Quantitative analysis of 3-OHB[a]P and (+)-anti-BPDE as biomarkers of B[a]P exposure in rats

The aim of this study was to develop an analytical method for the determination the levels of metabolites of benzo[a]pyrene (B[a]P), 3-hydroxybenzo(a)pyrene (3-OHB[a]P) and (+)-anti-benzo(a)pyrene diol-epoxide [(+)-anti-BPDE, combined with DNA to form adducts], in rat blood and tissues exposed to B[a]P exposure by high-performance liquid chromatography with fluorescence detection (HPLC/FD), and to investigate the usefulness of 3-OHB[a]P and (+)-anti-BPDE as markers of intragastrical exposure to B[a]P in rats. The levels of 3-OH-B[a]P and B[a]P-tetrol I-1 released after acid hydrolysis of (+)-anti-BPDE in the samples were measured by HPLC/FD. The calibration curves were linear (r(2) > 0.9904), and the lower limit of quantification ranged from 0.34 to 0.45 ng/mL for 3-OHB[a]P and from 0.43 to 0.58 ng/mL for (+)-anti-BPDE. The intra- and inter-day stability assay data suggested that the method is accurate and precise. The recoveries of 3-OHB[a]P and (+)-anti-BPDE were in the ranges of 73.6 ± 5.0 to 116.5 ± 6.3% and 73.3 ± 8.5 to 141.2 ± 13.8%, respectively. A positive correlation was found between the concentration of intragastrical B[a]P and the concentrations of 3-OH-B[a]P and (+)-anti-BPDE in the blood and in most of the tissues studied, except for the brain and kidney, which showed no correlation between B[a]P and 3-OHB[a]P and between B[a]P and (+)-anti-BPDE, respectively. A sensitive, reliable and rapid HPLC/FD was developed and validated for analysis of 3-OHB[a]P and (+)-anti-BPDE in rat blood and tissues. There was a positive correlation between the concentration of 3-OHB[a]P or (+)-anti-BPDE in the blood and the concentration of 3-OHB[a]P or (+)-anti-BPDE in the most other tissues examined. The concentration of 3-OHB[a]P or (+)-anti-BPDE in the blood could be used as an indicator of the concentration of 3-OHB[a]P or (+)-anti-BPDE in the other tissues in response to B[a]P exposure. These results demonstrate that 3-OHB[a]P and (+)-anti-BPDE are potential biomarkers of B[a]P exposure, which would also be useful to assess the carcinogenic risks from B[a]P exposure.

Development of a method to detect three monohydroxylated polycyclic aromatic hydrocarbons in human urine by liquid chromatographic tandem mass spectrometry

A liquid chromatographic tandem mass spectrometry method (LC-MS/MS) for the simultaneous determination of 1-hydroxypyrene (1-OHP), 3-hydroxybenzo[a]pyrene (3-OHBaP), and 3-hydroxybenz[a]anthracene (3-OHBaA) in human urine has been developed. With the exception of 3-OHBaP at a low spiking level, the average recoveries were greater than 80%. The method has good accuracy (72.1-107.7%) and reproducibility (1.8-11.4%) and was successfully used to study the uptake of pyrene, benzo[a]pyrene, and benzo[a]anthracene from cigarette smoke. The results indicated that urinary 1-OHP concentration in the smoking group (66.58 ± 70.91 ng/g creatinine) was higher than that observed in the nonsmoking group (58.16 ± 49.48 ng/g creatinine). Urinary 3-OHBaA concentrations in nonsmokers and smokers with 8 mg and 10 mg tar cigarettes were 10.98 ± 4.39 ng/g creatinine, 11.01 ± 13.30 ng/g creatinine, and 9.17 ± 12.89 ng/g creatinine, respectively. Urinary 3-OHBaP concentrations in nonsmokers and smokers with 8 mg and 13 mg tar cigarettes were 1.30 ± 0.20 ng/g creatinine, 2.83 ± 1.78 ng/g creatinine, and 6.00 ± 4.44 ng/g creatinine, respectively. Urinary 1-OHP levels exhibited a significant correlation with BaP yield in cigarette smoke under the Canadian intense smoking condition (y = 3.5563x + 30.171, R (2) = 0.9916, n = 227).

