Idiosyncratic Liver Injury Research Articles

Bypassing the compromised mitochondrial electron transport with methylene blue alleviates efavirenz/isoniazid-induced oxidant stress and mitochondria-mediated cell death in mouse hepatocytes

Efavirenz (EFV) is an anti-retroviral drug frequently combined with isoniazid (INH) to treat HIV-1/tuberculosis co-infected patients. Both drugs have been associated with idiosyncratic liver injury (DILI), but combined anti-retroviral and anti-tubercular therapy can increase the risk for DILI as compared to either drug class alone. Because both EFV and INH have been implicated in targeting mitochondria, we aimed at exploring whether the two drugs might cause synergistic effects on the electron transport chain. We found that EFV inhibited complex I activity in isolated mouse liver mitochondria (IC50 ˜30 μM), whereas hydrazine, a major metabolite of INH generated by acylamidase-mediated hydrolytic cleavage, inhibited complex II activity (IC50 ˜30 μM). Neither INH alone (≤1000 μM) nor EFV alone (≤30 μM) was able to induce cell injury in cultured mouse hepatocytes. However, combined EFV/INH exposure resulted in increased superoxide formation and peroxynitrite stress, leading to the opening of the cyclosporine A-insensitive mode of the mitochondrial permeability transition (mPT), and necrotic cell death. The peroxynitrite scavengers, CBA or Fe-TMPyP, protected against mPT induction and alleviated cell injury. The acylamidase inhibitor bis-p-nitrophenyl phosphate prevented cell injury, suggesting that hydrazine greatly contributed to the toxicity. Methylene blue, a redox-active alternative electron acceptor/donor that bypasses complex I/II, effectively protected against EFV/INH-induced toxicity. These data demonstrate that, in murine hepatocytes, the mitochondrial electron transport chain is a critical target of combined EFV/INH exposure, and that this drug combination can lead to peroxynitrite stress-induced mPT and hepatocellular necrosis. These results are compatible with the concept that underlying silent mitochondrial dysfunction may be a key susceptibility factor contributing to idiosyncratic drug-induced liver injury.

Isoniazid-induced liver injury and immune response in mice

Isoniazid (INH) is associated with one of the highest incidences of idiosyncratic drug-induced liver failure of any commonly prescribed drug. The mechanism of this liver injury remains uncertain, and a valid animal model would greatly facilitate mechanistic studies. Most studies of INH-induced liver toxicity have been acute studies performed in rats with high doses of the drug, and this is very different from the idiosyncratic liver injury that occurs in humans. It has previously been demonstrated that covalent binding of INH in the liver of mice is greater than in rats and more like that in humans. Therefore, mice should be a better species in which to develop an animal model of INH-induced liver injury. Treatment of Cbl-b−/− and PD1−/− mice, which have impaired immune tolerance, resulted in greater injury than their C57BL/6 background, but not liver failure. This suggested that the injury was mediated by the adaptive immune system; however, Rag−/− mice, which do not have competent T- and B-cells, sustained more liver injury than C57BL/6 wild-type mice. This suggested that the adaptive immune system also played a protective role. INH treatment also led to a decrease in the inflammatory cytokines IL-1α and IL-12, which suggests that the drug may have immunosuppressive properties. In short, a mouse model was developed of INH-induced liver injury in which the immune system appears to play a both protective and pathogenic role, but this study was unable to develop a model of INH-induced liver failure.

Lack of liver injury in Wistar rats treated with the combination of isoniazid and rifampicin

Isoniazid (INH) can cause serious idiosyncratic liver injury. An animal model would greatly facilitate mechanistic studies, but it is essential that the mechanism in the model be similar to the liver injury that can occur in humans. We attempted to replicate a previous study in which Wistar rats treated with INH and rifampicin (RMP) developed liver injury, which was promising because of its delayed onset similar to the liver injury that can occur in humans. Wistar rats were treated with either a high dose of INH (150 mg/kg/day) or a combination of INH and RMP (75 mg/kg/day and 50 mg/kg/day, respectively) for up to 4 weeks. However, we did not observe any liver injury or evidence of an inflammatory infiltrate as had been reported; rather, we observed an increase in CTLA4-positive cells in the cervical lymph nodes as well as a decrease in serum CXCL1 and MCP-1. In short, we were unable to reproduce a previously reported model of delayed onset INH-induced liver injury in Wistar rats.

