Genetic polymorphisms involved in toxicant-metabolizing enzymes and the risk of chronic benzene poisoning in Chinese occupationally exposed populations

Biological exposure indices of occupational exposure to benzene: A systematic review

The current study aimed to systematically review the studies concerning the biological monitoring of benzene exposure in occupational settings. A systematic literature review was conducted in Scopus, EMBASE, Web of Science, and Medline from 1985 through July 2021. We included peer-reviewed original articles that investigated the association between occupational exposure to benzene and biological monitoring. We identified 4786 unique citations, of which 64 cross-sectional, one case-control, and one cohort study met our inclusion criteria. The most studied biomarkers were urinary trans-trans muconic acid, S- phenyl mercapturic acid, and urinary benzene, respectively. We found the airborne concentration of benzene as a key indicator for choosing a suitable biomarker. We suggest considering urinary benzene at low (0.5-5.0 TLV), urinary SPMA and TTMA at medium (5.0-25 and 25-50 TLV, respectively), and urinary phenol and hydroquinone and catechol at very high concentrations (500 and 1000 TLV ≤, respectively). Genetic polymorphism of glutathione S-transferase and oral intake of sorbic acid have confounding effects on the level of U-SPMA and U-TTMA, respectively. The airborne concentration, smoking habit, oral consumption of sorbic acid, and genetic polymorphism of workers should be considered in order to choose the appropriate indicator for biological monitoring of benzene exposure.

Current practice and recommendations for advancing how human variability and susceptibility are considered in chemical risk assessment

A key element of risk assessment is accounting for the full range of variability in response to environmental exposures. Default dose-response methods typically assume a 10-fold difference in response to chemical exposures between average (healthy) and susceptible humans, despite evidence of wider variability. Experts and authoritative bodies support using advanced techniques to better account for human variability due to factors such as in utero or early life exposure and exposure to multiple environmental, social, and economic stressors.This review describes: 1) sources of human variability and susceptibility in dose-response assessment, 2) existing US frameworks for addressing response variability in risk assessment; 3) key scientific inadequacies necessitating updated methods; 4) improved approaches and opportunities for better use of science; and 5) specific and quantitative recommendations to address evidence and policy needs.Current default adjustment factors do not sufficiently capture human variability in dose-response and thus are inadequate to protect the entire population. Susceptible groups are not appropriately protected under current regulatory guidelines. Emerging tools and data sources that better account for human variability and susceptibility include probabilistic methods, genetically diverse in vivo and in vitro models, and the use of human data to capture underlying risk and/or assess combined effects from chemical and non-chemical stressors.We recommend using updated methods and data to improve consideration of human variability and susceptibility in risk assessment, including the use of increased default human variability factors and separate adjustment factors for capturing age/life stage of development and exposure to multiple chemical and non-chemical stressors. Updated methods would result in greater transparency and protection for susceptible groups, including children, infants, people who are pregnant or nursing, people with disabilities, and those burdened by additional environmental exposures and/or social factors such as poverty and racism.

The effects of genetic polymorphisms on benzene-exposed workers: A systematic review

BACKGROUND AND AIMS

Benzene is a group I carcinogen, which has been associated with leukemia and myelodysplastic syndrome. Moreover, it has been proposed that polymorphisms in benzene metabolizing genes influence the outcomes of benzene exposure in the human body. This systematic review aims to elucidate the existent relationship between genetic polymorphisms and the risk of developing adverse health effects in benzene-exposed workers.

METHODS

Three databases were systematically searched until April 2020. The preferred reporting items for systematic reviews and meta-analyses method was used to select articles published between 2005 and 2020. Quality assessment and risk of bias were evaluated by the Newcastle-Ottawa scale.

