OP0125 VISFATIN/NAMPT in Osteoarthritis: A Pro-Inflammatory Adipokine Involved in Synovium-Cartilage and Synovium-Bone Communications

Background Visfatin exerts a nicotinamide phosphoribosyltransferase (NAMPT) enzymatic activity, which is the rate-limiting stage in the salvage pathway of nicotinamide adenine dinucleotide (NAD) biosynthesis. NAD is involved in many biological processes including redox reactions, sirtuins activity and TNFαsynthesis (1). We have previously demonstrated the induction of prostaglandin E 2 release by visfatin-stimulated chondrocytes (2). Objectives i) Analyze the production and the enzymatic active conformation of visfatin/Nampt in human joint with osteoarthritis (OA), ii) Investigate its pro-inflammatory role on chondrocytes and osteoblasts, iii) Determine the involvement of the Nampt activity in the activation of those two cell types. Methods Human OA joint tissues (synovium, cartilage, subchondral bone) from patients undergoing total knee arthroplasty were frozen or incubated 24h in serum-free media. Visfatin/NAMPT conformation in OA synovial fluids, tissue media and extracts was evaluated by Immunoblot (IB). NAMPT/visfatin concentration in tissue media was measured by ELISA. NAMPT activity was assessed in OA synovium extracts using Cyclex colorimetric assay. Primary cultures of murine chondrocytes and osteoblasts were stimulated for 24h with recombinant visfatin/NAMPT (5 µg/mL) with or without APO866 (10nM), a pharmacologic inhibitor of NAMPT activity. mRNA and protein expression of IL-6, IL-8/Kc, MCP-1, VEGF TGFβ, Ihh, Runx2 and type X collagen was examined by qRT-PCR and ELISA. Results Human OA synovium, cartilage and subchondral bone all released visfatin/NAMPT (628±106, 152±46, 195±26 ng/g tissue, respectively) with significantly higher level for the synovium (p Image/graph Conclusions Visfatin/NAMPT is released by all OA tissues under a dimeric enzymatically active conformation and mostly by the synovium which displays a detectable NAMPT activity. The NAMPT activity of visfatin is involved in chondrocytes and osteoblasts activation. Thus, targeting its enzymatic activity with a compound like APO866 (being currently tested in hematological malignancies) may be a new therapeutic approach of OA. References Wang et al., Nature Structural & Molecular Biology, 2006; Gosset et al., Arthritis & Rheumatism, 2008 Acknowledgements Grant from the French Society of Rheumatology (SFR) Disclosure of Interest None Declared