Idiosyncratic drug-induced liver injury and the role of inflammatory stress with an emphasis on an animal model of trovafloxacin hepatotoxicity

Fluoroquinolones and the risk of aortic aneurysm or aortic dissection: an updated systematic review and meta-analysis including 53,651,283 patients

INTRODUCTION

The association between fluoroquinolone use and the risk of aortic aneurysm as well as the risk of aortic dissections remains uncertain, primarily due to conflicting findings from observational studies. We sought to conduct a double-systematic review and meta-analysis of all observational studies to assess the existence and extent of both these associations. The aim of our study is to assess the role of Fluoroquinolone on aortic aneurysm and aortic dissection in comparison to other antibiotics.

EVIDENCE ACQUISITION

MEDLINE and Cochrane CENTRAL were systematically searched up till June 2021 for observational studies studying the correlation between fluoroquinolone usage and aortic aneurysms and dissections. Random-effects pooling was used to calculate adjusted hazard ratios (HRs) with 95% confidence intervals (CI). To assess publication bias, propensity score matching was conducted, and heterogeneity was evaluated by using I2 statistics.

EVIDENCE SYNTHESIS

Of 688 potentially relevant articles, 635 titles were screened. Ten studies were included in the systematic review, and 4 observational studies with 53,651,283 participants were eligible to be included in the meta-analysis. Pooled estimates showed that fluoroquinolone use was associated with a higher risk of aortic aneurysm when compared to other Antibiotics (HR 1.84, 95% CI 1.10-2.48; P<0.00001). However, fluoroquinolones had no significant effect on the risk of developing aortic dissection (HR 1.09, 95% CI 0.96-1.25; P=0.19).

CONCLUSIONS

The present analysis suggests that fluoroquinolone usage is more strongly linked to aortic aneurysm than other antibiotics. However, there was no statistically significant link between fluoroquinolone and aortic dissection. As a result, clinicians should exercise caution when administering fluoroquinolone to patients who have a history of or are at risk of aortic disease.

National reflection on organs-on-chip for drug development: New regulatory challenges

Organs-on-chip (OoC) are innovative and promising in vitro models, particularly in the process of developing new drugs, to improve predictivity of preclinical studies in humans. However, a lack of regulatory consensus on acceptance criteria and standards around these technologies currently hinders their adoption and implementation by end-users. A reflection has been conducted at the National Agency for Medicines and Health products safety (ANSM) in order to address this issue, which has gained momentum at the international level in recent years. If the subject of OoC is of international interest, France is also in the process of structuring an OoC network, in order to best support the emergence of this new technological innovation. Focusing on liver-on-a-chip, the authors drafted a first list of regulatory requirements to help standardize these devices and their use. Technological and biological relevance of liver-on-a-chip was also evaluated, in comparison with current in vitro and in vivo models, based on the available literature. The authors offer an analysis of the current scientific and regulatory situation, highlighting the key regulatory issues for the future.

Multi-epitope vaccine against drug-resistant strains of Mycobacterium tuberculosis: a proteome-wide subtraction and immunoinformatics approach

Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis, one of the most deadly infections in humans. The emergence of multidrug-resistant and extensively drug-resistant Mtb strains presents a global challenge. Mtb has shown resistance to many frontline antibiotics, including rifampicin, kanamycin, isoniazid, and capreomycin. The only licensed vaccine, Bacille Calmette-Guerin, does not efficiently protect against adult pulmonary tuberculosis. Therefore, it is urgently necessary to develop new vaccines to prevent infections caused by these strains. We used a subtractive proteomics approach on 23 virulent Mtb strains and identified a conserved membrane protein (MmpL4, NP_214964.1) as both a potential drug target and vaccine candidate. MmpL4 is a non-homologous essential protein in the host and is involved in the pathogen-specific pathway. Furthermore, MmpL4 shows no homology with anti-targets and has limited homology to human gut microflora, potentially reducing the likelihood of adverse effects and cross-reactivity if therapeutics specific to this protein are developed. Subsequently, we constructed a highly soluble, safe, antigenic, and stable multi-subunit vaccine from the MmpL4 protein using immunoinformatics. Molecular dynamics simulations revealed the stability of the vaccine-bound Toll-like receptor-4 complex on a nanosecond scale, and immune simulations indicated strong primary and secondary immune responses in the host. Therefore, our study identifies a new target that could expedite the design of effective therapeutics, and the designed vaccine should be validated. Future directions include an extensive molecular interaction analysis, in silico cloning, wet-lab experiments, and evaluation and comparison of the designed candidate as both a DNA vaccine and protein vaccine.

Evaluation of drug-induced liver toxicity of trovafloxacin and levofloxacin in a human microphysiological liver model

Drug-induced liver injury induced by already approved substances is a major threat to human patients, potentially resulting in drug withdrawal and substantial loss of financial resources in the pharmaceutical industry. Trovafloxacin, a broad-spectrum fluoroquinolone, was found to have unexpected side effects of severe hepatotoxicity, which was not detected by preclinical testing. To address the limitations of current drug testing strategies mainly involving 2D cell cultures and animal testing, a three-dimensional microphysiological model of the human liver containing expandable human liver sinusoidal endothelial cells, monocyte-derived macrophages and differentiated HepaRG cells was utilized to investigate the toxicity of trovafloxacin and compared it to the structurally-related non-toxic drug levofloxacin. In the model, trovafloxacin elicited vascular and hepatocellular toxicity associated with pro-inflammatory cytokine release already at clinically relevant concentrations, whereas levofloxacin did not provoke tissue injury. Similar to in vivo, cytokine secretion was dependent on a multicellular immune response, highlighting the potential of the complex microphysiological liver model for reliably detecting drug-related cytotoxicity in preclinical testing. Moreover, hepatic glutathione depletion and mitochondrial ROS formation were elucidated as intrinsic toxicity mechanisms contributing to trovafloxacin toxicity.

Pharmacology of pannexin channels

Pannexin channels play fundamental roles in regulating inflammation and have been implicated in many diseases including hypertension, stroke, and neuropathic pain. Thus, the ability to pharmacologically block these channels is a vital component of several therapeutic approaches. Pharmacologic interrogation of model systems also provides a means to discover new roles for pannexins in cell physiology. Here, we review the state of the art for agents that can be used to block pannexin channels, with a focus on chemical pharmaceuticals and peptide mimetics that act on pannexin 1. Guidance on interpreting results obtained with pannexin pharmacologics in experimental systems is discussed, as well as strengths and caveats of different agents, including specificity and feasibility of clinical application.

Tandem mass tag-based quantitative proteomic profiling identifies candidate serum biomarkers of drug-induced liver injury in humans

Diagnosis of drug-induced liver injury (DILI) and its distinction from other liver diseases are significant challenges in drug development and clinical practice. Here, we identify, confirm, and replicate the biomarker performance characteristics of candidate proteins in patients with DILI at onset (DO; n = 133) and follow-up (n = 120), acute non-DILI at onset (NDO; n = 63) and follow-up (n = 42), and healthy volunteers (HV; n = 104). Area under the receiver operating characteristic curve (AUC) for cytoplasmic aconitate hydratase, argininosuccinate synthase, carbamoylphosphate synthase, fumarylacetoacetase, fructose-1,6-bisphosphatase 1 (FBP1) across cohorts achieved near complete separation (range: 0.94-0.99) of DO and HV. In addition, we show that FBP1, alone or in combination with glutathione S-transferase A1 and leukocyte cell-derived chemotaxin 2, could potentially assist in clinical diagnosis by distinguishing NDO from DO (AUC range: 0.65-0.78), but further technical and clinical validation of these candidate biomarkers is needed.

