title: Lethal synergism between organic and inorganic wood preservatives via formation of an unusual lipophilic ternary complex.
abstract: We have shown previously that exposing bacteria to wood preservatives pentachlorophenol (PCP) and copper-containing compounds together causes synergistic toxicity. However, it is not clear whether these findings also hold true in mammalian cells; and if so, what is the underlying molecular mechanism? Here we show that PCP and a model copper complex bis-(1,10-phenanthroline) cupric (Cu(OP)(2)), could also induce synergistic cytotoxicity in human liver cells. By the single crystal X-ray diffraction and atomic absorption spectroscopy assay, the synergism was found to be mainly due to the formation of a lipophilic ternary complex with unusual structural and composition characteristics and subsequent enhanced cellular copper uptake, which markedly promoted cellular reactive oxygen species (ROS) production, leading to apoptosis by decreasing mitochondrial membrane potential, increasing pro-apoptotic protein expression, releasing cytochrome c from mitochondria and activating caspase-3, and -9. Analogous results were observed with other polychlorinated phenols (PCPs) and Cu(OP)(2). Synergistic cytotoxicity could be induced by PCP/Cu(OP)(2) via formation of an unusual lipophilic complex in HepG2 cells. The formation of ternary complexes with similar lipophilic character could be of relevance as a general mechanism of toxicity, which should be taken into consideration especially when evaluating the toxicity of environmental pollutants found at currently-considered non- or sub-toxic concentrations.
authors.affiliation: State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Science, Chinese Academy of Sciences, Beijing 100085, PR China.
authors.forename: Zhi-Guo
authors.initials: ZG
authors.lastname: Sheng
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Rui-Mei
authors.initials: RM
authors.lastname: Fan
authors.forename: Xi-Juan
authors.initials: XJ
authors.lastname: Chao
authors.forename: Ben-Zhan
authors.initials: BZ
authors.lastname: Zhu
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D003300:Copper / Q000633:toxicity*; D004357:Drug Synergism; D005978:Glutathione / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects / Q000502:physiology; D010416:Pentachlorophenol / Q000633:toxicity*; D010618:Phenanthrolines / Q000633:toxicity*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D010618:Phenanthrolines; D017382:Reactive Oxygen Species; D003300:Copper; D010416:Pentachlorophenol; D020169:Caspases; D005978:Glutathione; C025205:1,10-phenanthroline