Inhibitory effects of glucosamine on endotoxin-induced uveitis in Lewis rats.
OBJECTIVE
Glucosamine sulfate (GS) is a naturally occurring sugar that exerts immunosuppressive effects in vitro and in vivo. The authors investigated whether GS modulates the inflammatory reaction in endotoxin-induced uveitis (EIU) of rats and the mechanisms by which it exerts its effects.


METHODS
Two-hundred micrograms of lipopolysaccharide (LPS) was injected subcutaneously into Lewis rats to induce EIU. Doses of GS (10, 100, or 1000 mg/kg) were divided into three aliquots and administered intraperitoneally 30 minutes before LPS injection, concurrently with LPS injection, and 30 minutes after LPS injection. Twenty-four hours after LPS injection, aqueous humor was collected for cell counting and measurement of protein concentration. Immunohistochemical staining of the iris-ciliary body was performed to evaluate the effects of GS on intercellular adhesion molecule (ICAM)-1 and nuclear factor (NF)-kappaB activation and to demonstrate macrophage infiltration. The effects of various doses of GS pretreatment were also examined using a mouse macrophage cell line (RAW264.7 cells) and LPS stimulation. Levels of prostaglandin (PG)-E2 and nitric oxide (NO) were determined. Expression of inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 were measured using Western blot analysis. The effect of GS on LPS-induced NF-kappaB activation in RAW cells was also examined.


RESULTS
Cell counting and analysis of protein concentration in aqueous humor revealed that GS suppressed EIU in rats treated with a high dose of GS (1000 mg/kg). Immunohistochemistry showed that treatment with GS reduced ICAM-1 expression and suppressed activation of NF-kappaB in the iris-ciliary body. The main inflammatory cells in the iris-ciliary body during EIU were macrophages. In LPS-stimulated macrophage RAW cell culture, GS inhibited the production of NO and PG-E2, the expression of iNOS and COX-2, and the activation of NF-kappaB.


CONCLUSIONS
GS suppresses EIU in rats by blockading the NF-kappaB-dependent signaling pathway and the subsequent production of ICAM-1 and proinflammatory mediators. This study has extended the authors' previous observation that GS is a potentially important compound for reducing ICAM-1-mediated inflammatory effects in the eye.
Chang
Yun-Hsiang
YH
Department of Ophthalmology, Tri-Service General Hospital, Taipei, Taiwan, Republic of China.
Horng
Chi-Ting
CT
Chen
Yi-Hao
YH
Chen
Po-Liang
PL
Chen
Ching-Long
CL
Liang
Chang-Min
CM
Chien
Ming-Wei
MW
Chen
Jiann-Torng
JT
D000818:Animals; D001082:Aqueous Humor / Q000276:immunology; D015153:Blotting, Western; D002452:Cell Count; D018929:Cell Culture Techniques; D002924:Ciliary Body / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism; D005944:Glucosamine / Q000008:administration & dosage / Q000494:pharmacology*; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D007498:Iris / Q000378:metabolism; D008070:Lipopolysaccharides / Q000633:toxicity*; D008264:Macrophages / Q000276:immunology; D008297:Male; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D012486:Salmonella typhimurium; D014606:Uveitis, Anterior / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*
D008070:Lipopolysaccharides; D016328:NF-kappa B; D018799:Intercellular Adhesion Molecule-1; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D051546:Cyclooxygenase 2; C489691:Ptgs2 protein, rat; D015232:Dinoprostone; D005944:Glucosamine