HLA-A33/B44/DR6 is highly related to intrahepatic cholestasis induced by tiopronin

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.

Genetic risk factors for autoimmune hepatitis: implications for phenotypic heterogeneity and biomarkers for drug response

Autoimmune hepatitis (AIH) is a rare chronic progressive liver disease with autoimmune features. It mainly affects middle-aged women. AIH is occasionally complicated with liver cirrhosis that worsens the prognosis. Genetic and environmental factors are involved in the pathogenesis of AIH. Genetic studies of other diseases have been revealing of pathogenesis and drug efficacy. In this review, we summarize the genetic risk factors for AIH, including human leukocyte antigen (HLA) and non-HLA genes. A genome-wide association study (GWAS) on European AIH revealed the strongest associations to be with single nucleotide variants (SNVs) in HLA. Predisposing alleles for AIH were DRB1*03:01 and DRB1*04:01 in Europeans; DRB1*04:04, DRB1*04:05, and DRB1*13:01 in Latin Americans; and DRB1*04:01 and DRB1*04:05 in Japanese. Other risk SNVs in non-HLA genes for AIH were found by a candidate gene approach, but several SNVs were confirmed in replication studies. Some genetic factors of AIH overlapped with those of other autoimmune diseases. Larger-scale GWASs of other ethnic groups are required. The results of genetic studies might provide an explanation for the phenotypic heterogeneity of AIH and biomarkers for drug responses.

Association of HLA-C*03:02 with methimazole-induced liver injury in Graves' disease patients

Methimazole (MMI) has been used for the treatment of Graves' Disease (GD) for more than half a century. The MMI treatment has been reported to be associated with hepatotoxicity. Previous studies have demonstrated that human leukocyte antigen (HLA) genetic polymorphisms were associated with many drugs-induced liver injuries. To investigate HLA genetic susceptibility to MMI-induced liver injury (MMI-DILI), we characterized both HLA class I and class Ⅱ in a well-characterized phenotypic cohort with 40 MMI-DILI cases and 118 MMI-tolerant controls. Among the 40 MMI-DILI cases, 57.5% were women and 50% were cholestatic liver damage with occurring time from days to months after MMI dosing. The frequency of HLA-C*03:02 was 6.7% (5/75) in the MMI-DILI case patients and 6.4% (4/62) in MMI-induced cholestatic/mixed liver damage, which were significantly different from the percentage of 0.4% (1/231) in the MMI-tolerant patients (odds ratio (OR) = 15.4, 95% confidence interval (CI) = 1.77-133.9, adjusted P = 0.0292; OR=14.9, 95% CI=2.38-182.9, adjusted P = 0.0323; respectively). HLA-A*02:01 was also found to be associated with MMI-induced cholestatic/mixed liver injury (OR = 3.13, 95%CI=1.45-6.91, adjusted P = 0.0464). The present study demonstrated that individuals carrying HLA-C*03:02 allele are at increased risk of developing MMI-induced DILI. These results may assist doctors to prevent the occurrence of hepatotoxicity in GD patients receiving MMI.

Analysis of 307 cases with drug-induced liver injury between 2010 and 2018 in Japan

AIM

In order to know the present status of drug-induced liver injury (DILI) in Japan, we present the data of prospectively collected DILI cases between 2010 and 2018 from 27 hospitals.

METHODS

Drug-induced liver injury cases diagnosed by DILI experts from 27 hospitals all over Japan have been prospectively collected since 2010. Alanine aminotransferase level ≥150 U/L and/or alkaline phosphatase ≥2× upper limit of normal were inclusion criteria.

