Mice as clinically relevant models for the study of cytochrome P450-dependent metabolism

Systematic health risks assessment of chiral fungicide famoxadone: Stereoselectivities in ferroptosis-mediated cytotoxicity and metabolic behavior

Famoxadone is a chiral fungicide frequently found in the environment and agricultural products. However, the health risks of famoxadone enantiomers are not well understood. This study investigated the stereoselective cytotoxicity and metabolic behavior of famoxadone enantiomers in mammals. Results showed that R-famoxadone was 1.5 times more toxic to HepG2 cells than S-famoxadone. R-famoxadone induced more pronounced ferroptosis compared to S-famoxadone. It caused greater upregulation of genes related to iron transport and lipid peroxidation, and greater downregulation of genes related to peroxide clearance. Furthermore, R-famoxadone induced more severe lipid peroxidation and reactive oxygen species (ROS) accumulation through ACSL4 activation and GPX4 inhibition. Additionally, the bioavailability of R-famoxadone in mice was six times higher than that of S-famoxadone. Liver microsome assays, cytochrome P450 (CYP450) inhibition assays, human recombinant CYP450 assays, and molecular docking suggested that the lower binding affinities of CYP2C8, CYP2C19, and CYP2E1 for R-famoxadone caused its preferential accumulation. Overall, R-famoxadone poses a higher risk than S-famoxadone due to its greater cytotoxicity and persistence. This study provides the first evidence of ferroptosis-induced stereoselective toxicity, offering insights for the comprehensive health risk assessment of chiral famoxadone and valuable references for the application of high-efficiency, low-risk pesticide enantiomers.

Assessment of metabolic activation of felbamate in chimeric mice with humanized liver in combination with in vitro metabolic assays

Felbamate (FBM) is an antiepileptic drug that has minimal toxicity in preclinical toxicological species but has a serious idiosyncratic drug toxicity (IDT) in humans. The formation of reactive metabolites is common among most drugs associated with IDT, and 2-phenylpropenal (2-PP) is believed to be the cause of IDT by FBM. It is important to consider the species difference in susceptibility to IDT between experimental animals and humans. In the present study, we used an in vitro and in vivo model system to reveal species difference in IDT of FBM. Human cytochrome P450 (CYP) and carboxylesterase (CES) expressing microsomes were used to clarify the isozymes involved in the metabolism of FBM. The remaining amount of FBM was significantly reduced in incubation with microsomes expressing human CYP2C8, 2C9, 2E1, and CES1c isozymes. Chimeric mice with humanized liver are expected to predict IDT in humans. Therefore, metabolite profiles in chimeric mice with humanized liver were investigated after administration of FBM. Metabolites after glutathione (GSH) conjugation of 2-phenylpropenal (2-PP), which is the reactive metabolite responsible for FBM-induced IDT, were detected in chimeric mice plasma and liver homogenate. Mass spectrometry imaging (MSI) visualizes distribution of FBM and endogenous GSH, and GSH levels in human hepatocyte were decreased after administration of FBM. In this study, we identified CYP and CES isozymes involved in the metabolism of FBM and confirmed reactive metabolite formation and subsequent decrease in GSH using humanized animal model. These results would provide useful information for the susceptibility to IDT between experimental animals and humans.

Regulation of drug-metabolizing enzymes by sex-related hormones: clinical implications for transgender medicine

Transgender medicine is a diverse and growing clinical field with unmet gaps in pharmacological knowledge. Hormone therapy (testosterone or estrogen treatment), one part of the standard of medical care for transgender adults, aligns secondary sex characteristics with an individual's gender identity and expression. Despite established effects of sex steroids on drug-metabolizing enzyme expression and activity in vitro and in animal models, the effect of long-term, supraphysiological sex hormone treatment on drug metabolism in transgender adults is not yet established. Here, we synthesize available in vitro and animal model data with pharmacological concepts in transgender medicine to predict potential effects of sex steroids on drug-metabolizing enzymes, and their relationship with potential hormone-drug interactions, in transgender medicine.

Empirical and theoretical approaches for the prediction of human hepatic clearance using chimeric mice with humanised liver: the use of physiologically based scaling, a novel solution for potential overprediction due to coexisting mouse metabolism

Chimeric mice are immunodeficient mice in which the majority of the hepatic parenchymal cells are replaced with human hepatocytes.Following intravenous administration of 24 model compounds to control and chimeric mice, human hepatic clearance (CL_h) was predicted using the single-species allometric scaling (SSS) method. Predictability of the chimeric mice was better than that of the control mice.Human CL_h was predicted by the physiologically based scaling (PBS) method, wherein observed CL_h in chimeric mice was first converted to intrinsic CL_h (CL_h,int). As the liver of chimeric mice contains remaining mouse hepatocytes, CL_h,int was corrected by in vitro CL_h ratios of the mouse to human hepatocytes according to their hepatocyte replacement index. Further, predicted human CL_h was calculated based on an assumption that CL_h,int in chimeric mice normalised for their liver weight was equal to CL_h,int per liver weight in humans. Consequently, better prediction performance was observed with the use of the PBS method than the SSS method.SSS method is an empirical method, and the effects of coexisting mouse metabolism cannot be avoided. However, the PBS method with in vitro CL_h correction might be a potential solution and may expand the application of chimeric mice in new drug development.

Toxicoproteomic Profiling of hPXR Transgenic Mice Treated with Rifampicin and Isoniazid

Tuberculosis is a global health threat that affects millions of people every year, and treatment-limiting toxicity remains a considerable source of treatment failure. Recent reports have characterized the nature of hPXR-mediated hepatotoxicity and the systemic toxicity of antitubercular drugs. The antitubercular drug isoniazid plays a role in such pathologic states as acute intermittent porphyria, anemia, hepatotoxicity, hypercoagulable states (deep vein thrombosis, pulmonary embolism, or ischemic stroke), pellagra (vitamin B₃ deficiency), peripheral neuropathy, and vitamin B₆ deficiency. However, the mechanisms by which isoniazid administration leads to these states are unclear. To elucidate the mechanism of rifampicin- and isoniazid-induced liver and systemic injury, we performed tandem mass tag mass spectrometry-based proteomic screening of mPxr^-/- and hPXR mice treated with combinations of rifampicin and isoniazid. Proteomic profiling analysis suggested that the hPXR liver proteome is affected by antitubercular therapy to disrupt [Fe-S] cluster assembly machinery, [2Fe-2S] cluster-containing proteins, cytochrome P450 enzymes, heme biosynthesis, homocysteine catabolism, oxidative stress responses, vitamin B₃ metabolism, and vitamin B₆ metabolism. These novel findings provide insight into the etiology of some of these processes and potential targets for subsequent investigations. Data are available via ProteomeXchange with identifier PXD019505.

