Testing in vitro tools for the prediction of cholestatic liver injury induced by non-pharmaceutical chemicals

Optimization of the drug-induced cholestasis index based on advanced modeling for predicting liver toxicity

Cholestatic drug-induced liver injury (cDILI) is a frequent reason for drug failure and withdrawal during premarketing and postmarketing stages of drug development. Strategies for reliable detection of cDILI in early drug development are therefore urgently needed. The drug-induced cholestasis index (DICI) concept was previously introduced as a tool for assessing the cholestatic potential of drug candidates. DICI is calculated as the ratio between the viability values obtained in drug-treated liver cells in the presence and absence of bile acids. The present in vitro study was set up to investigate the applicability of DICI in a novel high-throughput and large sample setting. Furthermore, the improvement of the predictivity of the DICI by introduction of advanced modeling was explored. Fifty-eight well-documented drugs were selected and categorized as drugs inducing cDILI, non-cholestatic DILI (ncDILI), and not inducing DILI (non-DILI). Cultures of human hepatoma HepaRG cells in 3D spheroid configuration were exposed to 9 half-log concentrations of each drug for 1, 3 and 7 days in the absence or presence of a concentrated mixture of human bile acids. The highest concentration of each drug was based on solubility and the maximum concentrations in human plasma (total Cmax). DICI values were computed for all drugs and time points. In addition, the area under the curve ratio and the occurrence of a trend in the cytotoxicity profiles were included as modeling descriptors. As such, 3 time-related scenarios were considered upon modeling, while categories were modeled on a nominal or an ordinal scale. Applying DICI with a cut-off value of 0.8 resulted in a high sensitivity for the cDILI class, but in turn, a low sensitivity for the non- DILI class. From the 28 predictive models generated, the best performing models integrated all descriptors and the ordinal scale for either the 7-day time point from a 3-time-point model or the 3-day time point. While these models were unable to accurately identify ncDILI drugs, the 7-day time point identified 84 % of the cDILI drugs and the 3-day time point correctly identified 94 % of non-DILI drugs. Based on the obtained results, it can be concluded that the reported DICI modeling provides an optimized approach that could be applied in an integrated DILI testing strategy.

Zebrafish Larvae as a Predictive Model for the Risk of Chemical-Induced Cholestasis: Phenotypic Evaluation and Nomogram Formation

Chemical-induced cholestasis (CIC) has become a concern in chemical safety risk assessment in pharmaceutical, food, cosmetic, and industrial manufacturing. Currently, known animal and in vitro liver models are unsuitable as high-throughput screening tools due to their high cost, time-consuming, or poor screening accuracy. Herein, a cohort of chemicals validated as cholestatic hepatotoxic in humans, rodents, and in vitro liver models was established for testing. The accuracy and reliability of the detection of CIC in zebrafish larvae were assessed by liver phenotype, bile flow inhibition rate, bile acid distribution, biochemical indices, and RT-qPCR. In addition, the nomogram prediction model was constructed using binomial logistic regression analysis. The model was constructed with three variables: aspartate aminotransferase (AST.FC) level, total bile acid (TBA.FC) level, and fold change in the number of bile acid nodes per unit of bile ducts in the zebrafish liver (NPL.FC), which showed high predictive power (areas under the ROC curve: 0.983). Furthermore, this study demonstrated that zebrafish larvae have some model specificity for CIC risk assessment of estrogen endocrine disruptors and that testing after 10 dpf provides more scientific results. Overall, combining zebrafish larval phenotyping and nomograms is an efficient and powerful tool for CIC risk monitoring of chemicals.

The food dye Tartrazine disrupts vascular formation both in zebrafish larvae and in human primary endothelial cells

Tartrazine (E102) is a controversial coloring agent whose potential impacts on human health are not fully understood. Our study reveals the vascular disrupting effects of tartrazine (TTZ) on developing zebrafish embryos in vivo and on human umbilical vein endothelial cells in vitro. The dye was shown to cause dose-dependent hemorrhages in zebrafish embryos. Analyzing transgenic zebrafish harboring fluorescent endothelial cells revealed that TTZ treatment disrupted cell organization into vessels in both the sub-intestinal vein and the brain area. Assays on human umbilical vein endothelial cells demonstrated that TTZ inhibited endothelial proliferation, tube formation, and migration in a dose-dependent manner. Taken together, our results indicate for the first time that TTZ can affect endothelial cell properties, possibly by disrupting Rho family GTPase pathways which control the cytoskeleton. Our finding provides a credible explanation for many reported human health impacts and offers prospective applications for biomedicine.

