title: Direct stimulation of human fibroblasts by nCeO2 in vitro is attenuated with an amorphous silica coating.
abstract: Nano-scaled cerium oxide (nCeO2) is used in a variety of applications, including use as a fuel additive, catalyst, and polishing agent, yet potential adverse health effects associated with nCeO2 exposure remain incompletely understood. Given the increasing utility and demand for engineered nanomaterials (ENMs) such as nCeO2, "safety-by-design" approaches are currently being sought, meaning that the physicochemical properties (e.g., size and surface chemistry) of the ENMs are altered in an effort to maximize functionality while minimizing potential toxicity. In vivo studies have shown in a rat model that inhaled nCeO2 deposited deep in the lung and induced fibrosis. However, little is known about how the physicochemical properties of nCeO2, or the coating of the particles with a material such as amorphous silica (aSiO2), may affect the bio-activity of these particles. Thus, we hypothesized that the physicochemical properties of nCeO2 may explain its potential to induce fibrogenesis, and that a nano-thin aSiO2 coating on nCeO2 may counteract that effect.
  
  
  
  Primary normal human lung fibroblasts were treated at occupationally relevant doses with nCeO2 that was either left uncoated or was coated with aSiO2 (amsCeO2). Subsequently, fibroblasts were analyzed for known hallmarks of fibrogenesis, including cell proliferation and collagen production, as well as the formation of fibroblastic nodules. The results of this study are consistent with this hypothesis, as we found that nCeO2 directly induced significant production of collagen I and increased cell proliferation in vitro, while amsCeO2 did not. Furthermore, treatment of fibroblasts with nCeO2, but not amsCeO2, significantly induced the formation of fibroblastic nodules, a clear indicator of fibrogenicity. Such in vitro data is consistent with recent in vivo observations using the same nCeO2 nanoparticles and relevant doses. This effect appeared to be mediated through TGFβ signaling since chemical inhibition of the TGFβ receptor abolished these responses.
  
  
  
  These results indicate that differences in the physicochemical properties of nCeO2 may alter the fibrogenicity of this material, thus highlighting the potential benefits of "safety-by-design" strategies. In addition, this study provides an efficient in vitro method for testing the fibrogenicity of ENMs that strongly correlates with in vivo findings.
authors.affiliation: National Institute for Occupational Safety and Health, Health Effects Laboratory Division, 1095 Willowdale Road, Morgantown, WV, 26505, USA.
authors.forename: Donna C
authors.initials: DC
authors.lastname: Davidson
authors.affiliation: National Institute for Occupational Safety and Health, Health Effects Laboratory Division, 1095 Willowdale Road, Morgantown, WV, 26505, USA.
authors.forename: Raymond
authors.initials: R
authors.lastname: Derk
authors.affiliation: Department of Pharmaceutical Sciences and Mary Babb Randolph Cancer Center, West Virginia University, Morgantown, WV, USA.
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: He
authors.affiliation: National Institute for Occupational Safety and Health, Health Effects Laboratory Division, 1095 Willowdale Road, Morgantown, WV, 26505, USA.
authors.forename: Todd A
authors.initials: TA
authors.lastname: Stueckle
authors.affiliation: Department of Environmental Health, Center for Nanotechnology and Nanotoxicology, Harvard T. H. Chan School of Public Health, Boston, MA, USA.
authors.forename: Joel
authors.initials: J
authors.lastname: Cohen
authors.affiliation: Department of Environmental Health, Center for Nanotechnology and Nanotoxicology, Harvard T. H. Chan School of Public Health, Boston, MA, USA.
authors.forename: Sandra V
authors.initials: SV
authors.lastname: Pirela
authors.affiliation: Department of Environmental Health, Center for Nanotechnology and Nanotoxicology, Harvard T. H. Chan School of Public Health, Boston, MA, USA.
authors.forename: Philip
authors.initials: P
authors.lastname: Demokritou
authors.affiliation: Department of Pharmaceutical Sciences and Mary Babb Randolph Cancer Center, West Virginia University, Morgantown, WV, USA.
authors.forename: Yon
authors.initials: Y
authors.lastname: Rojanasakul
authors.affiliation: National Institute for Occupational Safety and Health, Health Effects Laboratory Division, 1095 Willowdale Road, Morgantown, WV, 26505, USA. LRojanasakul@cdc.gov.
authors.forename: Liying
authors.initials: L
authors.lastname: Wang
mesh_terms: D000393:Air Pollutants / Q000737:chemistry / Q000633:toxicity*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D002563:Cerium / Q000737:chemistry / Q000633:toxicity*; D055598:Chemical Phenomena; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008168:Lung / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D053768:Metal Nanoparticles / Q000737:chemistry / Q000633:toxicity*; D010316:Particle Size; D055585:Physical Phenomena; D011658:Pulmonary Fibrosis / Q000139:chemically induced / Q000276:immunology / Q000473:pathology; D020545:Respiratory Mucosa / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D015398:Signal Transduction / Q000187:drug effects; D012822:Silicon Dioxide / Q000737:chemistry / Q000633:toxicity*; D013499:Surface Properties; D023382:Toxicity Tests, Acute; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism
chemical_list: D000393:Air Pollutants; D016212:Transforming Growth Factor beta; D002563:Cerium; C030583:ceric oxide; D012822:Silicon Dioxide
keywords: Cerium oxide nanoparticles; Engineered nanomaterials; Fibrosis; Nanotoxicology; in vitro dosimetry