Characterization of amoxicillin- and clavulanic acid-specific T cells in patients with amoxicillin-clavulanate-induced liver injury

Decreased Hepatic Functional Reserve Increases the Risk of Piperacillin/Tazobactam-Induced Abnormal Liver Enzyme Levels: A Retrospective Case-Control Study

BACKGROUND

Piperacillin/tazobactam (PIPC/TAZ), which is a combination of a beta-lactam/beta-lactamase inhibitor, often causes liver enzyme abnormalities. The albumin-bilirubin (ALBI) score is a simple index that uses the serum albumin and total bilirubin levels for estimating hepatic functional reserve. Although patients with low hepatic reserve may be at high risk for drug-induced liver enzyme abnormalities, the relationship between PIPC/TAZ-induced abnormal liver enzymes levels and the ALBI score remains unknown.

OBJECTIVE

This study aimed to elucidate the relationship between PIPC/TAZ-induced abnormal liver enzyme levels and the ALBI score.

METHODS

This single-center retrospective case-control study included 335 patients. The primary outcome was PIPC/TAZ-induced abnormal liver enzyme levels. We performed COX regression analysis with male gender, age (≥75 years), alanine aminotransferase level (≥20 IU/L), and ALBI score (≥-2.00) as explanatory factors. To investigate the influence of the ALBI score on the development of abnormal liver enzyme levels, 1:1 propensity score matching between the ≤-2.00 and ≥-2.00 ALBI score groups was performed using the risk factors for drug-induced abnormal liver enzyme levels.

RESULTS

The incidence of abnormal liver enzyme levels was 14.0% (47/335). COX regression analysis revealed that an ALBI score ≥-2.00 was an independent risk factor for PIPC/TAZ-induced abnormal liver enzyme levels (adjusted hazard ratio: 3.08, 95% coefficient interval: 1.207-7.835, P = 0.019). After 1:1 propensity score matching, the Kaplan-Meier curve revealed that the cumulative risk for PIPC/TAZ-induced abnormal liver enzyme levels was significantly higher in the ALBI score ≥-2.00 group (n = 76) than in the <-2.00 group (n = 76) (P = 0.033).

CONCLUSION AND RELEVANCE

An ALBI score ≥-2.00 may predict the development of PIPC/TAZ-induced abnormal liver enzyme levels. Therefore, frequent monitoring of liver enzymes should be conducted to minimize the risk of severe PIPC/TAZ-induced abnormal liver enzyme levels in patients with low hepatic functional reserve.

2,3,5,4'- tetrahydroxystilbene-2-O-β-D- glucopyranoside (TSG)-Driven immune response in the hepatotoxicity of Polygonum multiflorum

ETHNOPHARMACOLOGICAL RELEVANCE

2,3,5,4'-tetrahydroxystilbene-2-O-β-D-glucopyranoside (TSG) as the primary constituent of Polygonum multiflorum Thumb. (PM) possesses anti-oxidative, antihypercholesterolemic, anti-tumor and many more biological activities. The root of PM has been used as a tonic medicine for thousands of years. However, cases of PM-induced liver injury are occasionally reported, and considered to be related to the host immune status.

AIM OF THE STUDY

The primary toxic elements and specific mechanisms PM causing liver damage are still not thoroughly clear. Our study aimed to investigate the influences of TSG on the immune response in idiosyncratic hepatotoxicity of PM.

MATERIALS AND METHODS

The male C57BL/6 mice were treated with different doses of TSG and the alterations in liver histology, serum liver enzyme levels, proportions of T cells and cytokines secretion were evaluated by hematoxylin and eosin (HE), RNA sequencing, quantitative real time polymerase chain reaction (qRT-PCR), Flow cytometry (FCM), and enzyme-linked immunosorbent assay (ELISA), respectively. Then, primary spleen cells from drug-naive mice were isolated and cultured with TSG in vitro. T cell subsets proliferation and cytokines secretion after treated with TSG were assessed by CCK8, FCM and ELISA. In addition, mice were pre-treated with anti-CD25 for depleting regulatory T cells (Tregs), and then administered with TSG. Liver functions and immunological alterations were analyzed to evaluate liver injury.

RESULTS

Data showed that TSG induced liver damage, and immune cells infiltration in the liver tissues. FCM results showed that TSG could activate CD4+T and CD8+T in the liver. Results further confirmed that TSG notably up-regulated the levels of inflammatory cytokines including TNF-α, IFN-γ, IL-18, perforin and granzyme B in the liver tissues. Furthermore, based on transcriptomics profiles, some immune system-related pathways including leukocyte activation involved in inflammatory response, leukocyte cell-cell adhesion, regulation of interleukin-1 beta production, mononuclear cell migration, antigen processing and presentation were altered in TSG treated mice. CD8+T/CD4+T cells were also stimulated by TSG in vitro. Interestingly, increased proportion of Tregs was observed after TSG treatment in vitro and in vivo. Foxp3 and TGF-β1 mRNA expressions were up-regulated in the liver tissues. Depletion of Tregs moderately enhanced TSG induced the secretion of inflammatory cytokines in serum.

CONCLUSIONS

Our findings showed that TSG could trigger CD4+T and CD8+T cells proliferation, promote cytokines secretion, which revealed that adaptive immune response associated with the mild liver injury cause by TSG administration. Regulatory T cells (Tregs) mainly sustain immunological tolerance, and in this study, the progression of TSG induced liver injury was limited by Tregs. The results of our investigations allow us to preliminarily understand the mechanisms of PM related idiosyncratic hepatotoxicity.

Patients with naproxen-induced liver injury display T-cell memory responses toward an oxidative (S)-O-desmethyl naproxen metabolite but not the acyl glucuronide

BACKGROUND

Exposure to nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (IBU) and naproxen (NAP) is associated with idiosyncratic drug-induced liver injury (DILI). Carboxylate bioactivation into reactive metabolites (e.g., acyl glucuronides, AG) and resulting T-cell activation is hypothesized as causal for this adverse event. However, conclusive evidence supporting this is lacking.

METHODS

In this work, we identify CD4+ and CD8+ T-cell hepatic infiltration in a biopsy from an IBU DILI patient. Lymphocyte transformation test and IFN-γ ELIspot, conducted on peripheral blood mononuclear cells (PBMCs) of patients with NAP-DILI, were used to explore drug-specific T-cell activation. T-cell clones (TCC) were generated and tested for drug specificity, phenotype/function, and pathways of T-cell activation. Cells were exposed to NAP, its oxidative metabolite 6-O-desmethyl NAP (DM-NAP), its AG or synthesized NAP-AG human-serum albumin adducts (NAP-AG adduct).

RESULTS

CD4+ and CD8+ T-cells from patients expressing a range of different Vβ receptors were stimulated to proliferate and secrete IFN-γ and IL-22 when exposed to DM-NAP, but not NAP, NAP-AG or the NAP-AG adduct. Activation of the CD4+ TCC was HLA-DQ-restricted and dependent on antigen presenting cells (APC); most TCC were activated with DM-NAP-pulsed APC, while fixation of APC blocked the T-cell response. Cross-reactivity was not observed with structurally-related drugs.

CONCLUSION

Our results confirm hepatic T-cell infiltrations in NSAID-induced DILI, and show a T-cell memory response toward DM-NAP indicating an immune-mediated basis for the adverse event. Whilst bioactivation at the carboxylate group is widely hypothesized to be pathogenic for NSAID associated DILI, we found no evidence of this with NAP.

