Sister Chromatid Exchange Assay Research Articles

Genotoxicity studies on the antimicrobial drug sulfamethoxazole in cultured human lymphocytes

The genotoxicity of the antimicrobial drug sulfamethoxazole was evaluated in cultured human peripheral blood lymphocytes. The frequencies of sister-chromatid exchange (SCE) and micronuclei (MN) were scored as genetic endpoints. Both tests cover a wide range of induced genetic damage such as primary DNA damage, clastogenicity and aneugenicity. Cultures were set up with blood samples from two healthy donors and the treatment was done with different sulfamethoxazole concentrations ranging from 10 to 500 μg/ml. From the results obtained it appears that this drug is able to induce weak genotoxic effects, as revealed by the slight increase in the SCE and MN frequencies, at least at one of the two highest concentrations tested. However, the results of the SCE assay should be interpreted with caution because the increase is just significant. In addition, cyotoxic/cytostatic effects of sulfamethoxazole were revealed by a decrease in the proliferative rate index (PRI) and in the cytokinesis block proliferation index (CBPI).

Folic acid and beta-carotene decrease sister chromatid exchange (SCE) rate in patients undergoing controlled ovarian hyperstimulation (COH)

One of the commonly used methods to determine the DNA damages of mammalian cells is SCE. We1 had previously reported an association between DNA damage in infertile women’s lymphocytes with exogenous gonadotropins. Thus the aim of this study is to evaluate DNA repairing effect of antioxidant agents (Folate and beta-carotene) in patients undergoing COH. Prospective case-control study. A total of 20 women undergoing IVF/ICSI with standard luteal long GnRH-a suppression (leuprolide acetate) and step-down protocols (recombinant FSH) were included in the study. The inclusion criteria were the absence of any malignancy, no history of chemotherapy or radiotherapy or no smoking. All patients underwent ICSI cycle and maximum 3 embryos were transferred on day 3. Three heparinized peripheral blood samples from these patients were obtained at different time intervals referring as the baseline (prior to COH) (Time I), at the day of human chorionic gonadotropin injection (Time II) and 12 days after ET (Time III). Peripheral blood lymphocytes from each sample taken above mentioned time intervals were cultured in three different tubes. For each patient, folic acid (2.27×10-7 M) (Group 1) and beta-carotene (1×10-6 M) (Group 2) were added to tube 1 and tube 2 respectively after 24 hours of the culture, and 3rd tube added noting referred as control tube (Group 3). Chromosome harvesting was performed to each tube for a single patient after addition of colcemide at 68th hour. Differential staining of chromatids at the time of metaphase plaque was done with Hoechst-Giemsa treatment and SCE values for each sample were analyzed. The presence of disturbed color continuity and color changes between the opposite paired chromatids were assessed as a break. The scoring unit for SCE was the average of the chromatid changes per metaphase plaques after 200 metaphase plaques were counted. Values were expressed as mean ± SD. Mann-Whitney U and Wilcoxon-Sign rank tests were used to analyze data. Type 1 error was set at 0.05. Mean age±S.D. of the patients was 29.7±5.9. Mean duration of gonadotropin stimulation was 9.1±1.1 days and mean total dose of gonadotropins used was 1597.9±247.1 IU and mean estradiol level on the day of hCG administration was 1251.1±773.2 pg/ml. Although all tree groups had comparable mean number of SCE at the baseline, a statistically significant increment of SCE score was noted in control group when compared to group I and group II at both time I and II. All values of the SCE were given in Table 1. Increased DNA damage may indicate the increased potential for malignancies after superovulation. However, supplementation of patients with folic acid or beta-carotene may decrease this potential toxic effect. 1 Baltaci V, Zeyneloglu HB. Increased frequency of sister-chromatid exchange and altered alkaline comet assay scores in superovulation cycles for unexplained infertility. Eur J Obstet Gynecol Reprod Biol 2004;113:73.

