Inter-donor variability of phase I/phase II metabolism of three reference drugs in cryopreserved primary human hepatocytes in suspension and monolayer

A Review of CYP-Mediated Drug Interactions: Mechanisms and In Vitro Drug-Drug Interaction Assessment

Drug metabolism is a major determinant of drug concentrations in the body. Drug-drug interactions (DDIs) caused by the co-administration of multiple drugs can lead to alteration in the exposure of the victim drug, raising safety or effectiveness concerns. Assessment of the DDI potential starts with in vitro experiments to determine kinetic parameters and identify risks associated with the use of comedication that can inform future clinical studies. The diverse range of experimental models and techniques has significantly contributed to the examination of potential DDIs. Cytochrome P450 (CYP) enzymes are responsible for the biotransformation of many drugs on the market, making them frequently implicated in drug metabolism and DDIs. Consequently, there has been a growing focus on the assessment of DDI risk for CYPs. This review article provides mechanistic insights underlying CYP inhibition/induction and an overview of the in vitro assessment of CYP-mediated DDIs.

HepG2 spheroids as a biosensor-like cell-based system for (geno)toxicity assessment

3D spheroids developed from HepG2 cells were used as a biosensor-like system for the detection of (geno)toxic effects induced by chemicals. Benzo(a)pyrene (B(a)P) and amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) with well-known mechanisms of action were used for system validation. HepG2 spheroids grown for 3 days were exposed to BaP and PhIP for 24 and 72 h. The growth and viability of spheroids were monitored by planimetry and Live/Dead staining of cells. Multi-parametric flow cytometric analysis was applied for simultaneous detection of specific end-effects including cell cycle analysis (Hoechst staining), cell proliferation (KI67 marker), and DNA double-strand breaks (ℽH2AX) induced by genotoxic compounds. Depending on the exposure concentration/time, BaP reduced spheroid growth, affected cell proliferation by arresting cells in S and G2 phase and induced DNA double-strand breaks (DSB). Simultaneous staining of ℽH2AX formation and cell cycle analysis revealed that after BaP (10 μM; 24 h) exposure 60% of cells in G0/G1 phase had DNA DSB, while after 72 h only 20% of cells contained DSB indicating efficient repair of DNA lesions. PhIP did not influence the spheroid size whereas accumulation of cells in the G2 phase occurred after both treatment times. The evaluation of DNA damage revealed that at 200 μM PhIP 50% of cells in G0/G1 phase had DNA DSB, which after 72-h exposure dropped to 40%, showing lower repair capacity of PhIP-induced DSB compared to BaP-induced. The developed approach using simultaneous detection of several parameters provides mechanistic data and thus contributes to more reliable genotoxicity assessment of chemicals as a high-content screening tool.

Leveraging interacting signaling pathways to robustly improve the quality and yield of human pluripotent stem cell-derived hepatoblasts and hepatocytes

Pluripotent stem cell (PSC)-derived hepatocyte-like cells (HLCs) have shown great potential as an alternative to primary human hepatocytes (PHHs) for in vitro modeling. Several differentiation protocols have been described to direct PSCs toward the hepatic fate. Here, by leveraging recent knowledge of the signaling pathways involved in liver development, we describe a robust, scalable protocol that allowed us to consistently generate high-quality bipotent human hepatoblasts and HLCs from both embryonic stem cells and induced PSC (iPSCs). Although not yet fully mature, such HLCs were more similar to adult PHHs than were cells obtained with previously described protocols, showing good potential as a physiologically representative alternative to PHHs for in vitro modeling. PSC-derived hepatoblasts effectively generated with this protocol could differentiate into mature hepatocytes and cholangiocytes within syngeneic liver organoids, thus opening the way for representative human 3D in vitro modeling of liver development and pathophysiology.