Chronic polypharmacy impairs explorative behavior and reduces synaptic functions in young adult mice

A major challenge in the health care system is the lack of knowledge about the possible harmful effects of multiple drug treatments in old age. The present study aims to characterize a mouse model of polypharmacy, in order to investigate whether long-term exposure to multiple drugs could lead to adverse outcomes. To this purpose we selected five drugs from the ten most commonly used by older adults in Sweden (metoprolol, paracetamol, aspirin, simvastatin and citalopram). Five-month-old wild type male mice were fed for eight weeks with control or polypharmacy diet. We report for the first time that young adult polypharmacy-treated mice showed a significant decrease in exploration and spatial working memory compared to the control group. This memory impairment was further supported by a significant reduction of synaptic proteins in the hippocampus of treated mice. These novel results suggest that already at young adult age, use of polypharmacy affects explorative behavior and synaptic functions. This study underlines the importance of investigating the potentially negative outcomes from concomitant administration of different drugs, which have been poorly explored until now. The mouse model proposed here has translatable findings and can be applied as a useful tool for future studies on polypharmacy.

Methods to study mechanisms underlying altered hepatic drug elimination during pregnancy

Hepatic drug metabolism is a major route of drug elimination, mediated by multiple drug-metabolizing enzymes. Any changes in the rate and extent of hepatic drug metabolism can lead to altered drug efficacy or toxicity. Accumulating clinical evidence indicates that pregnancy is accompanied by changes in hepatic drug metabolism. In this article, we discuss in vitro and in vivo tools used to study the mechanisms underlying the altered drug metabolism during pregnancy, focusing on primary hepatocyte culture, transgenic animal models, and use of probe drugs to assess change in enzymatic activity. The information obtained from these studies has enabled prediction of clinical PK changes for a given drug in pregnant women.

Comparative Study of Protective Effect of Cimetidine and Verapamil on Paracetamol-Induced Hepatotoxicity in Mice

Paracetamol, chemically known as acetaminophen, if taken in higher doses has hepatotoxic potential. Cimetidine by inhibiting the cytochromal enzymes and reducing the production of the toxic metabolite can reduce the hepatotoxic potential while Verapamil can act as a hepatoprotective by maintaining calcium homeostasis. The present study was conducted to study the hepatoprotective activity of Cimetidine and Verapamil against the toxicity induced by paracetamol. In addition to the group receiving only distilled water or 300 mg/kg paracetamol additional groups were added treated with 150 mg/kg Cimetidine and Verapamil alone or both. The Liver function tests and histopathology revealed hepatotoxicity in the group receiving paracetamol (PCM) while normal parameters were observed in the groups receiving Cimetidine and Verapamil. Our results strongly suggested that Cimetidine and Verapamil possess hepatoprotective potential against paracetamol induced hepatotoxicity.

Modulating the Metabolic Phenotype of Cancer Microenvironment

This chapter provides a brief overview of the methods to study and modulate the metabolic phenotype of the tumor microenvironment, including own research work to demonstrate the impact that metabolic shifts in the host have on cancer. Firstly, we briefly discuss the relevance of using animal models to address this topic, and also the importance of acknowledging that animals have diverse metabolic phenotypes according to species, and even with strain, age or sex. We also present original data to highlight the impact that changes in metabolic phenotype of the microenvironment have on tumor progression. Using an acute leukemia mouse xenograft model and high-fat diet we show that a shift in the host metabolic phenotype, induced by high-fat feeding, significantly impacts on tumor progression. The mechanism through which this occurs involves a direct effect of the increased levels of circulating lipoproteins in both tumor and non-neoplastic cells.

Significantly Improved Pharmacokinetics Enhances In Vivo Efficacy of APX001 against Echinocandin- and Multidrug-Resistant Candida Isolates in a Mouse Model of Invasive Candidiasis

APX001 is a first-in-class, intravenous and orally available, broad-spectrum antifungal agent in clinical development for the treatment of life-threatening invasive fungal infections. The half-life of APX001A, the active moiety of APX001, is significantly shorter in mice than in humans (1.4 to 2.75 h in mice versus 2 to 2.5 days in humans), making the exploration of efficacy in mouse models difficult.

APX001 is a first-in-class, intravenous and orally available, broad-spectrum antifungal agent in clinical development for the treatment of life-threatening invasive fungal infections. The half-life of APX001A, the active moiety of APX001, is significantly shorter in mice than in humans (1.4 to 2.75 h in mice versus 2 to 2.5 days in humans), making the exploration of efficacy in mouse models difficult. After pretreatment with 1-aminobenzotriazole (ABT), a nonspecific cytochrome P450 inhibitor, greatly increased plasma APX001A exposure was observed in mice of different strains and of both genders. As a consequence, 26 mg/kg APX001 plus ABT sterilized kidneys in mice infected with Candida albicans, while APX001 alone at the same dose resulted in a modest burden reduction of only 0.2 log₁₀ CFU/g, relative to the vehicle control. In the presence of ABT, 2 days of once-daily dosing with APX001 at 26 mg/kg also demonstrated significant in vivo efficacy in the treatment of Candida glabrata infections in mice. Potent kidney burden reduction was achieved in mice infected with susceptible, echinocandin-resistant, or multidrug-resistant strains. In contrast, the standard of care (micafungin) was ineffective in treating infections caused by the resistant C. glabrata isolates.

Circadian Regulation of Hepatic Cytochrome P450 2a5 by Peroxisome Proliferator-Activated Receptor γ

Human CYP2A6 (Cyp2a5 in mice) plays an important role in metabolism and detoxification of various drugs and chemicals. Here, we investigated a potential role of peroxisome proliferator-activated receptor γ (Ppar-γ) in circadian regulation of the Cyp2a5 enzyme. We first showed that Cyp2a5 mRNA and protein in mouse liver displayed robust circadian oscillations. Consistent with a circadian protein pattern, Cyp2a5-mediated 7-hydroxylation of coumarin was circadian time-dependent. Formation of 7-hydroxycoumarin was more extensive at a dosing time of Zeitgeber time 2 (ZT2) than that at ZT14. Interestingly, the nuclear receptor Ppar-γ was also a circadian gene. Circadian Ppar-γ protein level was strongly correlated with the Cyp2a5 mRNA level (r = 0.989). Furthermore, Ppar-γ activation (by a selective agonist, rosiglitazone) upregulated Cyp2a5 expression in Hepa-1c1c7 cells, whereas Ppar-γ knockdown downregulated Cyp2a5 expression. Also, Ppar-γ knockdown blunted the rhythmicity of Cyp2a5 mRNA in serum-shocked Hepa-1c1c7 cells. In addition, a combination of promoter truncation analysis, mobility shift, and chromatin immunoprecipitation assays revealed that Ppar-γ directly bound to a PPAR response element (i.e., the -1418- to -1396-bp region) within Cyp2a5 promoter and activated the gene transcription. Taken together, Ppar-γ was a transcriptional activator of Cyp2a5, and its rhythmic expression contributed to circadian expression of Cyp2a5.

