Polycyclic aromatic hydrocarbons exposure and hematotoxicity in occupational population: A two-year follow-up study.

BACKGROUND: Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental and occupational pollutants. To date, the effect and mechanism by which PAHs exposure impaired hematopoietic system remains unclear. METHODS: We examined the capability of PAHs to disrupt hematopoiesis in a study of 639 male participants in China by measuring complete blood counts (CBC) in 2013 and 2014. Gas chromatography-mass spectrometry (GC/MS) method was used to measure airborne levels of PAHs and benzene. We measured 1-hydroxypyrene (1-OHP), S-phenylmercapturic acid (SPMA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in urinary by ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS/MS) method. RESULTS: We found decreased dose-response of white blood cells, eosinophils, monocytes and lymphocytes with increased PAHs exposure in two consecutive years. We did not find association between benzene with CBC in our study. After stratification analysis by smoking status, the findings were highly consistent. White blood cells, monocytes and red blood cell counts were decreased in high urinary 8-OHdG group. CONCLUSIONS: Our study showed that PAHs could impair the hematopoietic system independently, and oxidative stress might play an important role in potential hematotoxicity.

Mechanisms of oxidative DNA damage induced by carcinogenic arylamines.

Most arylamines are pro-carcinogens, and require metabolic activation to yield ultimate carcinogen metabolites. O-Acetylation of the N-hydroxy form of an arylamine yields an acetoxyarylamine, which can form a highly reactive arylnitrenium ion, the ultimate metabolite responsible for DNA adduct formation. However, we demonstrate here that the N-hydroxy and nitroso forms of arylamines can also induce DNA damage, including 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxodG) lesions, via reactive oxygen species formation. The N-hydroxy and nitroso derivatives of carcinogenic arylamines may contribute to the carcinogenic process through H2O2 formation. N-Hydroxy derivatives induce metal-mediated DNA damage, with remarkable enhancement by NADH. Nitroso derivatives induce NADH-dependent DNA damage in the presence of metal ions. Hydroxy derivatives of arylamines formed by enzymatic hydroxylation or as o- or p-aminophenols can also induce DNA damage in the presence of metal ions. The autoxidation of o-phenylenediamine and several arylamine metabolites is accelerated in the presence of SOD or manganese, resulting in the enhancement of metal-mediated DNA damage. The oxidative DNA damage induced by arylamine compounds may participate in chemical carcinogenesis, in addition to DNA adduct formation.

8-Hydroxy-2'-deoxyguanosine (8-OHdG) as a short-term predictor of regional and occupational health problems.

Exposure to a large number of environmental toxins can induce damage to DNA and may play an important role in the pathophysiological processes of atherosclerosis. To examine the effect of some specific environmental conditions that predispose to sudden coronary atherosclerotic death on the level of 8-OHdG, urine samples were collected from cases of certain occupations and polluted regions that showed a high prevalence of premature deaths. The samples were then analyzed for 8-OHdG. Analysis of 108 cases and 45 controls showed a significant high level of 8-OHdG in relation to occupations, habits, residency and work shift. The mean +/- standard deviation (M +/- SD) for the control group was 4.5 +/- 2.3 ng 8-OHdG/mg creatinine (n = 45), compared to 9.1 +/- 3.1 ng/mg in taxi drivers (n = 9), 10 +/- 5.5 ng/mg in chemical factory workers (n = 16), 12.0 +/- 8.9 ng/mg in paint workers (n = 9), 14.6 +/- 11.1 ng/mg in gasoline station workers (n = 15), 15 +/- 6.1 ng/mg in cement factory workers (n = 12), 16.4 +/- 3.2 ng/mg in city center inhabitants (n = 18) and 18.6 +/- 3.2 ng/mg in smokers (n = 15). These conditions at least in the pilot study done by the author, showed some form of precipitation of sudden atherosclerotic coronary death. This work proved that the recently used 8-OHdG DNA damage biomarker may be an important marker of environmental conditions that are expected to have a serious long-term impact on the cardiovascular system.

Real-time RT-PCR: considerations for efficient and sensitive assay design.