RESULTS

After full-text evaluation, 36 articles remained out of 645 initially screened. The most studied health effects within the reviewed papers were chronic benzene poisoning, hematotoxicity, altered urinary biomarkers of exposure, micronucleus/chromosomal aberrations, and gene methylation. Furthermore, some polymorphisms on NQO1, GSTT1, GSTM1, MPO, and CYP2E1, among other genes, showed a statistically significant relationship with an increased risk of developing at least one of these effects on benzene-exposed workers. However, there was no consensus among the reviewed papers on which specific polymorphisms were the ones associated with the adverse health-related outcomes, except for the NQO1 rs1800566 and the GSTT1 null genotypes. Additionally, the smoking habit was identified as a confounder, demonstrating worse health outcomes in exposed workers that smoked.

CONCLUSION

Though there is a positive relationship between genetic polymorphisms and detrimental health outcomes for benzene-exposed workers, broader benzene-exposed cohorts that take into account the genetic diversity of the population are needed in order to determine which specific polymorphisms incur in health risks.

The diverse functionality of NQO1 and its roles in redox control

In this review, we summarize the multiple functions of NQO1, its established roles in redox processes and potential roles in redox control that are currently emerging. NQO1 has attracted interest due to its roles in cell defense and marked inducibility during cellular stress. Exogenous substrates for NQO1 include many xenobiotic quinones. Since NQO1 is highly expressed in many solid tumors, including via upregulation of Nrf2, the design of compounds activated by NQO1 and NQO1-targeted drug delivery have been active areas of research. Endogenous substrates have also been proposed and of relevance to redox stress are ubiquinone and vitamin E quinone, components of the plasma membrane redox system. Established roles for NQO1 include a superoxide reductase activity, NAD+ generation, interaction with proteins and their stabilization against proteasomal degradation, binding and regulation of mRNA translation and binding to microtubules including the mitotic spindles. We also summarize potential roles for NQO1 in regulation of glucose and insulin metabolism with relevance to diabetes and the metabolic syndrome, in Alzheimer's disease and in aging. The conformation and molecular interactions of NQO1 can be modulated by changes in the pyridine nucleotide redox balance suggesting that NQO1 may function as a redox-dependent molecular switch.

Vib-PT, an Aromatic Prenyltransferase Involved in the Biosynthesis of Vibralactone from Stereum vibrans

Vibralactone, a hybrid compound derived from phenols and a prenyl group, is a strong pancreatic lipase inhibitor with a rare fused bicyclic β-lactone skeleton. Recently, a researcher reported a vibralactone derivative (compound C1) that caused inhibition of pancreatic lipase with a half-maximal inhibitory concentration of 14 nM determined by structure-based optimization, suggesting a potential candidate as a new antiobesity treatment. In the present study, we sought to identify the main gene encoding prenyltransferase in Stereum vibrans, which is responsible for the prenylation of phenol leading to vibralactone synthesis. Two RNA silencing transformants of the identified gene (vib-PT) were obtained through Agrobacterium tumefaciens-mediated transformation. Compared to wild-type strains, the transformants showed a decrease in vib-PT expression ranging from 11.0 to 56.0% at 5, 10, and 15 days in reverse transcription-quantitative PCR analysis, along with a reduction in primary vibralactone production of 37 to 64% at 15 and 21 days, respectively, as determined using ultra-high-performance liquid chromatography-mass spectrometry analysis. A soluble and enzymatically active fusion Vib-PT protein was obtained by expressing vib-PT in Escherichia coli, and the enzyme's optimal reaction conditions and catalytic efficiency (K_m /k _cat) were determined. In vitro experiments established that Vib-PT catalyzed the C-prenylation at C-3 of 4-hydroxy-benzaldehyde and the O-prenylation at the 4-hydroxy of 4-hydroxy-benzenemethanol in the presence of dimethylallyl diphosphate. Moreover, Vib-PT shows promiscuity toward aromatic compounds and prenyl donors.IMPORTANCE Vibralactone is a lead compound with a novel skeleton structure that shows strong inhibitory activity against pancreatic lipase. Vibralactone is not encoded by the genome directly but rather is synthesized from phenol, followed by prenylation and other enzyme reactions. Here, we used an RNA silencing approach to identify and characterize a prenyltransferase in a basidiomycete species that is responsible for the synthesis of vibralactone. The identified gene, vib-PT, was expressed in Escherichia coli to obtain a soluble and enzymatically active fusion Vib-PT protein. In vitro characterization of the enzyme demonstrated the catalytic mechanism of prenylation and broad substrate range for different aromatic acceptors and prenyl donors. These characteristics highlight the possibility of Vib-PT to generate prenylated derivatives of aromatics and other compounds as improved bioactive agents or potential prodrugs.

