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

UNLABELLED: 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.

The MprF homolog LysX synthesizes lysyl-diacylglycerol contributing to antibiotic resistance and virulence.

Lysyl-diacylglycerol (Lys-DAG) was identified three decades ago in Mycobacterium phlei, but the biosynthetic pathway and function of this aminoacylated lipid have since remained uncharacterized. Combining genetic methods, mass spectrometry, and biochemical approaches, we show that the multiple peptide resistance factor (MprF) homolog LysX from Corynebacterium pseudotuberculosis and two mycobacterial species is responsible for Lys-DAG synthesis. LysX is conserved in most Actinobacteria and was previously implicated in the synthesis of another modified lipid, lysyl-phosphatidylglycerol (Lys-PG), in Mycobacterium tuberculosis. Although we detected low levels of Lys-PG in the membrane of C. pseudotuberculosis, our data suggest that Lys-PG is not directly synthesized by LysX and may require an additional downstream pathway, which is as yet undefined. Our results show that LysX in C. pseudotuberculosis is a major factor of resistance against a variety of positively charged antibacterial agents, including cationic antimicrobial peptides (e.g., human peptide LL-37 and polymyxin B) and aminoglycosides (e.g., gentamycin and apramycin). Deletion of lysX caused an increase in cellular membrane permeability without dissipation of the membrane potential, suggesting that loss of the protein does not result in mechanical damage to the cell membrane. Furthermore, lysX-deficient cells exhibited an attenuated virulence phenotype in a Galleria mellonella infection model, supporting a role for LysX during infection. Altogether, Lys-DAG represents a novel molecular determinant for antimicrobial resistance and virulence that may be widespread in Actinobacteria and points to a richer landscape than previously realized of lipid components contributing to overall membrane physiology in this important bacterial phylum. IMPORTANCE In the past two decades, tRNA-dependent modification of membrane phosphatidylglycerol has been implicated in altering the biochemical properties of the cell surface, thereby enhancing the antimicrobial resistance and virulence of various bacterial pathogens. Here, we show that in several Actinobacteria, the multifunctional protein LysX attaches lysine to diacylglycerol instead of phosphatidylglycerol. We found that lysyl-diacylglycerol (Lys-DAG) confers high levels of resistance against various cationic antimicrobial peptides and aminoglycosides and also enhances virulence. Our data show that Lys-DAG is a lipid commonly found in important actinobacterial pathogens, including Mycobacterium and Corynebacterium species.

Circulating microRNAs as potential markers of human drug-induced liver injury.

UNLABELLED: New biomarkers of liver injury are required in the clinic and in preclinical pharmaceutical evaluation. Previous studies demonstrate that two liver-enriched microRNAs (miR-122 and miR-192) are promising biomarkers of acetaminophen-induced acute liver injury (APAP-ALI) in mice. We have examined these molecules, for the first time, in humans with APAP poisoning. Serum miR-122 and miR-192 were substantially higher in APAP-ALI patients, compared to healthy controls (median ΔΔCt [25th, 75th percentile]) (miR-122: 1,265 [491, 4,270] versus 12.1 [7.0, 26.9], P < 0.0001; miR-192: 6.9 [2.0, 29.2] versus 0.44 [0.30, 0.69], P < 0.0001). A heart-enriched miR-1 showed no difference between APAP-ALI patients and controls, whereas miR-218 (brain-enriched) was slightly higher in the APAP-ALI cohort (0.17 [0.07, 0.50] versus 0.07 [0.04, 0.12]; P = 0.01). In chronic kidney disease (CKD) patients, miR-122 and -192 were modestly higher, compared to controls (miR-122: 32.0 [21.1, 40.9] versus 12.1 [7.0, 26.9], P = 0.006; miR-192: 1.2 [0.74, 1.9] versus 0.44 [0.30, 0.69], P = 0.005), but miR-122 and -192 were substantially higher in APAP-ALI patients than CKD patients (miR-122: P < 0.0001; miR-192: P < 0.0004). miR-122 correlated with peak ALT levels in the APAP-ALI cohort (Pearson R = 0.46, P = 0.0005), but not with prothrombin time. miR-122 was also raised alongside peak ALT levels in a group of patients with non-APAP ALI. Day 1 serum miR-122 levels were almost 2-fold higher in APAP-ALI patients who satisfied King's College Criteria (KCC), compared to those who did not satisfy KCC, although this did not reach statistical significance (P = 0.15). CONCLUSION: This work provides the first evidence for the potential use of miRNAs as biomarkers of human drug-induced liver injury.

