The late event onset of a fraction of idiosyncratic drug-induced liver injury (DILI) cases and the link observed by genome-wide association studies (GWASs) of certain human leucocyte antigen (HLA) alleles with DILI due to specific drugs support the crucial role of the immune system (both innate and adaptive) in the pathogenesis of DILI. Recent advances in both flow and mass cytometry have allowed the profiling of all major immune cell types in a given sample. Therefore, determining the lymphocyte populations in samples from patients with DILI would facilitate the development of specific biomarkers for DILI diagnosis and prognosis. To date, a few studies have explored the immune landscape in DILI. In a recent study of leukocyte immunophenotyping using flow cytometry from the Spanish DILI Registry, an important role of adaptive immune response in DILI is suggested. DILI patients had significantly higher levels of T helper 1 (Th1) cells and activated helper and cytotoxic T cells than healthy controls. Furthermore, the increased expression of negative immune checkpoints and ligands in DILI patients could reflect a restoration of the immune homeostasis. Differences in the profile of cytokines in DILI patients from the Drug-Induced Liver Injury Network (DILIN) also suggest an involvement of both innate and adaptive immune systems in DILI development and prognosis. Moreover, several studies based on immunophenotyping of liver infiltrates showed a distinctive pattern of cellular infiltrates in patients with immune checkpoint inhibitors (ICIs)-DILI, with lower levels of plasma cells, CD20⁺ B cells and CD4⁺ T cells than in autoimmune hepatitis (AIH) patients. These pioneering studies highlight the importance of immunophenotyping for the mechanistic understanding of DILI. In this review, available data on immunophenotyping in DILI are gathered, and the potential clinical applications of cutting-edge, novel immunophenotyping techniques are discussed.

Zebrafish as a preclinical drug induced liver injury (DILI) model provides multiple advantages ranging from ease of breeding and maintenance, availability of different strains and transgenic fish amenable to study liver function, and highly conserved liver structure and function with the human liver. In this review, the authors have aimed to provide an account of the metabolic enzymes that take roles in drug detoxification in both human and zebrafish in a comparative manner and exemplify several recent models in studying liver functionality. Moreover, the authors emphasize the difficulties associated with studying idiosyncratic DILI in preclinical models and propose that zebrafish could be an important complement to mice in testing functions of genes that are associated with DILI with respect to different drugs in human genome-wide association studies (GWAS) Catalog. Finally, this review highlights the state-of-the-art in the development of novel transgenic reporter strains that can be used to study degree and molecular mechanisms of hepatotoxicity caused by drugs in zebrafish. All of these will help researchers to use effectively the available resources in the zebrafish DILI models, while advocating potential leads that can be taken to provide advancements in a better understanding and treatment of DILI.

Hereditary cholestasis comprises a broad spectrum of clinical phenotypes of varying severity. Severe forms such as progressive familial intrahepatic cholestasis (PFIC) mostly affect children with disease onset within their first years. Nevertheless, late-onset PFIC forms are increasingly diagnosed. Most adults present with less severe forms of hereditary cholestasis, often suffering from pruritus, gallstone disease, jaundice, or elevated liver enzymes. To identify the underlying genetic background and to rule out potential differential diagnoses, a broad genetic analysis like whole exome sequencing (WES) is recommended. Knowledge of the affected gene may have an impact not only on patient surveillance due to risk for disease progression or tumor development but also on potential therapeutic strategies. This case of the adult patient illustrates the importance of broad genetic analysis, which brought up the potentially relevant rare multidrug resistance protein 3 (MDR3) missense variant p.(Asn489Tyr) underlying the patient’s clinical phenotype of low phospholipid-associated cholelithiasis (LPAC). Patients with MDR3 disease may have an increased risk for cholangiocarcinoma (CCA) development and therefore need an individualized surveillance strategy. Most MDR3-affected patients benefit from life-long therapy with ursodeoxycholic acid (UDCA), which is well tolerated. Bezafibrate treatment can reduce pruritus, one of the main symptoms affecting the quality of life. Whether the administration of ileal bile acid transporter (IBAT) inhibitors is beneficial in adult patients with MDR3 disease is so far unknown.

Evaluation of the hepatobiliary function is critical for the clinicians, not only for the diagnosis of a large variety of liver diseases but also in the follow-up and management of some patients, for instance, those with different degrees of cholestasis suffering from a drug-induced liver injury (DILI) or scheduled for liver resection. Currently, the determination of global liver function mainly relies on laboratory tests, clinical scores, and data from images obtained with ultrasonography, computed tomography (CT), or magnetic resonance. Nuclear medicine scanning, displaying either planar or three-dimensional spatial distribution of liver function, is enhanced when using hepatotropic tracers based on classical radioisotopes such as technetium-99m (^99mTc) and with higher resolution using metabolized probes such as those based on monosaccharide derivatives labeled with ¹⁸F. Other cholephilic compounds, and hence selectively secreted into bile, have been proposed to visualize the correct function of the liver parenchyma and the associated secretory machinery. This review aims to summarize the state-of-the-art regarding the techniques and chemical probes available to monitor liver and gallbladder function, in some cases based on imaging techniques reflecting the dynamic of labeled cholephilic compounds.

Lysosomal hydrolases were once considered effectors of the waste disposal system of the cell, the endo-lysosomal system. However, they are now recognized as highly selective enzymes, which can modulate the function of several substrates, contributing to essential homeostatic and pathological cellular processes. There are more than 50 different lysosomal hydrolases that display optimal activity in the pH present in the acidic cellular compartment but can also be found in other cellular locations. They can work alone or in cooperation with other proteases building signaling pathways or amplification cascades. In the context of liver fibrosis lysosomal hydrolases, especially cysteine cathepsins have been described to participate in several fundamental cellular events contributing to the development, progression, perpetuation, and resolution of liver fibrosis. This paper comprehensively reviews the current knowledge on the contribution of lysosomal hydrolases to liver fibrosis.