In vitro effects of Sunset Yellow on Chromosomal Damage and Sister Chromatid Exchanges in Human Peripheral Lymphocytes

Sunset Yellow (SY) is an organic azo dye that is used extensively as a coloring agent in many industries, such as cosmetics, pharmaceuticals ,and foodstuffs. Many studies have conflicting results about the genotoxicity effect of SY. Thus, the purpose of this study was to provide additional data concerning SY genotoxicity in human lymphocytes by using chromosomal aberrations (CAs) and sister chromatid exchanges (SCEs) assay. Four concentrations of Sunset Yellow (1, 5, 20 ,and 50 mg/ml) were used on human lymphocyte cultures. Positive and negative controls were mitomycin C and distilled water, respectively. Compared to the control, SY caused a significant increase in CAs and SCEs frequencies at all concentrations. A total of five types of CAs were observed, such as gaps, fragments, RCF, stickiness,and polyploidy. According to the present results, high concentrations of SY are genotoxic in vitro to cultured human lymphocytes. To determine its full genotoxicity potential, SY should be tested in other test systems.

Genotoxicity of Mercury and Its Derivatives Demonstrated In Vitro and In Vivo in Human Populations Studies. Systematic Review

Beside partial coverage in three reviews so far (1994, 2009, 2019), there is no review on genotoxic studies dealing with mercury (Hg) and human exposure using the most usual genotoxic assays: sister chromatid exchanges (SCE), chromosomal aberrations (CA), cytochalasin B blocked micronucleus assay (CBMN), and single-cell gel electrophoresis (SCGE or alkaline comet assay). Fifty years from the first Hg genotoxicity study and with the Minamata Convention in force, the genotoxic potential of Hg and its derivatives is still controversial. Considering these antecedents, we present this first systematic literature overview of genotoxic studies dealing with Hg and human exposure that used the standard genotoxic assays. To date, there is not sufficient evidence for Hg human carcinogen classification, so the new data collections can be of great help. A review was made of the studies available (those published before the end of October 2021 on PubMed or Web of Science in English or Spanish language) in the scientific literature dealing with genotoxic assays and human sample exposure ex vivo, in vivo, and in vitro. Results from a total of 66 articles selected are presented. Organic (o)Hg compounds were more toxic than inorganic and/or elemental ones, without ruling out that all represent a risk. The most studied inorganic (i)Hg compounds in populations exposed accidentally, occupationally, or iatrogenically, and/or in human cells, were Hg chloride and Hg nitrate and of the organic compounds, were methylmercury, thimerosal, methylmercury chloride, phenylmercuric acetate, and methylmercury hydroxide.

The Effects of 1-Beta-D-Arabinofuranosylcytosine and Adriamycin on the Chromosomes of Cultured Human Lymphocytes

<p>A study of chromosome aberrations induced by 1-Beta-D-arabinofuranosylcytosine (Ara C) and Adriamycin (AM) in the chromosomes of cultured human lymphocytes was made. There were significant increases in the frequency of aberrations with increasing concentrations of both Ara C (2.5, 5.0 and 10.0 mug/ml) and AM (0.01, 0.05, 0.10 and 0.15 mug/ml). The frequency of aberrations induced by both drugs also showed a 'levelling off' above particular concentrations. For Ara C the effect of increasing treatment time was also studied. The frequency of aberrations increased significantly with increasing treatment times (2, 3 and 4 hrs) although no 'levelling off' in the number of aberrations was observed. The relationship between the frequency of the different types of aberrations induced by Ara C and AM was studied. AM allowed for a study of the relative frequency of chromosome versus chromatid aberrations and fragment versus exchange aberrations. There were always more fragments than exchanges, and always more chromatid aberrations than chromosome aberrations. Aberrations induced by Ara C were all of the chromatid fragment type. A study was made of the distribution of inter- and intra-chromosomal aberrations in relation to light and dark G banded chromosomes. Both drugs induced more aberrations in the light G bands than the dark G bands. Both drugs showed distinct clustering of aberrations in some regions of the chromosomes (hotspots), although the location of AM induced hotspots was different from the location of those induced by Ara C. The distribution of AM induced chromatid aberrations was different from the distribution of the chromosome aberrations, as were the distributions of the fragment and exchange aberrations. The different types of aberrations also differed in the number of AM induced aberrations per unit length between the p and q arms. There were more aberrations per unit length in the p arm than in the q arm for exchanges, whereas for fragments and chromosome aberrations the reverse was true. For chromatid aberrations, there was no significant difference in the number of aberrations per unit length between the p and q arms. Inter-individual differences in the frequency of AM induced aberrations were observed in the .AM dosage experiments. Also there was a suggestion that the distribution of Ara C induced aberrations was different for different donors. AM increased the frequency of sister chromatid exchanges. Comparable results were not sought for Ara C because after cells were exposed to Ara C they did not pass through an S phase of the cell cycle, as is the case for cells exposed to AM. The relevance of the present in vitro studies to cancer chemotherapy is briefly discussed.</p>

