Effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin on trace elements, inflammation and viral clearance in the myocardium during coxsackievirus B3 infection in mice

A myocarditic coxsackievirus B3 (CB3) infection in adult male A/J mice was used to investigate the effects of 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD) exposure on mortality and on inflammatory lesion, virus and trace element contents of the heart. The mice were injected with four weekly intraperitoneal (i.p.) injections of TCDD (a loading dose of 5 microg/kg followed by three maintenance doses of 1.4 microg/kg). To reach a steady-state body burden of TCDD the mice were allowed a 90-day recovery period before infection with CB3 virus. TCDD increased the infection-induced mortality rate, whereas in TCDD-exposed mice, heart lesions at day 7 after the virus inoculation (median value 0.67% of the tissue section area; interquartile range 0.28; not statistically significant) were one-third of that in non-exposed infected mice (2.07% of the tissue section area; interquartile range 3.06). The size of the inflammatory heart lesion correlated to the amount of virus (r(s) = 0.829, P < 0.01) as well as to the calcium (Ca: r(s) = 0.725, P < 0.01) and the magnesium (Mg: r(s) = -0.615, P < 0.05) contents. In TCDD-exposed mice in situ hybridisation of viral RNA in the myocardium at day 7 showed a tendency to decreased amounts of virus, as well as a less pronounced increase in myocardial Ca content, both supporting a milder myocardial disease after TCDD exposure. No effect of TCDD exposure was seen on the zinc (Zn) or selenium (Se) levels in the myocardium. In conclusion, although TCDD seemed to have a limiting effect on viral replication and the development of the inflammatory lesion in the myocardium, mortality was increased by TCDD in this infection model. However, TCDD had no significant effects on the selected trace elements that could be of importance for the severity of the inflammatory lesion (Ca, Se), for the local host response activation (Zn) or for the development of myocardial disease complications (Mg). Accordingly, the increased mortality may be a result of an infection-induced increase in TCDD toxicity to vital organs other than the heart, and/or a TCDD-induced change in the tissue affinity and virulence of the virus, possibly causing involvement of other target organs in the infectious process and changed pathogenesis.     

Virus induces metal-binding proteins and changed trace element balance in the brain during the course of a common human infection (coxsackievirus B3) in mice

Autopsy of the brain has shown a change in trace element balance in some virus-infected individuals, but it is not known whether this event was a result of the infection. In the present study coxsackievirus B3 (CVB3) adapted to Balb/c mice was used to study whether infection induces gene expression of the metal-binding/transporting proteins metallothionein (MT1 and MT3) and divalent-metal transporter 1 (DMT1) and whether it changes the balance of trace elements in the brain. Virus and MT1, MT3, and DMT1 were quantitatively measured by RT-PCR on days 3, 6 and 9 of the infection. Trace elements (13) were measured in serum and the brain by ICP-MS. High numbers of virus were found in the brain on days 3 and 6, but virus counts were decreased and present only in 50% of the mice on day 9. Gene expression of MT1 tended to increase on all days, whereas that of MT3 only showed a minor and not significant increase on day 3. No clear effect was observed in the expression of DMT1. The increase of MT3 was correlated to the brain concentration of Cu. The Cu/Zn ratio in serum increased as a response to the infection. There was a similar decrease in Cd in serum and the brain. On day 6 of the infection, Hg increased in the brain (p<0.05) and was positively correlated to a concomitant decrease (p<0.05) in serum. Virus numbers in the brain were on day 6 positively correlated (p<0.05) to As concentrations. Enteroviral infections may therefore be an underlying factor regarding the changes in essential as well as potentially toxic trace elements in the brain.     

Do new hypotheses on the mechanism of action of dioxins help in risk evaluation?

