Comparative study with the alkaline Comet assay and the chromosome aberration test

How to use an in vitro approach to characterize the toxicity of airborne compounds

As part of the development of new approach methodologies (NAMs), numerous in vitro methods are being developed to characterize the potential toxicity of inhalable xenobiotics (gases, volatile organic compounds, polycyclic aromatic hydrocarbons, particulate matter, nanoparticles). However, the materials and methods employed are extremely diverse, and no single method is currently in use. Method standardization and validation would raise trust in the results and enable them to be compared. This four-part review lists and compares biological models and exposure methodologies before describing measurable biomarkers of exposure or effect. The first section emphasizes the importance of developing alternative methods to reduce, if not replace, animal testing (3R principle). The biological models presented are mostly to cultures of epithelial cells from the respiratory system, as the lungs are the first organ to come into contact with air pollutants. Monocultures or cocultures of primary cells or cell lines, as well as 3D organotypic cultures such as organoids, spheroids and reconstituted tissues, but also the organ(s) model on a chip are examples. The exposure methods for these biological models applicable to airborne compounds are submerged, intermittent, continuous either static or dynamic. Finally, within the restrictions of these models (i.e. relative tiny quantities, adhering cells), the mechanisms of toxicity and the phenotypic markers most commonly examined in models exposed at the air-liquid interface (ALI) are outlined.

In vitro and integrated in vivo strategies to reduce animal use in genotoxicity testing

Scientific, financial, and ethical drivers have led to unprecedented interest in implementing human-relevant, mechanistic in vitro and in silico testing approaches. Further, as non-animal approaches are being developed and validated, researchers are interested in strategies that can immediately reduce the use of animals in toxicology testing. Here, we aim to outline a testing strategy for assessing genotoxicity beginning with standard in vitro methods, such as the bacterial reverse mutation test and the in vitro micronucleus test, followed by a second tier of in vitro assays including those using advanced 3D tissue models. Where regulatory agencies require in vivo testing, one demonstrated strategy is to combine genotoxicity studies traditionally conducted separately into a single test or to integrate genotoxicity studies into other toxicity studies. Standard setting organisations and regulatory agencies have encouraged such strategies, and examples of their use can be found in the scientific literature. Employing approaches outlined here will reduce animal use as well as study time and costs.

Genotoxicity of Asiasari Radix et Rhizoma (Aristolochiaceae) ethanolic extract in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional herbal medicines have diverse efficacy and are increasingly used worldwide. However, some of these herbal medicines have toxicities or side effects, but the scientific understanding of traditional herbal medicine toxicity has not yet been established. Asiasari Radix et Rhizoma (ARE) is known as a herbal medicine used to relieve pain, and recent studies have shown that ARE has anticancer and antimelanogenesis efficacy.

AIM OF THE STUDY

Current study was conducted to assess the potential genotoxicity of an ethanolic extract of ARE.

MATERIALS AND METHODS

The genotoxixity of ARE was confirmed by the bacterial reverse mutation assay (Ames test), a mammalian chromosomal aberration test, and a micronucleus test in vivo using ICR mice and comet assay using Sprague-Dawley rats.

RESULTS

ARE showed no genotoxicity in a micronucleus test up to 2000 mg/kg body weight in vivo. By contrast, the chromosomal aberration test showed that ARE induced an increase in the number of chromosomal aberrations after treatment for 6 h with a metabolic activation system and for 6 and 22 h without the metabolic activation system when compared with vehicle control. In the Ames test, all strains except TA1535, with or without a metabolic activation system, showed an increase in the number of revertant mutant colonies in the ARE-treated group. In comet assay, DNA damage was observed in the stomach when ARE was administered.

CONCLUSION

ARE potentially shows genotoxicity by inducing DNA damage.

DBD-FISH, an effective marker for detecting genotoxicity in buccal mucosa exfoliated cells of patients with oral cancer

Oral squamous cell carcinoma (OSCC) is characterized by increased genetic instability as an essential variable of event of neoplastic transformation. The aim of this study was to evaluate genomic instability in exfoliated cells from the buccal mucosa of patients with OSCC vs. the control group, using DNA Breakage Detection/Fluorescence In Situ hybridization (DBD-FISH). Exfoliated cells from the buccal mucosa were obtained from 38 patients with oral cancer (case group) and from 10 individuals without oral lesions (control group). DNA damage was evaluated by DBD-FISH using the whole-genome DNA probe and digital imaging analysis. Collaterally, HPV infection was determined utilizing the INNO-LiPA HPV kit. Patients with OSCC showed an increase in the hybridization signal five times more intense than that of the baseline level of DNA damage detected in control individuals. The best cutoff value for predicting oral squamous cell carcinoma was 67.46, and an Odds Ratio (OR) value of 87. HPV detection analysis revealed than one patient with OSCC (2.6%) was positive for HPV. All controls were negative HPV. In conclusion, DBD-FISH permitted the clear visualization of level high of DNA damage in the buccal epithelial cells of patients with OSSC respect to control group. Chromosome instability in oral mucosa may be an individual marker of malignant transformation in OSCC.

