The HepaRG cell line: a unique in vitro tool for understanding drug metabolism and toxicology in human

Pharmacokinetic Estimation Models-based Approach to Predict Clinical Implications for CYP Induction by Calcitriol in Human Cryopreserved Hepatocytes and HepaRG Cells

Calcitriol, a vitamin D₃ metabolite, is approved for various indications because it is the bioactive form of vitamin D in the body. The purpose of this study was to predict the clinical significance of cytochrome P450 (CYP) induction by calcitriol using in vitro human cryopreserved hepatocytes, HepaRG experimental systems, and various pharmacokinetic estimation models. CYP2B6, 3A4, 2C8, and 2C9 mRNA levels increased in a concentration-dependent manner in the presence of calcitriol in human cryopreserved hepatocytes and HepaRG cells. Using the half maximal effective concentration (EC₅₀) and maximum induction effect (E_max) obtained from the in vitro study, a basic kinetic model was applied, suggesting clinical relevance. In addition, a static mechanistic model showed the improbability of a clinically significant effect; however, the calculated area under the plasma concentration-time curve ratio (AUCR) was marginal for CYP3A4 in HepaRG cells. To clarify the effect of CYP3A4 in vivo, physiologically based pharmacokinetic (PBPK) modeling was applied as a dynamic mechanistic model, revealing a low clinically significant effect of CYP3A4 induction by calcitriol. Therefore, we conclude that CYP induction by calcitriol treatment would not be clinically significant under typical clinical conditions.

Differential effects on human cytochromes P450 by CRISPR/Cas9-induced genetic knockout of cytochrome P450 reductase and cytochrome b5 in HepaRG cells

HepaRG cells are increasingly accepted as model for human drug metabolism and other hepatic functions. We used lentiviral transduction of undifferentiated HepaRG cells to deliver Cas9 and two alternative sgRNAs targeted at NADPH:cytochrome P450 oxidoreductase (POR), the obligate electron donor for microsomal cytochromes P450 (CYP). Cas9-expressing HepaRG^VC (vector control) cells were phenotypically similar to wild type HepaRG cells and could be differentiated into hepatocyte-like cells by DMSO. Genetic POR-knockout resulted in phenotypic POR knockdown of up to 90% at mRNA, protein, and activity levels. LC–MS/MS measurement of seven CYP-activities showed differential effects of POR-knockdown with CYP2C8 being least and CYP2C9 being most affected. Further studies on cytochrome b5 (CYB5), an alternative NADH-dependent electron donor indicated particularly strong support of CYP2C8-dependent amodiaquine N-deethylation by CYB5 and this was confirmed by genetic CYB5 single- and POR/CYB5 double-knockout. POR-knockdown also affected CYP expression on mRNA and protein level, with CYP1A2 being induced severalfold, while CYP2C9 was strongly downregulated. In summary our results show that POR/NADPH- and CYB5/NADH-electron transport systems influence human drug metabolizing CYPs differentially and differently than mouse Cyps. Our Cas9-expressing HepaRG^VC cells should be suitable to study the influence of diverse genes on drug metabolism and other hepatic functions.

lnc-RHL, a novel long non-coding RNA required for the differentiation of hepatocytes from human bipotent progenitor cells

Objectives

The final stage of liver development is the production of hepatocytes and cholangiocytes (biliary epithelial cells) from bipotent hepatic progenitor cells. We used HepaRG cells, which are bipotent and able to differentiate into both hepatocytes and cholangiocytes, as a model to study the action of a novel lncRNA (lnc‐RHL) and its role in the regulation of bipotency leading to hepatocytes and cholangiocytes.

Materials and Methods

Differentiation of HepaRG cells was assessed by marker expression and morphology which revealed their ability to differentiate into hepatocytes and cholangiocytes (modelling the behaviour of hepatoblasts in vivo). Using a qRT‐PCR and RACE, we cloned a novel lncRNA (lnc‐RHL; regulator of hepatic lineages) that is upregulated upon HepaRG differentiation. Using inducible knockdown of lnc‐RHL concurrently with differentiation, we show that lnc‐RHL is required for proper HepaRG cell differentiation resulting in diminution of the hepatocyte lineage.

Results

Here, we report the discovery of lnc‐RHL, a spliced and polyadenylated 670 base lncRNA expressed from the 11q23.3 apolipoprotein gene cluster. lnc‐RHL expression is confined to hepatic lineages and is upregulated when bipotent HepaRG cells are caused to differentiate. HepaRG cells made deficient for lnc‐RHL have reduced ability to differentiate into hepatocytes, but retain their ability to differentiate into cholangiocytes.

Conclusions

Deficiency for lnc‐RHL in HepaRG cells converts them from bipotent progenitor cells to unipotent progenitor cells with impaired ability to yield hepatocytes. We conclude that lnc‐RHL is a key regulator of bipotency in HepaRG cells.

Effects of saikosaponin-d on CYP3A4 in HepaRG cell and protein-ligand docking study

Saikosaponin-d (SSd) is a major bioactive triterpenoid saponin extracted from Bupleurum, which has anti-inflammatory, anticancer, antioxidative and anti-hepatic fibrosis effects. Due to the effects of Bupleurum-related formulations on cytochrome P450 (CYPs) expression still remain unclear, the combination therapies involved formulations containing Bupleurum may sometimes lead to unexpected drug-drug interactions in clinical practice. These interactions can limit the clinical applications of related formulations. In this study, we tried to explore the effects of SSd on CYP3A4 mRNA, protein expression and the enzyme activity in HepaRG cells by real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR), Western blot (WB) and HPLC method, respectively. The interaction between SSd and CYP3A4 was analysed by molecular docking. HepaRG cells were cultured with different concentrations of SSd (0.5, 1, 5 and 10 μmol/L) for 72 hours. It is revealed that SSd can inhibit CYP3A4 mRNA and its protein expression, and also the enzyme activity. Molecular docking study demonstrated that SSd can bind to several key active sites of amino acid residues of CYP3A4 protein with hydrogen bonds and hydrophobic interactions. Thus, drug-drug interactions resulted by SSd inhibiting CYP3A4 need attention when formulations containing SSd or Bupleurum are co-administrated with drugs metabolized by CYP3A4.

Pyrrolizidine Alkaloids Induce Cell Death in Human HepaRG Cells in a Structure-Dependent Manner

Pyrrolizidine alkaloids (PAs) are a group of secondary metabolites produced in various plant species as a defense mechanism against herbivores. PAs consist of a necine base, which is esterified with one or two necine acids. Humans are exposed to PAs by consumption of contaminated food. PA intoxication in humans causes acute and chronic hepatotoxicity. It is considered that enzymatic PA toxification in hepatocytes is structure-dependent. In this study, we aimed to elucidate the induction of PA-induced cell death associated with apoptosis activation. Therefore, 22 structurally different PAs were analyzed concerning the disturbance of cell viability in the metabolically competent human hepatoma cell line HepaRG. The chosen PAs represent the main necine base structures and the different esterification types. Open-chained and cyclic heliotridine- and retronecine-type diesters induced strong cytotoxic effects, while treatment of HepaRG with monoesters did not affect cell viability. For more detailed investigation of apoptosis induction, comprising caspase activation and gene expression analysis, 14 PA representatives were selected. The proapoptotic effects were in line with the potency observed in cell viability studies. In vitro data point towards a strong structure–activity relationship whose effectiveness needs to be investigated in vivo and can then be the basis for a structure-associated risk assessment.

