Role of oxygen free radicals in the induction of sister chromatid exchanges by cigarette smoke

Evaluation of Antioxidant Capacity and Cotinine Levels of Saliva in Male Smokers and Non-smokers

Background

The cigarette compounds are associated with the increase in the incidence of oral cancer and precancerous lesions. Salivary antioxidant system plays an important role in anti-carcinogenic capacity of saliva. Cotinine, a nicotine metabolite, has a longer half-life in comparison with nicotine and is a suitable marker for exposure to cigarette smoke. This study aims to measure total antioxidant capacity (TAC) and cotinine level in saliva of smokers and non-smokers and compare salivary cotinine level and TAC in each group.

Methods

In this cross-sectional study, 32 smokers and 34 non-smokers were recruited by consecutive sampling from Department of Oral Medicine, School of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran. Salivary cotinine and TAC concentrations were determined using the enzyme-linked immunosorbent assay (ELISA) technique. For data analysis, correlation tests of Spearman, Mann-Whitney U, and independent samples t-test were used.

Findings

A significant difference was observed between the two groups in the mean cotinine level and in the mean TAC (P = 0.015, P = 0.027, respectively). TAC showed a weak negative correlation with the cotinine level, but the difference was not significant (P = 0.651).

Conclusion

Antioxidants are of great importance to smokers because antioxidants are able to scavenge free radicals found in cigarette smoke. According to the results of present study, the salivary TAC in smokers was lower than that of non-smokers, and the salivary cotinine level in smokers was higher than non-smokers. Therefore, smoking endangers the oral cavity health by reducing the salivary TAC. Further studies with a higher sample size and other factors affecting the salivary TAC are needed for definitive comment.

The effects of cigarette smoke extract on ovulation, oocyte morphology and ovarian gene expression in mice

Cigarette smoking can harm fertility, but the existing research has targeted primarily on ovarian follicles, embryos or sex hormone. In this study, we tested cigarette smoke extract on ovulation, oocyte morphology and ovarian gene expression associated with inhibition of oxidative stress using C57BL/6 mice. Mice in the experimental group were administered a cigarette smoke extract (CSE) solution (2 mg/ml) orally daily, while the blank control group was given dimethylsulfoxide (DMSO). A positive control group (menadione) was used that received an intraperitoneal injection of 15 mg/kg menadione in oil solution daily. We found that the CSE group manifested a reduced diameter of zona pellucida-free oocyte (ZP-free OD) and a morphologically misshapen first polar body (PB). Our results suggest that CSE exposure is associated with a shrink size and poor quality of oocytes. Quitting smoking is a wise choice to ensure good fertility.

Cigarette smoke-induced kinin B1 receptor promotes NADPH oxidase activity in cultured human alveolar epithelial cells

Pulmonary inflammation is an important pathological feature of tobacco smoke-related lung diseases. Kinin B1 receptor (B1R) is up-regulated in the rat trachea chronically exposed to cigarette-smoke. This study aimed at determining (1) whether exposure to total particulate matter of the cigarette smoke (TPM) can induce B1R in human alveolar epithelial A549 cells, (2) the mechanism of B1R induction, (3) the functionality of de novo synthesized B1R, and (4) the role of B1R in TPM-induced increase of superoxide anion (O₂(●⁻)) level. Results show that A549 cells exposed to 10 μg/ml TPM increased O₂(●⁻) level along with B1R (protein and mRNA) and IL-1β mRNA. In contrast, B2R and TNF-α mRNA were not affected by TPM. The increasing effect of TPM on O₂(●⁻) level was not significantly affected by the B1R antagonist SSR240612. TPM-increased B1R mRNA was prevented by co-treatments with N-acetyl-l-cysteine (potent antioxidant), diphenyleneiodonium (NADPH oxidase inhibitor), IL-1Ra (interleukin-1R antagonist) and SN-50 (specific inhibitor of NF-kB activation) but not by pentoxifylline (TNF-α release inhibitor), indomethacin and niflumic acid (COX-1 and -2 inhibitors). Stimulation of B1R with a selective agonist (des-Arg⁹-BK, 10 μM; 30 min) increased O₂(●⁻)production which was prevented by apocynin and diphenyleneiodonium (NADPH oxidase inhibitors). Data suggest that the increased expression of B1R by TPM in A549 cells is mediated by oxidative stress, IL-1β and NF-kB but not by cyclooxygenases or TNF-α. The amplification of O₂(●⁻) levels via the activation of B1R-NADPH oxidase may exacerbate pulmonary inflammation and contribute to the chronicity of tobacco smoke-related lung diseases.

