Search

Heparin is primarily used as an anticoagulant but has many biological functions as well. It binds with high affinity to a range of cytokines including interferon-gamma (IFN-gamma) and members of chemokine superfamily. IFN-gamma is a proinflammatory cytokine that plays a pivotal role in immune and inflammatory responses; and in endothelial cells, it regulates the expression of fractalkine/CX3CL1 that is a potent agonist for the chemotaxis and adhesion of monocytes and lymphocytes. We have investigated the effect of heparin on the fractalkine expression in human umbilical vein endothelial cells (HUVEC) in culture. HUVEC were treated with approximately 100 mg/mL heparin and the expression of the IFN-gamma-induced fractalkine mRNA and protein were measured by reverse transcription-PCR and western blotting. The IFN-gamma-induced expressions of fractalkine mRNA and protein were inhibited by heparin in a concentration-dependent manner. Heparin also inhibited adhesion of mononuclear cells (MNC) to HUVEC monolayers stimulated with IFN-gamma, but it did not inhibit the MNC adhesion to the monolayers stimulated with interleukin-1beta. Electrophoretic analysis demonstrated direct binding of heparin to IFN-gamma and heparin was found to partially block the binding of IFN-gamma to IFN-gamma receptor (IFN-gamma R). Heparin may play a regulatory role in inflammatory and immune responses by modulating the interaction between leukocytes and the vascular endothelium.

CX3CL1/fractalkine is a chemokine with a unique CX3C motif. Hypoxia mediates the expression of various genes, such as vascular endothelial growth factor (VEGF), cyclooxygenase-2, and plasminogen-activator inhibitor-1, in vascular endothelial cells. We studied the effect of hypoxia on the expression of fractalkine induced by interferon-gamma (IFN-gamma) in endothelial cells. Human umbilical vein endothelial cells were cultured, and the stimulation of the cells with IFN-gamma was found to induce the expression of fractalkine. Hypoxia inhibited the expression of fractalkine mRNA and protein by IFN-gamma, and this effect was observed with concomitant increase in VEGF expression. Desferrioxamine, an iron chelator that mimics hypoxia in vitro, also inhibited the fractalkine production induced by IFN-gamma. Hypoxia did not affect the degradation of fractalkine mRNA. The inhibition of fractalkine expression by hypoxia was reversed on returning the cultures to reoxygenation condition. Inhibition of IFN-induced fractalkine expression by hypoxia was not affected by the presence of a radical scavenger, N-acetyl-L-cysteine, and the involvement of reactive oxygen species may be excluded. Inhibition of fractalkine expression by hypoxia may be involved in the pathophysiology of ischemic diseases.

Background: Galectin-9 is involved in chemotaxis and adhesion of eosinophils, and is induced in vascular endothelial cells by interferon-gamma (IFN-gamma). 15-deoxy-delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) is a ligand for peroxisome proliferator-activated receptor-gamma (PPAR-gamma), and known to modulate the expression of various genes., Methods: We have studied the effect of 15d-PGJ(2) on the IFN-gamma-induced galectin-9 expression in human umbilical vein endothelial cells (HUVEC) in culture., Results: 15d-PGJ(2) inhibited the IFN-gamma-induced galectin-9 expression in a PPAR-gamma-independent manner, and also inhibited the adhesion of EoL-1 cells to an HUVEC monolayer treated with IFN-gamma. 15d-PGJ(2) partially inhibited IFN-gamma-induced phosphorylation of STAT-1 in HUVEC., Conclusions: 15d-PGJ(2) may regulate inflammatory reactions through the inhibition of galectin-9 expression., (Copyright 2003 S. Karger AG, Basel)

Galectin-9 is a member of the galectin family and has been identified as an eosinophil chemoattractant produced by activated T lymphocytes. Vascular endothelial cells play an important role in the initial step of eosinophil recruitment and activation in immune and inflammatory responses. We have addressed the stimulation of galectin-9 expression in endothelial cells. Galectin-9 was detected in membrane and cytosolic fractions of human umbilical vein endothelial cells stimulated with interferon-gamma (IFN-gamma). IFN-gamma also enhanced the adhesion of human eosinophilic leukemia-1 cells to endothelial monolayers, and it was inhibited by the presence of lactose. Interleukin-4, which induces eotaxin expression, did not affect the expression of galectin-9. The in situ endothelium from patients with inflammatory diseases was found to express galectin-9. IFN-gamma-induced production of galectin-9 by endothelial cells may play an important role in immune responses by regulating interactions between the vascular wall and eosinophils.

Fractalkine is a CX3C chemonkine that appears to be a neuron-to-microglia signal molecule in the central nervous system. We studied the expression of fractalkine in normal human astrocytes in culture, by using semi-quantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. We found that tumor-necrosis factor alpha (TNF-alpha) and interferon-gamma (IFN-gamma) synergistically enhance the expression of fractalkine. The expression of both fractalkine mRNA and protein was increased in time- and concentration-dependent manners in the cells co-stimulated with TNF-alpha and IFN-gamma. Cycloheximide, an inhibitor of protein synthesis, and dexamethasone had no effect on the synergy of the stimulation of fractalkine expression. We conclude that normal human astrocytes produce fractalkine by co-stimulation with pro-inflammatory cytokines and it may serve as a potential signal for immune and inflammatory responses in the central nervous system.