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We generated human hepatoblasts and hepatocyte-like cells (HLCs) from pluripotent stem cells

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Timed action on Wnt/β-catenin and TGFβ pathways improved maturity and yield of HLCs

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Hepatoblasts matured into hepatocytes and bile ducts within complex liver organoids

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The protocol is robust and showed potential for scalability and drug testing

Preclinical models of idiosyncratic drug-induced liver injury (iDILI): Moving towards prediction

Idiosyncratic drug-induced liver injury (iDILI) encompasses the unexpected harms that prescription and non-prescription drugs, herbal and dietary supplements can cause to the liver. iDILI remains a major public health problem and a major cause of drug attrition. Given the lack of biomarkers for iDILI prediction, diagnosis and prognosis, searching new models to predict and study mechanisms of iDILI is necessary. One of the major limitations of iDILI preclinical assessment has been the lack of correlation between the markers of hepatotoxicity in animal toxicological studies and clinically significant iDILI. Thus, major advances in the understanding of iDILI susceptibility and pathogenesis have come from the study of well-phenotyped iDILI patients. However, there are many gaps for explaining all the complexity of iDILI susceptibility and mechanisms. Therefore, there is a need to optimize preclinical human in vitro models to reduce the risk of iDILI during drug development. Here, the current experimental models and the future directions in iDILI modelling are thoroughly discussed, focusing on the human cellular models available to study the pathophysiological mechanisms of the disease and the most used in vivo animal iDILI models. We also comment about in silico approaches and the increasing relevance of patient-derived cellular models.

Human Organoids for Predictive Toxicology Research and Drug Development

Organoids are three-dimensional structures fabricated in vitro from pluripotent stem cells or adult tissue stem cells via a process of self-organization that results in the formation of organ-specific cell types. Human organoids are expected to mimic complex microenvironments and many of the in vivo physiological functions of relevant tissues, thus filling the translational gap between animals and humans and increasing our understanding of the mechanisms underlying disease and developmental processes. In the last decade, organoid research has attracted increasing attention in areas such as disease modeling, drug development, regenerative medicine, toxicology research, and personalized medicine. In particular, in the field of toxicology, where there are various traditional models, human organoids are expected to blaze a new path in future research by overcoming the current limitations, such as those related to differences in drug responses among species. Here, we discuss the potential usefulness, limitations, and future prospects of human liver, heart, kidney, gut, and brain organoids from the viewpoints of predictive toxicology research and drug development, providing cutting edge information on their fabrication methods and functional characteristics.

A new cell-sized support for 3D cell cultures based on recombinant spider silk fibers

It is now generally accepted that 2D cultures cannot accurately replicate the rich environment and complex tissue architecture that exists in vivo, and that classically cultured cells tend to lose their original function. Growth of spheroids as opposed to 2D cultures on plastic has now been hailed as an efficient method to produce quantities of high-quality cells for cancer research, drug discovery, neuroscience, and regenerative medicine. We have developed a new recombinant protein that mimics dragline spidersilk and that self-assembles into cell-sized coils. These have high thermal and shelf-life stability and can be readily sterilized and stored for an extended period of time. The fibers are flexible, elastic, and biocompatible and can serve as cell-sized scaffold for the formation of 3D cell spheroids. As a proof of concept, recombinant spidersilk was integrated as a scaffold in spheroids of three cell types: primary rat hepatocytes, human mesenchymal stem cells, and mouse L929 cells. The scaffolds significantly reduced spheroid shrinkage and unlike scaffold-free spheroids, spheroids did not disintegrate over the course of long-term culture. Cells in recombinant spidersilk spheroids showed increased viability, and the cell lines continued to proliferate for longer than control cultures without spidersilk. The spidersilk also supported biological functions. Recombinant spidersilk primary hepatocyte spheroids exhibited 2.7-fold higher levels of adenosine triphosphate (ATP) continued to express and secrete albumin and exhibited significantly higher basal and induced CYP3A activity for at least 6 weeks in culture, while control spheroids without fibers stopped producing albumin after 27 days and CPY3A activity was barely detectable after 44 days. These results indicate that recombinant spidersilk can serve as a useful tool for long-term cell culture of 3D cell spheroids and specifically that primary hepatocytes can remain active in culture for an extended period of time which could be of great use in toxicology testing.