Evaluation of the genotoxic effect of heavy metals in pigeons from urban and rural habitat in Monterrey, Mexico, using the chromatin dispersion assay

PURPOSE

Evaluate genotoxic effect of heavy metals on Pigeon Erythrocytes (PE) from urban and rural habitat (outside of the city) in Monterrey, Mexico, using the chromatin dispersion assay.

MATERIALS AND METHODS

We quantified metals concentrations (Cd, Hg, Cu and Pb) in tail feathers of 22 pigeons from an urban and a rural site in northeastern Mexico. DNA damage in peripheral blood erythrocytes was measured by chromatin dispersion assay in 13 pigeon living in urban habitat and in nine living in rural habitat as the control. MicroNucleus (MN) test was used to confirm levels of DNA damage.

RESULTS

Birds in urban habitat had highest concentrations in feathers for all the metallic elements analysed with respect to birds in rural habitat. Concentrations of Cu and Hg showed a significant increase (p < 0.05). Our results showed a significant increase of DNA damage in urban-habitat pigeons compared with that of pigeons in rural area. These results were confirmed by a MN test.

CONCLUSIONS

Our preliminary findings demonstrate that PE examination via chromatin dispersion assay is a reliable, precise and inexpensive morphological bioassay for evaluating environmental genotoxicity associated with heavy metals. Further studies for evaluating the individual participation of contaminants in DNA damage are needed.

Antimicrobial and Biocompatible Polycaprolactone and Copper Oxide Nanoparticle Wound Dressings against Methicillin-Resistant Staphylococcus aureus

One of the major health problems linked to methicillin-resistant Staphylococcus aureus (MRSA) is severe diabetic foot ulcers (DFU), which are associated with hospital-acquired infections, lower limb amputations and emerging resistance to the current antibiotics. As an alternative, this work aims to develop a biodegradable and biocompatible material with antimicrobial capacity to prevent DFU. This was achieved by producing active polymeric films with metallic nanoparticles dispersed through a polycaprolactone (PCL) dressing. First, the antimicrobial activity of copper oxide nanoparticles (CuONPs) was tested by the microdilution method, selecting the lowest concentration that has an inhibitory effect on MRSA. Then, active PCL films were prepared and characterized in terms of their physicochemical properties, antimicrobial performance, cytotoxicity, genotoxicity and hemocompatibility. Active films had chemical and thermal properties like the ones without the antimicrobial agents, which was confirmed through FTIR, Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) analysis. In relation to antimicrobial activity, active PCL films inhibited MRSA growth when treated with CuONPs at a concentration of 0.07% (w/w). After exposure to the active film extracts, human foreskin fibroblast cells (ATCC^® SCRC1041™) (HFF-1) exhibited a cell viability average above 80% for all treatments and no DNA damage was found. Finally, PCL films with 0.07% (w/w) CuONPs proved to be hemocompatible, and none of the films evaluated had red blood cell breakage greater than 5%, being within the acceptable limits established by the International Organization for Standardization ISO 10993-4:2002.

Assessment of DNA damages in lymphocytes of agricultural workers exposed to pesticides by comet assay in a cross-sectional study

PURPOSE

To assess the predictive power of the comet assay in the context of occupational exposure to pesticides.

MATERIALS AND METHODS

The recruited subjects completed a structured questionnaire and gave a blood sample. Exposure to pesticides was measured by means of an algorithm based on Dosemeci's work (Agricultural Health Study). Approximately 50 images were analyzed for each sample via fluorescence microscopy. The extent of DNA damage was estimated by tail moment (TM) and is the product of tail DNA (%) and tail Length.

RESULTS

Crude significant risks (odds ratios, ORs) for values higher than the 75th percentile of TM were observed among the exposed subjects (score > 1). The frequency of some confounding factors (sex, age and smoking) was significantly higher among the exposed workers. A significant dose-effect relationship was observed between TM and exposure score. Significant high-risk estimates (ORs), adjusted by the studied confounding factors, among exposure to pesticides and TM, % tail DNA and tail length were confirmed using unconditional logistic regression models.

CONCLUSIONS

The adjusted associations (ORs) between the comet parameters and exposure to pesticides were significant. The sensitivity of the comet test was low (41%), the specificity (89%) and the predictive positive value (0.77) were found acceptable.

