Correlation of human lymphocyte SCE frequency with smoking history

Can consumption of raw vegetables decrease the count of sister chromatid exchange? Results from a cross-sectional study in Krakow, Poland

Background

Sister chromatid exchange (SCE) is a widely used sensitive cytogenetic biomarker of exposure to genotoxic and cancerogenic agents. Results of human monitoring studies and cytogenetic damage have revealed that biological effects of genotoxic exposures are influenced by confounding factors related to life-style. Vegetable and fruit consumption may play a role, but available results are not consistent. The purpose of the study was to investigate the effect of consumption of raw and cooked vegetables and fruits on SCE frequency.

Methods

A total of 62 participants included colorectal cancer (CRC) patients, hospital-based controls and healthy laboratory workers. SCE frequency was assessed in blood lymphocytes. Frequency of vegetable and fruit consumption was gathered by structured semi-quantitative food frequency questionnaire.

Results

SCE frequency was lowest among hospital-based controls (4.4 ± 1.1), a bit higher in CRC patients (4.5 ± 1.0) and highest among laboratory workers (7.4 ± 1.2) (p < 0.05). Multivariable linear regression showed a significant inverse effect (b = −0.20) of raw vegetable consumption, but not so for intake of cooked vegetables and fruits.

Conclusions

The results of the study have shown the beneficial effect of consumption of raw vegetables on disrupted replication of DNA measured by SCE frequency, implying protection against genotoxic agents. Further effort is required to verify the role of cooked vegetables and fruits.

Sister chromatid exchanges in smokers and smokers with alcohol habit

Aim:

Sister chromatid exchange (SCE) test is a sensitive, biomarker of genotoxic substances. The present study was conducted to observe the frequency of SCEs in peripheral blood lymphocytes of 30 males with and without the habit of cigarette smoking and alcohol consumption.

Materials and Methods:

Subjects for this study were males aged between 25-50 years and were selected from the students, employees and the patients attending the outpatient department of Ragas dental college and Hospital, Chennai.

Results:

Controls, smokers, and smokers with alcohol habit were divided into two age groups as ≤30 years and ≥30 years. In controls the mean frequency of SCEs/cell in ≤30 years and ≥30 year's age group was 5.80 and 6.05, respectively. In Smokers SCEs/cell in ≤30 years and ≥30 year's age group was 7.7 and 8.8, respectively. In Smokers with alcohol habit SCEs/cell in ≤30 years and ≥30 years age group was 10.1 and 12.8, respectively.

Conclusions:

In this study, the duration of the smoking habit has shown a positive correlation with the mean SCE frequency. Whereas, frequency of the habit did not show any influence on the SCE levels. In smokers with alcohol habit, both the duration and frequency of their smoking habit has shown a significant effect on the SCE levels suggesting a synergistic effect of alcohol and smoking leading to excessive DNA damage.

The genotoxic risk in health care workers occupationally exposed to cytotoxic drugs--a comprehensive evaluation by the SCE assay

Present study aimed at an integral assessment of sister chromatid exchange (SCE) frequencies in the health care workers occupationally exposed to cytostatics. The results of 500 individual analyses were evaluated. Drug handling practice was investigated in parallel and the results showed that cytostatics are mostly prepared outside hospital pharmacy (98%) and mainly handled by nurses (96%). Mean frequency of SCE was 5.63 +/- 2.28, while HFC represented 9.65% of the cells analysed. Both values were higher compared to previously established control values for Croatian population. The duration of exposure, profession, age, gender, smoking habit, medical exposures, and simultaneous exposure to other occupational mutagens significantly contributed to SCE and HFC values. The usefulness both biomarkers in the assessment of cytogenetic damage is confirmed. Since current practice in Croatian hospitals does not include regular monitoring of workplaces, to ensure maximal occupational safety, a surveillance on exposed health care workers, including periodic biomonitoring, is recommended.

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.

Measurement of cytogenetic endpoints in women environmentally exposed to air pollution

The levels of sister chromatid exchanges (SCE), high-frequency cells (HFC) and chromosomal aberrations (CA) were studied in lymphocytes of Silesian women environmentally exposed to ambient air pollutants. Inhabitants of a less polluted but similarly urbanized area, in a rural region of Poland, served as controls. The study population was selected to minimize the major confounding factors influencing SCE and CA. These factors include age, gender, smoking status, and occupation. All donors were 35-46 years old non-smoking City Hall clerks. The levels of all three biomarkers were significantly higher in the exposed group than in controls as analyzed by the Mann-Whitney U-test. No correlation was found between levels of CA and SCE. Additional possible confounders, such as passive smoking, ex-smoking and X-ray chest examination did not influence the levels of biomarkers. This study builds upon our previous research in a male population but better controls for confounders. Thus, the results reveal genetic damage resulting from low-dose but chronic environmental exposure.

