Forms Of Drug-induced Liver Injury Research Articles

Drug-Induced Fatty Liver Disease (DIFLD): A Comprehensive Analysis of Clinical, Biochemical, and Histopathological Data for Mechanisms Identification and Consistency with Current Adverse Outcome Pathways

Drug induced fatty liver disease (DIFLD) is a form of drug-induced liver injury (DILI), which can also be included in the more general metabolic dysfunction-associated steatotic liver disease (MASLD), which specifically refers to the accumulation of fat in the liver unrelated to alcohol intake. A bi-directional relationship between DILI and MASLD is likely to exist: while certain drugs can cause MASLD by acting as pro-steatogenic factors, MASLD may make hepatocytes more vulnerable to drugs. Having a pre-existing MASLD significantly heightens the likelihood of experiencing DILI from certain medications. Thus, the prevalence of steatosis within DILI may be biased by pre-existing MASLD, and it can be concluded that the genuine true incidence of DIFLD in the general population remains unknown. In certain individuals, drug-induced steatosis is often accompanied by concomitant injury mechanisms such as oxidative stress, cell death, and inflammation, which leads to the development of drug-induced steatohepatitis (DISH). DISH is much more severe from the clinical point of view, has worse prognosis and outcome, and resembles MASH (metabolic-associated steatohepatitis), as it is associated with inflammation and sometimes with fibrosis. A literature review of clinical case reports allowed us to examine and evaluate the clinical features of DIFLD and their association with specific drugs, enabling us to propose a classification of DIFLD drugs based on clinical outcomes and pathological severity: Group 1, drugs with low intrinsic toxicity (e.g., ibuprofen, naproxen, acetaminophen, irinotecan, methotrexate, and tamoxifen), but expected to promote/aggravate steatosis in patients with pre-existing MASLD; Group 2, drugs associated with steatosis and only occasionally with steatohepatitis (e.g., amiodarone, valproic acid, and tetracycline); and Group 3, drugs with a great tendency to transit to steatohepatitis and further to fibrosis. Different mechanisms may be in play when identifying drug mode of action: (1) inhibition of mitochondrial fatty acid β-oxidation; (2) inhibition of fatty acid transport across mitochondrial membranes; (3) increased de novo lipid synthesis; (4) reduction in lipid export by the inhibition of microsomal triglyceride transfer protein; (5) induction of mitochondrial permeability transition pore opening; (6) dissipation of the mitochondrial transmembrane potential; (7) impairment of the mitochondrial respiratory chain/oxidative phosphorylation; (8) mitochondrial DNA damage, degradation and depletion; and (9) nuclear receptors (NRs)/transcriptomic alterations. Currently, the majority of, if not all, adverse outcome pathways (AOPs) for steatosis in AOP-Wiki highlight the interaction with NRs or transcription factors as the key molecular initiating event (MIE). This perspective suggests that chemical-induced steatosis typically results from the interplay between a chemical and a NR or transcription factors, implying that this interaction represents the primary and pivotal MIE. However, upon conducting this exhaustive literature review, it became evident that the current AOPs tend to overly emphasize this interaction as the sole MIE. Some studies indeed support the involvement of NRs in steatosis, but others demonstrate that such NR interactions alone do not necessarily lead to steatosis. This view, ignoring other mitochondrial-related injury mechanisms, falls short in encapsulating the intricate biological mechanisms involved in chemically induced liver steatosis, necessitating their consideration as part of the AOP’s map road as well.

Drug-Induced Liver Injury in the Elderly: Consensus Statements and Recommendations from the IQ-DILI Initiative.

The elderly demographic is the fastest-growing segment of the world's population and is projected to exceed 1.5 billion people by 2050. With multimorbidity, polypharmacy, susceptibility to drug-drug interactions, and frailty as distinct risk factors, elderly patients are especially vulnerable to developing potentially life-threatening safety events such as serious forms of drug-induced liver injury (DILI). It has been a longstanding shortcoming that elderly individuals are often a vulnerable population underrepresented in clinical trials. As such, an improved understanding of DILI in the elderly is a high-priority, unmet need. This challenge is underscored by recent documents put forward by the U.S. Food and Drug Administration (FDA) and European Medicines Agency (EMA) that encourage data collection in the elderly and recommend improved practices that will facilitate a more inclusive approach. To establish what is already known about DILI in the elderly and pinpoint key gaps of knowledge in this arena, a working definition of "elderly" is required that accounts for both chronologic and biologic ages and varying states of frailty. In addition, it is critical to characterize the biological role of aging on liver function, as well as the different epidemiological factors such as polypharmacy and inappropriate prescribing that are common practices. While data may not show that elderly people are more susceptible to DILI, DILI due to specific drugs might be more common in this population. Improved characterization of DILI in the elderly may enhance diagnostic and prognostic capabilities and improve the way in which liver safety is monitored during clinical trials. This summary of the published literature provides a framework to understand and evaluate the risk of DILI in the elderly. Consensus statements and recommendations can help to optimize medical care and catalyze collaborations between academic clinicians, drug manufacturers, and regulatory scientists to enable the generation of high-quality research data relevant to the elderly population.

