Biomarkers of drug-induced liver injury: progress and utility in research, medicine, and regulation

Novel Emerging Mechanisms in Acetaminophen (APAP) Hepatotoxicity

BACKGROUND

Drug-induced liver injury represents a critical public health issue, marked by unpredictable and potentially severe adverse reactions to medications, herbal products or dietary supplements.

AIMS

Acetaminophen is notably a leading cause of hepatotoxicity, impacting over one million individuals worldwide.

MATERIALS & METHODS

Extensive research has elucidated the intricate mechanisms driving APAP-induced liver injury, emphasising the significant roles of endoplasmic reticulum stress, oxidative stress, mitochondrial dysfunction and cell death.

RESULTS

These insights pave the way for innovative therapeutic strategies, including the use of magnesium, bile acids, microbiota modulation and mesenchymal stem cells.

DISCUSSION & CONCLUSION

This review explores into these pathological mechanisms, proposing viable therapeutic interventions for patients suffering from APAP-induced liver injury.

In vitro liver models for toxicological research

Drug-induced liver injury (DILI) presents a major challenge not only in new drug development but also in post-marketing withdrawals and the safety of food, cosmetics, and chemicals. Experimental model organisms such as the rodents have been widely used for preclinical toxicological testing. However, the tension exists associated with the ethical and sustainable use of animals in part because animals do not necessarily inform the human-specific ADME (adsorption, dynamics, metabolism and elimination) profiling. To establish alternative models in humans, in vitro hepatic tissue models have been proposed, ranging from primary hepatocytes, immortal hepatocytes, to the development of new cell resources such as stem cell-derived hepatocytes. Given the evolving number of novel alternative methods, understanding possible combinations of cell sources and culture methods will be crucial to develop the context-of-use assays. This review primarily focuses on 3D liver organoid models for conducting. We will review the relevant cell sources, bioengineering methods, selection of training compounds, and biomarkers towards the rationale design of in vitro toxicology testing.

BMP6 participates in the molecular mechanisms involved in APAP hepatotoxicity

Given the lack of accurate diagnostic methods of acetaminophen (APAP)-induced acute liver failure (ALF), the search for new biomarkers for its diagnosis is an urgent need. The aim of this study was to evaluate the role of bone morphogenetic protein 6 (BMP6) in APAP-induced ALF progression and its potential value as a biomarker of ALF. Hepatic and circulating BMP6 expression was assessed in APAP-treated mice and in serum samples from patients with APAP overdose. In addition, BMP6 expression and release was evaluated in hepatocytes after APAP exposure. BMP6 gene was silenced in Huh7 cells prior to APAP treatment and the culture medium (CM) was added to THP1 cells to evaluate the paracrine effects of hepatocyte BMP6 on APAP toxicity. Hepatic and serum BMP6 levels were increased in mice after APAP-induced ALF. In addition, a positive correlation was observed between circulating BMP6 and ALT activity in patients exposed to APAP overdose. Moreover, hepatocytes expressed and released BMP6 to the CM after APAP treatment. Indeed, the CM from APAP-treated Huh7 cells upregulated M1 and M2 markers in THP1 monocytes. The CM from BMP6-silenced Huh7, which was depleted of BMP6, reduced the expression of M2 markers in THP1 cells. In fact, expression of M2 markers was increased in THP1 cells exposed to BMP6. This study reveals that hepatic BMP6 expression is increased in APAP-induced acute liver injury, positioning it as a potential new biomarker of liver damage severity. Moreover, our data indicate that BMP6 might play a role in the hepatocyte-macrophage crosstalk during APAP-induced hepatotoxicity.

A selective mitochondria-targeted fluorescent probe for imaging cysteine in drug-induced liver injury

Cysteine (Cys) is involved in many physiological processes. It's challenging to detect Cys selectively as it has similar chemical structure with other biothiols such as homocysteine (Hcy) and glutathione (GSH). In this work, a novel fluorescence probe toward mitochondrial cysteine, HPXI-6C, has been developed by employing carbonate as a new recognizing unit and hemicyanine as a chromophore. HPXI-6C exhibits a high selectivity to Cys over hydrogen sulfide, homocysteine and glutathione. The limit of detection toward Cys was determined to be 42 nM. HPXI-6C can localize in mitochondria and produce strong fluorescence peaked at 725 nm in response to Cys in tumor cells. The uptake and generation pathways of Cys in acetaminophen hepatotoxicity cells was revealed by using HPXI-6C. HPXI-6C has been successfully applied in imaging of Cys in drug-induced liver injury in vivo. The research demonstrated that HPXI-6C is powerful in monitoring Cys and is conducive to the early diagnosis of drug-induced liver injury diseases.

