CYP3A4 Induction in the Liver and Intestine of Pregnane X Receptor/CYP3A-Humanized Mice: Approaches by Mass Spectrometry Imaging and Portal Blood Analysis

Development of an OATP1-humanized transchromosomic mouse model for prediction of hepatic drug uptake in humans

Transchromosomic technology using mouse artificial chromosomes (MACs) offers a promising approach for transferring gene clusters into host organisms. This study focused on the multispecific organic anion-transporting polypeptides (OATPs) in the liver, which exhibit significant species differences between mice (Oatp1a1/Slco1a1, Oatp1a4/Slco1a4, Oatp1b2/Slco1b2) and humans (OATP1B1/SLCO1B1 and OATP1B3/SLCO1B3). We generated an OATP1-humanized transchromosomic mouse model using a MAC vector (hOATP1-MAC mice) by transferring the human OATP1 gene cluster (SLCO1C1-SLCO1B3-SLCO1B7-SLCO1B1-SLCO1A2, 700 kbp) via an MAC into Slco1a/1b cluster knockout (KO) mice (Oatp1-KO). The human OATP1 genes were expressed in a tissue-specific manner. Plasma concentrations of the OATP1B biomarkers, coproporphyrin I and III, which were 7.2- and 23.3-fold higher in Oatp1-KO mice than in wild-type mice, were decreased by 68% and 96% in hOATP1-MAC mice, respectively. A pharmacokinetics study using pitavastatin revealed greater total body clearance (168 mL/min/kg) in hOATP1-MAC mice than in Oatp1-KO mice (100 mL/min/kg) but lower clearance than in wild-type mice (484 mL/min/kg), with bioavailability ranging from 0.66 to 0.77. In addition, drug-drug interactions were investigated using rifampicin, an OATP1B inhibitor. Rifampicin (60 mg/kg orally) increased the area under the plasma concentration-time curves of orally administered pitavastatin and grazoprevir in hOATP1-MAC mice, but not of asunaprevir. These findings demonstrated the functional expression of OATP1B1 and OATP1B3 in the mouse liver and their significant role in the systemic elimination of substrates. This is the first study to introduce multiple solute carrier drug transporter genes using artificial chromosome technology, highlighting its potential to overcome species differences in drug transport. SIGNIFICANCE STATEMENT: Transchromosomic technology holds promise for addressing species differences by introducing multiple solute carrier drug transporter genes such as OATP1. Mice OATP1-humanized using a mouse artificial chromosome vector demonstrated enhanced clearance of endogenous OATP1B biomarkers and probe drugs.

Induction of hepatic CYP3A4 expression by cholesterol and cholic acid: Alterations of gene expression, microsomal activity, and pharmacokinetics

Human cytochrome P450 3A4 (CYP3A4) is a drug-metabolizing enzyme that is abundantly expressed in the liver and intestine. It is an important issue whether compounds of interest affect the expression of CYP3A4 because more than 30% of commercially available drugs are metabolized by CYP3A4. In this study, we examined the effects of cholesterol and cholic acid on the expression level and activity of CYP3A4 in hCYP3A mice that have a human CYP3A gene cluster and show human-like regulation of the coding genes. A normal diet (ND, CE-2), CE-2 with 1% cholesterol and 0.5% cholic acid (HCD) or CE-2 with 0.5% cholic acid was given to the mice. The plasma concentrations of cholesterol, cholic acid and its metabolites in HCD mice were higher than those in ND mice. In this condition, the expression levels of hepatic CYP3A4 and the hydroxylation activities of triazolam, a typical CYP3A4 substrate, in liver microsomes of HCD mice were higher than those in liver microsomes of ND mice. Furthermore, plasma concentrations of triazolam in HCD mice were lower than those in ND mice. In conclusion, our study suggested that hepatic CYP3A4 expression and activity are influenced by the combination of cholesterol and cholic acid in vivo.

Exploring Acute Liver Damage: Slimming Health Foods and CYP3A4 Induction

Background

Patients taking multiple drugs and various health foods often develop acute hepatitis. We hypothesized that the interaction between health foods and drug metabolism was the cause of severe liver injury in these patients. Therefore, we studied changes in the activity of the drug-metabolizing enzyme, cytochrome P450 (CYP), using slimming health food extracts and elucidated the molecular mechanism of liver injury onset through hepatotoxicity evaluation.

