The use of in vitro data in risk assessment

Advancing food safety risk assessment in China: development of new approach methodologies (NAMs)

Novel techniques and methodologies are being developed to advance food safety risk assessment into the next-generation. Considering the shortcomings of traditional animal testing, new approach methodologies (NAMs) will be the main tools for the next-generation risk assessment (NGRA), using non-animal methodologies such as in vitro and in silico approaches. The United States Environmental Protection Agency and the European Food Safety Authority have established work plans to encourage the development and application of NAMs in NGRA. Currently, NAMs are more commonly used in research than in regulatory risk assessment. China is also developing NAMs for NGRA but without a comprehensive review of the current work. This review summarizes major NAM-related research articles from China and highlights the China National Center for Food Safety Risk Assessment (CFSA) as the primary institution leading the implementation of NAMs in NGRA in China. The projects of CFSA on NAMs such as the Food Toxicology Program and the strategies for implementing NAMs in NGRA are outlined. Key issues and recommendations, such as discipline development and team building, are also presented to promote NAMs development in China and worldwide.

Investigating nanoplastics toxicity using advanced stem cell-based intestinal and lung in vitro models

Plastic particles in the nanometer range-called nanoplastics-are environmental contaminants with growing public health concern. As plastic particles are present in water, soil, air and food, human exposure via intestine and lung is unavoidable, but possible health effects are still to be elucidated. To better understand the Mode of Action of plastic particles, it is key to use experimental models that best reflect human physiology. Novel assessment methods like advanced cell models and several alternative approaches are currently used and developed in the scientific community. So far, the use of cancer cell line-based models is the standard approach regarding in vitro nanotoxicology. However, among the many advantages of the use of cancer cell lines, there are also disadvantages that might favor other approaches. In this review, we compare cell line-based models with stem cell-based in vitro models of the human intestine and lung. In the context of nanoplastics research, we highlight the advantages that come with the use of stem cells. Further, the specific challenges of testing nanoplastics in vitro are discussed. Although the use of stem cell-based models can be demanding, we conclude that, depending on the research question, stem cells in combination with advanced exposure strategies might be a more suitable approach than cancer cell lines when it comes to toxicological investigation of nanoplastics.

Optimization of in vitro culture of honeybee nervous tissue for pesticide risk assessment

The most used pesticides have neurotoxic action on the neurotransmitter system of target and non-targeted insects, such as honeybees. However, honeybees have foremost importance worldwide, which has encouraged the development of tools to evaluate the action of specific pesticide molecules on their nervous system, providing accurate data on damage to their brain. In this sense, our study aimed to optimize in vitro honeybee nervous tissue culture to assess pesticide risks. To this end, six forager honeybee brains were dissected and transferred to different combinations of Leibovitz-15 (L-15) culture medium supplemented with Fetal Bovine Serum (FBS), Hank's Balanced Salt Solution (HBSS), and Insect Medium Supplement (IMS). Nervous tissues were collected after different incubation times (1, 6, 12, and 24 h) for morphology and Kenyon cell analyses. Our results showed that L-15 medium supplemented with HBSS and with HBSS plus FBS were the best media for culturing honey nervous tissue, as they resulted in less tissue spacing and cell disarrangement. Therefore, they may be assessed in future ecotoxicological tests.

Development of a Generic Physiologically Based Kinetic Model to Predict In Vivo Uterotrophic Responses Induced by Estrogenic Chemicals in Rats Based on In Vitro Bioassays

The present study assessed the potential of a generic physiologically based kinetic (PBK) model to convert in vitro data for estrogenicity to predict the in vivo uterotrophic response in rats for diethylstibestrol (DES), ethinylestradiol (EE2), genistein (GEN), coumestrol (COU), and methoxychlor (MXC). PBK models were developed using a generic approach and in vitro concentration-response data from the MCF-7 proliferation assay and the yeast estrogen screening assay were translated into in vivo dose-response data. Benchmark dose analysis was performed on the predicted data and available in vivo uterotrophic data to evaluate the model predictions. The results reveal that the developed generic PBK model adequate defines the in vivo kinetics of the estrogens. The predicted dose-response data of DES, EE2, GEN, COU, and MXC matched the reported in vivo uterus weight response in a qualitative way, whereas the quantitative comparison was somewhat hampered by the variability in both in vitro and in vivo data. From a safety perspective, the predictions based on the MCF-7 proliferation assay would best guarantee a safe point of departure for further risk assessment although it may be conservative. The current study indicates the feasibility of using a combination of in vitro toxicity data and a generic PBK model to predict the relative in vivo uterotrophic response for estrogenic chemicals.

