Prenatal developmental toxicity (PDT) as observed with some petroleum substances (PS) has been associated with the presence of 3-7 ring polycyclic aromatic hydrocarbons (PAHs). In the present study, the applicability of ES-D3 cell differentiation assay of the EST to evaluate in vitro embryotoxicity potencies of PS and gas-to-liquid (GTL) products as compared to their in vivo potencies was investigated. DMSO-extracts of a range of PS, containing different amounts of PAHs, and GTL-products, which are devoid of PAHs, were tested in the ES-D3 cell proliferation and differentiation assays of the EST. The results show that PS inhibited the differentiation of ES-D3 cells into cardiomyocytes in a concentration-dependent manner at non-cytotoxic concentrations, and that their potency was proportional to their PAH content. In contrast, as expected, GTL-products did not inhibit ES-D3 cell viability or differentiation at all. The in vitro PDT potencies were compared to published in vivo PDT studies, and a good correlation was found between in vitro and in vivo results (R=0.97). To conclude, our results support the hypothesis that PAHs are the primary inducers of the PDT in PS.

To quantify interindividual differences in the human intestinal microbial metabolism of (−)-epicatechin (EC), in vitro anaerobic incubations with fecal inocula from 24 healthy donors were conducted. EC-derived colonic microbial metabolites were qualitatively and quantitively analyzed by liquid chromatography triple quadrupole mass spectrometry (LC-TQ-MS) and liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS). Quantitative microbiota characterization was achieved by 16S rRNA analysis. The results obtained show 1-(3′,4′-dihydroxyphenyl)-3-(2″,4″,6″-dihydroxyphenyl)-2-propanol (3,4-diHPP-2-ol) and 5-(3′,4′-dihydroxyphenyl)-γ-valerolactone (3,4-diHPV) to be key intermediate microbial metabolites of EC and also revealed the substantial interindividual differences in both the rate of EC conversion and the time-dependent EC metabolite pattern. Furthermore, substantial differences in microbiota composition among different individuals were detected. Correlations between specific microbial phylotypes and formation of certain metabolites were established. It is concluded that interindividual differences in the intestinal microbial metabolism of EC may contribute to interindividual differences in potential health effects of EC-abundant dietary foods or drinks.

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Organophosphates have a long history of use as insecticides over the world. The aim of the present study was to investigate the interethnic differences in kinetics, biomarker formation, and in vivo red blood cell acetylcholinesterase inhibition of chlorpyrifos (CPF) in the Chinese and the Caucasian population. To this purpose, physiologically based kinetic models for CPF in both the Chinese and Caucasian population were developed, and used to study time- and dose-dependent interethnic variation in urinary biomarkers and to convert concentration-response curves for red blood cell acetylcholinesterase inhibition to in vivo dose-response curves in these 2 populations by reverse dosimetry. The results obtained revealed a marked interethnic difference in toxicokinetics of CPF, with lower urinary biomarker levels at similar dose levels and slower CPF bioactivation and faster chlorpyrifos-oxon detoxification in the Chinese compared with the Caucasian population, resulting in 5- to 6-fold higher CPF sensitivity of the Caucasian than the Chinese population. These differences might be related to variation in the frequency of single-nucleotide polymorphisms for the major biotransformation enzymes involved. To conclude, the interethnic variation in kinetics of CPF may affect both its biomarker-based exposure assessment and its toxicity and risk assessment and physiologically based kinetic modeling facilitates the characterization and quantification of these interethnic variations.

In vitro assays presently used for prenatal developmental toxicity (PDT) testing only assess the embryotoxic potential of parent substances and not that of potentially embryotoxic metabolites. Here we combined a biotransformation system, using hamster liver microsomes, with the ES‐D3 cell differentiation assay of the embryonic stem cell test (EST) to compare the in vitro PDT potency of two 5‐ring polycyclic aromatic hydrocarbons (PAHs), benzo[a]pyrene (BaP) and dibenz[a,h]anthracene (DBA), and dimethyl sulfoxide extracts from five PAH‐containing petroleum substances (PS) and a gas‐to‐liquid base oil (GTLb), with and without bioactivation. In the absence of bioactivation, DBA, but not BaP, inhibited the differentiation of ES‐D3 cells into beating cardiomyocytes in a concentration‐dependent manner. Upon bioactivation, BaP induced in vitro PDT, while its major metabolite 3‐hydroxybenzo[a]pyrene was shown to be active in the EST as well. This means BaP needs biotransformation to exert its embryotoxic effects. GTLb extracts tested negative in the EST, with and without bioactivation. The PS‐induced PDT in the EST was not substantially changed following bioactivation, implying that metabolism may not play a crucial role for the PS extracts under study to exert the in vitro PDT effects. Altogether, these results indicate that although some PAH require bioactivation to induce PDT, some do not and this latter appears to hold for the (majority of) the PS constituents responsible for the in vitro PDT of these complex substances.

Recent evidence suggests that the interaction of polycyclic aromatic hydrocarbons (PAHs), present in some petroleum substances (PS), with particular nuclear-hormone-receptors and/or the dioxin (aryl hydrocarbon receptor [AhR]) receptor, may play a role in the prenatal developmental toxicity (PDT) induced by these substances. To address this hypothesis, we evaluated the possible endocrine and dioxin-like activity of the dimethylsulfoxide (DMSO)-extracts of 9 PS, varying in PAH content, and 2 gas-to-liquid (GTL) products, containing no PAHs but having similar other properties as PS, using a series of Chemical Activated LUciferase gene eXpression (CALUX) assays. The results show that the extracts of PS tested in this study possess various endocrine and dioxin-like activities and these in vitro potencies are associated with the quantity and type of PAHs they contain. All tested DMSO-extracts of PS show a strong AhR agonist activity and rather weak antiprogesterone, antiandrogen, and estrogenic activities. In the assays that evaluate thyroid-related and antiestrogen activity, only minor effects of specific extracts, particularly those with a substantial amount of 4–5 ring PAHs, ie, sample No. 34, 98, and 99, were observed. None of the GTL extracts interacted with the selected receptors. Of all assays, the AhR agonist activity correlates best (R2 = 0.80) with the in vitro PDT of the substances as quantified previously in the embryonic stem cell test, suggesting an important role of the AhR in mediating this effect. Hierarchic clustering of the combined CALUX data clustered the compounds in line with their chemical characteristics, suggesting a PS class-specific effects signature in the various CALUX assays, depending on the PAH profile. To conclude, our findings indicate a high potential for endocrine and dioxin-like activity of some PS extracts which correlates with their in vitro PDT and is driven by the PAHs present in these substances.

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