Herb-drug interactions and toxicity: Underscoring potential mechanisms and forecasting clinically relevant interactions induced by common phytoconstituents via data mining and computational approaches

Herbals in the form of medicine are employed extensively around the world. Herbal and conventional medicine combination is a potentially dangerous practice mainly in comorbid, hepato insufficient and frail patients leading to perilous herb-drug interactions (HDI) and toxicity. This study features potential HDI of 15 globally famous plant species through data mining and computational methods. Several plant species were found to mimic warfarin. Phytochemicals from M. charantia induced hypoglycemica. M. chamomila and G. biloba possessed anticoagulant activities. S. hispanica reduces postprandial glycemia. R. officinalis has been reported to inhibit the efflux of anticancer substrates while A. sativum can boost the clearance of anticancer agents. P. ginseng can alter blood coagulation. A cross link of the biological and in silico data revealed that a plethora of herbal metabolites such as ursolic and rosmarinic acid among others are possible/probable inhibitors of specific CYP450 enzymes. Consequently, plant species/metabolites with a given pharmacological property/metabolizing enzyme should not be mixed with drugs having the same pharmacological property/metabolizing enzyme. Even if combined with drugs, herbal medicines must be used at low doses for a short period of time and under the supervision of a healthcare professional to avoid potential adverse and toxic effects.

Liver Organoids: Recent Developments, Limitations and Potential

Liver cell types derived from induced pluripotent stem cells (iPSCs) share the potential to investigate development, toxicity, as well as genetic and infectious disease in ways currently limited by the availability of primary tissue. With the added advantage of patient specificity, which can play a role in all of these areas. Many iPSC differentiation protocols focus on 3 dimensional (3D) or organotypic differentiation, as these offer the advantage of more closely mimicking in vivo systems including; the formation of tissue like architecture and interactions/crosstalk between different cell types. Ultimately such models have the potential to be used clinically and either with or more aptly, in place of animal models. Along with the development of organotypic and micro-tissue models, there will be a need to co-develop imaging technologies to enable their visualization. A variety of liver models termed "organoids" have been reported in the literature ranging from simple spheres or cysts of a single cell type, usually hepatocytes, to those containing multiple cell types combined during the differentiation process such as hepatic stellate cells, endothelial cells, and mesenchymal cells, often leading to an improved hepatic phenotype. These allow specific functions or readouts to be examined such as drug metabolism, protein secretion or an improved phenotype, but because of their relative simplicity they lack the flexibility and general applicability of ex vivo tissue culture. In the liver field these are more often constructed rather than developed together organotypically as seen in other organoid models such as brain, kidney, lung and intestine. Having access to organotypic liver like surrogates containing multiple cell types with in vivo like interactions/architecture, would provide vastly improved models for disease, toxicity and drug development, combining disciplines such as microfluidic chip technology with organoids and ultimately paving the way to new therapies.

Impacts of Drug Interactions on Pharmacokinetics and the Brain Transporters: A Recent Review of Natural Compound-Drug Interactions in Brain Disorders

Natural compounds such as herbal medicines and/or phyto-compounds from foods, have frequently been used to exert synergistic therapeutic effects with anti-brain disorder drugs, supplement the effects of nutrients, and boost the immune system. However, co-administration of natural compounds with the drugs can cause synergistic toxicity or impeditive drug interactions due to changes in pharmacokinetic properties (e.g., absorption, metabolism, and excretion) and various drug transporters, particularly brain transporters. In this review, natural compound–drug interactions (NDIs), which can occur during the treatment of brain disorders, are emphasized from the perspective of pharmacokinetics and cellular transport. In addition, the challenges emanating from NDIs and recent approaches are discussed.

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.