In Vitro and In Vivo Models of Non-Alcoholic Fatty Liver Disease: A Critical Appraisal

Non-alcoholic fatty liver disease (NAFLD), including non-alcoholic fatty liver (NAFL) and non-alcoholic steatohepatitis (NASH), represents the hepatic manifestation of obesity and metabolic syndrome. Due to the spread of the obesity epidemic, NAFLD is becoming the most common chronic liver disease and one of the principal indications for liver transplantation. However, no pharmacological treatment is currently approved to prevent the outbreak of NASH, which leads to fibrosis and cirrhosis. Preclinical research is required to improve our knowledge of NAFLD physiopathology and to identify new therapeutic targets. In the present review, we summarize advances in NAFLD preclinical models from cellular models, including new bioengineered platforms, to in vivo models, with a particular focus on genetic and dietary mouse models. We aim to discuss the advantages and limits of these different models.

Effects of Saikosaponin D on CYP1A2 and CYP2D6 in HepaRG Cells

Background

Bupleurum is one of the most important traditional Chinese medicines and an ingredient in many compound preparations. It is widely used together with other drugs in clinical practice, and thus there is great potential for drug–drug interactions. Saikosaponin D (SsD) is a major bioactive triterpenoid saponin extracted from Bupleurum with anti-inflammatory, anticancer, antioxidative, and antihepatic fibrosis effects. Effects of the main components of Bupleurum on cytochromes P450 (CYPs) need to be clarified in the clinical application of combination therapies of formulations containing SsD or Bupleurum.

Purpose

This study aimed to investigate the effects of SsD on the CYP1A2 and CYP2D6 mRNAs, protein expression, and relative enzyme activities in HepaRG cells.

Methods

HepaRG cells were cultured with SsD at concentrations of 0.5, 1, 5 and 10 μM for 72 hours. mRNA and protein expression of CYP1A2 and CYP2D6 were analyzed with real-time PCR and Western blot analysis. Relative enzyme activities were analyzed with HPLC based on consumption of the specific probe substrate.

Results

SsD significantly induced expression of mRNA and increased relative activity of CYP1A2 in HepaRG cells after the cells had been treated with SsD at concentrations of 1, 5 and 10 μM. SsD also induced protein expression of CYP1A2 at concentrations of 5 and 10 μM. SsD exhibited an inductive effect on CYP2D6 mRNA and protein expression, while increasing the relative activity of CYP2D6 at concentrations of 5 and 10 μM.

Conclusion

This study is the first to investigate the effect of SsD on CYP1A2 and CYP2D6 in HepaRG cells, and the results may provide some useful information on potential drug–drug interactions related to clinical preparations containing SsD or Bupleurum.

Current Perspective: 3D Spheroid Models Utilizing Human-Based Cells for Investigating Metabolism-Dependent Drug-Induced Liver Injury

Drug-induced liver injury (DILI) remains a leading cause for the withdrawal of approved drugs. This has significant financial implications for pharmaceutical companies, places increasing strain on global health services, and causes harm to patients. For these reasons, it is essential that in-vitro liver models are capable of detecting DILI-positive compounds and their underlying mechanisms, prior to their approval and administration to patients or volunteers in clinical trials. Metabolism-dependent DILI is an important mechanism of drug-induced toxicity, which often involves the CYP450 family of enzymes, and is associated with the production of a chemically reactive metabolite and/or inefficient removal and accumulation of potentially toxic compounds. Unfortunately, many of the traditional in-vitro liver models fall short of their in-vivo counterparts, failing to recapitulate the mature hepatocyte phenotype, becoming metabolically incompetent, and lacking the longevity to investigate and detect metabolism-dependent DILI and those associated with chronic and repeat dosing regimens. Nevertheless, evidence is gathering to indicate that growing cells in 3D formats can increase the complexity of these models, promoting a more mature-hepatocyte phenotype and increasing their longevity, in vitro. This review will discuss the use of 3D in vitro models, namely spheroids, organoids, and perfusion-based systems to establish suitable liver models to investigate metabolism-dependent DILI.

New insights into quetiapine metabolism using molecular networking

Metabolism is involved in both pharmacology and toxicology of most xenobiotics including drugs. Yet, visualization tools facilitating metabolism exploration are still underused, despite the availibility of pertinent bioinformatics solutions. Since molecular networking appears as a suitable tool to explore structurally related molecules, we aimed to investigate its interest in in vitro metabolism exploration. Quetiapine, a widely prescribed antipsychotic drug, undergoes well-described extensive metabolism, and is therefore an ideal candidate for such a proof of concept. Quetiapine was incubated in metabolically competent human liver cell models (HepaRG) for different times (0 h, 3 h, 8 h, 24 h) with or without cytochrom P450 (CYP) inhibitor (ketoconazole as CYP3A4/5 inhibitor and quinidine as CYP2D6 inhibitor), in order to study its metabolism kinetic and pathways. HepaRG culture supernatants were analyzed on an ultra-high performance liquid chromatography coupled with tandem mass spectrometry (LC-HRMS/MS). Molecular networking approach on LC-HRMS/MS data allowed to quickly visualize the quetiapine metabolism kinetics and determine the major metabolic pathways (CYP3A4/5 and/or CYP2D6) involved in metabolite formation. In addition, two unknown putative metabolites have been detected. In vitro metabolite findings were confirmed in blood sample from a patient treated with quetiapine. This is the first report using LC-HRMS/MS untargeted screening and molecular networking to explore in vitro drug metabolism. Our data provide new evidences of the interest of molecular networking in drug metabolism exploration and allow our in vitro model consistency assessment.

Effects of genetically modified human skin fibroblasts, stably overexpressing hepatocyte growth factor, on hepatic functions of cocultured C3A cells

Diseases leading to terminal hepatic failure are among the most common causes of death worldwide. Transplant of the whole organ is the only effective method to cure liver failure. Unfortunately, this treatment option is not available universally due to the serious shortage of donors. Thus, alternative methods have been developed that are aimed at prolonging the life of patients, including hepatic cells transplantation and bridging therapy based on hybrid bioartificial liver devices. Parenchymal liver cells are highly differentiated and perform many complex functions, such as detoxification and protein synthesis. Unfortunately, isolated hepatocytes display a rapid decline in viability and liver-specific functions. A number of methods have been developed to maintain hepatocytes in their highly differentiated state in vitro, amongst them the most promising being 3D growth scaffolds and decellularized tissues or coculture with other cell types required for the heterotypic cell-cell interactions. Here we present a novel approach to the hepatic cells culture based on the feeder layer cells genetically modified using lentiviral vector to stably produce additional amounts of hepatocyte growth factor and show the positive influence of these coculture conditions on the preservation of the hepatic functions of the liver parenchymal cells' model-C3A cells.

