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Spontaneous expulsion of micronuclei by enucleation in the micronucleus assay
Abstract:
The effect of enucleation on the frequency of micronuclei induced by mitomycin C (MMC) and vincristine (VCR) was examined in mouse L-929 cells enucleated with cytochalasin B (Cyt-B). Approximately 30% of the L-929 cells became enucleated cells during the 8-h incubation in medium containing 8 micrograms/ml of Cyt-B. Using this enucleation technique, we estimated the reduction rate of 2 mutagen-induced micronuclei by enucleation. Treatment with MMC caused a dose-dependent induction of micronuclei in L-929 cells, with the reduction rate being 38.6% at the lowest dosage (0.0125 microgram/ml), which induced mostly mono-micronuclei in L-929 cells, and 6.8% at the highest dosage (0.1 microgram/ml), which induced many multi-micronuclei. Furthermore, VCR also induced micronuclei in a dose-dependent way in L-929 cells, and the same tendency for micronucleus reduction as with MMC was observed. The reduction rate of micronucleated cells by enucleation was estimated to be about 31-39% when the micronucleated cells contain mono-micronuclei. Therefore, the rate of reduction is affected by the number of micronuclei per cell, and the reduction depends on the increase in the number of micronuclei per cell.
Insights
Enucleation, the removal of a cell
Area of Science:
- Cell biology
- Genotoxicity testing
- Mutagenesis research
Background:
- Micronuclei formation is a key indicator of genotoxicity.
- Enucleation is a cellular process that removes the nucleus.
- Understanding the impact of enucleation on mutagenicity is crucial for accurate genotoxicity assessments.
Purpose of the Study:
- To investigate the effect of enucleation on micronuclei frequency induced by mitomycin C (MMC) and vincristine (VCR).
- To determine the reduction rate of mutagen-induced micronuclei following enucleation in L-929 cells.
- To assess how the number of micronuclei per cell influences the reduction rate after enucleation.
Main Methods:
- Mouse L-929 cells were treated with cytochalasin B (Cyt-B) to induce enucleation.
- Enucleated and non-enucleated cells were exposed to varying doses of mitomycin C (MMC) and vincristine (VCR).
- Micronuclei frequency and the number of micronuclei per cell were quantified in both enucleated and non-enucleated populations.
Main Results:
- Enucleation reduced the frequency of micronuclei induced by both MMC and VCR in a dose-dependent manner.
- The reduction rate varied with the dose of the mutagen, being higher at lower doses (38.6% for MMC) and lower at higher doses (6.8% for MMC).
- The reduction rate was significantly influenced by the number of micronuclei per cell, with higher rates observed when cells contained predominantly mono-micronuclei.
Conclusions:
- Enucleation effectively reduces the observed frequency of mutagen-induced micronuclei.
- The efficacy of micronucleus reduction by enucleation is inversely related to the number of micronuclei present per cell.
- These findings highlight the importance of considering enucleation status in genotoxicity assays using micronucleus tests.