IL-4 mediates dicloxacillin-induced liver injury in mice

Serum interleukin-4 is elevated in clinical drug-induced liver injury

BACKGROUND

Drug-induced liver injury (DILI) remains a challenging diagnosis due to an absence of specific biomarkers. DILI due to volatile anaesthetics (VA-DILI) is characterised by trifluoroacetyl and CYP2E1 antibodies, but may not be seen for weeks after injury. Interleukin-4 (IL-4) may be involved in the production of these antibodies and may serve as a clinically useful early biomarker of VA-DILI.

AIM

To prospectively compare serum IL-4 levels between patients who develop VA-DILI and controls following exposure to the volatile anaesthetic.

METHODS

A nested case-control study of patients exposed to VA during surgery was conducted. Thirteen DILI cases were identified from the original cohort, and 26 controls were matched according to age, sex and VA agent. Serum samples were collected before and 48-96 h after VA exposure, and analysed for IL-4 using quantitative enzyme-linked immunosorbent assay techniques.

RESULTS

There was a statistically significant difference in serum IL-4 in post-VA samples between DILI cases and controls (control: 0.030 pg/mL, IQR: 0.030 - 0.030 pg/mL vs DILI: 0.044 pg/mL, IQR: 0.030 - 0.061 pg/mL; p = 0.039). A greater proportion of DILI cases had post-VA IL-4 levels above the assay lower limit of detection compared to controls (control: 23% vs DILI: 69%; p = 0.013).

CONCLUSION

IL-4 is a potential biomarker of DILI. Clinical diagnosis and understanding of DILI disease mechanisms may be improved by further investigation of novel biomarkers, and this IL-4 signal in serum is important as proof of concept for prospective study designs.

Risk evaluation of ampicillin/sulbactam-induced liver injury based on albumin-bilirubin score

BACKGROUND

Drug-induced liver injury (DILI) is an adverse reaction caused by ampicillin/sulbactam (ABPC/SBT). The albumin-bilirubin (ALBI) score is an index of hepatic functional reserve. However, the relationship between ABPC/SBT-induced DILI and ALBI score remains unknown; therefore, we aimed to elucidate the risk of ABPC/SBT-induced DILI based on the ALBI score.

METHODS

This was a single-center, retrospective, case-control study using electronic medical records. A total of 380 patients were enrolled in the present study, and the primary outcome was ABPC/SBT-induced DILI. The ALBI score was calculated using serum albumin and total bilirubin levels. In addition, we performed COX regression analysis using age ≥75 years, dose ≥9 g/day, alanine aminotransferase (ALT) ≥21 IU/L, and ALBI score ≥-2.00 as covariates. We also performed 1:1 propensity score matching between non-DILI and DILI groups.

RESULTS

The incidence of DILI was 9.5% (36/380). According to COX regression analysis, the adjusted hazard ratio for ABPC/SBT-induced DILI with an ALBI score ≥-2.00 was 2.55 (95% confidence interval: 1.256-5.191, P = 0.010), suggesting that patients with baseline ALBI score ≥-2.00 may be at high risk for ABPC/SBT-induced DILI. However, significant differences were not observed in cumulative risk for DILI between non-DILI and DILI patients regarding an ALBI score ≥-2.00 after propensity score matching (P = 0.146).

CONCLUSION

These findings suggest that ALBI score may be a simple and potentially useful index for predicting ABPC/SBT-induced DILI. In patients with an ALBI score ≥-2.00, frequent liver function monitoring should be considered to prevent ABPC/SBT-induced DILI.

Characterising the Intestinal Bacterial and Fungal Microbiome Associated With Different Cytokine Profiles in Two Bifidobacterium strains Pre-Treated Rats With D-Galactosamine-Induced Liver Injury

Multiple probiotics have protective effects against different types of liver injury. Different intestinal microbes could be beneficial to the protective effects of the probiotics on the treated cohorts in different aspects. The current study was designed to determine the intestinal bacterial and fungal microbiome associated with different cytokine profiles in the Bifidobacterium pseudocatenulatum LI09 and Bifidobacterium catenulatum LI10 pretreated rats with D-galactosamine-induced liver injury. In this study, partition around medoids clustering analysis determined two distinct cytokine profiles (i.e., CP1 and CP2) comprising the same 11 cytokines but with different levels among the LI09, LI10, positive control (PC), and negative control (NC) cohorts. All rats in PC and NC cohorts were determined with CP1 and CP2, respectively, while the rats with CP1 in LI09 and LI10 cohorts had more severe liver injury than those with CP2, suggesting that CP2 represented better immune status and was the “better cytokine profile” in this study. PERMANOVA analyses showed that the compositions of both bacterial and fungal microbiome were different in the LI10 cohorts with different cytokine profiles, while the same compositions were similar between LI09 cohorts with different cytokine profiles. The phylotype abundances of both bacteria and fungi were different in the rats with different cytokine profiles in LI09 or LI10 cohorts according to similarity percentage (SIMPER) analyses results. At the composition level, multiple microbes were associated with different cytokine profiles in LI09 or LI10 cohorts, among which Flavonifractor and Penicillium were the bacterium and fungus most associated with LI09 cohort with CP2, while Parabacteroides and Aspergillus were the bacterium and fungus most associated with LI10 cohort with CP2. These microbes were determined to influence the cytokine profiles of the corresponding cohorts. At the structure level, Corynebacterium and Cephalotrichiella were determined as the two most powerful gatekeepers in the microbiome networks of LI09 cohort CP2, while Pseudoflavonifractor was the most powerful gatekeeper in LI10 cohort with CP2. These identified intestinal microbes were likely to be beneficial to the effect of probiotic Bifidobacterium on the immunity improvement of the treated cohorts, and they could be potential microbial biomarkers assisting with the evaluation of immune status of probiotics-treated cohorts.