Activated carbon/diatomite-based magnetic nanocomposites for magnetic solid-phase extraction of S-phenylmercapturic acid from human urine

In this study, activated carbon/diatomite-based magnetic nancomposites (denoted as AC/DBMNs) were synthesized and applied as an adsorbent for magnetic solid-phase extraction of S-phenylmercapturic acid (S-PMA) from human urine prior to high-performance liquid chromatography. The surface morphologies and structures of AC/DBMNs were characterized by Fourier transform infrared spectroscopy, transmission and scanning electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller surface area, vibrating sample magnetometer and ζ-potential measurements. The experimental parameters including sample volume, sample pH, adsorbent amount, extraction time, elution solvent and desorption time were investigated in detail. Under the optimum conditions, the method exhibited good linearity (r > 0.9993) within the concentration ranges of 0.03-1.0 mg/L. Moreover, the limits of detection and quantification were 0.01 and 0.03 mg/L, respectively. The enrichment factor was 5, and good recoveries (88.9-97.3%) with relative standard deviations in the range of 5.6-6.8% (n = 6) for inter-day and 6.3-8.1% (n = 6) for intra-day were achieved. The developed method was successfully applied to the analysis of S-PMA in urine samples. In addition, this accurate and sensitive method has great potential to be applied in the early screening and clinical diagnosis of the workers exposed to benzene.

Biological monitoring of low level exposure to benzene in an oil refinery: Effect of modulating factors

The aim of the study was to investigate the effect of various factors that modulate the metabolism of benzene, including smoking habits, metabolic genotype of GST and co-exposure to toluene, on the levels of three biomarkers, i.e. urinary benzene (UB), S-phenylmercapturic acid (SPMA) and t,t-muconic acid (t,t-MA), in 146 refinery workers exposed to low levels of air benzene (AB) in the range <1.5-529.2 μg/m³ (mean value 32.6 μg/m³). The study confirmed the validity of SPMA as a good biomarker of benzene exposure even at low levels of exposure. It was also confirmed that cigarette smoking is the main confounding factor when assessing biological monitoring data of occupational exposure to AB. Our data indicate that the GSTT1, but not the GSTM1 genotype, significantly increases the urinary levels of SPMA, even at low levels of exposure. It is not known, though, whether subjects with a GSTT1 "null" genotype may be more susceptible to the effects of benzene. Finally, environmental toluene appears to inhibit the metabolism of benzene to SPMA even at low concentrations, also resulting in an underestimation by SPMA levels of the actual exposure of workers to benzene.

Ln(III)-Functionalized Metal-Organic Frameworks Hybrid System: Luminescence Properties and Sensor for trans, trans-Muconic Acid as a Biomarker of Benzene

By application of a straightforward postsynthetic modification strategy, a luminescent lanthanide-based MOFs hybrid material, Tb(III)@MOF-SO₃^-, is first fabricated by loading Tb(III) ions into the pores of Zn-based MOF-SO₃^-. This hybrid system is constructed on notable and specific luminous sensitization of MOF-SO₃^- to Tb(III) ions. The further study shows that bi-metal-loaded Eu(III)/Tb(III)@MOF-SO₃^- exhibits a Tb(III)-induced luminescence of Eu(III) ions, and the emissions of it all fall in the white region by altering the ratio of Eu(III)/Tb(III) ions and the excitation wavelengths. A kind of white-lighting thin film based on Eu(III)/Tb(III)@MOF-SO₃^- exhibits dazzling white light when excited at 295 nm ( X = 0.338, Y = 0.323). Furthermore, the Tb(III)@MOF-SO₃^- is first developed as a fluorescence sensor specifically toward biomarker of benzene, trans, trans-muconic acid ( tt-MA), based on fluorescence quenching. This reusable sensor with high water tolerance and photostability displays excellent selectivity and sensitivity with a detection limit as low as 0.1 ppm, while being provided with the high antijamming of other urinary chemicals. These results make the sensor has the potential for the practical detection of tt-MA in a urine system. The possible quenching mechanisms are also investigated in detail.