In vitro antigenotoxic potential of acitretin in human lymphocytes treated with the antineoplastic alkylating agent ASE (NSC-71964)

Acitretin is widely used in the systemic treatment of severe forms of psoriasis and other skin disorders. ASE, namely 3β-hydroxy-13α-amino-13,17-seco-5α-androstan-17-oic-13,17-lactam- p-bis(2-chloro-ethyl)amino phenylacetate (AzaSteroidalEster, NSC-71964), is an alkylating agent with antineoplastic activity and mutagenic properties. The aim of this study was to investigate the possible genotoxic and/or antigenotoxic effects of acitretin in human lymphocyte cultures in vitro, using sister chromatid exchange (SCE) and cytokinesis-blocked micronucleus (CBMN) assays. Micronucleus (MN) analysis was achieved in combination with fluorescence in situ hybridization (FISH), using an α-satellite DNA pancentromeric probe. It was found that acitretin alone demonstrated no clastogenic or aneugenic activity. However, simultaneous incubation of lymphocyte cultures with ASE and acitretin resulted in a reduction of ASE-induced SCEs. For MN analysis lymphocytes were treated with ASE and acitretin at 21 and 41 h after culture initiation, corresponding to G 1 and G 2 phases, respectively, and lasted until cell harvest. Acitretin caused a decrease in ASE-induced MN when treatment of cells started at 41 h, but exerted no effect on them when treatment started at 21 h. These findings suggest that acitretin exerts antigenotoxic effects in human lymphocyte cultures, the expression of which may be related to the cycle phase of the cells upon onset and duration of the treatment, at least as far as MN frequency is concerned.

Transient increase in micronucleus frequency and DNA effects in the comet assay in two patients after intoxication with 2,3,7,8-tetrachlorodibenzo- p-dioxin.

The genotoxic effects in two patients with 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) intoxication were measured; an association with the workplace was suspected. We determined sister chromatid exchange (SCE), micronuclei (MN) and comet assay tail factor in peripheral lymphocytes of the patients and of control persons. A determination of polychlorinated dibenzo- p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) revealed almost pure TCDD at a concentration of 144,000 pg/g blood lipids in patient 1 and 26,000 pg/g blood lipids in patient 2, the first value being the highest level ever reported in humans. The source of TCDD ingestion remains unclear, since TCDD blood levels in 30 employees from the same workplace were in the normal range (1.2-8.6 pg/g blood lipids, average 3.0 pg/g), with the exception of three employees with moderately increased TCDD levels of 93, 149 and 856 pg/g blood lipids, who, however, did not show any clinical symptoms. Systematic measurements of air and equipment did not identify the source of TCDD. We determined SCE and MN in the peripheral lymphocytes of the patients and of control persons. A first determination, a few months after the manifestation of chloracne, showed normal values (2.4 and 2.5 MN/500 binucleated cells; 6.7 +/- 2.2 and 6.0 +/- 2.5 SCEs/metaphase) in both patients. Two months later, when TCDD levels were 85,600 pg/g blood lipids and 17,700 pg/g blood lipids, respectively, MN had increased enormously to 16 and 21.8/500 binucleated cells, SCE remained within normal range. One employee had a TCDD level of 856 pg/g blood lipids but did not develop any clinical symptoms or genotoxic effects, nor did three healthy employees with TCDD levels within background range (1.5-2.9 pg/g blood lipids). Within a period of 13 months, MN had returned to a nearly normal range in both patients. SCE had been within normal ranges all the time. We also determined the comet assay tail factor (DNA damage level) in peripheral lymphocytes of the patients. A first determination, when the TCDD level was 85,600 pg/g blood lipids (proband 1), showed an enormously high value of 33.5%. Nine months later, when the TCDD level was at 73,900 pg/g blood lipids, we found only a moderately increased value of 6.9%. Proband 2 did not have a significantly elevated comet assay tail factor, neither at the TCDD level of 17,700 pg/g blood lipids nor at the level of 15,700 pg/g blood lipids. This delayed and transient effect seems to indicate some kind of "indirect" or "secondary" genotoxic effect of TCDD. However, DNA damaging effects, caused directly or indirectly, could be an indicator for a possible carcinogenic risk of TCDD.

Increased frequency of sister-chromatid exchange and altered alkaline comet assay scores in superovulation cycles for unexplained infertility.

