In vitro kinetics of amiodarone and its major metabolite in two human liver cell models after acute and repeated treatments

Life cell imaging of amiodarone sequestration into lamellar bodies of alveolar type II cells

Amiodarone is widely used to treat cardiac arrhythmias and is very effective in preventing these disorders. However, its use is limited by a wide range of adverse effects, mainly affecting the lungs, and ranging from mild shortness of breath to pulmonary fibrosis. Amiodarone has been shown to accumulate strongly in lung tissue, exceeding its plasma concentration by a hundredfold. However, the site of accumulation and the mechanisms of transport are not fully understood. In this study, we used live cell imaging of primary rat alveolar type II cells to show that amiodarone specifically accumulates in large amounts in lamellar bodies, the surfactant storage organelles. Fluorescence imaging and correlation, and colocalization studies combined with confocal Raman microscopy identified these organelles as a major target for sequestration. Accumulation was rapid, on the order of a few hours, while storage was much more persistent. Partial uptake was observed in chemically fixed, dead cells, or cells treated with bafilomycin A1. Not only was uptake pH dependent, but intraluminal pH, measured with lysosomotropic pH sensitive dyes, was also affected. From these observations and from the physicochemical properties of amiodarone, we propose that passive diffusion, ion-trapping and lipophilic interactions are the main mechanisms for intracellular bioaccumulation. Furthermore, we demonstrate that measurement of amiodarone autofluorescence is highly useful for tracking cellular uptake and sequestration.

Integrating distribution kinetics and toxicodynamics to assess repeat dose neurotoxicity in vitro using human BrainSpheres: a case study on amiodarone

For ethical, economical, and scientific reasons, animal experimentation, used to evaluate the potential neurotoxicity of chemicals before their release in the market, needs to be replaced by new approach methodologies. To illustrate the use of new approach methodologies, the human induced pluripotent stem cell-derived 3D model BrainSpheres was acutely (48 h) or repeatedly (7 days) exposed to amiodarone (0.625-15 µM), a lipophilic antiarrhythmic drug reported to have deleterious effects on the nervous system. Neurotoxicity was assessed using transcriptomics, the immunohistochemistry of cell type-specific markers, and real-time reverse transcription-polymerase chain reaction for various genes involved in the lipid metabolism. By integrating distribution kinetics modeling with neurotoxicity readouts, we show that the observed time- and concentration-dependent increase in the neurotoxic effects of amiodarone is driven by the cellular accumulation of amiodarone after repeated dosing. The development of a compartmental in vitro distribution kinetics model allowed us to predict the change in cell-associated concentrations in BrainSpheres with time and for different exposure scenarios. The results suggest that human cells are intrinsically more sensitive to amiodarone than rodent cells. Amiodarone-induced regulation of lipid metabolism genes was observed in brain cells for the first time. Astrocytes appeared to be the most sensitive human brain cell type in vitro. In conclusion, assessing readouts at different molecular levels after the repeat dosing of human induced pluripotent stem cell-derived BrainSpheres in combination with the compartmental modeling of in vitro kinetics provides a mechanistic means to assess neurotoxicity pathways and refine chemical safety assessment for humans.

The effects of hexabromocyclododecane on the transcriptome and hepatic enzyme activity in three human HepaRG-based models

The disruption of thyroid hormone homeostasis by hexabromocyclododecane (HBCD) in rodents is hypothesized to be due to HBCD increasing the hepatic clearance of thyroxine (T4). The extent to which these effects are relevant to humans is unclear. To evaluate HBCD effects on humans, the activation of key hepatic nuclear receptors and the consequent disruption of thyroid hormone homeostasis were studied in different human hepatic cell models. The hepatoma cell line, HepaRG, cultured as two-dimensional (2D), sandwich (SW) and spheroid (3D) cultures, and primary human hepatocytes (PHH) cultured as sandwich were exposed to 1 and 10 µM HBCD and characterized for their transcriptome changes. Pathway enrichment analysis showed that 3D models, followed by SW, had a stronger transcriptome response to HBCD, which is explained by the higher expression of hepatic nuclear receptors but also greater accumulation of HBCD measured inside cells in these models. The Pregnane X receptor pathway is one of the pathways most upregulated across the three hepatic models, followed by the constitutive androstane receptor and general hepatic nuclear receptors pathways. Lipid metabolism pathways had a downregulation tendency in all exposures and in both PHH and the three cultivation modes of HepaRG. The activity of enzymes related to PXR/CAR induction and T4 metabolism were evaluated in the three different types of HepaRG cultures exposed to HBCD for 48 h. Reference inducers, rifampicin and PCB-153 did affect 2D and SW HepaRG cultures' enzymatic activity but not 3D. HBCD did not induce the activity of any of the studied enzymes in any of the cell models and culture methods. This study illustrates that for nuclear receptor-mediated T4 disruption, transcriptome changes might not be indicative of an actual adverse effect. Clarification of the reasons for the lack of translation is essential to evaluate new chemicals' potential to be thyroid hormone disruptors by altering thyroid hormone metabolism.

