Molecular mechanisms of hepatotoxic cholestasis by clavulanic acid: Role of NRF2 and FXR pathways

Farnesoid X receptor: From Structure to Function and Its Pharmacology in Liver Fibrosis

The farnesoid X receptor (FXR), a ligand-activated transcription factor, plays a crucial role in regulating bile acid metabolism within the enterohepatic circulation. Beyond its involvement in metabolic disorders and immune imbalances affecting various tissues, FXR is implicated in microbiota modulation, gut-to-brain communication, and liver disease. The liver, as a pivotal metabolic and detoxification organ, is susceptible to damage from factors such as alcohol, viruses, drugs, and high-fat diets. Chronic or recurrent liver injury can culminate in liver fibrosis, which, if left untreated, may progress to cirrhosis and even liver cancer, posing significant health risks. However, therapeutic options for liver fibrosis remain limited in terms of FDA-approved drugs. Recent insights into the structure of FXR, coupled with animal and clinical investigations, have shed light on its potential pharmacological role in hepatic fibrosis. Progress has been achieved in both fundamental research and clinical applications. This review critically examines recent advancements in FXR research, highlighting challenges and potential mechanisms underlying its role in liver fibrosis treatment.

Idiosyncratic Drug-Induced Liver Injury and Amoxicillin-Clavulanate: Spotlight on Gut Microbiota, Fecal Metabolome and Bile Acid Profile in Patients

Several hepatic disorders are influenced by gut microbiota, but its role in idiosyncratic drug-induced liver injury (iDILI), whose main causative agent is amoxicillin-clavulanate, remains unknown. This pioneering study aims to unravel particular patterns of gut microbiota composition and associated metabolites in iDILI and iDILI patients by amoxicillin-clavulanate (iDILI-AC). Thus, serum and fecal samples from 46 patients were divided into three study groups: healthy controls (n = 10), non-iDILI acute hepatitis (n = 12) and iDILI patients (n = 24). To evaluate the amoxicillin-clavulanate effect, iDILI patients were separated into two subgroups: iDILI non-caused by amoxicillin-clavulanate (iDILI-nonAC) (n = 18) and iDILI-AC patients (n = 6). Gut microbiota composition and fecal metabolome plus serum and fecal bile acid (BA) analyses were performed, along with correlation analyses. iDILI patients presented a particular microbiome profile associated with reduced fecal secondary BAs and fecal metabolites linked to lower inflammation, such as dodecanedioic acid and pyridoxamine. Moreover, certain taxa like Barnesiella, Clostridia UCG-014 and Eubacterium spp. correlated with significant metabolites and BAs. Additionally, comparisons between iDILI-nonAC and iDILI-AC groups unraveled unique features associated with iDILI when caused by amoxicillin-clavulanate. In conclusion, specific gut microbiota profiles in iDILI and iDILI-AC patients were associated with particular metabolic and BA status, which could affect disease onset and progression.

Severe hepatic cholestasis after treatment with amoxicillin/clavulanic acid

Amoxicillin/clavulanate is a commonly used antibiotic. Though relatively rare, amoxicillin/clavulanate carries the highest incidence of idiosyncratic drug-induced liver disease. This case report presents an 80-year-old woman treated for simple respiratory tract infection with amoxicillin/clavulanate who was subsequently hospitalized with malaise and icterus and a biochemical cholestatic pattern with high alkaline phosphatase and bilirubin. Diagnostically challenging, ultimately, liver biopsy revealed drug-induced liver injury with a fatal course after attempt of supportive, symptomatic treatment.