Review of human risk factors for idiosyncratic drug-induced liver injury: latest advances and future goals

INTRODUCTION

Idiosyncratic drug-induced liver injury (DILI) is a common cause of acute liver injury and can lead to death from acute liver failure or require liver transplantation. Although the total burden of liver injury is high, the frequency of DILI caused by specific agents is often low. As the liver injury is by per definition idiosyncratic, the prediction of which patients will develop liver injury from specific drugs is currently a very difficult challenge.

AREAS COVERED

The current paper highlights the most important studies on prediction of DILI published in 2019-2023, including studies on genetic, metabolomic, and demographic risk factors, concomitant medication, and the role of comorbid liver diseases. Risk stratification using demographic, metabolomic, and multigenetic risk factors is discussed.

EXPERT OPINION

Great advances have been made in identifying genetic risk factors for DILI. Combining these risk factors with demographic information and other biomarkers into multigenetic risk models might become highly useful in risk stratifying patients exposed to DILI. However, a more detailed mapping of genetic risk factors is needed. Results of these studies need to be validated in the selected ethnic groups before applicability and cost-effectiveness can be determined.

Drug-Induced Liver Injury with Commonly Used Antibiotics in the All of Us Research Program

Antibiotics are a known cause of idiosyncratic drug-induced liver injury (DILI). According to the Centers for Disease Control and Prevention, the five most commonly prescribed antibiotics in the United States are azithromycin, ciprofloxacin, cephalexin, amoxicillin, and amoxicillin-clavulanate. We quantified the frequency of acute DILI for these common antibiotics in the All of Us Research Program, one of the largest electronic health record (EHR)-linked research cohorts in the United States. Retrospective analyses were conducted applying a standardized phenotyping algorithm to de-identified clinical data available in the All of Us database for 318,598 study participants. Between February 1984 and December 2022, more than 30% of All of Us participants (n = 119,812 individuals) had been exposed to at least 1 of our 5 study drugs. Initial screening identified 591 potential case patients that met our preselected laboratory-based phenotyping criteria. Because DILI is a diagnosis of exclusion, we then used phenome scanning to narrow the case counts by (i) scanning all EHRs to identify all alternative diagnostic explanations for the laboratory abnormalities, and (ii) leveraging International Classification of Disease 9th revision (ICD)-9 and ICD 10th revision (ICD)-10 codes as exclusion criteria to eliminate misclassification. Our final case counts were 30 DILI cases with amoxicillin-clavulanate, 24 cases with azithromycin, 24 cases with ciprofloxacin, 22 cases with amoxicillin alone, and < 20 cases with cephalexin. These findings demonstrate that data from EHR-linked research cohorts can be efficiently mined to identify DILI cases related to the use of common antibiotics.

Sex disparity and drug-induced liver injury

Drug-induced liver injury (DILI) is a potentially serious clinical condition that remains a major problem for patients, physicians and those involved in the development of new drugs. Population and hospital-based studies have reported incidences of DILI varying from 1.4 to 19.1/100.000. Overall, females have a 1.5- to 1.7-fold greater risk of developing adverse drug reactions and the female/male ratio increases after the age of 49 years, suggesting a clear susceptibility of DILI after menopause. Sex differences in pharmacokinetics and pharmacodynamic, sex-specific hormonal effects or interaction with signalling molecules that can influence drug efficacy and safety and differences in abnormal immune response following drug exposure are the main probable causes of the higher vulnerability observed among female patients. A novel phenotype of autoimmune-mediated DILI following the use of check-point inhibitors in oncology and haematology has been recently described. Finally, there have been increasing reports of DILI associated with use of herbal and dietary supplements that is more frequently reported in women.

Pathology of drug hypersensitivity reactions and mechanisms of immune tolerance

Immune-mediated type IV adverse drug reactions are idiosyncratic in nature, generally not related to the primary or secondary pharmacology of the drug. Due to their complex nature and rarity, these iatrogenic reactions are seldom predicted or encountered during preclinical/early clinical development stages, and often precipitate upon exposure to wider populations (i.e. phase III onwards). They confer a burden on the healthcare sector in both a clinical and financial sense presenting a severe impediment to the drug discovery and development process. Research over the past 50 years has improved our understanding of these reactions markedly as both in vitro and in vivo studies have placed the role of the immune system, in particular; drug-responsive T cells, firmly in the spotlight as the mediators of these reactions. Indeed, the role of different populations of T cells in adverse events and the interaction of drug molecules with HLA proteins expressed on the surface of antigen-presenting cells is of considerable interest. Herein, this review examines the pathways of immune-mediated adverse events including the various T cell subtypes implicated and the mechanisms of T cell activation. Additionally, we address the enigma of immunological tolerance and explore the role tolerance plays in determination of susceptibility to such adverse events even in individuals carrying immunogenic liabilities.

Shared Clavulanate and Tazobactam Antigenic Determinants Activate T-Cells from Hypersensitive Patients

β-Lactamase inhibitors such as clavulanic acid and tazobactam were developed to overcome β-lactam antibiotic resistance. Hypersensitivity reactions to these drugs have not been studied in detail, and the antigenic determinants that activate T-cells have not been defined. The objectives of this study were to (i) characterize clavulanate- and tazobactam-responsive T-cells from hypersensitive patients, (ii) explore clavulanate and tazobactam T-cell crossreactivity, and (iii) define the antigenic determinants that contribute to T-cell reactivity. Antigen specificity, pathways of T-cell activation, and crossreactivity with clavulanate- and tazobactam-specific T-cell clones were assessed by proliferation and cytokine release assays. Antigenic determinants were analyzed by mass spectrometry-based proteomics methods. Clavulanate- and tazobactam-responsive CD4⁺ T-cell clones were stimulated to proliferate and secrete IFN-γ in an MHC class II-restricted and dose-dependent manner. T-cell activation with clavulanate- and tazobactam was dependent on antigen presenting cells because their fixation prevented the T-cell response. Strong crossreactivity was observed between clavulanate- and tazobactam-T-cells; however, neither drug activated β-lactam antibiotic-responsive T-cells. Mass spectrometric analysis revealed that both compounds form multiple antigenic determinants with lysine residues on proteins, including an overlapping aldehyde and hydrated aldehyde adduct with mass additions of 70 and 88 Da, respectively. Collectively, these data show that although clavulanate and tazobactam are structurally distinct, the antigenic determinants formed by both drugs overlap, which explains the observed T-cell cross-reactivity.

Genetics of drug-induced liver injury: Current knowledge and future prospects

Idiosyncratic drug-induced liver injury (DILI) remains an important clinical problem, both during drug development and the prescription of a range of licensed drugs. Although rare, the consequences are serious. Ongoing studies on genetic risk factors for DILI, especially genomewide association studies, have resulted in the identification of a number of genetic risk factors, including particular HLA alleles and a few non-HLA genes, both immune-related and metabolic. Some non-HLA associations, such as N-acetyltransferase 2 in isoniazid DILI and interferon regulatory factor 6 in interferon-beta DILI are likely to be drug-specific due to the role of the associated gene, but there is also evidence for polygenic susceptibility involving pathways such as oxidative and endoplasmic reticulum stress and mitochondrial function for DILI induced by multiple drugs. Increased knowledge of genetic risk factors should assist in better understanding underlying DILI mechanisms and help improve methods for identifying hepatotoxic drugs early in development. HLA allele-specific T cell proliferation together with in silico prediction of drug binding to specific HLA proteins have confirmed genetic findings for certain common causes of DILI. However, studies in hepatocytes exposed to high drug concentrations suggest toxicity that is not dependent on genotype also occurs. It seems likely that susceptibility to DILI involves several genetic risk factors combining with other factors that affect drug levels. Despite recent progress in detecting genetic risk factors for DILI, low positive predictive values mean that general implementation of genotyping prior to prescription of potentially hepatotoxic drugs is not useful currently.

