Intrinsic Drug-induced Liver Injury Research Articles

Ferroptosis and Intrinsic Drug-induced Liver Injury by Acetaminophen and Other Drugs: A Critical Evaluation and Historical Perspective.

Drug-induced hepatotoxicity is a significant clinical issue worldwide. Given the limited treatment options for these liver injuries, understanding the mechanisms and modes of cell death is crucial for identifying novel therapeutic targets. For the past 60 years, reactive oxygen species and iron-dependent lipid peroxidation (LPO) have been hypothesized to be involved in many models of acute drug-induced liver injury. However, this mechanism of toxicity was largely abandoned when apoptosis became the primary focus of cell death research. More recently, ferroptosis-a novel, non-apoptotic form of cell death-was identified in NRAS-mutant HT-1080 fibrosarcoma cells exposed to erastin and other NRLs. Ferroptosis is characterized by glutathione depletion and the impairment of glutathione peroxidase 4 activity, which hinders the detoxification of lipid hydroperoxides. These hydroperoxides then serve as substrates for iron-dependent LPO propagation. This cell death mechanism is now receiving widespread attention, extending well beyond its original identification in cancer research, including in the field of drug-induced liver injury. However, concerns arise when such mechanisms are applied across different cell types and disease states without sufficient validation. This review critically evaluated the historical evidence for iron-dependent LPO as a mechanism of drug-induced hepatotoxicity and explored how these earlier findings have led to the current concept of ferroptosis. Overall, the published data support the idea that multi-layered endogenous antioxidant defense mechanisms in the liver limit the occurrence of pathophysiologically relevant LPO under normal conditions. Only when these defense mechanisms are severely compromised does ferroptosis become a significant mode of drug-induced cell death.

Drug-induced autoimmune-like liver injury

Drug-induced liver injury (DILI) is arare yet potentially life-threatening disease. Besides intrinsic DILI, which is mainly caused by paracetamol overdosing and which is dose-dependent and predictable, there is idiosyncratic DILI-an unpredictable and dose-independent injury of the liver caused by certain medications that only occurs in aminority of patients taking this drug. The reason why some patients react with DILI towards aspecific drug is still unknown. However, the immune system plays acentral role, which is underlined by the association of certain human leukocyte antigen (HLA) polymorphisms and DILI caused by specific drug classes. Due to the immunological processes that lead to the liver injury in DILI, there are great overlaps regarding laboratory and histological parameters between DILI and autoimmune hepatitis (AIH). Differentiating DILI and AIH can therefore be challenging, especially at the time of presentation. In addition, there are other immunologically mediated DILI phenotypes, in particular the newly defined drug-induced autoimmune-like hepatitis (DI-ALH) and liver injuries caused by checkpoint inhibitors (CPI). DI-ALH is characterized by autoimmune features and good responses towards corticosteroids, with the difference that DI-ALH mostly does not relapse after discontinuation of corticosteroids. CPI-induced liver injury has become more frequent with the rising use of those drugs and is characterized by adistinct histopathological pattern with granulomatous hepatitis and infiltration dominated by cytotoxic Tcells. Similarly, the recently recognized liver injury following vaccinations also shows an autoimmune phenotype; however, in contrast to AIH, cytotoxic Tcells seem to dominate the inflammatory infiltrates in the liver.

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.

Epidemiology and Management of Drug-induced Liver Injury: Importance of the Updated RUCAM.

Drug-induced liver injury (DILI) is a major cause of acute liver injury, liver failure, and liver transplantation worldwide. In recent years, immune checkpoint inhibitors have become widely used. This has led to an increase in DILI, for which pathophysiology and management methods differ significantly from the past. As the number of cases of acute liver injury and liver transplantation due to DILI is expected to increase, information about a DILI is becoming more valuable. DILI is classified into two types according to its etiology: intrinsic DILI, in which the drug or its metabolites cause liver damage that is dose-dependent and predictable; and idiosyncratic DILI, in which liver damage is also dose-independent but unpredictable. In addition, depending on the course of the disease, chronic DILI or drug-induced autoimmune hepatitis may be present. The number of DILI cases caused by antimicrobial agents is decreasing, whereas that caused by drugs for malignant tumors and health foods is increasing. The Roussel Uclaf Causality Assessment Method is widely used to assess causality in DILI. Liver injury is a type of immune-related adverse event. The pattern of hepatic injury in immune-related adverse events is mostly hepatocellular, but mixed type and bile stasis have also been reported. Sclerosing cholangitis caused by immune checkpoint inhibitors has also been reported as a unique type of injury. Treatment mainly comprises withdrawal of immune checkpoint inhibitors and steroid administration; however, mycophenolate mofetil may be considered if the disease is refractory to steroids.

Absence of Increased Susceptibility to Acetaminophen-Induced Liver Injury in a Diet-Induced NAFLD Mouse Model.

Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease and its influence on drug-induced liver injury (DILI) is not fully understood. We investigated whether NAFLD can influence acetaminophen (APAP [N-acetyl-p-aminophenol])-induced hepatotoxicity in a diet-induced obese (DIO) mouse model of NAFLD. The male C57BL/6NTac DIO mice, fed a high-fat diet for more than 12 weeks, developed obesity, hyperinsulinemia, impaired glucose tolerance, and hepatomegaly with hepatic steatosis, similar to human NAFLD. In the acute toxicity study after a single dose of APAP (150 mg/kg), compared with control lean mice, the DIO mice had decreased serum transaminase levels and less severe hepatocellular injury. The DIO mice also had altered expression of genes related to APAP metabolism. Chronic APAP exposure for 26 weeks did not predispose the DIO mice with NAFLD to more severe hepatotoxicity compared with the lean mice. These results suggested that the C57BL/6NTac DIO mouse model appears to be more tolerant to APAP-induced hepatotoxicity than lean mice, potentially related to altered xenobiotic metabolizing capacity in the fatty liver. Further mechanistic studies with APAP and other drugs in NAFLD animal models are necessary to investigate the mechanism of altered susceptibility to intrinsic DILI in some human NAFLD patients.

Plasma Sphingoid Base Profiles of Patients Diagnosed with Intrinsic or Idiosyncratic Drug-induced Liver Injury.

Sphingolipids are exceptionally diverse, comprising hundreds of unique species. The bulk of circulating sphingolipids are synthesized in the liver, thereby plasma sphingolipid profiles represent reliable surrogates of hepatic sphingolipid metabolism and content. As changes in plasma sphingolipid content have been associated to exposure to drugs inducing hepatotoxicity both in vitro and in rodents, in the present study the translatability of the preclinical data was assessed by analyzing the plasma of patients with suspected drug-induced liver injury (DILI) and control subjects. DILI patients, whether intrinsic or idiosyncratic cases, had no alterations in total sphingoid base levels and profile composition compared to controls, whereby cardiovascular disease (CVD) was a confounding factor. Upon exclusion of CVD individuals, elevation of 1-deoxysphingosine (1-deoxySO) in the DILI group emerged. Notably, 1-deoxySO values did not correlate with ALT values. While 1-deoxySO was elevated in all DILI cases, only intrinsic DILI cases concomitantly displayed reduction of select shorter chain sphingoid bases. Significant perturbation of the sphingolipid metabolism observed in this small exploratory clinical study is discussed and put into context, in the consideration that sphingolipids might contribute to the onset and progression of DILI, and that circulating sphingoid bases may function as mechanistic markers to study DILI pathophysiology.

Treatment of Drug-Induced Liver Injury.

