Induction of a CXCL8 binding site on endothelial syndecan-3 in rheumatoid synovium.
OBJECTIVE
To identify and characterize which endothelial heparan sulfate proteoglycans (HSPGs) bind the chemokine CXCL8 (interleukin-8) in human rheumatoid arthritis (RA) and nonrheumatoid synovia.


METHODS
CXCL8 binding to endothelial HSPGs in RA and nonrheumatoid synovia was determined by heparinase treatment followed by an in situ binding assay and autoradiography. Endothelial HSPGs were characterized by immunohistochemical analysis and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). Phosphatidyinositol-specific phospholipase C (PI-PLC) and antibodies to HSPGs were used in in situ binding experiments to identify which HSPGs bound CXCL8.


RESULTS
The expression of heparan sulfate on microvascular endothelial cells was demonstrated in RA and nonrheumatoid synovia. Using antibodies to syndecan-1-4 and glypican-1, -3, and -4, the selective expression of syndecan-3 by endothelial cells was detected in RA and nonrheumatoid synovia. In addition, RT-PCR showed the presence of syndecan-3 messenger RNA in endothelial cells extracted from RA and nonrheumatoid synovia. (125)I-CXCL8 bound to venular endothelial cells; treatment with heparinases I and III significantly reduced this binding in RA but not nonrheumatoid synovia. (125)I-CXCL8 binding was not reduced after treatment with PI-PLC, which cleaves glycosyl phosphatidylinositol linkages, suggesting that CXCL8 did not bind to glypicans. Treatment of synovia with a syndecan-3 antibody reduced CXCL8 binding to RA but not nonrheumatoid endothelial cells; however, no reduction in binding was observed with syndecan-2 or glypican-4 antibodies.


CONCLUSIONS
Our results show the selective induction of a CXCL8 binding site on endothelial syndecan-3 in RA synovium. This site may be involved in leukocyte trafficking into RA synovial tissue.
Patterson
Angela M
AM
University of Newcastle upon Tyne, UK.
Gardner
Lucy
L
Shaw
Jennifer
J
David
Guido
G
Loreau
Emilie
E
Aguilar
Luc
L
Ashton
Brian A
BA
Middleton
Jim
J
D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000378:metabolism*; D001665:Binding Sites; D016022:Case-Control Studies; D042783:Endothelial Cells / Q000378:metabolism*; D005260:Female; D006497:Heparan Sulfate / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D016209:Interleukin-8 / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008833:Microcirculation; D008875:Middle Aged; D011509:Proteoglycans / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053670:Syndecan-3; D013583:Synovial Membrane / Q000098:blood supply* / Q000378:metabolism*
D006497:Heparan Sulfate; D016209:Interleukin-8; D008562:Membrane Glycoproteins; D011509:Proteoglycans; D012333:RNA, Messenger; D053670:Syndecan-3; C508301:SDC3 protein, human