Acetaminophen-Induced Hepatotoxicity in Obesity and Nonalcoholic Fatty Liver Disease: A Critical Review

The epidemic of obesity, type 2 diabetes and nonalcoholic liver disease (NAFLD) favors drug consumption, which augments the risk of adverse events including liver injury. For more than 30 years, a series of experimental and clinical investigations reported or suggested that the common pain reliever acetaminophen (APAP) could be more hepatotoxic in obesity and related metabolic diseases, at least after an overdose. Nonetheless, several investigations did not reproduce these data. This discrepancy might come from the extent of obesity and steatosis, accumulation of specific lipid species, mitochondrial dysfunction and diabetes-related parameters such as ketonemia and hyperglycemia. Among these factors, some of them seem pivotal for the induction of cytochrome P450 2E1 (CYP2E1), which favors the conversion of APAP to the toxic metabolite N-acetyl-p-benzoquinone imine (NAPQI). In contrast, other factors might explain why obesity and NAFLD are not always associated with more frequent or more severe APAP-induced acute hepatotoxicity, such as increased volume of distribution in the body, higher hepatic glucuronidation and reduced CYP3A4 activity. Accordingly, the occurrence and outcome of APAP-induced liver injury in an obese individual with NAFLD would depend on a delicate balance between metabolic factors that augment the generation of NAPQI and others that can mitigate hepatotoxicity.

Performance assessment and economic analysis of a human Liver-Chip for predictive toxicology

BACKGROUND

Conventional preclinical models often miss drug toxicities, meaning the harm these drugs pose to humans is only realized in clinical trials or when they make it to market. This has caused the pharmaceutical industry to waste considerable time and resources developing drugs destined to fail. Organ-on-a-Chip technology has the potential improve success in drug development pipelines, as it can recapitulate organ-level pathophysiology and clinical responses; however, systematic and quantitative evaluations of Organ-Chips' predictive value have not yet been reported.

METHODS

870 Liver-Chips were analyzed to determine their ability to predict drug-induced liver injury caused by small molecules identified as benchmarks by the Innovation and Quality consortium, who has published guidelines defining criteria for qualifying preclinical models. An economic analysis was also performed to measure the value Liver-Chips could offer if they were broadly adopted in supporting toxicity-related decisions as part of preclinical development workflows.

RESULTS

Here, we show that the Liver-Chip met the qualification guidelines across a blinded set of 27 known hepatotoxic and non-toxic drugs with a sensitivity of 87% and a specificity of 100%. We also show that this level of performance could generate over $3 billion annually for the pharmaceutical industry through increased small-molecule R&D productivity.

CONCLUSIONS

The results of this study show how incorporating predictive Organ-Chips into drug development workflows could substantially improve drug discovery and development, allowing manufacturers to bring safer, more effective medicines to market in less time and at lower costs.

Pharmacokinetic and toxicodynamic concepts in idiosyncratic, drug-induced liver injury

INTRODUCTION

Idiosyncratic drug-induced liver injury (IDILI) causes morbidity and mortality in patients and leads to curtailed use of efficacious pharmaceuticals. Unlike intrinsically toxic reactions, which depend on dose, IDILI occurs in a minority of patients at therapeutic doses. Much remains unknown about causal links among drug exposure, a mode of action, and liver injury. Consequently, numerous hypotheses about IDILI pathogenesis have arisen.

AREAS COVERED

Pharmacokinetic and toxicodynamic characteristics underlying current hypotheses of IDILI etiology are discussed and illustrated graphically.

EXPERT OPINION

Hypotheses to explain IDILI etiology all involve alterations in pharmacokinetics, which lead to plasma drug concentrations that rise above a threshold for toxicity, or in toxicodynamics, which result in a lowering of the toxicity threshold. Altered pharmacokinetics arise, for example, from changes in drug metabolism or from transporter polymorphisms. A lowered toxicity threshold can arise from drug-induced mitochondrial injury, accumulation of toxic endogenous factors or harmful immune responses. Newly developed, interactive freeware (DemoTox-PK; https://bit.ly/DemoTox-PK) allows the user to visualize how such alterations might lead to a toxic reaction. The illustrations presented provide a framework for conceptualizing idiosyncratic reactions and could serve as a stimulus for future discussion, education, and research into modes of action of IDILI.

Pre-clinical 2D and 3D toxicity response to a panel of nanomaterials; comparative assessment of NBM-induced liver toxicity

Nanobiomaterials, or NBMs, have been used in medicine and bioimaging for decades, with wide-reaching applications ranging from their uses as carriers of genes and drugs, to acting as sensors and probes. When developing nanomedicine products, it is vitally important to evaluate their safety, ensuring that both biocompatibility and efficacy are achieved so their applications in these areas can be safe and effective. When discussing the safety of nanomedicine in general terms, it is foolish to make generalised statements due to the vast array of different manufactured nanomaterials, formulated from a multitude of different materials, in many shapes and sizes; therefore, NBM pre-clinical screening can be a significant challenge. Outside of their distribution in the various tissues, organs and cells in the body, a key area of interest is the impact of NBMs on the liver. A considerable issue for researchers today is accurately predicting human-specific liver toxicity prior to clinical trials, with hepatotoxicity not only the most cited reasons for withdrawal of approved drugs, but also a primary cause of attrition in pre-launched drug candidates. To date, no simple solution to adequately predict these adverse effects exists prior to entering human experimentation. The limitations of the current pre-clinical toolkit are believed to be one of the main reasons for this, with questions being raised on the relevance of animal models in pre-clinical assessment, and over the ability of conventional, simplified in vitro cell–based assays to adequately assess new drug candidates or NBMs. Common 2D cell cultures are unable to adequately represent the functions of 3D tissues and their complex cell–cell and cell–matrix interactions, as well as differences found in diffusion and transport conditions. Therefore, testing NBM toxicity in conventional 2D models may not be an accurate reflection of the actual toxicity these materials impart on the body. One such method of overcoming these issues is the use of 3D cultures, such as cell spheroids, to more accurately assess NBM-tissue interaction. In this study, we introduce a 3D hepatocellular carcinoma model cultured from HepG2 cells to assess both the cytotoxicity and viability observed following treatment with a variety of NBMs, namely a nanostructured lipid carrier (in the specific technical name = LipImage^™ 815), a gold nanoparticle (AuNP) and a panel of polymeric (in the specific technical name = PACA) NBMs. This model is also in compliance with the 3Rs policy of reduction, refinement and replacement in animal experimentation [1], and meets the critical need for more advanced in vitro models for pre-clinical nanotoxicity assessment.

