Polyphenol effects on CuO-nanoparticle-mediated DNA damage, reactive oxygen species generation, and fibroblast cell death

The ability of ten polyphenolic antioxidants to prevent CuO nanoparticle ((CuO)-Cu-NP) and H2O2-mediated DNA damage and cytotoxicity was investigated. Five of the polyphenols (MEPCA, PREGA, MEGA, ECG, and EGCG) prevent (CuO)-Cu-NP/H2O2-mediated DNA damage (IC50 values of 7.5-800 mu M), three have no effect (PCA, VA, and EC), and two (GA and EGC) result in increased DNA damage. Most polyphenols had similar antioxidant/ prooxidant activity in the presence of (CuO)-Cu-NP or free copper ions. Electron paramagnetic resonance (EPR) spectroscopy of reactive oxygen species (ROS) generated by (CuO)-Cu-NP/H2O2 in the presence of representative polyphenols correlate with results of DNA damage studies: in the presence of (CuO)-Cu-NP/H2O2, MEPCA prevents ROS formation, VA has no effect on ROS levels, and EGC increases ROS levels. EPR results with CuO nanoparticles washed to remove dissolved copper in solution (wCuO) in the presence of H2O2/ascorbate suggest that MEPCA prevents ROS formation on the nanoparticle surface in addition to preventing ROS formation from dissolved copper. In mouse fibroblast (L929) cells, combining (CuO)-Cu-NP with H2O2 results in significantly greater cytotoxicity than observed for either component alone. After 3 h incubation with MEPCA or MEGA, the viability loss in L929 cells induced by (CuO)-Cu-NP/H2O2 challenge was significantly rescued at physiologically relevant polyphenol levels (1 mu M). These studies show that polyphenols can protect DNA and inhibit cytotoxicity generated by (CuO)-Cu-NP under oxidative stress conditions.