In Vitro Toxicity Testing of Food Contact Materials: State-of-the-Art and Future Challenges

Currently, toxicological testing of food contact materials (FCMs) is focused on single substances and their genotoxicity. However, people are exposed to mixtures of chemicals migrating from food contact articles (FCAs) into food, and toxic effects other than genotoxic damage may also be relevant. Since FCMs can be made of more than 8 thousand substances, assessing them one-by-one is very resource-consuming. Moreover, finished FCAs usually contain non-intentionally added substances (NIAS). NIAS toxicity can only be tested if a substance's chemical identity is known and if it is available as a pure chemical. Often, this is not the case. Nonetheless, regulations require safety assessments for all substances migrating from FCAs, including NIAS, hence new approaches to meet this legal obligation are needed. Testing the overall migrate or extract from an FCM/FCA is an option. Ideally, such an assessment would be performed by means of in vitro bioassays, as they are rapid and cost-effective. Here, we review the studies using in vitro bioassays to test toxicity of FCMs/FCAs. Three main categories of in vitro assays that have been applied include assays for cytotoxicity, genotoxicity, and endocrine disruption potential. In addition, we reviewed studies with small multicellular animal-based bioassays. Our overview shows that in vitro testing of FCMs is in principle feasible. We discuss future research needs and FCM-specific challenges. Sample preparation procedures need to be optimized and standardized. Further, the array of in vitro tests should be expanded to include those of highest relevance for the most prevalent human diseases of concern.

Mechanical Properties and in Vitro and in Vivo Biocompatibility of a-C/a-C:Ti Nanomultilayer Films on Ti6Al4V Alloy as Medical Implants

Hydrogen-free a-C/a-C:Ti nanomultilayer films are deposited on medical Ti6Al4V alloy using a closed field unbalanced magnetron sputtering under graded bias voltage. The mechanical and tribological properties of the nanomultilayer films are performed on the nanoindentor, Rockwell and scratch tests, and ball-on-disk tribometer. The biological properties are evaluated by cell cytotoxicity, genotoxicity, subchronic systemic toxicity and implant. The hard a-C/a-C:Ti nanomultilayer films on medical alloy exhibit high adhesion strength and excellent tribological properties in both ambient air and Hank's solution. Biocompatibility results reveal the film no cytotoxity, no genotoxicity, no subchronic systemic toxicity and no contraindications in implant systems. Because of excellent mechanical properties and biosafety, the carbon-based films on medical alloy unveils a prospective application in medical implants.

The Effect of Fermented Papaya Preparation on Radioactive Exposure

Exposure to ionizing radiation causes cellular damage, which can lead to premature cell death or accumulation of somatic mutations, resulting in malignancy. The damage is mediated in part by free radicals, particularly reactive oxygen species. Fermented papaya preparation (FPP), a product of yeast fermentation of Carica papaya Linn, has been shown to act as an antioxidant. In this study, we investigated the potential of FPP to prevent radiation-induced damage. FPP (0-100 μg/ml) was added to cultured human foreskin fibroblasts and myeloid leukemia (HL-60) cells either before or after irradiation (0-18 Gy). After 1-3 days, the cells were assayed for: intracellular labile iron, measured by staining with calcein; reactive oxygen species generation, measured with dichlorofluorescein diacetate; apoptosis, determined by phosphatidylserine exposure; membrane damage, determined by propidium iodide uptake; and cell survival, determined by a cell proliferation assay. DNA damage was estimated by measuring 8-oxoguanine, a parameter of DNA oxidation, using a fluorescent-specific probe and by the comet assay. These parameters were also assayed in bone marrow cells of mice treated with FPP (by adding it to the drinking water) either before or after irradiation. Somatic mutation accumulation was determined in their peripheral red blood cells, and their survival was monitored. FPP significantly reduced the measured radiation-induced cytotoxic parameters. These findings suggest that FPP might serve as a radioprotector, and its effect on DNA damage and mutagenicity might reduce the long-term effects of radiation, such as primary and secondary malignancy.

Antioxidant activity of new ruthenium compounds

Many biological properties have been attributed to ruthenium complexes including anti-tumor activity and the attenuation of reperfusion damage and infarct size. In this work, we characterize the antioxidant activity of trans-[RuCl2(nic)4] where nic is 3-pyridinecarboxylic acid and trans-[RuCl2(i-nic)4] where i-nic is 4-pyridinecarboxylic acid by (i) evaluation of total antioxidant potential (TRAP); (ii) prevention of DNA damage induced by hydrogen peroxide using the alkaline comet assay; and (iii) the prevention of lipid peroxidation and cell death induced by iron in liver slices. Our results suggest that nic has stronger antioxidant potential when compared to the i-nic. Higher doses (above 200 microM) of these compounds gave genotoxic effects, but the antioxidant potential could be obtained with the use lower doses (0.1-10 microM).