Liver lobe and strain differences in the activity of murine cytochrome P450 enzymes

The cytochrome P450 (CYP) enzyme superfamily is the most important enzyme system for phase I biotransformation. For toxico- and pharmacokinetic studies, use of liver-based microsomes, including those of mice, is state-of-the-art to study CYP-dependent metabolism. However, reproducibility and interpretation of these data is still very variable, partly because current testing guidelines do not cover details on organ sampling and potential liver lobe differences. Hence, we analyzed CYP activity, CYP protein content, mRNA expression of CYP1A, CYP2C, CYP2D and CYP3A isozymes, and cytochrome P450 reductase (CPR) activity of the four different liver lobes and processus papillaris of male C57BL/6J mice in comparison to whole liver. Additionally, we used whole liver of Balb/cJ and 129S1/SvImJ for strain comparison. Our data show significant differences in CYP activity, being most prominent in lobus sinister lateralis and lobus medialis, and lowest in processus papillaris. These differences were not caused by varying Cyp gene expression or CYP protein level, but partly correspond with lobe specific CPR activities. We also observed significant strain differences in CYP mRNA expression and activities with overall high activities in 129S1/SvImJ mice and low activities in Balb/cJ mice compared to C57BL/6J mice. In addition, strain specific differences in CYP2C and CYP2D activity seem to be reflected in strain dependent differences in CPR activity. In summary, our results indicate that in mice CYP activity and gene expression are strain dependent and may vary highly between liver lobes. To ensure reproducibility and comparability of different probes and studies, this should be taken into account when liver samples are collected for the analysis of CYP-dependent metabolism.

Generation and Characterization of a CYP2C11-Null Rat Model by Using the CRISPR/Cas9 Method

CYP2C11 is involved in the metabolism of many drugs in rats. To assess the roles of CYP2C11 in physiology and drug metabolism, a CYP2C11-null rat model was generated using the clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9method. A 2-base pair insertion was added to exon 6 of CYP2C11 in Sprague-Dawley rats. CYP2C11 was not detected by western blotting in liver microsomes of CYP2C11-null rats. No off-target effects were found at 11 predicted sites of the knockout model. The CYP2C11-null rats were viable and had no obvious abnormalities, with the exception of reduced fertility. Puberty in CYP2C11-null rats appeared to be delayed by ∼20 days, and the average litter size fell by 43%. Tolbutamide was used as a probe in this drug metabolism study. In the liver microsomes of CYP2C11-null rats, the V_max and intrinsicclearance values decreased by 22% and 47%, respectively, compared with those of wild-type rats. The K_m values increased by 47% compared with that of wild types. However, our pharmacokinetics study showed no major differences in any parameters between the two strains, in both males and females. In conclusion, a CYP2C11-null rat model was successfully generated and is a valuable tool to study the in vivo function of CYP2C11.

Evaluating the regenerative potential and functionality of human liver cells in mice

Liver diseases afflict millions of patients worldwide. Currently, the only long-term treatment for liver failure is the transplantation of a new liver. However, intravenously transplanting a suspension of human hepatocytes might be a less-invasive approach to partially reconstitute lost liver functions in human patients as evinced by promising outcomes in clinical trials. The purpose of this essay is to emphasize outstanding questions that continue to surround hepatocyte transplantation. While adult primary human hepatocytes are the gold standard for transplantation, hepatocytes are heterogeneous. Whether all hepatocytes engraft equally and what specifically defines an "engraftable" hepatocyte capable of long-term liver reconstitution remains unclear. To this end, mouse models of liver injury enable the evaluation of human hepatocytes and their behavior upon transplantation into a complex injured liver environment. While mouse models may not be fully representative of the injured human liver and human hepatocytes tend to engraft mice less efficiently than mouse hepatocytes, valuable lessons have nonetheless been learned from transplanting human hepatocytes into mouse models. With an eye to the future, it will be crucial to eventually detail the optimal biological source (whether in vivo- or in vitro-derived) and presumptive heterogeneity of human hepatocytes and to understand the mechanisms through which they engraft and regenerate liver tissue in vivo.

Assembly of Hepatocyte Spheroids Using Magnetic 3D Cell Culture for CYP450 Inhibition/Induction

There is a significant need for in vitro methods to study drug-induced liver injury that are rapid, reproducible, and scalable for existing high-throughput systems. However, traditional monolayer and suspension cultures of hepatocytes are difficult to handle and risk the loss of phenotype. Generally, three-dimensional (3D) cell culture platforms help recapitulate native liver tissue phenotype, but suffer from technical limitations for high-throughput screening, including scalability, speed, and handling. Here, we developed a novel assay for cytochrome P450 (CYP450) induction/inhibition using magnetic 3D cell culture that overcomes the limitations of other platforms by aggregating magnetized cells with magnetic forces. With this platform, spheroids can be rapidly assembled and easily handled, while replicating native liver function. We assembled spheroids of primary human hepatocytes in a 384-well format and maintained this culture over five days, including a 72 h induction period with known CYP450 inducers/inhibitors. CYP450 activity and viability in the spheroids were assessed and compared in parallel with monolayers. CYP450 activity was induced/inhibited in spheroids as expected, separate from any toxic response. Spheroids showed a significantly higher baseline level of CYP450 activity and induction over monolayers. Positive staining in spheroids for albumin and multidrug resistance-associated protein (MRP2) indicates the preservation of hepatocyte function within spheroids. The study presents a proof-of-concept for the use of magnetic 3D cell culture for the assembly and handling of novel hepatic tissue models.

Pharmacokinetics, toxicity, and cytochrome P450 modulatory activity of plumbagin

Background

The antimalarial activity of plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone), a naturally occurring naphthoquinone widely distributed in the Plumbaginaceae family has previously been demonstrated in vitro (good activity) and in vivo (weak activity). The aim of the study was to investigate the pharmacokinetic profile following a single oral dosing to explain inconsistency of results of the in vitro and in vivo antimalarial activities. In addition, toxicity profiles and potential of modulation of cytochrome P450 enzymes (CYP1A2 and CYP3A11) were also investigated.

