DNA damage in human colonic mucosa cells induced by bleomycin and the protective action of vitamin E.

Using the alkaline comet assay, we showed that bleomycin at 0.1-5 microg/ml induced DNA strand breaks and/or alkali-labile sites, measurable as the comet tail moment, in human colonic mucosa cells. This DNA damage was completely repaired during a 120-minute post-treatment incubation of the cells. Post-treatment of the bleomycin-damaged DNA with 3-methyladenine-DNA glycosylase II (AlkA), an enzyme recognizing alkylated bases, gave rise to a significant increase in the extent of DNA damage, indicating that the drug could induce alkylative bases in DNA. We did not observe any change in the comet tail moment in the presence of catalase. Vitamin E ((+)-alpha -tocopherol) decreased DNA damage induced by bleomycin. The results obtained suggest that hydrogen peroxide might not be involved in the formation of DNA lesions induced by bleomycin in the colonic mucosa cells.