Oxidative Stress in C100 Cells Induced by Combined Treatmentof Benzo(a)pyrene and/or 2,3,7,8-Tetrachlorodibenzo-p-dioxin(TCDD)

When an organism is exposed to various toxicants chronically, reactive oxygen species(ROS) are accumulated and eventually result in several biological effects from gene expression to cell death. In the present study we investigated the oxidative damage of 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin(TCDD) and/or benzo(a)pyrene (B(a)P) in C100 cells. C100 cells treated with TCDD(30 nM) and B(a)P($3{\mu}M$) underwent diverse oxidative stress as determined through thiobarbituric acid-reactive substances(TBARS) formation, DNA fragmentation, DNA single strand break(SSB) assay, immunohistochemical staining of 8-hydroxy-2'-deoxyguanosine(8-OHdG), and mRNA expressions of antioxidant enzymatic genes such as Cu/Zn-SOD gene, GPx(glutathione peroxidase 5) gene, and catalase gene. Lipid peroxidation in C100 cells was determined through measuing the formation of TBARS. For theat, the cells were pretreated with TCDD(30 nM) and/or B(a)P($3{\mu}M$) for 0.5, 1, 2 and 4 days. TBARS formation was increased in TCDD(30 nM) and B(a)P($3{\mu}M$) and mixture($30nM\;TCDD+3{\mu}M\;B(a)P$) and positive control treatment groups comparing to the controls. Mixture treatment induced more DNA fragmentation than the single treatment group at day 6. Also, SSB in all treatment groups was clearly observed when compared with the negative control group. As with the expression of antioxidant enzyme, GPx 5mRNA, B(a)P alone and mixture($30nM\;TCDD+3{\mu}M\;B(a)P$) treatment were higher comparing to those of the negative control and TCDD treatment groups. Our results suggest that exposure of C100 cells to mixture of TCDD and B(a)P leads to significant oxidative damage comparing to the exposures to the individual chemicals. Mechanisms of action are discussed. Additional studies are needed to elucidate the detailed mechanism of mixture-induced toxicity.