Toll-like receptor 2 ligand mediates the upregulation of angiogenic factor, vascular endothelial growth factor and interleukin-8/CXCL8 in human rheumatoid synovial fibroblasts.
Rheumatoid arthritis (RA) is characterized by infiltrations of inflammatory cells accompanied by neovascularization in the joint. We hypothesized that cell activation via the toll-like receptor (TLR) may be involved in the induction of angiogenic molecules, which are relevant to the pathogenesis of RA. RA fibroblast like synoviocytes (FLS) were stimulated with TLR-2 ligand bacterial peptidoglycan (PGN), TLR-4 ligand lipopolysaccharide (LPS) and various cytokines. Vascular endothelial growth factor (VEGF) and IL-8 were measured by ELISA in culture supernatants; mRNA levels were assessed by RT-PCR and real time PCR. The levels of TLR-2, VEGF and IL-8 were analyzed by dual immunohistochemistry in RA synovium and compared with osteoarthritis (OA). Regulation of MyD88, IRAK4, IRAK1, IRAK-M and TRAF-6 mRNA expression levels by PGN were analyzed by RT-PCR. Phosphorylation of I kappa B alpha was evaluated by western blotting. Levels of VEGF and IL-8 were upregulated in culture supernatants of RA FLS stimulated with PGN, similar to the levels of IL-1beta and IL-17 stimulation. Neutralization of TLR-2 with a blocking monoclonal antibody significantly reduced both VEGF and IL-8 levels (P<0.05), which reflected the functional relevance of TLR-2 activation to the induction of VEGF and IL-8 production. Downstream intracellular signaling following TLR-2 stimulation involved MyD88-IRAK-4-TRAF-6 pathways, resulting in NF-kappaB activation. Thus, TLR-2 activation in RA FLS by microbial constituents could be involved in the induction of VEGF and IL-8 and thereby promote inflammation either directly or via angiogenesis. This possibly contributes to the perpetuation of synovitis in patients with RA.
Cho
Mi-La
ML
Division of Rheumatology, Department of Medicine, The Rheumatism Research Center (RhRC), Catholic University of Korea, Seoul, South Korea.
Ju
Ji-Hyeon
JH
Kim
Hae-Rim
HR
Oh
Hye-Joa
HJ
Kang
Chang-Min
CM
Jhun
Joo-Yeon
JY
Lee
Seon-Yeong
SY
Park
Mi-Kyung
MK
Min
Jun-Ki
JK
Park
Sung-Hwan
SH
Lee
Sang-Heon
SH
Kim
Ho-Youn
HY
D043925:Angiogenesis Inducing Agents / Q000378:metabolism*; D000906:Antibodies / Q000494:pharmacology; D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D053592:Interleukin-1 Receptor-Associated Kinases / Q000235:genetics; D016209:Interleukin-8 / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D010457:Peptidoglycan / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D048029:TNF Receptor-Associated Factor 6 / Q000235:genetics; D051195:Toll-Like Receptor 2 / Q000276:immunology / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*
D043925:Angiogenesis Inducing Agents; D000906:Antibodies; C508606:CXCL8 protein, human; D016207:Cytokines; D020672:I-kappa B Proteins; D016209:Interleukin-8; D008070:Lipopolysaccharides; C507779:MYD88 protein, human; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D010457:Peptidoglycan; D012333:RNA, Messenger; C495342:TLR2 protein, human; D048029:TNF Receptor-Associated Factor 6; D051195:Toll-Like Receptor 2; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C507768:IRAK1 protein, human; C507771:IRAK3 protein, human; C507773:IRAK4 protein, human; D053592:Interleukin-1 Receptor-Associated Kinases