Dose-related genotoxic effect of T-2 toxin measured by comet assay using peripheral blood mononuclear cells of healthy pigs

T-2 toxin is the most acutely toxic trichothecene mycotoxin: it inhibits protein, DNA and RNA synthesis. The main goal of this study was to evaluate the rate of DNA damage caused by T-2 toxin in porcine mononuclear cells in increasing concentrations (0.1, 0.5 and 1.0 μmol) and after two different incubation periods (24 and 42 h). The lowest concentration caused DNA damage and about 50% of the treated cells could be categorised as having 1 to 4 scores in comet assay. In parallel with the increase of T-2 toxin concentration, the frequency of intact lymphocytes decreased from 50.2% (0.1 μM) to 36.3% (1.0 μM) in the first 24 h. In case of score 3, the highest concentration of T-2 toxin resulted in a 5-fold change, as compared to the lowest dose. Cells with score 4 were found only after exposure to 1.0 μM T-2 toxin. The exposure time did not have a significant effect on the results, while concentration did (P < 0.0001). However, a significant interaction between concentration and time as fixed factors (P < 0.0001) was found. When these were combined as a single factor, the results showed a significant toxin treatment effect on the results. It was concluded that a time- and dose-dependent DNA damaging effect of T-2 toxin could be demonstrated using peripheral blood mononuclear cells from healthy pigs by comet assay.

Intercalation and induction of strand breaks by adriamycin and daunomycin: a study with human genomic DNA

The anticancer drugs Adriamycin (ADR) and Daunomycin (DNM) of the anthracycline family are effective in treating a variety of cancers. Although their interactions with other cellular targets may play a role in the selective cytotoxicity of these drugs, it is generally believed that intercalation with DNA is essential for their activity. However, a relationship has not yet been established between intercalation and cellular processes leading to cytotoxicity. The present study was designed to investigate the relationship, if any, between intercalation and DNA strand breaks. ADR and DNM were observed to be strong intercalators of human genomic DNA by absorption and fluorimetric methods that were further substantiated by rise in thermal melting temperature. DNM is the better intercalator of the two, which is also evident from circular dichroic spectral changes. DNA strand breaks, considered to be an index of genotoxicity, was assayed by single cell gel electrophoresis (SCGE; comet assay). ADR and DNM induced equivalent genotoxicity in normal human lymphocytes at a clinically used dose, which was observed to be independent of intercalation efficiency though positively correlated to yield of reactive oxygen species.

In vitro genotoxicity test approaches with better predictivity: summary of an IWGT workshop

Improving current in vitro genotoxicity tests is an ongoing task for genetic toxicologists. Further, the question on how to deal with positive in vitro results that are demonstrated to not predict genotoxicity or carcinogenicity potential in rodents or humans is a challenge. These two aspects were addressed at the 5th International Workshop on Genotoxicity Testing (IWGT) held in Basel, Switzerland, on August 17-19, 2009. The objectives of the working group (WG) were to make recommendations on the use of cell types or lines, if possible, and to provide evaluations of promising new approaches. Results obtained in rodent cell lines with impaired p53 function (L5178Y, V79, CHL and CHO cells) and human p53-competent cells (peripheral blood lymphocytes, TK6 and HepG2 cells) suggest that a reduction in the percentage of non-relevant positive results for carcinogenicity prediction can be achieved by careful selection of cells used without decreasing the sensitivity of the assays. Therefore, the WG suggested using p53- competent - preferably human - cells in in vitro micronucleus or chromosomal aberration tests. The use of the hepatoma cell line HepaRG for genotoxicity testing was considered promising since these cells possess better phase I and II metabolizing potential compared to cell lines commonly used in this area and may overcome the need for the addition of S9. For dermally applied compounds, the WG agreed that in vitro reconstructed skin models, once validated, will be useful to follow up on positive results from standard in vitro assays as they resemble the properties of human skin (barrier function, metabolism). While the reconstructed skin micronucleus assay has been shown to be further advanced, there was also consensus that the Comet assay should be further evaluated due to its independence from cell proliferation and coverage of a wider spectrum of DNA damage.

Type 1 ribosome-inactivating proteins - entomotoxic, oxidative and genotoxic action on Anticarsia gemmatalis (Hübner) and Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

Ribosome-inactivating proteins (RIPs) from plants inhibit protein synthesis by inactivating ribosomes. Some two-chain (type 2) RIPs are highly toxic and may play a role in plant defense. The lower toxicity of single-chain (type 1) RIPs reflects the lack of a protein domain able to bind to, and translocate the toxin across cell membranes. We studied the effect of single-chain RIPs, lychnin, momordin, gelonin, PAP-S and saporin S-6, in larvae of Anticarsia gemmatalis and Spodoptera frugiperda. After ingesting a total dose of 20 or 40 microg of the toxins, weight gain, survival rate, lesions in DNA and oxidative status (catalase and superoxide dismutase activities and lipidic peroxidation) of RIP-treated insects were assayed. Momordin was the less toxic in the biossays. S. frugiperda had a more pronounced weight loss on the 4th day of treatment and A. gemmatalis on the 10th day. RIP-induced mortality reached 57.13% for A. gemmatalis and 29.45% for S. frugiperda. RIP-treated insects showed a 2-3-fold increase in DNA lesions as assessed by the comet assay, but there were no correlations between stress markers and DNA damage. We conclude that single-chain RIPs are entomotoxic to lepidopteran insects causing extensive DNA lesions.