Idiosyncratic Hepatocellular Drug-Induced Liver Injury by Flucloxacillin with Evidence Based on Roussel Uclaf Causality Assessment Method and HLA B*57:01 Genotype: From Metabolic CYP 3A4/3A7 to Immune Mechanisms

Idiosyncratic drug-induced liver injury (iDILI) by flucloxacillin presents as both cholestatic and hepatocellular injury. Its mechanistic steps are explored in the present analysis as limited data exist on the cascade of events leading to iDILI in patients with an established diagnosis assessed for causality by the Roussel Uclaf Causality Assessment Method (RUCAM). Studies with human liver microsomes showed that flucloxacillin is a substrate of cytochrome P450 (CYP) with ist preferred isoforms CYP 3A4/3A7 that toxified flucloxacillin toward 5'-hydroxymethylflucloxacillin, which was cytotoxic to human biliary epithelial cell cultures, simulating human cholestatic injury. This provided evidence for a restricted role of the metabolic CYP-dependent hypothesis. In contrast, 5'-hydroxymethylflucloxacillin generated metabolically via CYP 3A4/3A7 was not cytotoxic to human hepatocytes due to missing genetic host features and a lack of non-parenchymal cells, including immune cells, which commonly surround the hepatocytes in the intact liver in abundance. This indicated a mechanistic gap regarding the clinical hepatocellular iDILI, now closed by additional studies and clinical evidence based on HLA B*57:01-positive patients with iDILI by flucloxacillin and a verified diagnosis by the RUCAM. Naïve T-cells from volunteers expressing HLA B*57:01 activated by flucloxacillin when the drug antigen was presented by dendritic cells provided the immunological basis for hepatocellular iDILI caused by flucloxacillin. HLA B*57:01-restricted activation of drug-specific T-cells caused covalent binding of flucloxacillin to albumin acting as a hapten. Following drug stimulation, T-cell clones expressing CCR4 and CCR9 migrated toward CCL17 and CCL25 and secreted interferon-γ and cytokines. In conclusion, cholestatic injury can be explained metabolically, while hepatocellular injury requires both metabolic and immune activation.

Drug induced liver injury - a 2023 update

Drug-Induced Liver Injury (DILI) constitutes hepatic damage attributed to drug exposure. DILI may be categorized as hepatocellular, cholestatic or mixed and might also involve immune responses. When DILI occurs in dose-dependent manner, it is referred to as intrinsic, while if the injury occurs spontaneously, it is termed as idiosyncratic. This review predominately focused on idiosyncratic liver injury. The established molecular mechanisms for DILI include (1) mitochondria dysfunction, (2) increased reactive oxygen species levels, (3) presence of elevated apoptosis and necrosis, (4) and bile duct injuries associated with immune mediated pathways. However, it should be emphasized that the underlying mechanisms responsible for DILI are still unknown. Prevention strategies are critical as incidences occur frequently, and treatment options are limited once the injury has developed. The aim of this review was to utilize retrospective cohort studies from across the globe to gain insight into epidemiological patterns. This review considers (1) what is currently known regarding the mechanisms underlying DILI, (2) discusses potential risk factors and (3) implications of the coronavirus pandemic on DILI presentation and research. Future perspectives are also considered and discussed and include potential new biomarkers, causality assessment and reporting methods.

Glutamate dehydrogenase combined with ferrochelatase as a biomarker of liver injury induced by antituberculosis drugs

AIMS

To explore the potential value of serum glutamate dehydrogenase (GLDH), ferrochelatase (FECH), heme oxygenase-1 (HO-1) and glutathione-S-transferase-α (GST-α) as diagnostic biomarkers for liver injury caused by antituberculosis drugs.

METHODS

We established a rat model of isoniazide-induced liver injury and recruited 122 hospitalized tuberculosis patients taking antituberculosis drugs. We detected the concentration of GLDH, FECH, HO-1 and GST-α by enzyme-linked immunosorbent assay. GraphPad Prism8 and SPSS 26.0 were used for statistical analysis.

RESULTS

In the rat model, serum GLDH concentration gradually increased during isoniazid (INH) administration, while serum FECH, HO-1 and GST-α concentrations significantly increased after INH administration was stopped. The receiver operating characteristic curve showed that the areas under the curve (AUCs) of serum GLDH and FECH for the diagnosis of anti-tuberculosis (TB) drug-induced liver injury (anti-TB-DILI) were 0.7692 (95% confidence interval [CI] 0.5442-0.9943) and 0.7284 (95% CI 0.4863-0.9705) and the diagnostic accuracies were 81.25% and 78.79%, respectively. In clinical research, the AUCs of GLDH and FECH were 0.9124 (95% CI 0.8380-0.9867) and 0.6634 (95% CI 0.5391-0.7877), and the optimal thresholds were 10.40 mIU/mL and 1.304 ng/mL, respectively. The diagnostic accuracy, specificity and positive predictive value (PPV) of GLDH were 82.61%, 79.38% and 47.22%. We performed a joint diagnostic test for GLDH and FECH. The diagnostic accuracy (90.43%), specificity (91.75%) and PPV (65.21%) of serial tests were better than for GLDH and FECH alone.

CONCLUSIONS

GLDH in the diagnosis of liver injury induced by anti-TB drugs has high sensitivity, but low specificity and low PPV. The combination of GLDH and FECH could significantly improve the specificity, PPV and diagnostic accuracy, and reduce the false-positive rate of anti-TB-DILI.