Sister-chromatid exchange analysis (SCE) and alkaline comet assay measure and analyze DNA damage in mammalian cells. This study assesses whether ovulation induction agents increase DNA damage in the lymphocytes of infertile women undergoing superovulation. Prospective case control study in a university based hospital. Baseline and hCG day peripheral blood samples were withdrawn from 20 women with undergoing superovulation for unexplained infertility and baseline and luteinizing hormone (LH) peak day samples were also withdrawn from another 20 infertile women with unexplained infertility. There was increased SCE frequency and DNA damage determined by comet assay on the hCG day compared to the basal state. The SCE increase was correlated with the hCG day estradiol (E2) but not with ampoules of follicular stimulating hormone (FSH). The SCE frequency was also increased naturally ovulating women; however this was significantly less than that in FSH receiving women. Increased DNA damage may indicate for increased potential for malignancies after superovulation.

Evaluation of the genotoxicity of cis-bis(3-aminoflavone)dichloroplatinum(II) in comparison with cis-DDP

Short-term tests that detect genetic damage have provided information needed for evaluating carcinogenic risks of chemicals to man. The mutagenicity of cis-bis(3-aminoflavone)dichloroplatinum(II) ( cis-[Pt(AF) 2Cl 2]) in comparison with cis-diamminedichloroplatinum(II) ( cis-DDP) was evaluated in the standard plate-incorporation assay in four strains of Salmonella typhimurium: TA97a, TA98, TA100 and TA102, in experiments with and without metabolic activation. It was shown that cis-[Pt(AF) 2Cl 2] acts directly and is mutagenic for three strains of S. typhimurium: TA97a, TA98 and TA100. In comparison with cis-DDP this compound showed a weaker genotoxicity. Contrary to cis-DDP it has not shown toxic properties in the tester bacteria. The genotoxicity of both tested compounds was evaluated using chromosomal aberration, sister chromatid exchange and micronucleus assays, without and with metabolic activation, in human lymphocytes in vitro. The inhibitory effects of both compounds on mitotic activity, cell proliferation kinetics and nuclear division index were also compared. In all test systems applied, cis-[Pt(AF) 2Cl 2] was a less effective clastogen and a weaker inducer of both sister chromatid exchanges and micronuclei in comparison with cis-DDP, with and without metabolic activation. cis-[Pt(AF) 2Cl 2] has a direct mechanism of action and is less cytostatic and cytotoxic than the other compound. These results provide important data on the genotoxicity of cis-[Pt(AF) 2Cl 2] and indicate its beneficial properties as a potential anticancer drug, especially in comparison with cis-DDP.

Correlation of sister chromatid exchange formation through homologous recombination with ribonucleotide reductase inhibition

We conducted the recombination and sister chromatid exchange (SCE) assays with five chemicals (hydroxyurea (HU), resveratrol, 4-hydroxy- trans-stilbene, 3-hydroxy- trans-stilbene, and mitomycin C) in Chinese hamster cell line SPD8/V79 to confirm directly that SCE is a result of homologous recombination (HR). SPD8 has a partial duplication in exon 7 of the endogenous hprt gene and can revert to wild type by homologous recombination. All chemicals were positive in both assays except for 3-hydroxy- trans-stilbene, which was negative in both. HU, resveratrol, and 4-hydroxy- trans-stilbene were scavengers of the tyrosyl free radical of the R2 subunit of mammalian ribonucleotide reductase. Tyrosyl free radical scavengers disturb normal DNA replication, causing replication fork arrest. Mitomycin C is a DNA cross-linking agent that also causes replication fork arrest. The present study suggests that replication fork arrest, which is similar to the early phases of HR, leads to a high frequency of recombination, resulting in SCEs. The findings show that SCE may be mediated by HR.

Effects of Carvacrol on Sister Chromatid Exchanges in Human Lymphocyte Cultures

Carvacrol is a predominant aromatic compound in oil of oregano. It has naturally remarkable antibacterial, antiviral, antifungal and antiparasital effects. In this study, genotoxic and antigenotoxic activities of carvacrol were investigated by the in vitro sister chromatid exchange (SCE) assay on human peripheral blood lymphocytes. The genotoxicity test was performed with carvacrol in two donors. On the other hand, inhibitory effect of carvacrol was tested in the presence of mitomycin C (MMC) in the same assay. According to data, all doses of carvacrol did not increase the formation of SCE, whereas it inhibited the rate of SCE induced by MMC. In conclusion, carvacrol exhibited a significant antigenotoxic activity in mammalian cells, indicating its potential for use as an antigenotoxic agent.

