Qingshan Qu

Global levels of histone modifications in peripheral blood mononuclear cells of subjects with exposure to nickel.

Background: Occupational exposure to nickel (Ni) is associated with an increased risk for lung and nasal cancers. Ni compounds exhibit weak mutagenic activity, cause gene amplification, and disrupt cellular epigenetic homeostasis. However, the Ni-induced changes in global histone modification levels have only been tested in vitro. Objective: This study was conducted in a Chinese population to determine whether occupational exposure to Ni is associated with alterations of global histone modification levels and to evaluate the inter- and intraindividual variance of global histone modification levels. Method: Forty-five subjects with occupational exposure to Ni and 75 referents were recruited. Urinary Ni and global H3K4 trimethylation, H3K9 acetylation, and H3K9 dimethylation levels were measured in peripheral blood mononuclear cells (PBMCs) of subjects. Results: H3K4me3 was elevated in Ni-exposed subjects (0.25% ± 0.11%) compared with referents (0.15% ± 0.04%; p = 0.0004), and H3K9me2 was decreased (Ni-exposed subjects, 0.11% ± 0.05%; referents, 0.15% ± 0.04%; p = 0.003). H3K4me3 was positively (r = 0.4, p = 0.0008) and H3K9ac was negatively (r = 0.1, p = 0.01) associated with urinary Ni. Interindividual variances of H3K4me3, H3K9ac, and H3K9me2 were larger compared with intraindividual variance in both exposure test groups, resulting in reliability coefficients (an estimate of consistency of a set of measurements) of 0.60, 0.67, and 0.79 for H3K4me3, H3K9ac, and H3K9me2, respectively, for Ni-exposed subjects and of 0.75, 0.74, and 0.97, respectively, for referent subjects. Conclusion: The results of this study indicate that occupational exposure to Ni is associated with alterations of global histone modification levels and that measurements of global levels of histone modifications are relatively stable over time in human PBMCs.

Validation of biomarkers in humans exposed to benzene: urine metabolites.

BACKGROUND The present study was conducted among Chinese workers employed in glue- and shoe-making factories who had an average daily personal benzene exposure of 31+/-26 ppm (mean+/-SD). The metabolites monitored were S-phenylmercapturic acid (S-PMA), trans, trans-muconic acid (t,t-MA), hydroquinone (HQ), catechol (CAT), 1,2, 4-trihydroxybenzene (benzene triol, BT), and phenol. METHODS S-PMA, t,t-MA, HQ, CAT, and BT were quantified by HPLC-tandem mass spectrometry. Phenol was measured by GC-MS. RESULTS Levels of benzene metabolites (except BT) measured in urine samples collected from exposed workers at the end of workshift were significantly higher than those measured in unexposed subjects (P < 0.0001). The large increases in urinary metabolites from before to after work strongly correlated with benzene exposure. Concentrations of these metabolites in urine samples collected from exposed workers before work were also significantly higher than those from unexposed subjects. The half-lives of S-PMA, t,t-MA, HQ, CAT, and phenol were estimated from a time course study to be 12.8, 13.7, 12.7, 15.0, and 16.3 h, respectively. CONCLUSIONS All metabolites, except BT, are good markers for benzene exposure at the observed levels; however, due to their high background, HQ, CAT, and phenol may not distinguish unexposed subjects from workers exposed to benzene at low ambient levels. S-PMA and t,t-MA are the most sensitive markers for low level benzene exposure.

Personal exposure to different levels of benzene and its relationships to the urinary metabolites S-phenylmercapturic acid and trans,trans-muconic acid

