Exploring novel mechanisms underlying synovial fibroblast-mediated pathogenesis in arthritis: role of ARNO and sialylation in stromal inflammation

Wang, Yilin (2022) Exploring novel mechanisms underlying synovial fibroblast-mediated pathogenesis in arthritis: role of ARNO and sialylation in stromal inflammation. PhD thesis, University of Glasgow.

Abstract

Synovial fibroblasts (SFs) not only maintain articular homeostasis in a health state, but also play a key role in joint destruction in immune articular diseases, such as rheumatoid arthritis (RA). In RA, activated SFs undergo intrinsic alterations, adopting an aggressive phenotype that damages cartilage and bone. The dysregulated cell migratory property and hyper-inflammatory responses are hallmarks of activated SFs. However, deactivation of these cells is not currently possible. This study investigated two potential novel sites of invention, namely defining the ARNO and Sialic acid arms of the project. The central aim of this study was to understand the regulation of ARNO and sialic acid in SFs in a proinflammatory microenvironment and the function of ARNO and sialic acid in SF-dependent migration and inflammation. On the one hand, ARNO (the ARF Nucleotide-Binding Site Opener) is a dominant activator of ARF (ADP-ribosylation factor) proteins that regulate cell adhesion, migration, and cytoskeleton reorganisation in many cell types. The elevated expression of ARNO in leukocyte-rich RA shows ARNO might be regulated in a pro-inflammatory milieu, indicating the potential role of ARNO in SF-dependent physiopathology. We demonstrated that IL-1β upregulated ARNO expression and ARF6 activation in SFs, whilst SFs transfected with ARNO siRNA exhibited reduced motility and formation of focal adhesion. Surprisingly therefore, ARNO modulated the IL-1β-induced inflammatory response in SFs and the inhibition of ARNO greatly reduced the production of cytokines, chemokines and other immunomodulators. On the other hand, glycosylation is one of the most common protein modifications, and the glycoconjugates on plasma membranes are involved in a wide range of biological functions, including cell-cell interactions and inflammation. Alterations in glycosylation have been observed in chronic diseases, but how changes in the cell glycome affect SF physiopathology remains largely unknown. We combined transcriptomic and glycomics analysis to investigate glycosylation-dependent SF physiopathology. We demonstrated that the pro-inflammatory cytokine TNFα modulates SF cell surface glycosylation by inhibiting the expression of ST6Gal1 and subsequently reducing α2-6 sialylation. In addition, SFs from arthritic mice exhibited reduced cell surface sialylation and sialylation was associated with functional SF subsets. Removal of cell surface sialic acid with sialidase from C. perfringens provided evidence that loss of sialic acid transforms SF into a pathogenic phenotype with hyper-inflammatory response and enhanced migration property. Overall, this work highlights the importance of ARNO and sialic acid in SFmediated inflammation and pathogenic migration, bridging cell motility to inflammatory responses, and offering new perspective on targeting SF deactivation in arthritic joints.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Supported by funding from China Scholarship Council.
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Funder's Name: China Scholarship Council
• Supervisor's Name: Pineda, Dr. Miguel
• Date of Award: 2022
• Depositing User: Theses Team
• Unique ID: glathesis:2022-83268
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 15 Nov 2022 11:31
• Last Modified: 10 Apr 2024 13:20
• Thesis DOI: 10.5525/gla.thesis.83268
• URI: https://theses.gla.ac.uk/id/eprint/83268

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