Methods

For cytotoxicity testing, health food extract samples were added to HepG2 cells derived from hepatic parenchymal cells and culture medium, and cell viability was calculated 48 h after culture. To evaluate CYP3A4 induction, 3-1-10 cells constructed with a reporter linked to CYP3A4 gene were used, and reporter activity was measured 48 h after culture.

Results

In the chronological order of the slimming health food intake history of the patient, niacinamide and Gymnema sylvestre extracts strongly inhibited HepG2 cell viability. In contrast, dietary supplements A and Coleus forskohlii extract strongly induced CYP3A4 reporter activity.

To confirm CYP3A4 induction in humans, humanized CYP3A/pregnane X receptor (PXR) mice were treated with forskolin. CYP3A4 mRNA expression levels were elevated 3.9 times compared to that of the control group (P < 0.05).

Conclusion

Coleus forskohlii extract showed the strongest transcriptional activation of CYP3A4 gene. In a mouse model of human-type drug metabolism, forskolin induced CYP3A4 transcription. Thus, we concluded that CYP3A4 induction by Coleus forskohlii is one of the causes of crucial hepatocellular injury, which is a type of liver injury caused by the active metabolite of acetaminophen produced by CYP3A4.

[Novel Regulatory Mechanisms for Expression of Drug Metabolism-related Factors]

Interindividual differences in the expression and activity of drug-metabolizing enzymes, including cytochrome P450, UDP-glucuronosyltransferase, and esterases, cause variability of therapeutic effectiveness and side effects during drug treatment. Conventional research has focused on transcriptional regulation by transcription factors and nuclear receptors such as aryl hydrocarbon receptor, pregnane X receptor (PXR), constitutive androstane receptor, and hepatocyte nuclear factor 4α, as the major mechanisms causing the differences in the expression of drug-metabolizing enzymes. Recently, we have revealed that adenosine-to-inosine RNA editing and methylation of adenosine at the N6 position on RNA, two major types of posttranscriptional modification, play a pivotal role in the regulation of drug metabolism. In addition, switch/sucrose non-fermentable complex, a chromatin remodeler, is required for PXR-mediated transcriptional regulation of drug-metabolizing enzymes. This review article introduces the significance of these epitranscriptomic and epigenetic regulations as factors in determining drug metabolism potency. Further research on this link is expected to lead to a deeper understanding of interindividual differences in the therapeutic effectiveness and side effects of medicines.

Predictability of human exposure by human-CYP3A4-transgenic mouse models: A meta-analysis

First-in-human dose predictions are primarily based on no-observed-adverse-effect levels in animal studies. Predictions from these animal models are only as effective as their ability to predict human results. To narrow the gap between human and animals, researchers have, among other things, focused on the replacement of animal cytochrome P450 (CYP) enzymes with their human counterparts (called humanization), especially in mice. Whereas research in humanized mice is extensive, the emphasis has been particularly on qualitative rather than quantitative predictions. Because the CYP3A4 enzyme is most involved in the metabolism of clinically used drugs, most benefit was expected from CYP3A4 models. There are several applications of these mouse models regarding in vivo CYP3A4 functionality, one of which might be their capacity to help improve first-in-human (FIH) dose predictions for CYP3A4-metabolized drugs. To evaluate whether human-CYP3A4-transgenic mouse models are better predictors of human exposure compared to the wild-type mouse model, we performed a meta-analysis comparing both mouse models in their ability to accurately predict human exposure of small-molecule drugs metabolized by CYP3A4. Results showed that, in general, the human-CYP3A4-transgenic mouse model had similar accuracy in the prediction of human exposure compared to the wild-type mouse model, suggesting that there is limited added value in humanization of the mouse Cyp3a enzymes if the primary aim is to acquire more accurate FIH dose predictions. Despite the results of this meta-analysis, corrections for interspecies differences through extension of human-CYP3A4-transgenic mouse models with pharmacokinetic modeling approaches seems a promising contribution to more accurate quantitative predictions of human pharmacokinetics.

ncBAF enhances PXR-mediated transcriptional activation in the human and mouse liver

