Single-walled carbon nanotube-induced mitotic disruption

Abstract

Carbon nanotubes were among the earliest products of nanotechnology and have many potential applications in medicine, electronics, and manufacturing. The low density, small size, and biological persistence of carbon nanotubes create challenges for exposure control and monitoring and make respiratory exposures to workers likely. We have previously shown mitotic spindle aberrations in cultured primary and immortalized human airway epithelial cells exposed to 24, 48 and 96 μg/cm 2 single-walled carbon nanotubes (SWCNT). To investigate mitotic spindle aberrations at concentrations anticipated in exposed workers, primary and immortalized human airway epithelial cells were exposed to SWCNT for 24-72 h at doses equivalent to 20 weeks of exposure at the Permissible Exposure Limit for particulates not otherwise regulated. We have now demonstrated fragmented centrosomes, disrupted mitotic spindles and aneuploid chromosome number at those doses. The data further demonstrated multipolar mitotic spindles comprised 95% of the disrupted mitoses. The increased multipolar mitotic spindles were associated with an increased number of cells in the G2 phase of mitosis, indicating a mitotic checkpoint response. Nanotubes were observed in association with mitotic spindle microtubules, the centrosomes and condensed chromatin in cells exposed to 0.024, 0.24, 2.4 and 24 μg/cm 2 SWCNT. Three- Conflict of interest statementThe authors declare that there are no conflicts of interest. Appendix A. Supplementary dataSupplementary data associated with this article can be found, in the online version, at doi:10.1016/j.mrgentox.2011.11.017. HHS Public Access Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript dimensional reconstructions showed carbon nanotubes within the centrosome structure. The lower doses did not cause cytotoxicity or reduction in colony formation after 24 h; however, after three days, significant cytotoxicity was observed in the SWCNT-exposed cells. Colony formation assays showed an increased proliferation seven days after exposure. Our results show significant disruption of the mitotic spindle by SWCNT at occupationally relevant doses. The increased proliferation that was observed in carbon nanotube-exposed cells indicates a greater potential to pass the genetic damage to daughter cells. Disruption of the centrosome is common in many solid tumors including lung cancer. The resulting aneuploidy is an early event in the progression of many cancers, suggesting that it may play a role in both tumorigenesis and tumor progression. These results suggest caution should be used in the handling and processing of carbon nanotubes.

Exposure to Carbon Nanotubes Leads to Changes in the Cellular Biomechanics

“…Specifically, our study shows that after 24 h exposure, MWCNTs localize at the cell nucleus, with nanotube localization inducing changes in the nucleus mechanics by increasing its stiffness and overall Young's modulus with more than 36.6% than for control cells (either cells exposed to 1 h acids-washed MWCNTs for 1 h or to the control cells). Combining our data with previous reports that indicate that MWCNTs interact with microtubules, [22,46] the mitotic spindle, [22] DNA and cell division apparatus, [17,18] we propose now that the observed stiffness due to exposure to 1 h acids-washed MWCNTs could lead the reorganization of the three-dimensional cellular cytoskeletal network. Such reorganization could potentially disrupt the mitotic spindle, [22] inducing errors in chromosome numbers to be propagated through further cellular division [19] as characteristics of cancer cells.…”

“…[16,17] Recent work has shown that in vitro and in vivo exposure to SWCNTs can lead to alterations in DNA structure. [18,19] For instance, our recent studies have shown that 24 to 72 h exposure of epithelial cells to SWCNTs induced centrosome fragmentation and aneuploidy [18,20] similar to the genotoxin vanadium pentoxide. [21] Likewise, cellular exposure to MWCNT disrupted the mitotic spindle by association with microtubules, [22] induced polyploidy [17] and changes in chromosome number in a fashion similar to crocidolite asbestos.…”

Keeping it small: towards a molecular definition of nanotoxicology

“…Sargent et al (28) provided evidence of SWCNT interference with the mitotic spindle in human airway epithelial cells leading to induction of aneuploidy, an early event in the progression of many cancers. Notably, significant disruption of the mitotic spindle by SWCNTs was detected at occupationally relevant doses (29). The CNT bundles are similar to the size of microtubules that form the mitotic spindle and this "bio-mimicry" may explain how these nanomaterials are incorporated into the mitotic spindle apparatus.…”

Carbon nanotubes – Characteristic of the substance, biological effects and occupational exposure levels

“…Stwierdzono, że SWCNT i MWCNT: Baytubes® oraz Nanotec (średnica 10-30 nm), nie wykazywały działania genotoksycznego (aberracji chromosomowych i zwiększenia częstości wymiany chromatyd siostrzanych) w fibroblastach chomika chińskiego lub ludzkich limfocytach [37,38]. W ludzkich komórkach nabłonka oddechowego eksponowanych na SWCNT zaobserwowano zaburzenia podziałów mitotycznych [43].…”