|
(17-09) Synergistic toxicity of metal/PAH mixtures: the role of reactive oxygen species in ecotoxicology. Greenberg, Bruce*,1, Huang, Xiao-Dong1, Babu, Sudhakar1, Tripuranthakan, Shree1, Lampi, Mark1, El-Alawi, Yousef1, Diener, Lara1, Akhtar, Tariq1, Nykamp, Julie1, 1 University of Waterloo, Waterloo, ON ABSTRACT- Polycyclic aromatic hydrocarbons (PAHs) and heavy metals are two prevalent classes of persistent contaminants in aquatic and terrestrial environments. Because they often share the same production sources, they frequently co-exist in contaminated environments. However, most toxicological studies of these contaminants are carried out on individual compounds. Few studies are focused on mixtures of the same class of contaminants, and even fewer investigate the hazards of mixtures of different classes of contaminants such as metals and PAHs. Further, photooxidation of PAHs in the environment will generate many new species of compounds that have not been identified or thoroughly investigated. Therefore, the hazards of environmentally relevant mixtures of these two classes of chemicals have not been evaluated. Further, the biochemical mechanisms of the effects of these two classes of chemicals are virtually unknown. We have found that mixtures of metals and photomodified PAHs cause synergistic toxicity. The synergistic effects are induced by different modes of action of metals and photomodified PAHs. For instance, an anthracene photoproduct, 1,2 dihydroxyanthquinone, inhibits cytochrome b/f and cytochrome c reductase, and thus, interrupts electron transport in chloroplasts and mitochondria, respectively. The heavy metal Cu uses a catalytic mechanism to generate reactive oxygen species (ROS) by accepting electrons from overly reduced quinones, and succinate or NADH dehydrogenase. Thus, photomodified PAHs inhibit electron transport, while Cu harvests the electrons from the blocked bioenergitic membranes to generate high levels of ROS. This results in synergistic toxicity due to the high ROS loads. This research reveals an important catalytic mechanism of metal toxicity, that being apoptosis due to ROS formation. Key words: Copper, Anthraquinone, Oxygen radical, Mechanisms |
