Background and aims: Galanin is a naturally occurring peptide that plays a critical role in regulating inflammation and energy metabolism, with expression in the liver. The exact involvement of galanin in non-alcoholic fatty liver disease and related fibrosis remains controversial.Methods: The effects of subcutaneously administered galanin were studied in mice with non-alcoholic steatohepatitis (NASH) induced by a high-fat and high-cholesterol diet for 8 weeks, and in mice with liver fibrosis induced by CCl₄ for 7 weeks. The underlying mechanism was also studied in vitro on murine macrophage cells (J774A.1 and RAW264.7).Results: Galanin reduced inflammation, CD68-positive cell count, MCP-1 level, and mRNA levels of inflammation-related genes in the liver of NASH mice. It also mitigated liver injury and fibrosis caused by CCl₄. In vitro, galanin had anti-inflammatory effects on murine macrophages, including reduced phagocytosis and intracellular reactive oxygen species (ROS). Galanin also activated AMP-activated protein kinase (AMPK)/acetyl-CoA carboxylase (ACC) signaling.Conclusion: Galanin ameliorates liver inflammation and fibrosis in mice, potentially by modifying macrophage inflammatory phenotype and activating AMPK/ACC signaling.

Macrophages are immune cells crucial for host defense and homeostasis maintenance, and their dysregulation is involved in multiple pathological conditions, such as liver fibrosis. The transcriptional regulation in macrophage is indispensable for fine-tuning of macrophage functions, but the details have not been fully elucidated. Prolyl endopeptidase (PREP) is a dipeptidyl peptidase with both proteolytic and non-proteolytic functions. In this study, we found that Prep knockout significantly contributed to transcriptomic alterations in quiescent and M1/M2-polarized bone marrow-derived macrophages (BMDMs), as well as aggravated fibrosis in an experimental nonalcoholic steatohepatitis (NASH) model. Mechanistically, PREP predominantly localized to the macrophage nuclei and functioned as a transcriptional coregulator. Using CUT&Tag and co-immunoprecipitation, we found that PREP was mainly distributed in active cis-regulatory genomic regions and physically interacted with the transcription factor PU.1. Among PREP-regulated downstream genes, genes encoding profibrotic cathepsin B and D were overexpressed in BMDMs and fibrotic liver tissue. Our results indicate that PREP in macrophages functions as a transcriptional coregulator that finely tunes macrophage functions, and plays a protective role against liver fibrosis pathogenesis.

Ductular reaction in non-alcoholic fatty liver disease: When Macbeth is perverted

Kupffer cells (KCs) can promote hepatic inflammation in metabolic dysfunction-associated steatotic liver disease (MASLD), but the underlying molecular mechanisms are not fully understood. C/EBPβ in macrophages can mediate metabolic and immune dysregulations. Therefore, we aimed to explore its role in KCs in MASLD pathogenesis. A 12-week high-fat and high-cholesterol diet (HFHCD) model was used in wild-type or KC-specific Cebpb heterozygous knockout mice (n = 10 per group), followed by liver evaluation using histopathology, flow cytometry, and RNA-seq. RNA-seq of liver tissue (n = 3 per group) and C/EBPβ CUT&Tag-seq of sorted KCs were comprehensively analyzed to elucidate the transcriptional regulatory network. Flow cytometry and immunofluorescence were used to detect the expression or distribution of key proteins. HFHCD induced prominent immune cell infiltration and a concomitant increase in C/EBPβ in KCs. KC-specific Cebpb heterozygous knockout significantly reduced HFHCD-induced lobular inflammation (p <0.05) and inflammation-related gene expression (p <0.05) in the liver. Multi-omics analysis revealed increased C/EBPβ activity in KCs in MASLD, leading to a selective promotive effect on MASLD-induced genes. Further integrated analysis identified Vcam1 as a key direct downstream gene of C/EBPβ in KCs in MASLD, which involves C/EBPβ-mediated activation of the Vcam1 promoter. VCAM1 was predominantly expressed in KCs in the hepatic tissue of MASLD mice and patients. KC-expressed VCAM1 was significantly increased in MASLD compared with healthy controls (p <0.01), and it promoted immune cell infiltration into the liver. Increased C/EBPβ in KCs promotes pathogenic transcriptional activation, leading to increased VCAM1 expression and inflammatory cell infiltration in MASLD. Inhibition of C/EBPβ in KCs might be a potential therapeutic strategy against hepatic inflammation in MASLD. Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most common chronic liver disease worldwide, but its pathogenesis remains elusive. In this study, we investigated the critical role of CCAAT/enhancer binding protein β (C/EBPβ) in Kupffer cells and its implications in MASLD pathogenesis. We found that an increased C/EBPβ level in Kupffer cells promotes hepatic inflammation in MASLD by upregulating VCAM1 expression. Our findings provide valuable insights into the molecular mechanisms driving MASLD and propose a potential novel therapeutic target to mitigate hepatic inflammation in MASLD.

Prolyl endopeptidase (PREP) is a serine endopeptidase that participates in many pathological processes including inflammation, oxidative stress, and autophagy. Our previous studies found that PREP knockout exhibited multiple benefits in high-fat diet (HFD) or methionine choline-deficient diet-induced metabolic dysfunction-associated fatty liver disease (MAFLD). However, cumulative studies have suggested that PREP performs complex functions during disease development. Therefore, further understanding the role of PREP in MAFLD development is the foundation of PREP intervention.