The mechanism of action of chlorinated dibenzodioxins such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is not known, but the prevailing hypothesis is the binding to a specific protein, the Ah-receptor, and subsequent alteration of the expression of specific genes. This Ah-receptor hypothesis does not explain all aspects of toxicity, notably the extreme variation of toxicity between different animal species. We have found two rat strains that differ widely in their sensitivity to TCDD. The resistant Han/Wistar (H/W) rat tolerates doses up to 3000 micrograms kg-1, while 20 micrograms kg-1 is lethal to Long-Evans (L-E) rats. Several morphological, biochemical and endocrinological parameters as well as pharmacokinetics have been screened, but the strains behave by and large similarly. However, there is a clear behavioural difference: TCDD causes anorexia in both strains, but H/W rats start eating again in 1-2 weeks, whereas the reduction of feed intake is permanent in L-E rats until they die in about 3 weeks. Han/Wistar rats, which recover after a single large dose of TCDD, behave aberrantly for months; they seem to have a supersensitive satiety response while they do not respond normally to energy deficiency. Therefore the regulation of feed intake or of body weight seem to be altered permanently by TCDD. It is also of interest that TCDD is more toxic after a central than after a peripheral administration. These findings may be of importance for the risk evaluation of dioxins, because they might help to explain the wide species/strain variation which complicates the assessment of dioxin risk to humans.     

165例肾移植手术患者CYP3A5基因多态性与他克莫司浓度/剂量相关性研究

目的 探讨165例肾移植患者362次检测他克莫司血药浓度/剂量（C/D）与CYP3A5基因多态性之间的关系,并通过不同基因型来估算给药剂量,为他克莫司个体化给药提供依据.方法 选择应用他克莫司＋吗替麦考酚酯＋强的松三联免疫抑制方案且移植术后维持此方案半年以上的165例肾移植患者.采用聚合酶链反应-限制性酶切法（PCR-RFLP）检测患者CYP3A5基因多态性,比较不同基因型[野生纯合子组（＊1/＊1）、突变型杂合子组（＊1/＊3）及突变型纯合子组（＊3/＊3）]移植患者他克莫司血药C/D的差异.结果 肾移植患者＊3型突变率为77.88%.肾移植患者CYP3A5基因型＊1/＊1型、＊1/＊3型和＊3/＊3型他克莫司血药C/D分别为（40.54±19.98）、（74.76±38.71）和（164.33±96.27）ng·mL-1·mg-1·d·kg,肾移植患者CYP3A5基因型＊1/＊1型的他克莫司血药C/D明显低于＊1/＊3型和＊3/＊3型（P〈0.001,P=0.021）,＊3/＊3型与＊1/＊3型患者之间血药C/D差异无统计学意义（P=0.132）.结论 他克莫司的C/D与CYP3A5基因多态性密切相关.含CYP3A5＊3等位基因的患者与纯野生型患者相比可减少他克莫司的给药剂量.     

Breast milk, dioxins and the possible effects on the health of newborn infants

The concentration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the fat of breast milk of 14 Dutch mothers varied from 5.35 to 17.0 ng kg-1 (nanograms per kilogram fat). Expressed as toxic equivalents the concentrations of the 17 different congeners of dioxin and furans in the fat of the breast milk were between 29.85 and 92.88 ng kg-1. These levels are sufficient to induce enzyme formation in the livers of infants. (The acceptable daily intake is 4 pg/kg bodyweight/day). Dioxin induces the same enzyme production in the liver as phenobarbital; therefore, because phenobarbital affects fat-soluble vitamins, such as vitamins D and K, a similar response was anticipated in response to exposure to dioxin. Consequently, one aim of this study was to investigate blood coagulation parameters. We found a statistically significant relationship with the mean concentration of TCDD in the breast milk of mothers whose babies suffered from bleeding problems. This association was not found for 2,3,4,7,8-pentachlorodibenzofuran concentrations, nor for the remaining congeners expressed as toxic equivalents. A simple laboratory test for measuring dioxins and furans is urgently needed.     

