Effect Of PCB126 On The B(a)P-induced Oxidative Stress And DNA Damage In HepG2 Cells

Object Benzo(a)pyrene (B(a)P), a potent carcinogen and representative compound of polycyclic aromatic hydrocarbons (PAHs), is ubiquitously distributed throughout the environment. Polychlorinated biphenyls (PCBs) are a class of persistent organic pollutants which is concerned internationally today. As the representative of PCBs, 3, 3', 4, 4', 5-pentachlorobipheny (PCB126) is one of most toxic PCBs congeners. Some researches found that B(a)P's metabolic activation can cause oxidative stress in cells, and PCBs can enhanced B(a)P metabolic activation, which could increase the oxidative stress and genetic damage of cells. For B(a)P usually coexisted with PCBs in various environmental media and human biological samples, it is practical to study the role of oxidative stress and genetic toxic effects in their joint action.Methods The HepG2 was used as target cells which were treated with 50μmol/L of B(a)P, or different concentrations of PCB126 (0.01,0.1 1 and 10 nmol/L) alone. Or we pre-treated the cells with PCB126 for 48h, then co-treated with PCB126 and B(a)P for another 24h. The levels of ROS, GSH and MDA in HepG2 cells were analyzed through flow cytometry, GSH and MDA assay kit respectively. DNA damage were detected by single cell gel electrophoresis assay.Result Compared with DMSO solvent control, no statistically significant increase in ROS level was observed in cells exposed to PCB126 alone, except for the highest concentration of 10 nmol/L of PCB126 (P<0.05). Treatment with both PCB126 and BaP dramatically enhanced ROS, compared with BaP treatment alone (P<0.05 for the co-exposure to 0.01, 0.1 nmol/L of PCB126 and BaP, P<0.01 for the co-exposure to 1, 10 nmol/L of PCB126 and BaP).Compared with DMSO solvent control, exposure to 50μmol/L of BaP alone caused a significant increase of GSH (P<0.01), but exposure to PCB126 alone dramatically decreased the level of GSH (P<0.01). Treatment with both PCB126 and BaP dramatically decreased GSH, compared with BaP treatment alone (P<0.01).Compared with DMSO solvent control, exposure to 50μmol/L of BaP alone caused a significant increase in MDA (P<0.05). Treatment with both PCB126 (0.1, 1 and 10 nmol/L) and BaP dramatically increased the level of MDA, compared with BaP alone (P<0.05 for the co-exposure to 0.1 nmol/L of PCB126 and BaP, P<0.01 for the co-exposure to two higher concentrations of PCB126 and BaP).Compared with DMSO solvent control, exposure to 50μmol/L of BaP alone caused a significant increase of OTM (P<0.01). Treatment with both PCB126 (1 and 10 nmol/L) and BaP dramatically increased the level of OTM, compared with BaP alone (P<0.05 for the co-exposure to 1 nmol/L of PCB126 and BaP, P<0.01 for the co-exposure to 1 nmol/L of PCB126 and BaP).Conclusion:PCB126 can increase B(a)P-induced oxidative stress and enhance DNA damage in HepG2 cells, which suggested that PCB126-induced oxidative stress maybe responsible for the enhancement of B(a)P- induced genotoxicity in joint action.