Chronic active hepatitis caused by benzarone

Nomenclature, diagnosis and management of drug-induced autoimmune-like hepatitis (DI-ALH): An expert opinion meeting report

Drug-induced liver injury (DILI) can mimic almost all other liver disorders. A phenotype increasingly ascribed to drugs is autoimmune-like hepatitis (ALH). This article summarises the major topics discussed at a joint International Conference held between the Drug-Induced Liver Injury consortium and the International Autoimmune Hepatitis Group. DI-ALH is a liver injury with laboratory and/or histological features that may be indistinguishable from those of autoimmune hepatitis (AIH). Previous studies have revealed that patients with DI-ALH and those with idiopathic AIH have very similar clinical, biochemical, immunological and histological features. Differentiating DI-ALH from AIH is important as patients with DI-ALH rarely require long-term immunosuppression and the condition often resolves spontaneously after withdrawal of the implicated drug, whereas patients with AIH mostly require long-term immunosuppression. Therefore, revision of the diagnosis on long-term follow-up may be necessary in some cases. More than 40 different drugs including nitrofurantoin, methyldopa, hydralazine, minocycline, infliximab, herbal and dietary supplements (such as Khat and Tinospora cordifolia) have been implicated in DI-ALH. Understanding of DI-ALH is limited by the lack of specific markers of the disease that could allow for a precise diagnosis, while there is similarly no single feature which is diagnostic of AIH. We propose a management algorithm for patients with liver injury and an autoimmune phenotype. There is an urgent need to prospectively evaluate patients with DI-ALH systematically to enable definitive characterisation of this condition.

A Case of Recent Liver Injury Induced by Benzbromarone

A 39-year-old male had a stomachache for 10 days before abnormal liver function tests were detected by a local doctor. Then, he was referred to us and admitted to our hospital for examination and treatment of elevated transaminases. He had taken benzbromarone to treat his hyperuricemia for seven months, and we diagnosed him with benzbromarone-induced liver injury. After the termination of benzbromarone, he finally recovered from his illness. There are several reports about benzbromarone-induced liver injury. In conclusion, as periodic liver function tests seem not to be completely performed, clinicians should regularly monitor liver function tests in patients taking benzbromarone.

Emerging club drugs: 5-(2-aminopropyl)benzofuran (5-APB) is more toxic than its isomer 6-(2-aminopropyl)benzofuran (6-APB) in hepatocyte cellular models

New phenylethylamine derivatives are among the most commonly abused new psychoactive substances. They are synthesized and marketed in lieu of classical amphetaminic stimulants, with no previous safety testing. Our study aimed to determine the in vitro hepatotoxicity of two benzofurans [6-(2-aminopropyl)benzofuran (6-APB) and 5-(2-aminopropyl)benzofuran (5-APB)] that have been misused as 'legal highs'. Cellular viability was assessed through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay, following 24-h drug exposure of human hepatoma HepaRG cells (EC₅₀ 2.62 mM 5-APB; 6.02 mM 6-APB), HepG2 cells (EC₅₀ 3.79 mM 5-APB; 8.18 mM 6-APB) and primary rat hepatocytes (EC₅₀ 964 μM 5-APB; 1.94 mM 6-APB). Co-incubation of primary hepatocytes, the most sensitive in vitro model, with CYP450 inhibitors revealed a role of metabolism, in particular by CYP3A4, in the toxic effects of both benzofurans. Also, 6-APB and 5-APB concentration-dependently enhanced oxidative stress (significantly increased reactive species and oxidized glutathione, and decreased reduced glutathione levels) and unsettled mitochondrial homeostasis, with disruption of mitochondrial membrane potential and decline of intracellular ATP. Evaluation of cell death mechanisms showed increased caspase-8, -9, and -3 activation, and nuclear morphological changes consistent with apoptosis; at concentrations higher than 2 mM, however, necrosis prevailed. Concentration-dependent formation of acidic vesicular organelles typical of autophagy was also observed for both drugs. Overall, 5-APB displayed higher hepatotoxicity than its 6-isomer. Our findings provide new insights into the potential hepatotoxicity of these so-called 'safe drugs' and highlight the putative risks associated with their use as psychostimulants.