Current pharmacotherapy options of drug-induced liver injury (DILI) remain under discussion and are now evaluated in this analysis. Needless to say, the use of the offending drug must be stopped as soon as DILI is suspected. Normal dosed drugs may cause idiosyncratic DILI, and drugs taken in overdose commonly lead to intrinsic DILI. Empirically used but not substantiated regarding efficiency by randomized controlled trials (RCTs) is the intravenous antidote treatment with N-acetylcysteine (NAC) in patients with intrinsic DILI by N-acetyl-p-aminophenol (APAP) overdose. Good data recommending pharmacotherapy in idiosyncratic DILI caused by hundreds of different drugs are lacking. Indeed, a recent analysis revealed that just eight RCTs have been published, and in only two out of eight trials were DILI cases evaluated for causality by the worldwide used Roussel Uclaf Causality Assessment Method (RUCAM), representing overall a significant methodology flaw, as results of DILI RCTs lacking RUCAM are misleading since many DILI cases are known to be attributable erroneously to nondrug alternative causes. In line with these major shortcomings and mostly based on anecdotal reports, glucocorticoids (GCs) and other immuno-suppressants may be given empirically in carefully selected patients with idiosyncratic DILI exhibiting autoimmune features or caused by immune checkpoint inhibitors (ICIs), while some patients with cholestatic DILI may benefit from ursodeoxycholic acid use; in other patients with drug-induced hepatic sinusoidal obstruction syndrome (HSOS) and coagulopathy risks, the indication for anticoagulants should be considered. In view of many other mechanistic factors such as the hepatic microsomal cytochrome P450 with a generation of reactive oxygen species (ROS), ferroptosis with toxicity of intracellular iron, and modification of the gut microbiome, additional therapy options may be available in the future. In summation, stopping the offending drug is still the first line of therapy for most instances of acute DILI, while various therapies are applied empirically and not based on good data from RCTs awaiting further trials using the updated RUCAM that asks for strict exclusion and inclusion details like liver injury criteria and provides valid causality rankings of probable and highly probable grades.

Identification of intrinsic hepatotoxic compounds in Polygonum multiflorum Thunb. using machine-learning methods

Ethnopharmacological relevancePolygonum multiflorum Thunb. (PM) is a herb, extracts of which have been used as Chinese medicine for years. Although it is believed to be beneficial to the liver, heart, and kidneys, it causes idiosyncratic drug-induced liver injury (DILI). Aim of the studyWe propose that the intrinsic DILI caused by natural products in PM (NPPM) is an important complementary mechanism to PM-related herb-induced liver injury, and aim to identify the ingredients with high DILI potential by machine learning methods. Materials and methodsOne hundred and ninety-seven NPPM were collected from the literature to identify the intrinsic hepatotoxic compounds. Additionally, a DILI-labeled dataset consisting of 2384 compounds was collected and randomly split into training and test sets. A diparametric optimization method was developed to tune the parameters of extended-connectivity fingerprints (ECFPs), Rdkit, and atom-pair fingerprints as well as those of machine-learning (ML) algorithms. Subsequently, K means were employed to cluster the NPPM that were predicted to have a high DILI risk. An in vitro cell-viability assay was performed using HepaRG cells to validate the prediction results. ResultsECFPs with the top 35% of features ranked by the F-value with support vector machine (SVM) yielded the best performance. The optimized SVM model achieved an accuracy of 0.761 and recall value of 0.834 on the test dataset. The silico screening for NPPM resulted in 47 ingredients with high DILI potential, which were clustered into six groups based on the elbow method. A representative subgroup that contained 21 ingredients, of which two dianthrones exhibited the lowest IC50 value (0.7–0.9 μM) and anthraquinones showed moderate toxicity (15–25 μM), was constructed. ConclusionUsing ML methods and in vitro screening, two classes of compounds, dianthrones and anthraquinones, were predicted and validated to have a high risk of DILI. The diparametric optimization method used in this study could provide a useful and powerful tool to screen toxicants for large datasets and is available at https://github.com/dreadlesss/Hepatotoxicity_predictor.

Role and Regulation of Hepatobiliary ATP-Binding Cassette Transporters during Chemical-Induced Liver Injury.

Severity of drug-induced liver injury (DILI) ranges from mild, asymptomatic, and transient elevations in liver function tests to irreversible liver damage, often needing transplantation. Traditionally, DILI is classified mechanistically as high-frequency intrinsic DILI, commonly dose dependent or DILI that rarely occurs and is idiosyncratic in nature. This latter form is not dose dependent and has a pattern of histopathological manifestation that is not always uniform. Currently, a third type of DILI called indirect hepatotoxicity has been described that is associated with the pharmacological action of the drug. Historically, DILI was primarily linked to drug metabolism events; however, the impact of transporter-mediated rates of drug uptake and excretion has gained greater prominence in DILI research. This review provides a comprehensive view of the major findings from studies examining the contribution of hepatic ATP-binding cassette transporters as key contributors to DILI and how changes in their expression and function influence the development, severity, and overall toxicity outcome. SIGNIFICANCE STATEMENT: Drug-induced liver injury (DILI) continues to be a focal point in drug development research. ATP-binding cassette (ABC) transporters have emerged as important determinants of drug detoxification, disposition, and safety. This review article provides a comprehensive analysis of the literature addressing: (a) the role of hepatic ABC transporters in DILI, (b) the influence of genetic mutations in ABC transporters on DILI, and (c) new areas of research emphasis, such as the influence of the gut microbiota and epigenetic regulation, on ABC transporters.

