Formation of Oxidative DNA Damage Corresponds to the Long Term Survival of Human Cells Treated with Nanosilver

Kapka-Skrzypczak, Lucyna ;   Gradzka, Iwona ;   Bartlomiejczyk, Teresa ;   Chwastowska, Jadwiga ;   Sommer, Sylwester ;   Grzelak, Agnieszka ;   Zuberek, Mariusz ;   Lankoff, Anna ;   Wojewódzka, Maria ;   Kruszewski, Marcin

A clonogenic potential of 3 human cell lines, HepG2, HT29 and A549, treated with bare 20 nm or 200 nm silver nanoparticles (AgNPs) was examined in relation to AgNPs uptake, formation of reactive oxygen species (ROS), DNA breakage estimated by the comet assay, oxidative base damage recognized by formamido-pyrimidine glycosylase (FPG) and estimated with the FPG+comet assay, frequencies of histone γH2AX foci and micronuclei (MN) were used as endpoints. A statistically significant increase in the AgNPs uptake was observed in A549 and HepG2 cells, whereas only slight uptake of AgNPs was observed in HT29. In accordance with the uptake data, an increase in oxidizing species was observed in A549 and HepG2 cells treated with 20 nm AgNPs, and only very slight increase in the ROS formation was observed in HT29 cells. Each cell line studied had a different pattern of DNA breakage and base damage versus NPs concentration and time of treatment. However, only the overall pattern of DNA breakage and base damage induction corresponded to the intracellular generation of reactive oxygen species. There were no increases in the frequencies of histone γH2AX foci and MN as compared to those in the untreated cells. The reported experiments suggest that only oxidative DNA damage corresponds to the loss of clonogenic ability of cells treated with AgNPs. This work was supported by the Polish Norwegian RF(PNRF-122-AI-1/07) and National Science Centre, decision number DEC-2013/09/B/NZ7/03934.