Characterization of cytochrome P450s (CYP)-overexpressing HepG2 cells for assessing drug and chemical-induced liver toxicity

Hepatic metabolism catalyzed by the cytochrome P450 (CYP) superfamily affects liver toxicity associated with exposures to natural compounds and xenobiotic agents. Previously we generated a battery of HepG2-derived stable cell lines that individually express 14 CYPs (1A1, 1A2, 1B1, 2A6, 2B6, 2C8, 2C9, 2C18, 2C19, 2D6, 2E1, 3A4, 3A5, and 3A7). In this study, we comprehensively characterized each cell line for its CYP expression and enzyme activity. Specifically, we measured the mRNA expression, protein expression, and metabolite formation. Using CYP3A4, 2D6, and 2C9-overexpressing cells as representatives, we examined the stability of these cells in long-term cultures for up to 10 passages. The results showed that CYPs can be stably overexpressed for up to 10 cell culture passages without losing their activities. The robustness of responses to stimuli among the cells at different passages was also investigated in CYP3A4-overexpressing cells and the response to amiodarone and dronedarone showed no difference between the cells at the passage 2 and 10. Moreover, the mRNA expression level of most CYPs was higher in CYP-overexpressing HepG2 cells than that in HepaRG cells and primary human hepatocytes. This study confirmed the stability of CYP-overexpressing HepG2 cell lines and provided useful information for a broader use of these cells in pharmacologic and toxicologic research.

Fumonisin B1 Epigenetically Regulates PTEN Expression and Modulates DNA Damage Checkpoint Regulation in HepG2 Liver Cells

Fumonisin B₁ (FB₁), a Fusarium-produced mycotoxin, is found in various foods and feeds. It is a well-known liver carcinogen in experimental animals; however, its role in genotoxicity is controversial. The current study investigated FB₁-triggered changes in the epigenetic regulation of PTEN and determined its effect on DNA damage checkpoint regulation in human liver hepatoma G2 (HepG2) cells. Following treatment with FB₁ (IC₅₀: 200 µM; 24 h), the expression of miR-30c, KDM5B, PTEN, H3K4me3, PI3K, AKT, p-ser473-AKT, CHK1, and p-ser280-CHK1 was measured using qPCR and/or Western blot. H3K4me3 enrichment at the PTEN promoter region was assayed via a ChIP assay and DNA damage was determined using an ELISA. FB₁ induced oxidative DNA damage. Total KDM5B expression was reduced, which subsequently increased the total H3K4me3 and the enrichment of H3K4me3 at PTEN promoters. Increased H3K4me3 induced an increase in PTEN transcript levels. However, miR-30c inhibited PTEN translation. Thus, PI3K/AKT signaling was activated, inhibiting CHK1 activity via phosphorylation of its serine 280 residue preventing the repair of damaged DNA. In conclusion, FB₁ epigenetically modulates the PTEN/PI3K/AKT signaling cascade, preventing DNA damage checkpoint regulation, and induces significant DNA damage.

Electrochemical microreactor combined with mass spectrometry for online oxidation and real-time detection of alkaloids

The main purpose of the present study was to investigate the prototypes and oxidation products of alkaloids with the use of an online electrochemistry/quadrupole time-of-flight mass spectrometry system. The metabolism of oxidative phase I and II was simulated in an electrochemical reaction cell. The metabolic processes for coptisine and jatrorrhizine were simulated in a thin-layer cell fitted with a glassy carbon working electrode, while the metabolic processes for berberine and palmatine were simulated by using a boron-doped diamond working electrode. By using the new experimental system, dehydrogenation, demethylation, methylation, hydroxylation, and the formation of two hydroxylation adducts were detected by applying different potentials to the electrochemical cell. The online reaction with glutathione yielded different covalent glutathione adducts. The results obtained from the electrochemical simulation were found to be in good accordance with those reported previously in vivo, showing that electrochemistry/mass spectrometry is an effective tool for studying metabolic reactions for various complex components. Moreover, analysis of alkaloids in liver microsomes by liquid chromatography coupled with mass spectrometry confirmed the possibility of using an electrochemistry technique to simulate the metabolism of target compounds.