Isoniazid-induced cell death is precipitated by underlying mitochondrial complex I dysfunction in mouse hepatocytes

Isoniazid (INH) is an antituberculosis drug that has been associated with idiosyncratic liver injury in susceptible patients. The underlying mechanisms are still unclear, but there is growing evidence that INH and/or its major metabolite, hydrazine, may interfere with mitochondrial function. However, hepatic mitochondria have a large reserve capacity, and minor disruption of energy homeostasis does not necessarily induce cell death. We explored whether pharmacologic or genetic impairment of mitochondrial complex I may amplify mitochondrial dysfunction and precipitate INH-induced hepatocellular injury. We found that INH (≤3000μM) did not induce cell injury in cultured mouse hepatocytes, although it decreased hepatocellular respiration and ATP levels in a concentration-dependent fashion. However, coexposure of hepatocytes to INH and nontoxic concentrations of the complex I inhibitors rotenone (3μM) or piericidin A (30nM) resulted in massive ATP depletion and cell death. Although both rotenone and piericidin A increased MitoSox-reactive fluorescence, Mito-TEMPO or N-acetylcysteine did not attenuate the extent of cytotoxicity. However, preincubation of cells with the acylamidase inhibitor bis-p-nitrophenol phosphate provided protection from hepatocyte injury induced by rotenone/INH (but not rotenone/hydrazine), suggesting that hydrazine was the cell-damaging species. Indeed, we found that hydrazine directly inhibited the activity of solubilized complex II. Hepatocytes isolated from mutant Ndufs4+/− mice, although featuring moderately lower protein expression levels of this complex I subunit in liver mitochondria, exhibited unchanged hepatic complex I activity and were therefore not sensitized to INH. These data indicate that underlying inhibition of complex I, which alone is not acutely toxic, can trigger INH-induced hepatocellular injury.

