Integrin β1-enriched extracellular vesicles mediate monocyte adhesion and promote liver inflammation in murine NASH

[摘要] Background & Aims: Hepatic recruitment of monocyte-derived macrophages (MoMFs) contributes to the inflammatory response in non-alcoholic steatohepatitis (NASH). However, how hepatocyte lipotoxicity promotes MoMF inflammation is unclear. Here we demonstrate that lipotoxic hepatocyte-derived extracellular vesicles (LPC-EVs) are enriched with active integrin beta(1) (ITG beta(1)), which promotes monocyte adhesion and liver inflammation in murine NASH. Methods: Hepatocytes were treated with either vehicle or the toxic lipid mediator lysophosphatidylcholine (LPC); EVs were isolated from the conditioned media and subjected to proteomic analysis. C57BL/6J mice were fed a diet rich in fat, fructose, and cholesterol (FFC) to induce NASH. Mice were treated with antiITG beta(1) neutralizing antibody (ITG beta(1)Ab) or control IgG isotype. Results: Ingenuity (R) Pathway Analysis of the LPC-EV proteome indicated that ITG signaling is an overrepresented canonical pathway. Immunogold electron microscopy and nanoscale flow cytometry confirmed that LPC-EVs were enriched with activated ITG beta(1). Furthermore, we showed that LPC treatment in hepatocytes activates ITG beta(1) and mediates its endocytic trafficking and sorting into EVs. LPC-EVs enhanced monocyte adhesion to liver sinusoidal cells, as observed by shear stress adhesion assay. This adhesion was attenuated in the presence of ITG beta(1)Ab. FFC-fed, ITG beta(1)Ab-treated mice displayed reduced inflammation, defined by decreased hepatic infiltration and activation of proinflammatory MoMFs, as assessed by immunohistochemistry, mRNA expression, and flow cytometry. Likewise, mass cytometry by time-of-flight on intrahepatic leukocytes showed that ITG beta(1)Ab reduced levels of infiltrating proinflammatory monocytes. Furthermore, ITG beta(1)Abtreatment significantly ameliorated liver injury and fibrosis. Conclusions: Lipotoxic EVs mediate monocyte adhesion to LSECs mainly through an ITG beta(1)-dependent mechanism. ITG beta(1)Abameliorates diet-induced NASH in mice by reducing MoMF-driven inflammation, suggesting that blocking ITG beta(1) is a potential anti-inflammatory therapeutic strategy in human NASH. Lay summary: Herein, we report that a cell adhesion molecule termed integrin (ITG beta(1)) plays a key role in the progression of non-alcoholic steatohepatitis (NASH). ITG beta(1) is released from hepatocytes under lipotoxic stress as a cargo of extracellular vesicles, and mediates monocyte adhesion to liver sinusoidal endothelial cells, which is an essential step in hepatic inflammation. In a mouse model of NASH, blocking ITG beta(1) reduces liver inflammation, injury and fibrosis. Hence, ITG beta(1) inhibition may serve as a new therapeutic strategy for NASH. (C) 2019 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

[发布日期] 2019-12-01

[关键词] Extracellular vesicles;Integrin beta(1);Integrin alpha(9);Adhesion;Inflammation;NASH;Monocytes;Liver sinusoidal endothelial cells;Mass cytometry;Fibrosis