RESULTS

In total, data of 307 cases (125 male and 182 female individuals) aged between 17 and 86 years old were collected. The types of liver injury were as follows: 64% hepatocellular type, 20% mixed type, and 16% cholestatic type. A drug-induced lymphocyte stimulation test was carried out in 59% of cases, and was positive in 48% and semipositive in 3% of cases. Eosinophilia ≥6% was observed in 27% of cases. Fifty-three percent of DILI cases occurred within 30 days and 79% of DILI cases occurred within 90 days after starting drug administration. By the diagnostic scale of the Digestive Disease Week (DDW)-Japan 2004 workshop, 93.8% of cases were diagnosed as "highly probable", and 5.9% as "possible".

CONCLUSIONS

Japanese DILI patients are somewhat different from those of Europe and North America. The diagnostic scale of the DDW-Japan 2004 workshop has been used in Japan. However, there are many issues to improve the causality assessment of DILI that we must investigate in the future. It is critical to elucidate the mechanisms of drug metabolism and the pathophysiology of liver injury by various drugs to prevent DILI.

Pharmacogenomics of drug-induced liver injury (DILI): Molecular biology to clinical applications

A 21-year old woman was admitted to hospital with a two-week history of painless jaundice, fatigue and anorexia having previously been fit and well. One month prior to presentation, the patient had taken a five-day course of amoxicillin-clavulanic acid for an infected skin cyst. Otherwise, she was only on the oral contraceptive pill and reported minimal alcohol intake. On examination, she was deeply jaundiced, but alert and oriented with no asterixis. She had no stigmata of chronic liver disease, but hepatomegaly extending 3 cm from below the right subcostal margin was evident. Investigations showed: white cell count 13.4 × 10⁹/L (normal 3.6-9.3), haemoglobin 11.8 g/dl (normal 11-15), platelet count 356 × 10⁹/L (normal 170-420), sodium 138 mmol/L (normal 134-144), potassium 3.5 mmol/L (normal 3.5-5.0), creatinine 32 µmol/L (normal 40-75), albumin 30 g/L (normal 35-48), alanine aminotransferase 707 IU/L (normal 15-54), alkaline phosphatase 151 IU/L (normal 30-130), bilirubin 384 µmol/L (normal 7-31) and prothrombin time 27.2 s (normal 11.7-14). Screening for hepatitis A, B, C, E, Epstein-Barr virus, cytomegalovirus and autoimmune hepatitis was negative. Tests for anti-smooth muscle, antinuclear, and anti-liver-kidney microsomal-1 antibodies were negative; immunoglobulin levels and ceruloplasmin levels were normal. Liver ultrasonography demonstrated a liver of normal contour with no biliary dilatation, a normal spleen size and patent vessels. Liver biopsy revealed severe portal interface hepatitis with lobular inflammation and scant plasma cells. Her clinical condition deteriorated in the following days with prothrombin time and bilirubin rising to 56.6 s and 470 µmol/L, respectively. At follow-up after 11 days, her alanine aminotransferase level was 1,931 IU/L. She developed grade 2 hepatic encephalopathy 14 days after presentation, and was listed for a super-urgent liver transplant. Human leucocyte antigen (HLA) typing was performed as a part of preparatory investigations and showed the patient carried the HLA haplotype HLA-DRB1∗15:02-DQB1∗06:01. Following orthotopic transplantation of a deceased donor graft her explant histology revealed severe ongoing hepatitis with multi-acinar necrosis (Fig. 1A and B). This case raised a number of important questions about the diagnosis of drug-induced liver injury and tools available for clinicians to make the best decisions for patient care: In this Grand Rounds article, we will explore these questions, describing the pathophysiology, diagnostic and prognostic biomarkers, and clinical management of drug-induced liver injury. We will also discuss ongoing areas of uncertainty.