Lipid patterns in the saliva of smoking young adults

Salivary lipids are important for the maintenance of oral cavity health. Elevated salivary lipid levels are associated with an increase of caries incidence, plaque development, calculus formation and periodontal disease. However, the regulation of lipid salivary levels is scarcely known. Cigarette smoke is considered a risk factor for oral cavity diseases. We study how cigarette smoke may affect the secretion of salivary lipids. To this purpose, we determine the salivary levels of cholesterol and of glycerolipids in saliva sampled from smokers and non-smokers at various times of day. We observe an increase of glycerophospholipid and a decrease of cholesterol levels in the smokers' saliva collected at 10 p.m. On the other hand, unsaturated fatty acids in chief phospholipids of saliva are lower in smokers at 7 a.m. Therefore, for the first time, we demonstrate that cigarette smoke induces variations of saliva lipid pattern in young people even moderately smoking.

Effects of cigarette smoking on reproduction

BACKGROUND Cigarette smoking is associated with lower fecundity rates, adverse reproductive outcomes and a higher risk of IVF failures. Over the last few decades, prevalence of smoking among women of reproductive age has increased. This review focuses on current knowledge of the potential effects of smoke toxicants on all reproductive stages and the consequences of smoke exposure on reproductive functions. METHODS We conducted a systematic review of the scientific literature on the impact of cigarette smoking and smoke constituents on the different stages of reproductive function, including epidemiological, clinical and experimental studies. We attempted to create hypotheses and find explanations for the deleterious effects of cigarette smoke observed in experimental studies. RESULTS Cigarette smoke contains several thousand components (e.g. nicotine, polycyclic aromatic hydrocarbons and cadmium) with diverse effects. Each stage of reproductive function, folliculogenesis, steroidogenesis, embryo transport, endometrial receptivity, endometrial angiogenesis, uterine blood flow and uterine myometrium is a target for cigarette smoke components. The effects of cigarette smoke are dose-dependent and are influenced by the presence of other toxic substances and hormonal status. Individual sensitivity, dose, time and type of exposure also play a role in the impact of smoke constituents on human fertility. CONCLUSIONS All stages of reproductive functions are targets of cigarette smoke toxicants. Further studies are necessary to better understand the deleterious effects of cigarette smoke compounds on the reproductive system in order to improve health care, help to reduce cigarette smoking and provide a better knowledge of the molecular mechanisms involved in reproductive toxicology.

Evaluation of in vitro assays for assessing the toxicity of cigarette smoke and smokeless tobacco

BACKGROUND

In vitro toxicology studies of tobacco and tobacco smoke have been used to understand why tobacco use causes cancer and to assess the toxicologic impact of tobacco product design changes. The need for toxicology studies has been heightened given the Food and Drug Administration's newly granted authority over tobacco products for mandating tobacco product performance standards and evaluate manufacturers' health claims about modified tobacco products. The goal of this review is to critically evaluate in vitro toxicology methods related to cancer for assessing tobacco products and to identify related research gaps.

METHODS

PubMed database searches were used to identify tobacco-related in vitro toxicology studies published since 1980. Articles published before 1980 with high relevance also were identified. The data were compiled to examine (a) the goals of the study, (b) the methods for collecting test substances, (c) experimental designs, (d) toxicologic end points, and (e) relevance to cancer risk.

RESULTS

A variety of in vitro assays are available to assess tobacco smoke that address different modes of action, mostly using non-human cell models. However, smokeless tobacco products perform poorly in these assays. Although reliable as a screening tool for qualitative assessments, the available in vitro assays have been poorly validated for quantitative comparisons of different tobacco products. Assay batteries have not been developed, although they exist for nontobacco assessments. Extrapolating data from in vitro studies to human risks remains hypothetical.

