Mechanistic biomarkers in acute liver injury: are we there yet?

Decoding the contributions of gut microbiota and cerebral metabolism in acute liver injury mice with and without cognitive dysfunction

AIMS

Patients with acute liver injury (ALI) can develop cognitive dysfunction (CD). The study investigated the role of gut microbiota and cerebral metabolism in ALI mice with and without CD.

METHODS

Male C57BL/6 mice that received thioacetamide were classified into ALI mice with (susceptible) or without (unsusceptible) CD-like phenotypes by hierarchical cluster analysis of behavior. The role of gut microbiota was investigated by 16S ribosomal RNA gene sequencing and feces microbiota transplantation (FMT). ¹ H-[¹³ C] NMR and electrophysiology were used to detect the changes in cerebral neurotransmitter metabolic and synaptic transition in neurons or astrocytes.

RESULTS

Apromixlay 55% (11/20) of mice developed CD and FMT from the susceptible group transmitted CD to gut microbiota-depleted mice. Alloprevotella was enriched in the susceptible group. GABA production was decreased in the frontal cortex, while hippocampal glutamine was increased in the susceptible group. Altered Escherichia. Shigella and Alloprevotella were correlated with behaviors and cerebral metabolic kinetics and identified as good predictors of ALI-induced CD. The frequencies of both miniature inhibitory and excitatory postsynaptic currents in hippocampal CA1 and prefrontal cortex were decreased in the susceptible group.

CONCLUSION

Altered transmitter metabolism and synaptic transmission in the hippocampus and prefrontal cortex and gut microbiota disturbance may lead to ALI-induced CD.

MicroRNA-122 and cytokeratin-18 have potential as a biomarkers of drug-induced liver injury in European and African patients on treatment for mycobacterial infection

Aims

Patients on antituberculosis (anti‐TB) therapy are at risk of drug‐induced liver injury (DILI). MicroRNA‐122 (miR‐122) and cytokeratin‐18 (K18) are DILI biomarkers. To explore their utility in this global context, circulating miR‐122 and K18 were measured in UK and Ugandan populations on anti‐TB therapy for mycobacterial infection.

Methods

Healthy subjects and patients receiving anti‐TB therapy were recruited at the Royal Infirmary of Edinburgh, UK (ALISTER—ClinicalTrials.gov Identifier: NCT03211208). African patients with human immunodeficiency virus–TB coinfection were recruited at the Infectious Diseases Institute, Kampala, Uganda (SAEFRIF—NCT03982277). Serial blood samples, demographic and clinical data were collected. In ALISTER samples, MiR‐122 was quantified using polymerase chain reaction. In ALISTER and SAEFRIF samples, K18 was quantified by enzyme‐linked immunosorbent assay.

Results

The study had 235 participants (healthy volunteers [n = 28]; ALISTER: active TB [n = 30], latent TB [n = 88], nontuberculous mycobacterial infection [n = 25]; SAEFRIF: human immunodeficiency virus‐TB coinfection [n = 64]). In the absence of DILI, there was no difference in miR‐122 and K18 across the groups. Both miR‐122 and K18 correlated with alanine transaminase (ALT) activity (miR‐122: R = .52, 95%CI = 0.42–0.61, P < .0001. K18: R =0.42, 95%CI = 0.34–0.49, P < .0001). miR‐122 distinguished those patients with ALT>50 U/L with higher sensitivity/specificity than K18. There were 2 DILI cases: baseline ALT, 18 and 28 IU/L, peak ALT 431 and 194 IU/L; baseline K18, 58 and 219 U/L, peak K18 1247 and 3490 U/L; baseline miR‐122 4 and 17 fM, peak miR‐122 60 and 336 fM, respectively.

Conclusion

In patients treated with anti‐TB therapy, miR‐122 and K18 correlated with ALT and increased with DILI. Further work should determine their diagnostic and prognostic utility in this global context‐of‐use.

