Generation of hydroxyl radical by anticancer quinone drugs, carbazilquinone, mitomycin C, aclacinomycin A and adriamycin, in the presence of NADPH-cytochrome P-450 reductase.

The generation of hydroxyl free radicals in the system consisting of purified NADPH-cytochrome P-450 reductase and anticancer quinone drugs, such as carbazilquinone, mitomycin C, aclacinomycin A and adriamycin, has been confirmed by two methods. In the spin trapping study, using N-tert-butyl-alpha-phenylnitrone as the spin trapping agent, four drugs generated hydroxyl radical-trapped signals, and the formation of the spin adduct was dependent on time and the enzyme concentration. Among the four drugs, the generation time of signal was in the order of carbazilquinone, aclacinomycin A, adriamycin and mitomycin C, but the magnitude of signal intensity was different. In both aclacinomycin A and adriamycin, the signal disappeared in a few minutes. Catalase completely inhibited the formation of the spin adduct, while superoxide dismutase did not significantly inhibit, but effected in some manner. The generation of hydroxyl radical was also confirmed by the ethylene production from methional. Among the four drugs, the order of the magnitude of ethylene production was different from that of signal intensity by ESR study. Catalase potently inhibited the ethylene production, while superoxide dismutase effected in some manner. From these results, the interactions of anticancer quinone drugs with NADPH-cytochrome P-450 reductase and oxygen, and the possible relations of the enzymes to the radical related actions of these drugs are discussed.