Evidence for hydroxyl radical generation by human Monocytes.

A number of highly reactive oxygen species have been implicated in the oxygen-dependent mechanisms involved in bactericidal activity of phagocytic leukocytes. Hydrogen peroxide and superoxide, two agents known to occur during phagocytosis, are thought to interact to generate hydroxyl radical, singlet oxygen, and other potentially reactive molecules. Using an assay system of ethylene generation from methional, cell preparations of human monocytes were demonstrated to generate hydroxyl radical or a similar agent during phagocytosis of zymosan particles. The generation of ethylene was impaired by agents which reduce superoxide or hydrogen peroxide concentrations as well as by agents reported to be hydroxyl radical scavengers. The ethylene generation did not appear to be dependent on myeloperoxidase in that azide enhanced ethylene generation. Monocytes from a patient with chronic granulomatous disease failed to generate ethylene during phagocytosis. This assay technique may be useful in exploring the metabolic events integral to the bactericidal and inflammatory activity of phagocytic leukocytes.