Sister chromatid exchange and micronucleus frequency in human lymphocytes of 1,650 subjects in an Italian population: II. Contribution of sex, age, and lifestyle

Sister chromatid exchange (SCE) and micronuclei (MN) analysis was carried out on 1,650 healthy individuals living in Pisa and in two nearby small cities, Cascina and Navacchio (Ca-Na). The effect of smoking on SCEs was linearly correlated with the number of cigarettes per day, and an increase of 7.3% SCEs was detectable for as few cigarettes as 1-10/day. Ex-smokers showed intermediate mean values of SCEs (8.09 +/- 1.88) in comparison with never smokers (7.54 +/- 1.61) and current smokers (8.45 +/- 1.94). Mean values of SCEs of ex-smokers decreased linearly with time of smoking cessation, reaching the mean values of never smokers within 8 years. The extent of SCE decrease was inversely proportional to the number of cigarettes previously smoked. No interaction between smoking habits and coffee or alcohol drinking on SCEs was observed. A borderline (P = 0.053) increase in mean SCE values in coffee drinkers (more than 3 cups/day) was found. The age effect on SCEs was remarkable in Ca-Na, but not in Pisa donors. Job type was not associated with significant modification of mean values of SCEs. Multiple logistic regression analysis revealed a statistically significant association between the proportion of high frequency cells (HCF) outliers and coffee consumption. Age and sex appeared to be by far the most important variables associated with modifications in MN frequency, which increased by 0.04 per thousand and 0.02 per thousand per year in males and females, respectively. Children and young donors (age < or = 40 years) showed lower MN frequency regardless of sex, whereas sex appeared to determine a significantly higher increase of MN only in females older than 40 years. In contrast, in males the MN rate by age tended to level off after the age of 30-50. MN frequencies of Pisa blue- and white-collar workers were statistically significantly higher than in students (+0.71 and +0.55 per thousand, respectively). Smoking did not determine any increase of MN frequency. A total lack of correlation (P = 0.913) between MN and SCEs was observed.

Genetic toxicities of human teratogens

Birth defects cause a myriad of societal problems and place tremendous anguish on the affected individual and his or her family. Current estimates categorize about 3% of all newborn infants as having some form of birth defect or congenital anomaly. As more precise means of detecting subtle anomalies become available this estimate, no doubt, will increase. Even though birth defects have been observed in newborns throughout history, our knowledge about the causes and mechanisms through which these defects are manifested is limited. For example, it has been estimated that around 20% of all birth defects are due to gene mutations, 5-10% to chromosomal abnormalities, and another 5-10% to exposure to a known teratogenic agent or maternal factor [D.A. Beckman, R.L. Brent, Mechanisms of teratogenesis. Ann. Rev. Pharmacol. Toxicol. 24 (1984) 483-500; K. Nelson, L.B. Holmes Malformations due to presumed spontaneous mutations in newborn infants, N. Engl. J. Med. 320 (1989) 19-23.]. Together, these percentages account for only 30-40%, leaving the etiology of more than half of all human birth defects unexplained. It has been speculated that environmental factors account for no more than one-tenth of all congenital anomalies [D.A. Beckman, R.L. Brent, Mechanisms of teratogenesis, Ann. Rev. Pharmacol. Toxicol. 24 (1984) 483-500]. Furthermore, since there is no evidence in humans that the exposure of an individual to any mutagen measurably increases the risk of congenital anomalies in his or her offspring' [J.F. Crow, C. Denniston, Mutation in human populations, Adv. Human Genet. 14 (1985) 59-121; J.M. Friedman, J.E. Polifka, Teratogenic Effects of Drugs: A Resource for Clinicians (TERIS). The John Hopkins University Press, Baltimore, 1994], the mutagenic activity of environmental agents and drugs as a factor in teratogenesis has been given very little attention. Epigenetic activity has also been given only limited consideration as a mechanism for teratogenesis. As new molecular methods are developed for assessing processes associated with teratogenesis, especially those with a genetic or an epigenetic basis, additional environmental factors may be identified. These are especially important because they are potentially preventable. This paper examines the relationships between chemicals identified as human teratogens (agents that cause birth defects) and their mutagenic activity as evaluated in one or more of the established short-term bioassays currently used to measure such damage. Those agents lacking mutagenic activity but with published evidence that they may otherwise alter the expressions or regulate interactions of the genetic material, i.e. exhibit epigenetic activity, have likewise been identified. The information used in making these comparisons comes from the published literature as well as from unpublished data of the U.S. National Toxicology Program (NTP).

Increased sister chromatid exchanges in peripheral lymphocytes of patients with Crohn's disease

A cytogenetic study was performed using Crohn's disease patients to determine whether the presence of chromosome instability is related to Crohn's disease, a chronic inflammatory bowel disease. Sister chromatid exchange (SCE) frequencies in peripheral blood lymphocyte cultures from 22 Crohn's disease patients and an equal number of healthy controls matched for sex and age were analyzed. The mean of SCE frequency in Crohn's disease patients was 11.64 +/- 0.42 (SEM) per cell, which was significantly higher than the value of 8.38 +/- 0.22 per cell in the matched controls (p < 0.0001). The Crohn's disease patients showed significantly increased high frequency cells (HFC) as compared to those among the matched controls. There was a significant correlation between HFC frequencies of the Crohn's disease patients and the severity of their disease as determined by the number of relapses per year and the degree of chronic activity after adjusting for the smoking status (r = 0.54, p = 0.011). In both smokers and non-smokers, the mean SCE and HFC frequencies of the patients were significantly higher than those of the controls. These results suggest that Crohn's disease is a condition with increased chromosome instability characterized by a high level of SCE frequencies which are associated with the inflammatory condition itself.

