Integrin ?₁-enriched extracellular vesicles mediate monocyte adhesion and promote liver inflammation in murine NASH.

ABSTRACT: 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 ?₁ (ITG?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 anti-ITG?₁ neutralizing antibody (ITG?₁Ab) or control IgG isotype. RESULTS:Ingenuity® 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?₁. Furthermore, we showed that LPC treatment in hepatocytes activates ITG?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?₁Ab. FFC-fed, ITG?₁Ab-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?₁Ab reduced levels of infiltrating proinflammatory monocytes. Furthermore, ITG?₁Ab treatment significantly ameliorated liver injury and fibrosis. CONCLUSIONS:Lipotoxic EVs mediate monocyte adhesion to LSECs mainly through an ITG?₁-dependent mechanism. ITG?₁Ab ameliorates diet-induced NASH in mice by reducing MoMF-driven inflammation, suggesting that blocking ITG?₁ is a potential anti-inflammatory therapeutic strategy in human NASH. LAY SUMMARY:Herein, we report that a cell adhesion molecule termed integrin ?₁ (ITG?₁) plays a key role in the progression of non-alcoholic steatohepatitis (NASH). ITG?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?₁ reduces liver inflammation, injury and fibrosis. Hence, ITG?₁ inhibition may serve as a new therapeutic strategy for NASH.

SUBMITTER: Guo Q 

PROVIDER: S-EPMC6864271 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature