Qianqian Guo1, Kunimaro Furuta1, Fabrice Lucien2, Luz Helena Gutierrez Sanchez3, Petra Hirsova1, Anuradha Krishnan1, Ayano Kabashima1, Kevin D Pavelko4, Benjamin Madden5, Husam Alhuwaish6, Yandong Gao7, Alexander Revzin7, Samar H Ibrahim8. 1. Division of Gastroenterology & Hepatology, Mayo Clinic, Rochester, Minnesota, United States. 2. Department of Urology, Mayo Clinic, Rochester, Minnesota, United States. 3. Division of Pediatric Gastroenterology, Mayo Clinic, Rochester, Minnesota, United States. 4. Department of Immunology, Mayo Clinic, Rochester, Minnesota, United States. 5. Proteomics Core Medical Genome Facility, Mayo Clinic, Rochester, Minnesota, United States. 6. School of Medicine, The Royal College of Surgeons in Ireland, Ireland. 7. Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States. 8. Division of Gastroenterology & Hepatology, Mayo Clinic, Rochester, Minnesota, United States; Division of Pediatric Gastroenterology, Mayo Clinic, Rochester, Minnesota, United States. Electronic address: ibrahim.samar@mayo.edu.
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 β1 (ITGβ1), 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-ITGβ1 neutralizing antibody (ITGβ1Ab) 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 ITGβ1. Furthermore, we showed that LPC treatment in hepatocytes activates ITGβ1 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 ITGβ1Ab. FFC-fed, ITGβ1Ab-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 ITGβ1Ab reduced levels of infiltrating proinflammatory monocytes. Furthermore, ITGβ1Ab treatment significantly ameliorated liver injury and fibrosis. CONCLUSIONS: Lipotoxic EVs mediate monocyte adhesion to LSECs mainly through 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. LAY SUMMARY: Herein, we report that a cell adhesion molecule termed integrin β1 (ITGβ1) plays a key role in the progression of non-alcoholic steatohepatitis (NASH). ITGβ1 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 ITGβ1 reduces liver inflammation, injury and fibrosis. Hence, ITGβ1 inhibition may serve as a new therapeutic strategy for NASH.
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 β1 (ITGβ1), 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-ITGβ1 neutralizing antibody (ITGβ1Ab) 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 ITGβ1. Furthermore, we showed that LPC treatment in hepatocytes activates ITGβ1 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 ITGβ1Ab. FFC-fed, ITGβ1Ab-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 ITGβ1Ab reduced levels of infiltrating proinflammatory monocytes. Furthermore, ITGβ1Ab treatment significantly ameliorated liver injury and fibrosis. CONCLUSIONS: Lipotoxic EVs mediate monocyte adhesion to LSECs mainly through 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. LAY SUMMARY: Herein, we report that a cell adhesion molecule termed integrin β1 (ITGβ1) plays a key role in the progression of non-alcoholic steatohepatitis (NASH). ITGβ1 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 ITGβ1 reduces liver inflammation, injury and fibrosis. Hence, ITGβ1 inhibition may serve as a new therapeutic strategy for NASH.
Authors: Kunimaro Furuta; Qianqian Guo; Kevin D Pavelko; Jeong-Heon Lee; Keith D Robertson; Yasuhiko Nakao; Jan Melek; Vijay H Shah; Petra Hirsova; Samar H Ibrahim Journal: J Clin Invest Date: 2021-03-15 Impact factor: 14.808