Sister chromatid exchanges in lymphocytes of nurses handling antineoplastic drugs

The effects of handling antineoplastic drugs were examined in a group of 23 nurses working in the hematology and oncology departments of different university hospitals in Ankara and in a group of 50 unexposed controls. The cytogenetic repercussions of exposure were assessed by examining sister chromatid exchanges (SCEs) in circulating lymphocytes which result from the breakage and rejoining of DNA at apparently homologous sites on the 2 chromatids of a single chromosome. A significant increased frequency of SCE is observed in nurses in daily contact with antineoplastics (n = 23, mean SCEs/cell +/- SE 6.5 +/- 0.2) as compared to a group of controls (n = 50, mean SCEs/cell 5.2 +/- 0.2). The nurses who smoked also had a higher SCE frequency (n = 15, mean SCEs/cell 7.0 +/- 0.3) than non-smokers, (n = 8, mean SCEs/cell 5.5 +/- 0.3). A significant increase (P less than 0.001) in the mean number of SCE was found for non-smoking nurses as compared to non-smoking controls (n = 27, mean SCEs/cell 4.1 +/- 0.2).     

Frequency of sister chromatid exchange in chrysotile-exposed workers.

Chrysotile, which is an industrial carcinogen, has been shown to induce a dose-dependent increase in the frequency of sister chromatid exchange (SCE) in vitro. Authors designed this study to examine the increase of SCEs frequency in the workers occupationally exposed to chrysotile. Heparinized whole blood samples from 45 chrysotile-exposed and 45 control volunteers were cultured for 72 h. The significant difference of SCE frequency was found between chrysotile-exposed workers and control group. The highest SCEs frequency was found in chrysotile-exposed smokers, and the lowest in control non-smokers. The effect of chrysotile exposure on SCEs was marginally significant after controlling the effects of age and smoking by multiple regression analysis.     

Sister chromatid exchange, (SCE), High-Frequency Cells (HFCs) and SCE distribution patterns in peripheral blood lymphocytes of Spanish adult smokers compared to non-smokers

According to the International Agency for Research on Cancer, smoking tobacco is a major cause of cancer in humans. It causes about half of all male cancer deaths and an ever increasing number of cancer deaths in females. The aim of this study was to establish whether cigarette smoking increases sister chromatid exchanges (SCEs) in peripheral blood lymphocytes in two Spanish population groups; light and heavy smokers. The mean number of High-Frequency Cells (HFCs) was determined and, the SCE distribution pattern among the chromosomes was analysed represented by a ratio described below. A local sample of 101 adult smokers (n = 48) and non-smokers (n = 53), aged from 18 to 49 years, was studied using SCE levels in peripheral lymphocytes. Heavy smoking (⩾10 cigarettes per day) increased significantly the SCE frequency and the HFC parameters. Neither age nor sex significantly influenced the frequencies in the groups studied.     

Cytogenetic biomarkers and genetic polymorphisms

Cytogenetic biomarkers have long been applied in surveillance of human genotoxic exposure and early effects of genotoxic carcinogens. Due to their wide use, it has been possible to evaluate, in international collaborative studies, if a high level of these biomarkers in peripheral lymphocytes is predictive of cancer risk. Thus far, such an association has been observed for chromosomal aberrations (CAs), but not for sister chromatid exchanges (SCEs) or micronuclei (MN). The cancer risk predictivity of CAs was not dependent on the time between CA analysis and cancer detection and did not appear to be explained by tobacco smoking or occupational exposure to carcinogens but was seen in unexposed non-smokers as well. This suggests a role for individual susceptibility factors. Genetic polymorphisms of various xenobiotic-metabolising enzymes, influencing the metabolic activation and detoxification of carcinogens, have been associated with cancer risk, and some of them also appear to affect cytogenetic biomarkers. The lack of glutathione S-transferase M1 (GSTM1 null genotype) is associated with increased sensitivity to genotoxicity of tobacco smoke, and GSTM1 null smokers also show an increased frequency of CAs and SCEs. N-Acetyltransferase (NAT2) slow acetylation genotype and glutathione S-transferase T1 (GSTT1) null genotype seem to elevate the baseline level of CAs and SCEs and CAs, respectively--possibly because of reduced capacity to detoxify some wide-spread or endogenous genotoxins. For some chemicals, in vitro cytogenetic studies with lymphocyte donors representing different genotypes have been able to predict a differential in vivo response. For instance, in vitro SCE induction by styrene and by epoxide metabolites of 1,3-butadiene is modified by GSTM1 and GSTT1 genotypes--which also influence the excretion of specific mercapturic acids in humans exposed to butadiene and styrene. Polymorphisms of DNA repair and folate metabolism are expected to be of special importance in modulating genotoxic effects. Some evidence exists for the effects of X-ray cross complementation group 1 (XRCC1) codon 280 and (in smokers) Xeroderma pigmentosum group D (XPD) codon 23 polymorphisms on baseline CAs, for XRCC1 codon 399 polymorphism on SCEs in smokers, and for methylene tetrahydrofolate reductase (MTHFR) codon 677 and methionine synthase reductase (MTRR) polymorphisms on spontaneous MN.     