MicroRNAs: Small molecules with big impacts in liver injury

A type of small noncoding RNAs known as microRNAs (miRNAs) fine-tune gene expression posttranscriptionally by binding to certain messenger RNA targets. Numerous physiological processes in the liver, such as differentiation, proliferation, and apoptosis, are regulated by miRNAs. Additionally, there is growing evidence that miRNAs contribute to liver pathology. Extracellular vesicles like exosomes, which contain secreted miRNAs, may facilitate paracrine and endocrine communication between various tissues by changing the gene expression and function of distal cells. The use of stable miRNAs as noninvasive biomarkers was made possible by the discovery of these molecules in body fluids. Circulating miRNAs reflect the conditions of the liver that are abnormal and may serve as new biomarkers for the early detection, prognosis, and evaluation of liver pathological states. miRNAs are appealing therapeutic targets for a range of liver disease states because altered miRNA expression is associated with deregulation of the liver's metabolism, liver damage, liver fibrosis, and tumor formation. This review provides a comprehensive review and update on miRNAs biogenesis pathways and mechanisms of miRNA-mediated gene silencing. It also outlines how miRNAs affect hepatic cell proliferation, death, and regeneration as well as hepatic detoxification. Additionally, it highlights the diverse functions that miRNAs play in the onset and progression of various liver diseases, including nonalcoholic fatty liver disease, alcoholic liver disease, fibrosis, hepatitis C virus infection, and hepatocellular carcinoma. Further, it summarizes the diverse liver-specific miRNAs, illustrating the potential merits and possible caveats of their utilization as noninvasive biomarkers and appealing therapeutic targets for liver illnesses.

Noninvasive biomarkers for the diagnosis and management of autoimmune hepatitis

Autoimmune hepatitis (AIH) is a rare disease of unclear etiology characterized by loss of self-tolerance that can lead to liver injury, cirrhosis, and acute liver failure. First-line treatment consists of systemic corticosteroids, or budesonide, and azathioprine, to which most patients are initially responsive, although predictors of response are lacking. Relapses are very common, correlate with histological activity despite normal serum transaminases, and increase hepatic fibrosis. Furthermore, current regimens lead to adverse effects and reduced quality of life, whereas medication titration is imprecise. Biomarkers that can predict the clinical course of disease, identify patients at elevated risk for relapse, and improve monitoring and medication dosing beyond current practice would have high clinical value. Herein, we review novel candidate biomarkers in adult and pediatric AIH based on prespecified criteria, including gene expression profiles, proteins, metabolites, and immune cell phenotypes in different stages of AIH. We also discuss biomarkers relevant to AIH from other immune diseases. We conclude with proposed future directions in which biomarker implementation into clinical practice could lead to advances in personalized therapeutic management of AIH.

Potential deleterious effects of paracetamol dose regime used in Nigeria versus that of the United States of America

Paracetamol, also known as acetaminophen (N-acetyl-para-aminophenol, APAP) is the world's most used over-the-counter analgesic-antipyretic drug. Despite its good safety profile, acetaminophen can cause severe hepatotoxicity in overdose, and poisoning from paracetamol has become a major public health concern. Paracetamol is now the major cause of acute liver failure in the United States and Europe. This systematic review aims at examining the likelihood of paracetamol use in Nigeria causing more liver toxicity vis-à-vis the reduced maximum recommended daily adult dose of 3 g for the 500 mg tablet. Online searches were conducted in the databases of PubMed, Google Scholar and MEDLINE for publications using terms like "paracetamol toxicity," "acetaminophen and liver toxicity," "paracetamol and liver diseases in Nigeria," and other variants. Further search of related references in PubMed was carried out, and synthesis of all studies included in this review finalized. There were 94 studies that met the inclusion criteria. Evaluation of hepatic disorder was predicated mostly on a constellation of clinical features and limited clinical laboratory investigations. Determination of blood paracetamol concentration was rarely reported, thus excluding paracetamol poisoning as one of the likely causes of liver disorders in Nigeria. In Nigeria and elsewhere, several factors are known to increase paracetamol's predisposition to liver injury. They include: the over-the-counter status of paracetamol, use of fixed-dose combinations of paracetamol with other drugs, malnutrition, dose miscalculations, and chronic alcohol consumption. The tendency to exceed the new paracetamol maximum daily dose of 3 g in Nigeria may increase its risk for hepatotoxicity than observed in the United States of America known for emphasizing lower dose of the drug. In addition to recommending the new maximal daily paracetamol dose allowance, the historical maximum daily adult dose of 4 g should be de-emphasized in Nigeria.

Redrawing the map to novel DILI biomarkers in circulation: Where are we, where should we go, and how can we get there?

Circulating biomarkers of drug-induced liver injury (DILI) have been a focus of research in hepatology over the last decade, and several novel DILI biomarkers that hold promise for certain applications have been identified. For example, glutamate dehydrogenase holds promise as a specific biomarker of liver injury in patients with concomitant muscle damage. It may also be a specific indicator of mitochondrial damage. In addition, microRNA-122 is sensitive for early detection of liver injury in acetaminophen overdose patients. However, recent events in the field of DILI biomarker research have provided us with an opportunity to step back, consider how biomarker discovery has been done thus far, and determine how to move forward in a way that will optimize the discovery process. This is important because major challenges remain in the DILI field and related areas that could be overcome in part by new biomarkers. In this short review, we briefly describe recent progress in DILI biomarker discovery and development, identify current needs, and suggest a general approach to move forward.

