Aporrectodea caliginosa, a relevant earthworm species for a posteriori pesticide risk assessment: current knowledge and recommendations for culture and experimental design

Ecotoxicological tests with earthworms are widely used and are mandatory for the risk assessment of pesticides prior to registration and commercial use. The current model species for standardized tests is Eisenia fetida or Eisenia andrei. However, these species are absent from agricultural soils and often less sensitive to pesticides than other earthworm species found in mineral soils. To move towards a better assessment of pesticide effects on non-target organisms, there is a need to performaposterioritestsusingrelevantspecies.TheendogeicspeciesAporrectodeacaliginosa(Savigny,1826)isrepresentative of cultivated fields in temperate regions and is suggested as a relevant model test species. After providing information on its taxonomy, biology, and ecology, we reviewed current knowledge concerning its sensitivity towards pesticides. Moreover, we highlighted research gaps and promising perspectives. Finally, advice and recommendations are given for the establishment of laboratory cultures and experiments using this soil-dwelling earthworm species

Fluoxetine effects assessment on the life cycle of aquatic invertebrates

International audienceFluoxetine is a serotonin re-uptake inhibitor, generally used as an antidepressant. It is suspected to provoke substantial effects in the aquatic environment. This study reports the effects of fluoxetine on the life cycle of four invertebrate species, Daphnia magna, Hyalella azteca and the snail Potamopyrgus antipodarum exposed to fluoxetine spiked-water and the midge Chironomus riparius exposed to fluoxetine-spiked sediments. For D. magna, a multi-generational study was performed with exposition of newborns from exposed organisms. Effects of fluoxetine could be found at low measured concentrations (around 10 micro g l(-1)), especially for parthenogenetic reproduction of D. magna and P. antipodarum. For daphnids, newborns length was impacted by fluoxetine and the second generation of exposed individuals showed much more pronounced effects than the first one, with a NOEC of 8.9 micro g l(-1). For P. antipodarum, significant decrease of reproduction was found for concentrations around 10 micro g l(-1). In contrast, we found no effect on the reproduction of H. azteca but a significant effect on growth, which resulted in a NOEC of 33 micro g l(-1), expressed in nominal concentration. No effect on C. riparius could be found for measured concentrations up to 59.5 mg kg(-1). General mechanistic energy-based models showed poor relevance for data analysis, which suggests that fluoxetine targets specific mechanisms of reproduction

An individual-based model of Zebrafish population dynamics accounting for energy dynamics

International audienceDeveloping population dynamics models for zebrafish is crucial in order to extrapolate from toxicity data measured at the organism level to biological levels relevant to support and enhance ecological risk assessment. To achieve this, a dynamic energy budget for individual zebrafish (DEB model) was coupled to an individual based model of zebrafish population dynamics (IBM model). Next, we fitted the DEB model to new experimental data on zebra-fish growth and reproduction thus improving existing models. We further analysed the DEB-model and DEB-IBM using a sensitivity analysis. Finally, the predictions of the DEB-IBM were compared to existing observations on natural zebrafish populations and the predicted population dynamics are realistic. While our zebrafish DEB-IBM model can still be improved by acquiring new experimental data on the most uncertain processes (e.g. survival or feeding), it can already serve to predict the impact of compounds at the population level

