The Multifaceted Roles of Macrophages in NAFLD Pathogenesis

E3 ubiquitin ligase TRIM38 regulates macrophage polarization to reduce hepatic inflammation by interacting with HSPA5

Metabolic dysfunction-associated steatotic liver disease (MASLD) encompasses pathologies from simple steatosis and steatohepatitis (MASH) to cirrhosis. Hepatic inflammation is a common cause of liver pathogenesis, with macrophage activation as a key indicator of both acute and chronic liver dysfunction. While M1 macrophages promote inflammation and M2 macrophages suppress it, their roles in MASLD are dynamic and shift according to disease stage and liver microenvironment. Tripartite motif (TRIM) family proteins, which possess E3 ubiquitin ligase activity, are involved in various cellular processes, including intracellular signaling, development, apoptosis, protein quality control, innate immunity, autophagy, and carcinogenesis. TRIM38 negatively regulates innate immunity and inflammation triggered by viruses, Toll-like receptor 3 and 4, and tumor necrosis factor α/interleukin-1β signaling; however, its role in liver pathogenesis remains unclear. This study investigates the role of macrophage TRIM38 in metabolic liver disease to identify key targets for controlling inflammation. TRIM38 overexpression suppressed lipopolysaccharide-induced macrophage activation and metabolic stress-induced hepatic lipid accumulation. Mechanistically, TRIM38 interacted with heat shock protein family A member 5 (HSPA5) and stabilized it via K63-dependent ubiquitination. This TRIM38-HSPA5 axis promoted the expression of M2 macrophage markers (arginase 1 and retinoic acid-related orphan receptor α), thereby ameliorating liver steatosis. Single-cell RNA sequencing revealed significant downregulation of TRIM38 expression in the liver macrophages of patients with MASLD and negative regulation of liver inflammation via modulation of macrophage polarization. Hence, macrophage TRIM38 suppresses metabolic liver disease progression via HSPA5-mediated M2 macrophage polarization and provides insights into potential therapeutic targets.

Crosstalk between Hepatic Stellate Cells and Hepatic Macrophages in Metabolic Dysfunction-Associated Steatohepatitis

Metabolic dysfunction-associated steatotic liver disease is the most prevalent liver condition worldwide. Its more severe manifestation, metabolic dysfunction-associated steatohepatitis (MASH), is accompanied by distinctive hepatocellular injury and inflammation with fibrosis. The involvement of chronic inflammation and accompanying immune cell activation in the maturation phases of MASH progression, mediated through hepatic stellate cells (HSCs), plays a central role. This review highlights the detailed molecular and cellular mechanisms of MASH, with special attention to the dynamic dialogue between HSCs and hepatic macrophages. This review will help narrow the existing gaps, with a summary of key roles HSCs and hepatic macrophages play within liver immunity to inflammation, discussing critical intercellular communication pathways as well as proposing new venues for research toward a better understanding of MASH pathobiology, which could pave ways toward breakthroughs in the clinical condition.

Macrophage inhibition in the alleviation of nonalcoholic steatohepatitis caused by bariatric surgery

The incidence of nonalcoholic steatohepatitis (NASH) is increasing worldwide, and effective treatment is urgently needed. To understand the molecular mechanisms behind the effectiveness of bariatric surgery in treating NASH, we integrated single-cell and bulk RNA sequencing data to identify the role of liver macrophage polarization in alleviating NASH and screen possible drugs for treatment. Analysis revealed that bariatric surgery alleviates NASH by inhibiting liver M1 macrophage polarization with 12 differentially expressed M1 macrophage-related genes. Additionally, 56 potentially effective drugs were predicted for NASH treatment. These findings shed light on the effectiveness of bariatric surgery in treating NASH and offer potential drug candidates for further exploration.

TREM2-expressing macrophages in liver diseases

Metabolic dysfunction-associated steatotic liver disease (MASLD) affects over 30% of the global population and spans a spectrum of liver abnormalities, including simple steatosis, inflammation, fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Recent studies have identified triggering receptors expressed on myeloid cells 2 (TREM2)-expressing macrophages as key regulators of MASLD progression. TREM2 plays a pivotal role in regulating macrophage-mediated processes such as efferocytosis, inflammatory control, and fibrosis resolution. Additionally, soluble TREM2 (sTREM2) was proposed as a noninvasive biomarker for diagnosing and monitoring MASLD progression. However, the molecular mechanisms through which TREM2 influences MASLD pathogenesis remain incompletely understood. This review summarizes the current understanding of TREM2-expressing macrophages in MASLD, with the goal of illuminating future research and guiding the development of innovative therapeutic strategies targeting TREM2 signaling pathways.

Knowledge landscape of macrophage research in liver fibrosis: a bibliometric review of the literature from WoSCC

Recent insights into the immune response in fibrosis have provided valuable perspectives for the treatment of liver fibrosis. Macrophages, as the most abundant immune cells in the liver, are key drivers of liver fibrosis. They are extensively involved in tissue damage, chronic inflammation, and the progression and regression of liver fibrosis. This study aims to conduct a bibliometric analysis and literature review on the mechanisms by which macrophages contribute to liver fibrosis. Specifically, we analyzed a bibliometric dataset comprising 1,312 papers from 59 countries, 1,872 institutions, and 9,784 authors. Keyword co-occurrence analysis identified key research hotspots, including the role of macrophage subtypes in obesity-related metabolic disorders, the crosstalk between macrophages and hepatic stellate cells through mechanoimmunology, emerging strategies for immune modulation targeting macrophages to promote fibrosis regression and liver regeneration, and new discoveries regarding macrophage crosstalk with other immune cells. In conclusion, this study provides a visual analysis of the current research landscape, hotspots, and trends in the field of macrophages and liver fibrosis, and discusses future directions for further exploration in this area.

Thymosin β4 Regulates Tissue Inflammatory Response in Mouse Nonalcoholic Fatty Liver Disease by Promoting Macrophage M2-Type Polarization

Introduction

Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic steatosis, insulin resistance, and systemic pro-inflammatory response. Thymosin β4 (Tβ4) is a bioactive polypeptide that inhibits extracellular matrix (ECM) deposition and protects the liver. It can achieve immune homeostasis by regulating the polarization of liver macrophages and is a potential treatment for NAFLD.

Methods

A dataset was used to evaluate the expression of Tβ4 in fatty and non-fatty adjacent tissues of primary hepatocellular carcinoma. NAFLD was induced in C57 mice with methionine and choline-deficient diet (MCD), siRNATβ4 was injected into the tail vein to reduce liver Tβ4, and the therapeutic effect of Tβ4 was observed by phagocytosis of macrophages with clodronate liposomes. Hematoxylin and Eosin staining (HE) staining was used to observe the inflammation of mice in each group, and oil red O staining was used to determine the lipid accumulation. Macrophage polarization was detected by immunofluorescence assay. In the extrachromosomal experiment of oil red O, human myeloid leukemia mononuclear (THP-1) cells was co-cultured with human hepatic (LO2) constructed with oleic acid to detect the changes of aspartate transaminase (AST) and alanine transaminase (ALT) in supernatant and the apoptosis of LO2 under the intervention of different concentrations of Tβ4.

Results

Tβ4 allowed the mice to recover from NAFLD and reduce liver inflammation more effectively. Liver steatosis was more severe in sirnat4 mice. Macrophages are involved in Tβ4 treatment of NAFLD. The expression level of M1 phenotype in macrophages treated with Tβ4 decreased, and the apoptosis of hepatocytes decreased. At the same time, Tβ4 down-regulates signal transduction and activator of transcription1 (STAT1) phosphorylation and increases suppressor of cytokine signaling1/3 (SOCS1/3) expression in hepatocytes.

