Effect of polymorphic metabolizing genes on micronucleus frequencies among benzene-exposed shoe workers in China

It is well-known that metabolism of benzene is required for the induction of toxicity and consequent health problems. Therefore, genetic variation in benzene (BZ) metabolism genes can influence health outcomes. However, large population studies are needed to provide more evidence for such relationship. We have conducted a large population investigation (385 BZ-exposed shoe workers and 197 matched healthy controls) on the association between inheritance of certain BZ metabolizing genes and the expression of micronuclei (MN). The latter was based on the cytokinesis-blocked MN assay. We analyzed the polymorphisms of GSTM1, GSTT1, GSTP1 (rs1695), CYP2E1 (rs3813867), CYP2E1 (rs2031920), CYP2E1 (rs6413432), mEH exon 3 (rs1051740), mEH exon 4 (rs2234922). Univariate Poisson regression analysis demonstrated that the BZ-exposed workers had significantly increased MN frequency compared with the controls (FR = 1.84, 95% CI: 1.56–2.18; P < 0.001), and showed a cumulative exposure dose–response relationship. The CYP2E1 rs3813867 mutant allele (CC + GC) (FR 1.15, 95% CI 1.02–1.29; P = 0.020) and rs2031920 variant allele (CT + TT) (FR = 1.23, 95% CI: 1.09–1.37, P < 0.01) was associated with higher MN frequency significantly compared with the wild genotype separately. Furthermore, the MN frequency in rs2031920 variant allele (CT + TT) (FR = 1.17, 95% CI: 1.04–1.31, P < 0.01) was also higher than the wild genotype when the age, gender and cumulative exposure dose was adjusted in Poisson regression. In addition, the CYP2E1, however, GSTM1null, GSTT1null, GSTP1 rs1695, rs6413432, rs1051740 and rs2234922 polymorphisms showed no association with MN frequency. Our results indicate that two promoter polymorphisms in the CYP2E1 gene, especially the rs2031920 variant allele, were involved with the BZ-induction of MN and may contribute to risk of cancer among exposed workers.     

姜黄素对环磷酰胺致微核形成率及染色体损伤的影响

目的:研究姜黄素(Cur)对化疗药物环磷酰胺(CP)所致微核形成及染色体损伤的影响。方法:昆明小鼠随机分成6组,即正常组,姜黄素组(100mg/kg),模型组,环磷酰胺(CP)+姜黄素低剂量(50mg/kg),环磷酰胺(CP)+姜黄素中剂量(100mg/kg),环磷酰胺(CP)+姜黄素高剂量组(200mg/kg)。正常组即阴性对照组,只喂基础饲料;模型组为环磷酰胺阳性对照组,处死前间隔24h腹腔注射环磷酰胺2次,浓度为50mg/kg;姜黄素组和环磷酰胺+姜黄素组在环磷酰胺给药前4周灌胃给药,每日1次。末次给环磷酰胺24h后将小鼠脱颈椎处死,每只小鼠取股骨作微核观测;另一部分小鼠在处死前2-3h腹腔注射秋水仙素,每10g体质量注射0.04%秋水仙素0.1mL,以积累分裂相,脱颈椎处死后取股骨制备染色体标本。结果:姜黄素对环磷酰胺所引起的微核发生有着显著的抑制作用;姜黄素对环磷酰胺所致的染色体损伤有显著的保护作用。结论:提示姜黄素不仅能改善环磷酰胺在肿瘤治疗中所导致的微核形成,而且能减少由环磷酰胺所诱发的染色体畸变。     

The antigenotoxic activities of cactus (Opuntia ficus-indica) cladodes against the mycotoxin zearalenone in Balb/c mice: Prevention of micronuclei,chromosome aberrations and DNA fragmentation

Zearalenone (ZEN) is a potent estrogenic metabolite. Evidence of its cytotoxicity and genotoxicity has recently emerged from several reports. This study was conducted to evaluate the ability of cactus (Opuntia ficus-indica) cladodes to protect Balb/c mice against ZEN induced genotoxicity. To this end, the effect of a single dose of ZEN (40 mg/kg b.w.) alone and with extract of cactus cladodes (25, 50 and 100 mg/kg b.w.) was monitored by measuring: (i) micronuclei induction in bone marrow cells, (ii) chromosome aberrations mainly breaks and gaps in bone marrow cells also and finally and (iii) DNA fragmentation in liver and kidney.     

No elevated genomic damage in children and adolescents with attention deficit/hyperactivity disorder after methylphenidate therapy

Background and objective

Attention-deficit/hyperactivity disorder (ADHD) is the most frequent psychiatric disorder in children and adolescents and is often treated with methylphenidate (MPH), resulting in MPH exposure in more than 1% of all children in many countries. A 2005 report on cytogenetic effects in peripheral lymphocytes from 12 ADHD children treated for 3 months with MPH raised questions about its genetic toxicity and potential carcinogenicity. In 2007, we described no elevated micronucleus frequency in 21 children after 3 months of MPH-treatment; since the difference between the two studies could not be explained we now enlarged the overall sample size, and added a healthy control group, a new chronically treated group and positive control slides. Furthermore, micronuclei were analyzed in a second tissue, buccal mucosa.

