Coenzyme Q(10) enrichment decreases oxidative DNA damage in human lymphocytes

Ubiquinol-10, the reduced form of coenzyme Q(10), is a powerful antioxidant in plasma and lipoproteins. It has been suggested that endogenous ubiquino l-10 also exerts a protective role even towards DNA oxidation mediated by l ipid peroxidation. Even though the antioxidant activity of coenzyme Q(10) i s mainly ascribed to ubiquinol-10, a role for ubiquinone-10 (the oxidized f orm), has been suggested not only if appropriate reducing systems are prese nt. To investigate whether the concentration of ubiquinol-10 or ubiquinone- 10 affects the extent of DNA damage induced by H2O2, we supplemented in vit ro human lymphocytes with both forms of coenzyme Q(10) and evaluated the DN A strand breaks by Comet assay. The exposure of lymphocytes to 100 mu M H2O 2 resulted in rapid decrease of cellular ubiquinol-10 content both in ubiqu inol-10-enriched and in control cells, whereas cu-tocopherol and p-carotene concentration were unchanged. After 30 min from H2O2 exposure, the amount of DNA strand breaks was lower and cells' viability was significantly highe r in ubiquinol-10-enriched cells compared with control cells. A similar tre nd was observed in ubiquinone-10-enriched lymphocytes when compared with co ntrol cells. Our experiments suggest that coenzyme Q(10) in vitro supplemen tation enhances DNA resistance towards H2O2-induced oxidation, but it doesn 't inhibit directly DNA strand break formation. (C) 1999 Elsevier Science I nc.