In Vitro-In Vivo Extrapolation by Physiologically Based Kinetic Modeling: Experience With Three Case Studies and Lessons Learned

Physiologically based kinetic (PBK) modeling has been increasingly used since the beginning of the 21st century to support dose selection to be used in preclinical and clinical safety studies in the pharmaceutical sector. For chemical safety assessment, the use of PBK has also found interest, however, to a smaller extent, although an internationally agreed document was published already in 2010 (IPCS/WHO), but at that time, PBK modeling was based mostly on in vivo data as the example in the IPCS/WHO document indicates. Recently, the OECD has published a guidance document which set standards on how to characterize, validate, and report PBK models for regulatory purposes. In the past few years, we gained experience on using in vitro data for performing quantitative in vitro–in vivo extrapolation (QIVIVE), in which biokinetic data play a crucial role to obtain a realistic estimation of human exposure. In addition, pharmaco-/toxicodynamic aspects have been introduced into the approach. Here, three examples with different drugs/chemicals are described, in which different approaches have been applied. The lessons we learned from the exercise are as follows: 1) in vitro conditions should be considered and compared to the in vivo situation, particularly for protein binding; 2) in vitro inhibition of metabolizing enzymes by the formed metabolites should be taken into consideration; and 3) it is important to extrapolate from the in vitro measured intracellular concentration and not from the nominal concentration to the tissue/organ concentration to come up with an appropriate QIVIVE for the relevant adverse effects.

Oxidative-stress and long-term hepatotoxicity: comparative study in Upcyte human hepatocytes and hepaRG cells

Drug-induced liver injury (DILI) is one of the most common and serious adverse drug reactions and a major cause of drug development failure and withdrawal. Although different molecular mechanisms are implicated in DILI, enhanced ROS levels have been described as a major mechanism. Human-derived cell models are increasingly used in preclinical safety assessment because they provide quick and relatively inexpensive information in early stages of drug development. We have analyzed and compared the phenotype and functionality of two liver cell models (Upcyte human hepatocytes and HepaRG cells) to demonstrate their suitability for long-term hepatotoxicity assessments and mechanistic studies. The transcriptomic and functional analysis revealed the maintenance of phase I and phase II enzymes, and antioxidant enzymes along time in culture, although the differences found between both test systems underlie the differential sensitivity to hepatotoxins. The evaluation of several mechanisms of cell toxicity, including oxidative stress, by high-content screening, demonstrated that, by combining the stable phenotype of liver cells and repeated-dose exposure regimes to 12 test compounds at clinically relevant concentrations, both Upcyte hepatocytes and HepaRG offer suitable properties to be used in routine screening assays for toxicological assessments during drug preclinical testing.

Integrating in vitro metabolomics with a 96-well high-throughput screening platform

INTRODUCTION

High-throughput screening (HTS) is emerging as an approach to support decision-making in chemical safety assessments. In parallel, in vitro metabolomics is a promising approach that can help accelerate the transition from animal models to high-throughput cell-based models in toxicity testing.

OBJECTIVE

In this study we establish and evaluate a high-throughput metabolomics workflow that is compatible with a 96-well HTS platform employing 50,000 hepatocytes of HepaRG per well.

METHODS

Low biomass cell samples were extracted for metabolomics analyses using a newly established semi-automated protocol, and the intracellular metabolites were analysed using a high-resolution spectral-stitching nanoelectrospray direct infusion mass spectrometry (nESI-DIMS) method that was modified for low sample biomass.

RESULTS

The method was assessed with respect to sensitivity and repeatability of the entire workflow from cell culturing and sampling to measurement of the metabolic phenotype, demonstrating sufficient sensitivity (> 3000 features in hepatocyte extracts) and intra- and inter-plate repeatability for polar nESI-DIMS assays (median relative standard deviation < 30%). The assays were employed for a proof-of-principle toxicological study with a model toxicant, cadmium chloride, revealing changes in the metabolome across five sampling times in the 48-h exposure period. To allow the option for lipidomics analyses, the solvent system was extended by establishing separate extraction methods for polar metabolites and lipids.