Boldine treatment protects acetaminophen-induced liver inflammation and acute hepatic necrosis in mice.

Drug-induced liver injury (DILI) is a frequent cause responsible for acute liver failure (ALF). Acetaminophen (APAP) is a known hepatotoxin predictably causing intrinsic DILI. At high doses, APAP causes acute liver necrosis and responsible for ALF and liver transplant cases in 50% and 20% of patients, respectively, in the United States alone. Oxidative stress and glutathione depletion are implicated in APAP-induced liver necrosis. Boldine, a plant-derived compound is shown to have promising antioxidant potential. Therefore, this study investigates the protective effect of boldine against APAP-induced acute hepatic necrosis in mice. A single toxic dose of APAP (300 mg/kg b.w. p.o.) was administered in overnight-fasted mice to induce acute liver necrosis. Separately, APAP + boldine and APAP + N-acetylcysteine (NAC) simultaneous treatments were also given. Serum transaminases and reduced glutathione, enzymic antioxidants, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and, IL-6 were evaluated in liver tissue. Acute APAP intoxication significantly elevated serum marker enzymes of hepatotoxicity. APAP administration increased lipid peroxidation, TNF-α, IL-1β, and IL-6 protein expressions. The enzymic antioxidants and reduced glutathione levels were decreased in liver tissue of APAP intoxicated mice. Boldine and NAC simultaneous treatments prevented APAP-induced oxidative stress, inflammation, and necrosis. The results of this study suggest the crucial role of boldine to protect against APAP induced hepatotoxicity by virtue of its antioxidant and anti-inflammatory properties.

Clinical manifestations and typing of drug-induced liver injury

Drug-induced liver injury (DILI) is one of the most common and severe adverse drug reactions in humans, which may lead to liver failure and even death in some patients. Liver injury caused by different drugs has various clinical manifestations and severities, and most patients with DILI have no symptoms or have mild symptoms. There are various typing methods for DILI based on clinical features, course of disease, and pathogenesis. According to the R value, DILI can be classified into hepatocellular injury type (R ≥5), cholestasis type (R ≤2), and mixed type (2 < R < 5); according to the course of the disease, DILI can be classified into acute DILI and chronic DILI; according to the pathogenesis, DILI can be classified into intrinsic DILI, idiosyncratic DILI, and indirect DILI. A comprehensive understanding of the clinical manifestations and typing methods of DILI helps to reveal its pathogenesis and perform diagnosis and treatment in a timely manner.

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.

The hepatotoxicity of Polygonum multiflorum: The emerging role of the immune-mediated liver injury.

Herbal and dietary supplements (HDS)-induced liver injury has been a great concern all over the world. Polygonum multiflorum Thunb., a well-known Chinese herbal medicine, is recently drawn increasing attention because of its hepatotoxicity. According to the clinical and experimental studies, P. multiflorum-induced liver injury (PM-DILI) is considered to be immune-mediated idiosyncratic liver injury, but the role of immune response and the underlying mechanisms are not completely elucidated. Previous studies focused on the direct toxicity of PM-DILI by using animal models with intrinsic drug-induced liver injury (DILI). However, most epidemiological and clinical evidence demonstrate that PM-DILI is immune-mediated idiosyncratic liver injury. The aim of this review is to assess current epidemiological, clinical and experimental evidence about the possible role of innate and adaptive immunity in the idiosyncratic hepatotoxicity of P. multiflorum. The potential effects of factors associated with immune tolerance, including immune checkpoint molecules and regulatory immune cells on the individual's susceptibility to PM-DILI are also discussed. We conclude by giving our hypothesis of possible immune mechanisms of PM-DILI and providing suggestions for future studies on valuable biomarkers identification and proper immune models establishment.