The role of Neu1 in the protective effect of dipsacoside B on acetaminophen-induced liver injury

Background

Pharmacological induction of autophagy can protect against acetaminophen (APAP) induced acute liver failure (ALF) by removing APAP adducts (APAP-AD), but its mechanism is not well understood. Hepatoprotective effect of saponins from traditional Chinese medicine has attracted widespread attention from all over the world. The content of saponins in Lonicerae Flos (Shanyinhua in Chinese) is up to 15–25%. Dipsacoside B (DB) is a common bioactive ingredient of different Shanyinhua, but its hepatoprotective effect and mechanism are still unknown. The present investigation aimed to study the benefit of DB in APAP-induced hepatotoxicity mouse model and different cell model.

Methods

Mice were treated with DB by intraperitoneal injection 1 h before treated with 500 mg/kg APAP, which caused ALF after 4 h. HepG2 cells were treated with DB for 1 h before treated with 10 mM APAP for 12 h. Hepatotoxicity was assessed via ALT and AST. Neuraminidase 1 (Neu1), lysosomal autophagy marker LC3 and P62 were examined by western blot. Neu1 activity was assayed using its substrate 2-(4-methylumbelliferyl)-D-N-acetylneuraminic acid. Apoptosis level was examined by TUNEL and caspase 3 activity. Molecular docking was used to predict the interaction between DB and protein Neu1.

Results

Our results demonstrated that pretreatment with 0.5 μM DB (in vitro) and 50 mg/kg DB (in vivo) respectively reversed increased level of AST and ALT induced by APAP. Histopathological examinations showed reduced necrosis and apoptosis in the liver of DB-treated APAP mice. DB promoted the removal of APAP-AD by lysosomal autophagy. These effects were associated with significant decrease in the level of Neuraminidase 1 (Neu1), a negative regulator of lysosomal exocytosis. Molecular docking results showed that DB could bind to Neu1 protein (binding energy =−7.86 kcal/mol). Akt/mTOR-mediated autophagy and inhibition of apoptosis may be the main mechanisms for the hepatoprotective effects of DB in acetaminophen-induced liver injury.

Conclusions

These data indicate that DB alleviated hepatotoxicity caused by APAP at least in part via Neu1 inhibition, Akt/mTOR pathway is involved in the detoxification effect of DB on acetaminophen-induced hepatotoxicity.

Patients with HBV-related acute-on-chronic liver failure have increased concentrations of extracellular histones aggravating cellular damage and systemic inflammation

Acute-on-chronic liver failure (ACLF) is the most common type of liver failure and associated with grave consequences. Systemic inflammation has been linked to its pathogenesis and outcome, but the identifiable triggers are absent. Recently, extracellular histones, especially H4, have been recognized as important mediators of cell damage in various inflammatory conditions. This study aimed to investigate whether extracellular histones have clinical implications in patients with hepatitis B virus (HBV)-related ACLF. One hundred and twelve patients with HBV-related ACLF, 90 patients with chronic hepatitis B, 88 patients with HBV-related liver cirrhosis and 40 healthy volunteers were entered into this study. Plasma histone H4 levels, cytokine profile and clinical data were obtained. Besides, patient's sera were incubated overnight with human L02 hepatocytes or monocytic U937 cells in the presence or absence of antihistone H4 antibody, and cellular damage and cytokine production were evaluated. We found that plasma histone H4 levels were greatly increased in patients with ACLF as compared with chronic hepatitis B, liver cirrhosis and healthy control subjects and were significantly associated with disease severity, systemic inflammation and outcome. Notably, ACLF patients' sera incubation decreased cultured L02 cell integrity and induced profound cytokine production in the supernatant of U937 cells. Antihistone H4 antibody treatment abrogated these adverse effects, thus confirming a cause-effect relationship between extracellular histones and organ injury/dysfunction. The data support the hypothesis that the increased extracellular histone levels in ACLF patients may aggravate disease severity by inducing cellular injury and systemic inflammation. Histone-targeted therapies may have potentially interventional value in clinical practice.

The Pathology of Acute Liver Failure

Acute liver failure (ALF) is a rare and severe liver disease that usually develops in 8 weeks or less in individuals without preexisting liver disease. Its chief causes worldwide are hepatitis virus infections (hepatitis A, B, and E) and drug hepatotoxicity (particularly intentional or unintentional acetaminophen toxicity). Massive hepatic necrosis is often seen in liver specimens in ALF and features marked loss of hepatocytes, variable degrees of inflammation, and a stereotypic proliferation of bile ductular structures (neocholangioles) derived from activated periportal hepatic progenitor cells. This paper reviews the liver pathology in ALF, including forms of zonal necrosis and their etiologies.

