Implication of hepatic transporters (MDR1 and MRP2) in inflammation-associated idiosyncratic drug-induced hepatotoxicity investigated by microvolume cytometry

Molecular and Clinical Links between Drug-Induced Cholestasis and Familial Intrahepatic Cholestasis

Idiosyncratic Drug-Induced Liver Injury (iDILI) represents an actual health challenge, accounting for more than 40% of hepatitis cases in adults over 50 years and more than 50% of acute fulminant hepatic failure cases. In addition, approximately 30% of iDILI are cholestatic (drug-induced cholestasis (DIC)). The liver's metabolism and clearance of lipophilic drugs depend on their emission into the bile. Therefore, many medications cause cholestasis through their interaction with hepatic transporters. The main canalicular efflux transport proteins include: 1. the bile salt export pump (BSEP) protein (ABCB11); 2. the multidrug resistance protein-2 (MRP2, ABCC2) regulating the bile salts' independent flow by excretion of glutathione; 3. the multidrug resistance-1 protein (MDR1, ABCB1) that transports organic cations; 4. the multidrug resistance-3 protein (MDR3, ABCB4). Two of the most known proteins involved in bile acids' (BAs) metabolism and transport are BSEP and MDR3. BSEP inhibition by drugs leads to reduced BAs' secretion and their retention within hepatocytes, exiting in cholestasis, while mutations in the ABCB4 gene expose the biliary epithelium to the injurious detergent actions of BAs, thus increasing susceptibility to DIC. Herein, we review the leading molecular pathways behind the DIC, the links with the other clinical forms of familial intrahepatic cholestasis, and, finally, the main cholestasis-inducing drugs.

Interleukin-6 regulates the expression of hepatic canalicular efflux drug transporters after cecal ligation and puncture-induced sepsis: A comparison with lipopolysaccharide treatment

Hepatic multidrug transporters expressed on the canalicular membrane play a role in the hepatobiliary excretion of xenobiotics and endogenous substrates. The aim of this study was to elucidate the role of pro-inflammatory cytokines in the regulation of hepatic drug transporter expression after cecal ligation and puncture (CLP), a valuable tool for studying polymicrobial sepsis, and to compare CLP with lipopolysaccharide (LPS) treatment. CLP reduced the expression of Mdr2/Abcb4, Mrp2/Abcc2, Bsep/Abcb11, Bcrp/Abcg2, and Mate1/Slc47a1 mRNAs in wild-type (WT) mouse livers in a time-dependent manner up to 48 h postoperation. LPS also reduced the expression of all transporters in WT mouse livers 24 h posttreatment; thereafter, expression levels tended to return to normal by 48 h posttreatment. IL-6^-/- mice exhibited inhibited downregulation of drug transporters following CLP, although IL-1^-/- and TNFα^-/- mice exhibited the reduced expression of all transporters in a manner similar to that found in WT mice. Compared with CLP, LPS treatment reduced the expression of all transporters in all cytokine-deficient mouse livers, except for the expression of Mrp2/Abcc2 in IL-6^-/- mice. Overall, these findings suggest that IL-6 is major factor in the downregulation of hepatic multidrug transporters following the onset of polymicrobial sepsis but not after LPS treatment.

A cell lines derived microfluidic liver model for investigation of hepatotoxicity induced by drug-drug interaction

The poor metabolic ability of cell lines fails to meet the requirements of an in vitro model for drug interaction testing which is crucial for the development or clinical application of drugs. Herein, we describe a liver sinusoid-on-a-chip device composed of four kinds of transformed cell lines (HepG2 cells, LX-2 cells, EAhy926 cells, and U937 cells) that were ordered in a physiological distribution with artificial liver blood flow and biliary efflux flowing in the opposite direction. This microfluidic device applied three-dimensional culturing of HepG2 cells with high density (107 ml-1), forming a tightly connected monolayer of EAhy926 cells and achieving the active transport of drugs in HepG2 cells. Results showed that the device maintained synthetic and secretory functions, preserved cytochrome P450 1A1/2 and uridine diphosphate glucuronyltransferase enzymatic activities, as well as sensitivity of drug metabolism. The cell lines derived device enables the investigation of a drug-drug interaction study. We used it to test the hepatotoxicity of acetaminophen and the following combinations: "acetaminophen + rifampicin," "acetaminophen + omeprazole," and "acetaminophen + ciprofloxacin." The variations in hepatotoxicity of the combinations compared to acetaminophen alone, which is not found in a 96-well plate model, in the device were -17.15%, 14.88%, and -19.74%. In addition, this result was similar to the one tested by the classical primary hepatocyte plate model (-13.22%, 13.51%, and -15.81%). Thus, this cell lines derived liver model provides an alternative to investigate drug hepatotoxicity, drug-drug interaction.

