Oxidative DNA damage by vitamin A and its derivative via superoxide generation

Abstract

Recent intervention studies revealed that β-carotene supplement to smokers resulted in a higher incidence of lung cancer. However, the causal mechanisms remain to be clarified. We reported here that vitamin A (retinol) and its derivative (retinal) caused cellular DNA cleavage detected by pulsed field gel electrophoresis. Retinol and retinal significantly induced 8-oxo- 7,8-dihydro-2'-deoxyguanosine formation in HL-60 cells but not in H2O2- resistant HP100 cells, suggesting the involvement of H2O2 in cellular DNA damage. Experiments using 32P-labeled isolated DNA demonstrated that retinol and retinal caused Cu(II)-mediated DNA damage, which was inhibited by catalase. UV-visible spectroscopic and electron spin resonance-trapping studies revealed the generation of superoxide and carbon-centered radicals, respectively. The superoxide generation during autoxidation of retinoids was significantly correlated with the formation of 8-oxo-7,8-dihydro-2'- deoxyguanosine, although the yield of carbon-centered radicals was not necessarily related to the intensity of DNA damage. These findings suggest that superoxide generated by autoxoidation of retinoids was dismutated to H2O2, which was responsible for DNA damage in the presence of endogenous metals. Retinol and retinal have prooxidant abilities, which might lead to carcinogenesis of the supplements of β-carotene.