title: Modulation of genotoxic effects in asbestos-exposed primary human mesothelial cells by radical scavengers, metal chelators and a glutathione precursor.
abstract: The genotoxicity of asbestos fibers is generally mediated by reactive oxygen species (ROS) and by insufficient antioxidant protection. To further elucidate which radicals are involved in asbestos-mediated genotoxicity and to which extent, we have carried out experiments with the metal chelators deferoxamine (DEF) and phytic acid (PA), and with the radical scavengers superoxide dismutase (SOD), dimethylthiourea (DMTU) and the glutathione precursor Nacystelyn trade mark (NAL). We investigated the influence of these compounds on the potency of crocidolite, an amphibole asbestos fiber with a high iron content (27%), and chrysotile, a serpentine asbestos fiber with a low iron content (2%), to induce micronuclei (MN) in human mesothelial cells (HMC) after an exposure time of 24-72 h. Our results show that the number of crocidolite-induced MN is significantly reduced after pretreatment of fibers with PA and DEF. This effect was not observed with chrysotile. In contrast, simultaneous treatment of cells with asbestos and the OH*scavenging DMTU or the O2- -scavenging SOD significantly decreased the number of MN induced by chrysotile and crocidolite. In particular, DMTU almost completely suppressed micronucleus induction by both fiber types. A similar effect was observed in the presence of the H(2)O(2)-scavenging NAL after chrysotile treatment of HMC. By means of kinetochore analysis, it could be shown that the number of clastogenic events is decreased after PA and DEF pretreatment of fibers as well as after application of the above-mentioned scavengers. Our results show that chrysotile asbestos induces an increased release of H(2)O(2) in contrast to crocidolite. Also, the iron content of the fiber plays an important role in radical formation, but nevertheless, chrysotile produces oxy radicals to a similar extent as crocidolite, probably by phagocytosis-mediated oxidative bursting.
authors.affiliation: Institute of Pathology, University Hospital Regensburg, Germany.
authors.forename: Ina
authors.initials: I
authors.lastname: Poser
authors.forename: Qamar
authors.initials: Q
authors.lastname: Rahman
authors.forename: Mohtashim
authors.initials: M
authors.lastname: Lohani
authors.forename: Santosh
authors.initials: S
authors.lastname: Yadav
authors.forename: Hans-Henner
authors.initials: HH
authors.lastname: Becker
authors.forename: Dieter G
authors.initials: DG
authors.lastname: Weiss
authors.forename: Dietmar
authors.initials: D
authors.lastname: Schiffmann
authors.forename: Elke
authors.initials: E
authors.lastname: Dopp
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000378:metabolism*; D017638:Asbestos, Crocidolite / Q000378:metabolism / Q000633:toxicity*; D017632:Asbestos, Serpentine / Q000378:metabolism / Q000633:toxicity*; D002614:Chelating Agents / Q000378:metabolism*; D003676:Deferoxamine; D004847:Epithelial Cells / Q000378:metabolism; D016166:Free Radical Scavengers / Q000378:metabolism*; D006801:Humans; D018386:Kinetochores; D008239:Lysine / Q000031:analogs & derivatives* / Q000378:metabolism*; D048629:Micronuclei, Chromosome-Defective / Q000187:drug effects*; D015162:Micronucleus Tests; D016296:Mutagenesis / Q000187:drug effects*; D010833:Phytic Acid; D013482:Superoxide Dismutase; D013890:Thiourea / Q000031:analogs & derivatives*
chemical_list: D017632:Asbestos, Serpentine; D002614:Chelating Agents; D016166:Free Radical Scavengers; C086501:N-acetylcysteine lysinate; D017638:Asbestos, Crocidolite; D010833:Phytic Acid; C038983:1,3-dimethylthiourea; D013482:Superoxide Dismutase; D013890:Thiourea; D003676:Deferoxamine; D008239:Lysine; D000111:Acetylcysteine