Apoptotic, inflammatory, and fibrogenic effects of two different types of multi-walled carbon nanotubes in mouse lung

• Published in: Archives of toxicology 2014-09, Vol.88 (9), p.1725-1737
• Main Authors: van Berlo, D., Wilhelmi, V., Boots, A. W., Hullmann, M., Kuhlbusch, T. A. J., Bast, A., Schins, R. P. F., Albrecht, C.
• Format: Article
• Language: English
• Subjects: Administration, Inhalation; Animals; Apoptosis - drug effects; Biomarkers - blood; Biomarkers - metabolism; Biomedical and Life Sciences; Biomedicine; Cell Line, Transformed; Environmental Health; Female; Fibrosis; Hydrogen Peroxide - metabolism; Lung - drug effects; Lung - immunology; Lung - metabolism; Lung - pathology; Lungs; Macrophage Activation - drug effects; Macrophages - drug effects; Macrophages - immunology; Macrophages - metabolism; Mice, Inbred C57BL; Microscopy, Electron, Scanning; Nanotubes; Nanotubes, Carbon - toxicity; Nanotubes, Carbon - ultrastructure; Occupational Medicine/Industrial Medicine; Organ Toxicity and Mechanisms; Particle Size; Particulate Matter - administration & dosage; Particulate Matter - chemistry; Particulate Matter - toxicity; Pharmacology/Toxicology; Pneumonia - chemically induced; Pneumonia - immunology; Pneumonia - metabolism; Pneumonia - pathology; Reactive Oxygen Species - metabolism; Respiratory Mucosa - drug effects; Respiratory Mucosa - immunology; Respiratory Mucosa - metabolism; Respiratory Mucosa - pathology; Rodents; Specific Pathogen-Free Organisms; Toxicity
• ISSN: 0340-5761; 1432-0738
• DOI: 10.1007/s00204-014-1220-z

There is increasing concern about the toxicity of inhaled multi-walled carbon nanotubes (MWCNTs). Pulmonary macrophages represent the primary cell type involved in the clearance of inhaled particulate materials, and induction of apoptosis in these cells has been considered to contribute to the development of lung fibrosis. We have investigated the apoptotic, inflammogenic, and fibrogenic potential of two types of MWCNTs, characterised by a contrasting average tube length and entanglement/agglomeration. Both nanotube types triggered H 2 O 2 formation by RAW 264.7 macrophages, but in vitro toxicity was exclusively seen with the longer MWCNT. Both types of nanotubes caused granuloma in the mouse lungs. However, the long MWCNT induced a more pronounced pro-fibrotic (mRNA expression of matrix metalloproteinase-8 and tissue inhibitor of metalloproteinase-1) and inflammatory (serum level of monocyte chemotactic protein-1) response. Masson trichrome staining also revealed epithelial cell hyperplasia for this type of MWCNT. Enhanced apoptosis was detected by cleaved caspase 3 immunohistochemistry in lungs of mice treated with the long and rigid MWCNT and, to a lesser extent, with the shorter, highly agglomerated MWCNT. However, staining was merely localised to granulomatous foci, and neither of the MWCNTs induced apoptosis in vitro, evaluated by caspase 3/7 activity in RAW 264.7 cells. In addition, our study reveals that the inflammatory and pro-fibrotic effects of MWCNTs in the mouse lung can vary considerably depending on their composition. The in vitro analysis of macrophage apoptosis appears to be a poor predictor of their pulmonary hazard.