Uncovering the toxicity mechanisms of a series of carboxylic acids in liver cells through computational and experimental approaches

Hepatotoxicity poses a significant concern in drug design due to the potential liver damage that can be caused by new drugs. Among common manifestations of hepatotoxic damage is lipid accumulation in hepatic tissue, resulting in liver steatosis or phospholipidosis. Carboxylic derivatives are prone to interfere with fatty acid metabolism and cause lipid accumulation in hepatocytes. This study investigates the toxic behaviour of 24 structurally related carboxylic acids in hepatocytes, specifically their ability to cause accumulation of fatty acids and phospholipids. Using high-content screening (HCS) assays, we identified two distinct lipid accumulation patterns. Subsequently, we developed structure-activity relationship (SAR) and quantitative structure-activity relationship (QSAR) models to determine relevant molecular substructures and descriptors contributing to these adverse effects. Additionally, we calculated physicochemical properties associated with lipid accumulation in hepatocytes and examined their correlation with our chemical structure characteristics. To assess the applicability of our findings to a wide range of chemical compounds, we employed two external datasets to evaluate the distribution of our QSAR descriptors. Our study highlights the significance of subtle molecular structural variations in triggering hepatotoxicity, such as the presence of nitrogen or the specific arrangement of substitutions within the carbon chain. By employing our comprehensive approach, we pinpointed specific molecules and elucidated their mechanisms of toxicity, thus offering valuable insights to guide future toxicology investigations.

Prenatal amoxicillin exposure induces developmental toxicity in fetal mice and its characteristics

Amoxicillin, a widely used antibiotic in human and veterinary pharmaceuticals, is now considered as an "emerging contaminant" because it exists widespreadly in the environment and brings a series of adverse outcomes. Currently, systematic studies about the developmental toxicity of amoxicillin are still lacking. We explored the potential effects of amoxicillin exposure on pregnancy outcomes, maternal/fetal serum phenotypes, and fetal multiple organ development in mice, at different doses (75, 150, 300 mg/(kg·day)) during late-pregnancy, or at a dose of 300 mg/(kg·day) during different stages (mid-/late-pregnancy) and courses (single-/multi-course). Results showed that prenatal amoxicillin exposure (PAmE) had no significant influence on the body weights of dams, but it could inhibit the physical development and reduce the survival rate of fetuses, especially during the mid-pregnancy. Meanwhile, PAmE altered multiple maternal/fetal serum phenotypes, especially in fetuses. Fetal multi-organ function results showed that PAmE inhibited testicular/adrenal steroid synthesis, long bone/cartilage and hippocampal development, and enhanced ovarian steroid synthesis and hepatic glycogenesis/lipogenesis, and the order of severity might be gonad (testis, ovary) > liver > others. Further analysis found that PAmE-induced multi-organ developmental and functional alterations had differences in stages, courses and fetal gender, and the most obvious changes might be in high-dose, late-pregnancy and multi-course, but there was no typical rule of a dose-response relationship. In conclusion, this study confirmed that PAmE could cause abnormal development and multi-organ function alterations, which deepens our understanding of the risk of PAmE and provides an experimental basis for further exploration of the long-term harm.

Melatonin improves cholestatic liver disease via the gut-liver axis

Cholestatic liver disease is characterized by disturbances in the intestinal microbiota and excessive accumulation of toxic bile acids (BA) in the liver. Melatonin (MT) can improve liver diseases. However, the underlying mechanism remains unclear. This study aimed to explore the mechanism of MT on hepatic BA synthesis, liver injury, and fibrosis in 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-fed and Mdr2-/- mice. MT significantly improved hepatic injury and fibrosis with a significant decrease in hepatic BA accumulation in DDC-fed and Mdr2-/- mice. MT reprogramed gut microbiota and augmented fecal bile salt hydrolase activity, which was related to increasing intestinal BA deconjugation and fecal BA excretion in both DDC-fed and Mdr2-/- mice. MT significantly activated the intestinal farnesoid X receptor (FXR)/fibroblast growth factor 15 (FGF-15) axis and subsequently inhibited hepatic BA synthesis in DDC-fed and Mdr2-/- mice. MT failed to improve DDC-induced liver fibrosis and BA synthesis in antibiotic-treated mice. Furthermore, MT provided protection against DDC-induced liver injury and fibrosis in fecal microbiota transplantation mice. MT did not decrease liver injury and fibrosis in DDC-fed intestinal epithelial cell-specific FXR knockout mice, suggesting that the intestinal FXR mediated the anti-fibrosis effect of MT. In conclusion, MT ameliorates cholestatic liver diseases by remodeling gut microbiota and activating intestinal FXR/FGF-15 axis-mediated inhibition of hepatic BA synthesis and promotion of BA excretion in mice.