Recent Advances in Models of Immune-Mediated Drug-Induced Liver Injury

Hepatic inflammation is a key feature of a variety of liver diseases including drug-induced liver injury (DILI), orchestrated by the innate immune response (Kupffer cells, monocytes, neutrophils, dendritic cells) and the adaptive immune system (T cells and natural killer T cells). In contrast to acute DILI, prediction of immune-mediated DILI (im-DILI) has been more challenging due to complex disease pathogenesis, lack of reliable models and limited knowledge of underlying mechanisms. This review summarizes in vivo and in vitro systems that have been used to model im-DILI. In particular, the review focuses on state-of-the-art in vitro human-based multicellular models which have been developed to supplement the use of in vivo models due to interspecies variation and increasing ethical concerns regarding animal use. Advantages of the co-cultures in maintaining hepatocyte functions and importantly, introducing heterotypic cell-cell interactions to mimic inflammatory hepatic microenvironment are discussed. Challenges regarding cell source and incorporation of different cells with physical cell-cell contact are outlined and potential solutions are proposed. It is likely that better understanding of the interplay of immune cells in liver models will allow for the development of more accurate systems to better predict hepatotoxicity and stratification of drugs that can cause immune-mediated effects.

Engineering Modular 3D Liver Culture Microenvironments In Vitro to Parse the Interplay between Biophysical and Biochemical Microenvironment Cues on Hepatic Phenotypes

In vitro models of human liver functions are used across a diverse range of applications in preclinical drug development and disease modeling, with particular increasing interest in models that capture facets of liver inflammatory status. This study investigates how the interplay between biophysical and biochemical microenvironment cues influence phenotypic responses, including inflammation signatures, of primary human hepatocytes (PHH) cultured in a commercially available perfused bioreactor. A 3D printing-based alginate microwell system was designed to form thousands of hepatic spheroids in a scalable manner as a comparator 3D culture modality to the bioreactor. Soft, synthetic extracellular matrix (ECM) hydrogel scaffolds with biophysical properties mimicking features of liver were engineered to replace polystyrene scaffolds, and the biochemical microenvironment was modulated with a defined set of growth factors and signaling modulators. The supplemented media significantly increased tissue density, albumin secretion, and CYP3A4 activity but also upregulated inflammatory markers. Basal inflammatory markers were lower for cells maintained in ECM hydrogel scaffolds or spheroid formats than polystyrene scaffolds, while hydrogel scaffolds exhibited the most sensitive response to inflammation as assessed by multiplexed cytokine and RNA-seq analyses. Together, these engineered 3D liver microenvironments provide insights for probing human liver functions and inflammatory response in vitro.

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.

Role of immune dysfunction in drug induced liver injury

Drug-induced liver injury (DILI) is one of the leading causes of liver failure and withdrawal of drugs from the market. A poor understanding of the precipitating event aetiology and mechanisms of disease progression has rendered the prediction and subsequent treatment intractable. Recent literature suggests that some drugs can alter the liver’s repair systems resulting in injury. The pathophysiology of DILI is complex, and immune dysfunction plays an important role in determining the course and severity of the disease. Immune dysfunction is influenced by the host response to drug toxicity. A deeper understanding of these processes may be beneficial in the management of DILI and aid in drug development. This review provides a structured framework presenting DILI in three progressive stages that summarize the interplay between drugs and the host defence networks.

Investigation of the idiosyncratic hepatotoxicity of Polygonum multiflorum Thunb. through metabolomics using GC-MS

BACKGROUND

The idiosyncratic hepatotoxicity of Polygonum multiflorum (PM) has attracted considerable interest, but the idiosyncratically hepatotoxic components and endogenous metabolite changes resulting from idiosyncratic hepatotoxicity of PM are not well understood. The aim of this study was to identify the idiosyncratically hepatotoxic components and potential endogenous metabolic biomarkers for PM-induced liver injury.

METHODS

Serum biochemical indicators and hematoxylin and eosin (H&E) staining were evaluated to identify pathological changes. Gas chromatography/mass spectrometry (GC-MS) was performed to identify changes in metabolic biomarkers. Orthogonal projection to latent structures discriminant analysis (OPLS-DA) was applied to determine group clustering trends and differential metabolites.

RESULTS

The results for the liver index, the liver function index and liver pathology showed that Polygonum multiflorum ethanol extract (PME), 50% ethanol elution fractions and tetrahydroxystilbene glucoside (TSG) from PME can induce idiosyncratic hepatotoxicity. TSG was the main idiosyncratically hepatotoxic component. Forty endogenous metabolites were identified in the rat liver. Six biomarkers, including lower levels of L-valine and higher levels of 3-hydroxybutyric acid, hexadecanoic acid, ribose, phosphoric acid and oxalic acid, were related to PM-induced liver injury. These differential biomarkers led to disruptions in amino acid, fatty acid, oxalate, energy and glucose metabolism. A total of 32 types of endogenous metabolites were identified in rat serum. Ten biomarkers were related to the liver injury induced by TSG, including lower levels of L-valine and L-proline and higher levels of urea, caproic acid, DL-malic acid, D-mannose, 3-hydroxybutyric acid, D-galactose, octadecane and hexadecanoic acid. These differential biomarkers led to disruptions in amino acid, glucose and fat metabolism. The mechanism of idiosyncratic hepatotoxicity in PM involves TSG-induced disruptions in amino acid metabolism, lipid metabolism, energy metabolism and glucose metabolism.

CONCLUSIONS

These findings reflect the material basis and metabolic mechanism of idiosyncratic PM hepatotoxicity.

Oxidative Stress in Drug-Induced Liver Injury (DILI): From Mechanisms to Biomarkers for Use in Clinical Practice

Idiosyncratic drug-induced liver injury (DILI) is a type of hepatic injury caused by an uncommon drug adverse reaction that can develop to conditions spanning from asymptomatic liver laboratory abnormalities to acute liver failure (ALF) and death. The cellular and molecular mechanisms involved in DILI are poorly understood. Hepatocyte damage can be caused by the metabolic activation of chemically active intermediate metabolites that covalently bind to macromolecules (e.g., proteins, DNA), forming protein adducts-neoantigens-that lead to the generation of oxidative stress, mitochondrial dysfunction, and endoplasmic reticulum (ER) stress, which can eventually lead to cell death. In parallel, damage-associated molecular patterns (DAMPs) stimulate the immune response, whereby inflammasomes play a pivotal role, and neoantigen presentation on specific human leukocyte antigen (HLA) molecules trigger the adaptive immune response. A wide array of antioxidant mechanisms exists to counterbalance the effect of oxidants, including glutathione (GSH), superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPX), which are pivotal in detoxification. These get compromised during DILI, triggering an imbalance between oxidants and antioxidants defense systems, generating oxidative stress. As a result of exacerbated oxidative stress, several danger signals, including mitochondrial damage, cell death, and inflammatory markers, and microRNAs (miRNAs) related to extracellular vesicles (EVs) have already been reported as mechanistic biomarkers. Here, the status quo and the future directions in DILI are thoroughly discussed, with a special focus on the role of oxidative stress and the development of new biomarkers.