Ambient Nonmethane Hydrocarbon Levels Along Colorado's Northern Front Range: Acute and Chronic Health Risks

Oil and gas (O&G) facilities emit air pollutants that are potentially a major health risk for nearby populations. We characterized prenatal through adult health risks for acute (1 h) and chronic (30 year) residential inhalation exposure scenarios to nonmethane hydrocarbons (NMHCs) for these populations. We used ambient air sample results to estimate and compare risks for four residential scenarios. We found that air pollutant concentrations increased with proximity to an O&G facility, as did health risks. Acute hazard indices for neurological (18), hematological (15), and developmental (15) health effects indicate that populations living within 152 m of an O&G facility could experience these health effects from inhalation exposures to benzene and alkanes. Lifetime excess cancer risks exceeded 1 in a million for all scenarios. The cancer risk estimate of 8.3 per 10 000 for populations living within 152 m of an O&G facility exceeded the United States Environmental Protection Agency's 1 in 10 000 upper threshold. These findings indicate that state and federal regulatory policies may not be protective of health for populations residing near O&G facilities. Health risk assessment results can be used for informing policies and studies aimed at reducing and understanding health effects associated with air pollutants emitted from O&G facilities.

Normas ocupacionais do benzeno: uma abordagem sobre o risco e exposição nos postos de revenda de combustíveis

Resumo Introdução: trabalhadores estão sujeitos a riscos decorrentes da exposição ambiental e ocupacional ao benzeno, situação ainda mais crítica quando associada a fatores como desigualdade social, múltipla exposição, suscetibilidade individual, degradação ambiental e às possíveis interações entre os contaminantes ambientais. Além disso, nem sempre as regulamentações são estabelecidas e/ou atualizadas apenas a partir de achados científicos, pois são processos permeados por conflitos de interesses. Objetivo: realizar análise crítica sobre a identificação de risco e avaliação da exposição ao benzeno. Métodos: revisão bibliográfica e documental do marco normativo brasileiro e internacional sobre exposição ao benzeno, com relação aos aspectos toxicológicos, de exposição ocupacional e ambiental e de avaliação de risco. Discussão: o controle da exposição ao benzeno permeia o campo da disputa técnico-política de saúde e segurança, constituindo-se em marco regulatório resultante de consenso de entendimentos. Esses entendimentos são marcados pela disputa entre a proteção à saúde e a gestão empresarial das condições de trabalho, em detrimento das evidencias científicas. Em tal contexto, os Limites de Exposição Ocupacional podem variar significativamente entre os países e agências, apesar do reconhecimento universal de que não há limites seguros para exposição ao benzeno, por ser um composto carcinogênico.

Utilização de biomarcadores de genotoxicidade e expressão gênica na avaliação de trabalhadores de postos de combustíveis expostos a vapores de gasolina

