The marker of alkyl DNA base damage, N7-methylguanine, is associated with semen quality in men.

Sperm DNA contains a range of DNA base damage that can arise, in part, from exposure to methylating agents. However, the effects are not fully characterized and so the aim of this study was to investigate associations between semen quality and the levels of N7-methyldeoxyguanosine (N7-MedG), a marker of exposure to methylating agents, and other markers of DNA damage and DNA methylation. Sperm samples were collected from 105 men attending an assisted reproduction clinic as part of a couple undergoing treatment for infertility and semen quality assessed manually according to WHO guidelines. Semen levels of N7-MedG, quantified by immunoslotblot, were significantly higher in men with sperm concentration < 15 × 106/ml (p ≤ 0.01), semen volume < 1.5 ml (p ≤ 0.05) and also in men with any aspect of semen quality below WHO reference levels (p ≤ 0.001). Measures of neutral Comet DNA damage were correlated with semen quality in a univariate analysis but not after adjustment for N7-MedG levels. Sperm concentration was negatively associated with % methylation at the gene for DAZL but no other marker of global or gene-specific DNA methylation. Results support the hypothesis that the known toxic and DNA damaging properties of alkylating agent exposure may have direct deleterious consequences on semen quality.

The role of bracken fern illudanes in bracken fern-induced toxicities.

Bracken fern is carcinogenic when fed to domestic and laboratory animals inducing bladder and ileal tumours and is currently classified as a possible human carcinogen by IARC. The carcinogenic illudane, ptaquiloside (PTQ) was isolated from bracken fern and is widely assumed to be the major bracken carcinogen. However, several other structurally similar illudanes are found in bracken fern, in some cases at higher levels than PTQ and so may contribute to the overall toxicity and carcinogenicity of bracken fern. In this review, we critically evaluate the role of illudanes in bracken fern induced toxicity and carcinogenicity, the mechanistic basis of these effects including the role of DNA damage, and the potential for human exposure in order to highlight deficiencies in the current literature. Critical gaps remain in our understanding of bracken fern induced carcinogenesis, a better understanding of these processes is essential to establish whether bracken fern is also a human carcinogen.

PON1 increases cellular DNA damage by lactone substrates.

Paraoxonase 1 (PON1) is a high-density lipoprotein (HDL)-associated enzyme that by hydrolysing exogenous and endogenous substrates can provide protection against substrate induced toxicity. To investigate the extent to which PON1 provides protection against lactone induced DNA damage, DNA damage was measured in HepG2 cells using the neutral Comet assay following lactone treatment in the presence and absence of exogenous recombinant PON1 (rPON1). Low dose lactones (10 mM) caused little or no damage while high doses (100 mM) induced DNA damage in the following order of potency: α-angelica lactone > γ-butyrolactone ~ γ-hexalactone > γ-heptalactone ~ γ-octaclactone ~ γ-furanone ~ γ-valerolactone > γ-decalactone. Co-incubation of 100 mM lactone with rPON1, resulted in almost all cells showing extensive DNA damage, particularly with those lactones that decreased rPON1 activity by > 25%. In contrast, with the lactones that are poor rPON1 subtrates (γ-decalactone and γ-furanone), rPON1 did not increase DNA damage. DNA damage induced by a 1 h co-treatment with 10 mM α-angelica lactone and rPON1 was reduced when cells when incubated for a further 4 h in fresh medium suggesting break formation was due to induced DNA damage rather than apoptosis. Preincubation (1-6 h) of α-angelica lactone with rPON1 in the absence of cells, decreased cellular DNA damage by around 40%  in comparison to cells treated without preincubation. These results suggest that in addition to its well-recognised detoxification effects, PON1 can increase genotoxicity potentially by hydrolysing certain lactones to reactive intermediates that increase DNA damage via the formation of DNA adducts.