TNFα enhances trovafloxacin-induced in vitro hepatotoxicity by inhibiting protective autophagy

Trovafloxacin (TVX) is associated with idiosyncratic drug-induced liver injury (iDILI) and inflammation-mediated hepatotoxicity. However, the inflammatory stress-regulated mechanisms in iDILI remain unclear. Herein, we elucidated the novel role of tumor-necrosis factor alpha (TNFα), an inflammatory stress factor, in TVX-induced in vitro hepatotoxicity and synergistic toxicity. TVX specifically induced synergistic toxicity in HepG2 cells with TNFα, which inhibits autophagy. TVX-treated HepG2 cells induced protective autophagy by inhibiting the expression of mTOR signaling proteins, while ATG5 knockdown in HepG2 cells, responsible for the impairment of autophagy, enhanced TVX-induced toxicity due to the increase in cytochrome C release and JNK pathway activation. Interestingly, the expression of mTOR signal proteins, which were suppressed by TVX, disrupted the negative feedback of the PI3K/AKT pathway and TNFα rebounded p70S6K phosphorylation. Co-treatment with TVX and TNFα inhibited protective autophagy by maintaining p70S6K activity, which enhanced TVX-induced cytotoxicity. Phosphorylation of p70S6K was inhibited by siRNA knockdown and rapamycin to restore TNFα-inhibited autophagy, which prevented the synergistic effect on TVX-induced cytotoxicity. These results indicate that TVX activates protective autophagy in HepG2 cells exposed to toxicity and an imbalance in negative feedback regulation of autophagy by TNFα synergistically enhanced the toxicity. The finding from this study may contribute to a better understanding of the mechanisms underlying iDILI associated with inflammatory stress.

Models of Idiosyncratic Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is a leading cause of attrition during the early and late stages of drug development and after a drug is marketed. DILI is generally classified as either intrinsic or idiosyncratic. Intrinsic DILI is dose dependent and predictable (e.g., acetaminophen toxicity). However, predicting the occurrence of idiosyncratic DILI, which has a very low incidence and is associated with severe liver damage, is difficult because of its complex nature and the poor understanding of its mechanism. Considering drug metabolism and pharmacokinetics, we established experimental animal models of DILI for 14 clinical drugs that cause idiosyncratic DILI in humans, which is characterized by the formation of reactive metabolites and the involvement of both innate and adaptive immunity. On the basis of the biomarker data obtained from the animal models, we developed a cell-based assay system that predicts the potential risks of drugs for inducing DILI. These findings increase our understanding of the mechanisms of DILI and may help predict and prevent idiosyncratic DILI due to certain drugs.

Nonexperimental Xenobiotics: Unintended Consequences of Intentionally Administered Substances in Terrestrial Animal Models

Review of the use of nonexperimental xenobiotics in terrestrial animal models and the potential unintended consequences of these compounds, including drug-related side effects and adverse reactions.

Screening for Susceptibility-Related Factors and Biomarkers of Xianling Gubao Capsule-Induced Liver Injury

Although increasing reports from the literature on herbal-related hepatotoxicity, the identification of susceptibility-related factors and biomarkers remains challenging due to idiosyncratic drug-induced liver injury (IDILI). As a well-known Chinese medicine prescription, Xianling Gubao Capsule (XLGB) has attracted great attention due to reports of potential liver toxicity. But the mechanism behind it is difficult to determine. In this paper, we found that XLGB-induced liver injury belongs to IDILI through the analysis of clinical liver injury cases. In toxicological experiment assessment, co-exposure to XLGB and non-toxic dose of lipopolysaccharide (LPS) could cause evident liver injury as manifested by significantly increased plasma alanine aminotransferase activity and obvious liver histological damage. However, it failed to induce observable liver injury in normal rats, suggesting that mild immune stress may be a susceptibility factor for XLGB-induced idiosyncratic liver injury. Furthermore, plasma cytokines were determined and 15 cytokines (such as IL-1β, IFN-γ, and MIP-2α etc) were acquired by receiver operating characteristic (ROC) curves analysis. The expression of these 15 cytokines in LPS group was significantly up-regulated in contrast to the normal group. Meanwhile, the metabolomics profile showed that mild immune stress caused metabolic reprogramming, including sphingolipid metabolism, phenylalanine metabolism, and glycerophospholipid metabolism. 8 potential biomarkers (such as sphinganine, glycerophosphoethanolamine, and phenylalanine etc.) were identified by correlation analysis. Therefore, these results suggested that intracellular metabolism and immune changes induced by mild immune stress may be important susceptibility mechanisms for XLGB IDILI.

Prediction and Characterization of CYP3A4-mediated Metabolisms of Azole Fungicides: an Application of the Fused-grid Template* system

Human CYP3A4 is involved in metabolisms of diverse hydrophobic chemicals. Using the data of therapeutic azole fungicides known to interact with CYP3A4, applicability of CYP3A4 Template system was first confirmed to reconstitute faithfully the interaction on Template. More than twenty numbers of pesticide azoles were then applied to the Template system. All the azole stereo-isomers applied, except for talarozole, interacted through nitrogen atoms of triazole or imidazole parts and sat stably for inhibitions through fulfilling three-essential interactions. For their CYP3A4-mediated oxidations, clear distinctions were suggested among the enantiomers and diastereomers of azole pesticides on Templates. Thus, the stereoisomers would have their-own regio- and stereo-selective profiles of the metabolisms. A combined metabolic profile of each azole obtained with CYP3A4 Template system, however, resembled with the reported profile of the in vivo metabolism in rats. These results suggest the major roles of CYP3A forms on the metabolisms of most of azole pesticides in both rats and humans. Free triazole is a metabolite of azole fungicides having a methylene-spacer between triazole and the rest of the main structures in experimental animals and humans. During the simulation experiments, a placement for the oxidation of a methylene spacer between the triazole and main carbon-skeleton was found to be available throughout the azole fungicides tested on Template. The occurrence of this reaction to lead to triazole-release is thus discussed in relation to the possible involvement of CYP3A forms.

Three-Dimensional Spheroids With Primary Human Liver Cells and Differential Roles of Kupffer Cells in Drug-Induced Liver Injury

Drug-induced liver injury (DILI) remains a challenge and a leading risk for drug discovery. Three-dimensional liver spheroids made from primary human hepatocytes (PHHs) with, or without, other liver cell types can provide more physiological relevance. In comparison to conventional 2-dimensional monolayer culture, our tests with 100 drugs of known DILI status indicate that PHH spheroids are significantly more sensitive in detecting drug-induced hepatotoxicity. To evaluate the role of Kupffer cells (KCs) in drug-induced liver toxicity, we have established conditions for generating co-culture spheroids with PHH and KCs. Inflammatory responses as shown by interleukin 6 secretion can be recapitulated in co-culture spheroids when treated with endotoxin lipopolysaccharides. KCs potentiated the cytotoxicity induced by trovafloxacin in co-culture spheroids at 48 h, but the differences between PHH spheroids and co-culture spheroids became less obvious after a 5-day treatment. Interestingly, a protective role of KCs was shown in co-culture spheroids treated with both acetaminophen and lipopolysaccharides. Additional tests with 14 DILI compounds comparing PHH spheroids and co-culture spheroids showed differential roles of KCs that were compound dependent. In summary, these 3-dimensional liver spheroid models are useful tools to understand the complex mechanisms underlying DILI.