Mechanism of anticlastogenicity of Agaricus blazei Murill mushroom organic extracts in wild type CHO (K 1) and repair deficient (xrs5) cells by chromosome aberration and sister chromatid exchange assays

Agaricus blazei Murill is a medicinal mushroom native to Brazil. The present work assessed the clastogenic and anticlastogenic potential of organic extracts (ethanol and chloroform/methanol) from the lineage AB97/11 in chinese hamster CHO-K 1 (wild type) and CHO-xrs5 (repair deficient) cells using the chromosome aberration (CA) and sister chromatid exchange (SCE) assays. In these experimental conditions were observed: (a) anticlastogenic effect at concentrations of 0.06 and 0.09% of the EtOH extract and at the 0.03 and 0.06% concentrations of the C/MetOH extract in CHO-K 1; (b) absence of protector effect on CHO-xrs5 cells; and (c) absence of protector effect in the SCE assay. These results indicate that organic extracts of A. blazei lineage AB97/11 present bio-antimutagenic type protective activity.

A review of the genotoxicity of triallate.

Triallate is a selective herbicidal chemical used for control of wild oats in wheat. It has an extensive genotoxicity database that includes a variety of in vitro and in vivo studies. The chemical has produced mixed results in in vitro assay systems. It was genotoxic in bacterial mutation Ames assays, predominantly in Salmonella typhimurium strains TA100 and TA1535 in the presence of S9. Weaker responses have been observed in TA100 and TA1535 in the absence of S9. Mixed results have been observed in strain TA98, whereas no genotoxicity has been observed in strains TA1537 and TA1538. The presence and absence of S9 and its source seem to play a role in the bacterial response to the chemical. There have also been conflicting results in other test systems using other bacterial genera, yeast, and mammalian cells. Chromosome effects assays (sister-chromatid exchange and cytogenetics assays) have produced mixed results with S9 but no genotoxicity without S9. Triallate has not produced any genotoxicity in in vitro DNA damage or unscheduled DNA synthesis assays using EUE cells, human lymphocytes, and rat and mouse hepatocytes. In a series of in vivo genotoxicity assays (cytogenetics, micronucleus, dominant lethal, and unscheduled DNA synthesis), there has been no indication of any adverse genotoxic effect. Metabolism data indicate that the probable explanation for the differences observed between the in vitro studies with S9 and without S9 and between the in vitro and the in vivo studies is the production of a mutagenic intermediate in vitro at high doses of triallate is expected to be at most only transiently present in in vivo studies. The weight of evidence strongly suggests that triallate is not likely to exert mutagenic activity in vivo due to toxicokinetics and metabolic processes leading to detoxification.

Use of the single cell gel electrophoresis/comet assay for detecting DNA damage in aquatic (marine and freshwater) animals.

The comet assay is a rapid, sensitive and inexpensive method for measuring DNA strand breaks. The comet assay has advantages over other DNA damage methods, such as sister chromatid exchange, alkali elution and micronucleus assay, because of its high sensitivity and that DNA strand breaks are determined in individual cells. This review describes a number of studies that used the comet assay to determine DNA strand breaks in aquatic animals exposed to genotoxicants both in vitro and in vivo, including assessment of DNA damage in aquatic animals collected from contaminated sites. One difficulty of using the comet assay in environmental work is that of comparing results from studies that used different methods, such as empirical scoring or comet tail lengths. There seems to be a consensus in more recent studies to use both the intensity of the tail and the length of the tail, i.e. DNA tail moment, percentage of DNA in the tail. The comet assay has been used to assess DNA repair and apoptosis in aquatic animals and modifications of the comet assay have allowed the detection of specific DNA lesions. There have been some recent studies to link DNA strand breaks in aquatic animals to effects on the immune system, reproduction, growth, and population dynamics. Further work is required before the comet assay can be used as a standard bio-indicator in aquatic environments, including standardization of methods (such as ASTM method E2186-02a) and measurements.