From the Cover: Three-Dimensional (3D) HepaRG Spheroid Model With Physiologically Relevant Xenobiotic Metabolism Competence and Hepatocyte Functionality for Liver Toxicity Screening

Effective prediction of human responses to chemical and drug exposure is of critical importance in environmental toxicology research and drug development. While significant progress has been made to address this challenge using invitro liver models, these approaches often fail due to inadequate tissue model functionality. Herein, we describe the development, optimization, and characterization of a novel three-dimensional (3D) spheroid model using differentiated HepaRG cells that achieve and maintain physiologically relevant levels of xenobiotic metabolism (CYP1A2, CYP2B6, and CYP3A4/5). This invitro model maintains a stable phenotype over multiple weeks in both 96- and 384-well formats, supports highly reproducible tissue-like architectures and models pharmacologically- and environmentally important hepatic receptor pathways (ie AhR, CAR, and PXR) analogous to primary human hepatocyte cultures. HepaRG spheroid cultures use 50-100× fewer cells than conventional two dimensional cultures, and enable the identification of metabolically activated toxicants. Spheroid size, time in culture and culture media composition were important factors affecting basal levels of xenobiotic metabolism and liver enzyme inducibility with activators of hepatic receptors AhR, CAR and PXR. Repeated exposure studies showed higher sensitivity than traditional 2D cultures in identifying compounds that cause liver injury and metabolism-dependent toxicity. This platform combines the well-documented impact of 3D culture configuration for improved tissue functionality and longevity with the requisite throughput and repeatability needed for year-over-year toxicology screening.

The role of hepatic antioxidant capacity and hepatobiliary transporter in liver injury induced by isopsoralen in zebrafish larvae

Isopsoralen is the main component of the Chinese medicine psoralen, which has antitumour activity and can be used for the treatment of osteoporosis. However, the mechanism behind its hepatotoxicity has not yet been elucidated. In this study, the hepatotoxicity of isopsoralen was investigated using zebrafish. Isopsoralen treatment groups of 25, 50 and 100 μM were established. The mortality, liver morphology changes, levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), liver histopathology and mRNA levels of liver injury–related genes in zebrafish larvae were measured. The results showed that isopsoralen resulted in the development of malformed zebrafish, dose-dependent increases in ALT and AST, decreased liver fluorescence and weakened fluorescence intensity. Histopathological examination showed that high-dose isopsoralen caused a large number of vacuolated structures in the larvae liver. The polymerase chain reaction results showed a significant decrease in the mRNA levels of genes related to antioxidant capacity ( lfabp, gstp2 and sod1) and drug transport ( mdr1, mrp1 and mrp2), indicating that isopsoralen significantly inhibited liver antioxidant capacity and drug efflux capacity in zebrafish larvae. Isopsoralen is hepatotoxic to zebrafish larvae via inhibition of drug transporter expression resulting in the accumulation of isopsoralen in the body and decreased antioxidant capacity, leading to liver injury.

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.

The pathogenesis of drug-induced liver injury

Drugs can induce liver injury when taken as an over-dose, or even at therapeutic doses in susceptible individuals. Although severe drug-induced liver injury (DILI) is a relatively uncommon clinical event, it is a potentially life threatening adverse drug reaction and is the most common indication for the drug withdrawal. Areas covered: However, the diagnosis of DILI remains a significant challenge, because the establishment of causality is very difficult, and the histopathologic findings of DILI may be indistinguishable from those of other hepatic disorders, such as viral and alcoholic hepatitis. In this review, we provide an overview of recent advances in identification of serologic markers of diagnosis and prognosis, etiologic factors for susceptibility and diagnostic evaluation of DILI, with a focus on its pathogenic mechanisms and the role of liver biopsy. Expert commentary: Further studies of divergent research platforms, using a systems biology approach such as genomics and transcriptomics, may provide a deeper understanding of human drug metabolism and the causes, risk factors, and pathogenesis of DILI.

Hepatoprotective Effect of A Polyherbal Extract Containing Andrographis Paniculata, Tinospora Cordifolia and Solanum Nigrum Against Paracetamol Induced Hepatotoxicity

Background:

Traditionally, a number of medicinal plants are used to treat various types of hepatic disorders but few of them were pharmacologically evaluated for their safety and efficacy. The combination of Andrographis paniculata (Kalmegha), Tinospora cordifolia (Guduchi), and Solanum nigrum (Kakmachi) was traditionally used in Indian System of Medicine (Ayurveda) for the treatment of various liver-related disorders.