L-ß-N-methylamino-l-alanine (BMAA) nitrosation generates a cytotoxic DNA damaging alkylating agent: An unexplored mechanism for neurodegenerative disease.

BACKGROUND: L-ß-N-methylamino-l-alanine (BMAA) is a non-proteinic amino acid, that is neurotoxic in vitro and in animals, and is implicated in the causation of amyotrophic lateral sclerosis and parkinsonism-dementia complex (ALS-PDC) on Guam. Given that natural amino acids can be N-nitrosated to form toxic alkylating agents and the structural similarity of BMAA to other amino acids, our hypothesis was that N-nitrosation of BMAA might result in a toxic alkylating agent, providing a novel mechanistic hypothesis for BMAA action. FINDINGS: We have chemically nitrosated BMAA with sodium nitrite to produce nitrosated BMAA (N-BMAA) which was shown to react with the alkyl-trapping agent, 4-(p-nitrobenzyl)pyridine, cause DNA strand breaks in vitro and was toxic to the human neuroblastoma cell line SH-SY5Y under conditions in which BMAA itself was minimally toxic. CONCLUSIONS: Our results indicate that N-BMAA is an alkylating agent and toxin suggesting a plausible and previously unrecognised mechanism for the neurotoxic effects of BMAA.

Modifiable and non-modifiable risk factors for poor sperm morphology.

STUDY QUESTION: Are common lifestyle factors associated with poor sperm morphology? SUMMARY ANSWER: Common lifestyle choices make little contribution to the risk of poor sperm morphology. WHAT IS KNOWN ALREADY: Although many studies have claimed that men's lifestyle can affect sperm morphology, the evidence is weak with studies often underpowered and poorly controlled. STUDY DESIGN, SIZE, DURATION: Unmatched case-referent study with 318 cases and 1652 referents. Cases had poor sperm morphology (<4% normal forms based on 200 sperm assessed). Exposures included self-reported exposures to alcohol, tobacco, recreational drugs as well as occupational and other factors. PARTICIPANTS/MATERIALS, SETTING, METHODS: Eligible men, aged 18 years or above, were part of a couple who had been attempting conception without success following at least 12 months of unprotected intercourse and also had no knowledge of any semen analysis before being enrolled. They were recruited from 14 fertility clinics across the UK during a 37-month period from 1 January 1999. MAIN RESULTS AND THE ROLE OF CHANCE: Risk factors for poor sperm morphology, after adjustment for centre and other risk factors, included: (i) sample production in summer [odds ratio (OR) = 1.99, 95% confidence interval (CI) 1.43-2.72]; and (ii) use of cannabis in the 3 months prior to sample collection in men aged ≤30 years (OR = 1.94, 95% CI 1.05-3.60). Men who produced a sample after 6 days abstinence were less likely to be a case (OR = 0.64, 95% CI 0.43-0.95). No significant association was found with body mass index, type of underwear, smoking or alcohol consumption or having a history of mumps. This suggests that an individual's lifestyle has very little impact on sperm morphology and that delaying assisted conception to make changes to lifestyle is unlikely to enhance conception. LIMITATIONS, REASONS FOR CAUTION: Data were collected blind to outcome and so exposure information should not have been subject to reporting bias. Less than half the men attending the various clinics met the study eligibility criteria and among those who did, two out of five did not participate. It is not known whether any of those who refused to take part did so because they had a lifestyle which they did not want subjected to investigation. Although the power of the study was sufficient to draw conclusions about common lifestyle choices, this is not the case for exposures that were rare or poorly reported. WIDER IMPLICATIONS OF THE FINDINGS: All participating clinics saw patients at no cost (under the UK National Health Service) and the study population may differ from those in countries without such provision. Even within the UK, low-income couples may choose not to undertake any investigation believing that they would subsequently be unable to afford treatment. Since a computer performed the measurements of sperm morphology, these results may not be comparable with studies where sperm morphology was assessed by other methods. STUDY FUNDING/COMPETING INTERESTS: The study was funded by the UK Health and Safety Executive, the UK Department of Environment, Transport and the Regions, the UK Department of Health (Grant Code DoH 1216760) and the European Chemical Industry Council (grant code EMSG19). No competing interests declared.

