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LPS-induced macrophage HMGB1-loaded extracellular vesicles trigger hepatocyte pyroptosis by activating the NLRP3 inflammasome

ABSTRACT: Extracellular vesicles (EVs) have emerged as important vectors of intercellular dialogue. High mobility group box protein 1 (HMGB1) is a typical damage-associated molecular pattern (DAMP) molecule, which is cytotoxic and leads to cell death and tissue injury. Whether EVs are involved in the release of HMGB1 in lipopolysaccharide (LPS)-induced acute liver injuries need more investigation. EVs were identified by transmission electron microscopy, nanoparticle tracking analysis (NTA), and western blotting. The co-localization of HMGB1, RAGE (receptor for advanced glycation end-products), EEA1, Rab5, Rab7, Lamp1 and transferrin were detected by confocal microscopy. The interaction of HMGB1 and RAGE were investigated by co-immunoprecipitation. EVs were labeled with the PKH67 and used for uptake experiments. The pyroptotic cell death was determined by FLICA 660-YVAD-FMK. The expression of NLRP3 (NOD-like receptor family pyrin domain containing 3) inflammasomes were analyzed by western-blot or immunohistochemistry. Serum HMGB1, ALT (alanine aminotransferase), AST (aspartate aminotransferase), LDH (lactate dehydrogenase) and MPO (myeloperoxidase) were measured using a commercial kit. The extracellular vesicle HMGB1 was detected in the serums of sepsis patients. Macrophages were found to contribute to HMGB1 release through the EVs. HMGB1-RAGE interactions participated in the loading of HMGB1 into the EVs. These EVs shuttled HMGB1 to target cells by transferrin-mediated endocytosis leading to hepatocyte pyroptosis by the activation of NLRP3 inflammasomes. Moreover, a positive correlation was verified between the sepsis serum EVs-HMGB1 level and clinical liver damage. This finding provides insights for the development of novel diagnostic and therapeutic strategies for acute liver injuries.

SUBMITTER: Wang G

PROVIDER: S-EPMC8572226 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background and Aims: The activation of stimulator of interferon genes (STING) and NOD-like receptors protein 3 (NLRP3) inflammasomes-mediated pyroptosis signaling pathways represent two distinct central mechanisms in liver disease. However, the interconnection between these two pathways and the epigenetic regulation of the STING-NLRP3 axis in hepatocyte pyroptosis during liver fibrosis remain unknown and is the focus of this study. Approach and Results: Liver fibrosis was induced in Sting knockout, Gasdermin D (Gsdmd) knockout mice, and in mice with hepatocyte-specific Nlrp3 deletion. RNA-sequencing, metabolomics, epigenetic compound screening system, and chromatin immunoprecipitation were utilized. STING and NLRP3 inflammasome signaling pathways were activated in cirrhotic livers but were suppressed by Sting knockout. Sting knockout also ameliorated hepatic pyroptosis, inflammation, and fibrosis in the murine cirrhotic model. In vitro, STING induced pyroptosis in primary murine hepatocytes via activating the NLRP3 inflammasome. H3K4-specific histone methyltransferase WD repeat-containing protein 5 (WDR5) and DOT1-like histone H3K79 methyltransferase (DOT1L) were identified to regulate NLRP3 expression in STING-overexpressed AML12 hepatocytes. WDR5/DOT1L-mediated histone methylation enhanced interferon regulatory transcription factor 3 (IRF3) binding to the Nlrp3 promoter and promoted STING-induced Nlrp3 transcription in hepatocytes. The RNA-sequencing and metabolomics analysis in murine livers and primary hepatocytes showed that metabolic reprogramming might participate in NLRP3-mediated hepatocyte pyroptosis and liver fibrosis. Moreover, hepatocyte-specific Nlrp3 deletion and downstream Gsdmd knockout attenuated hepatic pyroptosis, inflammation, and fibrosis in murine cirrhotic models. Conclusions: This study describes a novel epigenetic mechanism by which the STING-WDR5/DOT1L/IRF3-NLRP3 signaling pathway enhances hepatocyte pyroptosis and hepatic inflammation in liver fibrosis.

Project description:Inflammasome activation plays a central role in the development of drug-induced and obesity-associated liver disease. However, the sources and mechanisms of inflammasome-mediated liver damage remain poorly understood. Our aim was to investigate the effect of NLRP3 inflammasome activation on the liver using novel mouse models. We generated global and myeloid cell-specific conditional mutant Nlrp3 knock-in mice expressing the D301N Nlrp3 mutation (ortholog of D303N in human NLRP3), resulting in a hyperactive NLRP3. To study the presence and significance of NLRP3-initiated pyroptotic cell death, we separated hepatocytes from nonparenchymal cells and developed a novel flow-cytometry-based (fluorescence-activated cell sorting; FACS) strategy to detect and quantify pyroptosis in vivo based on detection of active caspase 1 (Casp1)- and propidium iodide (PI)-positive cells. Liver inflammation was quantified histologically by FACS and gene expression analysis. Liver fibrosis was assessed by Sirius Red staining and quantitative polymerase chain reaction for markers of hepatic stellate cell (HSC) activation. NLRP3 activation resulted in shortened survival, poor growth, and severe liver inflammation; characterized by neutrophilic infiltration and HSC activation with collagen deposition in the liver. These changes were partially attenuated by treatment with anakinra, an interleukin-1 receptor antagonist. Notably, hepatocytes from global Nlrp3-mutant mice showed marked hepatocyte pyroptotic cell death, with more than a 5-fold increase in active Casp1/PI double-positive cells. Myeloid cell-restricted mutant NLRP3 activation resulted in a less-severe liver phenotype in the absence of detectable pyroptotic hepatocyte cell death.Our data demonstrate that global and, to a lesser extent, myeloid-specific NLRP3 inflammasome activation results in severe liver inflammation and fibrosis while identifying hepatocyte pyroptotic cell death as a novel mechanism of NLRP3-mediated liver damage.

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LPS-induced macrophage HMGB1-loaded extracellular vesicles trigger hepatocyte pyroptosis by activating the NLRP3 inflammasome

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