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Open Access Highly Accessed Research article

Toll-like receptor 3 upregulation in macrophages participates in the initiation and maintenance of pristane-induced arthritis in rats

Liesu Meng12, Wenhua Zhu12, Congshan Jiang12, Xiaojing He12, Weikun Hou12, Fang Zheng12, Rikard Holmdahl3 and Shemin Lu12*

Author Affiliations

1 Department of Genetics and Molecular Biology, Xi'an Jiaotong University School of Medicine, Yanta West Road, Xi'an, Shaanxi 710061, PR China

2 Key Laboratory of Environment and Genes Related to Diseases (Xi'an Jiaotong University), Ministry of Education, Yanta West Road, Xi'an, Shaanxi 710061, PR China

3 Division of Medical Inflammation Research, Department of Medical Biochemistry and Biophysics, Karolinska Institute, Alfred Nobels Allé 8, Huddinge, SE-171 77 Stockholm, Sweden

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Arthritis Research & Therapy 2010, 12:R103  doi:10.1186/ar3034

Published: 25 May 2010

Abstract

Introduction

Toll-like receptors (TLRs) are involved in both innate and adaptive immune responses and are likely to play a complex role in the pathogenesis of human rheumatoid arthritis (RA) and experimental arthritis. The objective of this study was to identify the key TLR in pristane-induced arthritis (PIA), a rat model for RA, and to clarify its roles in the initiation and maintenance of arthritis.

Methods

Arthritis in DA rats was induced by pristane and the severity was evaluated by macroscopic and microscopic score systems. Spleen TLR and cytokine expression was detected at different time points by real-time polymerase chain reaction (PCR) and flow cytometry. Polyinosine-polycytidylic acid (polyI:C, a ligand of TLR3) or TLR3 specific short-hairpin RNA plasmid for RNA interference was administrated to PIA rats in vivo. Serum nitrogen oxide concentration was determined by Griess method, and tumor necrosis factor alpha (TNF-α) was determined by L929 biotest. In splenic macrophages, TLR3 expression was measured by flow cytometry. A rat macrophage cell line (NR8383) was stimulated by pristane, and anti-TLR3 antibody were used to block TLR3 pathway. TLR3 and cytokine expression in NR8383 were detected by real-time PCR.

Results

By screening the TLR expression profile in spleen of DA rats after pristane injection, we found that TLR3 was the most early and prominently upregulated TLR. Both TLR3 mRNA and protein expression of spleen were upregulated at 6 and 26 days after pristane injection. Furthermore, administration of polyI:C exacerbated, whereas RNA interference targeting TLR3 ameliorated, the arthritis. Particularly, TLR3 expression was induced in splenic macrophages of PIA rats, and also in the NR8383 cell line after pristane stimulation in a dose- and time- dependent manner. Upregulation of interferon beta (IFN-β) and TNF-α by pristane stimulation was blocked by anti-TLR3 antibody in NR8383.

Conclusions

TLR3 plays a pivotal role in the initiation and development of PIA which may dependent on macrophage. These findings are useful to understand the pathogenesis of RA and may provide an intriguing therapeutic opportunity for RA.