A case of severe jaundice caused by thiamazole therapy

S 21 ANNUAL CONFERENCE—2013 D LI industrial applications, on liver carcinogenesis still remain elusive. Aims: To study the role of isocyanate in liver carcinogenesis. Methods: Experiments were performed on the cultured human liver epithelial cell line to ascertain the possible molecular risks associated with isocyanate exposure using Nsuccinimidyl N-methylcarbamate, a chemical entity that mimics the effects of methyl isocyanatein vitro. Qualitative and quantitative assessment of phosphorylation states of ATM, H2AX, ATR and p53, put forth the kinetics of DNA damage. Analyses of apoptosis in treated cells and inflammatory cytokines secreted in culture supernatant were done through annexin-V FITC/PI assay and cytometric bead array respectively. Cytogenetic studies along with inter simple sequence repeat PCR were done in control and treated cells to check for the possible precariousness at the chromosomal and microsatellite levels of the genome. Results: An increasing trend of all the DNA damage responsive parameters along with the apoptotic index were displayed in treated cells. Isocyanate exposed cells secreted an elevated levels of inflammatory cytokines in the culture supernatant. Cytogenetic analysis and inter simple sequence repeat PCR revealed varied chromosomal anomalies with greater instability at the microsatellite level. Conclusion: To conclude, these findings demonstrate that human liver epithelial milieu could confront with molecular risks due to isocyanate exposure attributing to defective DNA repair pathway along with de-regulated cell cycle and genomic instability which may accelerate the development of HCC. Corresponding author. Kewal Krishan Maudar. E-mail: maudarji@yahoo.com A CASE OF SEVERE JAUNDICE CAUSED BY THIAMAZOLE THERAPY Maria Sergeevna Zharkova, Marina Trofimovich Maevskaya, Elena Nikolaevna Shirokova, Tatjana Petrovna Nekrasova, Marina Victorovna Ivashkin Hepatology Department, University Clinical Hospital N 2, First Moscow State Medical University, Moscow, Russia Objective:Hepatotoxicity is a rare serious adverse reaction to antithyroid agents. It occurs with a frequency of 0.1– 0.2% of treated patients. Here we describe a case of severe jaundice with expected poor prognosis in a Thiamazoletreated patient with thyrotoxicosis. Case report: A 48-year-old woman with thyrotoxicosis developed jaundice after two weeks of Thiamazole therapy (40 mg/day). Viral hepatitis and mechanical biliary obstruction were excluded. Drug-induced liver injury had S38 been suspected. Despite drug discontinuation, weakness, skin itching, weight loss intensified. She was hospitalized to our clinic six weeks after disease onset. There were significant jaundice and visible traces after scratching; tachycardia. Liver and spleen were not palpable. Laboratory analyses showed elevation of ALT> AST (5-6 times higher ULN), total bilirubin (36 times higher ULN) due to both fractions, hypoalbuminemia (2.6 g/dl). Tests for autoantibodies were negative. Serum thyroid-stimulating hormone level was less than 0.01 uIU/ml (N: 0.4–4), free thyroxine two times higher ULN. Liver biopsy revealed parenchymatous and canalicularbilirubinostasis, necrosis of some hepatocytes. We diagnosed: Thiamazole-induced hepatitis. Hepatic failure: jaundice, hypoalbuminemia, thyrotoxicosis. In spite of drug withdrawal and administration of Ademethionine, UDCA, plazmapheresis, we observed a very slow regression of jaundice. Prednisolone prescription led to a rapid full patient's recovery with normalization of all biochemical markers during a month. The patient passed later radioactive iodine ablation of the thyroid gland. Discussion: Here we observed a mixed (dose-dependent and idiosyncratic) liver injury. There was an untypical form of hepatotoxicity hepatocellular damage with jaundice, without increase in laboratory markers of cholestasis, what makes the uniqueness of this clinical case. Conclusion: Severe jaundice is a rare adverse effect of antithyroid drugs’ therapy. The liver injury is usually reversible after drug withdrawal but in some cases can require Prednizolone administration. Physicians should keep in mind such a rare adverse reaction of antithyroid drugs. Corresponding Author. Maria Sergeevna Zharkova. E-mail: zharkovamaria@mail.ru HCV INFECTION IN THE HIV PATIENT IN ORAN ALGERIA Nadjet Allab Mouffok, Fatima Bensadoun, Ahmed Kouiad Belkadi

Clinical and Histological Features of Idiosyncratic Acute Liver Injury Caused by Temozolomide

Objective To describe the clinical, biochemical and histological features of 4 patients with apparent hepatotoxicity due to temozolomide and to summarize the available literature of hepatotoxicity associated with this agent.

Valproic acid-induced idiosyncratic liver injury in 4 cases

Children with refractory epilepsy who suffered from severe liver function impairment during valproic acid (VPA) treatment at routine dosage were studied. The clinical manifestations and therapeutic approaches were investigated in order to improve its diagnosis and management. Clinical information as well as features and management of 4 inpatients who were suffered from intractable epilepsy with severe liver function impairment induced by VPA since 2006 were collected and analyzed, including age of onset of epilepsy, VPA using age and the time when liver injury occurred, clinical manifestations, auxiliary examinations and management. Among the 4 cases, three were male and one was female. The admitted age ranged from 1 - 9 years and 1 month. The course of disease was 25 d - 6 months. They manifested as refractory epilepsy of epilepsia partialis continua which was difficult to control. After using VPA for 62 d (50 - 76 d), all developed severe impairment of liver synthetic function which was not related to the concentration of VPA. One was diagnosed with Alpers syndrome, two were suspicious of Alpers syndrome, and the other was diagnosed gliocytoma after brain biopsy. VPA was stopped immediately and symptomatic therapies were used. Other than that, intravenous injection of L-carnitine in 3 cases recovered the liver function. VPA-associated severe hepatotoxicity can manifest first as impaired liver synthetic function. Besides alanin transaminase and aspartate transaminase, the liver synthetic function test is more important than monitoring of liver enzymatic functions in monitoring for the hepatotoxicity. Intravenous injection of L-carnitine in early stage showed good treatment effect.