S3281 A Rare Case of Drug-Induced Liver Injury (DILI) Due to Valproate Hepatocellular Injury

Introduction: Valproate is a widely-used antiepileptic drug which works by increasing gamma-aminobutyric acid (GABA) levels in the brain. We present a unique form of drug-induced liver injury (DILI) in a patient prescribed valproate for trigeminal neuralgia pain. Case Description/Methods: A 45-year old African American female with a history of hypertension and trigeminal neuralgia was prescribed divalproex for trigeminal neuralgia pain after trials of duloxetine, gabapentin, baclofen, oxcarbazepine, carbamazepine, topiramate, amitriptyline, and tizanidine failed to provide relief. Six weeks later she presented with a two week history of worsening nausea, diarrhea, fever, facial rash, production of dark phlegm, and grade 1 encephalopathy. Lab results showed acute liver failure (ALF) with total bilirubin 15.6 mg/dL, ALP 180 U/L, AST 937 U/L, ALT 943 U/L, and INR 2.8. Exam findings included scleral icterus, hepatomegaly, small volume ascites, and some small liver cysts. A diagnosis of DILI was made, with likely drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome. Divalproex was discontinued and the patient was admitted for two weeks of stabilizing treatment including N-acetylcysteine, lactulose, rifaximin, Vitamin K, and L-carnitine transfusion (Figure 1). The patient was evaluated for liver transplant, but it was ultimately not indicated given her subsequent improvement in liver function. An acute kidney injury developed but was resolved before patient discharge. Two weeks later the patient presented with signs of acute kidney injury. Upon readmission, complications including hepatic encephalopathy, macrocytic anemia, spontaneous bacterial peritonitis, and acute respiratory failure developed over the course of several weeks. All stabilizing treatment efforts were made but the patient ultimately developed septic shock and died. Discussion: DILI is the most common cause of ALF in the United States. Valproate-induced hepatotoxicity as a result of mitochondrial injury from impaired beta-oxidation and decreased tissue carnitine levels is one rare effect of use. Such hepatocellular injury typically shows very elevated AST and ALT levels with a smaller elevation in ALP. Early diagnosis of DILI is crucial to promptly discontinue use of the causative agent and begin optimal treatment. In the case of valproate, it is recommended that patients receive intravenous (IV) carnitine until symptoms improve. Liver transplant evaluation is crucial for ALF patients given the high morality risk.Figure 1.: 1A. Patient’s AST and ALT values over the course of her hospital admission. Figure 1B. Patient’s INR values over the course of her hospital admission.

Mitochondrial Glrx2 Knockout Augments Acetaminophen-Induced Hepatotoxicity in Mice.

Acetaminophen (APAP) is one of the most widely used drugs with antipyretic and analgesic effects, and thus hepatotoxicity from the overdose of APAP becomes one of the most common forms of drug-induced liver injury. The reaction towards thiol molecules, such as GSH by APAP metabolite, N-acetyl-p-benzo-quinonimine (NAPQI), is the main cause of APAP-induced hepatotoxicity. However, the role of many other thiol-related regulators in toxicity caused by APAP is still unclear. Here we have found that knockout of the Glrx2 gene, which encodes mitochondrial glutaredoxin2 (Grx2), sensitized mice to APAP-caused hepatotoxicity. Glrx2 deletion hindered Nrf2-mediated compensatory recovery of thiol-dependent redox systems after acetaminophen challenge, resulting in a more oxidized cellular state with a further decrease in GSH level, thioredoxin reductase activity, and GSH/GSSG ratio. The weakened feedback regulation capacity of the liver led to higher levels of protein glutathionylation and thioredoxin (both Trx1 and Trx2) oxidation in Glrx2−/− mice. Following the cellular environment oxidation, nuclear translocation of apoptosis-inducing factor (AIF) was elevated in the liver of Glrx2−/− mice. Taken together, these results demonstrated that mitochondrial Grx2 deficiency deteriorated APAP-induced hepatotoxicity by interrupting thiol-redox compensatory response, enhancing the AIF pathway-mediated oxidative damage.