Sister-chromatid exchanges in lymphocytes from 12 chromium platers: a 5-year follow-up study

To detect the mutagenic effects of hexavalent chromium (Cr) in humans, sister-chromatid exchange (SCE) frequency in lymphocytes and urinary Cr was determined in 66 blood-urine paired samples from 12 male Cr-platers during 5 years (1984-1989). Multiple regression of SCE frequency on age, urinary Cr and smoking habits was analyzed in all 66 samples. Neither age (P = 0.204) nor urinary Cr (P = 0.056) was a significant predictor for SCE frequency. Although urinalysis revealed obvious exposure to Cr in the platers, exposure was unable to influence SCE frequency. Smoking habits were a highly significant (P less than 0.001) positive predictor for SCE frequency, and smoking of one cigarette per day was associated with an increase of 0.054 SCEs/cell in SCE frequency. SCE frequency significantly fluctuated from year to year in 3 subjects. The smoking habits of these 3 subjects did not change during the follow-up period. The results suggest that there are other unknown factors influencing SCE frequency in addition to smoking habits.     

The association between frequencies of mitomycin C-induced sister chromatid exchange and cancer risk in arseniasis

In order to examine whether biomarkers of cytogenetic damage and susceptibility, such as spontaneous and mitomycin C-induced sister chromatid exchange (SCE) can predict cancer development, a nested case-control study was performed in a blackfoot endemic area with known high cancer risk. A cohort of 686 residents was recruited from three villages in the arseniasis area. Personal characteristics were collected and venous blood was drawn for lymphocyte culture and stored in a refrigerator. The vital status and cancer development was followed using the National Death Registry, Cancer Registry, and Blackfoot Disease Registry. The follow up period was from August 1991 to July 1997. During this 6-year-period, 55 residents developed various types of cancer. Blood culture samples from 23 of these subjects were unsuitable for spontaneous SCE experiments and 45 of these subjects were unsuitable for mitomycin C-induced SCE experiments due to improper storage. Finally, a total of 32 cancer cases had cytogenetic samples that could be analyzed. About 32 control subjects were selected from those who did not develop cancer in the study period and these subjects were matched to cases by sex, age, smoking habits, and residential area. The results showed that there was no significant difference in the frequencies of spontaneous and mitomycin C-induced SCE between the case and control groups. There was also no significant difference in the net difference of spontaneous and mitomycin C-induced SCE between the case and control groups. These results suggest that SCEs, either spontaneous or mitomycin C-induced, might not be good markers to predict cancer risk.     

Comparative studies of the mutagenicity of urine from smokers and non-smokers on a controlled non-mutagenic diet

