RESUMO
Alcohol ethoxylates (AEs) are a well-known class of non-ionic surfactants widely used by the personal care market. The aim of this study was to evaluate and characterize the in vitro metabolism of AEs and identify metabolites. Five selected individual homologue AEs (C8EO4, C10EO5, C12EO4, C16EO8, and C18EO3) were incubated using human, rat, and hamster liver S9 fraction and cryopreserved hepatocytes. LC-MS was used to identify metabolites following the incubation of AEs by liver S9 and hepatocytes of all three species. All AEs were metabolized in these systems with a half-life ranging from 2 to 139 min. In general, incubation of AE with human liver S9 showed a shorter half-life compared to rat liver S9. While rat hepatocytes metabolized AEs faster than human hepatocytes. Both hydrophobic alkyl chain and hydrophilic EO head group groups of AEs were found to be target sites of metabolism. Metabolites were identified that show primary hydroxylation and dehydrogenation, followed by O-dealkylation (shortening of EO head groups) and glucuronidation. Additionally, the detection of whole EO groups indicates the cleavage of the ether bond between the alkyl chain and the EO groups as a minor metabolic pathway in the current testing system. Furthermore, no difference in metabolic patterns of each individual homologue AE investigated was observed, regardless of alkyl chain length or the number of EO groups. Moreover, there is an excellent agreement between the in vitro experimental data and the metabolite profile simulations using in silico approaches (OECD QSAR Toolbox). Altogether, these data indicate fast metabolism of all AEs with a qualitatively similar metabolic pathway with some quantitative differences observed in the metabolite profiles. These metabolic studies using different species can provide important reference values for further safety evaluation.
Assuntos
Hepatócitos , Animais , Hepatócitos/metabolismo , Hepatócitos/efeitos dos fármacos , Humanos , Projetos Piloto , Masculino , Ratos , Redes e Vias Metabólicas , Simulação por Computador , Cricetinae , Tensoativos/metabolismo , Tensoativos/toxicidade , Especificidade da Espécie , Meia-Vida , Fígado/metabolismo , Cromatografia Líquida , Etilenoglicóis/metabolismo , Etilenoglicóis/toxicidade , Ratos Sprague-DawleyRESUMO
The present study evaluates the in vitro developmental toxicity and the possible underlying mode of action of DMSO extracts of a series of highly complex petroleum substances in the mouse embryonic stem cell test (mEST), the zebrafish embryotoxicity test (ZET) and the aryl hydrocarbon receptor reporter gene assay (AhR CALUX assay). Results show that two out of sixteen samples tested, both being poorly refined products that may contain a substantial amount of 3- to 7-ring polycyclic aromatic compounds (PACs), induced sustained AhR activation in the AhR CALUX assay, and concentration-dependent developmental toxicity in both mEST and ZET. The other samples tested, representing highly refined petroleum substances and petroleum-derived waxes (containing typically a very low amount or no PACs at all), were negative in all assays applied, pointing to their inability to induce developmental toxicity in vitro. The refining processes applied during the production of highly refined petroleum products, such as solvent extraction and hydrotreatment which focus on the removal of undesired constituents, including 3- to 7-ring PACs, abolish the in vitro developmental toxicity. In conclusion, the obtained results support the hypothesis that 3- to 7-ring PACs are the primary inducers of the developmental toxicity induced by some (i.e., poorly refined) petroleum substances and that the observed effect is partially AhR-mediated.
