Glucosamine Sulfate Inhibits Proinflammatory Cytokine-Induced ICAM-1 Production in Human Conjunctival CellsIn Vitro

Abstract

We investigated whether glucosamine sulfate modulates the production of ICAM-1 induced by proinflammatory cytokines and whether glucosamine sulfate inhibits leukocyte adhesion to a monolayer of human conjunctival epithelial cells stimulated with proinflammatory cytokines. We used flow cytometry and either primary cultured human conjunctival cells or the Chang conjunctival cell model to determine the effects of glucosamine sulfate on the production of ICAM-1 in response to tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, interleukin (IL)-1beta, IL-6, TNF-alpha plus IFN-gamma, or TNF-alpha plus IL-1beta. The effects of glucosamine sulfate on the expression of the ICAM-1 gene, upregulated by various cytokines, were determined by semiquantitative reverse transcription-polymerase chain reaction. The activation and nuclear translocation of the nuclear factors NF-kappaB and STAT1 were evaluated by the transient transfection of reporter gene systems and immunocytochemistry. The influence of glucosamine-sulfate-modulated ICAM-1 on neutrophil adhesion was demonstrated in a model that measures the adherence of conjunctival cells and neutrophils. TNF-alpha, IFN-gamma, and IL-1beta significantly increased the production of ICAM-1 by both primary cultured human conjunctival cells and Chang conjunctival cells. Glucosamine sulfate effectively downregulated the production of ICAM-1 induced by TNF-alpha, IFN-gamma, IL-1beta, TNF-alpha plus IFN-gamma, or TNF-alpha plus IL-1beta. This downregulation occurred through the interferon-stimulated response element, IFN-gamma activation sequence, and binding sequence of NF-kappaB at the mRNA and protein levels. Glucosamine sulfate further inhibited the nuclear translocation of p65 protein in TNF-alpha- and IL-1beta-stimulated Chang conjunctival cells and phosphorylated STAT1 in IFN-gamma-stimulated Chang conjunctival cells. Glucosamine sulfate also significantly reduced the number of neutrophils adhering to a conjunctival monolayer in response to TNF-alpha, IFN-gamma, or IL-1beta. Our results suggest that glucosamine sulfate inhibits ICAM-1 production in conjunctival epithelial cells in vitro. Therefore, glucosamine sulfate might be valuable in the treatment of inflammatory ocular-surface conditions.