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

Compound-dependent fetal toxicity after in utero exposure to chemotherapy in a pregnant mouse model

Although chemotherapy is integrated in the treatment of second-trimester pregnant cancer patients, its potential cyto- and genotoxicity to fetal tissue remains unknown. To investigate any causal relation between in utero chemotherapy exposure and fetal toxicity, late-gestation pregnant BL6 mice were exposed to vehicle, or one of six chemotherapeutic compounds, used to treat pregnant cases: cyclophosphamide, carboplatin, cisplatin (alkylating agents), epirubicin, doxorubicin (anthracyclines) or paclitaxel (taxane). fetuses were euthanized at gestational day 18.5, after 48 hours of in utero exposure. Fetuses in utero exposed to alkylating agents presented with morphological changes in liver, bone marrow and thymus. Furthermore, decreased expression of Ki67, and increased expression of caspase-3 and P-H2AX markers, pointed to inhibited proliferation and increased apoptosis and DNA-double stranded breaks respectively, in several fetal tissues. Moderate toxicity was seen after in utero exposure to anthracyclines and taxanes. These findings emphasize the importance of investigating fetal toxicity in the clinical setting.

Additive genotoxic effects in cord blood cells upon indirect exposure to chemotherapeutic compounds crossing an in vitro placental barrier

Prenatal exposure to toxins can adversely affect long-term health outcomes of the offspring. Though chemotherapeutics are now standard of care for treating cancer patients during pregnancy, certain compounds are known to cross the placenta and harm placental tissue. The consequences for the fetus are largely unexplored. Here we examined the responses of newborn cord blood mononuclear cells in tissue culture to two chemotherapeutic drugs, cyclophosphamide and epirubicin, when either directly exposed to these drugs, or indirectly after crossing a placenta trophoblast bilayer barrier. Cord blood mononuclear cells exposed to the conditioned media obtained from cyclophosphamide-exposed trophoblast barriers showed a significant 2.4-fold increase of nuclear ROS levels compared to direct exposure to cyclophosphamide. Indirect exposure to epirubicine-exposed trophoblast barriers not only enhanced nuclear ROS levels but also significantly increased the fraction of cord blood cells with double strand breaks, relative to directly exposed cells. Neither apoptosis nor proliferation markers were affected in cord mononuclear blood cells upon direct or indirect exposure to cyclophosphamide or epirubicin. Our data suggests that trophoblast cells exposed to cyclophosphamide or epirubicine may induce an indirect 'bystander' effect and can aggravate genotoxicity in the fetal compartment.

Assessment of transplacental and lactational genotoxicity of tembotrione in Wistar rats at different developmental stages by alkaline comet assay

This paper assessed the potential of trans-placental and -lactational genotoxicity and oxidative stress induction of tembotrione, a naturally derived allelopathic herbicide. Several treatment protocols were applied to measure primary DNA damage by alkaline comet assay in leucocytes and liver. To address the oxidative stress induction, TBARS, ROS, SOD, CA, GSH-Px activity were recorded. The dams were treated from the first gestation day and pups sacrificed after birth. The second treatment protocol comprised treating the dams during gestation and lactation and sacrificing the pups at weaning. The third group of pups comprised offspring of dams that were treated in gestation and lactation and sacrificed in puberty. To address translactational genotoxicity, dams were treated in lactation only. Dams treated in gestation and lactation were sacrificed after reentering the estrous cycle and analyzed for DNA damage and oxidative stress. Tembotrione doses encountered in everyday human exposure, as estimated by the EFSA, were applied in dam treatment in consecutive days (ADI: 0.0004 mg/kg b.w./day, AOEL: 0.0007 mg/kg b.w./day, 1/500 LD₅₀ 4.0 mg/kg b.w./day). Although we observed mitigated DNA integrity at the dose of 4.0 mg/kg/b.w./day in female pubertal rats, we can conclude that at the conditions employed in the study low doses of tembotrione do not pose a risk for DNA damage of the offspring of treated dams. Contrary to this, the highest dose significantly affected all the oxidative stress parameters in the liver and plasma of pubertal females, CAT and GSH-Px in the liver of males and ROS and CAT of dams.