Evaluation of 3D re-cellularized tissue engineering: a drug-induced hepatotoxicity model for hepatoprotectant research

Background: Application of hepatoprotectants, such as drugs or cytokines, can reduce drug-induced hepatotoxicity (DIH). Due to species-specific differences and abnormal cell polarity and drug-metabolizing enzymes (DMEs), in vivo animal models and in vitro 2D plastic dishes are not good DIH models. The aim of this study was to evaluate whether 3D re-cellularized liver is a sensitive, accurate and efficient DIH model for evaluation of hepatoprotectants. Methods: 2D plastic dishes and 3D decellular liver scaffolds were perfused with HepG2 cells or augmenter of liver regeneration (ALR)-HepG2 cells. These two cell lines were exposed to 4 μM troglitazone (TRO) or 20 μM diclofenac sodium (DIC) on day 8. DME-related genes were analyzed by quantitative reverse transcription polymerase chain reaction; morphological images were revealed by immunohistochemistry, scanning electron microscopy, transmission electron microscopy, and hematoxylin and eosin staining. Results: DME activity and cell polarity were retained and lower doses of TRO and DIC led to DIH in 3D re-cellularized liver. This DIH model reflected the protective effects and mechanism of ALR, which is one of the hepatoprotectants. ALR reduced mitochondrial damage, decreased transaminase level, and alleviated inflammation in TRO-DIH and DIC-DIH. Our re-cellularized liver lobe also showed the effect of ALR in suppressing expression of DMEs. Conclusions: Drug-induced 3D re-cellularized tissue engineering is a sensitive, accurate, and efficient DIH model for evaluation of hepatoprotectants.

The importance of inter-individual Kupffer cell variability in the governance of hepatic toxicity in a 3D primary human liver microtissue model

The potential for nanomaterial (NM) translocation to secondary organs is a realistic prospect, with the liver one of the most important target organs. Traditional in vitro or ex vivo hepatic toxicology models are often limiting and/or troublesome (i.e. short life-span reduced metabolic activity, lacking important cell populations, high inter-individual variability, etc.). Building on previous work, this study utilises a 3D human liver microtissue (MT) model (MT composed of mono-culture of hepatocytes or two different co-culture MT systems with non-parenchymal cell (NPC) fraction sourced from different donors) to investigate the importance of inter-donor variability of the non-parenchymal cell population in the overall governance of toxicological response following exposure to a panel of NMs. To the best of our knowledge, this is the first study of its kind to investigate inter-donor variability in hepatic NPC population. The data showed that the Kupffer cells were crucial in dictating the overall hepatic toxicity following exposure to the materials. Furthermore, a statistically significant difference was noted between the two co-culture MT models. However, the trend for particle-induced biological responses was similar between the co-cultures (cytotoxicity, cytokine production and caspase activity). Therefore, despite the recognition of some discrepancies in the absolute values between the co-culture models, the fact that the trends and patterns of biological responses were comparable between the multi-cellular models we propose the 3D liver MT to be a valuable tool in particle toxicology.

Joint toxicity on hepatic detoxication enzymes in goldfish (Carassius auratus) exposed to binary mixtures of lead and paraquat

Compared to single exposure, chemical mixtures might induce joint toxicity including additive, synergistic and antagonistic effects on both organisms and environment. Owing to the specific toxicity of oxidative stress and binding to proteins, lead (Pb) is generally recognized a non-essential and threatening heavy metal to animals and human. Paraquat (PQ) is a widely used herbicide in agriculture and can trigger oxidative stress as well as Pb. Little information was available about joint effects of the two chemicals on toxicological responses in organisms, especially in fish. In our present study, goldfish (Carassius auratus) were randomly exposed to single and combined experiments with different concentrations of Pb and PQ for 28 days. Activities of four enzyme biomarkers in liver, ethoxyresorufin-O-deethylase (EROD), 7-benzyloxy-4-trifluoromethyl-coumarin-O-debenzyloxylase (BFCOD), glutathione-S-transferase (GST) and UDP-glucuronosyltransferase (UGT) were evaluated in each experimental group on day 14 and 28. The results showed four enzyme levels were markedly reduced with the increase of concentrations in mixtures and prolonged exposure. The inhibitory EROD and BFCOD activities were not significantly changed in goldfish following PQ-treated groups with or without 0.5 mg/L Pb, which indicated PQ has more inhibitory toxicity on CYP450 enzymes than Pb in co-exposure groups. However, the reduced values of GST were observed only in the combinations containing high doses of Pb or PQ during experimental periods. Although the responses of UGT activity were similar to GST on 14th day, all combinations of Pb and PQ generated stronger inhibitions on UGT activities compared to individual Pb and PQ-treated group. These results suggested that combined exposure of Pb and PQ have more inhibitory toxicity on phase I enzymes than phase II enzymes.