P450s under Restriction (PURE) Screen Using HepaRG and Primary Human Hepatocytes for Discovery of Novel HBV Antivirals

Herein is reported a novel screening paradigm PURE (P450s under restriction) for the identification and optimization of hits as part of a hepatitis B virus (HBV) antiviral discovery program. To closely represent in vivo hepatocytes, differentiated HepaRG cells (dHRGs) and primary human hepatocytes (PHHs) were used as the basis for an HBV infection system. However, a significant challenge arose during potency evaluation in using cultured dHRGs and PHHs as screening platforms because, as with hepatocytes in vivo, these cells express active cytochrome P450 enzymes and thus can metabolize test compounds. The observed antiviral effects may be the cumulative result of a dynamic pool of parent compound and metabolites thus confounding structure activity relationship (SAR) interpretation and subsequent optimization design initiatives. We show here that PURE methodology restricts metabolism of HBV-infected dHRGs and PHHs and thus provides highly informative potency data for decision-making on key representative antiviral compounds.

Drug Administration Routes Impact the Metabolism of a Synthetic Cannabinoid in the Zebrafish Larvae Model

Zebrafish (Danio rerio) larvae have gained attention as a valid model to study in vivo drug metabolism and to predict human metabolism. The microinjection of compounds, oligonucleotides, or pathogens into zebrafish embryos at an early developmental stage is a well-established technique. Here, we investigated the metabolism of zebrafish larvae after microinjection of methyl 2-(1-(5-fluoropentyl)-1H-pyrrolo[2,3-b]pyridine-3-carboxamido)-3,3-dimethylbutanoate (7'N-5F-ADB) as a representative of recently introduced synthetic cannabinoids. Results were compared to human urine data and data from the in vitro HepaRG model and the metabolic pathway of 7'N-5F-ADB were reconstructed. Out of 27 metabolites detected in human urine samples, 19 and 15 metabolites were present in zebrafish larvae and HepaRG cells, respectively. The route of administration to zebrafish larvae had a major impact and we found a high number of metabolites when 7'N-5F-ADB was microinjected into the caudal vein, heart ventricle, or hindbrain. We further studied the spatial distribution of the parent compound and its metabolites by mass spectrometry imaging (MSI) of treated zebrafish larvae to demonstrate the discrepancy in metabolite profiles among larvae exposed through different administration routes. In conclusion, zebrafish larvae represent a superb model for studying drug metabolism, and when combined with MSI, the optimal administration route can be determined based on in vivo drug distribution.

Switching of cell fate through the regulation of cell growth during drug-induced intrahepatic cholestasis

Understanding the fundamental mechanisms that govern the fate of cells during drug-induced intrahepatic cholestasis provides strategies for the establishment of evaluation methods for drug screening. In the present study, the aggregates of a differentiated human hepatic cell line, HepaRG, were incubated in medium with Y27632 or bosentan to clarify the changes in the behavior of bile canaliculi (BC) with the growth of cells during drug-induced intrahepatic cholestasis. With elapsed exposure time, the aggregates in the culture with bosentan caused the dilation of BC, and the hepatocytes ultimately exhibited apoptotic death after the disruption of BC. Y27632 caused the disruption of BC in the aggregates after dilation. However, there was no change in the number of cells within the aggregates in the culture with Y27632, in spite of its cytotoxicity. After 144 h from the start of Y27632 exposure, the aggregates showed the rearrangement of BC. To inhibit cell division, the aggregates exposed to Y27632, which exhibited disruption of BC, were treated with mitomycin C for 2 h and continuously exposed to Y27632. The inhibition of cell division could not induce the rearrangement of BC within these aggregates, which was similar to the phenomenon observed in the aggregates exposed to bosentan. These findings indicate that growth is an important factor that influences the switching of cell fate toward survival or death in drug-induced intrahepatic cholestasis process. Thus, the autoregulation of growth is a major contributor to the rearrangement of BC within aggregates.

Utility of Common Marmoset (Callithrix jacchus) Embryonic Stem Cells in Liver Disease Modeling, Tissue Engineering and Drug Metabolism

The incidence of liver disease is increasing significantly worldwide and, as a result, there is a pressing need to develop new technologies and applications for end-stage liver diseases. For many of them, orthotopic liver transplantation is the only viable therapeutic option. Stem cells that are capable of differentiating into all liver cell types and could closely mimic human liver disease are extremely valuable for disease modeling, tissue regeneration and repair, and for drug metabolism studies to develop novel therapeutic treatments. Despite the extensive research efforts, positive results from rodent models have not translated meaningfully into realistic preclinical models and therapies. The common marmoset Callithrix jacchus has emerged as a viable non-human primate model to study various human diseases because of its distinct features and close physiologic, genetic and metabolic similarities to humans. C. jacchus embryonic stem cells (cjESC) and recently generated cjESC-derived hepatocyte-like cells (cjESC-HLCs) could fill the gaps in disease modeling, liver regeneration and metabolic studies. They are extremely useful for cell therapy to regenerate and repair damaged liver tissues in vivo as they could efficiently engraft into the liver parenchyma. For in vitro studies, they would be advantageous for drug design and metabolism in developing novel drugs and cell-based therapies. Specifically, they express both phase I and II metabolic enzymes that share similar substrate specificities, inhibition and induction characteristics, and drug metabolism as their human counterparts. In addition, cjESCs and cjESC-HLCs are advantageous for investigations on emerging research areas, including blastocyst complementation to generate entire livers, and bioengineering of discarded livers to regenerate whole livers for transplantation.

Predicting direct hepatocyte toxicity in humans by combining high-throughput imaging of HepaRG cells and machine learning-based phenotypic profiling

Accurate prediction of drug- and chemical-induced hepatotoxicity remains to be a problem for pharmaceutical companies as well as other industries and regulators. The goal of the current study was to develop an in vitro/in silico method for the rapid and accurate prediction of drug- and chemical-induced hepatocyte injury in humans. HepaRG cells were employed for high-throughput imaging in combination with phenotypic profiling. A reference set of 69 drugs and chemicals was screened at a range of 7 concentrations, and the cellular response values were used for training a supervised classifier and for determining assay performance by using tenfold cross-validation. The results showed that the best performing phenotypic features were related to nuclear translocation of RELA (RELA proto-oncogene, NF-kB subunit; also known as NF-kappa B p65), DNA organization, and the F-actin cytoskeleton. Using a subset of 30 phenotypic features, direct hepatocyte toxicity in humans could be predicted with a test sensitivity, specificity and balanced accuracy of 73%, 92%, and 83%, respectively. The method was applied to another set of 26 drugs and chemicals with unclear annotation and their hepatocyte toxicity in humans was predicted. The results also revealed that the identified discriminative phenotypic changes were related to cell death and cellular senescence. Whereas cell death-related endpoints are widely applied in in vitro toxicology, cellular senescence-related endpoints are not, although cellular senescence can be induced by various drugs and other small molecule compounds and plays an important role in liver injury and disease. These findings show how phenotypic profiling can reveal unexpected chemical-induced mechanisms in toxicology.

