Acute Drug-induced Liver Injury Research Articles

Ascites management by cell-free concentrated ascites reinfusion therapy during recovery from drug-induced acute liver injury: a case report

BackgroundThe symptoms of drug-induced hepatic injury are manifold; however, the presence of ascites indicates a severe disease condition. The rapid accumulation of ascites is distressing and requires palliative treatment. Because many cases are addressed by repeated large-volume paracentesis, often resulting in impairment due to protein and electrolyte loss, a different approach is required.Case presentationA 61-year-old Japanese man on maintenance dialysis was admitted to our hospital with acute liver injury. Our patient was diagnosed as having drug-induced liver injury due to warfarin or diltiazem, which started immediately after coronary artery bypass grafting 7 months previously. One month after admission, our patient’s hepatic encephalopathy remained grade 1 and his prothrombin time international normalized ratio was maintained at < 1.5. However, the liver was markedly atrophied with massive ascites. Although liver transplantation was desired, he was considered unfit for transplantation because of his renal and cardiac complications. Therefore, we devised a strategy to manage the massive ascites with cell-free concentrated ascites reinfusion therapy while awaiting liver regeneration. At first, cell-free concentrated ascites reinfusion therapy was required frequently because ascites accumulated rapidly. But the fluid retention interval was gradually extended as intended, and cell-free concentrated ascites reinfusion therapy was withdrawn after 8 months. During that time, the size of his liver increased from 1419 cm3 to 1587 cm3 on computed tomography.ConclusionsCell-free concentrated ascites reinfusion therapy is an apheresis therapy in which ascites are collected aseptically by paracentesis, concentrated, and then reinfused intravenously. This treatment has the advantage of preserving nutrition by reusing the fluid. Previously, cell-free concentrated ascites reinfusion therapy was used only for the management of ascites in patients with cirrhosis or carcinomatous peritonitis. This case suggests that palliation and maintenance of nutritional status with cell-free concentrated ascites reinfusion therapy may be useful as an adjunct to liver regeneration in drug-induced hepatic injury.

Smart Bimodal Imaging of Hypochlorous Acid In Vivo Using a Heterobimetallic Ruthenium(II)-Gadolinium(III) Complex Probe.

A unique heterobimetallic Ru(II)-Gd(III) complex, Ru-AN-Gd, is reported to serve as an effective probe for bimodal phosphorescence-magnetic resonance (MR) imaging of hypochlorous acid (HClO) in vitro and in vivo. The probe was designed by incorporating a MR contrast agent, Gd-DOTA, into a HClO-responsive bipyridine-Ru(II) complex derivative. The specific reaction between Ru-AN-Gd and HClO triggers the cleavage of an ether bond in the probe molecule, resulting in phosphorescence turn-on and MR turn-off responses to HClO. The integration of MR and phosphorescence detection modes allows the probe to be employed for detecting HClO in a quite wide concentration range (0.6-2000 μM) and for imaging HClO at various resolutions ranging from the subcellular level to the whole body without a depth limit. Its applicability was demonstrated by phosphorescence imaging of lysosomal HClO in live cells, visualization of HClO generation in a mouse arthritis model, and bimodal phosphorescence-MR imaging of HClO in drug-induced acute liver and kidney injury of a mouse. The research achievements suggested the potential of Ru-AN-Gd for diagnosis and treatment monitoring of HClO-related disease.

An Evaluation of Postmarketing Reports of Serious Idiosyncratic Liver Injury Associated with Ulipristal Acetate for the Treatment of Uterine Fibroids

