Glucosamine sulfate inhibits TNF-α and IFN-γ-induced production of ICAM-1 in human retinal pigment epithelial cells in vitro

PURPOSE. Glucosamine sulfate (GS) is a naturally occurring sugar that possesses some immunosuppressive effects in vitro and in vivo, but its mechanism is unknown. We investigated whether GS could modulate the proinflammatory cytokine-induced expression of the gene for intercellular adhesion molecule (ICAM)-1, an inflammatory protein in human retinal pigment epithelial (RPE) cells. METHODS. ARPE-19 cells were used as a model to determine the effects of GS on the expression of the ICAM-1 gene upregulated by TNF-alpha or IFN-gamma, by Western blot analysis and semiquantitative reverse transcription polymerase chain reaction (RT-PCR). The activation and nuclear translocation of the nuclear factors NF-kappa B and STAT1 were evaluated by immunocytochemistry, Western blot analysis, and electrophoretic mobility shift assay (EMSA). RESULTS. Both TNF-alpha and IFN-gamma increased the expression of ICAM-1 at the mRNA and protein levels in a time- and dose-dependent manner in ARPE-19 cells. GS effectively downregulated the TNF-alpha- or IFN-gamma- induced expression of ICAM-1 in the protein and mRNA level in a dose-dependent manner. GS further inhibited the nuclear translocation of p65 proteins in TNF-alpha and phosphorylated STAT1 in IFN-gamma- stimulated ARPE-19 cells. CONCLUSIONS. GS inhibits the expression of the ICAM-1 gene in ARPE-19 cell stimulated with TNF-alpha or IFN-gamma through blockade of NF-kappa B subunit p65 and nuclear translocation of STAT1. This study has demonstrated a potentially important property of GS in reducing ICAM-1 mediated inflammatory mechanisms in the eye.