Environmental effects on chromosomes in oncology and radiology department personnel

Long-term, low levels of antineoplastic drugs and ionizing radiation in the work environment may have genotoxic effects on chromosomes in personnel. The effects of ionizing radiation is acknowledged in occupational medicine and therefore various measures have been undertaken to prevent such effects. However, there are no protective measures for workers exposed to antineoplastic drugs. In this study metaphase chromosome preparations were analyzed in 126 nurses and radiology technicians. They were divided into three equal groups. The first group consisted of shift nurses in an oncology department handling antineoplastic drugs. The second group consisted of radiology technicians in a radiology department and the third group acted as controls. Structural chromosomal aberrations were increased among those nurses exposed to antineoplastic drugs in comparison with technicians (P less than 0.05) and controls (P less than 0.01), respectively.

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).

Chromosomal abnormalities among nurses occupationally exposed to antineoplastic drugs

The effect of handling antineoplastic drugs was examined in 42 nurses working in an oncology department, and the same number of nurses not exposed to antineoplastic drugs acted as controls. The exposure effect was evaluated by analysis of sister chromatid exchanges (SCE) incidence and structural chromosomal abnormalities. SCE as well as chromosomal abnormalities in the exposed group were increased (p less than 0.001 and p less than 0.01, respectively). Sign test for paired sample was used for statistical assessment.

Influence of cigarette smoking on the levels of DNA adducts in human bronchial epithelium and white blood cells

The presence of carcinogen-DNA adducts in human tissues is evidence of exposure to carcinogens and may be an indicator of cancer risk. DNA was isolated from non-tumorous bronchial tissue of 37 cigarette smokers, 8 former smokers and 8 non-smokers and analyzed for the presence of aromatic and/or hydrophobic DNA adducts in the 32P-post-labelling assay. Adducts were detected as bands of radioactive material when 5'-32P-labelled deoxyribonucleoside 3',5'-bisphosphates were chromatographed on polyethyleneimine-cellulose tlc plates, and the patterns indicated the formation of adducts by a large number of compounds. Adduct levels detected in DNA from non-smokers, former smokers and current smokers were 3.45 +/- 1.62, 3.93 +/- 1.92 and 5.53 +/- 2.13 adducts/10(8) nucleotides, respectively. The differences in adduct levels between smokers and former and non-smokers were statistically significant (p less than 0.01); and among the smokers, significant correlations were found between adduct levels and both daily cigarette consumption and total cigarette consumption (daily consumption X number of years smoked). DNA was also isolated from the peripheral-blood leukocytes of 31 heavy smokers (greater than 20 cigarettes/day) and 20 non-smokers and analyzed by 32P-post-labelling. Adduct levels in the smokers' samples were not significantly different from levels in the non-smokers' samples (2.53 +/- 1.31 and 2.12 +/- 1.44 adducts/10(8) nucleotides, respectively). Thus, evidence for carcinogen exposure was found in human bronchial epithelium, a target tissue for tobacco-induced tumour formation, but not in peripheral-blood cells, indicating possible limitations in the use of the latter as a surrogate, non-target tissue source of DNA for monitoring human exposure to inhaled carcinogens.

Cytogenetic monitoring of chemical workers in production of the drug 1-propoxy-2-acetamino-4-nitrobenzol with reference to their smoking habits

The induction of chromosome aberrations (CAs) and sister-chromatid exchanges (SCEs) was examined in cultured lymphocytes from 23 individuals employed in the production of the drug 1-propoxy-2-acetamino-4-nitrobenzol. Lymphocytes of workers were cultured before and 13 weeks after starting professional activity. The latter showed a significant increase in both CAs and SCEs. Smokers (11 individuals) and non-smokers (12 individuals) were indistinguishable with respect to the frequencies of CAs or SCEs before starting professional activity, 13 weeks later smokers exhibited significantly more SCEs than non-smokers. This strongly suggests a comutagenic interaction of cigarette smoke and exposure to chemicals during drug production. On the basis of the technology applied the compound inducing CAs and SCEs in lymphocytes of smoking workers seems to be 2-acetamino-4-nitrophenol.

Sister chromatid exchanges in patients with oral submucous fibrosis

The incidence of sister chromatid exchange (SCE) was investigated in the lymphocyte chromosomes of 45 patients with oral submucous fibrosis and 56 age- and sex-matched nonsmoking controls. The frequency of SCE was 9.26 +/- 2.15 in patients with oral submucous fibrosis, which was significantly higher than the mean SCE value of 5.49 +/- 1.24 observed in normal controls. The frequency of SCE in patients with oral submucous fibrosis addicted to the habit of betel with tobacco chewing, "bidi"/cigarette smoking and combined habits of chewing and smoking of tobacco were 8.12 +/- 1.69, 9.43 +/- 1.87, and 10.06 +/- 2.28, respectively. These values were also significantly higher as compared with the SCE values observed in normal controls.