Ulipristal acetate (ulipristal) is a selective progesterone receptor modulator that has been marketed for daily use in Europe and Canada to reduce symptoms caused by uterine fibroids. Long-term use ofsome other members of this class of 19-norprogesterone-derived agents has been associated with idiosyncratic hepatotoxicity. We analyzed postmarketing reports of suspected drug-induced liver injury associated with the daily use of 5mg of ulipristal to treat symptoms of uterine fibroids. We searched for reports of serious liver injury associated with ulipristal, submitted to the US Food and Drug Administration through 31 January, 2020. Cases of liver injury temporally associated with long-term ulipristal exposure that reported combined increases of serum aminotransferases and bilirubin were individually assessed using a five-tier categorical scale of likelihood for a causal association with the drug by individuals with expertise in drug-induced liver injury evaluation. Individual cases that did not culminate in liver failure, death, or liver transplantation were also assessed for their causal association with ulipristal by the Roussel Uclaf Causality Assessment Method. We identified nine non-US cases that met the criteria for inclusion in our search for cases of serious liver injury associated with ulipristal. Five cases reported clinical outcomes of liver transplantation and/or death and all were assessed to have a probable causal association with ulipristal acetate. Evaluation of the other four cases reporting resolution of liver injury after treatment discontinuation revealed a possible or probable causal relationship with ulipristal. We identified postmarketing cases of serious acute drug-induced liver injury causally associated with ulipristal used to treat uterine fibroids, some with outcomes of liver transplant and/or death. The presence of common structural features identified with certain selective progesterone receptor modulators in the treatment of chronic conditions may indicate a liability for idiosyncratic drug-induced liver injury.

In Vivo Assessment of Drug-Induced Hepatotoxicity Using Xenopus Embryos.

Failure to predict drug-induced toxicity reactions is a major problem contributing to a high attrition rate and tremendous cost in drug development. Drug screening in X. laevis embryos is high-throughput relative to screening in rodents, potentially making them ideal for this use. Xenopus embryos have been used as a toxicity model in the frog embryo teratogenesis assay on Xenopus (FETAX) for the early stages of drug safety evaluation. We previously developed compound-screening methods using Xenopus embryos and believe they could be used for in vitro drug-induced toxicity safety assessment before expensive preclinical trials in mammals. Specifically, Xenopus embryos could help predict drug-induced hepatotoxicity and consequently aid lead candidate prioritization. Here we present methods, which we have modified for use on Xenopus embryos, to help measure the potential for a drug to induce liver toxicity. One such method examines the release of the liver-specific microRNA (miRNA) miR-122 from the liver into the vasculature as a result of hepatocellular damage, which could be due to drug-induced acute liver injury. Paracetamol, a known hepatotoxin at high doses, can be used as a positive control. We previously showed that some of the phenotypes of mammalian paracetamol overdose are reflected in Xenopus embryos. Consequently, we have also included here a method that measures the concentration of free glutathione (GSH), which is an indicator of paracetamol-induced liver injury. These methods can be used as part of a panel of protocols to help predict the hepatoxicity of a drug at an early stage in drug development.

A case of acute drug-induced liver injury caused by oral metformin sustained-release tablets

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Acute hepatocellular drug-induced liver injury probably caused by doxazosin.

Drug-induced liver injury (DILI) is a diagnostic challenge, due to the hepatotoxic potential of drugs, herbs and dietary supplements, the variety of pathological phenotypes and the absence of specific biomarkers.

Interleukin-22 ameliorates acute-on-chronic liver failure by reprogramming impaired regeneration pathways in mice

