title: Comparative pulmonary toxicity assessment of pristine and functionalized multi-walled carbon nanotubes intratracheally instilled in rats: morphohistochemical evaluations.
abstract: Increasing interest in safety evaluation of carbon nanotubes (CNTs) has risen in relation to their wide applications, together with the evidence of their cytotoxic effects. It has been shown that chemical functionalization extends the applications of CNTs, conferring them new functions that cannot otherwise be acquired by pristine CNTs, but also impacts on biological response to CNTs, modifying their toxicological profile. We assessed the onset of pulmonary toxic effects caused by pristine MW-CNTs and functionalized MW-NH₂ or MW-COOH, 16 days after intratracheal instillation (1 mg/kg b.w.); major endpoints tested included (i) histopathology of lung (Haematoxylin/Eosin Staining), (ii) apoptotic/proliferating features examined by TUNEL and PCNA immunostaining, and (iii) presence/distribution of (1) Transforming Growth Factor-beta1 (TGFß1), (2) Interleukin-6 (IL-6) and (3) Collagen (Type I) investigated by immunochemical methods, as markers of lung toxicity, inflammation, and fibrosis, respectively. Lung histopathology from exposed animals showed dark, particulate-laden macrophages, reflecting carbon nanomaterial engulfing, both at alveolar and bronchiolar levels, after treatment with all the tested CNTs. Alteration of lung architecture was also observed in several areas showing collapsed thick-walled alveoli and the presence of micro-haemorrhagic foci. TUNEL and PCNA, indicative of apoptosis and cell proliferation respectively, showed a significant increase of immunopositive cells at bronchiolar, alveolar and macrophagic levels, as expression of an improved cellular turnover. Increased immunoreactivity for pulmonary TGFß1 and IL-6 was observed in treated rats, particularly in bronchiolar areas, collapsed alveoli and at stromal level, while evident changes for collagen were not detected. Taken together these findings demonstrated the general pulmonary toxicity coupled with inflammatory response after in vivo exposure to CNTs, without overt signs of fibrosis and granuloma formation, irrespectively of nanotube functionalization.
authors.affiliation: Department of Internal Medicine and Therapeutics, Toxicology Division, University of Pavia, Pavia, Italy. elisa.roda@unipv.it
authors.forename: E
authors.initials: E
authors.lastname: Roda
authors.forename: T
authors.initials: T
authors.lastname: Coccini
authors.forename: D
authors.initials: D
authors.lastname: Acerbi
authors.forename: S
authors.initials: S
authors.lastname: Barni
authors.forename: R
authors.initials: R
authors.lastname: Vaccarone
authors.forename: L
authors.initials: L
authors.lastname: Manzo
mesh_terms: D000280:Administration, Inhalation; D000818:Animals; D024042:Collagen Type I / Q000378:metabolism; D005260:Female; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D015850:Interleukin-6 / Q000378:metabolism; D007442:Intubation, Intratracheal; D008168:Lung / Q000473:pathology; D008171:Lung Diseases / Q000139:chemically induced* / Q000473:pathology*; D008297:Male; D037742:Nanotubes, Carbon / Q000737:chemistry / Q000633:toxicity*; D010316:Particle Size; D011014:Pneumonia / Q000139:chemically induced / Q000473:pathology; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011658:Pulmonary Fibrosis / Q000139:chemically induced / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D053773:Transforming Growth Factor beta1 / Q000378:metabolism
chemical_list: D024042:Collagen Type I; D015850:Interleukin-6; D037742:Nanotubes, Carbon; D018809:Proliferating Cell Nuclear Antigen; D053773:Transforming Growth Factor beta1