Cytotoxicity and genotoxicity of ingenamine G isolated from the Brazilian marine sponge Pachychalina alcaloidifera

Marine sponges belonging to the order Haplosclerida are one of the more prolific sources of new natural products possessing various biological activities. The present study examined the cytotoxic and genotoxic potential of ingenamine G, an alkaloid isolated from the Brazilian marine sponge Pachychalina alcaloidifera. Ingenamine G displayed a moderate cytotoxic activity against human proliferating lymphocytes evaluated by the MTT assay (IC(50) 15 microg/mL). The hemolytic assay showed that ingenamine G cytotoxic activity was not related to membrane disruption. The comet assay and chromosome aberration analysis were applied to determine the genotoxic and clastogenic potential of ingenamine G, respectively. Cultured human lymphocytes were treated with 5, 10, 15 and 20 microg/mL of ingenamine G during the G(1), G(1)/S, S (pulses of 1 and 6 h), and G(2) phases of the cell cycle. All tested concentrations were cytotoxic, reduced significantly the mitotic index, and were clastogenic in all phases of the cell cycle, especially in S phase. While an increase in DNA-strand breaks was observed starting with the concentration corresponding to the IC(50). The presence of genotoxicity and polyploidy during interphase and mitosis, respectively, suggests that ingenamine G at high concentrations is clastogenic and indirectly affects the construction of mitotic fuse.

Use of the alkaline comet assay for the detection of transplacental genotoxins in newborn mice

Several lines of evidence show that in utero exposure to different toxicants has greater consequences than their exposure during adult life. This may be due to involvement of critical developmental stages, physiological immaturity and the long later-life span over which disease may initiate, develop and progress. The in vivo alkaline comet (single-cell gel electrophoresis) assay has been favoured by the scientific community for the evaluation of genotoxins. The objective of this study was to demonstrate the suitability of alkaline comet assay in detecting transplacental genotoxins using newborn mice. Here, we report the successful use of the comet assay in detecting multi-organ genotoxicity of known transplacental genotoxins in newborn mice. Three well known transplacental genotoxic agents, cyclophosphamide (CP), mitomycin-C (MMC) and zidovudine (AZT) were tested in pregnant Swiss mice. These compounds were administered in the late gestational period (16-20th days of pregnancy) and the comet assay was performed with lymphocytes, bone marrow, liver and kidney cells of newborn mice. Significant DNA damage was observed in all the tissues with tested transplacental genotoxins. The results of the comet assay were confirmed by the micronucleus (MN) assay of the peripheral blood of newborn mice. The results of this study provide sufficient evidence that the comet assay can be applied successfully for the detection of transplacental genotoxins in newborn mice.

Genotoxic effects of tanshinones from Hyptis martiusii in V79 cell line

The genotoxic effect of two tanshinones isolated from roots of Hyptis martiussi Benth (Labiatae) was studied using V79 (Chinese hamster lung) cells by the alkaline comet assay and micronucleus test. Tanshinones were incubated with the cells at concentrations of 1, 3, 6 and 12 microg/mL for 3 h. Tanshinones were shown to be quite strongly genotoxic against V79 cells at all tested concentrations. The data obtained provide support to the view that tanshinones has DNA damaging activity in cultured V79 cells under the conditions of the assays.

Application of cytogenetic endpoints and comet assay on human lymphocytes treated with atorvastatin in vitro

This study investigated the genotoxic potential of atorvastatin on human lymphocytes using comet assay, structural chromosome aberrations (CA) and sister-chromatid exchange (SCE) analysis. Lymphocyte cultures were treated with a single drug at a concentration of 30.21 ng/mL. For comet assay, cells exposed to atorvastatin for 24 h, 48 h and 72 h were embedded in agarose slides, lysed with alkaline lysis solution and exposed to an electric field. DNA migrated within the agarose and formed comets whose length depends on the amount of DNA damage. For analysis of structural CA, cells were grown on medium for 48 h and for SCE analysis for 72 h. Structural CA did not induce significant damage to the genome, although a higher CA frequency was observed in cells treated with atorvastatin for 3 h, 20 h and 48 h than in control samples. Results of the SCE analysis did show statistically significant differences in the mean SCE number between atorvastatin-exposed and control human lymphocytes and between different exposure times. Comet assay also showed increased DNA damage caused in atorvastatin-exposed human lymphocytes than in corresponding control cells for exposure times of 24 h, 48 h and 72 h for the tail length and for 72 h for the tail moment. Results obtained in this study point to the significance of biological indicators providing information on the primary genome damage after long-term exposure, which can help to establish drug therapeutic concentrations that do not put patients with high blood cholesterol to a greater treatment-related risk.