Induction of nuclear aberrations by smokeless tobacco in epithelial cells of human oral mucosa

Cytologic and cytogenetic studies were performed to assess the prevalence of somatic cell genetic damage in 48 young adults equally divided to represent users and nonusers of smokeless tobacco. Exposure was ascertained by measuring saliva cotinine using capillary gas chromatography. Squamous epithelial cells sampled from the oral mucosa demonstrated significant cytologic alterations associated with tobacco exposure. The frequency of micronucleated cells was significantly (P less than .01) higher in the labial mucosa of exposed (2.22%) compared to unexposed (0.27%) individuals. The frequency of micronuclei varied widely between exposed subjects but was higher in heavily (2.48%) compared to lightly (1.29%) exposed individuals as measured by saliva cotinine levels. Morphologic classification of epithelial cell nuclei showed that the frequency of cells with normal nuclear structure was significantly (P less than .01) reduce in exposed individuals. Analysis of oral epithelial cells of five additional nonusers of smokeless tobacco but wearers of orthodontic appliances to stimulate abrasion demonstrated no difference from the nonexposed control group. Unlike the case with cigarette smokers, peripheral lymphocyte sister-chromatid exchange frequency was not affected by exposure to smokeless tobacco. The oral cytology data, however, support an interpretation of exposure-dependent nuclear alterations, including micronuclei, in the oral epithelium associated with the use of smokeless tobacco. Altogether, results suggest that use of smokeless tobacco may cause genetic damage to cells in the oral epithelium.

Analysis of sister-chromatid exchanges, cell kinetics and mitotic index in lymphocytes of smoking pesticide sprayers

Whole blood of 50 smokers who were exposed to pesticides was set up in RPMI 1640 medium, and observed for sister-chromatid exchanges (SCEs), cell kinetics (CK) and mitotic index (MI). As controls, blood samples were collected from 20 non-smokers (control I) and 27 smokers (control II) who were not exposed to pesticides. A significant increase in SCEs was observed as the duration of exposure increased. The frequency of M1 metaphases increased significantly whereas M2 and M3+ metaphases decreased in the exposed group. The mitotic index increased in control II and in the exposed population while it showed a decrease at 11-25 years' exposure.

Frequencies of chromosomal aberrations in smokers exposed to pesticides in cotton fields

Blood samples were collected from 50 smokers who were exposed to the pesticides DDT, BHC, endosulfan, malathion, methyl parathion, monocrotophos, quinolphos, dimethoate, phosphomidon, cypermethrin and fenvelrate. Samples were also collected from 20 non-smokers (control I) and 27 smokers (control II) who were unexposed to pesticides. Control II showed a significant increase in chromosomal aberrations when compared to control I. There was a significant increase in total chromosomal aberrations in smokers exposed to pesticides when compared to unexposed populations.

Constitutive heterochromatin polymorphism and chromosome damage in viral hepatitis

The frequencies of chromosomal aberrations and sister-chromatid exchanges (SCEs) were scored in relation to constitutive heterochromatin in 100 patients with viral hepatitis B, 100 patients with viral hepatitis A and 100 age- and sex-matched normal controls. 23.4%, 15% and 4% of the cells showed chromosomal aberrations in patients with hepatitis B, hepatitis A and normal controls respectively. Non-random involvement of chromosomal aberrations were also noted in chromosome 1 of patients with hepatitis B and A as compared to normal controls. The frequencies of SCEs (mean +/- S.D.) were found to be 10.40 +/- 2.83 in hepatitis B and 8.70 +/- 2.34 in hepatitis A. These values were significantly higher than the SCE frequency (mean +/- S.D.) of 5.88 +/- 2.25 observed in normal controls (P less than 0.001). The intra-chromosomal distribution of SCEs revealed a relatively increased incidence of SCEs in chromosome 1 of patients with hepatitis B and A as compared to normal controls. Analysis of constitutive heterochromatin polymorphism showed chromosome 1 qh+ to be the most frequent variant in patients with hepatitis B and A as compared to normal controls. The increased involvement of C-band variant 1 qh+ in patients with hepatitis B and A as compared to normal controls may indicate that extra heterochromatin offers additional sites for viral integration.

Correlation of DNA adduct levels in human lung with cigarette smoking

Lung cancer is the most common cancer in men in the United Kingdom and the second most common in women, accounting for between 25 and 40% of all cancer deaths. Cigarette smoking is widely accepted as the major cause of lung cancer and linear relationships have been established between the number of cigarettes smoked and lung cancer risk. Although approximately 50 carcinogenic chemicals have been identified in cigarette smoke, a causal link between specific compounds and lung cancer has yet to be made. Studies on cigarette smokers' urine, blood and placenta have provided indications of carcinogen exposure, and although the presence of covalently-bound adducts in human DNA provides evidence of exposure to carcinogens, there have been no reports of systematic studies on the levels of DNA adducts in human lung. We report here, using the 32P-post-labelling technique, that cigarette smokers have higher adduct levels than non-smokers, that there is a linear relationship between adduct levels and daily or lifetime cigarette consumption, and that people who have given up smoking for at least five years have adduct levels similar to those of non-smokers.