Drug-Induced Liver Injury: Cascade of Events Leading to Cell Death, Apoptosis or Necrosis

Drug-induced liver injury (DILI) can broadly be divided into predictable and dose dependent such as acetaminophen (APAP) and unpredictable or idiosyncratic DILI (IDILI). Liver injury from drug hepatotoxicity (whether idiosyncratic or predictable) results in hepatocyte cell death and inflammation. The cascade of events leading to DILI and the cell death subroutine (apoptosis or necrosis) of the cell depend largely on the culprit drug. Direct toxins to hepatocytes likely induce oxidative organelle stress (such as endoplasmic reticulum (ER) and mitochondrial stress) leading to necrosis or apoptosis, while cell death in idiosyncratic DILI (IDILI) is usually the result of engagement of the innate and adaptive immune system (likely apoptotic), involving death receptors (DR). Here, we review the hepatocyte cell death pathways both in direct hepatotoxicity such as in APAP DILI as well as in IDILI. We examine the known signaling pathways in APAP toxicity, a model of necrotic liver cell death. We also explore what is known about the genetic basis of IDILI and the molecular pathways leading to immune activation and how these events can trigger hepatotoxicity and cell death.

Association of Liver Injury From Specific Drugs, or Groups of Drugs, With Polymorphisms in HLA and Other Genes in a Genome-Wide Association Study

BACKGROUND & AIMS

We performed a genome-wide association study (GWAS) to identify genetic risk factors for drug-induced liver injury (DILI) from licensed drugs without previously reported genetic risk factors.

METHODS

We performed a GWAS of 862 persons with DILI and 10,588 population-matched controls. The first set of cases was recruited before May 2009 in Europe (n = 137) and the United States (n = 274). The second set of cases were identified from May 2009 through May 2013 from international collaborative studies performed in Europe, the United States, and South America. For the GWAS, we included only cases with patients of European ancestry associated with a particular drug (but not flucloxacillin or amoxicillin-clavulanate). We used DNA samples from all subjects to analyze HLA genes and single nucleotide polymorphisms. After the discovery analysis was concluded, we validated our findings using data from 283 European patients with diagnosis of DILI associated with various drugs.

RESULTS

We associated DILI with rs114577328 (a proxy for A*33:01 a HLA class I allele; odds ratio [OR], 2.7; 95% confidence interval [CI], 1.9-3.8; P = 2.4 × 10^-8) and with rs72631567 on chromosome 2 (OR, 2.0; 95% CI, 1.6-2.5; P = 9.7 × 10^-9). The association with A*33:01 was mediated by large effects for terbinafine-, fenofibrate-, and ticlopidine-related DILI. The variant on chromosome 2 was associated with DILI from a variety of drugs. Further phenotypic analysis indicated that the association between DILI and A*33:01 was significant genome wide for cholestatic and mixed DILI, but not for hepatocellular DILI; the polymorphism on chromosome 2 was associated with cholestatic and mixed DILI as well as hepatocellular DILI. We identified an association between rs28521457 (within the lipopolysaccharide-responsive vesicle trafficking, beach and anchor containing gene) and only hepatocellular DILI (OR, 2.1; 95% CI, 1.6-2.7; P = 4.8 × 10^-9). We did not associate any specific drug classes with genetic polymorphisms, except for statin-associated DILI, which was associated with rs116561224 on chromosome 18 (OR, 5.4; 95% CI, 3.0-9.5; P = 7.1 × 10^-9). We validated the association between A*33:01 terbinafine- and sertraline-induced DILI. We could not validate the association between DILI and rs72631567, rs28521457, or rs116561224.

CONCLUSIONS

In a GWAS of persons of European descent with DILI, we associated HLA-A*33:01 with DILI due to terbinafine and possibly fenofibrate and ticlopidine. We identified polymorphisms that appear to be associated with DILI from statins, as well as 2 non-drug-specific risk factors.

