Does the Interdependence between Oxidative Stress and Inflammation Explain the Antioxidant Paradox?

Figure 1

Major prooxidant-antioxidant reactions relevant in biological system. Superoxide () produced from a number of sources acts as a primary reactive species. rapidly reacts with nitric oxide to produce peroxynitrite (ONOO⁻) or is catalyzed by superoxide dismutase (SOD) to produce hydrogen peroxide (H₂O₂). H₂O₂ can be neutralized by catalase or glutathione peroxidase. However, in presence of transition metal ions, like iron (Fe²⁺) and copper (Cu⁺), highly toxic hydroxyl free radicals can be produced from H₂O₂ via the Fenton reaction. Reactive species are shown in red and antioxidant enzymes are shown in green boxes. GSH, reduced glutathione; GS-SG, oxidized glutathione.