Sister chromatid exchanges in the lymphocytes of patients with oral leukoplakia

The incidence of sister chromatid exchange (SCE) was investigated in lymphocyte chromosomes of 59 patients with oral leukoplakia and 65 age- and sex-matched nonsmoking controls. The frequency of SCE was found to be 8.61 +/- 1.89 in patients with oral leukoplakia, which was significantly higher than the mean SCE value of 5.58 +/- 1.26 observed in normal controls. The frequency of SCE in patients with oral leukoplakia addicted to the single habit of betel with tobacco chewing, bidi/cigarette smoking, and combined habits of chewing and smoking of tobacco were found to be 7.95 +/- 1.63, 8.17 +/- 1.66, and 9.23 +/- 2.14, respectively. These values were also significantly higher as compared to the SCE values observed in normal controls.

Variation in the human lymphocyte sister-chromatid exchange frequency: results of a long-term longitudinal study

The variation in lymphocyte sister-chromatid exchange (SCE) frequency as a function of time was investigated in nonsmokers and smokers. The smokers were divided into 3 groups depending on their smoking status. The group termed 'smokers' participated in a program to stop smoking but did not reduce or eliminate their use of tobacco; 'smoke enders' successfully completed the smokending program and remained free of tobacco for the duration of the study, while the 'variable' group stopped smoking for a limited time but then resumed smoking. 8 or more blood samples per person were obtained over a period of at least 12 months. The SCE frequencies for each of these groups were compared with each other and with those of two previous longitudinal study groups from our laboratory. The proportion of high-frequency cells (HFCs) was also determined for each sample. The results confirm our previous finding that SCE frequencies and the proportion of HFCs observed in separate samples from the same individual are more likely to be different as the time between samples increases. We also show that smokers have significantly more SCEs and HFCs than do nonsmokers, that SCE frequencies in smokers do not decline for at least 12 months when smoking is stopped, and that among smokers, significant seasonal variation in the SCE frequency occurs. These results provide useful information concerning the effects of smoking upon SCE frequencies, and will be helpful in designing and interpreting the results of long-term human population cytogenetic studies.

Factors that influence formation of sister chromatid exchanges in human blood lymphocytes

Sister chromatid exchange (SCE) reflects an interchange of DNA sequences between helices in a replicating chromosome. This was initially accomplished by Taylor and colleagues (1957) using tritiated thymidine incorporation followed by autoradiography. The development of an elegant technique for differential staining of sister chromatids by incorporating a thymidine analog, 5-bromodeoxyuridine (BrdU) has greatly simplified the detection of SCEs in metaphase chromosomes. In recent years, the analysis of SCE has been considered to be a highly sensitive and additional (i.e., with chromosome aberrations) end point for measuring mutagenic/carcinogenic potential of various environmental agents and is increasingly being used to detect and differentiate among chromosome fragility human diseases that predispose to neoplasia. Attention has been focused to see if the induction of SCEs in lymphocyte cultures can be used as a reliable "biological dosimeter" for genetic risk assessment and to monitor the exposed populations. Several physical or preparatory as well as biological factors that modify the response and formation of SCEs make the monitoring difficult. The purpose of this article is to review and analyze these factors to facilitate an effective development of a standard protocol for SCE testing and for appropriate evaluation of test results. This may also provide clues to understand the yet unknown molecular mechanism(s) and biological significance of SCE formation.

Increased sister chromatid exchange associated with smoking and coffee consumption

Sister chromatid exchange (SCE) is a very sensitive cytogenetic assay for detecting exposure to chemical mutagens and carcinogens. One application of SCE is the monitoring of populations believed to be exposed to such agents. We have, however, relatively little knowledge about common lifestyle factors that may influence SCE and therefore complicate any study designed to examine the effects of exposure to genotoxins. In this study, we assessed the effect of cigarette smoking and coffee consumption on SCE. Smoking was associated with an increase of approximately 2 SCEs per cell and a decrease in cell proliferation. A positive linear relationship between SCE and coffee consumption was also observed. This effect was similar for smokers and nonsmokers. Additionally, the folic acid content of cell culture medium seemed to affect neither SCE nor cell proliferation.

Variations of SCE frequencies in peripheral lymphocytes of ex-smokers

We measured SCE frequencies over a period of 8 months in 14 smokers who stopped smoking at the start of the study. In a first group of 10 subjects, who did not resume smoking during the period of cytogenetic follow-up, a lowering of SCE frequencies was already evident after 18 days and this became statistically significant after 78 days. SCE decrease was related to the logarithm of the period (in days) for which smoking was interrupted (r = 0.98; p less than 0.001). In a second group of 4 subjects, who at various times resumed smoking, the decrease of SCE followed the same pattern as in the first group during the period of nonsmoking, but SCE frequencies rose even higher once smoking was resumed. Our study indicates that the decrease of SCE in ex-smokers is rather rapid during the first 78 days after stopping smoking, and much slower from the 78th to the 233rd day.

