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

In Vitro Nonalcoholic Fatty Liver Disease Model Elucidating the Effect of Immune Environment on Disease Progression and Alleviation

Nonalcoholic fatty liver disease (NAFLD), which is a major cause of chronic liver disease, is characterized by fat accumulation in the liver. Existing models struggle to assess medication effects on liver function in the context of NAFLD's unique inflammatory environment. We address this by developing a 3D in vitro NAFLD model using HepG2 and THP-1 cells (mimicking liver and Kupffer cells) cocultured using transwell and hydrogel system. This mimics liver architecture and allows for manipulation of the immune environment. We demonstrate that the model recapitulates key NAFLD features: steatosis (induced by fatty acids), oxidative stress, inflammation, and impaired liver function embodying the interrelationship between NAFLD and the surrounding immune environment. This versatile model offers a valuable tool for preclinical NAFLD research by incorporating a disease-relevant immune environment.

Antagonistic effects of a COX1/2 inhibitor drug in human HepG2 cells exposed to an environmental carcinogen

Understanding interactions between legacy and emerging environmental contaminants has important implications for risk assessment, especially when mutagens and carcinogens are involved, whose critical effects are chronic and therefore difficult to predict. The current work aimed to investigate potential interactions between benzo[a]pyrene (B[a]P), a carcinogenic polycyclic aromatic hydrocarbon and legacy pollutant, and diclofenac (DFC), a non-steroidal anti-inflammatory drug and pollutant of emerging concern, and how DFC affects B[a]P toxicity. Exposure to binary mixtures of these chemicals resulted in substantially reduced cytotoxicity in human HepG2 cells compared to single-chemical exposures. Significant antagonistic effects were observed in response to high concentrations of B[a]P in combination with DFC at IC50 and ⅕ IC50. While additive effects were found for levels of intracellular reactive oxygen species, antagonistic mixture effects were observed for genotoxicity. B[a]P induced DNA strand breaks, γH2AX activation, and micronuclei formation at ½ IC50 concentrations or lower, whereas DFC induced only low levels of DNA strand breaks. Their mixture caused significantly lower levels of genotoxicity by all three endpoints compared to those expected based on concentration additivity. In addition, antagonistic mixture effects on CYP1 enzyme activity suggested that the observed reduced genotoxicity of B[a]P was due to its reduced metabolic activation as a result of enzymatic inhibition by DFC. Overall, the findings further support the growing concern that co-exposure to environmental toxicants and their non-additive interactions may be a confounding factor that should not be neglected in environmental and human health risk assessment.

Assessing immune hepatotoxicity of troglitazone with a versatile liver-immune-microphysiological-system

Drug-induced liver injury is a prevalent adverse event associated with pharmaceutical agents. More significantly, there are certain drugs that present severe hepatotoxicity only during the clinical phase, consequently leading to the termination of drug development during clinical trials or the withdrawal from the market after approval. The establishment of an evaluation model that can sensitively manifest such hepatotoxicity has always been a challenging aspect in drug development. In this study, we build a liver-immune-microphysiological-system (LIMPS) to fully demonstrate the liver injury triggered by troglitazone (TGZ), a drug that was withdrawn from the market due to hepatotoxicity. Leveraging the capabilities of organ-on-chip technology allows for the dynamic modulation of cellular immune milieu, as well as the synergistic effects between drugs, hepatocytes and multiple immune cells. Through the LIMPS, we discovered that 1) TGZ can promote neutrophils to adhered hepatocytes, 2) the presence of TGZ enhances the crosstalk between macrophages and neutrophils, 3) the induction of damage in hepatocytes by TGZ at clinically relevant blood concentrations not observed in other in vitro experiments, 4) no hepatotoxicity was observed in LIMPS when exposed to rosiglitazone and pioglitazone, structurally similar analogs of TGZ, even at the higher multiples of blood drug concentration levels. As an immune-mediated liver toxicity assessment method, LIMPS is simple to operate and can be used to test multiple drug candidates to detect whether they will cause severe liver toxicity in clinical settings as early as possible.

hiPSC-derived macrophages improve drug sensitivity and selectivity in a macrophage-incorporating organoid culture model