Utility of Lymphocyte Transformation Test for Assisting Updated Roussel Uclaf Causality Assessment Method in Drug-Induced Liver Injury: A Case-Control Study

Background: The Roussel Uclaf Causality Assessment Method (RUCAM) is a validated tool for assessing causality in cases of suspected drug-induced liver injury (DILI). However, RUCAM cannot discriminate between concomitant hepatotoxic drugs with the same temporal sequence.

Objective: To analyse the utility of the lymphocyte transformation test (LTT) for assisting updated RUCAM in 45 patients and 40 controls with a clinical diagnosis of DILI.

Methods: Suspected DILI cases were detected through the Prospective Pharmacovigilance Program from Laboratory Signals in Hospital (PPLSH) or by consultations. The controls completed the drug therapy with no adverse reactions during the study period. A receiver operating characteristics (ROC) curve analysis was performed to calculate the optimal cut-off value for the stimulation index (SI), corresponding to the largest sum for the specificity and sensitivity values of LTT for true DILI cases.

Results: Out of 45 patients diagnosed with DILI, 42 cases were detected by the PPLSH, two cases by consultation and one case by both methods. Most DILI cases (64.4%) arose during hospitalization. According to the biochemical parameters, 24 cases (53.3%) had the hepatocellular phenotype, 14 (31.1%) had the cholestatic phenotype, and 7 cases (15.6%) had the mixed phenotype. Considering the severity criteria, 7 (15.5%) cases were classified as moderate DILI, and 4 (8.9%) were severe DILI; there were no fatal cases. A total of 149 drugs (median/case, 3; IQR, 2–5) were suspected to be involved in the DILI cases (RUCAM score ≥3). In 8 cases, only one drug was suspected, and polypharmacy (≥5 drugs) was identified in 29% of the cases. Of all DILI cases, 46 (30.9%) of the 149 suspected drugs produced positive LTT results, and the LTT was positive in 34 (75.5%) of the 45 patients. No exposed controls produced positive LTT results. The optimal cut-off of 1.95 for the SI was obtained with a sensitivity of 77% and specificity of 100% (area under the curve, 0.91; 95% asymptotic confidence interval 0.84–0.97; p < 0.001). The sensitivity of the hepatocellular phenotype was 92%.

Conclusion: Our results demonstrate that LTT is an add on strengthening causality in cases of suspected idiosyncratic DILI, especially for patients with several suspected drugs and a hepatocellular phenotype.

The Immunological Mechanisms and Immune-Based Biomarkers of Drug-Induced Liver Injury

Drug-induced liver injury (DILI) has become one of the major challenges of drug safety all over the word. So far, about 1,100 commonly used drugs including the medications used regularly, herbal and/or dietary supplements, have been reported to induce liver injury. Moreover, DILI is the main cause of the interruption of new drugs development and drugs withdrawn from the pharmaceutical market. Acute DILI may evolve into chronic DILI or even worse, commonly lead to life-threatening acute liver failure in Western countries. It is generally considered to have a close relationship to genetic factors, environmental risk factors, and host immunity, through the drug itself or its metabolites, leading to a series of cellular events, such as haptenization and immune response activation. Despite many researches on DILI, the specific biomarkers about it are not applicable to clinical diagnosis, which still relies on the exclusion of other causes of liver disease in clinical practice as before. Additionally, circumstantial evidence has suggested that DILI is mediated by the immune system. Here, we review the underlying mechanisms of the immune response to DILI and provide guidance for the future development of biomarkers for the early detection, prediction, and diagnosis of DILI.

Lymphocyte Profile and Immune Checkpoint Expression in Drug-Induced Liver Injury: An Immunophenotyping Study

The identification of specific HLA risk alleles in drug-induced liver injury (DILI) points toward an important role of the adaptive immune system in DILI development. In this study, we aimed to corroborate the role of an adaptive immune response in DILI through immunophenotyping of leukocyte populations and immune checkpoint expressions. Blood samples were collected from adjudicated DILI (n = 12), acute viral hepatitis (VH; n = 13), acute autoimmune hepatitis (AIH; n = 9), and acute liver injury of unknown etiology (n = 15) at day 1 (recognition), day 7, and day >30. Blood samples from patients with nonalcoholic fatty liver disease (NAFLD; n = 20) and healthy liver controls (HLCs; n = 54) were extracted at one time point. Leukocyte populations and immune checkpoint expressions were determined based on cell surface receptors, except for CTLA-4 that was determined intracellularly, using flow cytometry. At recognition, DILI demonstrated significantly higher levels of activated helper T-cell (P < 0.0001), activated cytotoxic T-cells (P = 0.0003), Th1 (P = 0.0358), intracellular CTLA-4 level in helper T-cells (P = 0.0192), and PD-L1 presenting monocytes (P = 0.0452) than HLC. These levels approached those of HLC over time. No significant differences were found between DILI and VH. However, DILI presented higher level of activated helper T-cells and CTLA-4 than NAFLD and lower PD-L1 level than AIH. Our findings suggest that an adaptive immune response is involved in DILI in which activated CD4+ and CD8+ play an important role. Increased expression of negative immune checkpoints is likely the effect of peripheral tolerance regulation.

HLA Allele-Restricted Immune-Mediated Adverse Drug Reactions: Framework for Genetic Prediction

Human leukocyte antigen (HLA) is a hallmark genetic marker for the prediction of certain immune-mediated adverse drug reactions (ADRs). Numerous basic and clinical research studies have provided the evidence base to push forward the clinical implementation of HLA testing for the prevention of such ADRs in susceptible patients. This review explores current translational progress in using HLA as a key susceptibility factor for immune ADRs and highlights gaps in our knowledge. Furthermore, relevant findings of HLA-mediated drug-specific T cell activation are covered, focusing on cellular approaches to link genetic associations to drug-HLA binding as a complementary approach to understand disease pathogenesis. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Shedding Light on Drug-Induced Liver Injury: Activation of T Cells From Drug Naive Human Donors With Tolvaptan and a Hydroxybutyric Acid Metabolite

Exposure to tolvaptan is associated with a significant risk of liver injury in a small fraction of patients with autosomal dominant polycystic kidney disease. The observed delayed onset of liver injury of between 3 and 18 months after commencing tolvaptan treatment, along with rapid recurrence of symptoms following re-challenge is indicative of an adaptive immune attack. This study set out to assess the intrinsic immunogenicity of tolvaptan and pathways of drug-specific T-cell activation using in vitro cell culture platforms. Tolvaptan (n = 7), as well as oxybutyric (DM-4103, n = 1) and hydroxybutyric acid (DM-4107, n = 18) metabolite-specific T-cell clones were generated from tolvaptan naive healthy donor peripheral blood mononuclear cells. Tolvaptan and DM-4103 T-cell clones could also be activated with DM-4107, whereas T-cell clones originally primed with DM-4107 were highly specific to this compound. A signature cytokine profile (IFN-γ, IL-13, granzyme B, and perforin) for almost all T-cell clones was identified. Mechanistically, compound-specific T-cell clone activation was dependent on the presence of soluble drug and could occur within 4 h of drug exposure, ruling out a classical hapten mechanism. However, antigen processing dependence drug presentation was indicated in many T-cell clones. Collectively these data show that tolvaptan-associated liver injury may be attributable to an adaptive immune attack upon the liver, with tolvaptan- and metabolite-specific T cells identified as candidate effector cells in such etiology.