Update on Advances in Research on Idiosyncratic Drug-Induced Liver Injury.

Drug-induced liver injury (DILI) is a major concern for public health, as well as for drug development in the pharmaceutical industry, since it can cause liver failure and lead to drug withdrawal from the market and black box warnings. Thus, it is important to identify biomarkers for early prediction to increase our understanding of mechanisms underlying DILI that will ultimately aid in the exploration of novel therapeutic strategies to prevent or manage DILI. DILI can be subdivided into 'intrinsic' and 'idiosyncratic' categories, although the validity of this classification remains controversial. Idiosyncratic DILI occurs in a minority of susceptible individuals with a prolonged latency, while intrinsic DILI results from drug-induced direct hepatotoxicity over the course of a few days. The rare occurrence of idiosyncratic DILI requires multicenter collaborative investigations and phenotype standardization. Recent progress in research on idiosyncratic DILI is based on key developments in 3 areas: (1) newly developed high-throughput genotyping across the whole genome allowing for the identification of genetic susceptibility markers, (2) new mechanistic concepts on the pathogenesis of DILI revealing a key role of drug-responsive T lymphocytes in the immunological response, and (3) broad multidisciplinary approaches using different platform "-omics" technologies that have identified novel biomarkers for the prediction of DILI. An association of a specific human leukocyte antigen (HLA) allele with DILI has been reported for several drugs. HLA-restricted T-cell immune responses have also been investigated using lymphocytes and T-cell clones isolated from patients. A microRNA, miR-122, has been discovered as a promising biomarker for the early prediction of DILI. In this review, we summarize recent advances in research on idiosyncratic DILI with an understanding of the key role of adaptive immune systems.

MicroRNAs as Signaling Mediators and Biomarkers of Drug- and Chemical-Induced Liver Injury.

Drug-induced liver injury (DILI) is major problem for both the drug industry and for clinicians. There are two basic categories of DILI: intrinsic and idiosyncratic. The former is the chief cause of acute liver failure in several developed countries, while the latter is the most common reason for post-marketing drug withdrawal and a major reason for failure to approve new drugs in the U.S. Although considerably more progress has been made in the study of intrinsic DILI, our understanding of both forms of drug hepatotoxicity remains incomplete. Recent work involving microRNAs (miRNAs) has advanced our knowledge of DILI in two ways: (1) possible roles of miRNAs in the pathophysiological mechanisms of DILI have been identified, and (2) circulating miRNA profiles have shown promise for the detection and diagnosis of DILI in clinical settings. The purpose of this review is to summarize major findings in these two areas of research. Taken together, exciting progress has been made in the study of miRNAs in DILI. Possible mechanisms through which miRNA species contribute to the basic mechanisms of DILI are beginning to emerge, and new miRNA-based biomarkers have the potential to greatly improve diagnosis of liver injury and prediction of patient outcomes.

Establishment of animal models of drug-induced liver injury and analysis of possible mechanisms

Drug-induced liver injury (DILI) is one of leading causes of attrition during both early and late stages of drug development and postmarketing. DILI is generally classified into the intrinsic and idiosyncratic types. Intrinsic DILI is dose dependent and predictable as exemplified by acetaminophen toxicity. However, the occurrence of idiosyncratic DILI with very low incidence and severe liver damage is difficult to predict because of the complex nature of DILI and poor understanding of its mechanism. In this review, we summarize current knowledge and our accumulated experimental findings on the pathogenic mechanisms of DILI focusing on the reactive metabolites of drugs formed by drug-metabolizing enzymes and immune- and inflammation-related responses. Considering drug metabolism and pharmacokinetics, we have established nonclinical animal models of DILI for 10 types of clinical drug known to cause idiosyncratic DILI in humans. Using animal models, it has been shown that the formation of reactive metabolites and both innate and adaptive immunity are involved in the pathogenesis of drug hepatotoxicity. Based on information on biomarkers obtained from animal models, we developed a cell-based system that predicts the potential DILI risks of drugs. The results of these studies increased our understanding of the mechanisms of DILI and help to predict and prevent idiosyncratic DILI caused by drug candidates.