This report is part of an extensive study to verify the validity, specificity, and sensitivity of biomarkers of benzene at low exposures and assess their relationships with personal exposure and genetic damage. The study population was selected from benzene-exposed workers in Tianjin, China, based on historical exposure data. The recruitment of 130 exposed workers from glue-making or shoe-making plants and 51 unexposed subjects from nearby food factories was based on personal exposure measurements conducted for 3-4 weeks prior to collection of biological samples. In this report we investigated correlation of urinary benzene metabolites, S-phenylmercapturic acid (S-PMA) and trans,trans-muconic acid (t,t-MA) with personal exposure levels on the day of urine collection and studied the effect of dose on the biotransformation of benzene to these key metabolites. Urinary S-PMA and t,t-MA were determined simultaneously by liquid chromatography-tandem mass spectrometry analyses. Both S-PMA and t,t-MA, but specifically the former, correlated well with personal benzene exposure over a broad range of exposure (0.06-122 ppm). There was good correlation in the subgroup that had been exposed to <1 ppm benzene with both metabolites (P-trend <0.0001 for S-PMA and 0.006 for t,t-MA). Furthermore, the levels of S-PMA were significantly higher in the subgroup exposed to <0.25 ppm than that in unexposed subjects (n=17; P=0.001). There is inter-individual variation in the rate of conversion of benzene into urinary metabolites. The percentage of biotransformation of benzene to urinary S-PMA ranged from 0.005 to 0.3% and that to urinary t,t-MA ranged from 0.6 to approximately 20%. The percentage of benzene biotransformed into S-PMA and t,t-MA decreased with increasing concentration of benzene, especially conversion of benzene into t,t-MA. It appears that women excreted more metabolites than men for the same levels of benzene exposures. Our data suggest that S-PMA is superior to t,t-MA as a biomarker for low levels of benzene exposure.

The effect of exposure to carcinogenic metals on histone tail modifications and gene expression in human subjects

The precise mechanisms by which nickel and arsenic compounds exert their carcinogenic properties are not completely understood. In recent years, alterations of epigenetic mechanisms have been implicated in the carcinogenesis of compounds of these two metals. In vitro exposure to certain nickel or arsenic compounds induces changes in both DNA methylation patterns, as well as, in the levels of posttranslational modifications of histone tails. Changes in DNA methylation patterns have been reported in human subjects exposed to arsenic. Here we review our recent reports on the alterations in global levels of posttranslational histone modifications in peripheral blood mononuclear cells (PBMCs) of subjects with occupational exposure to nickel and subjects exposed to arsenic in their drinking water. Occupational exposure to nickel was associated with an increase in H3K4me3 and decrease in H3K9me2. A global increase in H3K9me2 and decrease in H3K9ac was found in subjects exposed to arsenic. Additionally, exposure to arsenic resulted in opposite changes in a number of histone modifications in males when compared with females in the arsenic population. The results of these two studies suggest that exposure to nickel or arsenic compounds, and possibly other carcinogenic metal compounds, can induce changes in global levels of posttranslational histone modifications in peripheral blood mononuclear cells.

Exposure to inhaled nickel nanoparticles causes a reduction in number and function of bone marrow endothelial progenitor cells

Introduction: Particulate matter (PM), specifically nickel (Ni) found on or in PM, has been associated with an increased risk of mortality in human population studies and significant increases in vascular inflammation, generation of reactive oxygen species, altered vasomotor tone, and potentiated atherosclerosis in murine exposures. Recently, murine inhalation of Ni nanoparticles have been shown to cause pulmonary inflammation that affects cardiovascular tissue and potentiates atherosclerosis. These adverse cardiovascular outcomes may be due to the effects of Ni on endothelial progenitor cells (EPCs), endogenous semi-pluripotent stem cells that aid in endothelial repair. Thus, we hypothesize that Ni nanoparticle exposures decrease cell count and cause impairments in function that may ultimately have significant effects on various cardiovascular diseases, such as, atherosclerosis. Methods: Experiments involving inhaled Ni nanoparticle exposures (2 days/5 h/day at ∼1200 µg/m3, 3 days/5 h/day at ∼700 µg/m3, and 5 days/5 h/day at ∼100 µg/m3), were performed in order to quantify bone marrow resident EPCs using flow cytometry in C57BL/6 mice. Plasma levels of human stromal cell-derived factor 1α (SDF-1α) and vascular endothelial growth factor (VEGF) were assessed by enzyme-linked immunosorbent assay and in vitro functional assessments of cultured EPCs were conducted. Results and conclusions: Significant EPC count differences between exposure and control groups for Ni nanoparticle exposures were observed. Differences in EPC tube formation and chemotaxis were also observed for the Ni nanoparticle exposed group. Plasma VEGF and SDF-1α differences were not statistically significant. In conclusion, this study shows that inhalation of Ni nanoparticles results in functionally impaired EPCs and reduced number in the bone marrow, which may lead to enhanced progression of atherosclerosis.