Assuntos
Petróleo , Hidrocarbonetos Policíclicos Aromáticos , Camundongos , Animais , Petróleo/toxicidade , Petróleo/análise , Peixe-Zebra , Células-Tronco Embrionárias MurinasRESUMO
Higher olefins (HO) are used primarily as intermediates in the production of other chemicals, such as polymers, fatty acids, plasticizer alcohols, surfactants, lubricants, amine oxides, and detergent alcohols. The potential toxicity of five HO (i.e., 1-Octene, Nonene, Decene, Hexadecene, and 1-Octadecene) with carbon ranging from C8 to C18 was examined in a combined repeated dose and reproduction/developmental toxicity screening study (OECD TG 422). These five HO were administered to Han Wistar rats by gavage at 0 (controls), 100, 300, and 1000 mg/kg bw/day. As a group of substances, adaptive changes in the liver (liver weight increase without pathological evidence), as well as increased kidney weight in male rats, were observed in HO with carbon numbers from C8 to C10. The overall systemic no observed adverse effect level (NOAEL) for all HO was determined at 1000 mg/kg bw/day. In the reproductive/developmental toxicity assessment, offspring viability, size, and weights were reduced in litters from females treated with Nonene at 1000 mg/kg bw/day. The overall no observed effects level (NOEL) for reproductive toxicity was considered to be 300 mg/kg bw/day for Nonene and 1000 mg/kg bw/day for the other four HO, respectively. These data significantly enrich the database on the toxicity of linear and branched HO, allowing comparison with similar data published on a range of linear and branched HO. Comparisons between structural class and study outcome provide further supportive data in order to validate the read-across hypothesis as part of an overall holistic testing strategy.
RESUMO
The present study evaluated the aryl hydrocarbon receptor (AhR), estrogen receptor-α (ER-α), and retinoic acid receptor (RAR) mediated activities of nine 4- and 5-ring unsubstituted and monomethylated polycyclic aromatic hydrocarbons (PAHs) using a series of Chemical-Activated LUciferase gene eXpression (CALUX) assays. The potential role of these aforementioned receptors in relation to the developmental toxicity of these PAHs was further assessed in the zebrafish embryotoxicity test (ZET). The results show that all nine tested PAHs were AhR agonists, benz[a]anthracene (BaA) and 8-methyl-benz[a]anthracene (8-MeBaA) were ER-α agonists, and none of the tested PAHs induced ER-α antagonistic or RAR (ant)agonistic activities. In the AhR CALUX assay, all the methylated PAHs showed higher potency (lower EC50) in activating the AhR than their respective unsubstituted PAHs, implying that the addition of a methyl substituent on the aromatic ring of PAHs could enhance their AhR-mediated activities. Co-exposure of zebrafish embryos with each individual PAH and an AhR antagonist (CH223191) counteracted the observed developmental retardations and embryo lethality to a certain extent, except for 8-methyl-benzo[a]pyrene (8-MeBaP). Co-exposure of zebrafish embryos with either of the two estrogenic PAHs (i.e., BaA and 8-MeBaA) and an ER-α antagonist (fulvestrant) neutralized embryo lethality induced by 50 µM BaA and the developmental retardations induced by 15 µM 8-MeBaA. Altogether, our findings suggest that the observed developmental retardations in zebrafish embryos by the PAH tested may partially be AhR- and/or ER-α-mediated, whereas the RAR seems not to be relevant for the PAH-induced developmental toxicity in the ZET.
Assuntos
Hidrocarbonetos Policíclicos Aromáticos , Animais , Hidrocarbonetos Policíclicos Aromáticos/toxicidade , Hidrocarbonetos Policíclicos Aromáticos/metabolismo , Peixe-Zebra/metabolismo , Antracenos/metabolismo , Receptores de Hidrocarboneto Arílico/metabolismoRESUMO
To reduce the number of animals and studies needed to fulfill the information requirements as required by Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) (EC no. 1907/2006), a read-across approach was used to support approximately 30 higher olefins. This study aimed to assess the absorption potential of higher olefins through the gut wall as the experimentally determined bioavailability which would strengthen the read-across hypothesis and justification, reducing the need for toxicity studies on all of the higher olefins. The absorption potential of a series of higher olefins (carbon range from 6 to 28, with five configurations of the double bond) was determined in the in vitro everted rat small intestinal sac model and subsequently ranked. In addition, in silico approaches were applied to predict the reactivity, lipophilicity, and permeability of higher olefins. In the in vitro model, everted sacs were incubated in "fed-state simulated small intestinal fluid" saturated with individual higher olefins. The sac contents were then collected, extracted, and analyzed for olefin content using gas chromatography with a flame ionization detector. The C6 to C10 molecules were readily absorbed into the intestinal sacs. Marked inter-compound differences were observed, with the amount of absorption generally decreasing with the increase in carbon number. Higher olefins with ≥C14 carbons were either not absorbed or very poorly absorbed. In the reactivity simulation study, the reactivity is well described by the position of the double bond rather than the number of carbon atoms. In the lipophilicity and permeability analysis, both parameter descriptors depend mainly on the number of carbon atoms and less on the position of the double bond. In conclusion, these new approach methodologies provide supporting information on any trends or breakpoints in intestinal uptake and a hazard matrix based on carbon number and position of the double bond. This matrix will further assist in the selection of substances for inclusion in the mammalian toxicity testing programme.
