title: An in vitro alveolar macrophage assay for predicting the short-term inhalation toxicity of nanomaterials.
abstract: BACKGROUND
  Most in vitro studies investigating nanomaterial pulmonary toxicity poorly correlate to in vivo inhalation studies. Alveolar macrophages (AMs) play an outstanding role during inhalation exposure since they effectively clear the alveoli from particles. This study addresses the applicability of an in vitro alveolar macrophage assay to distinguish biologically active from passive nanomaterials.
  
  
  METHODS
  Rat NR8383 alveolar macrophages were exposed to 18 inorganic nanomaterials, covering AlOOH, BaSO4, CeO2, Fe2O3, TiO2, ZrO2, and ZnO NMs, amorphous SiO2 and graphite nanoplatelets, and two nanosized organic pigments. ZrO2 and amorphous SiO2 were tested without and with surface functionalization. Non-nanosized quartz DQ12 and corundum were used as positive and negative controls, respectively. The test materials were incubated with the cells in protein-free culture medium. Lactate dehydrogenase, glucuronidase, and tumour necrosis factor alpha were assessed after 16 h. In parallel, H2O2 was assessed after 1.5 h. Using the no-observed-adverse-effect concentrations (NOAECs) from available rat short-term inhalation studies (STIS), the test materials were categorized as active (NOAEC < 10 mg/m(3)) or passive.
  
  
  RESULTS
  In vitro data reflected the STIS categorization if a particle surface area-based threshold of <6000 mm(2)/mL was used to determine the biological relevance of the lowest observed significant in vitro effects. Significant effects that were recorded above this threshold were assessed as resulting from test material-unspecific cellular 'overload'. Test materials were assessed as active if ≥2 of the 4 in vitro parameters undercut this threshold. They were assessed as passive if 0 or 1 parameter was altered. An overall assay accuracy of 95 % was achieved.
  
  
  CONCLUSIONS
  The in vitro NR8383 alveolar macrophage assay allows distinguishing active from passive nanomaterials. Thereby, it allows determining whether in vivo short-term inhalation testing is necessary for hazard assessment. Results may also be used to group nanomaterials by biological activity. Further work should aim at validating the assay.
authors.affiliation: IBR R&D gGmbH Institute for Lung Health, Mendelstraße 11, 48149, Münster, Germany. martin.wiemann@ibe-ms.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Wiemann
authors.affiliation: IBR R&D gGmbH Institute for Lung Health, Mendelstraße 11, 48149, Münster, Germany. vennemann@ibe-ms.de.
authors.forename: Antje
authors.initials: A
authors.lastname: Vennemann
authors.affiliation: Scientific Consultancy - Animal Welfare, Hallstattfeld 16, 85579, Neubiberg, Germany. ursula.sauer@sauerug.de.
authors.forename: Ursula G
authors.initials: UG
authors.lastname: Sauer
authors.affiliation: BASF SE, Experimental Toxicology and Ecology, GB/TB - Z470, 67056, Ludwigshafen, Germany. karin.wiench@basf.com.
authors.forename: Karin
authors.initials: K
authors.lastname: Wiench
authors.affiliation: BASF SE, Experimental Toxicology and Ecology, GB/TB - Z470, 67056, Ludwigshafen, Germany. lan.ma-hock@basf.com.
authors.forename: Lan
authors.initials: L
authors.lastname: Ma-Hock
authors.affiliation: BASF SE, Experimental Toxicology and Ecology, GB/TB - Z470, 67056, Ludwigshafen, Germany. robert.landsiedel@basf.com.
authors.forename: Robert
authors.initials: R
authors.lastname: Landsiedel
mesh_terms: D000818:Animals; D002460:Cell Line; D005290:Ferric Compounds / Q000009:adverse effects; D006108:Graphite / Q000009:adverse effects; D006861:Hydrogen Peroxide / Q000009:adverse effects; D019570:Inhalation Exposure / Q000009:adverse effects*; D008168:Lung / Q000187:drug effects; D016676:Macrophages, Alveolar / Q000187:drug effects*; D049329:Nanostructures / Q000008:administration & dosage* / Q000009:adverse effects*; D010316:Particle Size; D051381:Rats; D012822:Silicon Dioxide / Q000009:adverse effects; D014025:Titanium / Q000009:adverse effects
chemical_list: D005290:Ferric Compounds; D012822:Silicon Dioxide; D006108:Graphite; D006861:Hydrogen Peroxide; D014025:Titanium