Accurate simulation of different cell type interactions is crucial for physiological and precisein vitrodrug testing. Human tissue-resident macrophages are critical for modulating disease conditions and drug-induced injuries in various tissues; however, their limited availability has hindered their use inin vitromodeling. Therefore, this study aimed to create macrophage-containing organoid co-culture models by directly incorporating human-induced pluripotent stem cell (hiPSC)-derived pre-macrophages into organoid and scaffold cell models. The fully differentiated cells in these organoids exhibited functional characteristics of tissue-resident macrophages with enriched pan-macrophage markers and the potential for M1/M2 subtype specialization upon cytokine stimulation. In a hepatic organoid model, the integrated macrophages replicated typical intrinsic properties, including cytokine release, polarization, and phagocytosis, and the co-culture model was more responsive to drug-induced liver injury than a macrophage-free model. Furthermore, alveolar organoid models containing these hiPSC-derived macrophages also showed increased drug and chemical sensitivity to pulmonary toxicants. Moreover, 3D adipocyte scaffold models incorporating macrophages effectively simulated in vivo insulin resistance observed in adipose tissue and showed improved insulin sensitivity on exposure to anti-diabetic drugs. Overall, the findings demonstrated that incorporating hiPSC-derived macrophages into organoid culture models resulted in more physiological and sensitivein vitrodrug evaluation and screening systems.

Exploiting the predictive power of educated spheroids to detect immune-mediated idiosyncratic drug-induced liver injury: the case of troglitazone

Idiosyncratic drug-induced liver injury (iDILI) is a major concern in drug development because its occurrence is unpredictable. Presently, iDILI prediction is a challenge, and cell toxicity is observed only at concentrations that are much higher than the therapeutic doses in preclinical models. Applying a proprietary cell educating technology, we developed a person-dependent spheroid system that contains autologous educated immune cells that can detect iDILI risk at therapeutic concentrations. Integrating this system into a high-throughput screening platform will help pharmaceutical companies accurately detect the iDILI risk of new molecules de-risking drug development.

An evaluation of a hepatotoxicity risk induced by the microplastic polymethyl methacrylate (PMMA) using HepG2/THP-1 co-culture model

Inappropriate disposal of plastic wastes and their durability in nature cause uncontrolled accumulation of plastic in land/marine ecosystems, also causing destructive effects by bioaccumulating along the food chain. Microplastics may cause chronic inflammation in relation to their permanent structures, especially through oxidative stress and cytotoxic cellular damage, which could increase the risk of cancer development. The accumulation of microplastics in the liver is a major concern, and therefore, the identification of the mechanisms of their hepatotoxic effects is of great importance. Polymethyl methacrylate (PMMA) is a widely used thermoplastic. It has been determined that PMMA disrupts lipid metabolism in the liver in various aquatic organisms and causes reproductive and developmental toxicity. PMMA-induced hepatotoxic effects in humans have not yet been clarified. In our study, the toxic effects of PMMA (in the range of 3-10 μm) on the human liver were investigated using the HepG2/THP-1 macrophage co-culture model, which is a sensitive immune-mediated liver injury model. Cellular uptake of micro-sized PMMA in the cells was done by transmission electron microscopy. Determination of its effects on cell viability and inflammatory response, oxidative stress, along with gene and protein expression levels that play a role in the mechanism pathways underlying the effects were investigated. The results concluded that inflammation, oxidative stress, and disruptions in lipid metabolism should be the focus of attention as important underlying causes of PMMA-induced hepatotoxicity. Our study, which points out the potential adverse effects of microplastics on human health, supports the literature information on the subject.

The cyclin-dependent kinase inhibitor abemaciclib-induced hepatotoxicity: Insight on the molecular mechanisms in HepG2/THP-1 co-culture model