Network analysis of primary hepatocyte dedifferentiation using a shotgun proteomics approach.

The liver is the major site of xenobiotic metabolism and detoxification. Primary cultures of hepatocytes are a vital tool in the development of new therapeutic agents but their utility is hindered by the rapid loss of phenotype. Hepatocytes cultured in a sandwich of extracellular matrix protein maintain better hepatic function compared with cells cultured as a monolayer but a wide-ranging proteomics study of the differences in cultures has never been performed. We characterize the changing phenotype of rat hepatocytes in primary culture using iTRAQ proteomics and systems biology network analysis of the identified, significantly regulated, proteins. A total of 754 unique proteins were identified from 4 independent experiments. Of these, 413 proteins were common to at least 3 experiments and 328 proteins were identified in all experiments. Both culture systems displayed altered expression of many common proteins. Network analysis showed that the primary functions of these proteins were in metabolic pathways, immune responses and cytoskeleton remodelling. Monolayer cultures uniquely regulate proteins mapping to pathways of oxidative stress and cell migration, whereas sandwich culture affected translation regulation and apoptosis pathways. These experiments provide a detailed proteomics data set to direct further work into maintaining hepatic phenotype using cultured primary hepatocytes and stem cell derived hepatocyte-like cells.

Multi-Organ toxicity demonstration in a functional human in vitro system composed of four organs.

We report on a functional human model to evaluate multi-organ toxicity in a 4-organ system under continuous flow conditions in a serum-free defined medium utilizing a pumpless platform for 14 days. Computer simulations of the platform established flow rates and resultant shear stress within accepted ranges. Viability of the system was demonstrated for 14 days as well as functional activity of cardiac, muscle, neuronal and liver modules. The pharmacological relevance of the integrated modules were evaluated for their response at 7 days to 5 drugs with known side effects after a 48 hour drug treatment regime. The results of all drug treatments were in general agreement with published toxicity results from human and animal data. The presented phenotypic culture model exhibits a multi-organ toxicity response, representing the next generation of in vitro systems, and constitutes a step towards an in vitro "human-on-a-chip" assay for systemic toxicity screening.

In silico analysis of HLA associations with drug-induced liver injury: use of a HLA-genotyped DNA archive from healthy volunteers.

BACKGROUND: Drug-induced liver injury (DILI) is one of the most common adverse reactions leading to product withdrawal post-marketing. Recently, genome-wide association studies have identified a number of human leukocyte antigen (HLA) alleles associated with DILI; however, the cellular and chemical mechanisms are not fully understood. METHODS: To study these mechanisms, we established an HLA-typed cell archive from 400 healthy volunteers. In addition, we utilized HLA genotype data from more than four million individuals from publicly accessible repositories such as the Allele Frequency Net Database, Major Histocompatibility Complex Database and Immune Epitope Database to study the HLA alleles associated with DILI. We utilized novel in silico strategies to examine HLA haplotype relationships among the alleles associated with DILI by using bioinformatics tools such as NetMHCpan, PyPop, GraphViz, PHYLIP and TreeView. RESULTS: We demonstrated that many of the alleles that have been associated with liver injury induced by structurally diverse drugs (flucloxacillin, co-amoxiclav, ximelagatran, lapatinib, lumiracoxib) reside on common HLA haplotypes, which were present in populations of diverse ethnicity. CONCLUSIONS: Our bioinformatic analysis indicates that there may be a connection between the different HLA alleles associated with DILI caused by therapeutically and structurally different drugs, possibly through peptide binding of one of the HLA alleles that defines the causal haplotype. Further functional work, together with next-generation sequencing techniques, will be needed to define the causal alleles associated with DILI.