Background/Purpose: Fucosylation, catalyzed by fucosyltransferases (Futs), is an important glycosylation process involved in inflammation, cell death, and differentiation. We have observed an extremely high positive correlation between Tnfα and Fucosyltransferases 1 and 3 (Fut1 and Fut3, p=0.0001) in rheumatoid arthritis (RA) synovial tissues. However, the role of fucosylation in RA has not been extensively studied. The purpose of this study is to determine: (i) expression of Futs in different cell population isolated from human RA synovial fluid; (ii) the effect of a fucosylation inhibitor on RA effector cell differentiation; and (iii) the ability of a fucosylation inhibitor to suppress the development of collagen II-induced arthritis (CIA) in mice.

Methods: Twenty RA subjects were recruited in this study. Real-time PCR was used to determine the expression of Fut1 and Fut3 in FACS sorted cell subsets from fresh RA synovial fluids. Purified human synovial macrophages (MΦs) were cultured with GM-CSF and CD4 T cells were polarized towards Th1 and Th17 cells with and without the presence of 15 mM 6-Deoxy-L-galactose (fucose) or its analog, 2-Deoxy-D-galactose (2-D-gal) which can inhibit the fucosylation process. Cytokines in the supernatant were measured by ELISA. CIA was induced in DBA/1J mice. Fucose or 2-D-Gal (200 mg/kg BW, every 2-3 days) was administered via I.P. initiated on Day 1. FACS, ELISA and histopathology analysis were performed on Day 40.

Results: In FACS sorted cells from fresh human RA synovial fluid, the expression of Fut1 and Fut3 was five-fold higher in M1 inflammatory MΦ (CD68⁺CD80⁺) compared to M2 MΦ (CD68⁺CD80^–), with lower expression in  Th1, Th17, total memory and naïve CD4 T cells. In vitro 2-D-gal treatment for 3 days lead to dramatic cell death of purified human MΦ and reduced levels of TNF-α (3800 pg/ml vs 450 pg/ml, p<0.001) in the supernatant. There was, however, no inhibitory effect of 2-D-gal on human Th1 or Th17 differentiation in vitro. In vivo treatment of 2-D-gal in DBA/1J mice immunized with bovine CII abrogates the development of arthritis whereas the same dose of fucose exacerbated it (arthritis scores: control, 9.5±1.7; 2-D-gal, 0.5± 0.3; Fucose, 15.3± 2.2, p<0.01). FACS analysis revealed that the percentages of inflammatory MΦ (CD11b⁺TNF-α⁺) in the draining LN were reduced by 2-D-gal but were increased by Fucose (control 1.1±0.23; 2-D-gal, 0.6±0.10; Fucose, 1.5± 0.32, p<0.05). 2-D-gal treatment also resulted in significantly decreased levels of TNF-α (130.1 vs 39.4pg/ml, p<0.05) and anti-CII total IgM and IgG in the serum. Joint histopathology showed a significantly decreased macrophage infiltration, synovial hyperplasia, cartilage damage, and bone erosion in 2-D-gal treated mice. No significant liver and renal toxicity and dysfunction was observed.

Conclusion: Our results show that Futs are highly expressed in inflammatory MΦ and fucosylation is a critical process regulating MΦ differentiation and TNF-α production. Inhibition of fucose incorporation by 2-D-gal significantly impairs inflammatory macrophage development and function, completely blocking development of arthritis without systematic toxicity. Our results suggest that MΦ fucosylation may be a new therapeutic target for RA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/inhibition-of-fucose-incorporation-abrogates-the-development-of-arthritis-by-suppressing-the-inflammatory-macrophage-development-and-tnf-%ce%b1-production/