Inhibitory effect of fatty acids on 8-hydroxydeoxyguanosine formation in calf thymus DNA treated with bleomycin-Fe(II).

The effect of fatty acids on 8-hydroxydeoxyguanosine (8-OH-dG) formation in calf thymus DNA treated with bleomycin (BLM)-Fe(II) in vitro was studied. The formation of 8-OH-dG was greatly reduced in the presence of stearic acid (18:0) or oleic acid (18:1), however, it increased to the control level with an increase in the number of unsaturated bonds of fatty acids (18:2, 18:3). This increase in 8-OH-dG formation may have resulted from the indirect oxidation of DNA by the peroxidized unsaturated fatty acids formed by BLM-Fe(II). The inhibitory effect of saturated fatty acids on 8-OH-dG formation was observed with those possessing more than 12 methylene chains. Stearic acid also inhibited peroxidation of unsaturated fatty acids (18:2, 18:3) treated with BLM-Fe(II), however, it had no effect on ribose degradation of DNA treated with BLM-Fe(II). These results suggest that different active oxygen species are probably involved in DNA degradation and in formation of 8-OH-dG in DNA and of peroxidized products in fatty acids.