Priming, Triggering, Adaptation and Senescence (PTAS): A Hypothesis for a Common Damage Mechanism of Steatohepatitis

Understanding the pathomechanism of steatohepatitis (SH) is hampered by the difficulty of distinguishing between causes and consequences, by the broad spectrum of aetiologies that can produce the phenotype, and by the long time-span during which SH develops, often without clinical symptoms. We propose that SH develops in four phases with transitions: (i) priming lowers stress defence; (ii) triggering leads to acute damage; (iii) adaptation, possibly associated with cellular senescence, mitigates tissue damage, leads to the phenotype, and preserves liver function at a lower level; (iv) finally, senescence prevents neoplastic transformation but favours fibrosis (cirrhosis) and inflammation and further reduction in liver function. Escape from senescence eventually leads to hepatocellular carcinoma. This hypothesis for a pathomechanism of SH is supported by clinical and experimental observations. It allows organizing the various findings to uncover remaining gaps in our knowledge and, finally, to provide possible diagnostic and intervention strategies for each stage of SH development.

Urantide prevents CCl4‑induced acute liver injury in rats by regulating the MAPK signalling pathway

A number of drugs and other triggers can cause acute liver injury (ALI) in clinical practice. Therefore, identifying a safe drug for the prevention of liver injury is important. The aim of the present study was to investigate the potential preventive effect and regulatory mechanism of urantide on carbon tetrachloride (CCl4)‑induced ALI by investigating the expression of components of the MAPK signalling pathway and the urotensin II (UII)/urotensin receptor (UT) system. Liver oedema and severe fatty degeneration of the cytoplasm were observed in ALI model rats, and the serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were found to be significantly increased. Compared with those in the ALI model group, ALT and AST levels and the liver index did not significantly increase in each group given the preventive administration of urantide, and the liver tissue morphology was correspondingly protected. Moreover, the gene and protein expression levels of UII, G protein‑coupled receptor (GPR14) and the oxidative stress‑sensitive cytokines, α‑smooth muscle actin and osteopontin were decreased, indicating that the protein translation process was effectively maintained. However, the expression levels of MAPK signalling pathway‑related proteins and genes were decreased. It was found that urantide could effectively block the MAPK signalling pathway by antagonizing the UII/UT system, thus protecting the livers of ALI model rats. Therefore, it was suggested that ALI may be associated with the MAPK signalling pathway, and effective inhibition of the MAPK signalling pathway may be critical in protecting the liver.

The predictive values of GGT and Hcy in the risk stratifications and prognoses of NSTE-ACS patients

OBJECTIVE

This research was designed to probe into the predictive value of glutamyltransferase (GGT) and homocysteine (Hcy) in the risk stratifications and prognoses of non-ST segment elevation acute coronary syndrome (NSTE-ACS) patients.

METHODS

A total of 182 NSTE-ACS patients treated with percutaneous coronary intervention (PCI) in our hospital from February 2016 to May 2018 were recruited as a patient group (PG). They were followed up for one year, and the occurrences of any major adverse cardiovascular events (MACCE) were recorded. In addition, 90 healthy volunteers were recruited as a normal group (NG) during the same period. The GGT and Hcy expressions in the serum of both groups were tested, and the predictive values of these levels, the patient risk stratification, and the prognoses were analyzed.

RESULTS

Compared with the NG, the GGT and Hcy expressions in the PG were markedly higher (P < 0.05). Compared with the patients without MACE, the GGT and Hcy expressions in the serum of those with MACE increased dramatically (P < 0.05). The serum GGT and Hcy levels were positively correlated with the NSTE-ACS patients' SYNTAX scores (P < 0.05). A Kaplan-Meier curve indicated that the MACE-free survival rate of the patients with low GGT levels was dramatically higher than the survival rate of the patients with high GGT levels, and the MACE-free survival rate of low Hcy patients was significantly higher than the MACE-free survival rate of the high Hcy patients (P < 0.05). Our COX proportional hazards regression models indicated that the serum GGT and Hcy levels are independent predictors of MACCE in NSTE-ACS patients (P < 0.05). Our ROC curve analysis indicated that the serum GGT and Hcy levels are diagnostic criteria for predicting whether MACE occurred in NSTE-ACS patients.

CONCLUSION

The serum GGT and Hcy levels are positively correlated with the severity of coronary artery disease (CAD) in NSTE-ACS patients. They are independent predictors of adverse prognoses and can help refine the risk stratification management in clinical work.