Fluoroquinolone therapy and idiosyncratic acute liver injury: a population-based study

Although fluoroquinolones are sometimes associated with mild, transient elevations in aminotransferase levels, serious acute liver injury is uncommon. Regulatory warnings have identified moxifloxacin as presenting a particular risk of hepatotoxicity. Thus, we examined the risk of idiosyncratic acute liver injury associated with the use of moxifloxacin relative to other selected antibiotic agents. We conducted a population-based, nested, case-control study using health care data from Ontario for the period April 2002 to March 2011. We identified cases as outpatients aged 66 years or older with no history of liver disease, and who were admitted to hospital for acute liver injury within 30 days of receiving a prescription for 1 of 5 broad-spectrum antibiotic agents: moxifloxacin, levofloxacin, ciprofloxacin, cefuroxime axetil or clarithromycin. For each case, we selected up to 10 age- and sex-matched controls from among patients who had received a study antibiotic, but who were not admitted to hospital for acute liver injury. We calculated odds ratios (ORs) to determine the association between admission to hospital and previous exposure to an antibiotic agent, using clarithromycin as the reference. A total of 144 patients were admitted to hospital for acute liver injury within 30 days of receiving a prescription for one of the identified drugs. Of these patients, 88 (61.1%) died while in hospital. After multivariable adjustment, use of either moxifloxacin (adjusted OR 2.20, 95% confidence interval [CI] 1.21-3.98) or levofloxacin (adjusted OR 1.85, 95% CI 1.01-3.39) was associated with an increase in risk of acute liver injury relative to the use of clarithromycin. We saw no such risk associated with the use of either ciprofloxacin or cefuroxime axetil. Among older outpatients with no evidence of liver disease, moxifloxacin and levofloxacin were associated with an increased risk of acute liver injury relative to clarithromycin.

An Evaluation of Reproductive and Developmental Toxicity of Sitaxentan (Thelin) in Rats

Sitaxentan sodium (Thelin) is a once daily, orally bioavailable, highly selective endothelin A receptor antagonist. Initially approved for the treatment of pulmonary arterial hypertension, sitaxentan was withdrawn in 2010 following the recognition of a pattern of idiosyncratic liver injury. During development of this drug, a series of nonclinical studies investigated the effects of orally administered sitaxentan on fertility, embryofetal development, and pre- and postnatal development in the rat; results of these studies are reported here. In the fertility study, sitaxentan did not affect mating behavior, fertility, sperm morphology, or estrous cycle. Sitaxentan was teratogenic in the embyrofetal development study, which was expected based on its pharmacologic mechanism of action. Teratogenic effects included malformations of the head, mouth, face, and large blood vessels. In the pre- and postnatal study, sitaxentan administration was associated with reduced pup survival, large or abnormally shaped livers, and delays in markers of auditory and sexual development. Sitaxentan was detected in plasma of suckling pups receiving milk from females dosed with sitaxentan. These nonclinical study findings were reflected in the sitaxentan product label warnings.

Chimeric mice with a humanized liver as an animal model of troglitazone-induced liver injury

