Marcadores citogenéticos aplicados en biomedicina = Cytogentic biomarkers applied in biomedicine

Several biomarkers are used to identify and confirm human exposure to exogenous compounds. In cases where the exposure has an adverse effect on the genetic material, the interest is focused on the genotoxic biomarkers. If this effect on the genetic material results in changes in the chromosomal structure or number, which are observable and quantifiable by cytogenetic techniques, these changes can be used as biomarkers. Nowadays, cytogenetic biomarkers are endpoints frequently used in population studies; their sensitivity for measurement of exposure to genotoxic agents and the role of some of the cytoenetic biomarkers as early predictors of cancer risk have contributed to this success. Different cytogenetic biomarkers can be used according to the purpose of the study. Those generally used are micronucleus, sister chromatid exchanges and chromosomal aberrations. Among the wide variety of chemicals to which humans can be exposed, tobacco is a very important. A large number of compounds from tobacco and tobacco smoke have been classified by the International Agency for Research on Cancer (IARC) as carcinogens or probably carcinogens for humans. The DNA damage assessed by cytogenetic techniques is a useful tool in order to confirm the harmful effects of tobacco on the genetic material. Other types of chemicals, present in aerosol paints, caused a severe health impact in some workers in the textil painting factories in the region of Valencia (Spain). This outbreak was classified as the “Ardystil syndrome” and subsequently it was decided to carry out a health surveillance program in affected people. In order to evaluate a persistent alteration in chromosomes, the sister chromatid exchange technique was carried out. Ionizing radiation is another agent responsible for genetic damage. In specific situations these lesions in the DNA are an expected effect of radiation, such as radiotherapy. However, these methods of clinical treatment or medical diagnosis involving ionizing radiation can cause undesired effects involving an impact on human health. In order to avoid or mitigate these undesired effects many synthetic or natural products have been proposed, with an increasing interest in the latter. Cytogenetic biomarkers such as chromosomal aberrations can highlight the DNA damage in cells caused by radiation and therefore the possible damage reduction provided by compounds usually called radioprotectors. Similarly, the genotoxicity of these compounds which are under study can be evaluated. One of the groups of natural compounds with a major interest for application as radioprotectors is the polyphenols group. Related to ionizing radiation exposure, cytogenetic techniques can be used as a useful tool to evaluate the individual radiosensitivity because it is known that humans exhibit a range of individual variation in the frequency and severity of effects occurring after ionizing radiation exposure. This measure could help to assess the individual risk of subjects exposed to ionizing radiation, thus a better dose adjustment in case of medical intervention or an additional preventive measure in subjects working with radiation. In addition, the cytogenetic technique for the assessment of individual radiosensitivity can be used to evaluate, in vitro, whether certain compounds, which may be present simultaneously with radiation, are capable of modifying the cell response. In genotoxicity studies, the biomarkers analyzed were the chromosomal aberrations, sister chromatid exchanges, mitotic index and the proliferation index. From the analysis of sister chromatid exchanges, in the tobacco and “Ardystil syndrome” study, it was calculated the parameter of cells with a frequency of exchanges higher than the 95 percentil and a ratio which analyzed the clustering of exchanges in one chromosome instead of being uniformingly distributed among the metaphase. In these studies it is essential to differentiate the number of cell cycles of the lymphocytes; for this reason, at the beginning of the cell cultures a substance should be added which allows for the differentiation of the first, second and third cell divisions with the Fluorescence plus Giemsa staining. For the tobacco and “Ardystil syndrome” studies, human peripheral blood samples were processed for the cytogenetic analysis of the sister chromatid exchanges biomarker. In the study of the genotoxicity of the polyphenols curcumin and trans-resveratrol, blood samples were incubated with different concentrations of both compounds before starting the culture. Cytogenetic analysis included the study of biomarkers such as chromosomal aberrations, sister chromatid exchanges and mitotic and proliferation index. In the radioprotection studies, two different techniques were carried out. On the one hand, the dicentric chromosome assay, which is based on the curcumin and trans-resveratrol pre-incubated human peripheral blood irradiation with ionizing radiation, samples culture and cytogenetic analysis of chromosomal aberrations. Analysis was based in dicentric chromosomes wich are considered biomarders of radiation-induced damage. On the other hand, the premature chromosome condensation technique, which is based on the curcumin and trans-resveratrol pre-incubated lymphocytes isolated from human peripheral blood, fusion with mitotic hamster ovary cells, culture and cytogenetic analysis. Analysis was focused in the counting of chromosomal fragments radio-induced. For the radiosensitivity studies, the G2-assay was applied in two different experiments. On the one hand, study of the radiosensitivity induced by curcumin and trans-resveratrol, aimed at evaluating the in vitro radiosensitivization ability of both compounds by modifying the lymphoyctes radiosensitivity in G2-cell cycle phase. On the other hand, the G2-assay was implemented in a case report in order to evaluate the individual radiosensibility in a patient undergoing interventionist radiology who suffered adverse secondary effects. With this assay, the patient can be classified as “hiperradiosensitive”, “radiosensitive”, “normal” or “radioresistant” according to the classification of Terzoudi and Pantelias (2011). Possible alterations in the chromosomal material caused by different chemical and physical agents can be evaluated by using cytogenetic biomarkers. The analysis of biomarkers for the assessment of the genotoxicity of tobacco and some components used in textile airbrushing with non adequate preventive measures ("Ardystil Syndrome") allowed to observe a statistically significant genetic affectation increase in smokers and check whether this affectation was no longer present in subjects affected by "Ardystil syndrome" after ten years of the outbreak. The in vitro study of the genotoxic, radiosensitizing and radioprotective properties of polyphenolic compounds, curcumin and trans-resveratrol, demonstrates the versatility of these compounds depending on the concentrations used, the cell cycle phase in which they are absorbed by cells and the conditions to which samples are subjected. The application of the individual radiosensitivity G2-assya in a patient with secondary effects after a medical intervention with ionizing radiation constitutes a first step for the future application of this cytogenetic technique in preventive medicine. Patients and workers subjected to ionizing radiation treatment would have an additional tool to improve the individualization of treatments as well as improving the prevention of occupational hazards.