Differential expression of chemokine receptors on peripheral blood, synovial fluid, and synovial tissue monocytes/macrophages in rheumatoid arthritis

Abstract

Objective. Since it is likely that monocytes utilize chemokines to migrate to the rheumatoid arthritis (RA) joint, we investigated the expression of C-C chemokine receptors (CCR) 1-6 and C-X-C receptor 3 (CXCR3) in the peripheral blood (PB), synovial fluid (SF), and synovial tissue of patients with RA as well as in the PB of normal subjects. Methods. We compared chemokine receptor expression on CD14؉ monocytes from normal PB, RA PB, and RA SF using 2-color flow cytometry. Correlations with patient clinical data were determined. Chemokine and receptor expression were investigated in RA synovial tissue by immunohistochemistry and 2-color immunofluorescence to identify CD68؉ macrophages. Results. Most normal PB monocytes expressed CCR1 (87%) and CCR2 (84%), but not CCRs 3, 4, 5, or 6 or CXCR3. RA PB monocytes expressed CCR1 (56%) and CCR2 (76%), with significantly more expressing CCR3 (18%), CCR4 (38%), and CCR5 (17%) compared with normal PB monocytes. Significantly fewer SF monocytes from RA patients expressed CCR1 (17%), CCR2 (24%), and CCR4 (6%) while significantly more expressed CCR3 (35%) and CCR5 (47%) compared with RA and normal PB monocytes; CCR6 and CXCR3 were rarely detected. Clinically, the erythrocyte sedimentation rate was inversely correlated with the expression of CCR1 and CCR4 by RA PB, and CCR5 expression by RA SF was correlated with the SF white blood cell count. CCR1-, CCR2-, and CCR5-immunoreactive cells were found in RA synovial tissue and colocalized with CD68؉ macrophages. RA synovial tissue RANTES (regulated upon activation, normally T cell expressed and secreted chemokine)-and monocyte chemoattractant protein 1-immunoreactive cells colocalized with CCR1 and CCR2, respectively, on serial sections. Macrophage inflammatory protein 1␣ (MIP-1␣) was principally restricted to vascular endothelium, and MIP-1␤؉ macrophages were found throughout the sections. Conclusion. Monocytes mainly express CCR1 and CCR2 in normal and RA PB, CCR3 and CCR5 in RA PB and RA SF, and CCR4 in RA PB. The differential expression of chemokine receptors suggests that certain receptors aid in monocyte recruitment from the circulation while others are important in monocyte retention in the joint.

CXCL16‐mediated cell recruitment to rheumatoid arthritis synovial tissue and murine lymph nodes is dependent upon the MAPK pathway

“…Substantial progress in characterizing chemokines and chemokine receptor function in vitro has led to better understanding of cell migration (3,5,11,32), but the limitations of the in vitro environment make it difficult to interpret how chemokines and corresponding receptors function in vivo. Limitations of in vitro migration assays include evaluating the role of a particular chemokine as it relates to other chemokines and chemokine receptors, and ranking the importance of chemokines and chemokine receptors in a particular disease.…”

“…SF cells were obtained from the joints of RA patients undergoing arthrocentesis. CXCR6 expression on CD14ϩ monocytes was evaluated by FACS analysis as previously described (11). Briefly, cells were incubated with fluorescein isothiocyanate (FITC)-labeled mouse anti-human CD14 (PharMingen) and mouse anti-human CXCR6 antibodies (CXCR6 IgG; kindly provided by Millennium Pharmaceuticals, Cambridge, MA).…”

“…Some chemokines function in a variety of ways, including initiating angiogenesis (6)(7)(8), binding of human immunodeficiency virus (HIV) surface proteins (9), and directly regulating immune responses to antigen (10). However, one of the primary functions of chemokines is their contribution to leukocyte homing (11).…”

Role of osteopontin in induction of monocyte chemoattractant protein 1 and macrophage inflammatory protein 1β through the NF‐κB and MAPK pathways in rheumatoid arthritis

“…There is evidence supporting a similar role for MIP-1␤, a ligand of CCR5 and one of the critical mediators for trafficking of Th1 cells and other inflammatory cells into rheumatoid synovium (11)(12)(13). In addition, there are other proinflammatory molecules that act in synergy with chemokines to promote leukocyte migration in autoimmune arthritis, including matrix metalloproteinase and osteopontin (OPN) (14,15).…”

Chemokine receptor expression and in vivo signaling pathways in the joints of rats with adjuvant‐induced arthritis

“…This may imply that CCR1 is important in the initial recruitment of monocytes from the circulation to sites of inflammation (10). CCR2, the receptor for MCP-1, is mainly expressed on monocytes in normal and RA PB.…”