Effects of 5-bromo-2-deoxyuridine concentration and alpha-naphthoflavone on the association between smoking and the frequency of sister-chromatid exchanges in lymphocytes from maternal and cord blood

The frequency of sister-chromatid exchanges was analyzed in maternal and cord blood lymphocytes obtained at delivery from 23 nonsmokers and 21 smokers. Lymphocytes were cultured under 3 conditions: in the presence of 100 microM 5-bromo-2-deoxyuridine (BUdR), 20 microM BUdR and 20 microM BUdR with 40 microM alpha-naphthoflavone (ANF). Under all assay conditions, frequencies of SCEs were consistently higher for maternal lymphocytes than for cord lymphocytes. There was no association between SCE values for cultures of the same blood specimen with 100 microM BUdR and 20 microM BUdR. When cultured with 100 microM BUdR, maternal lymphocytes from smokers had a mean SCE frequency of 13.5, which was significantly higher than the value of 11.1 observed for nonsmokers (p = 0.001 by the Wilcoxon rank sum test). Maternal smoking had no significant effect on overall frequencies of SCEs in maternal blood cultured with 20 microM BUdR either with or without ANF or when the differential between cells cultured with and without ANF was considered. Use of caffeinated beverages was associated with increased SCE values for maternal lymphocytes cultured with 20 microM BUdR (Tau beta = 0.36, p = 0.02 for the Kendall's Rank Correlation), but no such association was seen with 100 microM BUdR. For cord blood lymphocytes, however, neither smoking nor caffeine use were associated with SCE values obtained by any of the assay conditions used. The findings suggest that results of human monitoring studies using SCEs could differ depending on the concentration of BUdR used in cultures.

The effect of tobacco smoking on the frequency of sister chromatid exchanges in human lymphocyte chromosomes

The incidence of sister chromatid exchange (SCE) was investigated in the lymphocyte chromosomes of 24 bidi smokers, 18 cigarette smokers, and 20 normal nonsmoking controls. Bidi and cigarette smokers had a mean SCE per cell of 10.12 +/- 2.41 and 8.15 +/- 1.62, respectively, which were significantly higher than the mean value of 5.48 +/- 1.29 found in controls. Higher frequencies of SCE were also observed in individuals who smoked more than ten bidis or cigarettes per day, compared with people who smoked less than ten bidis or cigarettes per day, respectively. Individuals who smoked bidis or cigarettes for more than 10 years also showed an increased frequency of SCE as compared with those who smoked bidis or cigarettes for less than 10 years.

Sister-chromatid exchange and cell proliferation in cultured lymphocytes of passively and actively smoking restaurant personnel

Sister-chromatid exchange frequencies were measured in peripheral lymphocytes of 12 cigarette smokers, 20 passive smokers, and 14 non-smokers with no regular exposure to tobacco smoke. All active and passive smokers worked as waiters and waitresses in restaurants. The passive smokers showed neither an increased mean SCE value nor an increased number of high SCE frequency cells (HFCs) when compared to non-exposed non-smokers. The incidence of SCEs and HFCs was observed to be elevated (P less than 0.01; P less than 0.05, resp.) among the active smokers. The proliferation rate of lymphocytes in whole blood cultures from the different exposure groups was also studied. The proportion of cells in first mitosis was lower and the mean replication index (RI) higher among the smokers than among non-smoker controls. However, no significant correlation was observed between the individual mean SCE and the replication index.

Characterization of noncholinergic nicotine receptors on human granulocytes

The noncholinergic nicotine receptor on leukocytes identified earlier [Davies et al., Molec. Cell. Biochem. 44, 23 (1982)] was further characterized. Structure-activity relationships showed that a pyrrolidine ring containing a basic N atom is an important structural feature for ligands that bind to the receptor. Accordingly, the carcinogenic component of tobacco smoke, N-nitrosonornicotine, does not bind to the receptor. The stereoselectivity for the d-isomer, which was confirmed using [3H]d-nicotine as a ligand, together with the absolute configurational relationship between d-nicotine and L-proline, suggested that basic peptides containing proline as the N-terminal amino acid would bind to the receptor. The finding that Pro-Lys-Pro-Arg, which has been reported to inhibit granulocyte phagocytosis, bound to the receptor with an IC50 value of 3.5 microM is compatible with this idea. An increase in receptor binding, which was observed in the presence of plasma, could be ascribed to bicarbonate. The presence of bicarbonate in the binding assay, even when the pH of the buffer was carefully controlled, resulted in an increase (approximately 2-fold) in the apparent number of receptors without affecting the Kd value significantly. Increasing the pH of the buffer in the absence of bicarbonate also increased receptor binding, suggesting that bicarbonate may increase receptor binding by its known ability to increase intracellular pH at constant extracellular pH. Preincubation of cells with d-nicotine under certain conditions reduced the subsequent binding of [3H]d-nicotine to the receptor.

Investigations of the influence of nonsteroidal antirheumatic drugs on the rates of sister-chromatid exchange

For detection of possible damage to genetic material due to nonsteroidal antirheumatic drugs, a technique was used to determine sister-chromatid exchange rates. The SCE rates before and after therapeutic application of several nonsteroidal antirheumatic drugs (diclofenac, flurbiprofen, ibuprofen, indomethacin, isoxicam, ketoprofen, piroxicam, pirprofen, tiaprofenic acid) were determined in human lymphocytes in vivo. The cytogenetic investigations of these nonsteroidal antirheumatic agents did not reveal any genetic effects during a treatment period of two weeks.