Pregnane X receptor (PXR) is one of the key regulators of drug metabolism, gluconeogenesis, and lipid synthesis in the human liver. Activation of PXR by drugs such as rifampicin, simvastatin, and efavirenz causes adverse reactions such as drug-drug interaction, hyperglycemia, and dyslipidemia. The inhibition of PXR activation has merit in preventing such adverse events. Here, we demonstrated that bromodomain containing protein 9 (BRD9), a component of non-canonical brahma-related gene 1-associated factor (ncBAF), one of the chromatin remodelers, interacts with PXR. Rifampicin-mediated induction of CYP3A4 expression was attenuated by iBRD9, an inhibitor of BRD9, in human primary hepatocytes and CYP3A/PXR-humanized mice, indicating that BRD9 enhances the transcriptional activation of PXR in vitro and in vivo. Chromatin immunoprecipitation assay reveled that iBRD9 treatment resulted in attenuation of the rifampicin-mediated binding of PXR to the CYP3A4 promoter region, suggesting that ncBAF functions to facilitate the binding of PXR to its response elements. Efavirenz-induced hepatic lipid accumulation was attenuated by iBRD9 in C57BL/6J mice, suggesting that the inhibition of BRD9 would be useful to reduce the risk of efavirenz-induced hepatic steatosis. Collectively, we found that inhibitors of BRD9, a component of ncBAF that plays a role in assisting transactivation by PXR, would be useful to reduce the risk of PXR-mediated adverse reactions.

Metabolic Disposition of Triazolam and Clobazam in Humanized CYP3A Mice with a Double-Knockout Background of Mouse Cyp2c and Cyp3a Genes

Knockout (KO) of mouse Cyp3a genes increases the expression of hepatic CYP2C enzymes, which can metabolize triazolam, a typical substrate of human CYP3A. There is still marked formation of 1'-hydroxytriazolam in Cyp3a-KO (3aKO) mice after triazolam dosing. Here, we generated a new model of humanized CYP3A (hCYP3A) mice with a double-KO background of Cyp3a and Cyp2c genes (2c3aKO), and we examined the metabolic profiles of triazolam in wild-type (WT), 2c3aKO, and hCYP3A/2c3aKO mice in vitro and in vivo In vitro studies using liver microsomes showed that the formation of 1'-hydroxytriazolam in 2c3aKO mice was less than 8% of that in WT mice. The formation rate of 1'-hydroxytriazolam in hCYP3A/2c3aKO mice was eightfold higher than that in 2c3aKO mice. In vivo studies showed that area under the curve (AUC) of 1'-hydroxytriazolam in 2c3aKO mice was less than 3% of that in WT mice. The AUC of 1'-hydroxytriazolam in hCYP3A/2c3aKO mice was sixfold higher than that in 2c3aKO mice. These results showed that formation of 1'-hydroxytriazolam was significantly decreased in 2c3aKO mice. Metabolic functions of human CYP3A enzymes were distinctly found in hCYP3A mice with the 2c3aKO background. Moreover, hCYP3A/2c3aKO mice treated with clobazam showed human CYP3A-mediated formation of desmethylclobazam and prolonged elimination of desmethylclobazam, which is found in poor metabolizers of CYP2C19. The novel hCYP3A mouse model without mouse Cyp2c and Cyp3a genes (hCYP3A/2c3aKO) is expected to be useful to evaluate human CYP3A-mediated metabolism in vivo SIGNIFICANT STATEMENT: Humanized CYP3A (hCYP3A/2c3aKO) mice with a background of double knockout (KO) for mouse Cyp2c and Cyp3a genes were generated. Although CYP2C enzymes played a compensatory role in the metabolism of triazolam to 1'-hydroxytriazolam in the previous hCYP3A/3aKO mice with Cyp2c genes, the novel hCYP3A/2c3aKO mice clearly showed functions of human CYP3A enzymes introduced by chromosome engineering technology.

Beyond the Michaelis-Menten: Accurate Prediction of Drug Interactions through Cytochrome P450 3A4 Induction

