HepaSH cells: Experimental human hepatocytes with lesser inter-individual variation and more sustainable availability than primary human hepatocytes

Human liver cell-based assays for the prediction of hepatic bile acid efflux transporter inhibition by drugs

INTRODUCTION

Drug-mediated inhibition of bile salt efflux transporters may cause liver injury. In vitro prediction of drug effects toward canalicular and/or sinusoidal efflux of bile salts from human hepatocytes is therefore a major issue, which can be addressed using liver cell-based assays.

AREA COVERED

This review, based on a thorough literature search in the scientific databases PubMed and Web of Science, provides key information about hepatic transporters implicated in bile salt efflux, the human liver cell models available for investigating functional inhibition of bile salt efflux, the different methodologies used for this purpose, and the modes of expression of the results. Applications of the assays to drugs are summarized, with special emphasis to the performance values of some assays for predicting hepatotoxicity/cholestatic effects of drugs.

EXPERT OPINION

Human liver cell-based assays for evaluating drug-mediated inhibition of bile acid efflux transporters face various limitations, such as the lack of method standardization and validation, the present poor adaptability to high throughput approaches, and some pitfalls with respect to interpretation of bile acid biliary excretion indexes. Hepatotoxicity of drugs is additionally likely multifactorial, highlighting that inhibition of hepatic bile salt efflux by drugs provides important, but not full, information about potential drug hepatotoxicity.

Switch/sucrose non-fermentable complex interacts with constitutive androstane receptor to regulate drug-metabolizing enzymes and transporters in the liver

Constitutive androstane receptor (CAR) is a nuclear receptor that plays an important role in regulating drug metabolism and bile acid homeostasis in the liver. Recently, it was revealed that the switch/sucrose non-fermentable (SWI/SNF) complex, a chromatin remodeler, regulates transactivation by nuclear receptors, such as the pregnane X receptor and vitamin D receptor. However, studies on the involvement of the SWI/SNF complex in CAR-mediated transactivation are limited. Here, we demonstrated that the induction of cytochrome P450 CYP2B6 expression by CAR activators, 6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde O-(3,4-dichlorobenzyl)oxime and phenobarbital, was enhanced by the inhibition of AT-rich interactive domain-containing protein (ARID) 1A, a canonical brahma-related gene 1-associated factor (cBAF) component, one of the SWI/SNF complexes, and was attenuated by inhibition of bromodomain-containing protein (BRD) 9, a noncanonical BAF (ncBAF) component, in primary hepatocytes from humanized mice. Coimmunoprecipitation assays revealed that ARID1A and BRD9 interacted with CAR. Chromatin immunoprecipitation assay revealed that the 6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde O-(3,4-dichlorobenzyl)oxime-induced binding of CAR to the 5'-flanking region of CYP2B6 gene increased with ARID1A inhibition and reduced with BRD9 inhibition. These results suggest that cBAF negatively regulates CAR-mediated transactivation by attenuating CAR binding to its response element, whereas ncBAF positively regulates it by facilitating CAR binding. Furthermore, ARID1A inhibition enhanced phenobarbital-induced increases in UDP-glucuronosyltransferase 1A1 expression and multidrug resistance-associated protein 2 mRNA level and activity. Collectively, our findings indicate that cBAF and ncBAF play essential roles in xenobiotic metabolism by regulating CAR-mediated transactivation and that ARID1A inhibitors may offer therapeutic benefits for hyperbilirubinemia and cholestasis by inducing UDP-glucuronosyltransferase 1A1 and multidrug resistance-associated protein 2 expression. SIGNIFICANCE STATEMENT: This study revealed that canonical brahma-related gene 1-associated factor and noncanonical brahma-related gene 1-associated factor, members of the switch/sucrose non-fermentable family, negatively and positively regulate constitutive androstane receptor (CAR) transactivation, respectively, through changes in the chromatin structure around the CAR response element in the 5'-flanking regions of CAR target genes. The inhibition of AT-rich interactive domain-containing protein 1A may be beneficial for cholestasis treatment by enhancing CAR-mediated transactivation.