Changes in the proteome of extracellular vesicles shed by rat liver after subtoxic exposure to acetaminophen

To identify changes in extracellular vesicles (EVs) secreted by the liver following drug-induced liver injury (DILI), rats were treated with a subtoxic dose (500 mg/kg) of the analgesic drug, acetaminophen (APAP). EVs were collected by liver perfusion of sham and APAP-treated rats. Changes in EVs morphology were examined by transmission electron microscopic analysis of negatively stained vesicles. Results from morphometric analysis of EVs revealed striking differences in their size and distribution. Proteome composition of EVs collected by liver perfusion was determined by mass spectrometry using methods of sample preparation that enabled better detection of both highly hydrophobic proteins and proteins with complex post-translational modifications. The collection of EVs after liver perfusion is an approach that enables the isolation of EVs shed not only by isolated hepatocytes, but also by the entire complement of hepatic cells. EVs derived after DILI had a lower content of alpha-1-macroglobulin, ferritin, and members of cytochrome 450 family. Fibronectin, aminopeptidase N, metalloreductase STEAP4, integrin beta, and members of the annexin family were detected only in APAP-treated samples of EVs. These results show that the present approach can provide valuable insights into the response of the liver following drug-induced liver injury.

Rational design of a fluorescent probe for the detection of LAP and its application in drug-induced liver injury

Drug-induced liver injury (DILI) has become a common adverse effect in routine clinical practice, which would further cause the disorder of enzymatic system that respond to multiple pathological progresses. Leucine aminopeptidase (LAP) is regarded as a biomarker in the early course of various liver diseases, in this work, a fluorescent probe NCPL was designed and synthesized for the detecting of LAP. NCPL possessed excellent properties including high selectivity, sensitivity and affinity toward LAP, it could real-time image the LAP activity in living cells and tissues. Additionally, the upregulation of LAP under the APAP-induced liver injury model was also illustrated by NCPL. In conclusion, NCPL as a novel tool could be used for the detection of LAP and monitoring liver function in clinic.

Biomarkers of drug-induced liver injury: a mechanistic perspective through acetaminophen hepatotoxicity

Introduction: Liver injury induced by drugs is a serious clinical problem. Many circulating biomarkers for identifying and predicting drug-induced liver injury (DILI) have been proposed.Areas covered: Biomarkers are mainly predicated on the mechanistic understanding of the underlying DILI, often in the context of acetaminophen overdose. New panels of biomarkers have emerged that are related to recovery/regeneration rather than injury following DILI. We explore the clinical relevance and limitations of these new biomarkers including recent controversies. Extracellular vesicles have also emerged as a promising vector of biomarkers, although the biological role for EVs may limit their clinical usefulness. New technological approaches for biomarker discovery are also explored.Expert opinion: Recent clinical studies have validated the efficacy of some of these new biomarkers, cytokeratin-18, macrophage colony-stimulating factor receptor, and osteopontin for DILI prognosis. Low prevalence of DILI is an inherent limitation to DILI biomarker development. Furthering mechanistic understanding of DILI and leveraging technological advances (e.g. machine learning/omics) is necessary to improve upon the newest generation of biomarkers. The integration of omics approaches with machine learning has led to novel insights in cancer research and DILI research is poised to leverage these technologies for biomarker discovery and development.

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

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

Psoralen induces liver injuries through endoplasmic reticulum stress signaling in female mice

Psoralen is the main coumarin component of Fructus psoraleae. Previously, we have found that psoralen induced hepatocytes apoptosis via PERK and ATF6 related ER stress pathways in vitro. In this study, we investigated the toxicity and ER stress induced by psoralen in female C57 mice. Mice were fed with 80 mg/kg of psoralen intra-gastrically for either 3, 7, or 21 days. Liver and kidney were weighed and their coefficients were calculated. The serum was isolated to examine the biochemical parameters including alanine aminotransferase (ALT) activity, aspartate aminotransferase (AST) activity, alkaline phosphatase (ALP) activity, blood urea nitrogen (BUN), total bile acid (TBA), total bilirubin (TBIL), and creatinine (CRE). The transcription and expression of ER stress-related markers were determined by Wes-automated Protein Simple system, Western blot and RT-PCR. Psoralen administration for 3 days significantly increased liver coefficients but decreased kidney coefficients of mice. Histopathological examination showed minimal inflammatory cell foci and vacuolar degeneration in the liver. Besides, serum levels of ALT, TBA, BUN, and CRE were markedly altered by psoralen. Moreover, psoralen significantly increased expression and transcription levels of ER stress related markers, including Grp78, PERK, eIF2α, ATF4, IRE1α, ATF6, and XBP1. These results illustrated that psoralen induced liver injuries through ER stress signaling in female mice.

Identification of Serum Biomarkers to Distinguish Hazardous and Benign Aminotransferase Elevations