Evaluation of in vitro models of stem cell-derived cardiomyocytes to screen for potential cardiotoxicity of chemicals

Cardiotoxicity is an important toxicological endpoint for chemical and drug safety assessment. The present study aims to evaluate two stemcell-based in vitro models for cardiotoxicity screening of chemicals. Eleven model compounds were used to evaluate responses of mouse embryonic stem cell-derived cardiomyocytes (mESC-CMs) using beating arrest as a readout and the analysis of electrophysiological parameters measured with a multi-electrode array (MEA) platform of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Results revealed that the hiPSC-CM MEA assay responded to all compounds. The mESC-CM beating arrest assay was not responsive to potassium channel blockers and showed a lower sensitivity to sodium channel blockers and Na⁺/K⁺ ATPase inhibitors compared to the hiPSC-CM MEA assay. Calcium channel blockers and a β-adrenergic receptor agonist showed comparable potencies in both models. The in vitro response concentrations from hiPSC-CMs were highly concordant with human effective serum concentrations of potassium and sodium channel blockers. It is concluded that both in vitro models enable the cardiotoxicity screening with different applicability domains. The mESC-CM beating arrest assay may be used as a first step in a tiered approach while the hiPSC-CM MEA assay may be the best starting point for quantitative in vitro to in vivo extrapolations.

Integrating in vitro data and physiologically based kinetic modeling-facilitated reverse dosimetry to predict human cardiotoxicity of methadone

Development of novel testing strategies to detect adverse human health effects is of interest to replace in vivo-based drug and chemical safety testing. The aim of the present study was to investigate whether physiologically based kinetic (PBK) modeling-facilitated conversion of in vitro toxicity data is an adequate approach to predict in vivo cardiotoxicity in humans. To enable evaluation of predictions made, methadone was selected as the model compound, being a compound for which data on both kinetics and cardiotoxicity in humans are available. A PBK model for methadone in humans was developed and evaluated against available kinetic data presenting an adequate match. Use of the developed PBK model to convert concentration–response curves for the effect of methadone on human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) in the so-called multi electrode array (MEA) assay resulted in predictions for in vivo dose–response curves for methadone-induced cardiotoxicity that matched the available in vivo data. The results also revealed differences in protein plasma binding of methadone to be a potential factor underlying variation between individuals with respect to sensitivity towards the cardiotoxic effects of methadone. The present study provides a proof-of-principle of using PBK modeling-based reverse dosimetry of in vitro data for the prediction of cardiotoxicity in humans, providing a novel testing strategy in cardiac safety studies.

Biogenic synthesis of gold nanoparticles from Terminalia arjuna bark extract: assessment of safety aspects and neuroprotective potential via antioxidant, anticholinesterase, and antiamyloidogenic effects

The development of neuroprotective drugs through eco-friendly production routes is a major challenge for current pharmacology. The present study was carried out to synthesize gold nanoparticles (AuNPs) through biogenic route using ethanolic bark extract of Terminalia arjuna, a plant of high interest in Asian traditional medicine, and to evaluate its neuroprotective effects. The synthesized AuNPs were characterized by UV-Vis spectroscopy, FTIR spectroscopy, XRD, FESEM, EDX, HRTEM, DLS, and zeta potential analyses. UV-Vis spectroscopy showed a characteristics SPR absorption band at 536 nm specific for AuNPs. XRD, TEM, and FESEM analyses revealed the formation of face-centered cubic crystalline, spherical and triangular shaped AuNPs, with size ranging between 20 and 50 nm. DLS and ZP analysis illustrated that the average size of AuNPs was 30 nm, which was found to be stable at 45 mv. The neuroprotective potential of AuNPs was evaluated by assessing its antioxidant, cholinesterase inhibitory, and antiamyloidogenic activities. AuNPs showed dose-dependant inhibition of acetylcholinesterase and butyrylcholinesterase with IC₅₀ value of 4.25 ± 0.02 and 5.05 ± 0.02 μg/ml, respectively. In vitro antioxidant assays illustrated that AuNPs exhibited the highest reducing power and DPPH radical scavenging activity. In addition, AuNPs also efficiently suppressed the fibrillation of Aβ and destabilized the preformed mature fibrils. Results of toxicity studies in PBMC and adult zebra fish illustrated that AuNPs are non-toxic and biocompatible. Overall, our results highlighted the AuNPs promising potential in terms of antioxidant, anticholinesterase, antiamyloidogenic effects, and non-lethality allowing us to propose these nanomaterials as a suitable candidate for the development of drugs helpful in the treatment of neurodegenerative disorders like Alzheimer's disease. Graphical abstract ᅟ.

