Extended lifespan and improved genome stability in HepaRG-derived cell lines through reprogramming by high-density stress.

The characteristics and fate of cancer cells partly depend on their environmental stiffness, i.e., the local mechanical cues they face. HepaRG progenitors are liver carcinoma cells exhibiting transdifferentiation properties; however, the underlying mechanisms remain unknown. To evaluate the impact of external physical forces mimicking the tumor microenvironment, we seeded them at very high density for 20 h, keeping the cells round and unanchored to the substrate. Applied without corticoids, spatial confinement due to very high density induced reprogramming of HepaRG cells into stable replicative stem-like cells after replating at normal density. Redifferentiation of these stem-like cells into cells very similar to the original HepaRG cells was then achieved using the same stress but in the presence of corticoids. This demonstrates that the cells retained the memory required to run the complete hepatic differentiation program, after bypassing the Hayflick limit twice. We show that physical stress improved chromosome quality and genomic stability, through greater efficiency of DNA repair and restoration of telomerase activity, thus enabling cells to escape progression to a more aggressive cancer state. We also show the primary importance of high-density seeding, possibly triggering compressive stress, in these processes, rather than that of cell roundness or intracellular tensional signals. The HepaRG-derived lines established here considerably extend the lifespan and availability of this surrogate cell system for mature human hepatocytes. External physical stress is a promising way to create a variety of cell lines, and it paves the way for the development of strategies to improve cancer prognosis.

Setup and Use of HepaRG Cells in Cholestasis Research.

Since HepaRG cells can differentiate into well-polarized mature hepatocyte-like cells that synthesize, conjugate, and secrete bile acids, they represent an appropriate surrogate to primary human hepatocytes for investigations on drug-induced cholestasis mechanisms. In this chapter, culture conditions for obtaining HepaRG hepatocytes and the main methods used to detect cholestatic potential of drugs are described. Assays for evaluation of bile canaliculi dynamics and morphology are mainly based on time-lapse and phase-contrast microscopy analysis. Bile acid uptake, trafficking, and efflux are investigated using fluorescent probes. Individual bile acids are quantified in both culture media and cell layers by high-pressure liquid chromatography/tandem mass spectrometry. Preferential cellular accumulation of toxic hydrophobic bile acids is easily evidenced when exogenous primary and secondary bile acids are added to the culture medium.

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.

Predictive Value of Cellular Accumulation of Hydrophobic Bile Acids As a Marker of Cholestatic Drug Potential.

Drug-induced cholestasis is mostly intrahepatic and characterized by alterations of bile canaliculi dynamics and morphology as well as accumulation of bile acids (BAs) in hepatocytes. However, little information exists on first changes in BA content and profile induced by cholestatic drugs in human liver. In this study, we aimed to analyze the effects of a large set of cholestatic and noncholestatic drugs in presence of physiological serum concentrations and 60-fold higher levels of 9 main BAs on cellular accumulation of BAs using HepaRG hepatocytes. BAs were measured in cell layers (cells + bile canaliculi) and culture media using high-pressure liquid chromatography coupled with tandem mass spectrometry after 24 h-treatment. Comparable changes in total and individual BA levels were observed in cell layers and media from control and noncholestatic drug-treated cultures: unconjugated BAs were actively amidated and lithocholic acid (LCA) was entirely sulfated. In contrast, cellular accumulation of LCA and in addition, of the 2 other hydrophobic BAs, chenodeoxycholic acid and deoxycholic acid, was evidenced only with cholestatic compounds in presence of BA mixtures at normal and 60-fold serum levels, respectively, suggesting that LCA was the first BA to accumulate. Cellular accumulation of hydrophobic BAs was associated with inhibition of their amidation and for LCA, its sulfation. In conclusion, these results demonstrated that cellular accumulation of unconjugated hydrophobic BAs can be caused by various cholestatic drugs in human hepatocytes and suggest that their cellular detection, especially that of LCA, could represent a new strategy for evaluation of cholestatic potential of drugs and other chemicals.

Expansion of human primary hepatocytes in vitro through their amplification as liver progenitors in a 3D organoid system.

