β1,4-galactosyltransferase-I in synovial tissue of collagen-induced rat model of rheumatoid arthritis.

β1,4-galactosyltransferase-I (β1,4-GalT-I), which is one of the best-studied glycosyltransferases, plays a key role in the synthesis of selectin ligands such as sialyl Lewis (sLe(x)) and sulfated sLe(x). Previous studies showed that inflammatory responses of β1,4-GalT-I-deficient mice were impaired because of the defect in selectin-ligand biosynthesis. However, the expression of β1,4-GalT-I and its biological function in rheumatoid arthritis (RA) remain to be elucidated. The mRNA and protein expression of β1,4-GalT-I increased in synovial tissue of the RA group compared with the Normal group at 10d and 15d after collagen-induced. Double staining indicated β1,4-GalT-I overlapped with macrophage-like synoviocytes (MLSs), fibroblast-like synoviocytes (FLSs), neutrophils and tumor necrosis factor-α (TNF-α). Moreover, β1,4-GalT-I mRNA in FLSs in vitro was affected in a dose- and time-dependent manner in response to TNF-α stimulation. ELISA revealed that expression of TNF-α was attenuated in FLSs in vitro treated with β1,4-GalT-I-Ab. We therefore suggest that β1,4-GalT-I may play an important role in the inflammation process of RA synovial tissue, which would provide the foundation for further researching into the concrete mechanism of β1,4-GalT-I in RA.