Activation of fibroblast-like synoviocytes derived from rheumatoid arthritis via lysophosphatidic acid lysophosphatidic acid receptor 1 cascade

Introduction: Lysophosphatidic acid (LPA) is a hioactive lipid that binds to G protein coupled receptors (LPAI. 5). Recently, we reported that abrogation of LPA receptor 1 (LPA1) ameliorated murine collagen -induced arthritis, probably via inhibition of inflammatory cell migration, Th17 differentiation and osteoclastogenesis. In this study, we examined the importance of the LPA LPAI axis in cell proliferation, cytokine/chemokine production and lymphocyte transmigration in fibroblast -like synoviocytes (ELSs) obtained from the synovial tissues of rheumatoid arthritis (RA) patients. Methods: FLSs were prepared from synovial tissues of RA patients. Expression of LPAI_6 was examined by quantitative real-time RT-PCR. Cell surface LPAI expression was analyzed by flow cytometry. Cell proliferation was analyzed using a cell counting kit Production of interleukin 6 (IL --6), vascular endothelial growth factor (VEGF), chemokine (C -C motif) ligand 2 (CCL2), metalloproteinase 3 (MMP 3) and chemokine (C X C motif) ligand 12 (CXCL12) was measured by enzyme linked immunosorbent assay Pseudoemperipolesis was evaluated using a coculture of RA FLSs and T or B cells. Cell motility was examined by scrape motility assay. Expression of adhesion molecules was determined by flow cytometry. Results: The expression of LPAI mRNA and cell surface LPAI was higher in RA FLSs than in FLSs from osteoarthritis tissue. Stimulation with LPA enhanced the proliferation of RA FLSs and the production of IL 6, VEGF, CCL2 and MMP-3 by FLSs, which were suppressed by an LPN inhibitor (LA 01). Ki16425, another LPAI antagonist, also suppressed IL 6 production by LPA-stimulated RA FLSs. However, the production of CXCL12 was not altered by stimulation with LPA. LPA induced the pseudoemperipolesis of T and B cells cocultured with RA FLSs, which was suppressed by LPAI inhibition. In addition, LPA enhanced the migration of RA FLSs and expression of vascular cell adhesion molecule and intercellular adhesion molecule on RA FLSs, which were also inhibited by an LPAI antagonist. Conclusions: Collectively, these results indicate that LPA LPAI signaling contributes to the activation of RA FLSs.