Mouse precision-cut liver slices as an ex vivo model to study drug-induced cholestasis

Drugs are often withdrawn from the market due to the manifestation of drug-induced liver injury (DILI) in patients. Drug-induced cholestasis (DIC), defined as obstruction of hepatic bile flow due to medication, is one form of DILI. Because DILI is idiosyncratic, and the resulting cholestasis complex, there is no suitable in vitro model for early DIC detection during drug development. Our goal was to develop a mouse precision-cut liver slice (mPCLS) model to study DIC and to assess cholestasis development using conventional molecular biology and analytical chemistry methods. Cholestasis was induced in mPCLS through a 48-h-incubation with three drugs known to induce cholestasis in humans, namely chlorpromazine (15, 20, and 30 µM), cyclosporin A (1, 3, and 6 µM) or glibenclamide (25, 50, and 65 µM). A bile-acid mixture (16 µM) that is physiologically representative of the human bile-acid pool was added to the incubation medium with drug, and results were compared to incubations with no added bile acids. Treatment of PCLS with cholestatic drugs increased the intracellular bile-acid concentration of deoxycholic acid and modulated bile-transporter genes. Chlorpromazine led to the most pronounced cholestasis in 48 h, observed as increased toxicity; decreased protein and gene expression of the bile salt export pump; increased gene expression of multidrug resistance-associated protein 4; and accumulation of intracellular bile acids. Moreover, chlorpromazine-induced cholestasis exhibited some transition into fibrosis, evidenced by increased gene expression of collagen 1A1 and heatshock protein 47. In conclusion, we demonstrate that mPCLS can be used to study human DIC onset and progression in a 48 h period. We thus propose this model is suited for other similar studies of human DIC.

Hepatotoxicity reports in the FDA adverse event reporting system database: A comparison of drugs that cause injury via mitochondrial or other mechanisms

Drug-induced liver injury (DILI) is a leading reason for preclinical safety attrition and post-market drug withdrawals. Drug-induced mitochondrial toxicity has been shown to play an essential role in various forms of DILI, especially in idiosyncratic liver injury. This study examined liver injury reports submitted to the Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS) for drugs associated with hepatotoxicity via mitochondrial mechanisms compared with non-mitochondrial mechanisms of toxicity. The frequency of hepatotoxicity was determined at a group level and individual drug level. A reporting odds ratio (ROR) was calculated as the measure of effect. Between the two DILI groups, reports for DILI involving mitochondrial mechanisms of toxicity had a 1.43 (95% CI 1.42–1.45; P < 0.0001) times higher odds compared to drugs associated with non-mitochondrial mechanisms of toxicity. Antineoplastic, antiviral, analgesic, antibiotic, and antimycobacterial drugs were the top five drug classes with the highest ROR values. Although the top 20 drugs with the highest ROR values included drugs with both mitochondrial and non-mitochondrial injury mechanisms, the top four drugs (ROR values > 18: benzbromarone, troglitazone, isoniazid, rifampin) were associated with mitochondrial mechanisms of toxicity. The major demographic influence for DILI risk was also examined. There was a higher mean patient age among reports for drugs that were associated with mitochondrial mechanisms of toxicity [56.1 ± 18.33 (SD)] compared to non-mitochondrial mechanisms [48 ± 19.53 (SD)] (P < 0.0001), suggesting that age may play a role in susceptibility to DILI via mitochondrial mechanisms of toxicity. Univariate logistic regression analysis showed that reports of liver injury were 2.2 (odds ratio: 2.2, 95% CI 2.12–2.26) times more likely to be associated with older patient age, as compared with reports involving patients less than 65 years of age. Compared to males, female patients were 37% less likely (odds ratio: 0.63, 95% CI 0.61–0.64) to be subjects of liver injury reports for drugs associated with mitochondrial toxicity mechanisms. Given the higher proportion of severe liver injury reports among drugs associated with mitochondrial mechanisms of toxicity, it is essential to understand if a drug causes mitochondrial toxicity during preclinical drug development when drug design alternatives, more clinically relevant animal models, and better clinical biomarkers may provide a better translation of drug-induced mitochondrial toxicity risk assessment from animals to humans. Our findings from this study align with mitochondrial mechanisms of toxicity being an important cause of DILI, and this should be further investigated in real-world studies with robust designs.

Sinusoidal dilatation and congestion in post-transplant liver biopsies from patients presenting with transaminitis.