HLA DRB1*15:01-DQB1*06:02-Restricted Human CD4+ T Cells Are Selectively Activated With Amoxicillin-Peptide Adducts

Amoxicillin-clavulanate is the most common cause of idiosyncratic drug-induced liver injury (DILI). Drug-specific CD4+ T cells have been detected in patients with DILI, suggestive of an immune etiology. Furthermore, genetic associations including the human leucocyte antigen (HLA) DRB1*15:01-DQB1*06:02 haplotype influence susceptibility. Amoxicillin forms protein adducts that are postulated to activate T cells, by conjugating with lysine residues. However, a role for such adducts has not been described. This study aimed to (1) investigate whether amoxicillin-modified HLA-DRB1*15:01-DQB1*06:02 binding peptides selectively activate DILI patient T cells and (2) define the nature of the T-cell response with respective to antigen structure. Peptides carrying lysine residues for amoxicillin binding in positions (KP) 2-6 and anchors for the HLA-DRB1*15:01-DQB1*06:02 haplotype were designed. The amoxicillin-modified peptides were characterized by mass spectrometry prior to culturing with patient peripheral blood mononuclear cell. T-cell clones were then tested for specificity with amoxicillin, unmodified- and amoxicillin-modified peptides, and structural variants. Amoxicillin-modified KP-2 and KP-3 peptide-specific CD4+ clones proliferated and secreted interferon gamma (IFN-γ), interleukin (IL)-10, perforin and/or IL-17/IL-22 in a dose-dependent manner and displayed no cross-reactivity with amoxicillin, unmodified peptide or with positional derivatives. The T cells response was HLA class II restricted and the amoxicillin-modified peptides bound selectively to HLA-DRB1*15:01 and/or DQB1*06:02. To conclude, we show that amoxicillin-modified peptides bind to both components of the risk haplotype to stimulate DILI patient T cells and describe the importance of the position of nucleophilic lysine residue in the HLA binding peptide sequence.

Molecular fingerprinting by single cell clone analysis in adverse drug reaction (ADR) assessment

Causality assessment for idiosyncratic ADRs mainly relies on epidemiology, signal detection and less often on proven or plausible mechanistic evidence of the drug at a cellular or organ level. Distinct clones of cells can exist within organs of individual patients, some conferring susceptibility to well recognised adverse drug reactions (ADRs). Recent advances in molecular biology has allowed the development of single cell clonal techniques, including single cell RNA sequencing (scRNA-seq) to molecularly fingerprint ADRs and distinguish between distinct clones of cells within organs in individuals, which may confer differing susceptibilities to ADRs. ScRNA-seq permits molecular fingerprinting of some serious ADRs, mainly in the skin, through identification of directly expressed genes (DEG) of interest within specific clones. Overexpressed DEGs provides an opportunity for targeted treatment strategies to be developed. scRNA-seq could be applied to a number of other ADRs involving tissues that can be biopsied/sampled (including skin, liver, kidney, blood, stem cells) as well as providing a molecular basis for rapid screening of potential therapeutic candidates, which may not otherwise be predictable from class of toxicity/organ involvement. . A framework for putative assessment for ADRs using scRNA-seq is proposed as well as speculating on potential regulatory implications for pharmacovigilance and drug development. Molecular fingerprinting of ADRs using scRNA-seq may allow better targeting for enhanced pharmacovigilance and risk minimisation measures for medicines with appropriate benefit risk profiles, although cost-effectiveness and other factors, such as frequency/severity of individual ADRs and population differences will still be relevant.

Setting the Beta-Lactam Therapeutic Range for Critically Ill Patients: Is There a Floor or Even a Ceiling?

Beta-lactam antibiotics exhibit high interindividual variability in drug concentrations in patients with critical illness which led to an interest in the use of therapeutic drug monitoring to improve effectiveness and safety. To implement therapeutic drug monitoring, it is necessary to define the beta-lactam therapeutic range-in essence, what drug concentration would prompt a clinician to make dose adjustments up or down. This objective of this narrative review was to summarize evidence for the "floor" (for effectiveness) and "ceiling" (for toxicity) for the beta-lactam therapeutic range to be used with individualized therapeutic drug monitoring.

DATA SOURCES

Research articles were sourced from PubMed using search term combinations of "pharmacokinetics," "pharmacodynamics," "toxicity," "neurotoxicity," "therapeutic drug monitoring," "beta-lactam," "cefepime," "meropenem," "piperacillin/tazobactam," "ICU," and "critical illness."

STUDY SELECTION

Articles were selected if they included preclinical, translational, or clinical data on pharmacokinetic and pharmacodynamic thresholds for effectiveness and safety for beta-lactams in critical illness.

DATA SYNTHESIS

Experimental data indicate a beta-lactam concentration above the minimum inhibitory concentration of the organism for greater than or equal to 40-60% of the dosing interval is needed, but clinical data indicate that higher concentrations may be preferrable. In the first 48 hours of critical illness, a free beta-lactam concentration at or above the susceptibility breakpoint of the most likely pathogen for 100% of the dosing interval would be reasonable (typically based on Pseudomonas aeruginosa). After 48 hours, the lowest acceptable concentration could be tailored to 1-2× the observed minimum inhibitory concentration of the organism for 100% of the dosing interval (often a more susceptible organism). Neurotoxicity is the primary dose-dependent adverse effect of beta-lactams, but the evidence remains insufficient to link a specific drug concentration to greater risk.

CONCLUSIONS

As studies advance the understanding of beta-lactam exposure and response in critically ill patients, it is essential to clearly define the acceptable therapeutic range to guide regimen selection and adjustment.

Drug-specific T-cell responses in patients with liver injury following treatment with the BACE inhibitor atabecestat

BACKGROUND

Atabecestat is an orally administered BACE inhibitor developed to treat Alzheimer's disease. Elevations in hepatic enzymes were detected in a number of in trial patients, which resulted in termination of the drug development programme. Immunohistochemical characterization of liver tissue from an index case of atabecestat-mediated liver injury revealed an infiltration of T-lymphocytes in areas of hepatocellular damage. This coupled with the fact that liver injury had a delayed onset suggests that the adaptive immune system may be involved in the pathogenesis. The aim of this study was to generate and characterize atabecestat(metabolite)-responsive T-cell clones from patients with liver injury.

METHODS

Peripheral blood mononuclear cells were cultured with atabecestat and its metabolites (diaminothiazine [DIAT], N-acetyl DIAT & epoxide) and cloning was attempted in a number of patients. Atabecestat(metabolite)-responsive clones were analysed in terms of T-cell phenotype, function, pathways of T-cell activation and cross-reactivity with structurally related compounds.

RESULTS

CD4⁺ T-cell clones activated with the DIAT metabolite were detected in 5 out of 8 patients (up to 4.5% cloning efficiency). Lower numbers of CD4⁺ and CD8⁺ clones displayed reactivity against atabecestat. Clones proliferated and secreted IFN-γ, IL-13 and cytolytic molecules following atabecestat or DIAT stimulation. Certain atabecestat and DIAT-responsive clones cross-reacted with N-acetyl DIAT; however, no cross-reactivity was observed between atabecestat and DIAT. CD4⁺ clones were activated through a direct, reversible compound-HLA class II interaction with no requirement for protein processing.

