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Abstract - Interleukin-8 (IL-8) has been implicated in the pathogenesis of inflammation and cancer. Intracellular levels of cytokine-induced IL-8 in human umbilical vein endothelial cells (HUVEC) were modulated using interferons and steroids to further elucidate their mechanism. Basal and cytokineinduced production of IL-8 was studied using a novel ELISA application, flow cytometry, and RTPCR. The intracellular amount of IL-8 increased after 6-h stimulation with TNF-[alpha] (30%) or IL-1[beta] (55%) which was doubled when Golgi transport was disrupted using monensin. IFN-[gamma] decreased the intracellular amount of IL-8 by 60% in both unstimulated and TNF-[alpha]-stimulated cells, but only when secretion was blocked using monensin. Dexamethasone inhibited the TNF-[alpha]-induced production by 33%, but had no effect in unstimulated cells. Our study indicated that both, dexamethasone and IFN inhibit TNF-[alpha]-induced upregulation of IL-8 at them RNA level. It could be speculated that they inhibit IL-8 production by affecting different gene regulatory mechanisms.
KEY WORDS: HUVEC; cytokines; IL-8; steroids; interferons.
INTRODUCTION
Inflammation is characterized by increased extravasation of activated neutrophils and other peripheral blood cells. The endothelial cells play a crucial role in mediating the inflammatory response through regulated expression of several molecules involved in the adhesion and activation of leukocytes. The endothelium also assists in the perpetuation of inflammation through production of several cytokines. Among these, some cytokines, so called chemokines, accelerate the recruitment of leukocytes even further by functioning as signals for directional chemotaxis (1, 2).
One of the chemokines produced by endothelial cells during inflammation is interleukin-8 (IL-8). IL-8 has been postulated to be a specific chemoattractant for neutrophils but can also attract, e.g. basophils, macrophages as well as stimulate endothelial cell proliferation and morphogenesis (1). This chemokine, a member of the CXC family, is produced by a number of cell types including endothelial cells, airway epithelial cells, fibroblasts, and inflammatory cells like monocytes, macrophages, and eosinophils. The production and expression of IL-8 is regulated by several cytokines, growth factors, hypoxia, acidosis, and free radicals (1). Further, the proinflammatory peptides IL-1[beta] and TNF-[alpha], produced and released as mediators at sites of inflammation, are potent inducers of IL-8 production and secretion (2, 3).
Increased levels of IL-8 have been implicated in the pathogenesis of a number of diseases like rheumatoid arthritis (RA), and other chronic inflammatory diseases...