Comparison of Hepatic 2D Sandwich Cultures and 3D Spheroids for Long-term Toxicity Applications: A Multicenter Study

Primary human hepatocytes (PHHs) are commonly used for in vitro studies of drug-induced liver injury. However, when cultured as 2D monolayers, PHH lose crucial hepatic functions within hours. This dedifferentiation can be ameliorated when PHHs are cultured in sandwich configuration (2Dsw), particularly when cultures are regularly re-overlaid with extracellular matrix, or as 3D spheroids. In this study, the 6 participating laboratories evaluated the robustness of these 2 model systems made from cryopreserved PHH from the same donors considering both inter-donor and inter-laboratory variability and compared their suitability for use in repeated-dose toxicity studies using 5 different hepatotoxins with different toxicity mechanisms. We found that expression levels of proteins involved in drug absorption, distribution, metabolism, and excretion, as well as catalytic activities of 5 different CYPs, were significantly higher in 3D spheroid cultures, potentially affecting the exposure of the cells to drugs and their metabolites. Furthermore, global proteomic analyses revealed that PHH in 3D spheroid configuration were temporally stable whereas proteomes from the same donors in 2Dsw cultures showed substantial alterations in protein expression patterns over the 14 days in culture. Overall, spheroid cultures were more sensitive to the hepatotoxic compounds investigated, particularly upon long-term exposures, across testing sites with little inter-laboratory or inter-donor variability. The data presented here suggest that repeated-dosing regimens improve the predictivity of in vitro toxicity assays, and that PHH spheroids provide a sensitive and robust system for long-term mechanistic studies of drug-induced hepatotoxicity, whereas the 2Dsw system has a more dedifferentiated phenotype and lower sensitivity to detect hepatotoxicity.

Incorporating population-level genetic variability within laboratory models in toxicology: From the individual to the population

Humans respond to chemical exposures differently due to many factors, such as previous and concurrent stressors, age, sex, and genetic background. The vast majority of laboratory-based toxicology studies, however, have not considered the impact of population-level variability within dose-response relationships. The lack of data dealing with the influence of genetic diversity on the response to chemical exposure provides a difficult challenge for risk assessment as individuals within the population will display a wide-range of responses following toxicant challenge. Notably, the genetic background of individuals plays a major role in the variability seen in a population-level response to a drug or chemical and, thus, there is growing interest in including genetic diversity into laboratory-models. Here we outline several laboratory-based models that can be used to assay the influence of genetic variability on an individual's response to chemicals: 1) genetically-diverse cell lines, 2) human primary cells, 3) and genetically-diverse mouse panels. We also provide a succinct review for several seminal studies to highlight the capability, feasibility, and power of each of these models. This article is intended to highlight the need to include population-level genetic diversity into toxicological study designs via laboratory-based models with the goal to provide and supplement evidence in assessing the risk posed by chemicals to the human population. As such, incorporation of genetic variability will positively impact human-based risk assessment and provide empirical data to aid and influence decision-making processes in relation to chemical exposures.

Direct comparison of UDP-glucuronosyltransferase and cytochrome P450 activities in human liver microsomes, plated and suspended primary human hepatocytes from five liver donors

