beta1 integrin-mediated signaling induces intercellular adhesion molecule 1 and Fas on rheumatoid synovial cells and Fas-mediated apoptosis.
OBJECTIVE
Rheumatoid arthritis (RA) synovial cells interact with inflammatory cells, as well as extracellular matrices, through integrins. However, the relevance of beta1 integrin to inflammatory processes in RA remains unclear. We examined the role of beta1 integrin-mediated signaling in RA.


METHODS
Expression of cell-surface molecules was assessed by FACScan. Engagement of beta1 integrins was performed by crosslinking using a specific monoclonal antibody (mAb) and ligand matrices such as fibronectin or collagen. To determine the involvement of tyrosine kinases in beta1 integrin-mediated signaling, the cells were pretreated with various inhibitors of intracytoplasmic signaling or were transfected with a wild-type focal adhesion kinase (FAK) or a dominant negative truncation of the FAK expression plasmid via cationic liposome-mediated transfection. Apoptosis of synovial cells was detected by double staining with propidium iodide and annexin V.


RESULTS
beta1 integrin was highly expressed on RA synovial cells. Engagement of beta1 integrins by crosslinking as well as by ligand matrices markedly up-regulated expression of intercellular adhesion molecule 1 (ICAM-1) and Fas. Up-regulation of ICAM-1 and Fas induced by beta1 integrin was mediated by the tyrosine kinase signaling pathway, especially involving FAK. Fas-mediated early apoptotic change in the cells was amplified by beta1 crosslinking.


CONCLUSIONS
Our results suggest that interaction of beta1 integrins with extracellular matrix augments expression of ICAM-1 and Fas on RA synovial cells, as well as Fas-mediated apoptosis of synovial cells. This might lead to the spontaneous growth arrest through the Fas/Fas ligand pathway observed in RA synovitis.
Nakayamada
Shingo
S
University of Occupational and Environmental Health, Kitakyushu, Japan.
Saito
Kazuyoshi
K
Fujii
Koichi
K
Yasuda
Manabu
M
Tamura
Masahito
M
Tanaka
Yoshiya
Y
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001172:Arthritis, Rheumatoid / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D024042:Collagen Type I / Q000494:pharmacology; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005353:Fibronectins / Q000494:pharmacology; D005434:Flow Cytometry; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D019012:Integrin beta1 / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology; D018799:Intercellular Adhesion Molecule-1 / Q000096:biosynthesis*; D010003:Osteoarthritis / Q000378:metabolism / Q000473:pathology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013583:Synovial Membrane / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D014162:Transfection; D015854:Up-Regulation; D019014:fas Receptor / Q000096:biosynthesis* / Q000276:immunology
D000911:Antibodies, Monoclonal; D024042:Collagen Type I; D003432:Cross-Linking Reagents; D004791:Enzyme Inhibitors; D005353:Fibronectins; D019012:Integrin beta1; D019014:fas Receptor; D018799:Intercellular Adhesion Molecule-1; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human