Multiparametric assay using HepaRG cells for predicting drug-induced liver injury

Control compounds for preclinical drug-induced liver injury assessment: Consensus-driven systematic review by the ProEuroDILI network

BACKGROUND & AIMS

Idiosyncratic drug-induced liver injury (DILI) is a complex and unpredictable event caused by drugs, and herbal or dietary supplements. Early identification of human hepatotoxicity at preclinical stages remains a major challenge, in which the selection of validated in vitro systems and test drugs has a significant impact. In this systematic review, we analyzed the compounds used in hepatotoxicity assays and established a list of DILI-positive and -negative control drugs for validation of in vitro models of DILI, supported by literature and clinical evidence and endorsed by an expert committee from the COST Action ProEuroDILI Network (CA17112).

METHODS

Following 2020 PRISMA guidelines, original research articles focusing on DILI which used in vitro human models and performed at least one hepatotoxicity assay with positive and negative control compounds, were included. Bias of the studies was assessed by a modified 'Toxicological Data Reliability Assessment Tool'.

RESULTS

A total of 51 studies (out of 2,936) met the inclusion criteria, with 30 categorized as reliable without restrictions. Although there was a broad consensus on positive compounds, the selection of negative compounds lacked clarity. 2D monoculture, short exposure times and cytotoxicity endpoints were the most tested, although there was no consensus on drug concentrations.

CONCLUSIONS

Extensive analysis highlighted the lack of agreement on control compounds for in vitro DILI assessment. Following comprehensive in vitro and clinical data analysis together with input from the expert committee, an evidence-based consensus-driven list of 10 positive and negative control drugs for validation of in vitro models of DILI is proposed.

IMPACT AND IMPLICATIONS

Prediction of human toxicity early in the drug development process remains a major challenge, necessitating the development of more physiologically relevant liver models and careful selection of drug-induced liver injury (DILI)-positive and -negative control drugs to better predict the risk of DILI associated with new drug candidates. Thus, this systematic study has crucial implications for standardizing the validation of new in vitro models of DILI. By establishing a consensus-driven list of positive and negative control drugs, the study provides a scientifically justified framework for enhancing the consistency of preclinical testing, thereby addressing a significant challenge in early hepatotoxicity identification. Practically, these findings can guide researchers in evaluating safety profiles of new drugs, refining in vitro models, and informing regulatory agencies on potential improvements to regulatory guidelines, ensuring a more systematic and efficient approach to drug safety assessment.

In vitro cell-based models of drug-induced hepatotoxicity screening: progress and limitation

Drug-induced liver injury (DILI) is one of the major causes of post-approval withdrawal of therapeutics. As a result, there is an increasing need for accurate predictive in vitro assays that reliably detect hepatotoxic drug candidates while reducing drug discovery time, costs, and the number of animal experiments. In vitro hepatocyte-based research has led to an improved comprehension of the underlying mechanisms of chemical toxicity and can assist the prioritization of therapeutic choices with low hepatotoxicity risk. Therefore, several in vitro systems have been generated over the last few decades. This review aims to comprehensively present the development and validation of 2D (two-dimensional) and 3D (three-dimensional) culture approaches on hepatotoxicity screening of compounds and highlight the main factors affecting predictive power of experiments. To this end, we first summarize some of the recognized hepatotoxicity mechanisms and related assays used to appraise DILI mechanisms and then discuss the challenges and limitations of in vitro models.

HepaRG Maturation in Silk Fibroin Scaffolds: Toward Developing a 3D In Vitro Liver Model

In vitro liver models are necessary tools for the development of new therapeutics. HepaRG cells are a commonly used cell line to produce hepatic progenitor cells and hepatocytes. This study demonstrates for the first time the suitability of 3% silk scaffolds to support HepaRG growth and differentiation. The modulus and pore size of 3% silk scaffolds were shown to be within the desired range for liver cell growth. The optimal seeding density for HepaRG cells on silk scaffolds was determined. The growth and maturation of scaffolded HepaRG cells was evaluated for 28 days, where the first 14 days of culture were a proliferation period and the last 14 days of culture were a differentiation period using dimethyl sulfoxide (DMSO) treatment. After the first 14 days of culture, the scaffolded HepaRG cells exhibited increased metabolic activity and albumin secretion compared to monolayer cultured controls and preserved these attributes through the duration of culture. Additionally, after the first 14 days of culture, the scaffolded HepaRG cells displayed a significantly reduced expression of genes associated with hepatocyte maturation. This difference in expression was no longer apparent after 28 days of culture, suggesting that the cells underwent rapid differentiation within the scaffold. The functionalization of silk scaffolds with extracellular matrix (ECM) components (type I collagen and/or an arginylglycylaspartic acid (RGD)-containing peptide) was investigated to determine the impact on HepaRG cell attachment and maturation. The inclusion of ECM components had no noticeable impact on cell attachment but did significantly influence CYP3A4 expression and albumin secretion. Finally, the matrix support provided by the 3% silk scaffolds could prime the HepaRG cells for steatosis liver model applications, as evidenced by lipid droplet accumulation and expression of steatosis-related genes after 24 h of exposure to oleic acid. Overall, our work demonstrates the utility of silk scaffolds in providing a modifiable platform for liver cell growth.