Novel next-generation sequencing-based methodologies to characterize the mutational consequences of (prenatal) chemotherapy exposure in noncancerous tissue

PURPOSE OF REVIEW

Although chemotherapeutics are considered as genotoxins for decades, their exact mutagenic impact on the genome of cancerous and normal cells of cancer patients was unknown for a long time. However, this knowledge is necessary to understand the long-term side effects of chemotherapy. A particular condition represents pregnant cancer patients being treated with chemotherapy. Since certain chemotherapeutics can cross the placenta, concerns exist about possible mutational effects on the fetus' genome with potential long-term health consequences.

RECENT FINDINGS

Recent advances of next-generation sequencing (NGS) techniques have opened possibilities to explore the exact mutational footprint of chemotherapies in healthy tissue from treated cancer patients. However, the ultra-low frequency of chemotherapy-induced mutations, introduction of technical artefacts, and inaccessibility of normal tissue has posed important limitations. This review discusses five state-of-the-art approaches that were recently designed to overcome these drawbacks.

SUMMARY

Results of the latest investigations give valuable insights into the genome-wide genotoxicity profile of frequently applied chemotherapies, with most of these drugs being associated with a signature of random base substitutions and small indels. Though these findings still might be limited to extrapolate to healthy tissue, they pave the way for studies on the origin of long-term chemotherapy-related adverse health effects.

Genotoxicity and mutagenicity research in Quilombola communities

The Quilombola communities are mostly isolated and deprived of sources of treated water, garbage collection and sewage, consuming fresh water from wells, streams, lakes, among others. This lack of basic infrastructure can be a relevant factor in exposing residents to substances and factors that are harmful to the integrity of their genetic material that can lead to carcinogenesis. Based on this, the objective of this study was to evaluate the genomic and mutagenic/cytotoxic damage in the adult population of two Quilombola communities (one urban and another rural region), in the state of Goiás, Brazil. For this purpose, the leukocyte of peripheral blood Comet Assay in 68 individuals and Micronucleus Test from exfoliated buccal cells of oral mucosa in 21 volunteers were performed. The results evidenced genomic damage, especially for the community of Aparecida de Goiânia city, which detected significant values (p < 0.05), for the length of the comet's tail and for of the Olive Tail Moment. In the micronucleus test, significant differences were only detected (p < 0.05), when it came to the distribution of nuclear changes among the groups. Therefore, it is essential to perform constant population biomonitoring studies to help guarantee health and, consequently, the quality of life.

Genotoxic and Cytotoxic Effects of Antiretroviral Combinations in Mice Bone Marrow

Commonly used guidelines for the management of human immunodeficiency virus (HIV) infection (highly active antiretroviral therapy, HAART) include drug combinations such as tenofovir disoproxil fumarate (TDF) + lamivudine (3TC) and combivir [zidovudine (AZT) + 3TC] + efavirenz (EFV). These combinations may enhance the genotoxic effects induced by such drugs individually, since the therapy requires lifelong adherence and the drugs have unknown effects during treatment. Thus, the evaluation of the benefits and risks of HAART is of great importance. In order to assess the cytotoxic and genotoxic potential of three concentrations of each of the antiretroviral combinations TDF + 3TC (800 + 400, 1600 + 800, and 3200 + 1600 mg/kg body weight, BW) and combivir + EFV (200 + 100 + 400, 400 + 200 + 800, and 800 + 400 + 1600 mg/kg BW) after two exposure periods (24 h and 48 h), in the present study the in vivo comet assay (single-cell gel electrophoresis) and the mouse bone marrow micronucleus test were used. Neither TDF + 3TC nor combivir + EFV induced DNA damage at any concentrations tested after 24 h or 48 h using the comet assay. After 24 h, both combinations increased the micronucleus frequency at all concentrations tested. After 48 h, combivir + EFV increased the micronucleated polychromatic erythrocyte (MNPCE) frequency at the two highest concentrations tested. Polychromatic erythrocytes (PCE)/normochromatic erythrocytes (NCE) ratio was high for both combinations, suggesting that they can be mitogenic. Since genotoxicity may be related to carcinogenesis, it is necessary to conduct further studies to verify the long-term mutagenic effects of these drugs.

