Antioxidants prevent the lymphocyte DNA damage induced by PMA-stimulated monocytes

Oxidative stress has been related to several degenerative diseases such as cancer and coronary heart disease. Reactive oxygen species can damage diffe rent cellular macromolecules, including DNA, which is directly responsible for mutation and carcinogenesis. In this study, monocytes that were activat ed by phorbol 12-myristate 13-acetate (PMA) were coincubated with lymphocyt es, and the DNA damage was measured by single-cell gel electrophoresis (com et) assay. Stimulation of monocytes with PMA activates the "respiratory bur st," which evokes DNA damage in lymphocytes. The extent of the damage is re lated to the concentration of monocytes and the exposure time. Exogenous ad dition of superoxide dismutase did not prevent the DNA damage, which sugges ts that superoxide ions are not directly responsible for the damage. Partia l protection was observed when catalase was included (60% protection), whic h indicates that other reactive species, in addition to H2O2, are responsib le for the damage. In this system, the protective activity of natural antio xidants at different concentrations was also investigated. After coincubati on of PMA-activated monocytes with lymphocytes in the presence of each anti oxidant for one hour at 37 degreesC, the lymphocyte DNA damage was determin ed. All the compounds protected the lymphocytes to a certain degree, with a maximum effect at different concentrations: 41% protection with 1 muM asco rbic acid, 55% protection with 40 muM alpha -tocopherol, 50% protection wit h 3 muM beta -carotene, and 56% protection with 5 muM quercetin. On the bas is of these results, we maintain that this "ex vivo model, " more closely r elated to physiological conditions, could be used to test the antioxidant a ctivity of different compounds.