DNA链断裂作为石棉接触的生物标志物的研究

为研究接触石棉粉尘工人的生物监测指标，利用简便、快速、敏感、经济的单细胞凝胶电泳法（ＳＣＧＥ，又称彗星试验），检测了某石棉制品厂５５名石棉作业工人和３０名对照人群的外周血白细胞ＤＮＡ断裂水平。结果表明：接尘组外周血白细胞ＤＮＡ链断裂的水平显著高于对照组（Ｐ＜０．０１）；性别、年龄、工龄和石棉尘浓度与ＤＮＡ迁移水平有关。     

Primary DNA damage in peripheral mononuclear blood cells of workers exposed to bitumen-based products

The genotoxic effect of occupational exposure to bitumen-based products was determined by the extent of DNA strand breaks and alkali-labile sites of the DNA of peripheral mononuclear blood cells from seven roofers, 18 road paving workers, and nine bitumen painters. In order to evaluate short-term genotoxic effect the workers were investigated on Fridays and on Mondays after a weekend free of occupational exposure. The roofers (all cigarette smokers) showed a significantly (P < 0.002) 43% higher mean level of alkaline DNA strand breaks on Friday than did the ten smoking controls included in this study. Also, comparison of the individual levels of alkaline strand breaks on Mondays and on Fridays revealed a significant increase (P < 0.05, Wilcoxon test) during the work week. In the road paving workers and the bitumen painters no statistically significant difference in the mean levels of alkaline strand breaks could be found compared to controls either for the measurement on Mondays or for that on Fridays. However, interesting tendencies were observed. As in the group of roofers, the mean level of alkaline DNA strand breaks as well as the majority of the individual levels of alkaline strand breaks of road paving workers was higher on Fridays than on Mondays. In contrast, bitumen painters exhibited a relatively high level of alkaline DNA strand breaks on Mondays and a decreased mean level of strand breaks on Fridays. DNA adducts could be detected at a low level (up to 2.9 adducts per 10⁹ bases) in 10 of 14 road paving workers and bitumen painters using the ³²p-postlabelling assay. The number of DNA adducts correlated with the years spent in the present job. Road paving workers and bitumen painters showed only suggestive evidence for a possible genotoxic effect due to their occupational exposure. Because we cannot exclude the formation of DNA cross-links in these workers, a more detailed investigation of the hazard is urgently needed. For roofers, substantial genotoxic damage in peripheral mononuclear blood cells was observed in this study.This study contains parts of an M.D. thesis by G. Boettler     

An evaluation of DNA double strand break formation and excreted guanine species post whole body PET/CT procedure

Ionizing radiation-induced oxidation and formation of deoxyribonucleic acid (DNA) double strand breaks (DSBs) are considered the exemplar of genetic lesions. Guanine bases are most prone to be oxidized when DNA and Ribonucleic acid (RNA) are damaged. The repair processes that are initiated to correct this damage release multiple oxidized guanine species into the urine. Hence, the excretion of guanine species can be related with the total repair process. Our study quantified the total DSBs formation and the amount of guanine species in urine to understand the DNA break and repair process after whole body (WB) exposure to ¹⁸F-FDG positron emission tomography/computed tomography (PET/CT). A total of 37 human participants were included with control and test groups and the average radiation dose was 27.50 ± 2.91 mSv. γ-H2AX foci assay in the collected blood samples was performed to assess the DSBs, and excreted guanine species in urine were analyzed by a competitive ELISA method. We observed a significant increase of DNA damage that correlated well with the increasing dose (p-value 0.009) and body weight (p-value 0.05). In the test group, excreted guanine species in urine sample significantly increased (from 24.29 ± 5.82 to 33.66 ± 7.20 mg/mmol creatinine). A minimum (r² = 0.0488) correlation was observed between DSBs formation and excreted guanine species. A significant difference of DNA damage and 8-OHdG formation was seen in the test group compared to controls. Larger population studies are needed to confirm these observations, describe the fine-scale timing of changes in the biomarker levels after exposure, and further clarify any potential risks to patients from PET/CT procedures.     

Use of biomarkers to characterize functions of polymorphic DNA repair genotypes

Inheritance of variant DNA repair genes is believed to influence individual susceptibility to the development of environmental cancer. However, the validity of the belief is dependent upon understanding the functions of the variant genes. Consequently, a variety of studies have been conducted to investigate the functions of variant DNA repair genes, e.g. using biomarkers. These studies on several representative polymorphic DNA repair genes are reviewed in this report. From a general overview, it appears that the biomarker investigations did not provide consistent observations. However, from a more careful evaluation, it is clear that the inconsistencies are probably caused by the use of populations and biomarkers that are not appropriate for investigating the repair activities of the genes. For example, the use of cigarette smokers and patients may not generate precise information for this type of investigations because these conditions can modify the functions of the investigated genes. Thus, the use of healthy non-smokers would be more appropriate. Other problems with these studies includes the small sample size used and the fact that some of the biomarkers used, such as sister chromatid exchanges, are not appropriate because the mechanisms for formation of the biomarkers and their biological significance are unknown. Nevertheless, the following conclusions can be derived from the review of the various biomarker studies that have been published. XRCC1 194Trp, OGG1 326Cys and APE1 148Glu probably have limited alterations in repair activities compared to the wild-type genotypes. XRCC1 399Gln and XRCC3 241Met are deficient in the repair of X-ray-, but not UV-light-induced chromosome aberrations, therefore the variant genes are defective in base excision repair. XPD 312Asn and XPD 751Gln are deficient in the repair of UV-light- but not X-ray-induced chromosome aberrations, therefore they are defective in nucleotide excision repair.     