Toxicological Evaluation of Honey as an Ingredient Added to Cigarette Tobacco

A tiered testing strategy has been developed to evaluate the potential for new ingredients, tobacco processes, and technological developments to increase or reduce the biological activity that results from burning tobacco. In the manufacture of cigarettes, honey is used as a casing ingredient to impart both aroma and taste. The primary objective of this document is to summarize and interpret chemical and toxicological studies that have been conducted to evaluate the potential impact of honey on the biological activity of either mainstream cigarette smoke or cigarette smoke condensate. As part of ongoing stewardship efforts, cigarettes produced with honey (5% wet weight) as an alternative to invert sugar in tobacco casing material were subjected to extensive evaluation. Principal components of this evaluation were a determination of selected mainstream smoke constituent yields, Ames assay, sister chromatid exchange assay in Chinese hamster ovary cells, a 30-wk dermal tumor promotion evaluation of cigarette smoke condensate in SENCAR mice, and a 13-wk inhalation study of cigarette smoke in Sprague-Dawley rats. Comparative analytical evaluations demonstrated that the substitution of honey for invert sugar as a casing material in cigarettes had no significant impact on mainstream smoke chemistry. In addition, in vitro and in vivo studies demonstrated that cigarettes containing tobacco cased with honey had comparable biological activity to cigarettes containing invert sugar. Collectively, these data demonstrate that the use of honey as an alternative casing material in the manufacture of cigarettes does not alter the potential toxicity of cigarette smoke condensate (CSC) or cigarette smoke; therefore the use of honey as an ingredient added to cigarette tobacco is acceptable from a toxicological perspective.

Effect of Oxymetholone on SCE frequency in human lymphocyte chromosomes in vitro

Genotoxicity evaluation of a commonly used synthetic androgen, Oxymetholone, was carried out in human peripheral blood lymphocytes in vitro. Sister chromatid exchange (SCE) was used as genetic end point. The concentrations of the drug were determined after observing its effects on the mitotic index. A wide range of concentrations, i.e., 25, 50, and 100 micro g/ml of the drug, were used to determine the genotoxic effects in the absence as well as in the presence of rat liver microsomal activation system (S9 mix). The drug did not induce any significant increase in the SCE frequency at any of the concentrations either in the presence or in the absence of S9 mix. The maximum value of SCE was observed in the absence of S9 mix at 100 microg/ml concentration (i.e., 1.38+/-0.080/cell), which was not significant statistically. Moreover, the drug was not effective in increasing the SCE frequency even in the presence of S9 mix. The maximum value of SCE (i.e., 1.78+/-0.103/cell) was observed at 50 microg/ml of concentration in the presence of S9 mix. A dose relationship was also not observed. It was concluded that Oxymetholone does not affect the genetic material in human lymphocytes at a wide range of concentrations in the SCE assay.

A new approach for evaluating in vivo anti-leukemic activity using the SCE assay: An application on three newly synthesised anti-tumour steroidal esters

Three newly synthesised steroidal esteric derivatives of nitrogen mustard (compounds 1– 3) were comparatively studied on a molar basis regarding their ability to induce sister chromatid exchanges (SCEs) in normal human lymphocytes in vitro and therapeutic effects on leukemia P388 bearing mice. Compounds 1 and 3 are modified steroidal esters of p-methyl- m- N, N-bis(2-chloroethyl)amino benzoic acid, and compound 2 is a modified steroidal ester of chlorambucil. All compounds induced statistically significant increases in SCEs and decreases in proliferation rate indices (PRIs) of cultured human lymphocytes and significantly increased the life span of P388 bearing mice. In this study, the doses applied for therapeutic purposes upon leukemia P388 bearing mice in vivo were derived from cytogenetic observations in normal human lymphocytes in vitro. A substantially better therapeutic effect was obtained compared to the effect achieved after the use of quite higher doses related with LD 10 values. We have demonstrated that the order of anti-tumour effectiveness of the treatment schedules of the three newly synthesised compounds tested (at doses derived from cytogenetic observations) coincides with the order of the cytogenetic effects they induce. The SCE assay appears to have an application in the clinical prediction of tumour sensitivity to potential chemotherapeutics.