Clavulanic Acid and its Potential Therapeutic Effects on the Central Nervous System

Clavulanic acid (CLAV) is a non-antibiotic β-lactam that has been used since the late 1970s as a β-lactamase inhibitor in combination with amoxicillin, another ß-lactam with antibiotic activity. Its long-observed adverse reaction profile allows it to say that CLAV is a well-tolerated drug with mainly mild adverse reactions. Interestingly, in 2005, it was discovered that β-lactams enhance the astrocytic expression of GLT-1, a glutamate transporter essential for maintaining synaptic glutamate homeostasis involved in several pathologies of the central nervous system (CNS). This finding, along with a favorable pharmacokinetic profile, prompted the appearance of several studies that intended to evaluate the effect of CLAV in preclinical disease models. Studies have revealed that CLAV can increase GLT-1 expression in the nucleus accumbens (NAcc), medial prefrontal cortex (PFC), and spinal cord of rodents, to affect glutamate and dopaminergic neurotransmission, and exert an anti-inflammatory effect by modulating the levels of the cytokines TNF-α and interleukin 10 (IL-10). CLAV has been tested with positive results in preclinical models of epilepsy, addiction, stroke, neuropathic and inflammatory pain, dementia, Parkinson's disease, and sexual and anxiety behavior. These properties make CLAV a potential therapeutic drug if repurposed. Therefore, this review aims to gather information on CLAV's effect on preclinical neurological disease models and to give some perspectives on its potential therapeutic use in some diseases of the CNS.

The Potential Effects of Quercetin-Loaded Nanoliposomes on Amoxicillin/Clavulanate-Induced Hepatic Damage: Targeting the SIRT1/Nrf2/NF-κB Signaling Pathway and Microbiota Modulation

Amoxicillin/clavulanate (Co-Amox), a commonly used antibiotic for the treatment of bacterial infections, has been associated with drug-induced liver damage. Quercetin (QR), a naturally occurring flavonoid with pleiotropic biological activities, has poor water solubility and low bioavailability. The objective of this work was to produce a more bioavailable formulation of QR (liposomes) and to determine the effect of its intraperitoneal pretreatment on the amelioration of Co-Amox-induced liver damage in male rats. Four groups of rats were defined: control, QR liposomes (QR-lipo), Co-Amox, and Co-Amox and QR-lipo. Liver injury severity in rats was evaluated for all groups through measurement of serum liver enzymes, liver antioxidant status, proinflammatory mediators, and microbiota modulation. The results revealed that QR-lipo reduced the severity of Co-Amox-induced hepatic damage in rats, as indicated by a reduction in serum liver enzymes and total liver antioxidant capacity. In addition, QR-lipo upregulated antioxidant transcription factors SIRT1 and Nrf2 and downregulated liver proinflammatory signatures, including IL-6, IL-1β, TNF-α, NF-κB, and iNOS, with upregulation in the anti-inflammatory one, IL10. QR-lipo also prevented Co-Amox-induced gut dysbiosis by favoring the colonization of Lactobacillus, Bifidobacterium, and Bacteroides over Clostridium and Enterobacteriaceae. These results suggested that QR-lipo ameliorates Co-Amox-induced liver damage by targeting SIRT1/Nrf2/NF-κB and modulating the microbiota.

An integrated strategy combining network toxicology and feature-based molecular networking for exploring hepatotoxic constituents and mechanism of Epimedii Folium-induced hepatotoxicity in vitro