Drug-induced liver injury and prospect of cytokine based therapy; A focus on IL-2 based therapies

Drug-induced liver injury (DILI) is one of the most frequent sources of liver failure and the leading cause of liver transplant. Common non-prescription medications such as non-steroidal anti-inflammatory drugs (NSAIDs), acetaminophen, and other prescription drugs when taken at more than the recommended doses may lead to DILI. The severity of DILI is affected by factors such as age, ethnicity, race, gender, nutritional status, on-going liver diseases, renal function, pregnancy, alcohol consumption, and drug-drug interactions. Characteristics of DILI-associated inflammation include apoptosis and necrosis of hepatocytes and hepatic infiltration of pro-inflammatory immune cells. If untreated or if the inflammation continues, DILI and associated hepatic inflammation may lead to development of hepatocarcinoma. The therapeutic approach for DILI-associated hepatic inflammation depends on whether the inflammation is acute or chronic. Discontinuing the causative medication, vaccination, and special dietary supplementation are some of the conventional approaches to treat DILI. In this review, we discuss a concise overview of DILI-associated liver complications, and current therapeutic options with special emphasis on biologics including the scope of cytokine therapy in hepatic repair and resolution of inflammation caused by over- the-counter (OTC) or prescription drugs.

Susceptibility-Related Cytokine Panel for Prediction of Polygonum multiflorum-Induced Hepatotoxicity in Humans

BACKGROUND

Drug-induced liver injury is a common adverse effect in clinical practice, with severe cases resulting in liver failure and even death. Identification and prediction of individuals susceptible to idiosyncratic DILI continues to remain a challenge.

METHODS

In this study, we report that cytokines in human serum can be used to identify and predict individuals susceptible to Polygonum multiflorum-induced DILI (PM-DILI) in retrospective and prospective cohort studies.

FINDINGS

In the retrospective pilot study, we compared serum cytokine expression profiles of the PM-DILI group (n=10) and the PM-Tolerant group (n=12) and found 10 cytokines with significant differences. In the replication cohort study, differences in the 10 cytokines between PM-DILI (n =11) and PM-Tolerant (n=13) groups were verified. Among them, 6 cytokines showed no significant differences at two time points, including liver injury and recovery stage of PM-DILI, suggesting that these 6 cytokines have no correlation with PM-DILI, however, they may be related to susceptibility. Furthermore, all the retrospective cohorts were combined, and a PM-DILI susceptibility prediction model was built by screening the 6 cytokines. The combination of (TNF-α and CCL-2) or VEGF showed the highest sensitivity and specificity. Finally, the efficacy of the above 3 cytokine combination models in predicting PM-DILI-susceptible individuals was verified before PM exposure in another independent prospective cohort (n=24), with sensitivity and specificity of 66.7% and 83.3%, respectively.

CONCLUSION

This proof-of-concept study demonstrates that the serum cytokine combination reflecting dysimmunity could be used as a new method to predict PM-DILI, thus providing a new perspective for improving the clinical management of IDILI.

Models of Idiosyncratic Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is a leading cause of attrition during the early and late stages of drug development and after a drug is marketed. DILI is generally classified as either intrinsic or idiosyncratic. Intrinsic DILI is dose dependent and predictable (e.g., acetaminophen toxicity). However, predicting the occurrence of idiosyncratic DILI, which has a very low incidence and is associated with severe liver damage, is difficult because of its complex nature and the poor understanding of its mechanism. Considering drug metabolism and pharmacokinetics, we established experimental animal models of DILI for 14 clinical drugs that cause idiosyncratic DILI in humans, which is characterized by the formation of reactive metabolites and the involvement of both innate and adaptive immunity. On the basis of the biomarker data obtained from the animal models, we developed a cell-based assay system that predicts the potential risks of drugs for inducing DILI. These findings increase our understanding of the mechanisms of DILI and may help predict and prevent idiosyncratic DILI due to certain drugs.