The influence of metabolic gene polymorphisms on urinary 1-hydroxypyrene concentrations in Chinese coke oven workers

Urinary 1-hydroxypyrene (1-OHP), a biomarker of polycyclic aromatic hydrocarbons (PAHs) exposure, may be influenced by metabolic gene polymorphisms. Such knowledge could benefit us in understanding the inter-individual difference in the mechanism of PAHs-induced carcinogenesis. We investigated the influence of gene polymorphisms on urinary 1-OHP concentrations in 447 coke oven workers from two coking plants in south China. After adjustment for age, plant, level of occupational exposure, body mass index, level of education, alcohol consumption, cigarette smoking and respirator usage, AhR R554K (rs2066853), UGT1A1 -3263T>G (rs4124874) and GSTP1 I105V (rs1695) were associated with urinary 1-OHP excretion with the p-value of 0.053, 0.006 and 0.021, respectively. The concentrations of urinary 1-OHP (Geometric mean, micromol/mol creatinine) in the homozygous major variant carriers and homozygous minor variant carriers for AhR R554K, UGT1A1 -3263T>G and GSTP1 I105V were listed as follows: 4.20 and 5.12, 5.11 and 3.92, 4.93 and 2.91, respectively. GSTT1 present carriers had a significantly higher urinary 1-OHP level than that in null carriers in the case with AhR R554K GA/AA carriers (5.17 vs. 3.64 micromol/mol creatinine, p=0.038), as well as in the case with UGT1A1 -3263T>G TG/GG carriers (5.67 vs. 3.38 micromol/mol creatinine, p=0.001). These results showed that AhR, UGT1A1, GSTP1 and GSTT1 polymorphisms were associated with urinary 1-OHP concentrations in Chinese coke oven workers. No influence was found in the association between urinary 1-OHP and other genetic polymorphisms such as CYP1A1, CYP1A2, CYP1B1, CYP2E1, EPHX1, EPHX2 in this population.     

Cytochrome P450 1B1 mRNA levels in peripheral blood cells and exposure to polycyclic aromatic hydrocarbons in Chinese coke oven workers

Cytochrome P450 1B1 (CYP1B1) is induced through the Ah receptor and is involved in the activation of polycyclic aromatic hydrocarbons (PAHs). To determine the validity of a quantitative analysis of CYP1B1 mRNA in peripheral human blood cells for the estimation of PAH exposure, a real-time quantitative polymerase chain reaction method was used to measure the relative levels of CYP1B1 mRNA in 37 Chinese coke oven workers and 13 control workers. A large inter-individual difference in the levels was observed. The average level of the CYP1B1 mRNA in workers at the top work site, where the PAH exposure level from the coke ovens was highest, was significantly higher than in workers at the middle site (P<0.01) or the controls (P=0.02). A non-significant positive correlation was found between the CYP1B1 mRNA levels and urinary 1-hydroxypyrene (R=0.22, P=0.13), and a significant correlation between these mRNA levels and urinary cotinine (R=0.33, P=0.02). It was interesting that a significant positive correlation between CYP1B1 mRNA and 1-hydroxypyrene was observed in subjects with the Leu/Leu type of CYP1B1 Leu432Val polymorphism (R=0.33, P=0.02, n=38) and a non-significant correlation in subjects with the Leu/Val and Val/Val types (R=-0.36, P=0.25, n=12), although the number of subjects in this strata analysis was small. Our preliminary study suggests that PAH exposure in coke ovens and smoking maybe associated with CYP1B1 mRNA levels in peripheral blood cells although mRNA is generally unstable and could be expressed following exposure to other agents.     

In vitro response of the brown bullhead catfish (BB) and rainbow trout (RTG-2) cell lines to benzo[a]pyrene