Epimedii Folium (EF), a commonly used herbal medicine to treat osteoporosis, has caused serious concern due to potential hepatotoxicity. Until now, its intrinsic hepatotoxic mechanism and hepatotoxic ingredients remain unclear. Here, a novel high-throughput approach was designed to investigate the intrinsic hepatotoxic of EF. High-content screen imaging (HCS) and biochemical tests were first performed to obtain the cytotoxicity parameter matrix of 17 batch EF samples. EF-treated alpha mouse liver 12 (AML12) cells showed increased reactive oxygen species (ROS), reduced glutathione (GSH) and mitochondrial membrane potential (MMP), and apoptosis and cholestasis were further observed. Network toxicology predicted that EF-triggered hepatotoxiciy was involved in transcription factor (TF) activity. The FXR expression, screened by a TF PCR array, exhibited down-regulation following EF extract administration. Moreover, EF inhibited bile acid (BA) metabolism pathway in an FXR-dependent manner. Pearson correlation between the cytotoxicity parameter matrix and quantification feature table obtained from UHPLC-QTOF data of EF suggested 7 prenylated flavonoids possessed potent hepatotoxicities and their cytotoxicity order was further summarized. The transcriptional repression effects of them on FXR were also verified. Collectively, our findings indicate that FXR is probably responsible for EF-induced hepatotoxicity and prenylated flavonoids may be a major class of hepatotoxic constituents in EF.

Molecular mechanism for the involvement of CYP2E1/NF-κB axis in bedaquiline-induced hepatotoxicity

Bedaquiline (BDQ) is a new class of anti-tubercular (anti-TB) drugs and is currently reserved for multiple drug resistance (MDR-TB). However, after receiving fast-track approval, its clinical studies demonstrate that its treatment is associated with hepatotoxicity and labeled as 'boxed warning' by the USFDA. No data is available on BDQ to understand the mechanism for drug-induced liver injury (DILI), a severe concern for therapeutic failure/unbearable tolerated toxicities leading to drug resistance. Therefore, we performed mechanistic studies to decipher the potential of BDQ at three dose levels (80 to 320 mg/kg) upon the repeated dose administration orally using a widely used mice model for TB. Results of BDQ treatment at the highest dose level showed that substantial increase of hepatic marker enzymes (SGPT and SGOT) in serum, oxidative stress marker levels (MDA and GSH) in hepatic tissue, and pro-inflammatory cytokine levels (TNF-α, IL-6, and IL-1β) in serum compared to control animals. Induction of liver injury situation was further evaluated by Western blotting for various protein expressions linked to oxidative stress (SOD, Nrf2, and Keap1), inflammation (NF-ĸB and IKKβ), apoptosis (BAX, Bcl-2, and Caspase-3) and drug metabolism enzymes (CYP3A4 and CYP2E1). The elevated plasma level of BDQ and its metabolite (N-desmethyl BDQ) were observed, corresponding to BDQ doses. Histopathological examination and SEM analysis of the liver tissue corroborate the above-mentioned findings. Overall results suggest that BDQ treatment-associated generation of its cytotoxic metabolite could act on CYP2E1/NF-kB pathway to aggravate the condition of oxidative stress, inflammation, and apoptosis in the liver and precipitating hepatotoxicity.

Multi-omics HeCaToS dataset of repeated dose toxicity for cardiotoxic & hepatotoxic compounds

The data currently described was generated within the EU/FP7 HeCaToS project (Hepatic and Cardiac Toxicity Systems modeling). The project aimed to develop an in silico prediction system to contribute to drug safety assessment for humans. For this purpose, multi-omics data of repeated dose toxicity were obtained for 10 hepatotoxic and 10 cardiotoxic compounds. Most data were gained from in vitro experiments in which 3D microtissues (either hepatic or cardiac) were exposed to a therapeutic (physiologically relevant concentrations calculated through PBPK-modeling) or a toxic dosing profile (IC20 after 7 days). Exposures lasted for 14 days and samples were obtained at 7 time points (therapeutic doses: 2-8-24-72-168-240-336 h; toxic doses 0-2-8-24-72-168-240 h). Transcriptomics (RNA sequencing & microRNA sequencing), proteomics (LC-MS), epigenomics (MeDIP sequencing) and metabolomics (LC-MS & NMR) data were obtained from these samples. Furthermore, functional endpoints (ATP content, Caspase3/7 and O2 consumption) were measured in exposed microtissues. Additionally, multi-omics data from human biopsies from patients are available. This data is now being released to the scientific community through the BioStudies data repository (https://www.ebi.ac.uk/biostudies/).

