title: Involvement of oxidative stress in motorcycle exhaust particle-induced DNA damage and inhibition of intercellular communication.
abstract: In this study, we investigated the involvement of reactive oxygen species (ROS) in the motorcycle exhaust particle (MEP)-induced genotoxic and non-genotoxic activity in mammalian cell systems. Initially, the capability of MEP to induce ROS was evaluated by using 2',7'-dichlorofluorescin diacetate (DCFH-DA) to detect hydrogen peroxide (H2O2). A five-fold increase in H2O2 was observed in Chinese hamster lung V79 and human lung carcinoma Calu-1 cells treated with 100 microg/ml MEP for 2 h. Under the same experimental conditions, only a two-fold elevation in H2O2 was detected in hepatic cell systems such as BNL.Cl.2, HepG2, and Hep3B. Treatment of the V79 cells with varying concentrations of MEP caused a dose-dependent increase in sister chromatid exchanges (SCEs), which are effectively inhibited by addition of antioxidants, N-acetyl-l-cysteine (NAC) and ascorbic acid. Furthermore, we determined the oxidized bases in the V79 cells after exposure to MEP. The result showed that 500 microg/ml MEP induced a 3.7-fold increase in thymine glycol (TG) and a seven-fold increase in 8-hydroxy-guanosine (8-OHGua) as compared to untreated cells. We subsequently examined whether MEP would affect gap junctional intercellular communication (GJIC), a tumor promotion process, in V79 cells. We found that MEP inhibited GJIC in a dose-response fashion. Maximal inhibition occurred at 500 microg/ml. The concentration that inhibited at 0.5 of the fraction of the control was 200 microg/ml. Interestingly, when cells were pretreated with NAC or ascorbic acid, they could abolish the MEP-mediated inhibition of GJIC. In addition, a moderate decrease of glutathione was observed in the V79 cells during exposure to MEP. Taken together, our findings suggest that MEP can induce oxidative stress in a broad range of cell lines, especially in lung cell systems. The MEP-induced oxidative stress was critically involved in both genotoxic and non-genotoxic activity.
authors.affiliation: Institute of Toxicology, College of Medicine, National Taiwan University, No. 1, Sec. 1, Jen-Ai Road, Taipei, Taiwan. toxkml@ha.mc.ntu.edu.tw
authors.forename: M L
authors.initials: ML
authors.lastname: Kuo
authors.forename: S H
authors.initials: SH
authors.lastname: Jee
authors.forename: M H
authors.initials: MH
authors.lastname: Chou
authors.forename: T H
authors.initials: TH
authors.lastname: Ueng
mesh_terms: D000818:Animals; D002450:Cell Communication / Q000187:drug effects*; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D004249:DNA Damage; D017629:Gap Junctions / Q000187:drug effects; D005978:Glutathione / Q000032:analysis; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity*; D051379:Mice; D018384:Oxidative Stress; D017382:Reactive Oxygen Species; D001335:Vehicle Emissions / Q000633:toxicity*
chemical_list: D017382:Reactive Oxygen Species; D001335:Vehicle Emissions; D006861:Hydrogen Peroxide; D005978:Glutathione