Impact of perfluoroalkyl substances (PFAS) and PFAS mixtures on lipid metabolism in differentiated HepaRG cells as a model for human hepatocytes

Per- and polyfluoroalkyl substances (PFAS) are environmental contaminants with various adverse health effects in humans including disruption of lipid metabolism. Aim of the present study was to elucidate the molecular mechanisms of PFAS-mediated effects on lipid metabolism in human cells. Here, we examined the impact of a number of PFAS (PFOS, PFOA, PFNA, PFDA, PFHxA, PFBA, PFHxS, PFBS, HFPO-DA, and PMPP) and of some exposure-relevant PFAS mixtures being composed of PFOS, PFOA, PFNA and PFHxS on lipid metabolism in human HepaRG cells, an in vitro model for human hepatocytes. At near cytotoxic concentrations, the selected PFAS and PFAS mixtures induced triglyceride accumulation in HepaRG cells and consistently affected the expression of marker genes for steatosis, as well as PPARα target genes and genes related to lipid and cholesterol metabolism, pointing to common molecular mechanisms of PFAS in disrupting cellular lipid and cholesterol homeostasis. PPARα activation was examined by a transactivation assay in HEK293T cells, and synergistic effects were observed for the selected PFAS mixtures at sum concentrations higher than 25 µM, whereas additivity was observed at sum concentrations lower than 25 µM. Of note, any effect observed in the in vitro assays occurred at PFAS concentrations that were at least four to five magnitudes above real-life internal exposure levels of the general population.

Leucine Aminopeptidase-Mediated Multifunctional Molecular Imaging Tool for Diagnosis, Drug Evaluation, and Surgical Guidance of Liver-Related Diseases

Traditional molecular imaging tools used for detecting liver diseases own several drawbacks, such as poor optical performance and limited applicability. Monitoring the concentration of leucine aminopeptidase (LAP), which is closely related to liver diseases such as liver cancer and liver injury, and analyzing it in diagnosis, drug evaluation, and surgical treatment is still a challenging task. Herein, we construct an intramolecular charge-transfer mechanism-based, ultrasensitive, near-infrared fluorescent probe (LAN-lap) for dynamic monitoring of LAP fluctuations in living systems. LAN-lap, with high specificity, stability, sensitivity, and water solubility, can achieve in vitro monitoring of LAP through both fluorescence and colorimetric methods. Moreover, LAN-lap can successfully be used for the localization imaging of endogenous LAP, confirming the upregulation of LAP expression in liver cancer and liver injury cells. In addition, LAN-lap can realize the imaging of liver tumors in living organisms. Meanwhile, it can intuitively present the degree of drug-induced liver injury, achieving semi-quantitative imaging evaluation of the hepatotoxicity of two drugs. Furthermore, LAN-lap can track liver cancer tumors in mice with peritoneal metastasis and can assist in fluorescence-guided surgical resection of liver cancer tumors. This multifunctional LAN-lap probe could play an important role in facilitating simultaneous diagnoses, imaging, and synergistic surgical navigation to achieve better point-of-care therapeutic efficacy.

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.

Primary Human Hepatocyte Spheroids as Tools to Study the Hepatotoxic Potential of Non-Pharmaceutical Chemicals

Drug-induced liver injury, including cholestasis, is an important clinical issue and economic burden for pharmaceutical industry and healthcare systems. However, human-relevant in vitro information on the ability of other types of chemicals to induce cholestatic hepatotoxicity is lacking. This work aimed at investigating the cholestatic potential of non-pharmaceutical chemicals using primary human hepatocytes cultured in 3D spheroids. Spheroid cultures were repeatedly (co-) exposed to drugs (cyclosporine-A, bosentan, macitentan) or non-pharmaceutical chemicals (paraquat, tartrazine, triclosan) and a concentrated mixture of bile acids for 4 weeks. Cell viability (adenosine triphosphate content) was checked every week and used to calculate the cholestatic index, an indicator of cholestatic liability. Microarray analysis was performed at specific time-points to verify the deregulation of genes related to cholestasis, steatosis and fibrosis. Despite the evident inter-donor variability, shorter exposures to cyclosporine-A consistently produced cholestatic index values below 0.80 with transcriptomic data partially supporting its cholestatic burden. Bosentan confirmed to be hepatotoxic, while macitentan was not toxic in the tested concentrations. Prolonged exposure to paraquat suggested fibrotic potential, while triclosan markedly deregulated genes involved in different types of hepatotoxicity. These results support the applicability of primary human hepatocyte spheroids to study hepatotoxicity of non-pharmaceutical chemicals in vitro.

Dataset on transcriptomic profiling of cholestatic liver injury induced by food additives and a cosmetic ingredient

The provided dataset describes the differential gene expression profile of human hepatoma HepaRG cells cultured in monolayer configuration upon treatment with chemical compounds with cholestatic potential, including food additives sunset yellow and tartrazine and cosmetic ingredient triclosan, while being exposed to a highly concentrated bile acid mixture. Whole genome microarray Affymetrix Human U133 plus 2.0 was used to obtain the raw data followed by normalization, summarization and background adjustments by means of Robust Multichip Average Express software. Raw data of the different conditions were included as .CEL files in the Gene Expression Omnibus with accession number GSE169072. These data may serve as the basis for further refinement studies to establish an adequate transcriptomic signature of chemical-induced cholestasis fit-for-purpose in screening the cholestatic liability of different types of chemical compounds.