6 research outputs found

    Interferon-γ regulates the interaction of RBL-2H3 cells with fibronectin through production of nitric oxide

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    Interferon-γ (IFN-γ) is an important regulatory cytokine in cell proliferation, differentiation, adhesion, mediator release, and gene induction. This diversity of effector roles is achieved by a variety of incompletely understood mechanisms. In the mast cell (MC), IFN-γ downregulates mediator synthesis and secretion. The present study demonstrates and characterizes for the first time IFN-γ inhibition of adhesion of the MC analogue RBL-2H3 to the extracellular matrix protein fibronectin (FN). Inhibition requires preincubation of the cells with IFN-γ for 20 hr, and is statistically significant at 100 U/ml IFN-γ. Flow cytometry indicates that cell surface expression of very late antigen-4 (VLA-4), VLA-5, and the vitronectin receptor (VNR) remain constant following IFN-γ treatment, indicating the inhibitory effect of IFN-γ on adhesion to FN is not achieved through a reduction in integrin receptors for FN. Fluorescent labelling with Texas red phalloidin demonstrated rearrangement of the actin cytoskeleton in response to IFN-γ was not significant. The tyrosine phosphatase inhibitor vanadate, and the nitric oxide (NO) synthase inhibitor L-NAME, reduced the IFN-γ effect on adhesion to FN by 62 and 70%, respectively, demonstrating that the IFN-γ effect is dependent upon the production of NO, potentially though a tyrosine phosphatase dependent mechanism. The NO donors sodium nitroprusside and S-nitrosoglutathione mimicked the effect of IFN-γ. Thus, following stimulation with IFN-γ, NO plays an autocrine role in the MC, and is able to modulate integrin function. This adds to the pathways NO is able to inhibit in the mast cell, shows that endogenous NO is able to inhibit these pathways, and suggests NO is impinging upon an element common to many signalling mechanisms in the MC
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