Occupational toluene exposure induces cytochrome P450 2E1 mRNA expression in peripheral lymphocytes

Chemorobust dye-encapsulated framework as dual-emission self-calibrating ratiometric sensor for intelligent detection of toluene exposure biomarker in urine

By taking advantages of confinement effect can effectively prevent dye aggregation caused luminescent quenching, Eosin Y (EY) was encapsulated into a chemorobust porous CoMOF as secondary fluorescent signal to construct the dual-emitting sensor of EY@CoMOF. And the photo-induced electron transfer from CoMOF to EY molecules induced EY@CoMOF presenting a weak blue emission at 421 nm and a strong yellow emission at 565 nm. Those dual-emission features also endow EY@CoMOF itself great potentials as a self-calibrating ratiometric sensor in visually and efficiently monitoring hippuric acid (HA) in urine, with fast response, high sensitivity and selectivity, excellent recyclable, and low LOD (0.24 μg/mL). Furthermore, based on a tandem combinational logic gate, an intelligent detection system was designed to improve the practicability and convenience of HA detection in urine. To the best of our knowledge, this is the first example of dye@MOF based sensor for HA detection. And this work provides a promising approach for developing dye@MOF based sensors to intelligent detect bioactive molecules.

Eu(III)-Functionalized MOF-Based Dual-Emission Ratiometric Sensor Integrated with Logic Gate Operation for Efficient Detection of Hippuric Acid in Urine and Serum

With the introduction of Eu³⁺ ions as the secondary fluorescent signal reporter and sensing active sites, a dual-emission ratiometric sensor of Eu³⁺@NiMOF (Eu³⁺ functional NiMOF) for hippuric acid (HA) detection in urine and serum was fabricated via the postsynthetic encapsulating strategy. Based on the two emission signals at 441 nm (turn-on) and 628 nm (turn-off), the produced Eu³⁺@NiMOF ratiometric sensor provided enhanced sensitivity, higher selectivity, and 9.7 times lower limits of detection (LOD) for the detection of HA (2.38 μM, 0.42 μg·mL^-1) than that of the pristine NiMOF. Considering the high sensitivity and visualization results, further exploration of intelligent applications in the HA sensing process was carried out by constructing a tandem combinational logic gate to improve the practicability and convenience with the help of a smartphone. This work provides a promising approach for developing MOF-based ratiometric sensors to detect biomarkers.

Biological effects of inhaled crude oil vapor. III. Pulmonary inflammation, cytotoxicity, and gene expression profile

OBJECTIVE

Workers may be exposed to vapors emitted from crude oil in upstream operations in the oil and gas industry. Although the toxicity of crude oil constituents has been studied, there are very few in vivo investigations designed to mimic crude oil vapor (COV) exposures that occur in these operations. The goal of the current investigation was to examine lung injury, inflammation, oxidant generation, and effects on the lung global gene expression profile following a whole-body acute or sub-chronic inhalation exposure to COV.

MATERIALS AND METHODS

To conduct this investigation, rats were subjected to either a whole-body acute (6 hr) or a sub-chronic (28 d) inhalation exposure (6 hr/d × 4 d/wk × 4 wk) to COV (300 ppm; Macondo well surrogate oil). Control rats were exposed to filtered air. One and 28 d after acute exposure, and 1, 28, and 90 d following sub-chronic exposure, bronchoalveolar lavage was performed on the left lung to collect cells and fluid for analyses, the apical right lobe was preserved for histopathology, and the right cardiac and diaphragmatic lobes were processed for gene expression analyses.

RESULTS

No exposure-related changes were identified in histopathology, cytotoxicity, or lavage cell profiles. Changes in lavage fluid cytokines indicative of inflammation, immune function, and endothelial function after sub-chronic exposure were limited and varied over time. Minimal gene expression changes were detected only at the 28 d post-exposure time interval in both the exposure groups.

CONCLUSION

Taken together, the results from this exposure paradigm, including concentration, duration, and exposure chamber parameters, did not indicate significant and toxicologically relevant changes in markers of injury, oxidant generation, inflammation, and gene expression profile in the lung.