CONCLUSION

The detection of atabecestat metabolite-responsive T-cell clones activated via a pharmacological interactions pathway in patients with liver injury is indicative of an immune-based mechanism for the observed hepatic enzyme elevations.

Immune-Mediated Drug-Induced Liver Injury: Immunogenetics and Experimental Models

Drug-induced liver injury (DILI) is a challenging clinical event in medicine, particularly because of its ability to present with a variety of phenotypes including that of autoimmune hepatitis or other immune mediated liver injuries. Limited diagnostic and therapeutic tools are available, mostly because its pathogenesis has remained poorly understood for decades. The recent scientific and technological advancements in genomics and immunology are paving the way for a better understanding of the molecular aspects of DILI. This review provides an updated overview of the genetic predisposition and immunological mechanisms behind the pathogenesis of DILI and presents the state-of-the-art experimental models to study DILI at the pre-clinical level.

In-Vitro Approaches to Predict and Study T-Cell Mediated Hypersensitivity to Drugs

Mitigating the risk of drug hypersensitivity reactions is an important facet of a given pharmaceutical, with poor performance in this area of safety often leading to warnings, restrictions and withdrawals. In the last 50 years, efforts to diagnose, manage, and circumvent these obscure, iatrogenic diseases have resulted in the development of assays at all stages of a drugs lifespan. Indeed, this begins with intelligent lead compound selection/design to minimize the existence of deleterious chemical reactivity through exclusion of ominous structural moieties. Preclinical studies then investigate how compounds interact with biological systems, with emphasis placed on modeling immunological/toxicological liabilities. During clinical use, competent and accurate diagnoses are sought to effectively manage patients with such ailments, and pharmacovigilance datasets can be used for stratification of patient populations in order to optimise safety profiles. Herein, an overview of some of the in-vitro approaches to predict intrinsic immunogenicity of drugs and diagnose culprit drugs in allergic patients after exposure is detailed, with current perspectives and opportunities provided.

HLA Class-II‒Restricted CD8+ T Cells Contribute to the Promiscuous Immune Response in Dapsone-Hypersensitive Patients

HLA-B∗13:01 is associated with dapsone (DDS)-induced hypersensitivity, and it has been shown that CD4+ and CD8+ T cells are activated by DDS and its nitroso metabolite (nitroso dapsone [DDS-NO]). However, there is a need to define the importance of the HLA association in the disease pathogenesis. Thus, DDS- and DDS-NO‒specific CD8+ T-cell clones (TCCs) were generated from hypersensitive patients expressing HLA-B∗13:01 and were assessed for phenotype and function, HLA allele restriction, and killing of target cells. CD8+ TCCs were stimulated to proliferate and secrete effector molecules when exposed to DDS and/or DDS-NO. DDS-responsive and several DDS-NO‒responsive TCCs expressing a variety of TCR sequences displayed HLA class-I restriction, with the drug (metabolite) interacting with multiple HLA-B alleles. However, activation of certain DDS-NO‒responsive CD8+ TCCs was inhibited with HLA class-II block, with DDS-NO binding to HLA-DQB1∗05:01. These TCCs were of different origin but expressed TCRs displaying the same amino acid sequences. They were activated through a hapten pathway; displayed CD45RO, CD28, PD-1, and CTLA-4 surface molecules; secreted the same panel of effector molecules as HLA class-I‒restricted TCCs; but displayed a lower capacity to lyse target cells. To conclude, DDS and DDS-NO interact with a number of HLA molecules to activate CD8+ TCCs, with HLA class-II‒restricted CD8+ TCCs that display hybrid CD4‒CD8 features also contributing to the promiscuous immune response that develops in patients.

Drug hapten-specific T-cell activation: Current status and unanswered questions

Drug haptens are formed from the irreversible, covalent binding of drugs to nucleophilic moieties on proteins, which can warrant adverse reactions in the body including severe delayed-type, T-cell mediated, drug hypersensitivity reactions (DHRs). While three main pathways exist for the activation of T-cells in DHRs, namely the hapten model, the pharmacological interaction model and the altered peptide repertoire model, the exact antigenic determinants responsible have not yet been defined. In recent years, progress has been made using advanced mass spectrometry-based proteomic methods to identify protein carriers and characterise the structure of drug-haptenated proteins. Since genome-wide association studies discovered a link between human leukocyte antigens (HLA) and an individual's susceptibility to DHRs, much effort has been made to define the drug-associated HLA ligands driving T-cell activation, including the elution of natural HLA peptides from HLA molecules and the generation of HLA-binding peptides. In this review, we discuss our current methodology used to design and synthesise drug-modified HLA ligands to investigate their immunogenicity using T-cell models, and thus their implication in drug hypersensitivity.

The complexity of T cell-mediated penicillin hypersensitivity reactions

Penicillin refers to a group of beta-lactam antibiotics that are the first-line treatment for a range of infections. However, they also possess the ability to form novel antigens, or neoantigens, through haptenation of proteins and can stimulate a range of immune-mediated adverse reactions-collectively known as drug hypersensitivity reactions (DHRs). IgE-mediated reactions towards these neoantigens are well studied; however, IgE-independent reactions are less well understood. These reactions usually manifest in a delayed manner as different forms of cutaneous eruptions or liver injury consistent with priming of an immune response. Ex vivo studies have confirmed the infiltration of T cells into the site of inflammation, and the subsets of T cells involved appear dependent on the nature of the reaction. Here, we review the evidence that has led to our current understanding of these immune-mediated reactions, discussing the nature of the lesional T cells, the characterization of drug-responsive T cells isolated from patient blood, and the potential mechanisms by which penicillins enter the antigen processing and presentation pathway to stimulate these deleterious responses. Thus, we highlight the need for a more comprehensive understanding of the underlying genetic and molecular basis of penicillin-induced DHRs.

Tolvaptan- and Tolvaptan-Metabolite-Responsive T Cells in Patients with Drug-Induced Liver Injury

Tolvaptan is an effective drug for the treatment of autosomal dominant polycystic kidney disease, but its use is associated with a significant risk of liver injury in a small number of patients. Herein we describe the presence of tolvaptan- and tolvaptan-metabolite-responsive T cell clones within the peripheral circulation of patients with liver injury. Drug treatment of the clones resulted in a proliferative response and secretion of IFN-γ, IL-13, and the cytolytic molecule granzyme B. Future work should explore pathways of tolvaptan driven T cell activation and the role of T cells in the disease pathogenesis.

Beta-lactam-induced immediate hypersensitivity reactions: A genome-wide association study of a deeply phenotyped cohort

BACKGROUND

β-lactam antibiotics are associated with a variety of immune-mediated or hypersensitivity reactions, including immediate (type I) reactions mediated by antigen-specific IgE.

OBJECTIVE

We sought to identify genetic predisposing factors for immediate reactions to β-lactam antibiotics.

METHODS

Patients with a clinical history of immediate hypersensitivity reactions to either penicillins or cephalosporins, which were immunologically confirmed, were recruited from allergy clinics. A genome-wide association study was conducted on 662 patients (the discovery cohort) with a diagnosis of immediate hypersensitivity and the main finding was replicated in a cohort of 98 Spanish cases, recruited using the same diagnostic criteria as the discovery cohort.

