Recently, we found that administration of glucosamine to adjuvant arthritis, a model for rheumatoid arthritis, suppressed the progression of arthritis in rats. To clarify its anti-inflammatory mechanism, we evaluated the actions of glucosamine on the activation of synoviocytes in vitro.
Synoviocytes isolated from human synovial tissues were stimulated with interleukin (IL)-1beta in the presence of 0.01-1 mM glucosamine. IL-8 and prostaglandin (PG) E(2) were measured by ELISA, and nitric oxide was quantitated by Griess assay. IL-8 mRNA was detected by RT-PCR. Furthermore, the effect of glucosamine on the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and the binding of [(125)I] IL-1beta to its receptors were examined using a primary human synovial cell line (CSABI- 479).
Glucosamine significantly suppressed the IL-1beta-induced IL-8 production as well as its mRNA expression (p < 0.05) at 1 mM. Furthermore, glucosamine (1 mM) inhibited the IL-1beta-induced nitric oxide and PGE(2) production (p < 0.05). Moreover, glucosamine suppressed the IL-1beta-induced phosphorylation of p38 MAPK (p < 0.05 at >0.1 mM) and the IL-1beta-binding to its receptors (p < 0.05 at 1 mM).
These observations suggest that glucosamine can suppress the IL-1beta-mediated activation of synoviocytes (such as IL-8-, nitric oxide- and PGE(2)-production, and phosphorylation of p38 MAPK), thereby possibly exhibiting antiinflammatory actions in arthritis.