Integrin β1-enriched extracellular vesicles mediate monocyte adhesion and promote liver inflammation in murine NASH
Guo, Q., Furuta, K., Lucien, F. et al.
BACKGROUND AND AIMS:
Hepatic recruitment of monocyte-derived macrophages (MoMF) contributes to the inflammatory response in nonalcoholic steatohepatitis (NASH). However, how hepatocyte lipotoxicity promotes MoMF inflammation is unclear. Here we demonstrate that lipotoxic hepatocyte-derived extracellular vesicles (EVs) are enriched with active integrin β1 (ITGβ1), which promotes monocyte adhesion and liver inflammation in murine NASH.
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 anti-ITGβ1 neutralizing antibody (ITGβ1Ab) or control IgG isotype.
Ingenuity Pathway Analysis of the lipotoxic hepatocyte-derived EV (LPC-EVs) proteome indicated that integrin signaling is an overrepresented canonical pathway. Immunogold electron microscopy and nanoscale flow cytometry confirmed enrichment of LPC-EVs with active ITGβ1. Furthermore, we showed that LPC treatment in hepatocytes activates ITGβ1 and mediates its endocytic trafficking and sorting into EVs. LPC-EVs-enhanced monocytes adhesion to liver sinusoidal endothelial cells (LSECs) was observed by shear stress adhesion assay, and was attenuated in the presence of ITGβ1Ab. FFC-fed, ITGβ1Ab-treated mice displayed reduced inflammation defined by decreased proinflammatory MoMF hepatic infiltration and activation as assessed by immunohistochemistry, mRNA expression, and flow cytometry. Likewise, mass cytometry by time-of-flight (CyTOF) on intrahepatic leukocytes (IHL) displayed reduced infiltrating proinflammatory monocytes. Furthermore, ITGβ1Ab treatment significantly ameliorated liver injury and fibrosis.
Lipotoxic EVs mediate monocyte adhesion to LSECs mainly by an ITGβ1-dependent mechanism. ITGβ1Ab ameliorates diet-induced NASH in mice by reducing MoMF-driven inflammation, suggesting that blocking ITGβ1 is a potential anti-inflammatory therapeutic strategy in human NASH.
Guo, Q., Furuta, K., Lucien, F. et al. "Integrin β1-enriched extracellular vesicles mediate monocyte adhesion and promote liver inflammation in murine NASH" Journal of Hepatology (2019): doi: 10.1016/j.jhep.2019.07.019.