RESULTS

Genome-wide association study identified rs71542416 within the Class II HLA region as the top hit (P = 2 × 10^-14); this was in linkage disequilibrium with HLA-DRB1∗10:01 (odds ratio, 2.93; P = 5.4 × 10^-7) and HLA-DQA1∗01:05 (odds ratio, 2.93, P = 5.4 × 10^-7). Haplotype analysis identified that HLA-DRB1∗10:01 was a risk factor even without the HLA-DQA1∗01:05 allele. The association with HLA-DRB1∗10:01 was replicated in another cohort, with the meta-analysis of the discovery and replication cohorts showing that HLA-DRB1∗10:01 increased the risk of immediate hypersensitivity at a genome-wide level (odds ratio, 2.96; P = 4.1 × 10^-9). No association with HLA-DRB1∗10:01 was identified in 268 patients with delayed hypersensitivity reactions to β-lactams.

CONCLUSIONS

HLA-DRB1∗10:01 predisposed to immediate hypersensitivity reactions to penicillins. Further work to identify other predisposing HLA and non-HLA loci is required.

Characterization of amoxicillin and clavulanic acid specific T-cell clones from patients with immediate drug hypersensitivity

BACKGROUND

Betalactam (BL) antibiotics are the most common cause of drug hypersensitivity. Amoxicillin (AX), which is often prescribed alongside clavulanic acid (Clav), is the most common elicitor. The aim of this study was to determine whether AX and Clav-responsive T-cells are detectable in patients with immediate hypersensitivity to AX-Clav, to assess whether these T-cells display the same specificity as that detected in skin and provocation testing, and to explore T-cell activation pathways.

METHODS

Drug-specific T-cell clones were generated from immediate hypersensitive patients´ blood by serial dilution and repetitive mitogen stimulation. Antigen specificity was assessed by measurement of proliferation and cytokine release. CD4+ /CD8+ phenotype and chemokine receptor expression were analyzed by flow cytometry.

RESULTS

110 AX-specific and 96 Clav-specific T-cell clones were generated from seven patients with positive skin test to either AX or Clav. Proliferation of AX- and Clav-specific clones was dose-dependent, and no cross-reactivity was observed. AX- and Clav-specific clones required antigen-presenting cells to proliferate, and drugs were presented to CD4+ and CD8+ T-cells by MHC class-II and I, respectively. A higher secretion of IL-13 and IL-5 was detected in presence of the culprit drug compared with the alternative drug. Clones expressed CD69, CCR4, CXCR3, and CCR10.

CONCLUSIONS

Our study details the antigen specificity and phenotype of T-cell clones generated from patients with AX-Clav-induced immediate hypersensitivity diagnosed by positive skin test. AX- and Clav-specific clones were generated from patients irrespective of whether AX or Clav was the culprit, although differences in cytokine secretion were observed.

Drug induced liver injury: an update

Drug induced liver injury (DILI) is a relatively rare hepatic condition in response to the use of medications, illegal drugs, herbal products or dietary supplements. It occurs in susceptible individuals through a combination of genetic and environmental risk factors believed to modify drug metabolism and/or excretion leading to a cascade of cellular events, including oxidative stress formation, apoptosis/necrosis, haptenization, immune response activation and a failure to adapt. The resultant liver damage can present with an array of phenotypes, which mimic almost every other liver disorder, and varies in severity from asymptomatic elevation of liver tests to fulminant hepatic failure. Despite recent research efforts specific biomarkers are not still available for routine use in clinical practice, which makes the diagnosis of DILI uncertain and relying on a high degree of awareness of this condition and the exclusion of other causes of liver disease. Diagnostic scales such as the CIOMS/RUCAM can support the causality assessment of a DILI suspicion, but need refinement as some criteria are not evidence-based. Prospective collection of well-vetted DILI cases in established DILI registries has allowed the identification and validation of a number of clinical variables, and to predict a more severe DILI outcome. DILI is also in need of properly designed clinical trials to evaluate the efficacy of new DILI treatments as well as older drugs such as ursodeoxycholic acid traditionally used to ameliorate cholestasis or corticosteroids now widely tried in the oncology field to manage the emergent type of hepatotoxicity related to immune checkpoint inhibitors.

Immune dysregulation increases the incidence of delayed-type drug hypersensitivity reactions

Delayed-type, T cell-mediated, drug hypersensitivity reactions are a serious unwanted manifestation of drug exposure that develops in a small percentage of the human population. Drugs and drug metabolites are known to interact directly and indirectly (through irreversible protein binding and processing to the derived adducts) with HLA proteins that present the drug-peptide complex to T cells. Multiple forms of drug hypersensitivity are strongly linked to expression of a single HLA allele, and there is increasing evidence that drugs and peptides interact selectively with the protein encoded by the HLA allele. Despite this, many individuals expressing HLA risk alleles do not develop hypersensitivity when exposed to culprit drugs suggesting a nonlinear, multifactorial relationship in which HLA risk alleles are one factor. This has prompted a search for additional susceptibility factors. Herein, we argue that immune regulatory pathways are one key determinant of susceptibility. As expression and activity of these pathways are influenced by disease, environmental and patient factors, it is currently impossible to predict whether drug exposure will result in a health benefit, hypersensitivity or both. Thus, a concerted effort is required to investigate how immune dysregulation influences susceptibility towards drug hypersensitivity.

Drug-Induced Liver Injury: Clinical and Etiologic Features at a Large Tertiary Teaching Hospital in China

BACKGROUND Since the epidemiological profile of drug-induced liver injury (DILI) in China, especially the western of China, it has rarely been studied. The aim of this study was to analyze the characteristics of DILI patients in a large tertiary teaching hospital at Chongqing, a municipality in western China. MATERIAL AND METHODS The medical records of hospitalized patients which diagnosed with DILI between January 2011 and December 2016 were searched retrospectively, and demographic, clinical data, and laboratory data were retrieved for analysis. RESULTS A total of 1811 patients had been diagnosed with DILI, accounting for 0.248% of the total admissions during the same period. Among the 1096 patients included in our analysis, DILI was caused by "medications" in 462 cases (42.15%), "herbs" in 391 cases (35.68%), and combined medications in 189 cases (17.24%). The profiles for each etiology were distinctive for age, sex, clinical features, laboratory features, and types and severity of DILI. CONCLUSIONS Our study provides a systematic etiological profile of DILI in Chinese patients, which can represent references for prevention, diagnosis and treatment, supporting and promoting efforts to ease the burden of this liver disease in China.

Characterization of Healthy Donor-Derived T-Cell Responses Specific to Telaprevir Diastereomers

Telaprevir, a protease inhibitor, was used alongside PEGylated interferon-α and ribavirin to treat hepatitis C viral infections. The triple regimen proved successful; however, the appearance of severe skin reactions alongside competition from newer drugs restricted its use. Skin reactions presented with a delayed onset indicative of a T-cell mediated reaction. Thus, the aim of this study was to investigate whether telaprevir and/or its diastereomer, which is generated in humans, activates T-cells. Telaprevir in its S-configured therapeutic form and the R-diastereomer were cultured directly with peripheral blood mononuclear cells from healthy donors prior to the generation of T-cell clones by serial dilution. Drug-specific CD4+ and CD8+ T-cell clones responsive to telaprevir and the R-diastereomer were generated and characterized in terms of phenotype and function. The clones proliferated with telaprevir and diastereomer concentrations of 5-20 µM and secreted IFN-γ, IL-13, and granzyme B. In contrast, the telaprevir M11 metabolite did not stimulate T-cells. The CD8+ T-cell response was MHC I-restricted and dependent on the presence of soluble drug. Flow cytometric analysis showed that clones expressed chemokine receptors CCR4 (skin homing) and CXCR3 (migration to peripheral tissue) and 1 of 3 distinct TCR Vβs; TCR Vβ 2, 5.1, or 22. These data show the propensity of both R- and S-forms of telaprevir to generate skin-homing cytotoxic T-cells that may induce the adverse reactions observed in human patients.