Immune-Mediated Drug-Induced Liver Injury: Immunogenetics and Experimental Models

Drug-induced liver injury (DILI) is a challenging clinical event in medicine, particularly because of its ability to present with a variety of phenotypes including that of autoimmune hepatitis or other immune mediated liver injuries. Limited diagnostic and therapeutic tools are available, mostly because its pathogenesis has remained poorly understood for decades. The recent scientific and technological advancements in genomics and immunology are paving the way for a better understanding of the molecular aspects of DILI. This review provides an updated overview of the genetic predisposition and immunological mechanisms behind the pathogenesis of DILI and presents the state-of-the-art experimental models to study DILI at the pre-clinical level.

Molecular Profiling of Human Induced Pluripotent Stem Cell-Derived Cells and their Application for Drug Safety Study

Drug-induced toxicity remains one of the leading causes of discontinuation of the drug candidate and post-marketing withdrawal. Thus, early identification of the drug candidates with the potential for toxicity is crucial in the drug development process. With the recent discovery of human- Induced Pluripotent Stem Cells (iPSC) and the establishment of the differentiation protocol of human iPSC into the cell types of interest, the differentiated cells from human iPSC have garnered much attention because of their potential applicability in toxicity evaluation as well as drug screening, disease modeling and cell therapy. In this review, we expanded on current information regarding the feasibility of human iPSC-derived cells for the evaluation of drug-induced toxicity with a focus on human iPSCderived hepatocyte (iPSC-Hep), cardiomyocyte (iPSC-CMs) and neurons (iPSC-Neurons). Further, we CSAHi, Consortium for Safety Assessment using Human iPS Cells, reported our gene expression profiling data with DNA microarray using commercially available human iPSC-derived cells (iPSC-Hep, iPSC-CMs, iPSC-Neurons), their relevant human tissues and primary cultured human cells to discuss the future direction of the three types of human iPSC-derived cells.

The evolution of strategies to minimise the risk of human drug-induced liver injury (DILI) in drug discovery and development

Early identification of toxicity associated with new chemical entities (NCEs) is critical in preventing late-stage drug development attrition. Liver injury remains a leading cause of drug failures in clinical trials and post-approval withdrawals reflecting the poor translation between traditional preclinical animal models and human clinical outcomes. For this reason, preclinical strategies have evolved over recent years to incorporate more sophisticated human in vitro cell-based models with multi-parametric endpoints. This review aims to highlight the evolution of the strategies adopted to improve human hepatotoxicity prediction in drug discovery and compares/contrasts these with recent activities in our lab. The key role of human exposure and hepatic drug uptake transporters (e.g. OATPs, OAT2) is also elaborated.

Mechanism-based integrated assay systems for the prediction of drug-induced liver injury

Drug-induced liver injury (DILI) can cause hepatic failure and result in drug withdrawal from the market. It has host-related and compound-dependent mechanisms. Preclinical prediction of DILI risk is very challenging and safety assessments based on animals inadequately forecast human DILI risk. In contrast, human-derived in vitro cell culture-based models could improve DILI risk prediction accuracy. Here, we developed and validated an innovative method to assess DILI risk associated with various compounds. Fifty-four marketed and withdrawn drugs classified as DILI risks of "most concern", "less concern", and "no concern" were tested using a combination of four assays addressing mitochondrial injury, intrahepatic lipid accumulation, inhibition of bile canalicular network formation, and bile acid accumulation. Using the inhibitory potencies of the drugs evaluated in these in vitro tests, an algorithm with the highest available DILI risk prediction power was built by artificial neural network (ANN) analysis. It had an overall forecasting accuracy of 73%. We excluded the intrahepatic lipid accumulation assay to avoid overfitting. The accuracy of the algorithm in terms of predicting DILI risks was 62% when it was constructed by ANN but only 49% when it was built by the point-added scoring method. The final algorithm based on three assays made no DILI risk prediction errors such as "most concern " instead of "no concern" and vice-versa. Our mechanistic approach may accurately predict DILI risks associated with numerous candidate drugs.