Despite decades of investigation on the proliferation of adult human primary hepatocytes, their expansion in vitro still remains challenging. To later be able to consider hepatocytes as a cell therapy alternative or bridge to liver transplantation, dramatically impeded by a shortage in liver donors, the first step is having an almost unlimited source of these cells. The banking of transplantable hepatocytes also implies a protocol for their expansion that can be compatible with large-scale production. We show that adult human primary hepatocytes when grown in 3D organoids are easily amplified, providing a substantial source of functional hepatocytes ready for transplantation. Following their plating, differentiated human hepatocytes are amplified during a transient and reversible step as liver progenitors, and can subsequently be converted back to mature differentiated hepatocytes. The protocol we propose is not only compatible with automated and high-throughput cell culture systems, thanks to the expansion of hepatocytes in suspension, but also guarantees the generation of a high number of functional cells from the same patient sample, with a relatively easy set up.

Endoplasmic reticulum stress precedes oxidative stress in antibiotic-induced cholestasis and cytotoxicity in human hepatocytes.

Endoplasmic reticulum (ER) stress has been associated with various drug-induced liver lesions but its participation in drug-induced cholestasis remains unclear. We first aimed at analyzing liver damage caused by various hepatotoxic antibiotics, including three penicillinase-resistant antibiotics (PRAs), i.e. flucloxacillin, cloxacillin and nafcillin, as well as trovafloxacin, levofloxacin and erythromycin, using human differentiated HepaRG cells and primary hepatocytes. All these antibiotics caused early cholestatic effects typified by bile canaliculi dilatation and reduced bile acid efflux within 2h and dose-dependent enhanced caspase-3 activity within 24h. PRAs induced the highest cholestatic effects at non cytotoxic concentrations. Then, molecular events involved in these lesions were analyzed. Early accumulation of misfolded proteins revealed by thioflavin-T fluorescence and associated with phosphorylation of the unfolded protein response sensors, eIF2α and/or IRE1α, was evidenced with all tested hepatotoxic antibiotics. Inhibition of ER stress markedly restored bile acid efflux and prevented bile canaliculi dilatation. Downstream of ER stress, ROS were also generated with high antibiotic concentrations. The protective HSP27-PI3K-AKT signaling pathway was activated only in PRA-treated cells and its inhibition increased ROS production and aggravated caspase-3 activity. Overall, our results demonstrate that (i) various antibiotics reported to cause cholestasis and hepatocellular injury in the clinic can also induce such effects in in vitro human hepatocytes; (ii) PRAs cause the strongest cholestatic effects in the absence of cytotoxicity; (iii) cholestatic features occur early through ER stress; (iv) cytotoxic lesions are observed later through ER stress-mediated ROS generation; and (v) activation of the HSP27-PI3K-AKT pathway protects from cytotoxic damage induced by PRAs only.

Progressive and Preferential Cellular Accumulation of Hydrophobic Bile Acids Induced by Cholestatic Drugs Is Associated with Inhibition of Their Amidation and Sulfation.

Drug-induced intrahepatic cholestasis is characterized by cellular accumulation of bile acids (BAs), whose mechanisms remain poorly understood. The present study aimed to analyze early and progressive alterations of BA profiles induced by cyclosporine A, chlorpromazine, troglitazone, tolcapone, trovafloxacin, and tacrolimus after 4-hour, 24-hour, and 6-day treatments of differentiated HepaRG cells. In BA-free medium, the potent cholestatic drugs cyclosporine A, chlorpromazine, and troglitazone reduced endogenous BA synthesis after 24 hours, whereas the rarely cholestatic drugs tolcapone, trovafloxacin, and tacrolimus reduced BA synthesis only after 6 days. In the presence of physiologic serum BA concentrations, cyclosporine A, chlorpromazine, and troglitazone induced early and preferential cellular accumulation of unconjugated lithocholic, deoxycholic, and chenodeoxycholic acids that increased 8- to 12-fold and 47- to 50-fold after 24 hours and 6 days, respectively. Accumulation of these hydrophobic BAs resulted from strong inhibition of amidation, and in addition, for lithocholic acid reduction of its sulfoconjugation, and was associated with variable alterations of uptake and efflux transporters. Trovafloxacin also caused BA accumulation, especially after 6 days, whereas tolcapone and tacrolimus were still without effect. However, when exogenous BAs were added to the medium at cholestatic serum concentrations, a 6-day treatment with all drugs resulted in cellular BA accumulation with higher folds of chenodeoxycholic and lithocholic acids. At the tested concentration, tolcapone had the lowest effect. These results bring the first demonstration that major cholestatic drugs can cause preferential and progressive in vitro cellular accumulation of unconjugated toxic hydrophobic BAs and bring new insights into mechanisms involved in drug-induced cellular accumulation of toxic BAs.