Understanding Idiosyncratic Toxicity: Lessons Learned from Drug-Induced Liver Injury

Idiosyncratic adverse drug reactions (IADRs) encompass a diverse group of toxicities that can vary by drug and patient. The complex and unpredictable nature of IADRs combined with the fact that they are rare makes them particularly difficult to predict, diagnose, and treat. Common clinical characteristics, the identification of human leukocyte antigen risk alleles, and drug-induced proliferation of lymphocytes isolated from patients support a role for the adaptive immune system in the pathogenesis of IADRs. Significant evidence also suggests a requirement for direct, drug-induced stress, neoantigen formation, and stimulation of an innate response, which can be influenced by properties intrinsic to both the drug and the patient. This Perspective will provide an overview of the clinical profile, mechanisms, and risk factors underlying IADRs as well as new approaches to study these reactions, focusing on idiosyncratic drug-induced liver injury.

T-Cell Activation by Low Molecular Weight Drugs and Factors That Influence Susceptibility to Drug Hypersensitivity

Drug hypersensitivity reactions adversely affect treatment outcome, increase the length of patients' hospitalization, and limit the prescription options available to physicians. In addition, late stage drug attrition and the withdrawal of licensed drugs cost the pharmaceutical industry billions of dollars. This significantly increases the overall cost of drug development and by extension the price of licensed drugs. Drug hypersensitivity reactions are characterized by a delayed onset, and reactions tend to be more serious upon re-exposure. The role of drug-specific T-cells in the pathogenesis of drug hypersensitivity reactions and definition of the nature of the binding interaction of drugs with HLA and T-cell receptors continues to be the focus of intensive research, primarily because susceptibility is associated with expression of one or a small number of HLA alleles. This review critically examines the mechanisms of T-cell activation by drugs. Specific examples of drugs that activate T-cells via the hapten, the pharmacological interaction with immune receptors and the altered self-peptide repertoire pathways, are discussed. Furthermore, the impacts of drug metabolism, drug-protein adduct formation, and immune regulation on the development of drug antigen-responsive T-cells are highlighted. The knowledge gained from understanding the pathways of T-cell activation and susceptibility factors for drug hypersensitivity will provide the building blocks for the development of predictive in vitro assays that will prevent or help to minimize the incidence of these reactions in clinic.

Definition of the Chemical and Immunological Signals Involved in Drug-Induced Liver Injury

Idiosyncratic drug-induced liver injury (iDILI), which is rare and often recognized only late in drug development, poses a major public health concern and impediment to drug development due to its high rate of morbidity and mortality. The mechanisms of DILI are not completely understood; both non-immune- and immune-mediated mechanisms have been proposed. Non-immune-mediated mechanisms including direct damage to hepatocytes, mitochondrial toxicity, interference with transporters, and alteration of bile ducts are well-known to be associated with drugs such as acetaminophen and diclofenac; whereas immune-mediated mechanisms involving activation of both adaptive and innate immune cells and the interactions of these cells with parenchymal cells have been proposed. The chemical signals involved in activation of both innate and adaptive immune responses are discussed with respect to recent scientific advances. In addition, the immunological signals including cytokine and chemokines that are involved in promoting liver injury are also reviewed. Finally, we discuss how liver tolerance and regeneration can have profound impact on the pathogenesis of iDILI. Continuous research in developing in vitro systems incorporating immune cells with liver cells and animal models with impaired liver tolerance will provide an opportunity for improved prediction and prevention of immune-mediated iDILI.

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

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

3D Primary Hepatocyte Culture Systems for Analyses of Liver Diseases, Drug Metabolism, and Toxicity: Emerging Culture Paradigms and Applications

Recent research has shown that the maintenance of relevant liver functions ex vivo requires models in which the cells exhibit an in vivo-like phenotype, often achieved by reconstitution of appropriate cellular interactions. Multiple different models have been presented that differ in the cells utilized, media, and culture conditions. Furthermore, several technologically different approaches have been presented including bioreactors, chips, and plate-based systems in fluidic or static media constituting of chemically diverse materials. Using such models, the ability to predict drug metabolism, drug toxicity, and liver functionality have increased tremendously as compared to conventional in vitro models in which cells are cultured as 2D monolayers. Here, the authors highlight important considerations for microphysiological systems for primary hepatocyte culture, review current culture paradigms, and discuss their opportunities for studies of drug metabolism, hepatotoxicity, liver biology, and disease.

The Beneficial Roles of SIRT1 in Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is a major cause of acute liver failure (ALF) as a result of accumulated drugs in the human body metabolized into toxic agents and helps generate heavy oxidative stress, inflammation, and apoptosis, which induces necrosis in hepatocytes and ultimately damages the liver. Sirtuin 1 (SIRT1) is said to have multiple vital roles in cell proliferation, aging, and antistress systems of the human body. The levels of SIRT1 and its activation precisely modulate its critical role in the interaction between multiple step procedures of DILI. The nuclear factor kappa-light-chain-enhancer of activated B cell- (NF-κB-) mediated inflammation signaling pathway, reactive oxygen species (ROS), DNA damage, mitochondrial membrane potential collapse, and endoplasmic reticulum (ER) stress also contribute to aggravate DILI. Apoptosis is regarded as the terminal reaction followed by multiple signaling cascades including caspases, p53, and mitochondrial dysfunction which have been said to contribute in DILI. The SIRT1 activator is regarded as a potential candidate for DILI, because the former could inhibit signaling of p53, NF-κB, and ER stress. On the other hand, overexpression of SIRT1 also enhances the activation of antioxidant responses via Kelch-like ECH-associated protein 1- (Keap1-) nuclear factor- (erythroid-derived 2-) like 2 (Nrf2) signaling. The current manuscript will highlight the mechanism of DILI and the interaction of SIRT1 with various cytoplasmic factors leading to DILI along with the summary of potent SIRT1 agonists.

Bibliometric Analysis of Global Research on Clavulanic Acid

Clavulanic acid (CA), a potent inhibitor of the β-lactam, ase enzyme, is frequently co-formulated with a broad spectrum of antibiotics to treat infections caused by β-lactamase-producing pathogens. In order to evaluate the impact and the progress of CA studies in the last four decades, a bibliometric analysis of the global scientific production of CA was carried out. A total of 39,758 records in the field of CA were indexed in the Scopus database for a 43-year period of study (1975⁻2017). The results indicated that CA studies have grown, showing three phases (1975⁻1999, 2000⁻2003 and 2004⁻2017) based on records of publications; the results showed a sigmoidal profile. Medicine was the main subject area for CA studies, whereas biochemistry, genetics and molecular biology were areas of research for CA production by Streptomyces clavuligerus (S. clavuligerus). Nevertheless, chemical engineering (as a subject area) had the highest increase in the percentage of publications related to CA production by S. clavuligerus. The United States, France, the United Kingdom, Spain and Brazil were the leading countries in the scientific production of studies on both CA and CA related to S. clavuligerus. This analysis allowed the identification of the area of knowledge with the highest impact on CA studies, the top researchers and their geographic distribution, and also helped to highlight the existence of antibiotic-resistant bacteria as an emergent area in CA research.

