title: Internalization of Libby amphibole asbestos and induction of oxidative stress in murine macrophages.
abstract: The community members of Libby, MT, have experienced significant asbestos exposure and developed numerous asbestos-related diseases including fibrosis and lung cancer due to an asbestos-contaminated vermiculite mine near the community. The form of asbestos in the contaminated vermiculite has been characterized in the amphibole family of fibers. However, the pathogenic effects of these fibers have not been previously characterized. The purpose of this study is to determine the cellular consequences of Libby amphibole exposure in macrophages compared to another well-characterized amphibole fiber; crocidolite asbestos. Our results indicate that Libby asbestos fibers are internalized by macrophages and localize to the cytoplasm and cytoplasmic vacuoles similar to crocidolite fibers. Libby asbestos fiber internalization generates a significant increase in intracellular reactive oxygen species (ROS) as determined by dichlorofluorescein diacetate and dihydroethidine fluorescence indicating that the superoxide anion is the major contributing ROS generated by Libby asbestos. Elevated superoxide levels in macrophages exposed to Libby asbestos coincide with a significant suppression of total superoxide dismutase activity. Both Libby and crocidolite asbestos generate oxidative stress in exposed macrophages by decreasing intracellular glutathione levels. Interestingly crocidolite asbestos, but not Libby asbestos, induces significant DNA damage in macrophages. This study provides evidence that the difference in the level of DNA damage observed between Libby and crocidolite asbestos may be a combined consequence of the distinct chemical compositions of each fiber as well as the activation of separate cellular pathways during asbestos exposure.
authors.affiliation: Division of Biological Sciences and Department of Biomedical & Pharmaceutical Sciences, Center for Environmental Health Sciences, University of Montana, Missoula 59812, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Blake
authors.forename: Celeste M
authors.initials: CM
authors.lastname: Bolin
authors.forename: David P
authors.initials: DP
authors.lastname: Cox
authors.forename: Fernando
authors.initials: F
authors.lastname: Cardozo-Pelaez
authors.forename: Jean C
authors.initials: JC
authors.lastname: Pfau
mesh_terms: D000818:Animals; D017636:Asbestos, Amphibole / Q000378:metabolism / Q000633:toxicity*; D017638:Asbestos, Crocidolite / Q000378:metabolism / Q000633:toxicity; D002460:Cell Line; D004249:DNA Damage; D045647:DNA Glycosylases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D051379:Mice; D009009:Montana; D018384:Oxidative Stress / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D017636:Asbestos, Amphibole; D017382:Reactive Oxygen Species; D017638:Asbestos, Crocidolite; D013482:Superoxide Dismutase; D045647:DNA Glycosylases; C485990:Ogg1 protein, mouse