Troglitazone (Tro) is a thiazolidinedione antidiabetic drug that was withdrawn from the market due to its association with idiosyncratic severe liver injury. Tro has never induced liver injury in experimental animals in vivo. It was assumed that the species differences between human and experimental animals in the pharmaco- or toxicokinetics of Tro might be associated with these observations. In this study, we investigated whether a chimeric mouse with a humanized liver that we previously established, whose replacement index with human hepatocytes is up to 92% can reproduce Tro-induced liver injury. When the chimeric mice were orally administered Tro for 14 or 23 days (1000mg/kg/day), serum alanine aminotransferase (ALT) was significantly increased by 2.1- and 3.6-fold, respectively. Co-administration of l-buthionine sulfoximine (10mM in drinking water), an inhibitor of glutathione (GSH) synthesis, unexpectedly prevented the Tro-dependent increase of ALT, which suggests that the GSH scavenging pathway will not be involved in Tro-induced liver injury. To elucidate the mechanism of the onset of liver injury, hepatic GSH content, the level of oxidative stress markers and phase I and phase II drug metabolizing enzymes were determined. However, these factors were not associated with Tro-induced liver injury. An immune-mediated reaction may be associated with Tro-induced liver toxicity in vivo, because the chimeric mouse is derived from an immunodeficient SCID mouse. In conclusion, we successfully reproduced Tro-induced liver injury using chimeric mice with a humanized liver, which provides a new animal model for studying idiosyncratic drug-induced liver injury.

An Integrated Analysis of Liver Safety Data from Orlistat Clinical Trials

Objective: Orlistat is an oral gastrointestinal lipase inhibitor and is indicated for treatment of obesity in combination with a hypocaloric diet. Post-marketing reports of adverse reactions revealed hints for possible drug-induced liver injury which has prompted changes to the product information. Orlistat’s development program, involving over 30,000 patients, did not indicate a hepatic safety issue. Methods: We analyzed liver function test data from randomized clinical trials of orlistat, using i) meta-analysis of published study safety data, ii) time-to-event analysis for individual patients, and iii) a novel and more sensitive method derived from the US Food and Drug Administration’s (FDA) Evaluation of Drug-Induced Serious Hepatotoxicity (eDISH) technique. Over 10,000 subjects were included. Results: The combined odds ratio from a simple summary-level fixed-effects meta-analysis of treatment-emergent abnormalities in serum alanine aminotransferase (ALT) (defined as greater than the upper level of normal for 2 successive measurements) was 1.09 (95% CI 0.93–1.28), and in total bilirubin 1.24 (95% CI 1.03–1.49). Part of the small apparent effect was due to longer exposure to orlistat than to placebo, on average. A patient-level display, adjusting for regression towards the mean, and Kaplan-Meier analysis of changes in ALT and bilirubin, taking account of different exposure, showed no significant difference between orlistat and placebo. This shows that there is no signal for hepatic damage in clinical studies of orlistat. Conclusion: While idiosyncratic liver injury following exposure to orlistat cannot be excluded, it is likely to be extremely rare.

Safety and efficacy of sitaxsentan 50 and 100 mg in patients with pulmonary arterial hypertension

ObjectiveTo assess safety and efficacy of sitaxsentan 50 and 100 mg in patients with pulmonary arterial hypertension (PAH). BackgroundSitaxsentan is a highly selective endothelin-A receptor antagonist that was recently withdrawn by the manufacturer because of a pattern of idiosyncratic liver injury. MethodsBefore sitaxsentan withdrawal, this 18-week double-blind, placebo-controlled study randomized patients with PAH to receive placebo or sitaxsentan 50 or 100 mg once daily. The primary efficacy endpoint was change from baseline in 6-min walk distance (6MWD) at week 18. Changes in World Health Organization (WHO) functional class and time to clinical worsening (TTCW) were secondary endpoints. The primary efficacy analysis was powered for sitaxsentan 100 mg versus placebo. ResultsOf 98 randomized patients, 61% were WHO functional class II at baseline. Improvement from baseline to week 18 in 6MWD occurred with sitaxsentan 100 but not 50 mg; a strong placebo effect was observed. At week 18, WHO functional class was improved or maintained in more patients receiving sitaxsentan 100 mg than placebo (P = 0.038); 0% versus 12% of patients deteriorated, respectively. TTCW was not significantly different for 100-mg sitaxsentan patients than placebo (P = 0.090). Adverse events (AEs) occurring more frequently with sitaxsentan (50 or 100 mg) included headache, peripheral edema, dizziness, nausea, extremity pain, and fatigue; most AEs were of mild or moderate severity. ConclusionSitaxsentan 100 mg improved functional class but not 6MWD in PAH patients who were mostly WHO functional class II at baseline. No patient receiving sitaxsentan 100 mg experienced clinical worsening; sitaxsentan was well tolerated.