Acute-on-chronic liver failure (ACLF) is a clinical syndrome defined by liver failure on pre-existing chronic liver disease. It is often associated with bacterial infection and high short-term mortality. Experimental models that fully reproduce ACLF are lacking, so too are effective pharmacological therapies for this condition. To mimic ACLF conditions, we developed a severe liverinjury model by combining chronic injury (chronic carbon tetrachloride [CCl4] injection), acute hepatic insult (injection of adouble dose of CCl4), and bacterial infection (intraperitoneal injection of bacteria). Serum and liver samples from patients with ACLF or acute drug-induced liver injury (DILI) were used. Liver injury and regeneration were assessed to ascertain the potential benefits of interleukin-22 (IL-22Fc) administration. This severe liver injury model recapitulated some of the key features of clinical ACLF, including acute-on-chronic liver injury, bacterial infection, multi-organ injury, and high mortality. Liver regeneration in this model was severely impaired because of a shift from the activation of the pro-regenerative IL-6/STAT3 pathway to the anti-regenerative IFN-γ/STAT1 pathway. The impaired IL-6/STAT3 activation was due to the inability of Kupffer cells to produce IL-6; whereas the enhanced STAT1 activation was due to a strong innate immune response and subsequent production of IFN-γ. Compared to patients with DILI, patients with ACLF had higher levels of IFN-γ but lower liver regeneration. IL-22Fc treatment improved survival in ACLF mice by reversing the STAT1/STAT3 pathway imbalance and enhancing expression of many antibacterial genes in a manner involving the anti-apoptotic protein BCL2. Acute-on-chronic liver injury or bacterial infection is associated with impaired liver regeneration due to a shift from a pro-regenerative to an anti-regenerative pathway. IL-22Fc therapy reverses this shift and attenuates bacterial infection, thus IL-22Fc may have therapeutic potential for ACLF treatment. A mouse model combining chronic liver injury, acute hepatic insult, and bacterial infection recapitulates some ofthe key features of acute-on-chronic liver failure (ACLF) in patients. Both fibrosis and bacterial infection contribute to theimpaired regenerative capacity of the liver in patients with ACLF. Herein, we show that IL-22Fc therapy improves ACLF by reprogramming impaired regenerative pathways and attenuating bacterial infection. Thus, it may have therapeutic potential for patients with ACLF.

Consensus guidelines: best practices for detection, assessment and management of suspected acute drug-induced liver injury occurring during clinical trials in adults with chronic cholestatic liver disease.

SummaryBackgroundImproved knowledge of the molecular pathophysiology and immunopathogenesis of cholestatic liver diseases in recent years has led to an increased interest in developing novel therapies. Patients with cholestatic liver disease often require different approaches to assessment and management of suspected drug‐induced liver injury (DILI) compared to those with healthy livers and those with parenchymal liver diseases. At present, there are no regulatory guidelines or society position papers, that systematically address best practices pertaining to detection of DILI in these patients.AimsTo outline best practices for detection, assessment and management of suspected acute DILI during clinical trials in adults with the cholestatic liver diseases – Primary Biliary Cholangitis (PBC) and Primary Sclerosing Cholangitis (PSC).MethodsThis is one of the several papers developed by the IQ DILI Initiative, which is comprised of members from 16 pharmaceutical companies, in collaboration with DILI experts from academia and regulatory agencies. The contents are the result of an extensive literature review, as well as in‐depth discussions among industry, regulatory and academic DILI experts, to achieve consensus recommendations on DILI‐related issues occurring during clinical trials for cholestatic liver diseases.ResultsRecommended best practices are outlined pertaining to hepatic eligibility criteria, monitoring of liver tests, approach to a suspected DILI signal, and hepatic discontinuation rules.ConclusionsThis paper provides a framework for the approach to detection, assessment and management of suspected acute DILI occurring during clinical trials in adults with cholestatic liver disease.

Endoplasmic Reticulum Targeting Ratiometric Fluorescent Probe for Carboxylesterase 2 Detection in Drug-Induced Acute Liver Injury.

Carboxylesterase 2 (CES2), an endoplasmic reticulum (ER) located phase I enzyme, plays a vital role in the metabolism of various endogenous and exogenous substances, and is regarded as an important target for the design of prodrugs. Unfortunately, superior highly selective ER targeting fluorescent probes for monitoring of CES2 are not currently available. Herein, we report an ER targeting CES2 selective and sensitive ratiometric fluorescent probe ERNB based on the ER localizing group p-toluenesulfonamide. ERNB possessed high specificity, sensitivity, and exhibited excellent subcellular localization when compared to commercial ER tracker, and was used to image CES2 in the ER of living cells. Additionally, using ERNB we evaluated the CES2 regulation under d,l-dithiothreitol and tunicamycin-induced ER stress. Furthermore, we determined the down regulation of CES2 activity and expression in the acetaminophen-induced acute liver injury model. On the basis of these results, we conclude that ERNB is a promising tool for highlighting the role of CES2 in the ER and in exploring the role of CES2 in the development of diseases associated with ER stress.