The GOLIATH Project: Towards an Internationally Harmonised Approach for Testing Metabolism Disrupting Compounds

The purpose of this project report is to introduce the European "GOLIATH" project, a new research project which addresses one of the most urgent regulatory needs in the testing of endocrine-disrupting chemicals (EDCs), namely the lack of methods for testing EDCs that disrupt metabolism and metabolic functions. These chemicals collectively referred to as "metabolism disrupting compounds" (MDCs) are natural and anthropogenic chemicals that can promote metabolic changes that can ultimately result in obesity, diabetes, and/or fatty liver in humans. This project report introduces the main approaches of the project and provides a focused review of the evidence of metabolic disruption for selected EDCs. GOLIATH will generate the world's first integrated approach to testing and assessment (IATA) specifically tailored to MDCs. GOLIATH will focus on the main cellular targets of metabolic disruption-hepatocytes, pancreatic endocrine cells, myocytes and adipocytes-and using an adverse outcome pathway (AOP) framework will provide key information on MDC-related mode of action by incorporating multi-omic analyses and translating results from in silico, in vitro, and in vivo models and assays to adverse metabolic health outcomes in humans at real-life exposures. Given the importance of international acceptance of the developed test methods for regulatory use, GOLIATH will link with ongoing initiatives of the Organisation for Economic Development (OECD) for test method (pre-)validation, IATA, and AOP development.

Synthesis and Evaluation of New Trivalent Ligands for Hepatocyte Targeting via the Asialoglycoprotein Receptor

Since the asialoglycoprotein receptor (also known as the "Ashwell-Morell receptor" or ASGPR) was discovered as the first cellular mammalian lectin, numerous drug delivery systems have been developed and several gene delivery systems associated with multivalent ligands for liver disease targeting are undergoing clinical trials. The success of these systems has facilitated the further study of new ligands with comparable or higher affinity and less synthetic complexity. Herein, we designed two novel trivalent ligands based on the esterification of tris(hydroxymethyl) aminomethane (TRIS) followed by the azide-alkyne Huisgen cycloaddition with azido N-acetyl-d-galactosamine. The presented triazolyl glycoconjugates exhibited good binding to ASGPR, which was predicted using in silico molecular docking and assessed by a surface plasmon resonance (SPR) technique. Moreover, we demonstrated the low level of in vitro cytotoxicity, as well as the optimal spatial geometry and the required amphiphilic balance, for new, easily accessible ligands. The conjugate of a new ligand with Cy5 dye exhibited selective penetration into HepG2 cells in contrast to the ASGPR-negative PC3 cell line.

Genome-wide expression profiling reveals increased stability and mitochondrial energy metabolism of the human liver cell line HepaRG-CAR

Human liver cell line HepaRG is a well-known source of human hepatocyte-like cells which, however, displays limited biotransformation and a tendency to transform after 20 passages. The new HepaRG-CAR cell line overexpressing constitutive androstane receptor (CAR, NR1I3), a regulator of detoxification and energy metabolism outperforms the parental HepaRG cell line in various liver functions. To further characterize this cell line and assess its stability we compared HepaRG-CAR with HepaRG cells at different passages for their expression profile, ammonia and lactate metabolism, bile acid and reactive oxygen species (ROS) production. Transcriptomic profiling of HepaRG-CAR vs. HepaRG early-passage revealed downregulation of hypoxia, glycolysis and proliferation and upregulation of oxidative phosphorylation genesets. In addition CAR overexpression downregulated the mTORC1 signaling pathway, which, as mediator of proliferation and metabolic reprogramming, may play an important role in the establishment of the HepaRG-CAR phenotype. The ammonia and lactate metabolism and bile acid production of HepaRG-CAR cells was stable for 10 additional passages compared to HepaRG cells. Interestingly, bile acid production was 4.5-fold higher in HepaRG-CAR vs. HepaRG cells, whereas lactate and ROS production were 2.7- and 2.0-fold lower, respectively. Principal component analysis showed clustering of HepaRG-CAR (early- and late-passage) and HepaRG early-passage and not with HepaRG late-passage indicating that passaging exerted larger effect on the transcriptional profile of HepaRG than HepaRG-CAR cells. In conclusion, overexpression of CAR in HepaRG cells improves their bile acid production, mitochondrial energy metabolism, and stability, with the latter possibly due to reduced ROS production, resulting in an optimized source of human hepatocytes.

Transcriptomic profiling of PBDE-exposed HepaRG cells unveils critical lncRNA- PCG pairs involved in intermediary metabolism

Polybrominated diphenyl ethers (PBDEs) were formally used as flame-retardants and are chemically stable, lipophlic persistent organic pollutants which are known to bioaccumulate in humans. Although its toxicities are well characterized, little is known about the changes in transcriptional regulation caused by PBDE exposure. Long non-coding RNAs (lncRNAs) are increasingly recognized as key regulators of transcriptional and translational processes. It is hypothesized that lncRNAs can regulate nearby protein-coding genes (PCGs) and changes in the transcription of lncRNAs may act in cis to perturb gene expression of its neighboring PCGs. The goals of this study were to 1) characterize PCGs and lncRNAs that are differentially regulated from exposure to PBDEs; 2) identify PCG-lncRNA pairs through genome annotation and predictive binding tools; and 3) determine enriched canonical pathways caused by differentially expressed lncRNA-PCGs pairs. HepaRG cells, which are human-derived hepatic cells that accurately represent gene expression profiles of human liver tissue, were exposed to BDE-47 and BDE-99 at a dose of 25 μM for 24 hours. Differentially expressed lncRNA-PCG pairs were identified through DESeq2 and HOMER; significant canonical pathways were determined through Ingenuity Pathway Analysis (IPA). LncTar was used to predict the binding of 19 lncRNA-PCG pairs with known roles in drug-processing pathways. Genome annotation revealed that the majority of the differentially expressed lncRNAs map to PCG introns. PBDEs regulated overlapping pathways with PXR and CAR such as protein ubiqutination pathway and peroxisome proliferator-activated receptor alpha-retinoid X receptor alpha (PPARα-RXRα) activation but also regulate distinctive pathways involved in intermediary metabolism. PBDEs uniquely down-regulated GDP-L-fucose biosynthesis, suggesting its role in modifying important pathways involved in intermediary metabolism such as carbohydrate and lipid metabolism. In conclusion, we provide strong evidence that PBDEs regulate both PCGs and lncRNAs in a PXR/CAR ligand-dependent and independent manner.