Understanding Idiosyncratic Toxicity: Lessons Learned from Drug-Induced Liver Injury

Idiosyncratic adverse drug reactions (IADRs) encompass a diverse group of toxicities that can vary by drug and patient. The complex and unpredictable nature of IADRs combined with the fact that they are rare makes them particularly difficult to predict, diagnose, and treat. Common clinical characteristics, the identification of human leukocyte antigen risk alleles, and drug-induced proliferation of lymphocytes isolated from patients support a role for the adaptive immune system in the pathogenesis of IADRs. Significant evidence also suggests a requirement for direct, drug-induced stress, neoantigen formation, and stimulation of an innate response, which can be influenced by properties intrinsic to both the drug and the patient. This Perspective will provide an overview of the clinical profile, mechanisms, and risk factors underlying IADRs as well as new approaches to study these reactions, focusing on idiosyncratic drug-induced liver injury.

Liver microphysiological systems development guidelines for safety risk assessment in the pharmaceutical industry

The liver is critical to consider during drug development because of its central role in the handling of xenobiotics, a process which often leads to localized and/or downstream tissue injury. Our ability to predict human clinical safety outcomes with animal testing is limited due to species differences in drug metabolism and disposition, while traditional human in vitro liver models often lack the necessary in vivo physiological fidelity. To address this, increasing numbers of liver microphysiological systems (MPS) are being developed, however the inconsistency in their optimization and characterization often leads to models that do not possess critical levels of baseline performance that is required for many pharmaceutical industry applications. Herein we provide a guidance on best approaches to benchmark liver MPS based on 3 stages of characterization that includes key performance metrics and a 20 compound safety test set. Additionally, we give an overview of frequently used liver injury safety assays, describe the ideal MPS model, and provide a perspective on currently best suited MPS contexts of use. This pharmaceutical industry guidance has been written to help MPS developers and end users identify what could be the most valuable models for safety risk assessment.

New incompatible pair of TCM: Epimedii Folium combined with Psoraleae Fructus induces idiosyncratic hepatotoxicity under immunological stress conditions

Epimedii Folium (EF) combined with Psoraleae Fructus (PF) is a common modern preparation, but liver injury caused by Chinese patent medicine preparations containing EF and PF has been frequently reported in recent years. Zhuangguguanjiewan pills (ZGW), which contain EF and PF, could induce immune idiosyncratic liver injury according to clinical case reports and a nonhepatotoxic dose of lipopolysaccharide (LPS) model. This present study evaluated the liver injury induced by EF or PF alone or in combination and investigated the related mechanism by using the LPS model. Liver function indexes and pathological results showed that either EF or PF alone or in combination led to liver injury in normal rats; however, EF or PF alone could lead to liver injury in LPS-treated rats. Moreover, EF combined with PF could induce a greater degree of injury than that caused by EF or PF alone in LPS-treated rats. Furthermore, EF or PF alone or in combination enhanced the LPS-stimulated inflammatory cytokine production, implying that IL-1β, which is processed and released by activating the NLRP3 inflammasome, is a specific indicator of EF-induced immune idiosyncratic hepatotoxicity. Thus, EF may induce liver injury through enhancing the LPS-mediated proinflammatory cytokine production and activating the NLRP3 inflammasome. In addition, the metabolomics analysis results showed that PF affected more metabolites in glycerophospholipid and sphingolipid metabolic pathways compared with EF in LPS model, suggesting that PF increased the responsiveness of the liver to LPS or other inflammatory mediators via modulation of multiple metabolic pathways. Therefore, EF and PF combination indicates traditional Chinese medicine incompatibility, considering that it induces idiosyncratic hepatotoxicity under immunological stress conditions.

Pro-inflammatory cytokines enhance dilatation of bile canaliculi caused by cholestatic antibiotics

Many drugs can induce liver injury, characterized by hepatocellular, cholestatic or mixed hepatocellular-cholestatic lesions. While an inflammatory stress is known to aggravate hepatocellular injury caused by some drugs much less evidence exists for cholestatic features. In this study, the influence of pro-inflammatory cytokines (IL-6, IL-1β and TNF-α), either individually or combined, on cytotoxic and cholestatic properties of antibiotics was evaluated using differentiated HepaRG cells. Six antibiotics of various chemical structures and known to cause cholestasis and/or hepatocellular injury in clinic were investigated. Caspase-3 activity was increased with all these tested hepatotoxic drugs and except with erythromycin, was further augmented in presence of cytokines mainly when these were co-added as a mixture. TNF-α and IL-1β aggravated cytotoxicity of TVX more than IL-6. Bile canaliculi (BC) dilatation induced by cholestatic drugs was increased by co-treatment with IL-6 and IL-1β but not with TNF-α. Reduced accumulation of carboxy-dichlorofluorescein, a substrate of the multi-drug resistance-associated protein 2, in antibiotic-induced dilatated BC, was further extended in presence of individual or mixed cytokines. In conclusion, our data demonstrate that pro-inflammatory cytokines either individually or in mixture, can modulate cholestatic and/or cytotoxic responses to antibiotics and that the extent of these effects is dependent on the cytokine and the cholestatic antibiotic.

Prominence of Oxidative Stress in the Management of Anti-tuberculosis Drugs Related Hepatotoxicity

Advanced medical services and treatments are available for treating Tuberculosis. Related prevalence has increased in recent times. Unfortunately, the continuous consumption of related drugs is also known for inducing hepatotoxicity which is a critical condition and cannot be overlooked. The present review article has focused on the pathways causing these toxicities and also the role of enzyme CYP2E1, hepatic glutathione, Nrf2-ARE signaling pathway, and Membrane Permeability Transition as possible targets which may help in preventing the hepatotoxicity induced by the drugs used in the treatment of tuberculosis.

Idiosyncratic Drug-Induced Liver Injury Due to Ciprofloxacin: A Report of Two Cases and Review of the Literature

Case series

Patient: Male, 35 • Male, 82

Final Diagnosis: Idiosyncratic DILI due to Ciprofloxacin

Symptoms: Abdominal discomfort • fever • jaundice • nausea

Medication: Ciprofloxacin

Clinical Procedure: —

Specialty: Gastroenterology and Hepatology

Maximizing the impact of microphysiological systems with in vitro-in vivo translation

Microphysiological systems (MPS) hold promise for improving therapeutic drug approval rates by providing more physiological, human-based, in vitro assays for preclinical drug development activities compared to traditional in vitro and animal models. Here, we first summarize why MPSs are needed in pharmaceutical development, and examine how MPS technologies can be utilized to improve preclinical efforts. We then provide the perspective that the full impact of MPS technologies will be realized only when robust approaches for in vitro-in vivo (MPS-to-human) translation are developed and utilized, and explain how the burgeoning field of quantitative systems pharmacology (QSP) can fill that need.