CONCLUSIONS

Experimental, analytical and informatics workflows reported here met pre-defined criteria in terms of sensitivity, repeatability and ability to detect metabolome changes induced by a toxicant and are ready for application in metabolomics-driven toxicity testing to complement HTS assays.

Scientific Opinion of the Scientific Panel on Plant Protection Products and their Residues (PPR Panel) on testing and interpretation of comparative in vitro metabolism studies

EFSA asked the Panel on Plant Protection Products and their residues to deliver a Scientific Opinion on testing and interpretation of comparative in vitro metabolism studies for both new active substances and existing ones. The main aim of comparative in vitro metabolism studies of pesticide active substances is to evaluate whether all significant metabolites formed in the human in vitro test system, as a surrogate of the in vivo situation, are also present at comparable level in animal species tested in toxicological studies and, therefore, if their potential toxicity has been appropriately covered by animal studies. The studies may also help to decide which animal model, with regard to a particular compound, is the most relevant for humans. In the experimental strategy, primary hepatocytes in suspension or culture are recommended since hepatocytes are considered the most representative in vitro system for prediction of in vivo metabolites. The experimental design of 3 × 3 × 3 (concentrations, time points, technical replicates, on pooled hepatocytes) will maximise the chance to identify unique (UHM) and disproportionate (DHM) human metabolites. When DHM and UHM are being assessed, test item-related radioactivity recovery and metabolite profile are the most important parameters. Subsequently, structural characterisation of the assigned metabolites is performed with appropriate analytical techniques. In toxicological assessment of metabolites, the uncertainty factor approach is the first alternative to testing option, followed by new approach methodologies (QSAR, read-across, in vitro methods), and only if these fail, in vivo animal toxicity studies may be performed. Knowledge of in vitro metabolites in human and animal hepatocytes would enable toxicological evaluation of all metabolites of concern, and, furthermore, add useful pieces of information for detection and evaluation of metabolites in different matrices (crops, livestock, environment), improve biomonitoring efforts via better toxicokinetic understanding, and ultimately, develop regulatory schemes employing physiologically based or physiology-mimicking in silico and/or in vitro test systems to anticipate the exposure of humans to potentially hazardous substances in plant protection products.

Drug-induced hepatic steatosis in absence of severe mitochondrial dysfunction in HepaRG cells: proof of multiple mechanism-based toxicity

Steatosis is a liver lesion reported with numerous pharmaceuticals. Prior studies showed that severe impairment of mitochondrial fatty acid oxidation (mtFAO) constantly leads to lipid accretion in liver. However, much less is known about the mechanism(s) of drug-induced steatosis in the absence of severe mitochondrial dysfunction, although previous studies suggested the involvement of mild-to-moderate inhibition of mtFAO, increased de novo lipogenesis (DNL), and impairment of very low-density lipoprotein (VLDL) secretion. The objective of our study, mainly carried out in human hepatoma HepaRG cells, was to investigate these 3 mechanisms with 12 drugs able to induce steatosis in human: amiodarone (AMIO, used as positive control), allopurinol (ALLO), D-penicillamine (DPEN), 5-fluorouracil (5FU), indinavir (INDI), indomethacin (INDO), methimazole (METHI), methotrexate (METHO), nifedipine (NIF), rifampicin (RIF), sulindac (SUL), and troglitazone (TRO). Hepatic cells were exposed to drugs for 4 days with concentrations decreasing ATP level by less than 30% as compared to control and not exceeding 100 × Cmax. Among the 12 drugs, AMIO, ALLO, 5FU, INDI, INDO, METHO, RIF, SUL, and TRO induced steatosis in HepaRG cells. AMIO, INDO, and RIF decreased mtFAO. AMIO, INDO, and SUL enhanced DNL. ALLO, 5FU, INDI, INDO, SUL, RIF, and TRO impaired VLDL secretion. These seven drugs reduced the mRNA level of genes playing a major role in VLDL assembly and also induced endoplasmic reticulum (ER) stress. Thus, in the absence of severe mitochondrial dysfunction, drug-induced steatosis can be triggered by different mechanisms, although impairment of VLDL secretion seems more frequently involved, possibly as a consequence of ER stress.