Evaluation of Cytochrome P4502E1 mRNA Expression and Its Effects in Antioxidant Defenses, and Cell Toxicity in Printing Workers

BACKGROUND

Cytochrome P4502E1 (CYP2E1) metabolizes environmental toxins, however, compound metabolism can produce oxidative stress, causing in-cell toxicity and sometimes transformation.

AIM

To evaluate CYP2E1 gene expression and its effects in antioxidant defenses, and cell toxicity in printing workers.

METHODS

The hierarchical method of health and chemical risk was used to evaluate chemical exposure in workplace. Blood samples and buccal epithelial cells were obtained from printing workers, and workers without any history of occupational exposure to chemicals (control group). Gene expression of CYP2E1, and antioxidant enzymes Superoxide dismutase (SOD) and Catalase (CAT) from leukocytes were evaluated. Hematic analysis and cell-free DNA from plasma were analyzed. Frequencies of cells with micronuclei (MN) and nuclear abnormalities from buccal epithelial cells were explored.

RESULTS

Evaluation of chemical exposure in working place demonstrated that ethyl alcohol, isopropyl alcohol, and isophorone represent 91% of the accumulated potential risk. CYP2E1 expression showed a 2.5-fold overexpression in the printing workers compared to the control group. SOD expression showed a 0.5-fold lower level in the printing workers than the control group, and CAT expression showed no differences between groups. Lower red blood cell and platelet values were detected in the printing workers than in the control group, and cell-free DNA plasma concentration was 3-fold higher in the printing workers than in the control group. The printing workers showed a higher frequency of cells with MN and nuclear anomalies than the control group.

CONCLUSION

CYP2E1 overexpression triggers antioxidant defenses and toxic cell effects in printing workers.

Human exposure to BTEX emitted from a typical e-waste recycling industrial park: External and internal exposure levels, sources, and probabilistic risk implications

Benzene, toluene, ethylbenzene, and xylene (BTEX) can be released during extensive activities associated with the disposal of electronic waste (e-waste), which might pose deleterious health effects on workers. In this study, pollution profiles of BTEX in air and their urinary excretive profiles in occupational workers were investigated in a typical e-waste recycling industrial park. The results showed that the workers in the park were generally exposed to high levels of BTEX. The median levels of urinary metabolites were approximately 6-orders of magnitude higher than those of unmetabolized BTEX, indicating that pollutants efficiently metabolize at those occupational levels. The analytes presented differential profiles in external and internal exposure. Among the metabolites, significant correlation (p < 0.05) was observed between N-acetyl-S-benzyl-L-cysteine (S-BMA) concentration and atmospheric individual BTEX derived from the e-waste recycling area, suggesting that S-BMA is a potential marker for BTEX exposure to e-waste occupational workers. Notably, 95.2 % of all the workers showed a cumulative carcinogenic risk induced by BTEX exposure via inhalation, with 99.9 % of the carcinogenic risk distribution based on concentration of benzene metabolite (N-acetyl-S-(phenyl)-L-cysteine) exceeding 1.0E-6. This study holds potential in providing valuable inferences for the development of remediation strategies focusing on BTEX exposure reduction to protect workers' health at e-waste recycling industries.

Toxicological responses of BEAS-2B cells to repeated exposures to benzene, toluene, m-xylene, and mesitylene using air-liquid interface method

In order to reduce exposure to toxic chemicals, the European REACH regulation (1907/2006) recommends substituting toxic molecules with compounds that are less harmful to human health and the environment. Toluene is one of the most frequently used solvents in industries despite its toxicity. The objective of this study is to better understand and compare the toxicity of toluene and its homologues in a bronchial cell model. Thus, human bronchial BEAS-2B cells were exposed to steams of toluene, m-xylene, mesitylene (1,3,5-trimethylbenzene), and benzene (20 and 100 ppm). Exposure was carried out using an air-liquid interface (ALI) system (Vitrocell) during 1 h/day for 1, 3, or 5 days. Cytotoxicity, xenobiotic metabolism enzyme gene expression, and inflammatory response were evaluated following cell exposures. BEAS-2B cell exposure to toluene and its homologues revealed the involvement of major (CYP2E1) and minor metabolic pathways (CYP1A1). A late induction of genes (EPHX1, DHDH, ALDH2, and ALDH3B1) was measured from Day 3 and can be linked to the formation of metabolites. An increase in the secretion level of inflammatory markers (TNF-α, IL-6, IL-8, MCP-1, and GM-CSF) was also observed. In parallel, regulation between inflammatory mediators and the expression of transmembrane glycoprotein mucin MUC1 was also studied. This in vitro approach with ALI system points out the relevance of conducting repeated exposures to detect potential late effects. The difference recorded after cell exposure to toluene and its homologues highlights the importance of substitution principle.

