Comparison of the effects of multiwall carbon nanotubes on the epithelial cells and macrophages
Effects of two kinds of multiwall carbon nanotubes (MWCNTs) on cells were examined. The effects of MWNT-7, which has been reported to be carcinogenic, and MWCNT-B, whose toxicity is unclear, were examined in both epithelial cells and macrophages. Human lung carcinoma A549 cells were used as representative epithelial cells and differentiated human monocyte THP-1 cells, as well as rat pulmonary macrophages NR8383, were employed to examine possible harmful effects of the MWCNTs. The MWCNTs induced the production of chemokines such as interleukin-8 (IL-8). MWCNTs were found to more strongly affect macrophages than epithelial cells. In addition, the toxicity was more pronounced in the MWNT-7 exposed cells than in those exposed to MWCNT-B. Cytochalasin D and amiloride treatment of differentiated THP-1 cells reduced cell-associated MWCNTs and IL-8 induction. To confirm these cellular influences in vivo, intratracheal administration of each type of MWCNT was performed by pharyngeal aspiration in the mouse lung. Analysis of bronchoalveolar lavage fluid (BALF) showed increase of inflammatory monocyte in MWNT-7 exposed animals at 1week after. In addition, neutrophils in the BALF were also significantly increased MWNT-7 exposed animals at 1 week and 1 month after. Aspiration of MWNT-7 caused formation of granulomas in the lung. Formation of the granulomas was not observed in the case of MWCNT-B. These results suggest that cellular uptake of the MWCNTs by phagocytosis and chemokine induction is important aspects of their toxicity.