Oxidative stress

Abstract Oxygen radicals and hydrogen peroxide are constantly produced in the human body. Some of this production is a chemical accident, such as generation of hydroxyl radicals (OH”) by our constant exposure to low levels of radiation from the environment (see Chapter 1) and of superoxide (O2·™) by leakage of electrons from electron transport chains (see Chapter 2). Other production of these species is deliberate, including the generation of H2O2 by such enzymes as o-amino acid oxidase (see Chapter 2). Perhaps the best-known examples of deliberate production of radicals in the human body are the generation of2·™ by activated phagocytic cells (see the Appendix to this chapter) and the generation of nitric oxide by the cells lining blood vessel walls (see Chapter 1).