The effect of Msh2 knockdown on toxicity induced by tert-butyl-hydroperoxide, potassium bromate, and hydrogen peroxide in base excision repair proficient and deficient cells.

The DNA mismatch repair (MMR) and base excision repair (BER) systems are important determinants of cellular toxicity following exposure to agents that cause oxidative DNA damage. To examine the interactions between these different repair systems, we examined whether toxicity, induced by t-BOOH and KBrO3, differs in BER proficient (Mpg (+/+), Nth1 (+/+)) and deficient (Mpg (-/-), Nth1 (-/-)) mouse embryonic fibroblasts (MEFs) following Msh2 knockdown of between 79 and 88% using an shRNA expression vector. Msh2 knockdown in Nth1 (+/+) cells had no effect on t-BOOH and KBrO3 induced toxicity as assessed by an MTT assay; knockdown in Nth1 (-/-) cells resulted in increased resistance to t-BOOH and KBrO3, a result consistent with Nth1 removing oxidised pyrimidines. Msh2 knockdown in Mpg (+/+) cells had no effect on t-BOOH toxicity but increased resistance to KBrO3; in Mpg (-/-) cells, Msh2 knockdown increased cellular sensitivity to KBrO3 but increased resistance to t-BOOH, suggesting a role for Mpg in removing DNA damage induced by these agents. MSH2 dependent and independent pathways then determine cellular toxicity induced by oxidising agents. A complex interaction between MMR and BER repair systems, that is, exposure dependent, also exists to determine cellular toxicity.

Respiratory and dermal symptoms in Thai nurses using latex products.

BACKGROUND: Despite known health risks related to the use of powdered latex gloves (PLGs), they are still widely used in hospitals in developing countries due to the high cost of alternatives. AIMS: To determine the prevalence of dermal and respiratory symptoms associated with latex glove use in nurses in Thailand and evaluate the influence of previously reported occupational risk factors in this population. METHODS: A cross-sectional study in female nurses working in three Thai hospitals. Participants completed a questionnaire on demographics, occupational and personal history, use of latex products at work and dermal and respiratory symptoms attributed to occupational use of latex gloves. RESULTS: Of 899 nurses, 18% reported health effects attributed to the use of latex products. After adjustment for confounding, occupational risk factors associated with increased reporting of dermal symptoms included wearing more than 15 pairs of PLG per day (odds ratio (OR): 2.10, 95% confidence interval (CI): [1.32-3.34]), using chlorhexidine (OR: 2.07, 95% CI: [1.22-3.52]) and being an operating theatre nurse (OR: 2.46, 95% CI: [1.47-4.12]). Being a labour ward nurse (OR: 3.52, 95% CI: [1.26-9.85]) was the only factor associated with increased reporting of respiratory symptoms. CONCLUSIONS: Continuing use of PLGs in Thai nurses is associated with increased prevalence of dermal symptoms compared with data from developed countries. Measures to reduce such health effects are well established and should be considered. Additionally, replacement of chlorhexidine with an alternative detergent seems advisable.

Acute ill-health in sheep farmers following use of pesticides.