Established cell lines from rainbow trout (RTG-2) and brown bullhead catfish (BB) were evaluated as bioindicators of benzo[a]pyrene (B[a]P) toxicity with 3-(4,5-dimethyltiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction and neutral red (NR) uptake assays. Cytochrome P450 1A1 (CYP1A1) enzymatic activity was also evaluated, and taken as a biological indicator of the B[a]P induction power by ethoxyresorufin O-deethylase (EROD) and ethoxycoumarin O-deethylase (ECOD) assays. The BB and RTG-2 cells were compared after 1 and 6 days of exposure to B[a]P. The photoactivation of the compound (B[a]PUV) was another parameter taken into consideration. Cytotoxicity was not observed after 1 day of incubation with B[a]P in both cell lines, although the enzymatic activities of ECOD and EROD presented an induction. Apparently, after 1 day, cells did not metabolise sufficient amounts of B[a]P to cytotoxic metabolites. After 6 days of exposure to this compound a significant reduction in cell viability was observed, this reduction being superior to 50% at the highest B[a]P concentrations for the RTG-2 cell line. These results are in agreement with the values observed for the ECOD and EROD induction. The B[a]P cytotoxicity determined in both cell lines could be ascribed to the significant increase of EROD activity by 6 days of exposure. The photoactivation of B[a]P showed marked differences in both cytotoxic assays and CYP1A1 enzymatic activities, for both cell lines. After 1 day of exposure there was a significant reduction in cell viability, superior to 50% for the RTG-2 cell line. However, it was observed that no induction occurred but rather a decrease in ECOD and EROD activities. Six days of incubation with B[a]PUV showed a decrease in cell viability at the highest concentrations for the BB cells and at the lowest concentrations for the RTG-2 cell line, and the CYP1A1 enzymatic activity presented a significant induction. These results and those observed after 1 day of exposure suggest that B[a]PUV acts as a direct-acting toxicant as well as a metabolism-mediated toxicant-like B[a]P. The RTG-2 cells were more sensitive to B[a]P and its toxic metabolites as well as to the photoactivation of the compound, in both exposure times tested. The finding that the cell lines responded to the CYP1A1 induction in a very efficient way gives proof of the applicability of this system to environmental biomonitoring and toxicology.     

2,3,7,8-TCDD equivalence and mutagenic activity associated with PM10 from three urban locations in New Zealand

Ambient particulate matter (PM(10)) in urban centres varies depending on emission sources, geography, demography, and meteorology. Hence physical (PM(10), wind speed, rainfall, temperature), chemical (polycyclic aromatic hydrocarbons, PAH), and toxicological (Ames Test, H4IIE EROD Assay) analyses were done on daily PM(10) (approximately 1640 m(3)/day) collected from three New Zealand urban sites where winter emissions were predominantly due to domestic home heating. Daily PM(10) levels ranged between 9.7 and 20.8 in summer and between 21.8 and 61.0 microg/m(3) in winter. Daily PAH concentrations were 0.5, 0.45, and 1.5 ng/m(3) in summer and 52.1, 128.9, and 5.8 ng/m(3) in winter at sites Christchurch, Alexandra and Dunedin, respectively. During winter, 74% of PM(10) extracts from all three sites showed significant mutagenicity in the Ames Test (TA 98, -S9), whereas approximately 25% of the daily PM(10) was mutagenic in summer. Benzo[a]pyrene and BaP carcinogenic equivalence concentrations during winter were strongly correlated to both mutagenicity and TCDD-like activity at two sites. Daily levels of TCDD toxicity equivalence concentrations ranged from 0.5 to 3.6 pg TCDD/m(3) air in summer and from 0.3 to 4009 pg TCDD/m(3) air in winter. Chemically and biologically derived TCDD toxicity equivalent concentrations were significantly correlated in all study locations indicating that PAH may represent most of the TCDD-like activity present in the PM(10).     

Determination of heavy metal uptake in transgenic plants harbouring the rabbit CYP450 2E1 using X-ray fluorescence analysis

