A new possible parameter for the detection of aneuploidy inducing substances: the analysis of qualitative and quantitative abnormalities of the spindle apparatus

Genomic damage induced by 1-MHz ultrasound in vitro

Genotoxic effects of therapeutic ultrasound are poorly documented, when compared with the wide use of this physical agent. The aim of this work was to investigate the clastogenic and aneugenic potential of 1 MHz ultrasound, employing intensities (200 and 300 mW/cm² ) above the cavitational threshold, but in the range of those normally used in therapeutics. Both normal fibroblasts (AG01522) and tumoral cells (MCF-7) were sonicated. While no effects on viability were noted, significant increases of CREST-negative micronuclei (indicative of clastogenesis) and CREST-positive micronuclei (indicative of aneuploidy) were detected. Clastogenesis was confirmed by increases of γ-H2AX foci, while increases of spindle anomalies confirmed the induction of aneuploidy. Our results confirm previous works that showed ultrasound-induced DNA breakage. Moreover, our experiments show that the known effect of ultrasound-induced damage to microtubules is also able to damage the mitotic spindle and induce aneuploidy. On the overall, this work highlights the importance to further investigate the potential risks related to therapeutics US. Environ. Mol. Mutagen. 59:60-68, 2018. © 2017 Wiley Periodicals, Inc.

Genotoxic and aneugenic properties of an imidazole derivative

To contribute to a more accurate characterization of the mutagenic and aneugenic effects of thiabendazole (TBZ), a widely used antiparasitic and food preservative drug, the induction of sister chromatid exchanges (SCEs) and mitotic spindle anomalies as cytogenetic end-points were investigated. Studies were carried out in Chinese hamster ovary (CHO) cells and human peripheral blood lymphocytes. A significant dose-dependent increase in SCE frequency was observed in CHO cells with S9-Mix (P < 0.01) in the 50-100 microg ml(-1) dose-range, while in the absence of S9-Mix, an enhancement of the SCE frequency was exhibited at the highest dose (P < 0.01). In CHO-K1 cells a significant increase in mitotic spindle anomalies (P < 0.01) was observed with the highest concentration assayed reflecting the specific effect of TBZ formulation at the microtubule level. Cell proliferation kinetics (CPK) were not modified by the addition of this pharmaceutical product. In human lymphocyte cultures, exposure to 100 microg ml(-1) TBZ formulation resulted in a significant decrease of the mitotic index (MI) (P < 0.003) and changes in the replication index (RI) (P < 0.05).

Effect of the dithiocarbamate pesticide zineb and its commercial formulation, the azzurro. V. Abnormalities induced in the spindle apparatus of transformed and non-transformed mammalian cell lines

Abnormalities induced in the mitotic spindle by zineb and azzurro (1.0-25.0 micro g/ml, 24h) were evaluated in Chinese hamster ovary (CHO) and HeLa cells, and in non-transformed human fibroblasts (NTHF). Spindles were stained with FITC-conjugated anti-beta tubulin. Treatment with 10.0 micro g/ml of zineb induced complete inhibition of cell viability in NTHF cells while 10.0 micro g/ml of azzurro decreased cell growth down to 62%. Higher doses of both compounds induced cell death. In HeLa and CHO cells, 15.0 micro g/ml of zineb and 10.0-15.0 micro g/ml of azzurro decreased viability, whereas 25.0 micro g/ml of both compounds was cytotoxic. A significantly decreased mitotic index (MI) was observed in NTHF treated with 5.0 micro g/ml zineb or azzurro, whereas 10.0 micro g/ml of both chemicals were necessary to induce the same phenomenon in HeLa and CHO cells. Treatment with 1.0-5.0 micro g/ml of zineb or azzurro induced a dose-dependent increase of degenerated spindles in NTHF and the number of degenerated or multipolar spindles in HeLa and CHO cells increased in a dose-dependent manner with 1.0-10.0 micro g/ml zineb and azzurro. Although zineb and azzurro were able to induce mitotic spindle abnormalities in all cell types, non-transformed cells were less resistant than immortalized cells.

