Phagocytes and oxidative stress

Neutrophils and other phagocytes manufacture O-2(-) (superoxide) by the one -electron reduction of oxygen at the expense of NADPH. Most of the O-2(-) r eacts with itself to form H2O2 (hydrogen peroxide). From these agents a lar ge number of highly reactive microbicidal oxidants are formed, including HO Cl (hypochlorous acid), which is produced by the myeloperoxidase-catalyzed oxidation of Cl- by H2O2; OH. (hydroxyl radical), produced by the reduction of H2O2 by Fe++ or Cu+; ONOO- (peroxynitrite), formed by the reaction betw een O-2(-) and NO-; and many others. These reactive oxidants are manufactur ed for the purpose of killing invading microorganisms, but they also inflic t damage on nearby tissues, and are thought to be of pathogenic significanc e in a large number of diseases. Included among these are emphysema, acute respiratory distress syndrome, atherosclerosis, reperfusion injury, maligna ncy and rheumatoid arthritis. Am J Med. 2000;109:33-44. (C) 2000 by Excerpt a Medica, Inc.