Hepatocyte dedifferentiation profiling in alcohol-related liver disease identifies CXCR4 as a driver of cell reprogramming

Pathogenesis of Alcohol-Associated Liver Disease

The pathogenesis of alcohol-associated liver disease (ALD) is complex and multifactorial. Several intracellular, intrahepatic, and extrahepatic factors influence development of early fatty liver injury leading to inflammation and fibrosis. Alcohol metabolism, cellular stress, and gut-derived factors contribute to hepatocyte and immune cell injury leading to cytokine and chemokine production. The pathogenesis of alcohol-associated hepatitis (AH), an advanced form of acute-on-chronic liver failure due to excessive chronic intake in patients with underlying liver disease, is not well understood. While pathogenic mechanisms in early ALD are studied, the pathogenesis of AH requires further investigation to help design effective drugs for patients.

Portal Fibrosis and the Ductular Reaction: Pathophysiological Role in the Progression of Liver Disease and Translational Opportunities

A consistent feature of chronic liver diseases and the hallmark of pathologic repair is the so-called "ductular reaction." This is a histologic abnormality characterized by an expansion of dysmorphic cholangiocytes inside and around portal spaces infiltrated by inflammatory, mesenchymal, and vascular cells. The ductular reaction is a highly regulated response based on the reactivation of morphogenetic signaling mechanisms and a complex crosstalk among a multitude of cell types. The nature and mechanism of these exchanges determine the difference between healthy regenerative liver repair and pathologic repair. An orchestrated signaling among cell types directs mesenchymal cells to deposit a specific extracellular matrix with distinct physical and biochemical properties defined as portal fibrosis. Progression of fibrosis leads to vast architectural and vascular changes known as "liver cirrhosis." The signals regulating the ecology of this microenvironment are just beginning to be addressed. Contrary to the tumor microenvironment, immune modulation inside this "benign" microenvironment is scarcely known. One of the reasons for this is that both the ductular reaction and portal fibrosis have been primarily considered a manifestation of cholestatic liver disease, whereas this phenomenon is also present, albeit with distinctive features, in all chronic human liver diseases. Novel human-derived cellular models and progress in "omics" technologies are increasing our knowledge at a fast pace. Most importantly, this knowledge is on the edge of generating new diagnostic and therapeutic advances. Here, we will critically review the latest advances, in terms of mechanisms, pathophysiology, and treatment prospects. In addition, we will delineate future avenues of research, including innovative translational opportunities.

Loss of GCN5L1 exacerbates damage in alcoholic liver disease through ferroptosis activation

BACKGROUND AND AIMS

Iron overload, oxidative stress and ferroptosis are associated with liver injury in alcohol-associated liver disease (ALD), however, the crosstalk among these regulatory pathways in ALD development is unclear.

METHODS

ALD mouse model and general control of amino acid synthesis 5 like 1 (GCN5L1) liver knockout mice were generated to investigate the role of GCN5L1 in ALD development. Proteomic screening tests were performed to identify the key factors mediating GCN5L1 loss-induced ALD.

RESULTS

Gene Expression Omnibus data set analysis indicates that GCN5L1 expression is negatively associated with ALD progression. GCN5L1 hepatic knockout mice develop severe liver injury and lipid accumulation when fed an alcohol diet. Screening tests identified that GCN5L1 targeted the mitochondrial iron transporter CISD1 to regulate mitochondrial iron homeostasis in ethanol-induced ferroptosis. GCN5L1-modulated CISD1 acetylation and activity were crucial for iron accumulation and ferroptosis in response to alcohol exposure.

CONCLUSION

Pharmaceutical modulation of CISD1 activity is critical for cellular iron homeostasis and ethanol-induced ferroptosis. The GCN5L1/CISD1 axis is crucial for oxidative stress and ethanol-induced ferroptosis in ALD and is a promising avenue for novel therapeutic strategies.

Alcohol-associated liver disease: Emerging therapeutic strategies

The large and growing burden of alcohol-associated liver disease-and the considerable burden of morbidity and mortality associated with it-has been a drive toward ongoing research into novel strategies for its treatment, with a particular focus upon alcohol-associated hepatitis (AH). Management of alcohol-use disorder forms the central pillar of alcohol-associated liver disease care, with evidence-based psychological and pharmacological approaches being well established, and certain models demonstrating improved clinical outcomes when hepatology and addiction services are co-located. Corticosteroids have previously been used somewhat indiscriminately in patients with severe AH, but effective tools now exist to assess early response (and limit futile ongoing exposure). Techniques to predict risk of corticosteroid-related infection are also available, although current clinical strategies to mitigate this risk are limited. A variety of novel therapeutic approaches to AH are at different phases of trials and evidence gathering, with some of the most promising signals related to cytokine manipulation, epigenetic modulation, and targeting of the gut microbiota (ie, by means of fecal microbiota transplant). While remaining an ongoing source of debate, early liver transplant in severe AH has grown in interest and acceptability over the past decade as evidence supporting its efficacy builds, in the process challenging paradigms about mandatory pretransplant sobriety periods. However, uncertainty remains regarding the optimal selection criteria, and whether liver transplant has a role for only a highly limited proportion of patients with AH or more widespread application. This review aims to provide an overview of this fast-moving field.

