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Open Access Highly Accessed Research article

Expression and function of visfatin (Nampt), an adipokine-enzyme involved in inflammatory pathways of osteoarthritis

Marie-Charlotte Laiguillon1, Xavier Houard1, Carole Bougault1, Marjolaine Gosset2, Geoffroy Nourissat13, Alain Sautet3, Claire Jacques1, Francis Berenbaum145* and Jérémie Sellam145

Author Affiliations

1 INSERM UMRS_938, UPMC, Univ Paris 06, 184 rue du Faubourg Saint-Antoine, 75012 Paris, France

2 EA 2496, Paris Descartes University, 1 rue Maurice Arnoux, 92120 Montrouge, France

3 Department of Orthopaedic Surgery and Traumatology, Saint-Antoine Hospital, AP-HP, Univ Paris 06, 184 rue du Faubourg Saint-Antoine, 75012 Paris, France

4 Department of Rheumatology, Assistance Publique – Hôpitaux de Paris, Saint-Antoine Hospital, 184 rue du Faubourg Saint-Antoine, 75012 Paris, France

5 Inflammation–Immunopathology–Biotherapy Department (DHU i2B), 184 rue du Faubourg Saint-Antoine, 75012 Paris, France

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Arthritis Research & Therapy 2014, 16:R38  doi:10.1186/ar4467

Published: 31 January 2014

Abstract

Introduction

Visfatin is an adipokine that may be involved in intertissular joint communication in osteoarthritis (OA). With a homodimeric conformation, it exerts nicotinamide phosphoribosyltransferase (Nampt) enzymatic activity, essential for nicotinamide adenine dinucleotide biosynthesis. We examined the tissular origin and conformation of visfatin/Nampt in human OA joints and investigated the role of visfatin/Nampt in chondrocytes and osteoblasts by studying Nampt enzymatic activity.

Methods

Synovium, cartilage and subchondral bone from human OA joints were used for protein extraction or incubated for 24 hours in serum-free media (conditioned media), and synovial fluid was obtained from OA patients. Visfatin/Nampt expression in tissular extracts and conditioned media was evaluated by western blot and enzyme-linked immunosorbent assay (ELISA), respectively. Nampt activity was assessed in OA synovium by colorimetric assay. Primary cultures of murine chondrocytes and osteoblasts were stimulated with visfatin/Nampt and pretreated or not with APO866, a pharmacologic inhibitor of Nampt activity. The effect on cytokines, chemokines, growth factors and hypertrophic markers expression was examined by quantitative reverse transcriptase polymerase chain reaction and/or ELISA.

Results

In tissular explants, conditioned media and synovial fluid, visfatin/Nampt was found as a homodimer, corresponding to the enzymatically active conformation. All human OA joint tissues released visfatin/Nampt (synovium: 628 ± 106 ng/g tissue; subchondral bone: 195 ± 26 ng/g tissue; cartilage: 152 ± 46 ng/g tissue), with significantly higher level for synovium (P <0.0005). Nampt activity was identified ex vivo in synovium. In vitro, visfatin/Nampt significantly induced the expression of interleukin 6, keratinocyte chemoattractant and monocyte chemoattractant protein 1 in chondrocytes and osteoblasts. APO866 decreased the mRNA and protein levels of these pro-inflammatory cytokines in the two cell types (up to 94% and 63% inhibition, respectively). Levels of growth factors (vascular endothelial growth factor, transforming growth factor β) and hypertrophic genes were unchanged with treatment.

Conclusion

Visfatin/Nampt is released by all human OA tissues in a dimeric enzymatically active conformation and mostly by the synovium, which displays Nampt activity. The Nampt activity of visfatin is involved in chondrocyte and osteoblast activation, so targeting this enzymatic activity to disrupt joint tissue interactions may be novel in OA therapy.