Irene Larripa

Genotoxicity of AMPA, the environmental metabolite of glyphosate, assessed by the Comet assay and cytogenetic tests.

Formulations containing glyphosate are the most widely used herbicides in the world. AMPA is the major environmental breakdown product of glyphosate. The purpose of this study is to evaluate the in vitro genotoxicity of AMPA using the Comet assay in Hep-2 cells after 4h of incubation and the chromosome aberration (CA) test in human lymphocytes after 48h of exposition. Potential in vivo genotoxicity was evaluated through the micronucleus test in mice. In the Comet assay, the level of DNA damage in exposed cells at 2.5-7.5mM showed a significant increase compared with the control group. In human lymphocytes we found statistically significant clastogenic effect AMPA at 1.8mM compared with the control group. In vivo, the micronucleus test rendered significant statistical increases at 200-400mg/kg. AMPA was genotoxic in the three performed tests. Very scarce data are available about AMPA potential genotoxicity.

Genotoxicity of glyphosate assessed by the comet assay and cytogenetic tests

It was evaluated the genotoxicity of glyphosate which up to now has heterogeneous results. The comet assay was performed in Hep-2 cells. The level of DNA damage in the control group (5.42±1.83 arbitrary units) for tail moment (TM) measurements has shown a significant increase (p<0.01) with glyphosate at a range concentration from 3.00 to 7.50mM. In the chromosome aberrations (CA) test in human lymphocytes the herbicide (0.20-6.00mM) showed no significant effects in comparison with the control group. In vivo, the micronucleus test (MNT) was evaluated in mice at three doses rendering statistical significant increases at 400mg/kg (13.0±3.08 micronucleated erythrocytes/1000 cells, p<0.01). In the present study glyphosate was genotoxic in the comet assay in Hep-2 cells and in the MNT test at 400mg/kg in mice. Thiobarbituric acid reactive substances (TBARs) levels, superoxide dismutase (SOD) and catalase (CAT) activities were quantified in their organs. The results showed an increase in these enzyme activities.

Developing a new generation of tests for genotyping hemophilia‐causative rearrangements involving int22h and int1h hotspots in the factor VIII gene

Summary.  Background: Inversions of F8‐intron 22 (Inv22) and F8‐intron 1 (Inv1) are responsible for 45–50% of severe hemophilia A cases. Objective: In order to improve the molecular diagnosis of Inv22 and Inv1, and to enable rapid discrimination of Inv22‐type 1 and Inv22‐type 2 patterns, int22h‐mediated deletions (Del22) and duplications (Dup22), we developed a genotyping system based on a novel inverse shifting‐polymerase chain reaction (IS‐PCR) approach. Methods: IS‐PCR involved BclI restriction, followed by self‐ligation to create ‘BclI circles’, and finally PCR analysis. Three PCR analysis tests were developed: (i) Inv22‐diagnostic for a pattern‐sensitive detection of deleterious mutations (Inv22 and Del22) from non‐deleterious variants (Dup22 and normal); (ii) Inv1‐diagnostic; and (iii) Inv22‐complementary for discrimination between Inv22 and Del22, and between Dup22 and normal. For rapid molecular analysis of F8, the Inv22 and Inv1 diagnostic tests can be performed simultaneously. The optional Inv22‐complementary test need only be used for specific purposes. Results and Conclusions: Diagnostic tests were validated using previously studied samples. IS‐PCR evaluated carrier mosaicisms and performed robustly over wide ranges of DNA qualities and procedural conditions. IS‐PCR improved the molecular diagnosis of hemophilia A. This genotyping strategy may potentially be adapted to virtually all known rearrangements in the human genome.

Thirteenfold increase of chromosomal aberrations non-randomly distributed in chagasic children treated with nifurtimox

Chromosomal aberrations were analyzed from cultures of peripheral lymphocytes in 2 groups of chagasic children, before and after treatment with nifurtimox. The mean incidence of chromosomal aberrations increased from control values of 1.75 +/- 1.39 (8 patients) to 23.55 +/- 9.55 (6 patients) at a significance of P less than 0.0001. G-banding analysis of chromosomal aberration sites revealed that treated patients present coincidence in the chromosome regions affected: 1p11, 1q11-12, 9q11-13, 17q11-21, 2p21, 2q23, 2q31, 2q33, 6p21, 6p21, 7q32, 13q14, 13q22, 15q22. These data indicate a non-random distribution of chromosomal aberrations induced by nifurtimox therapeutic treatment.

Genotoxic activity of azidothymidine (AZT) in in vitro systems

The genotoxic activity of azidothymidine (AZT) was evaluated in vitro, measuring cytogenetic parameters in two cell systems. In human lymphocytes AZT induced a statistically significant increase in chromosome breakage at 100 micrograms/ml and in micronucleated cells at the highest dose assayed (500 micrograms/ml). Sister-chromatid exchanges (SCE) showed a two-fold increase over control values at 50 micrograms/ml. Lymphocyte cycle kinetics showed an important delay at 500 micrograms/ml. In Chinese hamster ovary (CHO) cells, AZT produced a significant increase in chromosome aberrations and SCE at 1000 and 500 micrograms/ml, respectively. At 2500 micrograms/ml the drug produced a delay in cell cycle progression. These results suggest that AZT is a DNA-damaging agent in both cell systems assayed. Moreover, human lymphocytes seem to be more sensitive to AZT than CHO cells.