BACKGROUND: Sheep farmers often complain of acute ill-health, known colloquially as 'dipper's flu', immediately after treating sheep with pesticides. There have been few prospective epidemiological studies to determine it's nature and incidence. Aims To determine the nature and frequency of symptoms occurring in farmers treating sheep for ectoparasites. METHODS: In a longitudinal study, farmers who planned to treat their sheep for ectoparasites were recruited. Farmers kept a symptom diary for 7 days after starting pesticide treatment. Symptoms reported on days 1-6 were compared to those reported on day 7 via the McNemar's test and with previously published literature definitions of dipper's flu. A principal component analysis (PCA) was carried out on new symptoms occurring on days 1 and 2. RESULTS: Of 781 farmers recruited, 352 farmers (45%) completed the symptom diary. In the 7 days after starting pesticide treatment, symptom complex reporting typically peaked on day 2, but few farmers (7 or less; <2%) were identified as having dipper's flu using literature definitions. However, PCA identified two new patterns of symptom complexes that accounted for 35% of the variance. A pyrexial factor consisted of four symptom complexes (feeling generally ill; feeling sweaty, shivery, feverish, hot or cold; feeling unusually tired; and having a headache) and a respiratory factor consisted of three symptom complexes (runny, stuffy, blocked or irritated nose; cough, shortness of breath or wheeze; and eye irritation). CONCLUSIONS: Existing definitions of dipper's flu do not adequately describe symptoms that occur following the treatment of sheep for ectoparasites.

Modifiable and non-modifiable risk factors for poor semen quality: a case-referent study.

STUDY QUESTION: Are common lifestyle factors associated with low-motile sperm concentration (MSC)? SUMMARY ANSWER: Common lifestyle choices make little contribution to the risk of low MSC. WHAT IS KNOWN AND WHAT THIS PAPER ADDS: Reviews of male subfertility often highlight how aspects of men's adult lifestyle can significantly increase their risk of subfertility but the strength of supporting evidence is weak. In this study, although low MSC was associated with a history of testicular surgery, being in manual work, not wearing loose underwear and black ethnicity, no relation was found to consumption of alcohol, use of tobacco or recreational drugs or high body mass index (BMI). These results suggest that delaying assisted conception to make changes to lifestyle is unlikely to enhance conception. DESIGN: Unmatched case-referent study with 939 cases and 1310 referents. Cases had a low-MSC relative to the time since last ejaculation (<12 × 10(6) for 3 days of abstinence). Exposures included self-reported exposures to alcohol, tobacco, recreational drugs as well as occupational and other factors. PARTICIPANTS AND SETTING: Eligible men, aged 18 or above, were part of a couple who had been attempting conception without success following at least 12 months of unprotected intercourse and also had no knowledge of any semen analysis. They were recruited from 14 fertility clinics across the UK during a 37-month period from 1 January 1999. MAIN RESULTS AND THE ROLE OF CHANCE: Risk factors for low MSC, after adjustment for centre and confounding factors, included a history of testicular surgery [odds ratio = 2.39, 95% confidence interval (CI): 1.75, 3.28], being in manual work [odds ratio (OR) = 1.28, 95% CI: 1.07, 1.53] or not working (OR = 1.78, 95% CI: 1.22, 2.59) and having black ethnicity (OR = 1.99, 95% CI: 1.10, 3.63). Conversely, men who wore boxer shorts (OR = 0.76, 95% CI: 0.64, 0.92) or who had a previous conception (OR = 0.71, 95% CI: 0.60, 0.85) were less likely to be a case. No significant association was found with smoking and alcohol consumption, the use of recreational drugs, a high BMI or having a history of mumps or fever. BIAS, CONFOUNDING AND OTHER REASONS FOR CAUTION: Data were collected blind to outcome, and exposure information should not have been subject to reporting bias. Among men attending the various clinics less than half met the study eligibility criteria and among those who did, two out of five were not recruited. It is not known whether any of those who refused to take part did so because they had a lifestyle they did not want subjected to investigation. Although the power of the study was sufficient to draw conclusions about common lifestyle choices, it cannot comment on exposures that are perhaps rare and poorly reported: the finding that use of street drugs was unrelated to low MSC cannot be assumed to apply to all such drugs and all patterns of use. The case definition did not consider sperm morphology or sperm DNA integrity. GENERALIZABILITY TO OTHER POPULATIONS: All participating clinics saw patients at no cost (under the UK National Health Service) and the study population may differ from those in countries without such provision. Even within the UK, low-income couples may choose not to undertake any investigation believing that they would subsequently be unable to afford treatment.