Methods

The pharmacokinetics and toxicity of plumbagin were investigated in rats. The propensity of plumbagin to modulate the mRNA expression and activities of the two inducible forms of hepatic drug metabolizing enzyme cytochrome P450 (CYP450), i.e., CYP1A2 and CYP3A11, was investigated using microsomes prepared from mouse livers.

Results

Acute and subacute toxicity tests indicate low toxicity of plumbagin with maximum tolerated doses of 150 (single oral dose) and 25 (daily doses for 28 days) mg/kg body weight, respectively. The pharmacokinetic profile of plumbagin following a single oral dose of 100 mg/kg body weight suggests that delayed absorption and short residence time (median values of time to maximal concentration and elimination half-life = 9.63 and 5.0 h, respectively) in plasma. Plumbagin did not modulate mRNA expression and activities of CYP1A2 and CYP3A11.

Conclusions

Plumbagin was well tolerated following oral dose administration in rats. Pharmacokinetic property of this compound may be a limiting factor that explains the weak antimalarial activity of plumbagin observed in animal models. Potential metabolic interaction with co-administered drugs that are metabolized by CYP1A2 or CYP3A11 are unlikely.

Generation of a Humanized Mouse Liver Using Human Hepatic Stem Cells

A novel animal model involving chimeric mice with humanized livers established via human hepatocyte transplantation has been developed. These mice, in which the liver has been repopulated with functional human hepatocytes, could serve as a useful tool for investigating human hepatic cell biology, drug metabolism, and other preclinical applications. One of the key factors required for successful transplantation of human hepatocytes into mice is the elimination of the endogenous hepatocytes to prevent competition with the human cells and provide a suitable space and microenvironment for promoting human donor cell expansion and differentiation. To date, two major liver injury mouse models utilizing fumarylacetoacetate hydrolase (Fah) and uroplasminogen activator (uPA) mice have been established. However, Fah mice are used mainly with mature hepatocytes and the application of the uPA model is limited by decreased breeding. To overcome these limitations, Alb-toxin receptor mediated cell knockout (TRECK)/SCID mice were used for in vivo differentiation of immature human hepatocytes and humanized liver generation. Human hepatic stem cells (HpSCs) successfully repopulated the livers of Alb-TRECK/SCID mice that had developed lethal fulminant hepatic failure following diphtheria toxin (DT) treatment. This model of a humanized liver in Alb-TRECK/SCID mice will have functional applications in studies involving drug metabolism and drug-drug interactions and will promote other in vivo and in vitro studies.

Fit for purpose application of currently existing animal models in the discovery of novel epilepsy therapies

Animal seizure and epilepsy models continue to play an important role in the early discovery of new therapies for the symptomatic treatment of epilepsy. Since 1937, with the discovery of phenytoin, almost all anti-seizure drugs (ASDs) have been identified by their effects in animal models, and millions of patients world-wide have benefited from the successful translation of animal data into the clinic. However, several unmet clinical needs remain, including resistance to ASDs in about 30% of patients with epilepsy, adverse effects of ASDs that can reduce quality of life, and the lack of treatments that can prevent development of epilepsy in patients at risk following brain injury. The aim of this review is to critically discuss the translational value of currently used animal models of seizures and epilepsy, particularly what animal models can tell us about epilepsy therapies in patients and which limitations exist. Principles of translational medicine will be used for this discussion. An essential requirement for translational medicine to improve success in drug development is the availability of animal models with high predictive validity for a therapeutic drug response. For this requirement, the model, by definition, does not need to be a perfect replication of the clinical condition, but it is important that the validation provided for a given model is fit for purpose. The present review should guide researchers in both academia and industry what can and cannot be expected from animal models in preclinical development of epilepsy therapies, which models are best suited for which purpose, and for which aspects suitable models are as yet not available. Overall further development is needed to improve and validate animal models for the diverse areas in epilepsy research where suitable fit for purpose models are urgently needed in the search for more effective treatments.

Preclinical models for interrogating drug action in human cancers using Stable Isotope Resolved Metabolomics (SIRM)

AIMS

In this review we compare the advantages and disadvantages of different model biological systems for determining the metabolic functions of cells in complex environments, how they may change in different disease states, and respond to therapeutic interventions.

BACKGROUND

All preclinical drug-testing models have advantages and drawbacks. We compare and contrast established cell, organoid and animal models with ex vivo organ or tissue culture and in vivo human experiments in the context of metabolic readout of drug efficacy. As metabolism reports directly on the biochemical state of cells and tissues, it can be very sensitive to drugs and/or other environmental changes. This is especially so when metabolic activities are probed by stable isotope tracing methods, which can also provide detailed mechanistic information on drug action. We have developed and been applying Stable Isotope-Resolved Metabolomics (SIRM) to examine metabolic reprogramming of human lung cancer cells in monoculture, in mouse xenograft/explant models, and in lung cancer patients in situ (Lane et al. 2011; T. W. Fan et al. 2011; T. W-M. Fan et al. 2012; T. W. Fan et al. 2012; Xie et al. 2014b; Ren et al. 2014a; Sellers et al. 2015b). We are able to determine the influence of the tumor microenvironment using these models. We have now extended the range of models to fresh human tissue slices, similar to those originally described by O. Warburg (Warburg 1923), which retain the native tissue architecture and heterogeneity with a paired benign versus cancer design under defined cell culture conditions. This platform offers an unprecedented human tissue model for preclinical studies on metabolic reprogramming of human cancer cells in their tissue context, and response to drug treatment (Xie et al. 2014a). As the microenvironment of the target human tissue is retained and individual patient's response to drugs is obtained, this platform promises to transcend current limitations of drug selection for clinical trials or treatments.

CONCLUSIONS AND FUTURE WORK

Development of ex vivo human tissue and animal models with humanized organs including bone marrow and liver show considerable promise for analyzing drug responses that are more relevant to humans. Similarly using stable isotope tracer methods with these improved models in advanced stages of the drug development pipeline, in conjunction with tissue biopsy is expected significantly to reduce the high failure rate of experimental drugs in Phase II and III clinical trials.