Urine mutagenicity, chromosomal abnormalities and sister chromatid exchanges in lymphocytes of nurses handling cytostatic drugs

The effects of handling antineoplastic drugs were examined in 17 nurses working in a pneumology department in a hospital in the Paris area. Twenty-five others in the same department who were not handling such drugs acted as controls. Exposure to antineoplastic drugs was evaluated by questionnaire and by assessment of urine mutagenicity. The cytogenetic repercussions of exposure were assessed by examining sister chromatid exchanges and chromosomal abnormalities in circulating lymphocytes. The urine of the exposed nurses was significantly more mutagenic than that of the controls. No cytogenetic abnormalities were revealed in the exposed subjects since both these and the control nurses exhibited similar frequencies of chromosomal abnormalities and similar average numbers of sister chromatid exchanges in circulating lymphocytes. However, in smokers, the urine was significantly more mutagenic compared to that of nonsmokers, chromosomal abnormalities were twice as frequent, and the number of sister chromatid exchanges was significantly larger. Comparison of these results with the findings of other authors suggests that the moderate exposure to antineoplastic drugs prevailing in this pneumology department (i.e., an average of about 11 infusions per week) does not cause detectable cytogenetic abnormalities even though it significantly increases urine mutagenicity.

In vitro studies of biological effects of cigarette smoke condensate. II. Induction of sister-chromatid exchanges in human lymphocytes by weakly acidic, semivolatile constituents

Cigarette smoke condensate is known to enhance the frequency of sister-chromatid exchanges (SCE) in human lymphocytes in vitro and some of the activity has been found in the most volatile part of the particulate phase, the semivolatile fraction. In this study we have investigated the chemical composition and the SCE-inducing activity of the weakly acidic, semivolatile fraction of a cigarette smoke condensate. A number of individual weakly acidic compounds were also tested for their SCE-inducing effects. The weakly acidic fraction was separated by preparative gel chromatography into 11 subfractions (F1-F11). The chemical composition was determined by gas chromatography and gas chromatography-mass spectrometry. Measurements of the effects on SCE in human lymphocytes were used to evaluate the genotoxic effects. All fractions except F11 induced SCE in a dose-dependent way. The most active fraction was F4 which contained mainly alkyl-2-hydroxy-2-cyclopenten-1-ones. The individual compounds to be tested for induction of SCE were selected on the basis of their abundance in the weakly acidic subfractions and on the basis of their occurrence in the environment. Of 23 tested compounds, most of which were alkylphenols, 7 induced SCE, i.e., catechol, 2-(1-propenyl)phenol, cyclotene, maltol, isoeugenol, 2-methoxyphenol (guaiacol) and vanillin. Many of these are important flavor components that occur not only in tobacco and tobacco smoke but also in food, candies, beverages and perfumes.

A study of multiple biological markers in twins

Genetic and environmental influences on the phenotypic expressions of several biological markers were studied in 18 monozygous (MZ) and 8 dizygous (DZ) twin pairs. Zygosity was determined using ABO, Rh, and HLA. The biomarkers studied included: T & B lymphocytes, suppressor and helper T lymphocytes (T gamma, T mu), T cell (PHA) mitogen activation (MA), serum immunoglobulins (IgA, IgM, and IgG), plasma carcinoembryonic antigen (CEA), aryl-hydrocarbon hydroxylase (AHH) and sister chromatid exchange (SCE) in lymphocytes. Temporal variation of markers over a 6-month period was not significant. The mean absolute differences between levels from first and second blood draws were less than one standard deviation. Variability associated with age was not significant. Females had higher levels of T lymphocytes than males. A gender related association was observed for the IgM immunoglobulin test: females had a higher mean level of IgM. Smoking was found to influence the levels of SCE, T helper lymphocytes and mitogen activation. The variability of these biomarkers within and between twin pairs was quantified. Immunoglobulin levels, particularly that of IgM, showed statistically greater similarity within MZ twins than within DZ twins. Several other markers suggested heritability.

Dose-responsive increase in sister-chromatid exchanges in bone-marrow cells of mice exposed nose-only to whole cigarette smoke

The effect of whole cigarette smoke exposure on bone-marrow sister-chromatid exchanges (SCEs) was studied in B6C3F1 mice. Animals were exposed nose-only to 10% (v/v) cigarette smoke 5 days/week for 2 weeks. Four dose levels of cigarette smoke (1, 4, 9 and 18 exposures/day) were studied using 2 cigarette types, Kentucky reference 3A1 (3A1) and American Blend (AB). A single exposure represented approximately 1 cigarette. A dose-dependent increase in SCEs was observed for both the 3A1 and AB cigarettes at dose levels which had no effect on bone-marrow cell-replication kinetics. These findings represent the first demonstration of a dose-responsive increase in cigarette smoke-induced SCEs in a rodent model system.