The pharmacokinetics and metabolism of diclofenac in chimeric humanized and murinized FRG mice

The pharmacokinetics of diclofenac were investigated following single oral doses of 10 mg/kg to chimeric liver humanized and murinized FRG and C57BL/6 mice. In addition, the metabolism and excretion were investigated in chimeric liver humanized and murinized FRG mice. Diclofenac reached maximum blood concentrations of 2.43 ± 0.9 µg/mL (n = 3) at 0.25 h post-dose with an AUC_inf of 3.67 µg h/mL and an effective half-life of 0.86 h (n = 2). In the murinized animals, maximum blood concentrations were determined as 3.86 ± 2.31 µg/mL at 0.25 h post-dose with an AUC_inf of 4.94 ± 2.93 µg h/mL and a half-life of 0.52 ± 0.03 h (n = 3). In C57BL/6J mice, mean peak blood concentrations of 2.31 ± 0.53 µg/mL were seen 0.25 h post-dose with a mean AUC_inf of 2.10 ± 0.49 µg h/mL and a half-life of 0.51 ± 0.49 h (n = 3). Analysis of blood indicated only trace quantities of drug-related material in chimeric humanized and murinized FRG mice. Metabolic profiling of urine, bile and faecal extracts revealed a complex pattern of metabolites for both humanized and murinized animals with, in addition to unchanged parent drug, a variety of hydroxylated and conjugated metabolites detected. The profiles in humanized mice were different to those of both murinized and wild-type animals, e.g., a higher proportion of the dose was detected in the form of acyl glucuronide metabolites and much reduced amounts as taurine conjugates. Comparison of the metabolic profiles obtained from the present study with previously published data from C57BL/6J mice and humans revealed a greater, though not complete, match between chimeric humanized mice and humans, such that the liver humanized FRG model may represent a model for assessing the biotransformation of such compounds in humans.

Nonalcoholic Fatty Liver Disease Is a Susceptibility Factor for Perchloroethylene-Induced Liver Effects in Mice

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent pathological liver condition in developed countries. NAFLD results in severe alterations in liver function, including xenobiotic metabolism. Perchloroethylene (PERC) is a ubiquitous environmental pollutant, a known hepatotoxicant in rodents, and a probable human carcinogen. It is known that PERC disposition and metabolism are affected by NAFLD in mice; here, we examined how NAFLD changes PERC-associated liver effects. Male C57Bl6/J mice were fed a low-fat diet (LFD), high-fat diet (HFD), or methionine/folate/choline-deficient diet (MCD) to model a healthy liver, or mild and severe forms of NAFLD, respectively. After 8 weeks on diets, mice were orally administered PERC (300 mg/kg/day) or vehicle (5% aqueous Alkamuls-EL620) for 5 days. PERC-induced liver effects were exacerbated in both NAFLD groups. PERC exposure was associated with up-regulation of genes involved in xenobiotic, lipid, and glutathione metabolism, and down-regulation of the complement and coagulation cascades, regardless of the diet. Interestingly, HFD-fed mice, not MCD-fed mice, were generally more sensitive to PERC-induced liver effects. This was indicated by histopathology and transcriptional responses, where induction of genes associated with cell cycle and inflammation were prominent. Liver effects positively correlated with diet-specific differences in liver concentrations of PERC. We conclude that NAFLD alters the toxicodynamics of PERC and that NAFLD is a susceptibility factor that should be considered in future risk management decisions for PERC and other chlorinated solvents.

Omics-based identification of the combined effects of idiosyncratic drugs and inflammatory cytokines on the development of drug-induced liver injury

The mechanisms of idiosyncratic drug-induced hepatotoxicity remain largely unclear. It has demonstrated that the drug idiosyncrasy is potentiated in the context of inflammation and intracellular ceramides may play a role in this process. To study the mechanisms, HepG2 cells were co-treated with high and low doses of three idiosyncratic (I) and three non-idiosyncratic (N) compounds, with (I+ and N+) or without (I- and N-) a cytokine mix. Microarray, lipidomics and flow cytometry were performed to investigate the genome-wide expression patterns, the intracellular ceramide levels and the induction of apoptosis. We found that all I+ treatments significantly influenced the immune response- and response to stimulus-associated gene ontology (GO) terms, but the induction of apoptotic pathways, which was confirmed by flow cytometry, only appeared to be induced after the high-dose treatment. The ceramide signaling-, ER stress-, NF-kB activation- and mitochondrial activity-related pathways were biologically involved in apoptosis induced by the high-dose I+. Additionally, genes participating in ceramide metabolism were significantly altered resulting in a measurable increase in ceramide levels. The increases in ceramide concentrations may induce ER stress and activate the JNK pathway by affecting the expression of the related genes, and eventually trigger the mitochondria-independent apoptosis in hepatocytes. Overall, our study provides a potential mechanism to explain the role of inflammation in idiosyncratic drug reactions.

Opportunities and challenges in the wider adoption of liver and interconnected microphysiological systems

Liver disease represents a growing global health burden. The development of in vitro liver models which allow the study of disease and the prediction of metabolism and drug-induced liver injury in humans remains a challenge. The maintenance of functional primary hepatocytes cultures, the parenchymal cell of the liver, has historically been difficult with dedifferentiation and the consequent loss of hepatic function limiting utility. The desire for longer term functional liver cultures sparked the development of numerous systems, including collagen sandwiches, spheroids, micropatterned co-cultures and liver microphysiological systems. This review will focus on liver microphysiological systems, often referred to as liver-on-a-chip, and broaden to include platforms with interconnected microphysiological systems or multi-organ-chips. The interconnection of microphysiological systems presents the opportunity to explore system level effects, investigate organ cross talk, and address questions which were previously the preserve of animal experimentation. As a field, microphysiological systems have reached a level of maturity suitable for commercialization and consequent evaluation by a wider community of users, in academia and the pharmaceutical industry. Here scientific, operational, and organizational considerations relevant to the wider adoption of microphysiological systems will be discussed. Applications in which microphysiological systems might offer unique scientific insights or enable studies currently feasible only with animal models are described, and challenges which might be addressed to enable wider adoption of the technologies are highlighted. A path forward which envisions the development of microphysiological systems in partnerships between academia, vendors and industry, is proposed. Impact statement Microphysiological systems are in vitro models of human tissues and organs. These systems have advanced rapidly in recent years and are now being commercialized. To achieve wide adoption in the biological and pharmaceutical research communities, microphysiological systems must provide unique insights which translate to humans. This will be achieved by identifying key applications and making microphysiological systems intuitive to use.

Drug-Induced Liver Injury: Cascade of Events Leading to Cell Death, Apoptosis or Necrosis

Drug-induced liver injury (DILI) can broadly be divided into predictable and dose dependent such as acetaminophen (APAP) and unpredictable or idiosyncratic DILI (IDILI). Liver injury from drug hepatotoxicity (whether idiosyncratic or predictable) results in hepatocyte cell death and inflammation. The cascade of events leading to DILI and the cell death subroutine (apoptosis or necrosis) of the cell depend largely on the culprit drug. Direct toxins to hepatocytes likely induce oxidative organelle stress (such as endoplasmic reticulum (ER) and mitochondrial stress) leading to necrosis or apoptosis, while cell death in idiosyncratic DILI (IDILI) is usually the result of engagement of the innate and adaptive immune system (likely apoptotic), involving death receptors (DR). Here, we review the hepatocyte cell death pathways both in direct hepatotoxicity such as in APAP DILI as well as in IDILI. We examine the known signaling pathways in APAP toxicity, a model of necrotic liver cell death. We also explore what is known about the genetic basis of IDILI and the molecular pathways leading to immune activation and how these events can trigger hepatotoxicity and cell death.