Assuntos
Alcenos , Absorção Intestinal , Animais , Carbono/metabolismo , Intestino Delgado , Mamíferos , Permeabilidade , RatosRESUMO
In recent years concerns over consumer exposure to mineral oil aromatic hydrocarbons (MOAH), especially those containing alkylated polycyclic aromatic hydrocarbons (PAHs), have emerged. This is especially due to the fact that some PAHs are known to be genotoxic and carcinogenic upon metabolic activation. However, available toxicological data on PAHs mainly relate to non-substituted PAHs with limited data on alkyl substituted PAHs. Therefore, the aim of the present study was to characterize in more detail the effect of alkyl substitution on the metabolism and mutagenicity of benzo[a]pyrene (B[a]P), a PAH known to be genotoxic and carcinogenic. To this end, the oxidative metabolism and mutagenicity of B[a]P and a series of its alkyl substituted analogues were quantified using in vitro microsomal incubations and the Ames test. The results obtained reveal that upon alkylation the metabolic oxidation shifts to the aliphatic side chain at the expense of aromatic ring oxidation. The overall metabolism, including metabolism via aromatic ring oxidation resulting potentially in bioactivation, was substantially reduced with elongation of the alkyl side chain, with metabolism of B[a]P with an alkyl substituent of >6 C atoms being seriously hampered. In the Ames test upon metabolic activation, the methyl substitution of B[a]P resulted in an increase or decrease of the mutagenic potency depending on the substitution position. The relevant pathways for mutagenicity of the selected monomethyl substituted B[a]P may involve the formation of a 7,8-dihydrodiol-9,10-epoxide, a 4,5-oxide and/or a benzylic alcohol as an oxidative side chain metabolite which subsequently may give rise to an unstable and reactive sulfate ester conjugate. It is concluded that alkylation of B[a]P does not systematically reduce its mutagenicity in spite of the metabolic shift from aromatic to side chain oxidation.
Assuntos
Mutagênicos , Hidrocarbonetos Policíclicos Aromáticos , Benzo(a)pireno/toxicidade , Carcinógenos , Mutagênese , Testes de Mutagenicidade , Mutagênicos/toxicidade , Hidrocarbonetos Policíclicos Aromáticos/químicaRESUMO
The application of in vitro biological assays as new approach methodologies (NAMs) to support grouping of UVCB (unknown or variable composition, complex reaction products, and biological materials) substances has recently been demonstrated. In addition to cell-based phenotyping as NAMs, in vitro transcriptomic profiling is used to gain deeper mechanistic understanding of biological responses to chemicals and to support grouping and read-across. However, the value of gene expression profiling for characterizing complex substances like UVCBs has not been explored. Using 141 petroleum substance extracts, we performed dose-response transcriptomic profiling in human induced pluripotent stem cell (iPSC)-derived hepatocytes, cardiomyocytes, neurons, and endothelial cells, as well as cell lines MCF7 and A375. The goal was to determine whether transcriptomic data can be used to group these UVCBs and to further characterize the molecular basis for in vitro biological responses. We found distinct transcriptional responses for petroleum substances by manufacturing class. Pathway enrichment informed interpretation of effects of substances and UVCB petroleum-class. Transcriptional activity was strongly correlated with concentration of polycyclic aromatic compounds (PAC), especially in iPSC-derived hepatocytes. Supervised analysis using transcriptomics, alone or in combination with bioactivity data collected on these same substances/cells, suggest that transcriptomics data provide useful mechanistic information, but only modest additional value for grouping. Overall, these results further demonstrate the value of NAMs for grouping of UVCBs, identify informative cell lines, and provide data that could be used for justifying selection of substances for further testing that may be required for registration.
