The chemokine receptors CCR2 and CX3CR1 expressed by monocytes interact with chemokine ligands CCL2 (MCP-1) and CX3CL1 (fractalkine) respectively produced by FLS and this interaction promotes their migration and recruitment into RA synovium.
The mRNA expression level of TRAF1 and CTGF was significantly increased in OA and RA group (p < 0.05), while the expression level of CX3CL1 was only increased in OA group (p < 0.05).
The chemokine fractalkine (CX3C chemokine ligand 1; CX3CL1) and its receptor CX3CR1 are involved in the pathogenesis of several diseases, including inflammatory bowel diseases such as Crohn's disease and ulcerative colitis, rheumatoid arthritis, hepatitis, myositis, multiple sclerosis, renal ischemia, and atherosclerosis.
Increased serum levels of CX3CL1 protein were observed in SS patients compared with controls (P < 0.0001) and in RA patients compared with controls (P < 0.0001), but no difference was found between Sicca patients and controls (P = 0.22).
The CX3CL1-CX3CR1 axis may be a novel target for the therapeutic intervention of bone resorbing diseases such as rheumatoid arthritis, osteoporosis, and cancer bone metastasis.