Mutagenic bioassay of certain pharmacological drugs: III. Metronidazole (MTZ)

The genotoxic activity of MTZ was evaluated in vitro with the anaphase-telophase test in a CHO cell line, chromosomal aberration and micronucleus test in lymphocyte cultures, and in vivo using the micronucleus test in mouse bone marrow cells. The In vivo test was performed using clinical trial doses (23, 70 and 160 mg/kg). A significant increase in micronucleated cells (p < 0.02) was observed in the three assayed doses with a linear dose response (r = 0.91). In vitro studies showed a significant increase in the percentage of abnormal anaphases (p < 0.05), in chromosome aberrations (p < 0.01) and in the frequency of micronuclei (p < 0.02) at all the concentrations assayed (0.1, 1 and 10 micrograms/ml). These findings demonstrate the clastogenic effect of this drug which should be taken into account considering its wide human consumption.

Chromosomal damage in workers occupationally exposed to chronic low level ionizing radiation

Chromosomal aberrations were evaluated in cultures of peripheral lymphocytes from subjects working in diagnostic X-ray and nuclear medicine areas, exposed to electromagnetic ionizing radiation and particulate ionizing emissions, respectively. A 4-fold increase in the level of chromosomal aberrations was found between the exposed and control groups without qualitative or quantitative cytogenetic differences between X-rays and nuclear medicine-exposed workers. Results are discussed in view of the early damage detection from chronic exposures particularly related to biological controls, hygienic improvements and overwork in a developing country.

Assessment of cytogenetic damage in chagasic children treated with benznidazole

Chromosomal aberrations and induction of micronuclei were analyzed from cultures of peripheral lymphocytes in 2 groups of chagasic children, before and after treatment with benznidazole. The median incidence of micronucleated interphase lymphocytes (20 patients) and chromosomal aberrations (10 patients) increased from control values of 5/1000 and 3% to 11.5/1000 and 6%, respectively, at a significance of P = 0.05.

Partial and total monosomal karyotypes in myelodysplastic syndromes: comparative prognostic relevance among 421 patients.

Myelodysplastic syndromes (MDS) include a group of heterogeneous hematological disorders with a variable risk of leukemic evolution and short survival. Around 40–50% of patients show abnormal karyotypes that are mostly characterized by monosomies or deletions. Cytogenetic findings are an independent prognostic factor and the International prognostic scoring system (IPSS) differentiates three cytogenetic categories, despite the Intermediate one being heterogeneous. The aim of this study, including 421 Argentinean patients with primary MDS, is to characterize the cytogenetic profile, to test its prognostic value and to compare partial and monosomal karyotypes against other cytogenetic findings. An abnormal karyotype (median survival: 26 months) was observed in 176 patients. The presence of complex karyotypes, number of alterations, and the IPSS cytogenetic groups showed significant differences for predicting outcome. Behavior of patients with isolated deletions (median survival: 49 months) did not differ from those with normal karyotype (56 months, P = 0.654) or Good prognostic findings (43 months, P = 0.371). However, a worse prognosis was observed when another alteration was added (31 months, P = 0.043). Karyotypes with autosomal monosomies (median survival: 16 months) had a prognostic impact similar to other Poor cytogenetic findings (17 months, P = 0.626). In our population classified according to French‐American‐British (FAB) or World Health Organization (WHO), this new categorization of cytogenetic abnormalities, recognizing three different risk groups, showed an independent prognostic impact and a better discriminating power than the IPSS categories. It can be concluded that all isolate deletions (excluding 7q‐) are good prognostic findings and all monosomies (excluding Y chromosome loss) are bad indicators. Am. J. Hematol., 2011.

Topoisomerase II-mediated DNA damage is differently repaired during the cell cycle by non-homologous end joining and homologous recombination.

Topoisomerase II (Top2) is a nuclear enzyme involved in several metabolic processes of DNA. Chemotherapy agents that poison Top2 are known to induce persistent protein-mediated DNA double strand breaks (DSB). In this report, by using knock down experiments, we demonstrated that Top2α was largely responsible for the induction of γH2AX and cytotoxicity by the Top2 poisons idarubicin and etoposide in normal human cells. As DSB resulting from Top2 poisons-mediated damage may be repaired by non-homologous end joining (NHEJ) or homologous recombination (HR), we aimed to analyze both DNA repair pathways. We found that DNA-PKcs was rapidly activated in human cells, as evidenced by autophosphorylation at serine 2056, following Top2-mediated DNA damage. The chemical inhibition of DNA-PKcs by wortmannin and vanillin resulted in an increased accumulation of DNA DSB, as evaluated by the comet assay. This was supported by a hypersensitive phenotype to Top2 poisons of Ku80- and DNA-PKcs- defective Chinese hamster cell lines. We also showed that Rad51 protein levels, Rad51 foci formation and sister chromatid exchanges were increased in human cells following Top2-mediated DNA damage. In support, BRCA2- and Rad51C- defective Chinese hamster cells displayed hypersensitivity to Top2 poisons. The analysis by immunofluorescence of the DNA DSB repair response in synchronized human cell cultures revealed activation of DNA-PKcs throughout the cell cycle and Rad51 foci formation in S and late S/G2 cells. Additionally, we found an increase of DNA-PKcs-mediated residual repair events, but not Rad51 residual foci, into micronucleated and apoptotic cells. Therefore, we conclude that in human cells both NHEJ and HR are required, with cell cycle stage specificity, for the repair of Top2-mediated reversible DNA damage. Moreover, NHEJ-mediated residual repair events are more frequently associated to irreversibly damaged cells.