Novel urate transporter 1 (URAT1) inhibitors: a review of recent patent literature (2016-2019)

Introduction: Human urate transporter 1 (URAT1), which is an influx transporter protein, is located at the apical surface of renal tubular cells and presumed to be the major transporter responsible for the reabsorption of urate from blood. About 90% of patients develop hyperuricemia due to insufficient urate excretion; thus, it is important to develop URAT1 inhibitors that could enhance renal urate excretion by blocking the reabsorption of urate anion. Areas covered: In this review, the authors addressed the patent applications (2016-2019) about URAT1 inhibitors and some medicinal chemistry strategies employed in these patents. Expert opinion: Substituent decorating, bioisosterism, and scaffold hopping are three common medicinal chemistry strategies used in the discovery of URAT1 inhibitors. Meanwhile, the introduction of sulfonyl group into small molecules has become one of the important strategies for structural optimization of URAT1 inhibitors. Furthermore, developing drug candidates targeting both URAT1 and xanthine oxidase (XOD) has attracted lots of interest and attention.

Autoimmune hepatitis following drug-induced liver injury in an elderly patient

We describe a case of autoimmune hepatitis (AIH) that may have occurred following drug-induced liver injury with camostat mesilate and/or benzbromarone in an elderly patient. The patient's liver biopsy showed chronic active hepatitis and autoimmune hepatitis. Stopping the use of these drugs did not lead to complete remission, but the use of a low dose of corticosteroids completely cured his liver dysfunction. In the present case, liver dysfunction was caused by an autoimmune mechanism. Special attention should be paid to idiopathic AIH and drug-induced AIH in elderly patients.

Progress in research of drug-induced autoimmune hepatitis

Drug-induced autoimmune hepatitis (DIAIH) has been reported to be caused by many drugs, which possesses the characteristics of both drug-induced liver injury (DILI) and autoimmune hepatitis (AIH). A better understanding of the epidemiology, pathogenesis, pathology and clinical symptoms of DIAIH can help us better diagnose and treat this disease.

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.

Drug-induced autoimmune-like hepatitis

The clinical phenotype of classical autoimmune hepatitis can be mimicked by idiosyncratic drug-induced liver injury, and differentiation can be difficult. The goals of this review are to enumerate the major agents of drug-induced autoimmune-like hepatitis, describe the clinical findings and risk factors associated with it, detail the clinical tools by which to assess causality, discuss putative pathogenic mechanisms, and describe treatment and outcome. The frequency of drug-induced autoimmune-like hepatitis among patients with classical features of autoimmune hepatitis is 9%. Minocycline and nitrofurantoin are implicated in 90% of cases. Female predominance, acute onset, and absence of cirrhosis at presentation are important clinical manifestations. Genetic factors affecting phase I and phase II transformations of the drug, polymorphisms that protect against cellular oxidative stress, and human leukocyte antigens that modulate the immune response may be important pathogenic components. Clinical judgment is the mainstay of diagnosis as structured diagnostic methods for drug-induced liver injury are imperfect. The covalent binding of a reactive drug metabolite to a hepatocyte surface protein (commonly a phase I or phase II enzyme), formation of a neoantigen, activation of CD8 T lymphocytes with nonselective antigen receptors, and deficient immune regulatory mechanisms are the main bases for a transient loss of self-tolerance. Discontinuation of the offending drug is the essential treatment. Spontaneous improvement usually ensues within 1 month. Corticosteroid therapy is warranted for symptomatic severe disease, and it is almost invariably effective. Relapse after corticosteroid withdrawal probably does not occur, and its absence distinguishes drug-induced disease from classical autoimmune hepatitis.

Review article: drug-induced liver injury in clinical practice

BACKGROUND

Drug-induced liver injury (DILI) is an important differential diagnosis in many patients in clinical hepatology. DILI is the leading cause of acute liver failure and is an important safety issue when new drugs are developed.

AIMS

To provide a review of the recent data on DILI with particular focus on the most common and relevant issues seen in clinical practice.

METHODS

A Medline search was undertaken to identify relevant literature using search terms including 'drug-induced liver injury' and 'hepatotoxicity'.

RESULTS

The true incidence of DILI remains unknown but incidence up to 14 cases per 100 000 inhabitants and year has been reported. Antibiotics, analgesics and NSAIDs are the most common drugs causing liver injury. Idiosyncratic DILI has been shown to have a dose-dependent component and drugs without significant hepatic metabolism rarely cause DILI. Chronic elevation in liver enzymes can develop after DILI but this is rarely associated with clinical morbidity or mortality.

CONCLUSIONS

Drug-induced liver injury remains a diagnostic challenge. Multicentre studies and international collaborative work with well-characterized patients will increase our understanding of liver injury associated with drugs. New therapies for acute liver failure resulting from drugs are needed.

