Study On Molecular Mechanism In DNA Damage Response Induced By Endosulfan In K562 Cells

Endosulfan is a kind of organochlorine pesticides(OCPs)with toxicity,it can cause DNA damage and genomic instability and it has potential hazardous on human health.Epidemiological study demonstrated that endosulfan level was higher in the marrow of patients with leukemia than normal children.However,the molecular mechanism is unclear.The aim of this study is to explore molecular mechanism of endosulfan-induced DNA damage response in human leukemia cells,and provide important experimental evidence and reference for the relationship between endosulfan with leukemia.In the present study,the effect of endosulfan on the cytotoxicity of human chronic myeloid leukemia cell line K562 cells were performed by MTT assay.The results showed that endosulfan lowered cell viability in a dose-dependent manner.At relatively high concentrations(75 ?M),endosulfan can decrease the activity of SOD in K562 cells.We also observed DNA damage using comet assay and the increase of micronucleus in 75 ?M endosulfan-exposed cells.Endosulfan at 75 ?M caused the expression alterations of ATM and DNA repair genes such as FANCD2,and BRCAl/2 at different exposure time points(12,24,48 h),which was reversed by ATM inhibitor KU-55933.Endosulfan significantly increased the mRNA expression levels of DNA damage response genes TP53 and GADD45A,and decreased DNA replication gene PCNA and DNA repair gene XRCC2 at 48 h after exposure.Flow cytometry analysis showed that endosulfan at 50 and 75?M induced cell cycle G1 arrest,a response attributed to down-regulation of cell cycle-related gene CDK6 and up-regulation of p21.Endosulfan at 50 and 75 ?M induced a considerable percentage of cells to undergo apoptosis,as detected by Annexin-V binding assays.Endosulfan resulted in the activation of caspase-3,and elevated the expression levels of apoptosis-related gene PUMA and the ratio of BAX/Bcl-2.These findings suggest that endosulfan caused DNA damage,cell cycle arrest and apoptosis through ATM-p53 signaling pathway,implicating the potential correlation between endosulfan and leukemia.