Assuntos
Células-Tronco Pluripotentes Induzidas , Petróleo , Bioensaio , Células Endoteliais , Humanos , TranscriptomaRESUMO
Alkyl-substituted PAHs may be present in certain petroleum-derived products and in the environment and may eventually end up in consumer products, such as foodstuffs, cosmetics and pharmaceuticals. Safety concerns over possible exposure to alkylated PAHs have emerged. Bioactivation is a prerequisite for the mutagenicity and carcinogenicity of PAHs and has been extensively studied for non-substituted PAHs, while data on the bioactivation of alkyl-substituted PAHs are scarce. The present study investigated the effect of alkyl substitution on the CYP 450-mediated metabolism of phenanthrene and eight of its alkylated congeners by quantifying metabolite formation in rat and human liver microsomal incubations. Furthermore, the mutagenicity of four selected methylated phenanthrenes was compared to that of phenanthrene using the Ames test. The obtained results support the hypothesis that alkyl substitution shifts the oxidative metabolism from the aromatic ring to the alkyl side chain. Increasing the length of the alkyl chain reduced overall metabolism with metabolic conversion for 1-n-dodecyl-phenanthrene (C12) being negligible. 1- and 9-methyl-phenanthrene, in which the methyl group generates an additional bay region-like structural motif, showed mutagenicity toward Salmonella typhimurium TA98 and TA 100, whereas phenanthrene and also 2- and 3-methyl-phenanthrene, without such an additional bay region-like structural motif, tested negative. It is concluded that the position of the alkylation affects the metabolism and resulting mutagenicity of phenanthrene with the mutagenicity increasing in cases where the alkyl substituent creates an additional bay region-like structural motif, in spite of the extra possibilities for side chain oxidation.
Assuntos
Petróleo , Fenantrenos , Hidrocarbonetos Policíclicos Aromáticos , Animais , Mutagênese , Testes de Mutagenicidade , Mutagênicos/toxicidade , Estresse Oxidativo , Fenantrenos/toxicidade , RatosRESUMO
The present study evaluates the in vitro developmental toxicity of 4- and 5-ring polycyclic aromatic hydrocarbons (PAHs) including benz[a]anthracene (BaA) and benzo[a]pyrene (BaP) and six of their monomethylated congeners, and dibenz[a,h]anthracene (DB[a,h]A) using the zebrafish embryotoxicity test (ZET). In general, the tested PAHs induced various developmental effects in the zebrafish embryos including unhatched embryos, no movement and circulation, yolk sac and pericardial edemas, deformed body shape, and cumulative mortality at 96 h post fertilization (hpf). The methyl substituent on different positions of the aromatic ring of the PAHs appeared to change their in vitro developmental toxicity. Comparison to a previously reported molecular docking study showed that the methyl substituents may affect the interaction of the PAHs with the aryl hydrocarbon receptor (AhR) which is known to play a role in the developmental toxicity of some PAHs. Taken together, our results show that methylation can either increase or decrease the developmental toxicity of PAHs, and suggest this may in part relate to effects on the molecular dimensions and resulting consequences for interactions with the AhR.
Assuntos
Desenvolvimento Embrionário/efeitos dos fármacos , Hidrocarbonetos Policíclicos Aromáticos/toxicidade , Animais , Embrião não Mamífero , Metilação , Testes de Toxicidade/métodos , Peixe-ZebraRESUMO
Respiratory irritation is an important human health endpoint in chemical risk assessment. There are two established modes of action of respiratory irritation, 1) sensory irritation mediated by the interaction with sensory neurons, potentially stimulating trigeminal nerve, and 2) direct tissue irritation. The aim of our research was to, develop a QSAR method to predict human respiratory irritants, and to potentially reduce the reliance on animal testing for the identification of respiratory irritants. Compounds are classified as irritating based on combined evidence from different types of toxicological data, including inhalation studies with acute and repeated exposure. The curated project database comprised 1997 organic substances, 1553 being classified as irritating and 444 as non-irritating. A comparison of machine learning approaches, including Logistic Regression (LR), Random Forests (RFs), and Gradient Boosted Decision Trees (GBTs), showed, the best classification was obtained by GBTs. The LR model resulted in an area under the curve (AUC) of 0.65, while the optimal performance for both RFs and GBTs gives an AUC of 0.71. In addition to the classification and the information on the applicability domain, the web-based tool provides a list of structurally similar analogues together with their experimental data to facilitate expert review for read-across purposes.