Study participants

A healthy control group (23 individuals), a chronically MPH-treated (>12 months) group (21 patients), and a drug naïve group of ADHD-affected children (26 patients), which was analyzed again after 3 months (17 patients) and 6 months (11 patients), provided samples for analysis of micronucleated lymphocytes. With inclusion of 14 previously obtained blood samples, an overall group size of 31 patients was reached for the comparison of the 3 months observation time with before for micronucleated lymphocytes. For buccal mucosa cells, an additional inclusion of 10 more chronically treated patients (no lymphocytes donated) yielded sample numbers of 22 (healthy), 17 (chronically treated), 23 (ADHD drug naïve), 14 (3 months) and 11 (6 months).

Results

No significant alteration in genomic damage as seen as micronucleus frequency in peripheral lypmphocytes or buccal mucosa cells was detected after MPH treatment.

Conclusions

No indication for genomic damage induced by MPH was obtained in this study, as in our previous study. Together with our previous study, our overall number of MPH-treated patients is now 68 (30 chronically treated, 38 prospectively followed), plus 23 healthy controls. Ongoing studies in the USA, as well as continuation of recently published epidemiological cancer incidence analysis should provide additional reassurance for MPH-treated ADHD patients.     

Modulation of DNA repair capacity and mRNA expression levels of XRCC1, hOGG1 and XPC genes in styrene-exposed workers

Decreased levels of single-strand breaks in DNA (SSBs), reflecting DNA damage, have previously been observed with increased styrene exposure in contrast to a dose-dependent increase in the base-excision repair capacity. To clarify further the above aspects, we have investigated the associations between SSBs, micronuclei, DNA repair capacity and mRNA expression in XRCC1, hOGG1 and XPC genes on 71 styrene-exposed and 51 control individuals. Styrene concentrations at workplace and in blood characterized occupational exposure. The workers were divided into low (below 50 mg/m³) and high (above 50 mg/m³) styrene exposure groups. DNA damage and DNA repair capacity were analyzed in peripheral blood lymphocytes by Comet assay. The mRNA expression levels were determined by qPCR. A significant negative correlation was observed between SSBs and styrene concentration at workplace (R = − 0.38, p = 0.001); SSBs were also significantly higher in men (p = 0.001). The capacity to repair irradiation-induced DNA damage was the highest in the low exposure group (1.34 ± 1.00 SSB/10⁹ Da), followed by high exposure group (0.72 ± 0.81 SSB/10⁹ Da) and controls (0.65 ± 0.82 SSB/10⁹ Da). The mRNA expression levels of XRCC1, hOGG1 and XPC negatively correlated with styrene concentrations in blood and at workplace (p < 0.001) and positively with SSBs (p < 0.001). Micronuclei were not affected by styrene exposure, but were higher in older persons and in women (p < 0.001). In this study, we did not confirm previous findings on an increased DNA repair response to styrene-induced genotoxicity. However, negative correlations of SSBs and mRNA expression levels of XRCC1, hOGG1 and XPC with styrene exposure warrant further highly-targeted study.     

来氟米特3-甲基异构体对小鼠的致突变实验

目的:观察来氟米特3-甲基异构体的致突变作用。方法:取小鼠分为空白对照组、溶剂对照组、阳性对照组和来氟米特3-甲基异构体受试药不同剂量组;分别采用Ames实验观察每皿回变菌落数、小鼠骨髓嗜多染红细胞微核实验观察微核率、小鼠精子畸变实验观察精子畸变率。结果:Ames实验中受试药各剂量组回变菌落数均未超过溶剂对照组回变菌落数的2倍,实验结果为阴性;小鼠骨髓嗜多染红细胞微核实验及小鼠精子畸变实验中受试药各剂量组与空白对照组比较,微核率及精子畸变率无明显差异(P>0.05)。结论:在本次实验条件下,来氟米特3-甲基异构体未显示有致突变作用。     

The Assesment of Genotoxicity of Carbamazepine Using Cytokinesis-Block (CB) Micronucleus Assay in Cultured Human Blood Lymphocytes

The genotoxic effect of CBZ has been investigated in few studies. There is little evidence linking carbamazepine (CBZ) with any genotoxic effects, particularly in vitro micronucleus test using cytogenesis-block technique. In this study, the genotoxicity of the antiepileptic drug, carbamazepine, was tested using cytokinesis-block (CB) micronucleus assay. In vitro analysis was performed in human blood lymphocytes from four healthy persons at five different concentrations of carbamazepine (6, 8, 10, 12, 14 μg/mL). Genotoxic potential and cytotoxic effects of carbamazepine were evaluated by using micronucleus assay and cytokinesis-block proliferation index (CBPI), called the parameter of cytotoxicity in human peripheral blood lymphocyte cultures, respectively. The results of this study indicate that CBZ caused the genotoxic effect under in vitro conditions, except at the dose of 6 μg/mL, and cytotoxic effects of carbamazepine were revealed by a decrease in the cytokinesis-block proliferation index at all the concentrations.     

