Free Radicals and Reactive Oxygen Species

Free radicals are produced naturally in vivo, both by normal cellular metabolism and as a result of disease processes or through xenobiotic exposure. Free radicals have the potential to elicit many of the tissue changes associated with toxicities and disease processes but are also a consequence of such damage. Thus, the cause–effect relationship between radicals and disease or toxicities has been difficult to establish. In recent years, improvements in analytical methodologies, as well as the realization that subtle effects induced by free radicals and oxidants at the molecular level are important in modulating cellular signaling, have greatly improved our understanding of the roles of these reactive species in toxic mechanisms and disease processes. This chapter provides an overview of free radical and oxidant-mediated processes as related to mechanisms of cell and tissue injury.