In chemical risk assessment, default uncertainty factors are used to account for interspecies and interindividual differences, and differences in toxicokinetics and toxicodynamics herein. However, ...these default factors come with little scientific support. Therefore, our aim was to develop an in vitro method, using acetylcholinesterase (AChE) inhibition as a proof of principle, to assess both interspecies and interindividual differences in toxicodynamics. Electric eel enzyme and human blood of 20 different donors (12 men/8 women) were exposed to eight different compounds (chlorpyrifos, chlorpyrifos-oxon, phosmet, phosmet-oxon, diazinon, diazinon-oxon, pirimicarb, rivastigmine) and inhibition of AChE was measured using the Ellman method. The organophosphate parent compounds, chlorpyrifos, phosmet and diazinon, did not show inhibition of AChE. All other compounds showed concentration-dependent inhibition of AChE, with IC
50
s in human blood ranging from 0.2–29 µM and IC
20
s ranging from 0.1–18 µM, indicating that AChE is inhibited at concentrations relevant to the in vivo human situation. The oxon analogues were more potent inhibitors of electric eel AChE compared to human AChE. The opposite was true for carbamates, pointing towards interspecies differences for AChE inhibition. Human interindividual variability was low and ranged from 5–25%, depending on the concentration. This study provides a reliable in vitro method for assessing human variability in AChE toxicodynamics. The data suggest that the default uncertainty factor of ~ 3.16 may overestimate human variability for this toxicity endpoint, implying that specific toxicodynamic-related adjustment factors can support quantitative in vitro to in vivo extrapolations that link kinetic and dynamic data to improve chemical risk assessment.
The new challenges in toxicology demand novel and innovative in vitro approaches for deriving points of departure (PODs) and determining the mode of action (MOA) of chemicals. Therefore, the aim of ...this original study was to couple in vitro studies with untargeted metabolomics to model the concentration-response of extra- and intracellular metabolome data on human HepaRG cells treated for 48 h with three pyrrolizidine alkaloids (PAs): heliotrine, retrorsine and lasiocarpine. Modeling revealed that the three PAs induced various monotonic and, importantly, biphasic curves of metabolite content. Based on unannotated metabolites, the endometabolome was more sensitive than the exometabolome in terms of metabolomic effects, and benchmark concentrations (BMCs) confirmed that lasiocarpine was the most hepatotoxic PA. Regarding its MOA, impairment of lipid metabolism was highlighted at a very low BMC (first quartile, 0.003 µM). Moreover, results confirmed that lasiocarpine targets bile acids, as well as amino acid and steroid metabolisms. Analysis of the endometabolome, based on coupling concentration-response and PODs, gave encouraging results for ranking toxins according to their hepatotoxic effects. Therefore, this novel approach is a promising tool for next-generation risk assessment, readily applicable to a broad range of compounds and toxic endpoints.
Display omitted
•PA effects on HepaRG cells were studied by concentration-response modelling and BMC.•The endometabolome was found to be more sensitive than the exometabolome.•LAS had the highest hepatotoxic potency, followed by HEL and RET.•The bell shape is the most frequent trend in response to LAS.•Lipids, bile acids and amino acids were especially affected by LAS.
•Extensive literature review performed on in vivo GST activity in healthy humans.•Variability analysis of in vivo GST activity due to age, ethnicity, polymorphisms.•Tissue and organ distribution of ...GST activity is reported.•Bayesian meta-analysis was conducted to derive GST-related uncertainty factors.•Limited datasets highlighted large data gaps.
The input into the QIVIVE and Physiologically-Based kinetic and dynamic models of drug metabolising enzymes performance and their inter-individual differences significantly improve the modelling performance, supporting the development and integration of alternative approaches to animal testing. Bayesian meta-analyses allow generating and integrating statistical distributions with human in vitro metabolism data for quantitative in vitro-in vivo extrapolation. Such data are lacking on glutathione-S-transferases (GSTs). This paper reports for the first time results on the human variability of GST activities in healthy individuals, their tissue localisation and the frequencies of their major polymorphic variants by means of extensive literature search, data collection, data base creation and meta-analysis.
A limited number of papers focussed on in vivo GST inter-individual differences in humans. Ex-vivo total GST activity without discriminating amongst isozymes is generally reported, resulting in a high inter-individual variability.
The highest levels of cytosolic GSTs in humans are measured in the kidney, liver, adrenal glands and blood. The frequencies of GST polymorphisms for cytosolic isozymes in populations of different geographical ancestry were also presented. Bayesian meta-analyses to derive GST-related uncertainty factors provided uncertain estimates, due to the limited database.
Considering the relevance of GST activities and their pivotal role in cellular adaptive response mechanisms to chemical stressors, further studies are needed to identify GST probe substrates for specific isozymes and quantify inter-individual differences.
