Formation of ROS and RNS in response to CS

CS exposure activates immune cells, which generate superoxide radical (O₂^•−), through activation of NOX-2, which either reacts with NO to form harmful peroxynitrite (ONOO⁻) or be converted into harmful hydrogen peroxide (H₂O₂) under the influence of SOD, which in the presence of ferrous iron (Fe²⁺) is converted into hydroxyl radicals (•OH) via the Fenton reaction. Both GPx and CAT convert H₂O₂ into H₂O and O₂, reducing circulating ROS. Abbreviation: RNS, reactive nitrogen species.