CONCLUSIONS

In vitro toxicology methods are useful for screening toxicity, but better methods are needed for today's context of regulation and evaluation of health claims.

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.

Induction of oxyradicals by arsenic: implication for mechanism of genotoxicity

Although arsenic is a well-established human carcinogen, the mechanisms by which it induces cancer remain poorly understood. We previously showed arsenite to be a potent mutagen in human-hamster hybrid (A(L)) cells, and that it induces predominantly multilocus deletions. We show here by confocal scanning microscopy with the fluorescent probe 5',6'-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate that arsenite induces, within 5 min after treatment, a dose-dependent increase of up to 3-fold in intracellular oxyradical production. Concurrent treatment of cells with arsenite and the radical scavenger DMSO reduced the fluorescent intensity to control levels. ESR spectroscopy with 4-hydroxy-2,2,6,6-tetramethyl-1-hydroxypiperidine (TEMPOL-H) as a probe in conjunction with superoxide dismutase and catalase to quench superoxide anions and hydrogen peroxide, respectively, indicates that arsenite increases the levels of superoxide-driven hydroxyl radicals in these cells. Furthermore, reducing the intracellular levels of nonprotein sulfhydryls (mainly glutathione) in A(L) cells with buthionine S-R-sulfoximine increases the mutagenic potential of arsenite by more than 5-fold. The data are consistent with our previous results with the radical scavenger DMSO, which reduced the mutagenicity of arsenic in these cells, and provide convincing evidence that reactive oxygen species, particularly hydroxyl radicals, play an important causal role in the genotoxicity of arsenical compounds in mammalian cells.

Induction of oxyradicals by arsenic: implication for mechanism of genotoxicity

Although arsenic is a well-established human carcinogen, the mechanisms by which it induces cancer remain poorly understood. We previously showed arsenite to be a potent mutagen in human-hamster hybrid (A(L)) cells, and that it induces predominantly multilocus deletions. We show here by confocal scanning microscopy with the fluorescent probe 5',6'-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate that arsenite induces, within 5 min after treatment, a dose-dependent increase of up to 3-fold in intracellular oxyradical production. Concurrent treatment of cells with arsenite and the radical scavenger DMSO reduced the fluorescent intensity to control levels. ESR spectroscopy with 4-hydroxy-2,2,6,6-tetramethyl-1-hydroxypiperidine (TEMPOL-H) as a probe in conjunction with superoxide dismutase and catalase to quench superoxide anions and hydrogen peroxide, respectively, indicates that arsenite increases the levels of superoxide-driven hydroxyl radicals in these cells. Furthermore, reducing the intracellular levels of nonprotein sulfhydryls (mainly glutathione) in A(L) cells with buthionine S-R-sulfoximine increases the mutagenic potential of arsenite by more than 5-fold. The data are consistent with our previous results with the radical scavenger DMSO, which reduced the mutagenicity of arsenic in these cells, and provide convincing evidence that reactive oxygen species, particularly hydroxyl radicals, play an important causal role in the genotoxicity of arsenical compounds in mammalian cells.

Tobacco smoke induces mitochondrial depolarization along with cell death: effects of antioxidants

Smoking has been associated with a large number of diseases, in particular cancers. Among the many substances identified in tobacco smoke, reactive oxygen species (ROS) are major carcinogens. We have previously reported that exposure of mammalian cells to tobacco smoke induces the expression of stress proteins, as well as apoptosis (programmed cell death). Here we examined the effects of tobacco smoke on mitochondrial membrane potential (deltapsim), since mitochondria have been proposed to control the effector phase of apoptosis. We used normal human monocytes for these experiments, with the prospect for application of deltapsim as a biomarker of oxidative stress. Tobacco smoke induced mitochondrial depolarization at 3 h, and apoptosis (or necrosis for higher concentrations) after 16 h. Apoptosis was assessed by both a functional approach (annexin V binding) and morphological analysis (electron microscopy). N-acetyl-cysteine prevented tobacco smoke-induced deltapsim disruption and apoptosis, while the caspase inhibitor Z-VAD.Fmk did not affect deltapsim, though preventing apoptosis, and superoxide dismutase had no effect. Our data designate mitochondria as a target for ROS-mediated effects of tobacco smoke exposure.