The Role of Metal Components in the Cardiovascular Effects of PM2.5

Exposure to ambient fine particulate matter (PM2.5) increases risks for cardiovascular disorders (CVD). However, the mechanisms and components responsible for the effects are poorly understood. Based on our previous murine exposure studies, a translational pilot study was conducted in female residents of Jinchang and Zhangye, China, to test the hypothesis that specific chemical component of PM2.5 is responsible for PM2.5 associated CVD. Daily ambient and personal exposures to PM2.5 and 35 elements were measured in the two cities. A total of 60 healthy nonsmoking adult women residents were recruited for measurements of inflammation biomarkers. In addition, circulating endothelial progenitor cells (CEPCs) were also measured in 20 subjects. The ambient levels of PM2.5 were comparable between Jinchang and Zhangye (47.4 and 54.5µg/m3, respectively). However, the levels of nickel, copper, arsenic, and selenium in Jinchang were 82, 26, 12, and 6 fold higher than Zhangye, respectively. The levels of C-reactive protein (3.44±3.46 vs. 1.55±1.13), interleukin-6 (1.65±1.17 vs. 1.09±0.60), and vascular endothelial growth factor (117.6±217.0 vs. 22.7±21.3) were significantly higher in Jinchang. Furthermore, all phenotypes of CEPCs were significantly lower in subjects recruited from Jinchang than those from Zhangye. These results suggest that specific metals may be important components responsible for PM2.5-induced cardiovascular effects and that the reduced capacity of endothelial repair may play a critical role.

Sensitive biomarker of polycyclic aromatic hydrocarbons (PAHs): urinary 1-hydroxyprene glucuronide in relation to smoking and low ambient levels of exposure

Abstract The study was conducted in a Chinese population with occupational or environmental exposures to polycyclic aromatic hydrocarbons (PAHs). A total of 106 subjects were recruited from coke-oven workers (workers), residents in a metropolitan area (residents) and suburban gardeners (gardeners). All subjects were monitored twice for their personal exposures to PAHs. The biological samples were collected for measurements of 1-hydroxypyrene (1-OHP) and cotinine in urine. The geometric means of personal exposure levels of pyrene, benz(a)anthracene (BaA) and benzo(a)pyrene (BaP) in workers were 1.470, 0.978 and 0.805 µg m−3, respectively. The corresponding levels in residents were 0.050, 0.034 and 0.025 µg m−3; and those in gardeners were 0.011, 0.020 and 0.008 µg m−3, respectively. The conjugate of 1-OHP with glucuronide (1-OHP-G) is the predominant form of pyrene metabolite in urine and it showed strong associations with exposures not only to pyrene, but also to BaA, BaP and total PAHs. Most importantly, a significant difference in 1-OHP-G was even detected between the subgroups with exposures to BaP at < 0.010 and > 0.010 but < 0.020 µg m−3, suggesting that 1-OHP-G is a good marker that can be used for the risk assessment of BaP exposure at levels currently encountered in ambient air. Furthermore, multiple regression analyses of 1-OHP-G on PAHs exposure indicated that cigarette smoke was a major confounding factor and should be considered and adjusted for while using 1-OHP to estimate PAHs exposure.

Association of Systemic Inflammation with Marked Changes in Particulate Air Pollution in Beijing in 2008

Many studies have linked ambient fine particulate matter (aerodynamic diameters less than 2.5 μm, PM₂.₅) air pollution to increased morbidity and mortality of cardiovascular diseases in the general population, but the biologic mechanisms of these associations are yet to be elucidated. In this study, we aimed to evaluate the relationship between daily variations in exposure to PM₂.₅ and inflammatory responses in mice during and for 2 months after the Beijing Olympic Games. Male C57BL/6 mice were exposed to Beijing PM₂.₅ or filtered air (FA) in 2008 during the 2 months of Beijing Olympic and Paralympic Games, and for 2 months after the end of the Games. During the Games, circulating monocyte chemoattractant protein 1 and interleukin 6 were increased significantly in the PM₂.₅ exposure group, when compared with the FA control group, although there were no significant inter-group differences in tumor necrosis factor-α or interferon-γ, or in macrophages, neutrophils or lymphocytes in the spleen or thymus between these 2 groups. However, macrophages were significantly increased in the lung and visceral fat with increasing PM₂.₅. After the Olympic Games, there were no significant PM₂.₅-associated differences for macrophages, neutrophils or lymphocytes in the thymus, but macrophages were significantly elevated in the lung, spleen, subcutaneous and visceral fat with increasing PM₂.₅, and the numbers of macrophages were even higher after than those during the Games. Moreover, the number of neutrophils was markedly higher in the spleen for the PM₂.₅-exposed- than the FA-group. These data suggest that short-term increases in exposure to ambient PM₂.₅ leads to increased systemic inflammatory responses, primarily macrophages and neutrophils in the lung, spleen, and visceral adipose tissue. Short-term air quality improvements were significantly associated with reduced overall inflammatory responses.

