Sterigmatocystin-induced oxidative DNA damage in human liver-derived cell line through lysosomal damage

Sterigmatocystin (STC) is a carcinogenic and mutagenic mycotoxin produced by fungi of many Aspergillus species. As a precursor of the aflatoxins, STC is a risk factor of liver cancer. The objective of this study is to investigate STC-induced DNA damage and underlying mechanisms. The single cell gel electrophoresis (SCGE) assay was applied to assess DNA damage induced by STC. To clarify the underlying mechanisms, we measured the intracellular generation of reactive oxygen species (ROS) using dichlorofluorescein diacetate as a fluorochrome. The level of oxidative DNA damage was evaluated by immunocytochemical analysis of 8-hydroxydeoxyguanosine (8-OHdG) and the acridine orange (AO) was used to measure the changes of lysosomal membrane stability. A significant dose-dependent increase of DNA strand breaks was found after treatment with STC (3 and 6 μM) respectively for 1 h. Increases in ROS level and the expression of 8-OHdG were also observed. A statistically significant increase in AO fluorescence intensity was observed in cells treated with STC (1.5, 3 and 6 μM) for 1 h. The DNA strand breaks induced by STC were almost prevented in cells pretreated with NH4Cl (10 mM) and NAC (10 mM) for 1 h. Our results thus indicated that STC exerts genotoxic effects on HepG2 cells, most likely through oxidative stress and lysosomal leakage.