Systemic distribution of single-walled carbon nanotubes in a novel model: alteration of biochemical parameters, metabolic functions, liver accumulation, and inflammation in vivo

Abstract

The increasing use of carbon nanotubes (CNTs) in several industrial applications raises concerns on their potential toxicity due to factors such as tissue penetrance, small dimensions, and biopersistence. Using an in vivo model for CNT environmental exposure, mimicking CNT exposition at the workplace, we previously found that CNTs rapidly enter and disseminate in the organism, initially accumulating in the lungs and brain and later reaching the liver and kidneys via the bloodstream in CD1 mice. Here, we monitored and traced the accumulation of single-walled CNTs (SWCNTs), administered systemically in mice, in different organs and the subsequent biological responses. Using the novel in vivo model, MITO-Luc bioluminescence reporter mice, we found that SWCNTs induce systemic cell proliferation, indicating a dynamic response of cells of both bone marrow and the immune system. We then examined metabolic (water/food consumption and dejections), functional (serum enzymes), and morphological (organs and tissues) alterations in CD1 mice treated with SWCNTs, using metabolic cages, performing serum analyses, and applying histological, immunohistochemical, and ultrastructural (transmission electron microscopy) methods. We observed a transient accumulation of SWCNTs in the lungs, spleen, and kidneys of CD1 mice exposed to SWCNTs. A dose- and time-dependent accumulation was found in the liver, associated with increases in levels of aspartate aminotransferase, alanine aminotransferase and bilirubinemia, which are metabolic markers associated with liver damage. Our data suggest that hepatic accumulation of SWCNTs associated with liver damage results in an M1 macrophage-driven inflammation.

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Keywords:

• single-walled carbon nanotubes
• nanotoxicity
• metabolism
• hepatic function
• inflammation
• Kupffer cells
• mouse models

Supplementary material

Figure S1 Physiological monitoring of SWCNT-exposed CD1 mice.

Notes: Food and water consumption, urine and feces production, and fecal water content in samples collected 24 hours after the first administration (24h I), 24 hours after the second administration (24h II), 24 hours after the third administration (24h III), and 3 weeks after the third administration (3wk III) of SWCNTs. Following the first administration of SWCNTs, we observed increased water (A) and food consumption (B), associated with higher feces production (C) and fecal water percentage (D). Urine production was not affected (E). Similar effects were found for all SWCNT doses employed, and most parameters returned to near baseline 3 weeks from the last administration, in particular for the highest dose. Data are expressed as mean (n>6) ± standard error of the mean; statistical significance: *P≤0.05 and **P≤0.01.

Abbreviation: SWCNT, single-walled carbon nanotube.

Acknowledgments

This study was supported by the Fondazione CARIPLO (ID: 2011-2092) and the Associazione Italiana per la Ricerca sul Cancro (IG15895 to DMN and IG13234 to GP). RG and EG are participants in the PhD program of the Biotechnology, Biosciences and Surgical Technologies at the University of Insubria. EP, AB, and AP were supported by the Fondazione Italiana per la Ricerca sul Cancro. AB is a Fondazione Umberto Veronesi fellow. The authors thank Paola Corradino for data management and Alessandra Panvini Rosati for assistance.

Author contributions

AA, DMN, AG, GP, and MDE conceived the experiments, performed the statistical analysis, and wrote the article. EP, RG, EG, and AB performed the in vivo and in vitro experiments. TC performed the SEM analysis. IM performed the experiments with the MITO-Luc murine model. AB and DDS performed the statistical analysis and wrote the article. All authors contributed toward data analysis, drafting and critically revising the paper and agree to be accountable for all aspects of the work.

Disclosure

The authors declare no conflicts of interest in this work.