Measuring the mutagenicity of urine is widely viewed as a means of evaluating human exposure to potentially genotoxic materials. Diet and cigarette smoking have both been reported to affect the mutagenicity of human urine, but the relationship between smoking status and the expression of diet-related urinary mutagenicity is unknown. It has been reported that some promutagens are more active in in vitro assays when tested in the presence of urine from smokers than when tested in the presence of urine from non-smokers. We aimed to determine whether the differences in urinary mutagenicity between smokers and non-smokers result from increased urinary mutagenicity from dietary heterocyclic amine mutagens in smokers compared with non-smokers. Groups of smokers and non-smokers (6-12) were given identical diets, previously shown to be low in heterocyclic amines and very low in mutagenicity. The diet consisted exclusively of raw food and of food cooked in boiling water. After a 2-day dietary stabilization period, 24-hour urine samples were collected for three consecutive days. The regimen was repeated in the following week. For comparison, both groups were also placed on a "western" diet, consisting of a variety of foods prepared by several cooking methods, designed to reflect what a typical United States family might consume. Urine was concentrated using XAD-2 resin and then assayed for mutagenic activity in the Ames test. The urine of smokers was significantly more mutagenic than that of non-smokers when on both the raw/boiled and the "western" diets. These results indicate that the increased urinary mutagenicity observed in smokers compared with non-smokers is not due to enhanced mutagenicity of diet-related heterocyclic amine mutagens in the urine of smokers.     

Cell proliferation kinetics and genotoxicity in lymphocytes of smokers living in Mexico City

Genotoxicity caused by tobacco smoke was assessed in peripheral blood lymphocytes of smokers living in Mexico City by determining sister chromatid exchange (SCE), cell proliferation kinetics (CPK), replication index (RI) and mitotic index (MI). Nicotine levels, and its major metabolite cotinine, were also estimated in urine samples using gas-chromatography-mass spectrometry to quantify smoking intensity. The outcome of the analysis and the comparison of the 77-smoker group with a non-smoking control group showed that moderate and heavy smokers exhibited significant differences (P < 0.001 and P < 0.05, respectively) in CPK, with an underlying delay in the cellular cycle; similarly, RI was significantly different in these groups (P < 0.001 and P < 0.0001, respectively). There were significant correlations (P < 0.05) between age and number of years the subject had been smoking, as well as between RI and nicotine and cotinine levels and between CPK (M1, M2 and M3) and nicotine and cotinine levels. Smokers were classified for the analysis according to the nicotine levels (it is in relation to number of cigarettes smoked per day) found in urine (ng/mL) as: light (10-250), moderate (251-850) and heavy (851-4110). Significant differences in CPK were found (P < 0.05) between moderate and heavy smokers and non-smokers. Significant differences in RI were found between moderate (P < 0.001) and heavy smokers (P < 0.0001) and non-smokers, but not for the light smoking group. MI was determined in 57 of the smokers, whereas SCE frequency was only recorded in 34 smokers. Both parameters yielded no significant differences, nor correlations with any of the assessed variables. In conclusion, cytokinetic and cytostatic effects were mainly detected in heavy and moderate smokers. Cell cycle delay and RI decrease were found in all ;healthy' smokers. The nicotine and cotinine exposure (causing oxidative damage to DNA) may have implications in the decrease in cell replication due to direct damage to DNA and/or a decrease in the DNA repair mechanisms. Alternatively, nicotine and cotinine may possibly induce apoptosis.     

Lack of genotoxic effect in workers exposed to very low doses of 1,3-butadiene

1,3-butadiene (BD), a probable carcinogen to humans, has been shown to have an ill-defined genotoxicity in occupationally exposed workers. In the present study, the influence of exposure to very low doses of BD and to cigarette smoking was investigated on some cytogenetic endpoints, namely, sister chromatid exchanges (SCE), chromosomal aberrations (CA) and cells with a high frequency of SCE (HFC), in peripheral blood lymphocytes. Twenty-seven male workers employed in a petrochemical plant and 26 matched controls were included in the study. As regards the airborne BD values, there was a significant difference between exposed (median BD value 1.5, min–max 0.2–69.0 μg/m³) and non-exposed workers (median BD value 0.4, min–max <0.1–3.8 μg/m³). Genotoxic biomarkers were not able to distinguish between the two groups. The frequency of SCE was higher in smokers than in non-smokers (p=0.001), with a positive correlation between the number of cigarettes smoked per day and both SCE (r=0.4; p=0.004) and HFC frequency (r=0.3; p=0.04). Multiple regression analysis confirmed the influence of cigarette smoking on the level of SCE and HFC, while these parameters were not affected by personal exposure to BD. Overall, the biomarkers of genotoxic effect investigated in our study were not able to discriminate between workers with a very low exposure to BD and controls, while it was possible to distinguish between smokers and non-smokers on the basis of SCE.Piero Lovreglio and Nenad Bukvic have contributed equally to this study     