The Effects of 1-Beta-D-Arabinofuranosylcytosine and Adriamycin on the Chromosomes of Cultured Human Lymphocytes

<p>A study of chromosome aberrations induced by 1-Beta-D-arabinofuranosylcytosine (Ara C) and Adriamycin (AM) in the chromosomes of cultured human lymphocytes was made. There were significant increases in the frequency of aberrations with increasing concentrations of both Ara C (2.5, 5.0 and 10.0 mug/ml) and AM (0.01, 0.05, 0.10 and 0.15 mug/ml). The frequency of aberrations induced by both drugs also showed a 'levelling off' above particular concentrations. For Ara C the effect of increasing treatment time was also studied. The frequency of aberrations increased significantly with increasing treatment times (2, 3 and 4 hrs) although no 'levelling off' in the number of aberrations was observed. The relationship between the frequency of the different types of aberrations induced by Ara C and AM was studied. AM allowed for a study of the relative frequency of chromosome versus chromatid aberrations and fragment versus exchange aberrations. There were always more fragments than exchanges, and always more chromatid aberrations than chromosome aberrations. Aberrations induced by Ara C were all of the chromatid fragment type. A study was made of the distribution of inter- and intra-chromosomal aberrations in relation to light and dark G banded chromosomes. Both drugs induced more aberrations in the light G bands than the dark G bands. Both drugs showed distinct clustering of aberrations in some regions of the chromosomes (hotspots), although the location of AM induced hotspots was different from the location of those induced by Ara C. The distribution of AM induced chromatid aberrations was different from the distribution of the chromosome aberrations, as were the distributions of the fragment and exchange aberrations. The different types of aberrations also differed in the number of AM induced aberrations per unit length between the p and q arms. There were more aberrations per unit length in the p arm than in the q arm for exchanges, whereas for fragments and chromosome aberrations the reverse was true. For chromatid aberrations, there was no significant difference in the number of aberrations per unit length between the p and q arms. Inter-individual differences in the frequency of AM induced aberrations were observed in the .AM dosage experiments. Also there was a suggestion that the distribution of Ara C induced aberrations was different for different donors. AM increased the frequency of sister chromatid exchanges. Comparable results were not sought for Ara C because after cells were exposed to Ara C they did not pass through an S phase of the cell cycle, as is the case for cells exposed to AM. The relevance of the present in vitro studies to cancer chemotherapy is briefly discussed.</p>

A Systematic Review of Studies on Genotoxicity and Related Biomarkers in Populations Exposed to Pesticides in Mexico

In agricultural activities, pest control is essential, and the most effective method is the use of chemical agents that also represent an important source of exposure to potentially toxic compounds. Pesticides constitute a heterogeneous group of compounds designed specifically to control different pests. Besides measuring their levels or that of their metabolites in air, plasma, serum, blood, urine, etc., some studies reported increased DNA damage levels after occupational or environmental pesticides exposure, evidenced by several cytogenetic biomarkers such as chromosomal aberrations (CA), sister chromatid exchanges (SCE), micronuclei frequency (MN) together with other nuclear abnormalities (NA), alkaline comet assay, but also changes in oxidative stress parameters and miRNA levels. Single or combined, these techniques have also been used in genotoxic biomonitoring studies of workers occupationally exposed to pesticides in Mexico. Despite being a country with great agricultural activity and reported excessive pesticide use, genotoxic studies have been relatively few and, in some cases, contradictory. A review was made of the studies available (published until the end of 2020 on PubMed, Web of Science, Redalyc and Scielo, both in English and Spanish) in the scientific literature that evaluated occupational exposure of human samples to pesticides assessed with DNA damage and related biomarkers in Mexico.

Sister chromatid exchanges induced by perturbed replication are formed independently of homologous recombination factors

SummarySister chromatid exchanges (SCEs) are products of joint DNA molecule resolution, and are considered to form through homologous recombination (HR). Indeed, upon generation of irradiation-induced DNA breaks, SCE induction was compromised in cells deficient for canonical HR factors BRCA1, BRCA2 and RAD51. Contrarily, replication-blocking agents, including PARP inhibitors, induced SCEs independently of BRCA1, BRCA2 and RAD51. PARP inhibitor-induced SCEs were enriched at common fragile sites (CFSs), and were accompanied by post-replicative single-stranded DNA (ssDNA) gaps. Moreover, PARP inhibitor-induced replication lesions were transmitted into mitosis, suggesting that SCEs originate from mitotic processing of under-replicated DNA. We found that DNA polymerase theta (POLQ) was recruited to mitotic DNA lesions, and loss of POLQ resulted in reduced SCE numbers and severe chromosome fragmentation upon PARP inhibition in HR-deficient cells. Combined, our data show that PARP inhibition generates under-replicated DNA, which is transferred into mitosis and processed into SCEs, independently of canonical HR factors.