Inhibition and induction of CYP enzymes in humans: an update

The cytochrome P450 (CYP) enzyme family is the most important enzyme system catalyzing the phase 1 metabolism of pharmaceuticals and other xenobiotics such as herbal remedies and toxic compounds in the environment. The inhibition and induction of CYPs are major mechanisms causing pharmacokinetic drug–drug interactions. This review presents a comprehensive update on the inhibitors and inducers of the specific CYP enzymes in humans. The focus is on the more recent human in vitro and in vivo findings since the publication of our previous review on this topic in 2008. In addition to the general presentation of inhibitory drugs and inducers of human CYP enzymes by drugs, herbal remedies, and toxic compounds, an in-depth view on tyrosine-kinase inhibitors and antiretroviral HIV medications as victims and perpetrators of drug–drug interactions is provided as examples of the current trends in the field. Also, a concise overview of the mechanisms of CYP induction is presented to aid the understanding of the induction phenomena.

5'UTR methylation in different genes from workers exposed to volatile organic compounds: A new insight for considering an epigenetic mark as a functional correlate

Gene-specific methylation has been related with transcriptional/translational consequences in different cells; also, this epigenetic modification is affected by environmental exposures. In previous studies, CYP2E1 activity in toluene-exposed workers was decreased compared to controls, however, CYP2E1 promoter methylation levels did not show significant differences. Here, we compared gene-specific methylation levels at the 5'UTR region, in a subset of workers whom already participated in two former studies, compared to controls.

METHODS

DNA was obtained from whole blood in five different groups: occupationally exposed to a mixture of volatile organic compounds (VOC): high levels (n = 19); low levels (n = 19) and very low levels (n = 17), toluene-exposed workers (n = 19) and control group (n = 19). We performed PCR-pyrosequencing at the 5'UTR region from four genes: CYP2E1, IL-6, SOD1 and TNF-α.

RESULTS

In participants exposed to high levels of a VOC mixture, we found significant differences: lower methylation levels for IL-6, and higher methylation levels for TNF-α compared to controls. In toluene-exposed workers, we found significant, lower methylation levels for CYP2E1 compared to controls.

CONCLUSION

Lower methylation levels at the 5'UTR region from CYP2E1 in toluene exposed-workers, suggests that this epigenetic modification could represent a functional correlate regarding enzymatic activity, as a response to toluene biotransformation.

In vitro toxicological evaluation of emissions from catalytic oxidation removal of industrial VOCs by air/liquid interface (ALI) exposure system in repeated mode

Toxicity of toluene and by-products formed during its catalytic oxidative degradation was studied in human bronchial BEAS-2B cells repeatedly exposed. BEAS-2B cells were exposed using an Air-Liquid Interface (ALI) System (Vitrocell®) for 1 h per day during 1, 3 or 5 days to gaseous flows: toluene vapors (100 and 1000 ppm) and outflow after catalytic oxidation of toluene (10 and 100%). After exposure to gaseous flow, cytotoxicity, inflammatory response and Xenobiotic Metabolism Enzymes (XME) gene expression were investigated. No significant cytotoxicity was found after 5 days for every condition of exposure. After cells exposure to catalytic oxidation flow, IL-6 level increased no significantly in a time- and dose-dependent way, while an inverted U-shaped profile of IL-8 secretion was observed. XME genes induction, notably CYP2E1 and CYP2F1 results were in line with the presence of unconverted toluene and benzene formed as a by-product, detected by analytical methods. Exposure to pure toluene also demonstrated the activation of these XMEs involved in its metabolism. Repeated exposure permits to show CYP1A1, CYP1B1 and CY2S1 expression, probably related to the formation of other by-products, as PAHs, not detected by standard analytical methods used for the development of catalysts.