Pharmacogenetic testing in idiosyncratic drug-induced liver injury: current role in clinical practice

In contrast to the studies that have explored association of genetic variants with other complex traits, those investigating hepatotoxicity have identified risk alleles with substantially higher risk ratios for the susceptibility to drug-induced liver injury (DILI). In addition, a relatively small number of human leukocyte antigen (HLA) alleles have overlapping associations with a variety of adverse reactions including DILI, cutaneous hypersensitivity and drug-induced pancreatitis. However, if used as a test prior to prescription to prevent potential adverse reaction, genotyping would have a very high negative predictive value, yet a low positive predictive value based on the low incidence of DILI. One potential consideration is to treat all relevant HLA genotypes as one panel covering different forms of adverse drug reactions, thereby improving the positive predictive value of the panel and widen its application. The majority of HLA alleles associated with DILI have a very high negative predictive value; therefore, they can be used to rule out hepatotoxicity caused by particular drugs. A high negative predictive value of a genetic test can be used to identify the correct agent underlying DILI when the patient had been exposed to two concomitant medications with a potential to cause DILI. Inclusion of genetic tests in the causality assessment of an event, where DILI is suspected, may improve consistency and precision of causality assessment tools. A recent clinical trial used N-acetyltransferase 2 genotyping to determine the appropriate dose of isoniazid in an anti-tuberculosis therapeutic regimen and demonstrated that pharmacogenetic-based clinical algorithms have the potential to improve efficacy of a drug and to reduce DILI.

Genetics of Interstitial Lung Disease: Vol de Nuit (Night Flight)

Interstitial lung disease (ILD) is a chronic, progressive fibrotic lung disease with a dismal prognosis. ILD of unknown etiology is referred to as idiopathic interstitial pneumonia (IIP), which is sporadic in the majority of cases. ILD is frequently accompanied by rheumatoid arthritis (RA), systemic sclerosis (SSc), polymyositis/dermatomyositis (PM/DM), and other autoimmune diseases, and is referred to as collagen vascular disease-associated ILD (CVD-ILD). Susceptibility to ILD is influenced by genetic and environmental factors. Recent advances in radiographic imaging techniques such as high-resolution computed tomography (CT) scanning as well as high-throughput genomic analyses have provided insights into the genetics of ILD. These studies have repeatedly revealed an association between IIP (sporadic and familial) and a single nucleotide polymorphism (SNP) in the promoter region of the mucin 5B (MUC5B). HLA-DRB1*11 alleles have been reported to correlate with ILD in European patients with SSc, whereas in Japanese patients with RA, the HLA-DR2 serological group was identified. The aim of this review is to describe the genetic background of sporadic IIP, CVD-ILD, drug-induced-ILD (DI-ILD), pneumoconiosis, and hypersensitivity pneumonitis. The genetics of ILD is still in progress. However, this information will enhance the understanding of the pathogenesis of ILD and aid the identification of novel therapeutic targets for personalized medicine in future.

Human leukocyte antigen polymorphisms and personalized medicine for rheumatoid arthritis

Human leukocyte antigen (HLA) polymorphisms are the most important genetic risk factors for rheumatoid arthritis (RA), a chronic systemic inflammatory disease of unknown etiology. Certain HLA-DRB1 alleles, known as shared epitope (SE) alleles because they have the same amino-acid sequence at positions 70-74, are associated with susceptibility to RA. A gene dosage effect is present for RA-predisposing SE alleles, and protective alleles show epistasis. An important role of amino-acid polymorphisms at positions 11 and 13 of the HLA-DRβ chain was also reported recently. Rheumatoid factor and anticitrullinated peptide antibodies are present in many RA patients. Similar to extra-articular manifestations, the presence of these autoantibodies is also associated with certain DRB1 alleles. Different frequencies of RA risk alleles in different ethnicities explain the varying prevalence of RA in different populations and suggest genetic heterogeneity of RA with regard to phenotype and population subsets. Some drug-induced hypersensitivity reactions due to disease-modifying antirheumatic drugs are also associated with HLA alleles. Understanding the role of HLA as the most important genetic factor relevant to RA susceptibility may help in determining its pathogenesis and pave the way to personalized medicine.