Penicillinase-resistant antibiotics induce non-immune-mediated cholestasis through HSP27 activation associated with PKC/P38 and PI3K/AKT signaling pathways.

The penicillinase-resistant antibiotics (PRAs), especially the highly prescribed flucloxacillin, caused frequent liver injury via mechanisms that remain largely non-elucidated. We first showed that flucloxacillin, independently of cytotoxicity, could exhibit cholestatic effects in human hepatocytes in the absence of an immune reaction, that were typified by dilatation of bile canaliculi associated with impairment of the Rho-kinase signaling pathway and reduced bile acid efflux. Then, we analyzed the sequential molecular events involved in flucloxacillin-induced cholestasis. A crucial role of HSP27 by inhibiting Rho-kinase activity was demonstrated using siRNA and the specific inhibitor KRIBB3. HSP27 activation was dependent on the PKC/P38 pathway, and led downstream to activation of the PI3K/AKT pathway. Other PRAs induced similar cholestatic effects while non PRAs were ineffective. Our results demonstrate that PRAs can induce cholestatic features in human hepatocytes through HSP27 activation associated with PKC/P38 and PI3K/AKT signaling pathways and consequently support the conclusion that in clinic they can cause a non-immune-mediated cholestasis that is not restricted to patients possessing certain genetic determinants.

From the Cover: MechanisticInsights in Cytotoxic and Cholestatic Potential of the Endothelial Receptor Antagonists Using HepaRG Cells.

Several endothelin receptor antagonists (ERAs) have been developed for the treatment of pulmonary arterial hypertension (PAH). Some of them have been related to clinical cases of hepatocellular injury (sitaxentan [SIT]) and/or cholestasis (bosentan [BOS]). We aimed to determine if ambrisentan (AMB) and macitentan (MAC), in addition to BOS and SIT, could potentially cause liver damage in man by use of human HepaRG cells. Our results showed that like BOS, MAC-induced cytotoxicity and cholestatic disorders characterized by bile canaliculi dilatation and impairment of myosin light chain kinase signaling. Macitentan also strongly inhibited taurocholic acid and carboxy-2',7'-dichlorofluorescein efflux while it had a much lower inhibitory effect on influx activity compared to BOS and SIT. Moreover, these three drugs caused decreased intracellular accumulation and parallel increased levels of total bile acids (BAs) in serum-free culture media. In addition, all drugs except AMB variably deregulated gene expression of BA transporters. In contrast, SIT was hepatotoxic without causing cholestatic damage, likely via the formation of reactive metabolites and AMB was not hepatotoxic. Together, our results show that some ERAs can be hepatotoxic and that the recently marketed MAC, structurally similar to BOS, can also cause cholestatic alterations in HepaRG cells. The absence of currently known or suspected cases of cholestasis in patients suffering from PAH treated with MAC is rationalized by the lower therapeutic doses and Cmax, and longer receptor residence time compared to BOS.

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

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

Differential sensitivity of metabolically competent and non-competent HepaRG cells to apoptosis induced by diclofenac combined or not with TNF-α.

The role of reactive metabolites and inflammatory stress has been largely evoked in idiosyncratic hepatotoxicity of diclofenac (DCF); however mechanisms remain poorly understood. We aimed to evaluate the influence of liver cell phenotype on the hepatotoxicity of DCF combined or not with TNF-α using differentiated and undifferentiated HepaRG cells, and for comparison, HepG2 cells. Our results demonstrate that after a 24h-treatment metabolizing HepaRG cells were less sensitive to DCF than their undifferentiated non-metabolizing counterparts as shown by lower oxidative and endoplasmic reticulum stress responses and lower activation of caspase 9. Differentiated HepaRG cells were also less sensitive than HepG2 cells. Their lower sensitivity to DCF was related to their high content in glutathione transferases. DCF-induced apoptotic effects were potentiated by TNF-α only in death receptor-expressing differentiated HepaRG and HepG2 cells and were associated with marked activation of caspase 8. TNF-α co-treatment did not aggravate DCF-induced cholestatic features. Altogether, our results demonstrate that (i) lower sensitivity to DCF of differentiated HepaRG cells compared to their non-metabolically active counterparts was related to their high detoxifying capacity, giving support to the higher sensitivity of nonhepatic tissues than liver to this drug; (ii) TNF-α-potentiation of DCF cytotoxicity occurred only in death receptor-expressing cells.