Neutrophil–cytokine interactions in a rat model of sulindac-induced idiosyncratic liver injury

Previous studies indicated that lipopolysaccharide (LPS) interacts with the nonsteroidal anti-inflammatory drug sulindac (SLD) to produce liver injury in rats. In the present study, the mechanism of SLD/LPS-induced liver injury was further investigated. Accumulation of polymorphonuclear neutrophils (PMNs) in the liver was greater in SLD/LPS-cotreated rats compared to those treated with SLD or LPS alone. In addition, PMN activation occurred specifically in livers of rats cotreated with SLD/LPS. The hypothesis that PMNs and proteases released from them play critical roles in the hepatotoxicity was tested. SLD/LPS-induced liver injury was attenuated by prior depletion of PMNs or by treatment with the PMN protease inhibitor, eglin C. Previous studies suggested that tumor necrosis factor-α (TNF) and the hemostatic system play critical roles in the pathogenesis of liver injury induced by SLD/LPS. TNF and plasminogen activator inhibitor-1 (PAI-1) can contribute to hepatotoxicity by affecting PMN activation and fibrin deposition. Therefore, the role of TNF and PAI-1 in PMN activation and fibrin deposition in the SLD/LPS-induced liver injury model was tested. Neutralization of TNF or inhibition of PAI-1 attenuated PMN activation. TNF had no effect on PAI-1 production or fibrin deposition. In contrast, PAI-1 contributed to fibrin deposition in livers of rats treated with SLD/LPS. In summary, PMNs, TNF and PAI-1 contribute to the liver injury induced by SLD/LPS cotreatment. TNF and PAI-1 independently contributed to PMN activation, which is critical to the pathogenesis of liver injury. Moreover, PAI-1 contributed to liver injury by promoting fibrin deposition.

Amiodarone Exposure During Modest Inflammation Induces Idiosyncrasy-like Liver Injury in Rats: Role of Tumor Necrosis Factor-alpha

Amiodarone [2-butyl-3-(3′,5′-diiodo-4’α-diethylaminoethoxybenzoyl)-benzofuran] (AMD), a class III antiarrhythmic drug, is known to cause idiosyncratic hepatotoxic reactions in human patients. One hypothesis for the etiology of idiosyncratic adverse drug reactions is that a concurrent inflammatory stress results in decreased threshold for drug toxicity. To explore this hypothesis in an animal model, male Sprague-Dawley rats were treated with nonhepatotoxic doses of AMD or its vehicle and with saline vehicle or lipopolysaccharide (LPS) to induce low-level inflammation. Elevated alanine aminotransferase (ALT), aspartate aminotransferase, alkaline phosphatase, and gamma-glutamyltransferase activities as well as increased total bile acid concentrations in serum and midzonal hepatocellular necrosis were observed only in AMD/LPS-cotreated rats. The time interval between AMD and LPS administration was critical: AMD injected 16 h before LPS led to liver injury, whereas AMD injected 2–12 h before LPS failed to cause this response. The increase in ALT activity in AMD/LPS cotreatment showed a clear dose-response relationship with AMD as well as LPS. The metabolism and hepatic accumulation of AMD were not affected by LPS coexposure. Serum concentration of tumor necrosis factor-alpha (TNF) was significantly increased by LPS and was slightly prolonged by AMD. In Hepac1c7 cells, addition of TNF potentiated the cytotoxicity of both AMD and its primary metabolite, mono-N-desethylamiodarone. In vivo inhibition of TNF signaling by etanercept attenuated the AMD/LPS-induced liver injury in rats. In summary, AMD treatment during modest inflammation induced severe hepatotoxicity in rats, and TNF contributed to the induction of liver injury in this animal model of idiosyncratic AMD-induced liver injury.