Human leukocyte antigen genetic risk factors of drug-induced liver toxicology

INTRODUCTION

Drug-induced liver injury (DILI) is a rare adverse drug reaction, which impacts significantly on patients. Human leukocyte antigen (HLA) risk alleles have been found to be associated with DILI supporting an immunological basis to DILI pathogenesis.

AREAS COVERED

HLA alleles associated with risk of liver injury induced by specific therapeutic drugs are described. The evidence for a role of the adaptive immune system in DILI is presented; case-control studies showing an association between DILI and HLA alleles are reviewed. Clinical applications of pharmacogenomics are considered.

EXPERT OPINION

Increasing evidence points to a crucial role for the adaptive immune system in the pathogenesis of DILI. Identification of specific HLA alleles as risk factors through large genome-wide association studies has been instrumental in this and in vitro analyses have facilitated improved understanding of the molecular mechanisms. This provides the basis for developing clinical pharmacogenomic applications. Already, genotyping for hypersensitivity HLA risk alleles has been implemented and opportunities for pre-prescription testing in DILI identified. However, although associations are strong, the rarity of DILI means routine testing has not been formally evaluated. Nevertheless, enhanced understanding of how HLA alleles contribute to injury risk is valuable for drug development. Translation of this research into effective pre-emption and primary prevention remains the goal.

Central role of mitochondria in drug-induced liver injury

A frequent mechanism for drug-induced liver injury (DILI) is the formation of reactive metabolites that trigger hepatitis through direct toxicity or immune reactions. Both events cause mitochondrial membrane disruption. Genetic or acquired factors predispose to metabolite-mediated hepatitis by increasing the formation of the reactive metabolite, decreasing its detoxification, or by the presence of critical human leukocyte antigen molecule(s). In other instances, the parent drug itself triggers mitochondrial membrane disruption or inhibits mitochondrial function through different mechanisms. Drugs can sequester coenzyme A or can inhibit mitochondrial β-oxidation enzymes, the transfer of electrons along the respiratory chain, or adenosine triphosphate (ATP) synthase. Drugs can also destroy mitochondrial DNA, inhibit its replication, decrease mitochondrial transcripts, or hamper mitochondrial protein synthesis. Quite often, a single drug has many different effects on mitochondrial function. A severe impairment of oxidative phosphorylation decreases hepatic ATP, leading to cell dysfunction or necrosis; it can also secondarily inhibit ß-oxidation, thus causing steatosis, and can also inhibit pyruvate catabolism, leading to lactic acidosis. A severe impairment of β-oxidation can cause a fatty liver; further, decreased gluconeogenesis and increased utilization of glucose to compensate for the inability to oxidize fatty acids, together with the mitochondrial toxicity of accumulated free fatty acids and lipid peroxidation products, may impair energy production, possibly leading to coma and death. Susceptibility to parent drug-mediated mitochondrial dysfunction can be increased by factors impairing the removal of the toxic parent compound or by the presence of other medical condition(s) impairing mitochondrial function. New drug molecules should be screened for possible mitochondrial effects.

Clinical and pathological features of a prolonged type of acute intrahepatic cholestasis

AIM

We examined the clinical and pathological features of drug-induced acute intrahepatic cholestasis (AIC) to elucidate the pathogenesis of prolonged cases.

METHODS

Twenty-six cases of drug-induced AIC were divided into prolonged and non-prolonged groups. Serum bilirubin levels and other biochemical data were compared between the two groups. Biopsy liver specimens were examined by light and electron microscopy. The localization of multidrug resistance protein 2 (MRP2) was immunohistochemically assessed by the Envision technique.

