The Study Of DNA Damage And Repair Pathway In The Cellular Response To Ag Nanoparticles

Several recent studies have revealed that silver nanoparticles (AgNPs) possess the cytotoxicity and genotoxicity by increasing the production of ROS which can cause the interruption of ATP synthesis, DNA damage, apoptosis and necrosis. It is unclear how human cells respond to AgNPs. Whether DNA repair pathways are involved in the AgNPs-induced cellular response is unkown as well. This thesis illustrates that DNA repair pathways participate and play a crucial role in the cellular response to the AgNPs-induced stress.To determine the influence of AgNPs with different concentrations to the normal human cell lines and the DNA repair defective cell lines, the colony-forming assay has been employed. Compared with the normal human cells, the colony-forming ability of XPC mutated and XPF mutated cells reduced significantly following the same treatment. Since XPF mutation cell line is defective in nucleotide excision repair (NER) and partly defective in interstrand crosslink repair (ICLs repair), an enormous reduction of colony-forming ability has been observed in XPF cells. Our data indicates that the cellular reponse to AgNPs requires the participation of DNA repair pathways.With the treatment of AgNPs under different concentration for48hours, the p53level significantly increases in XPF cells and correlates with the concentration of AgNPs. Additionally, p53phosphorylation on Ser-15in XPF cells increased apparently. Hence, the inhibition of XPF mutant cells growth results from the activation of the p53network after the AgNPs treatment. We detected the transcription of a few p53regulated genes such as MDM2and APAF1by RT-PCR assay to determine the deeper activation of the p53network. Our data illustrates that the transcription of p53targeted genes are significantly altered in XPF cells compared with what happened in normal cells, suggesting that XPF involved DNA repair pathways are required for human cells to respond to the AgNPs-induced stress.It revealed that the normal growth of XPF mutant cells was inhibited after the treatment of Fe3O4NPs. The transcription of cell cycle related gene CHEK1and DNA damage repair related genes RPA1, RPA2and RPA3are significantly increased following cells exposure to Fe3O4NPs. Our results suggest that the XPF involved DNA repair pathways should be generally required for cellular response to nanoparticles in human cells.In summary, it demonstrates that XPF involved DNA repair pathways play a vital role not only in the cellular response to AgNPs-induced stress but also in the cellular response to Fe3O4NPs-induced stress. Thus, the DNA repair pathways are an essential component of the cellular response to AgNPs/Fe3O4NPs-induced stress in human cells.