A methylation functional detection hepatic cell system validates correlation between DNA methylation and drug-induced liver injury

Drug-induced liver injury (DILI) is a life-threatening, adverse reaction to certain drugs. The onset and extent of DILI can vary drastically in different patients using identical drugs. Association studies suggested that subtle differences in DNA methylation may help explain the individual differences in DILI. However, there are very few experimental methods to confirm such associations. In this study, we established a novel DNA methylation functional detection system in human hepatocytes, using CRISPR/dCas9 for targeted modification of DNA methylation, and set four parameters to indicate the liver injury by cell model. Using this system, we validated the association of hypermethylation of CYP2D6 and CYP2E1 with rifampin-induced DILI. Our results revealed that, following treatment of HepaRG cells with rifampin, the methylation levels of CYP2D6 and CYP2E1 were inversely proportional to cell viability and glutathione content, and directly proportional to caspase 3/7 activity. We expect that our methylation detection system will serve as a useful tool in validating correlations between DNA methylation and DILI in other in vitro systems. Our results establish a foundation for future investigations to better understand the mechanisms underlying DILI and may aid in advancing personalized DILI medicine.

Metabolite Profiling and Reaction Phenotyping for the in Vitro Assessment of the Bioactivation of Bromfenac †

Bromfenac is a nonsteroidal anti-inflammatory drug that was approved and subsequently withdrawn from the market because of reported cases of acute hepatotoxicity. Recently, in vitro studies have revealed that bromfenac requires UDPGA and alamethicin supplemented human liver microsomes (HLM) to form a major metabolite, bromfenac indolinone (BI). Bromfenac and BI form thioether adducts through a bioactivation pathway in HLM and hepatocytes. [J. P. Driscoll et al., Chem. Res. Toxicol. 2018, 31, 223-230.] Here, Cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT) reaction phenotyping experiments using recombinant enzymes were performed on bromfenac and BI to identify the CYP and UGT enzymes responsible for bromfenac's metabolism and bioactivation. It was determined that UGT2B7 converts bromfenac to BI, and that while CYP2C8, CYP2C9, and CYP2C19 catalyze the hydroxylation of bromfenac, only CYP2C9 forms thioether adducts when incubated with NAC or GSH as trapping agents. Although CYP2C9 was shown to form a reactive intermediate, no inhibition of CYP2C9 was observed when an IC₅₀ shift assay was performed. Reaction phenotyping experiments with BI and recombinant CYP enzymes indicated that CYPs 1A2, 2B6, 2C8, 2C9, 2C19, 2D6, and 3A4 were responsible for the formation of an aliphatic hydroxylated metabolite. An aromatic hydroxylation on the indolinone moiety was also formed by CYP1A2 and CYP3A4. The aromatic hydroxylated BI is a precursor to the quinone methide and quinone imine intermediates in the proposed bioactivation pathway. Through time-dependent inhibition (TDI) experiments, it was revealed that BI can cause an IC₅₀ shift in CYP1A2 and CYP3A4. However, BI does not inhibit the other isoforms that were also responsible for the formation of the aliphatic hydroxylation, an alternative biotransformation that does not undergo further downstream bioactivation. The results of these metabolism studies with bromfenac and BI add to our understanding of the relationship between biotransformation, reactive intermediate generation, and a potential mechanistic link to the hepatotoxicity of this compound.

Dr. Daniel Acosta and In Vitro toxicology at the U.S. Food and Drug Administration's National Center for Toxicological Research

For the past five years, Dr. Daniel Acosta has served as the Deputy Director of Research at the National Center for Toxicological Research (NCTR), a principle research laboratory of the U.S. Food and Drug Administration (FDA). Over his career at NCTR, Dr. Acosta has had a major impact on developing and promoting the use of in vitro assays in regulatory toxicity and product safety assessments. As Dr. Acosta nears his retirement we have dedicated this paper to his many accomplishments at the NCTR. Described within this paper are some of the in vitro studies that have been conducted under Dr. Acosta's leadership. These studies include toxicological assessments involving developmental effects, and the development and application of in vitro reproductive, heart, liver, neurological and airway cell and tissue models.

Predicting Drug-Induced Liver Injury Using Ensemble Learning Methods and Molecular Fingerprints

Drug-induced liver injury (DILI) is a major safety concern in the drug-development process, and various methods have been proposed to predict the hepatotoxicity of compounds during the early stages of drug trials. In this study, we developed an ensemble model using 3 machine learning algorithms and 12 molecular fingerprints from a dataset containing 1241 diverse compounds. The ensemble model achieved an average accuracy of 71.1 ± 2.6%, sensitivity (SE) of 79.9 ± 3.6%, specificity (SP) of 60.3 ± 4.8%, and area under the receiver-operating characteristic curve (AUC) of 0.764 ± 0.026 in 5-fold cross-validation and an accuracy of 84.3%, SE of 86.9%, SP of 75.4%, and AUC of 0.904 in an external validation dataset of 286 compounds collected from the Liver Toxicity Knowledge Base. Compared with previous methods, the ensemble model achieved relatively high accuracy and SE. We also identified several substructures related to DILI. In addition, we provide a web server offering access to our models (http://ccsipb.lnu.edu.cn/toxicity/HepatoPred-EL/).