Drug-induced liver injury (DILI) is one of the widespread causes of liver injury and immune system plays important role. Abemaciclib (ABE) is a cyclin-dependent kinase inhibitor used as monotherapy or combination therapy in the treatment of breast cancer. Like other kinase inhibitors, the underlying mechanisms of ABE-induced hepatotoxicity are not completely known yet. In the current study, hepatotoxicity of ABE was evaluated with HepG2/THP-1 co-culture model which has been developed in recent years for the evaluation of DILI potential. Following ABE treatment, oxidative stress, mitochondrial damage, cytokine secretion levels, apoptotic/necrotic cell death were determined. According to our results, ROS production along with GSH depletion was observed in HepG2 cells after ABE treatment. ABE promoted secretion of pro-inflammatory mediators (TNF-α and MCP-1) and declined anti-inflammatory cytokine IL-10 release. Besides, NFKβ and JNK1 protein expression levels increased following ABE treatment. ABE enhanced intracellular calcium levels, induced early apoptotic and necrotic cell deaths in HepG2 cells. Furthermore, the changes in some mitochondrial parameters including a reducement in intracellular ATP levels and complex V activity; hyperpolarized mitochondrial membrane potential and enhanced mitochondrial ROS levels were observed, whereas mitochondrial mass did not show any differences after ABE treatments. Therefore, ABE-induced hepatotoxic effects is probably via oxidative stress, inflammatory response and necrotic cell death rather than direct mitochondrial toxicity. In conclusion; the study makes a significant contribution to strengthening the infrastructure we have on in vitro toxicity mechanism evaluations, which are the basis of preclinical toxicity studies.

Mechanistic Understanding of Idiosyncratic Drug-Induced Hepatotoxicity Using Co-Cultures of Hepatocytes and Macrophages

Hepatotoxicity or drug-induced liver injury (DILI) is a major safety issue in drug development as a primary reason for drug failure in clinical trials and the main cause for post-marketing regulatory measures like drug withdrawal. Idiosyncratic DILI (iDILI) is a patient-specific, multifactorial, and multicellular process that cannot be recapitulated in current in vitro models; thus, our major goal is to develop and fully characterize a co-culture system and to evaluate its suitability for predicting iDILI. For this purpose, we used human hepatoma HepG2 cells and macrophages differentiated from a monocyte cell line (THP-1) and established the appropriate co-culture conditions for mimicking an inflammatory environment. Then, mono-cultures and co-cultures were treated with model iDILI compounds (trovafloxacin, troglitazone) and their parent non-iDILI compounds (levofloxacin, rosiglitazone), and the effects on viability and the mechanisms implicated (i.e., oxidative stress induction) were analyzed. Our results show that co-culture systems including hepatocytes (HepG2) and other cell types (THP-1-derived macrophages) help to enhance the mechanistic understanding of iDILI, providing better hepatotoxicity predictions.

Microphysiological Models for Mechanistic-Based Prediction of Idiosyncratic DILI

Drug-induced liver injury (DILI) is a major contributor to high attrition rates among candidate and market drugs and a key regulatory, industry, and global health concern. While acute and dose-dependent DILI, namely, intrinsic DILI, is predictable and often reproducible in preclinical models, the nature of idiosyncratic DILI (iDILI) limits its mechanistic understanding due to the complex disease pathogenesis, and recapitulation using in vitro and in vivo models is extremely challenging. However, hepatic inflammation is a key feature of iDILI primarily orchestrated by the innate and adaptive immune system. This review summarizes the in vitro co-culture models that exploit the role of the immune system to investigate iDILI. Particularly, this review focuses on advancements in human-based 3D multicellular models attempting to supplement in vivo models that often lack predictability and display interspecies variations. Exploiting the immune-mediated mechanisms of iDILI, the inclusion of non-parenchymal cells in these hepatoxicity models, namely, Kupffer cells, stellate cells, dendritic cells, and liver sinusoidal endothelial cells, introduces heterotypic cell-cell interactions and mimics the hepatic microenvironment. Additionally, drugs recalled from the market in the US between 1996-2010 that were studies in these various models highlight the necessity for further harmonization and comparison of model characteristics. Challenges regarding disease-related endpoints, mimicking 3D architecture with different cell-cell contact, cell source, and the underlying multi-cellular and multi-stage mechanisms are described. It is our belief that progressing our understanding of the underlying pathogenesis of iDILI will provide mechanistic clues and a method for drug safety screening to better predict liver injury in clinical trials and post-marketing.