Mechanisms of fibrosis in acute liver failure

BACKGROUND & AIMS

Acute liver failure (ALF) is a condition with high mortality and morbidity. Fibrosis in chronic liver disease was extensively researched, whereas fibrosis and underlying mechanism in acute liver failure remains unclear.

METHODS

Hepatitis B virus related ALF patients were recruited to investigate if there was ongoing fibrosis by liver histology and liver stiffness measurement(LSM) analysis as well as fibrosis markers assay. Sera HMGB1 were kinetically detected in progression and remission stage of ALF. Hepatic stellate cell(HSC) activation by HMGB1 was explored by testing mRNA and protein level of α-SMA and collagen 1a1 by using qPCR and western blot. Autophagy induction by HMGB1 was explored by LC3-II conversion, autophagy flux and fluorescence.

RESULTS

Firstly, ongoing fibrosis in progression stage of ALF was confirmed by histological analysis, LS measurement as well as fibrosis markers detection. HSC activation and autophagy induction in explanted liver tissue also revealed. Next, kinetic monitoring sera HMGB1 revealed elevated HMGB1 in progression stage of ALF vs HBsAg carrier, and drop back to base level in remission stage. Thirdly, rHMGB1 dose dependently activated HSCs, as indicated by increased mRNA and proteins level in α-SMA and collagen 1a1. Moreover, autophagy was induced in HSC treated with rHMGB1, as illustrated by increased LC3 lipidation, elevated autophagy flux and GFP-LC3 puncta.

CONCLUSIONS

Acute liver failure is accompanied by ongoing fibrosis, HSC activation and autophagy induction. Increased HMGB1 activates HSC via autophagy induction. Those findings integrate HMGB1, HSCs activation, autophagy into a common framework that underlies the fibrosis in ALF.

Circulating histones exacerbate inflammation in mice with acute liver failure

Circulating histones are a newly recognized mediator implicated in various inflammatory diseases. It is likely that the release of histones, from dying hepatocytes or inflammatory leukocytes, into the circulation initiates and amplifies inflammation during the course of acute liver failure (ALF). In this study, we investigated a putative pathogenic role of circulating histones in a murine model of ALF induced by D-galactosamine (GalN) plus lipopolysaccharide (LPS). Hepatic function and histological indexes, myeloperoxidase (MPO) activity, hepatocyte apoptosis and the levels of circulating histone were measured in GalN/LPS-treated mice. GalN/LPS caused severe liver damage and a notable increase in plasma concentration of circulating histones. To further assess the role of circulating histones in our model, we administered exogenous histones and anti-histone H4 antibody. Notably, exogenous histones aggravated GalN/LPS-induced hepatotoxicity, whereas anti-histone antibody significantly protected mice. Circulating histones may serve as both a functional marker of ALF activity and as an inflammatory mediator contributing to the progression of ALF. Blockade of circulating histones shows potent protective effects, suggesting a potential therapeutic strategy for ALF.

Mechanistic biomarkers provide early and sensitive detection of acetaminophen-induced acute liver injury at first presentation to hospital

Acetaminophen overdose is a common reason for hospital admission and the most frequent cause of hepatotoxicity in the Western world. Early identification would facilitate patient-individualized treatment strategies. We investigated the potential of a panel of novel biomarkers (with enhanced liver expression or linked to the mechanisms of toxicity) to identify patients with acetaminophen-induced acute liver injury (ALI) at first presentation to the hospital when currently used markers are within the normal range. In the first hospital presentation plasma sample from patients (n = 129), we measured microRNA-122 (miR-122; high liver specificity), high mobility group box-1 (HMGB1; marker of necrosis), full-length and caspase-cleaved keratin-18 (K18; markers of necrosis and apoptosis), and glutamate dehydrogenase (GLDH; marker of mitochondrial dysfunction). Receiver operator characteristic curve analysis and positive/negative predictive values were used to compare sensitivity to report liver injury versus alanine transaminase (ALT) and International Normalized Ratio (INR). In all patients, biomarkers at first presentation significantly correlated with peak ALT or INR. In patients presenting with normal ALT or INR, miR-122, HMGB1, and necrosis K18 identified the development of liver injury (n = 15) or not (n = 84) with a high degree of accuracy and significantly outperformed ALT, INR, and plasma acetaminophen concentration for the prediction of subsequent ALI (n = 11) compared with no ALI (n = 52) in patients presenting within 8 hours of overdose.

