Enzymatic Oxidants, Antioxidants, and Inflammatory Bowel Disease

The role of oxidants and antioxidants in inflammatory bowel disease (IBD) has been actively explored since the early 1980s, starting with the role of the respiratory burst of neutrophils and ischemia in bowel pathology. Since that time, the enzymatic components contributing to the pool of reactive oxygen species, including superoxide, H2O2, and lipid hydroperoxides, and the counteracting antioxidants—catalase, glutathione peroxidases (Gpx), peroxiredoxins (PRDX), superoxide dismutases, and others—have been fleshed out. My perspective on IBD is from the role of the balance or imbalance of enzymatic oxidant sources and enzymatic antioxidants in the inflammatory process. I will present evidence on the involvement of oxidant and antioxidant processes in IBD based, as much as possible, on my experiences with Gpxs. This evidence will be discussed in terms of both the immune system and local bowel oxidant and antioxidant systems. As Gpxs are generally selenium-dependent, possible deficiencies in selenium uptake in active IBD and the impact on Gpx expression will be explored. The more recently introduced ferroptosis, an iron-dependent lipid peroxidation-based pathological process, will be reviewed for its possible involvement in IBD.