1085 The Use of the Molecular Adsorbent Recirculating System (MARS) in Treatment of Cholestatic Drug Induced Liver Injury

INTRODUCTION: Cholestatic drug induced liver injury (DILI) is a subtype of DILI defined by elevated alkaline phosphatase (ALP) or bilirubin levels from exposure to a drug causing cholestasis. It is a challenging diagnosis with limited treatment options. The molecular adsorbent recirculating system (MARS) allows for hemofiltration of albumin-bound substances that can improve cholestatic hepatitis, pruritus, and hepatic encephalopathy (HE). Here we report six cases of acute cholestatic DILI treated with MARS. METHODS: Patients with cholestatic DILI who underwent MARS were identified at a single institution. Pre-MARS, post-MARS and post hospitalization data on ALP, bilirubin, INR and HE were collected. Completion of MARS therapy was defined as continuous therapy for three to five days. RESULTS: Six cases were identified, one of which progressed to acute liver failure (ALF). Hepatotoxic medications included acetaminophen, phentermine, methimazole, OxyElite and two cases of the anabolic steroid Methyl-1-etiocholenololepietiocholanolone. Mean total bilirubin prior to MARS was 34.5 mg/dl. Over the course of therapy, patients had significant improvement with an average bilirubin of 13.4 mg/dl at completion of MARS and 2.4 mg/dl at follow up. Coagulopathy was seen in the case of ALF from acetaminophen with pre-MARS INR of 1.9 and post-MARS INR of 1.7. This patient also had grade 4 HE prior to MARS with improvement to grade 0 post-MARS. ALP levels were not abnormal and did not change. Clinical improvement in pruritis and jaundice was seen in all cases. CONCLUSION: This case series highlights six patients with cholestatic DILI who had significant improvement in bilirubin, pruritis and jaundice with MARS. This improvement in cholestasis was thought to be due to filtration of bilirubin. Removal of bilirubin also improved jaundice. In conjunction with medical therapy and withdrawal of the offending agent, there was sustained improvement in bilirubin that continued even on outpatient follow up. There was also improvement in pruritis that was refractory to maximal medical therapy. It is unclear which substance is the principal pruritogen associated with cholestasis. However, MARS provided significant symptomatic relief that persisted. In the one case of cholestatic DILI causing acute liver failure, MARS resulted in resolution of HE and served as a bridge to spontaneous hepatic recovery. Our case series shows that MARS is a viable option in treating acute cholestatic liver injury refractory to medical therapy.

Red-Near-Infrared Fluorescent Probe for Time-Resolved in Vivo Alkaline Phosphatase Detection with the Assistance of a Photoresponsive Nanocontainer.

The monitoring of alkaline phosphatase (ALP) activity in different tissues is significant for disease diagnosis and therapy. However, the time-resolved in vivo sensing of ALP activity remained unresolved. Herein, a novel red-near-infrared fluorescent ALP probe (Cl2-BDCM-ALP) based on a dichloro-substituted dicyanomethylene-4H-chromene derivative was designed and synthesized with high fluorescence efficiency and stability under biological pH range. By using Cl2-BDCM-ALP, ALP activity under an acidic microenvironment such as a tumor site can be sensitively imaged, which cannot be achieved by some previously reported ALP probes. By further loading the Cl2-BDCM-ALP into a near-infrared (NIR) light-responsive nanocontainer, time-resolved long-term imaging of ALP activity was facilely achieved with noninvasive NIR light remote control. Time-resolved variation of ALP activity of the drug-induced acute liver injury mice was successfully monitored in vivo for the first time. This strategy holds great promise in the in situ ALP detection under a broad pH range with temporal resolution.

Efficacy and safety of magnesium isoglycyrrhizinate injection in patients with acute drug‐induced liver injury: A phase II trial