HSP70 overexpression increases resistance of V79 cells to cytotoxicity of airborne pollutants, but does not protect the mitotic spindle against damage caused by airborne toxins

Exposure of Chinese hamster V79 cells to extracts of airborne pollutants induced formation of multipolar or incomplete mitotic spindles. To find out whether overexpression of the HSP70 chaperone protein could protect spindles against airborne toxins we constructed V79 cells stably transfected with an expression vector containing rat heat-inducible hsp70.1 gene under the control of a constitutive CMV promoter. When cells were incubated with extracts of airborne pollutants (5-20 microg/ml) no protective effect of the HSP70 protein against mitotic spindle damage was observed. Moreover, at 20 microg/ml of extracts of airborne toxins the frequency of mitotic malformations was even higher in HSP70-overexpressing cells than in control ones. Extracts of airborne pollutants of 50 microg/ml blocked the formation of mitotic figures both in control and HSP70-overexpressing cells and led to destruction of cell nuclei. However, the HSP70-overproducing cells exhibited higher survival rates when exposed to heat shock and airborne toxins than the control ones, as determined by MTT assay. This suggests that HSP70 overexpression-a frequent feature of cancer cells-should be considered as a factor facilitating survival of cells with damaged mitotic spindles and aberrantly segregated chromosomes.

Induction of aneuploidy by nickel sulfate in V79 Chinese hamster cells

The ability of nickel sulfate (NiSO(4)) to induce chromosome aneuploidy was investigated in vitro using the V79 Chinese hamster cell line. V79 cells were treated with 100-400 microM NiSO(4) for 24h, and monitored up to 72 h following treatment with a chromosome aberration assay, a micronuclei assay using antikinetochore antibodies (CREST assay) and an anaphase/telophase assay. Aneuploid cells were induced in a significant fraction of the cell population 24-48 h following treatment with nickel sulfate. The majority of these cells were hyperdiploid. In addition, nickel sulfate caused increased frequency of cells with kinetochore-positive micronuclei as well as kinetochore-negative micronuclei. Abnormal chromosome segregation such as lagging chromosomes, chromosome bridges and asymmetric segregation were also observed in more than 50% of anaphase or telophase cells following treatment with NiSO(4). The incidences of these abnormalities were dose-dependent in general, although the effects were prominent in a sublethal dose. These results indicate that NiSO(4) has the ability to induce aneuploidy in V79 cells. In addition, the results in anaphase/telophase assay suggest that the compound may have an effect on spindle apparatus, which could result in aneuploidy following abnormal chromosome segregation.

Parathyroid hormone regulates the expression of the nuclear mitotic apparatus protein in the osteoblast-like cells, ROS 17/2.8

The parathyroid hormone (PTH) signaling pathways that effect changes in osteoblast gene expression also alter the organization of the cytoskeletal proteins. PTH regulates the expression of nucleoskeletal proteins, such as nuclear mitotic apparatus protein (NuMA) and topoisomerase II-alpha. NuMA is a structural component of the interphase nucleus and organizes the microtubules of the mitotic spindle during mitogenesis. We propose that PTH-induced alterations in osteoblast cytoarchitecture are accompanied by changes in osteoblast nuclear structure that contribute to changes in gene expression. We used immunofluorescence and confocal microscopy to determine the effect of PTH on the expression and nuclear distribution of NuMA in the rat osteosarcoma cell line, ROS 17/2.8. Cells were treated with PTH or vehicle, then fixed and stained with NuMA antibody. Optical sections of interphase naive cells revealed a diffuse distribution of NuMA, interspersed with speckles, in the central nuclear planes but not in nucleoli. During the metaphase and anaphase, NuMA localized at the mitotic spindle apparatus. The percentage of NuMA-immunopositive ROS 17/2.8 cells decreased with increasing confluence, but serum starvation did not attenuate NuMA expression. Cell density-dependent changes in cytoskeletal organization were observed in these cells. PTH treatment induced changes in cytoskeletal organization and increased the percentage of NuMA-immunopositive ROS 17/2.8 cells. These data suggest that PTH effects changes in osteoblast nuclear architecture by regulating NuMA, and that these alterations may be coupled to cytoskeletal organization.