Chemokine Secretion of Rheumatoid Arthritis Synovial Fibroblasts Stimulated by Toll-Like Receptor 2 Ligands

Abstract

To analyze the role of Toll-like receptors (TLR) in the pathogenesis of rheumatoid arthritis, we have assessed the effects of stimulation of cultured synovial fibroblasts by the TLR-2 ligand bacterial peptidoglycan. By using high density oligonucleotide microarray analysis we identified 74 genes that were up-regulated >2.5-fold. Fourteen CC and CXC chemokine genes were among the genes with the highest up-regulation. Quantitative real-time PCR analysis confirmed up-regulation of granulocyte chemotactic protein (GCP)-2, RANTES, monocyte chemoattractant protein (MCP)-2, IL-8, growth-related oncogene-2, and to a lesser extent, macrophage-inflammatory protein 1α, MCP-1, EXODUS, and CXCL-16. GCP-2, RANTES, and MCP-2 were detected in culture supernatants of synovial fibroblasts stimulated with peptidoglycan. Chemokine secretion induced by stimulation of rheumatoid arthritis synovial fibroblasts via TLR-2 was functionally relevant as demonstrated by chemotaxis assays. GCP-2 and MCP-2 expression, which have not been reported previously in rheumatoid arthritis, was demonstrated in synovial tissue sections of patients diagnosed with rheumatoid arthritis but not in those with osteoarthritis. Correspondingly, synovial fluid levels were significantly higher in patients diagnosed with rheumatoid arthritis as compared with osteoarthritis. Thus, we present evidence for an induction of chemokine secretion by activation of synovial fibroblasts via TLR-2, possibly contributing to the formation of inflammatory infiltrates characteristically found in rheumatoid arthritis joints.

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

“…It suggests that large amounts of CXCL16 may be produced in RA independently of established proinflammatory cytokines. This finding is consistent with results of a recent study showing that RA fibroblasts express CXCL16 directly when stimulated by way of the Toll-like receptor 2 ligand peptidoglycan (65).…”

PKC‐α controls MYD88‐dependent TLR/IL‐1R signaling and cytokine production in mouse and human dendritic cells

“…Recently, the adaptor protein MyD88 and its downstream pathway were shown to play a critical role in both spontaneous and carcinogeninduced tumor development [42,43]. Also, in rheumatoid arthritis and psoriasis, several works support evidence of an important role of endogenous TLR ligands that are involved in the induction of inflammation and initiation of diseases [44][45][46]. cPKC inhibitors that inhibit MyD88-dependent inflammatory signals downstream of TLR and IL-1R can be very promising molecules in the treatment of autoimmune inflammatory diseases, as it has been demonstrated with the AEB071 PKC inhibitor on psoriasis [47].…”

Pre–B cell colony‐enhancing factor/visfatin, a new marker of inflammation in rheumatoid arthritis with proinflammatory and matrix‐degrading activities

“…Moreover, in our experiments, down-regulation of PBEF in RASFs by siRNA not only decreased basal IL-6, MMP-1, and MMP-3 levels but also significantly inhibited TLR ligand-induced production of cytokines and destructive enzymes. TLRs were shown to be key players in inflammatory and destructive processes in RA (3,4,20,25). TLR ligands of microbial origin as well as endogenous TLR ligands were demonstrated to be present in RA synovial fluid as possible drivers of inflammatory processes (1,26).…”

“…Activation of cells by microbial components and also by endogenous molecules via pattern recognition receptors, such as Toll-like receptors (TLRs), results in the production of a variety of cytokines, chemokines, and matrix metalloproteinases (MMPs), some of which are characteristically observed in patients with RA (2). We previously reported induction in SFs of the proinflammatory cytokine interleukin-6 (IL-6) and the chemokines IL-8, granulocyte chemotactic protein 2, macrophage chemotactic protein 2, and RANTES by the TLR-2 ligand bacterial peptidoglycan (3,4). In a subsequent study, we demonstrated overexpression of TLR-3 in RA synovial tissue and established that RNA released by necrotic synovial fluid cells can act as endogenous ligand for TLR-3 on cultured RASFs (5).…”