Effects of inorganic selenium compounds on oxidative DNA damage

Abstract Exposure of Escherichia coli or mammalian cells to H 2 O 2 results in cell death due to iron-mediated DNA damage. Since selenium compounds have been examined for their ability to act as antioxidants to neutralize radical species, and inorganic selenium compounds are used to supplement protein mixes, infant formula, and animal feed, determining the effect of these compounds on DNA damage under conditions of oxidative stress is crucial. In the presence of Fe(II) and H 2 O 2 , the effects of Na 2 SeO 4 , Na 2 SeO 3 , SeO 2 (0.5–5000 μM), and Na 2 Se (0.5–200 μM) on DNA damage were quantified using gel electrophoresis. Both Na 2 SeO 4 and Na 2 Se have no effect on DNA damage, whereas SeO 2 inhibits DNA damage and Na 2 SeO 3 shows antioxidant or pro-oxidant activity depending on H 2 O 2 concentration. Similar electrophoresis experiments with [Fe(EDTA)] 2− (400 μM) and Na 2 SeO 3 or SeO 2 show that metal coordination by the selenium compound is required for antioxidant activity. In light of these results, Na 2 SeO 4 may be safer than Na 2 SeO 3 for nutritional supplements.