Screening for main components associated with the idiosyncratic hepatotoxicity of a tonic herb, Polygonum multiflorum

The main constituents of a typical medicinal herb, Polygonum multiflorum (Heshouwu in Chinese), that induces idiosyncratic liver injury remain unclear. Our previous work has shown that cotreatment with a nontoxic dose of lipopolysaccharide (LPS) and therapeutic dose of Heshouwu can induce liver injury in rats, whereas the solo treatment cannot induce observable injury. In the present work, using the constituent "knock-out" and "knock-in" strategy, we found that the ethyl acetate (EA) extract of Heshouwu displayed comparable idiosyncratic hepatotoxicity to the whole extract in LPS-treated rats. Results indicated a significant elevation of plasma alanine aminotransferase, aspartate aminotransferase, and liver histologic changes, whereas other separated fractions failed to induce liver injury. The mixture of EA extract with other separated fractions induced comparable idiosyncratic hepatotoxicity to the whole extract in LPS-treated rats. Chemical analysis further revealed that 2,3,5,4'-tetrahydroxy trans-stilbene-2-O-β-glucoside (trans-SG) and its cis-isomer were the two major compounds in EA extract. Furthermore, the isolated cis-, and not its trans-isomer, displayed comparable idiosyncratic hepatotoxicity to EA extract in LPS-treated rats. Higher contents of cis-SG were detected in Heshouwu liquor or preparations from actual liver intoxication patients associated with Heshouwu compared with general collected samples. In addition, plasma metabolomics analysis showed that cis-SG-disturbing enriched pathways remarkably differed from trans-SG ones in LPS-treated rats. All these results suggested that cis-SG was closely associated with the idiosyncratic hepatotoxicity of Heshouwu. Considering that the cis-trans isomerization of trans-SG was mediated by ultraviolet light or sunlight, our findings serve as reference for controlling photoisomerization in drug discovery and for the clinical use of Heshouwu and stilbene-related medications.

Evaluation of a human in vitro hepatocyte-NPC co-culture model for the prediction of idiosyncratic drug-induced liver injury: A pilot study

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Co-cultures of liver and immune cells can be used to detect iDILI compounds.

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Pro-inflammatory factors are involved in the development of iDILI.

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The co-exposure of a drug candidate with TNF might be sufficient to predict iDILI.

Interactions between hepatocytes and immune cells as well as inflammatory episodes are frequently discussed to play a critical role in the alteration of the individual susceptibility to idiosyncratic drug-induced liver injury (iDILI). To evaluate this hypothesis and to face the urgent need for predictive in vitro models, we established two co-culture systems based on two human cell lines in presence or absence of pro-inflammatory factors (LPS, TNF), i.e. hepatoma HepG2 cells co-cultured with monocytic or macrophage-like THP-1 cells. HepG2 monocultures served as control scenario. Mono- or co-cultures were treated with iDILI reference substances (Troglitazone [TGZ], Trovafloxacin [TVX], Diclofenac [DcL], Ketoconazole [KC]) or their non-iDILI partner compounds (Rosiglitazone, Levofloxacin, Acetylsalicylic Acid, Fluconazole). The liver cell viability was subsequently determined via WST-Assay. An enhanced cytotoxicity (synergy) or a hormetic response compared to the drug effect in the HepG2 monoculture was considered as iDILI positive. TGZ synergized in co-cultures with monocytes without an additional pro-inflammatory stimulus, while DcL and KC showed a hormetic response. All iDILI drugs synergized with TNF in the simple HepG2 monoculture, indicating its relevance as an initiator of iDILI. KC showed a synergy when co-exposed to both, monocytes and LPS, while TVX and DcL showed a synergy under the same conditions with macrophages. All described iDILI responses were not observed with the corresponding non-iDILI partner compounds. Our first results confirm that an inflammatory environment increases the sensitivity of liver cells towards iDILI compounds and point to an involvement of pro-inflammatory factors, especially TNF, in the development of iDILI.

Drug Hepatotoxicity: Environmental Factors

Drug-induced liver injury presents as various forms of acute and chronic liver disease. There is wide geographic variation in the most commonly implicated agents. Smoking can induce cytochrome P450 enzymes but this does not necessarily translate into clinically relevant drug-induced liver injury. Excessive alcohol consumption is a clear risk factor for intrinsic hepatotoxicity from acetaminophen and may predispose to injury from antituberculosis medications. Understanding of the role of infection, proinflammatory states, disorders of coagulation, and the hepatic clock in predisposing patients to drug-induced liver injury is evolving. More study focusing specifically on environmental risk factors predisposing patients to drug-induced liver injury is needed.

Idiosyncratic Drug-Induced Liver Injury (IDILI): Potential Mechanisms and Predictive Assays

Idiosyncratic drug-induced liver injury (IDILI) is a significant source of drug recall and acute liver failure (ALF) in the United States. While current drug development processes emphasize general toxicity and drug metabolizing enzyme- (DME-) mediated toxicity, it has been challenging to develop comprehensive models for assessing complete idiosyncratic potential. In this review, we describe the enzymes and proteins that contain polymorphisms believed to contribute to IDILI, including ones that affect phase I and phase II metabolism, antioxidant enzymes, drug transporters, inflammation, and human leukocyte antigen (HLA). We then describe the various assays that have been developed to detect individual reactions focusing on each of the mechanisms described in the background. Finally, we examine current trends in developing comprehensive models for examining these mechanisms. There is an urgent need to develop a panel of multiparametric assays for diagnosing individual toxicity potential.

Concurrent Inflammation Augments Antimalarial Drugs-Induced Liver Injury in Rats

Purpose: Accumulating evidence suggests that drug exposure during a modest inflammation induced by bacterial lipopolysaccharide (LPS) might increase the risk of drug-induced liver injury. The current investigation was designed to test if antimalarial drugs hepatotoxicity is augmented in LPS‑treated animals. Methods: Rats were pre-treated with LPS (100 µg/kg, i.p). Afterward, non-hepatotoxic doses of amodiaquine (25, 50 and 100 mg/kg, oral) and chloroquine (25, 50 and 100 mg/kg, oral) were administered. Results: Interestingly, liver injury was evident only in animals treated with both drug and LPS as estimated by pathological changes in serum biochemistry (ALT, AST, LDH, and TNF-α), and liver tissue (severe hepatitis, endotheliitis, and sinusoidal congestion). An increase in liver myeloperoxidase enzyme activity, lipid peroxidation, and protein carbonylation, along with tissue glutathione depletion were also detected in LPS and drug co-treated animals. Conclusion: Antimalarial drugs rendered hepatotoxic in animals undergoing a modest inflammation. These results indicate a synergistic liver injury from co-exposure to antimalarial drugs and inflammation.