Safety assessment of methanolic extract of Terminalia chebula fruit, Terminalia arjuna bark and its bioactive constituent 7-methyl gallic acid: In vitro and in vivo studies

Terminalia chebula and Terminalia arjuna were widely used in traditional medicine for the treatment of memory impairment, inflammatory disorders and as an anti-aging agent. However, reports regarding their safety aspects are lacking. Hence, the present study was carried out to investigate the toxicity of methanolic extracts of Terminalia chebula fruit (TCF), Terminalia arjuna bark (TAB) and its bioactive constituent 7- Methyl gallic acid (7MG) under in vitro and in vivo conditions. In vitro toxicity profile of TCF, TAB and 7MG (250-2000 μg/ml) were assessed through cytotoxicity, hemolytic activity, mutagenicity and genotoxicity assays. Results of Ames test, comet assay, MTT and hemolytic assays illustrated that TCF, TAB and 7MG exhibited neither cytotoxic and genotoxic effect in PBMC nor hemolytic activity in RBC and no mutagenic effect in TA 98 and TA 100 up to a limited dose of 2000 μg/ml. Acute and subacute toxicity studies showed no significant change in body weight, behavior, hematology, biochemical parameters, organ weight and histopathology. Over all the results of acute and subacute toxicity studies conclude that oral administration of TCF, TAB and 7MG were observed to be relatively non-toxic and affords practical guidance for selecting safe dose for further clinical trials.

The changing face of nanomaterials: Risk assessment challenges along the value chain

Risk assessment (RA) of manufactured nanomaterials (MNM) is essential for regulatory purposes and risk management activities. Similar to RA of "classical" chemicals, MNM RA requires knowledge about exposure as well as of hazard potential and dose response relationships. What makes MNM RA especially challenging is the multitude of materials (which is expected to increase substantially in the future), the complexity of MNM value chains and life cycles, the accompanying possible changes in material properties over time and in contact with various environmental and organismal milieus, and the difficulties to obtain proper exposure data and to consider the proper dose metric. This article discusses these challenges and also critically overviews the current state of the art regarding MNM RA approaches.

Evaluation of in vitro and in vivo safety profile of the Indian traditional medicinal plant Grewia tiliaefolia

Grewia tiliaefolia Vahl., is a subtropical tree used in Ayurvedic formulations and also by tribal communities in India for treatment of wounds, urinary infection and skin diseases. Despite of its medicinal use, the plant has not been previously tested for its safety. This study evaluated the toxicological profile of the methanolic extract of G. tiliaefolia leaves (MEGT) through in vitro (cytotoxic, mutagenic, genotoxic) and in vivo (acute and sub-acute) studies. In vitro assays conclude that there is no significant (p<0.05) level of cytotoxicity and genotoxicity at the tested concentrations (250-2000 μg/ml) in peripheral blood mononuclear cells. Ames assay in the tested Salmonella typhimurium strains revealed no significant (p<0.05) increase in the mutagenic index both in the presence and absence of metabolic activation. Alternatively, no change in mortality, physiological, behavioural, haematological and biochemical parameters were observed under in vivo acute (250, 500, 1000, 2000 mg/kg b.w) and sub-acute (100, 200, 1000 mg/kg b.w) toxicity studies in Wistar rats. Histopathological examinations of the animals did not reveal any treatment related changes and showed normal architecture, even at the highest concentration (1000 mg/kg b.w) following 28 days treatment. Overall, the results show that MEGT is non-toxic at the tested concentrations and is safe to be used as herbal medicine.