Quantitative prediction of drug disposition for uridine diphosphate-glucuronosyltransferase substrates using humanized mice

Drug clearance and drug-drug interactions are essential for pharmacokinetic assessment. However, current in vitro systems and animal scale-up approaches often fail to accurately predict drug disposition mediated by metabolizing enzymes, especially uridine diphosphate-glucuronosyltransferase (UGT). This study demonstrates how UGT-mediated drug disposition in humans can be predicted using hu-PXB mice (cDNA-uPA/severe combined immunodeficiency (SCID) mice transplanted with human-derived hepatocytes). To estimate human hepatic intrinsic clearance (CLh,int) in vitro, UGT substrates (acetaminophen, entacapone, ketoprofen, lorazepam, oxazepam, posaconazole, and zidovudine) were incubated with cryopreserved human hepatocytes. CLh,int was calculated based on the rate of substrate disappearance. In vivo human CLh,int values were calculated based on literature. To evaluate human CLh,int predictability, the 7 substrates were administered independently and intravenously to hu-PXB and SCID mice. We calculated the CLh,int in the mice and compared it with that in humans. For predicting UGT-mediated drug-drug interactions, 2 UGT substrates were administered intravenously to hu-PXB mice with or without probenecid (a UGT inhibitor). We compared the changes in clearance with those in humans. The in vitro assay using hepatocytes significantly underpredicted CLh,int in humans. Hu-PXB mice had a much better correlation with humans in CLh,int (R2 = 0.95) compared with SCID mice (R2 = 0.69). Hu-PXB mice predicted the CLh,int of UGT substrate drugs within 2-fold of the clinical values for every compound we evaluated. The decrease in clearance caused by probenecid in hu-PXB mice reflected that in humans. Our findings demonstrate that human drug disposition mediated by UGT can be predicted based on the in vivo studies using hu-PXB mice. SIGNIFICANCE STATEMENT: Human liver chimeric mice can accurately predict the clearance of uridine diphosphate-glucuronosyltransferase (UGT) substrate drugs and are likely to predict the magnitude of UGT-mediated drug-drug interactions. Findings from in vivo studies in humanized mice enable the selection of better candidates in drug discovery and allow for the more precise physiologically based pharmacokinetic modeling of UGT substrate drugs in clinical practice.

Exploiting metabolic vulnerability in glioblastoma using a brain-penetrant drug with a safe profile

Glioblastoma is one of the most treatment-resistant and lethal cancers, with a subset of self-renewing brain tumour stem cells (BTSCs), driving therapy resistance and relapse. Here, we report that mubritinib effectively impairs BTSC stemness and growth. Mechanistically, bioenergetic assays and rescue experiments showed that mubritinib targets complex I of the electron transport chain, thereby impairing BTSC self-renewal and proliferation. Gene expression profiling and Western blot analysis revealed that mubritinib disrupts the AMPK/p27Kip1 pathway, leading to cell-cycle impairment. By employing in vivo pharmacokinetic assays, we established that mubritinib crosses the blood-brain barrier. Using preclinical patient-derived and syngeneic models, we demonstrated that mubritinib delays glioblastoma progression and extends animal survival. Moreover, combining mubritinib with radiotherapy or chemotherapy offers survival advantage to animals. Notably, we showed that mubritinib alleviates hypoxia, thereby enhancing ROS generation, DNA damage, and apoptosis in tumours when combined with radiotherapy. Encouragingly, toxicological and behavioural studies revealed that mubritinib is well tolerated and spares normal cells. Our findings underscore the promising therapeutic potential of mubritinib, warranting its further exploration in clinic for glioblastoma therapy.

Induction of drug metabolizing enzyme and drug transporter expression by antifungal triazole pesticides in human HepaSH hepatocytes

