[Objective] To study the joint effect on reactive oxygen species (ROS) generation, cell viability, and oxidative stress induced by nanometer titanium dioxide (TiO2) and lead acetate (PbAc) in human derived fetal hepatocytes (L-02).
[Methods] The experimental groups were treated with PbAc (1.000 mg/L), TiO2 (10.000, 1.000, 0.100, 0.010, 0.001 mg/L), or all concentration combinations of PbAc and TiO2 for 24 h. The L-02 cells were also cultured with 0.1% dimethyl sulfoxide (negative control) and 30 μmol/L H2O2 (positive control). Cell toxicity and ROS generation were determined using methylthiazoltetrazolium assay and flow cytometry respectively. The levels of glutathione (GSH) and activities of superoxide dismutase (SOD) were used to determine intracellular antioxidant levels.
[Results] When treated with 10.000 mg/L TiO2, the cell viability was decreased significantly compared with the negative control, the PbAc, and the other single TiO2 dosage groups (P<0.05). When interfered with the combination of 1.000 mg/L PbAc + 10.000 mg/L TiO2, the cell viability was reduced significantly compared with the negative control, the PbAc, and the other combination groups (P<0.05). The cytotoxicity was notably higher in the combination group of 1.000 mg/L PbAc +1.000 or 0.100 mg/L TiO2 than in the negative controls (P<0.05). There were significant increases of the ROS levels in various combination groups in comparison with the negative controls and the PbAc group (P<0.05). The GSH levels were significantly increased after combined treatment of 1.000 mg/L PbAc + 1.000, 0.100 or 0.010 mg/L TiO2 (P<0.05), and the SOD levels were notably raised after 1.000 mg/L PbAc + 0.100 or 0.010 mg/L TiO2 combined treatment, in comparison with the negative controls (P<0.05).
[Conclusion] In these study settings, co-exposure to low doses of TiO2 and PbAc significantly induces elevated ROS levels in L-02, and subsequently elevation of GSH and SOD levels for cell self-protection. Along with increasing exposure dose, the antioxidant capacity is declined followed by significant increase of ROS level, resulting in decrease of cell viability.
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