Predicting Drug Extraction in the Human Gut Wall: Assessing Contributions from Drug Metabolizing Enzymes and Transporter Proteins using Preclinical Models

Intestinal metabolism can limit oral bioavailability of drugs and increase the risk of drug interactions. It is therefore important to be able to predict and quantify it in drug discovery and early development. In recent years, a plethora of models-in vivo, in situ and in vitro-have been discussed in the literature. The primary objective of this review is to summarize the current knowledge in the quantitative prediction of gut-wall metabolism. As well as discussing the successes of current models for intestinal metabolism, the challenges in the establishment of good preclinical models are highlighted, including species differences in the isoforms; regional abundances and activities of drug metabolizing enzymes; the interplay of enzyme-transporter proteins; and lack of knowledge on enzyme abundances and availability of empirical scaling factors. Due to its broad specificity and high abundance in the intestine, CYP3A is the enzyme that is frequently implicated in human gut metabolism and is therefore the major focus of this review. A strategy to assess the impact of gut wall metabolism on oral bioavailability during drug discovery and early development phases is presented. Current gaps in the mechanistic understanding and the prediction of gut metabolism are highlighted, with suggestions on how they can be overcome in the future.

CAR T-cell therapy: toxicity and the relevance of preclinical models

Chimeric antigen receptor (CAR) T cells form part of a broad wave of immunotherapies that are showing promise in early phase cancer clinical trials. This clinical delivery has been based upon preclinical efficacy testing that confirmed the proof of principle of the therapy. However, CAR T-cell therapy does not exist alone as T cells are generally given in combination with patient preconditioning, most commonly in the form of chemotherapy, and may also include systemic cytokine support, both of which are associated with toxicity. Consequently, complete CAR T-cell therapy includes elements where the toxicity profile is well known, but also includes the CAR T cell itself, for which toxicity profiles are largely unknown. With recent reports of adverse events associated with CAR T-cell therapy, there is now concern that current preclinical models may not be fit for purpose with respect to CAR T-cell toxicity profiling. Here, we explore the preclinical models used to validate CAR T-cell function and examine their potential to predict CAR T-cell driven toxicities for the future.

Spaceflight Effects on Cytochrome P450 Content in Mouse Liver

Hard conditions of long-term manned spaceflight can affect functions of many biological systems including a system of drug metabolism. The cytochrome P450 (CYP) superfamily plays a key role in the drug metabolism. In this study we examined the hepatic content of some P450 isoforms in mice exposed to 30 days of space flight and microgravity. The CYP content was established by the mass-spectrometric method of selected reaction monitoring (SRM). Significant changes in the CYP2C29, CYP2E1 and CYP1A2 contents were detected in mice of the flight group compared to the ground control group. Within seven days after landing and corresponding recovery period changes in the content of CYP2C29 and CYP1A2 returned to the control level, while the CYP2E1 level remained elevated. The induction of enzyme observed in the mice in the conditions of the spaceflight could lead to an accelerated biotransformation and change in efficiency of pharmacological agents, metabolizing by corresponding CYP isoforms. Such possibility of an individual pharmacological response to medication during long-term spaceflights and early period of postflight adaptation should be taken into account in space medicine.

Mechanism-based inhibition of Alantolactone on human cytochrome P450 3A4 in vitro and activity of hepatic cytochrome P450 in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Alantolactone (AL), one of the main active ingredients in Inula helenium L., has been included in various prescriptions of traditional Chinese medicine. The effects of AL on cytochrome P450 (CYP450) were still unclear. This study evaluated the inhibitory effect of AL on cytochrome P450s in vitro and in vivo.

MATERIALS AND METHODS

The inhibitory effects of AL on the CYPs activity were evaluated in human liver microsomes (HLMs) and recombinant cDNA-expressed enzymes incubation system, and then determined by LC-MS/MS based CYPs probe substrate assay. C57BL/6 mice were treated AL orally (0, 25, 50, 100 mg/kg) for 15 days. The inhibitory effects of AL on major Cyps in mice were examined at both the mRNA and enzyme activity levels.

RESULTS

AL showed a potent inhibitory effect on CYP3A4 activity with IC50 values of 3.599 (HLMs) and 3.90 (recombinant CYP3A4) μM, respectively. AL strongly decreased CYP3A4 activity in a dose-dependent but not time-dependent way in HLMs. Results from typical Lineweaver-Burk plots showed that AL could inhibit CYP3A4 activity noncompetitively, with a Ki value of 1.09 μM in HLMs. Moreover, activity of CYP2C19 could also be inhibited by AL with IC50 of 36.82 μM. Other CYP450 isoforms were not markedly affected by AL. The inhibition was also validated by in vivo study of mice. AL significantly decreased mRNA expression of Cyp2c and 3a family.

CONCLUSION

The study indicates that herb-drug interaction should be paid more attention between AL and drugs metabolized by CYP3A4.

Adverse Geriatric Outcomes Secondary to Polypharmacy in a Mouse Model: The Influence of Aging

We aimed to develop a mouse model of polypharmacy, primarily to establish whether short-term exposure to polypharmacy causes adverse geriatric outcomes. We also investigated whether old age increased susceptibility to any adverse geriatric outcomes of polypharmacy. Young (n= 10) and old (n= 21) male C57BL/6 mice were administered control diet or polypharmacy diet containing therapeutic doses of five commonly used medicines (simvastatin, metoprolol, omeprazole, acetaminophen, and citalopram). Mice were assessed before and after the 2- to 4-week intervention. Over the intervention period, we observed no mortality and no change in food intake, body weight, or serum biochemistry in any age or treatment group. In old mice, polypharmacy caused significant declines in locomotor activity (pre minus postintervention values in control 2 ± 13 counts, polypharmacy 32 ± 7 counts,p< .05) and front paw wire holding impulse (control -2.45 ± 1.02 N s, polypharmacy +1.99 ± 1.19 N s,p< .05), loss of improvement in rotarod latency (control -59 ± 11 s, polypharmacy -1.7 ± 17 s,p< .05), and lowered blood pressure (control -0.2 ± 3 mmHg, polypharmacy 11 ± 4 mmHg,p< .05). In young mice, changes in outcomes over the intervention period did not differ between control and polypharmacy groups. This novel model of polypharmacy is feasible. Even short-term polypharmacy impairs mobility, balance, and strength in old male mice.

Human hepatic stem cells transplanted into a fulminant hepatic failure Alb-TRECK/SCID mouse model exhibit liver reconstitution and drug metabolism capabilities

INTRODUCTION

Chimeric mice with humanized livers were recently established by transplanting human hepatocytes. This mouse model that is repopulated with functional human hepatocytes could be a useful tool for investigating human hepatic cell biology and drug metabolism and for other preclinical applications. Successfully transplanting human hepatocytes into mice requires that recipient mice with liver failure do not reject these human cells and provide a suitable microenvironment (supportive niche) to promote human donor cell expansion and differentiation. To overcome the limitations of current mouse models, we used Alb-TRECK/SCID mice for in vivo human immature hepatocyte differentiation and humanized liver generation.