CONCLUSION

Elevations in plasma miR-122, HMGB1, and necrosis K18 identified subsequent ALI development in patients on admission to the hospital, soon after acetaminophen overdose, and in patients with ALTs in the normal range. The application of such a biomarker panel could improve the speed of clinical decision-making, both in the treatment of ALI and the design/execution of patient-individualized treatment strategies.

A reproducible, clinically relevant, intensively managed, pig model of acute liver failure for testing of therapies aimed to prolong survival

BACKGROUND

A clinically relevant, translational large animal model of acute liver failure (ALF) is required for testing of novel therapies to prolong survival in acute liver failure, to permit spontaneous liver recovery or to act as a bridge to transplantation.

AIMS

The aim was to establish a pig model of acetaminophen-induced ALF that mimics the human clinical syndrome, is managed as in a human intensive care unit and has a predictable survival time.

METHODS

Nine female pigs were anaesthetised and instrumented for continuous intensive care monitoring and management using: target-driven protocols for treatment of cardiovascular collapse, metabolic acidosis and electrolyte abnormalities; intermittent positive pressure ventilation; and continuous renal replacement therapy. Six animals were induced to ALF with acetaminophen (paracetamol). Three animals acted as controls.

RESULTS

Irreversible acute liver failure, defined as rise in prothrombin time >3 times normal, occurred 19.3 ± 1.8 h after the onset of acetaminophen administration. Death occurred predictably 12.6 ± 2.7 h thereafter, with acute hepatocellular necrosis in all animals. Clinical progression of liver failure mimicked the human condition including development of coagulopathy, intracranial hypertension, hyperammonaemia, cardiovascular collapse, elevation in creatinine, metabolic acidosis and hyperlactataemia. In addition, cardiovascular monitoring clearly demonstrated progressive cardiac dysfunction in ALF.

CONCLUSIONS

A reproducible, clinically relevant, intensively managed, large animal model of acute liver failure, with death as a result of multi-organ failure, has been successfully validated for translational studies of disease progression and therapies designed to prolong survival in man.

Acute-on chronic liver failure

Acute-on-chronic liver failure (ACLF) is an increasingly recognised entity encompassing an acute deterioration of liver function in patients with cirrhosis, which is usually associated with a precipitating event and results in the failure of one or more organs and high short term mortality. Prospective data to define this is lacking but there is a large body of circumstantial evidence suggesting that this condition is a distinct clinical entity. From the pathophysiologic perspective, altered host response to injury and infection play important roles in its development. This review focuses upon the current understanding of this syndrome from the clinical, prognostic and pathophysiologic perspectives and indicates potential biomarkers and therapeutic targets for intervention.

Latest advances in predicting DILI in human subjects: focus on biomarkers

INTRODUCTION

The quest for a biomarker that would reliably identify patients at risk of developing acute drug-induced liver injury (DILI) to a specific agent or class of agents before it occurs, has been underway for years. Historical host factors for DILI, such as older age and female gender, are not considered sufficient to truly predict an individual's inherent risk of DILI. In vitro and animal-based biomarker discoveries, in many instances, have not been considered accurate enough for drug development in human subjects nor for use in clinical practice.

AREAS COVERED

In order to assess the current state of biomarkers to predict idiosyncratic human DILI, the authors utilized the PubMed literature search tool to identify research reports dealing with clinical DILI biomarkers covering the period of 2010 through to June 2012. Studies involving pharmacogenetic, proteomic and toxicogenomic analyses are preferentially reviewed.

EXPERT OPINION

Although acute DILI has been linked to specific genetic associations (e.g., flucloxacillin and HLA-B*5701; and certain polymorphisms seen with anti-TB agent DILI), such predictors have been able to identify only some patients at risk for only a limited number of drugs. Proteomic-based biomarkers from stored sera in the US DILI Network, such as apolipoprotein E, have been identified as potential candidates, but require further study. As it currently stands, the quest for a widely applicable, validated DILI biomarker remains an ongoing clinical challenge.