Real-time RT-PCR has been recognised as an accurate and sensitive method of quantifying mRNA transcripts. Absence of post amplification procedures allows rapid analysis with a greater sample throughput, yet with less risk of amplicon carry-over as reaction tubes are not opened. In order to maximise sensitivity, careful reaction design and optimisation is essential. Several aspects of assay design for real-time RT-PCR are discussed in this paper. We demonstrate the effect of amplicon secondary structure on reaction efficiency and its importance for primer design. Taq-man probes with a deoxyguanosine base at the 5' end fluoresce weakly when labelled with FAM, although weak fluorescence is not a problem when probes are labelled with Texas Red. DNA contamination of RNA samples purified using silica membrane columns is a significant problem but DNase digestion can be used to reduce this, particularly in-solution. MMLV and AMV enzyme systems using a variety of RT priming methods are compared and the problem of primer-dimer formation associated with RT enzymes is described.

Association of hepatitis virus infection, alcohol consumption and plasma vitamin A levels with urinary 8-hydroxydeoxyguanosine in chemical workers.

Urinary 8-hydroxydeoxyguanosine (8-OHdG) DNA adduct has been used as a biomarker in epidemiological studies. However, the determinants for urinary 8-OHdG have not been clearly identified. We tested urinary 8-OHdG levels in 205 male workers who had been exposed to vinyl chloride monomer (VCM). Epidemiological information was obtained by an interviewer-administered questionnaire. Hepatitis B surface antigen (HBsAg) and anti-hepatitis C antibody (anti-HCV) were also determined by immunoassay. Plasma antioxidants including Vitamins A and E, alpha- and beta-carotenes were assayed by high performance liquid chromatography. Median of urinary 8-OHdG level was 9.8 ng/mg creatinine (range, 1.4-60.1). Multiple linear regression analysis showed that alcohol drinkers had higher urinary 8-OHdG than those who did not, but there was no dose-response between the amount of alcohol consumption and urinary 8-OHdG. Workers with positive HBsAg, anti-HCV and elevated plasma Vitamin A level were independently associated with higher levels of urinary 8-OHdG, whereas age, smoking, body mass index, plasma alpha- and beta-carotenes, Vitamin E levels, or VCM exposure did not show such an association. The results suggest that active inflammation of hepatitis B and C, alcohol consumption and higher Vitamin A level can induce oxidative stress. Thus, we conclude that potential determinants need to be considered in epidemiological studies when urinary 8-OHdG is used as a biomarker.

Evaluation of beta-2'-deoxythioguanosine combined with methyl-CCNU or mitomycin in advanced colorectal cancer. A Southwest Oncology Group study.

Two hundred twenty eligible patients with metastatic colorectal carcinoma were treated with a combination of beta-2'-deoxythioguanosine (BTG), plus methyl-CCNU or mitomycin. There was no significant difference in overall response (CR/PR + stable) among fully evaluable patients between the mitomycin plus BTG arm 19/96 (19.7%) and the MeCCNU arm 26/87 (29.8%). Median survival of eligible patients was 19 weeks with mitomycin plus BTG versus 21 weeks with MeCCNU plus BTG: no difference. Median survival of responders (40 weeks) and patients with stable disease (35 weeks) was significantly better than patients with increasing disease (17 weeks): p + 0.001.

Pharmacology and toxicology of alpha-2'-deoxythioguanosine in cancer patients.

alpha-2'-Deoxythioguanosine (alpha-TGdR) was administered as a single dose to 13 cancer patients in 18 experiments at dose levels of 150--1500 mg/m2 and as a daily dose to 22 patients in 42 experiments at dose levels of 100--4000 mg/m2/day X 5 days. No significant toxicity was observed. Blood levels and rates of excretion were determined with radiosulfur-labeled alpha-TGdR. Approximately 80% of the dose was excreted in the urine in 24 hours, initially as unchanged alpha-TGdR and increasingly as metabolites. Metabolites appear to be nucleosides and do not include 6-thioguanine, 6-thioxanthine, or 6-thiouric acid to any measurable extent. Small amounts of the alpha-TGdR in blood samples were bound to albumin and to erythrocyte membranes. Blood plasma levels of alpha-TGdR at the highest doses were in the range of 200--300 micrometer, declining in 24 hours to 67--124 micrometer.