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Open Access Highly Accessed Research article

CCN4 induces IL-6 production through αvβ5 receptor, PI3K, Akt, and NF-κB singling pathway in human synovial fibroblasts

Chun-Han Hou1, Chih-Hsin Tang23, Chin-Jung Hsu45, Sheng-Mon Hou6* and Ju-Fang Liu7*

Author affiliations

1 Department of Orthopedic Surgery, National Taiwan University Hospital, 7, Zhongshan South Road, Taipei 100, Taiwan

2 Department of Pharmacology, School of Medicine, China Medical University, 91 Hsueh-Shih Road, Taichung 402, Taiwan

3 Graduate Institute of Basic Medical Science, China Medical University, 91 Hsueh-Shih Road, Taichung 402, Taiwan

4 School of Chinese Medicine, College of Chinese Medicine, China Medical University, 91 Hsueh-Shih Road, Taichung 402, Taiwan

5 Department of Orthopedic Surgery, China Medical University Hospital, 91 Hsueh-Shih Road, Taichung 402, Taiwan

6 Department of Orthopedic Surgery, Shin-Kong Wu Ho-Su Memorial Hospital, 95 Wen Chang Road, Taipei 111, Taiwan

7 Central Laboratory, Shin-Kong Wu Ho-Su Memorial Hospital, 95 Wen Chang Road, Taipei 111, Taiwan

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Citation and License

Arthritis Research & Therapy 2013, 15:R19  doi:10.1186/ar4151

Published: 23 January 2013

Abstract

Introduction

Osteoarthritis (OA) is the most common degenerative joint disease that is involved in the degradation of articular cartilage. The exact etiology of OA is not completely understood. CCN4 is related to up-regulation in the cartilage of patients with osteoarthritis. Previous studies have shown that CCN4 might be associated with the pathogenesis of OA, but the exact signaling pathways in CCN4-mediated IL-6 expression in synovial fibroblasts (SF) are largely unknown. Therefore, we explored the intracellular signaling pathway involved in CCN4-induced IL-6 production in human synovial fibroblast cells.

Methods

CCN4-induced IL-6 production was assessed with quantitative real-time qPCR and ELISA. The mechanisms of action of CCN4 in different signaling pathways were studied by using Western blotting. Neutralizing antibodies of integrin were used to block the integrin signaling pathway. Luciferase assays were used to study IL-6 and NF-κB promoter activity. Immunocytochemistry was used to examine the translocation activity of p65.

Results

Osteoarthritis synovial fibroblasts (OASFs) showed significant expression of CCN4 and the expression was higher than in normal SFs. OASF stimulation with CCN4 induced concentration- and time-dependent increases in IL-6 production. Pretreatment of OASFs with αvβ5 but not α5β1 and αvβ3 integrin antibodies reduced CCN4-induced IL-6 production. CCN4-mediated IL-6 production was attenuated by PI3K inhibitor (LY294002 and Wortmannin), Akt inhibitor (Akti), and NF-κB inhibitor (PDTC and TPCK). Stimulation of cells with CCN4 also increased PI3K, Akt, and NF-κB activation.

Conclusions

Our results suggest that CCN4 activates αvβ5 integrin, PI3K, Akt, and NF-κB pathways, leading to up-regulation of IL-6 production. According to our results, CCN4 may be an appropriate target for drug intervention in OA in the future.