二硫化碳对植入期小鼠子宫内膜细胞DNA损伤的研究

目的 用单细胞凝胶电泳(SCGE)技术检测二硫化碳(carbon disulfide,CS:)致植入期小鼠子宫内膜细胞DNA损伤,探讨其胚胎植人障碍机制.方法 用机械刮取法制备胚胎植入期小鼠子宫内膜单细胞悬液,台盼蓝检测细胞活性,用0、500、1000、2500μmol/L CS_2与细胞共培养1h后进行SCGE实验,采集彗旱图像,CASP系统自动分析各项指标.结果 不同剂量的CS_2染毒对DNA造成不同程度的损伤,形成较为典型的正常细胞和彗星细胞图像.与对照组比较,500、1000、2500 μmol/LCS_2染毒组彗星头部DNA含量百分比(HDNA%)分别减少了7.49%、12.19%、24.36%,差异均有统计学意义(P<0.01);500、1000、2500 μmol/LCS_2染毒组彗星尾部DNA含量百分比(TDNA%)、尾长(TL)、Olive尾矩(0TM)分别增加了7.13、11.60、23.18倍,3.68、5.98、9.62倍和9.16、16.84、39.32倍,差异均有统计学意义(P<0.01).与500、1000 μmol/L CS_2染毒组比较,2500μml/L CS_2染毒组的TDNA%、TL、彗星全长(CL)、尾矩(TM)、OTM增加了1.98、0.92、1.27、0.52、0.37倍和0.17、5.31、1.90、2.97、1.26倍,差异有统计学意义(P<0.01);与500 μmol/L CS_2染毒组比较,1000μmol/L CS_2染毒组的TDNA%、,TL、CL、TM、OTM增加了0.55、0.49、0.16、1.18、0.76倍,差异有统计学意义(P<0.01).HDNA%、TDNA%、TL、TM、OTM与染毒剂量的回归系数分别为-13.78,13.78,0.05,4.38,3.23,差异有统计学意义(P(0.01).结论 CS_2致植入期小鼠子宫内膜细胞DNA损伤,随着染毒剂量增加,损伤程度明显增加.CS_2损伤植入期小鼠母体子宫内膜细胞可能是影响胚胎正常植入的重要原因之一.     

Investigations of the frequency of DNA strand breakage and cross-linking and of sister chromatid exchange in the lymphocytes of electric welders exposed to chromium- and nickel-containing fumes

Summary A total of 39 electric welders exposed to chromium and nickel were compared with 18 controls standardized for age, smoking habits and sex with respect to the frequency of sister chromatid exchange (SCE) and of DNA strand breakage and cross-linking (measured by the method of alkaline filter elution) in their blood lymphocytes. A significant correlation was found between the frequency of SCE and of individual DNA strand breakage and the concentration of chromium in the urine. Less DNA from the welders than from the control group was eluted through the two filter types used (polycarbonate and polyvinylidene fluoride filters). This must be interpreted as resulting from the presence of DNA-protein cross-links, which has the secondary effect of leading to a relative reduction in the measurable frequency of strand breakage amongst the welders. The present results are in good agreement with in vitro and in vivo investigations that confirm the importance of DNA-protein cross-links for the carcinogenic effect of chromium.     

Vaxfectin enhances both antibody and in vitro T cell responses to each component of a 5-gene Plasmodium falciparum plasmid DNA vaccine mixture administered at low doses

We previously reported the capacity of the cationic lipid-based formulation, Vaxfectin^®, to enhance the immunogenicity and protective efficacy of a low dose plasmid DNA vaccine against Plasmodium yoelii malaria in mice. Here, we have extended this finding to human Plasmodium falciparum genes, evaluating the immune enhancing effect of Vaxfectin^® formulation on a mixture, designated CSLAM, of five plasmid DNA vaccines encoding antigens from the sporozoite (PfCSP, PfSSP2/TRAP), intrahepatic (PfLSA1), and erythrocytic (PfAMA1, PfMSP1) life cycle stages of P. falciparum administered at 2, 10 or 50 μg doses. Vaxfectin^® formulation enhanced both antibody and cellular immune responses to each component of the multi-antigen vaccine mixture, as assessed by ELISA, IFAT, and IFN-γ ELIspot, respectively. There was no apparent antigenic competition, as indicated by comparison of responses induced in mice immunized with PfCSP vs. CSLAM. These data showing that Vaxfectin^® can enhance the immunogenicity of plasmid DNA vaccines administered at low doses per body weight, and in combinations, has important clinical implications for the development of a vaccine against malaria, as well as against other public health threats.