Assuntos
Irritantes/química , Aprendizado de Máquina , Relação Quantitativa Estrutura-Atividade , Sistema Respiratório/efeitos dos fármacos , Administração por Inalação , Alternativas aos Testes com Animais/métodos , Medição de RiscoRESUMO
Historically, benzene has been widely used in a large variety of applications. Occupational exposure limits (OELs) were set for benzene as it was found to be acutely toxic, causing central nervous system depression at high exposures. OELs were lowered when it was discovered that chronic exposure to benzene could cause haematotoxicity. After confirmation that benzene is a human carcinogen causing acute myeloid leukaemia and possibly other blood malignancies, OEL were further lowered. The industrial application of benzene as solvent is almost completely discontinued but it is still used as feedstock for the production of other materials, such as styrene. Occupational exposure to benzene may also occur since it is present in crude oil, natural gas condensate and a variety of petroleum products and because benzene can be formed in combustion of organic material. In the past few years, lower OELs for benzene in the range of 0.05-0.25 ppm have been proposed or were already established to protect workers from benzene-induced cancer. The skin is an important potential route of exposure and relatively more important at lower OELs. Consequently, human biomonitoring - which integrates all exposure routes - is routinely applied to control overall exposure to benzene. Several potential biomarkers have been proposed and investigated. For compliance check of the current low OELs, urinary S-phenylmercapturic acid (S-PMA), urinary benzene and blood benzene are feasible biomarkers. S-PMA appears to be the most promising biomarker but proper validation of biomarker levels corresponding to airborne benzene concentrations below 0.25 ppm are needed.
Assuntos
Exposição Ocupacional , Petróleo , Humanos , Benzeno/toxicidade , Monitoramento Biológico , Exposição Ocupacional/análise , Biomarcadores , Monitoramento AmbientalRESUMO
Developmental toxicity testing is an animal-intensive endpoints in toxicity testing and calls for animal-free alternatives. Previous studies showed the applicability of an in vitro-in silico approach for predicting developmental toxicity of a range of compounds, based on data from the mouse embryonic stem cell test (EST) combined with physiologically based kinetic (PBK) modelling facilitated reverse dosimetry. In the current study, the use of this approach for predicting developmental toxicity of polycyclic aromatic hydrocarbons (PAHs) was evaluated, using benzo[a]pyrene (BaP) as a model compound. A rat PBK model of BaP was developed to simulate the kinetics of its main metabolite 3-hydroxybenzo[a]pyrene (3-OHBaP), shown previously to be responsible for the developmental toxicity of BaP. Comparison to in vivo kinetic data showed that the model adequately predicted BaP and 3-OHBaP blood concentrations in the rat. Using this PBK model and reverse dosimetry, a concentration-response curve for 3-OHBaP obtained in the EST was translated into an in vivo dose-response curve for developmental toxicity of BaP in rats upon single or repeated dose exposure. The predicted half maximal effect doses (ED50) amounted to 67 and 45 mg/kg bw being comparable to the ED50 derived from the in vivo dose-response data reported for BaP in the literature, of 29 mg/kg bw. The present study provides a proof of principle of applying this in vitro-in silico approach for evaluating developmental toxicity of BaP and may provide a promising strategy for predicting the developmental toxicity of related PAHs, without the need for extensive animal testing.
