Green tea polyphenols inhibit oxidant-induced DNA strand breakage in cultured lung cells

The influence of green tea polyphenols (GTP) on the formation of DNA strand breaks (DNA-SB) and lipid peroxidation products (LPP) in cultured human lung cells (A 549) exposed to different oxidants was investigated. Cells were pretreated with GTP for 2 h and then exposed to cigarette smoke solution, H2O2 or FeCl3 for 30 min. After exposure, the cells were analyzed for DNA-SB, LPP, and viability. In addition, the effects of GTP added directly to the incubation mixtures during exposure were examined, using the same end points. It appeared that pretreatment with GTP inhibited both cigarette smoke- and H2O2-induced DNA breakage; i.e., following exposure to cigarette smoke or H2O2, the fraction of DNA passing through a microfilter increased significantly in cells not subjected to GTP, but this effect was prevented or inhibited in GTP-treated cells. Pretreatment with GTP also reduced the overall toxicity of H2O2 as determined by cell growth after exposure. Moreover, addition of GTP during exposure reduced both cigarette smoke- and H2O2-induced DNA breakage as well as formation of LPP after exposure to Fe3+. These results indicate that GTP inhibit the formation of DNA-SB in cells exposed to oxidants. It is possible that this ability to GTP to inhibit DNA-SB formation might contribute to the antitumorogenic properties of green tea.