Sinusoidal dilatation and congestion (SDC) in liver biopsy may be obstructive (due to venous outflow impairment) or non-obstructive in nature. The significance of this finding in the post-liver transplant setting remains unexplored. We herein retrospectively analysed all post-transplant liver biopsies showing SDC and examined histopathological features in detail. Association with transaminitis and concurrent graft rejection was assessed. A total of 30 post-transplant liver biopsies from 27 patients showed SDC with atrophy of hepatocyte cords (SDC; incidence 7.4%). All patients had transaminitis. Most patients (n=22; 81.5%) were asymptomatic with deranged liver function tests (LFTs) detected during routine follow-up, raising clinical suspicion of graft rejection. SDC was non-obstructive in 19 (70.4%) and obstructive (due to sinusoidal obstruction syndrome (SOS)) in 8 (29.6%) cases. The incidence of SOS was 2%. SDC was mild, moderate and severe in 18 (66.7%), 7 (25.9%) and 2 (7.4%) cases, respectively. Perivenular and centrilobular sinusoidal fibrosis was seen in the obstructive SDC group (n=3, 11.1%). Concurrent graft rejection was present in 7 (25.9%) cases, of which acute cellular rejection comprised 5 (18.5%), and late acute rejection accounted for 2 cases (7.4%). Serum tacrolimus levels ranged from normal (n=14) to below and above normal (n=5 each). Modulation of immunosuppressive therapy led to normalisation of LFTs in one patient. Obstructive and non-obstructive SDC in post-liver transplant patients presenting with transaminitis mimics graft rejection clinically and may represent a form of drug-induced liver injury. Liver biopsy plays a crucial role in the diagnosis.

A Patient with Acute Liver Injury after Sulfamethoxazole/Trimethoprim Treatment for Pyelonephritis

Background: Sulfamethoxazole/Trimethoprim is a commonly used drug in a variety of clinically indicated scenarios, but it is not without side effect. Case-reports have stated that adverse reactions secondary to Sulfamethoxazole/Trimethoprim can present very early in the course of treatment, especially in patients who have a higher predisposition. Thus, the burden is placed on the clinician to be wary of these side effects and be able to recognize them in the correct clinic scenario. Objective: To discuss the risk of developing cholestatic hepatic dysfunction secondary to treatment with sulfamethoxazole/trimethoprim. Methods: We present the history, physical findings, laboratory investigations, and clinical course of a 47-year-old African-American female who developed cholestatic hepatic dysfunction after treatment with sulfamethoxazole/trimethoprim for pyelonephritis. Results: Drug-induced liver injury is a rare complication of sulfamethoxazole/trimethoprim therapy and only 20% of cases are secondary to cholestatic hepatic dysfunction. Our patient, who had been on sulfamethoxazole/trimethoprim for 7 days for pyelonephritis, presented to our hospital with a clinical picture consistent with hepatic injury; her laboratory investigations were noteworthy for an elevated white blood cell count, platelet count, and elevated transaminases, along with alkaline phosphatase levels greater than 2 times the upper limit of normal. Promptly following the discontinuation of sulfamethoxazole/trimethoprim, our patient improved clinically and her liver enzymes down-trended during the course of her hospital stay. She returned to normal at her 4 month follow up, thus confirming the diagnosis of cholestatic hepatic dysfunction secondary to sulfamethoxazole/trimethoprim. Conclusion: Cholestatic hepatic dysfunction is a form of drug-induced liver injury and a rare complication of sulfamethoxazole/trimethoprim treatment. The majority of cases resolve following discontinuation of the offending medication. However, a small percentage of patients may progress to liver failure and ultimately require liver transplantation. Clinicians should be aware of these risks to avoid delaying the discontinuation of sulfamethoxazole/trimethoprim.