Objective:

In the present study, an attempt was made to substantiate the ethnopharmacological use of a traditional formulation in hepatoprotection against paracetamol-induced hepatotoxicity.

Subjects and Methods:

Swiss albino mice (weight 20–25 g) were used for this study. Intraperitoneal injection of paracetamol (500 mg/kg body weight) was used to induce hepatotoxicity. Serum levels of alanine transaminase, aspartate aminotransferase, bilirubin, alkaline phosphatase, were used as indices of liver injury. In addition total cholesterol, triglyceride, low-density lipoprotein, high-density lipoprotein and creatinine were also assayed using the standard procedure.

Results:

Among the two different doses, pretreatment with Polyherbal extract at 500 mg/kg body weight exhibited a significant (P < 0.05) hepatoprotective activity as compared to paracetamol group.

Conclusion:

The polyherbal extract exhibits a significant hepatoprotective effect in vivo. The study contributes to its use in traditional Ayurveda system for the management of liver diseases.

SUMMARY

Traditionally, a number of medicinal plants are used to treat various types of liver disorders but few of them were pharmacologically evaluated for their safety and efficacy. Combination of Andrographis paniculata (Kalmegha), Tinospora cordifolia (Guduchi), and Solanum nigrum (Kakmachi) was traditionally used in Ayurveda for the treatment of various liver related disorders. In the present study an attempt was made to validate the ethnopharmacological use of a traditional formulation in hepatoprotection against paracetamol induced hepatotoxicity. Swiss albino mice (weight 20-25 g) were used for this study. Intraperitoneal injection (IP) of paracetamol (500 mg/kg body weight) was used to induce hepatotoxicity. Serum levels of Alanine transaminase (ALT), Aspartate Aminotransferase (AST), Bilirubin, Alkaline phosphatase (ALP),. were used as indices of liver injury. In addition total cholesterol, triglyceride, Low density lipoprotein (LDL), High density lipoprotein (HDL) and creatinine were also assayed using standard procedure. Among the two different doses, pre-treatment with Polyherbal extract at 500 mg/kg body weight exhibited a significant (P < 0.05) hepatoprotective activity as compared to paracetamol group. The polyherbal extract exhibits significant hepatoprotective effect in vivo. The study contributes to its use in traditional Ayurveda system for the management of liver diseases.

Evaluation of Adverse Drug Properties with Cryopreserved Human Hepatocytes and the Integrated Discrete Multiple Organ Co-culture (IdMOC(TM)) System

Human hepatocytes, with complete hepatic metabolizing enzymes, transporters and cofactors, represent the gold standard for in vitro evaluation of drug metabolism, drug-drug interactions, and hepatotoxicity. Successful cryopreservation of human hepatocytes enables this experimental system to be used routinely. The use of human hepatocytes to evaluate two major adverse drug properties: drug-drug interactions and hepatotoxicity, are summarized in this review. The application of human hepatocytes in metabolism-based drug-drug interaction includes metabolite profiling, pathway identification, P450 inhibition, P450 induction, and uptake and efflux transporter inhibition. The application of human hepatocytes in toxicity evaluation includes in vitro hepatotoxicity and metabolism-based drug toxicity determination. A novel system, the Integrated Discrete Multiple Organ Co-culture (IdMOC) which allows the evaluation of nonhepatic toxicity in the presence of hepatic metabolism, is described.

Age-related differences in reporting of drug-associated liver injury: data-mining of WHO Safety Report Database

BACKGROUND/AIMS

Age-differences in the frequency and manifestations of drug-induced liver injury are not fully characterized. Data-mining analyses were performed to assess the impact of age on liver event reporting frequency with different phenotypes and agents.

METHODS

236 drugs associated with hepatotoxicity were evaluated using the Empirical Bayes Geometric Mean (EBGM) of the relative reporting ratio with 90% confidence interval (EB05 and EB95) calculated for the age groups: 0-17, 18-64, and⩾65years (or elderly), for overall, serious (acute liver failure), hepatocellular, and cholestatic liver injury, using the WHO Safety Report Database.

RESULTS

Overall, cases of age 0-17, 18-64, and 65years or older comprised 6%, 62%, and 32% of liver event reports. Acute liver failure and hepatocellular injury were more frequently reported among children compared to adults and the elderly while reports with cholestatic injury were more frequent among the elderly (p<0.00001). A potential to cause mitochondrial dysfunction was more prevalent among the drugs with increased pediatric reporting frequency while high lipophilicity and biliary excretion were more common among the drugs associated with higher reporting frequency in the elderly.

CONCLUSION

Age-specific phenotypes and potential drug properties associated with age-specific hepatotoxicity were identified in reported liver events; further analyses are warranted.