Inflammation in Alcohol-Associated Hepatitis: Pathogenesis and Therapeutic Targets

Alcohol-associated hepatitis (AH) is an acute-on-chronic liver injury that occurs in patients with chronic alcohol-associated liver disease (ALD). Patients with severe AH have high short-term mortality and lack effective pharmacologic therapies. Inflammation is believed to be one of the key factors promoting AH progression and has been actively investigated as therapeutic targets over the last several decades, but no effective inflammatory targets have been identified so far. In this review, we discuss how inflammatory cells and the inflammatory mediators produced by these cells contribute to the development and progression of AH, with focus on neutrophils and macrophages. The crosstalk between inflammatory cells and liver nonparenchymal cells in the pathogenesis of AH is elaborated. We also deliberate the application of recent cutting-edge technologies in characterizing liver inflammation in AH. Finally, the potential therapeutic targets of inflammatory mediators for AH are briefly summarized.

Ductular Reactions in Liver Injury, Regeneration, and Disease Progression-An Overview

Ductular reaction (DR) is a complex cellular response that occurs in the liver during chronic injuries. DR mainly consists of hyper-proliferative or reactive cholangiocytes and, to a lesser extent, de-differentiated hepatocytes and liver progenitors presenting a close spatial interaction with periportal mesenchyme and immune cells. The underlying pathology of DRs leads to extensive tissue remodeling in chronic liver diseases. DR initiates as a tissue-regeneration mechanism in the liver; however, its close association with progressive fibrosis and inflammation in many chronic liver diseases makes it a more complicated pathological response than a simple regenerative process. An in-depth understanding of the cellular physiology of DRs and their contribution to tissue repair, inflammation, and progressive fibrosis can help scientists develop cell-type specific targeted therapies to manage liver fibrosis and chronic liver diseases effectively.

Alcohol-associated liver disease

Alcohol-associated liver disease (ALD) is a major cause of chronic liver disease worldwide, and comprises a spectrum of several different disorders, including simple steatosis, steatohepatitis, cirrhosis, and superimposed hepatocellular carcinoma. Although tremendous progress has been made in the field of ALD over the last 20 years, the pathogenesis of ALD remains obscure, and there are currently no FDA-approved drugs for the treatment of ALD. In this Review, we discuss new insights into the pathogenesis and therapeutic targets of ALD, utilizing the study of multiomics and other cutting-edge approaches. The potential translation of these studies into clinical practice and therapy is deliberated. We also discuss preclinical models of ALD, interplay of ALD and metabolic dysfunction, alcohol-associated liver cancer, the heterogeneity of ALD, and some potential translational research prospects for ALD.

Human Precision-Cut Liver Slices: A Potential Platform to Study Alcohol-Related Liver Disease

Alcohol-related liver disease (ALD) encompasses a range of pathological conditions that are complex to study at the clinical and preclinical levels. Despite the global burden of ALD, there is a lack of effective treatments, and mortality is high. One of the reasons for the unsuccessful development of novel therapies is that experimental studies are hindered by the challenge of recapitulating this multifactorial disorder in vitro, including the contributions of hepatotoxicity, impaired lipid metabolism, fibrosis and inflammatory cytokine storm, which are critical drivers in the pathogenesis of ALD in patients and primary targets for drug development. Here, we present the unique characteristics of the culture of human precision-cut liver slices (PCLS) to replicate key disease processes in ALD. PCLS were prepared from human liver specimens and treated with ethanol alone or in combination with fatty acids and lipopolysaccharide (FA + LPS) for up to 5 days to induce hepatotoxic, inflammatory and fibrotic events associated with ALD. Alcohol insult induced hepatocyte death which was more pronounced with the addition of FA + LPS. This mixture showed a significant increase in the cytokines conventionally associated with the prototypical inflammatory response observed in severe ALD, and interestingly, alcohol alone exhibited a different effect. Profibrogenic activation was also observed in the slices and investigated in the context of slice preparation. These results support the versatility of this organotypic model to study different pathways involved in alcohol-induced liver damage and ALD progression and highlight the applicability of the PCLS for drug discovery, confirming their relevance as a bridge between preclinical and clinical studies.

Multiscale integrative analyses unveil immune-related diagnostic signature for the progression of MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a chronic liver disease prevalent worldwide, with an increasing incidence associated with obesity, diabetes, and metabolic syndrome. The progression of MASLD to metabolic dysfunction-associated steatohepatitis (MASH) poses a pressing health concern, highlighting the significance of accurately identifying MASLD and its progression to MASH as a primary challenge in the field. In this study, a systematic integration of 66 immune cell types was conducted. Comprehensive analyses were performed on bulk, single-cell RNA-Seq, and clinical data to investigate the immune cell types implicated in MASLD progression thoroughly. Multiple approaches, including immune infiltration, gene expression trend analysis, weighted gene coexpression network analysis, and 4 machine learning algorithms, were used to examine the dynamic changes in genes and immune cells during MASLD progression. C-X-C motif chemokine receptor 4 and dedicator of cytokinesis 8 have been identified as potential diagnostic biomarkers for MASLD progression. Furthermore, cell communication analysis at the single-cell level revealed that the involvement of C-X-C motif chemokine receptor 4 and dedicator of cytokinesis 8 in MASLD progression is mediated through their influence on T cells. Overall, our study identified vital immune cells and a 2-gene diagnostic signature for the progression of MASLD, providing a new perspective on the diagnosis and immune-related molecular mechanisms of MASLD. These findings have important implications for developing innovative diagnostic tools and therapies for MASLD.