THE EFFECT OF VARIOUS ANTIOXIDANTS AND OTHER MODIFYING AGENTS ON OXYGEN-RADICAL-GENERATED DNA-DAMAGE IN HUMAN-LYMPHOCYTES IN THE COMET ASSAY

The effects of antioxidants and various other modifying agents on oxyg en-radical-generated DNA damage in human lymphocytes have been investi gated using the COMET assay. Hydrogen peroxide (H2O2) and bleomycin (B LM) have produced clear dose-related responses. In 38 independent expe riments, there was consistency between the two donors used in the stud y for the negative and positive control data. The endogenous antioxida nt catalase abolished effects with H2O2, but only slightly affected th e response with BLM. Superoxide dismutase did not alter the response w ith H2O2 and only slightly affected BLM. The exogenous antioxidant vit amin C produced a clear dose-related response on its own. In combinati on with H2O2, there were small protective effects at low doses and exa cerbating effects at high doses, but these were within the inter-exper imental variability range. Vitamin E (trolox) produced no effects with either H2O2 or BLM, or on its own. Silymarin protected against the ef fect due to H2O2. Other modifying agents such as apo-transferrin and d eferoxamine mesylate produced a clear dose-related protection of effec ts due to BLM. This protection was less due to H2O2. In the presence o f ferrous chloride, the effect due to BLM was exacerbated. In a small sample of 6 smokers and 6 non-smokers, responses from smokers approach ed borderline significance (P=0.054) by comparison with non-smokers. T hese observations would suggest that the COMET assay is a useful tool for examining issues related to oxidative stress in human lymphocytes.