Cell and Tissue Journal

Abstract Introduction: Heavy metal refers to any metal with relatively high density, with toxic effects even at ppb levels. Heavy metals are one of the main threats to human health. Arsenic (As) is a heavy metal found in our living environment due to its widespread use in industrial activities. Exposure to As and its absorption by different tissues may lead to damage to cardiovascular function, skin lesions, high blood pressure, and diabetes. As harmful effects on chromosome integrity have been proven a long time ago. It has also been classified as a potent carcinogen by the Environmental Protection Agency (EPA) and the International Agency for Research on Cancer (IARC).  One of the damages caused by As is chromosome breakages. These damages are the result of this heavy metal's ability in producing free radicals and their interaction with the DNA molecule. The role of aneuploidy in cancer induction has been suggested in several investigations. Aneuploidy can lead to drastic changes in the genetic balance of normal cells, potentially forcing them towards cancer formation.
Aims: Due to the close relation between chromosome instability and cancer induction and the ability of As to induce cancer, the question arises whether As can also play a role in chromosome instability? The design of this study is based on answering this question.
Materials and methods: In this study, to analyze potential cell toxicity and chromosome abnormalities induced in different treatments, MTT and Micronucleus assay on Binucleated cells were used, respectively. Cell toxicity of different doses of As was investigated on HDF cells. According to the results of MTT, three non-toxic doses of 100, 200, and 300 ng/ml were selected. To be able to understand the effect of As treatment on chromosome instability induced by aneugenic agent, vinblastine was used. Vinblastine is classified as an aneugen in several studies. Co-treatment of three doses of As and three doses of 0.75, 1.00, and 2.00 ng/ml of vinblastine (Vin) on the induction of chromosome abnormalities was investigated on the HDF cell line using the Micronucleus assay on Binucleated cells.
Results: According to the results of the MTT assay, cell toxicity induced by As at 24, 48, and 72 hours was at doses of 604.3, 397.3, and 228.6, respectively.   As also led to chromosomal abnormalities. Mean frequency of micronucleated binucleates (BiMn) was 0.296, 0497, and 7.270 for 100, 200, and 300 ng/ml, respectively, compared to the frequency of BiMn in the control (0.078). Vinblastine treatment also significantly increased the frequency of BiMn in all doses used compared to the control. Finally, Co-treatment with three doses of vinblastine and three doses of As significantly increased chromosomal abnormalities to almost three to seven times compared to solo vinblastine treatment.
Discussion: Results indicate that As can induce chromosomal abnormalities, which is represented by an increase in BiMn frequency. In addition, co-treatment with vinblastine and As leads to higher chromosomal abnormalities compared to solo treatment with vinblastine. Significant increase in frequency of BiMn in the later experiment suggests that As provides a suitable ground for chromosomal abnormalities induced by other aneugenic agents, here, vinblastine. This effect might be the result of direct interference of As with mechanisms of cell division control or inducing mutation in genes involved in such mechanisms through oxidative species, which leads to an increase in their errors. In both cases, the results of this study reveal an alternative mechanism for As-induced tumor formation.
Conclusion: As not only involves cancer formation by direct damage to chromosomes but also provides a suitable ground for chromosomal mis-segregation in cell divisions, which is believed to be a main step towards cancer formation.