Prediction of the dose range for adverse neurological effects of amiodarone in patients from an in vitro toxicity test by in vitro-in vivo extrapolation

Amiodarone is an antiarrhythmic agent inducing adverse effects on the nervous system, among others. We applied physiologically based pharmacokinetic (PBPK) modeling combined with benchmark dose modeling to predict, based on published in vitro data, the in vivo dose of amiodarone which may lead to adverse neurological effects in patients. We performed in vitro–in vivo extrapolation (IVIVE) from concentrations measured in the cell lysate of a rat brain 3D cell model using a validated human PBPK model. Among the observed in vitro effects, inhibition of choline acetyl transferase (ChAT) was selected as a marker for neurotoxicity. By reverse dosimetry, we transformed the in vitro concentration–effect relationship into in vivo effective human doses, using the calculated in vitro area under the curve (AUC) of amiodarone as the pharmacokinetic metric. The upper benchmark dose (BMDU) was calculated and compared with clinical doses eliciting neurological adverse effects in patients. The AUCs in the in vitro brain cell culture after 14-day repeated dosing of nominal concentration equal to 1.25 and 2.5 µM amiodarone were 1.00 and 1.99 µg*h/mL, respectively. The BMDU was 385.4 mg for intravenous converted to 593 mg for oral application using the bioavailability factor of 0.65 as reported in the literature. The predicted dose compares well with neurotoxic doses in patients supporting the hypothesis that impaired ChAT activity may be related to the molecular/cellular mechanisms of amiodarone neurotoxicity. Our study shows that predicting effects from in vitro data together with IVIVE can be used at the initial stage for the evaluation of potential adverse drug reactions and safety assessment in humans.

Integrating biokinetics and in vitro studies to evaluate developmental neurotoxicity induced by chlorpyrifos in human iPSC-derived neural stem cells undergoing differentiation towards neuronal and glial cells

•

Human iPSC-derived NSCs undergoing differentiation possess some metabolic competence.

•

CPF entered the cells and was biotrasformed into its two main metabolites (CPFO and TCP).

•

After repeated exposure, very limited bioaccumulation of CPF was observed.

•

Treatment with CPF decreased neurite outgrowth, synapse number and electrical activity.

•

Treatment with CPF increased BDNF levels and the percentage of astrocytes.

For some complex toxicological endpoints, chemical safety assessment has conventionally relied on animal testing. Apart from the ethical issues, also scientific considerations have been raised concerning the traditional approach, highlighting the importance for considering real life exposure scenario. Implementation of flexible testing strategies, integrating multiple sources of information, including in vitro reliable test methods and in vitro biokinetics, would enhance the relevance of the obtained results. Such an approach could be pivotal in the evaluation of developmental neurotoxicity (DNT), especially when applied to human cell-based models, mimicking key neurodevelopmental processes, relevant to human brain development.

Here, we integrated the kinetic behaviour with the toxicodynamic alterations of chlorpyrifos (CPF), such as in vitro endpoints specific for DNT evaluation, after repeated exposure during differentiation of human neural stem cells into a mixed culture of neurons and astrocytes. The upregulation of some cytochrome P450 and glutathione S-transferase genes during neuronal differentiation and the formation of the two major CPF metabolites (due to bioactivation and detoxification) supported the metabolic competence of the used in vitro model. The alterations in the number of synapses, neurite outgrowth, brain derived neurotrophic factor, the proportion of neurons and astrocytes, as well as spontaneous electrical activity correlated well with the CPF ability to enter the cells and be bioactivated to CPF-oxon. Overall, our results confirm that combining in vitro biokinetics and assays to evaluate effects on neurodevelopmental endpoints in human cells should be regarded as a key strategy for a quantitative characterization of DNT effects.