The genotoxic effects of anti-cancer drug gossypol on human lymphocytes and its mitigation by melatonin

Purpose of study: To determine melatonin as a potential natural antioxidant to mitigate the genotoxic effects of promising anti-cancer drug gossypol in human lymphocytes. Introduction: Gossypol, is a polyphenolic compound naturally occurring in cotton seed, was originally identified as a male contraceptive but it has several proposed clinical applications. Gossypol has anti-proliferative effects on cancer cell lines. However, its genotoxic effects on normal cells are not much studied. Hence, there is a paucity of data available. Hence, the study was conducted to investigate gossypol-induced genotoxic effects on lymphocytes. Methods: Peripheral blood lymphocyte cultures (PBLC) were done and exposed by two different doses of an anti-cancer drug, gossypol (0.274?mM, 1.645?mM) to check genotoxic effects. Melatonin (0.2?mM) is used as an antioxidant. Genotoxic indices such as sister chromatid exchanges (SCEs), cell cycle proliferative index (CCPI), average generation time (AGT), population doubling time (PDT) were assayed in the cultures. Result: Gossypol-treated groups indicated significant increases in frequency of SCEs calculated for SCE/plate and SCE/chromosome. Furthermore, CCPI showed a remarkable reduction and increased AGT and PDT levels were found in exposed cultures. When the higher dose of gossypol cultures was treated along with melatonin, these indices were found to be declined and comparable to control. Conclusion: Gossypol, an anti-cancer drug, induces genotoxicity on lymphocyte cells and co-supplementation of melatonin antioxidant ameliorates these toxic effects of gossypol.     

Promutagen activation of triazine herbicides metribuzin and ametryn through Vicia faba metabolism inducing sister chromatid exchanges in human lymphocytes in vitro and in V. faba root tip meristems.

The aim of our study was the induction of sister chromatid exchanges (SCE) in human lymphocytes in vitro and in root tip meristems of Vicia faba to evaluate the genotoxic effects of metribuzin and ametryn. Direct treatments of these herbicides on human lymphocytes in vitro applied 24 h after the beginning of culture did not induce SCE; however, they showed a cytotoxic effect in the cultures expressed as cellular death. On the contrary, when extracts of V. faba roots, treated for 4 h with metribuzin and ametryn (in vivo activation), were added to the lymphocyte cultures, SCEs were significantly induced with an asymptotic response. Negative responses appeared with the in vitro assays, in which metribuzin and ametryn were added directly to the 48 h lymphocyte cultures for 4 h. Nevertheless, in treatments in which the S10 metabolic mix was added, the SCE frequencies were significantly different to the control, although a concentration-response relationship was only observed with metribuzin. The results showed that both herbicides needed the V. faba metabolism to produce SCE in human lymphocyte cultures. Metribuzin and ametryn applied to V. faba root tip meristems for 4 h increased SCE frequency significantly, and a concentration-response relationship was observed with both herbicides.     

Vitamin B12 protects against DNA damage induced by hydrochlorothiazide

DNA damage induced by hydrochlorothiazide was previously reported in cultured human lymphocytes. In this study, we aimed to investigate the harmful effects of hydrochlorothiazide on DNA by measuring the spontaneous frequency of sister chromatid exchanges (SCEs) in cultured human lymphocytes. We also aimed to investigate the possible protection of that damage by vitamin B12. The results showed that hydrochlorothiazide (5?µg/mL) significantly increased the frequency of sister chromatid exchanges (P?<?0.001) in human lymphocytes in comparison with control. Additionally, the frequency of hydrochlorothiazide-induced SCEs was significantly decreased by co-treatment with vitamin B12 at concentration of 13.5?µg/mL (P?<?0.001). In conclusion, hydrochlorothiazide is genotoxic to human lymphocytes and its toxicity is reduced by vitamin B12.     

Inhibition of mitomycin C-induced sister chromatid exchanges by vitamin C in vivo.