Biomonitoring of the Genotoxic and Hepatotoxic Effects and Oxidative Stress Potentials of Itraconazole in Pregnant Rats

BACKGROUND

Pregnant women are more susceptible to both vaginal colonization and infection by yeast. One hundred million fungal infected patients have been treated worldwide with itraconazole (Caputo, 2003.

METHOD

Itraconazole was administrated orally to pregnant rats at doses of 75, 100, or 150 mg/kg during gestational days (GD) 1 to 7 or GD 8 to 14 or GD 14 to 20. The genotoxicity and hepatotoxicity of the antifungal drug itraconazole were assessed during different periods of pregnancy using different methods.

RESULTS

It was found that itraconazole was a genotoxic drug for both mothers and fetuses. This finding was observed via significant elevation in the estimated comet assay parameters (percentage of fragmented DNA, tail moment, and olive moment), percentage of fragmented DNA measured by diphenylamine assay and mixed smearing and laddering of DNA fragments of liver samples. In addition, itraconazole caused significant elevation in the level of hepatic malondialdehyde and depletion in the catalase activity and glutathione level. Furthermore, itraconazole induced histopathological alterations in the hepatic tissues of both mothers and fetuses.

CONCLUSION

These findings indicate that itraconazole administration at doses of 75, 100, or 150 mg/kg during pregnancy induced maternal and fetal toxicity that could be induced by the genotoxicity and the oxidative damage.

Effects of prenatal exposure to single-wall carbon nanotubes on reproductive performance and neurodevelopment in mice

Carbon nanotubes with extraordinary properties may become a novel drug and gene delivery tool in nanomedicine; however, insufficient information is available regarding their biosafety. Therefore, this work was performed to study the effect of prenatal exposure of single-walled carbon nanotubes (SWCNTs) on reproductive and neurobehavioral endpoints in mice. Thirty pregnant female mice were assigned to three groups ( n = 10 for each group). The two treated groups were injected intraperitoneally (i.p.) with 1 or 10 mg/kg body weight (b.w.) of SWCNTs suspended in 1 ml of phosphate buffer saline (PBS) on gestational days 0 and 3. The control group was injected i.p. with an equal volume of PBS. The neurobehavioral ontogeny of pups was evaluated using a modified Fox battery. A decrease in litter size on postnatal day 2 was observed in the group treated with 10 mg/kg b.w. of SWCNTs whereas no significant differences between groups were observed in any other parameters. The behavioral development of pups did not show significant differences during growth except for the surface righting reflex, which showed significant delay compared to control in the group treated with 1 mg/kg b.w. SWCNTs. Moreover, exposed offspring (10 mg/kg b.w. SWCNTs) displayed enhanced anxiety in the elevated plus maze; however, other ethological analysis (Morris water maze and open field test) did not show behavioral changes in the experimental groups. In conclusion, the present results demonstrated small changes in offspring sensory and motor development following exposure to SWCNTs and support the idea that SWCNT risk assessment merits further investigation.

Mechanistic insight into beta-carotene-mediated protection against ulcerative colitis-associated local and systemic damage in mice

PURPOSE

Ulcerative colitis (UC), a chronic gastrointestinal disorder, is a debilitating disease affecting many people across the globe. Research suggests that the levels of several antioxidants, including β-carotene (β-CAR), decrease in the serum of patients with UC. The present study was aimed at elucidating the molecular mechanisms involved in β-CAR-mediated protection against UC in mice.

METHODS

UC was induced in mice using 3%w/v dextran sulfate sodium in drinking water for two cycles; one cycle comprised of 7 days of dextran sulfate sodium-treated water followed by 14 days of normal drinking water. β-CAR was administered at the doses of 5, 10 and 20 mg/kg bw/day, po throughout the experiment. The effect of β-CAR in mice with UC was evaluated using biochemical parameters, histological evaluation, comet and micronucleus assays, immunohistochemistry and Western blot analysis.