Hepatotoxicity associated with statins: Reports of idiosyncratic liver injury post-marketing

Limited data exist on drug-induced liver injury (DILI) associated with statins. Reports on adverse reactions suspected to be due to statins received by the Swedish Adverse Drug Reactions Advisory Committe 1988-2010 were analyzed. Only cases with >5×upper limit of normal (ULN) in aminotransferases and/or alkaline phosphatase >2×ULN were included. The most common types of ADRs suspected were DILI in 124/217 (57%) cases. A total of 73/124 (59%) cases had at least possible relationship, median age 64 years (57-73), 55% males, whereas 25/124 cases (20%) were excluded due to mild elevations of liver tests and 26 due to unlikely relationship and/or lack of data. A statin-related DILI episode was reported in 1.2/100,000 users. Atorvastatin was implicated in 30/73 (41%) cases, simvastatin in 28 (38%), fluvastatin (15%), and others. Two patients died of acute liver failure, one underwent liver transplantation and 25 (34%) had jaundice. Three patients were rechallenged with the same statin producing similar patterns of liver injury. The median duration of therapy was 90 days (30-120), 120 (39-248) for atorvastatin, and 75 (30-150) for simvastatin (NS). Cholestatic/mixed injury was more common with atorvastatin, 17/30 (56%) than with simvastatin, 7/28 (24%) (p=0.018). Idiosyncratic liver injury associated with statins is rare but can be severe. After recovery, a similar pattern of liver injury can be reproduced on re-exposure. Most patients experience liver injury 3-4 months after start of therapy. Atorvastatin is mostly associated with cholestatic liver injury whereas hepatocellular injury is more common with simvastatin.

Hepatotoxicity Associated With Statins: Reports of Idiosyncratic Liver Injury Post-Marketing

Hepatotoxicity Associated With Statins: Reports of Idiosyncratic Liver Injury Post-Marketing

Oxidized low-density lipoprotein and tissue factor are involved in monocrotaline/lipopolysaccharide-induced hepatotoxicity

These studies were aimed at characterizing an animal model of inflammation-induced hepatotoxicity that would mimic features of idiosyncratic liver toxicity observed in humans. An attempt was made to identify oxidative damage and the involvement of coagulation system in liver after monocrotaline (MCT) administration under the modest inflammatory condition induced by lipopolysaccharide (LPS) exposure. Mice were given MCT (200mg/kg) or an equivalent volume of sterile saline (Veh.) po followed 4h later by ip injection of LPS (6mg/kg) or vehicle. Mice co-treated with MCT and LPS showed increased plasma alanine aminotransferase (ALT), decrease in platelet number, and a reduction in hematocrit. Accumulation of oxidized low-density lipoprotein (ox-LDL) was remarkably higher in the liver sections of mice co-treated with MCT and LPS compared to those given MCT or LPS alone. A similar trend was observed in the expression of CXCL16 receptor in the same liver sections. Elevated expression of tissue factor (TF) and fibrinogen was also observed in the liver sections of MCT/LPS co-treated mice. The in vitro results showed that incubation of HepG2 cells with CXCL16 antibody strongly diminished uptake of ox-LDL. Expression of ox-LDL, CXCL16, and TF represents an early event in the onset of hepatotoxicity induced by MCT/LPS; thus, it may contribute to our understanding of idiosyncratic liver injury and points to potential targets for protection or intervention.