[Recent advances in evaluation studies for drug-induced liver injury]

With the recent progress in drug metabolism and pharmacokinetics studies, the attrition due to pharmacokinetics in clinical trials and post-marketing was reduced to less than 1%. On the other hand, attrition of clinical trials due to adverse effects and toxicity has remained high. In particular, drug-induced liver injury (DILI) is a major cause of discontinuation of clinical trials and withdrawal of drug candidates after marketing. DILI is roughly divided into intrinsic and idiosyncratic. The former is relatively easy to predict its onset in preclinical drug development, but the latter's onset mechanism is still unknown and its onset prediction is difficult. We are investigating to develop an experimental animal model of idiosyncratic DILI (iDILI), clarify the pathogenic mechanism, and apply the obtained biomarker information to the establishment of an in vitro cell-based prediction test system. In this paper, we will introduce various animal models of iDILI, present status of pathogenic mechanism study, and classification of iDILI drugs, and introduce the recent progress of in vitro cell-based prediction test system and new causative factors of iDILI.

What have we learned from animal models of idiosyncratic, drug-induced liver injury?

INTRODUCTION

Idiosyncratic, drug-induced liver injury (IDILI) continues to plague patients and restrict the use of drugs that are pharmacologically effective. Mechanisms of IDILI are incompletely understood, and a better understanding would reduce speculation and could help to identify safer drug candidates preclinically. Animal models have the potential to enhance knowledge of mechanisms of IDILI.

AREAS COVERED

Numerous hypotheses have emerged to explain IDILI pathogenesis, many of which center on the roles of the innate and/or adaptive immune systems. Animal models based on these hypotheses are reviewed in the context of their contributions to understanding of IDILI and their limitations.

EXPERT OPINION

Animal models of IDILI based on an activated adaptive immune system have to date failed to reproduce major liver injury that is of most concern clinically. The only models that have so far resulted in pronounced liver injury are based on the multiple determinant hypothesis or the inflammatory stress hypothesis. The liver pathogenesis in IDILI animal models involves various leukocytes and immune mediators such as cytokines. Insights from animal models are changing the way we view IDILI pathogenesis and are leading to better approaches to preclinical prediction of IDILI potential of new drug candidates.

Establishment of a mouse model of troglitazone-induced liver injury and analysis of its hepatotoxic mechanism

Drug-induced liver injury is a major problem in drug development and clinical drug therapy. Troglitazone (TGZ), a thiazolidinedione antidiabetic drug for the treatment of type II diabetes mellitus, was found to induce rare idiosyncratic severe liver injury in patients, which led to its withdrawal in 2000. However, in normal experimental animals in vivo TGZ has never induced liver injury. To explore TGZ hepatotoxic mechanism, we established a novel mouse model of TGZ-induced liver injury. Administration of BALB/c female mice with a single intraperitoneal TGZ dose (300 mg/kg) significantly elevated alanine aminotransferase and aspartate aminotransferase levels 6 hours after the treatment. The ratio of oxidative stress marker glutathione/disulfide glutathione was significantly decreased. The increased hepatic mRNA levels of inflammation- and oxidative stress-related factors were observed in TGZ-treated mice. Subsequently, hepatic transcriptome profiles of TGZ-exposed liver were compared with those of non-hepatotoxic rosiglitazone. The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway was activated in TGZ-induced liver injury. The activation of the JAK/STAT pathway promoted phosphorylation of STAT3 in TGZ-treated mice. Consequently, upregulation of STAT3 activation increased mRNA levels of its downstream genes. In conclusion, a single intraperitoneal dose of TGZ exposure could induce liver injury in BALB/c female mice and, by a hepatic transcriptomic analysis, we found that the activation of JAK/STAT pathway might be related to TGZ-induced hepatotoxicity.

Strain and interindividual differences in lamotrigine-induced liver injury in mice

Lamotrigine (LTG) has been widely prescribed as an antipsychotic drug, although it causes idiosyncratic drug-induced liver injury in humans. LTG is mainly metabolized by UDP-glucuronosyltransferase, while LTG undergoes bioactivation by cytochrome P450 to a reactive metabolite; it is subsequently conjugated with glutathione, suggesting that reactive metabolite would be one of the causes for LTG-induced liver injury. However, there is little information regarding the mechanism of LTG-induced liver injury in both humans and rodents. In this study, we established an LTG-induced liver injury mouse model through co-administration with LTG and a glutathione synthesis inhibitor, l-buthionine-(S,R)-sulfoximine. We found an increase in alanine aminotransferase (ALT) levels (>10 000 U/L) in C57BL/6J mice, with apparent interindividual differences. On the other hand, a drastic increase in ALT was not noted in BALB/c mice, suggesting that the initiation mechanism would be different between the two strains. To examine the cause of interindividual differences, C57BL/6J mice that were co-administered LTG and l-buthionine-(S,R)-sulfoximine were categorized into three groups based on ALT values: no-responder (ALT <100 U/L), low-responder (100 U/L < ALT < 1000 U/L) and high-responder (ALT >1000 U/L). In the high-responder group, induction of hepatic oxidative stress, inflammation and damage-associated molecular pattern molecules in mRNA was associated with vacuolation and karyorrhexis in hepatocytes. In conclusion, we demonstrated that LTG showed apparent strain and interindividual differences in liver injuries from the aspects of initiation and exacerbation mechanisms. These results would support interpretation of the mechanism of LTG-induced liver injury observed in humans.

Role of cytochrome P450-mediated metabolism and involvement of reactive metabolite formations on antiepileptic drug-induced liver injuries

Several drugs have been withdrawn from the market or restricted to avoid unexpected adverse outcomes. Drug-induced liver injury (DILI) is a serious issue for drug development. Among DILIs, idiosyncratic DILIs have been a serious problem in drug development and clinical uses. Idiosyncratic DILI is most often unrelated to pharmacological effects or the dosing amount of a drug. The number of drugs that cause idiosyncratic DILI continue to grow in part because no practical preclinical tests have emerged that can identify drug candidates with the potential for developing idiosyncratic DILIs. Nevertheless, the implications of drug metabolism-related factors and immune-related factors on idiosyncratic DILIs has not been fully clarified because this toxicity can not be reproduced in animals. Therefore, accumulated evidence for the mechanisms of the idiosyncratic toxicity has been limited to only in vitro studies. This review describes current knowledge of the effects of cytochrome P450 (CYP)-mediated metabolism and its detoxification abilities based on studies of idiosyncratic DILI animal models developed recently. This review also focused on antiepileptic drugs, phenytoin (diphenyl hydantoin, DPH) and carbamazepine (CBZ), which have rarely caused severe adverse reactions, such as fulminant hepatitis, and have been recognized as sources of idiosyncratic DILI. The studies of animal models of idiosyncratic DILIs have produced new knowledge of chronic administration, CYP inductions/inhibitions, glutathione contents, and immune-related factors for the initiation of idiosyncratic DILIs. Considering changes in the drug metabolic profile and detoxification abilities, idiosyncratic DILIs caused by antiepileptic drugs will lead to understanding the mechanisms of these DILIs.

The in silico identification of human bile salt export pump (ABCB11) inhibitors associated with cholestatic drug-induced liver injury

Drug-induced liver injury (DILI) is one of the major causes of drug attrition and failure. Currently, there is increasing evidence that direct inhibition of the human bile salt export pump (BSEP/ABCB11) by drugs and/or metabolites is one of the most important mechanisms of cholestatic DILI. In the present study, we employ two in silico methods, random forest (RF) and the pharmacophore method, to recognize potential BSEP inhibitors that could cause cholestatic DILI, with the aim of mitigating the risk of cholestatic DILI to some extent. The RF model achieved the best prediction performance, producing AUC (area under receiver operating characteristic curve) values of 0.901, 0.929 and 0.996 for leave-one-out cross-validation, the test set and the external test set, respectively, indicating that the built RF model has a satisfactory identification ability. As a complement to the RF model, the pharmacophore model was also built and was proved to be reliable with good predictive performance based on the internal and external validation results. Further analysis indicates that hydrophobicity, molecular size and polarity are important factors that influence the inhibitory activity of BSEP. Furthermore, the two models are applied to screen FDA-approved small molecule drugs, among which the drugs with the potential risk of cholestatic DILI are reported. In conclusion, the RF and pharmacophore models that we present can be considered as integrated screening tools to indicate the potential risk of cholestatic DILI by inhibition of BSEP.

[Establishment of animal models of drug-induced liver injury and analysis of possible mechanisms]

Drug-induced liver injury (DILI) is one of leading causes of attrition during both early and late stages of drug development and postmarketing. DILI is generally classified into the intrinsic and idiosyncratic types. Intrinsic DILI is dose dependent and predictable as exemplified by acetaminophen toxicity. However, the occurrence of idiosyncratic DILI with very low incidence and severe liver damage is difficult to predict because of the complex nature of DILI and poor understanding of its mechanism. In this review, we summarize current knowledge and our accumulated experimental findings on the pathogenic mechanisms of DILI focusing on the reactive metabolites of drugs formed by drug-metabolizing enzymes and immune- and inflammation-related responses. Considering drug metabolism and pharmacokinetics, we have established nonclinical animal models of DILI for 10 types of clinical drug known to cause idiosyncratic DILI in humans. Using animal models, it has been shown that the formation of reactive metabolites and both innate and adaptive immunity are involved in the pathogenesis of drug hepatotoxicity. Based on information on biomarkers obtained from animal models, we developed a cell-based system that predicts the potential DILI risks of drugs. The results of these studies increased our understanding of the mechanisms of DILI and help to predict and prevent idiosyncratic DILI caused by drug candidates.