Use of a non-hepatic cell line highlights limitations associated with cell-based assessment of metabolically induced toxicity

Metabolically induced drug-toxicity is a major cause of drug failure late in drug optimization phases. Accordingly, in vitro metabolic profiling of compounds is being introduced at earlier stages of the drug discovery pipeline. An increasingly common method to obtain these profiles is through overexpression of key CYP450 metabolic enzymes in immortalized liver cells, to generate competent hepatocyte surrogates. Enhanced cytotoxicity is presumed to be due to toxic metabolite production via the overexpressed enzyme. However, metabolically induced toxicity is a complex multi-parameter phenomenon and the potential background contribution to metabolism arising from the use of liver cells which endogenously express CYP450 isoforms is consistently overlooked. In this study, we sought to reduce the potential background interference by applying this methodology in kidney-derived HEK293 cells which lack endogenous CYP450 expression. Overexpression of CYP3A4 resulted in increased HEK293 proliferation, while exposure to four compounds with reported metabolically induced cytotoxicity in liver-derived cells overexpressing CYP3A4 resulted in no increase in cytotoxicity. Our results indicate that overexpression of a single CYP450 isoform in hepatic cell lines may not be a reliable method to discriminate which enzymes are responsible for metabolic induced cytotoxicity.

High-content analysis of in vitro hepatocyte injury induced by various hepatotoxicants

In vitro prediction of hepatotoxicity can enhance the performance of non-clinical animal testing for identifying chemical hazards. In this study, we assessed high-content analysis (HCA) using multi-parameter cell-based assays as an in vitro hepatotoxicity testing model using various hepatotoxicants and human hepatocytes such as HepG2 cells and human primary hepatocytes (hPHs). Both hepatocyte types were exposed separately to multiple doses of ten hepatotoxicants associated with liver injury whose mechanisms of action have been described. HCA data were obtained using fluorescence probes for nuclear size (Hoechst), mitochondrial membrane potential (TMRM), cytosolic free calcium (Fluo-4AM), and lipid peroxidation (BODIPY). Cellular alterations were observed in response to all hepatotoxicants tested. The most sensitive parameter was TMRM, with high sensitivity at a low dose, next was BODIPY, followed by Fluo-4AM. HCA data from HepG2 cells and hPHs were generally concordant, although some inconsistencies were noted. Both hepatocyte types showed mild or severe mitochondrial impairment and lipid peroxidation in response to several hepatotoxicants. The results demonstrate that the application of HCA to in vitro hepatotoxicity testing enables more efficient hazard identification, and further, they suggest that certain parameters could serve as sensitive endpoints for predicting the hepatotoxic potential of chemical compounds.

In vitro Models and On-Chip Systems: Biomaterial Interaction Studies With Tissues Generated Using Lung Epithelial and Liver Metabolic Cell Lines

In vitro models are very important in medicine and biology, because they provide an insight into cells' and microorganisms' behavior. Since these cells and microorganisms are isolated from their natural environment, these models may not completely or precisely predict the effects on the entire organism. Improvement in this area is secured by organ-on-a-chip development. The organ-on-a-chip assumes cells cultured in a microfluidic chip. The chip simulates bioactivities, mechanics and physiological behavior of organs or organ systems, generating artificial organs in that way. There are several cell lines used so far for each tested artificial organ. For lungs, mostly used cell lines are 16HBE, A549, Calu-3, NHBE, while mostly used cell lines for liver are HepG2, Hep 3B, TPH1, etc. In this paper, state of the art for lung and liver organ-on-a-chip is presented, together with the established in vitro testing on lung and liver cell lines, with the emphasis on Calu-3 (for lung cell lines) and Hep-G2 (for liver cell lines). Primary focus in this review is to discuss different researches on the topics of lung and liver cell line models, approaches in determining fate and transport, cell partitioning, cell growth and division, as well as cell dynamics, meaning toxicity and effects. The review is finalized with current research gaps and problems, stating potential future developments in the field.