Resumo Introdução: a avaliação de uma exposição mensura sua intensidade, frequência e duração, podendo detectar danos precoces que, se ignorados, podem evoluir para um quadro nocivo. Nos campos da saúde ambiental e ocupacional, os biomarcadores de genotoxicidade tem sido largamente utilizados para essa avaliação. Objetivo: identificar, descrever e discutir os principais bioindicadores de genotoxicidade e seu uso conjunto com técnicas de avaliação de expressão gênica em estudos de exposição ocupacional ao benzeno em postos de revenda de combustíveis (PRC). Métodos: revisão bibliográfica de trabalhos publicados entre 1995 e 2015. Resultados: as técnicas identificadas foram: ensaio cometa, estresse oxidativo, micronúcleos, aberrações cromossômicas, polimorfismos, adutos de DNA e proteínas, fatores epigenéticos e expressão gênica. Foi observado que testes de danos genéticos e epigenéticos são utilizados em frentistas de PRC que participam de programas de saúde do trabalhador ou de pesquisas, embora um baixo número de publicações sobre o tema tenha sido identificado. Esse fato talvez possa ser explicado pelos poucos países onde a profissão persiste e pelas limitações para o desenvolvimento de pesquisas nesses países. Conclusão: os bioindicadores de genotoxicidade e as técnicas de expressão gênica são úteis na detecção de dano precoce desta exposição ocupacional e devem ser avaliados em conjunto.

Benzene oxide is a substrate for glutathione S-transferases

Benzene is a known human carcinogen which must be activated to benzene oxide (BO) to exert its carcinogenic potential. BO can be detoxified in vivo by reaction with glutathione and excretion in the urine as S-phenylmercapturic acid. This process may be catalyzed by glutathione S-transferases (GSTs), but kinetic data for this reaction have not been published. Therefore, we incubated GSTA1, GSTT1, GSTM1, and GSTP1 with glutathione and BO and quantified the formation of S-phenylglutathione. Kinetic parameters were determined for GSTT1 and GSTP1. At 37 °C, the putative Km and Vmax values for GSTT1 were 420 μM and 450 fmol/s, respectively, while those for GSTP1 were 3600 μM and 3100 fmol/s. GSTA1 and GSTM1 did not exhibit sufficient activity for determination of kinetic parameters. We conclude that GSTT1 is a critical enzyme in the detoxification of BO and that GSTP1 may also play an important role, while GSTA1 and GSTM1 seem to be less important.

Metabolic Polymorphisms and Clinical Findings Related to Benzene Poisoning Detected in Exposed Brazilian Gas-Station Workers

Benzene is a ubiquitous environmental pollutant and an important industrial chemical present in both gasoline and motor vehicle emissions. Occupational human exposure to benzene occurs in the petrochemical and petroleum refining industries as well as in gas-station workers, where it can lead to benzene poisoning (BP), but the mechanisms of BP are not completely understood. In Brazil, a significant number of gas-station service workers are employed. The aim of the present study was to evaluate alterations related to BP and metabolic polymorphisms in gas-station service workers exposed to benzene in the city of Rio de Janeiro, Brazil. Occupational exposure was based on clinical findings related to BP, and metabolic polymorphisms in 114 Brazilian gas-station attendants. These workers were divided into No Clinical Findings (NCF) and Clinical Findings (CF) groups. Neutrophil and Mean Corpuscular Volume (MCV) showed a significant difference between the two study groups, and neutrophil has the greatest impact on the alterations suggestive of BP. The clinical findings revealed higher frequencies of symptoms in the CF group, although not all members presented statistical significance. The frequencies of alleles related to risk were higher in the CF group for GSTM1, GSTT1, CYP2E1 7632T > A, but lower for NQO1 and CYP2E1 1053C > T genotypes. Moreover, an association was found between GSTM1 null and alterations related to BP, but we did not observe any effects of other polymorphisms. Variations in benzene metabolizing genes may modify benzene toxicity and should be taken into consideration during risk assessment evaluations.

