DNA adducts in human urinary bladder and other tissues

The Combined Effects of Healthy Lifestyle Behaviors on All-Cause Mortality: The Golestan Cohort Study

BACKGROUND

Most studies that have evaluated the association between combined lifestyle factors and mortality outcomes have been conducted in populations of developed countries.

OBJECTIVES

The aim of this study was to examine the association between combined lifestyle scores and risk of all-cause and cause-specific mortality for the first time among Iranian adults.

METHODS

The study population included 50,045 Iranians, 40 - 75 years of age, who were enrolled in the Golestan Cohort Study, between 2004 and 2008. The lifestyle risk factors used in this study included cigarette smoking, physical inactivity, and Alternative Healthy Eating Index. The lifestyle score ranged from zero (non-healthy) to 3 (most healthy) points. From the study baseline up to analysis, a total of 4691 mortality cases were recorded. Participants with chronic diseases at baseline, outlier reports of calorie intake, missing data, and body mass index of less than 18.5 were excluded from the analyses. Cox regression models were fitted to establish the association between combined lifestyle scores and mortality outcomes.

RESULTS

After implementing the exclusion criteria, data from 40,708 participants were included in analyses. During 8.08 years of follow-up, 3,039 cases of all-cause mortality were recorded. The adjusted hazard ratio of a healthy lifestyle score, compared with non-healthy lifestyle score, was 0.68 (95% CI: 0.54, 0.86) for all-cause mortality, 0.53 (95% CI: 0.37, 0.77) for cardiovascular mortality, and 0.82 (95% CI: 0.53, 1.26) for mortality due to cancer. When we excluded the first two years of follow up from the analysis, the protective association between healthy lifestyle score and cardiovascular death did not change much 0.55 (95% CI: 0.36, 0.84), but the inverse association with all-cause mortality became weaker 0.72 (95% CI: 0.55, 0.94), and the association with cancer mortality was non-significant 0.92 (95% CI: 0.58, 1.48). In the gender-stratified analysis, we found an inverse strong association between adherence to healthy lifestyle and mortality from all causes and cardiovascular disease in either gender, but no significant relationship was seen with mortality from cancer in men or women. Stratified analysis of BMI status revealed an inverse significant association between adherence to healthy lifestyle and mortality from all causes, cardiovascular disease and cancer among non-obese participants.

CONCLUSION

We found evidence indicating that adherence to a healthy lifestyle, compared to non-healthy lifestyle, was associated with decreased risk of all-cause mortality and mortality from cardiovascular diseases in Iranian adults.

XRCC1 Polymorphisms and Urinary 8-Hydroxydeoxyguanine Levels Are Associated with Urothelial Carcinoma

The aim of this study was to examine the associations between the combined effects of urinary 8-Hydroxydeoxyguanine (8-OHdG) level and polymorphisms of XRCC1 Arg194Trp and XRCC1 Arg399Gln on the risk of urothelial carcinoma (UC). We conducted a hospital-based case-control study that included 168 cases of UC and 336 age- and gender-matched healthy controls. We used polymerase chain reaction and restriction fragment length polymorphism analyses to examine the genotypes of XRCC1 Arg194Trp and XRCC1 Arg399Gln. We used a competitive in vitro enzyme-linked immunosorbent assay to determine urinary 8-OHdG levels. The XRCC1 399 Gln/Gln genotype and the XRCC1 194 Arg/Arg genotype were positively correlated to UC (OR [95%CI] = 2.27 [1.20-4.27] and 1.59 [1.06-2.36], respectively). Urinary 8-OHdG levels were associated with UC in a dose-dependent manner. Participants with the XRCC1 (Arg399Gln) Gln/Gln genotype or the G-C/A-C haplotype of XRCC1 and a high urinary 8-OHdG level had a significantly higher risk of UC than those with the Arg/Arg + Arg/Gln genotype or the G-T haplotype and a low urinary 8-OHdG level. This is the first study to investigate the combined effect of urinary 8-OHdG level and XRCC1 polymorphisms on UC risk. The findings are especially meaningful for participants with XRCC1 399Gln or XRCC1 Arg194 genotypes and a high urinary 8-OHdG level, since these variables are associated with an increased risk of UC.

Persistence of urothelial carcinoma of the bladder risk among former smokers: results from a contemporary, prospective cohort study

OBJECTIVES

Cigarette smoking is a known risk factor for urothelial carcinoma (UC) of the bladder. However, the persistence of an increased risk for UC following smoking cessation is not well established. We assessed the risk of UC among former smokers using a recent, prospective cohort with a high proportion of former smokers.