The Farnesoid X Receptor as a Master Regulator of Hepatotoxicity

The nuclear receptor farnesoid X receptor (FXR, NR1H4) is a bile acid (BA) sensor that links the enterohepatic circuit that regulates BA metabolism and elimination to systemic lipid homeostasis. Furthermore, FXR represents a real guardian of the hepatic function, preserving, in a multifactorial fashion, the integrity and function of hepatocytes from chronic and acute insults. This review summarizes how FXR modulates the expression of pathway-specific as well as polyspecific transporters and enzymes, thereby acting at the interface of BA, lipid and drug metabolism, and influencing the onset and progression of hepatotoxicity of varying etiopathogeneses. Furthermore, this review article provides an overview of the advances and the clinical development of FXR agonists in the treatment of liver diseases.

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.

Construction of a culture protocol for functional bile canaliculi formation to apply human iPS cell-derived hepatocytes for cholestasis evaluation

Cholestatic toxicity causes the failure of pharmaceutical agents during drug development and, thus, should be identified at an early stage of drug discovery and development. The formation of functional bile canaliculi in human hepatocytes is required for in vitro cholestasis toxicity tests conducted during the early stage of drug development. In this study, we investigated the culture conditions required for the formation of bile canaliculi using human-induced pluripotent stem cell-derived hepatocytes (hiPSC-Heps). When hiPSC-Heps were sandwich-cultured under the condition we established, extended bile canaliculi were formed on the whole well surfaces. Biliary efflux transporters were localized in the formed bile canaliculi structures which had junctional complexes. After the model substrates of the biliary efflux transporters were taken up into cells, their subsequent excretion into the bile canaliculi was observed and was found to be impeded by each inhibitor of the biliary efflux transporter. These findings suggest that bile canaliculi have transporter-specific bile excretion abilities. We will continue to study the application of this culture protocol to cell-based cholestasis assay system. As a result, the culture protocol could lead to a highly predictable, robust cell-based cholestasis assay system because it forms functional bile canaliculi reproducibly and efficiently.

Challenges and Future of Drug-Induced Liver Injury Research-Laboratory Tests

Drug-induced liver injury (DILI) is a rare but potentially severe adverse drug event, which is also a major cause of study cessation and market withdrawal during drug development. Since no acknowledged diagnostic tests are available, DILI diagnosis poses a major challenge both in clinical practice as well as in pharmacovigilance. Differentiation from other liver diseases and the identification of the causative agent in the case of polymedication are the main issues that clinicians and drug developers face in this regard. Thus, efforts have been made to establish diagnostic testing methods and biomarkers in order to safely diagnose DILI and ensure a distinguishment from alternative liver pathologies. This review provides an overview of the diagnostic methods used in differential diagnosis, especially with regards to autoimmune hepatitis (AIH) and drug-induced autoimmune hepatitis (DI-AIH), in vitro causality methods using individual blood samples, biomarkers for diagnosis and severity prediction, as well as experimental predictive models utilized in pre-clinical settings during drug development regimes.

Pediatric acute viral hepatitis with atypical variants: Clinical dilemmas and natural history

Classical acute viral hepatitis (AVH) has an uncomplicated outcome. Acute liver failure has a grave prognosis. Atypical manifestations of AVH are a group of disorders that causes significant morbidity and dilemmas in children. These include prolonged cholestasis, relapsing hepatitis, ascitic form of AVH, late-onset hepatic failure (LOHF), intravascular hemolysis, and provoking an autoimmune trigger leading to autoimmune hepatitis. These entities cause significant liver dysfunction or worsening and are often difficult to differentiate from chronic liver disease (CLD). Ascitic form of AVH, LOHF, decompensated CLD and acute-on-chronic liver failure have significant overlapping features that need to be carefully dissected out. In many cases, only on long-term follow-up, these clinical entities can be separately identified. Intravascular hemolysis is usually caused by associated glucose-6-phosphate dehydrogenase deficiency. Rarely CLD such as Wilson disease and autoimmune hepatitis can also present with hemolysis in the initial presentation, which can mimic AVH with hemolysis. Identifying deviations from typical manifestations aid in avoiding unnecessary investigations, allowing focused therapy and alleviating anxiety.