Oxidative stress is an environment where the balance of prooxidant species to antioxidant species is altered in favor of the former. Prooxidant species include free radicals (e.g., the superoxide ion; O2−) and nonradical species (e.g., hydrogen peroxide; H2O2), which together are classified as reactive oxygen and nitrogen species (RONS). RONS are produced as a consequence of normal cellular oxidation processes. Sources include the mitochondrial electron transport chain, peroxisomes, endothelial or hepatic xanthine oxidase, and leukocytes. RONS have a variety of roles in normal homeostasis, including respiration and cellular signaling: RONS are reported to act as transient signaling molecules in the Ras GDP/GTP cycle and MAP kinase cascades, through modification of protein-bound redox-sensitive thiol groups.
Antioxidants serve to delay or prevent the oxidation of substrates or cellular constituents. They may be endogenous, for example, the enzymes superoxide...
References and Readings
- Halliwell, B., & Gutteridge, J. (2007). Free radicals in biology and medicine (4th ed.). New York: Oxford University Press.Google Scholar