Duffy antigen receptor for chemokines and CXCL5 are essential for the recruitment of neutrophils in a multicellular model of rheumatoid arthritis synovium

Abstract

Objective. The role of chemokines and their transporters in rheumatoid arthritis (RA) is poorly described. Evidence suggests that CXCL5 plays an important role, because it is abundant in RA tissue, and its neutralization moderates joint damage in animal models of arthritis. Expression of the chemokine transporter Duffy antigen receptor for chemokines (DARC) is also up-regulated in early RA. The aim of this study was to investigate the role of CXCL5 and DARC in regulating neutrophil recruitment, using an in vitro model of RA synovium.Methods. To model RA synovium, RA synovial fibroblasts (RASFs) were cocultured with endothelial cells (ECs) for 24 hours. Gene expression in cocultured cells was investigated using TaqMan gene arrays. The roles of CXCL5 and DARC were determined by incorporating cocultures into a flow-based adhesion assay, in which their function was demonstrated by blocking neutrophil recruitment with neutralizing reagents.Results. EC-RASF coculture induced chemokine expression in both cell types. Although the expression of CXC chemokines was modestly up-regulated in ECs, the expression of CXCL1, CXCL5, and CXCL8 was greatly increased in RASFs. RASFs also promoted the recruitment of flowing neutrophils to ECs. Anti-CXCL5 antibody abolished neutrophil recruitment by neutralizing CXCL5 expressed on ECs or when used to immunodeplete coculture-conditioned medium. DARC was also induced on ECs by coculture, and anti-Fy6 antibody or small interfering RNA targeting of DARC expression effectively abolished neutrophil recruitment.Conclusion. This study is the first to demonstrate, in a model of human disease, that the function of DARC is essential for editing the chemokine signals presented by ECs and for promoting unwanted leukocyte recruitment.

Shedding light on DARC: the role of the Duffy antigen/receptor for chemokines in inflammation, infection and malignancy

“…The in vitro study by Smith et al [16] provides convincing evidence that DARC is important in neutrophil migration using an RA model. However, the only study investigate DARC expression in human RA found high levels on the synovial endothelium, but similar levels in patients with osteoarthritis.…”

“…DARC acts on CXCR5 to increase neutrophil migration to affected synovium. Furthermore, blocking the DARC interaction prevents neutrophil recruitment [16].…”

IL-17A and TNF-α Exert Synergistic Effects on Expression of CXCL5 by Alveolar Type II Cells In Vivo and In Vitro

“…CXCL5 (known as LPS-induced CXC chemokine [LIX] in mice and epithelial cell-derived neutrophil-activating peptide-78 in human) is a unique member of ELR + CXC family of chemokines, which are responsible for mediating neutrophil recruitment into tissues during inflammation and infection (17). ENA-78 has been found to be involved in a variety of human inflammatory diseases (18)(19)(20)(21)(22)(23)(24)(25)(26)(27), such as chronic obstructive pulmonary disease, exacerbation of asthma and chronic obstructive pulmonary disease, acute coronary syndromes, diabetes mellitus, and inflammatory bowel diseases. Murine Cxcl5 was first cloned as a LPS response gene that could be attenuated by glucocorticoids (28).…”

Multiple interests in structural models of DARC transmembrane protein

“…It supports transcytosis of chemokines from luminal to extravascular space and favours leucocyte migration and development of inflammatory reactions [36]. A similar mechanism might operate in in vitro model of rheumatoid arthritis in which overexpression of DARC does favour inflammatory reaction [37]. DARC could play a role in inflammatory diseases of the kidney [38].…”