In Vitro Models for Studying Chronic Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is a major clinical problem in terms of patient morbidity and mortality, cost to healthcare systems and failure of the development of new drugs. The need for consistent safety strategies capable of identifying a potential toxicity risk early in the drug discovery pipeline is key. Human DILI is poorly predicted in animals, probably due to the well-known interspecies differences in drug metabolism, pharmacokinetics, and toxicity targets. For this reason, distinct cellular models from primary human hepatocytes or hepatoma cell lines cultured as 2D monolayers to emerging 3D culture systems or the use of multi-cellular systems have been proposed for hepatotoxicity studies. In order to mimic long-term hepatotoxicity in vitro, cell models, which maintain hepatic phenotype for a suitably long period, should be used. On the other hand, repeated-dose administration is a more relevant scenario for therapeutics, providing information not only about toxicity, but also about cumulative effects and/or delayed responses. In this review, we evaluate the existing cell models for DILI prediction focusing on chronic hepatotoxicity, highlighting how better characterization and mechanistic studies could lead to advance DILI prediction.

Point-of-use, automated fabrication of a 3D human liver model supplemented with human adipose microvessels

Advanced in vitro tissue models better reflect healthy and disease tissue conditions in the body. However, complex tissue models are often manufactured using custom solutions and can be challenging to manufacture to scale. Here, we describe the automated fabrication of a cell-dense, thick (≤ 1 cm), human vascularized liver tissue model using a robotic biomanufacturing platform and off-the-shelf components to build, culture, and sample liver tissues hands-free without compromising tissue health or function. Fabrication of the tissue involved 3D bioprinting and incorporation of primary human hepatocytes, primary human non-parenchymal cells, and isolated fragments of intact human microvessels as vascular precursors. No differences were observed in select assessments of the liver tissues fabricated by hand or via automation. Furthermore, constant media exchange, via perfusion, improved urea output and elevated tissue metabolism. Interestingly, inclusion of adipose-derived human microvessels enhanced functional gene expression, including an enhanced response to a drug challenge. Our results describe the fabrication of a thick liver tissue environment useful for a variety of applications including liver disease modeling, infectious agent studies, and cancer investigations. We expect the automated fabrication of the vascularized liver tissue, at the point of use and using off-the-shelf platforms, eases fabrication of the complex model and increases its utility.

Disrupted Surfaces of Porous Membranes Reduce Nuclear YAP Localization and Enhance Adipogenesis through Morphological Changes

The disrupted surface of porous membranes, commonly used in tissue-chip and cellular coculture systems, is known to weaken cell-substrate interactions. Here, we investigated whether disrupted surfaces of membranes with micron and submicron scale pores affect yes-associated protein (YAP) localization and differentiation of adipose-derived stem cells. We found that these substrates reduce YAP nuclear localization through decreased cell spreading, consistent with reduced cell-substrate interactions, and in turn enhance adipogenesis while decreasing osteogenesis.

Three-dimensional (3D) liver cell models - a tool for bridging the gap between animal studies and clinical trials when screening liver accumulation and toxicity of nanobiomaterials

Despite the exciting properties and wide-reaching applications of nanobiomaterials (NBMs) in human health and medicine, their translation from bench to bedside is slow, with a predominant issue being liver accumulation and toxicity following systemic administration. In vitro 2D cell-based assays and in vivo testing are the most popular and widely used methods for assessing liver toxicity at pre-clinical stages; however, these fall short in predicting toxicity for NBMs. Focusing on in vitro and in vivo assessment, the accurate prediction of human-specific hepatotoxicity is still a significant challenge to researchers. This review describes the relationship between NBMs and the liver, and the methods for assessing toxicity, focusing on the limitations they bring in the assessment of NBM hepatotoxicity as one of the reasons defining the poor translation for NBMs. We will then present some of the most recent advances towards the development of more biologically relevant in vitro liver methods based on tissue-mimetic 3D cell models and how these could facilitate the translation of NBMs going forward. Finally, we also discuss the low public acceptance and limited uptake of tissue-mimetic 3D models in pre-clinical assessment, despite the demonstrated technical and ethical advantages associated with them.

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.

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.

