Ensayo del cometa como bioindicador de inestabilidad genómica en pacientes diabéticos hemodializados / Comet assay as a bioindicator of genomic instability in hemodialysis diabetic patients

Introducción: Procesos como la mutagénesis, la carcinogénesis y la teratogénesis son producto de la interacción de agentes de origen endógeno como exógeno que interactúan con la molécula de ADN en forma crónica produciendo rupturas en la doble hélice, y en cromosomas completos resultando en la inestabilidad genómica. El estrés oxidativo al que se encuentran sometidas las células al formarse las especies reactivas de oxígeno (ROS) y también las especies reactivas de nitrógeno (RNS), que pueden provenir de radicales producidos a consecuencia de la diabetes o en estados iniciales de la enfermedad renal crónica o como respuesta a procesos inflamatorios en estados avanzados de estas patologías, actúan como agentes genotóxicos endógenos.Objetivos: Esta investigación tuvo como objetivo determinar el daño basal en la molécula de ADN de pacientes diabéticos hemodializados, a través del ensayo del Cometa, como un bioindicador de inestabilidad genómica., durante seis meses de tratamiento. Materiales y métodos: Se planteó un estudio longitudinal prospectivo de cohorte para comparar los diferentes niveles de daño antes y durante los primeros seis del tratamiento de hemodiálisis. Se evaluó con el test del cometa o electroforesis de células individuales, el daño basal en muestras de sangre venosa de pacientes diagnosticados con Diabetes de tipo II como control negativo y en pacientes diabéticos con enfermedad renal crónica antes de iniciar el tratamiento de diálisis y luego durante el tratamiento. Se utilizó el test de t- Student para muestras independientes y emparejadas. Resultados: Se observó un aumento significativo de daño basal y oxidativo en el material genético de pacientes diabéticos con enfermedad renal crónica, comparados con los controles negativos (p< 0.005) y se observó, además, que el daño celular aumenta con el tratamiento de hemodiálisis (p<0.005). Conclusión: Los resultados obtenidos en esta investigación permiten concluir que el estrés oxidativo tiene un efecto genotóxico y que el nivel de daño genético es un buen bioindicador del avance de la enfermedad renal crónica y que la hemodiálisis induce a un aumento de daño a nivel del material genético, aumentando el riesgo de carcinogénesis.

Introduction: Processes such as mutagenesis, carcinogenesis and teratogenesis are the product of the interaction of agents of endogenous and exogenous origin that interact with the DNA molecule in a chronic way producing ruptures in the double helix, and in complete chromosomes resulting in genomic instability. The oxidative stress to which the cells are subjected when reactive oxygen species (ROS) and reactive nitrogen species (RNS) are formed, which may come from radicals produced as a result of diabetes or in initial stages of chronic kidney disease or in response to inflammatory processes in advanced stages of these pathologies, act as endogenous genotoxic agents. Objectives: This research aimed to determine the basal damage in the DNA molecule of hemodialyzed diabetic patients, through the Comet assay, as a bioindicator of genomic instability, during six months of treatment. Materials and methods: For this research, a prospective longitudinal cohort study was proposed to compare the different levels of genetic damage before and during the first six of hemodialysis treatment. Baseline damage was evaluated with the comet test or single cell electrophoresis, in venous blood samples from patients diagnosed with Type II Diabetes as a negative control and in diabetic patients with chronic kidney disease before starting dialysis treatment and then during treatment. Results: A significant increase in basal and oxidative damage was observed in the genetic material of diabetic patients with chronic kidney disease, compared to negative controls (p< 0.005) and it was also observed that cell damage increases with hemodialysis treatment (p<0.005). The t-Student test was used for independent and paired samples. Conclusion: The results obtained in this research allow us to conclude that oxidative stress has a genotoxic effect and that the level of genetic damage is a good bioindicator of the progression of chronic kidney disease and that hemodialysis induces an increase in damage at the level of the genetic material, increasing the risk of carcinogenesis.

DNA damage induced by exposure to pesticides in children of rural areas in Paraguay.

Background & objectives: Chronic exposure to pesticides can damage DNA and lead to cancer, diabetes, respiratory diseases and neurodegenerative and neurodevelopment disorders. The objective of this study was to determine the frequency of DNA damage through the comet assay and micronucleus (MN) test in two groups of children, under 10 yr of age living in rural Paraguay and in relation to pesticide exposure. Methods: Two groups of 5 to 10 yr old children were formed; the exposed group (group A, n=43), born and currently living in a community dedicated to family agriculture and surrounded by transgenic soybean crops, and the control group (group B, n=41), born and living in a community dedicated to family agriculture with biological control of pests. For each child, 2000 cells were studied for the MN test and 200 cells for the comet assay. Results: The comparison between exposed and control children revealed significant differences in biomarkers studied for the measurement of genetic damage (cell death and DNA damage). The median of MN was higher in the exposed group (6 vs. 1) (P <0.001). Binucleated cells (2.9 vs. 0.5, P <0.001); broken eggs (5.5 vs. 1.0, P <0.001); karyorrhexis (6.7 vs. 0.5, P <0.001); kariolysis (14.0 vs. 1.0, P <0.001); pyknosis (7.4 vs. 1.2, P <0.001) and condensed chromatin (25.5 vs. 7.0, P <0.001) were significantly higher in the exposed group. The values of tail length (59.1 vs 37.2 µm); tail moment (TM) (32.8 vs. 14.4 µm); TM olive (15.5 vs. 6); % DNA tail (45.2 vs. 27.6) and % DNA head (54.8 vs. 72.4), were significantly different between the two groups. Interpretations & conclusions: In children exposed to pesticides, a greater genotoxic and cytotoxic effect was observed compared to non-exposed children. Our findings suggest that monitoring of genetic toxicity in population exposed to pesticides and agrochemicals should be done.

Increased genetic damage found in waste picker women in a landfill in Paraguay measured by comet assay and the micronucleus test.

Cateura landfill located in Asunción-Paraguay is the site of final disposal of tons of garbage of all kinds coming from urban, industrial and commercial areas. Due to an inadequate waste management system, there is a big concern in our country on how it can affect people working within the landfill as waste pickers. When a high risk of exposure affecting workers in their work places is supposed, defining biomarkers of genotoxic damage is obligatory. The principal aim of this study was to evaluate the genetic damage in occupationally exposed women in their work environments through two established biomarkers: the single-cell gel electrophoresis assay (SCGE) accomplished in peripheral blood and the micronucleus test performed in exfoliated cells from oral mucosa (BMCyT). This is an analytical observational cohort study involving 50 women occupationally exposed and 34 unexposed women. A statistically significant increase (p < 0.05) in the parameters to measure genotoxicity was observed in the garbage recyclers of the landfill, compared to the control group. The frequency of Micronuclei (MN) and other nuclear abnormalities such as karyolytic and karyorrhectic cells were higher in exposed women. In addition, significant differences in the % of DNA in the tail of comets between exposed and control groups were found. Our results suggest that the increase in DNA damage and nuclear alterations found in exposed-waste pickers women can be explained as a result to their direct contact with chemicals, many of them identified as genotoxic and other alleged mutagens. This chronic exposure could be diminished by using safety procedures and suitable personal protective equipment inside the workplace. The burden of morbidity due to occupational exposure to genotoxic agents in this place is unknown, therefore, these types of studies should be addressed in order to advice to authorities on social policies of protection of landfills workers.