Assuntos
Benzo(a)pireno/administração & dosagem , Benzopirenos/metabolismo , Modelos Biológicos , Animais , Benzo(a)pireno/farmacocinética , Benzo(a)pireno/toxicidade , Simulação por Computador , Relação Dose-Resposta a Droga , Masculino , Ratos , Ratos Sprague-Dawley , Testes de Toxicidade/métodosRESUMO
The potential developmental toxicity and mode-of-action of fume condensate extracts of bitumen and oxidized asphalt were evaluated in the aryl hydrocarbon receptor (AhR) CALUX assay, the zebrafish embryotoxicity test (ZET), and the mouse embryonic stem cell test (mEST). In the AhR CALUX assay, both fume condensate extracts showed a concentration-dependent AhR induction following 6-h of exposure, but this activity was substantially reduced after 24-h, indicating a transient AhR activation. The main effect observed in the ZET was early embryonic lethality that occurred mostly in the 24 h-post-fertilization (hpf). This typically reflects non-specific toxicity rather than in vitro developmental toxicity of the fume condensate extracts tested since this effect was not seen as a result of the whole cumulative exposure period in the ZET (up to 96 hpf). No malformations were seen in any zebrafish embryo exposed to these fume condensate extracts, although some developed pericardial and/or yolk-sac edemas. Furthermore, both fume condensate extracts tested negative in the mEST. In conclusion, the results show that fume condensate extracts of bitumen and oxidized asphalt do not induce any in vitro developmental toxicity, which is in line with the results observed in the in vivo prenatal developmental toxicity studies performed with the same materials.
Assuntos
Misturas Complexas/toxicidade , Embrião não Mamífero/efeitos dos fármacos , Hidrocarbonetos/toxicidade , Células-Tronco Embrionárias Murinas/efeitos dos fármacos , Receptores de Hidrocarboneto Arílico/genética , Alternativas aos Testes com Animais , Animais , Bioensaio , Diferenciação Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Embrião não Mamífero/anatomia & histologia , Desenvolvimento Embrionário/efeitos dos fármacos , Genes Reporter , Camundongos , Testes de Toxicidade , Peixe-Zebra/anatomia & histologiaRESUMO
The prenatal developmental toxicity of the fumes of oxidised asphalt (OA) was tested by nose-only inhalation in the rat. The test material was generated by collecting fumes from the headspace of storage tanks filled with OA. The composition of these fumes was matched to fumes sampled at a workplace where the same OA was applied in a pour-and-roll operation, representing occupational exposure with high concentrations of fumes to not underestimate the possible hazard. In the main study, dams were exposed to 0, 53, 158 and 536â¯mg/m3 of fume (as total organic mass), for 6â¯h/day for 19 days p.c. The maternal NOAEC was 53â¯mg/m³ (lowest dose tested). In the high-dose group treatment-related effects on body weight gain were seen. In the mid- and high-dose groups treatment-related effects on food consumption, lung weights, and histopathological changes in lungs and the upper respiratory tract were observed. The NOAEC for prenatal developmental toxicity was 536â¯mg/m³ since no exposure-related effects were found in any of the exposure groups for any of the investigated reproductive endpoints. Furthermore, nose-only exposure to OA fumes in concentrations up to 536â¯mg/m³ from days 1-19 p.c. did not induce any significant fetal abnormalities.
Assuntos
Hidrocarbonetos/toxicidade , Exposição por Inalação , Animais , Feminino , Pulmão , Masculino , Exposição Ocupacional , Gravidez , Ratos , ReproduçãoRESUMO
One of the most challenging areas in regulatory science is assessment of the substances known as UVCB (unknown or variable composition, complex reaction products and biological materials). Because the inherent complexity and variability of UVCBs present considerable challenges for establishing sufficient substance similarity based on chemical characteristics or other data, we hypothesized that new approach methodologies (NAMs), including in vitro test-derived biological activity signatures to characterize substance similarity, could be used to support grouping of UVCBs. We tested 141 petroleum substances as representative UVCBs in a compendium of 15 human cell types representing a variety of tissues. Petroleum substances were assayed in dilution series to derive point of departure estimates for each cell type and phenotype. Extensive quality control measures were taken to ensure that only high-confidence in vitro data were used to determine whether current groupings of these petroleum substances, based largely on the manufacturing process and physico-chemical properties, are justifiable. We found that bioactivity data-based groupings of petroleum substances were generally consistent with the manufacturing class-based categories. We also showed that these data, especially bioactivity from human induced pluripotent stem cell (iPSC)-derived and primary cells, can be used to rank substances in a manner highly concordant with their expected in vivo hazard potential based on their chemical compositional profile. Overall, this study demonstrates that NAMs can be used to inform groupings of UVCBs, to assist in identification of representative substances in each group for testing when needed, and to fill data gaps by read-across.