2351 NAC of All Trades: Use of N-acetylcysteine in Cocaine-Induced Acute Liver Failure

INTRODUCTION: Among patients with acute liver failure (ALF), drug-induced liver injury (DILI) presents a challenging clinical syndrome with limited therapeutic options. N-acetylcysteine (NAC) is a mainstay of treatment in acetaminophen-induced ALF, acting as an antioxidant, a vasodilator and a glutathione precursor. However, it has been used with success in other toxic ingestions causing ALF, and its beneficial effects do not seem to be unique to acetaminophen-induced hepatotoxicity. We present a case of ALF after acute cocaine ingestion with rapid recovery after administration of IV NAC. CASE DESCRIPTION/METHODS: A 58 year-old-male with a past medical history of chronic hepatitis C without cirrhosis and polysubstance abuse presented with acute psychosis. On arrival he was tachycardic but hemodynamically stable, with psychomotor agitation and fear delusions. He endorsed recent heavy cocaine ingestion. Initial labs demonstrated acute kidney injury, rhabdomyolysis and mild transaminitis; AST 59, ALT 56. Toxicology workup was positive for cocaine with undetectable acetaminophen, ethanol and salicylate levels. The following day however, he developed fulminant hepatic failure, AST &gt;7000, ALT 2,568 (Figure 1) with progressive coagulopathy, INR 2.14, albumin 2.9, platelets 120. Of note, despite chronic hepatitis C, there was no evidence of cirrhosis and preserved liver synthetic function at presentation, INR 1.10, albumin 4.7, platelets 254. Our patient was not a candidate for liver transplant (LT), and decision was made to initiate IV NAC therapy, 140 mg/kg bolus followed by 70 mg/kg daily. Transaminases rapidly normalized after only 3 days of therapy, and he was discharged in stable condition. DISCUSSION: ALF is a rare but challenging syndrome, for which LT is the only curative treatment available. NAC is well established as an antidote in acetaminophen ALF, yet its mechanisms are applicable to other forms of DILI as well. Cocaine hepatotoxicity has been reported in humans, and is well studied in animal models. Studies in mice suggest toxic metabolites play a critical role, much like acetaminophen ALF. These species deplete glutathione, decrease hepatic blood flow, generate reactive oxygen species and cause lipid peroxidation of membranes. We present a case of ALF secondary to cocaine ingestion in the setting of underlying chronic hepatitis C, with rapid recovery after fluid resuscitation and IV NAC. NAC therapy has minimal adverse effects, and may be lifesaving in patients with ALF who are not candidates for LT.

Exosomal Transport of Hepatocyte-Derived Drug-Modified Proteins to the Immune System.

Idiosyncratic drug‐induced liver injury (DILI) is a rare, often difficult‐to‐predict adverse reaction with complex pathomechanisms. However, it is now evident that certain forms of DILI are immune‐mediated and may involve the activation of drug‐specific T cells. Exosomes are cell‐derived vesicles that carry RNA, lipids, and protein cargo from their cell of origin to distant cells, and they may play a role in immune activation. Herein, primary human hepatocytes were treated with drugs associated with a high incidence of DILI (flucloxacillin, amoxicillin, isoniazid, and nitroso‐sulfamethoxazole) to characterize the proteins packaged within exosomes that are subsequently transported to dendritic cells for processing. Exosomes measured between 50 and 100 nm and expressed enriched CD63. Liquid chromatography–tandem mass spectrometry (LC/MS‐MS) identified 2,109 proteins, with 608 proteins being quantified across all exosome samples. Data are available through ProteomeXchange with identifier PXD010760. Analysis of gene ontologies revealed that exosomes mirrored whole human liver tissue in terms of the families of proteins present, regardless of drug treatment. However, exosomes from nitroso‐sulfamethoxazole‐treated hepatocytes selectively packaged a specific subset of proteins. LC/MS‐MS also revealed the presence of hepatocyte‐derived exosomal proteins covalently modified with amoxicillin, flucloxacillin, and nitroso‐sulfamethoxazole. Uptake of exosomes by monocyte‐derived dendritic cells occurred silently, mainly through phagocytosis, and was inhibited by latrunculin A. An amoxicillin‐modified 9‐mer peptide derived from the exosomal transcription factor protein SRY (sex determining region Y)‐box 30 activated naïve T cells from human leukocyte antigen A*02:01–positive human donors. Conclusion: This study shows that exosomes have the potential to transmit drug‐specific hepatocyte‐derived signals to the immune system and provide a pathway for the induction of drug hapten‐specific T‐cell responses.

DILI Associated with Skin Reactions

Adverse drug reactions (ADR) frequently involve the liver and skin in the form of drug-induced liver injury or cutaneous drug eruption. Skin ADR can range from harmless rash to severe skin manifestations such as drug rash with eosinophilia and systemic symptom syndrome (DRESS syndrome), Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and acute generalized exanthematous pustulosis (AGEP), all of which can be associated with severe outcome, including a 30% mortality rate in case of TEN. The association with co-occurring liver injury varies and in DRESS and SJS/TEN can contribute to substantial morbidity and mortality. Liver and skin ADR are frequent but rarely severe; however, if severe, they are not uncommonly fatal.

Minocycline-Induced Autoimmune Hepatitis: A Rare But Important Cause of Drug-Induced Autoimmune Hepatitis

Drug-induced autoimmune hepatitis (DIAIH) is an increasingly recognized form of drug-induced liver injury that leads to a condition similar to idiopathic autoimmune hepatitis. A number of drugs have been associated with DIAIH, minocycline is one of the most well characterized. Minocycline is a semisynthetic tetracycline antibiotic used in the treatment of acne vulgaris. Minocycline-induced autoimmune hepatitis presents with serologic and histologic features similar to idiopathic autoimmune hepatitis. However, the natural history and outcomes of these two conditions differ significantly. The majority of patients with minocycline-induced autoimmune hepatitis experience complete resolution of symptoms after withdrawal of the medication. Some patients may require a short course of steroids and rarely use of an immunomodulator to achieve resolution of disease. Recurrence of symptoms is rare and typically only occurs with reintroduction of minocycline. It is important for primary care providers to consider minocycline-induced autoimmune hepatitis when liver injury develops during minocycline therapy.