The standard circulating biomarker of liver injury in both clinical settings and drug safety testing is alanine aminotransferase (ALT). However, ALT elevations sometimes lack specificity for tissue damage. To identify novel serum biomarkers with greater specificity for injury, we combined unique animal models with untargeted proteomics, followed by confirmation with immunoblotting. Using proteomics, we identified 109 proteins in serum from mice with acetaminophen (APAP)-induced liver injury that were not detectable in serum from mice with benign ALT elevations due to high-dose dexamethasone (Dex). We selected 4 (alcohol dehydrogenase 1A1 [Aldh1a1], aldehyde dehydrogenase 1 [Adh1], argininosuccinate synthetase 1 [Ass1], and adenosylhomocysteinase [Ahcy]) with high levels for further evaluation. Importantly, all 4 were specific for injury when using immunoblots to compare serum from Dex-treated mice and mice with similar lower ALT elevations due to milder models of APAP or bromobenzene-induced liver injury. Immunoblotting for ALDH1A1, ADH1, and ASS1 in serum from APAP overdose patients without liver injury and APAP overdose patients with mild liver injury revealed that these candidate biomarkers can be detected in humans with moderate liver injury as well. Interestingly, further experiments with serum from rats with bile duct ligation-induced liver disease indicated that Aldh1a1 and Adh1 are not detectable in serum in cholestasis and may therefore be specific for hepatocellular injury and possibly even drug-induced liver injury, in particular. Overall, our results strongly indicate that ALDH1A1, ADH1, and ASS1 are promising specific biomarkers for liver injury. Adoption of these biomarkers could improve preapproval drug safety assessment.

Immune-mediated drug-induced liver injury secondary to Omeprazole: A case report

Omeprazole is a rare cause of DILI with autoimmune hepatitis features and should be considered when seeing patients with acute liver injury. The causative drug should be promptly identified and discontinued to avoid any permanent liver damage.

Sleep deprivation aggravated lipopolysaccharide/D-galactosamine-induced acute liver injury by suppressing melatonin production

OBJECTIVE

Sleep loss is common in patients with liver injury, but the effects of sleep deprivation (SD) on liver injury remain unclear. In the present study, the potential effects of SD on acute liver injury and the underlying mechanisms have been investigated.

METHODS

The sleep of male BALB/c mice has been deprived by using a modified multiple platform water bath for 3 days and acute liver injury was induced by intraperitoneal injection of lipopolysaccharide (LPS) and D-galactosamine (D-Gal). The degree of liver injury was detected by aminotransferase determination, histopathology and survival rate analysis. Inflammatory response and melatonin (MT) were measured by enzyme-linked immunosorbent assay (ELISA). In addition, hepatocyte apoptosis was determined by caspase activity measurement and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay.

RESULTS

We observed that SD increased plasma aminotransferases, TUNEL-positive hepatocytes, histological abnormalities and mortality rates in mice with LPS/D-Gal treatment. SD also promoted LPS/D-Gal-induced production of TNF-α and upregulated hepatic caspase-8, caspase-9, and caspase-3 activities in LPS/D-Gal-exposed mice. In addition, SD significantly decreased MT contents in plasma of mice with acute liver injury, but supplementation with MT reversed these SD-promoted changes.

CONCLUSION

Our data suggested that SD exacerbated LPS/D-Gal-induced liver injury via decreasing melatonin production.

Contrasting model mechanisms of alanine aminotransferase (ALT) release from damaged and necrotic hepatocytes as an example of general biomarker mechanisms

Interpretations of elevated blood levels of alanine aminotransferase (ALT) for drug-induced liver injury often assume that the biomarker is released passively from dying cells. However, the mechanisms driving that release have not been explored experimentally. The usefulness of ALT and related biomarkers will improve by developing mechanism-based explanations of elevated levels that can be expanded and elaborated incrementally. We provide the means to challenge the ability of closely related model mechanisms to generate patterns of simulated hepatic injury and ALT release that scale (or not) to be quantitatively similar to the wet-lab validation targets, which are elevated plasma ALT values following acetaminophen (APAP) exposure in mice. We build on a published model mechanism that helps explain the generation of characteristic spatiotemporal features of APAP hepatotoxicity within hepatic lobules. Discrete event and agent-oriented software methods are most prominent. We instantiate and leverage a small constellation of concrete model mechanisms. Their details during execution help bring into focus ways in which particular sources of uncertainty become entangled with cause-effect details within and across several levels. We scale ALT amounts in virtual mice directly to target plasma ALT values in individual mice. A virtual experiment comprises a set of Monte Carlo simulations. We challenge the sufficiency of four potentially explanatory theories for ALT release. The first of the tested model theories failed to achieve the initial validation target, but each of the three others succeeded. Results for one of the three model mechanisms matched all target ALT values quantitatively. It explains how ALT externalization is the combined consequence of lobular-location-dependent drug-induced cellular damage and hepatocyte death. Falsification of one (or more) of the model mechanisms provides new knowledge and incrementally shrinks the constellation of model mechanisms. The modularity and biomimicry of our explanatory models enable seamless transition from mice to humans.

Acetaminophen Oxidation and Inflammatory Markers - A Review of Hepatic Molecular Mechanisms and Preclinical Studies

Acetaminophen is a widely used analgesic for pain management, especially useful in chronic diseases, such as rheumatoid arthritis. However, easy access to this medicine has increased the occurrence of episodes of poisoning. Patients often develop severe liver damage, which may quickly lead to death. Consequently, numerous studies have been conducted to identify new biomarkers that allow the prediction of the degree of acetaminophen intoxication and thus intervene in a timely manner to save patients' lives. This review highlights the main mechanisms of the induction and progression of liver damage arising from acetaminophen poisoning. In addition, we have discussed the possibility of using new clinical biomarkers for detecting acetaminophen poisoning.

