Toxic effects of carbon nanotubes in macrophage and bronchial epithelium cell cultures

Single- and multi-walled carbon nanotubes (SWCNTs / MWCNTs), being one of the most promising nanomaterials are becoming more and more common. Accumulated data suggest that there is a risk to human health, upon the occupational contact with carbon nanoparticles. The aim of this study was to evaluate the comparative toxic effects of industrial single-and multi-walled CNTs in macrophages and bronchial epithelial cells. RAW 264.7 murine macrophages culture exposure to MWCNT did not result in significant viability loss but was accompanied by an increase in lactate dehydrogenase (LDH) concentrations in the extracellular medium 48 hours post exposure at all doses (but not after 24 hours). Oxidative stress had a dose- and time-dependent nature, intracellular glutathione levels decreased with increasing dose and exposure time (for the highest dose). SWCNTs exposure of the RAW 264.7 culture reduced the viability by 10-15% after 24 hours, regardless of the dose. After 48 hours viability decreased to 78% at 2.4 ug/cm SWCNT, and at 24 ug/cm - down to 50% of the unexposed cells. LDH levels rose sharply 48 hours after exposure at concentrations of 0.2, 2.4 and 24 ug/cm, which generally coincides with the observed viability loss in the same groups. A significant decrease in reduced glutathione levels was found: the higher exposure dose and exposure time were, the lower were the levels. Bronchial epithelial cells BEAS-2B appeared to be little susceptible to the MWCNT introduction: after 24 and 48 hours there were no significant decrease in viability compared to the control culture. The same results were obtained when assessing the cell damage and oxidative stress indicators. BEAS-2B exposure to SWCNTs after 24 h and 48 h caused a small statistically significant dose- and time-dependent viability decrease and a considerable reduction in reduced glutathione levels at highest concentration of nanoparticles 24 ug/ cm. Macrophages (RAW 264.7) were much more sensitive to different types of CNTs than bronchial epithelial cells (BEAS-2B). The results show the necessity for available in vitro and in silico models to evaluate different parameters of nanoparticles toxicity. Comparison of different CNT types should be based not only on viability assessment, but also on specific exposure indicators and biomarkers, such as oxidative stress, cell membrane damage and cytokine profile changes. In addition, during the process of new regulations introduction, nanoparticles should be classified not only by chemical composition, but also by their morphological features.

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