MATERIALS AND METHODS

Study participants were members of the VITamins And Lifestyle cohort (VITAL), a group of 77,719 men and women between the ages of 50 and 76 years from western Washington State. Smoking history and other risk factors were obtained at the time of recruitment. The primary outcome was a new diagnosis of UC (n =385), as determined through linkage to a population-based cancer registry.

RESULTS AND LIMITATIONS

The cohort included 8% current and 44% former smokers, and among the UC cases, 15% were current and 60% former smokers. Both the current and former smoker had an increased risk of UC compared with never smokers (hazard ratio [HRs]: 3.81; 95% confidence intervals [CI] 2.71-5.35 and 2.0; 95% CI 1.55-2.58, respectively). Among former smokers, the risk of UC increased with the pack-years smoked and decreased with the years since quitting. When both the measures of smoking were considered together, the risk of UC was similar for long-term quitters and recent quitters for a given level of pack-years. For example, for those with pack-years of 22.5-37.5, the HR of UC was 1.91 (95% CI 1.17-3.11) for the distant quitters (≥ 23.5 y before baseline) and HR = 1.92 (95% CI 1.26-2.94) among the recent quitters. Limitations include the small number of cases at the extremes of smoking history and errors in self-reported smoking history.

CONCLUSIONS

The risk of bladder cancer in former smokers remains elevated>32 years after quitting, even among those with moderate smoking histories. This argues that a history of smoking confers a lifelong increased risk of UC.

Immunoperoxidase detection of 4-aminobiphenyl- and polycyclic aromatic hydrocarbons-DNA adducts in induced sputum of smokers and non-smokers

Tobacco smoke constituents, 4-aminobiphenyl (4-ABP) and polycyclic aromatic hydrocarbons (PAH) possess carcinogenic properties as their reactive metabolites form DNA adducts. We studied the formation of 4-ABP- and PAH-DNA adducts in induced sputum, a non-invasively obtainable matrix from the lower respiratory tract, of smokers (n=20) and non-smokers (n=24) utilizing a semi-quantitative immunohistochemical peroxidase assay. Smokers had significantly higher levels of 4-ABP-DNA adducts as compared to non-smokers (0. 08+/-0.02 versus 0.04+/-0.01, P=0.001, density of immunohistochemical staining), and the levels of adducts were related to current smoking indices (cigarettes/day: r=0.3, P=0.04 and tar/day: r=0.4, P=0.02). Likewise, smokers had elevated levels of PAH-DNA adducts as compared to non-smokers, however, the differences was not statistically significant (0.13+/-0.02 versus 0. 08+/-0.02, P=0.07). The levels of PAH-DNA adducts were only significantly related to the amount of tar consumed per day (r=0.4, P=0.04) but not to the number of cigarettes smoked per day. Neither the levels of 4-ABP-DNA adducts nor those of PAH-DNA adducts were related to smoking history index (pack years). Further, the levels of 4-ABP-DNA adducts were correlated with those of PAH-DNA adducts (r=0.4, P=0.02). We conclude that immunohistochemistry of 4-ABP-DNA adducts in induced sputum is a specific approach to assess current exposure to tobacco smoke in the lower respiratory tract, however, in the case of PAH-DNA adducts, such analysis is less specific as it does not explicitly reflect the magnitude of the exposure.

Stability of benzo[a]pyrene DNA adducts in rat tissues during their long-term storage at -20 degrees C or -80 degrees C

The aim of this study was to examine whether the storage of tissues at -80 degrees C or -20 degrees C affects the benzo[a]pyrene (B[a]P)-derived DNA adduct pattern and levels in rat tissues. Three rats were treated orally with a single dose of 100 mg B[a]P/kg b.w. and killed 24 h later. White blood cells (WBC) were isolated from the fresh blood. Livers, lungs and hearts were immediately removed, dissected into small fragments and were pooled for each organ. Pooled samples were proportionally divided into 7 aliquots. DNA from the first aliquot was immediately isolated (time 0). The other aliquots were frozen and stored at -20 degrees C or at -80 degrees C. DNA was isolated from the frozen samples at 1, 5 and 10 months later. 32P-postlabeling analysis was performed at the beginning and at the end of study with the whole set of samples. Two B[a]P-derived adducts were detected in all tissues but with different intensities for different tissue types. One of the adducts was found predominantly in WBC (approximately 85%) and liver (approximately 68%), while heart and lung accounted only for approximately 43% and approximately 39%, respectively. This adduct was tentatively identified as benzo[a]pyrene diol-epoxide-N2 adduct (BPDE-N2-dG) based on TLC and HPLC analyses of 32P-postlabeled adducts. The highest total DNA adduct level (sum of 2 spots) was found in lung (4.90 adducts/10(8) nucleotides) compared with heart, liver and WBC (3.55, 2.37 and 2.32 adducts/10(8) nucleotides, respectively). The analysis of variance provided evidence that storage of tissues at -20 degrees C or at -80 degrees C up to 10 months did not significantly affect B[a]P DNA adduct levels and patterns in the rat lung, heart and liver. Our study indicates that properly stored tissues can be used for DNA adduct analysis with confidence.