Epidemiology and trends in male subfertility.

The incidence and the causes of male infertility and male reproductive ill-health (in general) are important issues that remain poorly characterised. There does not appear to be a worldwide decline in semen quality but changes are more apparent in some regions than others. Furthermore, though the incidence of testicular cancer and congenital genital malformations had been increasing, the rate of increase has seemingly slowed over the past decade. Demographic data on UK fertility rates also provide scant evidence to suggest that infertility is increasing. Though this incidence data is reassuring, male infertility has been associated with an ever-increasing number of putative risk factors, including current exposures or parental exposures to occupational, lifestyle or environmental factors. It is currently unclear to what extent such risk factors (and others such as DNA damage) influence male infertility. Better characterisation of risk factors will aid our understanding of what is happening to male infertility. This brief review examines recent trends in male infertility and summarises the extent to which knowledge in this area has improved significantly.

Alkylation of sperm DNA is associated with male factor infertility and a reduction in the proportion of oocytes fertilised during assisted reproduction.

Approximately one-third of IVF cases in the UK are attributed to male factor infertility and in the majority of cases the origin of male infertility is unknown. The integrity of sperm DNA is important both for the success of assisted reproduction and the implications for the off-spring. One type of DNA damage that has not been investigated with respect to fertility outcomes is the adduct N7-methyldeoxyguanosine (N7-MedG), a biomarker for exposure to alkylating agents. A prospective cohort of couples attending for IVF had their N7-MedG levels in sperm measured using an immunoslot blot technique to examine whether sperm N7-MedG levels are associated with male factor infertility, semen quality measures or assisted reproduction outcomes. Sufficient DNA for analysis was obtained from 67/97 couples and N7-MedG was detected in 94% of sperm samples analysed. Men diagnosed with male factor infertility had significantly higher mean levels of N7-MedG in their sperm DNA (P=0.03). Logistic regression analysis showed that N7-MedG levels were significantly negatively associated with the proportion of oocytes successfully fertilised irrespective of the method of fertilisation used (IVF or intra-cytoplasmic sperm injection; ICSI, P<0.001). Therefore exposure to DNA alkylating agents is significantly associated with male infertility and the proportion of oocytes fertilised during assisted reproduction. Reducing such exposure may improve male fertility but further work is required to determine the relative importance of exogenous and endogenous sources of exposure.

The effect of Msh2 knockdown on methylating agent induced toxicity in DNA glycosylase deficient cells.

The DNA structure recognition protein MSH2 is an important protein in DNA mismatch repair due to its role in initiating the repair process. To examine the potential interactions between mismatch repair and base excision repair (BER) we have examined the effect of MSH2 knockdown on 6-thioguanine (6-TG), temozolomide (TMZ) and methylmethane sulphonate (MMS) induced toxicity in BER proficient and deficient cell lines. An shRNA expression vector containing Msh2 target sequences was designed and used to transfect mouse embryonic fibroblasts lacking either alkylpurine DNA N-glycosylase (Mpg) or endonuclease III homologue (Nth1). Significant knockdown of Msh2 gene expression was achieved with three different target sequences, with the highest level being shown by Msh2(283). Clonal selection resulted in differing levels of knockdown in Mpg(-/-) cells: (69.0+/-12.1% from 5 cell clones). Transfection of the Msh2(283) sequence in Mpg+/+, Nth1+/+ and Nth1(-/-) cells resulted in average knockdowns of 45.1+/-40.5% (3 clones), 58.0+/-21.4% (5 clones) and 74.9+/-14.8% (3 clones), respectively. Msh2 knockdown resulted in increased resistance to 6-TG in BER (MPG and NTH1) proficient and deficient cell lines with similar levels of knockdown (84+/-4%) but increased resistance to TMZ only in Mpg+/+ and Nth1(-/-) cell lines and not Mpg(-/-) or Nth1+/+ cells as assessed by an MTT assay. Msh2 knockdown had no effect on sensitivity to MMS induced toxicity. In a clonogenic assay, Msh2 silenced Mpg+/+, Mpg(-/-), Nth1+/+ and Nth1(-/-) cells were more resistant to TMZ. These results confirm previous studies showing that MSH2 is a key protein in influencing 6-TG and O(6)-methylguanine induced toxicity but also suggest that the effect of this protein depends upon the presence of other proteins in different DNA repair pathways.