The aim of this experiment was to test the modulation of genotoxicity produced by vitamin C (V-C) challenged against mitomycin C (MMC) in vivo, by analyzing the sister chromatid exchanges (SCE) and cell proliferation kinetics. We used the mouse bone marrow cytogenetic method, and tested three dosages of V-C (3, 5, and 7 g/kg of body weight), along with the appropriate positive (2 mg MMC/kg body weight) and negative V-C controls. The results showed that V-C caused a strong inhibition of SCEs induced by MMC in the three dosages administered. The highest dose (7 g/kg) caused an SCE inhibition of 70.02%, while the lower ones caused an inhibition of 54.61% and 52.30%, respectively. It was also clear that V-C per se does not increase the level of SCEs in mouse bone marrow cells. On the other hand, V-C induced a slight decrease in cell proliferation that was stronger when combined with MMC. Our data suggest that V-C effectively inhibit the SCE damage in vivo, but caution must be taken because of the observed cytotoxicity.     

Effects of natamycin on sister chromatid exchanges,chromosome aberrations and micronucleus in human lymphocytes

Natamycin (pimaricin) (E235) is an antifungal that can be used as an antibiotic to treat most fungus infections. It has been globally used in a variety of foods and beverages. In the present study, the effects of natamycin on chromosome aberrations (CAs), sister chromatid exchanges (SCEs), and micronucleus (MN) formation in human lymphocytes cells were investigated. The human lymphocytes were treated with 13, 18, 23, and 28 μg/mL of natamycin for 24 and 48 h. Natamycin induced the SCE frequency at the highest concentration for 48 h only; however, it induced the structural CA and MN frequency at all concentrations when compared to control and at all concentrations, except the lowest concentration (13 μg/mL), when compared to solvent control. Natamycin showed a cytotoxic effect by decreasing the replication index, mitotic index, and nuclear division index (NDI), especially at the highest concentrations for two treatment periods.     

Genotoxicity of selected pesticides in the mouse bone-marrow micronucleus test and in the sister-chromatid exchange test with human lymphocytes in vitro

Selected pesticides, (aldicarb, 1,3-dichloropropene, methidathion, parathion, triadimefon, vinclozolin) were tested for their clastogenic and aneugenic activities in the mouse bone-marrow micronucleus (MN) test in vivo and for their sister-chromatid exchange-inducing activities in human lymphocytes in vitro in the presence and absence of an exogenous metabolizing system from rat-liver S9. 1,3-Dichloropropene significantly increased the frequencies of micronucleated polychromatic erythrocytes (PCE) in bone-marrow cells of female mice from 3.3 MN/1000 PCE to 15.3 MN/1000 PCE (187 mg per kg body weight). 1,3-Dichloropropene (100 μM) induced 16.0 SCE/metaphase after 24 h of incubation as compared with the basal rate of 11.2 SCE/metaphase (− S9) and of 15.4 SCE/metaphase as compared with 10.5 SCE/metaphase of the control (+ S9). These values were statistically significantly different from each other. The other pesticides tested did neither increase the rate of micronuclei significantly in polychromatic erythrocytes in male nor in female animals. Aldicarb and methidathion induced a significant increase in SCEs in human lymphocytes in vitro only without the metabolic activating system: aldicarb, 5 μm, 24 h incubation: 15.5 SCE/metaphase; control: 12.6 SCE/metaphase; methidathion, 100 μM, 24 h incubation: 15.8 SCE/metaphase, control: 11.1 SCE/metaphase. Parathion, triadimefon and vinclozolin did not have any SCE-inducing effects.     

The genetic effects of the photochemical reaction products of propylene plus NO2 on cultured Chinese hamster cells exposed in vitro

A study was made on the genetic effects of the photochemical reaction products of propylene plus NO2 on cultured Chinese hamster V79 cells with the use of sister chromatid exchanges (SCE). The photochemical reaction products of propylene plus NO2 were produced by photochemical reaction of a propylene-NO2/dry air system in a photochemical smog chamber and then were exposed to cell cultures for 2 h. SCEs were induced at all concentrations of the photochemical reaction products employed in the present study, the frequency of SCEs being two or three times higher than that of the controls. The genetic effects of NO2 and ozone (O3) were also studied and compared with those of the photochemical reaction products of propylene plus NO2. NO2 and O3 both induced SCEs in V79 cells, but their effects were weaker than those induced by the photochemical reaction products of propylene plus NO2. It was ascertained that the photochemical reaction of the propylene-NO2/dry air system produced much stronger genotoxic factors than the reactants.     