METHODS

1.5 μg/kg diphtheria toxin was administrated into 8-week-old Alb-TRECK/SCID mice, and the degree of liver damage was assessed by serum aspartate aminotransferase activity levels. Forty-eight hours later, mice livers were sampled for histological analyses, and the human donor cells were then transplanted into mice livers on the same day. Chimeric rate and survival rate after cell transplantation was evaluated. Expressions of human hepatic-related genes were detected. A human albumin enzyme-linked immunosorbent assay was performed after 50 days of transplantation. On day 60 after transplantation, drug metabolism was examined in mice.

RESULTS

Both human primary fetal liver cells and hepatic stem cells were successfully repopulated in the livers of Alb-TRECK/SCID mice that developed lethal fulminant hepatic failure after administering diphtheria toxin; the repopulation rate in some mice was nearly 100%. Compared with human primary fetal liver cells, human hepatic stem cell transplantation rescued Alb-TRECK/SCID mice with lethal fulminant hepatic failure, and human hepatic stem cell-derived humanized livers secreted more human albumin into mouse sera and also functioned as a "human liver" that could metabolize the drugs ketoprofen and debrisoquine.

CONCLUSION

Our model of a humanized liver in Alb-TRECK/SCID mice may provide for functional applications such as drug metabolism, drug to drug interactions, and promote other in vivo and in vitro studies.

Novel pre-clinical methodologies for pharmacokinetic drug-drug interaction studies: spotlight on "humanized" animal models

Poly-therapy is common due to co-occurrence of several ailments in patients, leading to the elevated possibility of drug-drug interactions (DDI). Pharmacokinetic DDI often accounts for severe adverse drug reactions in patients resulting in withdrawal of drug from the market. Hence, the prediction of DDI is necessary at pre-clinical stage of drug development. Several human tissue and cell line-based in vitro systems are routinely used for screening metabolic and transporter pathways of investigational drugs and for predicting their clinical DDI potentials. However, ample constraints are associated with the in vitro systems and sometimes in vitro-in vivo extrapolation (IVIVE) fail to assess the risk of DDI in clinic. In vitro-in vivo correlation model in animals combined with human in vitro studies may be helpful in better prediction of clinical outcome. Native animal models vary remarkably from humans in drug metabolizing enzymes and transporters, hence, the interpretation of results from animal DDI studies is difficult. With the advent of modern molecular biology and engineering tools, novel pre-clinical animal models, namely, knockout rat/mouse, transgenic rat/mouse with humanized drug metabolizing enzymes and/or transporters and chimeric rat/mouse with humanized liver are developed. These models nearly simulate human-like drug metabolism and help to validate the in vivo relevance of the in vitro human DDI data. This review briefly discusses the application of such novel pre-clinical models for screening various type of DDI along with their advantages and limitations.

Dose-response of oridonin on hepatic cytochromes P450 mRNA expression and activities in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Oridonin, the major terpene found in Rabdosia rubescens, is widely used as a dietary supplement or therapeutic drug. The effects of oridonin on drug processing genes, such as cytochrome P450 and nuclear receptors, were still unclear. Therefore, the present study investigated the influence of oridonin on the hepatic drug metabolizing system to evaluate the safety through its drug interaction potential.

MATERIALS AND METHODS

In this study, eight-week-old male C57BL/6 mice were treated oridonin orally (0, 25, 50, 100, 200 mg/kg, i.g.) for 15 days. The effects of oridonin on major Cyps in mice livers were examined at both the mRNA and enzyme activity levels.

RESULTS

In general, there are no significant influence of various dose of oridonin on mice liver function. However, oridonin significantly increased Cyps (1a, 2a, 2d, 2e, 2c and 3a family) mRNA expression. In addition, it could induce Cyps activity in microsome incubation at maximum dosage. To our knowledge, it is the first time to identify oridonin as a Cyps inducer in vivo. It also promotes the expression of CAR, PXR and POR.

CONCLUSION

These results indicate that, if studies in mice extrapolate to humans by orthologous genes, oridonin appears to be a risk to herb-drug interactions due to its induction effects on drug processing genes expression and activation.

Experimental approaches for defining functional roles of microbes in the human gut

The complex and intimate relationship between humans and their gut microbial communities is becoming less obscure, due in part to large-scale gut microbial genome-sequencing projects and culture-independent surveys of the composition and gene content of these communities. These studies build upon, and are complemented by, experimental efforts to define underlying mechanisms of host-microbe interactions in simplified model systems. This review highlights the intersection of these approaches. Experimental studies now leverage the advances in high-throughput DNA sequencing that have driven the explosion of microbial genome and community profiling projects, and the loss-of-function and gain-of-function strategies long employed in model organisms are now being extended to microbial genes, species, and communities from the human gut. These developments promise to deepen our understanding of human gut host-microbiota relationships and are readily applicable to other host-associated and free-living microbial communities.

RNA-sequencing quantification of hepatic ontogeny of phase-I enzymes in mice

Phase-I drug metabolizing enzymes catalyze reactions of hydrolysis, reduction, and oxidation of drugs and play a critical role in drug metabolism. However, the functions of most phase-I enzymes are not mature at birth, which markedly affects drug metabolism in newborns. Therefore, characterization of the expression profiles of phase-I enzymes and the underlying regulatory mechanisms during liver maturation is needed for better estimation of using drugs in pediatric patients. The mouse is an animal model widely used for studying the mechanisms in the regulation of developmental expression of phase-I genes. Therefore, we applied RNA sequencing to provide a "true quantification" of the mRNA expression of phase-I genes in the mouse liver during development. Liver samples of male C57BL/6 mice at 12 different ages from prenatal to adulthood were used for defining the ontogenic mRNA profiles of phase-I families, including hydrolysis: carboxylesterase (Ces), paraoxonase (Pon), and epoxide hydrolase (Ephx); reduction: aldo-keto reductase (Akr), quinone oxidoreductase (Nqo), and dihydropyrimidine dehydrogenase (Dpyd); and oxidation: alcohol dehydrogenase (Adh), aldehyde dehydrogenase (Aldh), flavin monooxygenases (Fmo), molybdenum hydroxylase (Aox and Xdh), cytochrome P450 (P450), and cytochrome P450 oxidoreductase (Por). Two rapidly increasing stages of total phase-I gene expression after birth reflect functional transition of the liver during development. Diverse expression patterns were identified, and some large gene families contained the mRNA of genes that are enriched at different stages of development. Our study reveals the mRNA abundance of phase-I genes in the mouse liver during development and provides a valuable foundation for mechanistic studies in the future.