Discussion

This study revealed the molecular mechanism of the effective effect of Tβ4 on the polarization of liver macrophages, suggesting that Tβ4 may be a potential therapeutic measure for NAFLD.

Are glyphosate or glyphosate-based herbicides linked to metabolic dysfunction-associated steatotic liver disease (MASLD)? The weight of current evidence

Metabolic dysfunction-associated steatotic liver disease (MASLD) affects around 30 % of the world's population, increasing its prevalence by 50 % in the last three decades. MASLD pathogenesis is considered multiaxial, involving disturbances in the liver, adipose tissue (AT), and gut microbiome. In parallel with MASLD increasing trends, the total herbicide use has nearly tripled over the last three decades. Glyphosate (GLY) is the most used herbicide worldwide (825 mi kg/year). The intensive use of GLY-based herbicides (GBH) - largely driven by the adoption of glyphosate-tolerant genetically modified crops over the past two decades - has led to environmental (soil and water) and food contamination, resulting in continuous human exposure. Emerging (pre)clinical data highlights the significant implications of this herbicide on MASLD, marking a critical research area. Thus, this narrative review paper aimed at gathering and evaluating all epidemiological and (pre)clinical data on the implications of GLY or GBH on MASLD outcomes. Our work encompassed literature published between 2008-2025. Human urinary GLY levels are associated with different MASLD outcomes (steatosis risk, advanced fibrosis, increased transaminases) and comorbidities (higher risk for metabolic syndrome, diabetes, obesity and cardiovascular diseases) (6 studies). In vitro data indicate that GBH/GLY cause oxidative stress, genomic instability, apoptosis, and membrane disruption in hepatocytes, while promoting apoptosis and lipid peroxidation in (pre)adipocytes and cytokine production in monocytes (15 studies). In rodent studies (21 studies), GLY/GBH - in doses based on human exposure/toxicological limits - induces inflammatory and oxidative responses in the liver and AT, while causing dysbiosis and metabolic alterations in the gut microbiome axis. In the light of populational-, cell- and animal-based evidence, GLY/GBH disturbs key axis of MASLD pathogenesis and is hypothesized to be associated with its clinical outcomes.

Tanshinone IIA alleviate atherosclerosis and hepatic steatosis via down-regulation of MAPKs/NF-κB signaling pathway

OBJECTIVES

Tanshinone IIA (Tan IIA) exhibits therapeutic potential for atherosclerosis (AS) and hepatic steatosis (HS). The study aims to explore the mechanisms underlying the anti-atherosclerosis and anti-hepatic steatosis effects of Tan IIA.

METHODS

The LDLR-/-mice were divided into control, model, low/high Tan IIA and atorvastatin group, which fed with High-fat diet to build NAFLD-associated AS model, then administrated with 0.9 % saline, Tan IIA or atorvastatin. RAW264.7 cells divided into control, LPS, LPS plus low/high Tan IIA and LPS plus Tan IIA plus JNK activator group. The different goups' pathological changes visualized with H&E, Oil Red O and Immunofluorescence staining. The therapeutic effect of Tan IIA was reflected by lipids metabolism changes, hepatic indexes, inflammation levels. ELISA, RT-qPCR and Western blot assay were used to determine the inflammatory factors and upstream proteins. Molecular docking was used to reconfirm the importance of genes studied and locate the specific gene will study.

RESULTS

Tan IIA alleviated LDLR-/-mice AS and HS by reducing AS plaque area, lowering serum &liver lipid levels (TC, TG), improving liver function (AST, ALT). Tan IIA decreased serum inflammation levels (IL-1β, IL-6, TNF-α) and aorta & liver inflammatory-related cytokines levels (iNOS, VCAM-1, IL-6) and inhibited the phosphorylation of aorta & liver protein ERK1/2, JNK, p38 and NF-κB p65, which were validated in the LPS-stimulated macrophages supernatant and cells.

CONCLUSIONS

The study indicated that Tan IIA can alleviate atherosclerosis and hepatic steatosis via down-regulating MAPKs/NF-κB signaling pathway. This provides a potential therapeutic strategy for the co-existing situation of atherosclerosis and hepatic steatosis.

Inflammation and cancer: molecular mechanisms and clinical consequences

Inflammation, a hallmark of cancer, has been associated with tumor progression, transition into malignant phenotype and efficacy of anticancer treatments in cancer. It affects all stages of cancer, from the initiation of carcinogenesis to metastasis. Chronic inflammation induces immunosup-pression, providing an environment conducive to carcinogenesis, whereas acute inflammation induces an antitumor immune response, leading to tumor suppression. Solid tumors have an inflammatory tumor microenvironment (TME) containing cancer cells, immune cells, stromal cells, and soluble molecules, which plays a key role in tumor progression and therapy response. Both cancer cells and stromal cells in the TME are highly plastic and constantly change their phenotypic and functional properties. Cancer-associated inflammation, the majority of which consists of innate immune cells, plays an important role in cancer cell plasticity, cancer progression and the development of anticancer drug resistance. Today, with the combined used of advanced technologies, such as single-cell RNA sequencing and spatial molecular imaging analysis, the pathways linking chronic inflammation to cancer have been largely elucidated. In this review article, we highlighted the molecular and cellular mechanisms involved in cancer-associated inflammation and its effects on cancer progression and treatment response. We also comprehensively review the mechanisms linking chronic inflammation to cancer in the setting of GI cancers.

Tissue macrophages: origin, heterogenity, biological functions, diseases and therapeutic targets

Macrophages are immune cells belonging to the mononuclear phagocyte system. They play crucial roles in immune defense, surveillance, and homeostasis. This review systematically discusses the types of hematopoietic progenitors that give rise to macrophages, including primitive hematopoietic progenitors, erythro-myeloid progenitors, and hematopoietic stem cells. These progenitors have distinct genetic backgrounds and developmental processes. Accordingly, macrophages exhibit complex and diverse functions in the body, including phagocytosis and clearance of cellular debris, antigen presentation, and immune response, regulation of inflammation and cytokine production, tissue remodeling and repair, and multi-level regulatory signaling pathways/crosstalk involved in homeostasis and physiology. Besides, tumor-associated macrophages are a key component of the TME, exhibiting both anti-tumor and pro-tumor properties. Furthermore, the functional status of macrophages is closely linked to the development of various diseases, including cancer, autoimmune disorders, cardiovascular disease, neurodegenerative diseases, metabolic conditions, and trauma. Targeting macrophages has emerged as a promising therapeutic strategy in these contexts. Clinical trials of macrophage-based targeted drugs, macrophage-based immunotherapies, and nanoparticle-based therapy were comprehensively summarized. Potential challenges and future directions in targeting macrophages have also been discussed. Overall, our review highlights the significance of this versatile immune cell in human health and disease, which is expected to inform future research and clinical practice.

Novel translational mouse models of metabolic dysfunction-associated steatotic liver disease comparable to human MASLD with severe obesity

OBJECTIVE

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common cause of chronic liver disease, especially in patients with severe obesity. However, current mouse models for MASLD do not reflect the polygenetic background nor the metabolic changes in this population. Therefore, we investigated two novel mouse models of MASLD with a polygenetic background for the metabolic syndrome.

METHODS

TALLYHO/JngJ mice and NONcNZO10/LtJ mice were fed a high-fat- high-carbohydrate (HF-HC) diet with a surplus of cholesterol diet. A second group of TH mice was additional treated with empagliflozin.

RESULTS

After sixteen weeks of feeding, both strains developed metabolic syndrome with severe obesity and histological manifestation of steatohepatitis, which was associated with significantly increased intrahepatic CD8+cells, CD4+cells and Tregs, contributing to a significant increase in pro-inflammatory and pro-fibrotic gene activation as well as ER stress and oxidative stress. In comparison with the human transcriptomic signature, we could demonstrate a good metabolic similarity, especially for the TH mouse model. Furthermore, TH mice also developed signs of kidney injury as an extrahepatic comorbidity of MASLD. Additional treatment with empagliflozin in TH mice attenuates hepatic steatosis and improves histological manifestation of MASH.