Pharmacogenomics of drug-induced liver injury (DILI): Molecular biology to clinical applications

A 21-year old woman was admitted to hospital with a two-week history of painless jaundice, fatigue and anorexia having previously been fit and well. One month prior to presentation, the patient had taken a five-day course of amoxicillin-clavulanic acid for an infected skin cyst. Otherwise, she was only on the oral contraceptive pill and reported minimal alcohol intake. On examination, she was deeply jaundiced, but alert and oriented with no asterixis. She had no stigmata of chronic liver disease, but hepatomegaly extending 3 cm from below the right subcostal margin was evident. Investigations showed: white cell count 13.4 × 10⁹/L (normal 3.6-9.3), haemoglobin 11.8 g/dl (normal 11-15), platelet count 356 × 10⁹/L (normal 170-420), sodium 138 mmol/L (normal 134-144), potassium 3.5 mmol/L (normal 3.5-5.0), creatinine 32 µmol/L (normal 40-75), albumin 30 g/L (normal 35-48), alanine aminotransferase 707 IU/L (normal 15-54), alkaline phosphatase 151 IU/L (normal 30-130), bilirubin 384 µmol/L (normal 7-31) and prothrombin time 27.2 s (normal 11.7-14). Screening for hepatitis A, B, C, E, Epstein-Barr virus, cytomegalovirus and autoimmune hepatitis was negative. Tests for anti-smooth muscle, antinuclear, and anti-liver-kidney microsomal-1 antibodies were negative; immunoglobulin levels and ceruloplasmin levels were normal. Liver ultrasonography demonstrated a liver of normal contour with no biliary dilatation, a normal spleen size and patent vessels. Liver biopsy revealed severe portal interface hepatitis with lobular inflammation and scant plasma cells. Her clinical condition deteriorated in the following days with prothrombin time and bilirubin rising to 56.6 s and 470 µmol/L, respectively. At follow-up after 11 days, her alanine aminotransferase level was 1,931 IU/L. She developed grade 2 hepatic encephalopathy 14 days after presentation, and was listed for a super-urgent liver transplant. Human leucocyte antigen (HLA) typing was performed as a part of preparatory investigations and showed the patient carried the HLA haplotype HLA-DRB1∗15:02-DQB1∗06:01. Following orthotopic transplantation of a deceased donor graft her explant histology revealed severe ongoing hepatitis with multi-acinar necrosis (Fig. 1A and B). This case raised a number of important questions about the diagnosis of drug-induced liver injury and tools available for clinicians to make the best decisions for patient care: In this Grand Rounds article, we will explore these questions, describing the pathophysiology, diagnostic and prognostic biomarkers, and clinical management of drug-induced liver injury. We will also discuss ongoing areas of uncertainty.

Pharmacogenetics of Adverse Drug Reactions

Adverse drug reactions (ADRs) are an important cause of morbidity and mortality. Genetic factors predispose to many ADRs, affecting susceptibility to both type A and type B reactions. The overall contribution of genetics will vary according to drug and ADR, and should be considered when attempting to predict and prevent ADRs. Genetic risk factors are considered in detail for a number of type A ADRs, especially those relating to warfarin and thiopurines, and type B ADRs affecting skin, the liver, and the heart. As the availability of whole genome sequencing increases, it is likely that prospective genotype for particular ADRs prior to drug prescription will become more common in the future. Current examples of genetic testing to prevent ADRs which have already been implemented and future prospects for developments in the field are discussed in detail.

Development of a modified lymphocyte transformation test for diagnosing drug-induced liver injury associated with an adaptive immune response

Drug-induced liver injury (DILI) is a growing problem. Diagnostic methods to differentiate DILI caused by an adaptive immune response from liver injury of other causes or to identify the responsible drug in patients receiving multiple drugs, herbals and/or dietary supplements (polypharmacy) have not yet been established. The lymphocyte transformation test (LTT) has been proposed as a diagnostic method to determine if a subject with an apparent hypersensitivity reaction has become sensitized to a specific drug. In this test, peripheral blood mononuclear cells (PBMC) collected from a subject are incubated with drug(s) suspected of causing the reaction. Cell proliferation, measured by the incorporation of [³H]-thymidine into new DNA, is considered evidence of a drug-specific immune response. The objectives of the current studies were to: (1) develop and optimize a modified version of the LTT (mLTT) and (2) investigate the feasibility of using the mLTT for diagnosing DILI associated with an adaptive immune response and identifying the responsible drug. PBMC collected from donors with a history of drug hypersensitivity reactions to specific drugs (manifested as skin rash) were used as positive controls for assay optimization. Following optimization, samples collected from 24 subjects enrolled in the U.S. Drug-Induced Liver Injury Network (DILIN) were tested in the mLTT. Using cytokine and granzyme B production as the primary endpoints to demonstrate lymphocyte sensitization to a specific drug, most samples from the DILIN subjects failed to respond. However, robust positive mLTT responses were observed for two of four samples from three DILIN subjects with hepatitis due to isoniazid (INH). We conclude that the mLTT, as performed here on frozen and thawed PBMC, is not a reliable test for diagnosing DILI caused by all drugs, but that it may be useful for confirming the role of the adaptive immune response in DILI ascribed to INH.

"Autoimmune(-Like)" Drug and Herb Induced Liver Injury: New Insights into Molecular Pathogenesis

Idiosyncratic drug-induced liver injury (DILI) and hepatic injury due to herbal and dietary supplements (HDS) can adapt clinical characteristics of autoimmune hepatitis (AIH), such as the appearance of autoantibodies and infiltration of the liver by immune competent cells. To describe these cases of DILI/HDS, the poorly-defined term "autoimmune(-like)" DILI/HDS came up. It is uncertain if these cases represent a subgroup of DILI/HDS with distinct pathomechanistic and prognostic features different from "classical" DILI/HDS. Besides, due to the overlap of clinical characteristics of "immune-mediated" DILI/HDS and AIH, both entities are not easy to differentiate. However, the demarcation is important, especially with regard to treatment: AIH requires long-term, mostly lifelong immunosuppression, whereas DILI/HDS does not. Only through exact diagnostic evaluation, exclusion of differential diagnoses and prolonged follow-up can the correct diagnosis reliably be made. Molecular mechanisms have not been analysed for the subgroup of "autoimmune(-like)" DILI/HDS yet. However, several pathogenetic checkpoints of DILI/HDS in general and AIH are shared. An analysis of these shared mechanisms might hint at relevant molecular processes of "autoimmune(-like)" DILI/HDS.

Drug-induced bile duct injury

Drug-induced liver injury includes a spectrum of pathologies, some related to the mode of injury, some to the cell type primarily damaged. Among these, drug-induced bile duct injury is characterized by the destruction of the biliary epithelium following exposure to a drug. Most of the drugs associated with bile duct injury cause immune-mediated lesions to the epithelium of interlobular ducts. These share common histopathological features with primary biliary cholangitis, such as inflammation and necrosis at the expense of cholangiocytes and, if the insult persists, bile duct loss and biliary cirrhosis. Some drugs selectively target larger ducts. Such injury is often dose-dependent and thought to be the result of intrinsic drug toxicity. The histological changes resemble those seen in primary sclerosing cholangitis. This overview focuses on the clinical and pathological features of bile duct injury associated with drug treatment and on the immunological and biochemical effects that drugs exert on the biliary epithelium. This article is part of a Special Issue entitled: Cholangiocytes in Health and Disease edited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.