Drug-induced liver injury (DILI) is the most common reason for a drug to be withdrawn from the market. Apart from stopping the offending drug, no regimens are available for treating idiosyncratic DILI in clinical practice. We carried out a randomized, double-blind, multidoses, active drug controlled, multicentre phase II trial to assess the safety and efficacy of the study drug, magnesium isoglycyrrhizinate (MgIG), as compared to tiopronin, a standard therapy for DILI in China. The primary outcome was the proportion of alanine aminotransferase (ALT) normalization at week 4 after study drug administration. Logistic regression was used to examine the odds of ALT normalization between low dose (Group A) and high dose (Group B) vs active control (Group C). One hundred and seventy-four eligible subjects were randomized and enrolled into three groups: 59 in group A, 56 in group B and 59 in group C. It was shown that group A and group B lowered ALT level even at early stage of study drug administration; when compared with Group C (61.02%), the proportions of ALT normalization at week 4 were significantly greater in Group A (84.75%, P=.0029) and Group B (85.71%, P=.0037) respectively. The results from the univariate logistic model showed that the odds of ALT normalized among subjects in Group A were about 3.6 times greater (OR=3.55, 95% CI: 1.47-8.57, P=.0049) than subjects in Group C. Similar effect was observed among subjects in Group B (OR=3.83, 95% CI: 1.54-9.55, P=.0039). This trial provided preliminary evidence that MgIG is an effective and safe treatment for patients with acute DILI.

Assessment of Serious Acute and Chronic Idiosyncratic Drug-Induced Liver Injury in Clinical Practice.

Drug-induced liver injury (DILI) is the leading cause of acute liver failure (ALF) in developed countries. The extremely variable phenotype of DILI, both in presentation and in severity, is one of the distinctive characteristics of the disease and one of the major challenges that hepatologists face when assessing hepatotoxicity cases. A new Hy's law that more accurately predicts the risk of ALF related to DILI has been proposed and validated. Other prognostic scoring algorithms for the early identification of DILI patients who may go on to develop ALF have been developed as it is of most clinical relevance to stratify patients for closer monitoring. Recent data indicate that acute DILI often presents a more prolonged resolution or evolves into chronicity at a higher frequency than other forms of acute liver injury. Risk factors for chronicity, specific phenotypes, and histological features are discussed in this study. Biomarkers to predict DILI outcome are in need.

Shorter Therapy Duration in Low-Risk Patients with Acetaminophen Overdose

Acetaminophen overdose is a relatively common cause of acute drug-induced liver injury. Early administration of N-acetylcysteine (NAC) within 8 hours

Consensus: guidelines: best practices for detection, assessment and management of suspected acute drug-induced liver injury during clinical trials in patients with nonalcoholic steatohepatitis.

SummaryBackgroundThe last decade has seen a rapid growth in the number of clinical trials enrolling patients with nonalcoholic fatty liver disease and nonalcoholic steatohepatitis (NASH). Due to the underlying chronic liver disease, patients with NASH often require different approaches to the assessment and management of suspected drug‐induced liver injury (DILI) compared to patients with healthy livers. However, currently no regulatory guidelines or position papers systematically address best practices pertaining to DILI in NASH clinical trials.AimsThis publication focuses on best practices concerning the detection, monitoring, diagnosis and management of suspected acute DILI during clinical trials in patients with NASH.MethodsThis is one of several papers developed by the IQ DILI Initiative, comprised of members from 15 pharmaceutical companies, in collaboration with DILI experts from academia and regulatory agencies. This paper is based on extensive literature review, and discussions between industry members with expertise in drug safety and DILI experts from outside industry to achieve consensus on common questions related to this topic.ResultsRecommended best practices are outlined pertaining to hepatic inclusion and exclusion criteria, monitoring of liver tests, DILI detection, approach to a suspected DILI signal, causality assessment and hepatic discontinuation rules.ConclusionsThis paper provides a framework for the approach to assessment and management of suspected acute DILI during clinical trials in patients with NASH.