DNA adducts in human tissues: biomarkers of exposure to carcinogens in tobacco smoke

Tobacco smoking causes millions of cancer deaths annually. Tobacco smoke is a complex mixture of thousands of chemicals including many known animal carcinogens. Because many carcinogens from DNA adducts in target animal or human tissues, the detection of the formation of adducts using such methods as postlabeling, immunoassay, fluorescence spectroscopy, and mass spectrometry is a means of monitoring human exposure to tobacco carcinogens. Smokers are at increased risk of cancer in many organs, and studies have revealed either specific adducts related to smoking or increased levels of adducts in the lung, bronchus, larynx, bladder, cervix, and oral mucosa of smokers. In a limited number of studies, the adducts and the carcinogens responsible for them have been identified. Some studies have demonstrated higher levels of adducts in the white blood cells of smokers, while other studies indicate other sources of genotoxic agents, including diet, can contribute to the DNA damage observed in these cells.

32P-postlabeling analysis of DNA adducts in different populations

Blood samples were obtained from different populations exposed occupationally or by lifestyle habits to polycyclic aromatic hydrocarbons (PAH). DNA adducts were determined by 32P-postlabeling assay either in white blood cells (WBC) or lymphocytes. The level of DNA adducts ranged from 1.5 per 10(9) nucleotides in one of the control groups up to 7.1 per 10(9) nucleotides in one group of PAH-exposed workers. Comparison of the adduct thin layer chromatography (TLC) profiles revealed individual variation in both pattern and level of DNA adducts. Significant differences of adduct levels were detected between one group of PAH-exposed coke-oven workers and the corresponding control group. Only a weak influence of the smoking habits on the amount of adducts was detectable in occupationally exposed or unexposed individuals.

Prediction and monitoring of the carcinogenicity of polycyclic aromatic compounds (PACs)

Chemical carcinogenesis is a multistage process that includes initiation, promotion, and progression. Some carcinogenic PACs have been shown to activate proto-oncogenes and deactivate tumor-suppression genes in the carcinogenic process. The function of DNA repair processes appears to be changed in some cases by PACs. Many PACs are well known for their carcinogenic activity, but for this activity to be exerted, metabolic activation by microsomal enzymes must occur. The enzyme system responsible for PAC activation is the mixed-function oxidase system and, in particular, cytochrome P-450. In the case of PAHs, oxidation predominantly produces reactive diol-epoxides that can then be converted to carbonium ions as the reactive electrophiles that can then covalently bind to DNA. Regions of high activity exist in PAHs, namely, the "bay," "K," and "L" regions which are associated with pi electron distribution. The diol-epoxides can exist in either syn or anti forms, each of which has two enantiomers producing four stereoisomers in all. Energy considerations favor the formation of the anti form. Nitrogen-containing PACs can be metabolically activated in a manner similar to that for PAHs, or the nitrogen atom can be oxidized to form hydroxylamines. These reactive electrophiles can then form covalently bound DNA adducts. The monitoring of DNA adducts has been used in risk assessment for human exposure to PACs. This form of biomonitoring has advantages over the monitoring of external exposure or body levels of the chemicals in question. In the case of PACs, binding to DNA is an important step in the multistage carcinogenic process. The estimation of DNA adducts has been used in the monitoring of humans exposed to PAHs in a wide range of industrial situations. Recent research has shown a dose-response relationship between PAH adduct levels and human cancer, thus developing molecular epidemiology as a relevant science for the field of risk assessment. Techniques have been developed for the determination of DNA adducts and these include immunochemical, fluorescence spectroscopic, GC-MS, and 32P-postlabeling methods. The 32P-postlabeling assay is by far the most sensitive, with limits of detection being of the order of one adduct in 10(10) normal nucleotides. The use of HPLC for separation of adducted nucleotides in this postlabeling assay is becoming more common and gives better resolution of adducts than does the TLC technique used in the traditional assay. The detection of adducts on hemoglobin and other proteins has been used as a surrogate for DNA adduct estimation.(ABSTRACT TRUNCATED AT 400 WORDS)