Novel Uses of In Vitro Data to Develop Quantitative Biological Activity Relationship Models for in Vivo Carcinogenicity Prediction

The availability of large in vitro datasets enables better insight into the mode of action of chemicals and better identification of potential mechanism(s) of toxicity. Several studies have shown that not all in vitro assays can contribute as equal predictors of in vivo carcinogenicity for development of hybrid Quantitative Structure Activity Relationship (QSAR) models. We propose two novel approaches for the use of mechanistically relevant in vitro assay data in the identification of relevant biological descriptors and development of Quantitative Biological Activity Relationship (QBAR) models for carcinogenicity prediction. We demonstrate that in vitro assay data can be used to develop QBAR models for in vivo carcinogenicity prediction via two case studies corroborated with firm scientific rationale. The case studies demonstrate the similarities between QBAR and QSAR modeling in: (i) the selection of relevant descriptors to be used in the machine learning algorithm, and (ii) the development of a computational model that maps chemical or biological descriptors to a toxic endpoint. The results of both the case studies show: (i) improved accuracy and sensitivity which is especially desirable under regulatory requirements, and (ii) overall adherence with the OECD/REACH guidelines. Such mechanism based models can be used along with QSAR models for prediction of mechanistically complex toxic endpoints.

The long and winding road of progress in the use of in vitro data for risk assessment purposes: From "carnation test" to integrated testing strategies

This paper introduces the special issue on quantitative in vitro-in vivo extrapolations (QIVIVE). It highlights important issues in the development of in vitro toxicology towards its implementation in toxicological risk assessment.

Predicting carcinogenicity of diverse chemicals using probabilistic neural network modeling approaches

Robust global models capable of discriminating positive and non-positive carcinogens; and predicting carcinogenic potency of chemicals in rodents were developed. The dataset of 834 structurally diverse chemicals extracted from Carcinogenic Potency Database (CPDB) was used which contained 466 positive and 368 non-positive carcinogens. Twelve non-quantum mechanical molecular descriptors were derived. Structural diversity of the chemicals and nonlinearity in the data were evaluated using Tanimoto similarity index and Brock-Dechert-Scheinkman statistics. Probabilistic neural network (PNN) and generalized regression neural network (GRNN) models were constructed for classification and function optimization problems using the carcinogenicity end point in rat. Validation of the models was performed using the internal and external procedures employing a wide series of statistical checks. PNN constructed using five descriptors rendered classification accuracy of 92.09% in complete rat data. The PNN model rendered classification accuracies of 91.77%, 80.70% and 92.08% in mouse, hamster and pesticide data, respectively. The GRNN constructed with nine descriptors yielded correlation coefficient of 0.896 between the measured and predicted carcinogenic potency with mean squared error (MSE) of 0.44 in complete rat data. The rat carcinogenicity model (GRNN) applied to the mouse and hamster data yielded correlation coefficient and MSE of 0.758, 0.71 and 0.760, 0.46, respectively. The results suggest for wide applicability of the inter-species models in predicting carcinogenic potency of chemicals. Both the PNN and GRNN (inter-species) models constructed here can be useful tools in predicting the carcinogenicity of new chemicals for regulatory purposes.

Tissue distribution and maternal transfer of poly- and perfluorinated compounds in Chinese sturgeon (Acipenser sinensis): implications for reproductive risk

It is critical to investigate the tissue distribution and maternal transfer of poly- and perfluorinated compounds (PFCs) in wild fish for assessing potential effects on ecosystems. Concentrations of 23 PFCs in nine organs and egg were measured in 16 17- to 25-year-old female Chinese sturgeon (Acipenser sinensis, an anadromous fish), that died during propagation. Three polyfluorinated amides were detected in stomach, intestine, and gills and 7:3 FTCA was specifically accumulated in liver. The greatest total concentration of PFCs in egg was 35.1 +/- 10.4 ng/g ww and was predominated by perfluorooctane sulfonate (PFOS) and perfluorotridecanoate acid (PFTriDA). The longer-chain C(11)-C(14) and C(16) perfluorinated carboxylates were more accumulated in Chinese sturgeon than PFOS, partly due to the increasing trends of PFCAs with fish age. Maternal transfer ratios of PFCs expressed as ratios of concentrations in the egg to those in the liver ranged from 0.79 (perfluorooctanoate) to 5.5 (PFTriDA), depending on their carbon chain lengths or protein-water coefficients. The PFOS equivalent of PFC mixtures, calculated by multiplying the relative potency factor of each PFC to PFOS by the corresponding concentration, ranged from 90.6 to 262 ng/g. The hazard quotient was 0.20, implying potential reproductive effects of PFCs on Chinese sturgeon.