Metabolic polymorphisms and biomarkers of effect in the biomonitoring of occupational exposure to low-levels of benzene: state of the art

Current levels of occupational exposure to benzene, a genotoxic human carcinogen, in Western countries are reduced by two-three orders of magnitude (from ppm to ppb) as compared to the past. However, as benzene toxicity is strongly dependent on biotransformation and recent evidence underlines a higher efficiency of bio-activation pathways at lower levels of exposure, toxic effects at low doses could be higher than expected, particularly in susceptible individuals. Currently, biological monitoring can allow accurate exposure assessment, relying on sensitive and specific enough biomarkers of internal dose. The availability of similarly reliable biomarkers of early effect or susceptibility could greatly improve the risk assessment process to such an extent that risk could even be assessed at the individual level. As to susceptibility biomarkers, functional genetic polymorphisms of relevant biotransformation enzymes may modulate the risk of adverse effects (NQO1) and the levels of biomarkers of internal dose, in particular S-phenylmercapturic acid (GSTM1, GSTT1, GSTA1). Among biomarkers of early effect, genotoxicity indicators, although sensitive in some cases, are too aspecific for routine use in occupational health surveillance programmes. Currently only the periodical blood cell count seems suitable enough to be applied in the longitudinal monitoring of effects from benzene exposure. Novel biomarkers of early effect are expected from higher collaboration among toxicologists and clinicians, also using advanced "omics" techniques.

Influence of genetic polymorphism on t,t-MA/S-PMA ratio in 301 benzene exposed subjects

This study investigated the effect of polymorphic genes GSTT1, GSTM1, GSTA1, EHPX1, NQO1, CYP2E1, CYP1A and MPO on the urinary concentrations and ratio (R) of the benzene metabolites trans,trans-muconic acid (t,t-MA) and S-phenyl mercapturic acid (S-PMA) in 301 oil refinery workers. The metabolites' concentrations are lower and R is higher (100.66) in non-smokers (n=184) than in smokers (n=117, R=36.54). Non-smokers have lower S-PMA and a higher R in GSTT1 null genotypes than in positive, and a higher S-PMA and a lower R in GSTA1 wild type genotypes. In smokers the GSTT1 null genotype effect on both S-PMA and R is confirmed, and is also shown in GSTM1 null, but not in GSTA1 wild type genotypes. GSTT1 null polymorphism reduces the conjugation rate of benzene epoxide with GSH, and to a lesser extent also GSTTA1 mutant, GSTM1 null and NQO1 mutant genotypes. The activity of one GST is compensated by another in GSTM1 and GSTA1 defective subjects, but not in GSTT1 null genotypes, whose average S-PMA excretion is about 50% with respect to the positive ones, for the same benzene exposure. R showed to be a more sensitive marker for these effects than the metabolite levels.

The use of biomonitoring data in exposure and human health risk assessment: benzene case study

Abstract A framework of "Common Criteria" (i.e. a series of questions) has been developed to inform the use and evaluation of biomonitoring data in the context of human exposure and risk assessment. The data-rich chemical benzene was selected for use in a case study to assess whether refinement of the Common Criteria framework was necessary, and to gain additional perspective on approaches for integrating biomonitoring data into a risk-based context. The available data for benzene satisfied most of the Common Criteria and allowed for a risk-based evaluation of the benzene biomonitoring data. In general, biomarker (blood benzene, urinary benzene and urinary S-phenylmercapturic acid) central tendency (i.e. mean, median and geometric mean) concentrations for non-smokers are at or below the predicted blood or urine concentrations that would correspond to exposure at the US Environmental Protection Agency reference concentration (30 µg/m(3)), but greater than blood or urine concentrations relating to the air concentration at the 1 × 10(-5) excess cancer risk (2.9 µg/m(3)). Smokers clearly have higher levels of benzene exposure, and biomarker levels of benzene for non-smokers are generally consistent with ambient air monitoring results. While some biomarkers of benzene are specific indicators of exposure, the interpretation of benzene biomonitoring levels in a health-risk context are complicated by issues associated with short half-lives and gaps in knowledge regarding the relationship between the biomarkers and subsequent toxic effects.

Trans, trans-muconic acid as a biomarker of occupational exposure to high-level benzene in China

OBJECTIVE

The work aimed to study the potential correlation between the high-level benzene exposure and its urinary metabolites S-phenylmercapturic acid (SPMA) and trans, trans-muconic acid (t,t-MA) in Chinese shoe-making workers.