Current challenges and controversies in drug-induced liver injury

Current key challenges and controversies encountered in the identification of potentially hepatotoxic drugs and the assessment of drug-induced liver injury (DILI) are covered in this article. There is substantial debate over the classification of DILI itself, including the definition and validity of terms such as 'intrinsic' and 'idiosyncratic'. So-called idiosyncratic DILI is typically rare and requires one or more susceptibility factors in individuals. Consequently, it has been difficult to reproduce in animal models, which has limited the understanding of its underlying mechanisms despite numerous hypotheses. Advances in predictive models would also help to enable preclinical elimination of drug candidates and development of novel biomarkers. A small number of liver laboratory tests have been routinely used to help identify DILI, but their interpretation can be limited and confounded by multiple factors. Improved preclinical and clinical biomarkers are therefore needed to accurately detect early signals of liver injury, distinguish drug hepatotoxicity from other forms of liver injury, and differentiate mild from clinically important liver injury. A range of potentially useful biomarkers are emerging, although so far most have only been used preclinically, with only a few validated and used in the clinic for specific circumstances. Advances in the development of genomic biomarkers will improve the prediction and detection of hepatic injury in future. Establishing a definitive clinical diagnosis of DILI can be difficult, since it is based on circumstantial evidence by excluding other aetiologies and, when possible, identifying a drug-specific signature. DILI signals based on standard liver test abnormalities may be affected by underlying diseases such as hepatitis B and C, HIV and cancer, as well as the concomitant use of hepatotoxic drugs to treat some of these conditions. Therefore, a modified approach to DILI assessment is justified in these special populations and a suggested framework is presented that takes into account underlying disease when evaluating DILI signals in individuals. Detection of idiosyncratic DILI should, in some respects, be easier in the postmarketing setting compared with the clinical development programme, since there is a much larger and more varied patient population exposure over longer timeframes. However, postmarketing safety surveillance is currently limited by the quantity and quality of information available to make an accurate diagnosis, the lack of a control group and the rarity of cases. The pooling of multiple healthcare databases, which could potentially contain different types of patient data, is advised to address some of these deficiencies.

Humanized transgenic mouse models for drug metabolism and pharmacokinetic research

Extrapolation of the metabolic, pharmacokinetic and toxicological data obtained from animals to humans is not always straightforward, given the remarkable species difference in drug metabolism that is due in large part to the differences in drug-metabolizing enzymes between animals and humans. Furthermore, genetic variations in drug-metabolizing enzymes may significantly alter pharmacokinetics, drug efficacy and safety. Thus, humanized transgenic mouse lines, in which the human drug-metabolizing enzymes are expressed in mouse tissues in the presence or absence of mouse orthologues, have been developed to address such challenges. These humanized transgenic mice are valuable animal models in understanding the significance of specific human drug-metabolizing enzymes in drug clearance and pharmacokinetics, as well as in predicting potential drug-drug interactions and chemical toxicity in humans. This review, therefore, aims to summarize the development and application of some humanized transgenic mouse models expressing human drug-metabolizing enzymes. The limitations of these genetically modified mouse models are also discussed.

RNA sequencing reveals dynamic changes of mRNA abundance of cytochromes P450 and their alternative transcripts during mouse liver development

Cytochromes P450 (P450s) are a superfamily of enzymes that have critical functions in liver to catalyze the biotransformation of numerous drugs. However, the functions of most P450s are not mature at birth, which can markedly affect the metabolism of drugs in newborns. Therefore, characterization of the developmental profiles and regulatory mechanisms of P450 expression is needed for more rational drug therapy of pediatric patients. An animal model is indispensable for studying the mechanisms of postnatal development of the P450s. Hence we used RNA sequencing (RNA-Seq) to provide a "true quantification" of mRNA expression of all P450s in mouse liver during development. Liver samples of male C57BL/6 mice at 12 different ages from prenatal to adulthood were used. Total mRNAs of the 103 mouse P450s displayed two rapid increasing stages after birth, reflecting critical functional transition of liver during development. Four ontogenic expression patterns were identified among the 71 significantly expressed P450s, which categorized genes into neonatal-, adolescent-, adolescent/adult-, and adult-enriched groups. The 10 most highly expressed subfamilies of mouse P450s in livers of adult mice were CYP2E, -2C, -2D, -3A, -4A, -2F, -2A, -1A, -4F, and -2B, which showed diverse expression profiles during development. The expression patterns of multiple members within a P450 subfamily were often classified to different groups. RNA-Seq also enabled the quantification of known transcript variants of CYP2C44, CYP2C50, CYP2D22, CYP3A25, and CYP26B1 and identification of novel transcripts for CYP2B10, CYP2D26, and CYP3A13. In conclusion, this study reveals the mRNA abundance of all the P450s in mouse liver during development and provides a foundation for mechanistic studies in the future.

Drug-metabolizing enzyme, transporter, and nuclear receptor genetically modified mouse models

Determining the in vivo significance of a specific enzyme, transporter, or xenobiotic receptor in drug metabolism and pharmacokinetics may be hampered by gene multiplicity and complexity, levels of expression, and interaction between various components involved. The development of knockout (loss-of-function) and transgenic (gain-of-function) mouse models opens the door to the improved understanding of gene function in a whole-body system. There is also growing interest in the development of humanized mice to overcome species differences in drug metabolism and disposition. This review, therefore, aims to summarize and discuss some successful examples of drug-metabolizing enzyme, transporter, and nuclear-receptor genetically modified mouse models. These genetically modified mouse models have been proven as invaluable models for understanding in vivo function of drug-metabolizing enzymes, transporters, and xenobiotic receptors in drug metabolism and transport, as well as predicting potential drug-drug interaction and toxicity in humans. Nevertheless, concerns remain about interpretation of data obtained from such genetically modified mouse models, in which the expression of related genes is altered significantly.

Effect of prototypical inducers on ligand activated nuclear receptor regulated drug disposition genes in rodent hepatic and intestinal cells

AIM

The aim of this study was to investigate the impact on expression of mRNA and protein by paradigm inducers/activators of nuclear receptors and their target genes in rat hepatic and intestinal cells. Furthermore, assess marked inter laboratory conflicting reports regarding species and tissue differences in expression to gain further insight and rationalise previously observed species differences between rodent and human based systems.

