title: Atomic layer deposition coating of carbon nanotubes with aluminum oxide alters pro-fibrogenic cytokine expression by human mononuclear phagocytes in vitro and reduces lung fibrosis in mice in vivo.
abstract: BACKGROUND
  Multi-walled carbon nanotubes (MWCNTs) pose a possible human health risk for lung disease as a result of inhalation exposure. Mice exposed to MWCNTs develop pulmonary fibrosis. Lung macrophages engulf MWCNTs and produce pro-fibrogenic cytokines including interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and osteopontin (OPN). Atomic layer deposition (ALD) is a novel process used to enhance functional properties of MWCNTs, yet the consequence of ALD-modified MWCNTs on macrophage biology and fibrosis is unknown.
  
  
  METHODS
  The purpose of this study was to determine whether ALD coating with aluminum oxide (Al2O3) would alter the fibrogenic response to MWCNTs and whether cytokine expression in human macrophage/monocytes exposed to MWCNTs in vitro would predict the severity of lung fibrosis in mice. Uncoated (U)-MWCNTs or ALD-coated (A)-MWCNTs were incubated with THP-1 macrophages or human peripheral blood mononuclear cells (PBMC) and cell supernatants assayed for cytokines by ELISA. C57BL6 mice were exposed to a single dose of A- or U-MWCNTs by oropharyngeal aspiration (4 mg/kg) followed by evaluation of histopathology, lung inflammatory cell counts, and cytokine levels at day 1 and 28 post-exposure.
  
  
  RESULTS
  ALD coating of MWCNTs with Al2O3 enhanced IL-1β secretion by THP-1 and PBMC in vitro, yet reduced protein levels of IL-6, TNF-α, and OPN production by THP-1 cells. Moreover, Al2O3 nanoparticles, but not carbon black NPs, increased IL-1β but decreased OPN and IL-6 in THP-1 and PBMC. Mice exposed to U-MWCNT had increased levels of all four cytokines assayed and developed pulmonary fibrosis by 28 days, whereas ALD-coating significantly reduced fibrosis and cytokine levels at the mRNA or protein level.
  
  
  CONCLUSIONS
  These findings indicate that ALD thin film coating of MWCNTs with Al2O3 reduces fibrosis in mice and that in vitro phagocyte expression of IL-6, TNF-α, and OPN, but not IL-1β, predict MWCNT-induced fibrosis in the lungs of mice in vivo.
authors.affiliation: Environmental and Molecular Toxicology Program, Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, United States of America.
authors.forename: Alexia J
authors.initials: AJ
authors.lastname: Taylor
authors.affiliation: Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States of America.
authors.forename: Christina D
authors.initials: CD
authors.lastname: McClure
authors.affiliation: Environmental and Molecular Toxicology Program, Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, United States of America.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Shipkowski
authors.affiliation: Environmental and Molecular Toxicology Program, Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, United States of America.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Thompson
authors.affiliation: Clinical Research Unit, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States of America.
authors.forename: Salik
authors.initials: S
authors.lastname: Hussain
authors.affiliation: Clinical Research Unit, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States of America.
authors.forename: Stavros
authors.initials: S
authors.lastname: Garantziotis
authors.affiliation: Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States of America.
authors.forename: Gregory N
authors.initials: GN
authors.lastname: Parsons
authors.affiliation: Environmental and Molecular Toxicology Program, Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, United States of America.
authors.forename: James C
authors.initials: JC
authors.lastname: Bonner
mesh_terms: D000537:Aluminum Oxide / Q000494:pharmacology*; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism*; D006801:Humans; D007249:Inflammation / Q000473:pathology; D053583:Interleukin-1beta / Q000096:biosynthesis; D015850:Interleukin-6 / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism*; D008168:Lung / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D008810:Mice, Inbred C57BL; D036103:Nanotechnology / Q000379:methods*; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000648:ultrastructure; D053495:Osteopontin / Q000378:metabolism; D010586:Phagocytes / Q000187:drug effects / Q000378:metabolism*; D011658:Pulmonary Fibrosis; D053260:Soot / Q000494:pharmacology; D013499:Surface Properties; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D016207:Cytokines; D053583:Interleukin-1beta; D015850:Interleukin-6; D037742:Nanotubes, Carbon; D053260:Soot; D014409:Tumor Necrosis Factor-alpha; D053495:Osteopontin; D000537:Aluminum Oxide