The US Food and Drug Administration (FDA) guidance has recommended several model-based predictions to determine potential drug-drug interactions (DDIs) mediated by cytochrome P450 (CYP) induction. In particular, the ratio of substrate area under the plasma concentration-time curve (AUCR) under and not under the effect of inducers is predicted by the Michaelis-Menten (MM) model, where the MM constant ( K m $$ {K}_{\mathrm{m}} $$ ) of a drug is implicitly assumed to be sufficiently higher than the concentration of CYP enzymes that metabolize the drug ( E T $$ {E}_{\mathrm{T}} $$ ) in both the liver and small intestine. Furthermore, the fraction absorbed from gut lumen ( F a $$ {F}_{\mathrm{a}} $$ ) is also assumed to be one because F a $$ {F}_{\mathrm{a}} $$ is usually unknown. Here, we found that such assumptions lead to serious errors in predictions of AUCR. To resolve this, we propose a new framework to predict AUCR. Specifically, F a $$ {F}_{\mathrm{a}} $$ was re-estimated from experimental permeability values rather than assuming it to be one. Importantly, we used the total quasi-steady-state approximation to derive a new equation, which is valid regardless of the relationship between K m $$ {K}_{\mathrm{m}} $$ and E T $$ {E}_{\mathrm{T}} $$ , unlike the MM model. Thus, our framework becomes much more accurate than the original FDA equation, especially for drugs with high affinities, such as midazolam or strong inducers, such as rifampicin, so that the ratio between K m $$ {K}_{\mathrm{m}} $$ and E T $$ {E}_{\mathrm{T}} $$ becomes low (i.e., the MM model is invalid). Our work greatly improves the prediction of clinical DDIs, which is critical to preventing drug toxicity and failure.

Effects of Isosakuranetin on Pharmacokinetic Changes of Tofacitinib in Rats with N-Dimethylnitrosamine-Induced Liver Cirrhosis

Tofacitinib, a Janus kinase 1 and 3 inhibitor, is used to treat rheumatoid arthritis. It is mainly metabolized by the cytochromes p450 (CYP) 3A1/2 and CYP2C11 in the liver. Chronic inflammation eventually leads to cirrhosis in patients with rheumatoid arthritis. Isosakuranetin (ISN), a component of Citrus aurantium L., has hepatoprotective effects in rats. This study was performed to determine the effects of ISN on the pharmacokinetics of tofacitinib in rats with N-dimethylnitrosamine-induced liver cirrhosis (LC). After intravenous administration of 10 mg/kg tofacitinib to control (CON), LC, and LC treated with ISN (LC-ISN) rats, the total area under the plasma concentration-time curves (AUC) from time zero to infinity increased by 158% in LC rats compared to those in CON rats; however, the AUC of LC-ISN rats decreased by 35.1% compared to that of LC rat. Similar patterns of AUC changes were observed in the LC and LC-ISN rats after oral administration of 20 mg/kg tofacitinib. These results can be attributed to decreased non-renal clearance (CL_NR) and intestinal intrinsic clearance (CL_int) in the LC rats and increased intestinal and hepatic CL_int in the LC-ISN rats. Our findings imply that ISN treatment in LC rats restored the decrease in either CL_NR or CL_int, or both, through increased hepatic and intestinal expression of CYP3A1/2 and CYP2C11, which is regulated by the induction of pregnane X receptor (PXR) and constitutive androstane receptor (CAR).

Identifying Drug-Induced Liver Injury Associated With Inflammation-Drug and Drug-Drug Interactions in Pharmacologic Treatments for COVID-19 by Bioinformatics and System Biology Analyses: The Role of Pregnane X Receptor

Of the patients infected with coronavirus disease 2019 (COVID-19), approximately 14–53% developed liver injury resulting in poor outcomes. Drug-induced liver injury (DILI) is the primary cause of liver injury in COVID-19 patients. In this study, we elucidated liver injury mechanism induced by drugs of pharmacologic treatments against SARS-CoV-2 (DPTS) using bioinformatics and systems biology. Totally, 1209 genes directly related to 216 DPTS (DPTSGs) were genes encoding pharmacokinetics and therapeutic targets of DPTS and enriched in the pathways related to drug metabolism of CYP450s, pregnane X receptor (PXR), and COVID-19 adverse outcome. A network, constructed by 110 candidate targets which were the shared part of DPTSGs and 445 DILI targets, identified 49 key targets and four Molecular Complex Detection clusters. Enrichment results revealed that the 4 clusters were related to inflammatory responses, CYP450s regulated by PXR, NRF2-regualted oxidative stress, and HLA-related adaptive immunity respectively. In cluster 1, IL6, IL1B, TNF, and CCL2 of the top ten key targets were enriched in COVID-19 adverse outcomes pathway, indicating the exacerbation of COVID-19 inflammation on DILI. PXR-CYP3A4 expression of cluster 2 caused DILI through inflammation-drug interaction and drug-drug interactions among pharmaco-immunomodulatory agents, including tocilizumab, glucocorticoids (dexamethasone, methylprednisolone, and hydrocortisone), and ritonavir. NRF2 of cluster 3 and HLA targets of cluster four promoted DILI, being related to ritonavir/glucocorticoids and clavulanate/vancomycin. This study showed the pivotal role of PXR associated with inflammation-drug and drug-drug interactions on DILI and highlighted the cautious clinical decision-making for pharmacotherapy to avoid DILI in the treatment of COVID-19 patients.

