Galectin-3 and galectin-3 binding protein in rheumatoid arthritis

Galectin-3 (Gal-3) is one of the soluble lectins that has key functions in inflammation, chemotaxis, cell adhesion and apoptosis. We examined the role of Gal-3 and Gal-3 binding protein (Gal-3BP) in rheumatoid arthritis (RA). Localization of Gal-3 and Gal-3BP in rheumatoid synovium was examined by immunohistochemistry and in situ hybridisation. Gal-3 and Gal-3BP concentrations in plasma and synovial fluid were measured by ELISA. Gal-3 protein and mRNA stained throughout the synovial membrane, and Gal-3BP expressed at the site of erosion in RA. Lower and scattered expression of both Gal-3 and Gal-3BP were detected in osteoarthritis synovium and normal synovium. ELISA revealed a marked increase of Gal-3 and Gal-3BP in synovial fluid of patients with RA compared with osteoarthritis patients and normal controls. Furthermore, the level of Gal-3 in serum correlated with the level of C-reactive protein in RA. In vitro, Gal-3 can induce the production of matrix metalloproteinase (MMP)-1, MMP-3, and MMP-9 in synovial fibroblasts in a dose-dependent manner. Our data indicate that Gal-3 and Gal-3BP represent novel markers of disease activity in RA. Moreover, Gal-3 might contribute to the destruction of bone/cartilage in RA by the induction of MMPs.