Quantitative Evaluation of Cytochrome P450 3A4 Inhibition and Hepatotoxicity in HepaRG 3-D Spheroids

Predicting drug–drug interactions (DDIs) is an important step during drug development to avoid unexpected side effects. Cytochrome P450 (CYP) 3A4 is the most abundant human hepatic phase I enzyme, which metabolizes >50% of therapeutic drugs. Therefore, it is essential to test the potential of a drug candidate to induce CYP3A4 expression or inhibit its activity. Recently, 3-dimensional (3-D) mammalian cell culture models have been adopted in drug discovery research to assess toxicity, DDIs, and pharmacokinetics. In this study, we applied a human 3-D spheroid culture protocol using HepaRG cells combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to assess its ability to predict CYP3A4 inhibition. Levels of midazolam, a specific substrate of CYP3A4, were used to determine the long-term metabolic capacity of CYP3A4. Midazolam was decreased in the 3-D HepaRG culture system by ∼80% over 7 days, whereas its primary metabolite, 1-hydroxymidazolam, increased by ∼40%. Next, we assessed hepatotoxicity by determining the cytotoxicity of known hepatotoxicants in HepaRG spheroids, HepG2 cells, and primary human hepatocytes. Significant differences in cytotoxicity were detected in the system using 3-D HepaRG spheroids. These results suggest that 3-D HepaRG spheroids are a good model for prediction of CYP inhibition and hepatotoxicity in screening of early drug candidates.

Liver 'organ on a chip'

The liver plays critical roles in both homeostasis and pathology. It is the major site of drug metabolism in the body and, as such, a common target for drug-induced toxicity and is susceptible to a wide range of diseases. In contrast to other solid organs, the liver possesses the unique ability to regenerate. The physiological importance and plasticity of this organ make it a crucial system of study to better understand human physiology, disease, and response to exogenous compounds. These aspects have impelled many to develop liver tissue systems for study in isolation outside the body. Herein, we discuss these biologically engineered organoids and microphysiological systems. These aspects have impelled many to develop liver tissue systems for study in isolation outside the body. Herein, we discuss these biologically engineered organoids and microphysiological systems.

Cell-based assay using glutathione-depleted HepaRG and HepG2 human liver cells for predicting drug-induced liver injury

Immortalized liver cells have been used for evaluating the toxicity of compounds; however, excessive glutathione is considered to lessen cytotoxicity. In this study, we compared the effects of glutathione depletion on cytotoxicities of drugs using HepaRG and HepG2 cells, which express and lack drug-metabolizing enzymes, respectively, for predicting drug-induced liver injury (DILI) risks. These cells were pre-incubated with L-buthionine-S,R-sulfoximine (BSO) and then exposed to 34 test compounds with various DILI risks for 24 h. ATP level exhibited the highest predictability of DILI among tested parameters. BSO treatment rendered cells susceptible to drug-induced cytotoxicity when evaluated by cell viability and caspase 3/7 activity with the sensitivity of cell viability from 50% in non-treated HepaRG cells to 71% in BSO-treated HepaRG cells. These results indicate that cytotoxicity assays using GSH-depleted HepaRG cells improve the predictability of DILI risks. However, HepaRG cells were not always superior to HepG2 cells when assessed by ATP level. The combination of HepG2 and HepaRG cells index produced the best prediction in the cases of caspase 3/7 acitivity and ATP level. In conclusions, the developed highly sensitive cell-based assay using GSH-reduced cells would be useful for predicting potential DILI risks at an early stage of drug development.

Tools to Measure Cell Health and Cytotoxicity Using High Content Imaging and Analysis

High content screening (HCS)-based multiparametric measurements are very useful in early toxicity testing and safety assessment during drug development, and useful in evaluating the impact from new food supplements and environmental toxicants. Mitochondrial membrane potential, plasma membrane permeability, oxidative stress, phosphoplipidosis, and steatosis are a few of the important markers routinely studied for the assessment of drug-induced liver injury and toxicity. Mitochondrial dysfunction leads to oxidative stress and cell death. Liver injury from drug-induced phospholipidosis and steatosis is routinely studied in hepatotoxicity investigations to determine the risk factors and fate of drugs or chemical compounds as some drugs can lead to defects in lipid metabolism and accumulation of lipids in lysosomes. In this chapter, we describe fluorescent reagents and the protocols for the measurement of various parameters such as mitochondrial membrane potential, plasma membrane permeability, oxidative stress, phospholipidosis, and steatosis using high content imaging-based methodologies and instrumentation.

