title: ESR evidence for in vivo formation of free radicals in tissue of mice exposed to single-walled carbon nanotubes.
abstract: Nanomaterials are being utilized in an increasing variety of manufactured goods. Because of their unique physicochemical, electrical, mechanical, and thermal properties, single-walled carbon nanotubes (SWCNTs) have found numerous applications in the electronics, aerospace, chemical, polymer, and pharmaceutical industries. Previously, we have reported that pharyngeal exposure of C57BL/6 mice to SWCNTs caused dose-dependent formation of granulomatous bronchial interstitial pneumonia, fibrosis, oxidative stress, acute inflammatory/cytokine responses, and a decrease in pulmonary function. In the current study, we used electron spin resonance (ESR) to directly assess whether exposure to respirable SWCNTs caused formation of free radicals in the lungs and in two distant organs, the heart and liver. Here we report that exposure to partially purified SWCNTs (HiPco technique, Carbon Nanotechnologies, Inc., Houston, TX, USA) resulted in the augmentation of oxidative stress as evidenced by ESR detection of α-(4-pyridyl-1-oxide)-N-tert-butylnitrone spin-trapped carbon-centered lipid-derived radicals recorded shortly after the treatment. This was accompanied by a significant depletion of antioxidants and elevated biomarkers of inflammation presented by recruitment of inflammatory cells and an increase in proinflammatory cytokines in the lungs, as well as development of multifocal granulomatous pneumonia, interstitial fibrosis, and suppressed pulmonary function. Moreover, pulmonary exposure to SWCNTs also caused the formation of carbon-centered lipid-derived radicals in the heart and liver at later time points (day 7 postexposure). Additionally, SWCNTs induced a significant accumulation of oxidatively modified proteins, increase in lipid peroxidation products, depletion of antioxidants, and inflammatory response in both the heart and the liver. Furthermore, the iron chelator deferoxamine noticeably reduced lung inflammation and oxidative stress, indicating an important role for metal-catalyzed species in lung injury caused by SWCNTs. Overall, we provide direct evidence that lipid-derived free radicals are a critical contributor to tissue damage induced by SWCNTs not only in the lungs, but also in distant organs.
authors.affiliation: Pathology and Physiology Research Branch, HELD, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA; Physiology and Pharmacology, West Virginia University, Morgantown, WV 26506, USA. Electronic address: ats1@cdc.gov.
authors.forename: A A
authors.initials: AA
authors.lastname: Shvedova
authors.affiliation: Pathology and Physiology Research Branch, HELD, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA.
authors.forename: E R
authors.initials: ER
authors.lastname: Kisin
authors.affiliation: Pathology and Physiology Research Branch, HELD, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA; Physiology and Pharmacology, West Virginia University, Morgantown, WV 26506, USA.
authors.forename: A R
authors.initials: AR
authors.lastname: Murray
authors.affiliation: University of Liege, Liège 4000, Belgium.
authors.forename: A
authors.initials: A
authors.lastname: Mouithys-Mickalad
authors.affiliation: National Institute of Environmental Health Science, Research Triangle Park, NC 27709, USA.
authors.forename: K
authors.initials: K
authors.lastname: Stadler
authors.affiliation: National Institute of Environmental Health Science, Research Triangle Park, NC 27709, USA.
authors.forename: R P
authors.initials: RP
authors.lastname: Mason
authors.affiliation: National Institute of Environmental Health Science, Research Triangle Park, NC 27709, USA.
authors.forename: M
authors.initials: M
authors.lastname: Kadiiska
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D016207:Cytokines / Q000096:biosynthesis; D003676:Deferoxamine / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D005260:Female; D005355:Fibrosis / Q000473:pathology; D005609:Free Radicals / Q000378:metabolism*; D006321:Heart; D007249:Inflammation / Q000473:pathology; D050356:Lipid Metabolism; D008055:Lipids; D008099:Liver / Q000378:metabolism; D008103:Liver Cirrhosis / Q000473:pathology; D008168:Lung / Q000378:metabolism / Q000473:pathology*; D055370:Lung Injury / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D009206:Myocardium / Q000378:metabolism; D037742:Nanotubes, Carbon / Q000633:toxicity*; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects*; D011014:Pneumonia / Q000473:pathology; D012129:Respiratory Function Tests
chemical_list: D000975:Antioxidants; D016207:Cytokines; D005609:Free Radicals; D008055:Lipids; D037742:Nanotubes, Carbon; D003676:Deferoxamine
keywords: Carbon nanotubes; Free radicals; Inflammation; Oxidative stress; Tissues; in vivo