CONCLUSIONS

Overall, we have developed two promising new mouse models that are suitable for preclinical studies of MASLD as they recapitulate most of the key features of MASLD.

An immunoregulatory amphipathic peptide derived from Fasciola hepatica helminth defense molecule (FhHDM-1.C2) exhibits potent biotherapeutic activity in a murine model of multiple sclerosis

The helminth defense molecules (HDM) are a family of immune regulatory peptides exclusively expressed by trematode worms. We have previously demonstrated that in vivo FhHDM-1, the archetypal member of the HDMs, regulated macrophage responses to inflammatory ligands, thereby ameliorating the progression of immune-mediated tissue damage in several murine models of inflammatory disease. Accordingly, we postulated that an understanding of the structure-function relationship of the HDMs would facilitate the identification of the minimal bioactive peptide, which would represent a more synthesizable, cost-effective, potent biotherapeutic. Thus, using a combination of bioinformatics, structural analyses, and cellular assays we discovered a 40 amino acid peptide derivative termed FhHDM-1.C2. This peptide contains a 12 amino acid motif at its N-terminus, which facilitates cellular interaction and uptake, and an amphipathic α-helix within the C-terminus, which is necessary for lysosomal vATPase inhibitory activity, with both regions linked by a short unstructured segment. The FhHDM-1.C2 peptide exhibits enhanced regulation of macrophage function, compared with the full-length FhHDM-1, and potent prevention of the progression of relapsing-remitting-experimental autoimmune encephalomyelitis (EAE) when administered prophylactically or therapeutically. The protective effect of FhHDM-1.C2 is not associated with global immune suppression, which places the HDMs peptides as an improved class of biotherapeutics for the treatment of inflammatory diseases. Comparing the HDMs from several zoonotic trematodes revealed a similar capacity for immune regulation. These important new advances into the structure-function relationship of the lead HDM peptide, FhHDM-1, encourage further prospecting and screening of the broader trematode family of peptides for the discovery of novel and potent immune-biotherapeutics.

Increased serum GM-CSF at diagnosis of biliary atresia is associated with improved biliary drainage

BACKGROUND

The immune heterogeneity of biliary atresia (BA) presents a challenge for development of prognostic biomarkers. This study aimed to identify early immune signatures associated with biliary drainage after Kasai Portoenterostomy (KPE).

METHODS

Serum samples, liver slides, and clinical data were obtained from patients enrolled in the NIDDK-supported Childhood Liver Disease Research Network. Serum cytokines and hepatic immune cell subsets were measured at diagnosis and compared among 3 groups: 38 infants with BA (20 with evidence of bile flow after KPE; 18 without) and 17 non-BA cholestatic infants.

RESULTS

BA participants had lower numbers of lipid associated macrophages (LAM), and increased serum levels of Eotaxin-3, interleukin (IL) 12p70, and IL-8 versus non-BA groups (p < 0.05 for all). Among BA participants, monocyte like macrophages and serum levels of granulocyte-macrophage colony stimulating factor (GM-CSF) were increased in BA participants with good biliary drainage (p = 0.004 and p < 0.001 respectively). Levels of GM-CSF, IL-16, c-reactive protein, TNF-β predicted successful biliary drainage with an area under the receiver operating curve of 0.84 (p < 0.001).

CONCLUSION

These findings suggest that distinct macrophage-associated immune networks at diagnosis may impact biliary drainage after KPE. Identification of early prognostic immune-modulatory markers has potential to improve patient stratification for medical and surgical therapies.

IMPACT STATEMENT

We identify serum cytokines, particularly GM-CSF, that are associated with future biliary drainage in patients with biliary atresia. Characterization of macrophage-associated immune networks provides novel insight into early disease mechanism that may impact patient outcomes. Early prognostic biomarkers markers in biliary atresia can help in patient stratification for medical and surgical therapies.

Single-cell transcriptomic analysis reveals characteristic feature of macrophage reprogramming in liver Mallory-Denk bodies pathogenesis

Chronic liver diseases are highly linked with mitochondrial dysfunction and macrophage infiltration. Mallory-Denk bodies (MDBs) are protein aggregates associated with hepatic inflammation, and MDBs pathogenesis could be induced in mice by feeding 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC). Here, we investigate the macrophage heterogeneity and the role of macrophage during MDBs pathogenesis on DDC-induced MDBs mouse model by single-nucleus RNA sequencing (snRNA-seq). We defined liver macrophages into four distinct subsets including monocyte-derived macrophages (MDMs) subset and three Kupffer cells (KCs) subsets (Gpnmbhigh KCs, Peam1high KCs, and Gpnmblow Pecam1low KCs). Particularly, we identified a novel Gpnmbhigh KCs subset as lipid-associated macrophage (LAM) with high expression of Trem2, CD63, and CD9. Interestingly, LAM showed a potential immunosuppressive characteristic by expressing anti-inflammatory genes IL-7R during the MDBs formation. Using contact and transwell co-culture systems, the released mtDNA from hepatocytes was found to induce the activation of inflammasome in macrophages. Furthermore, we revealed the damaged DNA could activate the NOD-like receptor family pyrin domain containing-3 (NLRP3) inflammasome and subsequently form apoptosis-associated speck-like protein containing a caspase recruit domain (ASC) specks of liver macrophages. Collectively, our results firstly revealed macrophage heterogeneity and inflammasome activation by mtDNA from injured liver during MDBs pathogenesis, providing crucial understanding of pathogenesis of chronic liver disease.

Advances on the Role of Lung Macrophages in the Pathogenesis of Chronic Obstructive Pulmonary Disease in the Era of Single-Cell Genomics

Chronic Obstructive Pulmonary Disease (COPD) is a heterogeneous respiratory disorder characterized by persistent airflow limitation. The diverse pathogenic mechanisms underlying COPD progression remain incompletely understood. Macrophages, serving as the most representative immune cells in the respiratory tract, constitute the first line of innate immune defense and maintain pulmonary immunological homeostasis. Recent advances have provided deeper insights into the phenotypic and functional alterations of pulmonary macrophages and their role in COPD pathogenesis. Notably, the advent of single-cell RNA sequencing has revolutionized our understanding of macrophage molecular heterogeneity in COPD. Herein, we review principal investigations concerning the sophisticated mechanisms through which pulmonary macrophages influence COPD, encompassing inflammatory mediator production, protease/antiprotease release, and phagocytic activity. Additionally, we synthesize findings from available literature regarding all identified pulmonary macrophage sub-populations in COPD, thereby advancing our comprehension of macrophage heterogeneity's significance in the complex pathophysiological mechanisms of COPD.

