1002 - Knock-Down of Galectin-3 Inhibits Spontaneous and Lipopolysaccharide -Induced IL-6 Secretion In Fibroblast-Like Synoviocytes

Monday, November 7, 2011: 9:00 AM-6:00 PM
Hall F2 - Poster Hall (McCormick Place West)
Uri Arad, Avital Angel-Korman, Sharon Amir, Sharon Tzadok, Ortal Seagal, Ori Elkayam and Dan Caspi, Tel Aviv Sourasky Medical Center and the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
Presentation Number: 1002

Background/Purpose: Galectin-3 is a β-galactoside-binding lectin that plays an important role in the modulation of immune responses. Galectin-3 levels are increased in rheumatoid arthritis (RA) synovial tissue, synovial fluid and peripheral blood. Recombinant exogenous galectin-3 stimulates proinflammatory cytokine secretion by fibroblast-like synoviocytes (FLS). Our objective was to examine the effect of galectin-3 knock-down on spontaneous and lipopolysaccharide (LPS)-induced secretion of IL-6 in FLS from RA and osteoarthritis (OA) patients.

Method: FLS from RA and OA patients were harvested from synovial fluid aspirates or directly from synovial tissue obtained during orthopedic surgery. The expression of galectin-3 was knocked-down by transfection of siRNAGal3 vs. siRNACtrl. The XTT test was used to evaluate cell viability, and galectin-3 knock-down was confirmed by western blotting. IL-6 secretion with and without lipopolysacharide (LPS)-stimulation was determined by ELISA.

Result: Maximal knock-down of galectin-3 expression was observed on the 3rd day post transfection, in both RA and OA FLS (50-75% knock-down). Galectin-3 knock-down caused a significant decrease in IL-6 secretion in both cell types (OA – 46%, RA – 21.5%, p<0.05). The inhibition of IL-6 secretion was not caused by decreased cell viability. LPS-stimulation caused a 35-fold increase in IL-6 secretion, and galectin-3 knock-down substantially inhibited LPS-induced IL-6 secretion (OA- 74%, RA- 33%, p<0.05).

Conclusion: siRNA-transfection is an effective means of suppressing galectin-3 expression in FLS. Knock-down of galectin-3 inhibited both spontaneous and LPS-induced IL-6 secretion. It appears that galectin-3 is an important component in the regulation of IL-6 secretion in FLS and may be targeted for suppressing joint inflammation.

Keywords: galectin, interleukins (IL), osteoarthritis, rheumatoid arthritis, synovium and synovial cells, synovial fluid

Disclosure: U. Arad, None; A. Angel-Korman, None; S. Amir, None; S. Tzadok, None; O. Seagal, None; O. Elkayam, None; D. Caspi, None.