interleukin-8 and oleandrin

One of the first steps in host defence is the migration of leukocytes. IL-8 and its receptors are a chemokine system essential to such migration. Up-regulation of these receptors would be a viable strategy to treat dysfunctional host defence. Here, we studied the effects of the plant glycoside oleandrin on responses to IL-8 in a human monocytic cell line.. U937 cells were incubated with oleandrin (1-200 ng mL(-1) ) for either 1 h (pulse) or for 24 h (non-pulse). Apoptosis; activation of NF-κB, AP-1 and NFAT; calcineurin activity and IL-8 receptors (CXCR1 and CXCR2) were measured using Western blotting, RT-PCR and reporter gene assays.. Pulse exposure to oleandrin did not induce apoptosis or cytoxicity as observed after non-pulse exposure. Pulse exposure enhanced activation of NF-κB induced by IL-8 but not that induced by TNF-α, IL-1, EGF or LPS. Exposure to other apoptosis-inducing compounds (azadirachtin, resveratrol, thiadiazolidine, or benzofuran) did not enhance activation of NF-κB. Pulse exposure to oleandrin increased expression of IL-8 receptors and chemotaxis, release of enzymes and activation of NF-κB, NFAT and AP-1 along with increased IL-8-mediated calcineurin activation, and wound healing. Pulse exposure increased numbers of cell surface IL-8 receptors.. Short-term (1 h; pulse) exposure to a toxic glycoside oleandrin, enhanced biological responses to IL-8 in monocytic cells, without cytoxicity. Pulse exposure to oleandrin could provide a viable therapy for those conditions where leukocyte migration is defective.

Topics: Apoptosis; Cardenolides; Cell Movement; Cells, Cultured; Dose-Response Relationship, Drug; HeLa Cells; HT29 Cells; Humans; Interleukin-8; Jurkat Cells; Leukocytes; MCF-7 Cells; Receptors, Interleukin-8; Structure-Activity Relationship; Time Factors

Considering the potential role of interleukin-8 (IL-8) in inflammation, angiogenesis, tumorogenesis, and metastasis, and the involvement of different cell types especially neutrophils and macrophages in those processes, the regulation of IL-8-mediated biological responses is important. In this report we provide evidences that oleandrin, a cardiac glycoside potentially inhibited IL-8-, formyl peptide (FMLP)-, EGF-, or nerve growth factor (NGF)-, but not IL-1- or TNF-induced NF-kappaB activation in macrophages. Oleandrin inhibited IL-8-, but not TNF-induced NF-kappaB-dependent genes expression. Oleandrin inhibited the binding of IL-8, EGF, or NGF, but not IL-1 or TNF. It decreased almost 79% IL-8 binding without altering affinity towards IL-8 receptors and this inhibition of IL-8 binding was observed in isolated membrane. The IL-8, anti-IL-8Rs antibodies, or protease inhibitors were unable to protect oleandrin-mediated inhibition of IL-8 binding. Phospholipids significantly protected oleandrin-mediated inhibition of IL-8 binding thereby restoring IL-8-induced NF-kappaB activation. Oleandrin altered the membrane fluidity as detected by microviscosity parameter and a decrease in diphenylhexatriene, a lipid binding fluorophore binding in a dose-dependent manner. Overall, our results suggest that oleandrin inhibits IL-8-mediated biological responses in diverse cell types by modulating IL-8Rs through altering membrane fluidity and microviscosity. The study might help to regulate IL-8-mediated biological responses involved in inflammation, metastasis, and neovascularization.

Topics: Alkaline Phosphatase; Antibodies; Cardenolides; Cardiac Glycosides; Cell Line; Cell Line, Tumor; Cell Membrane; Cholesterol; Cyclooxygenase 2; Diphenylhexatriene; Dose-Response Relationship, Drug; Down-Regulation; Epidermal Growth Factor; Green Fluorescent Proteins; HL-60 Cells; Humans; I-kappa B Kinase; I-kappa B Proteins; Intercellular Adhesion Molecule-1; Interleukin-1; Interleukin-8; Macrophages; Membrane Fluidity; Membrane Proteins; N-Formylmethionine Leucyl-Phenylalanine; Nerve Growth Factor; Neutrophils; NF-kappa B; NF-kappa B p50 Subunit; NF-KappaB Inhibitor alpha; Phospholipids; Phosphorylation; Promoter Regions, Genetic; Protease Inhibitors; Receptors, Cell Surface; Receptors, Interleukin; Recombinant Fusion Proteins; Sphingosine; Transcription Factor RelA; Tumor Necrosis Factor-alpha; U937 Cells