activation of several specialized enzymes, such as the Nox, Xox, P450, COX, or NOS. SOD then converts the O₂ ^∙− to H₂O₂, which is then converted into the highly reactive ^∙OH or has to be rapidly removed from the system that is generally achieved by catalase or peroxidases, such as the GPx. Further, O₂ ^∙− can be either converted into ROO^∙ or can react with NO to yield ONOO⁻. NO is mostly generated by L-Arg via NOS. H₂O₂ can be converted to HOCl by the action of MPO. myeloperoxidase. O₂: molecular oxygen; H₂O: water; O₂ ^∙−: superoxide radical anion; ^∙OH: hydroxyl radical; ROO^∙: peroxyl radical; H₂O₂: hydrogen peroxide; ONOO⁻: peroxynitrite; NO: nitric oxide; L-Arg: L-arginine; HOCl: hypochlorous acid.