In vitro platforms for evaluating liver toxicity

The liver is a heterogeneous organ with many vital functions, including metabolism of pharmaceutical drugs and is highly susceptible to injury from these substances. The etiology of drug-induced liver disease is still debated although generally regarded as a continuum between an activated immune response and hepatocyte metabolic dysfunction, most often resulting from an intermediate reactive metabolite. This debate stems from the fact that current animal and in vitro models provide limited physiologically relevant information, and their shortcomings have resulted in "silent" hepatotoxic drugs being introduced into clinical trials, garnering huge financial losses for drug companies through withdrawals and late stage clinical failures. As we advance our understanding into the molecular processes leading to liver injury, it is increasingly clear that (a) the pathologic lesion is not only due to liver parenchyma but is also due to the interactions between the hepatocytes and the resident liver immune cells, stellate cells, and endothelial cells; and (b) animal models do not reflect the human cell interactions. Therefore, a predictive human, in vitro model must address the interactions between the major human liver cell types and measure key determinants of injury such as the dosage and metabolism of the drug, the stress response, cholestatic effect, and the immune and fibrotic response. In this mini-review, we first discuss the current state of macro-scale in vitro liver culture systems with examples that have been commercialized. We then introduce the paradigm of microfluidic culture systems that aim to mimic the liver with physiologically relevant dimensions, cellular structure, perfusion, and mass transport by taking advantage of micro and nanofabrication technologies. We review the most prominent liver-on-a-chip platforms in terms of their physiological relevance and drug response. We conclude with a commentary on other critical advances such as the deployment of fluorescence-based biosensors to identify relevant toxicity pathways, as well as computational models to create a predictive tool.

Biomarkers and human hepatocytes

The accuracy of preclinical safety evaluation to predict human toxicity is hindered by species difference in drug metabolism and toxic mechanism between human and nonhuman animals. In vitro human-based experimental systems allowing the assessment of human-specific drug properties represent a logical and practical approach to provide human-specific information. An advantage of in vitro approaches is that they require only limited amounts of time and resources, and, most importantly, do not invoke harm to human patients. Human hepatocytes, with complete hepatic metabolizing enzymes, transporters and cofactors, represent a practical and useful experimental system to assess drug metabolism. The use of human hepatocytes to evaluate two major adverse drug properties, drug–drug interactions and hepatotoxicity, are reviewed. The application of human hepatocytes in metabolism-based drug–drug interactions includes metabolite profiling, pathway identification, CYP450 inhibition, CYP450 induction, and uptake and efflux transporter inhibition. The application of human hepatocytes in toxicity evaluation includes in vitro hepatotoxicity and metabolism-based drug toxicity determination. Correlation of drug toxicity with proteomics and genomics data may allow the discovery of clinical biomarkers for early detection of liver toxicity.

Selective and cytokine-dependent regulation of hepatic transporters and bile acid homeostasis during infectious colitis in mice

Various disease models have been shown to alter hepatic drug-metabolizing enzyme (DME) and transporter expression and to induce cholestasis through altered enzyme and transporter expression. Previously, we detailed the regulation of hepatic DMEs during infectious colitis caused by Citrobacter rodentium infection. We hypothesized that this infection would also modulate hepatic drug transporter expression and key genes of bile acid (BA) synthesis and transport. Mice lacking Toll-like receptor 4 (TLR4), interleukin-6 (IL-6), or interferon-gamma (IFNγ) and appropriate wild-type animals were orally infected with C. rodentium and sacrificed 7 days later. In two wild-type strains, drug transporter mRNA expression was significantly decreased by infection for Slc22a4, Slco1a1, Slco1a4, Slco2b1, and Abcc6, whereas the downregulation of Abcc2, Abcc3, and Abcc4 were strain-dependent. In contrast, mRNA expressions of Slco3a1 and Abcb1b were increased in a strain-dependent manner. Expression of Abcb11, Slc10a1, the two major hepatic BA transporters, and Cyp7a1, the rate-limiting enzyme of BA synthesis, was also significantly decreased in infected animals. None of the above effects were caused by bacterial lipopolysaccharide, since they still occurred in the absence of functional TLR4. The downregulation of Slc22a4 and Cyp7a1 was absent in IFNγ-null mice, and the downregulation of Slco1a1 was abrogated in IL-6-null mice, indicating in vivo roles for these cytokines in transporter regulation. These data indicate that C. rodentium infection modulates hepatic drug processing through alteration of transporter expression as well as DMEs. Furthermore, this infection downregulates important genes of BA synthesis and transport and may increase the risk for cholestasis.