The role of macrophages in liver fibrosis: composition, heterogeneity, and therapeutic strategies

Macrophages, the predominant immune cells in the liver, are essential for maintaining hepatic homeostasis and responding to liver injury caused by external stressors. The hepatic macrophage population is highly heterogeneous and plastic, mainly comprised of hepatic resident kuffer cells (KCs), monocyte-derived macrophages (MoMφs), lipid-associated macrophages (LAMs), and liver capsular macrophages (LCMs). KCs, a population of resident macrophages, are localized in the liver and can self-renew through in situ proliferation. However, MoMφs in the liver are recruited from the periphery circulation. LAMs are a self-renewing subgroup of liver macrophages near the bile duct. While LCMs are located in the liver capsule and derived from peripheral monocytes. LAMs and LCMs are also involved in liver damage induced by various factors. Hepatic macrophages exhibit distinct phenotypes and functions depending on the specific microenvironment in the liver. KCs are critical for initiating inflammatory responses after sensing tissue damage, while the MoMφs infiltrated in the liver are implicated in both the progression and resolution of chronic hepatic inflammation and fibrosis. The regulatory function of liver macrophages in hepatic fibrosis has attracted significant interest in current research. Numerous literatures have documented that the MoMφs in the liver have a dual impact on the progression and resolution of liver fibrosis. The MoMφs in the liver can be categorized into two subtypes based on their Ly-6C expression level: inflammatory macrophages with high Ly-6C expression (referred to as Ly-6Chi subgroup macrophages) and reparative macrophages with low Ly-6C expression (referred to as Ly-6Clo subgroup macrophages). Ly-6Chi subgroup macrophages are conducive to the occurrence and progression of liver fibrosis, while Ly-6Clo subgroup macrophages are associated with the degradation of extracellular matrix (ECM) and regression of liver fibrosis. Given this, liver macrophages play a pivotal role in the occurrence, progression, and regression of liver fibrosis. Based on these studies, treatment therapies targeting liver macrophages are also being studied gradually. This review aims to summarize researches on the composition and origin of liver macrophages, the macrophage heterogeneity in the progression and regression of liver fibrosis, and anti-fibrosis therapeutic strategies targeting macrophages in the liver.

Understanding the complex macrophage landscape in MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) represents a spectrum of disease states ranging from simple steatosis to metabolic dysfunction-associated steatohepatitis (MASH), which can eventually lead to the development of cirrhosis and hepatocellular carcinoma. Macrophages have long been implicated in driving the progression from steatosis to end-stage disease, yet we still know relatively little about the precise involvement of these cells in MASLD progression and/or regression. Rather, there are a considerable number of conflicting reports regarding the precise roles of these cells. This confusion stems from the fact that, until recently, macrophages in the liver were considered a homogenous population. However, thanks to recent technological advances including multi-parameter flow cytometry, single-cell RNA sequencing and spatial proteogenomics, we now know that this is not the case. Rather hepatic macrophages, even in the healthy liver, are heterogenous, existing in multiple subsets with distinct transcriptional profiles and hence likely functions. This heterogeneity is even more prominent in MASLD, where the macrophage pool consists of multiple different subsets of resident and recruited cells. To probe the unique functions of these cells and determine if targeting macrophages may be a viable therapeutic strategy in MASLD, we first need to unravel this complexity and decipher which populations and/or activation states are present and what functions each of these may play in driving MASLD progression. In this review, we summarise recent advances in the field, highlighting what is currently known about the hepatic macrophage landscape in MASLD and the questions that remain to be tackled.

Exosomes derived from apical papilla stem cells improve NASH by regulating fatty acid metabolism and reducing inflammation

BACKGROUND

Apical papilla stem cells (SCAPs) exhibit significant potential for tissue repair, characterized by their anti-inflammatory and pro-angiogenic properties. Exosomes derived from stem cells have emerged as safer alternatives that retain comparable physiological functions. This study explores the therapeutic potential of exosomes sourced from SCAPs in the treatment of non-alcoholic steatohepatitis (NASH).

METHODS

A NASH mouse model was established through the administration of a high-fat diet (HFD), and SCAPs were subsequently isolated for experimental purposes. A cell model of NASH was established in vitro by treating hepatocellular carcinoma cells with oleic acid (OA) and palmitic acid (PA). Exosomes were isolated via differential centrifugation. The mice were treated with exosomes injected into the tail vein, and the hepatocytes were incubated with exosomes in vitro. After the experiment, physiological and biochemical markers were analyzed to assess the effects of exosomes derived from SCAPs on the progression of NASH in both NASH mouse models and NASH cell models.

RESULTS

After exosomes treatment, the weight gain and liver damage induced by HFD were significantly reduced. Additionally, hepatic fat accumulation was markedly alleviated. Mechanistically, exosomes treatment promoted the expression of genes involved in hepatic fatty acid oxidation and transport, while simultaneously suppressing genes associated with fatty acid synthesis. Furthermore, the levels of serum inflammatory cytokines and the mRNA expression of inflammatory markers in liver tissue were significantly decreased. In vitro cell experiments produced similar results.

Role of gut microbiota and immune cells in metabolic-associated fatty liver disease: clinical impact

In 2020, a revised definition of fatty liver disease associated with metabolic dysfunction (MAFLD) was proposed to replace non-alcoholic fatty liver (NAFLD). Liver steatosis and at least one of the three metabolic risk factors, including type 2 diabetes, obesity, or signs of metabolic dysregulation, are used to diagnose MAFLD. MAFLD, similarly to NAFLD, is characterized by a spectrum of disease ranging from simple steatosis to advanced metabolic steatohepatitis with or without fibrosis, and may progress to cirrhosis and liver cancer, including increased risk of other critical extrahepatic diseases. Even though the pathophysiology of MAFLD and potential therapeutic targets have been explored in great detail, there is yet no Food and Drug Administration approved treatment. Recently, gut microbiome-derived products (e.g., endotoxins and metabolites) involved in intestinal barrier disruption, systemic inflammation, and modification of intrahepatic immunity have been associated with MAFLD development and progression. Therefore, different strategies could be adopted to modify the gut microbiome to improve outcomes in early and progressive MAFLD. Here, we provide an overview of mechanisms that may link the gut microbiome and immune response during the onset of liver steatosis and progression to steatohepatitis and fibrosis in patients with MAFLD. Finally, gut microbiota-based approaches are discussed as potential personalized treatments against MAFLD.

Identification of conserved and tissue-restricted transcriptional profiles for lipid associated macrophages (LAMs)

Macrophages are essential immune cells present in all tissues, and are vital for maintaining tissue homeostasis, immune surveillance, and immune responses. Considerable efforts have identified shared and tissue-specific gene programs for macrophages across organs during homeostasis. This information has dramatically enhanced our understanding of tissue-restricted macrophage programming and function. However, few studies have addressed the overlapping and tissue-specific responses of macrophage subsets following inflammatory responses. One subset of macrophages that has been observed across several studies, lipid-associated macrophages (LAMs), have gained interest due to their unique role in lipid metabolism and potential as a therapeutic target. LAMs have been associated with regulating disease outcomes in metabolically related disorders including atherosclerosis, obesity, and nonalcoholic fatty liver disease (NAFLD). In this study, we utilized single-cell RNA sequencing (scRNAseq) data to profile LAMs across multiple tissues and sterile inflammatory conditions in mice and humans. Integration of data from various disease models revealed that LAMs share a set of conserved transcriptional profiles, including Trem2 and Lpl, but also identified key sets of tissue-specific LAM gene programs. Importantly, the shared LAM markers were highly conserved with human LAM populations that also emerge in chronic inflammatory settings. Overall, this analysis provides a detailed transcriptional landscape of tissue-restricted and shared LAM gene programs and offers insights into their roles in metabolic and chronic inflammatory diseases. These data may help instruct appropriate targets for broad or tissue-restricted therapeutic interventions to modulate LAM populations in disease.

Identification of common signature genes and pathways underlying the pathogenesis association between nonalcoholic fatty liver disease and heart failure

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) and heart failure (HF) are related conditions with an increasing incidence. However, the mechanism underlying their association remains unclear. This study aimed to explore the shared pathogenic mechanisms and common biomarkers of NAFLD and HF through bioinformatics analyses and experimental validation.

METHODS

NAFLD and HF-related transcriptome data were extracted from the Gene Expression Omnibus (GEO) database (GSE126848 and GSE26887). Differential analysis was performed to identify common differentially expressed genes (co-DEGs) between NAFLD and HF. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and gene set enrichment analysis (GSEA) were conducted to explore the functions and regulatory pathways of co-DEGs. Protein-protein interaction (PPI) network and support vector machine-recursive feature elimination (SVM-RFE) methods were used to screen common key DEGs. The diagnostic value of common key DEGs was assessed by receiver operating characteristic (ROC) curve and validated with external datasets (GSE89632 and GSE57345). Finally, the expression of biomarkers was validated in mouse models.

