Exacerbating effect of vitamin E supplementation on DNA damage induced in cultured human normal fibroblasts by UVA radiation

The effects of vitamin E supplementation were evaluated in cultured human n ormal fibroblasts exposed to ultraviolet A radiation (320-380 nm) (WA). Cel ls were incubated in medium containing alpha -tocopherol, ol-tocopherol ace tate or the synthetic analog Trolox for 24 h prior to UVA exposure. DNA dam age in the form of frank breaks and alkali-labile sites, collectively terme d single-strand breaks (SSB), was assayed by the technique of single cell g el electrophoresis (comet assay), immediately following irradiation or afte r different repair periods. The generation of hydrogen peroxide (H2O2) and superoxide ion (O-2(.-)) was measured by how cytometry through the oxidatio n of indicators into fluorescent dyes. It was observed that pretreatment of cells with any form of vitamin E resulted in an increased susceptibility t o the photoinduction of DNA SSB and in a longer persistence of damage, wher eas no significant change was observed in the production of H2O2 and O-2(.- ) reactive oxygen species, compared to untreated controls. These findings i ndicate that in human normal fibroblasts, exogenously added vitamin E exert s a promoting activity on DNA damage upon UVA irradiation and might lead to increased cytotoxic and mutagenic risks.