Protective effects of caffeic acid phenethyl ester and thymoquinone on toluene induced liver toxicity

Toluene is an organic solvent that is toxic to humans. Caffeic acid phenethyl ester (CAPE) and thymoquinone (TQ) exhibit antioxidant and antitoxic effects. We investigated the protective effects of CAPE and TQ on toluene induced hepatotoxicity. Wistar albino rats were divided into seven groups of eight. The animals were injected intraperitoneally (i.p.) with 0.1 ml/10 g/day corn oil (control I), 0.1 ml/10 g/day corn oil + 2 ml/kg/day 10% ethanol (control II), 20 mg/kg/day TQ dissolved in 0.1 ml/10 g corn oil (TQ), 10 µmol/kg/day CAPE dissolved in 10% ethanol (CAPE), 500 mg/kg/day toluene (T), toluene and TQ together (T + TQ), or toluene and CAPE together (T + CAPE). All rats were sacrificed on day 15. Liver samples were obtained for histological analysis. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were measured to evaluate liver function. Liver sections from the control I and TQ groups exhibited normal histology. Sections from the T group exhibited sinusoid dilation, hemorrhage, vacuolization and necrosis. TQ and CAPE protected against toluene induced histopathological changes. AST and ALT levels were increased significantly in T group compared to both control groups. CAPE decreased significantly the toluene induced increase in AST and ALT levels, while TQ did not. CAPE and TQ exhibited some antitoxic and hepato-protective effects on toluene induced liver damage.

Inhalation toxicity of indoor air pollutants in Drosophila melanogaster using integrated transcriptomics and computational behavior analyses

We conducted an inhalation toxicity test on the alternative animal model, Drosophila melanogaster, to investigate potential hazards of indoor air pollution. The inhalation toxicity of toluene and formaldehyde was investigated using comprehensive transcriptomics and computational behavior analyses. The ingenuity pathway analysis (IPA) based on microarray data suggests the involvement of pathways related to immune response, stress response, and metabolism in formaldehyde and toluene exposure based on hub molecules. We conducted a toxicity test using mutants of the representative genes in these pathways to explore the toxicological consequences of alterations of these pathways. Furthermore, extensive computational behavior analysis showed that exposure to either toluene or formaldehyde reduced most of the behavioral parameters of both wild-type and mutants. Interestingly, behavioral alteration caused by toluene or formaldehyde exposure was most severe in the p38b mutant, suggesting that the defects in the p38 pathway underlie behavioral alteration. Overall, the results indicate that exposure to toluene and formaldehyde via inhalation causes severe toxicity in Drosophila, by inducing significant alterations in gene expression and behavior, suggesting that Drosophila can be used as a potential alternative model in inhalation toxicity screening.

Usefulness of toxicological validation of VOCs catalytic degradation by air-liquid interface exposure system

Toluene is one of the most used Volatile Organic Compounds (VOCs) in the industry despite its major health impacts. Catalytic oxidation represents an efficient remediation technique in order to reduce its emission directly at the source, but it can release by-products. To complete the classical performance assessment using dedicated analytical chemistry methods, we propose to perform an untargeted toxicological validation on two efficient catalysts. Using biological system allows integrating synergy and antagonism in toxic effects of emitted VOCs and by-products, often described in case of multi-exposure condition. Catalysts Pd/α-Al₂O₃ and Pd/γ-Al₂O₃ developed for the oxidation of toluene were both coupled to a Vitrocell^® Air-Liquid Interface (ALI) system, for exposure of human A549 lung cells during 1h to toluene or to catalysts exhaust before quantification of xenobiotics metabolizing enzymes. This study validated initially the Vitrocell^® as an innovative, direct and dynamic model of ALI exposure in the assessment of the performances of new catalysts, showing the presence of chemically undetected by-products. The comparison of the two catalysts showed then that fewer organic compounds metabolizing genes were induced by Pd/γ-Al₂O₃ in comparison to Pd/α-Al₂O₃, suggesting that Pd/γ-Al₂O₃ is more efficient for toluene total oxidation from a toxicological point of view.