Dietary variables associated with DNA N7-methylguanine levels and O6-alkylguanine DNA-alkyltransferase activity in human colorectal mucosa.

Components of human diets may influence the incidence of colorectal adenomas, by modifying exposure or susceptibility to DNA-damaging alkylating agents. To examine this hypothesis, a food frequency questionnaire was used to assess the diet of patients recruited for a case-referent study where biopsies of normal colorectal mucosa were collected during colonoscopy and subsequently analysed for DNA N7-methylguanine (N7-MeG) levels, as an indicator of exposure, and activity of the DNA repair protein O6-alkylguanine DNA-alkyltransferase (MGMT), as an indicator of potential susceptibility. Cases with histologically proven colorectal adenomas (n = 38) were compared with referents (n = 35) free of gastrointestinal neoplasia. The case group consumed significantly more red meat (4.5 versus 3.4 servings/week, P < 0.05), processed meats, (4.7 versus 3.2 servings/week, P < 0.05) and % food energy as fat (34.9 versus 30.7%, P < 0.001). N7-MeG [mean: 95% confidence interval (CI)] levels were significantly lower in the group that consumed the highest proportion of dietary fibre/1000 kcal in comparison with the group with the lowest intake (0.61; 0.35-0.86 versus 1.88; 0.88-2.64 micromol/mol dG, P < 0.05). N7-MeG levels were also inversely associated with folate consumption (P < 0.05). MGMT activity (mean; 95% CI) was significantly higher in the group with the lowest consumption of vegetables than in the group with the greatest vegetable consumption (7.02; 5.70-8.33 versus 4.93; 3.95-5.91 fmol/microg DNA, P < 0.05). Our results are consistent with the hypothesis that dietary factors may modify exposure or susceptibility, respectively, to DNA damage by alkylating agents.

GST CYP and PON1 polymorphisms in farmers attributing ill health to organophosphate-containing sheep dip.

Previously we reported that in sheep dippers exposed to organophosphates the frequency of paraoxonase (PON1) polymorphisms differed between those with or without self-reported ill health. We have now examined whether polymorphisms in other genes involved in xenobiotic metabolism alter disease risk in this population. There were elevated but non-significant risks associated with the CYP2D6 WT genotype (odds ratio (OR) 1.47, 95% CI 0.83-2.60), or a GSTP1*B or *C allele (OR 1.37, 95% CI 0.88-2.01) or being GSTM1*2/GSTT1*2 homozygous (OR 1.61, 95% CI 0.74-3.48). Similar results were generally obtained after the exclusion of subjects to obtain a more homogenous case-referent population: for double null GSTM1 and GSTT1 homozygotes the OR was 2.06 (95% CI 0.85-2.04). In those also likely to have been exposed to diazinon, risks associated with a GSTP1*B or *C allele (OR 1.82, 95% CI 0.92-3.63) or a GSTM1*2/GSTT1*2 homozygous (OR 2.60, 95% CI 0.72-10.42) were elevated but not to a significant extent. Risk associated with PON1 genotype and phenotype varied with CYP2D6 and GSTP1 genotype but not consistently with a priori hypotheses. Further work is necessary to delineate more clearly pathways of organophosphate activation and non-PON1 pathways of detoxification and to confirm whether CYP and GST polymorphisms alter disease risk in populations exposed to organophosphates.

