Abstract
Photodynamic deoxyribonucleic acid (DNA) strand breaking activities of 9 widely used drugs suspected of inducing photodermatological toxicity in humans, were examined. Enoxacin and afloqualone induced single strand breaks in supercoiled plasmid DNA following irradiation with common fluorescent lamps. The ED50 (effective dose which change 50% of supercoiled closed circular DNA to the open circular form) of enoxacin was 2 mM and that of afloqualone was approximately 860 μM. DNA strand breaking activity of photoirradiated enoxacin was markedly inhibited by NaN3 and partly by superoxide dismutase and D-mannitol. That of afloqualone was inhibited by NaN3 primarily and by catalase partly.These results suggest that enoxacin and afloqualone are active photosensitizers and that these drugs induce phototoxicity in biological systems through type II photodynamic mechanisms. The experimental system used in assessing the photodynamic activity of drugs (i.e., induction of single strand breaks in plasmid DNA) may also be useful for screening phototoxic compounds in our environment and for determining the active oxygen species involved.