Long-term monitoring of sister chromatid exchanges and micronucleus frequencies in pharmacy personnel occupationally exposed to cytostatic drugs

Objectives: Many antineoplastic drugs were found to have carcinogenic, mutagenic and teratogenic potential. The aim of this study was to carry out cytogenetic and internal dose monitoring of hospital pharmacy personnel regularly involved in the preparation of cytostatic agents, in order to test possible cytostatics-induced genotoxic effects due to occupational exposure under routine working conditions, and in cases of accidental contamination. Methods: Platinum in whole blood and anthracyclines in plasma were measured to assess internal exposure to cytostatics. The level of cytogenetic damage was determined in peripheral blood lymphocytes with the micronucleus test and the sister chromatid exchange assay. Five series of monitoring were performed over a period of 2 years. Results: No significant differences in the mean frequencies of sister chromatid exchanges (SCE) and micronuclei (MN) were found between occupationally exposed probands and controls (9.9 ± 1.4 vs 10.1 ± 1.2 SCEs/cell and 21.2 ± 7.2 vs 23.3 ± 7.5 MN/2000 binucleated (BN) cells, n=16). Significant elevations of SCE or MN were detected in seven out of 12 cases of accidental contamination at the workplace, whereas no increase in platinum in blood and anthracyclines in plasma was observed in these probands. Two cases of non-reported contamination were identified by measurement of epirubicin in plasma. Smoking was found to increase the SCE significantly. No correlation between individual SCE scores and MN scores was observed. Conclusions: Our findings support a transient increase in SCE or MN after relevant exposure to cytostatic drugs in cases of accidental contamination. The lack of significant differences in SCE and MN between hospital pharmacy personnel and unexposed controls, points to high standards of safety at the corresponding workplaces. Received: 11 October 1999 / Accepted: 25 April 2000     

流式细胞术对小鼠外周血红细胞微核自动化检测的研究

本文报道双激光流式术对小鼠外周血嗜多染红细胞（ＰＣＥ）和成熟红细胞（ＮＣＥ）微核（ＭＮ）的自动化检测新方法。用噻唑橙染ＲＮＡ以区分ＰＣＥ和ＮＣＥ，用Ｈｏｅｃｈｓｔ３３３４２染ＤＮＡ以检测红细胞内ＭＮ。在用ＭＭＣ和ＣＯＬ进行的ＭＮ量效和时效关系研究中，其机检们和镜检结果吻合很好（ｒ＞０．９５），流式仪分选验证，证实其ＭＮ真实性在９５％以上，而检测速度比人工提高４０倍以上。本方法具有高速、精确、客观和完全自动化的特点，标志着流式仪对ＭＮ的自动化检测已达到实用化程度。     

Chromosomal aberrations and frequency of micronuclei in sheep subchronically exposed to the fungicide Euparen Multi (tolylfluanid)

We analyzed chromosome aberrations, micronucleus frequency, mitotic index (MI), and nuclear division index (NDI) in peripheral lymphocytes of sheep subchronically exposed to the fungicide Euparen Multi (containing 50% tolylfluanid). Euparen Multi was administered by rumen sonde to group of Merino sheep (seven sheep/group) at 93 mg/kg body weight (1/20 LD50) daily for 28 days to assess its genotoxic effects. The frequencies of aberrant cells (ABC) in the experimental and control groups were 5.50+/-1.38% and 2.40+/-1.14%, respectively, and the increase in ABC in the treated group was significant (P = 0.003). Significantly increased numbers of chromatid breaks (5.67+/-1.21% against 2.40+/-1.14%; P = 0.001), chromatid gaps (10.33+/-2.73% against 4.00+/-1.23%; P = 0.001), and chromosome gaps (1.83+/-0.75% against 0.80+/-0.45%; P = 0.025) and exchanges (3.17+/-1.94% against 0.20+/-0.45%; P = 0.009) were observed in exposed animals in comparison to control animals. The frequency of micronuclei (MN) was 29.40+/-5.86 per 1000 binucleated cells in peripheral lymphocytes of sheep in the control group and 49.57+/-19.12 per 1000 binucleated cells in the treated group. A significant increase in the frequency of MN in peripheral lymphocytes also was observed between the two groups (P = 0.0477). No statistical differences in MI and NDI values were found in the groups (P = 0.181 and 0.761, respectively). Thus, our results suggest that exposure to Euparen Multi may cause genome damage in somatic cells.