UDP-glucuronosyltransferases (UGTs) and cytochrome P450s (CYPs) are the major enzymes involved in hepatic metabolism of drugs. Hepatic drug metabolism is commonly investigated using human liver microsomes (HLM) or primary human hepatocytes (PHH). We describe the development of a sensitive assay to phenotype activities of six major hepatic UGT isoforms (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9 and UGT2B7) in intact PHH by analysis of glucuronidation of selective probe substrates. The non-selective, general substrate 7-hydroxycoumarin was included for comparison. For each liver donor preparation (five donors) UGT activities in cryopreserved suspended and plated PHH were compared to HLM prepared from the same donors. Standard CYP reaction phenotyping of seven major isoforms was performed in parallel. For all donors, CYP- and UGT-isoforms activity profiles were comparable in PHH and HLM, indicating that reaction phenotyping with selective probe substrates in intact cells primarily reflects respective CYP or UGT activity. System-dependent effects on UGT and CYP isoform activity were still found. While UGT activity of UGT1A1 was equivalent in plated and suspended PHH, UGT1A3, UGT1A6 and UGT2B7 activity was higher in suspended PHH and UGT1A9 and UGT1A4 activity was higher in plated PHH. The well-known decrease in activity of most CYP isoforms in plated compared to suspended PHH was confirmed. Importantly, we found a significant loss in CYP2C19 and CYP2B6 in HLM, activity being lower than in intact cells. Taken together, these findings implicate that, dependent on the UGT or CYP isoforms involved in the metabolism of a given compound, the outcome of metabolic assays is strongly dependent on the choice of the in vitro system. The currently described UGT- and CYP- activity profiling method can be used as a standard assay in intact cells and can especially aid in reaction phenotyping of in vitro systems for which a limited number of cells are available.

Herb-Drug Interactions of Commonly Used Chinese Medicinal Herbs

With more and more popular use of traditional herbal medicines, in particular Chinese herbal medicines, herb-drug interactions have become a more and more important safety issue in the clinical applications of the conventional drugs. Researches in this area are increasing very rapidly. Herb-drug interactions are complicated due to the fact that multiple chemical components are involved, and these compounds may possess diverse pharmacological activities. Interactions can be in both pharmacokinetics and pharmacodynamics. Abundant studies focused on pharmacokinetic interactions of herbs and drugs. Herbs may affect the behavior of the concomitantly used drugs by changing their absorption, distribution, metabolism, and excretion. Studies on pharmacodynamics interactions of herbs and drugs are still very limited. Herb-drug interactions are potentially causing changes in drug levels and drug activities and leading to either therapeutic failure or toxicities. Sometime it can be fatal. The exposures to drugs, lacking of knowledge in the potential adverse herb-drug interactions, will put big risk to patients' safety in medical services. On the contrary, some interactions may be therapeutically beneficial. It may be used to help develop new therapeutic strategies in the future. This chapter is trying to review the development in the area of herb-drug interactions based on the recently published research findings. Information on the potential interactions among the commonly used Chinese medicinal herbs and conventional drugs is summarized in this chapter.

In Vitro Intestinal and Liver Models for Toxicity Testing

The human body is exposed to hundreds of chemicals every day. Many of these toxicants have unknown effects on the body that can be deleterious. Furthermore, chemicals can have a synergistic effect, resulting in toxic responses of cocktails at relatively low individual exposure levels. The gastrointestinal (GI) tract and the liver are the first organs to be exposed to ingested pharmaceuticals and environmental chemicals. As a result, these organs often experience extensive damage from xenobiotics and their metabolites. In vitro models offer a promising method for testing toxic effects. Many advanced in vitro models have been developed for GI and liver toxicity. These models strive to recapitulate the in vivo organ architecture to more accurately model chemical toxicity. In this review, we discuss many of these advances, in addition to recent efforts to integrate the GI and the liver in vitro for a more holistic toxicity model.

Evidence-based selection of training compounds for use in the mechanism-based integrated prediction of drug-induced liver injury in man

The current test systems employed by pharmaceutical industry are poorly predictive for drug-induced liver injury (DILI). The ‘MIP-DILI’ project addresses this situation by the development of innovative preclinical test systems which are both mechanism-based and of physiological, pharmacological and pathological relevance to DILI in humans. An iterative, tiered approach with respect to test compounds, test systems, bioanalysis and systems analysis is adopted to evaluate existing models and develop new models that can provide validated test systems with respect to the prediction of specific forms of DILI and further elucidation of mechanisms. An essential component of this effort is the choice of compound training set that will be used to inform refinement and/or development of new model systems that allow prediction based on knowledge of mechanisms, in a tiered fashion. In this review, we focus on the selection of MIP-DILI training compounds for mechanism-based evaluation of non-clinical prediction of DILI. The selected compounds address both hepatocellular and cholestatic DILI patterns in man, covering a broad range of pharmacologies and chemistries, and taking into account available data on potential DILI mechanisms (e.g. mitochondrial injury, reactive metabolites, biliary transport inhibition, and immune responses). Known mechanisms by which these compounds are believed to cause liver injury have been described, where many if not all drugs in this review appear to exhibit multiple toxicological mechanisms. Thus, the training compounds selection offered a valuable tool to profile DILI mechanisms and to interrogate existing and novel in vitro systems for the prediction of human DILI.

