Reactive oxygen species and mitochondria mediate the induction of apoptosis in human hepatoma HepG2 cells by the rodent peroxisome proliferator and hepatocarcinogen, perfluorooctanoic acid

We have previously shown that one of the most potent rodent hepatocarcinogens, perfluorooctanoic acid (PFOA), induces apoptosis in human HepG2 cells in a dose- and time-dependent manner. In this study we have investigated the involvement of reactive oxygen species (ROS), mitochondria, and caspase-9 in PFOA-induced apoptosis. Treatment with 200 and 400 μM PFOA was found to cause a dramatic increase in the cellular content of superoxide anions and hydrogen peroxide after 3 h. Measurement of the mitochondrial transmembrane potential (ΔΨ_m) after PFOA treatment showed a dissipation of ΔΨ_m at 3 h. Caspase-9 activation was seen at 5 h after treatment with 200 μM PFOA. In order to evaluate the importance of these events in PFOA-induced apoptosis, cells were cotreated with PFOA and N-acetylcysteine (NAC), a precursor of glutathione, or Cyclosporin A (CsA), an inhibitor of mitochondrial permeability transition pore (MPT pore). NAC reduced ΔΨ_m dissipation, caspase 9 activation, and apoptosis, indicating a role for PFOA-induced ROS. In addition, CsA also reduced ΔΨ_m dissipation, caspase 9 activation, and apoptosis, indicating a role for PFOA-induced opening of the MPT pore. In summary, we have delineated a ROS and mitochondria-mediated pathway for induction of apoptosis by PFOA.