Roles of MAPK pathway activation during cytokine induction in BEAS-2B cells exposed to fine World Trade Center (WTC) dust

The World Trade Center (WTC) collapse on September 11, 2001 released copious amounts of particulate matter (PM) into the atmosphere of New York City. Follow-up studies on persons exposed to the dusts have revealed a severely increased rate for asthma and other respiratory illnesses. There have only been a few studies that have sought to discern the possible mechanisms underlying these untoward pathologies. In one study, an increased cytokine release was detected in cells exposed to WTC fine dusts (PM2.5 fraction or WTC2.5). However, the mechanism(s) for these increases has yet to be fully defined. Because activation of the mitogen-activated protein kinase (MAPK) signaling pathways is known to cause cytokine induction, the current study was undertaken to analyze the possible involvement of these pathways in any increased cytokine formation by lung epithelial cells (as BEAS-2B cells) exposed to WTC2.5. Our results showed that exposure to WTC2.5 for 5 hr increased interleukin-6 (IL-6) mRNA expression in BEAS-2B cells, as well as its protein levels in the culture media, in a dose-dependent manner. Besides IL-6, cytokine multiplex analyses revealed that formation of IL-8 and -10 was also elevated by the exposure. Both extracellular signal-regulated kinase (ERK) and p38, but not c-Jun N-terminal protein kinase, signaling pathways were found to be activated in cells exposed to WTC2.5. Inactivation of ERK signaling pathways by PD98059 effectively blocked IL-6, -8, and -10 induction by WTC2.5; the p38 kinase inhibitor SB203580 significantly decreased induction of IL-8 and -10. Together, our data demonstrated activation of MAPK signaling pathway(s) likely played an important role in the WTC2.5-induced formation of several inflammatory (and, subsequently, anti-inflammatory) cytokines. The results are important in that they help to define one mechanism via which the WTC dusts may have acted to cause the documented increases in asthma and other inflammation-associated respiratory dysfunctions in the individuals exposed to the dusts released from the WTC collapse.

CrVI exposure and biomarkers: Cr in erythrocytes in relation to exposure and polymorphisms of genes encoding anion transport proteins

Abstract A total of 195 subjects, including 141 exposed workers and 54 farmers, were recruited in China to evaluate the usefulness of chromium (Cr) in erythrocytes as a biomarker of exposure to CrVI. The levels of Cr in red blood cells (RBC) were remarkably elevated even in a group of workers routinely exposed to CrVI as low as 5–15 µg m−3 and showed a significant exposure–response trend over the exposure range from 0.002 to 1152 µg m−3 (p<0.0001). Multiple linear regression analyses indicated that age and cigarette smoke were not associated with Cr in RBC. However, female subjects had lower Cr in RBC compared with their male counterparts for about the same exposure levels (p<0.05). The genotypes of band III, which encodes for anion transport protein and may regulate across cell membranes, were also identified and included for analysis. The ratios of Cr in RBC to CrVI exposure were higher in subjects with a wild genotype than in those who had heterozygous or homozygous variant alleles. However, the difference was not statistically significant probably due to the limited number of participating subjects. In addition, 15 of the 141 workers were selected for multiple exposure monitoring and blood sample collections to evaluate the inter- and intraindividual variations of Cr in RBC. Compared with the personal exposure levels, Cr in RBC had small intraindividual variations with a reliability coefficient of 0.88. The study suggests that Cr in RBC may serve as a sensitive and reliable biomarker for long-term exposure to CrVI.