Structure-activity relationship study: Mechanism of cyto-genotoxicity of Nitropyrazole-derived high energy density materials family

Stringent toxicological tests have to be performed prior to the industrial development of alternative chemicals particularly high energy dense materials (HEDMs) such as explosives. The properties (e.g., power, stability) of these compounds are constantly being improved, the current axis of research being the nitration of nitrogen heterocycles leading to HEDMs such as nitropyrazole-derived molecules. However, except for 3,4,5-trinitropyrazole (3,4,5-TNP), which was shown to be highly toxic in mice, the toxicological impact of these HEDMs has so far not been investigated. Furthermore, as industrials are strongly advised to develop alternative safety testing assays to in vivo experiments, we herein focused on determining the cytotoxic and genotoxic effects of seven Nitropyrazole-derived HEDMs on three rodent cell lines (mouse embryonic BALB/3T3 clone A31 cells, Chinese hamster ovary cells CHO-K1 and mouse lymphoma L5178Y TK +/- clone (3.7.2C) cells), two human fibroblast lines (CRC05, PFS04062) and on the human hepatic HepaRG model (both in proliferative and differentiated cells). A stronger cytotoxic effect was observed for 1,3-dinitropyrazole (1, 3-DNP) and 3,4,5-TNP in all cell lines, though differentiated HepaRG cells clearly displayed fewer likely due to the metabolism and elimination of these molecules by their functional biotransformation pathways. At the mechanistic level, the sub-chronic cytotoxic and genotoxic effects were linked to ROS/RNS production (experimental assays), HA2.X and to transcriptomic data highlighting the increase in DNA repair mechanisms.

Pro-inflammatory cytokines enhance dilatation of bile canaliculi caused by cholestatic antibiotics

Many drugs can induce liver injury, characterized by hepatocellular, cholestatic or mixed hepatocellular-cholestatic lesions. While an inflammatory stress is known to aggravate hepatocellular injury caused by some drugs much less evidence exists for cholestatic features. In this study, the influence of pro-inflammatory cytokines (IL-6, IL-1β and TNF-α), either individually or combined, on cytotoxic and cholestatic properties of antibiotics was evaluated using differentiated HepaRG cells. Six antibiotics of various chemical structures and known to cause cholestasis and/or hepatocellular injury in clinic were investigated. Caspase-3 activity was increased with all these tested hepatotoxic drugs and except with erythromycin, was further augmented in presence of cytokines mainly when these were co-added as a mixture. TNF-α and IL-1β aggravated cytotoxicity of TVX more than IL-6. Bile canaliculi (BC) dilatation induced by cholestatic drugs was increased by co-treatment with IL-6 and IL-1β but not with TNF-α. Reduced accumulation of carboxy-dichlorofluorescein, a substrate of the multi-drug resistance-associated protein 2, in antibiotic-induced dilatated BC, was further extended in presence of individual or mixed cytokines. In conclusion, our data demonstrate that pro-inflammatory cytokines either individually or in mixture, can modulate cholestatic and/or cytotoxic responses to antibiotics and that the extent of these effects is dependent on the cytokine and the cholestatic antibiotic.

Importance of in vitro conditions for modeling the in vivo dose in humans by in vitro-in vivo extrapolation (IVIVE)

In vitro studies are increasingly proposed to replace in vivo toxicity testing of substances. We set out to apply physiologically based pharmacokinetic (PBPK) modeling to predict the in vivo dose of amiodarone that leads to the same concentration-time profile in the supernatant and the cell lysate of cultured primary human hepatic cells (PHH). A PBPK human model was constructed based on the structure and tissue distribution of amiodarone in a rat model and using physiological human parameters. The predicted concentration-time profile in plasma was in agreement with human experimental data with the unbound fraction of amiodarone in plasma crucially affecting the goodness-of-fit. Using the validated kinetic model, we subsequently described the in vitro concentration-time data of amiodarone in PHH culture. However, this could be only appropriately modeled under conditions of zero protein binding and the very low clearance of the in vitro system in PHH culture. However, these represent unphysiological conditions and, thus, the main difference between the in vivo and the in vitro systems. Our results reveal that, for meaningful quantitative extrapolation from in vitro to in vivo conditions in PBPK studies, it is essential to avoid non-intended differences between these conditions. Specifically, clearance and protein binding, as demonstrated in our analysis of amiodarone modeling, are important parameters to consider.