Triazole pesticides are widely used fungicides, to which humans are rather highly exposed. They are known to activate drug-sensing receptors regulating expression of hepatic drug metabolizing enzymes and drug transporters, thus suggesting that the hepatic drug detoxification system is modified by these agrochemicals. To investigate this hypothesis, the effects of 9 triazole fungicides towards expression of drug metabolizing enzymes and transporters were characterized in cultured human HepaSH cells, that are human hepatocytes deriving from chimeric humanized liver TK-NOG mice. Most of triazoles used at 10 μM were found to act as inducers of cytochrome P-450 (CYP) 1A1, CYP1A2, CYP2B6, CYP3A4 and UDP-glucuronosyltransferase 1A1 mRNA levels and of CYP3A4 protein; some triazoles also enhanced mRNA expression of the canalicular transporters P-glycoprotein/MDR1, multidrug resistance-associated protein 2 and breast cancer resistance protein. Triazoles however concomitantly inhibited CYP2B6 and CYP3A4 activities and thus appeared as dual regulators of these CYPs, being both inducers of their expression and inhibitors of their activity. The inducing effect however predominated, at least for bromuconazole, propiconazole and tebuconazole. Bromuconazole was moreover predicted to enhance CYP2B6 and CYP3A4 expression in humans exposed to this fungicide in a chronic, acute or occupational context. These data demonstrate that key-actors of the human hepatic detoxification system are impacted by triazole pesticides, which may have to be considered for the risk assessment of these agrochemicals. They additionally highlight that the use of human HepaSH cells as surrogates to primary human hepatocytes represents an attractive and promising way for studying hepatic effects of environmental chemicals.

Impact of miR-222-3p-mediated downregulation of arylacetamide deacetylase on drug hydrolysis and lipid accumulation

Arylacetamide deacetylase (AADAC) is involved in drug hydrolysis and lipid metabolism. In 23 human liver samples, no significant correlation was observed between AADAC mRNA (19.7-fold variation) and protein levels (137.6-fold variation), suggesting a significant contribution of post-transcriptional regulation to AADAC expression. The present study investigated whether AADAC is regulated by microRNA in the human liver and elucidate its biological significance. Computational analysis predicted two potential miR-222-3p recognition elements in the 3'-untranslated region (UTR) of AADAC. Luciferase assay revealed that the miR-222-3p recognition element was functional in downregulating AADAC expression. In HEK293 cells transfected with an AADAC expression plasmid containing 3'-UTR, miR-222-3p overexpression decreased AADAC protein level and activity, whereas miR-222-3p inhibition increased them. Similar results were observed in human hepatoma-derived Huh-1 cells endogenously expressing AADAC and HepaSH cells that are hepatocytes from chimeric mice with humanized livers. In individual human liver samples, AADAC protein levels inversely correlated with miR-222-3p levels. Overexpression of miR-222-3p resulted in increased lipid accumulation in Huh-1 cells, which was reversed by AADAC overexpression. In contrast, miR-222-3p inhibition decreased lipid accumulation, which was reversed by AADAC knockdown. In conclusion, we found that hepatic AADAC was downregulated by miR-222-3p, resulting in decreased drug hydrolysis and increased lipid accumulation.

In Vivo and In Vitro Induction of Cytochrome P450 3A4 by Thalidomide in Humanized-Liver Mice and Experimental Human Hepatocyte HepaSH cells

Autoinduction of cytochrome P450 (P450) 3A4-mediated metabolism of thalidomide was investigated in humanized-liver mice and human hepatocyte-derived HepaSH cells. The mean plasma ratios of 5-hydroxythalidomide and glutathione adducts to thalidomide were significantly induced (3.5- and 6.0-fold, respectively) by thalidomide treatment daily at 1000 mg/kg for 3 days and measured at 2 h after the fourth administration (on day 4). 5-Hydroxythalidomide was metabolically activated by P450 3A4 in HepaSH cells pretreated with 300 and 1000 μM thalidomide, and 5,6-dihydroxythalidomide was detected. Significant induction of P450 3A4 mRNA expression (4.1-fold) in the livers of thalidomide-treated mice occurred. Thalidomide exerts a variety of actions through multiple mechanisms following bioactivation by induced human P450 3A enzymes.