Development of Decision Forest Models for Prediction of Drug-Induced Liver Injury in Humans Using A Large Set of FDA-approved Drugs

Drug-induced liver injury (DILI) presents a significant challenge to drug development and regulatory science. The FDA’s Liver Toxicity Knowledge Base (LTKB) evaluated >1000 drugs for their likelihood of causing DILI in humans, of which >700 drugs were classified into three categories (most-DILI, less-DILI, and no-DILI). Based on this dataset, we developed and compared 2-class and 3-class DILI prediction models using the machine learning algorithm of Decision Forest (DF) with Mold2 structural descriptors. The models were evaluated through 1000 iterations of 5-fold cross-validations, 1000 bootstrapping validations and 1000 permutation tests (that assessed the chance correlation). Furthermore, prediction confidence analysis was conducted, which provides an additional parameter for proper interpretation of prediction results. We revealed that the 3-class model not only had a higher resolution to estimate DILI risk but also showed an improved capability to differentiate most-DILI drugs from no-DILI drugs in comparison with the 2-class DILI model. We demonstrated the utility of the models for drug ingredients with warnings very recently issued by the FDA. Moreover, we identified informative molecular features important for assessing DILI risk. Our results suggested that the 3-class model presents a better option than the binary model (which most publications are focused on) for drug safety evaluation.

A cell-based assay using HepaRG cells for predicting drug-induced phospholipidosis

The utility of HepaRG cells as an in vitro cell-based assay system for predicting drug-induced phospholipidosis (PLD) was investigated. In experiment 1, 10 PLD-positive compounds and 11 PLD-negative compounds were selected. HepaRG cells were treated with each compound for 48 hr. In experiment 2, loratadine and desloratadine, a major metabolite of loratadine, were used to assess metabolic activation for PLD. HepaRG cells were treated with loratadine and desloratadine in the presence or absence of 500 μM 1-aminobenzotriazole (ABT), a broad CYP inhibitor, for 48 hr. After treatment with compounds in experiments 1 and 2, the relative fluorescence intensity (RFI) was measured using LYSO-ID Red dye to assess the PLD induction. In experiment 1, our cell-based assay system using HepaRG cells exhibited 100% sensitivity and 100% specificity for predicting drug-induced PLD. In experiment 2, loratadine increased the RFI in the PLD assay. However, the increase in the RFI was not observed in co-treatment with loratadine and ABT. In addition, desloratadine increased the RFI in the presence and absence of ABT. These results suggested that metabolic activation of loratadine may contribute to PLD in HepaRG cells. We newly demonstrated that HepaRG cells have a high ability for predicting drug-induced PLD. In addition, we newly showed that HepaRG cells may predict drug-induced PLD mediated by metabolic activation of loratadine. Thus, a cell-based assay system using HepaRG cells is a useful model for predicting drug-induced PLD.

Content decline of SERCA inhibitors saikosaponin a and d attenuates cardiotoxicity and hepatotoxicity of vinegar-baked Radix bupleuri

Improper usage of unprocessed Radix bupleuri root (chaihu) may cause cardiotoxicity and liver injury. Baking herb with vinegar is believed to attenuate the adverse responses. However, the chemical and molecular basis involved remained unclear. To this end, we investigated the in vitro toxicity of saikosaponin a, c, d, and their hydrolysates saikosaponin b1 and b2. Results showed that SSa and SSd possessed higher affinity with sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) by molecular docking, and exhibited stronger toxic responses on cardiomyocytes and hepatocytes than the other three saikosaponins in equivalent concentrations. Further, SSa and SSd induced LC3 puncta formation in U2OS-mCherry-EGFP-LC3 cells. Blockage of autophagy by 3-methyladenine did not abrogate the cytotoxicities induced by SSa and SSd. In parallel, none of SSc, SSb1, or SSb2 caused cell injury. Our study reveals how changes in chemical ingredients are connected to the toxicity of Chaihu during vinegar baking process and also provides a guidance for structure optimization to reduce drug induced toxicity.

Evaluation of HepaRG cells for the assessment of indirect drug-induced hepatotoxicity using INH as a model substance

HepaRG cells are widely used as an in vitro model to assess drug-induced hepatotoxicity. However, only few studies exist so far regarding their suitability to detect the effects of drugs requiring a preceding activation via the cytochrome P450 (CYP) system. A prototypic substance is the anti-tuberculosis agent INH, which is metabolized into N-acetylhydrazine, which then triggers hepatotoxicity. Therefore, the aim of the present study was to test if this effect can also be detected in HepaRG cells and if it can be counteracted by the known hepatoprotectant silibinin. For this purpose, differentiated HepaRG cells were treated with increasing concentrations of INH (0.1-100 mM) or 10 mM INH plus escalating concentrations of silibinin (1-100 µM). After 48 h of treatment, cell morphology and parameters indicating cell vitality, oxidative stress, and liver cell function were assessed. High concentrations of INH led to severe histopathological changes, reduced cell vitality and glutathione content, increased LDH and ASAT release into the medium, enhanced lipid peroxidation, and elevated cleaved caspase-3 expression. Additionally, glycogen depletion and reduced biotransformation capacity were seen at high INH concentrations, whereas at low concentrations an induction of biotransformation enzymes was noticed. Silibinin caused clear-cut protective effects, but with few parameters INH toxicity was even aggravated, most probably due to increased metabolization of INH into its toxic metabolite. In conclusion, HepaRG cells are excellently suited to evaluate the effects of substances requiring prior toxification via the CYP system, such as INH. They additionally enable the identification of complex substance interactions.