Sister chromatid exchanges: a reexamination of the evidence for sex and race differences in humans

Published evidence for human sex and race differences in sister chromatid exchange (SCE) levels is reexamined. There is substantial support for the conclusion that women average approximately 0.5 SCE/cell higher than men among normal healthy adults. An index of heterogeneity for SCE counts for cells from a single subject is introduced, and this statistic is applied to the data of Butler [1981], who compared Caucasians, Blacks, Native Americans, and Orientals with regard to SCE levels. There is evidence in Butler's data of differences in the heterogeneity index among these four racial groups, but this finding needs independent verification in a larger study.

Sister-chromatid exchanges in lymphocytes of smokers in an experimental study

The frequency of sister-chromatid exchanges (SCEs) was studied in peripheral blood lymphocytes of 26 young male smokers and 10 non-smokers who had recently entered military service. The levels of SCEs were examined in 4 consecutive blood samples taken after short experimental periods of smoking only low-tar (LT) or medium-tar (MT) cigarettes. The incidence of SCEs was significantly higher in the the group of smokers than in the group of non-smokers. The SCE levels of the smokers were found to be associated with the personal smoking history; the observed increase in the SCE frequency correlated with the years of smoking measured as cumulative pack years. The difference in type of cigarette did not influence the SCE frequencies.

Increased sister-chromatid exchange in bone-marrow cells of mice exposed to whole cigarette smoke

Using defined cigarette smoke exposure conditions, BC3F1/Cum mice were exposed nose-only to two different types of whole cigarette smoke on a daily basis for 1 week and up to 46 weeks. The number of sister-chromatid exchanges (SCEs) per metaphase was determined in bone-marrow cells. Studies were scheduled so that all cytogenetic observations were made 2-3 days after the last smoke exposure. Exposure to either type of smoke on a daily basis for 1 week or up to 46 weeks resulted in a 2-fold increase in SCEs over sham-exposed control mice. In animals exposed either chronically or for 1 week to either type of smoke, the increase in SCEs persisted for at least 1 week after cessation of smoke exposure. This is the first demonstration of the induction of SCEs in laboratory animals that have been exposed to cigarette smoke in vivo.

Human health situation and chromosome alterations: sister chromatid exchange frequency in lymphocytes from passive smokers and patients with hereditary diseases

Lymphocytes from passive smokers, and patients with FA, Alz, or FPC were studied for SCEs in cultures treated with MMC, 4NQO, or MNNG. Fanconi anemia lymphocytes were also studied for cell cycle Tab. 3. Mean SCE frequencies in FPC or normal cells. (Table; see text) kinetics, and CAs after completion of 1, 2, or 3 or more divisions in MMC-treated cultures. The results can be summarized as follows: (1) lymphocytes from passive smokers showed a slightly higher induction of SCEs than nonsmokers when exposed to MMC. (2) FA cells had about 1.4 times higher frequencies of SCEs than normal cells in both MMC-treated and untreated cultures while they showed several times higher frequencies of CAs in both cultures. Analyses of cell cycle kinetics by the sister chromatid differential staining method revealed that MMC treatments of FA and normal cells led to a clearly dose-related delay in cell turnover times, the duration of delay being much longer in FA than in normal cells. (3) Alz cells showed about 1.5 times higher induction of SCEs in MMC-treated cultures whereas they had only 10% as much SCEs as controls when exposed to 4NQO. Familial polyposis coli cells showed no significant difference in the induction of SCEs in untreated cultures and cultures treated with MMC, 4NQO, and MNNG.

The SCE test as a tool for cytogenetic monitoring of human exposure to occupational and environmental mutagens

The sister chromatid exchange (SCE) test system using human peripheral lymphocytes is proposed as a valuable tool for the cytogenetic monitoring of exposure to potential chemical mutagens in the occupational environment. We examined the SCE frequencies in organic solvent-exposed workers and reviewed the effects of occupational and environmental chemicals on SCE frequencies. The results obtained in these exposed populations are rather contradictory, which may be related to confounding factors, such as personal life style (smoking, drinking, and drugs) of the examinees, tissue culture conditions and the number of subjects examined. We discussed some practical problems for exposure estimation and sample size determination and are led to the following conclusions. 1) The possible combined effects of potential mutagens and cigarette smoking should be taken into consideration when using the SCE test system. 2) Cell cycle kinetic analysis by differential chromatid staining would provide valuable information as a biological indicator for the monitoring of the workers exposed to xenobiotics. 3) By appropriately setting the number of examinees, monitoring would become more efficient in detecting an increased SCE frequency in the exposed populations. Further studies are also required to enhance the sensitivity of the SCE test system for monitoring purposes.

Sister-chromatid exchange frequency in lymphocytes of smoking and nonsmoking mothers and their newborn infants

Sister-chromatid exchange (SCE) frequency in lymphocytes of 8 smoking mothers and their 9 newborns (one subject bearing twins) was compared to 6 mothers who had never smoked and their 6 newborn infants. Mothers in the first group were required to have smoked throughout pregnancy and to have a minimum of 15 pack-years smoking history. Results confirm our earlier smoking effect reported for adults, deny an effect on the newborn, and concur with other studies that show neonates have consistently lower SCE frequencies than adults. Overall, results are consistent with the idea that toxic substances in tobacco smoke interact with chromosomal DNA of circulating human lymphocytes.