Validation of an automatic comet assay analysis system integrating the curve fitting of combined comet intensity profiles

In recent years, the single-cell gel electrophoresis (comet) assay has become a reference technique for the assessment of DNA fragmentation both in vitro and in vivo at the cellular level. In order to improve the throughput of genotoxicity screening, development of fully automated systems is clearly a must. This would allow us to increase processing time and to avoid subjectivity brought about by frequent manual settings required for the 'classical' analysis systems. To validate a fully automatic system developed in our laboratory, different experiments were conducted in vitro on murine P388D1 cells with increasing doses of ethyl methanesulfonate (up to 5 mM), thus covering a large range of DNA damage (up to 80% of DNA in the tail). The present study (1) validates our 'in house' fully automatic system versus a widely used semi-automatic commercial system for the image-analysis step, and versus the human eye for the image acquisition step, (2) shows that computing tail DNA a posteriori on the basis of a curve fitting concept that combines intensity profiles [G. Dehon, P. Bogaerts, P. Duez, L. Catoire, J. Dubois, Curve fitting of combined comet intensity profiles: a new global concept to quantify DNA damage by the comet assay, Chemom. Intell. Lab. Syst. 73 (2004) 235-243] gives results not significantly different from the 'classical' approach but is much more accurate and easy to undertake and (3) demonstrates that, with these increased performances, the number of comets to be scored can be reduced to a minimum of 20 comets per slide without sacrificing statistical reliability.

Use of sensitive methods for detection of DNA damage on human lymphocytes exposed to p,p'-DDT: Comet assay and new criteria for scoring micronucleus test

Wide distribution, stability and long persistence in the environment of dichlorodiphenyltrichloroethane (DDT), probably the best-known and most useful insecticide in the world, imposes the need for further examination of the effect of this chemical on human health and especially on the human genome. In this study, peripheral blood human lymphocytes from a healthy donor were exposed to 0.025 mg/L concentration of p,p'-DDT at different time periods (1, 2, 24 and 48 h). For the assessment of genotoxic effect, the new criteria for scoring micronucleus test and alkaline comet assay were used. Both methods showed that p,p'-DDT induces DNA damage in low concentration used in this research. Results of micronucleus test showed a statistically significant (p < 0.05) genotoxic effect of p,p'-DDT on human lymphocytes compared with corresponding control and a different exposure time. A comet assay also showed increased DNA damage caused in p,p'-DDT-exposed human lymphocytes than in corresponding control cells for the tail length. Results obtained by measuring the level of DNA migration and incidence of micronuclei (MN), nucleoplasmic bridges (NPBs) and nuclear buds (NBUDs) indicate the sensitivity of these tests and their application in detection of primary genome damage after long-term exposure to establish the effect of p,p'-DDT on human genome.

DNA-damaging ability of isoprene and isoprene mono-epoxide (EPOX I) in human cells evaluated with the comet assay

Isoprene is produced in combustion processes and is widely used as an industrial chemical. It is a natural product emitted by plants and endogenously produced by humans and other mammals. Therefore, exposure to isoprene from both endogenous and exogenous sources is unavoidable and occurs during the entire human life. Based on evaluations of the International Agency for Research on Cancer (IARC), isoprene has been classified in Group 2B (possibly carcinogenic to humans). In the present work, we have demonstrated, by use of the single-cell gel electrophoresis assay (SCGE or comet assay), that isoprene is able to induce DNA damage in peripheral blood mononuclear cells (PBMCs) in the presence of metabolic activation. In addition, treatment of cells with the main isoprene mono-epoxide (EPOX I) induced time- and dose- dependent DNA damage in both PBMCs and human leukaemia cells (HL60). The metabolic activation system, represented by rat liver post-mitochondrial fractions (S9), was obtained from rats that had been treated - or not - with inducing agents such as phenobarbital and ethanol. The inclusion of S9 fractions (4mg protein/mL) from non-induced or phenobarbital-induced rats resulted in a statistically significant enhancement of isoprene genotoxicity. A different pattern was obtained by the addition of ethanol-induced S9, which appeared highly genotoxic by itself even in the absence of isoprene. Reducing the concentration of ethanol-induced S9 to 0.25mg protein/mL resulted in a considerable enhancement of isoprene genotoxicity. In the absence of clear epidemiological evidence of the carcinogenicity of isoprene in humans, the results of this study seem to be particularly important since they add new findings to support the classification of this chemical as possibly carcinogenic to humans.

In vitro biological efficiency of tenocyclidine – TCP and its adamantane derivative TAMORF

Tenocyclidine-TCP showing a broad spectrum of pharmacological activity including antidotal effect in organophosphorus compounds poisoning, radioprotective and anticancer effects. We investigated in vitro interactions of TCP and its adamantane derivative--TAMORF with human erythrocyte acetylcholinesterase (AChE). Moreover, their genotoxicity and radioprotective activity on human white blood cells were studied using the alkaline comet assay, viability testing and the analysis of the structural chromosome aberrations. The tested compounds were found to be weak inhibitors of AChE, for TCP IC(50)=1 x 10(-5)M and for TAMORF IC(50)>1 x 10(-3)M, without reactivating and protective effects on AChE inhibited by soman. Results suggest that TCP modified by the replacement of the cyclohexyl ring with an adamantly ring and piperidine with morpholine group (TAMORF) have lower toxicity. Both compounds possess low cytotoxicity and radioprotective activity, but TAMORF also shows cell growth inhibitory effects. To clarify differences in their biological efficiency observed in vitro and in vivo, additional analyses are necessary. Since TAMORF was found to significantly inhibit cell growth and proliferation in vitro, it is reasonably to consider it as a source molecule promising for further modifications and development of more potent substances with antitumor properties rather then radioprotector or antidote in organophosphorus poisoning.