Identifying potential protein targets for toluene using a molecular similarity search, in silico docking and in vitro validation

The toxicity of chemicals greatly depends on their interaction with macromolecular targets.

The protective effects of caffeic acid phenethyl ester against toluene-induced nephrotoxicity in rats

Caffeic acid phenethyl ester (CAPE) has antioxidant and anti-inflammatory properties. The aim of this study is to examine the negative effects of toluene on kidney tissues and functions and to investigate the protective effects of CAPE against toluene-induced nephrotoxicity in rats. A total of 21 male Wistar rats were divided into three groups of equal number in each. The rats in group I were the controls. Toluene was intraperitoneally injected into the rats in group II with a dose of 500 mg/kg. Rats in group III received CAPE daily while exposed to toluene. After 14 days of experimental period, all rats were killed by decapitation. Enzymatic activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) and malondialdehyde (MDA) levels were studied in the rat kidneys. Blood urea nitrogen (BUN) and serum creatinine levels were measured for renal function. The CAT and SOD enzyme activities and serum creatinine levels were significantly increased in rats treated with toluene when compared with the controls. But GSH-Px activity, MDA, and BUN levels showed statistically nonsignificant changes. However, increased CAT and SOD enzyme activities and decreased serum creatinine levels were detected in the rats that received CAPE while exposed to toluene. The GSH-Px activity and MDA and BUN levels in the same group did not show statistically significant changes. The results of our study demonstrated that toluene damages kidney tissue and is a nephrotoxic substance. CAPE was able to prevent the renal damage as antioxidant, antitoxic, and nephroprotective agent.

AKRs expression in peripheral blood lymphocytes from smokers: the role of body mass index

Aldo-keto reductases (AKRs) metabolize a wide range of substrates, including polycyclic aromatic hydrocarbons (PAHs), generating metabolites (o-quinones) and reactive oxygen species (ROS), which are capable of initiating and promoting carcinogenesis. Exposure to PAHs, their metabolites, and ROS further increase AKRs isoform expression that may amplify oxidative damage. Human AKR enzymes are highly polymorphic, and allelic variants may contribute to different AKRs expression in individuals. Despite the importance of AKRs in PAHs metabolism, there are no studies that evaluate, in general human populations, the effect of PAHs on AKRs expression in peripheral blood lymphocytes (PBLs). The aim of this study was to determine the effect of tobacco smoke exposure, and AKR1A1*2 and AKR1C3*2 polymorphisms, on AKR1A1 and AKR1C1-AKR1C3 messenger RNA (mRNA) levels in PBLs from smokers. In the smoker group, there is a statistically significant positive association between AKR1A1, AKR1C1, and AKR1C3 mRNA induction and urine cotinine levels in individuals with a body mass index (BMI) less than 25. However, AKR1A1*2 and AKR1C3*2 alleles did not influence AKR1A1 and AKR1C1-AKR1C3 mRNA levels. These results suggest that AKRs induction by PAHs in smokers' PBLs is associated with BMI; therefore, the role of adipose tissue accumulation in PAHs' effects needs further investigation.

The protective effects of omega-3 fatty acid against toluene-induced neurotoxicity in prefrontal cortex of rats

OBJECTIVE

Toluene is used as an organic solvent, and it has neurotoxic effects. Omega-3 is an essential fatty acid required for brain development. The aim of this study was to investigate the protective effects of omega-3 fatty acid against toluene-induced neurotoxicity in prefrontal cortex of rats.

MATERIALS AND METHODS

A total of 21 male Wistar rats were divided into three groups with seven rats in each group. Rats in group I were the controls. Toluene was intraperitoneally injected into the rats of group II with a dose of 0.5 ml/kg. Rats in group III received omega-3 fatty acid with a dose of 0.4 g/kg/day while exposed to toluene. After 14 days, all the rats were killed by decapitation. Enzymatic activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and the level of malondialdehyde (MDA) were spectrophotometrically studied in the prefrontal cortex of rats.

