title: System-based identification of toxicity pathways associated with multi-walled carbon nanotube-induced pathological responses.
abstract: The fibrous shape and biopersistence of multi-walled carbon nanotubes (MWCNT) have raised concern over their potential toxicity after pulmonary exposure. As in vivo exposure to MWCNT produced a transient inflammatory and progressive fibrotic response, this study sought to identify significant biological processes associated with lung inflammation and fibrosis pathology data, based upon whole genome mRNA expression, bronchoaveolar lavage scores, and morphometric analysis from C57BL/6J mice exposed by pharyngeal aspiration to 0, 10, 20, 40, or 80 μg MWCNT at 1, 7, 28, or 56 days post-exposure. Using a novel computational model employing non-negative matrix factorization and Monte Carlo Markov Chain simulation, significant biological processes with expression similar to MWCNT-induced lung inflammation and fibrosis pathology data in mice were identified. A subset of genes in these processes was determined to be functionally related to either fibrosis or inflammation by Ingenuity Pathway Analysis and was used to determine potential significant signaling cascades. Two genes determined to be functionally related to inflammation and fibrosis, vascular endothelial growth factor A (vegfa) and C-C motif chemokine 2 (ccl2), were confirmed by in vitro studies of mRNA and protein expression in small airway epithelial cells exposed to MWCNT as concordant with in vivo expression. This study identified that the novel computational model was sufficient to determine biological processes strongly associated with the pathology of lung inflammation and fibrosis and could identify potential toxicity signaling pathways and mechanisms of MWCNT exposure which could be used for future animal studies to support human risk assessment and intervention efforts.
authors.affiliation: Pathology and Physiology Research Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA.
authors.forename: Brandi N
authors.initials: BN
authors.lastname: Snyder-Talkington
authors.forename: Julian
authors.initials: J
authors.lastname: Dymacek
authors.forename: Dale W
authors.initials: DW
authors.lastname: Porter
authors.forename: Michael G
authors.initials: MG
authors.lastname: Wolfarth
authors.forename: Robert R
authors.initials: RR
authors.lastname: Mercer
authors.forename: Maricica
authors.initials: M
authors.lastname: Pacurari
authors.forename: James
authors.initials: J
authors.lastname: Denvir
authors.forename: Vincent
authors.initials: V
authors.lastname: Castranova
authors.forename: Yong
authors.initials: Y
authors.lastname: Qian
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Guo
mesh_terms: D000818:Animals; D001992:Bronchoalveolar Lavage Fluid; D002478:Cells, Cultured; D019295:Computational Biology / Q000379:methods* / Q000706:statistics & numerical data; D004785:Environmental Pollutants / Q000633:toxicity*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D020869:Gene Expression Profiling; D019570:Inhalation Exposure; D008297:Male; D008390:Markov Chains; D051379:Mice; D008810:Mice, Inbred C57BL; D009010:Monte Carlo Method; D037742:Nanotubes, Carbon / Q000633:toxicity*; D011014:Pneumonia / Q000139:chemically induced* / Q000235:genetics / Q000276:immunology / Q000473:pathology; D011658:Pulmonary Fibrosis / Q000139:chemically induced* / Q000235:genetics / Q000276:immunology / Q000473:pathology; D015398:Signal Transduction / Q000187:drug effects; D059467:Transcriptome
chemical_list: D004785:Environmental Pollutants; D037742:Nanotubes, Carbon
keywords: Computational toxicology; In vitro studies; In vivo studies; Multi-walled carbon nanotubes; Signaling pathways