Effects of smoking on spontaneous and induced sister chromatid exchanges in lymphocytes

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.

Genotoxicity of tobacco smoke and tobacco smoke condensate: a review

This report reviews the literature on the genotoxicity of mainstream tobacco smoke and cigarette smoke condensate (CSC) published since 1985. CSC is genotoxic in nearly all systems in which it has been tested, with the base/neutral fractions being the most mutagenic. In rodents, cigarette smoke induces sister chromatid exchanges (SCEs) and micronuclei in bone marrow and lung cells. In humans, newborns of smoking mothers have elevated frequencies of HPRT mutants, translocations, and DNA strand breaks. Sperm of smokers have elevated frequencies of aneuploidy, DNA adducts, strand breaks, and oxidative damage. Smoking also produces mutagenic cervical mucus, micronuclei in cervical epithelial cells, and genotoxic amniotic fluid. These data suggest that tobacco smoke may be a human germ-cell mutagen. Tobacco smoke produces mutagenic urine, and it is a human somatic-cell mutagen, producing HPRT mutations, SCEs, microsatellite instability, and DNA damage in a variety of tissues. Of the 11 organ sites at which smoking causes cancer in humans, smoking-associated genotoxic effects have been found in all eight that have been examined thus far: oral/nasal, esophagus, pharynx/larynx, lung, pancreas, myeoloid organs, bladder/ureter, uterine cervix. Lung tumors of smokers contain a high frequency and unique spectrum of TP53 and KRAS mutations, reflective of the PAH (and possibly other) compounds in the smoke. Further studies are needed to clarify the modulation of the genotoxicity of tobacco smoke by various genetic polymorphisms. These data support a model of tobacco smoke carcinogenesis in which the components of tobacco smoke induce mutations that accumulate in a field of tissue that, through selection, drive the carcinogenic process. Most of the data reviewed here are from studies of human smokers. Thus, their relevance to humans cannot be denied, and their explanatory powers not easily dismissed. Tobacco smoke is now the most extreme example of a systemic human mutagen.

Biological monitoring of young workers exposed to polycyclic aromatic hydrocarbons in engine repair workshops

Several polycyclic aromatic hydrocarbons (PAHs) are carcinogenic in rodents, while exposure to these compounds has been associated with various types of human cancer. Engine exhaust and used engine oils are major PAH sources in engine repair workshops. Urinary 1-hydroxypyrene (1-OHP) levels and some genotoxicity parameters (sister-chromatid exchange, SCE; micronucleus, MN) have been compared among engine repair workers (n = 61, age: between 13 and 18) and workers not occupationally exposed to PAH (n = 30, age: between 13 and 19). The mean value (+/- S.E.) of urinary 1-OHP excretions of workers was 4.71 +/- 0.53 micromol/mol creatinine and also mean urinary 1-OHP for controls was found to be as 1.55 +/- 0.28 micromol/mol creatinine. The mean values (+/- S.E.) of SCE frequency per cell in peripheral lymphocytes from the workers and controls were 4.47 +/- 0.09 and 4.06 +/- 0.16, respectively (p < 0.05). The mean (+/- S.E.) MN (per thousand) frequencies in peripheral lymphocytes from the workers and controls were 1.87 +/- 0.04 and 1.56 +/- 0.06, respectively (p < 0.0001). The effect of smoking for the above parameters were also evaluated.

Sister-chromatid exchanges in lymphocytes of workers exposed to trichloroethylene

To detect mutagenic effects of trichloroethylene (TCE) on humans, sister-chromatid exchanges (SCEs) were analyzed in lymphocytes of 22 workers occupationally exposed to TCE and 22 matched controls. Although urinalysis in the workers revealed their obvious exposure to TCE, no increase in SCE frequencies was found in lymphocytes of the workers. SCE analysis in lymphocytes could not detect mutagenic effects by occupational exposure to TCE on humans.

No increase in sister-chromatid exchange frequency in lymphocytes of chromium platers

To detect mutagenic effects of hexavalent chromium (Cr) in vivo, sister-chromatid exchange (SCE) frequency was analyzed in lymphocytes of 24 Cr platers occupationally exposed to hexavalent Cr and 24 matched controls. There were no significant differences in SCE frequency between the two groups. Smokers, both Cr platers and controls, had a significantly higher SCE frequency than non-smokers.