Flow cytometric micronucleus assay and TGx-DDI transcriptomic biomarker analysis of ten genotoxic and non-genotoxic chemicals in human HepaRG™ cells

Background

Modern testing paradigms seek to apply human-relevant cell culture models and integrate data from multiple test systems to accurately inform potential hazards and modes of action for chemical toxicology. In genetic toxicology, the use of metabolically competent human hepatocyte cell culture models provides clear advantages over other more commonly used cell lines that require the use of external metabolic activation systems, such as rat liver S9. HepaRG™ cells are metabolically competent cells that express Phase I and II metabolic enzymes and differentiate into mature hepatocyte-like cells, making them ideal for toxicity testing. We assessed the performance of the flow cytometry in vitro micronucleus (MN) test and the TGx-DDI transcriptomic biomarker to detect DNA damage-inducing (DDI) chemicals in human HepaRG™ cells after a 3-day repeat exposure. The biomarker, developed for use in human TK6 cells, is a panel of 64 genes that accurately classifies chemicals as DDI or non-DDI. Herein, the TGx-DDI biomarker was analyzed by Ion AmpliSeq whole transcriptome sequencing to assess its classification accuracy using this more modern gene expression technology as a secondary objective.

Methods

HepaRG™ cells were exposed to increasing concentrations of 10 test chemicals (six genotoxic chemicals, including one aneugen, and four non-genotoxic chemicals). Cytotoxicity and genotoxicity were measured using the In Vitro MicroFlow® kit, which was run in parallel with the TGx-DDI biomarker.

Results

A concentration-related decrease in relative survival and a concomitant increase in MN frequency were observed for genotoxic chemicals in HepaRG™ cells. All five DDI and five non-DDI agents were correctly classified (as genotoxic/non-genotoxic and DDI/non-DDI) by pairing the test methods. The aneugenic agent (colchicine) yielded the expected positive result in the MN test and negative (non-DDI) result by TGx-DDI.

Conclusions

This next generation genotoxicity testing strategy is aligned with the paradigm shift occurring in the field of genetic toxicology. It provides mechanistic insight in a human-relevant cell-model, paired with measurement of a conventional endpoint, to inform the potential for adverse health effects. This work provides support for combining these assays in an integrated test strategy for accurate, higher throughput genetic toxicology testing in this metabolically competent human progenitor cell line.

Time-dependent enzyme inactivation: Numerical analyses of in vitro data and prediction of drug-drug interactions

Cytochrome P450 (CYP) enzyme kinetics often do not conform to Michaelis-Menten assumptions, and time-dependent inactivation (TDI) of CYPs displays complexities such as multiple substrate binding, partial inactivation, quasi-irreversible inactivation, and sequential metabolism. Additionally, in vitro experimental issues such as lipid partitioning, enzyme concentrations, and inactivator depletion can further complicate the parameterization of in vitro TDI. The traditional replot method used to analyze in vitro TDI datasets is unable to handle complexities in CYP kinetics, and numerical approaches using ordinary differential equations of the kinetic schemes offer several advantages. Improvement in the parameterization of CYP in vitro kinetics has the potential to improve prediction of clinical drug-drug interactions (DDIs). This manuscript discusses various complexities in TDI kinetics of CYPs, and numerical approaches to model these complexities. The extrapolation of CYP in vitro TDI parameters to predict in vivo DDIs with static and dynamic modeling is discussed, along with a discussion on current gaps in knowledge and future directions to improve the prediction of DDI with in vitro data for CYP catalyzed drug metabolism.

Generation of expandable human pluripotent stem cell-derived hepatocyte-like liver organoids

BACKGROUND & AIMS

The development of hepatic models capable of long-term expansion with competent liver functionality is technically challenging in a personalized setting. Stem cell-based organoid technologies can provide an alternative source of patient-derived primary hepatocytes. However, self-renewing and functionally competent human pluripotent stem cell (PSC)-derived hepatic organoids have not been developed.

METHODS

We developed a novel method to efficiently and reproducibly generate functionally mature human hepatic organoids derived from PSCs, including human embryonic stem cells and induced PSCs. The maturity of the organoids was validated by a detailed transcriptome analysis and functional performance assays. The organoids were applied to screening platforms for the prediction of toxicity and the evaluation of drugs that target hepatic steatosis through real-time monitoring of cellular bioenergetics and high-content analyses.

RESULTS

Our organoids were morphologically indistinguishable from adult liver tissue-derived epithelial organoids and exhibited self-renewal. With further maturation, their molecular features approximated those of liver tissue, although these features were lacking in 2D differentiated hepatocytes. Our organoids preserved mature liver properties, including serum protein production, drug metabolism and detoxifying functions, active mitochondrial bioenergetics, and regenerative and inflammatory responses. The organoids exhibited significant toxic responses to clinically relevant concentrations of drugs that had been withdrawn from the market due to hepatotoxicity and recapitulated human disease phenotypes such as hepatic steatosis.

CONCLUSIONS

Our organoids exhibit self-renewal (expandable and further able to differentiate) while maintaining their mature hepatic characteristics over long-term culture. These organoids may provide a versatile and valuable platform for physiologically and pathologically relevant hepatic models in the context of personalized medicine.

LAY SUMMARY

A functionally mature, human cell-based liver model exhibiting human responses in toxicity prediction and drug evaluation is urgently needed for pre-clinical drug development. Here, we develop a novel human pluripotent stem cell-derived hepatocyte-like liver organoid that is critically advanced in terms of its generation method, functional performance, and application technologies. Our organoids can contribute to the better understanding of liver development and regeneration, and provide insights for metabolic studies and disease modeling, as well as toxicity assessments and drug screening for personalized medicine.

In vitro hepatotoxicity of Petasites hybridus extract (Ze 339) depends on the concentration, the cytochrome activity of the cell system, and the species used

Ze 339, a CO₂ extract prepared from the leaves of Petasites hybridus, possesses antispasmodic and anti‐inflammatory effects and is proven to be effective in the treatment of allergic rhinitis. To study possible hepatotoxic effects of Ze 339, its main constituents and metabolites, a series of in vitro investigations were performed. Furthermore, different reconstituted fractions of extract (petasins and fatty acid fraction) were examined in three in vitro test systems using hepatocytes: Two human cell lines, with lower and higher activity of cytochrome P450 enzymes (HepG2, HepaRG) as well as a rodent cell line with high cytochrome P450 activity (H‐4‐II‐E), were used. Metabolic activity, assessed by the WST‐1 assay, was chosen as indicator of cytotoxicity. To assess potential bioactivation of Ze 339 compounds, metabolic experiments using S9 fractions from rats, dogs, and humans and isolated cytochromes (human/rat) were performed, and the formation of reactive metabolites was assessed by measuring cellular concentrations of glutathione and glutathione disulphide.

Our data revealed that the cytotoxicity of Ze 339, its single constituents, and main metabolites depends on the concentration, the cytochrome activity of the cell system, and the species used.