RESULTS

A total of 161 co-DEGs were screened out in NAFLD and HF patients. GO, KEGG, and GSEA analyses indicated that these co-DEGs were mainly enriched in immune-related pathways. PPI network revealed 14 key DEGs, and SVM-RFE model eventually identified two genes (CD163 and CCR1) as common key DEGs for NAFLD and HF. Expression analysis revealed that the expression levels of CD163 and CCR1 were significantly down-regulated in HF and NAFLD patients. ROC curve analysis showed that CD163 and CCR1 had good diagnostic values for HF and NAFLD. Single-gene GSEA suggested that CD163 and CCR1 were mainly engaged in immune responses and inflammation. Experimental validation indicated unbalanced macrophage polarization in HF and NAFLD mouse models, and the expression of CD163 and CCR1 were significantly down-regulated.

CONCLUSION

This study identified M2 polarization impairment characterized by decreased expression of CD163 and CCR1 as a common pathogenic pathway in NAFLD and HF. The downregulation of CD163 and CCR1 may reflect key pathological changes in the development and progression of NAFLD and HF, suggesting their potential as diagnostic and therapeutic targets.

Lipid-associated macrophages' promotion of fibrosis resolution during MASH regression requires TREM2

While macrophage heterogeneity during metabolic dysfunction-associated steatohepatitis (MASH) has been described, the fate of these macrophages during MASH regression is poorly understood. Comparing macrophage heterogeneity during MASH progression vs regression, we identified specific macrophage subpopulations that are critical for MASH/fibrosis resolution. We elucidated the restorative pathways and gene signatures that define regression-associated macrophages and establish the importance of TREM2+ macrophages during MASH regression. Liver-resident Kupffer cells are lost during MASH and are replaced by four distinct monocyte-derived macrophage subpopulations. Trem2 is expressed in two macrophage subpopulations: i) monocyte-derived macrophages occupying the Kupffer cell niche (MoKC) and ii) lipid-associated macrophages (LAM). In regression livers, no new transcriptionally distinct macrophage subpopulation emerged. However, the relative macrophage composition changed during regression compared to MASH. While MoKC was the major macrophage subpopulation during MASH, they decreased during regression. LAM was the dominant macrophage subtype during MASH regression and maintained Trem2 expression. Both MoKC and LAM were enriched in disease-resolving pathways. Absence of TREM2 restricted the emergence of LAMs and formation of hepatic crown-like structures. TREM2+ macrophages are functionally important not only for restricting MASH-fibrosis progression but also for effective regression of inflammation and fibrosis. TREM2+ macrophages are superior collagen degraders. Lack of TREM2+ macrophages also prevented elimination of hepatic steatosis and inactivation of HSC during regression, indicating their significance in metabolic coordination with other cell types in the liver. TREM2 imparts this protective effect through multifactorial mechanisms, including improved phagocytosis, lipid handling, and collagen degradation.

Multiomics analyses decipher intricate changes in the cellular and metabolic landscape of steatotic livers upon dietary restriction and sleeve gastrectomy

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a chronic, progressive liver disease that encompasses a spectrum of steatosis, steatohepatitis (or MASH), and fibrosis. Evidence suggests that dietary restriction (DR) and sleeve gastrectomy (SG) can lead to remission of hepatic steatosis and inflammation through weight loss, but it is unclear whether these procedures induce distinct metabolic or immunological changes in MASLD livers. This study aims to elucidate the intricate hepatic changes following DR, SG or sham surgery in rats fed a high-fat diet as a model of obesity-related MASLD, in comparison to a clinical cohort of patients undergoing SG. Single-cell and single-nuclei transcriptome analysis, spatial metabolomics, and immunohistochemistry revealed the liver landscape, while circulating biomarkers were measured in serum samples. Artificial intelligence (AI)-assisted image analysis characterized the spatial distribution of hepatocytes, myeloid cells and lymphocytes. In patients and experimental MASLD rats, SG improved body mass index, circulating liver injury biomarkers and triglyceride levels. Both DR and SG attenuated liver steatosis and fibrosis in rats. Metabolism-related genes (Ppara, Cyp2e1 and Cyp7a1) were upregulated in hepatocytes upon DR and SG, while SG broadly upregulated lipid metabolism on cholangiocytes, monocytes, macrophages, and neutrophils. Furthermore, SG promoted restorative myeloid cell accumulation in the liver not only ameliorating inflammation but activating liver repair processes. Regions with potent myeloid infiltration were marked with enhanced metabolic capacities upon SG. Additionally, a disruption of periportal hepatocyte functions was observed upon DR. In conclusion, this study indicates a dynamic cellular crosstalk in steatotic livers of patients undergoing SG. Notably, PPARα- and gut-liver axis-related processes, and metabolically active myeloid cell infiltration indicate intervention-related mechanisms supporting the indication of SG for the treatment of MASLD.

Exosome prospects in the diagnosis and treatment of non-alcoholic fatty liver disease

The growing prevalence of NAFLD and its global health burden have provoked considerable research on possible diagnostic and therapeutic options for NAFLD. Although various pathophysiological mechanisms and genetic factors have been identified to be associated with NAFLD, its treatment remains challenging. In recent years, exosomes have attracted widespread attention for their role in metabolic dysfunctions and their efficacy as pathological biomarkers. Exosomes have also shown tremendous potential in treating a variety of disorders. With increasing evidence supporting the significant role of exosomes in NAFLD pathogenesis, their theragnostic potential has become a point of interest in NAFLD. Expectedly, exosome-based treatment strategies have shown promise in the prevention and amelioration of NAFLD in preclinical studies. However, there are still serious challenges in preparing, standardizing, and applying exosome-based therapies as a routine clinical option that should be overcome. Due to the great potential of this novel theragnostic agent in NAFLD, further investigations on their safety, clinical efficacy, and application standardization are highly recommended.

Liver Fibrosis: From Basic Science towards Clinical Progress, Focusing on the Central Role of Hepatic Stellate Cells

The burden of chronic liver disease is globally increasing at an alarming rate. Chronic liver injury leads to liver inflammation and fibrosis (LF) as critical determinants of long-term outcomes such as cirrhosis, liver cancer, and mortality. LF is a wound-healing process characterized by excessive deposition of extracellular matrix (ECM) proteins due to the activation of hepatic stellate cells (HSCs). In the healthy liver, quiescent HSCs metabolize and store retinoids. Upon fibrogenic activation, quiescent HSCs transdifferentiate into myofibroblasts; lose their vitamin A; upregulate α-smooth muscle actin; and produce proinflammatory soluble mediators, collagens, and inhibitors of ECM degradation. Activated HSCs are the main effector cells during hepatic fibrogenesis. In addition, the accumulation and activation of profibrogenic macrophages in response to hepatocyte death play a critical role in the initiation of HSC activation and survival. The main source of myofibroblasts is resident HSCs. Activated HSCs migrate to the site of active fibrogenesis to initiate the formation of a fibrous scar. Single-cell technologies revealed that quiescent HSCs are highly homogenous, while activated HSCs/myofibroblasts are much more heterogeneous. The complex process of inflammation results from the response of various hepatic cells to hepatocellular death and inflammatory signals related to intrahepatic injury pathways or extrahepatic mediators. Inflammatory processes modulate fibrogenesis by activating HSCs and, in turn, drive immune mechanisms via cytokines and chemokines. Increasing evidence also suggests that cellular stress responses contribute to fibrogenesis. Recent data demonstrated that LF can revert even at advanced stages of cirrhosis if the underlying cause is eliminated, which inhibits the inflammatory and profibrogenic cells. However, despite numerous clinical studies on plausible drug candidates, an approved antifibrotic therapy still remains elusive. This state-of-the-art review presents cellular and molecular mechanisms involved in hepatic fibrogenesis and its resolution, as well as comprehensively discusses the drivers linking liver injury to chronic liver inflammation and LF.