METHODS

Individual benzene-exposed levels were determined by gas chromatography analysis, urinary t,t-MA, and urinary SPMA were determined by high performance liquid chromatography-an ultraviolet detector and liquid chromatography/electrospray tandem mass spectrometry method, respectively.

RESULTS

The concentration of benzene ranged from 2.57 to 146.11 mg/m³. And the correlation between benzene and t,t-MA was significantly higher than that of SPMA at the postshift, for example, the correlation coefficient was 0.905 and 0.537 for t,t-MA and SPMA, respectively. Moreover, The relative internal exposure index of t,t-MA (0.28 mg/g Cr: mg/m³) was more similar to the data supplied by American Conference of Governmental Industrial Hygienists compared to the index of SPMA (0.025 mg/g Cr:mg/m³).

CONCLUSIONS

t,t-MA appeared to be a more specific biomarker than SPMA at high-level benzene exposure.

Genetic variation in metabolic genes, occupational solvent exposure, and risk of non-hodgkin lymphoma

Using 1996-2000 data among Connecticut women, the authors evaluated whether genetic variation in 4 metabolic genes modifies organic solvent associations with non-Hodgkin lymphoma and 5 major histologic subtypes. P(interaction) values were determined from cross-product terms between dichotomous (ever/never) solvent variables and genotypes at examined loci in unconditional logistic regression models. The false discovery rate method was used to account for multiple comparisons. Overall associations between the chlorinated solvents dichloromethane (odds ratio (OR) = 1.69, 95% confidence interval (CI): 1.06, 2.69), carbon tetrachloride (OR = 2.33, 95% CI: 1.23, 4.40), and methyl chloride (OR = 1.44, 95% CI: 0.94, 2.20) and total non-Hodgkin lymphoma were increased among women TT for rs2070673 in the cytochrome P4502E1 gene, CYP2E1 (dichloromethane: OR = 4.42, 95% CI: 2.03, 9.62; P(interaction) < 0.01; carbon tetrachloride: OR = 5.08, 95% CI: 1.82, 14.15; P(interaction) = 0.04; and methyl chloride: OR = 2.37, 95% CI: 1.24, 4.51; P(interaction) = 0.03). In contrast, no effects of these solvents were observed among TA/AA women. Similar patterns were observed for diffuse large B-cell lymphoma and follicular lymphoma, as well as marginal zone lymphoma for dichloromethane. The weak, nonsignificant overall association between benzene and diffuse large B-cell lymphoma (OR = 1.29, 95% CI: 0.84, 1.98) was increased among women AA for rs2234922 in the microsomal epoxide hydrolase gene, EPHX1 (OR = 1.77, 95% CI: 1.06, 2.97; P(interaction) = 0.06). In contrast, no effect was observed among AG/GG women. Additional studies with larger sample size are needed to replicate these findings.

Xenobiotic exposure and autoimmune hepatitis

Although genetics contributes to the development of autoimmune diseases, it is clear that "environmental" factors are also required. These factors are thought to encompass exposure to certain drugs and environmental pollutants. This paper examines the mechanisms that normally maintain immune unresponsiveness in the liver and discusses how exposure to certain xenobiotics such as trichloroethylene may disrupt those mechanisms and promote autoimmune hepatitis.

Benzene toxicity: The role of the susceptibility factor NQO1 in bone marrow endothelial cell signaling and function

