Up-regulated expression and activation of the orphan chemokine receptor, CCRL2, in rheumatoid arthritis.
OBJECTIVE
Rheumatoid arthritis (RA) is a chronic inflammatory condition characterized by a cellular influx and destruction of the joint architecture. Chemokines characteristically regulate leukocyte recruitment and activation. Chemokine (CC motif) receptor-like 2 (CCRL2) is an orphan receptor with homology to other CC chemokine receptors. We undertook this study to examine CCRL2 expression in RA, cytokine regulation of expression, and the source of a putative ligand in an attempt to determine the role of this receptor during inflammation.


METHODS
Expression of CCRL2 on joint-infiltrating leukocytes was examined by immunocytochemistry. In vitro studies evaluated CCRL2 expression in primary neutrophils using Northern and Western blotting and reverse transcriptase-polymerase chain reaction. HEK 293 cells expressing two splice variants of CCRL2 (HEK/CCRL2A or HEK/CCRL2B) were generated with a retroviral expression system, and their migration in response to fractions of synovial fluid (SF) from RA patients was examined using a 48-well chamber.


RESULTS
CCRL2 expression was observed on all infiltrating neutrophils and on some macrophages obtained from the SF of 5 RA patients. In vitro studies of primary neutrophils revealed that CCRL2 messenger RNA (mRNA) was rapidly up-regulated following stimulation with lipopolysaccharide (1 microg/ml) or tumor necrosis factor (5 ng/ml). The mRNA for both CCRL2A and CCRL2B were expressed in cytokine-stimulated neutrophils. Cells expressing either of these splice variants migrated in response to a fraction of RA SF.


CONCLUSIONS
CCRL2 expression is up-regulated on synovial neutrophils of RA patients. Inflammatory products present in the SF activate this receptor, indicating that CCRL2 is a functional receptor that may be involved in the pathogenesis of RA.
Galligan
Carole L
CL
National Cancer Institute at Frederick, Frederick, Maryland 21702, USA.
Matsuyama
Wataru
W
Matsukawa
Akihiro
A
Mizuta
Hiroshi
H
Hodge
David R
DR
Howard
O M Zack
OM
Yoshimura
Teizo
T
D000368:Aged; D000595:Amino Acid Sequence; D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000378:metabolism / Q000503:physiopathology*; D002118:Calcium / Q000378:metabolism; D002465:Cell Movement / Q000276:immunology; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D007668:Kidney / Q000166:cytology; D008024:Ligands; D008264:Macrophages / Q000502:physiology; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D054388:Receptors, CCR; D019707:Receptors, Chemokine / Q000235:genetics* / Q000378:metabolism*; D015854:Up-Regulation / Q000276:immunology
C487531:CCRL2 protein, human; D008024:Ligands; D012333:RNA, Messenger; D054388:Receptors, CCR; D019707:Receptors, Chemokine; D002118:Calcium