A Multi-Parametric Fluorescent Assay for the Screening and Mechanistic Study of Drug-Induced Steatosis in Liver Cells in Culture

Human hepatic cells have been used for drug safety risk evaluations throughout early development phases. They provide rapid, cost-effective early feedback to identify drug candidates with potential hepatotoxicity. This unit presents a cell-based assay to evaluate the risk of liver damage associated with steatogenic drugs. Detailed protocols for cell exposure to test compounds and for the assessment of steatosis-related cell parameters (intracellular lipid content, reactive oxygen species production, mitochondrial impairment, and cell death) are provided. A few representative results that illustrate the utility of this procedure for the screening of drug-induced steatosis are shown. © 2017 by John Wiley & Sons, Inc.

An Automated Multiplexed Hepatotoxicity and CYP Induction Assay Using HepaRG Cells in 2D and 3D

Drug-induced liver injury (DILI) and drug-drug interactions (DDIs) are concerns when developing safe and efficacious compounds. We have developed an automated multiplex assay to detect hepatotoxicity (i.e., ATP depletion) and metabolism (i.e., cytochrome P450 1A [CYP1A] and cytochrome P450 3A4 [CYP3A4] enzyme activity) in two-dimensional (2D) and three-dimensional (3D) cell cultures. HepaRG cells were cultured in our proprietary micromold plates and produced spheroids. HepaRG cells, in 2D or 3D, expressed liver-specific proteins throughout the culture period, although 3D cultures consistently exhibited higher albumin secretion and CYP1A/CYP3A4 enzyme activity than 2D cultures. Once the spheroid hepatic quality was assessed, 2D and 3D HepaRGs were challenged to a panel of DILI- and CYP-inducing compounds for 7 days. The 3D HepaRG model had a 70% sensitivity to liver toxins at 7 days, while the 2D model had a 60% sensitivity. In both the 2D and 3D HepaRG models, 83% of compounds were predicted to be CYP inducers after 7 days of compound exposure. Combined, our results demonstrate that an automated multiplexed liver spheroid system is a promising cell-based method to evaluate DILI and DDI for early-stage drug discovery.

Predicting drug-induced liver injury in human with Naïve Bayes classifier approach

Drug-induced liver injury (DILI) is one of the major safety concerns in drug development. Although various toxicological studies assessing DILI risk have been developed, these methods were not sufficient in predicting DILI in humans. Thus, developing new tools and approaches to better predict DILI risk in humans has become an important and urgent task. In this study, we aimed to develop a computational model for assessment of the DILI risk with using a larger scale human dataset and Naïve Bayes classifier. The established Naïve Bayes prediction model was evaluated by 5-fold cross validation and an external test set. For the training set, the overall prediction accuracy of the 5-fold cross validation was 94.0 %. The sensitivity, specificity, positive predictive value and negative predictive value were 97.1, 89.2, 93.5 and 95.1 %, respectively. The test set with the concordance of 72.6 %, sensitivity of 72.5 %, specificity of 72.7 %, positive predictive value of 80.4 %, negative predictive value of 63.2 %. Furthermore, some important molecular descriptors related to DILI risk and some toxic/non-toxic fragments were identified. Thus, we hope the prediction model established here would be employed for the assessment of human DILI risk, and the obtained molecular descriptors and substructures should be taken into consideration in the design of new candidate compounds to help medicinal chemists rationally select the chemicals with the best prospects to be effective and safe.

Key Challenges and Opportunities Associated with the Use of In Vitro Models to Detect Human DILI: Integrated Risk Assessment and Mitigation Plans

Drug-induced liver injury (DILI) is a major cause of late-stage clinical drug attrition, market withdrawal, black-box warnings, and acute liver failure. Consequently, it has been an area of focus for toxicologists and clinicians for several decades. In spite of considerable efforts, limited improvements in DILI prediction have been made and efforts to improve existing preclinical models or develop new test systems remain a high priority. While prediction of intrinsic DILI has improved, identifying compounds with a risk for idiosyncratic DILI (iDILI) remains extremely challenging because of the lack of a clear mechanistic understanding and the multifactorial pathogenesis of idiosyncratic drug reactions. Well-defined clinical diagnostic criteria and risk factors are also missing. This paper summarizes key data interpretation challenges, practical considerations, model limitations, and the need for an integrated risk assessment. As demonstrated through selected initiatives to address other types of toxicities, opportunities exist however for improvement, especially through better concerted efforts at harmonization of current, emerging and novel in vitro systems or through the establishment of strategies for implementation of preclinical DILI models across the pharmaceutical industry. Perspectives on the incorporation of newer technologies and the value of precompetitive consortia to identify useful practices are also discussed.