Validation of in vitro methods for human cytochrome P450 enzyme induction: Outcome of a multi-laboratory study

CYP enzyme induction is a sensitive biomarker for phenotypic metabolic competence of in vitro test systems; it is a key event associated with thyroid disruption, and a biomarker for toxicologically relevant nuclear receptor-mediated pathways. This paper summarises the results of a multi-laboratory validation study of two in vitro methods that assess the potential of chemicals to induce cytochrome P450 (CYP) enzyme activity, in particular CYP1A2, CYP2B6, and CYP3A4. The methods are based on the use of cryopreserved primary human hepatocytes (PHH) and human HepaRG cells. The validation study was coordinated by the European Union Reference Laboratory for Alternatives to Animal Testing of the European Commission's Joint Research Centre and involved a ring trial among six laboratories. The reproducibility was assessed within and between laboratories using a validation set of 13 selected chemicals (known human inducers and non-inducers) tested under blind conditions. The ability of the two methods to predict human CYP induction potential was assessed. Chemical space analysis confirmed that the selected chemicals are broadly representative of a diverse range of chemicals. The two methods were found to be reliable and relevant in vitro tools for the assessment of human CYP induction, with the HepaRG method being better suited for routine testing. Recommendations for the practical application of the two methods are proposed.

Advanced Organ-on-a-Chip Devices to Investigate Liver Multi-Organ Communication: Focus on Gut, Microbiota and Brain

The liver is a key organ that can communicate with many other districts of the human body. In the last few decades, much interest has focused on the interaction between the liver and the gut microbiota, with their reciprocal influence on biosynthesis pathways and the integrity the intestinal epithelial barrier. Dysbiosis or liver disorders lead to0 epithelial barrier dysfunction, altering membrane permeability to toxins. Clinical and experimental evidence shows that the permeability hence the delivery of neurotoxins such as LPS, ammonia and salsolinol contribute to neurological disorders. These findings suggested multi-organ communication between the gut microbiota, the liver and the brain. With a view to in vitro modeling this liver-based multi-organ communication, we describe the latest advanced liver-on-a-chip devices and discuss the need for new organ-on-a-chip platforms for in vitro modeling the in vivo multi-organ connection pathways in physiological and pathological situations.

Targeting CYP4A attenuates hepatic steatosis in a novel multicellular organotypic liver model

Background

Non-alcoholic fatty liver disease (NAFLD) begins as simple hepatic steatosis, but further progress to chronic liver diseases results in severe liver damage and hepatic failure. However, therapeutic options are scarce due to the lack of reliable human in vitro liver models for understanding disease progression mechanisms and developing therapies.

Results

We describe here a novel method for generating 3D hepatic spheroids using HepaRG cells, vascular endothelial cells, and mesenchymal stem cells cultured on a thick layer of soft matrix in a narrow conical tube; this method improved self-organization efficiency and functional competence. We further developed a 3D hepatic steatosis model with excess glucose and palmitate, accurately recapitulating steatosis phenotypes such as neutral lipid accumulation, enhanced expression of lipogenesis and gluconeogenesis markers, increased intracellular triglyceride content, and reduced glucose uptake. The expression and activity of cytochrome P450 4A (CYP4A), a hepatic glucose and lipid homeostasis enzyme, that is highly expressed in liver tissues from NAFLD patients, was induced in our in vitro steatosis model, and inhibiting CYP4A with the selective inhibitor HET0016 or a specific siRNA ameliorated steatosis-related pathology through reduced ER stress and improved insulin signaling.

Conclusions

We provide here a novel 3D human cell-based hepatic model that can be easily generated and reliably simulate hepatic steatosis pathology. We have experimentally validated its potential for target validation and drug evaluation by focusing on CYP4A, which may serve as a translational platform for drug development.

Development of an in vitro cholestatic drug-induced liver injury evaluation system using HepG2-hNTCP-C4 cells in sandwich configuration

Toxicological approaches in screening drugs that cause drug-induced liver injury (DILI) are urgently needed to reduce the risk of developing DILI and avoid immense costs resulting from late-stage drug withdrawal from clinical trials. Cholestatic DILI is characterized by bile acid (BA) accumulation in hepatocytes, typically caused by drug-induced inhibition of important bile transporters, such as bile salt export pump (BSEP) and multidrug resistance-associated protein 2/3/4 (MRP2/3/4). Therefore, NTCP expression is essential for construction of an in vitro hepatocellular toxicity evaluation system. Here, we investigated whether sandwich-cultured HepG2-hNTCP-C4 (SCHepG2-hNTCP-C4) cells were applicable for evaluation of cholestatic DILI. In SCHepG2-hNTCP-C4 cells, NTCP and MRP2/4 expression levels were comparable to those in human primary hepatocytes; however, BSEP expression was low. In addition, the substrates tauro-nor-THCA-24 DBD and CDF confirmed the functionality of NTCP and MRP2, respectively. When 22 known hepatotoxins were exposed to BAs to evaluate cholestatic DILI, cytotoxicity in SCHepG2-hNTCP-C4 cells was more frequent than that in SCHepG2 cells. Thus, SCHepG2-hNTCP-C4 cells may be useful preclinical screening tools to predict the risk of cholestatic DILI induced by drug candidates. However, further studies are needed to determine why the cholestatic cytotoxicity of some compounds would be still insufficient in SCHepG2-hNTCP-C4 cells.

Hepatitis B Virus-Hepatocyte Interactions and Innate Immune Responses: Experimental Models and Molecular Mechanisms

Chronic hepatitis B virus (HBV) infection is a major cause of liver disease and cancer worldwide. While current therapeutic approaches can efficiently control viral infection, efficient curative antivirals are absent. The understanding of virus-hepatocyte interactions and sensing of viral infection is an important prerequisite for the development of novel antiviral therapies for cure. Hepatocyte intrinsic innate immunity provides a rapid first line of defense to combat viral infection through the upregulation of antiviral and inflammatory genes. However, the functional relevance of many of these antiviral signaling pathways in the liver and their role in HBV pathogenesis is still only partially understood. The recent identification of intracellular RNA and DNA sensing pathways and their involvement in disease biology, including viral pathogenesis and carcinogenesis, is currently transforming our understanding of virus-host interactions. Here the authors review the current knowledge on intrinsic antiviral innate immune responses including the role of viral nucleic acid sensing pathways in the liver. Since HBV has been designated as a "stealth virus," the study of the impact of HBV on signaling pathways in the hepatocyte is of significant interest to understand viral pathogenesis. Characterizing the mechanism underlying these HBV-host interactions and targeting related pathways to enhance antiviral innate responses may open new strategies to trigger noncytopathic clearance of covalently closed circular DNA to ultimately cure patients with chronic HBV infection.