Niacin deficiency increases spontaneous and etoposide-induced chromosomal instability in rat bone marrow cells in vivo

Poly(ADP-ribose) polymerase (PARP) binds to DNA single and double strand breaks and uses NAD in the synthesis of poly(ADP-ribose) (pADPr). Niacin deficiency in rats decreases bone marrow NAD + and limits pADPr synthesis in response to DNA damage, while pharmacological supplementation with nicotinic acid (NA) increases bone marrow NAD + and pADPr. The purpose of this study was to determine if niacin status alters the extent of DNA damage and chromosomal instability before and after treatment with the chemotherapy drug etoposide (ETO). Genotoxicity was evaluated using the comet, micronucleus and sister chromatid exchange (SCE) assays. Male Long–Evans rats were fed niacin deficient (ND), or pair-fed (PF) niacin replete (30 mg niacin/kg) or NA supplemented (4 g niacin/kg) diets for 3 weeks. Rats were gavaged with ETO (1–25 mg/kg) suspended in corn oil or an equal volume of vehicle (CON). Comet analysis demonstrated that ETO-induced DNA damage (mean tail moment (MTM) and proportion of cells with significant damage) was greater in bone marrow cells from ND rats, compared to PF or NA rats. Surprisingly, niacin deficiency alone caused 6.2- and 2.8-fold increases in spontaneous micronucleus formation and SCE frequency, respectively. As expected, ETO treatment increased the level of micronuclei (MN) and SCEs in all diet groups; however, the absolute increases were greater in ND bone marrow. These data show that niacin is required for the maintenance of chromosomal stability and may facilitate DNA repair in vivo, in a tissue that is sensitive to niacin depletion and impaired pADPr metabolism. Pharmacological intakes of niacin do not appear to be further protective compared to adequate intakes. Niacin supplementation may help to protect the bone marrow cells of cancer patients with compromised nutritional status from the side effects of genotoxic chemotherapy drugs.

Fenvalerate-induced chromosome aberrations and sister chromatid exchanges in the bone marrow cells of mice in vivo

Fenvalerate, a synthetic pyrethroid insecticide, is commonly used in agriculture and other domestic applications due to its high insecticidal activity and low mammalian-, avian- and phyto-toxicities. However, the genotoxic effect of fenvalerate is highly equivocal. In the present study the genotoxic effects of fenvalerate was evaluated using structural chromosome aberration (CA) and sister chromatid exchange (SCE) assays in mice. Out of the three doses (5, 10 and 20 mg/kg) tested, statistically significant increase in CA was found following intra peritoneal (i.p.) treatment of 20 mg/kg of fenvalerate for 24 h ( P<0.01) and 48 h ( P<0.05) only. Neither the acute doses of 5 and 10 mg/kg, nor the sub-acute dose ( 5×4 mg/ kg ) of fenvalerate could induce any significant effect. All the three acute doses induced significant increase in the frequency of SCEs ( P<0.01) in the bone marrow cells, which showed a significant dose-response correlation ( r=0.9541, P<0.05). With certain reservations to possible impurities, from the present findings technical grade fenvalerate may be considered as a weak clastogen and a potent inducer of SCEs in mice.

Reversible G(1) arrest by dimethyl sulfoxide as a new method to synchronize Chinese hamster cells.

Dimethyl sulfoxide (DMSO), a well-known differentiation inducer in several myeloid cells, also induces a reversible G(1) arrest in many cell lines. We recently showed that DMSO induces a G(1) phase arrest in Chinese hamster ovary (CHO) cells, by restoring contact inhibition and preventing high density-dependent apoptosis. CHO cells are frequently used in cell biology and mutagenesis studies due to their good growth capacity and ease of manipulation but are very difficult to synchronize by serum starvation since they detach from monolayers when they reach confluence. In this study we investigated the possibility of using DMSO to reversibly synchronize CHO cells in the G(1) phase of the cell cycle and analysed whether toxic effects follow the arrest using growth curve, sister chromatid exchange and micronuclei assays. We carried out a kinetic analysis of the arrest by DMSO and re-entry into the cell cycle after drug release by cytofluorimetric analysis of DNA content and bromodeoxyuridine incorporation. We show that CHO cells are efficiently and reversibly arrested in G(1) by DMSO in concentrations ranging between 1 and 2%. In our experiments, >90% of cells grown for 96 h in presence of the drug were arrested in G(1) and synchronously re-entered S phase approximately 8-12 h after release. Furthermore, expression levels of p27 were down-regulated during G(1) progression and cyclin D3 and E expression patterns were similar to those observed after serum starvation. No detectable cytotoxicity or genetic damage were induced in G(1) released cells as revealed by the tests employed. Our results show that DMSO is a very powerful inducer of G(1) synchronization in CHO cells without detectable cytotoxic or genetic effects in cell populations released from G(1) arrest. DMSO synchronization represents a model system in which to analyse protein activities regulating G(1) progression and investigate the response of G(1) cells to mutagen treatments.

