Effect of glucosamine and related compounds on the degranulation of mast cells and ear swelling induced by dinitrofluorobenzene in mice.

AIMS Glucosamine has been used safely to relieve osteoarthritis in humans, but the precise mechanism underlying its efficacy is still unclear. In this study, we investigated the direct effects of glucosamine and related compounds on mast cell mediated inflammation using cultured mast cells and an animal model. MAIN METHODS Dinitrophenyl (DNP)-IgE-sensitized rat basophilic leukemia RBL-2H3 cells were treated with glucosamine-HCl (GlcN-HCl), N-acetylglucosamine (GlcNAc), chitin oligomer or chitosan oligomer. Cells were stimulated by DNP-BSA to induce degranulation and released beta-hexosaminedase was determined colorimetrically to measure the degree of degranulation. Dinitrofluorobenzene (DNFB) sensitized BALB/c mice were administrated orally with 1 or 0.1mg GlcN-HCl or GlcNAc for 6 days. One hour after the final administration, mice were challenged by DNFB to induce ear swelling. KEY FINDINGS GlcN-HCl significantly inhibited the antigen-induced degranulation of RBL-2H3 cells at higher than 0.01 mg/mL for 24h-treatment while GlcNAc, a chitin oligomer and a chitosan oligomer had no effect. GlcN-HCl also suppressed intracellular calcium mobilization. GlcN-HCl and GlcNAc significantly suppressed the antigen-induced up-regulation of TNF-alpha and IL-6 mRNA. Ear swelling and histamine levels of plasma and ear in DNFB-treated mice were significantly suppressed by oral administration of GlcN-HCl or GlcNAc (0.1 and 1mg) for 6 days. SIGNIFICANCE Our results strongly suggest that GlcN-HCl and GlcNAc have anti-inflammatory effects in vivo by suppressing the activation of mast cells.