Long-term and mechanistic evaluation of drug-induced liver injury in Upcyte human hepatocytes

Drug-induced liver injury (DILI) constitutes one of the most frequent reasons of restricted-use warnings as well as withdrawals of drugs in postmarketing and poses an important concern for the pharmaceutical industry. The current hepatic in vivo and in vitro models for DILI detection have shown clear limitations, mainly for studies of long-term hepatotoxicity. For this reason, we here evaluated the potential of using Upcytes human hepatocytes (UHH) for repeated-dose long-term exposure to drugs. The UHH were incubated with 15 toxic and non-toxic compounds for up to 21 days using a repeated-dose approach, and, in addition to conventional examination of effects on viability, the mechanisms implicated in cell toxicity were also assessed by means of high-content screening. The UHH maintained the expression and activity levels of drug-metabolizing enzymes for up to 21 days of culture and became more sensitive to the toxic compounds after extended exposures, showing inter-donor differences which would reflect variability among the population. The assay also allowed to detect the main mechanisms implicated in the toxicity of each drug as well as identifying special susceptibilities depending on the donor. UHH can be used for a long-term repeated detection of DILI at clinically relevant concentrations and also offers key mechanistic features of drug-induced hepatotoxicity. This system is therefore a promising tool in preclinical testing of human relevance that could help to reduce and/or replace animal testing for drug adverse effects.

Activity of the antiarrhythmic drug amiodarone against Leishmania (L.) infantum: an in vitro and in vivo approach

Background

Considering the high toxicity and limited therapies available for treating visceral leishmaniasis (VL), the drug repositioning approach represents a faster way to deliver new therapies to the market.

Methods

In this study, we described for the first time the activity of a potent antiarrhythmic, amiodarone (AMD), against L. (L.) infantum and its in vitro and in vivo activity.

Results

The evaluation against promastigotes has shown that amiodarone presents leishmanicidal effect against the extracellular form, with an IC₅₀ value of 10 μM. The activity was even greater against amastigotes in comparison with promastigotes with an IC₅₀ value of 0.5 μM. The selectivity index in relation to the intracellular form demonstrated that the antiparasitic activity was approximately 56 times higher than its toxicity to mammalian cells. Investigation of the in vivo AMD activity in the L. infantum-infected hamster model showed that 51 days after the initial infection, amiodarone was unable to reduce the parasite burden in the spleen and liver when treated for 10 consecutive days, intraperitoneally, at 50 mg/kg/day, as determined by qPCR. Although not statistically significant, AMD was able to reduce the parasite burden by 20% in the liver when treated for 10 consecutive days, orally, at 100 mg/kg/day; no reduction in the spleen was found by qPCR.

Conclusions

Our findings may help further drug design studies seeking new AMD derivatives that may provide new candidates with an in vitro selectivity close to or even greater than that observed in the prototype delivering effectiveness in the experimental model of VL.

Metabolomics and cytotoxicity of monomethylhydrazine (MMH) and (E)-1,1,4,4-tetramethyl-2-tetrazene (TMTZ), two liquid propellants

Hydrazine-based liquid propellants are routinely used for space rocket propulsion, in particular monomethylhydrazine (MMH), although such compounds are highly hazardous. For several years, great efforts were devoted to developing a less hazardous molecule. To explore the toxicological effects of an alternative compound, namely (E)-1,1,4,4-tetramethyl-2-tetrazene (TMTZ), we exposed various cellular animal and human models to this compound and to the reference compound MMH. We observed no cytotoxic effects following exposure to TMTZ in animal, as well as human models. However, although the three animal models were unaffected by MMH, exposure of the human hepatic HepaRG cell model revealed that apoptotic cytotoxic effects were only detectable in proliferative human hepatic HepaRG cells and not in differentiated cells, although major biochemical modifications were uncovered in the latter. The present findings indicate that the metabolic mechanisms of MMH toxicity is close to those described for hydrazine with numerous biochemical alterations induced by mitochondrial disruption, production of radical species, and aminotransferase inhibition. The alternative TMTZ molecule had little impact on cellular viability and proliferation of rodent and human dermic and hepatic cell models. TMTZ did not produce any metabolomic effects and appears to be a promising putative industrial alternative to MMH.

Early Alterations of Bile Canaliculi Dynamics and the Rho Kinase/Myosin Light Chain Kinase Pathway Are Characteristics of Drug-Induced Intrahepatic Cholestasis