Rho-kinase/myosin light chain kinase pathway plays a key role in the impairment of bile canaliculi dynamics induced by cholestatic drugs.

Intrahepatic cholestasis represents a frequent manifestation of drug-induced liver injury; however, the mechanisms underlying such injuries are poorly understood. In this study of human HepaRG and primary hepatocytes, we found that bile canaliculi (BC) underwent spontaneous contractions, which are essential for bile acid (BA) efflux and require alternations in myosin light chain (MLC2) phosphorylation/dephosphorylation. Short exposure to 6 cholestatic compounds revealed that BC constriction and dilation were associated with disruptions in the ROCK/MLCK/myosin pathway. At the studied concentrations, cyclosporine A and chlorpromazine induced early ROCK activity, resulting in permanent MLC2 phosphorylation and BC constriction. However, fasudil reduced ROCK activity and caused rapid, substantial and permanent MLC2 dephosphorylation, leading to BC dilation. The remaining compounds (1-naphthyl isothiocyanate, deoxycholic acid and bosentan) caused BC dilation without modulating ROCK activity, although they were associated with a steady decrease in MLC2 phosphorylation via MLCK. These changes were associated with a common loss of BC contractions and failure of BA clearance. These results provide the first demonstration that cholestatic drugs alter BC dynamics by targeting the ROCK/MLCK pathway; in addition, they highlight new insights into the mechanisms underlying bile flow failure and can be used to identify new predictive biomarkers of drug-induced cholestasis.

Novel optimization of valmerins (tetrahydropyrido[1,2-a]isoindolones) as potent dual CDK5/GSK3 inhibitors.

An efficient synthetic strategy able to modulate the structure of the tetrahydropyridine isoindolone (Valmerin) skeleton was developed. A library of more than 30 novel final structures was generated. Biological activities on CDK5 and GSK3 as well as cellular effects on cancer cell lines were measured for each novel compound. Additionally to support the SAR, a docking study was performed. A potent GSK3/CDK5 dual inhibitor (37, IC50 CDK5/GSK3 35/7 nM) was obtained. Best antiproliferative effects were obtained on lung and prostate cell lines with IC50 = 20 nM.

Hepatic differentiation of human pluripotent stem cells on human liver progenitor HepaRG-derived acellular matrix.

Human hepatocytes are extensively needed in drug discovery and development. Stem cell-derived hepatocytes are expected to be an improved and continuous model of human liver to study drug candidates. Generation of endoderm-derived hepatocytes from human pluripotent stem cells (hPSCs), including human embryonic stem cells and induced pluripotent stem cells, is a complex, challenging process requiring specific signals from soluble factors and insoluble matrices at each developmental stage. In this study, we used human liver progenitor HepaRG-derived acellular matrix (ACM) as a hepatic progenitor-specific matrix to induce hepatic commitment of hPSC-derived definitive endoderm (DE) cells. The DE cells showed much better attachment to the HepaRG ACM than other matrices tested and then differentiated towards hepatic cells, which expressed hepatocyte-specific makers. We demonstrate that Matrigel overlay induced hepatocyte phenotype and inhibited biliary epithelial differentiation in two hPSC lines studied. In conclusion, our study demonstrates that the HepaRG ACM, a hepatic progenitor-specific matrix, plays an important role in the hepatic differentiation of hPSCs.

Functional polymer-dependent 3D culture accelerates the differentiation of HepaRG cells into mature hepatocytes.

