The Study Of Cytotoxicity And Its Mechanisms On Human Lung Epithelial Cell Induced By Airborne Quinones

China has experienced rapid industrialization, urbanization, and transportationdevelopment in the past decades. As one of the fast developing countries with densepopulation, the air pollution levels in China are at the higher end of the world airpollution level. Numerous epidemiological studies have confirmed the associationsbetween atmospheric particulate matter (PM) and cardiopulmonary morbidity andmortality. Diesel exhaust particles, urban particulate matter and traffic-relatedparticles are proved to be very toxic, because of the large amounts of toxic andhazardous substances on the surface, such as transition metals, organics, etc.Quinones are important components of oxygenated PAHs (oxy-PAHs) in the fineparticles (PM2.5). The concentrations of quinones are sometimes even higher thanbenzo[a]pyrene and other PAHs. Quinones can particupate in the pathogenesis of PMthrough the generation of reactive oxygen radicals (ROS), during the redox cycling ofquinones. Airborne quinones could be detected in both particulate and gaseous phases.Recently, quinones are hypothesized to contribute to the adverse health effects causedby PM because of their high redox potency in producing ROS and are believed tosome extent to be more toxic than their parent PAHsIn this study, we aimed to explore the toxicological effects and relatedmechanisms in human lung epithelial A549cells induced by five typical quinones inthe air, to further clarify the harmful effects of quinones on the human body, and toprompte more scholars recognize the important role of quinones in toxicity of PM.First the oxidative potential of five typical airborne quinones (including1,2-naphthoquinone (1,2-NQ), acenaphthenequinone (ACQ)，2-methyl-1,4-naphtho-quinone (MNQ),2-methylanthra-quinone (MAQ) and9,10-phenanthrenequinone(PQ)) in cell-free systems and in A549cells were studied. The generation of ROS andthe changes of SOD activity involved in oxidative stress were detected. The resultsshow that three of the quinones (1,2-NQ, MNQ and PQ) can reacte with dithiothreitol(DTT) All of the five quinones can increase the SOD activity and promote thegeneration of ROS, leading to intracellular oxidative stress in A549cells. Second the toxic effects of the five airborne quinones, on viability, LDH release, DNA damage,intracellular calcium homeostasis, and mitochondrial damage, were studied in humanlung epithelial A549cells. The dose-and time-dependent relationships were studied.An antioxidant N-acetylcysteine (NAC) was used to examine the involvement of ROSin these adverse biological responses induced by quinones. The results showed thatthe five quinones can cause cell death, cell membrane and mitochondrial damages.1,2-NQ and MNQ can cause DNA damage. Only1,2-NQ can increased the Ca2+concentration. After addition of NAC, these biological effects induced by quinoneswere significantly decreased, proving the hypothesis that ROS generation may be oneof the mechanisms of the cytotoxicity induced by these quinones. Finally, the mRNAexpressions of four inflammatory cytokines (IL-6, IL-8, TNF-α, MCP-1), cytochromeP450enzymes (Cyp1a1, Cyp1b1) and heme oxygenase (HO-1) were investigated inA549cells after exposed to these quinones. The results showed that the five quinonesmay promote at least one of the expressions of the inflammatory cytokines. All of thequinones could up-regulate cyp1a1and cyp1b1expressions except for PQ.1,2-NQ,MNQ and PQ could induce the expressions of HO-1. In addition MAQ and ACQ caninduce the highest expressions of inflammatory cytokines and Cyp1a1.The major contribution of this study is the demonstration that these five quinonespresent in PM exert different cellular biological responses.1,2-NQ and MNQ, but notMAQ, ACQ or PQ, caused significant DNA damage, as detected by the Comet assay.Only1,2-NQ significantly elevated Ca2+levels in A549cells. Most of these biologicaleffects induced by quinones were suppressed by NAC, suggesting that ROS formationmight be the initial stressor. Quinones can also promote the inflammation processthrough the generation of cytokines. Our results highlight that the types of quinones aswell as the concentrations can significantly affect the intensity and the type of in vitrobiological effects, emphasizing the importance of the PM chemical composition on itsbiological effect. Consequently, it will be necessary to establish specific air qualitystandards for the individual components in particles, especially for the highly activequinones.