Advantageous use of HepaRG cells for the screening and mechanistic study of drug-induced steatosis

Only a few in vitro assays have been proposed to evaluate the steatotic potential of new drugs. The present study examines the utility of HepaRG cells as a cell-based assay system for screening drug-induced liver steatosis. A high-content screening assay was run to evaluate multiple toxicity-related cell parameters in HepaRG cells exposed to 28 compounds, including drugs reported to cause steatosis through different mechanisms and non-steatotic compounds. Lipid content was the most sensitive parameter for all the steatotic drugs, whereas no effects on lipid levels were produced by non-steatotic compounds. Apart from fat accumulation, increased ROS production and altered mitochondrial membrane potential were also found in the cells exposed to steatotic drugs, which indicates that all these cellular events contributed to drug-induced hepatotoxicity. These findings are of clinical relevance as most effects were observed at drug concentrations under 100-fold of the therapeutic peak plasmatic concentration. HepaRG cells showed increased lipid overaccumulation vs. HepG2 cells, which suggests greater sensitivity to drug-induced steatosis. An altered expression profile of transcription factors and the genes that code key proteins in lipid metabolism was also found in the cells exposed to drugs capable of inducing liver steatosis. Our results generally indicate the value of HepaRG cells for assessing the risk of liver damage associated with steatogenic compounds and for investigating the molecular mechanisms involved in drug-induced steatosis.

The HepaRG cell line, a superior in vitro model to L-02, HepG2 and hiHeps cell lines for assessing drug-induced liver injury

Drug-induced liver injury (DILI) is a leading cause of discontinuation of new drug approval or withdrawal of marketed medicine based on safety due to organ vulnerability. The aim of this research is to investigate the potential abilities of four different in vitro cell models (L-02, HepG2, HepaRG, and hiHeps cell lines) in assessing marketed drugs labeled with apparently different types of liver injury. A total of 17 drugs with versatile pharmacological profiles were chosen, of which, 14 drugs are recognized as DILI agents and 3 drugs are DILI irrelevant. Preliminary cellular screening assays indicated that the HepaRG cell line had an advantage over other cell lines in predicting drugs associated with DILI in vitro as it had the highest Youden's index (71.4%). A multi-parametric screening assay showed that oxidative stress, mitochondrial damage, and disorders of neutral lipid metabolism were changed notably in the HepaRG cell line after DILI-related drugs exposure, accounting for its high sensitivity in comparison with other three cell lines. In addition, aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and malate dehydrogenase (MDH) all correlated with the cytotoxic effects of diclofenac sodium (p < 0.05), buspirone hydrochloride (p < 0.01), and danazol (p < 0.01) in the HepaRG cell line. We conclude that the HepaRG cell line is a superior in vitro cell model to other three cell lines for evaluating drugs with DILI potential.

Primary-like human hepatocytes genetically engineered to obtain proliferation competence display hepatic differentiation characteristics in monolayer and organotypical spheroid cultures

Primary human hepatocytes are in great demand during drug development and in hepatology. However, both scarcity of tissue supply and donor variability of primary cells create a need for the development of alternative hepatocyte systems. By using a lentivirus vector system to transfer coding sequences of Upcyte® proliferation genes, we generated non-transformed stable hepatocyte cultures from human liver tissue samples. Here, we show data on newly generated proliferation-competent HepaFH3 cells investigated as conventional two-dimensional monolayer and as organotypical three-dimensional (3D) spheroid culture. In monolayer culture, HepaFH3 cells show typical cobblestone-like hepatocyte morphology and anchorage-dependent growth for at least 20 passages. Immunofluorescence staining revealed that characteristic hepatocyte marker proteins cytokeratin 8, human serum albumin, and cytochrome P450 (CYP) 3A4 were expressed. Quantitative real-time PCR analyses showed that expression levels of analyzed phase I CYP enzymes were at similar levels compared to those of cultured primary human hepatocytes and considerably higher than in the liver carcinoma cell line HepG2. Additionally, transcripts for phase II liver enzymes and transporter proteins OATP-C, MRP2, Oct1, and BSEP were present in HepaFH3. The cells produced urea and converted model compounds such as testosterone, diclofenac, and 7-OH-coumarin into phases I and II metabolites. Interestingly, phases I and II enzymes were expressed at about the same levels in convenient monolayer cultures and complex 3D spheroids. In conclusion, HepaFH3 cells and related primary-like hepatocyte lines seem to be promising tools for in vitro research of liver functions and as test system in drug development and toxicology analysis.