Twenty-First Century Challenges for In Vitro Neurotoxicity

During the last 40 years, studies incorporating in vitro methodologies have greatly advanced our understanding of human nerve cell biology. Attempts have been made to apply these to investigations of neurotoxicity. Due to the complexity of the nervous system, underpinned by an array of integrated interactions between a host of cell types, it is concluded that, at present, alternative neural models are most successful in determining the underlying mechanisms which can cause perturbation of normal functioning of the nervous system, both in adults and during the embryonic period. The use of tiered batteries of test models has been proposed in screening programmes for neurotoxicity, with the generation of much encouraging data in laboratories across the globe. This review aims to discuss the development of neural alternatives, considers the various model systems available, and highlights specific neuronal endpoints which can be tested, in addition to the cytotoxic evaluation of neuronal viability. Developments in molecular and stem cell biology, which are appropriate to neural tissue, and which offer the prospect of exciting advances for the next decade, are cited.

Bioactivity studies and chemical profile of the antidiabetic plant Genista tenera

AIM OF THE STUDY

Genista tenera is a plant endemic to the island of Madeira and is used in folk medicine to control diabetes. In the present work we evaluate the antihyperglycaemic activity of its n-butanol extract and determine its chromatographic profile. In addition, this extract, the ethyl acetate and diethyl ether plant extracts were studied in order to assess the plant antioxidant and acetylcholinesterase inhibitory activities, as well as its cyto- and genotoxicities.

MATERIALS AND METHODS

HPLC-DAD-ESI-MS was used to analyze the flavonoid profile of the n-butanol extract. The antihyperglycaemic activity of this extract was performed over streptozotocin induced diabetic Wistar rats (200 mg/kg, bw/day), for 15 days. Antioxidant activity (DPPH assay) and acetylcholinesterase inhibitory effect (Ellman method) were also performed. Acute cytotoxicity and genotoxicity were assessed by proliferative index quantification and the short-term chromosomal aberration technique, after exposure of lymphocytes to the extracts.

RESULTS AND CONCLUSIONS

The n-butanol extract, where 21 monoglycosyl and 12 diglycosyl flavonoids were detected, significantly lowered blood glucose levels, bringing them to normal values after 15 days of treatment. The best radical scavenging activity was observed for the ethyl acetate extract (48.7% at 139.1 microg/mL), which was also the most effective one at the minimal concentration tested. The highest acetylcholinesterase inhibitory activity (77.0% at 70.0 microg/mL) was also obtained with the ethyl acetate extract. In vitro toxicity studies showed no evidence for acute cytotoxicity or genotoxicity. This is the first report on antidiabetic activity of genus Genista.

Regulatory assessment of chemicals within OECD member countries, EU and in Russia

The chemical risk assessment is essesntial part of new chemical legislation registration, evaluation, and authorization of chemicals (REACH). The article presents a review of chemical legislation policies in the European Union (EU) and in Russia, and changes in chemicals regulations to meet the requirement of REACH. The risk assessment paradigm, toxicological parameters, safe limits and classification criteria used by different agencies and authorities in different countries are reported. Our investigation also focuses on comparison of chemical risk assessment criteria used in OECD member countries and in Russia. Tendencies in harmonization in accordance with the globally harmonized system of classification and labeling of chemicals (GHS) are discussed.

Whole-body physiologically based pharmacokinetic models

This review summarizes the most recent developments in and applications of physiologically based pharmacokinetic (PBPK) modeling methodology originating from both the pharmaceutical and environmental toxicology areas. It focuses on works published in the last 5 years, although older seminal papers have also been referenced. After a brief introduction to the field and several essential definitions, the main body of the text is structured to follow the major steps of a typical PBPK modeling exercise. Various applications of the methodology are briefly described. The major future trends and perspectives are outlined. The main conclusion from the review of the available literature is that PBPK modeling, despite its obvious potential and recent incremental developments, has not taken the place it deserves, especially in pharmaceutical and drug development sciences.

Predictive value of in vitro safety studies

The predictive value of in vitro safety studies is discussed for three important areas of pharmaceutical safety evaluations. In genetic toxicology, currently assays are sensitive for the prediction of cancer, but their overall predictive value is strongly diminished because of their low specificity. In the area of safety pharmacology blockage of hERG channel in vitro has recently been introduced to predict cardiac repolarization delay (QT interval prolongation) in patients. There is a plethora of in vitro methods to predict and characterize liver toxicity. However, little data is available that demonstrate a reliable prediction for hepatotoxicity in vivo over a wide range of chemical structures. In all three areas, further improvements are needed. 'Omics' technologies and new cell lines derived from stem cells are expected to strongly contribute to establish new and more predictive in vitro assays.