Assuntos
Alternativas aos Testes com Animais/métodos , Substâncias Perigosas/química , Células-Tronco Pluripotentes Induzidas/efeitos dos fármacos , Petróleo/análise , Petróleo/toxicidade , Testes de Toxicidade/métodos , Substâncias Perigosas/toxicidade , HumanosRESUMO
The prenatal developmental toxicity of bitumen fume was tested by nose-only inhalation in the rat. The fumes for exposure were collected from the headspace of a storage tank filled with a bitumen corresponding in composition to an anticipated worst-case occupational exposure. The composition of these fumes was compared to actual paving site fumes to ensure its representativeness for workplace exposures. In a dose-range-finding study male and female rats were exposed to 0, 103, 480 or 1043â¯mg/m3 of fume (as total organic mass), for 6â¯h/day during 20 days post conception (p.c.). Dose-related effects on body weight and lungs were observed in the mid- and high-dose groups. In the main study, dams were exposed to 0, 52, 151 and 482â¯mg/m3 of fume, for 6â¯h/day during 19 days p.c. The maternal NOAEL was 52â¯mg/m³. In the high-dose group treatment-related effects on body weight (gain), food consumption, lung weights, and histopathological changes in lungs and larynx were observed. In the mid-dose group only histopathological changes in the larynx and lungs were found. The NOAEL for prenatal developmental toxicity was 151â¯mg/m³ based on reduced fetal weight in the high-dose group (482â¯mg/m³). However, these changes are most likely a consequence of the maternal toxicity, in particular the reduction of maternal body weight gain by 26 % as compared to control. Nose-only exposure to bitumen fumes in concentrations up to 482â¯mg/m³ from days 1-19 p.c. did not induce any significant fetal anomalies.
Assuntos
Poluentes Ocupacionais do Ar/toxicidade , Hidrocarbonetos/toxicidade , Administração por Inalação , Aerossóis/análise , Aerossóis/toxicidade , Poluentes Ocupacionais do Ar/análise , Animais , Peso Corporal/efeitos dos fármacos , Monitoramento Ambiental , Feminino , Feto/efeitos dos fármacos , Humanos , Hidrocarbonetos/análise , Exposição por Inalação/análise , Laringe/efeitos dos fármacos , Laringe/patologia , Pulmão/efeitos dos fármacos , Pulmão/patologia , Masculino , Troca Materno-Fetal , Nível de Efeito Adverso não Observado , Exposição Ocupacional/análise , Gravidez , Ratos WistarRESUMO
This paper derives an occupational exposure limit for benzene using quality assessed data. Seventy-seven genotoxicity and 36 haematotoxicity studies in workers were scored for study quality with an adapted tool based on that of Vlaanderen et al., 2008 (Environ Health. Perspect. 116 1700-5). These endpoints were selected as they are the most sensitive and relevant to the proposed mode of action (MOA) and protecting against these will protect against benzene carcinogenicity. Lowest and No- Adverse Effect Concentrations (LOAECs and NOAECs) were derived from the highest quality studies (i.e. those ranked in the top tertile or top half) and further assessed as being "more certain" or "less certain". Several sensitivity analyses were conducted to assess whether alternative "high quality" constructs affected conclusions. The lowest haematotoxicity LOAECs showed effects near 2â¯ppm (8â¯h TWA), and no effects at 0.59â¯ppm. For genotoxicity, studies also showed effects near 2â¯ppm and showed no effects at about 0.69â¯ppm. Several sensitivity analyses supported these observations. These data define a benzene LOAEC of 2â¯ppm (8â¯h TWA) and a NOAEC of 0.5â¯ppm (8â¯h TWA). Allowing for possible subclinical effects in bone marrow not apparent in studies of peripheral blood endpoints, an OEL of 0.25â¯ppm (8â¯h TWA) is proposed.