Novel indirect co-culture of immortalised hepatocytes with monocyte derived macrophages is characterised by pro-inflammatory cytokine networks

The liver is composed of different cell populations. Interactions of different cell populations can be investigated by a newly established indirect co-culture system consisting of immortalised primary human hepatocytes and human monocyte derived macrophages (MDMs). Using the time-dependent cytokine secretion of the co-cultures and single cultures, correlation networks (including the cytokines G-CSF, CCL3, MCP-1, CCL20, FGF, TGF-β1, GM-CSF, IL-8 IL-6, IL-1β, and IL-18) were generated and the correlations were validated by application of IL-8 and TNF-α-neutralising antibodies. The data reveal that IL-8 is crucial for the interaction between hepatocytes and macrophages in vitro. In addition, transcriptome analyses showed that a change in the ratio between macrophages and hepatocytes may trigger pro-inflammatory signalling pathways of the acute phase response and the complement system (release of, e.g., certain cyto- and chemokines). Using diclofenac and LPS showed that the release of cytokines is increasing with higher ratios of MDMs. Altogether, we could demonstrate that the current co-culture system is better suited to mirror the in vivo situation when compared to previously established co-culture systems composed of HepG2 and differentiated THP-1 cells. Further, our data reveal that the cytokine IL-8 is crucial for the interaction between hepatocytes and macrophages in vitro.

A Critical Perspective on 3D Liver Models for Drug Metabolism and Toxicology Studies

The poor predictability of human liver toxicity is still causing high attrition rates of drug candidates in the pharmaceutical industry at the non-clinical, clinical, and post-marketing authorization stages. This is in part caused by animal models that fail to predict various human adverse drug reactions (ADRs), resulting in undetected hepatotoxicity at the non-clinical phase of drug development. In an effort to increase the prediction of human hepatotoxicity, different approaches to enhance the physiological relevance of hepatic in vitro systems are being pursued. Three-dimensional (3D) or microfluidic technologies allow to better recapitulate hepatocyte organization and cell-matrix contacts, to include additional cell types, to incorporate fluid flow and to create gradients of oxygen and nutrients, which have led to improved differentiated cell phenotype and functionality. This comprehensive review addresses the drug-induced hepatotoxicity mechanisms and the currently available 3D liver in vitro models, their characteristics, as well as their advantages and limitations for human hepatotoxicity assessment. In addition, since toxic responses are greatly dependent on the culture model, a comparative analysis of the toxicity studies performed using two-dimensional (2D) and 3D in vitro strategies with recognized hepatotoxic compounds, such as paracetamol, diclofenac, and troglitazone is performed, further highlighting the need for harmonization of the respective characterization methods. Finally, taking a step forward, we propose a roadmap for the assessment of drugs hepatotoxicity based on fully characterized fit-for-purpose in vitro models, taking advantage of the best of each model, which will ultimately contribute to more informed decision-making in the drug development and risk assessment fields.

Recent Progress in Prediction Systems for Drug-induced Liver Injury Using in vitro Cell Culture

BACKGROUND

In order to avoid drug-induced liver injury (DILI), in vitro assays, which enable the assessment of both metabolic activation and immune reaction processes that ultimately result in DILI, are needed.

OBJECTIVE

In this study, the recent progress in the application of in vitro assays using cell culture systems is reviewed for potential DILI-causing drugs/xenobiotics and a mechanistic study on DILI, as well as for the limitations of in vitro cell culture systems for DILI research.

METHODS

Information related to DILI was collected through a literature search of the PubMed database.

RESULTS

The initial biological event for the onset of DILI is the formation of cellular protein adducts after drugs have been metabolically activated by drug metabolizing enzymes. The damaged peptides derived from protein adducts lead to the activation of CD4+ helper T lymphocytes and recognition by CD8+ cytotoxic T lymphocytes, which destroy hepatocytes through immunological reactions. Because DILI is a major cause of drug attrition and drug withdrawal, numerous in vitro systems consisting of hepatocytes and immune/inflammatory cells, or spheroids of human primary hepatocytes containing non-parenchymal cells have been developed. These cellular-based systems have identified DILIinducing drugs with approximately 50% sensitivity and 90% specificity.

CONCLUSION

Different co-culture systems consisting of human hepatocyte-derived cells and other immune/inflammatory cells have enabled the identification of DILI-causing drugs and of the actual mechanisms of action.

