Antioxidant Induces DNA Damage, Cell Death and Mutagenicity in Human Lung and Skin Normal Cells

Clinical trials have shown that antioxidant supplementation increased the risk of lung and skin cancers, but the underlying molecular mechanism is unknown. Here, we show that epigallocatechin gallate (EGCG) as an exemplary antioxidant induced significant death and DNA damage in human lung and skin normal cells through a reductive mechanism. Our results show direct evidence of reductive DNA damage in the cells. We found that EGCG was much more toxic against normal cells than H(2)O(2) and cisplatin as toxic and cancer-causing agents, while EGCG at low concentrations (≤100 μM) increased slightly the lung cancer cell viability. EGCG induced DNA double-strand breaks and apoptosis in normal cells and enhanced the mutation frequency. These results provide a compelling explanation for the clinical results and unravel a new reductive damaging mechanism in cellular processes. This study therefore provides a fresh understanding of aging and diseases, and may lead to effective prevention and therapies.