RESULTS

The results indicated that β-CAR treatment ameliorated the severity of UC by modulating various molecular targets such as nuclear factor-kappa B, cyclooxygenase-2, interleukin 17, signal transducer and activator of transcription 3, nuclear erythroid 2-related factor 2, matrix metalloproteinase-9 and connective tissue growth factor. Further, β-CAR treatment maintained the gut integrity by increasing the expression of a tight junction protein, occludin, which was decreased in the colon of mice with UC. Also β-CAR treatment significantly reduced UC-associated elevated plasma lipopolysaccharide level, systemic inflammation and genotoxicity.

CONCLUSION

β-CAR ameliorated UC-associated local and systemic damage in mice by acting on multiple targets.

Melatonin reduces ulcerative colitis-associated local and systemic damage in mice: investigation on possible mechanisms

BACKGROUND AND AIMS

Ulcerative colitis (UC) is a chronic gastrointestinal disorder. Substantial research reveals that melatonin has beneficial effects in ulcerative colitis both experimentally and clinically. We have previously reported that ulcerative colitis was associated with local and systemic damage in mice. The purpose of this study was to reveal the novel targets of melatonin in its protective mechanism against ulcerative colitis in mice. We also wished to determine whether or not melatonin protected against ulcerative colitis-induced systemic damage in mice.

METHODS

Ulcerative colitis was induced in mice by use of 3% (w/v) dextran sulfate sodium for two cycles. One cycle comprised 7 days of DSS-treated water followed by 14 days of normal drinking water. Melatonin was administered at doses of 2, 4, or 8 mg/kg bw/day, po throughout. The effect of melatonin in mice with UC was evaluated by use of biochemical data, histological evaluation, comet and micronucleus assays, immunohistochemistry, and western blot analysis.

RESULTS

The results indicated that melatonin treatment ameliorated the severity of ulcerative colitis by modulating a variety of molecular targets, for example nuclear factor kappa B, cyclooxygenase-2, interleukin 17, signal transducer and activator of transcription 3, nuclear erythroid 2-related factor 2, matrix metalloproteinase-9, and connective tissue growth factor. Further, ulcerative colitis increased gut permeability, plasma lipopolysaccharide level, systemic inflammation, and genotoxicity. Melatonin treatment led to mucosal healing and reduced ulcerative colitis-induced elevated gut permeability and reduced the plasma LPS level, systemic inflammation, and genotoxicity.

CONCLUSION

Melatonin ameliorated ulcerative colitis-associated local and systemic damage in mice.

Polycyclic aromatic hydrocarbons (PAHs) as determinants of various anthropometric measures of birth outcome

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants that are known to induce oxidative stress. There have been several reports about the link between PAH exposure and complications in pregnancy. This cross-sectional study was conducted to: (1) measure the levels of benzo(a)anthracene (BaA), chrysene (Ch), benzo(b)fluoranthene (BbF), benzo(a)pyrene (BaP), and dibenzo(a,h)anthracene (DBahA) in placentas and maternal and -umbilical cord blood obtained at delivery from 1578 women between June 2005 and 2006 in the area of Al-Kharj, Saudi Arabia; (2) assess their influence on various anthropometric measures of birth outcome taking into consideration the carcinogenic properties of these PAHs; and (3) determine the degree of PAH-related oxidative DNA damage and birth outcome. Among the five tested PAHs, only BaP was carcinogenic; therefore, the levels of the other four probable or possible carcinogenic PAHs (BaA, Ch, BaF, and DBahA) were summed as ∑4-PAHs. Levels of 1-hydroxypyrene (1-HP) were determined in maternal urine samples as a biomarker of PAH internal dose. Urinary cotinine (COT) was measured as an index of smoking. The following markers of oxidative stress were selected: malondialdehyde (MDA) in cord (C-MDA) and maternal (M-MDA) serum and 8-hydroxy-2-deoxyguanosine (8-OHdG) in maternal urine. None of the tested PAHs was found in maternal or cord blood. However, all five PAH compounds were detected in placentas; Ch was the highest (6.582 μg/kg dry wt.), and BaA was the lowest (0.236 μg/kg dry wt.). The mean concentration of urinary 1-HP found in this study was 0.216 ± 0.856 μg/g Cr. After adjusting for gestational age and other confounding variables, regression models revealed an inverse relationship between placental weight, cord length and placental BaP. A similar trend was observed between cord length and ∑4-PAHs in placental tissues. Urinary 1-HP, though, cannot be used as an unequivocal biomarker of PAH exposure, but it can be an appropriate indicator of exposure to environmental tobacco smoke (ETS). The data demonstrate that ETS exposure (as measured by urinary COT) may adversely affect birth outcome as shown by reduced head circumference, birth weight, and birth length, as well as increased cephalization index. The positive relationship between 8-OHdG levels and 1-HP in urine provides evidence of an oxidative stress mechanism. Although this study provides no direct evidence of an association between PAH exposure and DNA damage, increased oxidative stress in the form of lipid peroxidation significantly affected various birth measures. Therefore, there is a need for studies regarding PAH exposure and its associated biological effects to determine the extent of potential fetal damage as well as possible long-term effects, such as cancer.