Intrahepatic cholestasis represents 20%-40% of drug-induced injuries from which a large proportion remains unpredictable. We aimed to investigate mechanisms underlying drug-induced cholestasis and improve its early detection using human HepaRG cells and a set of 12 cholestatic drugs and six noncholestatic drugs. In this study, we analyzed bile canaliculi dynamics, Rho kinase (ROCK)/myosin light chain kinase (MLCK) pathway implication, efflux inhibition of taurocholate [a predominant bile salt export pump (BSEP) substrate], and expression of the major canalicular and basolateral bile acid transporters. We demonstrated that 12 cholestatic drugs classified on the basis of reported clinical findings caused disturbances of both bile canaliculi dynamics, characterized by either dilatation or constriction, and alteration of the ROCK/MLCK signaling pathway, whereas noncholestatic compounds, by contrast, had no effect. Cotreatment with ROCK inhibitor Y-27632 [4-(1-aminoethyl)-N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride] and MLCK activator calmodulin reduced bile canaliculi constriction and dilatation, respectively, confirming the role of these pathways in drug-induced intrahepatic cholestasis. By contrast, inhibition of taurocholate efflux and/or human BSEP overexpressed in membrane vesicles was not observed with all cholestatic drugs; moreover, examples of noncholestatic compounds were reportedly found to inhibit BSEP. Transcripts levels of major bile acid transporters were determined after 24-hour treatment. BSEP, Na⁺-taurocholate cotransporting polypeptide, and organic anion transporting polypeptide B were downregulated with most cholestatic and some noncholestatic drugs, whereas deregulation of multidrug resistance-associated proteins was more variable, probably mainly reflecting secondary effects. Together, our results show that cholestatic drugs consistently cause an early alteration of bile canaliculi dynamics associated with modulation of ROCK/MLCK and these changes are more specific than efflux inhibition measurements alone as predictive nonclinical markers of drug-induced cholestasis.

Multiscale modelling approaches for assessing cosmetic ingredients safety

The European Union's ban on animal testing for cosmetic ingredients and products has generated a strong momentum for the development of in silico and in vitro alternative methods. One of the focus of the COSMOS project was ab initio prediction of kinetics and toxic effects through multiscale pharmacokinetic modeling and in vitro data integration. In our experience, mathematical or computer modeling and in vitro experiments are complementary. We present here a summary of the main models and results obtained within the framework of the project on these topics. A first section presents our work at the organelle and cellular level. We then go toward modeling cell levels effects (monitored continuously), multiscale physiologically based pharmacokinetic and effect models, and route to route extrapolation. We follow with a short presentation of the automated KNIME workflows developed for dissemination and easy use of the models. We end with a discussion of two challenges to the field: our limited ability to deal with massive data and complex computations.

Biokinetics in repeated-dosing in vitro drug toxicity studies

The aim of the EU FP7 Predict-IV project was to improve the predictivity of in vitro assays for unwanted effects of drugs after repeated dosing. The project assessed the added benefit of integrating long-lived in vitro organotypic cell systems with 'omics' technologies and in silico modelling, including systems biology and pharmacokinetic assessments. RPTEC/TERT1 kidney cells, primary rat and human hepatocytes, HepaRG liver cells and 2D and 3D primary brain cultures were dosed daily or every other day for 14 days to a selection of drugs varying in their mechanism of pharmacological action. Since concentration-effect relationships not only depend on the activity of the drug or the sensitivity of the target, but also on the distribution of compounds in the in vitro system, the concentration of a selection of drugs in cells, microtitre plate plastic and medium was measured over time. Results, reviewed in this paper, indicate that lipophilic drugs bind significantly to plastic labware. A few drugs, including less lipophilic drugs, bind to cell-attachment matrices. Chemicals that reach high concentrations in cells, including cyclosporin A and amiodarone, significantly accumulate over time after repeated dosing, partly explaining their increased toxicity after repeated dosing, compared to a single dose.

Drug biokinetic and toxicity assessments in rat and human primary hepatocytes and HepaRG cells within the EU-funded Predict-IV project

The overall aim of Predict-IV (EU-funded collaborative project #202222) was to develop improved testing strategies for drug safety in the late discovery phase. One major focus was the prediction of hepatotoxicity as liver remains one of the major organ leading to failure in drug development, drug withdrawal and has a poor predictivity from animal experiments. In this overview we describe the use and applicability of the three cell models employed, i.e., primary rat hepatocytes, primary human hepatocytes and the human HepaRG cell line, using four model compounds, chlorpromazine, ibuprofen, cyclosporine A and amiodarone. This overview described the data generated on mode of action of liver toxicity after long-term repeat-dosing. Moreover we have quantified parent compound and its distribution in various in vitro compartments, which allowed us to develop biokinetic models where we could derive real exposure concentrations in vitro. In conclusion, the complex data set enables quantitative measurements that proved the concept that we can define human relevant free and toxic exposure levels in vitro. Further compounds have to be analyzed in a broader concentration range to fully exploit these promising results for improved prediction of hepatotoxicity and hazard assessment for humans.