The French Nutrition and Health Survey (ENNS) reported higher biomarker levels of exposure to pyrethroids than those observed in North American and German biomonitoring studies. The authors therefore ...investigated aggregate exposure to permethrin as an initial case study because this compound is one of the most widely-used pyrethroid insecticides. We assessed several contamination sources—such as indoor and outdoor air, settled dust and diet—and several pathways, including oral, inhalation and dermal routes. We used permethrin exposure level estimations (computed from ENNS data) and a PBPK model calibrated with human kinetic data (from 6 individuals) to simulate an internal dose of cis- and trans-3-(2,2 dichlorovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylic acid (cis- or trans-DCCA) in a population of 219 individuals. The urinary concentrations of cis- and trans -DCCA predicted by the PBPK model according to three permethrin exposure scenarios (“lower”, “intermediate”, and “upper”), were compared to the urinary levels measured in the ENNS study. The ENNS levels were between the levels simulated according to permethrin exposure scenarios “lower” and “intermediate”. The “upper” scenario led to an overestimation of the predicted urinary concentration levels of cis - and trans -DCCA compared to those measured in the ENNS study. The most realistic scenario was the “lower” one (permethrin concentration of left-censored data considered as 0). Using PBPK modeling, we estimated the contribution of each pathway and source to the internal dose. The main route of permethrin exposure was oral (98%), diet being the major source (87%) followed by dust (11%) then the dermal route (1.5%) and finally inhalation (0.5%).
•Assessment of the adult French population’s aggregate exposure to permethrin•Adjustment of a PBPK model of permethrin to predict urinary concentrations of DCCA•Estimation of the contributions of each source and pathway to permethrin exposure
•Extensive literature research on CYP1A2, CYP2A6, CYP2D6, CYP3A4/3A5, CYP3A7 activity.•Open source OpenCYP database provides data for healthy adult variability in CYP activities.•Quantitative ...comparisons are hampered by different experimental conditions used.•Data gaps identified on specific age groups (e.g. elderly, children and neonates).•OpenCYP database as a promising tool for PBk modelks and chemical risk assessment.
The open source database “OpenCYP database” has been developed based on the results of extensive literature searches from the peer-reviewed literature. OpenCYP provides data on human variability on baseline of activities and polymophism frequencies for selected cytochrome P-450 isoforms (CYP1A2, CYP2A6, CYP2D6, CYP3A4/3A5 and CYP3A7) in healthy adult populations from world populations. CYP enzymatic activities were generally expressed as the metabolic ratio (MR) between an unchanged probe drug and its metabolite(s) in urine or plasma measured in healthy adults. Data on other age groups were very limited and fragmented, constituting an important data gap. Quantitative comparisons were often hampered by the different experimental conditions used. However, variability was quite limited for CYP1A2, using caffeine as a probe substrate, with a symmetrical distribution of metabolic activity values. For CYP3A4, human variability was dependent on the probe substrate itself with low variability when data considering the dextromethorphan/demethilathed metabolite MR were used and large variability when the urinary 6β-hydroxycortisol/cortisol ratio was used. The largest variability in CYP activity was shown for CYP2D6 activity, after oral dosing of dextromethorphan, for which genetic polymorphisms are well characterised and constitute a significant source of variability.
It is foreseen that the OpenCYP database can contribute to promising tools to support the further development of QIVIVE and PBK models for human risk assessment of chemicals particularly when combined with information on isoform-specific content in cells using proteomic approaches.
Recent studies succeeded in developing a method to automatically record honeybees going in and out of the hive. Honeybees were individualized with radio frequency identification (RFID) tags glued ...onto their dorsal surface and detected at the hive entrance by readers emitting high-frequency (HF) radio waves. In this work we search for a possible adverse effect of HF on honeybees’ survival. Eight-day-old honeybees were exposed to HF (13.56 MHz) or ultra-high-frequency (UHF, 868 MHz) radio waves for 2 h split into ON and OFF periods. The ON/OFF ratio was 1:3 (OFF duration 3, 90, 180, 370 and 360 s) or 1:5 (OFF duration 300 s). Dead individuals were counted every day, and the cumulative mortality rates of exposed and non-exposed honeybees were compared 7 days after exposure. Out of the five experimental conditions, we observed an increase in mortality in two conditions, once after HF and once after UHF exposure, with OFF duration of 5 min or more. We then recommend limiting exposure of honeybees to radio waves to less than 2 h per day, and we conclude that the RFID parameters, like those we used in the field for monitoring hive activity, present no adverse effects for honeybees.
This publication is linked to the following EFSA Supporting Publications articles: http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2023.EN-8441/full, ...http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2023.EN-8440/full, http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2023.EN-8437/full
This technical report provides a user guide for the TKPlate 1.0 platform which allows to implement New Approach Methodologies in the chemical risk assessment process by means of toxicokinetic and ...toxicodynamic modelling of chemicals in humans, laboratory animals, farm animals and species of ecological relevance. TKPlate 1.0 is available as an open access web-based tool or a downloadable application. The platform is built as a workflow of 7 modules: 1. Input module for which the user can select the species, kinetic or physiologically-based kinetic model, the chemical to be modelled, exposure scenarios and simulation times, 2. Forward dosimetry allowing the user to simulate kinetic parameters, body fluid and organ concentrations, 3. Reverse dosimetry for the reconstruction of exposure distributions using internal dose such as biomonitoring data, 4. Benchmark dose modelling using model averaging on an internal dose basis, 5. Dynamic energy budget modelling, 6. Mixture risk characterisation using the methods available from EFSA's Scientific committee guidance document, 7. Automated report where the user can access input and output data in a technical report, graphs and datasets. For each module, the structure and applications are described with examples. The technical development of TKPlate 1.0 is described in an external scientific report which is associated with an EFSA editorial and two technical reports namely a user guide and case studies illustrating applications of TKPlate 1.0. Finally, all models and associated files are also available published in Zenodo (https://zenodo.org/record/7494936).
PDF
