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

The ability of ten polyphenolic antioxidants to prevent CuO nanoparticle (^NPCuO) and H₂O₂-mediated DNA damage and cytotoxicity was investigated. Five of the polyphenols (MEPCA, PREGA, MEGA, ECG, and EGCG) prevent ^NPCuO/H₂O₂-mediated DNA damage (IC₅₀ values of 7.5-800 μM), 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 ^NPCuO or free copper ions. Electron paramagnetic resonance (EPR) spectroscopy of reactive oxygen species (ROS) generated by ^NPCuO/H₂O₂ in the presence of representative polyphenols correlate with results of DNA damage studies: in the presence of ^NPCuO/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 ^NPCuO 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 ^NPCuO/H₂O₂ challenge was significantly rescued at physiologically relevant polyphenol levels (1 μM). These studies show that polyphenols can protect DNA and inhibit cytotoxicity generated by ^NPCuO under oxidative stress conditions.