Role of fibre characteristics on cytotoxicity and induction of anaphase/telophase aberrations in rat pleural mesothelial cells in vitro: correlations with in vivo animal findings

Abstract

Thirteen samples of natural fibres and five samples of man-made fibres (MMF) were tested to determine their cytotoxicity and ability to produce chromosome missegregation in cultures in rat pleural mesothelial cells (RPMC). The natural samples included attapulgite, two amphiboles (amosite and crocidolite); seven consisted of chrysotile from various origins and three were obtained after chemical treatment of chrysotile. MMF included three refractory ceramic fibres (RCF) and two vitreous fibres (MMVF). All fibre samples were characterized by electron microscopic measurement of the fibre dimensions. Cytotoxicity was assayed on the basis of determination of mitochondrial integrity and chromosome missegregation by light microscopy examination of anaphases/telophases. The carcinogenic potency of 10 natural samples has been previously investigated using intrapleural inoculation in rats. It was therefore possible to establish correlations between in vitro and in vivo data obtained with the same set of samples. The various samples of chrysotile produced different in vitro effects, in agreement with the dispersion of response also observed in vivo. Cytotoxicity appears to be dependent on both fibre length and fibre diameter, as the longest or thickest fibres were the most toxic. The production of abnormal anaphases/telophases appears to depend on the presence of fibres of selected size, such as those previously defined by Stanton et al. (L > 8 micrograms; D < or = 0.25 microns); a threshold values was determined below which no abnormal anaphases/telophases were detected. This non-observable effect level was estimated to be 2.5 x 10(5) 'Stanton' fibres per cm2. There was no correlation between cytotoxicity and mesothelioma induction; in contrast, a correlation was found between the ability of a sample to produce chromosome missegregation in vitro and mesothelioma in vivo.

Single-walled carbon nanotube-induced mitotic disruption

“…Centrosome fragmentation, mitotic spindle disruption, and aneuploidy are characteristics of cancer cells and may lead to an increased risk of cancer [23,25]. Consistent with this hypothesis, research with inorganic fibers indicate that in vivo asbestos-induced mesothelioma is correlated with the ability of the fiber to cause chromosomal missegregation, not with cytotoxicity [81]. The current research demonstrating mitotic spindle disruption and errors in chromosome number indicates caution should be used during the production and processing of carbon nanotubes.…”

“…Mitotic spindle damage with a predominantly multipolar phenotype and aneuploidy have also been observed following in vitro treatment with 0.25 μg/mL of the potent occupational carcinogen, chrysotile asbestos [80]. The ability of asbestos fibers to induce aneuploidy in vitro is highly correlated with the ability to induce mesotheliomas in vivo; this provides data supporting the importance of aneuploidy in carcinogenesis due to particulates with high aspect ratios [81]. Chrysotile has also been observed to cause a G2/M block similar to the block observed with SWCNT [48].…”

Mechanisms of fiber-induced genotoxicity.

“…The formation of abnormal anaphases was not dependent on the presence of antioxidant enzymes (103). The physical presence of fibers in dividing cells seems a more likely mechanism by which fibers impair mitosis.…”

“…Pelin et al (102) found that chrysotile and crocidolite produced a significant enhancement of the percentage of abnormal anaphases in HMC treated with chrysotile and crocidolite, but amosite produced only a slight increase. Similarly, Yegles et al (103) observed that crocidolite and several samples of chrysotile produced a significant number of abnormal anaphases, but amosite and MMMF [refractory ceramic fibers (RCFs), MMVF] were inactive. The authors suggest that the absence of effect from some fiber types may be due to an insufficient number of relevant fibers.…”

“…In these processes, fiber dimensions play a critical role. Samples enriched with long and thin fibers tend to produce abnormal anaphases (103) and aneuploidy-dependent cell transformation of SHE cells by unmilled glass fibers; milled fibers, though they phagocytosed at approximately the same rate, were not efficient (123).…”