Protective effect of Fuzheng Yanggan Mixture on drug-induced liver injury

The model of drug-induced liver injury (DILI) induced by acetaminophen (APAP) in mice was established to investigate the anti-oxidation and anti-ferroptosis mechanisms of Fuzheng Yanggan Mixture on DILI. C57BL/6 mice were randomly divided into five groups: control group, model group, positive group, and low and high-dose Fuzheng Yanggan Mixture groups (0.12, 0.24 g·kg⁻¹). Mice were intragastrically administration with Fuzheng Yanggan Mixture (0.12, 0.24 g·kg⁻¹) once per day for 21 consecutive days, and at the same time, mice were weighted every day. The mice were injected intraperitoneally with 600 mg·kg⁻¹ of APAP to establish a mouse model of acute DILI after 16 h from the last administration of Fuzheng Yanggan Mixture. After 6 h from APAP challenge, the experimental animals were weighted and sacrificed to collect blood and liver tissue samples. And then, the effect of Fuzheng Yanggan Mixture on liver weight and the liver weight ratio of mice were examined; the content of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in the serum and the level of malondialdehyde (MDA), glutathione (GSH) and nicotinamide adenine dinucleotide phosphate (NADPH) in the liver tissue were measured. Prostaglandinendoperoxide synthase 2(ptgs2) mRNA level in liver tissues was detected by Q-PCR, and protein expression levels of SLC7A11 and GPX4 in liver tissues were detected by Western blot. Moreover, HE staining, immunohistochemical assay and TUNEL staining were used to observe pathological changes of the liver tissue sections. It is found that Fuzheng Yanggan Mixture could relieve APAP-induced liver enlargement and inhibit hepatic weight ratio increase. Compared with model group, the mice in Fuzheng Yanggan Mixture groups showed decreases in the content of ALT, AST and MDA, and increases in the content of GSH and NADPH. What is more, Fuzheng Yanggan Mixture could down-regulate ptgs2 mRNA level and up-regulate SLC7A11 and GPX4 protein levels. All of the results lead to a conclusion that Fuzheng Yanggan Mixture plays a protective effect on DILI in mice, which may be associated with the inhibition of ferroptosis.

Cytokine profiles in acute liver injury-Results from the US Drug-Induced Liver Injury Network (DILIN) and the Acute Liver Failure Study Group.

Changes in levels of cytokines and chemokines have been proposed as possible biomarkers of tissue injury, including liver injury due to drugs. Recently, in acute drug-induced liver injury (DILI), we showed that 19 of 27 immune analytes were differentially expressed and that disparate patterns of immune responses were evident. Lower values of serum albumin (< 2.8 g/dL) and lower levels of only four analytes, namely, IL-9, IL-17, PDGF-bb, and RANTES, were highly predictive of early death [accuracy = 96%]. The goals of this study were to assess levels of the same 27 immune analytes in larger numbers of subjects to learn whether the earlier findings would be confirmed in new and larger cohorts of subjects, compared with a new cohort of healthy controls. We studied 127 subjects with acute DILI enrolled into the US DILIN. We also studied 118 subjects with severe acute liver injury of diverse etiologies, enrolled into the ALF SG registry of subjects. Controls comprised 63 de-identified subjects with no history of liver disease and normal liver tests. Analytes associated with poor outcomes [death before 6 months, n = 32 of the total of 232 non-acetaminophen (Apap) subjects], were lower serum albumin [2.6 vs 3.0 g/dL] and RANTES [6,458 vs 8,999 pg/mL] but higher levels of IL-6 [41 vs 18], IL-8 [78 vs 48], and MELD scores [30 vs 24]. Similar patterns were observed for outcome of death/liver transplant within 6 months. A model that included only serum albumin < 2.8 g/dL and RANTES below its median value of 11,349 had 83% (or 81%) accuracy for predicting early death (or early death/liver transplant) in 127 subjects from DILIN. No patterns of serum immune analytes were reflective of the etiologies of acute liver failure, but there were cytokine patterns that predicted prognosis in both acute DILI and ALF.

Uncommon Presentations of Idiosyncratic Drug-Induced Liver Injury

Idiosyncratic drug-induced liver injury (DILI) typically presents acutely with liver test abnormalities, sometimes with associated symptoms of abdominal pain, nausea, vomiting, jaundice, fevers, and rash. Histologic abnormalities in such cases of DILI typically range from lobular or portal hepatitis to hepatocyte necrosis. However, sometimes the drug-related liver injuries present with clinical and/or histological features atypical of garden variety DILI and they may be related to uncommon mechanisms of injury, histologic features, or clinical presentation. Multiple agents or classes of agents can result in uncommon forms of liver injury that are phenotypically unique and differ from commonly recognized acute DILI. These include unusual presentations of drugs commonly associated with typical acute DILI, such as drug-induced autoimmune hepatitis. Atypical DILI also includes histologically atypical manifestations of DILI, such as nodular regenerative hyperplasia, sinusoidal obstruction syndrome, granulomatous hepatitis, and steatosis/steatohepatitis. Atypical DILI encompasses recognized patterns of injury associated with specific agents or drug classes. These can manifest by atypical biochemical, clinical, and histopathological signatures. An understanding of these types of liver injury is important for the timely recognition of such atypical DILI.