Plasma exosomes exacerbate alcohol- and acetaminophen-induced toxicity via CYP2E1 pathway

Cellular CYP2E1 is well-known to mediate alcohol- (ALC) and acetaminophen- (APAP) induced toxicity in hepatic and extra-hepatic cells. Although exosomes have been gaining importance in understanding mechanism of intra- and inter-cellular communication, the functional role of drug metabolizing cytochrome P450 (CYP) enzymes in human plasma exosomes are yet to be explored. In our previous study, we reported that human plasma-derived exosomes contain substantial level of functional CYP2E1. In the current project, we investigated the potential role of plasma exosomal CYP2E1 in mediating ALC- and APAP-induced toxicity. We treated hepatic and extra-hepatic (monocytic) cells with exosomes ± ALC/APAP. We observed that the plasma exosomes containing CYP2E1 cargo further exacerbate ALC- and APAP-induced toxicity in both hepatic and monocytic cells. Further, both exosomes- and ALC/APAP-induced toxicity was reduced/abolished by a selective inhibitor of CYP2E1 enzyme activity (diallyl ether). However, only ALC-, but not exosome-induced toxicity was reduced/abolished by CYP2E1 siRNA. These findings suggest that ALC/APAP-induced toxicity in the presence of exosomes are mediated, at least in part, by CYP2E1 enzyme. To validate these in vitro findings, we characterized plasma exosomal contents in a binge-drinking animal model and their effect on ALC/APAP-induced toxicity in monocytic cells. Our results showed that ALC exposure caused a significant induction of the plasma exosomal CYP2E1 level in a binge drinking murine model. These exosomes containing increased levels of CYP2E1 caused significant toxicity in monocytic cells compared to exosomes derived from control mice. Overall, our results showed an important role of exosomal CYP2E1 in exacerbating ALC- and APAP-induced toxicity. The study is significant in terms of understanding the role of exosomal CYP2E1 in cell-cell interactions, and their effects on drug-induced toxicity.

In-Depth Proteome Analysis Highlights HepaRG Cells as a Versatile Cell System Surrogate for Primary Human Hepatocytes

Of the hepatic cell lines developed for in vitro studies of hepatic functions as alternatives to primary human hepatocytes, many have lost major liver-like functions, but not HepaRG cells. The increasing use of the latter worldwide raises the need for establishing the reference functional status of early biobanked HepaRG cells. Using deep proteome and secretome analyses, the levels of master regulators of the hepatic phenotype and of the structural elements ensuring biliary polarity were found to be close to those in primary hepatocytes. HepaRG cells proved to be highly differentiated, with functional mitochondria, hepatokine secretion abilities, and an adequate response to insulin. Among differences between primary human hepatocytes and HepaRG cells, the factors that possibly support HepaRG transdifferentiation properties are discussed. The HepaRG cell system thus appears as a robust surrogate for primary hepatocytes, which is versatile enough to study not only xenobiotic detoxification, but also the control of hepatic energy metabolism, secretory function and disease-related mechanisms.

Stem-cell based organ-on-a-chip models for diabetes research

Diabetes mellitus (DM) ranks among the severest global health concerns of the 21st century. It encompasses a group of chronic disorders characterized by a dysregulated glucose metabolism, which arises as a consequence of progressive autoimmune destruction of pancreatic beta-cells (type 1 DM), or as a result of beta-cell dysfunction combined with systemic insulin resistance (type 2 DM). Human cohort studies have provided evidence of genetic and environmental contributions to DM; yet, these studies are mostly restricted to investigating statistical correlations between DM and certain risk factors. Mechanistic studies, on the other hand, aimed at re-creating the clinical picture of human DM in animal models. A translation to human biology is, however, often inadequate owing to significant differences between animal and human physiology, including the species-specific glucose regulation. Thus, there is an urgent need for the development of advanced human in vitro models with the potential to identify novel treatment options for DM. This review provides an overview of the technological advances in research on DM-relevant stem cells and their integration into microphysiological environments as provided by the organ-on-a-chip technology.

Cell-printed 3D liver-on-a-chip possessing a liver microenvironment and biliary system

To overcome the drawbacks of in vitro liver testing during drug development, numerous liver-on-a-chip models have been developed. However, current liver-on-a-chip technologies are labor-intensive, lack extracellular matrix (ECM) essential for liver cells, and lack a biliary system essential for excreting bile acids, which contribute to intestinal digestion but are known to be toxic to hepatocytes. Therefore, fabrication methods for development of liver-on-a-chip models that overcome the above limitations are required. Cell-printing technology enables construction of complex 3D structures with multiple cell types and biomaterials. We used cell-printing to develop a 3D liver-on-a-chip with multiple cell types for co-culture of liver cells, liver decellularized ECM bioink for a 3D microenvironment, and vascular/biliary fluidic channels for creating vascular and biliary systems. A chip with a biliary fluidic channel induced better biliary system creation and liver-specific gene expression and functions compared to a chip without a biliary system. Further, the 3D liver-on-a-chip showed better functionalities than 2D or 3D cultures. The chip was evaluated using acetaminophen and it showed an effective drug response. In summary, our results demonstrate that the 3D liver-on-a-chip we developed is promising in vitro liver test platform for drug discovery.

mRNA Expression and Activity of Nucleoside Transporters in Human Hepatoma HepaRG Cells

The HepaRG cell line is a highly differentiated human hepatoma cell line, displaying the expression of various drug transporters. However, functional expression of nucleoside transporters remains poorly characterized in HepaRG cells, although these transporters play a key role in hepatic uptake of antiviral and anticancer drugs. The present study was, therefore, designed to characterize the expression, activity and regulation of equilibrative (ENT) and concentrative (CNT) nucleoside transporter isoforms in differentiated HepaRG cells. These cells were found to exhibit a profile of nucleoside transporter mRNAs similar to that found in human hepatocytes, i.e., notable expression of ENT1, ENT2 and CNT1, with very low or no expression of CNT2 and CNT3. ENT1 activity was, next, demonstrated to be the main uridine transport activity present in HepaRG cells, like in cultured human hepatocytes. Various physiological factors, such as protein kinase C (PKC) activation or treatment by inflammatory cytokines or hepatocyte growth factor (HGF), were additionally found to regulate expression of ENT1, ENT2 and CNT1; PKC activation and HGF notably concomitantly induced mRNA expression and activity of ENT1 in HepaRG cells. Overall, these data suggest that HepaRG cells may be useful for analyzing cellular pharmacokinetics of nucleoside-like drugs in human hepatic cells, especially of those handled by ENT1.

Functional polarization of human hepatoma HepaRG cells in response to forskolin

HepaRG is an original human hepatoma cell line, acquiring highly differentiated hepatic features when exposed to dimethylsulfoxide (DMSO). To search alternatives to DMSO, which may exert some toxicity, we have analyzed the effects of forskolin (FSK), a cAMP-generating agent known to favor differentiation of various cell types. FSK used at 50 µM for 3 days was found to promote polarization of high density-plated HepaRG cells, i.e., it markedly enhanced the formation of functional biliary canaliculi structures. It also increased expressions of various hepatic markers, including those of cytochrome P-450 (CYP) 3A4, of drug transporters like NTCP, OATP2B1 and BSEP, and of metabolism enzymes like glucose 6-phosphatase. In addition, FSK-treated HepaRG cells displayed enhanced activities of CYP3A4, NTCP and OATPs when compared to untreated cells. These polarizing/differentiating effects of FSK were next shown to reflect not only the generation of cAMP, but also the activation of the xenobiotic sensing receptors PXR and FXR by FSK. Co-treatment of HepaRG cells by the cAMP analog Sp-5,6-DCl-cBIMPS and the reference PXR agonist rifampicin reproduced the polarizing effects of FSK. Therefore, FSK may be considered as a relevant alternative to DMSO for getting polarized and differentiated HepaRG cells, notably for pharmacological and toxicological studies.

