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(22-01) Study on the Oxidative Stress Induced by UV and PAHs Using DNA integrity as a Biomarker. Zhang, Xiaowei*,1, Wu, Rudolf S S1, Lam, Paul K S1, 1 Department of Biology and Chemistry. City University of Hong Kong, Hong Kong, none ABSTRACT- The increased exposure to solar ultra-violet (UV) irradiation as a result of ozone depletion has caused global concern. Recent scientific evidence further suggested that UV irradiation may synergistically enhance the toxicity of a number of polycyclic aromatic hydrocarbons (PAHs) and genotoxicants. The underlying mechanisms leading to synergism however remain unclear. It is hypothesized that UV will enhance the production of reactive oxygen species (ROS), which in turn, induces oxidative DNA damage in the presence of genotoxic PAHs. In this study, experiments were designed to investigate the relationship between ROS production and the formation of 8-OhdG, a specific marker for oxidative DNA damage, upon exposure to UVA (320nm-400nm; 0.50mW/cm). KB Cells were exposed to different combinations of UV irradiation and concentration of benzo[a]pyrene (B[a]P), and levels of ROS in cells was measured, using flow cytometry coupled with the fluorescence probes dihydrorhodamine 123 (DHR) and 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA). Levels of 8-OHdG were measured using HPLC with a EC detector. Cell viability was also measured using propidium iodide and flow cytometry. ROS production in cells with intact membrane showed a linear relationship to combined effects of UV irradiation and B[a]P exposure . Results of this study suggest that UVA and B[a]P act synergistically in causing DNA damage, probably through an increased formation of ROS. Key words: Ultraviolet Radiation (UVR), polycyclic aromatic hydrocarbons (PAHs), ROS, 8-OHdG |