[Recent findings regarding the mechanism of idiosyncratic drug toxicity]

Animal experiments cannot predict the probability of idiosyncratic drug toxicity; consequently, an important goal of the pharmaceutical industry is to develop a new methodology for preventing this form of drug reaction. Although the mechanism remains unclear, immune reactions are likely involved in the toxic processes underlying idiosyncratic drug toxicity: the drug is first activated into a chemically reactive metabolite that binds covalently to proteins and then acts as an immunogen. Therefore, screening tests to detect chemically reactive metabolites are conducted early during drug development and typically involve trapping with glutathione. More quantitative methods are then used in a later stage of drug development and frequently employ (14)Cor (3)H-labeled compounds. It has recently been demonstrated that a zone classification system can be used to separate risky drugs from likely safe drugs: by plotting the amount of each protein-bound reactive metabolite in vitro against the dose levels in vivo, the risk associated with each drug candidate can be assessed. A mechanism for idiosyncratic drug-induced hepatotoxicity was proposed by analogy to virus-induced hepatitis, in which cytotoxic T lymphocytes play an important role. This mechanism suggests that polymorphism in human leukocyte antigens is involved in idiosyncrasy, and a strong correlation with a specific genotype of human leukocyte antigens has been found in many cases of idiosyncratic drug toxicity. Therefore, gene biomarkers hold promise for reducing the clinical risk and prolonging the life cycle of otherwise useful drugs.

Characterization of hepatic lipid profiles in a mouse model with nonalcoholic steatohepatitis and subsequent fibrosis

Nonalcoholic steatohepatitis (NASH) is a major health problem since it often leads to hepatocellular carcinoma. However, the underlying mechanisms of NASH development and subsequent fibrosis have yet to be clarified. We compared comprehensive lipidomic profiles between mice with high fat diet (HFD)-induced steatosis and STAM mice with NASH and subsequent fibrosis. The STAM mouse is a model that demonstrates NASH progression resembling the disease in humans: STAM mice manifest NASH at 8 weeks, which progresses to fibrosis at 12 weeks, and finally develop hepatocellular carcinoma. Overall, 250 lipid molecules were detected in the liver using liquid chromatography-mass spectrometry. We found that STAM mice with NASH presented a significantly higher abundance of sphingolipids and lower levels of triacylglycerols than the HFD-fed control mice. The abundance of certain fatty acids in phospholipid side chains was also significantly different between STAM and control mice, although global levels of phosphatidylcholines and phosphatidylethanolamines were comparable. Finally, increase in levels of acylcarnitines and some diacylglycerols was observed in STAM mice toward the fibrosis stage, but not in age-matched control mice. Our study provides insights into the lipid status of the steatotic, NASH, and fibrotic liver that would help elucidate the molecular pathophysiology of NASH progression.

Immunological aspects of drug-induced liver injury

Drug induced liver injury (DILI) is a common condition of increasing incidence. Many environmental and genetic factors are involved in its pathogenesis, and immunological mechanisms are also thought to contribute to the development and severity of DILI. This review summarizes current understanding of the immunological pathogenesis of DILI and discusses the perspective for clinical applications.

Thymic stromal lymphopoietin and interleukin-4 mediate the pathogenesis of halothane-induced liver injury in mice

Liver eosinophilia has been associated with incidences of drug-induced liver injury (DILI) for more than 50 years, although its role in this disease has remained largely unknown. In this regard, it was recently shown that eosinophils played a pathogenic role in a mouse model of halothane-induced liver injury (HILI). However, the signaling events that drove hepatic expression of eosinophil-associated chemokines, eotaxins, eosinophil infiltration, and subsequent HILI were unclear. We now provide evidence implicating hepatic epithelial-derived cytokine thymic stromal lymphopoietin (TSLP) and type 2 immunity, in particular, interleukin-4 (IL-4) production, in mediating hepatic eosinophilia and injury during HILI. TSLP was constitutively expressed by mouse hepatocytes and increased during HILI. Moreover, the severity of HILI was reduced in mice deficient in either the TSLP receptor (TSLPR) or IL-4 and was accompanied by decreases in serum levels of eotaxins and hepatic eosinophilia. Similarly, concanavalin A-induced liver injury, where type 2 cytokines and eosinophils play a significant role in its pathogenesis, was also reduced in TSLPR-deficient mice. Studies in vitro revealed that mouse and human hepatocytes produce TSLP and eotaxins in response to treatment with combinations of IL-4 and proinflammatory cytokines IL-1β and tumor necrosis factor alpha.

CONCLUSION

This report provides the first evidence implicating roles for hepatic TSLP signaling, type 2 immunity, and eosinophilia in mediating liver injury caused by a drug.

Drug-induced hepatotoxicity: metabolic, genetic and immunological basis

Drug-induced hepatotoxicity is a significant cause of acute liver failure and is usually the primary reason that therapeutic drugs are removed from the commercial market. Multiple mechanisms can culminate in drug hepatotoxicity. Metabolism, genetics and immunology separately and in concert play distinct and overlapping roles in this process. This review will cover papers we feel have addressed these mechanisms of drug-induced hepatotoxicity in adults following the consumption of commonly used medications. The aim is to generate discussion around "trigger point" papers where the investigators generated new science or provided additional contribution to existing science. Hopefully these discussions will assist in uncovering key areas that need further attention.