Acrylamide and Glycidamide: Approach towards Risk Assessment Based on Biomarker Guided Dosimetry of Genotoxic/Mutagenic Effects in Human Blood

Acrylamide (AA) is a carcinogen as demonstrated in animal experiments, but the relevance for the human situation is still unclear. AA and its metabolite glycidamide (GA) react with nucleophilic regions in biomolecules. However, whereas AA and GA react with proteins, DNA adducts are exclusively formed by GA under conditions simulating in vivo situations. For risk assessment it is of particular interest to elucidate whether AA or GA within the plasma concentration range resulting from food intake are "quenched" by preferential reaction with non-critical blood constituents or whether DNA in lymphocytes is damaged concomitantly under such conditions. To address this question dose- and time-dependent induction of hemoglobin (Hb) adducts as well as genotoxic and mutagenic effects by AA or GA were studied in human blood as a model system.

In vitro testing for genotoxicity of violacein assessed by Comet and Micronucleus assays

Chromobacterium violaceum is a Gram (-) bacteria found in water samples and soils from tropical and subtropical regions of the world. Violacein, the major pigment produced by these bacteria, has been shown to have antibiotic, antitumoral and trypanocidal activities. In the present work, the genotoxicity of violacein was investigated in four different cell lines by using the alkaline Comet assay and in VERO cells using the Micronucleus test. In the alkaline Comet assay, violacein, when tested at concentrations ranging from 0.19 to 1.5 microM, did not induce a significant increase in DNA damage in HEp-2 and MA104 cells. However, violacein was positive for DNA damage in FRhK-4 cells and for both DNA damage and micronuclei in VERO cells, in a concentration-response relationship. The results of this study indicated that violacein is genotoxic in VERO and FRhK-4 cells. These findings contribute to a comprehensive evaluation of the pharmacological potential of violacein.

Assessment of DNA damage in nuclear medicine personnel--comparative study with the alkaline comet assay and the chromosome aberration test

Despite much research over the last few decades, there still remains considerable uncertainty as to the genetic impact of ionizing radiation on human populations, particularly at low levels. The aim of the present study was to provide data on the genetic hazards due to occupational exposure of low doses of ionizing radiation in nuclear medicine departments. The assessment of primary DNA damage in peripheral blood leukocytes of medical staff was performed using the alkaline comet assay and the data obtained were compared with the results of conventional cytogenetic biodosimetry using the chromosome aberration (CA) test. Altogether 120 subjects (60 exposed and 60 controls) participated in the study. Statistically significant increases in primary DNA damage and increased frequencies of CAs compared to controls were observed. Within the exposed population, significant inter-individual differences in DNA damage were found, indicating differences in genome sensitivity. Age and gender were not confounding factors, while smoking enhanced the levels of primary DNA damage only in control subjects, as revealed by both biomarkers studied. The present study suggests that genotoxic damage results from exposure to chronic low doses of ionizing radiation in nuclear medicine departments. Therefore, the exposed medical personnel should carefully comply with the radiation protection procedures and should minimize radiation exposure where possible to avoid potential genotoxic effects. The results obtained in this study point to the significance of biological indicators providing information on the actual risk to the radiation exposed individuals. According to our results, the alkaline comet assay and CA test are sensitive biomarkers that can be used as additional complements to physical dosimetry for assessing exposure to radiation in nuclear medicine personnel.

Prenatal and perinatal fenarimol-induced genotoxicity in leukocytes of in vivo treated rats

The identification of environmental compounds that have adverse effects on reproductive health and animal development is particularly challenging. Fenarimol, a systemic fungicide, is considered non or weakly genotoxic. However, its available toxicological data are controversial and incomplete. This study was conducted in rat in vivo to determine whether this compound (150 and 300 mg/kg) had adverse effects on DNA integrity in dams and pups after maternal subcutaneous exposure. The animals were exposed during early gestation (1-6 days), late gestation (last 6 days), or first 6 days of lactation. Findings on fenarimol genotoxicity showed an adverse effect when detected by the Comet assay, both in dams and pup, and state that animal sensitivity to fenarimol is higher during postnatal period. Since the DNA damage increases during the time of exposure (2 h to 6 days after the birth), our data on pups suggest that fenarimol can mainly act on cell DNA through direct exposure of litter via milk.