AIM: The hepatoma-derived cell line HepaRG is regarded as an in vitro model of drug metabolism because fully differentiated HepaRG cells demonstrate functional metabolic responses comparable to those of primary human hepatocytes. Recently, it was demonstrated that the 3D culture of HepaRG cells enhanced their metabolic functions and toxicological responses. We approached the mechanisms underlying these enhancement effects. METHODS: We compared 2D-cultured HepaRG cells with 3D-cultured HepaRG spheroids in the gene expression patterns and the metabolic functions. In the present study, we performed 3D culture of HepaRG cells using functional polymers (FP). To reveal the in vivo differentiation ability, we transplanted the 3D-cultured HepaRG spheroids into TK-NOG mice. RESULTS: A comparison between 2D and 3D cultures revealed that 3D-cultured HepaRG spheroids demonstrated reductions in bile duct marker expression, accelerated expression of cytochrome P450 3A4, and increases in the ratio of albumin-expressing hepatocytes. Furthermore, catalytic activities of cytochrome P450 3A4 were modified by omeprazole and rifampicin in the 3D-cultured HepaRG spheroids. Transplantation analysis revealed that 3D-cultured HepaRG spheroids formed hepatocyte-like colonies rather than cholangiocytes in vivo. CONCLUSION: Our results indicated that the enhancement of hepatic functions in 3D-cultured HepaRG cells was induced by selective hepatocyte differentiation and accelerated hepatocyte maturation. HepaRG spheroids reproduced the metabolic responses of human hepatocytes. Therefore, FP-dependent 3D-cultured HepaRG cells may serve as an excellent in vitro model for evaluating the hepatic metabolism and toxicity.

Advances in tetrahydropyrido[1,2-a]isoindolone (valmerins) series: Potent glycogen synthase kinase 3 and cyclin dependent kinase 5 inhibitors.

An efficient synthetic strategy was developed to modulate the structure of the tetrahydropyridine isoindolone (Valmerin) skeleton. A library of more than 30 novel final structures was generated. Biological activities on CDK5 and GSK3 as well as cellular effects on cancer cell lines were measured for each novel compound. Additionally docking studies were performed to support medicinal chemistry efforts. A strong GSK3/CDK5 dual inhibitor (38, IC50 GSK3/CDK5 32/84 nM) was obtained. A set of highly selective GSK3 inhibitors was synthesized by fine-tuning structural modifications (29 IC50 GSK3/CDK5 32/320 nM). Antiproliferative effects on cells were correlated with the in vitro kinase activities and the best effects were obtained with lung and colon cell lines.

Two persistent organic pollutants which act through different xenosensors (alpha-endosulfan and 2,3,7,8 tetrachlorodibenzo-p-dioxin) interact in a mixture and downregulate multiple genes involved in human hepatocyte lipid and glucose metabolism.

Individuals, typically, are exposed to mixtures of environmental xenobiotics affecting multiple organs and acting through different xenosensors and pathways in species and cell-type specific manners. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and α-endosulfan are Persistent Organic Pollutants (POPs) and endocrine disruptors which act through different xenosensors and accumulate in the liver. Our objective in this HEALS study was to investigate the effects of the mixture of these POPs on gene expression in a human-derived hepatocyte cell line, HepaRG. We found that, in spite of having largely uncorrelated effects, TCDD and α-endosulfan, when mixed, alter the expression of genes. The combined effects of the mixture of the POPs significantly altered the expression of 100 genes (42 up- and 58 down-regulated) whereas the same concentration of either POP alone did not alter significantly the expression of these genes. For 32 other genes, selective inhibitory crosstalk between TCDD and α-endosulfan was observed. One of the POPs inhibited the effect, on gene expression, of the other in the mixture although, when used alone, that POP did not affect expression. The expression of another 82 genes was significantly altered (up- or down-regulated) by a single POP. The addition of the second POP either increased, in the same direction, the effect on gene expression or had no further effect. At low concentrations (0.2 nM TCDD and 1 µM α-endosulfan), the POPs still had significant effects and the levels of expression of the corresponding proteins were found to be affected for some genes. Particularly striking was the 80-90% inhibition, by the mixture, of the expression of a number of genes of several hepatic intermediary metabolic pathways (glycerolipid metabolism, FXR/RXR activation, glycolysis/gluconeogenesis, retinoid and bile acid biosynthesis), whereas each pollutant alone had only a moderate effect.

Comparative Localization and Functional Activity of the Main Hepatobiliary Transporters in HepaRG Cells and Primary Human Hepatocytes.