Alkaline, Endo III and FPG modified comet assay as biomarkers for the detection of oxidative DNA damage in rats with experimentally induced diabetes

Increased production of reactive oxygen species under diabetic condition underlines the higher oxidatively damaged DNA in different tissues. However, it is practically difficult to assess the oxidatively damaged DNA in different internal organs. Therefore, the present study was aimed to evaluate the extent of oxidative stress-induced DNA damage in different organs with the progression of diabetes. Diabetic and control Sprague Dawley rats were sacrificed in time-dependent manner and the lung, liver, heart, aorta, kidney, pancreas and peripheral blood lymphocytes (PBL) were analyzed for both alkaline and modified comet assay with endonuclease-III (Endo III) and formamidopyrimidine-DNA glycosylase (FPG) (hereafter called modified comet assay) for the detection of oxidative DNA damage. The statistically significant increase in olive tail moment (OTM) was found in all the tested tissues. The extent of DNA damage was increased with the progression of diabetes as revealed by the parameter of OTM in alkaline and modified comet assay. Further, the positive correlations were observed between OTM of the lung, liver, heart, aorta, kidney and pancreas with PBL of diabetic rat in the alkaline and modified comet assay. Moreover, significant increase in the 8-oxodG positive nuclei in the lung, liver, heart, aorta, kidney and pancreas was observed in 4th and 8th week diabetic rat as compared to control. Results of the present study clearly indicated the suitability of alkaline and modified comet assay for the detection of multi-organ oxidative DNA damage in streptozotocin (STZ)-induced diabetic rat and showed that damaged DNA of PBL can be used as a suitable biomarker to assess the internal organs response to DNA damage in diabetes.

Transplacental genotoxicity evaluation of cypermethrin using alkaline comet assay

Transplacental genotoxic effect of cypermethrin technical was investigated. Three doses (25, 50 and 75 mg/kg body weight) were administered to groups of pregnant Wistar rats during 6-15 days of gestation. Animals were killed on gestation day 20. Fetal blood and liver samples were evaluated for DNA damage using alkaline comet assay. A marginal increase in the mean percentage of DNA damage was recorded in both blood and liver samples of fetuses from cypermethrin-treated dams, but the values were not statistically significant. No skeletal or visceral fetal abnormalities were recorded in treated groups. Nevertheless, the results lead to an understanding that transplacental exposure to cypermethrin can induce low levels of DNA damage in fetuses. This observation could be an explanation for the teratogenic effect exhibited by this chemical in many other studies. The results indicate that cypermethrin may be transplacentally genotoxic. The authors propose more detailed investigations for validating the current findings.