Development of a cell-based assay system considering drug metabolism and immune- and inflammatory-related factors for the risk assessment of drug-induced liver injury

Drug-induced liver injury (DILI) is a major safety concern in drug development and clinical pharmacotherapy. However, prediction of DILI is difficult because the underlying mechanisms are not fully understood. To establish a novel cell-based screening system to suggest drugs with hepatotoxic potential in preclinical drug development, comprehensive gene expression analyses during in vivo DILI are necessary. Using in vivo mouse DILI models and 4 sets of hepatotoxic positive and non-hepatotoxic drugs, we found that the hepatic mRNA levels of S100A8; S100A9; "NATCH, LRR, and pyrin domain-containing protein 3" (NALP3); interleukin (IL)-1β; and the receptor for advanced glycation endproducts (RAGE) were commonly increased in hepatotoxic drug-administered mice compared to non-hepatotoxic drug-administered mice. To clarify whether these 5 in vivo biomarkers can be applied to a cell-based screening system, we adapted human liver microsomes (HLM) in the presence of NADPH to assess the metabolic activation reaction, and we also adapted human monocytic leukemia cells HL-60, K562, KG-1 and THP-1 to assess the effects on mRNA expression of immune- and inflammatory-related factors. We investigated 30 clinical drugs with different safety profiles with regard to DILI and found that the total sum score of gene expression levels of S100A8, S100A9, RAGE, NALP3 and IL-1β mRNA in HL-60 or K562 cells incubated with HLM, could identify drugs at high risk for hepatotoxicity. We proposed the use of the total sum score of gene expression level for assessing metabolic activation by drug-metabolizing enzymes and immune- and inflammatory-related factors for the risk assessment of DILI in preclinical drug development.

Involvement of miRNAs in the early phase of halothane-induced liver injury

MicroRNAs (miRNA) form a class of small non-coding RNA molecules that negatively regulate gene expression. Most cellular pathways are modulated by miRNAs. However, the pathophysiological role of miRNAs during drug-induced liver injury (DILI) remains largely unknown. In this study, the possible involvement of miRNAs in DILI caused by the hepatotoxic drug halothane (HAL) was investigated. Toward this purpose, miRNA microarray studies of HAL-induced liver injury were performed in mice at five different time points up to 24h after dosing. To exclude any pharmacological effects on miRNA expression, isoflurane was used as a low hepatotoxic drug because it is structurally similar to HAL. Approximately 30-50% of the miRNA expression levels changed more than two-fold at every time point. In silico biological pathway analysis was performed to predict the targeted genes. Consequently, the miRNA gene down-regulation that occurred 1h after HAL administration was primarily related to inflammation, immune systems and liver injury. Based on additional in silico analyses, we identified miR-106b. Subsequently target of miR-106b was investigated using liver samples from mice with HAL-induced liver injury. Among the predicted targets, we discovered that a signal transducer and activator of transcription 3 (STAT3) was particularly up-regulated beginning during the early phase of HAL-induced liver injury. Collectively, the suppressed miR-106b expression, as well as the subsequent up-regulation of STAT3, was critical for the pathogenesis of HAL-induced liver injury.

Profiles of serum cytokines in acute drug-induced liver injury and their prognostic significance

Drug-induced liver injury (DILI) is the most common cause of acute liver failure in the United-States. The aim of the study was to describe serum immune profiles associated with acute DILI, to investigate whether there are profiles associated with clinical features or types of DILI and/or with prognosis, and to assess temporal changes in levels. Twenty-seven immune analytes were measured in the sera of 78 DILI subjects in the Drug-Induced Liver Injury Network (DILIN) and compared with 40 healthy controls. Immune analytes (14 cytokines, 7 chemokines and 6 growth factors) were measured by BioPlex multiplex ELISA at DILI onset and after 6 months. A modeling process utilizing immune principles was used to select a final set of variables among 27 immune analytes and several additional clinical lab values for prediction of early death (within 6 months of DILI onset). Nineteen of the 27 immune analytes were differentially expressed among healthy control, DILI onset and 6-month cohorts. Disparate patterns of immune responses, especially innate and adaptive cellular (mostly TH17) immunity were evident. Low values of four immune analytes (IL-9, IL-17, PDGF-bb and RANTES) and serum albumin are predictive of early death [PPV = 88% (95% CI, 65%-100%), NPV = 97% (95% CI, 93%-100%), accuracy = 96% (95% CI, 92%-100%)].

Involvement of oxidative stress and immune- and inflammation-related factors in azathioprine-induced liver injury

Drug-induced liver injury (DILI) is a growing concern in the fields of drug development and clinical drug therapy because numerous drugs have been linked to hepatotoxicity. However, it is difficult to predict DILI in humans due to the lack of experimental animal models. Although azathioprine (AZA), which is a widely used immunosuppressive drug, is generally well tolerated, a small number of patients prescribed AZA develop severe hepatitis. However, the mechanism underlying this process has not yet been elucidated. In this study, we developed a mouse model of AZA-induced liver injury and investigated the mechanisms responsible for the hepatotoxicity of AZA. Female BALB/c mice were orally administered AZA. After AZA administration, the plasma levels of alanine aminotransferase and aspartate aminotransferase were increased, and liver damage was confirmed through a histological evaluation. In addition, the hepatic glutathione levels and superoxide dismutase activity were significantly decreased. The plasma levels of reactive oxygen species were significantly increased during the early phase of AZA-induced liver injury, and the hepatic mRNA levels of immune- and inflammation-related factors were also significantly changed. In conclusion, oxidative stress and the subsequently activated immune- and inflammation-related factors are involved in AZA-induced liver injury.

