Purpose: 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.
Methods: 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)-α, interferon (IFN)-γ, interleukin
(IL)-1β, IL-6, (TNF)-α plus (IFN)-γ, or (TNF)-α plus (IL)-1β. 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-κB 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.
Results: (TNF)-α, (IFN)-γ, and (IL)-1β 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)-α, (IFN)-γ, (IL)-1β,
(TNF)-α plus (IFN)-γ, or (TNF)-α plus (IL)-1β. This downregulation occurred through the interferon-stimulated response element, (IFN)-γ activation sequence, and binding sequence of NF-κB at the mRNA and protein levels. Glucosamine sulfate further inhibited the nuclear translocation
of p65 protein in (TNF)-α- and (IL)-1β-stimulated Chang conjunctival cells and
phosphorylated STAT1 in (IFN)-γ-stimulated Chang conjunctival cells. Glucosamine sulfate
also significantly reduced the number of neutrophils adhering to a conjunctival monolayer
in response to (TNF)-α, (IFN)-γ, or (IL)-1β.
Conclusions: 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.