Chronic liver injury induced by drugs and toxins.

Drug-induced liver injury (DILI) occurs in a small fraction of individuals exposed to drugs, herbs or dietary supplements and is a relatively rare diagnosis compared with other liver disorders. DILI can be serious, resulting in hospitalization and even life-threatening liver failure, death or need for liver transplantation. Toxic liver damage usually presents as an acute hepatitis viral-like syndrome or as an acute cholestasis that resolves upon drug discontinuation. However, un-resolving chronic outcome after acute DILI can ensue in some subjects, the mechanisms and risk factors for this particular evolution being yet scarcely known. Furthermore, the definition of chronicity after acute DILI is controversial, regarding both the time frame of liver injury persistence and the magnitude of the abnormalities required. Besides this, in some instances the phenotypes and pathological manifestations are those of chronic liver disease at the time of DILI diagnosis. These include non-alcoholic fatty liver disease, vascular lesions, drug-induced autoimmune hepatitis, chronic cholestasis leading to vanishing bile duct syndrome and even cirrhosis, and some drugs such as amiodarone or methotrexate have been frequently implicated in some of these forms of chronic DILI. In addition, all of these DILI phenotypes can be indistinguishable from those related to other etiologies, making the diagnosis particularly challenging. In this manuscript we have critically reviewed the more recent data on chronicity in DILI with a particular focus on the epidemiology, mechanisms and risk factors of atypical chronic DILI phenotypes.

Noninvasive Imaging of Drug-Induced Liver Injury with 18F-DFA PET.

Drug-induced liver failure is a significant indication for a liver transplant, and unexpected liver toxicity is a major reason that otherwise effective therapies are removed from the market. Various methods exist for monitoring liver injury but are often inadequate to predict liver failure. New diagnostic tools are needed. Methods: We evaluate in a preclinical model whether 18F-2-deoxy-2-fluoroarabinose (18F-DFA), a PET radiotracer that measures the ribose salvage pathway, can be used to monitor acetaminophen-induced liver injury and failure. Mice treated with vehicle, 100, 300, or 500 mg/kg acetaminophen for 7 or 21 h were imaged with 18F-FDG and 18F-DFA PET. Hepatic radiotracer accumulation was correlated to survival and percentage of nonnecrotic tissue in the liver. Mice treated with acetaminophen and vehicle or N-acetylcysteine were imaged with 18F-DFA PET. 18F-DFA accumulation was evaluated in human hepatocytes engrafted into the mouse liver. Results: We show that hepatic 18F-DFA accumulation is 49%-52% lower in mice treated with high-dose acetaminophen than in mice treated with low-dose acetaminophen or vehicle. Under these same conditions, hepatic 18F-FDG accumulation was unaffected. At 21 h after acetaminophen treatment, hepatic 18F-DFA accumulation can distinguish mice that will succumb to the liver injury from those that will survive it (6.2 vs. 9.7 signal to background, respectively). Hepatic 18F-DFA accumulation in this model provides a tomographic representation of hepatocyte density in the liver, with a R2 between hepatic 18F-DFA accumulation and percentage of nonnecrotic tissue of 0.70. PET imaging with 18F-DFA can be used to distinguish effective from ineffective resolution of acetaminophen-induced liver injury with N-acetylcysteine (15.6 vs. 6.2 signal to background, respectively). Human hepatocytes, in culture or engrafted into a mouse liver, have levels of ribose salvage activity similar to those of mouse hepatocytes. Conclusion: Our findings suggest that PET imaging with 18F-DFA can be used to visualize and quantify drug-induced acute liver injury and may provide information on the progression from liver injury to hepatic failure.