Chemiluminescent detection of oxidants in vascular tissue - Lucigenin but not coelenterazine enhances superoxide formation

Lucigenin-amplified chemiluminescence has frequently been used to assess th e formation of superoxide in vascular tissues. However, the ability of luci genin to undergo redox cycling in purified enzyme-substrate mixtures has ra ised questions concerning the use of lucigenin as an appropriate probe for the measurement of superoxide production. Addition of lucigenin to reaction mixtures of xanthine oxidase plus NADH resulted in increased oxygen consum ption, as well as superoxide dismutase-inhibitable reduction of cytochrome c, indicative of enhanced rates of superoxide formation. Additionally, it w as revealed that lucigenin stimulated oxidant formation by both cultured bo vine aortic endothelial cells and isolated rings from rat aorta, Lucigenin treatment resulted in enhanced hydrogen peroxide release from endothelial c ells, whereas exposure to lucigenin resulted in inhibition of endothelium-d ependent relaxation in isolated aortic rings that was superoxide dismutase inhibitable. In contrast, the chemiluminescent probe coelenterazine had no significant effect on xanthine oxidase-dependent oxygen consumption, endoth elial cell hydrogen peroxide release, or endothelium-dependent relaxation, Study of enzyme and vascular systems indicated that coelenterazine chemilum inescence is a sensitive marker for detecting both superoxide and peroxynit rite.