Detection of early-stage NASH using non-invasive hyperpolarized 13C metabolic imaging

Non-alcoholic steatohepatitis (NASH) is characterized from its early stages by a profound remodeling of the liver microenvironment, encompassing changes in the composition and activities of multiple cell types and associated gene expression patterns. Hyperpolarized (HP) 13C MRI provides a unique view of the metabolic microenvironment, with potential relevance for early diagnosis of liver disease. Previous studies have detected changes in HP 13C pyruvate to lactate conversion, catalyzed by lactate dehydrogenase (LDH), with experimental liver injury. HP ∝ -ketobutyrate ( ∝ KB) is a close molecular analog of pyruvate with modified specificity for LDH isoforms, specifically attenuated activity with their LDHA-expressed subunits that dominate liver parenchyma. Building on recent results with pyruvate, we investigated HP ∝ KB in methionine-choline deficient (MCD) diet as a model of early-stage NASH. Similarity of results between this new agent and pyruvate (~ 50% drop in cytoplasmic reducing capacity), interpreted together with gene expression data from the model, suggests that changes are mediated through broad effects on intermediary metabolism. Plausible mechanisms are depletion of the lactate pool by upregulation of gluconeogenesis (GNG) and pentose phosphate pathway (PPP) flux, and a possible shift toward increased lactate oxidation. These changes may reflect high levels of oxidative stress and/or shifting macrophage populations in NASH.

Dried tangerine peel polysaccharide (DTPP) alleviates hepatic steatosis by suppressing TLR4/MD-2-mediated inflammation and endoplasmic reticulum stress

Non-alcoholic fatty liver disease (NAFLD) is a complex pathogenic metabolic syndrome characterized by increased inflammation and endoplasmic reticulum stress. In recent years, natural polysaccharides derived from traditional Chinese medicine have shown significant anti-inflammatory effects, making them an attractive therapeutic option. However, little research has been conducted on the therapeutic potential of dried tangerine peel polysaccharide (DTPP) - one of the most important medicinal resources in China. The results of the present study showed that DTPP substantially reduced macrophage infiltration in vivo and suppressed the expression of pro-inflammatory factors and endoplasmic reticulum stress-related genes. Additionally, surface plasmon resonance analysis revealed that DTPP had a specific affinity to myeloid differentiation factor 2, which consequently suppressed lipopolysaccharide-induced inflammation via interaction with the toll-like receptor 4 signaling pathway. This study provides a potential molecular mechanism underlying the anti-inflammatory effects of DTPP on NAFLD and suggests DTPP as a promising therapeutic strategy for NAFLD treatment.

Cenicriviroc Suppresses and Reverses Steatohepatitis by Regulating Macrophage Infiltration and M2 Polarization in Mice

The inhibition of hepatic macrophage and Kupfer cell recruitment and activation is a potential strategy for treating insulin resistance and nonalcoholic steatohepatitis (NASH). Cenicriviroc (CVC), a dual C-C chemokine receptor 2 (CCR2) and CCR5 antagonist, has shown antifibrotic activity in murine models of NASH and has been evaluated in clinical trials on patients with NASH. This study investigated the effects of CVC on macrophage infiltration and polarization in a lipotoxic model of NASH. C57BL/6 mice were fed a high-cholesterol, high-fat (CL) diet or a CL diet containing 0.015% CVC (CL + CVC) for 12 weeks. Macrophage recruitment and activation were assayed by immunohistochemistry and flow cytometry. CVC supplementation attenuated excessive hepatic lipid accumulation and peroxidation and alleviated glucose intolerance and hyperinsulinemia in the mice that were fed the CL diet. Flow cytometry analysis revealed that compared with the CL group, mice fed the CL + CVC diet had fewer M1-like macrophages, more M2-like macrophages, and fewer T cell counts, indicating that CVC caused an M2-dominant shift of macrophages in the liver. Similarly, CVC decreased lipopolysaccharide-stimulated M1-like macrophage activation, whereas it increased interleukin-4-induced M2-type macrophage polarization in vitro. In addition, CVC attenuated hepatic fibrosis by repressing hepatic stellate cell activation. Lastly, CVC reversed insulin resistance as well as steatosis, inflammation, and fibrosis of the liver in mice with pre-existing NASH. In conclusion, CVC prevented and reversed hepatic steatosis, insulin resistance, inflammation, and fibrogenesis in the liver of NASH mice via M2 macrophage polarization.

Unveiling the role of disulfidptosis-related genes in the pathogenesis of non-alcoholic fatty liver disease

Backgrounds

Non-alcoholic fatty liver disease (NAFLD) presents as a common liver disease characterized by an indistinct pathogenesis. Disulfidptosis is a recently identified mode of cell death. This study aimed to investigate the potential role of disulfidptosis-related genes (DRGs) in the pathogenesis of NAFLD.

Methods

Gene expression profiles were obtained from the bulk RNA dataset GSE126848 and the single-cell RNA dataset GSE136103, both associated with NAFLD. Our study assessed the expression of DRGs in NAFLD and normal tissues. Weighted gene co-expression network analysis (WGCNA) and differential expression analysis were employed to identify the key NAFLD-specific differentially expressed DRGs (DE-DRGs). To explore the biological functions and immune regulatory roles of these key DE-DRGs, we conducted immune infiltration analysis, functional enrichment analysis, consensus clustering analysis, and single-cell differential state analysis. Finally, we validated the expression and biological functions of DRGs in NAFLD patients using histology and RNA-sequencing transcriptomic assays with human liver tissue samples.

Results

Through the intersection of WGCNA, differentially expressed genes, and DRGs, two key DE-DRGs (DSTN and MYL6) were identified. Immune infiltration analysis indicated a higher proportion of macrophages, T cells, and resting dendritic cells in NAFLD compared to control liver samples. Based on the key DE-DRGs, Two disulfidptosis clusters were defined in GSE126848. Cluster 1, with higher expression of the key DE-DRGs, exhibited increased immune infiltration abundance and was closely associated with oxidative stress and immune regulation compared to cluster 2. High-resolution analysis of mononuclear phagocytes highlighted the potential role of MYL6 in intrahepatic M1 phenotype Kupffer cells in NAFLD patients. Our transcriptome data revealed that the expression levels of the majority of DRGs were significantly increased in NAFLD patients. NAFLD patients exhibit elevated MYL6 correlating with inflammation, oxidative stress, and disease severity, offering promising diagnostic specificity.

Conclusion

This comprehensive study provides evidence for the association between NAFLD and disulfidptosis, identifying potential target genes and pathways in NAFLD. The identification of MYL6 as a possible treatment target for NAFLD provided a novel understanding of the disease's development.

Advances in Metabolic Regulation of Macrophage Polarization State

Macrophages are significant immune-related cells that are essential for tissue growth, homeostasis maintenance, pathogen resistance, and damage healing. The studies on the metabolic control of macrophage polarization state in recent years and the influence of polarization status on the development and incidence of associated disorders are expounded upon in this article. Firstly, we reviewed the origin and classification of macrophages, with particular attention paid to how the tricarboxylic acid cycle and the three primary metabolites affect macrophage polarization. The primary metabolic hub that controls macrophage polarization is the tricarboxylic acid cycle. Finally, we reviewed the polarization state of macrophages influences the onset and progression of cancers, inflammatory disorders, and other illnesses.