Application of zebrafish to safety evaluation in drug discovery

Traditionally, safety evaluation at the early stage of drug discovery research has been done using in silico, in vitro, and in vivo systems in this order because of limitations on the amount of compounds available and the throughput ability of the assay systems. While these in vitro assays are very effective tools for detecting particular tissue-specific toxicity phenotypes, it is difficult to detect toxicity based on complex mechanisms involving multiple organs and tissues. Therefore, the development of novel high throughput in vivo evaluation systems has been expected for a long time. The zebrafish (Danio rerio) is a vertebrate with many attractive characteristics for use in drug discovery, such as a small size, transparency, gene and protein similarity with mammals (80% or more), and ease of genetic modification to establish human disease models. Actually, in recent years, the zebrafish has attracted interest as a novel experimental animal. In this article, the author summarized the features of zebrafish that make it a suitable laboratory animal, and introduced and discussed the applications of zebrafish to preclinical toxicity testing, including evaluations of teratogenicity, hepatotoxicity, and nephrotoxicity based on morphological findings, evaluation of cardiotoxicity using functional endpoints, and assessment of seizure and drug abuse liability.

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.

An in vitro coculture system of human peripheral blood mononuclear cells with hepatocellular carcinoma-derived cells for predicting drug-induced liver injury

Preventing clinical drug-induced liver injury (DILI) remains a major challenge, because DILI develops via multifactorial mechanisms. Immune and inflammatory reactions are considered important mechanisms of DILI; however, biomarkers from in vitro systems using immune cells have not been comprehensively studied. The aims of this study were (1) to identify promising biomarker genes for predicting DILI in an in vitro coculture model of peripheral blood mononuclear cells (PBMCs) with a human liver cell line, and (2) to evaluate these genes as predictors of DILI using a panel of drugs with different clinical DILI risk. Transcriptome-wide analysis of PBMCs cocultured with HepG2 or differentiated HepaRG cells that were treated with several drugs revealed an appropriate separation of DILI-positive and DILI-negative drugs, from which 12 putative biomarker genes were selected. To evaluate the predictive performance of these genes, PBMCs cocultured with HepG2 cells were exposed to 77 different drugs, and gene expression levels in PBMCs were determined. The MET proto-oncogene receptor tyrosine kinase (MET) showed the highest area under the receiver-operating characteristic curve (AUC) value of 0.81 among the 12 genes with a high sensitivity/specificity (85/66%). However, a stepwise logistic regression model using the 12 identified genes showed the highest AUC value of 0.94 with a high sensitivity/specificity (93/86%). Taken together, we established a coculture system using PBMCs and HepG2 cells and selected biomarkers that can predict DILI risk. The established model would be useful in detecting the DILI potential of compounds, in particular those that involve an immune mechanism.

Indirect co-cultivation of HepG2 with differentiated THP-1 cells induces AHR signalling and release of pro-inflammatory cytokines

HepG2 and THP-1 cells, the latter differentiated by phorbol 12-myristate 13-acetate (PMA), were co-cultured and characterized for typical liver-specific functions, such as xenobiotic detoxification, lipid and cholesterol metabolism. Furthermore, liver injury-associated pathways, such as inflammation, were studied. In general, the co-cultivation of these cells produced a pro-inflammatory system, as indicated by increased levels of cytokines (IL-8, TGF-α, IL-6, GM-CSF, G-CSF, TGF-β, and hFGF) in the respective supernatant. Increased expression levels of target genes of the aryl hydrocarbon receptor (AHR), e.g., CYP1A1, CYP1A2 and CYP1B1, were detected, accompanied by the increased enzyme activity of CYP1A1. Moreover, transcriptome analyses indicated a significant upregulation of cholesterol biosynthesis, which could be reduced to baseline levels by lovastatin. In contrast, total de novo lipid synthesis was reduced in co-cultured HepG2 cells. Key events of the adverse outcome pathway (AOP) for fibrosis were activated by the co-cultivation, however, no increase in the concentration of extracellular collagen was detected. This indicates, that AOP should be used with care. In summary, the indirect co-culture of HepG2/THP-1 cells results in an increased release of pro-inflammatory cytokines, an activation of the AHR pathway and an increased enzymatic CYP1A activity.

