JUL 29, 2020 11:00 AM EDT

STAT3 phosphorylation during phagocytosis is required to activate autophagy and prevent macrophage immuno-senescence

C.E. Credits: P.A.C.E. CE Florida CE
Speaker
  • Research Fellow, Post-doctoral research Associa, Centre for Regenerative Medicine, University of Edinburgh
    Biography
      Experienced Postdoctoral Fellow with a demonstrated history of working in the research industry. Lara is a strong research professional with a Doctorate of Philosophy (Ph.D.) in Cellular and Molecular Immunology from The Open University and the Vita-Salute San Raffaele University (Milan, Italy). She started her career studying the role of innate immunity in acute muscle injury and repair, and she participated as collaborator on projects aimed at understanding the role of macrophages in development, tumour and autoimmune diseases. The results of her PhD studies have been published into various peer-reviewed journals, including The Journal of Leukocyte Biology, PlosOne and The Journal of Immunology. She won the prize as best oral communications at the PhD Meeting 2011. She progressed by moving to Edinburgh to analyze the role of phagocytosis in acute and chronic liver disease. The results of her post-doctoral research have been published, either as first author or as collaborators on peer reviewed journals such as The Journal of Immunology, Journal of Hepatology and Nature Communications.
      Her core expertise is in the development and analysis of cell-based assays for macrophage function; set up and analysis of multiparametric flow cytometry panels; in vivo models of acute and chronic liver disease and of acute and chronic muscle disease; literature meta-analysis in inflammation and tissue repair. Lara has also an extensive experience as public speaker, having presented at various universities, conferences and events, either as selected or invited talk.
      During her post-doctoral training she participated to the local academic life by teaching in various undergrad courses, and by demonstrating at various public and community engagement projects. She completed her teaching qualification as Fellow of the Higher Education Academy (FHEA) of the UK in 2016, and her application to Member of the Royal Society of Biology was accepted in 2018.

    Abstract

    Background: Acute liver injury (ALI) is characterised by hepatocyte death and liver inflammation. Macrophages play a pivotal role in ALI by phagocytosing dead cells and producing pro-regenerative signals. We have previously demonstrated that phagocytic cargo-dependent activation of phosphoSTAT3 is required to maintain phagocytosis efficiency in macrophages. In this study, we aim to understand the molecular mechanisms underlying the pro-phagocytic function of phosphoSTAT3.

    Methods: Phagocytosing bone marrow derived macrophages (BMDMs) treated with and without a phosphoSTAT3 inhibitor, or from mice deficient for the cargo digestion step of phagocytosis (Gpnmb-), were analysed using flow cytometry, transmission electron microscopy (TEM), and qPCR. We used paracetamol overdose (POD) as mouse model for ALI. We FAC-Sorted and analysed infiltrating macrophages from livers at early stages of POD (10h post-overdose) with the nCounter® technology (Nanostring) and using proteomics.

    Results: Gpnmb- mice are unable to regenerate their liver efficiently after POD: infiltrating phagocytosing macrophages FAC-Sorted from these mice showed increased expression of senescence-related genes, such as Tnfrsf1b and Cdkn1a, but not of apoptosis-related genes, such as Card9. This suggests that macrophages unable to process the internalised cargo enter immuno-senescence, a condition characterised by elevated production of inflammatory cytokines and reduced phagocytosis. TEM and qPCR analyses showed that both Gpnmb- and phosphoSTAT3 inhibitor-treated BMDMs develop a senescent phenotype during phagocytosis, suggesting that cargo digestion-dependent phosphorylation of STAT3 prevents immuno-senescence in phagocytosing macrophages. Autophagy is a mechanism widely used by cells to cope with stress: interestingly, TEM and qPCR analyses unveiled a lower activation of autophagy in Gpnmb- and phosphoSTAT3 inhibitor-treated BMDMs.

    Conclusions: Phagocytosing macrophages require phosphoSTAT3 activation.

     

    Learning Objectives:

    1. Understand the use of flow cytometry-based medium throughput screening assays as an essential tool to investigate macrophage phagocytosis

    2. Describe the role of pSTAT3 as a pro-phagocytic pathway in macrophages

    3. Explain that other pathways are controlled downstream of pSTAT3, including autophagy and senescence


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