Acrylamide and glycidamide: genotoxic effects in V79-cells and human blood

Acrylamide (AA) can be formed in certain foods by heating, predominantly from the precursor asparagine. It is a carcinogen in animal experiments, but the relevance of dietary exposure for humans is still under debate. There is substantial evidence that glycidamide (GA), metabolically formed from AA by Cyp 2E1-mediated epoxidation, acts as ultimate mutagenic agent. We compared the mutagenic potential of AA and GA in V79-cells, using the hprt mutagenicity-test with N-methyl-N'-nitro-N-nitroso-guanidine (MNNG) as positive control. Whereas MNNG showed marked mutagenic effectivity already at 0.5 microM, AA was inactive up to a concentration of 10 mM. In contrast, GA showed a concentration dependent induction of mutations at concentrations of 800 microM and higher. Human blood was used as model system to investigate genotoxic potential in lymphocytes by single cell gel electrophoresis (comet assay) and by measuring the induction of micronuclei (MN) with bleomycin (BL) as positive control. AA did not induce significant genotoxicity or mutagenicity up to 6000 microM. With GA, concentration dependent DNA damage was observed in the dose range of 300-3000 microM after 4 h incubation. Significant MN-induction was not observed with AA (up to 5000 microM) and GA (up to 1000 microM), whereas BL (4 microM) induced significantly enhanced MN frequencies. Thus, in our systems GA appears to exert a rather moderate genotoxic activity.

DNA Damage in Patients Infected by Helicobacter pylori

Helicobacter pylori (H. pylori) is considered to predispose carriers to gastric cancer but its role on gastric carcinogenesis is still unknown. The aim of this study was to investigate DNA damage by the comet assay in gastric epithelial cells from antrum and corpus in H. pylori-infected patients with gastritis of different degrees. H. pylori status, gastric histology, and DNA damage were studied in 62 H. pylori-infected and 18 non-infected patients, all of them non-smokers, non-alcoholics, and non-drug users. DNA damage was significantly higher in H. pylori-infected patients presenting gastritis than in non-infected patients with normal mucosa. A direct correlation between the levels of DNA damage and the intensity of gastritis was observed in H. pylori-infected patients. Association between DNA damage and age was also found. The levels of DNA damage were significantly higher in patients older than 50 years than in younger patients with the same degree of gastritis. Our results indicate that H. pylori infection is associated with DNA damage in gastric epithelial cells, which could be a biomarker of risk for gastric cancer in humans.

DNA damage in frog erythrocytes after in vitro exposure to a high peak-power pulsed electromagnetic field

Till the present time, the genotoxic effects of high peak-power pulsed electromagnetic fields (HPPP EMF) on cultured cells have not been studied. We investigated possible genotoxic effects of HPPP EMF (8.8 GHz, 180 ns pulse width, peak power 65 kW, repetition rate 50 Hz) on erythrocytes of the frog Xenopus laevis. We used the alkaline comet assay, which is a highly sensitive method to assess DNA single-strand breaks and alkali-labile lesions. Blood samples were exposed to HPPP EMF for 40 min in rectangular wave guide. The specific absorption rate (SAR) calculated from temperature kinetics was about 1.6 kW/kg (peak SAR was about 300 MW/kg). The temperature rise in the blood samples at steady state was 3.5 +/- 0.1 degrees C. The data show that the increase in DNA damage after exposure of erythrocytes to HPPP EMF was induced by the rise in temperature in the exposed cell suspension. This was confirmed in experiments in which cells were incubated for 40 min under the corresponding temperature conditions. The results allow us to conclude that HPPP EMF-exposure at the given modality did not cause any a-thermal genotoxic effect on frog erythrocytes in vitro.

DNA damage in blood cells from children exposed to arsenic and lead in a mining area

In this work, we studied the frequency of DNA damage in children living in Villa de la Paz, Mexico, a mining site contaminated with arsenic and lead. DNA damage in blood cells was assessed using the Comet assay, and the results were compared to those found in children living in a less exposed town (Matehuala). In Villa de la Paz, high concentrations of arsenic and lead in surface soil and household dust were found. All of the soil samples had concentrations above 100 mg/kg of arsenic, and 58% of the samples were higher than 400 mg/kg of lead (these concentrations are used as intervention guidelines by the United States Environmental Protection Agency). In agreement with the environmental results, urinary arsenic in children living in Villa de la Paz (geometric mean 136 microg/g creatinine) was significantly higher than that found in children living in Matehuala (34 microg/g creatinine). Blood lead levels were also significantly higher in children from Villa de la Paz (11.6 microg/dL) than in children from Matehuala (8.3 microg/dL). The results of the Comet assay showed that the tail length and the tail moment in children living in Villa de la Paz were higher than those observed for children in Matehuala (P<0.05). Taking all the data into account, our study has shown increased DNA damage in children exposed to arsenic and lead in the mining site of Villa de la Paz.