Twelfth-Position Deuteration of Nevirapine Reduces 12-Hydroxy-Nevirapine Formation and Nevirapine-Induced Hepatocyte Death

Cytochrome P450-dependent metabolism of the anti-HIV drug nevirapine (NVP) to 12-hydroxy-NVP (12-OHNVP) has been implicated in NVP toxicities. We investigated the impact of twelfth-position trideuteration (12-D3NVP) on the hepatic metabolism of and response to NVP. Formation of 12-OHNVP decreased in human (10.6-fold) and mouse (4.6-fold) hepatocytes incubated with 10 μM 12-D3NVP vs NVP. An observed kinetic isotope effect of 10.1 was measured in human liver microsomes. During mouse hepatocyte treatment (400 μM) with NVP or 12-D3NVP, cell death was reduced 30% with 12-D3NVP vs NVP, while glucuronidated and glutathione-conjugated metabolites increased with 12-D3NVP vs NVP. Using mass spectrometry proteomics, changes in hepatocyte protein expression, including an increase in stress marker insulin-like growth factor-binding protein 1 (IGFBP-1), were observed with 12-D3NVP vs NVP. These results demonstrate that while deuteration can reduce P450 metabolite formation, impacts on phase II metabolism and hepatocyte protein expression should be considered when employing deuteration to reduce P450 metabolite-related hepatotoxicity.

Micropatterned Poly(ethylene glycol) Islands Disrupt Endothelial Cell-Substrate Interactions Differently from Microporous Membranes

Porous membranes are ubiquitous in cell co-culture and tissue-on-a-chip studies. These materials are predominantly chosen for their semi-permeable and size exclusion properties to restrict or permit transmigration and cell-cell communication. However, previous studies have shown pore size, spacing and orientation affect cell behavior including extracellular matrix production and migration. The mechanism behind this behavior is not fully understood. In this study, we fabricated micropatterned non-fouling polyethylene glycol (PEG) islands to mimic pore openings in order to decouple the effect of surface discontinuity from potential grip on the vertical contact area provided by pore wall edges. Similar to previous findings on porous membranes, we found that the PEG islands hindered fibronectin fibrillogenesis with cells on patterned substrates producing shorter fibrils. Additionally, cell migration speed over micropatterned PEG islands was greater than unpatterned controls, suggesting that disruption of cell-substrate interactions by PEG islands promoted a more dynamic and migratory behavior, similarly to enhanced cell migration on microporous membranes. Preferred cellular directionality during migration was nearly indistinguishable between substrates with identically patterned PEG islands and previously reported behavior over micropores of the same geometry, further confirming disruption of cell-substrate interactions as a common mechanism behind the cellular responses on these substrates. Interestingly, compared to respective controls, there were differences in cell spreading and a lower increase in migration speed over PEG islands compared prior results on micropores with identical feature size and spacing. This suggests that membrane pores not only disrupt cell-substrate interactions, but also provide additional physical factors that affect cellular response.

HMGB1 protein as a novel target for cancer

Highly conserved nuclear protein High Mobility Group Box1 (HMGB1) present in mammals has functionality as an immuno-modulator in the form of cytokine molecule, as a nuclear factor to regulate these molecules and DNA structural determination. It has proximal homologous DNA binding domains Box-A, Box-B and distal C-terminal domain. Reduced form exists in basic condition has chemotaxis activity, while form with disulphide bond reduced at 106th cysteine showed cytokine activity. The oxidized form is devoid of both activities. HMGB1 binds and bends dsDNA and also activates genes for secretion of inflammatory cytokines such as IL-1β, TNF-α, IL-6 and IL-18. It can interact with transcription factors Rel/NF-κB and p53 responsible for up-regulating oncogenes. Oxidative stressed injured tissues actively secrete HMGB1 outside cells to necrotize other nearby tissues passively in cytosol. Acetylation of HMGB1 weakens its binding with DNA, and promotes its migration to different tissues leading to secretion of inflammatory-cytokines. HMGB1 expression has been found very important in the genesis and promotion of different cancer by promoting metastasis. In current article, we emphasized on condition based structural variability of HMGB1, mechanism of release, physiological functions and its functionality as a biomarker for cancer to be targeted to curb cancer genesis and progression.