Liver nuclear NADPH-cytochrome P-450 reductase may be involved in redox cycling of bleomycin-Fe(III), oxy radical formation and DNA damage.
When NADPH-cytochrome P-450 reductase isolated from rat liver microsomes was aerobically incubated with bleomycin, FeCl3, NADPH and DNA parallel NADPH and oxygen were consumed and malondialdehyde was formed. A similar parallelism of NADPH- and oxygen-consumption and malondialdehyde formation was observed when cell nuclei isolated from rat liver were incubated under the same conditions. The formation of malondialdehyde which was identified by HPLC and which was most likely released from oxidative cleavage of deoxyribose of nuclear DNA required oxygen, bleomycin, FeCl3 and NADPH. This indicates that a nuclear NADPH-enzyme, presumably NADPH-cytochrome P-450 reductase, is able to redox cycle a bleomycin-iron-complex which in the reduced form can activate oxygen to a DNA-damaging reactive species. The data suggest that the activity of this enzyme in the cell nucleus could play an important role in the cytotoxicity of bleomycin in tumor cells.
Kappus
H
H
Free University of Berlin, West-Germany.
Mahmutoglu
I
I
Kostrucha
J
J
Scheulen
M E
ME
D000818:Animals; D001761:Bleomycin / Q000378:metabolism* / Q000031:analogs & derivatives; D002467:Cell Nucleus / Q000201:enzymology; D004249:DNA Damage; D005609:Free Radicals; D066298:In Vitro Techniques; D008099:Liver / Q000201:enzymology*; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D051381:Rats; D011919:Rats, Inbred Strains
D005609:Free Radicals; C023503:iron bleomycin; D001761:Bleomycin; D008315:Malondialdehyde; D009249:NADP; D009251:NADPH-Ferrihemoprotein Reductase; D010100:Oxygen