Determination of diclofenac concentrations in human plasma using a sensitive gas chromatography mass spectrometry method

Background

A gas chromatography mass spectrometry (GCMS) method for the determination of diclofenac in human plasma has been developed and validated.

Results

This method utilizes hexane which is a relatively less toxic extraction solvent compared to heptane and benzene. In addition, phosphoric acid and acetone were added to the samples as deproteination agents, which increased the recovery of diclofenac. These revised processes allow clean extraction and near-quantitative recovery of analyte (approx. 89–95 %). Separation was achieved on a BP-1 column with helium as carrier gas. The molecular ion peaks of the indolinone derivatives of diclofenac ion (m/z 277) and the internal standard, 4-hydroxydiclofenac ion (m/z 439) were monitored by a mass-selective detector using selected ion monitoring (SIM) mode. The linear range for the newly developed and highly sensitive assay was between 0.25–50 ng/mL. The detection and lower quantifiable limits were 0.125 and 0.25 ng/mL, respectively. The inter-day and intra-day coefficients of variation for high, medium and low quality control concentrations were less than 9 %. The robustness and efficacy of this sensitive GCMS method was further demonstrated by using it for a pharmacokinetic study of an oral dosage form of diclofenac, 100 mg of modified-release capsules (Rhumalgan XL), in human plasma.

Conclusions

This method is rapid, sensitive, specific, reproducible and robust, and offers improved sensitivity over previous methods. This method has considerable potential to be used for detailed pharmacokinetics, pharmacodynamics and bioequivalence studies of diclofenac in humans.

Cytotoxicity evaluation using cryopreserved primary human hepatocytes in various culture formats

Sixteen training compounds selected in the IMI MIP-DILI consortium, 12 drug-induced liver injury (DILI) positive compounds and 4 non-DILI compounds, were assessed in cryopreserved primary human hepatocytes. When a ten-fold safety margin threshold was applied, the non-DILI-compounds were correctly identified 2h following a single exposure to pooled human hepatocytes (n=13 donors) in suspension and 14-days following repeat dose exposure (3 treatments) to an established 3D-microtissue co-culture (3D-MT co-culture, n=1 donor) consisting of human hepatocytes co-cultured with non-parenchymal cells (NPC). In contrast, only 5/12 DILI-compounds were correctly identified 2h following a single exposure to pooled human hepatocytes in suspension. Exposure of the 2D-sandwich culture human hepatocyte monocultures (2D-sw) for 3days resulted in the correct identification of 11/12 DILI-positive compounds, whereas exposure of the human 3D-MT co-cultures for 14days resulted in identification of 9/12 DILI-compounds; in addition to ximelagatran (also not identified by 2D-sw monocultures, Sison-Young et al., 2016), the 3D-MT co-cultures failed to detect amiodarone and bosentan. The sensitivity of the 2D human hepatocytes co-cultured with NPC to ximelagatran was increased in the presence of lipopolysaccharide (LPS), but only at high concentrations, therefore preventing its classification as a DILI positive compound. In conclusion (1) despite suspension human hepatocytes having the greatest metabolic capacity in the short term, they are the least predictive of clinical DILI across the MIP-DILI test compounds, (2) longer exposure periods than 72h of human hepatocytes do not allow to increase DILI-prediction rate, (3) co-cultures of human hepatocytes with NPC, in the presence of LPS during the 72h exposure period allow the assessment of innate immune system involvement of a given drug.