Soluble Thrombomodulin Attenuates Endothelial Cell Damage in Hepatic Sinusoidal Obstruction Syndrome.

Hepatic sinusoidal obstruction syndrome (SOS), also known as veno-occlusive disease, is a form of drug-induced liver injury, the initial morphological changes associated with which occur in liver sinusoidal endothelial cells (LSECs). Recombinant human soluble thrombomodulin (rTM) is reported to have anti-inflammatory and cytoprotective effects. Therefore, we investigated the ability of rTM to protect endothelial cells and enhance their functions in a monocrotaline (MCT)-induced model of SOS. Human umbilical vein endothelial cells were assessed in vitro following administration of MCT (2-4 mM) with/without rTM (10-100 ng/ml) to investigate the effect of rTM on cell proliferation and apoptosis. In vivo experiments were performed with Crl:CD1 mice divided into three groups: rTM (rTM + MCT), placebo (control diluent + MCT), and control (control diluent only). LSECs [cluster of differentiation (CD) 31+CD34+ vascular endothelial growth factor receptor 3 (VEGFR3)+ cells] from these mice were identified using fluorescence-activated cell sorting and assessed by quantitative real-time polymerase chain reaction (qPCR). In vitro, caspase-3 and -7 activities were significantly lower and cell viability (as assessed by MTT assays) significantly higher in the rTM group than in the placebo group. Moreover, levels of p-AKT increased upon rTM administration. In vivo, damage to LSECs in zone 3 of the hepatic acinus was attenuated and the number of LSECs were maintained in the rTM group, in contrast to the placebo group. Furthermore, expression of Nos3 (encoding endothelial nitric oxide synthase) was higher and that of plasminogen activator inhibitor 1 (Pai1) lower in LSECs from mice in the rTM group than in those from the placebo group. rTM can attenuate SOS by protecting LSECs and enhancing their functions.

Inferring transcription factor activity from microarray data reveals novel targets for toxicological investigations

Transcription factors (TFs) are important modulators of the inducible portion of the transcriptome, and therefore relevant in the context of exposure to exogenous compounds. Current approaches to predict the activity of TFs in biological systems are usually restricted to a few entities at a time due to low-throughput techniques targeting a limited fraction of annotated human TFs. Therefore, high-throughput alternatives may help to identify new targets of mechanistic and predictive value in toxicological investigations. In this study, we inferred the activity multiple TFs using publicly available microarray data from primary human hepatocytes exposed to hundreds of chemicals and evaluated these molecular profiles using multiple correspondence analysis. Our results demonstrate that the lowest dose and latest exposure time (24h) in a subset of chemicals generates a signature indicative of carcinogenicity possibly due to DNA-damaging properties. Furthermore, profiles from the earliest exposure time (2h) and highest dose creates clusters of chemicals implicated in the development of diverse forms of drug-induced liver injury (DILI). Both approaches yielded a number of TFs with similar activity across groups of chemicals, including TFs known in toxicological responses such as AhR, NFE2L2 (Nrf2), NF-κB and PPARG. FOXM1, IRF1 and E2F4 were some of the TFs identified that may be relevant in genotoxic carcinogenesis. SMADs (SMAD1, SMAD2, SMAD5) and KLF5 were identified as some of potentially new TFs whose inferred activities were linked to acute and progressive outcomes in DILI. In conclusion this study offers a novel mechanistic approach targeting TF activity during chemical exposure.

Minocycline hepatotoxicity: Clinical characterization and identification of HLA-B∗35:02 as a risk factor

