Antioxidant enzymes and human diseases

Objectives: To describe the importance of the antioxidant enzymes superoxid e dismutase, glutathione peroxidase, and catalase working together in human cells against toxic reactive oxygen species, their relationship with sever al pathophysiologic processes and their possible therapeutic implications. Conclusions: Reactive oxygen species (ROS) are involved in the cell growth, differentiation, progression, and death. Low concentrations of ROS may be beneficial or even indispensable in processes such as intracellular signali ng and defense against micro-organisms. Nevertheless, higher amounts of ROS play a role in the aging process as well as in a number of human disease s tates, including cancer, ischemia, and failures in immunity and endocrine f unctions. As a safeguard against the accumulation of ROS, several nonenzyma tic and enzymatic antioxidant activities exist. Therefore, when oxidative s tress arises as a consequence of a pathologic event, a defense system promo tes the regulation and expression of these enzymes. Copyright (C) 1999 The Canadian Society of Clinical Chemists.