8m-ine K-caseinoglycopeptide (residues lOfr169, CGP) completely inhibited the PH A-induced proliferation of mouse splenocytes when CGP was added simultaneously with PHA. The inhibitory effect, however, was reduced to about one-half when CGP was added after 24 h of cultinting the splenocytes with PHA or when anti-IL-Ira antibody was added simultaneously with PHA and CGP. On the other hand, CG P bound to mouse CD4 + T cells but not to CDS + T cells. CGP suppressed IL-2 receptor expression of the PHA-stimulated mouse CD4 + T cells.

Osteoclasts are the only bone-resorbing cells in organisms and understanding their differentiation mechanism is crucial for the treatment of osteoporosis. In the present study, we investigated the effect of Thiamet G, an O-GlcNAcase specific inhibitor, on osteoclastogenic differentiation. Thiamet G treatment increased global O-GlcNAcylation in murine RAW264 cells and suppressed receptor activator of nuclear factor-κB ligand (RANKL)-dependent formation in tartrate-resistant acid phosphatase (TRAP)-positive multinuclear cells, thereby suppressing the upregulation of osteoclast specific genes. Meanwhile, knockdown of O-linked N-acetylglucosamine (O-GlcNAc) transferase promoted the formation TRAP-positive multinuclear cells. Thiamet G treatment also suppressed RANKL and macrophage colony-stimulating factor (M-CSF) dependent osteoclast formation and bone-resorbing activity in mouse primary bone marrow cells and human peripheral blood mononuclear cells. These results indicate that the promotion of O-GlcNAc modification specifically suppresses osteoclast formation and its activity and suggest that chemicals affecting O-GlcNAc modification might potentially be useful in the prevention or treatment of osteoporosis in future.