Effect of smoking one cigarette on antioxidant metabolites in the saliva of healthy smokers

Concentrations of glutathione, uric acid and total antioxidant activity, expressed as Trolox (a water-soluble vitamin E analogue) equivalent, were measured in the saliva of healthy non-smokers and smokers before and just after smoking a single cigarette. There was no statistically significant difference between smokers and non-smokers in uric acid concentrations and total radical-trapping antioxidant capacity, but glutathione concentrations were significantly (p < 0.05) higher in smokers. Smoking of a single cigarette induced a significant reduction in glutathione concentration (p < 0.05). Salivary antioxidant power may affect individual sensitivity toward tobacco stress.

Iron-induced tissue damage and cancer: the role of reactive oxygen species-free radicals

Oxygen is poisonous, but we cannot live without it. The high oxidizing potential of oxygen molecules (dioxygen) is a valuable source of energy for the organism and its reactivity is low; that is, spin forbidden. However, the dioxygen itself is a 'free radical' and, especially in the presence of transition metals, it is a major promoter of radical reactions in the cell. Humans survive only by virtue of their elaborate defense mechanisms against oxygen toxicity. Iron is the most abundant transition metal in the human body. Because iron shows wide variation in redox potential with different co-ordination ligands, it may be used as a redox intermediate in many biological mechanism. However, it is precisely this redox activeness that makes iron a key participant in free radical production. The current research on the relationship between iron and cancer is briefly reviewed. Research results are reported here which indicate that iron, when bound to certain ligands, can cause free-radical mediated tissue damage and become carcinogenic. The present study also suggests that iron may also have a significant role in spontaneous human cancer.

Genotoxicity and DNA adduct formation of incense smoke condensates: comparison with environmental tobacco smoke condensates

Indoor air pollution has now been recognized as a potentially important problem for public health, since people spend most of their day in closed environments. Incense burning is possibly associated with elevated risks of leukemia and brain tumor in children from the epidemiological studies. Thus, evaluation of the genotoxicity of smoke condensates from incense burning is needed. We examined the genotoxicity of incense smoke condensates (ISC) using the Ames test in S. typhimurium strains with different mutagenic specificity and level of metabolic enzyme, the SOS chromotest in E. coli PQ37, and sister chromatid exchange assay in Chinese hamster ovary cells (SCE/CHO). The genotoxicity of environmental tobacco smoke condensates (TSC) was also evaluated by the three assays to compare with the genotoxicity of ISC. ISC showed a positive response in TA98, but not in TA100. It suggested that ISC only contained frame shift mutagens. The mutagenicity of ISC in both strains of TA98NR with deficient nitroreductase and TA98/1,8-DNP6 with deficient O-acetyltransferase was markedly decreased compared to that in TA98 strain. However, the mutagenicity was enhanced in YG1024 with overexpression of O-acetyltransferase activity. Thus, nitroarenes seemed to be responsible in part for the mutagenicity of ISC. Interestingly, all of the four ISC and two TSC samples showed a dose-dependent genotoxic response in the SOS chromotest with E. coli PQ37 but a low SCE induction of those samples were observed in CHO cells. When the genotoxicity was analyzed based on the condensates per one gram of original samples, the genotoxicity of two TSC condensates in prokaryotic cells was higher than that of four ISC samples except for the genotoxicity of TSC-2 in TA98 strain. However, the genotoxicity of certain ISC in eukaryotic cells based on the SCE/CHO assay was higher than that of TSC. To compare the covalent binding of DNA reactive intermediates of ISC and TSC to S. typhimurium TA98, the DNA adducts were evaluated by the 32P-postlabeling method with butanol extraction version. Similar diagonal radioactive zone (DRZ) was observed between ISC and CSC. However, DNA adduct levels induced by TSC were much greater than that of ISC.