Assuntos
Poluentes Ocupacionais do Ar/toxicidade , Benzeno/toxicidade , Mutagênicos/toxicidade , Exposição Ocupacional/análise , Estudos Epidemiológicos , Humanos , Concentração Máxima Permitida , Nível de Efeito Adverso não Observado , Exposição Ocupacional/efeitos adversos , Medição de Risco , Níveis Máximos PermitidosRESUMO
Mineral oils are widely applied in food production and processing and may contain polycyclic aromatic hydrocarbons (PAHs). The PAHs that may be present in mineral oils are typically alkylated, and have been barely studied. Metabolic oxidation of the aromatic ring is a key step to form DNA-reactive PAH metabolites, but may be less prominent for alkylated PAHs since alkyl substituents would facilitate side chain oxidation as an alternative. The current study investigates this hypothesis of preferential side chain oxidation at the cost of aromatic oxidation using naphthalene and a series of its alkyl substituted analogues as model compounds. The metabolism was assessed by measuring metabolite formation in rat and human liver microsomal incubations using UPLC and GC-MS/MS. The presence of an alkyl side chain markedly reduced aromatic oxidation for all alkyl-substituted naphthalenes that were converted. 1-n-Dodecyl-naphthalene was not metabolized under the experimental conditions applied. With rat liver microsomes for 1-methyl-, 2-methyl-, 1-ethyl-, and 2-ethyl- naphthalene, alkyl side chain oxidation was preferred over aromatic oxidation. With human liver microsomes this was the case for 2-methyl-, and 2-ethyl-naphthalene. It is concluded that addition of an alkyl substituent in naphthalene shifts metabolism in favor of alkyl side chain oxidation at the cost of aromatic ring oxidation. Furthermore, alkyl side chains of 6 or more carbon atoms appeared to seriously hamper and reduce overall metabolism, metabolic conversion being no longer observed with the C12 alkyl side chain. In summary, alkylation of PAHs likely reduces their chances of aromatic oxidation and bioactivation.
Assuntos
Alquilantes/metabolismo , Microssomos Hepáticos/metabolismo , Naftalenos/metabolismo , Alquilação/fisiologia , Animais , Cromatografia Gasosa/métodos , Cromatografia Líquida de Alta Pressão/métodos , Humanos , Oxirredução , Hidrocarbonetos Policíclicos Aromáticos/metabolismo , Ratos , Espectrometria de Massas em Tandem/métodosRESUMO
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.
Assuntos
Diferenciação Celular/efeitos dos fármacos , Microssomos Hepáticos/metabolismo , Células-Tronco Embrionárias Murinas/efeitos dos fármacos , Miócitos Cardíacos/efeitos dos fármacos , Petróleo/toxicidade , Hidrocarbonetos Policíclicos Aromáticos/toxicidade , Ativação Metabólica , Animais , Benzo(a)Antracenos/toxicidade , Benzo(a)pireno/toxicidade , Linhagem Celular , Relação Dose-Resposta a Droga , Masculino , Mesocricetus , Camundongos , Células-Tronco Embrionárias Murinas/patologia , Miócitos Cardíacos/patologia , Petróleo/metabolismo , Hidrocarbonetos Policíclicos Aromáticos/metabolismo , Medição de Risco , Testes de ToxicidadeRESUMO
To test the hypothesis that 3-7 ring polycyclic aromatic hydrocarbons (PAHs) are responsible for the prenatal developmental toxicity (PDT) as observed with some petroleum substances (PS), the present study evaluates the PDT potency of DMSO-extracts of 7 heavy fuel oils (HFO), varying in their PAH content, and 1 highly refined base oil (HRBO), containing no aromatics, in the embryonic stem cell test (EST). All DMSO-extracts of HFO inhibit ES-D3 cell differentiation in a concentration-dependent manner and their potency is proportional to the amount of 3-7 ring PAHs they contain. All DMSO-extracts of HFOs also show aryl hydrocarbon receptor (AhR)-mediated activities, as tested in the AhR-CALUX assay. Contrarily, the HRBO-extract tested negative in both assays. Co-exposure of ES-D3 cells with selected DMSO-extracts of PS and the AhR-antagonist trimethoxyflavone, successfully counteracted the PS-induced inhibition of ES-D3 cell differentiation, confirming the role of the AhR in mediating the observed PDT of PS extracts in the EST. A good correlation exists when comparing the in-vitro with the in-vivo PDT potencies of the PS under study. Altogether, our findings corroborate the hypothesis that PS-induced PDT is caused by 3-7 ring PAHs present in these substances and that the observed PDT is partially AhR-mediated.