Modeled Hepatic/Plasma Exposures of Omeprazole Prescribed Alone in Cytochrome P450 2C19 Poor Metabolizers Are Likely Associated with Hepatic Toxicity Reported in a Japanese Adverse Event Database

Omeprazole, a gastric acid pump inhibitor, is repeatedly administered and is oxidatively metabolized mainly by polymorphic cytochrome P450 2C19. The prescribed dosage of omeprazole was discontinued or reduced in 47 of the 135 patients who received omeprazole alone in this survey, as recorded in the Japanese Adverse Drug Event Report database. The days to onset of omeprazole-related disorders were 3-4 d (median) and 16 d for intravenous 20-40 mg and oral 20 mg daily doses, respectively, in 34 patients for whom relevant data were available. The maximum plasma concentration of omeprazole was pharmacokinetically modeled after a single oral 40-mg dose in P450 2C19-defective poor metabolizers and was 2.4-fold higher than that in extensive metabolizers. The modeled area under the hepatic concentration curves of omeprazole in P450 2C19 poor metabolizers after virtual daily 40-mg doses for 7 d was 5.2-fold higher than that in the extensive metabolizers. Omeprazole-induced P450 2C19 (approx. 2-fold), resulting in increased hepatic intrinsic clearance in repeated doses, was considered after the second day. Virtual plasma/hepatic exposure estimated using pharmacokinetic modeling in subjects with P450 2C19 poor metabolizers indicated that these exposure levels virtually estimated could be one of causal factors for unexpected hepatic disorders induced by prescribed omeprazole, such as those resulting from drug interactions with repeatedly co-administered medicines.

Cytochrome P450 1A2 and 2C enzymes autoinduced by omeprazole in dog hepatocytes and human HepaRG and HepaSH cells are involved in omeprazole 5-hydroxylation and sulfoxidation

The induction assay for the cytochromes P450 (P450s) is an important tool in drug discovery and development. The inductions of dog P450 1A2 and 3A12 by omeprazole and rifampicin were functionally characterised in dog hepatocytes and were compared with induction in human HepaRG and HepaSH cells.P450 1A2-dependent ethoxyresorufin O-deethylation was induced by R,S-omeprazole and P450 3 A-dependent midazolam 1'-hydroxylation was induced by rifampicin, and both reactions were significantly enhanced in cultured dog hepatocytes and human HepaRG and HepaSH cells.Recombinant dog P450 1A2 exhibited activities towards R- and S-omeprazole 5-hydroxylation with low Km values of 23-28 µM, whereas dog P450 2C21 and 3A12 efficiently mediated S-omeprazole 5-hydroxylation and sulfoxidation, respectively, with high Vmax values of 12-17 min-1.Although omeprazole 5-hydroxylation by human P450 2C19 (and sulfoxidation by P450 3A4) in human HepaSH cells were slightly (∼2-fold) induced by R,S-omeprazole, dog P450 1A2 was autoinduced by omeprazole in dog hepatocytes and showed enhanced R-omeprazole 5-hydroxylation activity (∼5-fold).These results indicate that omeprazole can be an autoinducer of P450 1A2 in hepatocytes, and this enzyme was found to be involved in omeprazole 5-hydroxylation and sulfoxidation in dog hepatocytes and human HepaRG and HepaSH cells.

SGX523 causes renal toxicity through aldehyde oxidase-mediated less-soluble metabolite formation in chimeric mice with humanized livers

SGX523 is a c-Met tyrosine kinase inhibitor that failed in clinical trials because of renal toxicity caused by crystal deposits in renal tubules. SGX523 is metabolized by aldehyde oxidase (AOX) in a species-dependent manner to the considerably less soluble 2-quinolinone-SGX523, which is likely involved in the clinically observed obstructive nephropathy. This study investigated the metabolism and renal toxicity of SGX523 in chimeric mice with humanized livers (humanized-liver mice). The 2-quinolinone-SGX523 formation activity was higher in humanized-liver mouse and human hepatocytes than in mouse hepatocytes. Additionally, this activity in the liver cytosolic fraction from humanized-liver mice was inhibited by the AOX inhibitors raloxifene and hydralazine. After oral SGX523 administration, higher maximum concentrations, larger areas under the plasma concentration versus time curves, and higher urinary concentrations of 2-quinolinone-SGX523 were observed in humanized-liver mice than in non-humanized mice. Serum creatinine and blood urea nitrogen levels were elevated in humanized-liver mice following repeated oral SGX523 administration. The accumulation of amorphous material in the tubules and infiltration of inflammatory cells around tubules were observed in the kidneys of humanized-liver mice after repeated oral SGX523 administration. These findings demonstrate that humanized-liver mice are useful for understanding the metabolism and toxicity of SGX523.