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

Less than additive interaction between cigarette smoke and chromium(VI) in inducing clastogenic damage in rodents

A combination of tobacco smoking with certain agents has been shown to exert synergistic carcinogenic effects. On the other hand, antagonism betweeen smoke and other pulmonary carcinogens has also been documented by both epidemiological and experimental data. In spite of a very large number of studies carried out for decades in workers exposed to hexavalent chromium, the influence of smoking habits on lung carcinogenesis induced by this metal has not been clarified. For this reason, we performed two studies evaluating clastogenic effects in rodents. In the first one, BDF(1) mice were exposed whole-body to mainstream cigarette smoke for 5 days and, on the last day, they received an i.p. injection of potassium dichromate. In the second study, Sprague-Dawley rats were exposed whole-body to environmental cigarette smoke for 18 consecutive days and for the same period of time they received daily intra-tracheal instillations of sodium dichromate. Individually, the two hexavalent chromium salts and cigarette smoke, either mainstream or environmental, enhanced the frequency of micronuclei in bone marrow polychromatic erythrocytes of both mice and rats. Moreover, individual exposure to either environmental cigarette smoke or sodium dichromate enhanced the frequency of micronuclei and multiple nuclei in pulmonary alveolar macrophages of rats. In both studies, combined exposure to cigarette smoke and hexavalent chromium produced less than additive clastogenic effects. These results are consistent with our previous data, showing that hexavalent chromium and either benzo[a]pyrene or cigarette smoke condensate behave antagonistically in in vitro mutagenicity test systems and that the chromium reducing capacity of human pulmonary alveolar macrophages and peripheral lung parenchyma is enhanced in smokers. Taken together, in the absence of any epidemiological evidence, these findings rule out any occurrence of synergism between cigarette smoke and hexavalent chromium, at least in certain stages of the carcinogenesis process.

Sister-chromatid exchange inducing effect of smokeless tobacco using on T-lymphocyte chromosomes

A kind of a smokeless tobacco (Maras powder) is widely used instead of cigarettes in the South Eastern region of Turkey. In this study we investigated the sister-chromatid exchange (SCE) inducing effect of this powder on the chromosomes of its users compared with smokers and nonsmokers using standard cell culture methods and SCE staining techniques. Average SCE per metaphase and total SCEs increased significantly among both smokeless tobacco users and smokers compared to nonsmokers (p < 0.01). However, the effect is significantly lower in smokeless tobacco users than in smokers (p < 0.05).

Dominant-lethal mutations and micronucleus induction in male BALB/c, BDF1 and H mice by tobacco smoke

The mutagenicity of whole tobacco smoke (TS) was examined in male BALB/c, BDF1 and H mice using the dominant lethal and micronucleus tests in bone marrow polychromatic erythrocytes. Male mice (about 80 days old) from the three strains were treated with TS on 5 days/week for 8 weeks. The animals were divided into three groups for every strain: control and two experimental groups. Two doses--low (1h treatment/day) and high (2 h treatment/day)--were used. In the first case 8 exposures of 7.5 min each with 1-min intervals were given and to realize the high dose this was repeated 4 h later. It was found that TS induces significant dominant-lethal mutations in both experimental groups of BALB/c, BDF1 and H mice (p < 0.001), but some strain differences existed. The data obtained suggest that in BALB/c and BDF1 mice TS induces dominant-lethal mutations mainly in spermatocytes, spermatogonia and gonial stem cells, while in H mice only spermatids and spermatocytes are affected. The bone marrow from each strain and each dose group was investigated for the presence of micronucleated polychromatic erythrocytes (PCE) at 5, 19, 38, 54, and 63 days after beginning of the treatment with TS, using the same exposure regimen. Exposure of male mice to TS caused an up to 2-3-fold increase in the number of PCE in the bone marrow of BALB/c and BDF1 mice in both dose groups. In H mice this effect is observed only on days 19 and 38 of sampling. No cumulative or dose-dependent effects were detected. Increased formation of micronuclei within PCE of femoral bone marrow after passive smoking was regarded as being due to the effect of TS.

Cytogenetic effects of cigarette smoke on pulmonary alveolar macrophages of the rat

To determine accurately the potential genetic damage induced by toxic inhaled agents, the cells that receive a high concentration of such agents should be analyzed. Pulmonary alveolar macrophages (PAMs) represent such cells. We compared the cytogenetic effects of cigarette smoke on PAMs of rats exposed repeatedly by different methods. This study was part of a larger investigation of the health effects resulting from different methods of exposing rats to cigarette smoke. Fischer 344/N male rats (4/group) were randomly selected from five different exposure groups: 1) nose-only sham-exposed (air) control, 2) whole-body sham-exposed control, 3) nose-only intermittent, 4) nose-only continuous, and 5) whole-body continuous. The rats were exposed 6 hr/day, 5 days/week for 22-24 days. All smoke-exposed rats received the same daily concentration x time product (600 mg.hr.m-3 for the first week, 1200 mg.hr.m-3 thereafter) of cigarette smoke. Rats were injected intraperitoneally with colchicine at the end of exposure. PAMs were obtained by lung lavage and chromosomal damage was measured. Highly significant smoke-induced differences in both structural and numerical aberrations were observed in continuously exposed rats vs. sham controls, regardless route of exposure. The structural aberrations observed were chromatid-type deletions. Both hypoploid and hyperploid cells were detected. Our data suggest that cigarette smoke is clastogenic and may disrupt spindle-fiber formation. These activities may play a role in the induction of human carcinogenesis caused by cigarette smoke exposure.

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.

Investigation of the mutagenic activity of tobacco smoke

The genotoxic effect of whole tobacco smoke was studied employing the Salmonella/microsome mutagenicity assay, the micronucleus test in mouse bone marrow and UDS in peripheral human lymphocytes. It was established that tobacco smoke (120-480 cm3 in a 16-1 glass chamber, at 1-10 min exposure time) induced a 3-9-fold increase of spontaneous his+ reversion mutation rate in S. typhimurium TA98, but not in strains TA97a, TA100 and TA102. Addition of S9 mix obtained from the liver of Aroclor 1254-treated rats was necessary to reveal the mutagenic activity of tobacco smoke. Treatment of BDF1 mice placed in a 14-1 glass chamber with tobacco smoke (600 cm3 smoke, 2 exposures of 30 min each, with a 1-min interval between them) caused a 2-fold dose-dependent elevation of the number of micronucleated PCE in bone marrow. No cumulative effect was detected when mice were treated with tobacco smoke during 2-28 consecutive days. The effect observed 24 h after tobacco-smoke exposure was abolished 48 h later. Tobacco smoke (180 or 360 cm3) passed through the culture medium (with or without S9 mix) of human peripheral lymphocytes (the cells were then incubated for 60 min at 37 degrees C) did not increase the spontaneous rate of UDS. Both the Salmonella/microsome mutagenicity assay employing S. typhimurium TA98 strain and the micronucleus test in mouse bone marrow might be useful in studying tobacco smoke-induced mutagenesis.