Human cytochrome P450 expression in bacteria: Whole-cell high-throughput activity assay for CYP1A2, 2A6 and 3A4

Cytochrome P450s (CYPs) are key enzymes involved in drug and xenobiotic metabolism. A wide array of in vitro methodologies, including recombinant sources, are currently been used to assess CYP catalysis, to identify the metabolic profile of compounds, potential drug-drug interactions, protein-protein interactions in the CYP enzyme complex and the role of polymorphic enzymes. We report here on a bacterial whole-cells high-throughput method for the activity evaluation of human CYP1A2, 2A6, and 3A4, when sustained by NADPH cytochrome P450 oxidoreductase (CPR), in the absence or presence of cytochrome b₅ (CYB5). This new assay consists of a microplate real-time fluorometric method, with direct measurement of metabolite formation, in a suspension of Escherichia coli BTC-CYP bacteria, a human CYP competent tester strain when incubated with specific fluorogenic substrates. Overall, the maximum turnover (k_cat) velocities of the three human CYPs resulting from the whole-BTC cells assays were similar to those obtained when applying the corresponding standard reference membrane fractions assays. CYP activity screening with co-expression of CYB5 suggests an enhancing effect of CYB5 on the k_cat of specific isoforms, when using the whole-BTC cells assay. Our results demonstrate that this new approach can offer an efficient high-throughput method for screening of CYP1A2, 2A6 and 3A4 activity and can be potentially applicable for other human CYPs. This can be of particular use for timely and efficient screening of chemical libraries or mutant libraries of CYP enzyme complex proteins, without the necessity for labor intensive isolation of subcellular fractions.

Effects of Panax Notoginseng Saponins on Esterases Responsible for Aspirin Hydrolysis In Vitro

Herb–drug interactions strongly challenge the clinical combined application of herbs and drugs. Herbal products consist of complex pharmacological-active ingredients and perturb the activity of drug-metabolizing enzymes. Panax notoginseng saponins (PNS)-based drugs are often combined with aspirin in vascular disease treatment in China. PNS was found to exhibit inhibitory effects on aspirin hydrolysis using Caco-2 cell monolayers. In the present study, a total of 22 components of PNS were separated and identified by UPLC-MS/MS. Using highly selective probe substrate analysis, PNS exerted robust inhibitory potency on human carboxylesterase 2 (hCE2), while had a minor influence on hCE1, butyrylcholinesterase (BChE) and paraoxonase (PON). These effects were also verified through molecular docking analysis. PNS showed a concentration-dependent inhibitory effect on hydrolytic activity of aspirin in HepaRG cells. The protein level of hCE2 in HepaRG cells was suppressed after PNS treatment, while the level of BChE or PON1 in the extracellular matrix were elevated after PNS treatment. Insignificant effect was observed on the mRNA expression of the esterases. These findings are important to understand the underlying efficacy and safety of co-administration of PNS and aspirin in clinical practice.

Innovation for hepatotoxicity in vitro research models: A review

Many categories of drugs can induce hepatotoxicity, so improving the prediction of toxic drugs is important. In vitro models using human hepatocytes are more accurate than in vivo animal models. Good in vitro models require an abundance of metabolic enzyme activities and normal cellular polarity. However, none of the in vitro models can completely simulate hepatocytes in the human body. There are two ways to overcome this limitation: enhancing the metabolic function of hepatocytes and changing the cultural environment. In this review, we summarize the current state of research, including the main characteristics of in vitro models and their limitations, as well as improved technology and developmental prospects. We hope that this review provides some new ideas for hepatotoxicity research.

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.

Relative potency of fifteen pyrrolizidine alkaloids to induce DNA damage as measured by micronucleus induction in HepaRG human liver cells

Plant-based 1,2-unsaturated Pyrrolizidine Alkaloids (PAs) can be found as contaminants in foods like teas, herbs and honey. PAs are responsible for liver genotoxicity/carcinogenicity following metabolic activation, making them a relevant concern for safety assessment. Current regulatory risk assessments take a precautionary approach and assume all PAs are as potent as the known most potent representatives: lasiocarpine and riddelliine. Our study investigated whether genotoxicity potency differed as a consequence of structural differences, assessing micronuclei in vitro in HepaRG cells which express metabolising enzymes at levels similar to primary human hepatocytes. Benchmark Dose (BMD) analysis was used to calculate the critical effect dose for 15 PAs representing 6 structural classes. When BMD confidence intervals were used to rank PAs, lasiocarpine was the most potent PA and plotted distinctly from all other PAs examined. PA-N-oxides were least potent, notably less potent than their corresponding parent PA's. The observed genotoxic potency compared favorably with existing in vitro data when metabolic competency was considered. Although further consideration of biokinetics will be needed to develop a robust understanding of relative potencies for a realistic risk assessment of PA mixtures, these data facilitate understanding of their genotoxic potencies and affirm that not all PAs are created equal.

Role of Cytochrome P450 Enzymes in the Metabolic Activation of Tyrosine Kinase Inhibitors

Tyrosine kinase inhibitors are a rapidly expanding class of molecular targeted therapies for the treatment of various types of cancer and other diseases. An increasing number of clinically important small molecule tyrosine kinase inhibitors have been shown to undergo cytochrome P450-mediated bioactivation to form chemically reactive, potentially toxic products. Metabolic activation of tyrosine kinase inhibitors is proposed to contribute to the development of serious adverse reactions, including idiosyncratic hepatotoxicity. This article will review recent findings and ongoing studies to elucidate the link between drug metabolism and tyrosine kinase inhibitor-associated hepatotoxicity.

Emodin induces apoptosis in human hepatocellular carcinoma HepaRG cells via the mitochondrial caspase‑dependent pathway

Emodin-induced hepatotoxicity in vivo and in vitro has been gaining increasing attention. However, the exact molecular pathways underlying these effects remain poorly clarified. The aim of the present study was to evaluate the cytotoxic effect of emodin on HepaRG cells and to define the underlying mechanism. The results demonstrated that emodin evidently inhibited HepaRG cell growth in a dose- and time-dependent manner by blocking cell cycle progression in the S and G2/M phase and by inducing apoptosis. Emodin treatment also resulted in generation of reactive oxygen species (ROS), which abrogated mitochondrial membrane potential (MMP). The above effects were all suppressed by antioxidants, such as N-acetylcysteine (NAC). Further studies by western blot analysis howed that emodin upregulated p53, p21, Bax, cyclin E, cleaved caspase-3, 8 and 9, and cleaved poly(ADP-ribose)polymerase (PARP). However, the protein expression of Bcl-2, cyclin A and CDK2 was downregulated. Taken together, our results suggest that emodin induces apoptosis via the mitochondrial apoptosis pathway through cell cycle arrest and ROS generation in HepaRG cells.