Ochratoxin A (OTA), one of the most abundant
mycotoxin food contaminants, is classified as "possibly carcinogenic to humans." Our previous study showed that OTA could induce a G2 arrest in immortalized human gastric epithelium cells (GES-1). To explore the putative roles of oxidative DNA damage and the
ataxia telangiectasia-mutated (ATM) pathways on the OTA-induced G2 arrest, the current study systematically evaluated the roles of
reactive oxygen species (ROS) production, DNA damage, and ATM-dependent pathway activation on the OTA-induced G2 phase arrest in GES-1 cells. The results showed that OTA exposure elevated intracellular ROS production, which directly induced DNA damage and increased the levels of 8-OHdG and
DNA double-strand breaks (DSBs). In addition, it was found that OTA treatment induced the phosphorylation of the
ATM protein, as well as its downstream molecules Chk2 and p53, in response to
DNA DSBs. Inhibition of ATM by the pharmacological inhibitor
caffeine or
siRNA effectively prevented the activation of ATM-dependent pathways and rescued the G2 arrest elicited by OTA. Finally, pretreatment with the
antioxidant N-acetyl-L-cysteine (NAC) reduced the OTA-induced
DNA DSBs, ATM phosphorylation, and G2 arrest. In conclusion, the results of this study suggested that OTA-induced oxidative DNA damage triggered the ATM-dependent pathways, which ultimately elicited a G2 arrest in GES-1 cells.