Human colorectal mucosal O6-alkylguanine DNA-alkyltransferase activity and DNA-N7-methylguanine levels in colorectal adenoma cases and matched referents.

BACKGROUND AND AIMS: O(6)-alkylguanine DNA-alkyltransferase (MGMT) provides protection against alkylating agent-induced GC-->AT transition mutations. Such mutations are frequently seen in the KRAS oncogene of large colorectal adenomas, but whether adenoma or mutational risk in humans is influenced by MGMT activity and alkylating agent exposure is unclear. Hence, MGMT activity and, as an indicator of alkylating agent exposure, DNA-N7-methylguanine (N7-MeG) levels were determined in the normal tissue of patients with and without adenomas. METHODS: Biopsy specimens of normal colorectal mucosa were collected during colonoscopy from 85 patients with histologically proved colorectal adenomas (cases) and from 85 patients free of gastrointestinal neoplasia (referents) matched by age, sex and biopsy location. MGMT activity and N7-MeG levels were measured in colorectal tissue extracts and DNA, respectively. RESULTS: MGMT activity was higher in the normal mucosa of cases than in referents (6.65+/-3.03 vs 5.61+/-2.74 fmol/micro g DNA, p = 0.01). On stratification of cases, MGMT activity was found to be considerably greater in the normal mucosa of cases with large adenomas (p = 0.003) and slightly higher in cases with a GC-->AT transition mutation in the K-ras gene (p = 0.03). Elevated MGMT levels were associated with an increased risk of adenoma (OR 1.17, 95% CI 1.03 to 1.33 per unit increase in activity). Detectable levels of N7-MeG were found in DNA from 89% of cases and 93% of referents, with levels ranging from <0.1 to 7.7 micro mol/mol dG. Cases and referents had similar DNA-N7-MeG levels. CONCLUSIONS: Human exposure to methylating agents is widespread. MGMT activity is increased in the normal mucosa of patients with adenomas.

Meta- and pooled analysis of GSTT1 and lung cancer: a HuGE-GSEC review.

Lung cancer is the most common malignancy in the Western world, and the main risk factor is tobacco smoking. Polymorphisms in metabolic genes may modulate the risk associated with environmental factors. The glutathione S-transferase theta 1 gene (GSTT1) is a particularly attractive candidate for lung cancer susceptibility because of its involvement in the metabolism of polycyclic aromatic hydrocarbons found in tobacco smoke and of other chemicals, pesticides, and industrial solvents. The frequency of the GSTT1 null genotype is lower among Caucasians (10-20%) than among Asians (50-60%). The authors present a meta- and a pooled analysis of case-control, genotype-based studies that examined the association between GSTT1 and lung cancer (34 studies, 7,629 cases and 10,087 controls for the meta-analysis; 34 studies, 7,044 cases and 10,000 controls for the pooled analysis). No association was observed between GSTT1 deletion and lung cancer for Caucasians (odds ratio (OR) = 0.99, 95% confidence interval (CI): 0.87, 1.12); for Asians, a positive association was found (OR = 1.28, 95% CI: 1.10, 1.49). In the pooled analysis, the odds ratios were not significant for either Asians (OR = 0.97, 95% CI: 0.83, 1.13) or Caucasians (OR = 1.09, 95% CI: 0.99, 1.21). No significant interaction was observed between GSTT1 and smoking on lung cancer, whereas GSTT1 appeared to modulate occupational-related lung cancer.

Paraoxonase polymorphisms and self-reported chronic ill-health in farmers dipping sheep.