Transgenic Sesbania grandiflora (L.) pers (Fabaceae) and Arabidopsis thaliana (L.) (Brassicaceae) plants harbouring the rabbit cytochrome p450 2E1 enzyme were evaluated for their ability to accumulate heavy metals, potassium (K), calcium (Ca), manganese (Mn), zinc (Zn), copper (Cu), iron (Fe), lead (Pb) and bromine (Br), using X-ray Fluorescence analysis. When grown for 15?days on heavy metal-contaminated soils, transgenic cuttings of S. grandiflora and T3 A. thaliana plants recorded higher dry and fresh weight compared with their respective controls (A. thaliana and S. grandiflora plants transformed with an empty vector). Dry weight of transgenic S. grandiflora plants (0.321?g) was seven times higher than that of the wildtype (0.049?g), and the fresh weight (4.421?g) was about 4.6 times higher. Likewise, the dry weight of CYP450 2E1 A. thaliana (0.198?g) was more than eight times higher than that seen in the control (0.024?g). Moreover, Fe, Mn, K, and Ca concentrations in transgenic plants were significantly higher than those in their corresponding controls. For instance, concentrations of accumulated K (~3000 and 2000?mg/kg dry weight in S. grandiflora and A. thaliana, respectively) were significantly higher than those recorded in their corresponding controls (2500 and 1500?mg/kg, respectively). In the same vein, translocation of all studied metals from soils cultured with transgenic plants was higher than in those cultured with the control plants. In conclusion, the obtained results show the potential in using transgenic Sesbania and Arabidopsis plants harbouring the rabbit CYP450 2E1 for phytoremediation of mixed environmental contaminants.     

Bioaccumulation and effects of PCBs and heavy metals in sea stars (Asterias rubens, L.) from the North Sea: a small scale perspective

Sea stars (Asterias rubens L.) were collected in different stations distributed in the Southern Bight of the North Sea. Concentrations of four heavy metals and six PCB congeners were measured in two body compartments (body wall and pyloric caeca). In order to assess the potential harm of these contaminants, two biochemical parameters were measured in sea stars, viz. reactive oxygen species (ROS) production by amoebocytes and cytochrome P450 immunopositive protein (CYP1A IPP) induction in pyloric caeca. Sea stars from stations located in the plume of the Scheldt river showed the highest contamination levels. Other stations, similarly located, displayed lower levels. No simple relationship could be established between ROS production by sea star amoebocytes and contaminant levels measured in sea star tissues. CYP1A IPP induction displayed more contrasted responses, and highly significant regressions were found between PCB concentrations measured in pyloric caeca and CYP1A IPP. Both biological parameters were found to vary significantly over the study area. On the whole, data indicated that contamination levels and subsequent effects in sea stars were comparable to those described in previous large-scale studies, but that working at a smaller scale highlighted the existence of patterns of contamination which can blur general trends due to major contamination sources like contaminated rivers.     

Induction of the imbalance of helper T-cell functions in mice exposed to diesel exhaust

Administration of diesel exhaust particles (DEP) increases antigen-specific IgE production and IgE-secreting cells, and induces Th2-type cytokine profiles in the airway in mice and humans. To determine the early effects of diesel exhaust (DE) inhalation on the cytokine production profile, BALB/c mice were exposed to 0 (controls) and 1.0 mg/m3 DE inhalation for 4 weeks. Intraperitoneal sensitization with ovalbumin (OVA) was conducted immediately before DE inhalation. Mice were treated with anti-CD4 or anti-CD8 mAb 1 day before and after the sensitization. On day 21, these mice were boosted with OVA and blood; bronchoalveolar lavage (BAL) fluid, and spleens were collected on day 28. In BAL fluid, both TNFalpha and IL-10 production in DE-exposed and control mice remained basically the same. IL-6 production in the anti-CD4 treatment group of DE-exposed mice, however, significantly increased compared with that of the controls. In vitro antigen-stimulated interleukin-4 (IL-4) and -10 (IL-10) production in spleen cells of exposed mice were not affected by low-dose DE inhalation. In vitro interferon (IFN)-gamma production in the anti-CD4 treated group of exposed mice decreased markedly. Although anti-OVA IgE production in the plasma of sham-treated mice exposed to DE was the same level as for controls, anti-CD4 mAb treatment in DE-exposed mice significantly reduced IgE production compared to controls. In anti-OVA IgG1 production, anti-CD4 or anti-CD8 mAb treatment in DE-exposed groups also significantly reduced. Anti-OVA IgG2a production was reduced by treatment with anti-CD4 mAb, but increased by anti-CD8 mAb treatment in DE-exposed mice. Low dose DE inhalation is thus shown to adversely affect the cytokine and antibody production in mice by altering CD4+ and CD8+ T-cell functions.     

