Concepts of oxidative stress and antioxidant defense in Crohn’s disease

Figure 1 Reactions of superoxide (^•O₂^-) that generate highly reactive oxygen species. ^•O₂^- can be dismutated into H₂O₂, which, in the presence of Fe²⁺, can generate the highly reactive hydroxyl radical, HO^•. ^•O₂^- may react with NO^• to form the strong pro-oxidant peroxynitrite (ONOO^-); alternatively, it may react with HO^• to form singlet oxygen (¹O₂); NADPH: Nicotinamide adenine dinucleotide phosphate.

Figure 2 Initiation and propagation of the free-radical chain reaction of lipid peroxidation. Reactions D and E represent the metal-catalyzed Fenton reaction.

Figure 3 Two proposed mechanisms through which linoleic acid could increase the production of interleukin-8 via the activation of arachidonic acid pathways. By the generation of reactive oxygen species (ROS) from the cyclooxygenase and lipoxygenase enzymes to activate Nuclear factor-κB (NF-κB), increasing interleukin (IL)-8 production; or by the use of AA metabolites to increase IL-8 production. LTs: Leukotrienes; Tx: Thromboxane.