The role of hepatobiliary transporters in drug-induced liver injury remains poorly understood. Various in vivo and in vitro biological approaches are currently used for studying hepatic transporters; however, appropriate localization and functional activity of these transporters are essential for normal biliary flow and drug transport. Human hepatocytes (HHs) are considered as the most suitable in vitro cell model but erratic availability and inter-donor functional variations limit their use. In this work, we aimed to compare localization of influx and efflux transporters and their functional activity in differentiated human HepaRG hepatocytes with fresh HHs in conventional (CCHH) and sandwich (SCHH) cultures. All tested influx and efflux transporters were correctly localized to canalicular [bile salt export pump (BSEP), multidrug resistance-associated protein 2 (MRP2), multidrug resistance protein 1 (MDR1), and MDR3] or basolateral [Na(+)-taurocholate co-transporting polypeptide (NTCP) and MRP3] membrane domains and were functional in all models. Contrary to other transporters, NTCP and BSEP were less abundant and active in HepaRG cells, cellular uptake of taurocholate was 2.2- and 1.4-fold and bile excretion index 2.8- and 2.6-fold lower, than in SCHHs and CCHHs, respectively. However, when taurocholate canalicular efflux was evaluated in standard and divalent cation-free conditions in buffers or cell lysates, the difference between the three models did not exceed 9.3%. Interestingly, cell imaging showed higher bile canaliculi contraction/relaxation activity in HepaRG hepatocytes and larger bile canaliculi networks in SCHHs. Altogether, our results bring new insights in mechanisms involved in bile acids accumulation and excretion in HHs and suggest that HepaRG cells represent a suitable model for studying hepatobiliary transporters and drug-induced cholestasis.

Impact of inflammation on chlorpromazine-induced cytotoxicity and cholestatic features in HepaRG cells.

Several factors are thought to be implicated in the occurrence of idiosyncratic adverse drug reactions. The present work aimed to question as to whether inflammation is a determinant factor in hepatic lesions induced by chlorpromazine (CPZ) using the human HepaRG cell line. An inflammation state was induced by a 24-hour exposure to proinflammatory cytokines interleukin-6 (IL-6) and IL-1ß; then the cells were simultaneously treated with CPZ and/or cytokine for 24 hours or daily for 5 days. The inflammatory response was assessed by induction of C-reactive protein and IL-8 transcripts and proteins as well as inhibition of CPZ metabolism and down-regulation of cytochrome 3A4 (CYP3A4) and CYP1A2 transcripts, two major cytochrome P450 (P450) enzymes involved in its metabolism. Most effects of cotreatments with cytokines and CPZ were amplified or only observed after five daily treatments; they mainly included increased cytotoxicity and overexpression of oxidative stress-related genes, decreased Na(+)-taurocholate cotransporting polypeptide mRNA levels and activity, a key transporter involved in bile acids uptake, and deregulation of several other transporters. However, CPZ-induced inhibition of taurocholic acid efflux and pericanalicular F-actin distribution were not affected. In addition, a time-dependent induction of phospholipidosis was noticed in CPZ-treated cells, without obvious influence of the inflammatory stress. In summary, our results show that an inflammatory state induced by proinflammatory cytokines increased cytotoxicity and enhanced some cholestatic features induced by the idiosyncratic drug CPZ in HepaRG cells. These changes, together with inhibition of P450 activities, could have important consequences if extrapolated to the in vivo situation.

Liver X receptor α (LXRα/NR1H3) regulates differentiation of hepatocyte-like cells via reciprocal regulation of HNF4α.

BACKGROUND & AIMS: Hepatocyte-like cells, differentiated from different stem cell sources, are considered to have a range of possible therapeutic applications, including drug discovery, metabolic disease modelling, and cell transplantation. However, little is known about how stem cells differentiate into mature and functional hepatocytes. METHODS: Using transcriptomic screening, a transcription factor, liver X receptor α (NR1H3), was identified as increased during HepaRG cell hepatogenesis; this protein was also upregulated during embryonic stem cell and induced pluripotent stem cell differentiation. RESULTS: Overexpressing NR1H3 in human HepaRG cells promoted hepatic maturation; the hepatocyte-like cells exhibited various functions associated with mature hepatocytes, including cytochrome P450 (CYP) enzyme activity, secretion of urea and albumin, upregulation of hepatic-specific transcripts and an increase in glycogen storage. Importantly, the NR1H3-derived hepatocyte-like cells were able to rescue lethal fulminant hepatic failure using a non-obese diabetic/severe combined immunodeficient mouse model. CONCLUSIONS: In this study, we found that NR1H3 accelerates hepatic differentiation through an HNF4α-dependent reciprocal network. This contributes to hepatogenesis and is therapeutically beneficial to liver disease.