Toxicity and elemental composition of particulate matter from outdoor and indoor air of elementary schools in Munich, Germany

Outdoor particulate matter (PM(10)) is associated with detrimental health effects. However, individual PM(10) exposure occurs mostly indoors. We therefore compared the toxic effects of classroom, outdoor, and residential PM(10). Indoor and outdoor PM(10) was collected from six schools in Munich during teaching hours and in six homes. Particles were analyzed by scanning electron microscopy and X-ray spectroscopy (EDX). Toxicity was evaluated in human primary keratinocytes, lung epithelial cells and after metabolic activation by several human cytochromes P450. We found that PM(10) concentrations during teaching hours were 5.6-times higher than outdoors (117 ± 48 μg/m(3) vs. 21 ± 15 μg/m(3), P < 0.001). Compared to outdoors, indoor PM contained more silicate (36% of particle number), organic (29%, probably originating from human skin), and Ca-carbonate particles (12%, probably originating from paper). Outdoor PM contained more Ca-sulfate particles (38%). Indoor PM at 6 μg/cm(2) (10 μg/ml) caused toxicity in keratinocytes and in cells expressing CYP2B6 and CYP3A4. Toxicity by CYP2B6 was abolished with the reactive oxygen species scavenger N-acetylcysteine. We concluded that outdoor PM(10) and indoor PM(10) from homes were devoid of toxicity. Indoor PM(10) was elevated, chemically different and toxicologically more active than outdoor PM(10). Whether the effects translate into a significant health risk needs to be determined. Until then, we suggest better ventilation as a sensible option. PRACTICAL IMPLICATIONS: Indoor air PM(10) on an equal weight base is toxicologically more active than outdoor PM(10). In addition, indoor PM(10) concentrations are about six times higher than outdoor air. Thus, ventilation of classrooms with outdoor air will improve air quality and is likely to provide a health benefit. It is also easier than cleaning PM(10) from indoor air, which has proven to be tedious.     

Evidence from surface tension and fluorescence data of a pyrene-assisted micelle-like assemblage of humic substances

Surface activity and fluorescence of humic substances (HS) and HS/pyrene solutions were monitored under various pH conditions. For HS alone the surface tension of the solutions decreased with increasing acidity, with a minimum at around pH 4. This effect, which is a consequence of an increase in the amphiphilic character of structures, is much more pronounced in humic (HA) than in fulvic acids (FA). The addition of pyrene (0.1 micromolL(-1)) results, for HA, in a marked reduction in the migration of amphiphilic species to the solution surface. FA profiles are not modified in presence of pyrene at that concentration. A decrease in the pyrene I1/I3 ratio in HS solutions shows that below pH 9 pyrene molecules react progressively to the change to a more hydrophobic environment, the greatest effect being observed at around pH 6 to 7. These signals are followed by a significant increase in the pyrene excimer fluorescence (lambda(exc)/lambda(em)=334 nm/450 nm), which is a consequence of the proximity of pyrene molecules. For FA, the I1/I3 decrease is less significant and no excimers develop. This set of effects is explained in view of conformational adjustments of HS, mainly HA, which become arranged in micelle-like domains in aqueous solution, the aromatic moieties being assembled around the pyrene molecules.     

川芎嗪对CVB3感染小鼠心肌细胞凋亡的影响

目的探讨川芎嗪对病毒性心肌炎（VM）小鼠心肌细胞凋亡的影响。方法将50只BALB/c小鼠随机分为A、B、C、D、E 5组,每组10只。A组腹腔注射生理盐水0.5 mL;B、C、D、E组均腹腔注射柯萨奇病毒B组（CVB3）0.5 mL诱导小鼠,建立VM模型。1 d后,A、B组给予腹腔注射生理盐水10 mg·kg^-1,1次·d^-1,连用7 d;C、D、E组分别腹腔注射盐酸川芎嗪注射液5 mg·kg^-1、10 mg·kg^-1、15 mg·kg^-1,1次·d^-1,均连用7 d;9 d后处死小鼠。采用TUNEL法检测心肌细胞凋亡;光镜下观察心肌病理变化;免疫组织化学技术检测各组小鼠心肌细胞中Fas/FasL蛋白的表达。结果心肌病理变化：A组无病变;心肌病变积分B组明显高于C、D、E组（均P〈0.01）;细胞凋亡：与A组比较,B、C、D、E组细胞凋亡指数明显升高（P〈0.01或P〈0.05）,与B组比较C、D、E组细胞凋亡指数明显降低（P〈0.01）;Fas/FasL蛋白阳性染色指数：B、C、D、E组均显著高于A组（P〈0.01或P〈0.05）,C、D、E组显著低于B组（P〈0.01）。结论川芎嗪可通过下调病毒性心肌炎小鼠心肌细胞Fas/FasL蛋白表达,减少心肌细胞凋亡和心肌损伤。     

