Detection of superoxide radicals from alveolar macrophages by electron spin resonance and chemiluminescence and the effects of endotoxin

Abstract

Oxygen-derived free radicals have been suggested to play an important roles in the pathogenesis of some pulmonary tissue damages such as adult respiratory distress syndrome (ARDS). In the case of ARDS, the production of superoxide from polymolphonuclear leukocyte has been reported to be increased. Alveolar macrophages play important roles in the pulmonary defense by participating in specific immunologic reactions, releasing chemotactic factors and releasing superoxide anions. However, oxygen-derived free radicals released from alveolar macrophages by the stimulation of endotoxin may cause pulmonary tissue damage.
In the present study, we could detect superoxide anions from alveolar macrophages by electron spin resonance using 5, 5-dimethyl-pyroline-N-oxide as a spin trap and chemiluminescence using 2-metyl-6 (p-methooxy-phenyl) 3, 7-dihydroimidazo (1, 2-a) pyrazin-3-one as a chemiluminescence probe. The administration of endotoxin to rats increases the production of superoxide radicals from alveolar macrophages stimmulated by phorbol myristate acetate (PMA). Moreover, by the preincubation of alveolar macrophages with endotoxin, the production of superoxide radicals was significantly increased. The administration of endotoxin to rats significantly increases total protein, albumin and angiotensin I converting enzyme in bronchoalveolar lavage fluid.
Although endotoxin did not cause superoxide production by alveolar macrophages, it enhanced superoxide production induced by PMA. It was suggested that superoxide from alveolar macrophages was one of the toxic factors which induced pulmonary injury by endotoxin.