Assessing cytochrome P450 function using genetically engineered mouse models

The ability to knock out and/or humanize different genes in experimental animals, globally or in cell- and tissue-specific patterns, has revolutionized scientific research in many areas. Genetically engineered mouse models, including knockout models, transgenic models, and humanized models, have played important roles in revealing the in vivo functions of various cytochrome P450 (CYP) enzymes. These functions are very diverse, ranging from the biotransformation of drugs and other xenobiotics, events that often dictate their pharmacokinetic or toxicokinetic properties and the associated therapeutic or adverse actions, to the metabolism of endogenous compounds, such as steroid hormones and other bioactive substances, that may determine susceptibility to many diseases, such as cancer and metabolic diseases. In this review, we provide a comprehensive list of Cyp-knockout, human CYP-transgenic, and CYP-humanized mouse models that target genes in the CYP1-4 gene families, and highlight their utility in assessing the in vivo metabolism, bioactivation, and toxicity of various xenobiotic compounds, including therapeutic agents and chemical carcinogens. We aim to showcase the advantages of utilizing these mouse models for in vivo drug metabolism and toxicology studies, and to encourage and facilitate greater utility of engineered mouse models to further improve our knowledge of the in vivo functions of various P450 enzymes, which is integral to our ability to develop safer and more effective therapeutics and to identify individuals predisposed to adverse drug reactions or environmental diseases.

In vivo evaluation of intestinal human CYP3A inhibition by macrolide antibiotics in CYP3A-humanised mice

It is important to predict drug-drug interactions via inhibition of intestinal cytochrome P450 3A (CYP3A) which is a determinant of bioavailability of orally administered CYP3A substrates. However, inhibitory effects of macrolide antibiotics on CYP3A-mediated metabolism are not entirely identical between humans and rodents.We investigated the effects of macrolide antibiotics, clarithromycin and erythromycin, on in vitro and in vivo metabolism of triazolam, a CYP3A substrate, in CYP3A-humanised mice generated by using a mouse artificial chromosome vector carrying a human CYP3A gene.Metabolic activities of triazolam were inhibited by macrolide antibiotics in liver and intestine microsomes of CYP3A-humanised mice.The area under the plasma concentration-time curve ratios of 4-hydroxytriazolam to triazolam after oral dosing of triazolam were significantly decreased by multiple administration of macrolide antibiotics. The plasma concentrations ratios of α-hydroxytriazolam and 4-hydroxytriazolam to triazolam in portal blood were significantly decreased by multiple administration of clarithromycin in CYP3A-humanised mice.These results suggest that intestinal CYP3A activity was inhibited by macrolide antibiotics in CYP3A-humanised mice in vitro and in vivo. The plasma concentrations of triazolam and its metabolites in the portal blood of CYP3A-humanised mice would be useful for direct evaluation of intestinal CYP3A-mediated drug-drug interactions.

Transchromosomic technology for genomically humanized animals

"Genomically" humanized animals are invaluable tools for generating human disease models and for biomedical research. Humanized animal models have generally been developed via conventional transgenic technologies; however, conventional gene delivery vectors such as viruses, plasmids, bacterial artificial chromosomes, P1 phase-derived artificial chromosomes, and yeast artificial chromosomes have limitations for transgenic animal creation as their loading gene capacity is restricted, and the expression of transgenes is unstable. Transchromosomic (Tc) techniques using mammalian artificial chromosomes, including human chromosome fragments, human artificial chromosomes, and mouse artificial chromosomes, have overcome these limitations. These tools can carry multiple genes or Mb-sized genomic loci and their associated regulatory elements, which has facilitated the creation of more useful and complex transgenic models for human disease, drug development, and humanized animal research. This review describes the history of Tc animal development, the applications of Tc animals, and future prospects.