Effects of intravenous benzo[a]pyrene dose administration on levels of exposure biomarkers, DNA adducts, and gene expression in rats

The effects of benzo[a]pyrene (BaP) administration on biomarkers of exposure and early effects were studied in male Sprague-Dawley rats intravenously injected with doses of 0.4, 4, 10, or 40 μmol BaP/kg . Blood, tissues, and excreta were collected 8 and 24 h posttreatment. BaP and several of its metabolites were simultaneously measured in blood, tissues and excreta by ultra-high-performance liquid chromatography (UHPLC)/fluorescence. DNA adducts of BaP diol epoxide (BaPDE) in lungs were quantified using an ultrasensitive immunoassay with chemiluminescence detection. Expression of selected genes in lungs of treated rats (lung RNA) compared to control rats was also assessed by quantitative real-time polymerase chain reaction. There was a dose-dependent increase in blood, tissue, and excreted levels of BaP metabolites. At 8 and 24 h postinjection, BaP and hydroxyBaP were found in higher concentrations in blood and tissues compared to other analytes. However, diolBaP were excreted in greater amounts in urine and apparently more rapidly than hydroxyBaP. Mean percentages (± SD) of injected dose excreted in urine as 4,5-diolBaP during the 0-8 h and 0-24 h period posttreatment were 0.16 ± 0.027% and 0.14 ± 0.083%, respectively. Corresponding values for 3-OHBaP were 0.0045 ± 0.0009% and 0.026 ± 0.014%. BaP-diones were not detectable in blood, tissues, and excreta; 7,8-diolBaP and BaPtetrol were found to be minor metabolites. There was also a dose-dependent increase in DNA adduct formation in lung. Analysis of gene expression further showed a modulation of Cyp1a1, Cyp1b1, Nqo1, Nrf2, Fos, and Ahr expression at 10- and 40-μmol/kg doses, but not at the lower doses. This study provided a better assessment of the influence of absorbed BaP doses on biological levels of diolBaP and OHBaP exposure biomarkers and association of the latter with early biological alterations, such as DNA adducts and gene expression.

Kinetics of Diol and Hydroxybenzo[a]pyrene Metabolites in Relation to DNA Adduct Formation and Gene Expression in Rats

Benzo[a]pyrene (BaP) is a human carcinogen, but there are no validated biomarkers of exposure and the relationship of carcinogenesis with early biological alterations is not fully documented. This study aimed at better documenting the toxicokinetics of diolBaP and hydroxyBaP metabolites as potential biomarkers of exposure to BaP in relation to DNA adduct formation and gene expression. Rats were intravenously (iv) injected with 40 μmol/kg BaP. BaP and several metabolites were measured in blood, tissues, and excreta collected at frequent intervals over 72 h posttreatment. BaP diol epoxide (BaPDE)-DNA adduct formation and gene expression were assessed in lungs. 3-HydroxyBaP (3-OHBaP) and 4,5-diolBaP were the most abundant measured metabolites, and differences in time courses were apparent between the two metabolites. Over the 0-72 h period, mean proportions of BaP dose recovered in urine as 3-OHBaP and 4,5-diolBaP (±SD) were 0.017 ± 0.003% and 0.1 ± 0.03%. Corresponding values in feces were 1.5 ± 0.5% and 0.42 ± 0.052%. BaPDE-DNA adducts were significantly increased in lungs and a correlation was observed with urinary 3-OHBaP and 4,5-diolBaP. Analysis of gene expression showed a modulation of expression of metabolic genes (Cyp1a1, Cyp1b1, Nqo1, Ahr) and oxidative stress and repair genes (Nrf2, Rad51). However, BaPDE adducts formation did not exhibit any significant correlation with expression of genes, except a negative correlation with Rad51 expression. Similarly, there was no significant correlation between urinary excretion of OHBaP and diolBaP and expression of genes, except for urinary 7-OHBaP excretion, which was negatively correlated with Rad51 expression. Results indicate that concomitant measurements of diolBaP and OHBaP may serve to better assess the extent of exposure as compared to single metabolite measurements, given kinetic differences between metabolites. Further, although some urinary metabolites were correlated with BaPDE adducts, links with gene expression need to be further investigated.

Polycyclic aromatic hydrocarbon residues in serum samples of autopsied individuals from Tennessee

This study reports the concentrations of Polycyclic Aromatic Hydrocarbons (PAHs) in human blood sera samples (n = 650) obtained at autopsy from individuals who died of drug abuse, alcohol toxicity, homicide, suicide and other unknown causes. The analyzed samples from decedents revealed the presence of PAHs of which B(a)P was the most predominant one, followed by benzo(b)fluoranthene and benzo(k)fluoranthene. The other PAHs detected sporadically and measured were benzo(g,h,i)perylene, acenaphthene, anthracene, phenanthrene, and fluoranthene The mean concentrations of PAHs were greater in the twenties to fifties age groups compared to others. The PAH residue levels detected were high in African Americans compared to Caucasians, Asians, and Hispanics. It appears that environmental exposure, dietary intake and in some cases occupational exposure may have contributed to the PAH body burden. While the PAH residue concentrations measured fall within the range of those reported for healthy adults elsewhere, in isolated cases, the concentrations detected were high, calling the need for a reduction in PAH emissions and human biomonitoring studies for purposes of risk assessment.