Mitochondrial involvement in drug-induced liver injury

Mitochondrial dysfunction is a major mechanism of liver injury. A parent drug or its reactive metabolite can trigger outer mitochondrial membrane permeabilization or rupture due to mitochondrial permeability transition. The latter can severely deplete ATP and cause liver cell necrosis, or it can instead lead to apoptosis by releasing cytochrome c, which activates caspases in the cytosol. Necrosis and apoptosis can trigger cytolytic hepatitis resulting in lethal fulminant hepatitis in some patients. Other drugs severely inhibit mitochondrial function and trigger extensive microvesicular steatosis, hypoglycaemia, coma, and death. Milder and more prolonged forms of drug-induced mitochondrial dysfunction can also cause macrovacuolar steatosis. Although this is a benign liver lesion in the short-term, it can progress to steatohepatitis and then to cirrhosis. Patient susceptibility to drug-induced mitochondrial dysfunction and liver injury can sometimes be explained by genetic or acquired variations in drug metabolism and/or elimination that increase the concentration of the toxic species (parent drug or metabolite). Susceptibility may also be increased by the presence of another condition, which also impairs mitochondrial function, such as an inborn mitochondrial cytopathy, beta-oxidation defect, certain viral infections, pregnancy, or the obesity-associated metabolic syndrome. Liver injury due to mitochondrial dysfunction can have important consequences for pharmaceutical companies. It has led to the interruption of clinical trials, the recall of several drugs after marketing, or the introduction of severe black box warnings by drug agencies. Pharmaceutical companies should systematically investigate mitochondrial effects during lead selection or preclinical safety studies.

The long-term follow-up after idiosyncratic drug-induced liver injury with jaundice

BACKGROUND/AIMS

Chronic evolution after drug-induced liver injury (DILI) has been reported. How often this leads to liver-related morbidity and mortality is unexplored.

METHODS

Patients who survived DILI and concomitant jaundice reported to the Swedish Adverse Drug Reaction Advisory Committee (1970-2004) were linked to the Swedish Hospital Discharge and Cause of Death Registries.

RESULTS

Among the 712 survivors, 27 could not be retrieved but 685 patients could be linked to the registries, 392 females (57.2%) and 293 males (42.8%) median age 58 (41-74), a mean follow-up of 10 years. A total of 23/685 (3.4%) patients had been hospitalized for liver disease and 5 had liver-related mortality. Eight patients developed cirrhosis (7 decompensated, 5 died), 5 had "cryptogenic" cirrhosis in which DILI might have played a role in this development. Duration of therapy before DILI was longer in patients with liver-related morbidity/mortality (135+/-31 days vs. 53+/-3; p<0.0001). Autoimmune hepatitis developed in 5/23 (22%), all of female gender after a mean of 5.8 years.

CONCLUSIONS

Development of clinically important liver disease after severe DILI associated with jaundice is rare after acute DILI. However decompensated "cryptogenic" cirrhosis developed in some patients with fatal outcome in which DILI might have played a role in this development.

Long-term follow-up of patients with mild to moderate drug-induced liver injury

AIM

To evaluate the long-term prognosis of patients diagnosed with drug-induced liver injury, and the nature of the liver injury.

METHODS

Patients with a diagnosis of drug-induced liver injury between 1994 and 2005 were identified in a university hospital clinic. Patients surviving drug-induced liver injury-associated liver failure were excluded.

RESULTS

Seventy-seven cases were identified and those who were alive (69) were invited to attend follow-up. Of those patients who had died, none had died of liver disease. Of those patients who had survived, 59 were reviewed in the clinic. Patients had a median follow-up of 48 months. Before the diagnosis of drug-induced liver injury, nine had a chronic liver disease, four with autoimmune hepatitis, two with non-alcoholic liver disease, one each with non-alcoholic fatty liver disease, primary biliary cirrhosis and primary sclerosing cholangitis. There was no evidence of progression of their liver disease during follow-up. Among 50 patients without a known liver disease prior to the drug-induced liver injury, 10 had abnormal liver tests. Diagnostic work-up revealed alternative cause of liver disease in all except three patients (6%), who had asymptomatic abnormal liver tests (but normal bilirubin in all).

CONCLUSIONS

Chronic abnormalities in liver tests, not explained by an identified liver disease, are very rare in patients previously diagnosed with drug-induced liver injury. This group of patients did not seem to have a clinically significant liver injury at long-term follow-up.