Liver macrophage activation: Relation with hepatic histopathological changes in patients with metabolic associated steatotic liver disease

Aim of the study

Metabolic associated steatotic liver disease (MASLD) is one of the most frequent chronic liver diseases in the world; macrophage activation is reflected by increased expression of CD163, which sheds as serum soluble CD163 that is linked to hepatic steatosis, inflammation, and fibrosis. Aim of the study was assessment of liver macrophage activation and hepatic histopathological changes in patients with MASLD.

Material and methods

A total of 30 patients with MASLD and equal numbers of age- and sex-matched healthy controls were enrolled in the study. Quantitative serum levels of soluble CD163 (sCD163) were determined using a commercially available standard sandwich ELISA kit. Core liver biopsies were obtained from patients with MASLD and evaluation of CD163 using anti-CD163 Ab-1 (Clone 10D6) - mouse monoclonal antibody.

Results

The median sCD163 level was significantly higher in patients with MASLD compared with healthy controls. It can discriminate patients with MASLD from healthy controls at a cut-off value of 814 pg/ml. sCD163 level and intrahepatic total CD163-positive cell count were positively correlated, and both showed positive correlations with nonalcoholic fatty liver disease activity score.

Conclusions

Soluble CD163 can discriminate MASLD patients from healthy controls after the exclusion of other causes of inflammation.

Histidine-rich glycoprotein in metabolic dysfunction-associated steatohepatitis-related disease progression and liver carcinogenesis

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously non-alcoholic fatty liver disease (NAFLD), is a leading cause of chronic liver disease worldwide. In 20%-30% of MASLD patients, the disease progresses to metabolic dysfunction-associated steatohepatitis (MASH, previously NASH) which can lead to fibrosis/cirrhosis, liver failure as well as hepatocellular carcinoma (HCC). Here we investigated the role of histidine-rich glycoprotein (HRG), a plasma protein produced by hepatocytes, in MASLD/MASH progression and HCC development.

METHODS

The role of HRG was investigated by morphological, cellular, and molecular biology approaches in (a) HRG knock-out mice (HRG-/- mice) fed on a CDAA dietary protocol or a MASH related diethyl-nitrosamine/CDAA protocol of hepatocarcinogenesis, (b) THP1 monocytic cells treated with purified HRG, and (c) well-characterized cohorts of MASLD patients with or without HCC.

RESULTS

In non-neoplastic settings, murine and clinical data indicate that HRG increases significantly in parallel with disease progression. In particular, in MASLD/MASH patients, higher levels of HRG plasma levels were detected in subjects with extensive fibrosis/cirrhosis. When submitted to the pro-carcinogenic protocol, HRG-/- mice showed a significant decrease in the volume and number of HCC nodules in relation to decreased infiltration of macrophages producing pro-inflammatory mediators, including IL-1β, IL-6, IL-12, IL-10, and VEGF as well as impaired angiogenesis. The histopathological analysis (H-score) of MASH-related HCC indicate that the higher HRG positivity in peritumoral tissue significantly correlates with a lower overall patient survival and an increased recurrence. Moreover, a significant increase in HRG plasma levels was detected in cirrhotic (F4) patients and in patients carrying HCC vs. F0/F1 patients.

CONCLUSION

Murine and clinical data indicate that HRG plays a significant role in MASLD/MASH progression to HCC by supporting a specific population of tumor-associated macrophages with pro-inflammatory response and pro-angiogenetic capabilities which critically support cancer cell survival. Furthermore, our data suggest HRG as a possible prognostic predictor in HCC patients with MASLD/MASH-related HCCs.

Altered lipid metabolism as a predisposing factor for liver metastasis in MASLD

Recently, the incidence of metabolic dysfunction-associated steatotic liver disease (MASLD) is increasing due to the high prevalence of metabolic conditions, such as obesity and type 2 diabetes mellitus. Steatotic liver is a hotspot for cancer metastasis in MASLD. Altered lipid metabolism, a hallmark of MASLD, remodels the tissue microenvironment, making it conducive to the growth of metastatic liver cancer. Tumors exacerbate the dysregulation of hepatic metabolism by releasing extracellular vesicles and particles into the liver. Altered lipid metabolism influences the proliferation, differentiation, and functions of immune cells, contributing to the formation of an immunosuppressive and metastasis-prone liver microenvironment in MASLD. This review discusses the mechanisms by which the steatotic liver promotes liver metastasis progression, focusing on its role in fostering an immunosuppressive microenvironment in MASLD. Furthermore, this review highlights lipid metabolism manipulation strategies for the therapeutic management of metastatic liver cancer.

The role of N6-methyladenosine in macrophage polarization: A novel treatment strategy for non-alcoholic steatohepatitis

RNA methylation modifications, as a widespread type of modification in eukaryotic cells, especially N6-methyladenosine (m6A), are associated with many activities in organisms, including macrophage polarization and progression of non-alcoholic steatohepatitis (NASH). Macrophages in the liver are of diverse origin and complex phenotype, exhibiting different functions in development of NASH. In the review, we discuss the functions of m6A and m6A-related enzymes in macrophage polarization. Furthermore, we retrospect the role of macrophage polarization in NASH. Finally, we discuss the prospects of m6A in macrophages and NASH, and provide guidance for the treatment of NASH.

Endpoints in NASH Clinical Trials: Are We Blind in One Eye?

This narrative review aims to illustrate the notion that nonalcoholic steatohepatitis (NASH), recently renamed metabolic dysfunction-associated steatohepatitis (MASH), is a systemic metabolic disorder featuring both adverse hepatic and extrahepatic outcomes. In recent years, several NASH trials have failed to identify effective pharmacological treatments and, therefore, lifestyle changes are the cornerstone of therapy for NASH. with this context, we analyze the epidemiological burden of NASH and the possible pathogenetic factors involved. These include genetic factors, insulin resistance, lipotoxicity, immuno-thrombosis, oxidative stress, reprogramming of hepatic metabolism, and hypoxia, all of which eventually culminate in low-grade chronic inflammation and increased risk of fibrosis progression. The possible explanations underlying the failure of NASH trials are also accurately examined. We conclude that the high heterogeneity of NASH, resulting from variable genetic backgrounds, exposure, and responses to different metabolic stresses, susceptibility to hepatocyte lipotoxicity, and differences in repair-response, calls for personalized medicine approaches involving research on noninvasive biomarkers. Future NASH trials should aim at achieving a complete assessment of systemic determinants, modifiers, and correlates of NASH, thus adopting a more holistic and unbiased approach, notably including cardiovascular-kidney-metabolic outcomes, without restricting therapeutic perspectives to histological surrogates of liver-related outcomes alone.

Macrophages and platelets in liver fibrosis and hepatocellular carcinoma

During fibrosis, (myo)fibroblasts deposit large amounts of extracellular matrix proteins, thereby replacing healthy functional tissue. In liver fibrosis, this leads to the loss of hepatocyte function, portal hypertension, variceal bleeding, and increased susceptibility to infection. At an early stage, liver fibrosis is a dynamic and reversible process, however, from the cirrhotic stage, there is significant progression to hepatocellular carcinoma. Both liver-resident macrophages (Kupffer cells) and monocyte-derived macrophages are important drivers of fibrosis progression, but can also induce its regression once triggers of chronic inflammation are eliminated. In liver cancer, they are attracted to the tumor site to become tumor-associated macrophages (TAMs) polarized towards a M2- anti-inflammatory/tumor-promoting phenotype. Besides their role in thrombosis and hemostasis, platelets can also stimulate fibrosis and tumor development by secreting profibrogenic factors and regulating the innate immune response, e.g., by interacting with monocytes and macrophages. Here, we review recent literature on the role of macrophages and platelets and their interplay in liver fibrosis and hepatocellular carcinoma.