Pulmonary exposure to carbon black by inhalation or instillation in pregnant mice: effects on liver DNA strand breaks in dams and offspring

Effects of maternal pulmonary exposure to carbon black (Printex 90) on gestation, lactation and DNA strand breaks were evaluated. Time-mated C57BL/6BomTac mice were exposed by inhalation to 42 mg/m³ Printex 90 for 1 h/day on gestation days (GD) 8-18, or by four intratracheal instillations on GD 7, 10, 15 and 18, with total doses of 11, 54 and 268 (μg/animal. Dams were monitored until weaning and some offspring until adolescence. Inflammation was assessed in maternal bronchoalveolar lavage (BAL) 3-5 days after exposure, and at weaning. Levels of DNA strand breaks were assessed in maternal BAL cells and liver, and in offspring liver. Persistent lung inflammation was observed in exposed mothers. Inhalation exposure induced more DNA strand breaks in the liver of mothers and their offspring, whereas intratracheal instillation did not. Neither inhalation nor instillation affected gestation and lactation. Maternal inhalation exposure to Printex 90-induced liver DNA damage in the mothers and the in utero exposed offspring.

A core in vitro genotoxicity battery comprising the Ames test plus the in vitro micronucleus test is sufficient to detect rodent carcinogens and in vivo genotoxins

In vitro genotoxicity testing needs to include tests in both bacterial and mammalian cells, and be able to detect gene mutations, chromosomal damage and aneuploidy. This may be achieved by a combination of the Ames test (detects gene mutations) and the in vitro micronucleus test (MNvit), since the latter detects both chromosomal aberrations and aneuploidy. In this paper we therefore present an analysis of an existing database of rodent carcinogens and a new database of in vivo genotoxins in terms of the in vitro genotoxicity tests needed to detect their in vivo activity. Published in vitro data from at least one test system (most were from the Ames test) were available for 557 carcinogens and 405 in vivo genotoxins. Because there are fewer publications on the MNvit than for other mammalian cell tests, and because the concordance between the MNvit and the in vitro chromosomal aberration (CAvit) test is so high for clastogenic activity, positive results in the CAvit test were taken as indicative of a positive result in the MNvit where there were no, or only inadequate data for the latter. Also, because Hprt and Tk loci both detect gene-mutation activity, a positive Hprt test was taken as indicative of a mouse-lymphoma Tk assay (MLA)-positive, where there were no data for the latter. Almost all of the 962 rodent carcinogens and in vivo genotoxins were detected by an in vitro battery comprising Ames+MNvit. An additional 11 carcinogens and six in vivo genotoxins would apparently be detected by the MLA, but many of these had not been tested in the MNvit or CAvit tests. Only four chemicals emerge as potentially being more readily detected in MLA than in Ames+MNvit--benzyl acetate, toluene, morphine and thiabendazole--and none of these are convincing cases to argue for the inclusion of the MLA in addition to Ames+MNvit. Thus, there is no convincing evidence that any genotoxic rodent carcinogens or in vivo genotoxins would remain undetected in an in vitro test battery consisting of Ames+MNvit.

Intervention of alpha-lipoic acid ameliorates methotrexate-induced oxidative stress and genotoxicity: A study in rat intestine

Methotrexate (MTX) is an anti-metabolite, widely used in the cancer chemotherapy and rheumatoid arthritis. However, its long-term clinical use is restricted on account of its severe intestinal toxicity. The present study was aimed to investigate the intestinal toxicity of MTX and the possible protective effect of alpha-lipoic acid (LA) on Sprague-Dawley rats. MTX-induced intestinal toxicity was evaluated at the dose of 2.5mg/kg for short-term (5 days treatment) and 1mg/kg for long-term (5 days in a week for four consecutive weeks treatment) study. The possible protective effect of LA was evaluated in both short- as well as long-term study in a dose-dependent manner. MTX treatment induced diarrhoea and mortality in rats, indicating its severe toxicity in the target organ of investigation, i.e., intestine. Further, the intestinal toxicity of MTX was assessed by evaluating different parameters of oxidative stress, DNA damage, cytotoxicity as well as histological changes. Immunostaining for p53 revealed higher genotoxic assault in the intestinal cells due to MTX treatment. Pretreatment of rats with LA led to significant decrease in the oxidative stress, DNA damage, cellular damage, inflammatory changes and apoptosis as determined by malondialdehyde level, glutathione level, comet assay parameters, histological evaluation, immunostaining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. In the present investigation, we report that LA pretreatment ameliorates MTX-induced intestinal toxicity in rat as evident from the protection against oxidative stress, decrease in DNA damage and protection of cellular morphology as well as improvement in the stool consistency and animal survival rate.