Metabolomic Study on Idiosyncratic Liver Injury Induced by Different Extracts of Polygonum multiflorum in Rats Integrated with Pattern Recognition and Enriched Pathways Analysis

Currently, numerous liver injury cases related to a famous Chinese herb- Polygonum Multiflorum (Heshouwu in Chinese) have attracted great attention in many countries. Our previous work showed that Heshouwu-induced hepatotoxicity belonged to idiosyncratic drug-induced liver injury (IDILI). Unfortunately, the components and mechanisms attributed to IDILI of Heshouwu are difficult to determine and thus remain unknown. Attempts to explore puzzles, we prepared the chloroform (CH)-, ethyl acetate (EA)-, and residue (RE) extracts of Heshouwu to investigate IDILI constituents and underlying mechanisms, using biochemistry, histopathology, and metabolomics examinations. The results showed that co-treatment with non-toxic dose of lipopolysaccharide (LPS) and EA extract could result in evident liver injury, indicated by the significant elevation of plasma alanine aminotransferase and aspartate aminotransferase activities, as well as obvious liver histologic damage; whereas other two separated fractions, CH and RE extracts, failed to induce observable liver injury. Furthermore, 21 potential metabolomic biomarkers that differentially expressed in LPS/EA group compared with other groups without liver injury were identified by untargeted metabolomics, mainly involved two pathways: tricarboxylic acid cycle and sphingolipid metabolism. This work illustrated EA extract had close association with the idiosyncratic hepatotoxicity of Heshouwu and provided a metabolomic insight into IDILI of different extracts from Heshouwu.

Co-culture of Hepatocytes and Kupffer Cells as an In Vitro Model of Inflammation and Drug-Induced Hepatotoxicity

Immune-mediated drug-induced hepatotoxicity is often unrecognized as a potential mode of action due to the lack of appropriate in vitro models. We have established an in vitro rat donor-matched hepatocyte and Kupffer cell co-culture (HKCC) model to study immune-related responses to drug exposure. Optimal cell culture conditions were identified for the maintenance of co-cultures based on cell longevity, monolayer integrity, and cytokine response after lipopolysaccharide (LPS) exposure. Hepatocyte monocultures and HKCCs were then used to test a subset of compounds associated with hepatotoxic effects with or without LPS. Cytokine levels and metabolic activity (cytochrome P450 3A [Cyp3A]) were measured after a 48-h exposure to monitor endotoxin-induced changes in acute phase and functional end points. LPS-activated HKCCs, but not hepatocyte monocultures, treated with trovafloxacin or acetaminophen, compounds associated with immune-mediated hepatotoxicity, showed LPS-dependent decreases in interleukin-6 production with concomitant increases in Cyp3A activity. Differential endotoxin- and model-dependent alterations were observed in cytokine profiles and Cyp3A activity levels that corresponded to specific compounds. These results indicate the utility of the HKCC model system to discern compound-specific effects that may lead to enhanced or mitigate hepatocellular injury due to innate or adaptive immune responses.

Idiosyncratic Drug-Induced Liver Injury: Is Drug-Cytokine Interaction the Linchpin?

Idiosyncratic drug-induced liver injury continues to be a human health problem in part because drugs that cause these reactions are not identified in current preclinical testing and because progress in prevention is hampered by incomplete knowledge of mechanisms that underlie these adverse responses. Several hypotheses involving adaptive immune responses, inflammatory stress, inability to adapt to stress, and multiple, concurrent factors have been proposed. Yet much remains unknown about how drugs interact with the liver to effect death of hepatocytes. Evidence supporting hypotheses implicating adaptive or innate immune responses in afflicted patients has begun to emerge and is bolstered by results obtained in experimental animal models and in vitro systems. A commonality in adaptive and innate immunity is the production of cytokines, including interferon-γ (IFNγ). IFNγ initiates cell signaling pathways that culminate in cell death or inhibition of proliferative repair. Tumor necrosis factor-α, another cytokine prominent in immune responses, can also promote cell death. Furthermore, tumor necrosis factor-α interacts with IFNγ, leading to enhanced cellular responses to each cytokine. In this short review, we propose that the interaction of drugs with these cytokines contributes to idiosyncratic drug-induced liver injury, and mechanisms by which this could occur are discussed.

A transgenic rat hepatocyte - Kupffer cell co-culture model for evaluation of direct and macrophage-related effect of poly(amidoamine) dendrimers

Increasing number of papers demonstrate that Kupffer cells (KCs) play a role in the development of drug induced liver injury (DILI). Furthermore, elevated intracellular Ca²⁺ level of hepatocytes is considered as a common marker of DILI. Here we applied an in vitro model based on hepatocyte mono- and hepatocyte/KC co-cultures (H/KC) isolated from transgenic rats stably expressing the GCaMP2 fluorescent Ca²⁺ sensor protein to investigate the effects of polycationic (G5), polyanionic (G4.5) and polyethylene-glycol coated neutral (G5 Peg) dendrimers known to accumulate in the liver, primarily in KCs. Following dendrimer exposure, hepatocyte homeostasis was measured by MTT cytotoxicity assay and by Ca²⁺ imaging, while hepatocyte functions were studied by CYP2B1/2 inducibility, and bilirubin and taurocholate transport. G5 was significantly more cytotoxic than G4.5 for hepatocytes and induced Ca²⁺ oscillation and sustained Ca²⁺ signals at 1μM and10 μM, respectively both in hepatocytes and KCs. Dendrimer-induced Ca²⁺ signals in hepatocytes were attenuated by macrophages. Activation of KCs by lipopolysaccharide and G5 decreased the inducibility of CYP2B1/2, which was restored by depleting the KCs with gadolinium-chloride and pentoxyphylline, suggesting a role of macrophages in the hindrance of CYP2B1/2 induction by G5 and lipopolysaccharide. In the H/KC, but not in the hepatocyte mono-culture, G5 reduced the canalicular efflux of bilirubin and stimulated the uptake and canalicular efflux of taurocholate. In conclusion, H/KC provides a good model for the prediction of hepatotoxic potential of drugs, especially of nanomaterials known to be trapped by macrophages, activation of which presumably contributes to DILI.

MicroRNA-877-5p is involved in the trovafloxacin-induced liver injury

Trovafloxacin develops severe hepatotoxicity; however, the underlying mechanism of the trovafloxacin-induced liver injury has not been cleared. It has been shown that microRNAs (miRNAs) can be involved in the development of drug-induced liver injuries. We performed a miRNA microarray analysis to identify hepatic miRNAs that were induced or reduced by trovafloxacin in mice. It was demonstrated that miR-877-5p was the most increased miRNA in the mouse liver 24h after the trovafloxacin administration. To investigate the role of miR-877-5p in the liver, we established miR-877-5p-overexpressed HepG2 cells. Microarray analysis detected altered expressions in 2077 (>2-fold) and 1547 (<0.5-fold) genes in the miR-877-5p overexpressing cells compared to the mock cells. Especially, SLCO4C1, PEPCK, MT1M, HIST1H2BM, LGI1, and PLA2G2A were markedly increased or decreased in the miR-877-5p overexpressing cells. We conducted a correlation analysis between the expression levels of miR-877-5p and the six genes in eight miR-877-5p stably-expressed clones. It was shown that the PEPCK expression levels were correlated with miR-877-5p expression levels. PEPCK is associated with development of apoptotic cell death; therefore, the increased miR- 877-5p-induced PEPCK can be a trigger that is involved in the development of trovafloxacin-induced liver injury.