How single-cell transcriptomics provides insight on hepatic responses to TCDD

The prototypical aryl hydrocarbon receptor (AHR) ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), has been a valuable model for investigating toxicant-associated fatty liver disease (TAFLD). TCDD induces dose-dependent hepatic lipid accumulation, followed by the development of inflammatory foci and eventual progression to fibrosis in mice. Previously, bulk approaches and in vitro examination of different cell types were relied upon to study the mechanisms underlying TCDD-induced liver pathologies. However, the advent of single-cell transcriptomic technologies, such as single-nuclei RNA sequencing (snRNAseq) and spatial transcriptomics (STx), has provided new insights into the responses of hepatic cell types to TCDD exposure. This review explores the application of these single-cell transcriptomic technologies and highlights their contributions towards unraveling the cell-specific mechanisms mediating the hepatic responses to TCDD.

Role of the co-stimulatory molecule inducible T-cell co-stimulator ligand (ICOSL) in the progression of experimental metabolic dysfunction-associated steatohepatitis

BACKGROUND AND AIMS

Inducible T-cell Co-Stimulator (ICOS) present on T-lymphocytes and its ligand ICOSL expressed by myeloid cells play multiple roles in regulating T-cell functions. However, recent evidence indicates that reverse signalling involving ICOSL is also important in directing the differentiation of monocyte-derived cells. In this study, we investigated the involvement of ICOS/ICOSL dyad in modulating macrophage functions during the evolution of metabolic dysfunction-associated steatohepatitis (MASH).

RESULTS

In animal models of MASH, ICOS was selectively up-regulated on CD8+ T-cells in parallel with an expansion of ICOSL-expressing macrophages. An increase in circulating soluble ICOSL was also evident in patients with MASH as compared to healthy individuals. ICOSL knockout (ICOSL-/-) mice receiving choline/methionine deficient (MCD) diet for 6 weeks had milder steatohepatitis than wild type mice. MASH improvement was confirmed in mice fed with cholesterol-enriched Western diet for 24 weeks in which ICOSL deficiency greatly reduced liver fibrosis along with the formation of crown-like macrophage aggregates producing the pro-fibrogenic mediators osteopontin (OPN) and galectin-3 (Gal-3). These effects associated with a selective shewing of F4-80+/CD11bhigh monocyte-derived macrophages (MoMFs) expressing the Triggering Receptor Expressed on Myeloid cells 2 (TREM2) to CD11blow/F4-80+ cells positive for the Kupffer cell marker C-type lectin-like type 2 receptor (CLEC-2), thus indicating an increased MoMF maturation toward monocyte-derived Kupffer cells.

CONCLUSIONS

These results suggest that CD8+ T-cells interaction with monocyte-derived macrophages through ICOS/ICOSL critically supports a specific subset of TREM2+-expressing cells contributing to the evolution of steatohepatitis. The data also point ICOS/ICOSL dyad as a possible target for therapeutic interventions in MASH.

Ambiguous Pathogenic Roles of Macrophages in Alcohol-Associated Liver Diseases

Alcohol-associated liver disease (ALD) represents a major public health issue worldwide and is a leading etiology of liver cirrhosis. Alcohol-related liver injuries include a range of manifestations including alcoholic hepatitis (AH), simple steatosis, steatohepatitis, hepatic fibrosis, cirrhosis and liver cancer. Liver disease occurs from several pathological disturbances such as the metabolism of ethanol, which generates reactive oxygen species (ROS) in hepatocytes, alterations in the gut microbiota, and the immune response to these changes. A common hallmark of these liver affections is the establishment of an inflammatory environment, and some (broad) anti-inflammatory approaches are used to treat AH (eg, corticosteroids). Macrophages, which represent the main innate immune cells in the liver, respond to a wide variety of (pathogenic) stimuli and adopt a large spectrum of phenotypes. This translates to a diversity of functions including pathogen and debris clearance, recruitment of other immune cells, activation of fibroblasts, or tissue repair. Thus, macrophage populations play a crucial role in the course of ALD, but the underlying mechanisms driving macrophage polarization and their functionality in ALD are complex. In this review, we explore the various populations of hepatic macrophages in alcohol-associated liver disease and the underlying mechanisms driving their polarization. Additionally, we summarize the crosstalk between hepatic macrophages and other hepatic cell types in ALD, in order to support the exploration of targeted therapeutics by modulating macrophage polarization.

Small Heterodimer Partner Modulates Macrophage Differentiation during Innate Immune Response through the Regulation of Peroxisome Proliferator Activated Receptor Gamma, Mitogen-Activated Protein Kinase, and Nuclear Factor Kappa B Pathways

Hepatic macrophages act as the liver's first line of defense against injury. Their differentiation into proinflammatory or anti-inflammatory subpopulations is a critical event that maintains a delicate balance between liver injury and repair. In our investigation, we explored the influence of the small heterodimer partner (SHP), a nuclear receptor primarily associated with metabolism, on macrophage differentiation during the innate immune response. During macrophage differentiation, we observed significant alterations in Shp mRNA expression. Deletion of Shp promoted M1 differentiation while interfering with M2 polarization. Conversely, overexpression of SHP resulted in increased expression of peroxisome proliferator activated receptor gamma (Pparg), a master regulator of anti-inflammatory macrophage differentiation, thereby inhibiting M1 differentiation. Upon lipopolysaccharide (LPS) injection, there was a notable increase in the proinflammatory M1-like macrophages, accompanied by exacerbated infiltration of monocyte-derived macrophages (MDMs) into the livers of Shp myeloid cell specific knockout (Shp-MKO). Concurrently, we observed significant induction of tumor necrosis factor alpha (Tnfa) and chemokine (C-C motif) ligand 2 (Ccl2) expression in LPS-treated Shp-MKO livers. Additionally, the mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) pathways were activated in LPS-treated Shp-MKO livers. Consistently, both pathways were hindered in SHP overexpression macrophages. Finally, we demonstrated that SHP interacts with p65, thereby influencing macrophage immune repones. In summary, our study uncovered a previously unrecognized role of SHP in promoting anti-inflammatory macrophage differentiation during the innate immune response. This was achieved by SHP acting as a regulator for the Pparg, MAPK, and NF-κB pathways.

C-C motif chemokine receptor 2 inhibition reduces liver fibrosis by restoring the immune cell landscape

The accumulation of extracellular matrix (ECM) proteins in the liver leads to liver fibrosis and end-stage liver cirrhosis. C-C motif chemokine receptor 2 (CCR2) is an attractive target for treating liver fibrosis. However, limited investigations have been conducted to explore the mechanism by which CCR2 inhibition reduces ECM accumulation and liver fibrosis, which is the focus of this study. Liver injury and liver fibrosis were induced by carbon tetrachloride (CCl₄) in wild-type mice and Ccr2 knockout (Ccr2^-/-) mice. CCR2 was upregulated in murine and human fibrotic livers. Pharmacological CCR2 inhibition with cenicriviroc (CVC) reduced ECM accumulation and liver fibrosis in prevention and treatment administration. In single-cell RNA sequencing (scRNA-seq), CVC was demonstrated to alleviate liver fibrosis by restoring the macrophage and neutrophil landscape. CVC administration and CCR2 deletion can also inhibit the hepatic accumulation of inflammatory FSCN1⁺ macrophages and HERC6⁺ neutrophils. Pathway analysis indicated that the STAT1, NFκB, and ERK signaling pathways might be involved in the antifibrotic effects of CVC. Consistently, Ccr2 knockout decreased phosphorylated STAT1, NFκB, and ERK in the liver. In vitro, CVC could transcriptionally suppress crucial profibrotic genes (Xaf1, Slfn4, Slfn8, Ifi213, and Il1β) in macrophages by inactivating the STAT1/NFκB/ERK signaling pathways. In conclusion, this study depicts a novel mechanism by which CVC alleviates ECM accumulation in liver fibrosis by restoring the immune cell landscape. CVC can inhibit profibrotic gene transcription via inactivating the CCR2-STAT1/NFκB/ERK signaling pathways.