Understanding the linked kinetics of benzo(a)pyrene and 3-hydroxybenzo(a)pyrene biomarker of exposure using physiologically-based pharmacokinetic modelling in rats

3-hydroxybenzo(a)pyrene (3-OHBaP) in urine has been proposed as a biomarker of occupational exposure to polycyclic aromatic hydrocarbons. However, to reconstruct exposure doses in workers from biomarker measurements, a thorough knowledge of the kinetics of the benzo(a)pyrene (BaP) and 3-OHBaP given different routes of exposure is needed. A rat physiologically-based pharmacokinetic model of BaP and 3-OHBaP was built. Organs (tissues) represented as compartments were based on in vivo experimental data in rats. Tissue: blood partition coefficients, permeability coefficients, metabolism rates, excretion parameters, and absorption fractions and rates for different routes-of-entry were obtained directly from published in vivo time courses of BaP and 3-OHBaP in blood, various tissues and excreta of rats. The latter parameter values were best-fitted by least square procedures and Monte Carlo simulations. Sensitivity analyses were then carried out to ensure the stability of the model and the key parameters driving the overall modeled kinetics. This modeling pointed out critical determinants of the kinetics: (1) hepatic metabolism of BaP and 3-OHBaP elimination rate as the most sensitive parameters; (2) the strong partition of BaP in lungs compared to other tissues, followed by adipose tissues and liver; (3) the strong partition of 3-OHBaP in kidneys; (4) diffusion-limited tissue transfers of BaP in lungs and 3-OHBaP in lungs, adipose tissues and kidneys; (5) significant entero-hepatic recycling of 3-OHBaP. Very good fits to various sets of experimental data in rats from four different routes-of-entry (intravenous, oral, dermal and inhalation) were obtained with the model.

Benzo(a)pyrene induced structural and functional modifications in lung cystatin

Cystatins are thiol proteinase inhibitors ubiquitously present in the mammalian body. They serve a protective function to regulate the activities of endogenous proteinases, which may cause uncontrolled proteolysis and damage. In the present study, the effect of benzo(a)pyrene [BaP] on lung cystatin was studied to explore the hazardous effects of environmental pollutant on structural and functional integrity of the protein. The basic binding interaction was studied by UV-absorption, FT-IR, and fluorescence spectroscopy. The enhancement of total protein fluorescence with a red shift of 5 nm suggests structural scratch of lung cystatin by benzo(a)pyrene. Further, ANS binding studies reaffirm the unfolding of the thiol protease inhibitor (GLC-I) after treating with benzo(a)pyrene. The results of FT-IR spectroscopy reflect perturbation of the secondary conformation (alpha-helix to β-sheet) in goat lung cystatin on interaction with BaP. Finally, functional inactivation of cystatin on association with BaP was checked by its papain inhibitory activity. Benzo(a)pyrene (10 μM) caused complete inactivation of goat lung cystatin. Benzo(a)pyrene-induced loss of structure and function in the thiol protease inhibitor could provide a caution for lung injury caused by the pollutants and smokers.

Modeling of the internal kinetics of benzo(a)pyrene and 3-hydroxybenzo(a)pyrene biomarker from rat data

Measurements of 3-hydroxybenzo(a)pyrene (3-OHBaP) in urine has been proposed for the biomonitoring of exposure to benzo(a)pyrene (BaP) in workers. To allow a better understanding of the toxicokinetics of BaP and its key biomarker, a multicompartment model was developed based on rat data previously obtained by this group. According to the model, iv injected BaP is rapidly distributed from blood to tissues (t₁/₂ = 3.65 h), with particular affinity for tissue lipid components and liver and lung proteins. BaP is then rapidly distributed to lungs, where significant tissue uptake occurs, followed by the skin, liver, and adipose tissues. Once in liver, BaP is readily metabolized, and 3-OHBaP is formed with a t₁/₂ of 3.32 h. Lung metabolism of BaP was also accounted for, but its contribution to the whole kinetics was found to be negligible. Once formed, 3-OHBaP is distributed from blood to the various organs almost as fast as the parent compound (t₁/₂ = 2.26 h). In kidneys, 3-OHBaP builds up as a result of the smaller rate of 3-OHBaP urinary excretion (t₁/₂ = 4.52 h) as compared with its transfer rate from blood to kidneys (t₁/₂ = 27.8 min). However, overall clearance of 3-OHBaP from the body is driven by its biliary transfer from liver to the gastrointestinal tract (t₁/₂ = 3.81 h). The model provides a great fit to independent sets of published data on 3-OHBaP urinary excretion time course (χ² = 0.019). This model proves useful in establishing the main biological determinants of the overall kinetics of these compounds.