RESULTS

The causative drugs of four prolonged cases were found to be tiopronin, chlorpromazine and diclofenac. Two of the patients either died or underwent liver transplantation. The maximal total bilirubin levels (35.2 +/-> 13.8 mg/dL) were significantly higher and a half-life of total bilirubin (78.8 +/-> 69.6 days) was markedly longer in the prolonged cases, in comparison to the non-prolonged cases (16.8 +/-> 8.1 mg/dL, 22.1 +/-> 12.7 days, respectively). The liverbiopsy specimens revealed canalicular cholestasis and a slight degree of lobular inflammation. In the prolonged cases, liver cell injury and cholestasis was marked, and the interlobular bile ducts disappeared in the portal triads. The reaction products of MRP2, recognized on the bile canaliculi in a control liver, were weakened and found in the pericanalicular vesicles in AIC.

CONCLUSION

These results indicated disturbances in the canalicular bilirubin transport through MRP2 in the prolonged cases, resulting from severe cholestasis, liver cell injury and vanishing bile ducts. The histological findings of the liver at the acute icteric phase may be important to understand the pathogenesis and to predict the prognosis in AIC.

Ticlopidine-induced hepatotoxicity is associated with specific human leukocyte antigen genomic subtypes in Japanese patients: a preliminary case-control study

Genetic risk factors for ticlopidine-induced hepatotoxicity were determined in 22 Japanese patients with ticlopidine-induced hepatotoxicity and 85 Japanese patients who tolerated ticlopidine therapy without experiencing adverse reactions. There was a significant correlation between ticlopidine-induced hepatotoxicity and five human leukocyte antigen (HLA) alleles: HLA-A*3303, HLA-B*4403, HLA-Cw*1403, HLA-DRB1*1302 and HLA-DQB1*0604 (corrected probability (P)-value (Pc)<0.01). In particular HLA-A*3303 was present in 15 (68%) of the 22 patients with ticlopidine-induced hepatotoxicity and in 12 (14%) of the 85 ticlopidine-tolerant patients (odds ratio, 13.04; 95% confidence interval (CI), 4.40-38.59; the corrected P-value (Pc)=1.24 x 10(-5)). HLA-A*3303 was present in 12 (86%) of the 14 patients with ticlopidine-induced cholestatic hepatotoxicity (odds ratio, 36.50; 95% CI, 7.25-183.82, Pc=7.32 x 10(-7)). Ticlopidine-induced severe cholestatic hepatotoxicity occurred more frequently in subjects with HLA-A*3303 and its haplotype in Japanese patients. These findings may explain the high incidence of ticlopidine-induced hepatotoxicity in Japanese patients mediated via an immune-mediated mechanism.

Drug-induced cholestasis

Drugs may cause several overlapping syndromes of cholestasis, the pathophysiological syndrome resulting from impaired bile flow. These reactions comprise approximately 17% of all hepatic adverse drug reactions (ADRs) and they may be severe. Causes of 'pure' (bland) cholestasis include oestrogens and anabolic steroids; rarer associations are with antimicrobials and NSAIDs. 'Cholestatic hepatitis' is a common drug reaction in which liver injury and inflammation cause significant elevation of serum alanine aminotransferase (ALT) as well as cholestasis. Chlorpromazine and ketoconazole are classic examples, but it is now exemplified by amoxycillin-clavulanate and other oxy-penicillins. Chronic cholestasis results from small bile duct injury leading to the vanishing bile duct syndrome (VBDS), a disorder mimicking primary biliary cirrhosis, or from injury to larger bile ducts causing secondary sclerosing cholangitis. Whilst there is increasing evidence of a genetic predisposition to cholestatic drug reactions, there are currently no pretreatment tests to predict drug safety. Prevention of severe reactions therefore relies on early detection of liver injury and prompt drug withdrawal. Symptomatic management includes relief of pruritus and correction of fat-soluble vitamin deficiency. In small cohort studies, ursodeoxycholic acid (UDCA) arrested progressive cholestasis in two-thirds of cases, but evidence for use of corticosteroids is anecdotal. This review considers diagnosis, pathogenesis, prevention and management of drug-induced cholestasis, with particular reference to frequently- and newly-described causes.