Minocycline hepatotoxicity can present with prominent autoimmune features in previously healthy individuals. The aim of this study was to identify genetic determinants of minocycline drug-induced liver injury (DILI) in a well-phenotyped cohort of patients. Caucasian patients with minocycline DILI underwent genome-wide genotyping and were compared to unexposed population controls. Human leukocyte antigen (HLA) binding of minocycline was assessed using AutoDock Vina. Among the 25 cases, 80% were female, median age was 19years and median latency from drug start to DILI onset was 318days. At presentation, 76% had acute hepatocellular liver injury, median ALT 1,077U/L (range: 63 to 2,333), median bilirubin 4.5mg/dl (range: 0.2 to 16.7), and 90% had a +ANA. During follow-up, 50% were treated with corticosteroids and no participants died or required a liver transplant. A significant association was noted between HLA-B∗35:02 and risk for minocycline DILI; a 16% carrier frequency in DILI cases compared to 0.6% in population controls (odds ratio: 29.6, 95% CI: 7.8-89.8, p=2.5×10-8). Verification of HLA-B∗35:02 imputation was confirmed by sequence-based HLA typing. HLA-B∗35:02 carriers had similar presenting features and outcomes compared to non-carriers. In silico modeling studies support the hypothesis that direct binding of minocycline to this novel HLA risk allele might be an important initiating event in minocycline DILI. HLA-B∗35:02 is a rare HLA allele that was more frequently identified in the 25 minocycline DILI cases compared to population controls. If confirmed in other cohorts, this HLA allele may prove to be a useful diagnostic marker of minocycline DILI. Development of liver injury following prolonged use of minocycline for acne is a rare but potentially severe form of drug-induced liver injury. Our study demonstrates that individuals who are HLA-B∗35:02 carriers are at increased risk of developing minocycline related liver injury. These results may help doctors more rapidly and confidently diagnose affected patients and possibly reduce the risk of liver injury in individuals receiving minocycline going forward.

Early Detection of Acute Drug-Induced Liver Injury in Mice by Noninvasive Near-Infrared Fluorescence Imaging

Hepatocellular and cholestatic forms of drug-induced liver injury (DILI) are major reasons for late-stage termination of small-molecule drug discovery research projects. Biochemical serum markers are limited in their ability to sensitively and specifically detect both of these common DILI forms in preclinical models, and tissue-specific approaches to assessing this are labor intensive, requiring extensive animal dosing, tissue preparation, and pathology assessment. In vivo fluorescent imaging offers noninvasive detection of biologic changes detected directly in the livers of living animals. Three different near-infrared fluorescent imaging probes, specific for cell death (Annexin-Vivo 750), matrix metalloproteases (MMPSense 750 FAST), and transferrin receptor (Transferrin-Vivo 750) were used to measure the effects of single bolus intraperitoneal doses of four different chemical agents known to induce liver injury. Hepatocellular injury–inducing agents, thioacetamide and acetaminophen, showed optimal injury detection with probe injection at 18–24 hours, the liver cholestasis-inducing drug rifampicin required early probe injection (2 hours), and chlorpromazine, which induces mixed hepatocellular/cholestatic injury, showed injury with both early and late injection. Different patterns of liver responses were seen among these different imaging probes, and no one probe detected injury by all four compounds. By using a cocktail of these three near-infrared fluorescent imaging probes, all labeled with 750-nm fluorophores, each of the four different DILI agents induced comparable tissue injury within the liver region, as assessed by epifluorescence imaging. A strategy of probe cocktail injection in separate cohorts at 2 hours and at 20–24 hours allowed the effective detection of drugs with either early- or late-onset injury.

Are Polymorphisms in Genes Relevant to Drug Disposition Predictors of Susceptibility to Drug-Induced Liver Injury?

Despite considerable progress in identifying specific HLA alleles as genetic risk factors for some forms of drug-induced liver injury, progress in understanding whether genetic polymorphisms relevant to drug disposition also contribute to risk for developing this serious toxicity has been more limited. Evidence from both candidate-gene case control studies and genome-wide association studies is now discussed. In the case of genes relevant to drug metabolism, polymorphisms in cytochromes P450, UDP-glucuronosyltransferases, N-acetyltransferases and glutathione S-transferases as risk factors for DILI are assessed. The relevance of ABC transporters to drug-induced liver injury is also considered, together with data showing associations of particular ABCB11, ABCB1 and ABCC2 polymorphisms with some forms of drug-induced liver injury. Very few of the associations with genes relevant to drug disposition that have been reported have been well replicated. Even apparently well-studied associations such as that between isoniazid liver injury and N-acetyltransferase 2 slow acetylators remain problematic, though it seems likely that polymorphisms in drug metabolism genes do contribute to risk for some specific drugs. A better understanding of genetic risk factors for drug-induced liver injury will require further genome-wide association studies with larger numbers of cases, especially for forms of drug-induced liver injury where HLA genotype does not appear to be a risk factor.

NAT2 slow acetylator associated with anti-tuberculosis drug-induced liver injury in Thai patients.

