Ambient particulate matter on DNA damage in HepG2 cells

Abstract

Ambient particulate matter (PM) has been reported to be associated with increased respiratory, cardiovascular, and malignant lung diseases. The aim of the present study was to investigate the variability of the DNA-damage induced by thoracic particles (PM( 10)) sampled in different locations and seasons (2006) in Dalian, China, in human hepatoma G2 (HepG2) cells. Significant differences in percentage of tail DNA induced by the extractable organic matter of PM(10) were revealed between summer and winter seasons and among monitoring sites in single cell gel electrophoresis (SCGE) assay. The percentage of tail DNA in HepG2 cells significantly increased in a dose-dependent manner after exposure to 7.5 and 30 μg/mL extractable organic matter of PM(10) for 1 hour. In order to clarify the underlying mechanisms, we evaluated the level of reactive oxygen species (ROS) production with the 2, 7-dichloro-fluorescein diacetate (DCFH-DA) assay. Significantly increased level of ROS was observed in HepG2 cells at higher concentrations (15 and 30 μg/mL). Significantly increased levels of 8-hydroxydeoxyguanosine (8-OHdG) were also shown in HepG2 cells. In this study, the accumulation of nuclear factor kappa B (NF-κB) p65 protein induced by the extractable organic matter of PM(10) was detected by western blotting in HepG2 cells, and the protein expression of NF-κB p65 significantly increased after the treatment with 30 μg/mL extractable organic matter of PM(10) for 24 hours. These results indicate that the extractable organic matter of PM(10) causes DNA strand breaks in HepG2 cells, and significant differences in percentage of tail DNA in dependence on locality and season are revealed. The extractable organic matter of PM(10) exerts DNA damage effects in HepG2 cells, probably through oxidative DNA damage induced by intracellular ROS, increase of 8-OHdG formation, and protein expression of NF-κB p65.