The homozygous NQO1*2 polymorphism results in a null NQO1 phenotype and is a susceptibility factor for occupational benzene poisoning. NQO1 plays an important role in detoxification of benzene-derived quinones but plays a role in numerous other non-metabolic cellular functions. NQO1 is expressed in endothelial cells of bone marrow which form the vascular stem cell niche important in stem cell homing and mobilization. We therefore employed a transformed human bone marrow endothelial cell (HBMEC) line to define the effects of compromising NQO1 on endothelial function. Either inhibition or knockdown of NQO1 led to decreased expression of the adhesion molecules E-selectin, VCAM-1 and ICAM-1 and decreased functional adhesion of CD34+ progenitor cells after TNFα stimulation. Suicide inhibition or knockdown of NQO1 decreased NFκB p105 precursor and NFκB p50 subunit levels as well as leading to decreased nuclear levels of NFκB phospho-p65. An additional function of endothelial cells is tube formation and angiogenesis which was inhibited by the benzene metabolite hydroquinone suggesting that endothelial function may be affected at multiple levels after exposure of NQO1*2 polymorphic individuals to benzene. These data demonstrate that NQO1 plays an upstream role in NFκB signaling and adhesion molecule expression in HBMEC and that NQO1 has important regulatory effects in its own right in addition to being a marker for Nrf-2 activation. Metabolic susceptibility factors such as NQO1 have roles in addition to detoxification of reactive intermediates and interrogation of these novel roles can inform both mechanisms of toxicity and human risk assessment.

Relationships between metabolic and non-metabolic susceptibility factors in benzene toxicity

Reactive metabolites formed from benzene include benzene oxide, trans,trans muconaldehyde, quinones, thiol adducts, phenolic metabolites and oxygen radicals. Susceptibility to the toxic effects of benzene has been suggested to occur partly because of polymorphisms in enzymes involved in benzene metabolism which include cytochrome P450 2E1, epoxide hydrolases, myeloperoxidase, glutathione-S-transferases and quinone reductases. However, susceptibility factors not directly linked to benzene metabolism have also been associated with its toxicity and include p53, proteins involved in DNA repair, genomic stability and expression of cytokines and/or cell adhesion molecules. In this work, we examine potential relationships between metabolic and non-metabolic susceptibility factors using the enzyme NAD(P)H:quinone oxidoreductase (NQO1) as an example. NQO1 may also impact pathways in addition to metabolism of quinones due to protein-protein interactions or other mechanisms related to NQO1 activity. NQO1 has been implicated in stabilizing p53 and in maintaining microtubule integrity. Inhibition or knockdown of NQO1 in bone marrow endothelial cells has been found to lead to deficiencies of E-selectin, ICAM-1 and VCAM-1 adhesion molecule expression after TNFalpha stimulation. These examples illustrate how the metabolic susceptibility factor NQO1 may influence non-metabolic susceptibility pathways for benzene toxicity.

Application of OMICS technologies in occupational and environmental health research; current status and projections

OMICS technologies are relatively new biomarker discovery tools that can be applied to study large sets of biological molecules. Their application in human observational studies (HOS) has become feasible in recent years due to a spectacular increase in the sensitivity, resolution and throughput of OMICS-based assays. Although, the number of OMICS techniques is ever expanding, the five most developed OMICS technologies are genotyping, transcriptomics, epigenomics, proteomics and metabolomics. These techniques have been applied in HOS to various extents. However, their application in occupational environmental health (OEH) research has been limited. Here, we will discuss the opportunities these new techniques provide for OEH research. In addition we will address difficulties and limitations to the interpretation of the data that is generated by OMICS technologies. To illustrate the current status of the application of OMICS in OEH research, we will provide examples of studies that used OMICS technologies to investigate human health effects of two well-known toxicants, benzene and arsenic.

Lack of association of NQO1 and GSTP1 polymorphisms with multiple myeloma risk

Individual differences in xenobiotica metabolising capacity can influence susceptibility to multiple myeloma. NQO1 and GSTT1 polymorphisms were recently reported as risk factors for multiple myeloma and GSTP1 genotype was found to be a prognostic marker for therapy outcome in multiple myeloma. The aim of this study was to determine whether specific defective alleles of NQO1 (P187S) and GSTP1 (I105V) genes are associated with increased risk of multiple myeloma. Individual genotypes of 128 patients affected by multiple myeloma and 245 healthy controls were determined and our results do not support any major role of NQO1 or GSTP1 polymorphisms in multiple myeloma pathogenesis.