Squalene but not n-3 fatty acids protect against hydrogen peroxide-induced sister chromatid exchanges in Chinese hamster V79 cells

Fish-oil derived n-3 PUFA such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) has been shown to exhibit anti-carcinogenic effects in vivo and in vitro. Squalene, found in shark liver oil and olive oil, can effectively inhibit chemically induced tumorigenesis in rodents. The aim of the present study was to investigate whether supplementation with EPA (50 μmol/l), DHA (50 μmol/l) or squalene (50 μmol/l) for 24 h would protect Chinese hamster V79 fibroblast cells against oxidant-induced DNA damage. EPA and DHA were delivered to the cells either complexed to bovine serum albumin (BSA) or dissolved in ethanol. DNA damage was assessed using the sister chromatid exchange (SCE) assay. V79 cells exposed to hydrogen peroxide (H 2O 2) alone showed a significant increase in SCE ( P < 0.05) when compared with control levels. Pre-incubation with either EPA or DHA did not significantly affect H 2O 2-induced SCE regardless of the delivery vehicle employed. However, pre-treatment with squalene significantly decreased the frequency of SCE induced by H 2O 2 ( P < 0.05). Results indicate that squalene was more effective than EPA and DHA in protecting against H 2O 2-induced SCE.

Micronuclei and sister chromatid exchanges induced by capsaicin in human lymphocytes

Capsaicin is the main pungent and irritating component of hot peppers (species Capsicum annuum and C. frutescens). Genotoxicity and carcinogenicity studies evaluating capsaicin effects are sparse and contradictory. In this study, we investigated the genotoxicity of capsaicin (10–200 μM) in human peripheral blood lymphocytes using the cytokinesis-block micronucleus (CBMN) assay and the sister chromatid exchange (SCE) assay in the presence or absence of external metabolic activation. Capsaicin induced the formation of micronuclei (MN) in a dose-dependent manner in the cytokinesis-blocked lymphocytes. This increase was more evident in the absence of metabolic activation, with a maximum of 3.4-fold increase above the background. Some inter-individual variability was observed. The results for the SCE assay also show that capsaicin is genotoxic and in this case with a more homogenous response among donors. This end-point, however, has proven to be less sensitive than the CBMN assay for capsaicin.

Potential Late Health Effects of Depleted Uranium and Tungsten Used in Armor-Piercing Munitions: Comparison of Neoplastic Transformation and Genotoxicity with the Known Carcinogen Nickel

Limited data exist to permit an accurate assessment of risks for carcinogenesis and mutagenesis from embedded fragments or inhaled particulates of depleted uranium (DU). Ongoing studies have been designed to provide information about the carcinogenic potential of DU using in vitro and in vivo assessments of morphological transformation as well as cytogenetic, mutagenic, and oncogenic effects. For comparison, we also examined tungsten alloys used in military projectiles and the known carcinogen nickel. Quantitative and qualitative in vitro transformation studies were done to assess the carcinogenic potential of radiation and chemical hazards. Using a human osteosarcoma cell model, we demonstrated that soluble and insoluble DU compounds can transform cells to the tumorigenic phenotype, as characterized by morphological, biochemical, and oncogenic changes consistent with tumor cell behavior. Tungsten alloys and nickel were also shown to be neoplastic transforming agents, although at a frequency less than that of DU. Sister chromatid exchange, micronuclei, and alkaline filter elution assays showed DU and tungsten alloys were genotoxic. Exposure to a nontoxic, nontransforming dose of DU induced a small but statistically significant increase in the number of dicentrics formed in cells. These results suggest that long-term exposure to DU or tungsten alloys could be critical to the development of neoplastic disease in humans and that additional studies are needed.