BACKGROUND: Serum paraoxonase (PON1) provides protection against organophosphate induced toxicity. Recently we reported that the frequency of paraoxonase polymorphisms in sheep dippers with self-reported chronic ill-health differed from that in dippers with a similar dipping history but no ill-health. As these analyses may have included subjects with conditions unrelated to organophosphate exposure, the aim of this study was to examine whether the risk associated with PON1 polymorphisms varied using a more homogenous case and referent population. METHODS: Each subject completed a detailed symptom questionnaire and their general practitioner was asked whether there was any history of neurological disease that could be confused with the effects of organophosphate poisoning. Subjects were then excluded both on clinical grounds and where identified as atypical on discriminant analysis. RESULTS: Risk associated with the PON1 192 and 55 genotypes altered little with these changes in the population. CONCLUSIONS: These findings are consistent with the hypothesis that organophosphates contribute to the self-reported ill-health of sheep dippers.

Glutathione S-transferase M1, T1 and P1 polymorphisms and bladder cancer risk in Egyptians.

Previous studies suggest that bladder cancer risk may vary with GST genotype but these results are inconsistent. The aim of this study was to explore whether GSTM1, GSTT1 and GSTP polymorphisms were associated with increased bladder cancer risk in an Egyptian population. GSTM1, GSTT1 and GSTP1 genotype frequencies were determined in bladder cancer cases (n=72) and healthy controls with no history of malignancies (n=82) using PCR-based techniques. The GSTT1*2 genotype was particularly associated with increased risk (OR 2.71, 95%CI 1.27-5.73) and the GSTM1*2 genotype to a lesser extent (OR 1.63, 95%CI 0.85-3.10). 18.1% of cases but only 7.3% of controls were GSTP1*B*B homozygotes (OR 2.38, 95%CI 0.83-6.87). The presence of two or more a priori at-risk genotypes was associated with increased bladder cancer risk (OR 2.42; 95%CI 1.47-3.97). These results suggest that polymorphisms in the GST genes are associated with increased risk of bladder cancer among Egyptians.

Levels of the DNA adduct, N7-methyldeoxyguanosine, are associated with increased risk of failure of treatment of cervical intraepithelial neoplasia.

OBJECTIVE: To determine whether exposure to methylating agents was a risk factor for treatment failure in women undergoing colposcopic examination. METHODS: Nine hundred fifty-eight women attending for colposcopic examination after abnormal cervical smear test results were recruited into the study cohort. Information on demographic factors, smoking and other risk factors was obtained and a pre-treatment biopsy was taken and stored at -70 degrees C. After follow-up, cases who had treatment failure of cervical intraepithelial neoplasia (CIN) within 2 years following treatment were identified (n = 77) and matched to women with no treatment failure of CIN in this time period (controls, n = 154). DNA was extracted from the pre-treatment biopsies and levels of N7-methyl-deoxyguanosine (N7-MedG), a marker of exposure to methylating agents, were quantified as the ring-opened form of the base damage by a validated immunoslotblot assay. RESULTS: Sufficient DNA for N7-MedG analysis was extracted from 61 subjects corresponding to 20 matched case control pairs. N7-MedG was detected in cervical DNA with levels ranging from non-detected (<0.1 micromol/mol dG) to 4.83 micromol/mol dG. N7-MedG levels were significantly higher in cases (geometric mean 0.99 micromol/mol dG) than controls (0.33 micromol/mol dG; P = 0.01). There were no associations between N7-MedG levels and HPV or smoking status. Log N7-MedG content, after adjustment for HPV status at time of treatment, was found to be significantly associated with increased risk of treatment failure (OR 5.74, 95% CI 1.05-31.23). CONCLUSIONS: The association between pre-treatment levels of DNA damage induced by methylating agents and subsequent treatment failure implicates methylating agent exposure as a causative factor in treatment failure.

Longitudinal variation in O(6)-alkylguanine DNA-alkyltransferase activity in the human colon and rectum.

In a systematic study of O(6)-alkylguanine DNA-alkyltransferase activity in the human colon and rectum, tumours were found to occur in regions of low activity. These results are consistent with the hypothesis that O(6)-alkylguanine DNA-alkyltransferase levels and alkylating agent exposure may be important determinants of large bowel tumorigenesis.