Mechanisms of benzarone and benzbromarone-induced hepatic toxicity

Treatment with benzarone or benzbromarone can be associated with hepatic injury. Both drugs share structural similarities with amiodarone, a well-known mitochondrial toxin. Therefore, we investigated the hepatotoxicity of benzarone and benzbromarone as well as the analogues benzofuran and 2-butylbenzofuran. In isolated rat hepatocytes, amiodarone, benzarone, and benzbromarone (20 micromol/L) decreased mitochondrial membrane potential by 23%, 54% or 81%, respectively. Benzofuran and 2-butylbenzofuran had no effect up to 100 micromol/L. In isolated rat liver mitochondria, amiodarone, benzarone, and benzbromarone, but not benzofuran, decreased state 3 oxidation and respiratory control ratios for L-glutamate (50% decrease of respiratory control ratio at [micromol/L]: amiodarone, 12.9; benzarone, 10.8; benzbromarone, <1). Amiodarone, benzarone, and benzbromarone, but not benzofuran, also uncoupled oxidative phosphorylation. Mitochondrial beta-oxidation was decreased by 71%, 87%, and 58% with 100 micromol/L amiodarone or benzarone and 50 micromol/L benzbromarone, respectively, but was unaffected by benzofuran, whereas ketogenesis was not affected. 2-Butylbenzofuran weakly inhibited state 3 oxidation and beta-oxidation only at 100 micromol/L. In the presence of 100 micromol/L amiodarone, benzarone or benzbromarone, reactive oxygen species production was increased, mitochondrial leakage of cytochrome c was induced in HepG2 cells, and permeability transition was induced in isolated rat liver mitochondria. At the same concentrations, amiodarone, benzarone, and benzbromarone induced apoptosis and necrosis of isolated rat hepatocytes. In conclusion, hepatotoxicity associated with amiodarone, benzarone, and benzbromarone can at least in part be explained by their mitochondrial toxicity and the subsequent induction of apoptosis and necrosis. Side chains attached to the furan moiety are necessary for rendering benzofuran hepatotoxic.

Toxicity of amiodarone and amiodarone analogues on isolated rat liver mitochondria

BACKGROUND

Amiodarone is a well-known mitochondrial toxin consisting of a benzofuran ring (ring A) coupled to a p-OH-benzene structure substituted with 2 iodines and a diethyl-ethanolamine side chain (ring B).

AIM

To find out which part of amiodarone is responsible for mitochondrial toxicity.

METHODS

Amiodarone, ring A and B without the ethanolamine side-chain and iodines (B0), ring A and B with iodines but no ethanolamine (B2), ring B with 1 iodine and no ethanolamine (C1) and ring B with ethanolamine and 2 iodines (D2) were studied.

RESULTS

In freshly isolated rat liver mitochondria, amiodarone inhibited state 3 glutamate and palmitoyl-CoA oxidation and decreased the respiratory control ratios. B0 and B2 were more potent inhibitors than amiodarone and B2 more potent than B0. C1 and D2 showed no significant mitochondrial toxicity. After disruption, mitochondrial oxidases and complexes of the electron transport chain were inhibited by amiodarone, B0 and B2, whereas C1 and D2 revealed no inhibition. Beta-oxidation showed a strong inhibition by amiodarone, B0 and B2 but not by C1 or D2. Ketogenesis was almost unaffected.

CONCLUSIONS

Amiodarone, B0 and B2 are uncouplers of oxidative phosphorylation, and inhibit complexes I, II and III, and beta-oxidation. The benzofuran structure is responsible for mitochondrial toxicity of amiodarone and the presence of iodine is not essential.

Severe hepatotoxicity related to benzarone: a report of three cases with two fatalities

We report three cases of severe hepatotoxicity related to benzarone, a benzofuran derivative. Our cases include a 35-year-old woman with (sub)fulminant hepatitis, a 67-year-old woman with macronodular cirrhosis, and a 68-year-old man with severe chronic active hepatitis and cirrhosis, with positivity of anti-smooth muscle antibodies. Two patients died. We stress the potential of benzarone to cause hepatotoxicity, which usually resembles severe chronic active hepatitis. Our cases constitute the most severe cases of benzarone hepatotoxicity reported so far, and comprise the first cases of (sub)fulminant hepatitis and cirrhosis related to benzarone.

Hepatic injury caused by benzbromarone

This case study describes a woman who developed a predominantly hepatocellular injury, approximately 3 months after starting treatment with 100 mg benzbromarone daily. She had also taken 250 mg methyldopa daily for several years. Infections with hepatitis A and B were excluded serologically, no autoantibodies were demonstrated, and ultrasonography and endoscopic retrograde cholangiopancreatography did not show extrahepatic obstruction. The patient recovered after discontinuation of both drugs. Two years later, readministration of benzbromarone was followed by a relapse. Later, methyldopa was used without problems. We conclude that hepatic injury in this patient was caused by benzbromarone.