Interlaboratory Evaluation of Rodent Pulmonary Responses to Engineered Nanomaterials: The NIEHS Nano GO Consortium

BACKGROUND: Engineered nanomaterials (ENMs) have potential benefits, but they also present safety concerns for human health. Inter-laboratory studies in rodents using standardized protocols are needed to assess ENM toxicity. METHODS: Four laboratories evaluated lung responses in C57BL/6 mice to ENMs delivered by oropharyngeal aspiration (OPA), and three labs evaluated Sprague-Dawley (SD) or Fisher 344 (F344) rats following intratracheal instillation (IT). ENMs tested included three forms of titanium dioxide (TiO2) [anatase/rutile spheres (TiO2-P25), anatase spheres (TiO2-A), and anatase nanobelts (TiO2-NBs)] and three forms of multiwalled carbon nanotubes (MWCNTs) [original (O), purified (P), and carboxylic acid "functionalized" (F)]. One day after treatment, bronchoalveolar lavage fluid was collected to determine differential cell counts, lactate dehydrogenase (LDH), and protein. Lungs were fixed for histopathology. Responses were also examined at 7 days (TiO2 forms) and 21 days (MWCNTs) after treatment. RESULTS: TiO2-A, TiO2-P25, and TiO2-NB caused significant neutrophilia in mice at 1 day in three of four labs. TiO2-NB caused neutrophilia in rats at 1 day in two of three labs, and TiO2-P25 and TiO2-A had no significant effect in any of the labs. Inflammation induced by TiO2 in mice and rats resolved by day 7. All MWCNT types caused neutrophilia at 1 day in three of four mouse labs and in all rat labs. Three of four labs observed similar histo-pathology to O-MWCNTs and TiO2-NBs in mice. CONCLUSIONS: ENMs produced similar patterns of neutrophilia and pathology in rats and mice. Although inter-laboratory variability was found in the degree of neutrophilia caused by the three types of TiO2 nano-particles, similar findings of relative potency for the three types of MWCNTs were found across all laboratories, thus providing greater confidence in these inter-laboratory comparisons.