RESULTS

Enzymatic activities of SOD and GSH-Px were decreased, and MDA levels were significantly increased in rats treated with toluene compared with the controls. However, the increased SOD and decreased GSH-Px enzymatic activities and MDA levels were detected in the rats administered with omega-3 fatty acid while exposed to toluene.

CONCLUSION

The results of this experimental study indicate that omega-3 fatty acid treatment can prevent toluene-induced neuronal damage in the prefrontal cortex of rats.

Occupational toxicology in Mexico: current status and the potential use of molecular studies to evaluate chemical exposure

Occupational toxicology is of considerable concern for several world organizations including the International Labour Organization, the World Health Organization and the International Commission for Occupational Health and, in Latin America, the Pan American Health Organization. The countries of this Region, including Mexico, own manufacturing, chemical, and petrochemical industries that employ thousands workers who are continually exposed to hazardous chemicals such as solvents, particles and exhaust fumes, many of which are very complex mixtures. Traditionally, physicians have used biochemical analyses to assess the damage caused by chronic chemical exposure. Presently, recent advances in molecular biology may offer tools to perform more thorough and precise evaluations on worker health damage, risk and current health status. In this review, we present a perspective of occupational toxicology in Mexico, as an example for Latin America and developing countries. Moreover, we summarize current reports about occupational disease associated with chemical exposure, and we present an array of molecular studies proposed for the analysis and diagnosis of workers related with industry and the relevance of including molecular biology testing to complement traditional occupational medical assays in order to improve occupational health. We conclude that developing countries, e.g., Mexico, should improve work environment standards by using new technical approaches that will result in more reliable and precise data to design better health policy strategies.

Subclinical abnormalities in workers with continuous low-level toluene exposure

Short-term exposure to a high concentration (TWA > 100 ppm) of toluene can cause hepatotocixity and neurotoxicity in humans. Data on the effects of exposure to low levels of toluene, however, are controversial. In addition, few studies on the effects of toluene exposure on the autonomic nervous system have been conducted. Urine samples from 34 male factory workers in Taiwan who were exposed to low levels of toluene either intermittently (n = 13) or continuously (n = 21) were taken on a Monday morning after a 2-day hiatus and at the end of the workweek on Friday evening. Urinary hippuric acid levels were measured using high-performance liquid chromatography (HPLC). A complete blood work-up was also performed for each subject. The prevalence and severity of neurotoxic symptoms were investigated by a self-reported questionnaire, a neuropsychiatric battery, and sympathetic and peripheral nerve function tests. The mean value of urinary hippuric acid corrected for creatinine (Cr) was 0.34 ± 0.18 g/g Cr on Monday morning and 0.43 ± 0.26 g/g Cr on Friday evening. The difference in the mean value of urinary hippuric acid between the two periods (p < 0.01) and the odds ratio of impairment of sympathetic (OR = 4.13, p = 0.11) and peripheral nerves (OR = 6.94, p = 0.074) were higher in workers continuously exposed to toluene. In addition, workers who were continuously exposed to toluene had a lower mean platelet count (216 ± 41 × 10(6) /µL) than workers who were intermittently exposed (252 ± 40 × 10(6)/µL), (p = 0.018). Furthermore, there was a positive relationship between neurological abnormalities and a self-reported neuropsychiatric measurement (r = 0.35-0.66, p < 0.05) in all workers. These data suggest that continuous exposure to low levels of toluene may be associated with sympathetic and peripheral nerve dysfunction and sub-clinical hematological damage. Further research needs to be carried out regarding how chronic exposure to low-levels of toluene affects workers.

The role of molecular biology in the biomonitoring of human exposure to chemicals

Exposure to different substances in an occupational environment is of utmost concern to global agencies such as the World Health Organization and the International Labour Organization. Interest in improving work health conditions, particularly of those employees exposed to noxious chemicals, has increased considerably and has stimulated the search for new, more specific and selective tests. Recently, the field of molecular biology has been indicated as an alternative technique for monitoring personnel while evaluating work-related pathologies. Originally, occupational exposure to environmental toxicants was assessed using biochemical techniques to determine the presence of higher concentrations of toxic compounds in blood, urine, or other fluids or tissues; results were used to evaluate potential health risk. However, this approach only estimates the presence of a noxious chemical and its effects, but does not prevent or diminish the risk. Molecular biology methods have become very useful in occupational medicine to provide more accurate and opportune diagnostics. In this review, we discuss the role of the following common techniques: (1) Use of cell cultures; (2) evaluation of gene expression; (3) the “omic” sciences (genomics, transcriptomics, proteomics and metabolomics) and (4) bioinformatics. We suggest that molecular biology has many applications in occupational health where the data can be applied to general environmental conditions.