Advances in biomarker development in acetaminophen toxicity

Acetaminophen liver injury is the most common cause of acute liver injury in the United States and several other countries. Diagnosis of acetaminophen-induced acute liver injury in the clinic is challenging due to the lack of validated and specific biomarkers. The following chapter provides an overview of recent advances evaluating candidate biomarkers in development for acetaminophen acute liver injury. Relationships of biomarkers to mechanisms of acetaminophen toxicity and their potential role in confirming the diagnosis and/or predicting evolving toxicity are addressed.

GSTM1 and GSTT1 genetic polymorphisms and their association with antituberculosis drug-induced liver injury

Antituberculosis (anti-TB) drugs are the most common cause of drug-induced liver injury (DILI). There are numerous studies revealing the associations between the polymorphisms of pharmacogenes and the risk of anti-TB DILI (ATDILI). In the present study, relevant studies regarding the pharmacogenes associated with ATDILI were systematically searched in PubMed and Scopus. A total of 24 genes associated with ATDILI were reported on and the top five reported genes in terms of frequency were revealed to be N-acetyltransferase 2, cytochrome P450 family 2 subfamily E member 1, glutathione S-transferases [glutathione S-transferase mu 1 (GSTM1) and glutathione S-transferase theta 1 (GSTT1)] and solute carrier organic anion transporter family member 1B1. As ATDILI may be the result of direct and indirect interactions, the encoded proteins were further analysed using the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) to observe the protein-protein interactions and the associations amongst these proteins. The results suggested that only GSTT1 and GSTM1 were central proteins associated with all the other analysed proteins. Therefore, the association between GSTT1 or GSTM1 and the risk of developing ATDILI were further analysed. The results revealed that a GSTM1 deletion genotype was significantly associated with risk of ATDILI [odds ratio (OR), 1.28; 95% confidence interval (CI), 1.08-1.51; P=0.004], whereas the GSTT1 deletion genotype and GSTM1/GSTT1 dual-deletion genotype were not significantly associated with risk of ATDILI. Subgroup analysis based on ethnicity was performed and the results demonstrated a significant association between GSTM1 and ATDILI in South Asian individuals (OR, 1.48; 95% CI, 1.12-1.95; P=0.005), which has not been reported previously, to the best of our knowledge. In conclusion, GSTM1 was associated with ATDILI in South Asian individuals.

Drug-Induced Liver Injury: Highlights of the Recent Literature

Drug-induced liver injury (DILI), herbal-induced liver injury, and herbal and dietary supplement (HDS)-induced liver injury are an important aspect of drug safety. Knowledge regarding responsible drugs, mechanisms, risk factors, and the diagnostic tools to detect liver injury have continued to grow in the past year. This review highlights what we considered the most significant publications from among more than 1800 articles relating to liver injury from medications, herbal products, and dietary supplements in 2017 and 2018. The US Drug-Induced Liver Injury Network (DILIN) prospective study highlighted several areas of ongoing study, including the potential utility of human leukocyte antigens and microRNAs as DILI risk factors and new data on racial differences, the role of alcohol consumption, factors associated with prognosis, and updates on the clinical signatures of autoimmune DILI, thiopurines, and HDS agents. Novel data were also generated from the Spanish and Latin American DILI registries as well as from Chinese and Korean case series. A few new agents causing DILI were added to the growing list in the past 2 years, including sodium-glucose co-transporter-2 inhibitors, as were new aspects of chemotherapy-associated liver injury. A number of cases reported previously described hepatotoxins confirmed via the Roussel Uclaf Causality Assessment Method (RUCAM; e.g., norethisterone, methylprednisolone, glatiramer acetate) and/or the DILIN method (e.g., celecoxib, dimethyl fumarate). Additionally, much work centered on elucidating the pathophysiology of DILI, including the importance of bile salt export pumps and immune-mediated mechanisms. Finally, it must be noted that, while hundreds of new studies described DILI in 2017-2018, the quality of such reports must always be addressed. Björnsson reminds us to remain very critical of the data when addressing the future utility of a study, which is why it is so important to adhere to a standardized method such as RUCAM when determining DILI causality. While drug-induced hepatotoxicity remains a diagnosis of exclusion, the diverse array of publications that appeared in 2017 and 2018 provided important advances in our understanding of DILI, paving the way for our improved ability to make a more definitive diagnosis and risk assessment.

MRI-based preclinical discovery of DILI: A lesson from paracetamol-induced hepatotoxicity

Worldwide, drug-induced liver injury (DILI) is a major cause of hepatic failure. It is also the leading cause of withdrawal, cautionary labeling, and restricted usage of licensed drugs; therefore, European Medicines Agency (EMA) and United States Food and Drug Administration (FDA) warn that the existing methods of assessing DILI are insufficient and that some of the translational biomarkers of hepatotoxicity must be relooked. Magnetic resonance imaging (MRI) seems to be a proper tool in elucidating the effects of DILI in both preclinical and clinical studies, providing excellent visualization of the morphology of the liver parenchyma. Therefore, herein, we propose preclinical MRI assessment of liver injury in experimental paracetamol-treated rats. Quantitative MRI clearly provides evidence of adverse effects in the liver tissue caused by a single overdose of paracetamol (1 g kg^-1 and 1.5 g kg^-1 b.w.). The results of the MRI were confirmed by the histopathological examination (H&E) of the rat liver specimen, however the adverse effects were not disclosed due to standard aminotransferase assays (ALT/AST) in rat blood serum. The results of our analysis demonstrate the successful application of MRI in the examination of paracetamol-induced hepatotoxicity in rats; it has a potential to serve as the early diagnostic tool for the prediction of DILI in preclinical evaluation.

