The Role Of Oxidative Stress In HQ-induced DNA Damage In HEK293 Cells

Objective:Hydroquinone (1,4-dihydroxybenzene, HQ) is an important industrial chemical used as a developer in the photographic industry, as an anti-oxidant in the rubber industry, as an intermediate in the manufacturing of food anti-oxidants, and as a polymerization inhibitor for vinyl and acrylic monomers. It is widely used solvent in industry and daily life. Its exposure is mainly to those industrial workers or people who use HQ containing cosmetic or medicine, also HQ is one production of benzene metabolizations, and it plays important roles in benzene leukemia toxicity. HQ mainly metabolized in liver and be expelled from urine, but partly could cumulate in bone marrow where it is further oxidative to p-benzoquinone. Human epidemiology and animal experiments both find HQ induces toxic effects to body. It could do harms to liver, kidney, bone marrow and hematopoiesis.In 1999 the International Agency for Research on Cancer (IARC), assessed HQ as a Group 3 carcinogen. HQ was mutagentic in many mammalian cells in vitro using a variety of end-points.The overall object of present study is to explore whether HQ causes DNA damage in HEK293 cells and to elucidate the underlying mechanism of HQ-induced DNA damage. Thus it may provide some information for safety assessment to humans on HQ.Method:DNA damage induced by HQ was assessed by standard single cell gel electrophoresis(SCGE)assays. We used the Rhodamine 123 and acridine orange (AO), to monitor mitochondrial membrane potential and lysosomal membrane stability;2,7-dichlorofluorescein diacetate (DCFH-DA) and O-phthalaldehyde(OPT) to monitor the levels of reactive oxygen species (ROS)and glutathione (GSH).We analyzed the oxidative DNA damage in HQ-treated cells by immunocytochemistry staining of 8-hydroxy deoxy-guanosine (8-OHdG).To further evaluate the involvements of MMP and ROS in the formation of HQ-induced DNA strand breaks, we study the protective effect of hydroxytyrosol and the damage effect of BSO.Result:Using the standard SCGE assay, a significant dose-dependent increment in DNA migration was detected at the concentration of HQ (3.125,6.25,12.5μM).The present study showed that HQ induced the levels of LMS and ROS, and the depletion of MMS and GSH in HEK293 cells. Moreover,HQ significantly caused 8-hydroxydeoxyguanosine(8-OHdG) formation in HEK293 cells. Hydroxytyrosol (HT), a recognized antioxidant, prevented the formation of DNA strand breaks caused by HQ.Conclusion:We conclude that the DNA damage of HQ is mediated by the increase of LMS, formation of ROS, and depletion of MMP and GSH, which cause oxidative DNA damage.