Reduction of enantioselectivity in the kinetic disposition and metabolism of verapamil in rats exposed to toluene

Toluene and verapamil are subject to extensive oxidative metabolism mediated by CYP enzymes, and their interaction can be stereoselective. In the present study we investigated the influence of toluene inhalation on the enantioselective kinetic disposition of verapamil and its metabolite, norverapamil, in rats. Male Wistar rats (n = 6 per group) received a single dose of racemic verapamil (10 mg/kg) orally at the fifth day of nose-only toluene or air (control group) inhalation for 6 h/day (25, 50, and 100 ppm). Serial blood samples were collected from the tail up to 6 h after verapamil administration. The plasma concentrations of verapamil and norverapamil enantiomers were analyzed by LC-MS/MS by using a Chiralpak AD column. Toluene inhalation did not influence the kinetic disposition of verapamil or norverapamil enantiomers (p > 0.05, Kruskal-Wallis test) in rats. The pharmacokinetics of verapamil was enantioselective in the control group, with a higher plasma proportion of the S-verapamil (AUC 250.8 versus 120.4 ng x h x mL(-1); p < or = 0.05, Wilcoxon test) and S-norverapamil (AUC 72.3 versus 52.3 ng x h x mL(-1); p < or = 0.05, Wilcoxon test). Nose-only exposure to toluene at 25, 50, or 100 ppm resulted in a lack of enantioselectivity for both verapamil and norverapamil. The study demonstrates the importance of the application of enantioselective methods in studies on the interaction between solvents and chiral drugs.

Applications of CYP-450 expression for biomonitoring in environmental health

Cytochrome P450s (CYPs) are one of the first steps in the metabolism of xenobiotics, such as polycyclic aromatic hydrocarbons (PAHs), which are bioactivated into carcinogens. As such, changes in CYP expression are potential biomarkers in human biomonitoring applications. For the proper biomonitoring of environmental toxicants, it is important to understand the biological relevance of each biomarker and the associations among the biomarkers for uses as exposure, effects, and susceptibility biomarkers. Here, we have reviewed various aspects of CYPs for biomonitoring environmental health in terms of the CYP substrates, such as PAHs, aromatic amines, benzene/toluene, and tobacco smoking-related nitrosamines. This review also includes association studies between CYP phenotypical alterations and other exposure, susceptibility, and effect biomarkers. The association studies were mainly performed in CYP gene-transfected cells and noninvasive human biospecies, such as urine and peripheral blood. In conclusion, we suggest that phenotypical alterations in CYPs with exposure to environmental toxicants are useful as susceptibility or effect biomarkers, particularly when the phenotype-related genotypes are unknown.

Past and future applications of CYP450-genetic polymorphisms for biomonitoring of environmental toxicants

Cytochrome P450s (CYPs) are a huge gene superfamily of heme enzymes involved in xenobioitc as well as endobiotic metabolism. They play a critical role in adaptation to environmental changes for survival of living organisms. In addition, the huge environmental loads of human-made chemicals are biotransformed into bioactive or detoxified forms by CYPs. Thus, CYPs have been used for biomonitoring of environmental pollutants, screening of their metabolisms and exploring remedy. In particular, the induction or inhibition of CYPs has been applied to exposure monitoring of environmental toxicants, which are biotransformed by CYPs. This review considers past and future applications of CYP-genetic polymorphisms as susceptibility biomarkers for biomonitoring. Furthermore, we suggest the needs for further understanding of the characteristics of each CYP isozyme, consideration of real-life exposures such as mixed contamination with various chemicals, and incorporation of the presence of other phase I and phase II enzymes, for proper applications of CYP polymorphisms on biomonitoring.