Biomarkers of drug-induced liver injury

Drug-induced liver injury (DILI) is a major clinical and regulatory challenge. As a result, interest in DILI biomarkers is growing. So far, considerable progress has been made in identification of biomarkers for diagnosis (acetaminophen-cysteine protein adducts), prediction (genetic biomarkers), and prognosis (microRNA-122, high mobility group box 1 protein, keratin-18, glutamate dehydrogenase, mitochondrial DNA). Many of those biomarkers also provide mechanistic insight. The purpose of this chapter is to review major advances in DILI biomarker research over the last decade, and to highlight some of the challenges involved in implementation. Although much work has been done, more liver-specific biomarkers, more DILI-specific biomarkers, and better prognostic biomarkers for survival are all still needed. Furthermore, more work is needed to define reference intervals and medical decision limits.

Acetaminophen hepatotoxicity: A mitochondrial perspective

Acetaminophen (APAP) is a highly effective analgesic, which is safe at therapeutic doses. However, an overdose can cause hepatotoxicity and even liver failure. APAP toxicity is currently the most common cause of acute liver failure in the United States. Decades of research on mechanisms of liver injury have established the role of mitochondria as central players in APAP-induced hepatocyte necrosis and this chapter examines the various facets of the organelle's involvement in the process of injury as well as in resolution of damage. The injury process is initiated by formation of a reactive metabolite, which binds to sulfhydryl groups of cellular proteins including mitochondrial proteins. This inhibits the electron transport chain and leads to formation of reactive oxygen species, which induce the activation of redox-sensitive members of the MAP kinase family ultimately causing activation of c-Jun N terminal kinase, JNK. Translocation of JNK to the mitochondria then amplifies mitochondrial dysfunction, ultimately resulting in mitochondrial permeability transition and release of mitochondrial intermembrane proteins, which trigger nuclear DNA fragmentation. Together, these events result in hepatocyte necrosis, while adaptive mechanisms such as mitophagy remove damaged mitochondria and minimize the extent of the injury. This oscillation between recovery and necrosis is predominant in cells at the edge of the necrotic area in the liver, where induction of mitochondrial biogenesis is important for liver regeneration. All these aspects of mitochondria in APAP hepatotoxicity, as well as their relevance to humans with APAP overdose and development of therapeutic approaches will be examined in detail in this chapter.

Role of extracellular vesicles in release of protein adducts after acetaminophen-induced liver injury in mice and humans

Formation of acetaminophen (APAP) protein adducts are a critical feature of APAP hepatotoxicity, and circulating protein adducts have recently been utilized in bioassays for identification of APAP overdose in humans. Despite their clinical significance, mechanisms of adduct release into the circulation are not well understood. Extracellular vesicles (EVs) are discrete membrane bound vesicles, which package cellular cargo and function in extracellular transport. Clarification of their role in transport of APAP adducts is relevant since adduct packaging within these vesicles could shield them from detection by antibody based methods, resulting in under-estimating adduct levels. Hence, this study evaluated EV release after APAP overdose in primary mouse hepatocytes and human HepaRG cells in vitro, in mice and APAP overdose patients in vivo and examined their role in transport of APAP-protein adducts. EVs were characterized by size and protein composition and the levels of APAP-protein adducts were measured. Significant elevations in circulating EV numbers were observed 6 h after APAP overdose in vivo and by 4 h in primary mouse hepatocytes in culture. EVs were also elevated in media from HepaRG cells by 24 h after APAP exposure, an effect recapitulated in APAP overdose patients, where EV numbers were elevated compared to healthy controls. Although APAP-protein adducts were elevated in circulation and media parallel to the increased exosome release, no detectable adducts were observed within EVs. This suggests that although APAP overdose enhances EV release from hepatocytes in mice and humans, it is not a significant mechanism of release of APAP protein adducts into circulation.

Animal models of drug-induced liver injury

Drug-induced liver injury (DILI) presents unique challenges for consumers, clinicians, and regulators. It is the most common cause of acute liver failure in the US. It is also one of the most common reasons for termination of new drugs during pre-clinical testing and withdrawal of new drugs post-marketing. DILI is generally divided into two forms: intrinsic and idiosyncratic. Many of the challenges with DILI are due in large part to poor understanding of the mechanisms of toxicity. Although useful models of intrinsic DILI are available, they are frequently misused. Modeling idiosyncratic DILI presents greater challenges, but promising new models have recently been developed. The purpose of this manuscript is to provide a critical review of the most popular animal models of DILI, and to discuss the future of DILI research.