The CRTH2 agonist Pyl A prevents lipopolysaccharide-induced fetal death but induces preterm labour

We have previously demonstrated that the anti-inflammatory prostaglandin 15-deoxy-Δ 12,14-prostaglandin J(2) (15dPGJ(2)) delays inflammation-induced preterm labour in the mouse and improves pup survival through the inhibition of nuclear factor-κB (NF-κB) by a mechanism yet to be elucidated. 15dPGJ(2) is an agonist of the second prostaglandin D(2) receptor, chemoattractant receptor homologous to the T helper 2 cell (CRTH2). In human T helper cells CRTH2 agonists induce the production of the anti-inflammatory interleukins IL-10 and IL-4. We hypothesized that CRTH2 is involved in the protective effect of 15dPGJ(2) in inflammation-induced preterm labour in the murine model. We therefore studied the effects of a specific small molecule CRTH2 agonist on preterm labour and pup survival. An intrauterine injection of lipopolysaccharide (LPS) was administered to CD1 mice at embryonic day 16, ± CRTH2 agonist/vehicle controls. Mice were killed at 4.5 hr to assess fetal wellbeing and to harvest myometrium and pup brain for analysis of NF-κB, and T helper type 1/2 interleukins. To examine the effects of the CRTH2 agonist on LPS-induced preterm labour, mice were allowed to labour spontaneously. Direct effects of the CRTH2 agonist on uterine contractility were examined ex vivo on contracting myometrial strips. The CRTH2 agonist increased fetal survival from 20 to 100% in LPS-treated mice, and inhibited circular muscle contractility ex vivo. However, it augmented LPS-induced labour and significantly increased myometrial NF-κB, IL-1β, KC-GRO, interferon-γ and tumour necrosis factor-α. This suggests that the action of 15dPGJ(2) is not via CRTH2 and therefore small molecule CRTH2 agonists are not likely to be beneficial for the prevention of inflammation-induced preterm labour.

Hepatoprotective effect of tamoxifen on steatosis and non-alcoholic steatohepatitis in mouse models

Non-alcoholic fatty liver disease (NAFLD) is characterized by hepatic lipid accumulation that starts with steatosis and progresses to non-alcoholic steatohepatitis (NASH). Recently, the number of patients with such liver diseases has increased, but the understanding of the fundamental mechanisms and appropriate therapies are lacking. Tamoxifen (TAM) is a selective estrogen receptor modulator. We previously reported that TAM plays a protective role against drug-induced and chemical-induced acute liver injuries. However, the effects of TAM on chronic liver injury, including steatosis and NASH, remain to be addressed. We first found that the administration of TAM to mouse models of steatosis and NASH significantly decreased the plasma ALT and AST levels. The administration of TAM decreased the accumulated fat and inflammation in the livers in both mouse models. In addition, we observed decreased hepatic mRNA levels of triglyceride synthesis, acyl-CoA: diacylglycerol acyltransferase 2 (DGAT2), proinflammatory cytokines, tumor necrosis factor (TNF) α, and chemokines, monocyte chemoattractant protein (MCP) -1. TAM increased the extracellular signal-regulated kinase (ERK) phosphorylation, which is related to the proliferation and regeneration of liver and to decreased DGAT2 gene expression. Furthermore, a decrease in eukaryotic translational initiation factor (eIF2α), which is involved in apoptosis, was observed in both models. These findings suggest that TAM treatment exerts a hepatoprotective effect against steatosis and NASH, presumably via up-regulation of the ERK pathways and attenuation of eIF2α activation. These pathways represent a potential therapeutic target for steatosis and NASH in drug development.

microRNAs as mediators of drug toxicity

microRNAs (miRNAs) represent the most abundant class of gene expression regulators that bind complementarily to transcripts to repress their translation or mRNA degradation. These small ( 21-23 nucleotides in length) noncoding RNAs are derived through a multistep process by miRNA genes located in genomic DNA. Because miRNAs regulate fundamental cellular functions, their dysregulation affects a large range of physiological processes, such as development, immune responses, metabolism, and diseases as well as toxicological outcomes. Cancer-related miRNAs have been extensively studied; however, the roles of miRNAs in xenobiotic metabolism and in toxicology have only recently been explored. This review focuses on the current knowledge of miRNA-dependent regulation of drug-metabolizing enzymes and nuclear receptors and the associated potential toxicological implications. The potential modulation of toxicology-related changes in miRNA expression, the role of miRNA in immune-mediated drug-induced liver injuries, the use of circulating miRNAs in body fluids as potential toxicological biomarkers, and the link between miRNA-related pharmacogenomics and adverse drug reactions are highlighted.