Polymerase γ Gene POLG Determines the Risk of Sodium Valproate-Induced Liver Toxicity

Sodium valproate (VPA) is widely used throughout the world to treat epilepsy, migraine, chronic headache, bipolar disorder, and as adjuvant chemotherapy. VPA toxicity is an uncommon but potentially fatal cause of idiosyncratic liver injury. Rare mutations in POLG, which codes for the mitochondrial DNA polymerase γ (polγ), cause Alpers-Huttenlocher syndrome (AHS). AHS is a neurometabolic disorder associated with an increased risk of developing fatal VPA hepatotoxicity. We therefore set out to determine whether common genetic variants in POLG explain why some otherwise healthy individuals develop VPA hepatotoxicity. We carried out a prospective study of subjects enrolled in the Drug Induced Liver Injury Network (DILIN) from 2004 to 2008 through five US centers. POLG was sequenced and the functional consequences of VPA and novel POLG variants were evaluated in primary human cell lines and the yeast model system Saccharomyces cerevisiae. Heterozygous genetic variation in POLG was strongly associated with VPA-induced liver toxicity (odds ratio = 23.6, 95% confidence interval [CI] = 8.4-65.8, P = 5.1 × 10⁻⁷). This was principally due to the p.Q1236H substitution which compromised polγ function in yeast. Therapeutic doses of VPA inhibited human cellular proliferation and high doses caused nonapoptotic cell death, which was not mediated through mitochondrial DNA depletion, mutation, or a defect of fatty acid metabolism. These findings implicate impaired liver regeneration in VPA toxicity and show that prospective genetic testing of POLG will identify individuals at high risk of this potentially fatal consequence of treatment.

Trovafloxacin, a fluoroquinolone antibiotic with hepatotoxic potential, causes mitochondrial peroxynitrite stress in a mouse model of underlying mitochondrial dysfunction

Trovafloxacin (TVX) is a fluoroquinolone antibiotic whose therapeutic use was severely restricted due to an unacceptable risk of idiosyncratic liver injury. Oxidative stress and mitochondrial injury have been implicated in fluoroquinolone toxicity, but the mechanisms underlying liver injury are poorly understood. Because TVX-induced hepatotoxicity cannot be modeled in normal healthy rodents, we asked whether an underlying genetic defect (heterozygous deficiency in mitochondrial superoxide dismutase, Sod2) might aggravate TVX-induced mitochondrial adverse effects. Wild-type and Sod2 +/− mice were treated with vehicle or alatrofloxacin (the prodrug of TVX, 33 mg/kg/day, ip) for 28 days. We found that hepatic protein carbonyls were increased by 2.5-fold and hepatic mitochondrial aconitase activity was decreased by 20% in mutant, but not wild-type mice. Because aconitase is a major target of peroxynitrite, we determined the extent of nitrotyrosine residues in hepatic mitochondrial proteins. Trovafloxacin significantly increased nitrotyrosine in Sod2 +/− mice only. Using the NO-selective probe DAF-2, we found that TVX increased the production of mitochondrial NO in immortalized human hepatocytes. Similarly, mitochondrial Ca 2+ was increased by TVX, suggesting Ca 2+-dependent activation of mitochondrial NOS activity. Furthermore, the transcript levels of the mtDNA-encoded gene Cox2/mtCo2 were decreased in Sod2 +/− mice only, while the expression of nDNA-encoded mitochondrial genes was not significantly altered in both genotypes, suggesting selective effects on mtDNA expression. The amount of mtDNA (copy number) was, however, unchanged. These data indicate that TVX enhances hepatic mitochondrial peroxynitrite stress in mice with underlying increased basal levels of superoxide, leading to the disruption of critical mitochondrial enzymes and gene regulation.

Lifrarskaði af völdum lyfja

Drug-induced liver injury (DILI) is a well known adverse reaction of many drugs. Direct toxic liver damage is associated with paracetamol toxicity whereas most other drugs causing liver damage have an unpredictable or idiosyncratic pattern of injury. Although idiosyncratic liver injury was initially thought to be dose independent, it has been shown that many drugs leading to idiosyncratic injury have a dose dependent component. Physicians need to bear in mind DILI in all patients who present with symptoms or signs of liver dysfunction. Clinically and histologically DILI can mimick any known liver disease and there are no pathognomonic histological features of DILI. The diagnosis is one of exclusion. In patients with a high clinical suspicion of DILI the causative drug need to be discontinued and patients with jaundice and/or coagulopathy have to be hospitalized and some cases considered for a liver transplantation.