The genotoxic and antigenotoxic effects of Salvia fruticosa leaf extract in human blood lymphocytes

Abstract

The aim of this study was to investigate the genotoxic and antigenotoxic effects of Salvia fruticosa (Sf) leaf extract with the absence and presence of S9 mix using sister chromatid exchange (SCE), chromosome aberration (CA) and micronucleus (MN) formation test systems in human peripheral blood lymphocytes (HPBLs) that were treated with 1.5-, 3.0- and 6.0-µL/mL concentrations for 24- and 48-hour treatment periods. The cytotoxicity of Sf leaf extract was also investigated by calculating the mitotic index (MI), proliferation index (PI) and nuclear division index (NDI). In the absence of S9 mix, Sf leaf extract alone increased SCE frequency at the 48-hour treatment period; however, it induced the CA and MN at all concentrations and at all treatment periods. Sf plus MMC (mitomycin C) synergically induced SCE and CA, except the highest concentration of Sf leaf extract and MMC on induction of SCE. In addition, Sf leaf extract induced the effect of MMC on MN frequency for 24 hours, but it significantly decreased the effect of MMC on MN frequency for the 48-hour treatment period. Sf leaf extract showed a cytotoxic effect by decreasing the MI; however, it did not decrease the PI and NDI. In the presence of S9 mix, Sf leaf extract did not increase the SCE, when compared to solvent control, whereas it reduced the effect of cyclophosphamide (Cyp). Sf leaf extract induced the CA and MN, but could not increase the effect of Cyp on CA and MN formation. Sf leaf extract had no cytotoxic effect; however, it induced the cytotoxicity of Cyp.     

Sister chromatid exchanges, proliferating rate index, and micronuclei in biomonitoring of internal exposure to vinyl chloride monomer in plastic industry workers

The frequency of micronuclei (MN), sister chromatid exchange (SCEs), and the proliferating rate index in peripheral blood lymphocytes from 93 individuals were measured. Fifty-two of the individuals were workers in the plastics industry where they were exposed to vinyl chloride monomer while the remaining 41 individuals served as a control group. In our results, an increase of SCEs and MN, as well as inhibited cell kinetics, was observed in the group of exposed workers. Of the tests used, SCE was found to be the most sensitive endpoint for indicating a biological response. However, since methods for restricting the MN analysis to only cells at risk (i.e., second generation interphase cells) were not used, this statement requires verification.     

The effects of patulin and patulin-cysteine mixtures on dna synthesis and the frequency of sister-chromatid exchanges in human lymphocytes

The effects of patulin and patulin-cysteine mixtures on DNA synthesis in human blood lymphocytes were measured by assaying incorporation of [³H]thymidine into cellular DNA. Patulin inhibited and patulin-cysteine mixtures stimulated the incorporation of [³H]thymidine into DNA. The inhibitory action of patulin diminished with time in culture. Patulin was found to be unstable in the culture medium. The sister-chromatid exchange (SCE) frequency was significantly elevated by intermediate concentrations (0.1–0.2 μg/ml culture) of the toxin. The cells are protected from the effect at low concentrations of the toxin. There may be excessive damage at higher concentrations but only the unaffected cells go into mitosis. Therefore an increased frequency of SCEs is detected only at intermediate concentrations, or. at higher concentrations, with early harvesting. Cysteine seems to potentiate the effect of patulin on SCE frequency.     

Vinyl chloride: an example for evaluating mutagenic effects in mammals in vivo after exposure to inhalation

As part of a programme of investigations on the mutagenic effects in mammals in vivo after inhalation of environmental chemicals, the effects of the industrial compound vinyl chloride (VC) was analysed.Chinese hamsters were exposed to 1.25%, 2.5% or 5% (v/v) VC in air for 6, 12 or 24 h. Bone marrow chromosomes were analysed for induced chromosome aberrations and sister-chromatid-exchanges (SCEs) 26 h after beginning of exposure.The frequency of VC-induced chromosome aberrations and SCEs both depend on dose and length of exposure. The highest measured effects were 33.25 SCEs/cell after an exposure to 2.5% VC for 24 h and 25.7% metaphases with aberrations, when exposed to 5% VC for 24 h.This study was supported by the Bundesministerium für Forschung und Technologie. Contract No. CMT16.