STAT proteins - key regulators of anti-viral responses, inflammation, and tumorigenesis in the liver

Since its discovery in the early 1990s, the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway has been found to play key roles in regulating many key cellular processes such as survival, proliferation, and differentiation. There are seven known mammalian STAT family members: STAT1, 2, 3, 4, 5a, 5b, and 6. In the liver, activation of these STAT proteins is critical for anti-viral defense against hepatitis viral infection and for controlling injury, repair, inflammation, and tumorigenesis. The identification of functions for these STAT proteins has increased our understanding of liver disease pathophysiology and treatments, while also suggesting new therapeutic modalities for managing liver disease.

Involvement of immune-related factors in diclofenac-induced acute liver injury in mice

Drug-induced liver injury (DILI) is a major safety concern in drug development and clinical drug therapy. However, the underlying mechanism of DILI is little known. It is difficult to predict DILI in humans due to the lack of experimental animal models. Diclofenac, a non-steroidal anti-inflammatory drug rarely causes severe liver injury in human, but there is some evidence for immunoallergic idiosyncratic reactions. In this study, the mechanism of diclofenac-induced liver injury in mice was investigated. First, we established the dosing condition for liver injury in normal mice. Plasma ALT and AST levels were significantly increased in diclofenac-administered (80 mg/kg, i.p.) mice in a dose- and time-dependent manner. Among several interleukins (ILs) and chemokines, mRNA expression of helper T (Th) 17 cell-mediated factors, such as retinoid orphan receptor (ROR)-γt, and signal transducers and activators of transcription factor (STAT) 3 in the liver, and the plasma IL-17 level were significantly increased. Neutralization of IL-17 tended to suppress the hepatotoxicity of diclofenac, suggesting that IL-17 was partly involved. Gadolinium chloride (GdCl₃) administration demonstrated that Kupffer cells are not likely to be involved in diclofenac hepatotoxicity. Hepatic expressions of IL-1β mRNA and plasma IL-1β were significantly increased soon after the diclofenac administration. Then, the results of an in vivo neutralization study of IL-1β suggested that IL-1β was involved early in the time of pathogenesis of the diclofenac-induced liver injury. In conclusion, we firstly developed a diclofenac-induced acute liver injury model in normal mice, and the involvement of IL-17 and IL-1β was clarified.

Involvement of Th2 cytokines in the mouse model of flutamide-induced acute liver injury

Drug-induced liver injury is a growing concern for pharmaceutical companies and patients because numerous drugs have been linked to hepatotoxicity and it is the most common reason for a drug to be withdrawn. Flutamide rarely causes liver dysfunction in humans, and immune allergic reactions have been suggested in some cases. In this study, we investigated the mechanisms of flutamide-induced liver injury in BALB/c mice. Plasma alanine aminotransferase and aspartate aminotransferase levels were significantly increased 3, 6 and 9 h after flutamide (1500 mg kg⁻¹ , p.o.) administration. The biomarker for oxidative stress was not changed, but Th2-dominant immune-related factors, such as interleukin (IL)-4, IL-5, STAT6 and GATA-binding protein (GATA)-3, were induced in flutamide-administered mice. The pre-administration of monoclonal-IL-4 antibody suppressed the hepatotoxicity of flutamide. In addition, we investigated the effect of 13,14-dihydro-15-keto-PGD₂ (DK-PGD₂; 10 µg per mouse, i.p.) administration on flutamide-induced acute liver injury. Coadministration of DK-PGD₂ and flutamide resulted in a significant increase in alanine aminotransferase and a remarkable increase of macrophage inflammatory protein-2. In conclusion, we demonstrated that flutamide-induced acute liver injury is mediated by Th2-dominant immune responses in mice.

Toxicological implications of modulation of gene expression by microRNAs

MicroRNAs (miRNAs) are a large family of non-coding RNAs that are evolutionarily conserved, endogenous, and 21-23 nucleotides in length. miRNAs regulate gene expression by targeting messenger RNAs (mRNAs) by binding to complementary regions of transcripts to repress their translation or mRNA degradation. miRNAs are encoded by the genome, and more than 1000 human miRNAs have been identified so far. miRNAs are predicted to target ∼60% of human mRNAs and are expressed in all animal cells and have fundamental roles in cellular responses to xenobiotic stresses, which affect a large range of physiological processes such as development, immune responses, metabolism, tumor formation as well as toxicological outcomes. Recently, many reports concerning miRNAs related to cancer have been published; however, the miRNA research in the metabolism of xenobiotics and endobiotics and in toxicology has only recently been established. This review describes the current knowledge on the miRNA-dependent regulation of drug-metabolizing enzymes and nuclear receptors and its potential toxicological implications. In this review, miRNAs with reference to target prediction, potential modulation of toxicology-related changes of miRNA expression, role of miRNA in immune-mediated drug-induced liver injury, miRNA in plasma as potential toxicological biomarkers, and relevance of miRNA-related genetic polymorphisms are discussed.