METHODS

Quantitative real time-polymerase chain reaction (QRT-PCR) and immunoblots were used to assess messenger RNA (mRNA) and protein expression for CYP2B2, CYP3A1, CYP3A2, CYP3A9, ABCB1a, ABCB1b, ABCC1, ABCC2, pregnane X receptor (PXR), farnesoid X receptor (FXR) and constituitive androstane receptor (CAR) in rat hepatoma cell line H411E, intestinal cells, Iec-6, and rat primary hepatocytes, in response to exposure for 18 h with prototypical inducers.

RESULTS

Dexamethasone (DEX) and pregnenolone 16alpha carbonitrile (PCN) significantly induced PXR, CYP3A9, ABCB1a and ABCB1b. However, when co-incubated, DEX appeared to restrict PCN-dependent induction. Chenodeoxycholic acid (CDCA) was the only ligand to induce FXR in all three cell types. Despite previously reported species differences between PCN and rifampicin (RIF), both compounds exhibited a similar profile of induction.

CONCLUSION

Data presented herein may explain some of the discrepancies previously reported with respect to species differences from different laboratories and have important implications for study design.

Long-term virus-induced alterations of CYP3A-mediated drug metabolism: a look at the virology, immunology and molecular biology of a multi-faceted problem

Virus infections are on the rise. Although the first description of CYP expression during virus infection was recorded 50 years ago, mechanistic studies of this phenomenon only began to appear in the last decade due to breakthroughs in molecular biology, genomic and transgenic technology. This review describes the relationship(s) among CYP-mediated drug metabolism, virus infection and the immune response and evaluates in vitro and in vivo models for mechanistic studies. The first studies that assessed CYP expression during infection focused on inflammatory mediators and the innate immune response at early time points. Recent studies assessing virus infection and its effect on hepatic CYP expression noted more long-term effects. An obvious approach toward understanding how viruses affect hepatic CYP3A expression and function would be to assess key regulators of CYP during infection. Improvements in techniques to identify post-translational modifications of CYP and systems that focus on virus-receptor interactions which allow subtraction and addition of immunological and regulatory elements that drive CYP will demonstrate that long-term changes in drug metabolism start from the time the virus enters the circulation, are reinforced by virus binding to cellular targets and further solidified by changes in cellular processes long after the virus is cleared.

The uPA(+/+)-SCID mouse with humanized liver as a model for in vivo metabolism of 4-androstene-3,17-dione

The metabolism in primary human hepatocyte cultures often deviates from that in clinical studies, which in turn are hampered by ethical constraints. Here the use of urokinase-type plasminogen activator-severe combined immunodeficiency [uPA(+/+)-SCID] mice transplanted with human hepatocytes was investigated as a model for in vivo metabolic studies. The urinary excretion profile after oral administration of 4-androstene-3,17-dione (AD) in chimeric mice was investigated by using gas chromatography-mass spectrometry detection and was compared with previously reported metabolites of AD in humans and cell cultures. Chimeric mice exhibited an AD metabolic profile similar to that of humans, showing androsterone and etiocholanolone as major metabolites. Several hydroxylated steroids were detected as minor metabolites in the chimeric mice compared with hepatocyte cultures. A significant correlation between the extent of liver replacement and the relative abundances of human-type metabolites was established. The results for AD showed that humanized liver uPA-SCID mice can serve as an alternative model for in vivo metabolism studies in humans. In the future, this model could possibly be used for other steroids or pharmaceutical compounds.

Safety assessment of drug metabolites: implications of regulatory guidance and potential application of genetically engineered mouse models that express human P450s

Species differences in drug metabolism present two challenges that may confound the nonclinical safety assessment of candidate drugs. The first challenge is encountered when metabolites are formed uniquely or disproportionately in humans. Another challenge is understanding the human relevance of toxicities associated with metabolites formed uniquely or disproportionately in a nonclinical species. One potential approach to minimize the impact of metabolite related challenges is to consider genetically engineered mouse models that express human P450 enzymes. Human P450 expressing mouse models may have the ability to generate major human metabolites and eliminate or reduce the formation of mouse specific metabolites. Prior to determining the utility of any particular model, it is important to qualify by characterizing protein expression, establishing whether the model generates an in vivo metabolite profile more closely related to that of humans than the wild-type mouse, verifying genetic stability, and evaluating animal health. When compared to the current strategy for handling metabolite challenges (i.e., direct administration of metabolite), identifying an appropriate human P450 expressing model could provide a number of benefits. Such benefits include improved scientific relevance of the evaluation, decreased resource needs, and a possible reduction in the number of animals used. These benefits may ultimately improve the quality and speed by which promising new drug candidates are developed and delivered to patients.

Neurodevelopment genes in lampreys reveal trends for forebrain evolution in craniates

The forebrain is the brain region which has undergone the most dramatic changes through vertebrate evolution. Analyses conducted in lampreys are essential to gain insight into the broad ancestral characteristics of the forebrain at the dawn of vertebrates, and to understand the molecular basis for the diversifications that have taken place in cyclostomes and gnathostomes following their splitting. Here, we report the embryonic expression patterns of 43 lamprey genes, coding for transcription factors or signaling molecules known to be involved in cell proliferation, stemcellness, neurogenesis, patterning and regionalization in the developing forebrain. Systematic expression patterns comparisons with model organisms highlight conservations likely to reflect shared features present in the vertebrate ancestors. They also point to changes in signaling systems –pathways which control the growth and patterning of the neuroepithelium-, which may have been crucial in the evolution of forebrain anatomy at the origin of vertebrates.

Understanding the role of reactive metabolites in drug-induced hepatotoxicity: state of the science

Drug-induced liver injury (DILI) represents a major impediment to the development of new drugs and is a leading cause of drug withdrawal. The occurrence of hepatotoxicity has been closely associated with the formation of chemically reactive metabolites. Huge investment has focused on the screening of chemically reactive metabolites to offer a pragmatic approach to produce safer drugs and also reduce drug attrition and prevent market place withdrawal. However, questions surrounding the importance of chemically reactive metabolites still remain. Increasing evidence now exists for the multi-factorial nature of DILI, in particular the role played by the host immune system or disease state in the pathogenesis of DILI. This review aims to evaluate the current measures for the prediction and diagnosis of DILI and to highlight investigations being made to understand the multidimensional nature. Some of the steps being made to generate improved physiological systems to identify more sensitive, reflective mechanism-based biomarkers to aid the earlier identification of DILI and develop safer medicines are also discussed.