Use of a toxicokinetic model in the analysis of cancer mortality in relation to the estimated absorbed dose of dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD).

We performed an analysis of All cancer and Lung cancer mortality in relation to estimated absorbed dose of dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD) in the cohort of chemical workers at 12 US plants assembled by the US National Institute for Occupational Safety and Health (NIOSH) (n = 5172). Estimates of cumulative exposure to TCDD were based on a minimal physiologic toxicokinetic model (MPTK) that accounts for inter- and intra-individual variations in body mass index (BMI) over time. Population-level parameters related to liver elimination and background (input or concentration) of TCDD were estimated from separate data with repeated measures of serum TCDD (US Air Force Health Study). An occupational TCDD input parameter was estimated based on one-point-in-time TCDD data available for a subset (n = 253) of the NIOSH cohort. Model-based time-dependent cumulative dose estimates (area under the curve (AUC) of the lipid-adjusted serum TCDD concentration over time) were obtained for members of the full cohort with recorded body height and weight (n = 4049), as this information is required by the MPTK model to compute dose. Missing-value problems arose in the estimation of the occupational input parameter (n = 42) and in TCDD-dose calculation in the full cohort (n = 886) and they were handled with multiple imputation methods. Risk-regression analyses were based on Cox log-linear models including age at entry, year of entry and duration of employment as categorical covariates in addition to the logarithm of cumulative TCDD dose in ppt-years. Risk sets were stratified on birth cohort. Estimates of the unlagged exposure coefficient in these models were 0.1249 [95% confidence interval (CI) 0.0144, 0.2354] for All cancer and 0.2158 (95% CI 0.02376, 0.4078) for lung cancer. A 10-year lag produced an increase in the estimate for all cancer (0.1539, 95% CI 0.0387, 0.2691), whereas, the estimate for lung cancer was not affected much (0.2125, 95% CI 0.0138, 0.4112). At a dose level of 100 times the background the estimates obtained with a 10-year lag translate into a relative risk of 2.03 (95% CI 1.19-3.45) for all cancer and of 2.66 (95% CI 1.07-6.64) for lung cancer. Higher estimates of the exposure coefficients were obtained after imputation of missing values. This increase in risk seemed due to the inclusion of short-term workers, who may exhibit a higher mortality for reasons other than dioxin exposure.     

Glutathione-S-transferase polymorphism, metallothionein expression, and mercury levels among students in Austria

BACKGROUND: Detoxification is an essential process in all living organisms. Humans accumulate heavy metals primarily as a result of lifestyle and environmental contamination. However, not all humans experience the estimated individual exposure. This suggests the presence of genetic regulatory mechanisms. OBJECTIVE: In order to identify genetic factors underlying the inter-individual variance in detoxification capacity for the heavy metal mercury, 192 students were investigated. We focused on the relationship between polymorphisms in glutathione-S-transferase (GST) genes and mercury concentrations in blood, urine, and hair. The correlation between blood mercury levels, GSTT1 and GSTM1 polymorphism, and gene expression of certain metallothionein subgroups (MT1, MT3) was evaluated in a further group of students (N=30). METHODS: Mercury levels in acid digested samples were measured by cold vapor AAS. Genotyping of the GSTT1 and GSTM1-gene deletion polymorphism was performed by means of PCR. Gene expression of several MT genes was analyzed in lymphocytes from fresh peripheral blood by semiquantitative RT-PCR. RESULTS: The following was noted: a) hair mercury concentrations are significantly increased in persons with the double deleted genotype (GSTT1-/- and GSTM1-/-) as compared to persons with the intact genotype, and b) MT1X expression is higher in persons with the intact genotype (GSTT1+/+ and GSTM1+/+). CONCLUSIONS: We conclude that the epistatic effect of the GSTT1 and the GSTM1 deletion polymorphism is a risk factor for increased susceptibility to mercury exposure. The relationship between MT gene expression and GST gene polymorphisms needs further investigation. If MT expression depends on GST polymorphisms it would have important implications on the overall metal detoxification capability of the human organism.     

