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THU0039 B1-Integrin is a Critical Mediator of TLR2-Induced Migrational and Invasive Mechanisms in RA Synovial Fibroblast Cells
  1. T. Mcgarry1,
  2. U. Fearon1,
  3. W. Gao1,
  4. M. Jackson2,
  5. J. McCormick1,
  6. D. Veale1,
  7. M. Connolly1
  1. 1Rheumatology Department, St. Vincent’s University Hospital, Dublin Academic Medical Centre and The Conway Institute of Biomolecular and Biomedical Research, Dublin, Ireland
  2. 2Center for Synthesis and Chemical Biology, School of Chemistry and Chemical Biology, UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland., Dublin, Ireland

Abstract

Background Rheumatoid arthritis (RA) is a chronic, progressive autoimmune disease, characterized by synovial proliferation and destruction of cartilage and bone. Engagement of integrin receptors induces cell migration/invasion through attachment to the extracellular matrix and downstream activation of RhoGTPases [1]. TLR2 has been implicated in the pathogenesis of joint destruction in RA [2], however, the mechanisms involved have yet to be elucidated.

Objectives This study investigates the role of β1-integrin in mediating TLR2-induced cytoskeletal rearrangement, cell migration and invasion processes in vivo and in vitro.

Methods β1-integrin expression and cytoskeletal rearrangement were assessed by immunohistochemistry, F-actin immunoflourescent staining and RT-PCR. β1-integrin binding (β1-4, β6, avβ5, a5β1), cytoskeletal rearrangement and RhoGTPase Rac-1 activation in response to Pam3CSK4 (1μg/ml)(TLR2-ligand) in RASFC and HMVEC were assessed by a multiplex adhesion binding assay, F-actin immunofluorescent staining and Rac-1 pull down assays/Western blot. The effect of Pam3CSK4 on cell migration, invasion and Rac-1 activation in the presence of anti-β1-integrin or anti-IgG control was assessed by wound repair assays, ex vivo RA synovial explant matrigel outgrowths, transwell matrigel™ invasion chambers and Rac-1 pulldown/western blot.

Results β1-integrin expression is significantly increased in RA synovial tissue lining layer, sub-lining layer and vasculature in comparison to OA and control tissue (p<0.05). Pam3CSK4 specifically induced β1-integrin binding in RASFC (p<0.05), with no effect observed for β2-4, β6, avβ5 or a5β1 binding. Pam3CSK4 significantly induced β1-integrin mRNA and protein expression in RASFC (p<0.05), and promoted RASFC/HMVEC cytoskeletal disassembly, microspike formation and filopodia extensions. Downstream from β1-intgerin, Pam3CSK4 induced Rac-1 activation, critical for cytoskeletal dynamics and cell motility. Consistent with this Pam3CSK4 induced RASFC/HMVEC migration, invasion, RA synovial explant outgrowths and Rac-1 activation were inhibited in the presence of anti-β1-integrin (p<0.05), with no effect observed for anti-IgG control.

Conclusions TLR2 activation induces migrational and invasive mechanisms through β1-integrin-induced cytoskeletal pathways, processes which are critically involved in the pathogenesis of RA.

References

  1. Brakebusch, C., Bouvard, D., Stanchi, F. et al (2002) Integrins in Invasive Growth J Clin Invest. 109:999-1006

  2. Seibl, R., Birchler, T., Loeliger, S. et al (2003) Expression and Regulation of Toll-like Receptor 2 in rheumatoid arthritis synovium. Am J Pathol 162:1221-7

  3. Brentano, F., Kyburz, D., Schorr, O. et al (2005) The role of Toll-like receptor signalling in the pathogenesis of arthritis. Cell Immunol 233:90-6

Disclosure of Interest T. Mcgarry: None Declared, U. Fearon: None Declared, W. Gao: None Declared, M. Jackson: None Declared, J. McCormick: None Declared, D. Veale Grant/research support from: Abbott, Opsona, Pfizer, Roche, Consultant for: MSD, Pfizer, Roche, Speakers bureau: Janssen, MSD, Pfizer, UCB, M. Connolly: None Declared

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