Anti-tuberculosis drug-induced liver injury (AT-DILI) is one of the most common forms of drug-induced liver injury (DILI) in high tuberculosis (TB) burden countries. Among anti-tuberculosis drugs, isoniazid is the main cause of hepatotoxicity in patients with AT-DILI. To investigate the association of AT-DILI with N-acetyltransferase 2 (NAT2) genotype status in Thai TB patients. We enrolled 53 patients diagnosed with AT-DILI and 85 patients who tolerated anti-tuberculosis treatment as controls. Acetylator status was determined based on the inferred NAT2 haplotypes from four common single-nucleotide polymorphisms (SNPs) in Thais using Sanger sequencing. Phenotype frequencies of the NAT2 acetylator in AT-DILI patients were respectively 71.7%, 22.6% and 5.7% for slow, intermediate and rapid acetylators. Among slow, intermediate, and rapid acetylators in treatment tolerant controls, phenotype frequencies were respectively 22.4%, 62.4% and 15.3%. Slow NAT2 acetylators demonstrated a significant association with risk of AT-DILI. The odds ratio of comparing slow NAT2 acetylator in DILI patients and tolerance was 8.80 (95%CI 4.01-19.31, P = 1.53 × 10-8). Slow acetylator status in the NAT2 genotype is a significant risk factor for DILI in Thai patients with TB. This evidence provides confirmatory data in support of the role of NAT2 in AT-DILI in the Thai population.

Identification of susceptible HLA class II co‐amoxiclav genotypes based on the analysis of drug‐specific T‐cells from patients with liver injury

Drug-induced liver injury (DILI) is a major concern for public health. Several forms of DILI are associated with the expression of specific MHC genes suggesting that the adaptive immune system is involved in the disease pathogenesis. We have identified drug-responsive T-cells in patients with flucloxacillin induced DILI and shown that the drug antigen is presented to T-cells in the context of the HLA risk allele (HLA-B*5701). The combination of amoxicillin and clavulanic acid (coamoxiclav) is one of the most frequently prescribed drugs. Occasionally, human exposure is associated with DILI. Individual susceptibility can be influenced by HLA genotypes (e.g. DRB1*1501 risk; DRB1*07:01 risk) and we have recently characterized drug-specific T-cells in patients with co-amoxiclav-induced DILI. The objective of this study was to use amoxicillin-specific CD4+ T-cell clones from 2 DILI patients to investigate the mechanisms of drug antigen presentation and to identify susceptible HLA class II genotypes based on analysis of drug specific T-cell responses. Method Antigen presenting cells (APC) expressing different HLA alleles generated from our HLA-typed PBMC cell bank were used to investigate the latter. EBV-transformed B-cell lines from 15 donors expressing HLA alleles of interest were generated and used as APC. To characterize mechanism(s) of T-cell activation, APC were (1) omitted from the assay, (2) pulsed with amoxicillin for 1-16h and (3) treated with MHC blocking antibodies. Results

Immunological aspects of drug hypersensitivity—from molecule to man

ImmuNologICal aSpeCTS of drug hyperSeNSITIVITy—from moleCule To maN K. Park Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom Summary: Drug-induced liver injury (DILI) accounted for > 50% of cases of acute liver failure and 15% of patients undergoing liver transplantation between 1990 and 2002. One of the biggest fears is unpredictable idiosyncratic drug-induced liver injury (IDILI), which is a major contributor to the failure of a drug to process through development and is a major cause of withdrawal and black box warnings. Due to the low concordance of the hepatotoxicity of drugs in animals and humans, a fundamental understanding of the mechanistic basis from novel human-relevant in vitro models and biomarkers is critical for the development of effective strategies to prevent and predict DILI. Hepatocellular activation of drugs has been widely implicated in immune-mediated DILI with concomitant activation of the adaptive immune system. Consistent with this hypothesis, a number of HLA alleles that are associated with DILI have been identified. Studies with patient PBMC and PBMC from drug-naive donors carrying HLA risk alleles have shown that drugs form specific associations with HLA risk alleles generating T-cell antigens and hence provide the immunogenetic basis for the reaction. The identification of HLA alleles as predisposing factors for IDILI suggests that the adaptive immune system also participates in reactions targeting the liver. Furthermore, the release of damage-associated molecular pattern molecules (DAMPs), such as high mobility group box-1, may serve to activate cells of the innate immune system. Certain mediators produced by innate immune cells may cause liver injury, but other factors are actually important to promote tissue repair and regeneration. However, to fully define cause and effect (bioactivation vs liver failure), an integrated approach based on clinical studies, in vitro experiments, and animal models will be required, underpinned by appropriate bioanalysis. We have been able to characterize covalent protein adducts in man formed by reactive drug metabolites (nevirapine, diclofenac) using techniques developed for β -lactam antibiotics that associate with various types of drug hypersensitivity. We have also developed in vitro models to look at the interplay between, genetic, chemical, and immunologic factors using cells from both hypersensitive and drug-naive individuals. Such techniques and concepts should enable us to elucidate various mechanistic pathways and thus define both chemical and biological variables that underpin this rare but serious form of DILI. Disclosure of Interest: None declared.