肢体缺血预处理对大鼠脊髓缺血再灌注损伤的作用及机制

目的探讨肢体缺血预处理对大鼠脊髓缺血再灌注损伤的作用及机制。方法将72只SD大鼠按随机数字表法分为3组：假手术组（Sham组）、缺血再灌注损伤组（I/R组）和缺血预处理组（LIPC组）,每组24只。Sham组仅暴露腹主动脉,不结扎;I/R组采用Zivin法建立脊髓缺血再灌注损伤模型,麻醉后夹闭左肾下腹主动脉30 min;LIPC组大鼠在麻醉后使用止血带阻断右下肢血运10 min,恢复血运10 min,反复2次后同I/R组办法建模。3组分别于手术缝合后6 h（T1）、1 d（T2）、3 d（T3）和7 d（T4）时随机抽取6只大鼠,采用改良Tarlov评分法进行下肢神经功能评分。各组在T1—T4时的评分结束后,取L2-4脊髓组织,行HE染色,双目光学显微镜下观察脊髓组织的病理变化,并采用免疫组织化学法检测脊髓组织中胶质纤维酸性蛋白（GFAP）的表达水平。结果与Sham组比较：I/R组、LIPC组大鼠T1—T3时改良Tarlov得分均明显降低（均P〈0.05）,T1—T4时大鼠GFAP表达水平均明显升高（P〈0.05）;与I/R组比较：LIPC组大鼠T1—T3时改良Tarlov得分,T2、T3时大鼠脊髓组织中GFAP表达水平均明显升高（均P〈0.05）。结论肢体缺血预处理有减轻大鼠脊髓缺血再灌注损伤的作用,其机制可能与GFAP表达上调有关。     

Induction of CYP1A and DNA damage in the fathead minnow (Pimephales promelas) following exposure to biosolids

Biosolids (treated sewage sludge) are increasingly disposed of on land. Thus particle-sorbed and dissolved constituents have the potential to enter nearby watersheds. Although organic contaminants are known to be present in biosolids these are not currently regulated and little data exist on their potential toxicity to aquatic organisms. We exposed Pimephales promelas to two concentrations of biosolids (0.5 and 2.5 g l(-1)) for 28-days (static-renewal) and characterized contaminants present and the extent of CYP1A and DNA damage induction at various time points. Many organic contaminants were detected in the biosolids, with polycyclic aromatic hydrocarbons (PAHs) being the dominant class. Substantial levels of polybrominated diphenyl ethers (PBDEs) and nonylphenols (NPs) were also present. Significant induction of hepatic CYP1A protein compared with controls (P<0.05) was observed in both low (0.5 g l(-1)) and high (2.5 g l(-1)) exposed fish from Day 7. CYP1A levels peaked at Day 21 with 21-fold and 8-fold inductions over controls in high and low dose fish respectively. Induction of DNA damage in hepatocytes (single strand breaks as measured using the COMET assay) was observed in both exposures compared with controls on Days 14 and 28 (P<0.05). A significant correlation was found between CYP1A induction and DNA damage (Pearson correlation index, P<0.05). It is plausible that activation of PAHs may be responsible for the induction of CYP1A and resulting increase in DNA damage. Our data show the potential for detrimental effects in the event of exposure of aquatic organisms to biosolids and the need for further investigations of possible impacts due to constituents not covered by current guidelines.