No influence of beta-carotene on smoking-induced DNA damage as reflected by sister chromatid exchanges

The putative cancer-preventive potential of beta-carotene may be explained by its anti-oxidant capacity to prevent free-radical-induced DNA damage. To evaluate this hypothesis, we studied the effect of 14 weeks of beta-carotene supplementation on the frequency of sister chromatid exchanges (SCE) in lymphocytes in 143 heavy smokers in a randomized, double-blind, placebo-controlled intervention trial. Age, smoking habits and pretreatment blood levels of cotinine, beta-carotene, retinol and vitamins C and E were similar in the placebo group (n = 73) and the treatment group (n = 70). Plasma beta-carotene levels increased 13-fold in the treatment group during intervention, whereas the other parameters remained stable in both groups. Initial SCE levels were similar in the treatment and placebo groups (5.10 +/- 0.98 vs. 5.00 +/- 0.99 SCE/lymphocyte). During the intervention, both groups showed an almost identical decrease, and at the end of the intervention period there was no difference in SCE levels between the treatment and the placebo groups (4.37 +/- 0.38 vs. 4.24 +/- 0.37 SCE/lymphocyte). This study shows no protective effect of beta-carotene on DNA damage as reflected by sister chromatid exchanges in lymphocytes. Our results thus do not yield support for a cancer-preventive mechanism of beta-carotene involving this form of DNA damage. It cannot be excluded, however, that beta-carotene prevents other forms of smoking-induced DNA damage, affects other tissues, or is preventive in later stages of carcinogenesis.

Blood superoxide dismutase and plasma malondialdehyde among workers exposed to asbestos

Blood superoxide dismutase (SOD) and plasma malondialdehyde (MDA) (an indicator of lipid peroxidation [LPO]) were determined in 97 randomly selected asbestos exposed workers (age range: 25-60 years, mean duration of exposures 19.8 +/- 8.3 years) and in 42 healthy male controls. MDA, SOD, and MDA/SOD ratio in asbestos exposed workers were significantly higher than in controls. Among both the controls and exposed workers neither age nor smoking was related to SOD or MDA levels. SOD was significantly positively correlated with MDA among the exposed workers. Such correlation was not observed among the controls. SOD but not MDA was significantly positively correlated with the duration of exposure to asbestos. Mean levels of SOD or MDA in exposed workers with radiographic signs of lung fibrosis or pleural thickening did not differ significantly from those without such signs. The results confirm the possible involvement of LPO and development of anti-oxidant mechanism(s) of prolonged exposure to asbestos in humans. However, SOD seems not to be the essential anti-asbestos-induced LPO. Relation between these factors and lung fibrosis is still unclear.

Sister chromatid exchange frequency in directly prepared cytotrophoblasts: demonstration of in vivo deoxyribonucleic acid damage in pregnant women who smoke cigarettes

Assessing frequency of sister chromatid exchange is a sensitive method of monitoring exposure to clastogens, mutagens, and other substances that induce deoxyribonucleic acid damage. Aware that cigarette smoke is associated with increased sister chromatid exchange in many cell types, we sought to determine whether an in vivo effect of cigarette smoke could be demonstrated by study of sister chromatid exchange in chorionic villus cells. Directly prepared cytotrophoblasts and cultured mesenchymal core cells were analyzed. Mean sister chromatid exchange frequency in cytotrophoblasts from smoking subjects (8.87 sister chromatid exchanges per cell) was significantly greater than in nonsmoking subjects (5.81 sister chromatid exchanges per cell; p less than 0.001); however, no significant difference in cultured mesenchymal core cells was found. Our results demonstrate that maternal exposure to cigarette smoke results in direct placental deoxyribonucleic damage, which in turn could explain deleterious effects of smoking on pregnancy. Increased sister chromatid exchange frequency was observed only in directly prepared cytotrophoblasts, showing the necessity of using this cell type to evaluate the effects of clastogens on placentas.

Hemolysis of rabbit erythrocytes induced by cigarette smoke

Cigarette smoke has been found to induce the hemolysis of rabbit erythrocytes. The particulate phase had more profound effect than the gas phase. Neither free radical scavengers such as ascorbic acid, uric acid and water-soluble vitamin E analogue nor antioxidant enzymes such as catalase and superoxide dismutase suppressed the cigarette smoke-induced hemolysis, suggesting that free radicals, hydrogen peroxide, and superoxide were not the active species.