Multi-scale modeling : prediction of in vivo hepatotoxicity from in vitro data

The March 2013 European Directive banned testing cosmetic ingredients on animals and new in vitro technologies have been developed to facilitate safety assessment. However, there is a gap in bridging in vitro to in vivo toxicity assessment. We thus propose a methodology for in vitro in vivo extrapolation based on mathematical modelling of in vitro data coupled to toxicokinetics modeling at whole body scale. We focused on hepatotoxicity since the liver is the first affected by toxicity after exposure to repeated doses. Impedance metrics is a recently developed technology which provides real time cell impedance data. Analyzing these new data requires new methodologies, moving from static to dynamic toxicity assessment of acute and chronic exposures. We thus built TK/TD (toxicokinetic/toxicodynamic) models to describe and analyze impedance in vitro hepatotoxicity data obtained for HepaRG cells after single and repeated exposures to three hepatotoxic cosmetic ingredients (coumarin, isoeugenol and benzophenone-2). These models account for cyto-morphological and cell viability change over time. We integrated in the models: i) cosmetic uptake and elimination by the cells, ii) decrease of exposure concentration (due to evaporation, binding to well walls, or metabolism by cells), iii) cell morphological modifications due to exposure to cosmetics, iv) possible heterogeneity of sensitivity between cells. The model which described at best the acute data was based on a quasi-instantaneous equilibrium between cells and medium, a decrease of compound due to metabolism, and equal sensitivity between cells. We challenged the acute toxicity model to predict chronic data obtained for the same substances at 4-week exposure. Although the model predicted quite well chronic data of coumarin, it underestimated cell viability at intermediate concentration for isoeugenol and benzophenone-2. Therefore, a calibration of the model with chronic data has been performed for these compounds, which provided a better fit of these data. Once the TK/TD models were calibrated, they were coupled with human physiologicallybased pharmacokinetics (PBPK) models to predict a scaled-up liver toxicity. PBPK models consist in a series of compartments which represent an organ or groups of similar organs governed by blood flows. They permit to relate unique or repeated doses of exposure with the concentration time-profile in different organs. All the parameters of PBPK models have sound biological or toxicological basis and can be estimated based on QSAR models and in vitro data, as we did for the three compounds investigated. Another advantage of these models is that the consequences of inter-individual variability (in terms of age, sex, bodyweight or metabolism capacity) can be investigated, which we performed for coumarin, predicting long-term differences of sensitivity between low and fast metabolizers

Analysis of in vitro hepatotoxicity mixtures data after chronic exposure to cosmetic related compounds

Purpose: With the ban of cosmetic products tested on animals in march 2013, the cosmetic industry has to put additional efforts in the development of alternatives to animal testing to assess the safety of its ingredients. Hepatotoxicity is a major concern as it is the main organ affected by repeated exposure to xenobiotics (Bitsch et al., 2006). It can be evaluated by cytotoxicity studies. These studies are traditionally quantified at a final time point after exposure. We propose to move to real time cell viability data measurements by impedance metrics. This permits to assess the temporal dimension of the appearance of effects, which improves the relevance of in vitro - in vivo extrapolations through toxicokinetics modeling. Here, we propose toxicokinetics/toxicodynamics (TK/TD) models to analyze real time data for HepaRG cells exposed repatedly to mixtures of hepatotoxic cosmetic related compounds. Methods: HepaRG cells were exposed for 4 weeks to the binary and ternary mixtures of coumarin, isoeugenol and benzophenone-2. The single compounds cell viabilities were first analyzed using TK/TD models. Then, the estimated parameters from these models were implemented in the mixture TK/TD models by either considering concentration additivity or independent action approaches. Finally, in order to extrapolate the in vitro cytotoxicity to the in vivo hepatotoxicity, human toxicokinetic models with parameters either predicted by QSAR models or referenced in literature were coupled with the in vitro TD models. Results and conclusions: We showed no interaction between the tested compounds relative to effects but interactions relative to metabolism, which influences the fate of the compounds in the exposure system. We also showed the relevance of the coupling of the human toxicokinetic models and the TK/TD models to assess risk under repeated exposure to mixtures of cosmetic related compounds

Dynamic energy budget as a basis to model population-level effects of zinc-spiked sediments in the gastropod Valvata piscinalis.

Dynamic energy budget as a basis to model population-level effects of zinc-spiked sediments in the gastropod Valvata piscinalis

COSMOS : An International Cooperative Project Developing Computational Models for Repeated Dose Toxicity

The COSMOS (Integrated In Silico Models for the Prediction of Human Repeated Dose Toxicity of COSMetics to Optimise Safety) Project is a unique international collaboration developing computational approaches for the prediction of repeated dose toxicity. The project comprises 15 partners from academia, industry, regulatory agencies and SMEs from across Europe and the US. Moreover, COSMOS is part of a cluster of six research projects within the SEURAT-1 (Safety Evaluation Ultimately Replacing Animal Testing) Research Initiative. Organ level toxicity involves complex mechanisms, thus it cannot be predicted by a single simplified in silico model. Therefore COSMOS is taking an innovative approach integrating different technologies, e.g. the threshold of toxicological concern approach, grouping of chemicals, (Q)SARs for toxicity prediction and modelling of biokinetics. All are being developed with a special emphasis on the mechanistic basis of the models considered. Computational workflows as well as a new comprehensive database with reliable structures and repeated dose toxicity data will be freely available to support safety assessment without the use of animals and will thus contribute to the 3Rs. The international dimension is important for the development and especially regulatory acceptance of the models proposed, the international companies having to assure the safety of their products on a global scale. Therefore industry, regulatory agencies and NGOs in Europe and the US are involved either as project partners or as external experts