Biomarkers of Genotoxicity in Medical Workers Exposed to Low-Dose Ionizing Radiation: Systematic Review and Meta-Analyses

Medical staff represent the largest group of workers occupationally exposed to ionizing radiation (IR). Chronic exposure to low-dose IR may result in DNA damage and genotoxicity associated with increased risk of cancer. This review aims to identify the genotoxicity biomarkers that are the most elevated in IR-exposed vs. unexposed health workers. A systematic review of the literature was performed to retrieve relevant studies with various biomarkers of genotoxicity. Subsequent meta-analyses produced a pooled effect size for several endpoints. The search procedure yielded 65 studies. Chromosome aberrations (CA) and micronuclei (MN) frequencies were significantly different between IR-exposed and unexposed workers (θpooled = 3.19, 95% CI 1.46–4.93; and θpooled = 1.41, 95% CI 0.97–1.86, for total aberrant cells and MN frequencies, respectively), which was not the case for ring chromosomes and nucleoplasmic bridges. Although less frequently used, stable translocations, sister chromatid exchanges (SCE) and comet assay endpoints were also statistically different between IR-exposed and unexposed workers. This review confirms the relevance of CA and MN as genotoxicity biomarkers that are consistently elevated in IR-exposed vs. unexposed workers. Other endpoints are strong candidates but require further studies to validate their usefulness. The integration of the identified biomarkers in future prospective epidemiological studies is encouraged.

ATRX and RECQ5 define distinct homologous recombination subpathways

Homologous recombination (HR) is an important DNA double-strand break (DSB) repair pathway that copies sequence information lost at the break site from an undamaged homologous template. This involves the formation of a recombination structure that is processed to restore the original sequence but also harbors the potential for crossover (CO) formation between the participating molecules. Synthesis-dependent strand annealing (SDSA) is an HR subpathway that prevents CO formation and is thought to predominate in mammalian cells. The chromatin remodeler ATRX promotes an alternative HR subpathway that has the potential to form COs. Here, we show that ATRX-dependent HR outcompetes RECQ5-dependent SDSA for the repair of most two-ended DSBs in human cells and leads to the frequent formation of COs, assessed by measuring sister chromatid exchanges (SCEs). We provide evidence that subpathway choice is dependent on interaction of both ATRX and RECQ5 with proliferating cell nuclear antigen. We also show that the subpathway usage varies among different cancer cell lines and compare it to untransformed cells. We further observe HR intermediates arising as ionizing radiation (IR)-induced ultra-fine bridges only in cells expressing ATRX and lacking MUS81 and GEN1. Consistently, damage-induced MUS81 recruitment is only observed in ATRX-expressing cells. Cells lacking BLM show similar MUS81 recruitment and IR-induced SCE formation as control cells. Collectively, these results suggest that the ATRX pathway involves the formation of HR intermediates whose processing is entirely dependent on MUS81 and GEN1 and independent of BLM. We propose that the predominant ATRX-dependent HR subpathway forms joint molecules distinct from classical Holliday junctions.

In vitro risk assessment of Padina pavonica (Linnaeus) (Brown algae)

Padina pavonica (Linnaeus) Thivy 1960 is a brown algae that is antioxidant, antimicrobial, and anticancer effects and is generally used in soup, salad, and other dishes. However, no studies have been reported on safe consumption in humans to date. For this purpose, this study was conducted to determine the cytotoxic and genotoxic effects of P. pavonica on lymphocytes cultured from human blood. The water extract of P. pavonica was added into culture tubes at various concentrations (0.5-1000 μg/mL). Cytotoxic effects were determined by MTT assay. Antioxidant/oxidant status was evaluated by total antioxidant capacity (TAC) and total oxidative status (TOS) assays. Genotoxic effects were investigated by sister chromatid exchanges and micronucleus assays. Our results showed that P. pavonica had no genotoxic effects, even at higher concentrations. 1000 μg/mL concentration of P. pavonica caused an increase (P<0.05) TOS levels while significantly reducing cell viability. However, low concentrations (50 and 100 μg/mL) significantly increased (P<0.05) TAC levels. In conclusion, P. pavonica can be safely consumed with its non-genotoxic and antioxidant properties in a manner dose-dependent.